Current Issue

• Analyses on Distribution and Vertical Gradient of Air Temperature on the North Slope of Mt. Qomolangma
• 2013 Vol. 32 (1): 1-8.  DOI:10.7522/j.issn.1000-0534.2012.00001
• Abstract ( ) PDF (990KB) ( )
• Themeteorological observation on the north slope of Mt. Qomolangmais valuable to research the climate change and the influence on glacier， especially in the regions where the observational data are limit．The distribution of temperature and characteristic of its gradient change in the surface layerand free atmosphere are analyzed based on the observed meteorological data and the radiosonde data infour different elevations (5 207, 5 550, 5 792, 5 955 m heights above sea level).The results are obtained as follows: The rising rate of mean diurnal variation of temperatureper year is largest at  5 207 m height, the larger at  5 550 m height, the smallest at  5 792 and 5 955 m heights.The monthly mean maximum (minimum) temperature at four observation stationsis 5.7 ℃（-9.3 ℃）, 4 ℃（-6.5 ℃）, 1.4 ℃（-14.8 ℃）and 1.3 ℃（-15.4 ℃）, respectively.The lapse rate of air temperature shows seasonal characteristic. The maximum (minimum) value is about 1.07 ℃·(100 m)-1(0.12 ℃·(100 m)-1), present in January (March), amplitude of mean diurnal variations in year (spring,summer and autumn) is large in daytime, little at nighttime and stable all the day in winter. Thevalue is positiveduring 00:00 and 09:00and positiveall the day in other seasons. The value of the lapse rate of free atmospheric temperature is almost 0~1  ℃·(100 m)-1, and the value during 5 200~ 6 000 m heights above sea levelis about 0.78  ℃·(100 m)-1.

• Analyses on Micrometeorology Characteristic and Energy Exchange in Surface Layer in Dali Region of the Southeastern Margin of Tibetan Plateau
• 2013 Vol. 32 (1): 9-22.  DOI:10.7522/j.issn.1000-0534.2012.00002
• Abstract ( ) PDF (1738KB) ( )
• Based on the observational data in Dali region of the southeastern margin of the Tibetan Plateau from January 2008 to February 2010， the diurnal and seasonal variations of the basic meteorological elements， surface radiation  and turbulent fluxes are analyzed. The results show that the diurnal cycles， the parameter variations in dry and wet season such as wind speed， air temperature， relative humidity and so on are evident. The wind speed， air temperature， momentum flux and so on in the surface layer reach the maximum in the afternoon and the minimum in the early morning. The relative humidity， soil temperature  in the wet season are higher than that in the dry season. The prevailing winds are east-southeast and east winds in the daytime， static and west winds at night at 2 m height in the surface layer， and the shift of prevailing wind has a good correspondence with time of sunrise and sunset. Surface radiation flux reaches the maximum at noon and the minimum before sunrise， apart from the upward short-wave radiation in the dry season is bigger than that in the wet season， other components are in the opposite situation. The diurnal variation of surface albedo shows asymmetrical ‘U’ type， and the values of surface albedo are the biggest in the early morning， bigger in the evening， the smallest at noon. The surface albedo difference between the morning and the afternoon may be due to influences of the dew， cloud and mountain blocking on the eastern and western sides. The sensible heat and latent heat fluxes have the similar daily variation processes in the whole year， the amplitude changes from season to season， but latent heat flux is obviously larger than the sensible heat flux， which indicates that the latent heat plays a dominate role in the heat transfer between the atmosphere and surface， while the sensible heat transfer is secondary. Sensible heat flux reaches the minimum around 20:00 in the evening， which mainly caused by wind speed weakens and Land-atmosphere temperature difference rises again to result in the change of heat exchange coefficient. The heating effect of the surface to atmosphere is evident and mainly through the heating way of latent heat. The land surface is atmospheric heat source in the whole year， with the strong heat source in the daytime and the weak cold source at night.

• Spatial and Temporal Changes of Atmospheric Precipitable Water in Tibet Region in Recent 30 Years
• 2013 Vol. 32 (1): 23-30.  DOI:10.7522/j.issn.1000-0534.2012.00003
• Abstract ( ) PDF (1107KB) ( )
• The spatial and temporal distributions of atmospheric precipitable water (APW) and precipitation conversion efficiency (PCE) in Tibet region were investigated using NCEP/NCAR reanalysis data with monthly precipitation at 34 meteorological stations from 1980 to 2009. The results show that: (1) APW is gradually decreasing from  southeast to  northwest parts of Tibet region,  APW during the recent 30 years has decreasing and its interannual variability is relatively small, which appeared an obvious seasonal difference,  the maximum value was in summer and the minimum value was in winter. There is no more difference for the amount of APW between more and less rain years indicating that the water content in the air is relatively stable in Tibet region, which is beneficial to its reasonable exploitation and utilization. (2) The highest PCE in Tibet region is in the middle and the eastern parts of Nagqu and the southeast part of Nyingchi, while the lowest PCE is in the northwest of Tibet. PCE appears the increasing trend during the recent 30 years and the interannual variability is relatively large while it has same seasonal variation as APW. The amount of the PCE determines the year will be more rain year or less rain year to some extent. (3) The spatial distribution of APW is quite similar with the distribution of natural precipitation, but it has opposite temporal variation trend to the increasing trend of precipitation while PCE has basically same variation trend as natural precipitation during the recent 30 years. The ascending (descending) of the PCE is corresponded to the increase (decrease) of precipitation.

• Characteristic Analyses on Hydrological and Related Meteorological Factors on the North Slope of Mount Qomolangma
• 2013 Vol. 32 (1): 31-37.  DOI:10.7522/j.issn.1000-0534.2012.00004
• Abstract ( ) PDF (884KB) ( )
• The characteristics of air temperature, precipitation, water surface evaporation, soil temperature and soil moisture have been analyzed using the observational data from 2008 to 2011 at Qomolangma station for Atmospheric and Environmental Observation and Research, Chinese Academy of Sciences. A brief results of the influence of the air temperature and precipitation on runoff have been analyzed using the measured data at gauging station in Rongbuk River during ablation period in 2010. Annual mean air temperature at Qomolangma station is 4.3 ℃, the  daily temperature range of air temperatures in winter half year is greater than that in summer half year. Average annual precipitation is 213.4 mm, which concentrates in July and August, its interannual variation is large. Annual water surface evaporation is 2 104 mm, and it is larger in summer than in winter, the largest water surface evaporation happen in June. During ablation period of Rongbuk River runoff, the air temperature dominates runoff and they have a good positive correlation. Precipitation can reduce runoff on the same day, especially the precipitation smaller than 10 mm has apparent negative impact on runoff on the same day.

