Plateau Meteorology

Current Issue

28 October 2021, Volume 40 Issue 5   
  • Study on the Warming Characteristics during the Ice-covered Period of Ngoring Lake in the Qinghai-Xizang Plateau
  • Mengxiao WANG;Lijuan WEN;Zhaoguo LI;Dongsheng SU
  • 2021 Vol. 40 (5): 965-976.  DOI:10.7522/j.issn.1000-0534.2020.00112
  • Abstract ( ) HTML ( ) PDF (5350KB) ( )
  • The water temperature of most of the frozen lakes is stable at a certain value during the ice period.However， the water temperature of Ngoring Lake， a typical lake in the Qinghai-Xizang Plateau， will continue to rise during the ice period， and this phenomenon generally exists in the whole water body， but the reason for this phenomenon is still unclear.Based on station observation and lake temperature observation data in Ngoring Lake， Enonteki? Kilpisj?rvi Kyl?keskus station observation data， MODIS surface temperature data， China Meteorological Administration precipitation data and NCEP-DOE reanalysis data， the applicability of LAKE2.3 model in Ngoring lake was evaluated， and the influence of local climate characteristics and main physical parameters affecting radiation transmission in water body on the phenomenon is analyzed.The assessment results show that LAKE2.3 can well simulate the temperature change and thermal stratification in Ngoring lake， especially during the ice period， and the simulated and observed lake temperature profiles are relatively consistent.However， the simulated ice thickness is about 30% smaller than the observed value， which may be due to the limitation of shore observation and one-dimensional model that can’t simulate the lake ice accumulation phenomenon caused by three-dimensional dynamic action.The results of sensitivity experiments show that the strong downward short-wave radiation is the main climate factor that causes the continuous rise of water temperature in Ngoring Lake during the ice period.The larger wind speed further increases the rising range and speed of water temperature range and rate of the temperature rise， while the smaller downward long wave radiation shortens the ice duration.The rising rate and amplitude of lake temperature in ice period decrease when ice albedo and ice extinction coefficient increased， while the temperature of deep layer of the lake in ice free period decreases with the increase of water extinction coefficient.
  • Evaluation of Extreme Weather Indices over Qinghai-Xizang Plateau in NEX-GDDP
  • Hongju CHEN;Jianping YANG;Yongjian DING;Qingshan HE;Qin JI
  • 2021 Vol. 40 (5): 977-990.  DOI:10.7522/j.issn.1000-0534.2020.00104
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  • NEX-GDDP data has the advantages of high resolution and uniform resolution with all the models.However， there are few studies on evaluating the NEX-GDDP’s ability to simulate the extreme climate on the Qinghai-Xizang Plateau.Based on the daily observation dataset of meteorological stations for the period of 1986-2005 over the Qinghai-Xizang Plateau， this study selected ten extreme climate indices， i.e.， Frost days （FD）， Ice days （ID）， Min Tmin （TNn）， Max Tmax （TXx）， Warm spell duration indicator （WSDI）， Cold spell duration indicator （CSDI）， annual Total wet-day precipitation （PRCPTOT）， Consecutive dry days （CDD）， Consecutive wet days （CWD） and Max 1-day precipitation amount （Rx1day）， which can directly reflect the influence of climate change on social and economic activities and geographical landforms in the plateau area， and comprehensively evaluated the abilities of 21 models that participate the NASA Earth Exchange/Global Daily Down-scaled Projection（NEX-GDDP）in simulating extreme climate indices.The main conclusions are drawn as follows： （1） Except for the average values of TNn and TXx calculated by all models are lower than the average values calculated from observation dataset， the average values of other extreme climate indices calculated by all models are higher than the average values calculated by observation dataset.With respect to the variation trend of extreme climate indices， the FD， ID， CSDI and CDD trends calculated by observation shows strong consistency with those calculated by all models while weak consistency was seen for others extreme climate indices.（2） Large differences in spatial simulation ability can be seen among the 21 models， and in terms of correlation coefficient （r）， the spatial simulation ability of all the models is better than that of time sequential simulation ability， while in terms of root mean square error （RMSE）， the ability of sequential simulation ability is better than that of spatial simulation.（3） According to the data used to identify the extreme climate indices， the extreme climate indices is divided into three categories： daily minimum temperature category （FD， TNn and CSDI）， daily maximum temperature category （ID， TXx and WSDI） and daily precipitation category （PRCPTOT， CDD， CWD and RX1day）.Based on the 21 models’ abilities to simulate the spatio-temporal variations of the extreme climate indices， five optimal modes for three extreme climate indices were selected as follows： ① daily minimum temperature category： GFDL-ESM2G， GFDL-CM3， CCSM4， MIROC5 and ACCESS1-0.② daily maximum temperature category： CanESM2， BNU-ESM， MIROC-ESM-CHEM， inmcm4 and CCSM4.③ daily precipitation category： BNU-ESM， CanESM2， CSIRO-Mk3-6-0， MIROC-ESM and MIROC-ESM-CHEM.Based on the above statements， the above optimal models are recommended when the NEX-GDDP is used to investigate the extreme climate change over the Qinghai-Xizang Plateau in the future.
