Plateau Meteorology

Current Issue

28 October 2017, Volume 36 Issue 5   
  • Progresses in Variability of Snow Cover over the Qinghai-Tibetan Plateau and Its Impact on Water Resources in China
  • WANG Shunjiu
  • 2017 Vol. 36 (5): 1153-1164.  DOI:10.7522/j.issn.1000-0534.2016.00117
  • Abstract ( ) HTML PDF (1669KB) ( )
  • The major advances in the researches on the variability of snow cover over the Qinghai-Tibetan Plateau (QTP) and its impact on water resources in China are summarized.Some existing problems in the related studies and the researches needing further investigation are also discussed.The distribution of the snow cover over the QTP is far from uniformity.In the peripheral high mountains snow cover distributes extensively and has a long duration, but in the vast interior it is rare or even thin.The snow cover region in the east of QTP is the most significant region of the interannual variation of snow cover on the QTP, and dominates the interannual variation of snow cover in the whole plateau.So the snow anomalies over the eastern QTP should be paid more attention.The snow cover on the QTP increased from 1960s to 1990s, and its extent slowly increased in summer and autumn but decreased in winter and spring in the early 21st century.The research progresses on the impact of snow cover over the QTP on water resources are focused on precipitation and drought-flood.The abnormal snow cover over the QTP can affect the atmospheric circulation and Asian summer monsoon precipitation in terms of changing ground surface albedo, temperature and thermal conditions.The impact of abnormal snow cover over the QTP on precipitation is high consequence and wide areas.The abnormality of snow cover over the QTP has certain influences on droughts and floods of China.The snow cover abnormality could be applied in drought and flood forecast, too.
  • Advances and Perspectives in Precipitation Research for Himalayan Mountains
  • OUYANG Lin;YANG Kun;QIN Jun;WANG Yan;LU Hui
  • 2017 Vol. 36 (5): 1165-1175.  DOI:10.7522/j.issn.1000-0534.2016.00111
  • Abstract ( ) HTML PDF (4556KB) ( )
  • Exploring the spatiotemporal variability of precipitation is very important to the understanding of climate, hydrology and glacier processes in Himalaya.With the emergence of the "Third Pole Environment (TPE)" international program that is initiated by Chinese scientists, it is urgent to understand the processes and drivers of precipitation around the region.This study reviews the research progresses of precipitation in Himalayan region, based on which we put forward frontier issues of hydro-meteorological studies for this region.Previous progresses are summarized as follows:(1) Precipitation in Himalaya has distinct diurnal variation, with a nocturnal peak at night in low-elevation zone, which is related to Plateau-scale wind convergence/divergence and mountain-valley scale asymmetric diurnal variation of wind field during South Asian monsoon.(2) Precipitation in summer usually dominates the annual precipitation amount, but in northwest high elevation regions spring and winter precipitation may account for 50% of annual precipitation.(3) In south slope of Himalaya, precipitation amount increases with the increase of elevation up to 2500 m (above sea level), and then decreases toward higher elevations.(4) Regional climate modeling shows reasonable applicability in Less Himalaya, but there is, lack of valid precipitation assessments for ultra-high-elevation regions.So we propose research priorities in future to enhance observing network for high-elevation regions, evaluate satellite-based global precipitation measurements, analyze the difference of climate between south and north slopes, and to improve the skill of regional climate models in the complex mountain region.
  • Probability Distribution for the Summer Extreme Precipitation in the Qinghai-Tibetan Plateau
  • CAO Yu;YOU Qinglong;MA Qianrong;MENG Xianhong
  • 2017 Vol. 36 (5): 1176-1187.  DOI:10.7522/j.issn.1000-0534.2016.00131
  • Abstract ( ) HTML PDF (12838KB) ( )
  • Based on the homogenous historical precipitation dataset in the eastern and central Qinghai-Tibetan Plateau (QTP), the two-parameter and three-parameter Weibull distribution, generalized extreme value distribution, Pearson type-Ⅲ distribution and log-logistic distribution selected to fit the summer extreme precipitation indices to study the characteristics of the probability distribution of summer extreme precipitation indices over the QTP during 1961-2014.The results are showed as follows:The distribution of extreme precipitation decreased gradually from southeast to northwest of the eastern and central QTP, with a maximum center located in the southeast of Sichuan province, and the Rikeze station at southeast of Tibet Autonomous Region was the other max value center, while the minimum center was seated at the northwest of Qinghai province.Through the fitting of extreme precipitation indices by the extremum probability function, we found that different probability functions are fitted for different indices, and which probability function to choose is depends on the comparison of a variety probability function models combined with the actual physical sense.Then, Gumbel distribution was used to calculate different return levels of summer extreme precipitation indices, and it had the same spatial distribution of the 50 a and 100 a return levels that the precipitation was more at southeast and less at northwest of the region.After testing by moving t-test, R95 and R99 average value abruptly changed at the year 2006, and the extreme precipitation increased after 2006 according to the return level values of Gumbel probability distribution for summer extreme precipitation indices.
