Current Issue

• Observations of East Qinghai-Xizang Plateau Snow Cover Effects on Surface Energy and Water Exchange in Different Seasons
• Wenjing LI;Siqiong LUO;Xiaohua HAO;Jingyuan WANG;Yuxuan WANG
• 2021 Vol. 40 (3): 455-471.  DOI:10.7522/j.issn.1000-0534.2020.00001
• Abstract ( ) HTML ( ) PDF (15133KB) ( )
• The observation data from three filed observation stations in the east of the Qinghai-Xizang Plateau （the plateau）， namely Maqu， Maduo and Yakou， were selected to study the influence of snow cover processes in different seasons on surface energy and soil temperature（moisture）.The results show that， under the influence of high albedo of snow cover， the net shortwave radiation decreases after snowfall in the eastern plateau， and the net radiation decreases by about 60%~140%.Sensible heat， latent heat and soil heat flux decreased in the accumulation period， sensible heat flux and soil heat flux showed negative value.In the course of snow cover in spring and autumn， energy is distributed in the form of sensible heat， latent heat and soil heat flux.In the process of winter snow cover， sensible heat and soil heat flux are the main energy distribution， while latent heat flux is small， with a daily average about 10 W·m^-2.However， the latent heat flux in the melting period of summer snow is larger about 80 W·m^-2.The process of repeated accumulation and melting of snow cover in each season has a major cooling effect on the atmosphere and soil.After snowfall in autumn， the temperature of air and shallow soil temperature decrease.When the soil temperature drops below the freezing point， the soil enters the freezing period in advance and when snow falls in spring， it could cause the melting soil to freeze again.During the process of snow accumulation on sunny days in winter， snow accumulation plays a warming role on soil， and the daily average temperature of 0~20 cm soil temperature increases by 1~2 ℃， which leads to shallow frozen soil melting and soil moisture content increasing.In the melting stage， snow accumulation still plays a cooling role on soil.Snow cover on cloudy days in winter has a cooling effect on soil.Snow accumulation period in summer is short， and snowfall also has a significant cooling effect on soil.

• Diurnal Variation Characteristics of Summer Convection over the Qinghai-Xizang Plateau and South Asia Area based on the High-resolution OLR Data
• Yingwen KANG;Yuanfa GONG
• 2021 Vol. 40 (3): 472-485.  DOI:10.7522/j.issn.1000-0534.2020.00105
• Abstract ( ) HTML ( ) PDF (8799KB) ( )
• Based on the high-resolution （the spatial resolution is 0.25°×0.25°， the temporal resolution is once every 3 hours， 8 times a day） outgoing longwave radiation （OLR） data of the geostationary meteorological satellite Kalpana-1 from 2004 to 2017， the characteristics of convection diurnal variations over the Qinghai-Xizang Plateau and South Asia area in summer are analyzed.Combined with ERA-Interim analysis data and the observed precipitation data in China， the relationship among convective activity anomaly， vertical velocity anomaly and precipitation anomaly in 2006 and 2007 is studied.The results show that： （1） In June to September of summer， especially from July to August， the severe convection mainly occurs in the central and southeastern Qinghai-Xizang Plateau， the northeastern Indian Peninsula， the Bay of Bengal and the Indochina Peninsula.Minimum value of mean OLR in the strongest convection area is less than 190 W·m^-2.（2） The characteristics of convection diurnal variations over the Qinghai-Xizang Plateau and South Asia area are obvious.In the central-southern and the southeastern Qinghai-Xizang Plateau， the northeastern Indian Peninsula and the southern Indochina Peninsula， the strong convective areas with OLR below 210 W·m^-2 begin to appear around 09:00 （UTC， the same as after）， the strongest convective activity takes place at 12:00， and the convective activity can continue until the next morning.However， in the East Coast of the Bay of Bengal， the obvious convective activity occurs throughout the day and reaches its twice maximum at 09:00 and 21:00.Compared with convection diurnal variations over the Qinghai-Xizang Plateau， South Asia area and the Bay of Bengal， the land areas have one cycle one day， the East Coast of the Bay of Bengal has two cycles one day， and the strongest diurnal oscillation occurs in the central-southern Qinghai-Xizang Plateau.（3） A comparative analysis of OLR， vertical velocity and precipitation anomaly over the Qinghai-Xizang Plateau and Southwest China from July to August in 2006 and 2007 shows that negative （positive） anomaly of the high-resolution OLR indicates that the abnormal strong （weak） convection is closely related to the abnormal ascending （sinking） movement and the abnormal more （less） precipitation， which can be used to characterize the variation characteristics of convective activity over the Qinghai-Xizang Plateau and make up for the lack of observational data.

