Current Issue

• Preliminary Study of Thermodynamic of Oasis-Desert Interaction in Hexi Area in Summer
• Lü Shi-hua;CHEN Yu-chun;CHEN Shi-qiang;Peter C Chu
• 2004 Vol. 23 (2): 127-131. 
• Abstract ( ) PDF (213KB) ( )
• Based on the surface heat and water balance facts in desert and oasis, the equations of atmospheric stability and circulation over the oasis are given.It shows that the main causes that makes oasis surface temperature lower is the obvious great evaporation from the oasis surface.The atmospheric stability over the oasis is an important self-protection mechanism to maintain oasis.From dynamic point of view, obvious downdraft (updraft) over the oasis leads to stabilization (destabilization) of the atmosphere.The albedo effect will reduce the oasis circulation, on the contrary, the evaporation from the oasis can drive the oasis circulation.The excessive evaporation from oasis (than from the desert surface) makes the oasis surface is colder than the surrounding desert surface.The temperature difference between oasis and surrounding desert drives an oasis breeze circulation, in which there is the downdraft over the oasis and the updraft over the desert.

• Some Aspects of the Turbulent Transportation in Boundary Layer along with Atmospheric Linear Thermodynamics
• HU Yin-qiao;ZUO Hong-chao
• 2004 Vol. 23 (2): 132-138. 
• Abstract ( ) PDF (421KB) ( )
• Some aspects of the turbulent transportation in atmospheric boundary layer are discussed, the basic theory of the atmospheric linear thermodynamics is summarized.Up to now, theory of the turbulent transportation in atmospheric boundary layer is established also under the condition of uniformity underlying surface, as result the application of the theory of the turbulent transportation in atmospheric boundary layer encounters difficulties for heterogeneous underlying surface.The classic K turbulence closure theory of atmospheric boundary layer is viewed as that the vertical turbulent transport flux of any macroscopic quantity is equivalent to the vertical gradient transport flux of the macroscopic quantity.However the atmospheric linear thermodynamics demonstrates there exists the cross coupling between the thermodynamic processes and dynamic processes to cause that the atmospheric convergence or divergence affects on the turbulent transportation processes in the vertical direction.Thus the vertical turbulent transport flux of any macroscopic quantity can not be equivalent to its vertical gradient transport flux, but should add the cross coupling effect caused by the atmospheric convergence or divergence, except for the vertical gradient transport flux of macroscopic quantity.??? The cross coupling affection caused by the convergence or divergence movement on the vertical turbulent transportation under the condition of the heterogeneous underlying surface or the convection boundary layer is important especially.These theoretical results offer an important clue to solve the subject of turbulent transportation about the heterogeneous underlying surface, along with the boundary layer parameterization of land surface processes and the energy budget on the ground surface.These theoretical results give the reasonable explanation to the antinomy that the turbulent transportation coefficient of large eddy convection is with infinitely great value.

• Satellite Remote Sensing Parameterization of Regional Land Surface Heat Fluxes over Heterogeneous Surface of Arid and Semi-Arid Areas
• MA Yao-ming;DAI You-xue;MA Wei-qiang;LI Mao-shan;WANG Jie-min;WEN Jun;SUN Fang-lin
• 2004 Vol. 23 (2): 139-146. 
• Abstract ( ) PDF (369KB) ( )
• To estimate regional land surface heat fluxes over heterogeneous surface in arid and semi-arid areas,the utilization of satellite remote sensing is indispensable.Satellite remote sensing parameterization methodology of regional land surface heat fluxes over heterogeneous surface of arid area, the results of cases study and difficultieson the procedure of parameterization are introduced in this study.The solving way of the difficulties is also proposed.

• Numerical Simulation of Summer Boundary Layer Characteristics in Dunhuang Oasis
• Lü Shi-hua;LUO Si-qiong
• 2004 Vol. 23 (2): 147-154. 
• Abstract ( ) PDF (367KB) ( )
• To study desert-oasis circulation and boundarylayer characteristics in Dunhuang Oasis summer, a set of triple nested numerical simulation experiments with and without the Dunhuang Oasis was conducted, using NCAR nonhydrostatic meso-scale model, MM5V3.6 and the NCEP reanalysed grid data on July 24, 2001.The main results show: The oasis surrounded desert is a cold source in summer.The surface sensitive heat and latent heat fluxes in the oasis are different from its surroundings.In oasis, the sensitiveheat flux is small and latent heat flux is large;but vice versa, in desert.The boundary layer height is low in oasis and high indesert.Oasis could make the unstable stratified atmosphere in desert change to stablein oasis and it changes the circulation and the distribution of temperature and humidity there.The vertical motion is downwards over oasis and upwards over desert, then the air is dry and cold over oasis;warm and moist over desert.There is the wet air colume around oasis, which playsa key role in protecting oasis.It is divergence flow in lower layer over oasis which slow down the desert wind speed in upstream direction of the oasis, but quicken the desert wind speed in downstream direction of the oasis.