  • Characteristics of the Precipitation Diurnal Variation over Qinghai-Tibetan Plateau in Summer
  • JI Xiaolong;WU Haomin;HUANG Anning;ZHAO Wei;WU Yang
  • 2017 Vol. 36 (5): 1188-1200.  DOI:10.7522/j.issn.1000-0534.2016.00119
  • Abstract ( ) HTML PDF (22139KB) ( )
  • Based on the hourly emerged precipitation product with the horizontal resolution of 0.1° over China from 2008 to 2014 which was derived from the hourly precipitation observed by automatic weather stations (AWS) in China and retrieved from CMORPH satellite data, the characteristics of precipitation diurnal variations over Qinghai-Tibetan Plateau in summer had been studied.The impact of the precipitation with different duration and categories on the diurnal cycle of precipitation amount was also further revealed.Results show that the diurnal cycles of precipitation amount and frequency over the entire Qinghai-Tibetan Plateau exhibit two diurnal peaks with one in late afternoon and the other in early morning.However, the diurnal variation of the precipitation intensity shows an early morning maximum and a weaker peak at midnight.Further analysis shows that the precipitation diurnal variations over western-central Qinghai-Tibetan Plateau resemble that over the entire Qinghai-Tibetan Plateau, however, the diurnal variation of the precipitation amount and frequency over northern (eastern) Qinghai-Tibetan Plateau shows a late afternoon (midnight-early morning) maximum.In addition, the duration time of precipitation plays an important role in the diurnal cycle of precipitation amount.Diurnal variation of the summer precipitation amount over Qinghai-Tibetan Plateau showing two obvious peaks is resulted from the precipitation with both short (1~3 hours) and long (over 6 hours) duration time.The midnight-early morning (late afternoon) diurnal peak of the summer precipitation is attributed to the precipitation with long (short) duration time.Furthermore, the diurnal peak of the light to heavy (torrential) precipitation over northern Qinghai-Tibetan Plateau occurs in the afternoon (midnight).The diurnal variation of the precipitation for different categories consistently shows two peaks (one occurs in late afternoon, the other appears in midnight to early morning).Meanwhile, the diurnal variations of precipitation for different precipitation categories over eastern Qinghai-Tibetan Plateau show very similar features with a midnight-early morning maximum.
  • Characteristics of Different Patterns of South Asia High and Their Relationships with Summer Precipitation in Xinjiang
  • WANG Qian;ZHAO Yong;CHEN Fei;YANG Qing;HUANG Anning
  • 2017 Vol. 36 (5): 1209-1220.  DOI:10.7522/j.issn.1000-0534.2016.00123
  • Abstract ( ) HTML PDF (19142KB) ( )
  • By using the ERA-Interim reanalysis data and precipitation data which was provided by 88 observation stations in Xinjiang, the relationships between the characteristics of different patterns of South Asia High and the summer precipitation (July and August) in Xinjiang during 1979-2013 were analyzed.The results showed that except Iran high pattern and Qinghai-Tibetan high pattern, the South Asia High could also be divided into Two centers pattern and Multiple centers pattern.The precipitation of Iran high pattern and Two centers pattern accounted for 70%~90% of summer total precipitation in Xinjiang, while the precipitation of Qinghai-Tibetan high pattern accounted for 10%~30% of summer total precipitation.Iran high pattern, Qinghai-Tibetan high pattern and Two centers pattern have different characteristics, and different patterns of South Asia High have different effects on the summer precipitation in Xinjiang.The precipitation of Iran high pattern increased in most parts of northern and eastern Xinjiang and decreased in the Tarim Basin in Xinjang compared to the averaged summer precipitation.Qinghai-Tibetan high pattern had the opposite precipitation distribution compared with the precipitation distribution of Iran high pattern.The precipitation of Qinghai-Tibetan high pattern decreased in most parts of Xinjiang except in southwestern parts of the Tarim Basin compared to the averaged summer precipitation.Two centers pattern had the largest impact on summer precipitation in the Tarim Basin.The precipitation of two centers pattern increased in the Tarim Basin compared to the averaged summer precipitation while the precipitation of Iran high pattern and Qinghai-Tibetan high pattern decreased in Tarim Basin.Based on the method of composite analysis, the results indicated that the changes of two centers positions of South Asia High had different impacts on circulation and moisture transport.Due to the different characteristics of circulation and moisture transport, the distributions of summer precipitation in the Tarim Basin were relatively different.The precipitation in central and western parts of the Tarim Basin increased compared to the averaged summer precipitation when two centers of South Asia High were both on the west of the averaged longitude, and the water vapor came into the Tarim Basin in Xinjiang from low latitudes by a two-step process.The precipitation in the whole Tarim Basin increased compared to the averaged summer precipitation when two centers of South Asia High were both on the north of the averaged latitude, and the water vapor came into the Tarim Basin along the east side of Qinghai-Tibetan Plateau.