  • Circulation Evolution Characteristics of the Qinghai-Xizang Plateau Rainy Season under the Warming Background
  • Tingting WEN;Xiaoqing GAO;Di YU;Hongyan SHEN;Ziwen WANG;Qingchun WANG
  • 2021 Vol. 40 (5): 991-1001.  DOI:10.7522/j.issn.1000-0534.2020.00096
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  • The article based on the Qinghai-Xizang Plateau 110 stations daily precipitation data and NCEP daily reanalysis data from May to September from1961 to 2017， and using the methods of the climatic mean rainfall which through the threshold stably and ordered samples segmentation to divide the Qinghai-Xizang Plateau rainy season onset and offset date and then analyzed the characteristics of the time and spatial evolution about Qinghai-Xizang Plateau rainy season onset and offset， finally the anomalous characteristics of atmospheric circulation at the Qinghai-Xizang Plateau rainy season onset and offset are discussed especially.The results shows that： （1） Qinghai-Xizang Plateau rainy season onset date in the Qinghai-Xizang Plateau shows an advanced trend， but the offset date shows an slightly delay trend， thus the Plateau rainy season duration become longer； （2） The establish of the Qinghai-Xizang Plateau summer monsoon is helpful to low level airflow convergence， after with the beginning of East Asian summer monsoon， the Bay of Bengal westsouthern wind provide water for the Qinghai-Xizang Plateau which is helpful to the plateau precipitation； （3） The South Asia High eatablished in Indochina， and its westnorthern movement is consistent with the evolution of the Qinghai-Xizang Plateau rainy season onset， and its movemnet of southeast shrinking and weakening is also consistent with the evolution of the plateau rainy season offset； （4） Before the onset of the Qinghai-Xizang Plateau rainy season， the convective upwelling first starts at the middle-low levels in the southern part of the plateau， with the advancement of the plateau rainy season， the convective upwelling is increasing over the whole layer of the plateau from the south to north continuelly； （5）The onset or end of plateau rainy season composite difference show that South Asian high more weaker and souther or the subtropical high more wester and higher or the plateau summer monsoon stronger is beneficial to the beginning and ending of the plateau rainy season onset earlier or offset later； Contrawise， the plateau rainy season onset later or offset earlier.
  • Evaluation on Simulation of the Inter-decadal Variation Characteristics of the Stratospheric Polar Vortex Boundary in the Northern Hemisphere by NECP CFSv2
  • Yajing LIU;Zhigang WEI;Guangyu CHEN;Yujia LIU
  • 2021 Vol. 40 (5): 1012-1023.  DOI:10.7522/j.issn.1000-0534.2020.00076
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  • By using the ERA-I， the NECP CFSR reanalysis data and the CFSv2 of NECP reforecasts and forecasts data， the inter-decadal variations of the stratospheric polar vortex boundary in the northern hemisphere since the 1980s are analyzed， the ability of the CFSv2 to simulate the polar vortex boundary is evaluated.Results show that， from 1980 to 2017， the Arctic polar vortex retreats northward in North American and expands southward in Eurasia in winter， but the polar vortex expands in North America and retreats in Europe in autumn.The polar vortex expands obviously from the 1980s to the 2000s and retreats in the 2010s in Asia.In winter， the retraction of the polar vortex occurs mainly in the 1990s in North America， but the expansion of the polar vortex occurs mainly in the 2000s in Europe and in the 1990s in Asia.In autumn， the southern expansion of the polar vortex boundary in North America is mainly in the 1990s， the retraction of polar vortexes in Eurasia occurs in the 2010s， and the retraction in Western Europe is the most obvious.The overall trend of the winter polar vortex boundary and area simulated by CFSv2 is consistent with the ERA-I data in the 1980s -2010s， especially for the trend of expansion in North America and Asia in the 2010s.However， the boundary of the polar vortex simulated by CFSv2 is more to the east， and more to the south in the 2010s in North America.The boundary of the polar vortex simulated by CFSv2 is north in the 1990s and south in the 2010s in Europe.The expansions of Asia polar vortex boundary in the 1990s and 2000s in Asia cannot be simulated.In autumn， the simulation abilities of CFSv2 on the boundary positions and areas are poor than that in the winter， the simulations on the overall trend of polar vortex boundary and area variation are poor.The North American polar vortex boundaries simulated by CFSv2 are consistent with the ones of the ERA-I data in 1990s -2010s， but the range of expansion is larger in the 1990s.The retraction of the polar vortex boundary is mainly in the 2000s from CFSv2 while in the 2010s from ERA-I in Europe.The polar vortex boundary simulated by CFSv2 is consistent in the 1990s but exists more errors in the 2000s -2010s with the one of the ERA-I data in Asia.