• Analysis on Cloud Microphysical Property over Qinghai-Xizang Plateau Using Satellite Data
• 2013 Vol. 32 (1): 38-45.  DOI:10.7522/j.issn.1000-0534.2012.00005
• Abstract ( ) PDF (1275KB) ( )
• The unique topography of the Qinghai-XizangPlateau throws a great impact on ambient circulation,  climate changing and the evolution of severe weather in East Asia. Many researches obtained some valued results using either ground based observation data or satellite data. But it is worth noting that there are less ground observation stations and unevenly distributed. The satellite observation is a good supplement for ground based observations. However,  most research used ISCCP data that its spatial resolution is only 2.5°×2.5°. It can′t explain cloud properties related to complex surface properties. This study first compared the different spatial resolution data on the results of the analysis of cloud properties. The results showed that the cloud has the similar change trend using either MODIS data with 0.01°×0.01° resolution or ISCCP data with 2.5°×2.5° resolution. Comparing with ISCCP data,  MODIS data can show more local characteristicsofcloud. Then  the cloud properties were analyzed over the Qinghai-Xizang Plateau using EOS/MODIS data with 1 km spatial resolution in past 10 years. The results show that the cloud optical thickness tends to decrease inpast 10 years. At the same time, the cloud liquid water path changes slightly fluctuations in season,  but there is no significant change in the trend for many years. From the spatial distribution,  the cloud optical thickness and cloud water path over the Qinghai-XizangPlateau decrease from southeast to northwest,  and fully reflects the fact that there is drought in northwest part of the Qinghai-Xizang Plateau and is humid and rainy in southeastern part of the Qinghai-XizangPlateau.

• Applicability Research of Planetary Boundary Layer Parameterization Scheme in WRF Model over the Alpine Grassland Area
• 2013 Vol. 32 (1): 46-55.  DOI:10.7522/j.issn.1000-0534.2012.00006
• Abstract ( ) PDF (1178KB) ( )
• Toverify the applicability of the WRF model to theunderlying surfacearea, using the observation data at the Zoige field over the alpine grassland area, the high-resolution simulations on some meteorological variablesin several clear days are inter-compared and evaluated quantitatively using the WRF model with four planetary boundary layer(PBL) parameterization schemes. The results show that： For 2 m temperature,all schemes give no significant differences with the observed valuesin daytime, while MYNN2.5 scheme shows farther away from the observed values and the differences are not obvious among other schemes atnighttime. Comparing with the shortwave radiation, the simulations of longwave radiation aremore susceptible to PBL schemes. All simulations of ground heat flux with non-local schemes show much less bias than that with the TKE schemes.The simulations ofnet radiation flux， sensible heat flux and latent heat flux with MYNN2.5 scheme have the best relationshipwith the observed valuesthan that with other schemes.Moreover, thesuper-adiabatic phenomenon, temperature inversion and humidity inversion are well simulated by all schemes, even though there are some differences between different PBL schemes.

• Observation Study in Desert Homogeneous of Arid Region in Northwestern of China Using Large Aperture Scintillometers
• 2013 Vol. 32 (1): 56-64.  DOI:10.7522/j.issn.1000-0534.2012.00007
• Abstract ( ) PDF (973KB) ( )
• Using the experimental data that came from the  instrument parallel comparison in  Gulang HeterogeneousUnderlying Surface Layer Experiment,  the consistency of friction velocity and sensible heat flux observed by four sets of EC (Eddy Covariance System) which equidistantly lay on light path line of LAS (LargeAperture Scintillometer) was analyzed at first, and then the difference among the calculated regional sensible heat fluxs observed by LAS based on universal stability functions established by four different kinds of underlying surface employing the mean value of observationfriction velocity from four sets of EC was analyzed, finally a further comparison between the two observationsof LAS and EC was made. The results show that, friction velocity and sensible heat flux observed by four sets of EC have a good trend of consistency; the difference of friction velocity is less than 10%, and the difference of sensible heat flux is about 10%. The regional sensible heat flux of LAS calculated by four kinds of universal stability functions in the daytime and nighttime have identical changing trend with the average observed by EC, the calculated value is usuallybigger than normal, the calculated value of TAG universal stability function is closer to the average value observed by EC. Except for the main reason that universal stability functions from experiments of different underlying surfacehave some differences, the sensible heat flux observed by Kipp&Zonen LAS is systemic higher can not be ignored too.

• Effect of the Instrument Surface Heating on CO2 Flux from Open-Path Eddy Covariance System at Linze Station
• 2013 Vol. 32 (1): 65-77.  DOI:10.7522/j.issn.1000-0534.2012.00008
• Abstract ( ) PDF (1687KB) ( )
• The instrument surface heating of LI-7500 analyzer has a significant impact on the measurement of CO2flux from open-path eddy covariance system, and the Burba correction to CO2flux is a most critical requirement for improving CO2measurement, net ecosystem exchange (NEE) estimate, and global CO2 exchange and climate change modeling, etc. The sensible heat flux inside the optical path, latent heat flux and CO2flux were corrected using Burba correction approach for one annual datasets of measurements from an open-path eddy covariancesystem and from an automatic meteorological observation tower installed a maize field at Linze station. The results show that heat exchange from the bottom window and spars are the main contributor of the correction term of sensible heat flux inside the path with the mean values of 6.81 W·m-2 and 2.68 W·m-2, respectively. For latent heat flux, themagnitude of the correction term is least and negligible, and themean value is only about 0.24 W·m-2. However, the measurements of CO2flux and seasonal NEE are significantlyaffected by theBurba correction approach, and the mean values of the correction term are 19.14 μg·CO2·m-2·s-1and 313.21 mg·C·m-2·d-1, respectively. Furthermore, with lower air temperature, themagnitude of the correction term is larger expect for the latent heat flux. For instance, during the growing season, the corrected terms of sensible heat flux inside the path, latent heat flux, CO2flux and daily NEE are 6.94 W·m-2, 0.33 W·m-2, 12.86 μg·CO2·m-2·s-1and 161.58 mg·C·m-2·d-1, and are about 60.4%, 220.0%, 50.6% and 37.4% of the values of the coordinatesduring the non-growing season, respectively. Most of all, no-using the Burba correction procedurecould let to overestimate the carbon uptake with value around  25.85 g·C·m-2 during the growing season, and underestimate thecarbon emissionfrom theagroecosystem with the value around 88.47 g·C·m-2 during the non-growing season.