  • Differentiation Characteristic of the Annual Precipitation Pulse in Kerqin Sandy Land Region
  • MENG Qinglan;ZHAO He;GAO Junkai;LU Xiaoqian;LIU Liangxu;CHANG Xueli
  • 2017 Vol. 36 (5): 1234-1244.  DOI:10.7522/j.issn.1000-0534.2016.00114
  • Abstract ( ) HTML PDF (4361KB) ( )
  • Annual precipitation pulse is one of the principal factors in climatic change research.It is not only an important indicator of that, but also a dominant factor for vegetation production prediction.In order to realize the recognition of the annual precipitation pulse characteristics, the research focused on the Morlet wavelet analysis method to analyze the temporal and spatial change based on eighteen meteorological station data during past decades in Kerqin sandy land region.The results showed that the annual precipitation were 337.4±76 mm, 369.2±73.2 mm, 422.6±68.8 mm and 483.4±97.1 mm in Ⅰ, Ⅱ, Ⅲ and Ⅳ sub-area during study period, respectively.The characteristics were gradually decreased from the southeast (Ⅳ sub-area) to the northwest (Ⅰ sub-area) in spatial scale and the complexity enhanced in temporal scale.On the aspects of interdecadal mean precipitation, the Ⅰ sub-area had the maximum percentage as 12.95% when the precipitation increased and the minimum percentage as -19.26% when the precipitation decreased.In addition, the Morlet wavelet analysis showed that there were double significant milt-temporal changing periods of 5~11 years and 23~32 years, and oscillation period was weak gradually in the above mentioned spatial scale and the periodic duration was gradually decreased simultaneously.However, the periodic intensity was more in 23~32 years than in 5~11 years and the most modulus value emerged in 26~32 years among 23~32 period, which indicated the precipitation periodic changed most significantly in this period.There were rest temporal scale periods too, but had less periodic change.Due to sub-area's wavelet variance results, we also indicated that Ⅰ, Ⅱ and Ⅲ sub-area had same dominant period at 10~11 year cycle and Ⅳ sub-area emerged at 25 years.So, it could be concluded that the regional precipitation fluctuation characteristics had same regime when annual precipitation is less than 450 mm and the regime was significantly different when the annual precipitation is more than 450 mm.According to the period oscillation change trait of the annual precipitation, we also predicted that the precipitation could be less than normal from 2016 to 2020 in Kerqin sandy land region.
  • An Ensemble Sensitivity Analysis of a Heavy Rainfall over Sichuan Basin under Interaction between Plateau Vortex and Southwest Vortex
  • WANG Yi;HE Lifu;DAI Kan;GUO Yunqian
  • 2017 Vol. 36 (5): 1245-1256.  DOI:10.7522/j.issn.1000-0534.2016.00102
  • Abstract ( ) HTML PDF (6169KB) ( )
  • Based on the ECMWF ensemble data and NCEP 1°×1° reanalysis data, the characteristics of a heavy rainfall over the Sichuan Basin on June 30 in 2013 under interaction between Plateau Vortex (PV) and Southwest Vortex (SWV) are analyzed.Results show that:(1) PV moved eastward coupling with SWV which caused persistent heavy rainfall.Correlation coefficients of dynamic parameters (geopotential height and vorticity) between PV and SWV of ensemble forecast increased with time during the process indicating the characteristics of gradual coupling and intensifying of PV and SWV; (2) Ensemble sensitivity analysis can be used to reveal the sensitivity of rainfall to weather system and demonstrate the influence of vortex system on the heavy rainfall combined with geopotential height and wind fields.Heavy rainfall of this event was more sensitive to PV than SWV.When the forecast uncertainty of SWV of ensemble forecast was smaller, the forecast of PV was the key factor for forecasting of intensity and location of rainfall.Best ensemble members whose rainfall forecast was similar to the observed rainfall have stronger and easter location of PV compared to control member; (3) Heavy rainfall at night on June 30 was more sensitive to dynamic parameters of vortex systems than that in the day.Because heavy rainfall at night is caused by coupling of PV and SWV, which was characterized by more significant dynamic effect.In contrast, heavy rainfall in daytime was characterized by more significant thermodynamic effect.
