Numerical Simulation and Analysis on the Phoenix Typhoon Rainstorm Using WRF
Rainstorm caused by the Typhoon Phoenix, between July 28th and 31st 2008, is studied by using the meso-scale numerical simulation model WRF and some NCEP reanalysis data of 1¡ã¡Á1¡ãwith 6h interval. Results show that, the distribution of the SLP, wind and rain belt was simulated successfully by the WRF model. The research shows that the strong upward motion at the 600 -700hPa and 100 -200hPa of 24¡ãN and two closure centers of near 21¡ãN-22¡ãN and 31¡ãN-33¡ãN at the high troposphere induced convective cloud cluster to develop.
NUMERICAL EXPERIMENTS AND ANALYSIS OF DIGITAL FILTER INITIALIZATION FOR WRF MODEL
Initialization and initial imbalance problem were discussed in the context of a three-dimensional variational data assimilation system of the new generation "Weather Research and Forecasting Model". Several options of digital filter initialization have been tested with a rain storm case. It is shown that digital filter initialization, especially diabatic digital filter initialization and twice digital filter initialization, have effectively removed spurious high frequency noise from initial data for numerical weather prediction and produced balanced initial conditions. For six consecutive intermittent data assimilation cycles covering a 3-day period, mean initialization increments and impact on forecast variables are studied. DFI has been demonstrated to provide better adjustment of the hydrometeors and vertical velocity, reduced spin-up time, and improved forecast variables quantity.
Atmospheric drag effects on the KOMPSAT-1 satellite during geomagnetic superstorms
We examine the atmospheric drag on the low earth-orbiting satellite, KOMPSAT-1 in a sun-synchronous orbit at ~685-km altitude starting in 1999, during a 3-month (October-December) period in 2003. This 3-month interval includes the October 29-30 and November 20 magnetic superstorms and weak to moderate storms. We observed that the daily KOMPSAT-1 drag acceleration transiently responses to transient storm-time disturbances. That is, there is an one-to-one correspondence between the KOMPSAT-1 drag accelerations and the storm events. We find that the drag acceleration correlates strongly with the level of geomagnetic disturbance. This indicates that the trajectory of KOMPSAT-1 is significantly perturbed during extremely disturbed intervals because of atmospheric density increase. The main contributor to the density increase is Joule heating associated with the geomagnetic activity rather than the solar EUV radiation, as reported by previous studies. We suggest that understanding how the upper atmosphere responses to the geomagnetic-associated heating is important to predict space weather impacts on low earth-orbiting satellites.