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Comparative Analysis of Temporal and Spatial Distribution Characteristics of Extreme Short-duration Heavy Rainfall in Shandong Province Based on Encrypted Automatic and National Meteorological Observatory Data
HOU Shu-mei, Sun Jing-wen, Sun Peng-cheng, Gu Shan-qing, qiu can
Available online: December 02, 2019 , DOI:
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Using the more than 1mm hourly precipitation data of the encrypted automatic weather observatory (referred to as the all stations) and the national meteorological observatory (referred to as the national stations) in Shandong Province from April to October 2008-2017, this study compared the characterization of spatiotemporal distribution of extreme short-duration heavy precipitation with different resolution data. The results indicated that:(1) the skewed characteristics of all stations hourly precipitation were more obvious than those of the national stations. For the average state of hourly precipitation, both were representative. However, for the analysis of the extremes of short-duration heavy rainfall, all-stations data was more advantageous. (2)It was most reasonable to use the 99.5th percentile of each station as the threshold for extreme short-duration heavy precipitation. The spatial distribution characteristics of the 30-45mm threshold were similar for all stations and national stations. For thresholds above 45 mm, the values and ranges of all stations were both greater than the national stations. (3)The extreme short-duration heavy precipitation intensity in most parts of the province was concentrated at 40-60mm?h-1, and the spatial distribution characteristics of all stations and national stations in this interval were similar. National-station data cannot characterize the spatial distribution of extreme short-duration heavy precipitation with intensity below 40 mm?h-1 and above 60 mm?h-1. (4)The spatial distribution characteristics of extreme short-duration heavy precipitation intensity were closely related to geographical location and topographical features. The extreme short-duration precipitation intensity, daily maximum precipitation, summer precipitation and annual precipitation in the southeastern Shandong Province ranked first in the province. Although the frequency and intensity of heavy precipitation were high in northwestern Shandong, it had no positive correlation with annual precipitation and summer precipitation. (5)The monthly and diurnal variations of the extreme short-duration heavy precipitation frequency of all stations were consistent with those of the national stations. However, the national-station data cannot fully represent the monthly and diurnal variation of the extreme short-duration heavy precipitation intensity in the province. The data of all stations can more accurately reflect the time variation characteristics of precipitation in the province.
Assessing Model of Casualty Loss in Rainstorms Based on Random Forest and Its Application
Liu Yang, Wang Weiguo
Available online: November 25, 2019 , DOI:
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Based on historic casualty loss records of heavy rainfall occurred in Guangxi at county level from 2009 to 2017, seven factors were selected as explanatory variables by comprehensively considering the trigger factors, disaster formative environment and exposure units, and the prediction model of casualty loss caused by rainstorms was built up by using random forest algorithms. The refined grid precipitation analysis and forecast products were used to drive the model to predict loss of life. The results show that the classification accuracies of model are both above 90% in training and testing samples. Disaster-triggering factors (precipitation) are the most significant explanatory variables. The importance of these precipitation variables in turn are the anomaly percentage of accumulated precipitation over the previous 10 days, the maximum daily precipitation, the maximum hourly precipitation and the frequency of short-time heavy rainfall. By applying the intelligent grid precipitation products, several rainstorm processes in Guangxi in recent two years are used to verify the model, and the results show that prediction accuracies are above 70%.
The validation of FY-3C MWRI total precipitable water products
Wu Qiong
FY-3C is the second generation polar meteorological satellite which is developed by china independently and launched in September 23, 2013. MWRI (Microwave Radiance Imager) is an important microwave load which can monitor air, ocean and land. As a product of MWRI,TPW (Total Precipitable water) can be used in numerical weather prediction(NWP) and climate research. But, the result of application relied on the accuracy of TPW. By using 4-years satellite observation data, the quality of TPW products is validated through the comparison between TPW products and radiosonde TPW or SSMIS TPW. As a result, the RMSE (Root Mean Square Error) of orbit product is 2.6mm and the average relative error is 7%. What's more, the RMSE of day product is 3mm and 2.1mm when separately compare with SSMIS and radiosonde. The accuracy of month product is stable and less than 1.3mm. The above conclusions show that FY-3C MWRI TPW products have a high precision and good stability. FY-3C MWRI TPW products have the application ability in weather and climate field.
Characteristics of precipitable water vapor over the Tianshan Mountains based on GPS observations
YU Xiaojing<sub>, Tang yonglan, Yu Zhixiang
Based on the precipitable water vapor (PWV) data observed by Global Positioning System (GPS), the radiosonde data and daily precipitation data, employing several statistical methods, characteristics of summer PWV over the Tianshan Mountains and their possible reasons are analyzed. For the distribution of summer PWV average, remarkable differences exist among stations over the Tianshan Mountains, and there is a significant negative relationship between PWV and station altitude. And PWV at lower altitudes exhibits more variabilities and divergences than that at higher altitudes. The extreme and median of PWV in rainy days exceed those in rainless days. Monthly variation of summer PWV is considerable, which behaves maximum in July and minimum in August at most stations. As to diurnal variation, most stations appear maximum at about 10:00 while individual stations exhibit opposite characteristics, and discrepancies still exit between rainy days and rainless days. There is no direct connection between precipitation and PWV. However, precipitation and water cycle index are positively related to station altitude, which maybe be attributed to more local convective precipitation processes over higher mountains in summer and more water cycle frequencies.
On the Relationship Between Atmospheric Precipitable Water Vapor and Precipitaton in Liaoning Province
QIN Xin, ZHAO Shuhui, MA Jiali, SUN Li, LIU Yang, FANG Bin
Precipitation is likely to take place as precipitable water vapor (PWV) of the atmosphere reaches a certain value,thus, the threshold of PWV(PWVt),which can be regarded the research bridge between PWV and precipitation. In the aim of calculating PWVt precisely, this paper has brought in "Precipitable Water Vapor Saturation(PWVsat)" of the atmosphere and deduced the computing formula of PWVsat under various atmosphere conditions. From the formula ,it is shown that PWVsat ,indicating the maximum water vapor a bottom-up saturated atmosphere is capable to hold ,is a function of surface temperature(ts). The atmosphere needs to be wet enough to form clouds and rains, therefore, it is inferred that ts is a factor in PWVt. To prove that, PWVt and ts of 36 gauge stations ranging from May 2015 to October 2016 are studied and 1122 precipitation cases are selected and fitted.The result shows that the fitting formula of PWVt and computing formula of PWVsat are highly alike, proving the 2 variables are closely correlated. Fitting parameters of each of 36 stations are given for relating PWV to precipitation. This method has gone through statistical examination to find that its accuracy rate, missing rate and vacancy rate to be 93.69%、2.32% and 3.99% respectively in precipitation prediction, showing a sound application value in predicting rainfall. Finally, the method is applied in a rainfall case to show that PWVt have well predicted precipitation, and the difference between PWV and PWVt is correlated to precipitation amount.