• A Study of the Response of Snow Disaster Frequency to Sea Surface Temperature Forcing Anomaly Forcing over the Qinghai-Xizang Plateau
• Caihong LIU;Jinhua YU;Yanhua YANG
• 2021 Vol. 40 (3): 486-494.  DOI:10.7522/j.issn.1000-0534.2020.00046
• Abstract ( ) HTML ( ) PDF (6454KB) ( )
• The snow disaster over the Qinghai-Xizang Plateau is the most destructive meteorological disaster in the region， and the causes of its changes have been receiving much attention.In this paper， the daily snow cover data of 72 stations over the Qinghai-Xizang Plateau and the monthly mean sea surface temperature data of the Hadley Center were used， and the optimal feedback mode analysis method combining generalized balanced feedback analysis with principal component analysis （GEFA-EOF） was adopted.We studied the response relationship between the frequency of snow disasters in the Qinghai-Xizang Plateau and the modes of SST anomalies in critical areas， and discussed the contribution of SST anomalies to the frequency of snow disasters and the possible mechanism of their occurrence.The results show that the frequency of snow disasters over the Qinghai-Xizang Plateau responds significantly to the El-Ni?o mode （TP1） and the tropical Indian Ocean temperature dipole mode （TI2） in the equatorial Middle East Pacific Ocean SST anomalies.The contribution of the two modes to the frequency of snow disaster is 45.9%.The response of the snow disaster frequency to the sea temperature anomaly is mainly realized through the atmospheric circulation anomaly associated with it.When the TP1 sea temperature is forcing， the mid-high latitude of Eurasia presents a "＋－＋" situation from west to east at the height of 500 hPa， forming a typical pattern of two ridges and one trough； when the TI2 is forcing， it mainly causes low-and middle-level water vapor anomalies， the warm and wet air flow from the Arabian sea enters the southern part of the plateau， and the wet air flow from the northwest Pacific enters the northern part of the plateau， providing moisture conditions for snowfall.Under the configuration of this high and low layer， it is prone to snowy years.

• Research of the Difference of Energy Budget and Its Cause in Different Types of Underlying Surfaces in the Middle and Lower Reaches of Heihe River
• Yuxuan WANG;Yinhuan AO;Zhaoguo LI;Wenjing LI
• 2021 Vol. 40 (3): 495-509.  DOI:10.7522/j.issn.1000-0534.2020.00100
• Abstract ( ) HTML ( ) PDF (10574KB) ( )
• The observation data of different underlying surfaces （desert， cornfield， wetland， populus， mixed forest of populus and tamarix） in the middle and lower reaches of Heihe River basin are selected to study the changes of energy budget on different underlying surfaces.The influence of different meteorological factors and irrigation on the latent heat flux transport is discussed.The results show that the annual variation of latent heat flux is consistent with those of downward short-wave radiation and air temperature.The energy budgets of different underlying surfaces were significantly different.The average monthly peak of latent heat in corn fields is up to 200 W·m^-2， while that in desert is only 100 W·m^-2.The seasonal variation range of latent heat flux on the underlying surface of the desert was smaller， and the seasonal variation range of wetland， mixed forest and Populus were more obvious and larger， among which wetland was the largest.The latent heat flux on the undersurface of cornfield is greatly affected by irrigation.Irrigation can make a sudden increase in soil moisture and a rapid increase in the latent heat flux.The surface heat flux accounts for a small part in the energy budget and has little change with the seasons.

• Statistical Analysis on Hourly Heavy Rainfall in Northeast China Induced by Cold Vortices
• Xiangfu CHEN;Yu ZHAO
• 2021 Vol. 40 (3): 510-524.  DOI:10.7522/j.issn.1000-0534.2020.00092
• Abstract ( ) HTML ( ) PDF (14821KB) ( )
• By using hourly precipitation observation of automated weather stations， conventional observation and NCEP/NCAR 1°×1° reanalysis data from June to August during 2011 -2020， a statistical analysis of the spatiotemporal characteristics of hourly heavy rainfall events caused by cold vortices in Northeast China was performed.Focusing on locations of rainfall， the hourly heavy rainfall events were classified into northwest airflow type （NW）， zonal type （ZT）， south vortex type （SV）， subtropical high type （SH） and meridional type （MT） based on the position， shape and development stage of cold vortices as well as interaction with tropical systems.In addition， the features of convection parameters of these five types were studied.Results show that induced mostly by middle vortices in June， hourly heavy rainfall events were mainly caused by north vortices in July and August.The hourly heavy rainfall often occurred in the afternoon， reaching the peak at 17:00 （Beijing Time）.In the spatial distribution， the high frequency area of hourly heavy rainfall was situated in Liaoning Province， while the sub-high frequency area was located in the central Jilin Province and central-western and north-eastern Heilongjiang Province.The precipitation locations had differences not only in different types but also in phases of evolution of cold vortices.Moreover， hourly heavy rainfall events usually appeared in the conditional instability atmosphere.The temperature difference of NW， ZT and MT between 850 hPa and 500 hPa exceeded 25 ℃， while those of SH and SV were less than 24 ℃ with higher dew point and larger precipitable water.The convective available energy of all types were relatively moderate， mostly less than 1500 J·kg^-1.In most situation， the hourly heavy rainfall events of SH happened under moderate vertical wind shear， while others generally appeared in the environment with weak vertical wind shear.