• Flux Calculation of Eddy-Covariance Method and Comparison of Three Main Softwares
• 2013 Vol. 32 (1): 78-87.  DOI:10.7522/j.issn.1000-0534.2012.00009
• Abstract ( ) PDF (1158KB) ( )
• For flux observation at present research of land-atmosphere exchange system, eddy-covariance method (EC) is the most fundamental method. The calculated fluxes based on observation data are significantly influenced by the settings of turbulence data processing softwares. This paper comparatively analyzed the performance of three softwares (EdiRe, TK2/TK3 and EddyPro) based on EC data for different underlying surface collected from five domestic and foreign flux observation stations. Results calculated by EdiRe-w, which had been improved based on EdiRe modules from 2006, showed a good agreement with those calculated by the other two softwares. The specific conclusions are listed in the following: (1) Results of the three softwares showed a high correlation, and most of determination coefficients (R2) were higher than 0.99; (2) The mean values respectively calculated by three softwares were almost consistent with each other for wind speed, air temperature, vapor concentration and carbon dioxide concentration; (3) For the momentum flux (or friction velocity u*), the calculation differences were less than 3% for three softwares; and less than 5% for sensible heat flux, latent heat flux and carbon dioxide flux calculated by Edire-w and EddyPro; the differences between Edire-w and TK3 were a little larger, however, even for the latent heat flux and CO2 flux which are the most difficult to measure, they were still less than 9%. Finally, the comparatively analysis results suggested that EdiRe  is an optimal software for processing EC data which is, with the characteristic of perfect function, flexibility in calling modules and fast computational speed.

• Bicubic-Surface Topography Computing the Horizontal Pressure Gradient Force in the Numerical Wenther Prediction Model
• 2013 Vol. 32 (1): 88-96.  DOI:10.7522/j.issn.1000-0534.2012.00010
• Abstract ( ) PDF (993KB) ( )
• In the numerical analysis of weathey prediction(NWP) model, the cubic spline function consists of cubic spline, bicubic surface and tri-cubic (3-D cubic) cube, all of which possess the 2-order differentiable ‘convergence’ and ‘optimality’ of the mathematical laws. In this paper,  fitting a C3-continuous bicubic surface to topography in a global numerical model was studied, on which the height-based terrain following coordinates ( coordinates) be set for the bicubic terrain has its stationary slopes, curvatures and torsions. Then,  horizontal pressure gradient force (HPGF) of the atmosphere model based on the bicubic terrain in the   coordinates was studied. It is on the bicubic mountains that  reduce level pressure field to every horizontal Z-plane of a one-to-one correspondence of every  -plane, where the Z= , for instance, the sea level is the plane of Z=0, by means of integrating the fitted, meridional and zonal cycle splines of log pressure differences on ‘hydrostatic balance’ along the mountain slopes horizontally with using the temperature and moisture fields at each corresponding -plane, in fact, it′s just a time-dependent reference atmosphere mapped in the dynamic model atmosphere. The calculation accuracy of HPGF totally depends on the pressure fields interpolated to every Z-plane (sea level). In principle, it is suitable for judging reasonable local areas (single point) to be smooth, according to their curvatures of fitting splines to a variable field, so dose the bicubic terrain.

• Comparative Analysis on Monthly Mean Characteristic of Free Atmospheric Temperature between Three Reanalysis Datasets and Radiosonde Dataset in China
• 2013 Vol. 32 (1): 97-109.  DOI:10.7522/j.issn.1000-0534.2012.00011
• Abstract ( ) PDF (1653KB) ( )
• Based on the radiosonde dataset from 105 stations in China, NCEP/NCAR reanalysis dataset, ERA reanalysis dataset and JRA reanalysis dataset, the study of reliability of free atmospheric temperature from reanalysis datasets based on the monthly mean in China is performed using the means of linear analysis and EOF(Empirical Orthogonal Function) decomposition. The results show that: In numerical aspects, the situations in spring, summer and autumn are similar, differing from winter, which show that NCEP dataset is more close to the radiosonde dataset in upper troposphere while ERA and JRA dataset are more close to the radiosonde dataset in middle and lower troposphere. In terms of long-term trend, the different datasets in different seasons reveal the different characters, especially the cooling trend in the south region of China in middle troposphere in summer. In different areas, three reanalysis datasets display more reliable in the north area of China than in the south area, and more reliable in the east area than in the west area when compared to the radiosonde dataset. In the aspect of spatial and temporal variation characteristics, there are quite differences of three reanalysis datasets in the distribution of the first mode. The second mode correlates quite the same with each other in four seasons, which displays the feature of the opposite phase change between north and south of the whole layer temperature.

