Study of thermal bubbles in the lower atmosphere based on the data detected using wind profiler radar

KeyWord:Wind Profiler Radar(WPR), Radio-acoustic Sounding System(RASS), Thermal bubble

Abstract:

      The phenomena of thermal bubbles and the heat convection process in the atmospheric boundary layer are studied by using the data from the Wind Profiler Radar (WPR) and Radio-acoustic Sounding System (RASS). A case of thermal bubbles observed by WPR is described and discussed. At the beginning of the heat convection, thermal bubbles associated with a stronger updraft move upward to a higher level. During the strong convective period, it is obvious that the merge of thermal bubbles occur with the vertical velocity, no matter it is upward or downward, more than 1 m/s and the height of convective reached more than 2 km, as well as a closed vertical circulation of about one hour period. In the decay stage of heat convection, the height of convective is decreased, and the vertical movement is getting gentle and lasts for very long time. Thermal bubbles are able to cause fluctuation of temperature with the difference between thermal bubble and its surroundings reached 2-4 ℃. The analyses show that WPR is very sensitive to the echo of thermal bubbles. And the high temporal and altitudinal resolutions of WPR make the fine description of the distribution and development of thermal bubbles become possible, and in addition, combining RASS data can also obtain accurately the temperature distribution and its impact on the vertical profiles of surrouding temperature. The preliminary analyses of WPR data, in a certain extent, can help us to further understand the nature of thermal bubbles and the motion characteristics of heat convection in the atmospheric boundary layer. WPR provides an efficient approach to improve the observations of the lower atmosphere, which is benefitial to numerical study of dynamic and thermal processes as well as to improving meso-scale model andprecipitation forecast.