Application of wind profiler data to rainstorm analyses in Aksu, Xinjiang



The Urumqi Institute of Desert Meteorology of the China Meteorological Administration (CMA) launched an atmospheric experiment on rainstorm weather with a wind profiler from 10 July to 10 August 2010 in Aksu, Xinjiang. This paper presents some outcomes of the analyses on the wind field characteristics of a rainstorm process that happened on 28–29 July 2010 in Aksu, using the wind profiler data collected from the experiment, and addresses some additional scientific issues. Findings show that because of their high temporal and vertical resolutions, the wind profiler data can be used to analyse the detailed vertical structure of rainstorm processes. In this case, before the occurrence of the rainstorm, a horizontal wind shear appeared in the lower atmosphere, which was the precursor of the weather system's arrival. When a southwesterly wind appeared in the 3000 m layer it presaged the invasion of an upper trough over Aksu. During the event, there were three airflows from different directions in the upper, mid and lower atmosphere, and a mesoscale wind shear line at the lower level, which apparently increased the atmospheric instability and updraft convergence. The temperature advections derived from the wind profiler data can represent the major characteristics of thermodynamic evolution in the lower atmosphere during a rainstorm process, based on which the variation of hydrostatic atmospheric instability can be judged. It was also found that during the rainstorm process the lower atmosphere was mostly subjected to warm advection which had accumulated enough energy to create atmospheric instability, a favourable condition for creating updrafts and rainfall. The ‘large-value zone’ of the reflectivity factor Z was virtually consistent with the onset and end of the rainstorm, formation height of rain droplets, and rainfall intensity. The reflectivity factor varied in the 20–36 dBZ range. The cloud water content was approximately 0.5 g m−3 in the 3000–3450 m layer, and 0.1–0.4 g m−3 below 3000 m.