• Analysis on Strong Convective Weather Triggered by Southwest Vortex
• Jinqing LIU;Hongwu LIU;Jingyu XU
• 2021 Vol. 40 (3): 525-534.  DOI:10.7522/j.issn.1000-0534.2020.00027
• Abstract ( ) HTML ( ) PDF (5409KB) ( )
• In order to improve the understanding of the strong convective weather triggered by Southwest Vortex （SWV） and better study its forecasting and early warning methods.Based on Southwest China Vortex Yearbook， national meteorological station observation data， ground-based lightning data， dangerous weather reports and ERA-Interim reanalysis data during 2014 -2017， the characteristics of strong convective weather and weather situation of severe precipitation caused by SWV are investigated.Similarities and differences in dynamics and thermodynamic of SWV severe precipitation with different moving paths are further analyzed.The results show that： （1） About a quarter of SWV would cause strong convective weather and strong convection fall area was mainly located in the southeast quadrant.The type was mainly short-time severe precipitation with intensity concentrated in 22~32 mm·h^-1.This was due to coupling and interaction between the southeast quadrant of SWV and the southwest flow brought strong advection of high temperature and humidity， which easily caused convective instability and convective precipitation.（2） SWV severe precipitation was concentrated in spring and summer， and moving SWV （about two fifths） was more likely to cause precipitation than quasi-stationary （about one fifth）， but only the moving SWV would trigger severe precipitation in spring， which was related to the more vigorous warm moisture airflow and water vapor transport.（3） The precipitation intensity of quasi-stationary SWV was stronger than moving SWV， which may be due to the stronger vertical wind shear of moving SWV， which was not conducive to efficient precipitation.（4） Although SWV was frequent in autumn and winter， the threat of triggering strong convective weather was small.The moving SWV in spring and all SWV of different path in summer were more likely to cause strong convective weather， and attention should be paid to the severe precipitation that may occur in southeast quadrant within 450 km.

• Trend Analysis of Future Temperature and Precipitation in Shule River Basin based on BCC-CSM2-MR Model
• Yapei LI;Rui ZHU;Tao LIU;Yabin CHANG;Zhenliang YIN
• 2021 Vol. 40 (3): 535-546.  DOI:10.7522/j.issn.1000-0534.2020.00078
• Abstract ( ) HTML ( ) PDF (4288KB) ( )
• The Shule River is one of the three major inland rivers in the Hexi Corridor.The ecological environment and water resources in the area are vulnerable to climate change.The analysis and research on the future temperature and precipitation trends in the area will help to clarify future climate changes in the Shule River Basin.The status provides a reference for climate change risk assessment.Based on the temperature and precipitation data from 1961 to 2014 and the output data of the medium-resolution climate model BCC-CSM2-MR （1961 -2100）， this paper uses the MBC （Multivariate Bias Correction） method to correct the model output data， in which trend analysis and spatial interpolation analysis as well as other methods are used to study the variation trend of temperature and precipitation in the Shule River Basin.The results show that： （1） In the historical period （1961 -2014）， the model output data corrected by the MBC method， except for very few months， fits well with the observed value.In terms of spatial distribution， the model output data can also roughly reproduce the distribution law of the study area； （2） In different climate change scenarios （SSP1-2.6， SSP2-4.5， SSP3-7.0， SSP5-8.5） in the future period （2015 -2100）， The comparison result of precipitation increase of model output data is SSP5-8.5>SSP3-7.0>SSP2-4.5>SSP1-2.6， the comparison result of the average temperature increase of model output data is SSP5-8.5>SSP3-7.0>SSP2-4.5>SSP1-2.6， and the maximum temperature increase of model output data is SSP5 -8.5>SSP3-7.0>SSP2-4.5>SSP1-2.6， the minimum temperature increase of model output data is SSP5-8.5>SSP1-2.6>SSP2-4.5>SSP3-7.0； （3） The change characteristics of the three periods （2015 -2040， 2041 -2070， and 2071 -2100） in the future period （2015 -2100） show that the precipitation in the period 2015 -2040 and 2041 -2070 will drastically decrease， while the temperature has increased and decreased， and the range of change is large， showing a trend of oscillation.During the period from 2071 -2100， the temperature and precipitation have changed abruptly and showed a trend of rapid growth； （4） The precipitation change rate in the future period will show a trend of high in the middle and low in the surrounding area； and the high value of the average temperature change is concentrated in the sparse water system areas of the Shule River Basin； the areas with the most obvious changes in the maximum temperature are concentrated in the upper reaches of the Shule River Basin； the areas with the most obvious minimum temperature changes are concentrated in the north and south ends of the Shule River Basin.

• Simulation and Projection of Precipitation in the Upper Yellow River Basin by CMIP6 Multi-Model Ensemble
• Mengxia ZHAO;Buda SU;Tong JIANG;Anqian WANG;Hui TAO
• 2021 Vol. 40 (3): 547-558.  DOI:10.7522/j.issn.1000-0534.2020.00066
• Abstract ( ) HTML ( ) PDF (7375KB) ( )
• The ground-based observational dataset is applied to evaluate the performance of 5 GCMs from the Coupled Model Intercomparison Project Phase 6 （CMIP6） in the Upper Yellow River Basin during 1995 -2014.And then， precipitation trends in the near term （2021 -2040）， mid-term （2041 -2060）， and long term （2081 -2100） under 7 SSP-RCP scenarios are projected， respectively.The results show that： （1） Multi-model ensemble mean can capture the inner-annual distribution of precipitation in the Upper Yellow River Basin， and the characteristic of more precipitation in the South and less precipitation in the north can also be captured.The spatial correlation coefficient between the simulated data and the observed data is above 0.9.That is to say， the spatial-temporal characteristics of precipitation in the Upper Yellow River Basin can be simulated satisfactorily by an ensemble mean of 5 GCMs.（2） In the 21^st century， annual precipitation in the Upper Yellow River Basin will demonstrate a significant increase tendency with obvious inter-decadal fluctuations.Relative to the baseline period 1995 -2004， the ascended annual precipitation will be faster in the near-term and then slow down in the 21^st century under SSP1-1.9 and SSP1-2.6 scenarios.Annual precipitation will rise continuously from near term to the end of 21^st under SSP2-4.5， SSP3-7.0， and SSP5-8.5 scenarios.Under SSP4-3.4 and SSP4-6.0 scenarios， annual precipitation will decrease slightly in the near term， but a turning point is detected in the mid-term， and precipitation will increase afterward.Spatially， the largest increase will be in the areas where precipitation is relatively small， including the headstream region above Huangheyan station and the region between Lanzhou and Toudaoguai.（3） Seasonal precipitation in the 21^st century in the Upper Yellow River Basin will show an overall rising trend with fluctuation， and the growth rate varies with scenarios and seasons.Except for the SSP4-6.0 scenario， precipitation trend under high radiation forcing scenarios will be greater than that of low radiation forcing scenarios.The growth rate is the largest for winter precipitation， while the growth rate is the smallest for summer precipitation， both passing the 0.1 significance level.Spatially， the highest growth of spring and autumn precipitation is projected in the headstream region above Huangheyan station and the region between Lanzhou and Toudaoguai.While the smallest growth of spring and autumn precipitation will be in the region between Huangheyan and Lanzhou.The area with the highest increase of winter precipitation is projected in the region between Lanzhou and Toudaoguai， and the smallest increase in the region between Huangheyan and Lanzhou.Summer precipitation will decrease in most of the Upper Yellow River Basin under SSP4-3.4 and SSP4-6.0 scenarios， but it will increase in most of the Basin with the highest growth in the headstream region above Huangheyan under all other scenarios.