  • Spatial and Temporal Variation Characteristics of Accumulated Negative Temperature in Qilian Mountains under Climate Change
  • WANG Xiqiang;CHEN Rensheng;LIU Junfeng
  • 2017 Vol. 36 (5): 1267-1275.  DOI:10.7522/j.issn.1000-0534.2016.00096
  • Abstract ( ) HTML PDF (7736KB) ( )
  • Under the background of climate change, the warming trend in China is significant, especially in winter, which has changed the degree and the spatio-temporal distributions of heat resources.Based on the meteorological data of 32 meteorological stations over the past 56 years in and around the Qilian Mountains and DEM data, rasterizing accumulated negative temperature data was conducted using the "multiple regression plus residual interpolation" method.Results of cross-validation errors revealed that OK gave the best simulation.The results of spatial and temporal variation showed that:(1) Annual average absolute values of accumulated negative temperature were ranged from 607℃ to 3507℃ in the study area, and the differentiation of regional distributing was large; The area of accumulated temperature segment Ⅲ, Ⅳ and Ⅱcaptured nearly 91.31% of total area; The accumulated temperature segments presented nearly ring distribution and rised gradually from outside to inside except Ⅵ; On grid scale, the dynamic index of accumulated negative temperature decreased gradually from south to north.(2) By using the methods of linear trend estimates, from 1960 to 2015, the results indicated that the initial date showed an obvious delaying tendency with the linear rate of 1.3 d·(10a)-1, the termination date showed an obvious forward tendency with the linear rate of 2.4 d·(10a)-1, and the sustainable days showed an obvious declining tendency with the linear rate of 3.7 d·(10a)-1.Most of the stations passed the statistical tests of P < 0.1.(3) From 1960s to 2000s, the area of accumulated temperature segment Ⅰ and Ⅱ decreased significantly, and accumulated temperature segment Ⅴ and Ⅵ increased significantly, which was the most obvious characteristic in Qilian Mountains.However, the trend was opposite from 2000s to after 2010 (2010-2015), which may be the result of warming stagnation.The area of accumulated temperature segment Ⅲ and Ⅳ decreased and increased respectively, which showed fluctuation changes.(4) The main types of the change of accumulated temperature segment in the study area were Ⅲ~Ⅳ(25.72%), Ⅳ~Ⅴ(19.66%)andⅡ~Ⅲ(17.90%), which captured 97.73% of the total change.The area which keeped unchanged captured 32.48% of the total change.The transfer matrix of accumulated negative temperature indicated that, from 1960s to after 2010, accumulated negative temperature segment was one-way transfer, which transferred from the higher absolute values of accumulated negative temperature to the lower.However, in adjacent time, it presented two-way transfer.The way from the higher absolute values of accumulated negative temperature to the lower was dominant.
  • Numerical Simulation of Rain Enhancement Seeding of a Snowfall Case in Beijing Area
  • SHI Yu;LOU Xiaofeng;SHAN Yunpeng;HU Fei
  • 2017 Vol. 36 (5): 1276-1289.  DOI:10.7522/j.issn.1000-0534.2016.00116
  • Abstract ( ) HTML PDF (28878KB) ( )
  • In recent years, the drought situation in Beijing area is very serious, especially in the winter.How to effectively utilize the water resources in the air and carry out rain enhancement operation is important.Rain enhancement operation in winter is also likely to be used to remove fog and haze, and furthermore to improve air quality and visibility.Cloud models have been used in weather modification to formulate cloud-seeding hypotheses, assessments of the cloud-seeding potential or "seed ability".In this study, the numerical simulations of a snowfall case was carried out by using the two-moment explicit cloud scheme (nssl) of WRF model.The nssl scheme can predict the particle number concentration and mixing ratio of cloud water, rain, ice, snow, graupel and hail.For the snowfall case in Beijing on 19 March 2013, several seeding tests were designed to study the effects of different seeding time and seeding rate on cloud processes and precipitation amounts.The experimental results showed that all seeding tests could increase rainfall amount.When seeding with an amount of 1×107 kg-1 in cloud developing period, the rain enhancement effect was the best.The water vapor and supercooled cloud water mixing ratio in seeding area decreased after seeding, meanwhile the mixing ratios of ice and snow increased.The updraft and temperature of this area also increased.In 40 min after seeding, snow mixing ratios mainly grew through microphysical processes of deposition, the automatic conversion of ice to snow, snow accretion of cloud droplets, the collision between ice and snow.In 200 min after seeding, microphysical conversion processes of snow sources in the catalytic clouds were all higher than the natural clouds.Because of the consumption of supercooled cloud water in seeding clouds, the accretion process between cloud droplets and snow was very small.The snow mixing ratio mainly increased through terms of snow deposition and the interaction between snow and ice.The research results are helpful to understand the seeding effects on the macro and micro-processes of winter stratiform clouds, which will provide the basis for the rainfall enhancement field operations.
  • Observation and Study of Macro and Micro Response in Cold Cloud Catalysis
  • SUN Yuwen;YIN Yan;SUN Xia;LIU Wei;HAN Yang;YAN Xusheng
  • 2017 Vol. 36 (5): 1290-1303.  DOI:10.7522/j.issn.1000-0534.2016.00113
  • Abstract ( ) HTML PDF (24333KB) ( )
  • A synoptic reflux process of westerly trough occurred over the central and southern part of Hebei Province on 15 April 2014.The airplane detection on cloud physics combined with the artificial seeding operation was conducted by the Hebei Province Weather Modification Office, besides, a special flight route was designed to investigate the variation of the micro and macro physical parameters before and after the operation in this paper.This precipitation cloud system characteristics were analyzed based on the airborne Particle Measurement System (PMS) observation dataset, the radar and the satellite data.It is found that precipitation in the upper layer of "pre-trough cloud" was weaker than that in the lower reflux cloud, with no high cloud present.The descending precipitation particles growed in the "reflux cloud" during the operation observation, with large amounts of precipitation particles smaller than 3 mm in diameter existing in this layer.Small cloud particle number concentration normally was higher than 20 cm-3, with a maximum of 300 cm-3 in the operation layer.Large cloud particles number concentration lied below 0.02 cm-3.The macro and micro physical responses of cloud after the operation are as follows:The FY-2 satellite cloud image brightness temperature reduced from -25℃ to about -30℃, and the middle clouds developed with increased cloud top; Radar echo intensity increased after the seeding operation with a maximum intensity of 45 dBZ.The radar echo area larger than 35 dBZ in cloud was also increased; According to the radar sectional profile, the strong radar echo area dropped to 500~1000 m; Small cloud particles and large cloud particles number concentration were both increased, with precipitation number concentration increased first and then reduced, and the process lasted about 25 minutes based on the PMS observation dataset; The precipitation particle size distribution presented a bimodal distribution, with the second peak located at 10.5 μm.The number concentration of particles with diameters between 10.5~150 μm decreased exponentially.However, there was no significant change on the number concentration of particles with diameters between 150 to 1000 μm, although their diameters were found to be increased rapidly.The sharp decrease of the number concentration of particles with diameter larger than 1000 μm was associated with the particle deposition mechanism.The effective diameter of cloud moved to a higher value with a more disperse distribution of the average diameter, the square root diameter and cube root diameter, indicating a discrete particle distribution.The precipitation increased and kept three hours after the operation.