Probabilistic Forecasting of the Precipitation over the Qingjiang River Basin Using BMA Multimodel Ensemble Technique
QI Haixia, pengtao, linchunze, pengting, jiluying, lilan, 孟翠丽
ased on the TIGGE datasets including the European Centre for Medium Range Weather Forecasts(ECMWF),the United Kingdom Met Office(UKMO), the China Meteorological Administration (CMA), and the Japan Meteorological Agency (JMA),and its multi-center ensemble systems,and observations in the Qingjiang basin,Bayesian model averaging (BMA) probability forecast models were established.The results show that the optimal length of the training period is about 40 days, and the BMA models for multi- center ensemble outperform those for single center system for lead times of 24h.The mean absolute error (MAE) and continuous ranked probability score(CRPS) skills of the BMA models were improved approximately 11% and 15%, respectively,compared with those of raw ensemble forecasts. In business operation, when the BMA90 percentile site predicted precipitation to be extreme precipitation, the 75-90 percentile site predicted precipitation could be used as the forecast reference, and the heavy precipitation warning could be carried out. For the forecast of heavy precipitation, the forecast result of the 50 to 75 percent site predicted by BMA can be taken as a reference, while for the general precipitation, the reference of BMA deterministic forecast is relatively strong.BMA probability forecast could give both the PDF curve with full probability and the probability greater than a certain precipitation level, which could provide the basis for the probability forecast in the business. However, it is also limited, and the small probability value is often ignored, resulting in omission. So how to capture more useful information through the probabilistic prediction method and increase the accuracy of the prediction of extreme weather events will be a challenge for the probabilistic prediction technology.
Comparisions of the Multi-source Datasets in calculation of the Atmospheric Heat Sources over the Tibetan Plateau
Wang Meirong, Guo Dong, Zhong Shanshan
Atmospheric heat source is one of the main points of the theory of plateau meteorology. The studies on its calculation method and applicability are of great significance to deepen the understanding of plateau meteorology and broaden the horizon of students of this course. The precise calculation of atmospheric heat source remains a challenge. We in this study introduce two methods for calculating the atmospheric heat sources in detail. Based on historical observations of meterological stations, satellite-based radiation datasets (ISCCP and SRB) and four reanalysis datasets (NCEP/NCAR, NCEP/DOE, ERA-Interim and JRA55), we calculated the atmospheric heat sources in summer season over the Tibetan Plateau and compared their differences in multiscale vaiabilities. Results show that radiation data should be carefully selected in calculating the atmospheric column energy budget. When calculating the atmospheric apparent heat sources, we should carefully select the reanalysis data according to the focus of the timescale owing to their quite different performances. In terms of the long-term trend, -JRA55 is closest to the observations; on the interannual time scale, -ERAI and -JRA55 these two results can repeat the variability of the heat source from observations, and on the intraseasonal oscillation, the differences of multiple sets of reanalysis data have been narrowed, and they all can be used well to describe the changes of the heat source over the TP.
Error analysis on the assessment algorithm of clearance environment of weather radar based on SRTM
jinghaoran
SRTM data was used to evaluate the clearance environment and effectively improve the site-selection evaluation efficiency of radar. In this paper, the comparative experiment of weather radar clearance environment assessment is carried out by using manual measurement data and SRTM data. Error analysis of this method suggested that the evaluation algorithm of weather radar clearance environment based on SRTM was good matching with the artificial measured data. The calculation error was significantly reduced when corrected with azimuth correction and range correction.
Radar Echo Forecasting Capability Analysis in DifferentHigh -Resolution Models
Liu Jing, CAI Kuizhi, Tan Zhenghua
Using the forecasting Radar echo data from GRAPES_3KM(Global/Regional Assimilation and Prediction System) and WRFRUC of July and August in 2018,the real Radar echo data from SWAN(),based of FSS(Fractions Skill Score),the Radar echo forecast ability in system of typhoon and subtropical anticyclone in two high-resolution models are analyzed.The result showed that:Weak Radar echo forecast in two models have better skill ,with increase of Radar echo,The forecasting skill score decreases.when Radar echo reached 55 dBz, FSS even equal zero.When spatial neighborhood radius is 3, forecasting is more skilled in the typhoon rain than subtropical anticyclone rain when Radar echo is less than 35dBz.If Radar echo is bigger than 35dBz,it is in contrast.The forecasting of Radar echo in WRFRUC model alway better in typhoon rain than subtropical anticyclone rain .When spatial neighborhood radius increasing to 9,the echo forecasting FSS is higher in WRFRUC model than GRAPES model in typhoon rain ,but in subtropical anticyclone rain,GRAPES model has the higher skill than WRFRUC model.The biggest FSS in GRAPES and WRFRUC model are both at the spatial neighborhood radius of 11,value are 0.239 and 0.195.In the first three time of the forecasting ,FSS is bigger than other hours in the model of GRAPES. In the middle times of the echo forecasting of WRFRUC model ,FSS is higher than other hours.
Validation of the rotorcraft UAV boundary layer meteorological observation data and its application in a heavy fog event
WANG Hongbin, WU Hong, LI Yong, XU Jiaping, ZU Fan, ZHANG Zhiwei
The observation experiments of boundary layer meteorological by rotorcraft UAV were carried out from 28 to 30 March 2018, from 20 to 26 June 2018 and from 5 to 13 September 2018 in Yancheng, Jiangsu province, China, respectively. Comparison with L-band radar sounding data to verify the accuracy of UAV observation data. The results show that the observation data of temperature, relative humidity, wind direction and wind speed vertical profile measured by UAV are in good agreement with the observation data of the L-band radar sounding data. The correlation coefficient of temperature, RH (Relative Humidity) and WS (Wind Direction) of UAV and L-band radar sounding are 0.98, 0.98 and 0.91, respectively. The absolute deviation of temperature, RH, WD and WS (Wind Speed) are 0.57 ℃, 4.25%, 11.5&amp;#176; and 1.88m/s. The wind speed observed by the UAV is the instantaneous wind speed at the corresponding height, which can better reflect the wind speed details characteristics in the boundary layer. During the observation experiments, the UAV observed the detailed changes of boundary layer structure with a summer heavy fog process. The heavy fog dissipated with the disappearance of the temperature inversion when the ground surface was heated after sunrise. The result of verification shows that the UAV has a good application prospect in the boundary layer meteorological observation.
Research on Wind Changes at Different Height in the Atmospheric Boundary Layer Based on Sounding Wind Data
mengdan, chenzhenghong, chencheng, sunpengjie, yangwei
Based on the data of air sounding winds from 93 high-altitude meteorological stations (300m, 600m, and 900m above the radar) with complete data from 1981 to 2014 in China, the spatial and temporal variations of wind speed and its trends at different altitudes in the boundary layer were analyzed using GIS. The following conclusions were obtained: 1) At the height of 300-900 m, the average wind speed over the years in northeast and north China was relatively large, while the mean annual wind speed in southwestern and northwestern China was relatively small. 2) The monthly variation trend of average wind speed in the same level at various heights in the boundary layer was basically the same, but the seasonal wind speed variations in different regions were different. The annual range of monthly average wind speed in the same region, increases with altitude. 3) The annual average wind speed at an altitude of 300m decreases significantly. At 600m and 900m, the average annual wind speed in North China, Northwest China and Central China showed an upward trend while the average annual wind speed in Northeast China showed a decreasing trend, but none of them passed the significance test. 4) The spatial distribution of average annual wind speed at all altitudes is relatively large in northeast China, especially in the Greater Khingan Mountains and the northeast plains. The wind speed from east to west gradually decreases from the coast to the inland. 5) At 300m, the annual average wind speed in the country shows mainly a decreasing trend. At 600m, annual average wind speed in most parts of the country shows an increasing trend, especially in central China, northwest China and eastern coastal areas. At 900m, the change in annual average wind speed nationwide shows a trend of encircling from the boundary to the interior, with the central area showing an increasing trend and the border areas showing a downward trend. However, there are few areas that pass the significance test.