• Tracking Diagnosis Analysis of Grid Precipitation Forecast based on Time-Domain Object
• Hongfang ZHANG;Liujie PAN;Shan LU;Xiaoxuan JU;Yueqin SHI
• 2021 Vol. 40 (3): 559-568.  DOI:10.7522/j.issn.1000-0534.2020.00021
• Abstract ( ) HTML ( ) PDF (7190KB) ( )
• Understanding the time and position deviation of model precipitation forecast is very important to improve the forecast accuracy， but the traditional point-to-point verify methodscan not do anything about it.Based on the precipitation forecast data of the European Center for Medium-Range Weather Forecasts （ECMWF） from June to August of 2018 and 2019， the object-based diagnostic evaluation （MODE） and time domain diagnostic analysis methods （MTD） are used to evaluate the life cycle， initial occurrence and dissipation of the model precipitation forecast objects.The main results are as follows： （1） Case analysis shows that MTD can easily extract three-dimensional precipitation objects， thereby objectively describing the start and end time of the objects， and has unique advantages in evaluating the time deviation of precipitation objects.（2） Under the low threshold， the model forecast describes the spatial distribution of precipitation objects well， but the number of objects is less than that of observations.As the precipitation threshold increases， the frequency of forecasting and observing precipitation objects shows a significant difference， indicating that the location of heavy precipitationforecast still needs to be improved.（3） The precipitation objects are defined with the minimum convolution radius and precipitation threshold， 80% of the precipitation objects last less than 15 hours， and the objects life cycle decrease with the increase of the precipitation threshold and the convolution radius.（4） Compared with observations， the duration of 3D precipitation forecast objects is shorter and the moving speed is slower.

• Simulation Analysis of Evolution Characteristics of the Convective System during a Hail Storm Course
• Haiying WU;Mingjian ZENG;Yifang JIANG;Haixia MEI;Bing ZHANG
• 2021 Vol. 40 (3): 569-579.  DOI:10.7522/j.issn.1000-0534.2020.00016
• Abstract ( ) HTML ( ) PDF (9645KB) ( )
• The high resolution numerical model WRF is used to simulate the hail weather occurring over Jiangsu and Anhui provinces on 28 April 2015 under the background of cold vortex.Combined with simulation data and observation data such as surface dense automatic station and Doppler weather radar， the evolution characteristics of the convective system structure and the possible mechanism affecting its organization and development are studied.The results show that the development， propagating and organization of the convective system causing hails is associated with the mesoscale gravity wave， which is triggered during the development of initial convection near the mesoscale low pressure.Then gravity waves motivate and organize a row of wavelike convective stormss during propagating in the conditional instability and strong vertical wind shear environment.The dynamic structure of the convective storms train is highly organized with updraft and downdraft flows arranged alternately.Each storm is accompanied by strong updraft， and the downdraft behind the storm reaches the ground and form a secondary circulation on both sides of the front and back of the low level of the storm， then the belt of wavelike convective storms are well-organized.Convective storms and gravity wave promote and develop mutually by means of wave-CISK mechanism， thus lead to the sequence of hail occurring in the north of Jiangsu and Anhui provinces.With the further development of stratification instability， the propagation environment of gravity wave is no longer suitable， and the development of convective storm train is unbalanced.The storm cell at the front of the wave train is strengthened， while the storm at the back is weakened， and the wavelike structure is gradually changed.