  • Boundary Layer Height's Variation Characteristics Research of Arid and Semiarid Areas over East Asia and North Africa in Recent 100 Years
  • ZHAO Yanru;ZHANG Kequan;MAO Wenqian;FAN Xu;LIU Chen;ZHANG Wenyu
  • 2017 Vol. 36 (5): 1304-1314.  DOI:10.7522/j.issn.1000-0534.2016.00107
  • Abstract ( ) HTML PDF (2682KB) ( )
  • Based on ERA-20C, ERA-Interim and ERA40, the ECMWF's reanalysis data, the interdecadal variation characteristics of the boundary-layer height of arid and semiarid areas over East Asia and North Africa spanning from 1900 to 2015 was analysed.The results showed that:(1) From 1900 to 2015, the average boundary layer of Arid and Semiarid Areas of East Asia and North Africa were 755 m and 834 m, respectively.It presented significant upward trend over East Asia with the climate tendency rate of 2.0 m·(10a)-1 and the decadal oscillation cycle of 20 years, and it presented downward trend over North Africa with the climate tendency rate of -0.6 m·(10a)-1 and the decadal oscillation cycle of 40 years.The year 1964 and 1940 were the significant turning point of East Asia and North Africa, respectively.After 1964, the boundary layer height of East Asia had a apparent rise and the boundary layer height's oscillation amplitude of North Africa increased obviously after 1940.(2) In arid and semiarid areas over East Asia, the most obvious upward trend region was at the east with the climate tendency rate of 10.7~12.4 m·(10a)-1, followed by central section, with the climate tendency rate of 3.8 m·(10a)-1, and the slowly upward trend region was at the north, with the climate tendency rate of 0.4~1.8 m·(10a)-1, the Taklamakan Desert showed downward trend with the climate tendency rate of -1.2 m·(10a)-1.Meanwhile, in the decadal fluctuations, the severe concussion presented in the sixties and seventies of East Asia boundary layer height was mainly associated with the change of central and east regions.(3) In arid and semiarid areas over North Africa, the central and north regions showed significant downward trend with the climate tendency rate of -5.1~-1.48 m·(10a)-1, and the south region showed upward trend with the climate tendency rate of 0.8~2.5 m·(10a)-1.However, in the decadal fluctuations, the intensified concussion after the forties of North Africa boundary layer height was mainly associated with the change of south region.
  • Analysis of the Data Reliability and Wind Field Characteristics Near Surface Boundary Layer with Doppler Sodar Observations
  • CAO Yang;CHEN Hongbin;WANG Pucai
  • 2017 Vol. 36 (5): 1315-1324.  DOI:10.7522/j.issn.1000-0534.2016.00100
  • Abstract ( ) HTML PDF (10095KB) ( )
  • Based on the Doppler Sodar data and radiosonde data observed in Huangsi meteorological observation station of Xingtai, Hebei during 1 May to 15 June in 2016, the correlation of Doppler Sodar data and radiosonde data and the wind field characteristics near surface boundary layer are analyzed.The results indicate that:There is a good correlation between Doppler Sodar data and radiosonde data, and the correlation of Sodar and radiosonde data from Graw and station are better than the correlation of Sodar and tethered balloon, the Doppler Sodar data can be used to analyze the wind field characteristics of the study area and also can be used as the supplemental data for other application; According to the analysis of wind field characteristics, the mountain-valley breeze was significant in this area, the valley breeze prevailed at local time from 09:00 to 20:00 with larger vertical wind speed and strong convection when the wind was blow from east, the mountain breeze prevailed at local time from 21:00 to 08:00 with small vertical wind speed when the wind was blow from west; On the vertical structure, the wind was blow from east or west in 30~50 m height and been weakened with increased height, the wind was blow from southeast and northeast beyond 50 m height, and the large wind speed ratio and the average wind speed increased gradually with height; The vertical wind speed were mainly between -0.1~0.1 m·s-1 which means that most of the time convection was weak, with zero value of shaft, left and right sides was symmetrical which means that the frequency of updraft and downdraft was similar.Besides, according to the percentage of good quality wind observations by Sodar as a function of range gate, the ability of Sodar to detect atmospheric wind speed that more than 400 m height is limited, other wind profile instruments are necessary to study the dynamics and thermodynamic characteristics of atmospheric boundary layer.
