Vertical Structure and Macro-Micro Differences of Cold and Warm Cloud-Precipitation in Ya'an During Autumn Rainy Season

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  • 1. College of Atmospheric SciencesChengdu University of Information TechnologyChengdu 610225SichuanChina
    2. College of Electronic Engineering/College of Meteorological ObservationChengdu University
    of Information Technology
    Chengdu 610225SichuanChina
    3. Institute of Plateau MeteorologyChina Meteorological AdministrationChengdu 610072SichuanChina
    4. Dianjiang Meteorological ServiceChongqing 408300China

Online published: 2025-10-20

Abstract

The Ya'an area has a typical "windward slope" and "trumpet" topographythe observation and study of cloud-precipitation in the Ya'an area has always been one of the hot issues of mountain meteorology in China. In this paperusing the observation data of Ka-band millimeter-wave cloud radarK-band micro-rain radar and DSG4 laser raindrop spectrometer during the autumn rainy season in Ya'an area in 2023the two types of cloudprecipitation in Ya'an during the autumn rainy period are studied and compared. The results show that1the frequency of warm cloud-precipitationWCPis higher than that of cold cloud-precipitationCCPduring the autumn rainy period in Ya'anbut the intensity of precipitation is generally weaker and the cumulative rainfall is less.2In terms of vertical structure and macroscopic featuresthere are obvious differences between WCP and CCPthe radar echo reflectivity factor Z high-frequency region of CCP has a wider distribution and stronger echoand the magnitude of the slope of Z high-frequency region at different heights reflects the difference be‐ tween the ice-phase particles' growth mechanism and rate and that of WCP's liquid cloud raindrops' touch-and-go growth rateCCP's linear depolarization ratioLDRincreases abruptly near the zero-degree layer due to the melting of ice-phase particles. The mean Doppler velocity Vm has a smaller value in the high-frequency region and the velocity spectral width W has a larger value in the high-frequency regionsuggesting a larger mean drop‐ let scale and a wider concentration distribution. In terms of macroscopic parametersthe cloud base and cloud top of the CCP are significantly higherthe cloud layer is thickerand the distribution of values is more dispersed.3In terms of microscopic characteristicsthe raindrop spectra of the two types of cloud-precipitation are different with altitudethe concentration of small raindrops in the CCP increases and then decreases with de‐ creasing altitude due to the melting of ice-phase particles and raindrops mergingwhereas that in the WCP fluctuates due to the effects of evaporationmergingwater vapor transportand updraft lifting altitude. The mediumand large-sized raindrop concentrations of both types of cloud-precipitation increase with decreasing altitude on the whole. In terms of the differences in raindrop concentrations at different heightsabove 455 mthe concentration of raindrops of all grain sizes in WCP is almost lower than that in CCPbelow 455 mthe concentration of small and large raindrops in WCP is higher than that in CCPand the concentration of medium raindrops is low‐ er.4Comparison of the raindrop spectra under different precipitation intensities showed that when the precipitation is weakthe WCP had lower concentrations of raindrops of all particle sizes than the CCPbut when the precipitation reached a certain intensityrainfall intensity R≥5 mm·h-1),the WCP produced more small rain‐ drops and a small number of larger raindrops. The few extreme values of ZLDRVm and W of WCP are larger than those of CCP at altitudes below 3 km due to the synergistic effect of low-altitude rapids and topographic up‐ lift in the regionwhich makes the small WCP raindrops repeatedly touch and form medium-to-large raindrops in the re-uplift airflow.

Cite this article

CHEN Fan, ZHENG Jiafeng, WANG Hao, DONG Yuanchang, CHEN Shaojie, YU Wenqian . Vertical Structure and Macro-Micro Differences of Cold and Warm Cloud-Precipitation in Ya'an During Autumn Rainy Season[J]. Plateau Meteorology, 0 : 1 . DOI: 10.7522/j.issn.1000-0534.2025.00090

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