Research on image data quality control method in crop real landscape observation
licuina, shiguangyu, yuzhenghong, baixiaodong
Abstracts:The automatic monitoring system for crops has the advantages of automatic, non- contact and non-destructive, and is a useful supplement to traditional agrometeorological observations. The CCD sensor protects the cover from water, dust, and smog, rain and snow, etc., which may cause observation data of automatic crop monitoring system error. Therefore, the quality control is the basis for the rational use of the automatic crops monitoring system to detect data. Based on the historical crop image detection data of Zhengzhou, Tai&amp;#39;&amp;#39;an and Gucheng, this paper designs a quality control method for image data based on color feature parameter detection and dark channel prior histogram detection. According to different weather conditions,we carried out quality control on the summer maize and winter wheat image observation data in 2010-2012, and the effects were tested. The results show that both types of inspection methods can determine the anomaly data of image observation data in the automatic crops monitoring system;The color feature parameter detection method can effectively identify the missing image of pixels, the accuracy rate can reach100%; the average precision is 95.67% and recall average is 87.5%.The proposed method based on the histogram of dark channel can effectively identify the contaminated image; the quality control method can reduce the error between the model estimate and the observed data. At present, this method has been applied to automatic agricultural meteorology observation oprational software.
The Analysis of Forecast Focuses of Binary Typhoons Nesat and Haitang
donglin, Lyu xinyan, Xu yinglong, Gao shuanzhu
Available online: October 29, 2019 , DOI:
The accurate prediction of the first-time landing position and the second-time landing intensity are very difficult because of the rare near-distance for the binary typhoons Nesat (No. 1709) and Haitang (No. 1710). Although CMA issued an accurate official forecast, the performance of most models including ECMWF and NCEP is far from satisfactory. Forecast experience and focus in the operation are analyzed and summarized in this paper. First, the rationality of model prediction for the large-scale circulation such as subtropical high is analyzed based on synoptic models, deviation revision experience and the performance of ensemble forecasting system. Second, the main circulation is determined by analyzing the relative intensity of the closest time of the binary typhoons, so as to judge the difference between the landing times of two typhoons, their extreme strength and the onshore maintenance mechanism. Third, paying more attention to two influencing factors of the typhoon track angle with Taiwan's Central Mountain Range and cross-island time is helpful to revise the second-time landing intensity.
Study on the application of ensemble forecast in extreme wind prediction in Bohai Sea
huhaichuan
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By using the hourly extreme wind from the routine surface meteorological observation and the 6-hour extreme wind forecast data from ECMWF between February 2015 and February 2018, the representative stations in the Bohai Sea are selected to analyze the prediction error characteristics of the extreme wind products in the ensemble forecast. The analysis shows that the spread of the maximum wind product in ensemble forecasting is obviously smaller than the root mean square error, and whether the forecasting results of each forecasting member are concentrated or not cannot reflect the reliability of forecasting. Due to the limitation of model prediction ability, it is impossible to select the most credible prediction results simply by ensemble prediction. The ensemble average, 75 percentile and maximum ensemble forecasting have their own advantages and disadvantages in maximum wind forecasting. Therefore, based on the above three statistics and the frequency of different magnitude wind speed occurrence, an objective correction method for maximum wind forecasting in the Bohai Sea is established. The comparative analysis of experiments shows that the correction method can effectively improve the accuracy of maximum wind forecasting. The forecast of extreme wind process provides important reference.
Effect of Meteorological Factors on Grain Filling Rate of Semi-winter Wheat
Xin Zhihong, Guo Jianping, Tan Kaiyan, Zhang Lihua, Sun Yi, Yang Rongguang
Four semi-winter wheat varieties Tanmai 98, Shannong 18, Xumai 33 and Wanmai 52 in Huanghuaihai winter wheat area were selected as test materials. Through the sowing date tests, the trends of grain filling rate and the influence of meteorological factors on the filling rate were analyzed by means of analysis of variance, correlation analysis, stepwise regression and path analysis. The results showed that the fluctuation of grain filling rate was the least and the 1000-grain weight was the highest in the normal sowing date, the late-sowed 10d winter wheat had the highest volatility and the smallest 1000-grain weight. The grain filling rate of Tanmai 98 was the most stable and the 1000-grain weight was the highest in winter wheat area of North China, while the grain filling rate of Wanmai 52 was the highest in Huanghuai winter wheat area. The grain filling duration of semi-winter wheat was 35~39 days. The difference between north and south climate was one of the reasons that affected the different filling rate of winter wheat. The temperature conditions have significant effects on the grain filling rate of winter wheat, the highest temperature factor is the common key factor affecting the filling rate of different sowing date and varieties. The change curve of grain filling rate of semi-winter wheat is roughly "M" type, and the significant changes of meteorological factors are also obvious "M" type or "W" type. The filling rate of each sowing period showed a trend of "slow-fast-slow", and the peak period of grain filling generally appeared 15~25d after flowering, the appearance time is earlier of the maximum filling rate of late sowed winter wheat than the control treatment, which is not conducive to increasing the grain weight. Path analysis shows that the effect of maximum temperature on filling rate is determined by its direct effect, while the effect of sunshine hours and minimum temperature on filling rate is consistent with indirect effect. The average of highest temperature has the most important effect on filling rate, sunshine time and the average of minimum temperature has a weak influence on the filling rate. The averages of highest and lowest temperature and the sunshine hours are the limiting factors of the filling rate, and the average of highest temperature has the greatest decision-making effect on the change of filling rate, the decision-making of sunshine hours role is minimal.
Effect of large eddy vertical resolution on analysis of entrainment and tracer vertical transport simulation
wangrong, huangqian, yueping, wangminzhong
Available online: September 24, 2019 , DOI:
The effects of different scales of turbulent vortices in vertical direction on entrainment process and vertical transmission of tracers were studied, and the role of model vertical resolution in the analysis of simulation results was clarified by using field intensive observation data in Dunhuang and large eddy model (LEM). The results show that, in the vertical direction, the small scale turbulence contributed more to the entrainment, and the small scale turbulences were more, the clamping layer was warmer. However, the thickness, strength and wind speed of the clamping layer were less affected by the scale of the vertical direction turbulent vortices. Over the upper part of the entrainment layer, the updrafts and downdrafts flow were distributed more and more intensively in the 50m vertical resolution test. The distributions of vertical velocities, potential and tracer concentration at different heights of the clamping layer has little differences in the 10m、20m and 30m vertical resolution tests. In addition, the vertical turbulent vortices scales has little effects on the tracer vertical transport height, but has a certain affect on the spatial distribution of tracer. When the large scale turbulences were more and stronger, high concentration tracer vertical transmissions were more favorable. Considering the greater the noise generated in the simulation process and the longer computing time by the high resolution simulations, the use of 30 m grid spacing as LEM vertical resolution in simulating is an ideal choice, which the model can not only simulate the average structure of the entrainment layer, but also the very fine turbulence distribution in the clamping layer could be simulated.