• Analysis on the Evolution Characteristics of Storm Parameters and Z_DR Column for Two Long Life Supercells
• Xiuguang DIAO;Chuanfeng YANG;Qian ZHANG;Qingli Lü
• 2021 Vol. 40 (3): 580-589.  DOI:10.7522/j.issn.1000-0534.2020.00034
• Abstract ( ) HTML ( ) PDF (6793KB) ( )
• Based on the S-band dual-polarization Doppler weather radar data of Jinan， combined with sounding and ground data， the evolution characteristics of storm parameters and Z_DR column of two long-lived supercells are analyzed.The results show that the two processes have strong thermodynamic instability， medium or above intensity of CAPE and vertical wind shear from 0 to 6 km， which is conducive to the generation and maintenance of highly organized storms.The two supercell storms lasted for more than 4 hours， and the high reflectivity factor （≥60 dBZ） maintained for more than 3 hours， the average DBZM value was 65.8 dBZ， at the same time， both supercell storms had large C-VIL.The moving direction of the two strong storms is basically the same， but the difference of moving speed is obvious.The main factor leading to the difference of moving speed is the difference of guiding airflow of 500 hPa.The Z_DR column is the Z_DR high value area above the environmental 0 ℃ level and located in the strong updraft zone of the storm， indicating a small number of large oblate raindrops and a few horizontally oriented wet ice particles.The existence of mixed phase particles in Z_DR column leads to low CC.The storm developed rapidly after the appearance of Z_DR column and weakened gradually after the disappearance of Z_DR column.Z_DR column can be used as one of the early warning of hail.The appearance of Z_DR column indicates that the strength and height of the updraft in the storm increase， which indicates that the storm will develop rapidly.The disappearance of Z_DR column indicates that the intensity and the height of updraft in the storm will decrease， and indicates that the centroid of the storm will be reduced and the intensity of the storm will be weakened.The top of the Z_DR column of the two storms is obviously different， but there is no significant difference between the top of the Z_DR column and the height of 0 ℃ layer.

• Study on the Climatic and Discriminative Characteristics of Tropospheric and Lower Stratospheric Gravity Wave of Taiyuan
• Huhua CHENG;Liang ZHAO;Shuai WU;Juan LI;Qifa CAI
• 2021 Vol. 40 (3): 590-602.  DOI:10.7522/j.issn.1000-0534.2020.00042
• Abstract ( ) HTML ( ) PDF (2998KB) ( )
• Atmospheric gravity waves have a significant effect on the dynamic and thermal structure of the global atmosphere.Studying the climatic characteristic of gravity wave parameters constitute an important part of the parameterization of gravity waves in the development of a global atmospheric model.By introducing the effect of gravity waves are conducive to improve the forecasting ability of the atmospheric model.In this paper， based on the high-vertical resolution sounding data of Taiyuan （112.55°E， 37.78°N） from 2014 to 2017， a study is conducted on the climatic characteristics of the atmospheric gravity wave parameters of the troposphere （2~9 km） and lower stratosphere （17~24 km） and their differences in between.The results show that： （1） From January to December， compared with the troposphere， the average gravity wave horizontal wavelength， period， horizontal phase velocity and fraction of upgoing energy are larger in the lower stratosphere， the gravity wave vertical wavelength is smaller； moreover， gravity wave ground-based horizontal group velocity in lower stratosphere is higher in February and from May to September and lower in other months； （2） Gravity wave parameters in the troposphere and lower stratosphere show larger deviation and absolute difference， and weak correlation； （3） Gravity wave parameters in the troposphere and lower stratosphere and their deviation in between show significant difference in their occupancy distribution within different ranges.By studying the climatic characteristics of gravity wave parameters in the troposphere and lower stratosphere over Taiyuan， and characteristics of their differences are further supplemented the climatic characteristics of atmospheric gravity wave parameters in China； it is beneficial to the development of a parameterization scheme that is more suitable for the Chinese regional numerical prediction model.

• Analysis of the Characteristics and Atmospheric Circulation Causes of Two Types of Extreme Cold Events in Winter in China
• Mingxin LIU;Yan LI;Chunyan Lü
• 2021 Vol. 40 (3): 603-620.  DOI:10.7522/j.issn.1000-0534.2020.00093
• Abstract ( ) HTML ( ) PDF (8183KB) ( )
• There has been an increase of extreme cold events in China for the past few years， with distinctly different characteristics and causes of formation.The extreme cold events are classified into two types， i.e.the extensive and persistent extreme cold events （EPECE） and the cold wave events （CWE）.The results show that the average duration of CWE is 3~5 days.During the process， while the temperature drops rapidly， it also rises quickly.The precipitation occurs in the early stage of the process.In contrast， EPECE lasts for more than 15 days on average， with a more drastical temperature drop and a wider temperature reduction range.The precipitation mainly occurs in the later stages of the process.With further analysis of the cause of atmospheric circulation， the anomalies of tropospheric system appear at 11days prior to （-11） the event， indicating wave anomalies are transmited to the stratosphere in the EPECE.It makes the center of stratospheric polar vortex to be further east.The energy is transmitted down to the troposphere with the anticyclonic Rossby wave breaking（AWB） which extends eastward at -9 days.The blocking high abnormally extends eastward to 90°E.The maximum blocking intensity exceeds 24， and the maximum blocking frequency exceeds 50% of the climatology.The intensity of Siberian high pressure increases to 1053 hPa.The above abnormalities maintain until 7 （+7） days after the occurrence of the event.As a result， when the cold air breaks out， the temperature is drastically reduced with a longer duration.By comparison， there are no such premature precursor signals in CWE.Accompanied by AWB at day 0， the center of the stratospheric polar vortex is near the pole at -3 days.The maximum blocking intensity exceeds 20， and the maximum blocking frequency exceeds 45% of the climatology.But the blocking limited to 60°E around Ural Mountain area.The maximum intensity of the Siberian high reaches 1050 hPa.+3 days later， the anomalies of the circulation systems almost disappeared.Therefore， in the CWE， the temperature drop is also intense， but the duration is shorter compared with that in the EPECE.

