Application of boundary layer wind‐profiling radar data to a Springtime Snowstorm Analysis in Urumqi

AbstractThe Urumqi Institute of Desert Meteorology under the China Meteorological Administration (CMA) launched an observational experiment with a boundary layer wind‐profiling radar in Urumqi City in February to March 2010. As described in this paper, wind profiles from the experiment were used to first compare with radiosonde data measured simultaneously to verify the confidence of wind‐profiling radar data, which was used to analyse the wind field characteristics and other related issues in a snowstorm process that took place in Urumqi on 28 March 2010. Both wind direction and speed derived from wind‐profiling radar data have good consistency with those from radiosonde data (wind velocity coefficient: 0.85; wind direction coefficient: 0.78). Before the snowstorm, a surface wind shear occurred. After outbreak of the event, the local weather was dominated by northwesterly and northerly winds at increasing velocities, while temperature was dropping and air pressure increased. Through in‐depth analyses of the time‐height profiles of the snowstorm process, it can be determined on a preliminary basis that the snowstorm was induced by a cold front system that entered the area around 2200–2300 LST on 27 March. A shear line that developed from a lower to a higher altitude represented both height and location of the frontal zone, and the cold front motion was broadly in a northeast‐southwest direction. The wind direction in the process changed counterclockwise with height: this was mainly governed by cold advection, and baroclinic instability was established soon after the overpass of the cold front, eventually leading to the snowstorm. During the weather event, the equivalent reflectivity factor Ze was consistent with the onset and end of the snowstorm, the height at which rain (snow) particles were formed and snowfall intensity. Copyright © 2011 Royal Meteorological Society