Construction and validation of remote sensing dust recognition algorithm in daytime and nighttime
wang wei, hu xiu qing, zhang peng, min min
Himawari-8 is a new generation of geostationary meteorological satellite launched by Japan. Compared with the previous generation of MTSAT-2, it has greatly improved its time and spatial resolution. The number of infrared channels of Himawari-8 increased from 4 to 10 compared with MTSAT-2, providing new observation data for infrared remote sensing of dust. This research makes full use of Himawari-8 infrared observation data and develops an all-day dust identification algorithm using only infrared channels, which can realize continuous monitoring during the day and at night. The algorithm is based on previous algorithms, and does not use visible light channels, but uses more infrared channels for cloud detection and dust recognition. As surface temperature change during the day, two different sets of discriminant thresholds are set up for daytime and night to ensure the applicability of the whole day. Finally, two dust events were used to analyze and verify the results of dust discrimination. The consistency between ground-based and remote sensing results shows that it is feasible to use the infrared channel to identify sand and dust all day.
Comparison of two Lateral Boundary Perturbation Method in the Regional Ensemble Prediction System of GRAPES
fan yu en, chen jing, deng guo, chen fa jing, liu xue qing, xu zhi zhen
Abstract: The Numerical Weather Prediction Center of CMA(China Meteorological Administration) has established the GRAPES-REPS (Global and Regional Assimilation and Prediction Enhanced System-Regional Ensemble Prediction System) system since 2014. The lateral boundary perturbation are provided by a global ensemble prediction system. In order to understand the impact of lateral boundary perturbation on GRAPES regional ensemble prediction. In this paper, based on the GRAPES-REPS regional ensemble prediction model with 15 km horizontal resolution, two lateral boundary perturbation are constructed. The 6-day ensemble prediction test is carried out in July 2015. Using root mean square error, set dispersion degree, CRPS, Outlier, BS score, TS score, AROC methods analyze two kinds of lateral boundary perturbation methods for Regional Ensemble Prediction System and impact of distribution characteristics. The energy of the lateral boundary perturbation obtained by dynamic downscaling(DOWN) is greater than the energy of the SLAF experiment at each vertical level, resulting in the spread of DOWN experiment greater than the dispersion of SLAF experiment. For the isobaric elements and the ground elements, the scores of DOWN experiment better than the scores of SLAF experiment, indicating that the lateral boundary perturbation of the DOWN experiment structure are more reasonable; In the aspect of precipitation probability prediction techniques, the SLAF experiment has certain advantages in scoring, but the improvement of the score does not pass the significance test, so it is considered that the two experiments are equivalent to the improvement of precipitation forecast. Key words:regional ensemble forecast,lateral boundary perturbation,dynamic downscaling,SLAF(scaled lagged average forecasting)
Analysis on the Impact of Background Field in the Numerical Simulation on the 7 May 2017 Extremely Severe Rainstorm in Guangzhou
XU GUOQIANG
Available online: August 09, 2019 , DOI:
A torrential rainfall event occurred in Guangzhou on May 7, 2017. In order to study the impact of different background field data on the simulation of rainstorm process, the NCEP Global Forecast System (GFS) data and CMA T639 data were used separately to develop lateral boundary and initial conditions for the numerical simulation and impact analysis of the rainstorm with the GRAPES_Meso model. Results indicate that different background fields had a significant impact on the simulation of rainstorm process. The precipitation forecasts using T639 data as initial and boundary conditions seem to be reasonably simulated, while the location of the rainfall simulated by GFS data is obviously northerly. The reason is that there is a deep water vapor transport and strong ascending motion in the rainstorm area of South China using T639 data as the background field, which can produce extremely heavy rainfall. The updraft and water vapor transport is weak in the actual storm area simulated by GFS data, making the heavy precipitation area northerly. Overall, the height of cloud top is higher and the temperature of cloud top is lower simulated in GRAPES_Meso model. Relatively speaking, the simulation result using T639_RUN is better than GFS_RUN. The research result can provide a reference for the improvement and optimization of the calculation about the water substances and cloud fraction in cloud schemes.
A Preliminary Test for the Correction of the Humidity Observation Deviation of the Vaisala RS92/90 Detector
haomin
Sounding observation data are the most basic and important data source in weather forecast and numerical weather prediction. Vaisala Radiosonde 92/90 data account for a large proportion of this kind of observation. The quality of the humidity observation data directly affects the assimilation analysis and model forecast, so it is necessary to evaluate the quality of the data and correct the deviation. The humidity observation deviation of RS92/90 detector is found by comparing with the humidity field of NCEP and EC reanalysis. Based on the deviation correction scheme of Yoneyama for the humidity observation of the instrument, the revised scheme which is the most significant for the analysis and improvement and which takes into account the influence of solar radiation and other factors are selected from the comparison of several revised schemes. The scheme is applied to GRAPES-GFS test. The experimental results show that the deviation of humidity observation for the RS92/90 sounding is corrected. Assimilation analysis and prediction have neutral bias effect. After the correction of prediction anomaly correlation in the continuous experiment, there is an improvement in East Asia and tropics, and the forecast score shows tropics. The Northern Hemisphere score is slightly higher, so the correction scheme of humidity observation deviation of RS92/90 sounding instrument has its application value in practical operation.
Field investigation and analysis of wind disaster and estimation of disaster wind speed of the capsizing accident of cruise ship "Oriental Star"
WANG Kai, LIANG Yitong, LUI Min
Available online: July 17, 2019 , DOI:
Take the capsizing accident of cruise ship "Oriental Star" as an example,the analysis of the previous study and the field investigation shows that on June 1st, from 21:00 to 21:15, severe weather such as thunderstorms, strong winds, heavy rains and tornadoes occurred in the investigation area.The duration is about 30 minutes; The disaster process was characterized by the most severe windstorms, with spatial discontinuities and small scales.The survey results show that: there are vertical shear and horizontal shear in the wind field along the Yangtze River in the incident area, radar monitoring shows that the mesocyclone moves from the west bank of the Yangtze River to the east bank, having vortex characteristics.This process is mainly based on windstorms, the severely affected area is concentrated within 8km north of the incident, the SiTai villages on the east bank of the Yangtze River, which is about 4km away from the incident, are the most seriously affected,the region has strong wind shear and signs of divergence.The main affected objects are trees, crops, houses, boats, etc., causing the most damage to trees, a total of 31 disaster sites, accounting for 72.1% of the total survey sites.In the incident area, the trees on the west bank of the Yangtze River are broken or the direction of lodging is mainly southeast, the trees on the east bank is mainly east,the direction of the trees dumping is clearly consistent,however, there are horizontal shears on both sides of the Yangtze River, and the wind direction is deflected by nearly 90º. The quantitative evaluation method of wind disaster is explored by combining actual disaster with mechanical model. ,taking the severely affected poplar as an example, the anti-overturning moment calculation method is used to estimate the disaster rate.The results show that strong wind is one of the important causes of the incident, the wind speed of the disaster is 28.7m/s,reaching 10 or above,it basically coincides with the results of Zheng Y G et al.