• Observation and Numerical Simulation of Heterogenous Underlying Surface Boundary Layer (I): The Whole Physical Picture of Cold Island Effect and Inverse Humidity
• ZUO Hong-chao;Lü Shi-hua;HU Yin-qiao;MA Yao-ming
• 2004 Vol. 23 (2): 155-162. 
• Abstract ( ) PDF (353KB) ( )
• Using the observational data of HEIFE, DHEX and GAME/Tibet experiments and at some routine meteorological stations, the whole physical picture of the clod island effect and inverse humidity under heterogeneous land-surface condition over west China and their effect on surface energy and tramsformation among atmospheric water, surface water, soil water, under ground water and plant water were analyzed.The analyzed results show that the characteristics of heterogenous underlying surface have clearly effected on water transformations.The clod island effect and inverse humidity are certain result of underlying surface heterogencity, and they exist common in nature.The existed land-surface process models are hard to depict the cold island effect and inverse humidity phenomenona.They can not transfer heat advection in cold island effect into latent heat of evaporation.Meanwhile, it can not distinguish the inverse humidity phenomenon and cooling condensation of atmospheric water in the underlying surface.This review is useful for future study of heterogeneous land-surface processes.

• Observation and Numerical Simulation of Heterogenous Underlying Surface Boundary Layer (II): Numerical Simulation of Inverse Humidity Phenomenon
• ZUO Hong-chao;Lü Shi-hua;HU Yin-qiao;MA Yao-ming
• 2004 Vol. 23 (2): 163-170. 
• Abstract ( ) PDF (348KB) ( )
• Bascd on the whole physical of inverse humidity given in literature, a new scheme of land-surface process parameterization is designed.The new scheme has successfully simulated appearing the inverse humidity phenomenon in desert near oasis.The simulated result is coincident with the observed ones, so that the new scheme of land-surface process parameterization is feasible.These conclusions are beneficial to study heterogeneous land-surface process.

• Numerical Simulation of Boundary Layer Character in Oasis Basin
• Lü Shi-hua
• 2004 Vol. 23 (2): 171-176. 
• Abstract ( ) PDF (275KB) ( )
• Using the NCAR nonhydrostatic mesoscale model MM5V3.5 and through triple nested technique, the idealized circular oasis terrain was designed, the circulation and boundary layer character in oasis were simulated.It is found that the sensitive heat flux in oasis changes with terrain elevation, but the latent heat flux doesn't change with terrain elevation, which is related to the characteristic of underlying surface in oasis.The sensitive heat flux in oasis is small and the latent heat flux is large, climatic effect in oasis is obvious.The circulation in oasis is consistent with terrain ones, but the intensity of terrain circulation is weaker than that of in oasis.The influence of oasis on humidity profile of boundary layer is obvious.The water vapour transport in oasis is enhanced through downdraft in terrain, making the climatic effect in oasis of mountain valley to enhance as well.The result showed that the climatic effect in oasis is enhanced because the terrain circulation is consistent with oasis ones.

• Numerical Simulation of Circulation and Boundary Layer Characteristics in Oases on Different Scales
• CHEN Yu-chun;Lü Shi-hua;GAO Yan-hong
• 2004 Vol. 23 (2): 177-183. 
• Abstract ( ) PDF (342KB) ( )
• Using the US NCAR non-static equilibrium meso-scale model, new version MM5V3.4 with triple nested mesh and one way interaction technique, the circulation and boundary layer characteristics in oasis on different scales were investigated in this study.The results demonstrated that the transportations oasis and water vapor depended upon the sizes of the oasis system.The surface latent heat flux was large while sensible heat flux was small in oasis on small scale.The oasis-desert circulation and oasis microclimatic system could be established over the oasis on a scale larger than 15 km, the boundary layer height was low and a water vapour wall could be formed over those oases border;but not for the small oasis on the scales of several kilometers.The temperature and moisture boundary layer structures established over the large size oasis together with oasis-desert circulation drove the oasis to build a self-protecting microclimatic environment;this is useful for the development of the oasis ecological system.