  • Analysis of Turbulent Flux on Different Underlying Surfaces over Semi-arid Area
  • CHEN Lijing;ZHANG Lei;LIANG Jiening;ZHOU Xu
  • 2017 Vol. 36 (5): 1325-1335.  DOI:10.7522/j.issn.1000-0534.2016.00101
  • Abstract ( ) HTML PDF (5434KB) ( )
  • In order to understand the land-atmosphere interaction between different conditions more deeply, we take eddy covariance technique proposed by Swinbank in 1951 primarily to analyse the turbulent flux which could describe the land-atmosphere interaction quantificationally on three types of underlying surfaces.We contrast the diurnal and seasonal variations of heat flux and momentum flux on loess plateau, grassland and cropland in semi-arid area by using turbulent data from January 2007 to December 2008, which comes from Semi-arid Climate and Environment Observatory of Lanzhou University (SACOL), the grassland and the cropland station in Tongyu.Combined with the conventional meteorological elements, the results show that:(1) At the SACOL, grassland station and cropland station of Tongyu, the diurnal variations of sensible and latent heat flux both show a typical "single-peak" structure.The peak value of sensible heat flux (Hs) in SACOL, grassland and cropland is 157.3 W·m-2, 144.8 W·m-2 and 140.3 W·m-2, which is the double of latent heat flux (LvE).(2) The heat flux mainly locate in -22.6~24.2 W·m-2 at night, and Hs is negative, LvE is positive.(3) The diurnal variation of the momentum flux(τ) shows the same law in the three station, the daily peak of τ in Tongyu is 0.25 kg·m-1·s-2, which in SACOL is 0.08 kg·m-1·s-2.(4) The diurnal variation of τ has an obvious difference in difference seasons, the daily range in spring and autumn is bigger than other seasons.(5) Except thermal factors, loess plateau has a stronger extinction effect on turbulent, atmosphere will be stable easier and quicker.

CONTENTS

  • Temporal and Spatial Characteristics of Winter Temperature in Guizhou and Its Relationships with Ocean and Atmosphere
  • YAN Xiaodong;SONG Yan;HUANG Chenran;YANG Chunyan;XIA Yang
  • 2017 Vol. 36 (5): 1336-1345.  DOI:10.7522/j.issn.1000-0534.2016.00122
  • Abstract ( ) HTML PDF (17108KB) ( )
  • Using winter monthly mean temperature data of 39 representative stations in Guizhou from 1962 to 2014, 500 hPa height field data in the Northern Hemisphere and global sea surface temperature (SST) data, temporal and spatial characteristics of winter temperature and their relationships with the 500 hPa height field in the Northern Hemisphere and the global SST field were analyzed by composite analysis, correlation analysis, wavelet analysis and so on.The results show that the winter temperature is about 6.3℃ in Guizhou for recent 53 years, and it appears to be warming up, especially in the northeastern and southwestern edge of the province.The winter temperature is dominated by quasi 7 year and quasi 12 year oscillation.The winter temperature changes suddenly in 1988.The winters are obviously cold before the mutation and warm after the mutation.In abnormal warm winter years, the 500 hPa height anomaly fields are positive at the Greenland, the North American and the middle Pacific, while the rest of regions are negative.The potential height deviation of Eurasia continent is presented as "positive-negative-positive".In abnormal cold winter years, the 500 hPa height fields are positive at the central Siberia region, Western Europe-North Atlantic and the North American, while the rest of regions are negative.In the Eastern Hemisphere, the potential height deviation is presented as "negative-positive-negative" both from west to east and from north to south.The correlation between the winter temperature in Guizhou and the SST in the northeastern Pacific, equatorial eastern Pacific Ocean and the eastern India Ocean in the early autumn is very significant.In the autumn before abnormal warm winter, the sea surface temperature anomaly (SSTA) of the North Pacific (especially the Northwest of Pacific) and the central India Ocean (most significantly) is remarkable.In the autumn before abnormal cold winter, the SSTA of the East and Middle Pacific in the Northern Hemisphere (most significantly) and the Middle India Ocean is obvious.Meanwhile, the SSTA difference center in the anomalous cold and warm winter years is concentrated in the Northeast Pacific and the Middle India Ocean in the Southern Hemisphere.