• Primarily Analyses on Variations of Summer Extreme Precipitation in South China and Its Relation to the Sea-Air Anomaly in Northwestern Pacific Ocean
• 2013 Vol. 32 (1): 110-121.  DOI:10.7522/j.issn.1000-0534.2012.00012
• Abstract ( ) PDF (1493KB) ( )
• Based on the long time observation and reanalysis data, the spatio-temporal variations of summer extremeprecipitation event (SEPE) anomalyin South China during 1958-2008 were investigated and their possible relationship with the anomalies of sea surface temperature (SST),latent heat flux and water vapor transport in the northwestern Pacific ocean were primarily discussed. The dominate mode of the SEPE anomaly in South China indicates that, for most part of South China, the SEPE anomaly generally varies in phase with striking interannual variation of 2~5 years. In the recent 50 years, there is a significant shifting in the trend of the SEPE around the end of 1980s, that is, the trend is decreasing before 1989 while increasing subsequently. The analyses suggestthat, the South China Sea (SCS) and its adjacentregion of western Pacific  warm pool is the key sea area of the northwestern Pacific ocean, where theair-sea anomalies are significantly associated with the SEPE anomaly in South China. The anomalies of SST andlatent heat flux in thekey sea area can be considered as important factors to impact theSEPE, and the anomalous meridional water vapor transport over the north of SCS is very likely one of key processes to induce the SEPE anomaly in South China. The results above would provide the essentialreference for thefurther research of rules, mechanisms and forecasts of theSEPE in South China.

• Application of Variational Quality Control to  Regional GRAPES-3DVAR
• 2013 Vol. 32 (1): 122-132.  DOI:10.7522/j.issn.1000-0534.2012.00013
• Abstract ( ) PDF (1494KB) ( )
• Quality control of observational data is an important and indispensable componentsin the numerical prediction system. Quality control impactson the observational data using the numerical weather prediction analysis system, impacts the effect of the initial analysis field, also directly affect the model prediction results. In recent yearsthe variationalassimilation has developed,the variational quality control began the widespread use of applied research. The basic idea is based on the quality of the error distribution principles so that the different observations of the variational assimilation in the more reasonable contribution. This article attempts to the variational quality control program applied to Chineseregional GRAPES-3DVAR assimilation system to improve the numerical prediction results. A simulation test is done. It was a rainstorm in southern China from 2 to 3 July. The numerical simulation tests are also done for three months of the summer of 2009. Acase testing and continuous results show that: After quality control of the variational analysis is reasonable. Despite the geopotential and wind field changes are not significant, but the humidity field results improved water vapor transmission intensity is adjusted, close to live a more rational analysis of forecast models to improve the initial value of positive significance. Meanwhilet the pattern of precipitation areaandforecasting intensity are improved.

• Analysis on a Heavy Rainstorm from Southwest Vortex Moving Toward Northeast Direction in Sichuan and Shaanxi Provinces
• 2013 Vol. 32 (1): 133-144.  DOI:10.7522/j.issn.1000-0534.2012.00014
• Abstract ( ) PDF (2012KB) ( )
• The influential systems, upper jet, stream field and convective vorticity vector for a heavy rainstorm impacted southwest vortex in northeast part of Sichuan and southeast part of Shaanxi on 16-19 July 2010 are diagnostically analyzed based on the conventional observation data, NCEP reanalysis data, automatic station data, satellite cloud image and radar data. The results show that the stable saddle field provides the background for the occurring and developing of the southwest vortex and northeastward moving. A deep trough in north and southwest vortex in south pattern is important reason for the southwest vortex to maintain. The division area, which is formed by between the northeast airflow on south side of the northeast-southwest direction upper jet center and the southeast airflow on northeast side of the South Asia high, offers the dynamic condition for ascending motion. The south warm-wet airflow caused by the strong pressure gradient force between typhoon and Subtropical High supplies the abundant water vapor for the heavy rainstorm area. The precipitation intensity caused by southwest vortex during the developing phase is significantly greater than decaying phase. The heavy rainstorm locates in the coincidence area of the vertical component of convective vorticity vector and atmospheric column cloud water.

• Diagnostic Analysis on Generalized Moist Potential Vorticity of a Torrential Rainstorm Caused Flood in Dunhuang, Gansu
• 2013 Vol. 32 (1): 145-155.  DOI:10.7522/j.issn.1000-0534.2012.00015
• Abstract ( ) PDF (1617KB) ( )
• Using the sounding and surface data, the satellite cloud images and the NCEP reanalysis data with 1°×1°, the synoptic situation, water vapor condition and generalized moist potential vorticity (GMPV) of the torrential rainstorm occurred in Dunhuang from 15 to 16 June 2011 are analyzed. The results show that this torrential rainstorm is caused by the interaction of the middle-high latitude weather system and the low latitude weather system. The water vapor transport is originated from the westerly air current on 700 hPa in the eastern Xinjiang and the easterly air current near 600 hPa in the western Hexi Corridor. The positive anomaly of GMPV mainly occurs in the dense region of generalized potential temperature isoline between 850~750 hPa, which reflects the water vapor distribution during torrential rainstorm. The GMPV positive anomaly area on 800 hPa is basically consistent with the torrential rainstorm area. Comparing with the MPV, the GMPV can diagnose location of this torrential rainstorm well. The GMPV positive anomaly is occurring the region of overlap between the absolute vorticity great anomaly value and the great relative humidity gradient. The transformation from negative to positive, the transformation from positive to negative and the peak value change of the GMPV tendency of single point are consistent with the precipitation beginning, ending and the rainstorm intensity change, respectively. The GMPV and its tendency not only can be taken as dynamical variables to analyze the location and intensity tendency of torrential rainstorm, but also can reflect the distribution and concentration of water vapor, which are useful for the analysis of torrential rainstorm cases.