• The Response of Environment Element Variations in Upper Reach of Heihe River Valley to Watershed Flow Convergence Process
• GAO Yan-hong;Lü Shi-hua
• 2004 Vol. 23 (2): 184-191. 
• Abstract ( ) PDF (340KB) ( )
• The mesoscale atmospheric model MM5 coupled with the Oregen State University Land Surface Model (OSULSM) was used, in which the four-layer soil scheme and the canopy scheme are included.The flood event of Heihe river basin in July 2002 was successfully simulated using this coupling model.Some environmental element changes during the confluent process of the flood event were analyzed.After adding the slope convergence,the atmospheric model redistributesthe surface water.The redistribution of the surface water changes firstthe land surface conditions and thenthe atmospheric element fields gradually.In whole, the interaction between land surface hydrology process and the local climate change was considered synthetically.

• Climatic Effects of Frozen Soil Process in CCM3
• ZHANG Yu;Lü Shi-hua;SUN Shu-fen
• 2004 Vol. 23 (2): 192-199. 
• Abstract ( ) PDF (445KB) ( )
• A simple frozen soil parameterization that developed by Zhang et al.was couple to NCAR Community Climate Model (CCM3), and its climatic effects were investigated.The simulation results indicates that the permafrost distribution over the Northern Hemisphere and mountainousregions were properly described, and some improvements on the simulation of surface air temperature, upper air temperature, and humidity fields were archived.Furthermore, it is the facility to study the interaction of frozen soil andclimatic change.

• Numerical Simulation of Characteristic of Atmospheric Boundary Layer in Jinta Oasis, Gansu
• AN Xing-qin;Lü Shi-hua
• 2004 Vol. 23 (2): 200-207. 
• Abstract ( ) PDF (399KB) ( )
• The characteristics of circulation, air temperature and humidity of Jinta oasis are simulated by WRF model, which is the newest weather research and forecast model of NCAR.The results show that the WRF model has good quality in simulating the characteristics of daily variation and space structureof oasis-desert circulations.The simulated results reappea "the cold island effect" of oasis and "inversion humidity phenomenon" of the desert which is near to the oasis.And also the feature of low wet region of oasis humidity field on daily time is found out by the simulation.

• Numerical Simulation of Oasis Effect in Gansu Corridor
• AN Xing-qin;Lü Shi-hua;CHEN Yu-chun
• 2004 Vol. 23 (2): 208-214. 
• Abstract ( ) PDF (403KB) ( )
• Using the numerical model MM5V3.6, the control and "removing oasis" tests have been designed and the latter has been used to simulate the wind,temperature and circulation of background field.Correspondingly, the characters of wind, temperature and humidity of control test have been simulated and analyzed.The comparative analyses clearly representthe "oasis effect" in Gansu Corridor.

• Characteristic Analysis of Different Terrain PBL in Hexi Region
• AO Yin-huan;Lü Shi-hua;CHEN Yu-chun
• 2004 Vol. 23 (2): 215-219. 
• Abstract ( ) PDF (239KB) ( )
• Using the gradient observational data obtained from the HEIFE experiment in October, 1991, the vertical distribution characteristics of wind speed, temperature and moisture at the three kinds of different underlying surfaces (Oasis, Desert and Gobi) in Linze area, mid reach of Heihe River are analyzed.The fact that there are the low-level jet and the inverse humidity in Hexi region at midnight in autumn are verified.This work provided the fact basis for further studying the effect of water and energy cycle in Heihe region on environment, the reasonable use of the land resources.

• The Effect of Improved Land Surface Process Parameters in Arid Area on Climatic Simulation in GCM
• BAO Yan;ZUO Hong-chao;Lü Shi-hua;ZHANG Yu
• 2004 Vol. 23 (2): 220-227. 
• Abstract ( ) PDF (448KB) ( )
• The air-land interaction has an important effect on the global and regional climates.In this paper, we do some comparisons of numerical simulation results between original CCM3 and CCM3 with the validated land surface process parameters (LCCM3 for short).Comparing with the original CCM3 results, LCCM3 can make better simulations of East Asia monsoon and precipitation in Northwest China, and modify the simulations of sensible and latent heat fluxes in part regions of Northwest China.It shows that the simulation ability of CCM3 model can be somewhat improved by changing the land surface process parameterization based on the observation.

