Advanced Search

2004 Vol. 21, No. 1

Display Method:
A Possible Role of Solar Radiation and Ocean in the Mid-Holocene East Asian Monsoon Climate
WEI Jiangfeng, WANG Huijun
2004, 21(1): 1-12. doi: 10.1007/BF02915675
An atmospheric general circulation model (AGCM) and an oceanic general circulation model (OGCM) are asynchronously coupled to simulate the climate of the mid-Holocene period.The role of the solarradiation and ocean in the mid-Holocene East Asian monsoon climate is analyzed and some mechanisms are revealed.At the forcing of changed solar radiation induced by the changed orbital parameters and the changed SST simulated by the OGCM,compared with when there is orbital forcing alone,there is more precipitation and the monsoon is stronger in the summer of East Asia,and the winter temperature increases over China.These agree better with the reconstructed data.It is revealed that the change of solar radiation can displace northward the ITCZ and the East Asia subtropical jet,which bring more precipitation over the south of Tibet and North and Northeast China.By analyzing the summer meridional latent heat transport,it is found that the influence of solar radiation change is mainly to increase the convergence of atmosphere toward the land,and the influence of SST change is mainly to transport more moisture to the sea surface atmosphere.Their synergistic effect on East Asian precipitation is much stronger than the sum of their respective effects.
A Study of the Effect of Topography on the Merging of Vortices
CHEN Lianshou, LUO Zhexian
2004, 21(1): 13-22. doi: 10.1007/BF02915676
Eight sets of numerical experiments are performed in 48 hours of integtation by using a barotropic primitive equation model with a topographic term so as to investigate the effect of topography on the merging of vortices.It is pointed out that the introduction of topography may change the track of vortices,and it causes the low vortices and vorticity lumps to be detained on the southeast side of the topography,thus creating a favorable condition for the merging of the low vortex and vorticity lumps.It is also shown that the effect of topography may cause double mergers of vortices in a horizontally shearing basic flow,and it can strengthen the low vortex remarkably.
Numerical Simulation of the 1999 Yangtze River Valley Heavy Rainfall Including Sensitivety Experiments with Different SSTA
GUO Yufu, WANG Jia, ZHAO Yan
2004, 21(1): 23-33. doi: 10.1007/BF02915677
With the IAP/LASG GOALS model,the heavy rainfall of the summer of 1999 in the Yangtze River valley is simulated with observational sea surface temperature (SST).Comparing the simulations of 1999 with the corresponding ones of 1998 and the sensitivity experiments with different sea surface temperature anomalies (SSTA) at different ocean regions,the relationships between the floods in the Yangtze River valley and the SSTA in the Pacific and Indian Oceans are studied.The results show that the positive SSTAin the tropical Indian Ocean are a major contributor to the heavy rainfall and may be a very important index to predict the heavy rainfall over the Yangtze River valley in the summer.The simulations also show that the relationships between the SSTA in the tropical eastern Pacific and the heavy rainfall in the Yangtze River valley are very complicated,and the heavy rainfall in the Yangtze River valley can occur in both a decaying and an intensifying El Ninio event and also in a La Nina event.However,the different SSTA of different periods in the above three cases play different parts.
Physical Mechanism and Model of Turbulent Cascades in a Barotropic Atmosphere
HUANG Feng, LIU Shikuo
2004, 21(1): 34-40. doi: 10.1007/BF02915678
In a barotropic atmosphere,new Reynolds mean momentum equations including turbulent viscosity,dispersion,and instability are used not only to derive the KdV-Burgers-Kuramoto equation but also to analyze the physical mechanism of the cascades of energy and enstrophy.It shows that it is the effects of dispersion and instability that result in the inverse cascade.Then based on the conservation laws of the energy and enstrophy,a cascade model is put forward and the processes of the cascades are described.
