Temporal and Spatial Distribution and Influence Systems of Spring Thunderstorms in 2013 in Sichuan Province

Based on the lightning monitoring data, automatic and routine weather station observation data in spring （March-May） of 2013 of Sichuan Province, the corresponding relationship between the spatial distribution and the different regions, and the characteristics of atmospheric circulation and evolution of influence the sys- tem were analyzed and summarized. The results show that： the lightning and thunderstorm showed great regional differences in the spring of 2013 in Sichuan Province and the thunderstorm activity period was not the same in different areas. Because of the change of atmospheric circulation, the influence system from March to May corresponding to the thunderstorms in Sichuan tended to be volatile, also.

Analysis of a Cold Wave Weather Process in Chengdu in March 2010

[Objective] The aim was to analyze one cold wave weather process in Chengdu in March in 2010.[Method] Based on the NCEP 1°×1° 6 h interval reanalysis data and daily observation data,using synoptic analysis and diagnosis methods,and combining with the cold wave forecast index in spring of Sichuan,a cold wave event covering the whole region between March 21 and 24,2010 was analyzed from the aspects of circulation background,influencing weather systems and weather causation.[Result] Results showed that the 500 high-altitude cold vortex,700-850 hPa low layer shear,and ground cold front were the main systems that influenced this cold wave;there was a ridge from Lake Balkhash across Lake Baikal at 500 hPa.The early stage of the process was controlled by the high pressure ridge and the temperature was increasing obviously.The daily mean temperature was high.The range of cold high pressure was large and the central intensity was 1 043.0 hPa;the cold air was strong and deep which was in accordance with the strong surface temperature reduction center.The strong north airstream of Lake Balkhash to Lake Baikal,ground cold high pressure center intensity changes,north and south ocean pressure and temperature differences,850 hPa temperature changes,cold advection movement route and intensity were considered as reference factors for the forecast of cold wave intensity.[Conclusion] The study provided theoretical basis for improving the forecast ability of cold wave weather.

Analysis on the Heavy Snowstorm Process in Northeast China during March 3-5 in 2007

Based on the routine observation data,the satellite cloud images and so on,the synoptics analysis and the diagnostic analysis of physical quantity field were used to analyze the heavy snowstorm process which happened in Northeast China during March 3-5 in 2007.The results showed that the main influence systems in the process were the eastward shift and up north of southern cyclone,the combination of south and north branches upper troughs in 500 hPa.The dynamic mechanisms of heavy snowstorm formation were the strong ascending movement which was caused by the configuration of high-layer divergence and low-layer convergence,the generation and maintenance of deep and thick positive vorticity in the middle and low layers.The sufficient water vapor in the East China Sea and the South China Sea which was brought by 700 hPa by south low-level jet stream reached Northeast China.The falling zones of strong precipitation were consistent with the big value zones of 850 hPa positive vorticity and 200 hPa positive divergence.Meanwhile,the intensity of temperature advection and the position of cold warm transition zone could reflect well the intensity and falling zone of precipitation.

Contrast and Analysis of Many Times Heavy Fog Processes in Zhangjiajie in December,2009

By using the observation data,routine data and NCEP reanalysis data in the automatic station,5 times heavy fog weather processes in Zhangjiajie City in December,2009 were contrasted and analyzed.The results showed that 3 conditions were the essential conditions of heavy fog occurrence in Zhangjiajie area.3 conditions were that the wind speed was during 0.1-3.0 m/s,the relative humidity ≥90% and the depression of dew point ΔT ≤1.5 ℃.The fog concentration had no positive correlation relationship with the above conditions.The accumulation of humidity condition in the previous period was also the main reason which affected the generation of heavy fog.The physical quantity field which related to the stability and the relative humidity field which related to the water vapor condition had the certain directive significance for forecasting the heavy fog weather.The fog concentration presented the positive correlation relationship with the inversion intensity.

Conventional Analysis on a Heavy or Torrential Rain Weather Process

[Objective] The research aimed to analyze a turning weather process in Binzhou City of Shandong Province in midsummer of 2010.[Method] Started from the short-term forecast ideas,the formation reason of heavy or torrential rain and local heavy rainstorm in Binzhou City during 4-5 August,2010 was analyzed from the circulation situation,physical quantity field,radar echo and so on.[Result] The westerly trough and cold air were the trigger mechanisms of precipitation.The warm wet air flow at the edge of subtropical high and the high-altitude low trough were the main systems of precipitation.It was the typical precipitation process that the northwest of subtropical high overlapped with the westerly trough.In the prior period,the high temperature continued.The cold air at 500 hPa made the convection strengthen.It was the main reason that the local precipitation was strong.In the forecast of rainstorm,the specific humidity,K index and SI index were the good physical quantities and reference indexes.In the formation process of rainstorm,K index had the increasing process.When the rainstorm finished,or the rain intensity weakened,K index decreased obviously.SI index indicated the development of convective precipitation.The radar echo analysis found that the mesocyclone appeared in the process for a short time.For it weakened quickly and disappeared in the shift process,the strong precipitation and gale were formed in the west of Binzou,but the hail wasn’t generated.[Conclusion] The research provided the experience for the forecast of such weather in future.

Diagnosis Analysis on the Moist Potential Vorticity of a Regional Rainstorm on May 27,2013 in Eastern Jiangxi Province

Based on conventional meteorological data and NCEP 1°×1° DEG reanalysis data, reasons for a regional rainstorm in Fuzhou, Jiangxi Province on May 27, 2013 was analyzed from the aspects of weather situation, influencing systems, water vapor, dynamic and thermal instability. The results showed that the regional rainstorm happened in the warm area while the Jianghuai cyclone moved eastwards, and it was a short-dura- tion strong convective rainstorm. Jianghuai cyclone, 500 hPa trough, low vortex and southwesterly jet were the main influencing systems of the rain- storm. The precipitation was mainly the result of release of convective unstable energy in the lower troposphere. MPVl was negative in the lower troposphere and positive in the middle and upper troposphere. Moist potential vorticity in the upper troposphere moved downwards, which was ad- vantageous to the release of the unstable energy and then increased precipitation. The negative moist potential vorticity center in the lower tropo- sphere can reflect the position and intensity of the rainstorm, and the intensity and duration of precipitation were consistent with the increase of the negative MPVl. The distribution of MPV2 showed that as atmospheric baroclinicity increased, heavy rain always occurred in the lower troposphere where baroclinicity was strong. The areas with negative baroclincity in the lower troposphere matched with rainstorm center very well.

Diagnosis and Analysis of a Rainstorm Process in Summer in Hami,Xinjiang

Based on conventional meteorological detection data and NCEP global reanalysis data,a rainstorm process in Hami,Xinjiang at the end of July 2018 was diagnosed and analyzed.The results show that this rare rainstorm occurred in the large-scale circulation situation of South Asia high,two ridges and one trough.The heavy precipitation area appeared on the right side of the southeasterly wind convergence area at 700 hPa,southerly flow at 500 hPa and the inlet area of southwest jet core at 200 hPa.The structure of high-level divergence and low-and middle-level convergence and strong vertical speed were important dynamic conditions for the occurrence and development of this rare rainstorm.The warm and moist air from the southern Sea of Japan and the Bay of Bengal was transported through different routes,providing a constant supply of water vapor and energy to the rainstorm area.Both EC and NCEP models have good predictive significance for this rainstorm,and the former is slightly better than the latter in terms of prediction effect.