  • A Preliminary Analysis of the Characteristics of Drylines and Its Triggering Convections in the Hetao and Surrounding Regions
  • Yiping ZHANG;Xiaoding YU;Di WANG;Yakai GUO;Wenbo WU;Xiaozhen HAO
  • 2021 Vol. 40 (5): 1024-1037.  DOI:10.7522/j.issn.1000-0534.2020.00068
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  • Based on the conventional aerological sounding and surface data and the satellite images， the paper preliminary discussed 52 convective weather processes triggered by drylines in Hetao and its surrounding regions during May to September from 2013 to 2017， and statistically analyzed the temporal and spatial distribution， the influence systems and the characteristics of surface meteorological elements and sounding environmental parameters around the drylines.The result shows that， （1） the drylines in the Hetao and its vicinity areas mainly appears on the north of Hetao， including its northwest and northeast， and the inner region， with the main orientations from east-northeast to south-southwest and northeast to southwest， the width of 80~100 km， and the length of about 300~800 km.The occurrence frequency of drylines has obvious annual change with the annual average of 10.4 times， that always appearing during June to August and at 11:00（Beijing time， the same as after） -17:00， especially at 14:00.（2） The convective weather processes triggered by drylines mostly occur in the situation of high-altitude northwest flow and Mongolia vortex with the influence of low trough south of the vortex， associated with convergence lines or shear lines in the atmospheric boundary layer.The drylines is mostly located at the intersection of the westerly flow in the south and southeast of the continental low and Mongolia low （or cyclone） and the southerly flow behind the coastal high in the surface weather chart.（3）The statistical characteristics of ground factors are as follows： the temperature on the dry side of the drylines is higher than on the wet side with the difference of 1~2 ℃.The sea level pressure on the wet side is slightly higher than that on the dry side and the pressure difference between the two sides generally ranges from 1.5~2 hPa.In addition， one of the most important features is the large dew point difference on both sides， with the average of 11 ℃， primarily between 10 and 16 ℃.The dew point gradient is generally above 10 ℃·（100 km）-1， with the maximum of 20 ℃·（100 km）-1 or above.The westerly wind is prevalent on the dry side while the southly wind on the wet side， producing the convergence flow field， which is another important feature.（4） According to the statistical results of sounding environmental parameters， the atmospheric precipitable water and the specific humidity of 700 and 850 hPa on the wet side are significantly larger than those on the dry side.The average atmospheric precipitable water on the wet and dry side are 2.5 cm and 1.5 cm separately.The average convective available potential energy on the wet side reaches the moderate intensity of 1440 J·kg-1.while on the dry side less than 10 J·kg-1， and the thermal instability on the wet side is more abundent.The deep vertical wind shear of 0~6 km on both sides is mostly moderate or above and slightly larger on the dry side， with the average of 12.2 m·s-1 and 13.1 m·s-1 on the wet and dry side respectively.
  • Variation Characteristics of Rainy Season and Precipitation on the Qinghai Plateau from 1961 to 2017
  • Hongmei LI;Hongyan SHEN;Qingchun WANG;Youxuan MA
  • 2021 Vol. 40 (5): 1038-1047.  DOI:10.7522/j.issn.1000-0534.2020.00113
  • Abstract ( ) HTML ( ) PDF (5558KB) ( )
  • Based on the daily precipitation data from 46 meteorological stations in the Qinghai Plateau from 1961 to 2017， the whole plateau was divided into three regions using the REOF method.The variable characteristics of the beginning and ending of the rainy season， and the precipitation in different regions were analyzed.The results shows： （1） From the southeast to the northwest in the plateau， the rainy season beginning delays， the rainy season ending advances， the duration period of the rainy season is short and the precipitation decrease gradually； （2） The change in longitude had a significant impact on the rainy season in the northwest and south of the plateau.For each increase of 1°， the rainy season beginning advanced 2.4 d and 2.0 d； the end was delayed 2.3 d and 1.2 d； and the duration period was extended 4.6 d and 3.2 d， respectively； （3） Altitude has a great influence on the precipitation across the plateau.In the northwest and east area of the plateau where the altitude is relatively low， with an increase of 46.8 mm and 8.3 mm for every 100 m rise， while in the southern area of the plateau where the average altitude is above 4000 m， and a diminish of 20.3 mm for every 100 m rise； （4） The mean rainy season beginning was advanced by 1.4 d， the end period was delayed by 0.8 d， the duration was extended by 2.2 d， and the precipitation increased by 6.5 mm respectively per 10 years from 1961 to 2017.（5） The extreme precipitation during the rainy season in the plateau has Intensified significantly， especially since 2007.Comparison of the mean value from 1961 to 2017 with the mean value from 1985 to 200， the days of moderate rain， maximum precipitation within 1 day， heavy precipitation and precipitation intensity increased by 1.0 d， 9.3%， 16.9% and 0.4 mm·m-1， respectively.