• Characteristic Analyses on Environmental Parameters in Short-Term Severe Convective Weather in China
• 2013 Vol. 32 (1): 156-165.  DOI:10.7522/j.issn.1000-0534.2012.00016
• Abstract ( ) PDF (1166KB) ( )
• The characteristics of environmental parameters of severe short-term precipitation, large hail, severe thunderstorm winds and the co-existence convective weather in China are studied, based on the rainfall data from more than 2 000 national weather stations and part of the sounding data during 2002-2011. The conclusions are: (1) The following parameters, including the shape of stratification and dew curve, the temperature  difference   between 700 hPa and 500 hPa, the temperature difference  between 850 hPa and 500 hPa, the height of 0  ℃, -20  ℃ and balance layer, the dew point temperature on the surface and at 1.5 km height, the temperature-dew point spread on 1.5 km height, the convective available potential energy (CAPE) and the vertical wind shear in 0~6 km, can be used to effectively distinguish the environmental background of the four types of severe convective weather. (2) Differences of the environmental background are relatively significant between the pure short-term heavy rain (including type I, II ) and large hail and severe thunderstorm winds. Comparing with the latter, the former has smaller temperature difference between 700 hPa and 500 hPa, smaller temperature difference between 850 hPa and 500 hPa, weak vertical wind shear, relatively high altitude of 0  ℃, -20  ℃ and balance layer, larger dew point temperature on the surface and 1.5 km height. The type I (accounting for the majority of the short-term heavy rain), with its higher relative humidity at the whole layer, is obviously different from the others. (3) Co-existence severe weather is similar to the large hail weather and the severe thunderstorm wind weather, in the following aspects: The shape of stratification and dew curve, the value of CAPE and the 0~6 km vertical wind shear. There is an obvious dry layer at the middle troposphere and larger value of CAPE and shear. However, the co-existence weather has relatively high altitude of balance layer, larger dew point temperature on the surface and the 1.5 km height and smaller  temperature difference  between 850 hPa and 500 hPa. In these respects, the co-existence weather is closer to the pure short-term heavy precipitation.

• Numerical Studies on Cloud Physics Characteristic and Influence of the Graupel/Hail Category on Cloud and Precipitation during a Heavy Rainstorm over North China
• 2013 Vol. 32 (1): 166-178.  DOI:10.7522/j.issn.1000-0534.2012.00017
• Abstract ( ) PDF (1651KB) ( )
• A mesoscale convective system which produces heavy rainstorm in North China on 22-24 July 2005 is selected as a research case. This heavy rainstorm process is reappeared successfully by ARPS model. On the base of analysis of cloud-precipitation characteristics, the influence of graupel/hail category by varying the value of (N0h, ρg) on development and evolvement of cloud-precipitation, macro-and micro-structures of cloud are studied. The results show that the meso-β scale convective system (MCS) locat in region between north of Henan Province and south of Hebei Province. Graupel/hail melting (cold cloud process) is the main source of rain water. Graupel/hail category has smaller influence on distribution of precititation, but has bigger influence on rainfall amount in heavy rainstorm area. Graupel/hail category almost has great influence on cloud distribution, cloud thickness in different parts of cloud and total water content of cloud. When (N0h, ρg) stand for large hail, cloud system has direction of falling into dissipation stage early. Graupel/hail category almost has no effect on the microphysical structure of cloud and vertical distribution range of most particles in cloud, but has obviously effect on vertical distribution range of graupel/hail and rain, the maximum of their water content. When (N0h, ρg) stand for large hail, the vertical distribution range of graupel/hail extends downwards, the maximum water content of graupel/hail decreases, the maximum of rain increases and the height of it falls. Graupel/hail category also has effect on updraft in cloud. When (N0h, ρg) stand for large hail, updraft is decreased, and height of cloud and water content of cloud is decreased, too. Furthermore, the development of updraft is restrained, which directly caused reduction of graupel/hail melting and water vapor condensation, and reduction of latent heat of microphysical processes.

• Simulation Study on Precipitation Phase State in Two Snowfall Processes of South China
• 2013 Vol. 32 (1): 179-190.  DOI:10.7522/j.issn.1000-0534.2012.00018
• Abstract ( ) PDF (1796KB) ( )
• Atmospheric circulation, temperature and humidity profiles， and middle-low level wind field characteristics in weather processes of cold wave  blizzard and the cold and warm air confrontational snow types were comparative analyzed. Results show that the maximum difference in the two  processes is the intensity and height level of the temperature advection. The intensity and outbreak time of the strong cold air can be judged by the low-level wind direction in the eastern coast of China. In view of heat budget, the main impact factors for vertical profiles of temperature are horizontal advection of temperature and non-adiabatic process. The emergence of temperature inversion layer is main attributed to horizontal advection of temperature. Non-adiabatic heating with the increasing of horizontal temperature advection  is equivalent during the severe pricipitation period. Advection cooling in cold and warm air confrontational snowfall is significantly smaller than of cold-wave snowfall, there is more warm advection in the lower level of confrontational type snow. The mixed precipitation condensation ratio on 950 hPa can be used for a predictor of precipitation phase state. When the mixed precipitation condensation ratio is close to 100% and snow mixing ratio is above 0.2 g·kg-1, the precipitation type is snow. Condensation ratio between 95% and 100% is the transition region of precipitation type, combined with non-adiabatic temperature cooling amplitude and ground temperature, which can be determined as ground precipitation types in the transition region. If the condensation ratio is below 90% and surface temperature is above 0 ℃, the precipitation type is rain.

• Cause Analysis on  Rare Rainstorm in West of Southern Xinjiang
• 2013 Vol. 32 (1): 191-200.  DOI:10.7522/j.issn.1000-0534.2012.00019
• Abstract ( ) PDF (1609KB) ( )
• Using the convention observation, T639, NECP data, stationary satellite and weather radar data, a rare rainstorm in West of Southern Xinjiang from 16 to 20 September 2010 was analyzed and there were three heavy rainfall time periods from 08:00 to 17:00 on 17, from 02:00 to 17:00 on 18 and from 08:00 to 17:00 on 19. The results showed that the  rare rainstorm occurred the background of favorable large-scale circulation is double body of  south asia high(high pressure center located in Iran Plateau and the east  of Tibetan Plateau) and central Asia trough to south cutting vortex low. Favorable configuration about three jet streams where the higher southwest, south in middle and lower east to provides the power and water conditions for the rainstorm. The mesoscale convection is the direct effect of rainstorm. Water vapor source payments calculation analysis showed that there are three parts of water vapor sources at three  rainstorm stage: One is thick central Asian vortex itself carry water vapor from southwest airflow, the second is by east of airflow water vapor concentration and convergence from hami south to Southern basin on middle-low level, the third is conveying the relay water vapor that warm-moist from south air flow in South Central Asia on middle-high level, 85% of water vapor transmission from the east and south airflow. Severe convection occurres on warm side, rainstorm fall area located the maximum gradient of TBB and corresponds to a higher divergence of  cloud drift  wind. Three times of rainstorm caused by the mixed precipitation echoes, among them are the development of mesoscale convection, but three times of echoes are differently what moving path and strong center.