• Study on Heat Budget Characteristics and Evaporanspiration for Tamaris Spp
• ZHANG Xiao-you;GONG Jia-dong;ZHOU Mao-xian;SI Jian-hua
• 2004 Vol. 23 (2): 228-232. 
• Abstract ( ) PDF (217KB) ( )
• The Bowen ratioenergy balance can be used widely in observing the evapotranspiration of all kinds of scrubby vegetable.In this paper, the improved Bowen ratioenergy balance system is used in observing the evapotranspiration of Tamarix spp.Through the measurement of sensible heat, latent heat and soil heat fluxes from June to September, the evapotranspiration of Tamarix sppis 335.31 mm;the latent heat flux, 62.85 percent of total energy;and sensible heat flux, 32.85;while the soil heat flux, 4.44 in August.As for their daily variation, the latent heat flux is larger than the sensible heat flux in the moring, but vice versa in the afternoon.

• The Characteristic Analyses of Climate Change of Oasis System in Shule River
• LI Dong-liang;Lü Shi-hua;DENG Zhen-yong
• 2004 Vol. 23 (2): 233-237. 
• Abstract ( ) PDF (225KB) ( )
• The basic climate characteristic of oasis system in Shule River area and the evolution characteristic of climate in last 50 years were analysed, the interdecade change features of main climate element in upper stream output flow area and developing regions of mid-and lower reaches of Shule River oasis are analysed as well.It indicates that the excessive development of the artificial oasis in upper stream could cause the degeneration in nature ecological environment in the down stream of Shule River under the limited water resource condition.

• Variations Trend of Yearly Mean Air Temperature and Precipitation in China in the Last 50 Years
• ZUO Hong-chao;Lü Shi-hua;HU Yin-qiao
• 2004 Vol. 23 (2): 238-244. 
• Abstract ( ) PDF (386KB) ( )
• Some characteristics of climate changes are gained by analyzing 385 Chinese Meteorological Stations Data (CMSD).The results show that the variations of annual mean air temperature of CMSDexcept for a few stations are obvious increase warming trend, North and Northeast China is annual mean air temperature rapid increasing and the warmest region.The China-averaged precipitation has no obvious trend.The analysis of variation of CMSD shows that the China precipitation varies with differentregions.The area-averaged precipitation is the increasing trend in most of Xinjiang, while the area-averaged precipitation is obvious decreasing trendin central andnorth China.Both the annual area-averaged precipitations have good correlations with global mean sea surface temperature.Theseclimate change characteristics are explained by general circulationof atmosphere with reanalysis data (NCEP/NCAR)in this paper.

• Analyese on Temporal-Spatial Features of Annual Precipitation in Northwest China in 1961-2000
• HUANG Yu-xia;LI Dong-liang;WANG Bao-jian;HE Jin-mei
• 2004 Vol. 23 (2): 245-252. 
• Abstract ( ) PDF (357KB) ( )
• On the basis of the monthly precipitation data from 137 stations in Northwest China(NWC) for the period of 1961_2000, the temporal-spatial distributions and the evolution rule of annual precipitation in NWC have been studied using the methods of EOF, ROEF and wavelet analyses.The results are as follows: (1) The annual precipitation in NWC is affected by the large-scale weather systems.When the first eigenvector is positive value, the whole NWC will be rainy, and vice versa, but there are the rainfall anomaly differences between in the east and west, and in the south and in the over NWC.(2) The precipitation abnormal area can be divided into six subregions: Northeast Qinghai-Xizang Plateau, Northern Xingjiang, Eastern Qinghai, Eastern part of NWC(ENWC), Southern Xingjiang and Gansu Corridor.(3) The precipitation in each region changes with time, in recent 40 years, the precipitation in Northeast Qinghai-Xizang Plateauand ENWC are decreasing and those over the other subregions are increasing.(4) The precipitation in each subregion has a long-and-short periodic oscillations, but their main periodic and annual change laws are different from each other.