An Index Measuring the Interannual Variation of the East Asian Summer Monsoon--The EAP Index
2004, 21(1): 41-52. doi: 10.1007/BF02915679
Based on the EAP (East Asia/Pacific) teleconnection in the summer circulation anomalies over the Northern Hemisphere,an index measuring the strength of the East Asian summer monsoon,i.e.,the socalled EAP index,is defined in this paper.From the analyses of observed data,it is clearly shown that the EAP index defined in this study can well describe the interannual variability of summer rainfall and surfaceair temperature in East Asia,especially in the Yangtze River valley and the Hualhe River valley,Korea,and Japan.Moreover,this index can also reflect the interannual variability of the East Asian summer monsoon system including the monsoon horizontal circulation and the vertical-merldional circulation cell over East Asia.From the composite analyses of climate and monsoon circulation anomalies for high EAP index and for low EAP index,respectively,it is well demonstrated that the EAP index proposed in this study can well measure the strength of the East Asian summer monsoon.
Retrieval of Upper Tropospheric Relative Humidity by the GMS-5 Water Vapor Channel: A Study of the Technique
HUANG Yi, WANG Meihua, MAO Jietai
2004, 21(1): 53-60. doi: 10.1007/BF02915680
This paper presents an analysis of a technique for retrieving upper tropospheric relative humidity through the GMS-5 satellite's 6.7-micron water vapor channel brightness temperature.NCEP analysis shows that a critical assumption of the retrieval theory,namely the constant temperature lapse rate,matches only in the tropical atmosphere.By statistical analyses of brightness temperature simulated by a radiative transfer model and of relative humidity,we examine the effect of lapse rate on this retrieval method and obtain retrieval parameters and error estimates applicable to the GMS-5 satellite over East Asia.If the retrieval parameters are properly chosen,the relative error of retrieving the upper tropospheric relative humidity in this region is less than 10%,and if applied to the low-latitude summer atmosphere,it is less than 5%.
Modeling Marine Stratocumulus with a Detailed Microphysical Scheme
ZHAO Chunsheng, Yutaka ISHIZAKA
2004, 21(1): 61-74. doi: 10.1007/BF03342546
A one-dimensional 3rd-order turbulence closure model with size-resolved microphysics and radiative transfer has been developed for investigating aerosol and cloud interactions of the stratocumulus-topped marine boundary layer.A new method is presented for coupling between the dynamical model and the microphysical model.This scheme allows the liquid water related correlations to be directly calculated rather than parameterized.On 21 April 2001,a marine stratocumulus was observed by the Caesar aircraft over the west Pacific Rim south of Japan during the 2001 APEX/ACE-Asia field measurements.This cloud is simulated by the model we present here.The model results show that the general features of the stratocumulus-topped marine boundary layer predicted by the model are in agreement with the measurements.A new onboard cloud condensation nuclei (CCN) counter provides not only total CC Nnumber concentration (as the traditional CCN counters do at a certain supersaturation) but also the CCN size distribution information.Using these CCN data,model responses to different CCN initial concentrations are examined.The model results are consistent with both observations and expectations.The numerical results show that the cloud microphysical properties are changed fundamentally by differentinitial CCN concentrations but the cloud liquid water content does not differ significantly.Different initial CCN loadings have large impacts on the evolution of cloud microstructure and radiation transfer while they have a modest effect on thermodynamics.Increased CCN concentration leads to significant decrease of cloud effective radius.
The Role of -effect and a Uniform Current on Tropical Cyclone Intensity
DUAN Yihong, WU Rongsheng, YU Hui, LIANG Xudong, Johnny C L CHAN
2004, 21(1): 75-86. doi: 10.1007/BF02915681
A limited-area primitive equation model is used to study the role of the -effect and a uniform current on tropical cyclone (TC) intensity.It is found that TC intensity is reduced in a non-quiescent environment compared with the case of no uniform current.On an f-plane,the rate of intensification of a tropical cyclone is larger than that of the uniform flow.A TC on a -plane intensifies slower than one on an f-plane.The main physical characteristic that distinguishes the experiments is the asymmetric thermodynamic (including convective) and dynamic structures present when either a uniform flow or -effect is introduced.But a fairly symmetric TC structure is simulated on an f-plane.The magnitude of the warm core and the associated subsidence are found to be responsible for such simulated intensity changes.On an f-plane,the convection tends to be symmetric,which results in strong upper-level convergence near the center and hence strong forced subsidence and a very warm core.On the other hand,horizontal advection of temperature cancels part of the adiabatic heating and results in less warming of the core,and hence the TC is not as intense.This advective process is due to the tilt of the vortex as a result of the -effect.A similar situation occurs in the presence of a uniform flow.Thus,the asymmetric horizontal advection of temperature plays an important role in the temperature distribution.Dynamically,the asymmetric angular momentum (AM) flux is very small on an f-plane throughout the troposphere.However,the total AM exports at the upper levels for a TC either on a-plane or with a uniform flow environment are larger because of an increase of the asymmetric as well as symmetric AM export on the plane at radii >450 km,and hence there is a lesser intensification.