  • Analysis of Radar Echo Characteristics of Short-term Heavy Precipitation Weather with Different Circulation Pattern in East Gansu Province
  • Xiangwei KONG;Jiancai YANG;Hong LI;Yi YANG
  • 2021 Vol. 40 (5): 1057-1070.  DOI:10.7522/j.issn.1000-0534.2020.00084
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  • In order to try to establish the connection between large-scale synoptic situation configuration patterns and the medium and small scale radar characteristics， 15 regional short-term heavy precipitation weather processes from 2010 to 2015 in East Gansu Province are used.These short-term heavy precipitation synoptic situation configuration patterns are divided into three patterns： eastward moving plateau low trough pattern， edge of subtropical high pattern， and northwest airflow pattern according to the difference of the main influence system in the 500 hPa.The common characteristics of weather radar echo structure and its’ evolution under different patterns are also analyzed.The results show that： （1） The radar echo of the eastward moving plateau low trough pattern is usually a mid-β-scale stratified mixed band echo of NNE-SSW trend， which is consistent with the trend and position of the low-level jet axis on the right side of 700 hPa cold shear line.The band echo is mostly formed in southeast Gansu， and the southerly low-level jet has an important influence on its propagation direction， which makes it maintain for 3~4 hours， even 5~6 hours， often accompanied by "train effect".The radar echo center of mass is low， warm cloud precipitation is dominant， and with high precipitation efficiency.（2） The radar echo edge of subtropical high pattern is usually a mid-β-scale narrow band echo of NE-SW direction located near the ground front， which is slightly ahead of 700 hPa cold shear line.This kind of radar echo is usually generated when the rapid moved cold air （cold front） intrudes into the central area of Gansu Province.When the cold front moves to the southeast of Gansu Province， the radar echo gradually evolves into the characteristics that of eastward moving plateau low trough pattern.However， its speed of moving southeast is faster than eastward moving plateau low trough pattern.（3） The radar echo of northwest airflow pattern is relatively scattered and localized， it is mainly a mid-γ-scale block echo.Either short life cycle convective cell generates and eliminates， or multi-cell storm organizes， combinates and reinforces.The development of convective cell is more vigorous than the former two patterns， belongs to deep convection.
  • Characteristics of the Raindrop Size Distribution during a Short-time Heavy Rainfall and a Squall Line Accompanied by Hail
  • Jun WANG;Wenqing WANG;Hong WANG;Qiuchen ZHANG;Dianli GONG
  • 2021 Vol. 40 (5): 1071-1086.  DOI:10.7522/j.issn.1000-0534.2020.00091
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  • To better understand the differences of rain drop size distribution （DSD） and its integral parameters， such as intercept parameter， volume weight diameter， rain intensity and radar reflectivity factor， between warm rainfall and cold rainfall processes， the characteristics of rain DSD during a heavy rainfall and a squall line accompanied by hail （rain intensity higher than 10 mm·h-1） are analyzed based on data observed by Parsivel disdrometers and CINRADA/SA Doppler radars.The results are shown as follows.（1） The DSD of the convective type in heavy rainfall includes single-peak spectrum （peak diameter between 0.2 and 0.3 mm）， double peak spectrum （peak diameter being 0.9 or 2.0 mm） and multi-peak spectrum （the second and third peaks appear simultaneously when particle diameter is 1.0 mm and 2.0 mm）， indicating that the coalescence and collision-breakup of raindrops in warm rainfall are dominant processes.The intercept parameter and the mean mass-weighted diameter （lgNw-Dm） of the normalized Gamma function show the continental convective characteristics of rain DSD during the heavy rainfall.The Z-R relationship is close to that of the new generation Doppler radar.Although the heavy rain is fully developed in the high-altitude cold rainfall processes， the collision-coalescence and breakup in the warm rainfall have enough time to operate owing to the high position of 0 ℃， and the equilibrium DSD appears.（2） The DSD of the convective precipitation accompanied by hail is mainly single-peak spectrum （peak diameter between 0.2 and 0.7mm）， lacks the second peak with larger diameter， has more small and large diameter particles， and the curve of DSD larger than the peak diameter is a concave upward.The distribution of lgNw-Dm shows a larger Dm compared with the DSD of continental convective precipitation， while the Z-R relationship has a larger index and coefficient， deviating from that of the new generation Doppler radar.The differences between cold rainfall and warm rainfall processes lead to the obvious differences between ground DSD and integral parameters.In the precipitation process accompanied by hail， ice particles such as graupel and hail constantly melt and breakup in the falling process， leading to the large number of small and large raindrop on the ground.Therefore， the differences in microphysical processes bring about different characteristics of DSD.（3） When different order moments are used to calculate the exponential bn， it is necessary to make a reasonable choice according to the characteristics of DSD.The difference of number density between large， medium and small particles will lead to the great difference of the variation of different order moments with rain intensity.The analysis of a scaling law formalism shows that the general distribution function g（x） for the DSD of the heavy rainfall can be exponential function or Gamma function with shape factor less than 1.0， while the general distribution function g（x） for the DSD of the convective precipitation accompanied by hail is more suitable for Gamma function with shape factor less than 0.
