Winds and temperatures of the Arctic middle atmosphere during January measured by Doppler lidar
Abstract. We present an extensive data set of simultaneous temperature and wind measurements in the Arctic middle atmosphere. It consists of more than 300 h of Doppler Rayleigh lidar observations obtained during three January seasons (2012, 2014, and 2015) and covers the altitude range from 30 km up to about 85 km. The data set reveals large year-to-year variations in monthly mean temperatures and winds, which in 2012 are affected by a sudden stratospheric warming. The temporal evolution of winds and temperatures after that warming are studied over a period of 2 weeks, showing an elevated stratopause and the reformation of the polar vortex. The monthly mean temperatures and winds are compared to data extracted from the Integrated Forecast System of the European Centre for Medium-Range Weather Forecasts (ECMWF) and the Horizontal Wind Model (HWM07). Lidar and ECMWF data show good agreement of mean zonal and meridional winds below  ≈ 55 km altitude, but we also find mean temperature, zonal wind, and meridional wind differences of up to 20 K, 20 m s−1, and 5 m s−1, respectively. Differences between lidar observations and HWM07 data are up to 30 m s−1. From the fluctuations of temperatures and winds within single nights we extract the potential and kinetic gravity wave energy density (GWED) per unit mass. It shows that the kinetic GWED is typically 5 to 10 times larger than the potential GWED, the total GWED increases with altitude with a scale height of  ≈ 16 km. Since temporal fluctuations of winds and temperatures are underestimated in ECMWF, the total GWED is underestimated as well by a factor of 3–10 above 50 km altitude. Similarly, we estimate the energy density per unit mass for large-scale waves (LWED) from the fluctuations of nightly mean temperatures and winds. The total LWED is roughly constant with altitude. The ratio of kinetic to potential LWED varies with altitude over 2 orders of magnitude. LWEDs from ECMWF data show results similar to the lidar data. From the comparison of GWED and LWED, it follows that large-scale waves carry about 2 to 5 times more energy than gravity waves.
Validation of middle-atmospheric wind in observations and models
Wind profile information throughout the upper stratosphere and lower mesosphere (USLM) is important for the understanding of atmospheric dynamics but became available only recently, thanks to developments in remote sensing techniques and modelling approaches. However, as wind measurements from these altitudes are still very rare, such products have generally not yet been validated with (other) observations. This paper presents the first long-term intercomparison of wind observations in the USLM by opposing co-located microwave radiometer and lidar instruments at Andenes (69.3° N, 16.0° E). Good correspondence has been found at all altitudes for both horizontal wind components for nighttime as well as daylight conditions. Biases are mostly within the random errors and do not exceed 5–10 m/s which is less than 10 % of the typically encountered wind speeds. Moreover, comparisons of the observations with the major re-analyses and models covering this altitude range are shown, especially also with the freshly released ERA5, ECMWF's first re-analysis to cover the whole USLM region. The agreement between models and observations is very good in general, but temporally limited occurrences of pronounced discrepancies (up to 40 m/s) exist. In the article's appendix the possibility of obtaining nighttime wind information about the mesopause region by means of microwave radiometry is investigated.
First simultaneous and common volume observations of noctilucent clouds and polar mesosphere summer echoes by lidar and radar
We present the results of first simultaneous and common volume observations of noctilucent clouds (NLC) and polar mesosphere summer echoes (PMSE) by two ground-based lidars and one VHF radar. The measurements were performed at the ALOMAR facility (69°N, 16°E) during the time period July 23 through August 18, 1994. Throughout this period, NLC layers were observed by the lidars on four occasions. During each of these four lidar-observed NLC events, PMSE layers were also observed overhead by the radar. These joint NLC/PMSE events divide into two distinct types : (1) tightly coupled and (2) loosely coupled NLC and PMSE layers. In one of the events, the PMSE layer developed into a well-defined double layer with only 0.8-km vertical separation, while the lidar-observed NLC layer matched closely in time and space the lower PMSE sublayer. Within all four NLC/PMSE layers, the wind speed increased sharply with increasing altitude with wind shears amounting to 0.03 s -1 and larger. Current theories can explain some of the observed layer features.