A Study of Rainfall-Runoff Response in a Catchment Using TOPMODEL
SUN Shufen, DENG Huiping
2004, 21(1): 87-95. doi: 10.1007/BF02915682
The simplicity of Topography-based hydrological model (TOPMODEL),as a way of reflecting the topographic controls on soil water storage and runoff generation,has become more attractive and morepopular for land surface process study since digital elevation models (DEMs) have become widely available.In this paper,the effect of the topography index on soil water storage distribution,which is the key to TOPMODEL,is explained.Then a simple water cycle model for estimating other components of the surface water cycle is developed,which is implemented into the TOPMODEL to integrate the water cycle of the catchment.Using the output of a DEM from 100 m × 100 m resolution data and a single flow direction algorithm,the index distribution function is calculated for a catchment (around 2500 km2 )in the upper reaches of the Yangtze River under different channel initiation thresholds.Finally,the daily and monthly rainfall-runoff response from 1960 to 1987 for the catchment is simulated with the TOPMODEL coupled with the simple water cycle model.
Diagnostic Analyses and Application of the Moist Ageostrophic Vector Q
YAO Xiuping, YU Yubin, SHOU Shaowen
2004, 21(1): 96-102. doi: 10.1007/BF02915683
Considering the main thermal forcing factor,which is critical for the development of synoptic systems,the concept of the moist ageostrophic vector Q is introduced.A formula of the moist ageostrophic Q and the ageostrophic diabatic equation,in which the divergence of the moist ageostrophic Q is taken as a single forcing term,is derived.Meanwhile,the moist ageostrophic Q is applied to diagnose a torrential rain process in North China.The results suggest that the moist ageostrophic Q can clearly reveal the system development during the torrential rain process; the corresponding relationship between the divergence of the moist ageostrophic Q and the rainfall area is better than that of the vertical velocity (ω) and the divergence of the dry Q; the 6-h rainfall region can be correctly drawn according to the negative area of the divergence of the moist ageostrophic Q,and its precipitation is positively correlated to the magnitude of the divergence of the moist ageostrophic Q.The research provides valuable information for improving short-term weather forecast.
The Multi-Scale Numerical Modeling System for Research on the Relationship between Urban Planning and Meteorological Environment
FANG Xiaoyi, JIANG Weimei, MIAO Shiguang, ZHANG Ning, XU Min, JI Chongping, CHEN Xianyan, WEI Jianmin, WANG Zhihua, WANG Xiaoyun
2004, 21(1): 103-112. doi: 10.1007/BF02915684
Considering the urban characteristics,a customized multi-scale numerical modeling system is established to simulate the urban meteorological environment.The system mainly involves three spatial scales:the urban scale,urban sub-domain scale,and single to few buildings scale.In it,different underlying surface types axe employed,the building drag factor is used to replace its roughness in the influence on the urban wind field,the effects of building distribution,azimuth and screening of shortwave radiation are added,and the influence of anthropogenic heating is also taken into account.All the numerical tests indicate that the simulated results are reasonably in agreement with the observational data,so the system can be used to simulate the urban meteorological environment.Making use of it,the characteristics of the meteorological environment from the urban to urban sub-domain scales,even the among-buildings scale,can be recognized.As long as the urban planning scheme is given,the corresponding simulated results can be obtained so as to meet the need of optimizing urban planning.