  • Analysis of Difference in Distribution of Rainstorms in the Later Two Stages of Northward-Moving Typhoon Ampil
  • Hong CHEN;Xiaojun YANG;Xiaoyuan YI;Yinghua WEI;Yang YANG;Qing ZHANG;Jing SUN
  • 2021 Vol. 40 (5): 1087-1100.  DOI:10.7522/j.issn.1000-0534.2020.00088
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  • Based on China Meteorological Administration （CMA） typhoon path data， surface-observed hourly data， NCEP/NCAR （1°×1°） re-analysis data， black-body temperature equivalent （TBB） of FY-2F satellite data， radar data， and conventional observation data， the reason for the distribution characteristics of the asymmetry of the later two stages of northward-moving typhoon Ampil （1810） was analyzed.The intensity of the typhoon remained unchanged when Ampil went northward， but it caused the Shandong torrential rain to locate on the east side of the typhoon track， while the Tianjin torrential rain located on the west side of the track.The result indicated that after Typhoon Ampil went northward， the cloud system around it developed into an asymmetrically distributed cloud system， with obvious asymmetry in the structure of rainfall and circulation.In the two heavy-rainfall areas that located in Shandong and Tianjin， the enhanced development of rainfall was consistent with the development characteristics of convective cloud clusters.Short-term heavy-rainfall sites with low centroids were distributed in the high-value area of the TBB gradient.When the typhoon was in Shandong， mesoscale cloud clusters and heavy rainfall mainly located in the central of Shandong， east of the typhoon path， because weak vertical wind shear was conducive to maintaining the heart-warming structure and strength of the typhoon.The high-temperature and humidity environment carried by the typhoon itself caused the conditional symmetry and instability of the lower troposphere， and triggered short-term heavy rainfall on the east side of the typhoon.The center of heavy rain was affected by the combined effects of positive vorticity， vertical velocity， water-vapor convergence， and topography of Mount Tai.After the typhoon entered Tianjin， cold air infiltrated from the westerly trough， infiltrating the typhoon circulation from the northwest side， causing the intersection of cold and warm air.This additionally inspired an asymmetric mesoscale system， leading to vertical wind shear and positive vorticity increasing significantly， resulting in high-level divergence and low-level convergence， causing obvious suction.Together， these events caused strong upward movement on the west side of the typhoon and the thickness of unstable stratification increased significantly， providing favorable conditions for the development of mesoscale systems.At the same time， the southeast jet in the lower troposphere caused water vapor to be replenished after passing through the Bohai Sea， forming an obvious belt-shaped water-vapor convergence zone on the northwest side of the typhoon.This convergence zone led to the band-shaped mesoscale cloud cluster of cyclonic circulation that developed in the northwestern side of the typhoon cloud system at the junction of Beijing and Tianjin.Together， these events led to short-term （5-h duration） heavy rainfall on the northwest side of the typhoon.
  • Comparative Analysis of Two Disaster-Induced Rainstorms in Hunan Province in Flood Season of 2019
  • Hongwu LIU;Yan HU;Tao SU;Huanqian LIU;Chenghao FU
  • 2021 Vol. 40 (5): 1101-1114.  DOI:10.7522/j.issn.1000-0534.2020.00087
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  • In the main flood season of 2019， there were two rare extreme rainstorms in Hunan Province， in which rainfalls of several meteorological observation stations exceeded historical extremes， resulting in more than 10 deaths （missing）.By using Global Data Assimilation System （GDAS） data and reanalysis data from the National Centers for Environmental Prediction （NCEP）， and observation data， based on the particle trajectory tracking and clustering algorithm from Hybrid Single-Particle Lagrangian Integrated Trajectory （HYSPLIT4）， the similarities and differences of two disaster-induced rainstorm processes from June 6 to 9 （process 1） and July 6 to 9 （process 2） in 2019 are comparatively analyzed.The results show that the two processes are characterized by extreme， continuity and convection， and the second process has greater rainfall intensity， more concentrated heavy rainfall areas and more serious disasters than the first one.Besides， there are obvious difference in that circulation field between the two processes.For the process 1， the intensity of the subtropical high was significantly stronger， its location was northerly， and the western ridge point of 588 dagpm was westward by 26 longitudes than that of the same period over the years.The northeast cold vortex developed deeply.The maximum wind speed of the 850 hPa jet stream core reached 14 m·s-1， and there were double vortex and shear lines.While for process 2， the subtropical high was stable， the ridge line was south by over 8 latitudes.There was a significant cold shear at 850 hPa， and the wind speed on the south side of the shear was large， which led to the strong cold and warm convergence， causing the convective characteristics of the rainstorm clearer.Furthermore， the occurrence and evolution of mesoscale cloud clusters in the two processes are slightly different.For process 1， there was the eastern section of the herringbone shear line triggering the generation of mesoscale convective clouds， which developed and grew in an organized way after the adding of the weak cold air.For process 2， the warm and humid airflow and cold airflow met in front of the long wave trough in the westerlies， and mesoscale cloud clusters of α， β and γ were continuously emerging， merging and developing.The "train effect" of multiscale convective cloud clusters moving through the same place caused strong disaster-induced rainstorm.At last， that source and distribution of water vapor are different.For process 1， the significant convergence center of water vapor was located at 850 hPa.The source of water vapor was the South China Sea.There were three water vapor transmission channels， and the main water vapor channel was the southerly airflow in the South China Sea.For process 2， the significant convergence center was located at 925 hPa.The water vapor sources were the Indian Ocean.There were four water vapor transmission channels， among which the main water vapor transmission channel came from southwest air flow in the Bay of Bengal.