Meteorological and hydrological characteristics of severe floods over the upper Changjing River Basin in 2018
gaoqi
Available online: June 10, 2019 , DOI:
Based on NCEP/NCAR reanalysis data and conventional meteorological and hydrological observation data, the meteorological and hydrological characteristics of the upper Changjing River Basin during the severe flooding period from June to July 2018 are analyzed. The results show that three heavy precipitation processes occurred during the flooding period of the upper Changjing River Basin in 2018, and the precipitation falling areas overlap highly in the northern part of the upper Changjing River Basin, causing serious disaster. Large-scale circulation analysis shows that the low trough, subtropical high, Okhotsk resistance high and Ural resistance high in middle and high latitudes are stronger than those in the same period in history. The north-south swing of subtropical high is larger. When the subtropical high jumps northward, it will encounter with the cold air behind the trough in the upper Changjing River Basin, forming a heavy precipitation process. The &amp;quot;saddle&amp;quot; configuration of large-scale circulation facilitates the water vapor transport from the Bay of Bengal and the South China Sea to the upper Changjing River Basin, and the convergence of water vapor in the region and the mid-latitude westerly zone forms heavy precipitation. The historical results show that the precipitation in the upper Changjing River Basin in 2018 is characterized by strong surface intensity, strong extreme precipitation in the northern tributaries and more concentrated rain period. Compared with 2012, the northern tributary of the upper Changjing River Basin have high water level and long time of exceeding the warning water level. The flood situation of Tuojiang, Fujiang and Jialing rivers is stronger than that of 2012. In 2018, the total precipitation and peak flow of the upper Changjing River Basin did not exceed 2012, but the flood disasters caused by the Tuojiiang, Fujiang and Jialing rivers in the north of the upper Changjing River Basin could exceed 2012.
Comparative Analysis of Two Abrupt Heavy Rain Processes in Sichuan Basin in July 2011
XIAO Dixiang, YANG Kangquan and QI Shengxiu
2012,38(12):1482-1491, DOI: 10.7519/j.issn.1000-0526.2012.12.005
[Abstract] (1841) [FullText HTML] (5) [PDF 10.45 M] (34315)
By using the conventional meteorological data, Doppler radar data and NCEP/NCAR reanalysis data, the characteristics of Doppler radar's reflectivity, environmental condition and trigger mechanism of the heavy rain are analyzed and compared between two abrupt heavy rain processes occurring in Sichuan Basin on 3 July (7.3) and 23 July (7.23) 2011. The results show that: the "7.3" heavy rain happened under a typical circulation background, and moisture transporting to the heavy rain area from the South China Sea was smoothly, thus the heavy rainfall maintained so long, but the "7.23" heavy rain occurred behind the upper cold vortex, and convective unstable energy was abundant and vertical wind shear was strong, thus this heavy rain process happened with hail and thunderstorm weather accompanied, its radar reflectivity was 5 dBz stronger than "7.3" case and had the characteristics of severe storms such as the low level weak reflectivity and the upper echo overhang. As a whole, the non equilibrium force is contributed to the occurrence of heavy rain and it is the excited mechanism of the two heavy rainfalls, and the change of the divergence evolvement is consistent with the strength and the position of the heavy rain which would happen 6 hours later.
第七讲 大气中的波动
黄荣辉
1983,9(8):35-39, DOI: 10.7519/j.issn.1000-0526.1983.08.014
[Abstract] (775) [FullText HTML] (0) [PDF 482.29 K] (24485)
Products of CINRAD-SA Doppler Radar Applied to Different Typical Weather
李云川, 王福侠, 裴宇杰, 刘晓霞
2006,32(10):64-69, DOI: 10.7519/j.issn.1000-0526.2006.10.010
[Abstract] (1348) [FullText HTML] (12) [PDF 14.01 M] (19691)
Based on the data of CINRAD Doppler Radar which located at Xinle of Hebei Province,the hail,strong wind and heavy rainfall weather events in mid-south Hebei in 2004 are statistically analyzed.The routine radar products,such as echo reflectivity,radial velocity,Vertically Integrated Liquid(VIL)Water,hail index,mesocyclone,velocity azimuth display wind profile,etc.are used in this statistics.The results show that hail's VIL value is larger than generic thunder storm's.At the same time,greater VIL value and longer sustaining will bring about greater diameter hail and larger effect area.It is the very useful index to indicate strong wind in mesocyclone products and the wind direction sudden change in radial velocity products.A reference based on analyzing this type synoptic forecast with radar system in future is proposed.
Retrieval and Preliminary Test of Cloud Physical  Parameters from Combination of FY-2C/D Geostationary  Satellite Data and Other Observation Data
Zhou Yuquan, Chen Yingying, Li Juan, Huang Yimei, He Xiaodong, Zhou Feifei, Wu Menxin, Hu Bo and Mao Jietai
Cloud macro and micro physical characteristic parameters play an important role not only in the field of the analysis and forecast of the weather and climate, but also in the field of weather modification to identify the seeding c ondition. Based on the data from FY-2C/D stationary satellite and SBDART radiati on transfer model, associated with the sounding data and surface information, a method retrieving cloud macro and micro physical parameters is established in th is research. These parameters include cloud top height, cloud top temperature, d epth of super-cooled layer, depth of warm layer, cloud bottom height, depth of c loud, cloud optical thickness, cloud effective particle radius and cloud liquid water content. It has been run operationally. In this paper, the correlated info rmation such as physical meaning, retrieving method and technology, retrieving p rocess and data format are simply introduced. Furthermore, comparing with the ob servation of Cloudsat up to the minute, the retrieving results of main cloud par ameters are proved to be reasonable and usable. By contrast with same kind produ cts of MODIS, it also shows good corresponding relationship.