• Character Study on Rainfall to Soil Water and Heat Forcing
• WANG Sheng;ZHANG Qiang;WEI Guo-an;GUO Qin-li
• 2004 Vol. 23 (2): 253-258. 
• Abstract ( ) PDF (247KB) ( )
• Utilizing the data of the "experiment on land-atmosphere interaction over arid region in Northwestern China" in Dunhuang, Gansu Province, the effect of different rainfall intensities on soil moisture, albedo and surface temperature are analyzed.With the precipitation increasing, the time of surface physical variable restoring to primary state is longer.The relaxation time of soil moisture at 5 cm is about 7 days under heavy rainfall condition;middle rainfall, 4 days;and small rainfall, 2 days.Both the effect of surface physical variable on rainfall in winter and summer is similar, but the restoring time in winter is longer than one in summer because the character of rainfall and soil state is different.The correlation between the relaxation time of soil moisture and albedo with rainfall is good.

• Spatial and Temporal Characters of Surface Wind in Gansu Corridor Oasis in Recent 50 Years
• LI Zhen-chao;WEI Zhi-gang;GAO Rong
• 2004 Vol. 23 (2): 259-263. 
• Abstract ( ) PDF (208KB) ( )
• The spatial and temporal characters of the surface wind in the Gansu Corridor Oasis are analyzed by using the surface wind data of 13 weather stations in the oasis from January 1951 to December 2000.At the most of stations, the prevailing wind near the surface in Gansu Corridor Oasis is east wind in summer, west wind inwinter.The highest wind velocity of the weather stations in the oasis usually appears in spring.And the frequency of stationary windin the oasis is higher than that in the other regions.There was a peak value of surface wind velocity in the 1950's, but the span was short.After that, the velocity began to increase wavely.In the 1970's, it reached another peak, and falled then again.The prevailingwind direction in the oasis changed in 1970's at most of the weather stations in the Gansu Corridor Oasis, And the phenomenona that the surface wind direction the reverses its direction from daytime to night observed on some weather stations in the oasis.

• The Degradation of Ecological Environment in Ejinaqi and Its Cause Analysis
• SU Yong-hong;FENG Qi;Lü Shi-hau;ZHANG Yan-wu;SI Jian-hua
• 2004 Vol. 23 (2): 264-270. 
• Abstract ( ) PDF (294KB) ( )
• Ejinaqi lies in the lower reach of Heihe River basin.In the recent years, serious environment and hydrological degradation have been formed: About three fourths wells have dried and ground water has decreased 2~3 m according to observational data from a part of different ground water levels, water quality has deteriorated, the diversity of biology has decreased, even some of them have been extinct.The situation of land has seriously desertified and oases have diminished.For example, between the years 1987 and 1991, the areas of Gobi and desertification land have increased by 5.6, and the annual rate reached to 1.63×10 ⁴km ².The causes of ecological enviroment degradation is the unreasonable utilization of water resources of Heihe, population increasing in the region and excess grazing.Basing on these problems, some reasonable countermeasures are put forward.

• Influences of Westerly Wind Interannual Change on Water Vapor Transport over Northwest China Summer
• FENG Wen;WANG Ke-li;JIANG Hao
• 2004 Vol. 23 (2): 271-275. 
• Abstract ( ) PDF (225KB) ( )
• The zonal index and the divergence of summer water vapor transport flux over Northwest China are analysed by using NCEP/NCAR monthly mean reanalysis data from 1970 to 1997.The analysed results show that the interannual change of moisture flux divergence resulted by moisture advection is constant, but resulted by wind field convergence or divergence is unstable.The wind field convergence is stronger in strong west wind years.So we can conclude that the interannual changes of summer water vapor over Northwest China is mainly resulted by wind field convergence or divergence.

• Change Characteristics of Corn Biomass at Oasis in East Part of Hexi Corridor Region
• WANG Run-yuan;ZHANG Qiang;YANG Xing-guo;MI Xiao-dong;MA Xing-xiang
• 2004 Vol. 23 (2): 276-280. 
• Abstract ( ) PDF (208KB) ( )
• Using observation data (1994-2001) of corn biomass in Wuwei agricultural meteorology experimental research station located at oasis in the east part of Hexi corridor region, the growth stage and interannual changes of corn biomass were studied.The results showed that the stage change of corn leaf area, leaf area index and dry weights of leaf, ear and plant was S-curve trend, but stage change of fresh weights of leaf, stem, ear, sheath, plant and dry weights of stem and sheath was slow increasing-fast increasing-slow increasing-slow decreasing trend.The interannual change of numerical value of each biomass was not same in different growth stages, but trends of stage change of each biomass were same in different years.The study showed that the basic accumulation characteristics of crop biomass did not change during global climatic change, but the global climatic change influenced the accumulation of crop biomass and biology process of crop.