  • Variation and Precursory Signals of Persistent Rainstorm during the First Rainy Season in Guangdong Province from 1961 to 2019
  • Lingling YU;Zhongping JI;Jianhua MAI
  • 2021 Vol. 40 (5): 1115-1126.  DOI:10.7522/j.issn.1000-0534.2020.00108
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  • In order to improve the short-term climate prediction ability of precipitation concentration period and rainfall during the first rainy season in Guangdong Province， the variation characteristics of persistent rainstorm days in recent 59 years， the precursory signals in the atmospheric circulation and SST field in pre-winter， and the physical mechanism were studied by using wavelet analysis， correlation analysis and other methods.The results show that： （1） there were 108 persistent rainstorm processes， and 398 persistent rainstorm days during the first rainy season in Guangdong in recent 59 years.Most of persistent rainstorm processes occurred from May to June， and long-lasting torrential rain reaching or exceeding 10 days mainly occurred in June.The number of persistent rainstorm days exhibited quasi 2-， 7-and 12-year periodic oscillations； （2） The precursory signals in pre-winter over the atmospheric circulation affecting the more（less） number of persistent rainstorm days were stronger ridge （trough） in European （45°N -60°N， 0° -30°E） and stronger trough （ridge） in northwest Asia and mid-Asia （30°N -50°N， 50°E -70°E） and its north at 500 hPa， and the stronger （weaker） southerly in northern SCS （18°N -22°N， 107°E -120°E） at 850 hPa.They affected the number of persistent rainstorm days in the first rainy season by mainly adjusting the strength of the East Asian Trough and the wind over northern SCS in the later stage.（3） The SST in pre-winter in the central North Pacific （15°N -30°N， 170°E -160°W） was the key SST region affecting the number of persistent rainstorm days in the first rainy season in Guangdong Province.They had a good inverse relationship on the periodic scale of 4~8 years and 8~18 years.It affected the number of persistent rainstorm days in the first rainy season in Guangdong Province by influencing the later atmospheric circulation.
  • Climatic Characteristics and Causes of Severe Drought in the Central and Southern Shanxi Province from May to August in 2019
  • Dayong WANG;Ying CHEN;Dongfeng ZHANG;Jiahai YAN;Guohong ZHANG
  • 2021 Vol. 40 (5): 1127-1135.  DOI:10.7522/j.issn.1000-0534.2021.00036
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  • From May to August in 2019， a severe drought climate events occurred in the central and southern Shanxi Province （an important agricultural production center in the region）， which caused great economic losses. This severe drought event on a large scale in Shanxi Province can be attributed to the lack of precipitation for a long time. Based on the monthly precipitation data of 108 stations in Shanxi Province， NCEP / NCAR reanalysis data and COBE-SST sea surface temperature data provided by Japan Meteorological Agency， the characteristics of atmospheric circulation anomaly and sea surface temperature anomaly during drought period and their influence on drought are analyzed. The results show that： （1） During the drought period， the 500 hPa height field over the middle and high latitudes of Asia was dominated by the latitudinal circulation. And Shanxi Province was mainly affected by the strong high pressure ridge near Lake Baikal. Overall， Shanxi Province is controlled by the positive anomaly of the height field. Compared with normal years， the Western Pacific subtropical high showed southwestward extension and southward expansion in the study period， which is unfavorable for the water vapor transportation to northern China； The South Asia high is located more eastward than 10 degree longitudes with stronger intensity， which is not conducive to the precipitation over Shanxi. （2） There is a weak northerly wind anomaly at low altitude 850 hPa wind field during the drought period over Shanxi with multiple branches of water vapor from the equator and the western Pacific Ocean converging to reach the south of Yangtze River in China. The strong water vapor transport flux paths do not pass through Shanxi and it is located by the south， resulting in an overall lack of abundant water vapor conditions in Shanxi. （3） During the drought period， the SST in the equatorial Middle East Pacific shows a neutral warming state. And the SST in Indian Ocean shows a uniform warm mode. For the North Atlantic triode， the SST shows a positive phase， which is conducive to the less precipitation in Shanxi. In addition， the characteristics of anomal in SST in the winter of 2019 are also favorable for the less precipitation from May to August in 2019 in Shanxi Province. In general， the characteristics of anomalies in atmospheric synoptic circulation and sea surface temperature during the drought period are consistent with the typical conditions of anomalies in the years with weak precipitation in Shanxi Province.
  • Analysis of the Applicability of Drought Indexes in the Northeast， Southwest and Middle-lower Reaches of Yangtze River of China
  • Wusan XIE;Qiang ZHANG;Wei LI;Biwen WU
  • 2021 Vol. 40 (5): 1136-1146.  DOI:10.7522/j.issn.1000-0534.2020.00102
  • Abstract ( ) HTML ( ) PDF (8392KB) ( )
  • Based on the data of temperature， precipitation， soil moisture and historical drought disasters， this paper analyses the applicability of SPI， SPEI， MI and MCI in the northeast， southwest and middle-lower reaches of Yangtze River of China from the aspects of spatial and temporal distribution characteristics of drought， diagnosis of typical drought processes， unreasonable jump times analysis and correlation with soil moisture and drought disasters， etc.The results show that the four indexes are basically the same in diagnosing the interannual variation of drought days， while as to diagnosis of the spatial distribution of drought days， the MCI and MI indexes are more consistent with the actual situation.As far as the daily diagnosis of typical drought processes is concerned， MCI has the best effect on the description of drought process， and the unreasonable jump times are 82.6%， 73.8% and 97.8% lower than that of SPI， SPEI and MI respectively.There are the least unreasonable jump times of each index in the middle-lower reaches of Yangtze River， followed by that in the southwest China and the northeast China.Compared to SPI， SPEI and MI， MCI is the best in the correlation with soil moisture， which has passed the confident level of 99%， and increases by 9.2%， 54.7% and 68.8% respectively.The correlation between the soil moisture and representative stations in southwest China is the best， followed by that in the middle-lower reaches of Yangtze River， and that in the northeast China is relatively poor.In terms of correlation with drought-affected area， MCI is also the best， which is 16.9%， 37.1% and 27.6% higher than SPI， SPEI and MI respectively.The correlation between the indexes and the drought-affected area in northeast China is better than that in the middle-lower reaches of Yangtze River， while that in southwest China is worse.On the whole， the applicability of MCI is the best， which is closely related to the construction methods of drought indexes， drought influence factors， time scales， weight of precipitation in different periods and so on.