Analysis on Boundary Layer Features and Sources of Water Vapor of One Continuous Dense Fog in Nanjing
ZHANG Lichun, ZHU Bin, GENG Hui and MA Guozhong
Based on the fog observation data during 24-27 December 2006 (advection radiation fog), NCEP NC reanalysis data (2.5°×2.5°) and GDAS global meteorological data (1°×1°), detailed trajectory analysis of the boundary layer characteristics and water vapor transport of the fog is investigated, combined with the weather condition, meteorological elements and physical quantity field. The results show that: (1) there is thick inversion layer, even multi layer inversion throughout the dense fog event. Temperatures of different inversion tops in the middle and high levels are 2-5℃ higher than the surface temperature. The thickness of inversion layer is more than 200 m, and it gets to 500 m at 08:00 BT 26 December, indicating the atmosphere is very stable and conducive to the convergence of water vapor before the fog forms. However, it is not favorable for the divergence of water vapor after the formation of fog, which helps the development and maintenance of the fog, causing the fog to last about 64 hours with dense fog (visibility <50 m) about 37 hours; (2) The divergence of water vapor flux in low level is negative in the advection fog event. The upper air has persistent moisture convergence and the strongest moisture convergence appears at 02:00 BT 25 December, being -30×10-7 g·s-1·cm-2·hPa-1. The accumulation of low level water vapor makes fog form and develop while the divergence of water vapor flux speeds up its dissipation. 〖JP2〗The long lasting advection radiation fog is mainly caused by the continuous water vapor convergence; (3) The water vapor path is from the coastal area in easten China to Nanjing. The water vapor is continuously supplied from sea during the fog event, with the water vapor flux maximum getting to 2 g·s-1·hPa-1·cm-1. The sufficient supply and supplementary of water vapor determines the duration of the fog.
Analysis of a Strong Gust Front and Downburst with Doppler Weather Radar Data
Wu Fangfang, Wang Hui, Wei Yingying and Wang Qun
2009,35(1):55-64, DOI: 10.7519/j.issn.1000-0526.2009.1.007
A strong rainstorm is analysis which occurred in Xinghua located the north of Ji angsu province on 25 July 2007. Results show that wind disaster originated from two kinds of rainstorm. One kind was the gust front which occurred at the front of the storm. Strong wind of grade 7-9 was attained when it happened. Another ki nd was the downburst arose in the multi cell storm. The original height of refl ectivity core was higher than -20℃ isotherm. It had the characteristics of conv ergence on the mid level and descending of reflectivity core. The strong wind ab ove grade 10 was attained, when the descending airflow diverged strongly on the ground. A new cell was combined with the former storm above the gust front, thus the storm enhanced. When the downburst happened, the storm weakened, and another new cell was combin ed with the former storm. The downburst happened continuously, and the impact of gust front persisted.
Environmental Characteristics of Severe Convective Wind over South China
YANG Xinlin, SUN Jianhua, LU Rong and ZHANG Xian
2017,43(7):769-780, DOI: 10.7519/j.issn.1000-0526.2017.07.001
[Abstract] (1813) [FullText HTML] (26) [PDF 3.95 M] (13967)
The spatial distributions of severe convective wind (SCW) and nonsevere thunderstorms (NT) over South China, occurring between 08:00 BT and 20:00 BT during spring and summer in 2010-2014, were analyzed by using the observational data from China Meteorological Administration. And then, their environmental characteristics were compared between SCW and NT in spring and summer. It was found that SCW in summer is more frequently than that in spring and that NT in summer is about 3.6 times the counts of NT in spring. SCW events mainly concentrate in the western Guangdong to the Pearl River Delta Region. Compared to NT, SCW is generally associated with stronger baroclinity, instability and stronger dynamic forcing. The precipitable water and averaged relative humidity between 700-500 hPa of SCW tend to be higher than those of NT in spring, while the opposite is the case for the pattern in summer. In conclusion, it is obvious that the dynamic forcing for SCW in spring is much better than these in summer, while the thermal condition is more significant in summer.
Typhoon Activities over the Western North Pacific and Atmospheric Intraseasonal Oscillation
Li Chongyin, Pan Jing, Tian Hua and Yang Hui
2012,38(1):1-16, DOI: 10.7519/j.issn.1000-0526.2012.1.001
In this paper, the modulation of atmospheric MJO on typhoon generation over the northwestern Pacific and its mechanism are first studied by using the MJO index. The results show that the MJO plays an important modulation role in typhoon generation over the northwestern Pacific: The proportion of typhoon number is 21 between active period and inactive period; During the MJO active period, the proportion of typhoon number is also 2:1 between phases 5-6 and phases 2-3 of MJO. The composite analyses of atmospheric circulation show that there are different circulation patterns over the northwestern Pacific in different phases of the MJO, which will affect the typhoon generation. In phases 5-6 (2-3), the dynamic factor and convective heating patterns over western Pacific are favorable (unfavorable) for typhoon generation. Then, the comparing analyses of the 30-60 day low frequency kinetic energy in lower and higher levels of the troposphere show that the atmospheric intraseasonal oscillation over the northwestern Pacific has a clear impact on the typhoon generation. There is an evident positive (negative) anomaly area of 30-60 day low frequency kinetic energy in the more (less) typhoon years over the northwestern Pacific east of the Philippines, which means that strong (weak) atmospheric intraseasonal oscillation (ISO) over the northwestern Pacific is favorable (unfavorable) for typhoon generation. The analyses of 200 hPa velocity potential show that there is a clear divergence (convergence) pattern over the northwestern Pacific in the more (less) typhoon years, which is favorable (unfavorable) for typhoon generation. The modulation of the intraseasonal oscillation on the typhoon tracks over the northwestern Pacific is studied by observational data analyses. We classified the main classes of typhoon tracks into 5 types as straight west moving typhoons (I), northwest moving typhoons (II), recurving to Korea/west of Japan typhoons (III), landing on Japan typhoons (IV) and recurving to the east of Japan typhoons (V). Then the composite analyses of atmospheric low-frequency wind fields at 850, 500 and 200 hPa, corresponding to the typhoon forming date, for every typhoon track are completed. The analysis results of relationships between the low-frequency (ISO) wind fields and typhoon tracks have indicated that the typhoon tracks will be affected by wind pattern of the ISO. The low frequency positive vorticity belt (the maximum value line of cyclonic vorticity) associated with low-frequency cyclone (LFC) at 850 hPa is so closely related to the typhoon track, that the maximum value line (belt) of low frequency cyclonic vorticity can be an important factor to predicate the typhoon tracks over the northwestern Pacific. And the typhoon tracks will be also affected by the ISO circulation pattern at 200 hPa, particularly the strong low frequency wind associated with low frequency anticyclone (LFAC).
Analysis on Water Vapor Transport and Budget of the Severe Torrential Rain over Beijing Region on 21 July 2012
WANG Jingyu, CUI Chunguang, WANG Xiaofang and CUI Wenjun
By using the NCEP reanalysis data, the vapor budget of the area covered by the severe torrential rain over the northeast of North China on 21 July, 2012 is calculated according to the vapor budget equation. The results show that meridional water vapor transportation is dominant while the extremely heavy rain hits Beijing Region, where most moist vapor comes from the southern boundary below 500 hPa. The low level regional moisture convergence is consistent with the time and space when the torrential rain breaks out and develops. Above the middle level the vertical vapor transport is more prominent. Then the variation features of the vapor transport corridors and their moisture contributions are got through the HYSPLIT mode. The backward trajectory analyses illustrate two major vapor transport corridors. The moistest vapor derived from Yellow Sea and East China Sea along the low level make the main moisture contribution during the heavy precipitation. Moisture from the South China Sea and the Bay of Bengal strengthens the water vapor in the region when the heavy rain starts and develops. Also the drier vapor corridor along the high level from the northwest of China plays an important role in this case.