• Impact of Soil Texture on the Simulation of CLDAS/Noah-MP on Simulating Soil Moisture
• Lei LI;Runping SHEN;Anqi HUANG;Ting GAO;Chunxiang SHI
• 2021 Vol. 40 (3): 621-631.  DOI:10.7522/j.issn.1000-0534.2020.00082
• Abstract ( ) HTML ( ) PDF (6931KB) ( )
• Soil moisture is a key physical quantity in the land-atmosphere interaction， and also an important parameter in the research of land surface model simulation.However， it is very difficult to obtain the spatiotemporal continuous data in high resolution.Land surface models （LSMs） can simulate the multilayer soil moisture with high spatial and temporal resolution， the community Noah land surface model with multiparameterization options （Noah-MP） has been proved to be a good model for simulating soil moisture in China， but the accuracy needs to be further improved.Soil texture data is an important input data of Noah-MP， and its quality affects the accuracy and reliability of simulation results， it is of great significance to study the effect of soil texture on Noah-MP on simulating soil moisture.Here， we used two different soil texture data to study the effect of soil texture on simulation of Noah-MP LSM driven by CLDAS-V2.0.The results showed that there was a significant difference between the simulated daily mean of soil moisture by the soil texture data from the Second Soil survey of China （SNSS） and the mode inherent soil texture data （FAO） in 2014.The difference of the 0~10 cm depth simulation was greater than 10% in 23.2% areas and 1% in 74.9% areas.For 10~40 cm depth， they were 20.8% and 69.8% respectively.From the analysis of time series， the simulation results of the two group tests of SNSS and FAO can basically reflect the law of soil moisture changing with time.According to the daily results of correlation coefficient， bias and RMSE analysis between simulation and observation， the simulation results of SNSS at 0~10 cm depth were better than those of FAO in almost every day， but in 10~40 cm depth， the simulation results simulated by SNSS are obviously underestimated than the observations.From the analysis of spatial distribution， the soil moisture simulation results of CLDAS/Noah-MP showed that there were many areas with negative deviation from the observed values， especially the depth of 10~40cm， and most of the simulated values were underestimated.Compared with FAO， simulation results simulated by SNSS in the southeast and southwest region at 0~10 cm depth and 10~40 cm depth were improved.The simulation simulated by SNSS at 0~10 cm depth was better than that by FAO in northeast China， but there was little difference between them at 10~40 cm depth.This study provides a scientific basis for the study and application of soil parameter data in CLDAS/Noah-MP.

• The Response of Stomatal Conductance of Three Typical Shrubs to Environmental Change and Stomatal Regulation of Transpiration in an Arid Desert-oasis Ecotone
• Fei GUO;Xibin JI;Bowen JIN;Liwen ZHAO;Wenyue ZHAO;D
• 2021 Vol. 40 (3): 632-643.  DOI:10.7522/j.issn.1000-0534.2021.00011
• Abstract ( ) HTML ( ) PDF (2899KB) ( )
• LI-6400XT Portable Photosynthesis System and Model 1505 Pressure Chamber were used to measure the water vapor exchange process and leaf water potential （Ψ） changes of three dominant shrub species （i.e.， C₄ plant Haloxylon ammodendron， Calligonum mongolicum and C₃ plant Nitraria sphaerocarpa） growing in a desert-oasis ecotone of the central Hexi Corridor.The changes of water transfer factors prior to and following rainfall events during the growing season were compared， the responses of stomatal conductance to main environmental factors and leaf water potential were quantified respectively.The regulation mechanism of stomatal conductance on transpiration of desert shrubs was also analyzed.The results showed that the main factors affecting stomatal conductance of three shrubs were vapor pressure deficit （VPD）， air temperature （T） and Ψ in turn： stomatal conductance decreased with the increasing VPD and T and decreased with the decrease in Ψ.The integrated responses of stomatal conductance of these three desert plants to environmental factors and leaf water potential showed that C₃ plant Nitraria sphaerocarpa was more sensitive to these factors than C₄ plant Haloxylon ammodendron and Calligonum mongolicum.By analogy to Ohm’s law， the product of stomatal conductance and VPD can be used to properly simulate the transpiration rate with a linear relationship.

• Evaluation and Bias Correction on the Subseasonal Forecast of Summer Precipitation over Southwestern China Forecasted by the Beijing Climate Center Sub-seasonal to Seasonal Predication System
• Qu GUO;Anning HUANG;Zhipeng FU;Hongyu TANG;Yonghua LI;Huigeng HE
• 2021 Vol. 40 (3): 644-655.  DOI:10.7522/j.issn.1000-0534.2020.00028
• Abstract ( ) HTML ( ) PDF (13519KB) ( )
• The capability of the Beijing Climate Center （BCC） sub-seasonal to seasonal （S2S） prediction system in forecasting the summer precipitation in Southwestern China has been evaluated based on the 20-year （1994 -2013） hindcast data.Meanwhile， the singular value decomposition （SVD） bias correction scheme was subsequently adopted to improve the forecast skill of the BCC S2S prediction system.The results show that the skill of BCC S2S prediction system in forecasting the summer precipitation over Southwestern China was decreases continuously with the early forecast lead time.It shows certain forecasting skills within 10 days ahead of the starting time， but basically has no skills exceeding 10 days ahead of the starting time.In addition， the forecast skill exhibits obvious regional and inter-annual differences.The sub-seasonal prediction skill of the summer precipitation in Southwestern China could be well improved by adopting the SVD bias correction scheme.The abnormal correlation coefficients between the original prediction results and observations are 0.50， 0.31 and 0.25 with the forecast lead time of 0~10， 11~20， 21~30 days， which are increased to 0.70， 0.75 and 0.70 after the correction， respectively.Moreover， in comparison with the spatial correlation coefficient （SCC） between the bias original prediction results and observations， the SCC between the bias corrected prediction results and observations is increased by about 0.3 at the forecast lead time of 0~10 days， especially for the prediction results with the forecast lead time of 11~30 days， the spatial correlation coefficient for the bias corrected results is significantly increased by 0.6 compared to the original results.