  • Monitoring and Cause Analysis of Drought on Urat Grassland in the First Half of 2018
  • Fengjuan LIANG;Baolong ZHANG
  • 2021 Vol. 40 (5): 1147-1153.  DOI:10.7522/j.issn.1000-0534.2020.00083
  • Abstract ( ) HTML ( ) PDF (2310KB) ( )
  • Drought is a complex abnormal phenomena in nature， which is of great significance to drought analysis and research based on meteorological factors.Based on the precipitation and temperature data selected from 1971 to 2018 and the climate survey from March to June in 2018， the effect of meteorological factors on drought was analysed combined with the evolution of atmospheric circulation in Eurasia.By methods of soil moisture measurement and UAV aerial photography， 22 typical regions were selected in Urat grassland， where the soil relative humidity were measured at the depth of 10， 20， 30 and 40 cm.In order to study the spatial distribution of drought grade and the occurrence degree of drought， the vegetation growth of Urat grassland in mid June was monitored by remote sensing with high resolution satellite， and compared with that of the corresponding period of last year and of the recent three year.The results show that： （1） In the spring of 2018， the East Asian Trough was weak and the Asian zonal circulation was abnormally strong.From March to May， Urat grassland， at the northern foot of Yinshan Mountain， whose 500 hPa was under the control of high pressure ridge， has abnormally less precipitation， abnormally high temperature， long sunshine time， windy sand weather， large surface water evaporation， and severe surface soil moisture loss， leading to the delay of grass returning to green.（2） At the turn of spring and summer in 2018， the subtropical high was still southward and distributed in a latitudinal pattern， which hindered the water vapor of South， Southeast and Southwest to transport to the North.As a result， there was no soaking rain in Urat grassland until the mid June.Soil moisture was not effectively replenished and maintained； soil moisture conservation ability was poor， and dry soil layer was thick， which led to the occurrence and development of drought in Urat grassland， resulting in severe drought.
  • Analysis on the Variations of Gales and Two Southerly Gale Events in Huashan Mountain Scenic Spot
  • Aijuan BAI;Yonghong ZHANG;Jiahao WU;Jinjiang YU;Limin Ding
  • 2021 Vol. 40 (5): 1154-1163.  DOI:10.7522/j.issn.1000-0534.2020.00101
  • Abstract ( ) HTML ( ) PDF (7004KB) ( )
  • This paper analyzed the variations on different time scales of gales in the Huashan mountain scenic spot of Shaanxi， by using the hourly observations from the year of 2012 to 2017 in the Huashan’s station.Two representative southerly events were analyzed in this paper to get the mechanism of gales of Huashan.The main conclusions were as follows.Taking the wind velocity of more than 17 m·s-1 as a thread， the gales of Huashan tended to occur from 21:00 （Beijing Time the same as affer） to the next early morning frequently， on the contrary， less gales occurred after noon and before 20:00.The southern peak located at higher altitude and more southward position， so it encountered more southerly gales.The Huashan station meet with not only southerly gale， but also northwestern strong wind， because of its northerly position and lower altitude.During the two gale southerly events， the similar circulation of characterized by ‘East High and West Low’ at the low-level was explored.Huashan was located in the contour-intensive transition region of from North China High to Northwest Low.The dynamic theory of gradient wind resulted in the high velocity.Before the gales， the 3h variable pressure field displayed a strong negative center of lower than -4 hPa in central Shaanxi， which made the convergence and ascending motion.At the same time， the southerly alee was accelerated in the night and enforces the gales， accompanied with the instability-ascending motion.The significant temperature and pressure changes were found before the strong wind.In the autumn gale， the temperature decreased by 5 °C 3 hours before the maximum velocity， accompanying the pressure decreased by 4 hPa about 7 hours before.The early changed pressure and temperature can be the important factors of wind forecasting.From the observations of Jinghe radar site， 100 km away from Huashan， the echoes in the Huashan gale were weakened and cannot display the extreme velocity， because of the terrain occlusion of high mountain peaks.
