Causes of a Heavy Snowfall Process in Eastern Yunnan in 2022

Based on NCEP/NCAR reanalysis data, Micaps data and ground observation data, the physical characteristics of a heavy snowfall process in eastern Yunnan from January 31 to February 3, 2022 were analyzed. The results show that the circulation background of the heavy snowfall process was "north-ridge and south-trough" type, and the cold air accumulated in the deep East Asian transverse trough. The cold advection behind the trough moved southwards into eastern Yunnan under the movement of the transverse trough. The establishment of upper and lower air jet provided abundant water vapor, and the snowfall area coincided with the strong water vapor convergence area. The strong cold center near the ground was maintained, and the cold air moved southwards. As a result, the cold pad was lasting and deep, and the ground temperature was 0 ℃ or below, which was conducive to snow accumulation on the ground. Seen from the spatial distribution of pseudo-equivalent potential temperature, the low layer always had certain warm and wet conditions during the heavy snowfall, which was conducive to the establishment of unstable energy. The snowfall occurred near the θ se steep area and the warm and wet unstable area. The vertical distribution of temperature had a good indication of precipitation form. The upper layer was controlled by strong cold advection, while the middle and lower troposphere was controlled by warm advection, and there was a warm inversion layer, which was conducive to the transformation of ice crystals into snowflakes, so that ice crystals fell to the ground in the form of snowflakes.

Analysis on a Cold Wave Weather Process in Winter in Gansu

[Objective]The research aimed to analyze a cold wave weather process in winter in Gansu.[Method] Based on routine observation data and numerical forecast products,formation reason and physical quantity characteristics of a cold wave process during 2-5 December,2008 were comprehensively analyzed by synoptic analysis and diagnostic analysis methods.[Result]The cold wave weather belonged to ' translot turning vertical type'.Collapse of the Urals ridge,turning vertical of the translot and strengthening south of the ground cold high induced the cold wave.Development of the Siberian low vortex drove the small branch of cold air in polar region supplementing south,playing certain promoting role in outbreak of the cold wave.Physical quantities in the cold wave process also had very good expression,such as vorticity,temperature advection,etc.[Conclusion]This research had important indication effect for early warning,forecast and decision service of the future similar weather process.

Analysis on Severe Convection Process in Shunde during May 10-11,2020

Using meteorological observation data,Doppler radar,and NCEP 0.25°×0.25°of 6 h reanalysis data,comparative analysis of circulation background,trigger conditions,physical quantity characteristics,and radar image characteristics of two severe convection weather processes in Shunde District during May 10-11,2020 was conducted,and similarities and differences of severe convection processes were explored.The results showed that the two severe convection processes occurred in the situation that there lacked high-altitude trough moving eastward,but low altitude was accompanied by shear line,which was triggered under conditional thermal instability.Vertical velocity profile displayed that severe convection was accompanied by strong convergence and upward movement,and K index and water vapor flux divergence had good corresponding relationship with the occurrence and extinction of severe convection weather in time.The occurrence of strong wind area had certain indicative significance for the prediction of severe convection weather.