  • Bias Correction of AMDAR Temperature Data and Its Impact on GRAPES System
  • WANG Ruiwen;GONG Jiandong;HAN Wei;ZHANG Lin
  • 2017 Vol. 36 (5): 1346-1356.  DOI:10.7522/j.issn.1000-0534.2016.00124
  • Abstract ( ) HTML PDF (20190KB) ( )
  • Bias correction of AMDAR(Aircraft Meteorological Data Relay) temperature data is used to improve numerical weather forecast effect in this paper.6 hour forecast of global forecast system in national center for environmental prediction is as reference field, and bias statistic of AMDAR temperature data minus reference filed has been done.The equation of linear regression of bias of AMDAR temperature is fitted by the method of least square method according to the rate of rise and descend, and bias of AMDAR temperature can be corrected by combing the radiosonde data.The AMDAR data is from real-time database in National Meteorological Information Centre (NMIC), and the two period for the data is from June to August 2014 and from December 2014 to February 2015.One month numerical experiment has been done by the use of corrected AMDAR temperature data in GRAPES (Global Regional Assimilation and Prediction System).The results show that Bias and RMSE (root mean square error) of height analysis are decreased by assimilating corrected AMDAR temperature data than uncorrected data.Bias and RMSE of height decrease 2 gpm on 300~150 hPa.The maximum reduction of bias and RMSE of temperature is close to 0.15℃.Forecast anomaly correlation of height and temperature is increased above 250 hPa than before correction.The period of validity of temperature improve 0.5 days.
  • Classification of Winter Typical Sea Surface Temperature Variabilities Based on Statistical Method
  • ZHAO Yuheng;FENG Guolin;ZHENG Zhihai
  • 2017 Vol. 36 (5): 1357-1367.  DOI:10.7522/j.issn.1000-0534.2016.00108
  • Abstract ( ) HTML PDF (6648KB) ( )
  • 25 Sea surface temperature (SST) indexes in winter, which was utilized in monitoring service of the National Climate Centre for characterizing Sea surface temperature anomalies (SSTA) distribution in different regions from 1951 to 2014, was selected to be clustered by using the Systematic Clustering Analysis to study the main types of global SST variability's (except the Arctic Ocean).The global SST indexes were divided into four categories by analyzing the correlation between the SST of different regions.Four kinds of SSTA distribution and characteristics types in winter have been put forward according to the corresponding sea areas space distribution and the time series variation characteristics described by each category:Eastern ENSO SSTA type (CategoryⅠ), central ENSO SSTA type (CategoryⅡ), Inter-decadal SSTA variation features type in the west Pacific warm pool and the North Atlantic Ocean (CategoryⅢ).The SSTA diffusion distribution type under the action of equatorial wind current and western boundary current(CategoryⅣ).The indexes of the first and second category have shown an obvious inter-annual oscillation characteristics while the indexes of the third category showed the Inter-decadal characteristics evidently.On these basis, the index of each category was integrated, merging the global SST variabilities into less variances and laying a foundation for further studies of the characteristics of global SST and cooperative effects of SSTA in multi sea areas on climate variabilities.
  • Temporal and Spatial Distribution of North China Thunder-gust Winds and the Statistical Analysis of Physical Characteristics
  • FANG Chong;WANG Xigui;SHENG Jie;CAO Yancha
  • 2017 Vol. 36 (5): 1368-1385.  DOI:10.7522/j.issn.1000-0534.2016.00083
  • Abstract ( ) HTML PDF (20573KB) ( )
  • This study analysed the temporal and spatial distributions of thunder-gust winds in North China (Beijing, Tianjin, Hebei, Shanxi) based on the observed thunder data and significant weather reports from April to September during 2011-2015.The results showed that the thunder-gust winds occur mostly in June and July and from afternoon to early night; The start times of the large-scale thunder-gust winds are mainly from 13:00 (Beijing time, the same as after) to 15:00 and the durations are 4 to 8 hours; The frequency of gust on the plateau is greater than that on the flatland.This study divides the stations in North China into plateau stations and flatland stations based the altitudes of the stations, and analyzed the physical indicative characteristics of the thunder-gust wind processes by using the NCEP physical analysis field from April to September during 2011-2013.The results showed that most of the commonly used thermodynamic indexes need to take into account the seasonal factors; The threshold of DCAPE does not change with the seasons and has some indication of the occurrence and range of thunder-gust winds on the plateau and the flatland.In addition, CIN, vertical wind shear between 0 and 3 km, low-level divergence, the 500 hPa wind field, PWAT and the changes of the relative humidity of 500 hPa from 08:00 to 14:00 have some indication of the occurrence and range of thunder-gust winds in some specific aspects.The relative humidity of 850 hPa is below 50% when the thunder-gust wind process happened on the plateau, and the relative humidity of 850 hPa is larger than 50% when the thunder-gust wind process happened on the flatland.For the large-scale thunder-gust wind process occurring with large relative humidity of 850 hPa, the temperature difference between 850 hPa and 500 hPa is around 24~28℃, and for the large-scale thunder-gust wind process occurring with small relative humidity of 850 hPa, the temperature difference between 850 hPa and 500 hPa must be over 30℃.
