Comprehensive radar observations of clouds and precipitation over the Tibetan Plateau and preliminary analysis of cloud properties

Abstract

Intensive field experiment is an important approach to obtain microphysical information about clouds and precipitation. From 1 July to 31 August 2014, the third Tibetan Plateau Atmospheric Science Experiment was carried out and comprehensive measurements of water vapor, clouds, and precipitation were conducted at Naqu. The most advanced radars in China, such as Ka-band millimeter-wave cloud radar, Ku-band micro-rain radar, C-band continuous-wave radar and lidar, and microwave radiometer and disdrometer were deployed to observe high spatial-temporal vertical structures of clouds and precipitation. The C-band duallinear polarization radar was coordinated with the China new generation weather radar to constitute a dual- Doppler radar system for the measurements of three-dimensional wind fields within convective precipitations and the structure and evolution of hydrometeors related to precipitation process. Based on the radar measurements in this experiment, the diurnal variations of several important cloud properties were analyzed, including cloud top and base, cloud depth, cloud cover, number of cloud layers, and their vertical structures during summertime over Naqu. The features of reflectivity, velocity, and depolarization ratio for different types of clouds observed by cloud radar are discussed. The results indicate that the cloud properties were successfully measured by using various radars in this field experiment. During the summertime over Naqu, most of the clouds were located above 6 km and below 4 km above ground level. Statistical analysis shows that total amounts of clouds, the top of high-level clouds, and cloud depth, all demonstrated a distinct diurnal variation. Few clouds formed at 1000 LST (local standard time), whereas large amounts of clouds formed at 2000 LST. Newly formed cumulus and stratus clouds were often found at 3-km height, where there existed significant updrafts. Deep convection reached up to 16.5 km (21 km above the mean sea level), and updrafts and downdrafts coexisted in the convective system. Supercooled water might exist in such kinds of deep convective system. The above measurements and preliminary analysis provide a basis for further study of cloud physics and precipitation process over the Tibetan Plateau. These observations are also valuable for modeling studies of cloud and precipitation physics as well as in the development of parameterization schemes in numerical prediction models.