• Study of Sensitivity Simulation of Planetary Boundary Layer Parameterization Schemes in Beijing
• Tian LIANG;Liang CHEN;Jianjun HE;Lei ZHANG;Shanling GONG;Huizheng CHE
• 2021 Vol. 40 (3): 656-670.  DOI:10.7522/j.issn.1000-0534.2020.0095
• Abstract ( ) HTML ( ) PDF (11187KB) ( )
• In order to study the characteristic of planetary boundary layer structure and near surface meteorological elements in Beijing， the Weather Research and Forecasting Model （WRF） is used to simulate the boundary layer meteorological field in Beijing during clear days.The simulation differences of the four sets of planetary boundary layer parameterization schemes （YSU， ACM2， MYJ， BL） on radiation， surface energy budget， meteorological elements and planetary boundary layer structure are studied through sensitivity tests.Then， the measured data of observation stations， including 2 m-temperature， 2 m-specific humidity and 10 m-windspeed， the sounding data and the observed data of 325 m meteorological tower are used to compare with the simulated data.The study is divided into four parts.The first part is the introduction.The second part mainly introduces the research area， data and methods.The third part analyzes the research results comparing the WRF model simulation results with the actual observation data and evaluates the simulation results.Then the fourth part is about the result and discussion.The results indicate that： All schemes can accurately simulate the downward shortwave radiation， and the abilities to simulate the longwave radiation are similar.MYJ scheme has the best simulation effect for 2 m-temperature， YSU scheme performs the best in 2 m-specific humidity and 10 m-wind speed， in general， YSU scheme is superior in simulating surface meteorological elements.However， all the experiments simulation results of 2 m-temperature at night are higher than the observed temperature， which may be caused by the model's insufficient consideration of the urban surface and the particularity of the urban boundary layer.And the further research will be focused on this aspect.In addition， the temperature profiles which simulated by four PBL schemes are colder than the observation， the specific humidity profiles are higher and the wind speed profiles are lower.In order to analyze the vertical structure of the planetary boundary layer more precisely， the observation data of the 325 m meteorological tower is used as supplement.The result shows that the four experiments could accurately reflect the temperature vertical profile and the relative humidity result simulated by YSU scheme above 15 m is the closest to the observed value in the daytime.YSU scheme has the highest planetary boundary layer height （PBLH）， and the non-local schemes show higher PBLH than the local schemes， moreover， the result of the PBLH simulated by MYJ scheme is not satisfactory.This study further deepens the understanding of planetary boundary layer in Beijing， which provides theoretical basis for further study of urban canopy layer and urban environment.

• Analysis on the Relationship between Black Carbon Concentration and Meteorological Factors in Xingtai City
• Jufei HAO;Yunling YANG;Erjie LI;Zhijie WU
• 2021 Vol. 40 (3): 671-679.  DOI:10.7522/j.issn.1000-0534.2020.00049
• Abstract ( ) HTML ( ) PDF (3721KB) ( )
• Based on the monitoring data of black carbon （BC） concentration by EA-12 type and the meteorological observation data in Xingtai city from January to December 2019， analyzed the characteristics， sources and relationship between BC pollution and meteorological factors， The results showed that： The daily average concentration of BC was 0.85 μg·m^-3 in Xingtai， the concentration frequency of 79.80% in the whole year was concentrated in the range of 0.30~1.20 μg·m^-3； but in January， the concentration frequency of 90.62% was concentrated in the range of 1.05~5.05 μg·m^-3， the serious BC pollution in January has contributed significantly to the deterioration of air quality throughout the year.When the wind speed was more than 8 m·s^-1， there was a transportation in the north direction， and when the wind speed was less than 8 m·s^-1， there was a transportation in the direction of west and south； Precipitation and precipitation duration were equally important to the wet removal of BC， The BC pollution in Xingtai city was mainly affected by local and local sources of coal-fired and motor vehicle emissions， when the atmospheric inverse temperature was less than 200 m， the concentration of BC will increase obviously due to the decrease of diffusion capacity and the accumulation effect.