  • Study on the Characteristics and Sources of Acid Rain in the Source Region of the Yangtze River
  • WANG Liefu;SONG Lingling;CAI Yuqin;LI Yongge;LV Yuemin;YUAN Ruifeng;GUI Juan;LI Zongjie;LI Zongxing
  • 2017 Vol. 36 (5): 1386-1393.  DOI:10.7522/j.issn.1000-0534.2016.00112
  • Abstract ( ) HTML PDF (2815KB) ( )
  • In order to research the characteristics and sources of acid rain in the source region of the Yangtze River.This paper collected 402 precipitation samples from January 1, 2010 to December 31, 2015.From the analysis of pH value, electrical conductivity (EC), precipitation and wind speed of precipitation samples in the source region of the Yangtze River, especially for the analysis of the 14 acid rain events.And applied the HYSPLIT model to study the source of acid rain in the source area of the Yangtze River.The results show that:(1) Acid rain event occurred in the source region of the Yangtze river, and the precipitation of pH value less than 6.5 accounted for 61.69% of the total precipitation, the precipitation of pH value between 6.5 and 7.0 accounted for 37.56%, the precipitation of pH value was over 7 accounted for 0.75%.The source region of the Yangtze River had been seriously affected by the pollution sources from the surrounding area; (2) During the period of sampling, the variation range of pH value was 4.0~8.57, with the mean value 6.37.And the range of EC was 5.2~124.4 μs·cm-1, the average was 27.59 μs·cm-1.The order of pH in four seasons was summer > spring = winter > autumn, the value was 6.41, 6.37, 6.37 and 6.25, respectively.And the order of conductivity in the four seasons was spring > winter > summer > autumn, with the value was 37.62, 31.86, 25.75 and 24.04 μs·cm-1, respectively.(3) The source area of the Yangtze River was affected by the southwest monsoon from January 1, 2010 to December 31, 2015, which had occurred 5 times, accounted for 35.71% of the total number of acid rain events.And the occurrence of acid rain events affected by the westerly circulation has been up to 64.29% of the total number of times.So acid rain in the source region of the Yangtze River was mainly affected by the southwest monsoon and the westerly circulation.On the one hand, the occurrence of acid rain mainly controlled by industrial pollution and other pollutants coming from India, Nepal and other countries.On the other hand, because of the Qinghai Tibetan highway and the Qinghai Tibetan railway, there were a lot of cars coming and going.And the people in the summer to plateau tourism increased year by year, and more for self-driving travelling.This added additional pollutants (automobile exhaust) for the source of the Yangtze River.
  • Long-term Analysis of Urban Heat Island using Remote Sensing Data in Lake Tai Basin
  • ZHAO Yafang;ZHANG Ning;CHEN Yan;ZHU Yan
  • 2017 Vol. 36 (5): 1394-1403.  DOI:10.7522/j.issn.1000-0534.2016.00097
  • Abstract ( ) HTML PDF (20928KB) ( )
  • Based on MODIS/Aqua LST product (MYD11A1), the temporal-spatial characteristics of land surface temperature (LST) and urban heat island (UHI) from 2003 to 2013 were analyzed, and the relationships between UHI and atmospheric stability, land use covers was studied in Lake Tai Basin.The results show that the number of days of unstable stability class in the region is the largest in the daytime, accounting for 50% of the total number of days and it increases from 2003 to 2010, and then decreases since 2010.The annual variation of neutral class is consistent with the variation of slightly unstable class, while it is opposite to the variation of unstable stability class.The quality of MODIS images decreases as the atmospheric stability changes from unstable to neutral class.The phenomenon of UHI in the urban area is evident under unstable stability, and the UHI intensity decreases as the atmospheric stability turns to neural stability.Due to the fast economic development in Suzhou, Wuxi and Changzhou which leads to the urban area expansion over the last decade, the annual average LST in 2010 is about 1℃ higher and in some newly-built urban area it is up to 3℃ higher than that in 2004.Since the area of high LST area expands widely forming a high-temperature zone around Lake Tai, it is important to analyze the temporal-spatial changes of LST and UHI to study the regional climate effect caused by urbanization.
  • Analysis of Meteorology Detection Data During a Heavy Pollution Event
  • HAO Jufei;ZHANG Gongwen;WANG Xiaojuan;YANG Yunling
  • 2017 Vol. 36 (5): 1404-1411.  DOI:10.7522/j.issn.1000-0534.2016.00118
  • Abstract ( ) HTML PDF (9253KB) ( )
  • A large scale heavy pollution process occurred from 17 to 27 December 2015 in the eastern china.Using the data of micro pulse lidar and microwave radiometer which located in the pollution center of Xingtai City, analyzed the extinction coefficient, inversion layer, moisture content in the process of pollution.The results showed that:Local meteorological conditions change was the main pollution forming source during the process, the background of the heavy environmental pollution event was stable high-altitude atmospheric circulation and ground pressure, air mass at 100 m altitude played a major role on the accumulation and regional transport of pollutants; The correlation coefficient between extinction coefficient and PM2.5 concentration, vapor pressure were 0.8622, 0.7421, with the increase of PM2.5 concentration and vapor pressure, the extinction coefficient increased exponentially.Extinction coefficient of PM2.5 concentration and vapor pressure build regression equation (R2=0.8811) could be a good characterization of the actual change.The inversion strength reached the maximum in pollution development stage, the moisture content reached the maximum in pollution aggravation stage, the inversion strength and moisture content was a significant decline in pollution mitigation stage.

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