• Analyses on Multi-Scale System  Configuration and District of a Disaster Snowstorm
• 2013 Vol. 32 (1): 201-210.  DOI:10.7522/j.issn.1000-0534.2012.00020
• Abstract ( ) PDF (1618KB) ( )
• Using the high spatial and temporal resolutions of T639, FY-2C and Doppler radar products, the multi-scale system and physical field configurations and districts of the rare snowstorm in the centre of Tian Mountain north slope, Xinjiang on February 23 were analyzed, The results showed that the merger and enhancement of North-south trough resulting in the intersection of cold and warm air was  main circulation background in the snowstorm process.The main trigger mechanism of the snowstorm was the low-level jet, convergence and shear line. The low-level jet transported a large number of water vapor. And the upper-and lower-jet streams contributed to strengthen the upward motion on low level. These all provided the favorable conditions for the enhancement of snowfall intensity. The snowstorm appeared in the junction where north and south short-wave trough join up, the divergence zone of right behind the jet stream entrance area, the convergence zone  on the left side of low level southwest warm jet exit area, in the front of convergence line, on the south side of shear line and the overlapping region near the surface cold front. During the snowfall, there were strong increased movement and thick layer of wet, moisture convergence. Meso-α and meso-β scale cold clouds were the main system resulting in the severe snowstorm. The intensity, scope and duration of snowfall were positively correlated with the enhanced intensity range, area and life history of cold cloud. And the great blizzard occurred during the phase when the internal cold clouds part enhanced, which located the maximum gradient of TBB  within the meso-α scale cloud with TBB≤-65  ℃ and the meso-β scale clouds with TBB≤-70 ℃. The radar echo was zonal distribution during the heavy snowfall. The direction of echo movement was consistent with the direction of long axis of ribbon, resulting in a longer duration of snowfall. The range of echo intensity evolution and echo intensity center were consistent with the range of snowfall distribution and heavy snowfall center. The echo intensity of heavy snowfall center was 35～40 dBZ. The echo intensity gradient was large.The curvature of velocity field with ‘S’ type was also large.The content of vertical accumulation of liquid water had a short-term growth.The evolution of echo had a short-term weak convection characteristic.

• Analysis on Climatic Transition Characteristic from Warm-Dry to Warm-Wet in Tsaidam Basin
• 2013 Vol. 32 (1): 211-220.  DOI:10.7522/j.issn.1000-0534.2012.00021
• Abstract ( ) PDF (1089KB) ( )
• Using the meteorological, hydrological and vegetation data in the Tsaidam basin from 1961 to 2010, the characteristic of climate from warm-dry turn to warm-wet in the Tsaidam basin is studied. The results show that, it is the fact that many characteristics of climate transformation appeared in the last of 1980's, such as temperature rising, precipitation and run-off increasing, sandstorm day decreasing, potential evapotranspiration decreasing, lake level rising and vegetation coverage increasing. The main reason of climate transformation are global warming, water cycle accelerating, water vapor in upper level and black carbon aerosol increasing.

• Study on Circulation Situation of Drought-Flood Abrupt Alternation before and after Meiyu Periods and Structure Feature of Meiyu Front in Zhejiang Province in 2011
• 2013 Vol. 32 (1): 221-233.  DOI:10.7522/j.issn.1000-0534.2012.00022
• Abstract ( ) PDF (2204KB) ( )
• The most typical and strongest precipitation processes during Meiyu period since 1999 wasoccurred in Zhejiang province in 2011,and  the sharp turned from drought to flood caused by four continuous heavy precipitation processes during Meiyu period. Using the objective analysisdata, large scale circulation backgroundbefore and after Meiyu periods are analyzed and contrasted at the same period in the history. At the same time, the different strcture of Meiyu front in the four heavy precipitation processes were compared. The results show that: (1) Before and after the alternationof the middle-high latitude circulation has obvious meridionality. The circulation situation is three-trough and three-ridge before the alternation turning to two-trough and one-ridge after the alternation.There is only one blocking high in Meiyu period. Northwesterlyariflowin front of the Lake Baikal blocking high provides cold air  for Meiyu. The India-Burma trough and the west Pacific subtropical high in low latitude become stronger than the pre-alternation, which helps to build continuous steady water vapor channel on the northwest side of the subtropical high. Southwesterly and easterly are joined together and form quasi-zonal shear near Zhejiang Province, which makes abundant warm and wet air current convergent and rise in this area. Northerly on the north side of Qinghai-Tibetcausedhigh creates forceful divergence on upper level. All above situations offer the good dynamic and moisture conditions for heavy rain. (2) There is heavy precipitation in front of Meiyu front. Ascending motion in the Meiyu frontal zone coordinates with two branches of subsidence, the north one delivers cold air to Meiyu front, while the southone and the updraft in Meiyu frontal zone shapes counter meridional vertical circulation. It also reinforces ascending motion in the Meiyu frontal zone. (3) The Meiyu front is always equivalent potential temperature intensive ribbonand nearly upright at low level of troposphere. Since the affect of cold air, there is obvious horizontal temperature gradient in Meiyu frontal zone with northward bias of lower level frontal zone during the first, third and fourth rainstorm. On the contrary, no cold air in the second rainstorm process, there isno temperature gradient in frontal zoneand the Meiyu front tilts toward south.

• Analyses on Spatial and Temporal Characteristics of AOD in Guanzhong Region of Shaanxi Province Using Long Term MODIS Data
• 2013 Vol. 32 (1): 234-242.  DOI:10.7522/j.issn.1000-0534.2012.00023
• Abstract ( ) PDF (1195KB) ( )
• Based on the CE318-sun photometer data in north part of Xi’an, the applicability of the aerosol optical thickness (AOD) products from MODIS Collection 5 over Guanzhong region of Shanxi Province is validated. The result shows that there is a good relationship between the AOD product of MODIS Collection C5 data and CE318-sun photometer data, and its correlation coefficient is about 0.91. Using the MODIS Collection 5 AOD product from 2000 to 2010, the long term variations of AOD and FMF (the fine-mode fraction) are analyzed. It is found that the main source of aerosol over Guanzhong region is dust storm and urban/industrial aerosols. At the east region of Guanzhong, due to the effect of special terrain and prevailing wind, the urban/industrial aerosol and dust aerosols are accumulated. While the main source of aerosol over the west part of Guanzhong is urban/industrial aerosol. Further more, it is found that the time series of AOD over the different parts of Guanzhong exist difference. Over the west part of Guanzhong there is a slightly decrease of AOD, and there is an obviously increase over the east part. After the analyzing the ten-year trend of FMF, it is also found that, although the ratio of fine-mode AOD is became smaller from west to east over Guanzhong region, the pollution of fine-mode aerosol over the whole region is worsening.