• Sand and Dust Monitoring Using FY-4A Satellite Data based on the Random Forests and Convolutional Neural Networks
• Hong JIANG;Qing HE;Xiaoqing ZENG;Ye TANG;Keming ZHAO;Xinying DOU
• 2021 Vol. 40 (3): 680-689.  DOI:10.7522/j.issn.1000-0534.2020.00060
• Abstract ( ) HTML ( ) PDF (6249KB) ( )
• Sand and dust is a typical weather disaster which outbreaks in arid and semi-arid areas globally.This natural phenomenon， which is the result of stormy winds， raises a lot of dust from desert surfaces and decreases visibility to less than 1 km.The dust aerosol generated from dust storm dominates the aerosol loading in the troposphere and has comprehensive impacts on the global environment， weather， climate and ecology.Monitoring sand and dust from space using satellite remote sensing has become one of the most important issues in this field.However， sand and dust is difficult to accurately characterize by using single-band and linear models.Feng Yun-4A （FY-4A） imagery provides a good data source for timely and accurate monitoring of sand and dust.The machine learning models are important tools in sand and dust monitoring and forecasting.In this paper， the Normalized Difference Dust Index （NDDI）， Random Forests （RF） and Convolutional Neural Networks （CNN） were employed to monitor sand and dust based on the Advanced Geostationary Radiation Imager （AGRI） of geostationary FY-4A meteorological satellite in the Tarim Basin.The results showed that， sand and dust can be identified by NDDI_AGRI thresholds calculated using AGRI data.The determination of the NDDI_AGRI thresholds were obtained through statistical analysis of pixels， but it is necessary to take different thresholds for different times AGRI data.There are some identification errors in the cross region of cloud and land， and some vegetation coverage and desert by the NDDI_AGRI thresholds.The values of Precision， Recall， and F1-score of testing samples were all 100%； and the accuracy of cross validation of training samples was 99.5% for the sand and dust model of RF.The Loss and Accuracy in the estimation obtained using the CNN algorithm were about 0.1% and 99.9%， respectively， versus the training samples and testing samples.Both RF and CNN models have the ability and robustness to be used in sand and dust monitoring.The efficiency of two models had been checked using new dust events.Results show that the CNN algorithm preforms better than RF algorithm in identifying the junction of dust and non-dust.The RF and CNN algorithm have identification errors in some parts of sand and dust monitoring process， such as the mixed area of dust and clouds， and the Gobi area.The research results of this paper provide an important basis application of machine learning combined with FY-4A meteorological satellite data to monitor sand and dust operational.

• Eco-hydrological Effects of Photovoltaic Power Generation Facilities on Dryland Ecosystems： A Review
• Chu;ong WU;Zebing SU;Hu LIU;Wenzhi ZHAO
• 2021 Vol. 40 (3): 690-701.  DOI:10.7522/j.issn.1000-0534.2020.00065
• Abstract ( ) HTML ( ) PDF (1561KB) ( )
• Arid and semi-arid regions are characterized by low annual rainfall and high solar radiation， which， together with plentiful land supplies and clear sky conditions， result in an ideal area for developing photovoltaic industry.However， both the construction and operation processes of photovoltaic facilities may put substantial influences on the fragile dryland ecosystems by changing the spatial pattern of local environmental variables （e.g.， radiation and rainfall）.This paper reviewed those potential impacts of photovoltaic facilities on the dryland ecosystems from the perspectives of local microclimate， eco-hydrological processes， regional ecological pattern， and energy conservation and emissions reduction， and summarized the related research progresses in understanding the eco-environmental effects of photovoltaic generation systems on the local and regional environments during past decades.It was pointed out that the microclimate， soil temperature and humidity between photovoltaic arrays could be improved by photovoltaic facilities in dryland ecosystems， which in turn， may increase the local vegetation coverage and carbon sequestration potential.However， photovoltaic generation systems are also likely to negatively impact the local environments， e.g.， destroying animal habitats， limiting their food availability， lowering the regional biodiversity and even threating dryland ecosystem stability.The review indicates that ongoing and future researches should be oriented towards the multi-scale temporal-spatial understanding of the influence of widely-deployed photovoltaic system on dryland ecosystems， through extending the observation scales， and improve the modeling capabilities.Special focus should be put on the development of mechanism-based models for the ecohydrology of dryland environments affected by photovoltaic facilities， and the development of "cross-border integrated" photovoltaic system protocols.

• The Impact of Photovoltaic Power Plants on Ecological Environment and Climate： A Literature Review
• Peidu LI;Xiaoqing GAO
• 2021 Vol. 40 (3): 702-710.  DOI:10.7522/j.issn.1000-0534.2020.00020
• Abstract ( ) HTML ( ) PDF (1869KB) ( )
• Solar energy plays an essential role in mitigating fossil fuels shortage and resolving， environmental issues caused by burning fossil fuel， and global warming.Resources such as oil， natural gas and coal are diminishing day by day.Tradition energy consumption causes environment problem.Renewable energy has become an inevitable road and extensive consensus for the international community to respond to climate change.As a clean renewable energy， solar energy is gradually becoming an important alternative energy.Thus， the photovoltaic industry witnesses a rapid global growth.However， the deployment of photovoltaic modules on a large scale has also caused certain influence on the ecological environment and climate.The author summarized the impacts of photovoltaic power plants on the ecological environment and climate developed globally， nationally and locally， analyzed and discussed the feedback effect of photovoltaic power plants construction on the environment at different scale.The research results show that there is no consistent conclusion on the feedback effect of building photovoltaic power plants.The major mechanism is that the decrease of solar radiation on the surface causing by shielding effect of photovoltaic modules and the absorption and conversion of solar radiation， which then affects the surrounding environment， and causes the change of ecological environment and climate.The physical mechanism appears complex.And the research to the impact of photovoltaic power plant on the ecological environment and climate in China is still in the elementary stage.Therefore， the mechanism needs further research.