Abstract
A Chinese Ka-band solid-state transmitter cloud radar (CR) was employed to investigate clouds and precipitation over the Tibetan Plateau (TP) in summer 2014. After performing quality control and merging the output from the three work modes of CR, the Doppler spectral density data were analyzed to estimate the vertical air motion (Vair) and particle fall speed (Vfall) in clouds. The reproduced radar reflectivity was employed to retrieve the ice water content (IWC) and ice effective radius (Re). The cloud type classification algorithm was developed to classify cloud conditions into eight different categories. The vertical and daily variations of reflectivity, Vair, Vfall, IWC, and Re were then analyzed, and as a result, four conclusions were formulated. First, the clouds with reflectivity less than −10 dBZ were mainly located above 7 km, and the precipitable particles were formed below this layer (rain echo top) due to the abundant supercooled water therein. Second, the weak updraft in the range of 2–4 km caused the high occurrence of weak clouds during 04:00–12:00 Beijing local time (BT), and the rain echo top did not exceed 7 km due to the existing downdraft in 4–6 km. After 14:00 BT, convective clouds quickly developed, and the averaged updraft, reflectivity, and the echo top notably increased. Third, particular cloud types commonly exhibited weak reflectivity, low IWC, and less vertical variations, while the others more obvious vertical variations with larger IWC and Re. Last, compared with the radar sensitivity and range from radar, Vair biases that were introduced by the Doppler spectra broadening due to turbulence, wind shear, and radar beam width, could be neglected.
Highlights
The Tibetan Plateau (TP) located in the southwest region of China is the highest plateau with the most complex terrain in the world
[11], indicating that summer convective activities reached their strongest was similar to the results reported by Fu et al [11], indicating that summer convective activities state at ~16:00 and lessstate convection wasBT, presented in the morning.was
Turbulence wind shear exist in atmosphere and cloud systems [38,39,40]
Summary
The Tibetan Plateau (TP) located in the southwest region of China is the highest plateau with the most complex terrain in the world. Owing to its thermodynamic forcing, the TP significantly influences the atmospheric circulation, the surface–atmosphere momentum exchange, and the hydrologic cycle in its surrounding areas, as well as in Eastern Asia [1,2,3]. Clouds and precipitation impose a considerable impact on atmospheric moisture transfer and surface heating over the plateau. Microphysics processes underlying the changes in the atmosphere above the TP often differ from those over low altitude areas (1000 m above sea level). Due to strong surface heating, convection often develops quickly after noon. Unlike in the downstream plain areas, convective processes are more frequently triggered in the Atmosphere 2020, 11, 818; doi:10.3390/atmos11080818 www.mdpi.com/journal/atmosphere
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