• Spatial-Temporal Changes of Summer Precipitation in the Bohai Rim in Recent 50 Years
• 2013 Vol. 32 (1): 243-249.  DOI:10.7522/j.issn.1000-0534.2012.00024
• Abstract ( ) PDF (870KB) ( )
• The spatial-temporal changes in 4 dominant areas dividedby the methods of EOF and REOF were analyzedbased on the daily precipitation data at 60 stationsin the Bohai Rim during summer of 1961-2008. The results showed that the summer precipitationin the Bohai Rim had obvious regional consitency, as well as interdecadal and interdecadal variations. The precipitationgenerally exhibited a decreasing trend in the whole region. For all divided areas, there was significant decadal periodic oscillation of 2～3 years in summer precipitation. However, the interdecadal period of summer precipitation had large difference in these areas. There were 10 or 11 years periodic oscillations in Liaodong Peninsulaand the north area of Bohai Rim, whereas it was 14 or 15 years in the west of Bohai Rim, and ShandongPeninsula. Significant abrupt change was observed in Liaodong Peninsula in the late 1960s and in Shandong Peninsula in the early 1970s, while the significant abrupt change occurredin the late 1990s in western and north areas of the Bohai Rim.

• Analysis on Weather Process of Classic Supercell Storm in Northern Part of Fujian on 5 March 2010
• 2013 Vol. 32 (1): 250-267.  DOI:10.7522/j.issn.1000-0534.2012.00025
• Abstract ( ) PDF (3053KB) ( )
• A severe convective weather occurred in northern Fujian from 16:20 to 19:50 on 5 March 2010 was mainly caused by three local severe storms in mesoscale convective echo group. The strongest cell of three local server stroms was a classic(CL) supercell storm,  which produced sever hail in 220 km along the way. Using  radar data of Jianyang CINRAD/SA, routine upper-air and surface observation data, the CL supercell's evolving feature and environmental conditions were analyzed. The main results are as follows: (1)The storm appeared in a mesoscale low pressure which had the characteristic of the terrain occlusion in surface. The low pressure was in the front of the upper-troposphere trough, under the southwest middle-level jet, on the south side of shear-line and  frontal zone on 850 hPa and in the front of low-level jet; the storm was produced from the cold front which located on the west of the low pressure, then the storm moved along the concentrated line in surface and passed through the center of the low pressure, at last the storm reached cold zone of stationary front which located on the east of the low pressure and quickly weakened then. The storm always maintained the relative isolated state and life-history was 4 h 52 min, the storm's average speed was 75 km·h-1 and the storm was a high centroid convective system. (2) During the mature stage (15:57-18:47) the storm maintained the classic supercell characteristics of the moderate intensity or more mesocyclone, the correlative bounded weak echo regions (BWER), lower-level hook-echo and other features. Moreover it come through three times peak development (16:03-16:34, 16:52-17:17, 17:41-18:47, respectively); correspondingly, the mesocyclone of the storm enhanced and stretched to the ground in the peak period. In the second peak period, the storm appeared the phenomenon of declining of echo-overhang, updating lower level hook-echo and disappearing of BWER, these evolving features were in accordance with the model of tornado-arising supercell. Moreover, in the second peak period the characteristic of the TVS further indicated the produced possibility of tornad to be large. In the third peak period the storm came up the similar evolving feature but the more typical is the mesocyclone came to occlusion at last, and then the storm formed vortex-echo which lasted half hour. Besides, in the first and the second peak period the gust-front-echo appeared in the left front of the storm several times rather than right-backward, which was favorable for lasting of the storm. (3) The main characteristics of storm-scale environment were the medium CAPE (Convective Available Potential Energy, 1 685 J·kg-1) , significant vertical wind shear (39 m·s-1 , over 0～6 km) , strong storm-relative inflow velocity (17 m·s-1, over 0～2 km) and strong storm-relative helicity (418 m2·s-2, over 0～2 km). However, Wind direction veered with altitude (90 °, below 300 hPa) was not only on low-level but also on middle-upper-level (25 °, over 500～300 hPa), which was certain different to those of CL supercell previously observed in middle latitudes. At lest, the mechanisms of three times peak development of the storm in the mature stage was also discussed.

• Analyses on Lightning Feature and Formation Condition for a Thunderstorm Process in Yunnan
• 2013 Vol. 32 (1): 268-277.  DOI:10.7522/j.issn.1000-0534.2012.00026
• Abstract ( ) PDF (1508KB) ( )
• Using NCEP/NCAP data and new generation monitoring detection data of radar echo, satellite cloud image and lightning position system, the thunderstorm process in Yunnan from 21 to 23  September 2010 is analyzed. The results show that westward moving of tropical depression ‘FANAPI’  provided the advantageous circulation background conditions of easterly convergence, warm between 300 K and 302 K on the low level and wet (relativity is above 80% ) on the upper level. Negative lightning plays a role in the whole lifetime of a thunderstorm cloud cluster. The cloud top brightness temperature decreases and all lightning is negative and its frequency reaches up to 1 245 times·(30 min)-1 at the development stage. The cloud top brightness temperature gradually increases, the negative lightning decreases, a small amount of positive lightning emerge and rise gradually from mature to disappear stages. In addition, the spatial distributions of thunderstorm cloud cluster structure and lightning are asymmetric. The structure feature is that the front is main convective zone and the rearward is plume or high cloud. The cloud top brightness temperature in the front is lower than that the rearward, and its gradient larger. Dense negative lightning mainly located in the region with cloud top brightness temperature≤-60 ℃ and its big gradient in the front. Sparse positive lightning disperse in the rearward of dense negative lightning and the cloud center. From Doppler weather radar, it is found that the cloud zone in the front of thunderstorm cloud cluster appears the mesoscale band echo of nonuniform structure, and echo free space in the rearward. The dense negative lightning mainly locate at the severe echo with intensity≥40 dBz and ET≥10 km, and nearby the nonuniform wind field of mesoscale. And the more the echo intensity, the higher the ET and the denser the negative lightning. Sparse positive lightning disperse in the rearward of severe or weak convective echoes or sheet echo at the later stage of development.