Climate Characteristics and Variation of Rainstorm in South China
Wu Hongyu, DU Yaodong and Qin Peng
Based on the daily precipitation data at 110 observational stations during 1961-2008 in South China, the climatic characteristics and variation of torrential rain days, rainstorm intensity and contribution which is in annual, the first and second flood seasons in South China were studied by using statistical and diagnostic methods, such as linear regression analysis, Mann Kendall test, wavelet analysis and the computation of trend coefficients. The results have shown that the annual mean torrential rain days have a decreasing trend from coastal regions to inland in South China in recent 48 years, the highest center is in Dongxing of Guangxi (14.9 d), and the lowest center is in Longlin of Guangxi (3.2 d). About 72% of the total torrential rain days occurred in the flood seasons with about 45% in the first season and 27% in the second season. The mean torrential rain days have increased faintly in annual, the first and second flood seasons in South China, but it is not obvious. There are the characteristics of interannual and interdecadal changes. The mean rainstorm intensity has increased faintly in annual and in the first flood season in South China. However, since 2005 it has become obviously. The mean rainstorm intensity has declined in the second flood season, but it is not obvious. The annual mean rainstorm contribution to the total rainfall has increased obviously, but the mean contribution is not obvious in the first and second flood seasons. The wavelet analysis has shown that the changes of torrential rain days, intensity and contribution which is in annual, the first and second flood seasons in South China have two significant periods of 2-3 a and 3-4 a.
Climate Variational Characteristics of Snowfall  in Yunnan Province for the Last 50 Years
DUAN Changchun, DUAN Xu, DUAN Suqin, TAO Yun and REN Juzhang
2011,37(5):599-606, DOI: 10.7519/j.issn.1000-0526.2011.5.012
[Abstract] (1601) [FullText HTML] (8) [PDF 1.03 M] (10577)
Using the diurnal snow data of 120 meteorological stations in Yunnan Province during 1961-2008, the temporal and spatial distribution characteristics and the trend of climatic change of the annual and monthly snow fall are analyzed. It is pointed out that the total trend of snow frequency and covering stations has been decreasing in Yunnan in the recent 50 years. And the annual snow frequency has declined at a mean rate of 4.5 times per year. The temporal trends of monthly snow frequency and covering stations are all negative. Moreover the reduction of snow frequency in December is the largest in magnitude, therefore, it is the most remarkable. And the reduction of snow stations in April is the largest. As far as the spatial change of the secular trend variation of annual snow frequency is concerned, the reduction of annual snow frequency is larger in Northwest Yunnan than in its northeast and east, where the reduction rate is 0.44 times per year. And the temporal changes of annual snowfall and depth of snow cover are studied, the results show that the secular trends of annual snowfall and the maximum depth of snow cover are all positive. This means that in the nearly 50 years the heavy snow frequency has increased over Yunnan Province.
Spatio Temporal Characteristics of Rainstorm in China During 1981-2010
LIN Jian and YANG Guiming
[Abstract] (2037) [FullText HTML] (19) [PDF 13.74 M] (9910)
In term of precipitation data of 2400 stations from 1981 to 2010, annual, seasonal and monthly distribution and evolution characteristics of rainstorm were analyzed. The results show that the processes of rainstorm have been increased evidently since 21 century especially in the south of China, but the duration is relatively short. Rainstorm days have been increased, but the amount of precipitation is not as much as in 1990s. Variation trend of the annual (monthly) precipitation amount is in accordance with that of rainstorm days, but rainfall is averagely more while the rainstorm days are less during spring rainfall phase over the south of Yangtze River. Distribution of the maximum annual rainstorm days is very similar with that of the annual mean rainstorm days, revealing the feature of more in south and east but less in north and west. Maximum annual rainstorm days are more than double of annual average rainstorm days with multi centers due to the effect of topography. The months of maximum monthly rainstorm days over different regions of the same province are incompletely same as the result of the impact of different weather systems. Generally, rainstorm days have been increased since 2000, rainstorm begins earlier, ends latter and lasts longer than before. Nowadays, as the extreme rainfall events and secondary disasters happen frequently, it is conducive for the forecast of quantitative precipitation forecast (QPF) to learn the spatio temporal distribution and evolution features of rainstorm.
Development of a Comprehensive Analysis and Process System Based on ArcGIS
Huang Yimei, Chen Yue, Zhou Yuquan, Zhang Qiang and Shi Aili
2007,33(12):116-120, DOI: 10.7519/j.issn.1000-0526.2007.12.018
[Abstract] (1167) [FullText HTML] (9) [PDF 30.54 M] (9531)
A comprehensive analysis and process system based on ArcGIS, and its chief targ et, its software frame, standardized data, database system, basic functions and its key technique, etc. are are described. The system is professional especially to weather modification, and it mainly applies to comprehensive analysis and pr ocess for weather modification, decision-making of operation schemes, appraisal of operation effectiveness, and services for enhancement precipitation or suppre ssion hail by ways of cannons or rocks, etc. In this system, information collect ion, analysis, management and comprehensive application of the weather modificat ion are realized. It also can be used in other fields in meteorology.
Response of Lake Water Level of Honghu Lake to SPEI/SPI Drought Indices at Different Time Scales
LIU Min, QIN Pengcheng, LIU Kequn, XIA Zhihong and WANG Miao
2013,39(9):1163-1170, DOI: 10.7519/j.issn.1000-0526.2013.09.011
Drought and flood have significant impacts on catchment water use and ecological balance. To develop practical drought/flood monitoring indicators that only need a few climate variables, it is fundamentally necessary to explore the relationship between hydrology variables and climate variables for the specific catchment. This study investigates the correlations between lake water level and various time scale climatological indices according to the standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI), based on the monthly water level records from Honghu Lake representative gauging stations and the monthly observations of 8 meteorological stations in the Four Lake Basin. The results showed that extreme droughts and floods are primarily controlled by precipitation variability over the Four Lake Basin, and both SPEI and SPI are well related with lake water level of Honghu Lake while the degree of the correlation varies between different seasons and SPEI/SPI time scales, with the highest correlations for rainy summer and autumn months. Generally, the 4-6 month scale SPEI/SPI drought index is most closely correlated with lake water level of Honghu Lake, showing an apparent response of lake water level to the current and former months' water surplus and deficiency. When compared with the historical time series of monthly average lake water level of Honghu Lake, the 5 month scale SPEI/SPI agrees well with the variability of the lake water level. The response relationship found during the study can not only aid the monitoring and forecasting of flood and drought conditions in the Four Lake Basin based on conventional weather data, but also provides some references for other places of China.