  • Analysis of the Characteristics and Synoptic Situation Classifications of Thunderstorms in Shuangliu Airport
  • Diannan LI;Dongbei XU
  • 2021 Vol. 40 (5): 1164-1176.  DOI:10.7522/j.issn.1000-0534.2020.00110
  • Abstract ( ) HTML ( ) PDF (10388KB) ( )
  • Using the 2013-2018 hourly meteorological observation data of Shuangliu International Airport's， ECMWF ERA-interim and ERA5 reanalysis data， MICAPS conventional meteorological observation data and airport Doppler weather radar product data， the spatiotemporal characteristics and features in four types of thunderstorm weather at Shuangliu Airport are analyzed.The results show that the 77.03% of thunderstorms at Shuangliu Airport were accompanied by precipitation during 2013 and 2018.The occurrence of thunderstorm in summer （June， July and August） is more than half of that of the whole year， which is featured with "more night thunder and less day thunder".82.7% of the thunderstorms have a duration within 3 hours and the thunderstorms are most active over the east of the airport.The thunderstorms occured at Shuangliu Airport are divided into four types， cold advection forced， warm advection forced， baroclinic frontogenesis and weak advection， according to different baroclinic frontogenesis and thermal conditions of the environmental field.The northwest cold air in the upper level plays a crutial role in the occurrence of cold advection forced thunderstorms.When this type of thunderstorm occurs， Shuangliu Airport is mostly located behind the 500 hPa trough， and the wind rotates counterclockwise with height from the middle to the upper troposphere.The atmosphere exhibited strong unstable energy， thus this type of thunderstorms are often accompanied by thunderstorm gale， hail， and short-time heavy rainfall.The associated radar echo of precipitation shows combined features from cumuliform clouds and stratiform clouds.In contrast， the strong warm and humid southerly is more important in the warm advection forced thunderstorm.Shuangliu Airport is often located in front of the 500 hPa trough and wind tends to rotate clockwise with height in this type of thunderstorm.Although the unstable energy of the atmosphere is relatively weak， the thunderstorm can still induce short-time heavy rainfall as the atmosphere is generally moist.The radar echo of precipitation is mainly featured with the stratiform clouds.Baroclinic frontogenesis type of thunderstorms occur in the background of strong intersection of cold and warm air in the middle and lower troposphere where the function of frontogenesis is significant.The atmospheric baroclinicity is strong and the dynamic condition is good during this thunderstorm.Strong convection occures along with various synoptic processes.The realated radar echo shows a radar bow-shaped echo band near the Shuangliu Airport that is arranged laterally by many thunderstorm cells in the northeast-southwest direction.Weak advection thunderstorms often occur under the weak baroclinic condition.During this thunderstorm， the atmosphere is approximately quasi-barotropic with a small frontogenesis function and the temperature advection is insignificant.The horizontal distribution of atmospheric water vapor is relatively uniform.The air at the near-surface is characterized by high temperature and high humidity， and unstable energy is accumulated at the lower level.Once triggered by somehow mechanisms， the thundershower and gusty winds will be generated after overcoming convective instability.The map of radar echo is shown with many echoes in small range and weak intensity scattering around the Shuangliu Airport and have no obvious typical characteristics.
  • Evaluation to the Solar Energy Resources in the Sandy Regions of Northern China from 1990 to 2019
  • Chun LIU;Liqing REN;Xuejun LI;Bing JIA;Tengfei YU;Chengqi ZHANG;Jianhua XIAO;Chunyan ZHAO;Meng ZHU
  • 2021 Vol. 40 (5): 1213-1223.  DOI:10.7522/j.issn.1000-0534.2021.00058
  • Abstract ( ) HTML ( ) PDF (7161KB) ( )
  • The solar radiation， as a kind of clean energy， is increasingly being developed in recent years under the background of energy crisis and global climate warming.An evaluation of the spatial patterns and storage of solar energy is of great importance for potential solar energy resources development.The deserts in northern China are characterized by abundant solar energy resources and sparse vegetation cover， which are very suitable for solar energy resources development.However， as the number of solar radiation observation stations in sandy regions of northern China is very limited， dedicated evaluation to solar energy resources in the sandy regions of northern China is still characterized by large uncertainties.In this study， data from 46 solar radiation stations and 189 common weather stations in the sandy regions （including deserts， sandy lands， Gobi， and salinity lands） of northern China were employed to estimate the global solar radiation based on a high-efficient machine learning model， i.e.， the xgboost algorithm.The solar resources were assessed by analyzing the spatiotemporal patterns of annual， seasonal， and monthly radiation.The results showed that the average sunshine duration and global solar radiation from 1990 to 2019 are 2927.90 h and 5888.39 MJ·m-2， respectively.The average decreasing rates of sunshine hours and solar radiation over the past thirty years were 22.48 h·（10a）-1 and 8.66 MJ·m-2， respectively， which were not significant at the 0.05 level.The spatial patterns of sunshine duration and total solar radiation were characterized by higher values occurring in the middle parts while lower values in the east and west parts of northern China.The radiation was maximal in the deserts of Qinghai and Hexi Corridor with values higher than 6300 MJ·m-2， while minimum in the sandy lands of Northeast China with values less than 5300 MJ·m-2.The solar radiation was maximal in summer， followed by spring， and the lowest in autumn and winter.Generally， solar energy in deserts of the Qinghai and west Hexi Corridor were ranked as the most abundant level， while other sandy regions were very abundant level.However， in terms of the stability of solar energy， only deserts in the Qinghai and the southern Hexi Corridor were ranked as a relatively stable level， and other sandy regions are fewer stable levels.Therefore， the potential of solar energy resources in the sandy regions of Qinghai and Hexi Corridor was maximal， and should be given priority in terms of solar resources development， to promote the regional economic development and further improve the ecological environment of sandy regions.

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