• Mesoscale and Doppler Radar Observation Analyses on a Severe Convective Weather Process in Middle Shaanxi Province in September 2010
• 2013 Vol. 32 (1): 278-289.  DOI:10.7522/j.issn.1000-0534.2012.00027
• Abstract ( ) PDF (1861KB) ( )
• Using  the mesoscale weather chart analysis technique and Doppler radar observation data, the mesoscale features of severe convective weather process in middle Shaanxi Province on 1 September 2010 are analyzed. The obtained results are as follows: (1) The synoptic-scale analysis can't well confirm the potential conditions of severe convective weather under the influence of weak synoptic-scale weather system. (2) The mesoscale and comprehensive analysis of radiosonde data can   clearly  reflect temperature advection, dry line, moisture tongue, significantly streamline, which is an effective means of analysis of severe convective weather. (3)The surface and dew point temperature at 08:00 can well indicate potential conditions of severe convective weather trigger in Loess Plateau in the north of Shaanxi, while the position of surface cold front and intersection region of clod and warm air or wet and dry air can be well shown by analyzing 14:00 surface data, which can help to determine the exact region of severe convective trigger. (4) Dry line and terrain have significant effects on convective cloud initiation, which mainly lies near underlying. Although more convection cloud triggered in southwestern Shaanxi, but cloud top height is lower than other region, so it has little possibility that lightning, hailstorm and thunderstorm are triggered. (5)The formated radar echo in the process of convection cloud developing plays an important role in severe weather warning. There is ‘V’-shaped gap, echo fornix and overshooting cloud top in process of the hail cloud development, and the central horizontal displacement between the middle level strong echo and the low level one is more than 1 km. The 45 dBz strong echo extended height in the storm is over 7.0 km. All of these metrics above are good indications of the severe convective weather warning.

• Analyses on Disaster Weather Characteristics of Masssive Mudslide in Zhouqu, Gansu on 8 August 2010
• 2013 Vol. 32 (1): 290-297.  DOI:10.7522/j.issn.1000-0534.2012.00028
• Abstract ( ) PDF (1223KB) ( )
• Because of the mountainous area terrain and unreasonable exploring activities of the human being, debris flows occurred more frequently, which seriously obstructs the economic development. Therefore, in order to improve the ability to disaster prevention and reduction and enhance the monitoring and warning on the debris flow,  using the conventional meteorological data,  satellite and radar data,  the massive mudslide in Zhouqu, Gansu  on  8 August 2010  studied.  The results show that on the background of pre-drought and low soil moisture, the heavy precipitation caused the heaviest massive mudslide. The reasons  why the heavy precipitation occured were that invasion of on the cold advection combined with the shear line on 700 hPa and that weak cold air diffused triggered off releasing  unsteady energy.  Extremely non-uniform precipitation was caused by a series of γ meso-scale cyclone which were formed by terrain and so on. The corresponding relationship between heavy precipitation and brightness temperature was very good, but the brightness temperature was not the unique factors led to heavy precipitation. For γ mesoscale vortex, radial velocity was a good indicator since rotary speed can indicate the cyclone intensity. There was a good positive correlation between precipitation and γ mesoscale cyclone. According to the topographic feature on edge of the Tibetan Plateau provides reasonable prevention measures, so as to decrease happening the debris flow disaster.

• Study of the Characteristic and Difference between Sea and Land Wind of Bohai
• 2013 Vol. 32 (1): 298-304.  DOI:10.7522/j.issn.1000-0534.2012.00029
• Abstract ( ) PDF (656KB) ( )
• Using the data of buoy site of Bohai Sea in 2009—2011,  the feature of gale in Bohai Sea is analyzed. The result shows that the gale and strong wind appear in 2009,  and lasted for 57 days,  for 101 days in 2010,  and for 38 days in 2011. The largest  day number of strong wind occurrs in November,  the second is January,  and  the less strong wind day is in summer. From the view of wind direction,  the north and north-easterly winds  have the most strong wind days. Comparing with winds at the buoy site and two coastal stations,  on the gale day,  the maximum wind speed of northeast and east winds at Wafangdian station is more closed to the buoy site,  but other wind direction,  lüshun station  is more closed to buoy site. In the strong wind day,  from the places of the eight wind directions at lüshun  station are relatively close to the buoy site. From the maximum value of wind speed difference,  the coastal station is less than 2~4 grades at buoy site.

• Advances in Research of the North Boundary Belt of East Asia Subtropical Summer Monsoon in China
• 2013 Vol. 32 (1): 305-314.  DOI:10.7522/j.issn.1000-0534.2012.00030
• Abstract ( ) PDF (1250KB) ( )
• As the transition zone between monsoon  and non-monsoon zones, the north boundary belt of East Asia Subtropical Summer Monsoon has significant influences on the weather, climate change and extremely severe weather or climate events in the eastern part of Northwest China, North China and Northeast China especially in Yellow River basin. The present work reviews the definition, characteristics, change trends of the north boundary belt of East Asia Subtropical Summer Monsoon and also summarizes some factors which may impact the boundary belt. The north boundary belt of the East Asia monsoon is in the juncture of continental climate and marine one in East Asia. This region can be divided into semi-humid and semi-arid subareas along the northeast-southwest direction, according to modern climate study. Climate in this boundary belt is variable and is infuenced by multifactor, resulting in large amount of natural disasters. Due to the lack of the spatial and temporal distribution refinements on the northern edge of the summer monsoon, further worthy study is proposed in the last stage of this review.