Analysis of the October 2010 Atmospheric General Circulation and Weather
DAI Kan
The following are the main characteristics of the general atmospheric circulation in October 2010. There were two polar vortex centers in the Northern Hemisphere. The circulation presents a four wave pattern in middle high latitudes, in which the strong Ural ridge corresponds to a large 40 gpm positive anomaly area. Strength of the Western Pacific subtropical high is weaker than normal years. The monthly mean temperature (10.1 ℃) is 0.5 ℃ higher than the same period of normal years, and the mean precipitation (42.6 mm) is 15.1% above normal. The major weather events include: 8 precipitation processes occuring, in which a rare heavy rain has struck on Hainan in the first and middle dekad of October; two tropical cyclones generated, with one super typhoon (Chaba, numbered 1013) landed in Fujian; in the last dekad of October, strong cold air outbreak across most areas of China; heavy fog aroused in the central and eastern China.
Characteristics and Synoptic Mechanism of the July 2016 Extreme Precipitation Event in North China
FU Jiaolan, MA Xuekuan, CHEN Tao, ZHANG Fang, ZHANG Xidi, SUN Jun, QUAN Wanqing, YANG Shunan and SHEN Xiaolin
An extremely severe precipitation event took place in North China in 19-20 July 2016. It was characterized by large rainfall, persistent rainfall, warm cloud rainfall, strong local rainfall intensity and orographic precipitation. Its rainfall was larger than that of the extreme rainfall in 3-5 August 1996, and only next to the amount of the 2-7 August 1963 extreme rainfall event. It occurred under the circulation background of the South Asia high moving eastward, the West Pacific subtropical high moving northwestward and the low vortex in the westerlies developing in mid high latitude. The abnormal development of Huanghuai cyclone, southwest and southeast low level jets, and the abnormally abundant moisture indicates that the dynamic lifting and moisture conditions favored this severe rainfall process significantly. The whole rainfall event presented clearly the phase characteristics, and could be divided into two stages. The first stage was the orographic rainfall caused by the easterly winds ahead of the trough from the early morning to the daytime of 19 July, while the second part was produced by spiral rain bands in the north side of Huanghuai cyclone from the night of 19 to the daytime of 20 July. In the first stage, the easterly low level jet was lifted by the Taihang Mountains, which continuously triggered the convective cells along the east edge of the mountains. The weak dry and cold advection at mid level and the strong warm and wet advection at low level jointly maintained the convective instability. The cold pool generated by heavy rainfall and the mesoscale frontogenesis process created by local orographic effect provided favorable conditions for severe convections to occur continuously. The second stage rainfall was mainly related to the development of cut off vortex and Huanghuai cyclone. The blocking of the high pressure system slowed the steps of Huanghuai cyclone in North China, thus leading to the long lasting rainfall process.
Analysis on Dynamic Effects of Low Level Southerly Airflows on One Rainstorm Process and the Numerical Simulation
XIAO Dixiang, XIAO Dan, ZHOU Changchun, ZHOU Chunhua and CHEN Guixun
By using conventional observation data and NCEP reanalysis data, diagnostic analysis is performed on a rainstorm process, which occurred on 22-25 July 2010 in the western part of Sichuan Basin. The result shows that the rainstorm was generated under the circulation background that low level southerly airflows had remained over the region from the South China Sea to Sichuan Basin, so this rainstorm was closely related to the evolution of the southerly wind speeds. The rainfall intensity increased as the south winds grew stronger. Speed convergence formed by the enhanced south winds and positive vorticity advections became main dynamic trigger factors for the rainstorm. Therefore, the rainstorm is pretty consistent with the low level convergence and the positive vorticity advection. In addition, the result of WRF numerical simulation further indicates that: the evolution of 3 h wind speed at 850 hPa has good indication for the development of mesoscale convective systems. On the leeward side of the 3 h wind speed increasing area, convective cloud clusters are to develop rapidly in the next 3 hours. Moreover, the topographic influence simulation tests suggest that the airflow convergence generated in the west of the Basin is closely related to the topography of plateau.
基于高分辨率卫星影像的高炮作业点安全射界图的制作
杨凡, 黄明政, 薛允传, 钟志伟, 吕明先, 孙琪
[Abstract] (851) [FullText HTML] (13) [PDF 10.66 M] (7200)
随着青岛地区经济社会的高速发展,各个高炮作业点所在地的周边环境已经发生了很大变化 ,为确保高炮人工增雨防雹作业的安全,利用最新的高分辨率的卫星影像,结合高炮作业点 周边的实际情况,按照有关规定的要求,制作了高炮安全射界图。
The Contrastive Analysis of Formation of  Dry and Moist Thunderstorms in Beijing
WANG Tingting, WANG Yingchun, CHEN Mingxuan and ZHANG Wenlong
Using the Variational Doppler Radar Analysis System (VDRAS) combined with local unconventional observation data, a more in depth contrastive analysis is carried on the initiation mechanism of two storm cases in Beijing, one is 814 (August 14, 2008) case with strong rainfall that we call it as moist storm and the other is 824 (August 24, 2008) case with little rainfall that we call it as dry storm. The results show: (1) The synoptic scale systems of 814 storm were stable Northeast cold vortex low trough at 500 hPa and shear line at 850 hPa, the specific humidity that more than 12 g·kg-1 below 850 hPa and the relative humidity that more than 90% in the surface indicated that the atmosphere was very moist. It had convective instability caused by humidity advection in lower levels. The 824 storm had a prevailing straight west wind in high levels, an anticyclone in lower levels, and a surface cold front moving fast.The specific humidity that less than 6 g·kg-1, and the relative humidity that less than 30% below 850 hPa indicated that the atmosphere was very dry. It had convective instability caused by temperature advection. (2) There was much strong vertical wind shear in the whole vertical layer for 814 storm case, the clockwise wind direction with height within 500-1500 m intensified the warm and humidity inflow of lower layer advantageous to storm initiation and development. While there was weak vertical wind shear and unobvious warm and humidity inflow of lower layer for 824 case, which was not conducive to storm initiation and development. In addition, composited wind of the whole troposphere and storm movement speed were very low for 814 case, but they were very high for 824 case. (3) The 814 storm was formed by the collision and mergence of multi cell storms, a convergence line was formed by the cold pool outflow produced by the precipitation of the upstream of thunderstorm cell and the east wind in low levels which forced the low level warm and moist air to uplift, additionally the strong convective instability and vertical wind shear supported the formation and development of new storm. The interactions (collisions) of gust fronts in the leading edge of cold pool of multi cell thunderstorm group, further exacerbating the low level instability, leading to the regeneration and mergence of new convective thunderstorms. The 824 storm was a line convective system accompanied with cold front that rapid moved eastward and lasted for short time, there was no east wind with warm and moisture air accompanying the cold pool outflow produced by the downdrafts of thunderstorm. The absence of mesoscale lifting mechanism and moisture inflow couldn't support the formation and development of new storm.
Theory and Application of Potential Vorticity
SHOU Shaowen
[Abstract] (2696) [FullText HTML] (121) [PDF 1.59 M] (6931)
Potential vorticity (PV) is one of the important concepts in advanced synoptic and dynamic meteorology. This paper is a brief introduction to the theory of potential vorticity, including the concept of PV, the conservation and invertibility of PV, PV thinking, moist PV (MPV), and the application of PV theory.
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