Numerical Simulation of the Critical Scale of Oasis Maintenance and Development in the Arid Regions of Northwest China
GAO Yanhong, CHEN Yuchun, Lü Shihua
2004, 21(1): 113-124. doi: 10.1007/BF02915685
Oasis is a special geographic landscape among the vast desert/Gobi in Northwest China (NWC).The surface sensitive heat flux and latent heat flux at Zhangye Oasis during I to 11 August 1991 are simulated using the NCAR nonhydrostatic mesoscale model MM5 Version 3.The horizontal grid resolution is set as lkm.By comparing the simulation results with HEIFE observations,it is proved that the model can be used to simulate the surface energy and water mass exchange of arid and semiarid regions in NWC.Based on the above results,the influence of different oasis scales on the local atmospheric field near the ground surface,and the critical scale of oasis maintenance,in NWC are studied dynamically.The following conclusion is obtained: the local thermal circulation between the oasis and the desert/Gobi is formed in the oasis downstream if the oasis scale is larger than 4 km.This local thermal circulation between the oasis and the desert adjacent to the oasis helps to conserve water vapor over the oasis.At the same time,it transfers the abundant water vapor from the oasis into the desert/Gobi near to the oasis to supply relatively plentiful water vapor for desert crops to grow on the fringe of the oasis.So,it is advantageous for oasis extension.However,if the scale of the oasis is smaller than 4 km,it is not easy for the local thermal circulation between the oasis and the desert/Gobi to take shape.This study provides a new standpoint for oasis maintenance and development.
A Scheme for Pixel-Scale Aerodynamic Surface Temperature over Hilly Land
MIN Wenbin, CHEN Zhongming, SUN Linsheng, GAO Wenliang, LUO Xiuling, YANG Tingrong, PU Jian, HUANG Guanglun, YANG Xiurong
2004, 21(1): 125-131. doi: 10.1007/BF02915686
Hilly-land satellite pixel-scale aerodynamic surface temperatures (AdST) are investigated using LAS (Large Aperture Scintillometer) and meteorological observations during 21-22 May 2001,indicating that the calculated temperatures are predominantly subject to estimated roughness lengths and,to a less extent,to estimated Bowen ratios,with errors to within 3.0 K between the AdST calculations and hilly radiometric surface temperatures retrieved from satellite data with the split window model.The errors depend heavily on the model used and the zenith angles and azimuth of the satellite and sun with respect to the observational site.
NOx Change over China and Its Influences
LIU Yu, I. S. A. ISAKSEN, J. K. SUNDET, HE Jinhai, YAN Peng
2004, 21(1): 132-140. doi: 10.1007/s00376-002-0071-3
A 3-D chemical transport model (OSLO CTM2) is used to investigate the impact of the increase of NOx emission over China.The model is capable to reproduce basically the seasonal variation of surface NOx and ozone over eastern China.NOx emission data and observations reveal that NOx over easternChina increases quite quickly with the economic development of China.Model results indicate that NOxconcentration over eastern China increasingly rises with the increase of NOx emission over China,and accelerates to increase in winter.When the NOx emission increases from 1995 to its double,the ratio of NO2/NOx abruptly drops in winter over northern China.Ozone at the surface decreases in winter with the continual enhancement of the NOx level over eastern China,but increases over southern China in summertime.It is noticeable that peak ozone over northern China increases in summer although mean ozone changes little.In summer,ozone increases in the free troposphere dominantly below 500 hPa.Moreover,the increases of total ozone over eastern China are proportional to the increases of NOx emission.In a word,the model results suggest that the relationship between NOx and ozone at the surface would change with NOx increase.
On the Variability and Correlation of Surface Ozone and Carbon Monoxide Observed in Hong Kong Using Trajectory and Regression Analyses
WANG Tijian, K. S. LAM, C. W. TSANG, S. C. KOT
2004, 21(1): 141-152. doi: 10.1007/BF02915688
This paper investigates,the variability and correlation of surface ozone (03) and carbon monoxide (CO) observed at Cape D'Aguilar in Hong Kong from I January 1994 to 31 December 1995.Statistical analysis shows that the average 03 and CO mixing ratios during the two years are 32:k17 ppbv and 305:k191ppbv,respectively.The O3/CO ratio ranges from 0.05 to 0.6 ppbv/ppbv with its frequency peaking at 0.15.The raw dataset is divided into six groups using backward trajectory and cluster analyses.For data assigned to the same trajectory type,three groups are further sorted out based on CO and NOx mixing ratios.The correlation coefficients and slopes of O3/CO for the 18 groups are calculated using linear regression analysis.Final]y,five kinds of air masses with different chemical features are identified:continental background (CB),marine background (MB),regional polluted continental (RPC),perturbed marine (P'M),and local polluted (LP) air masses.Further studies indicate that 03 and CO in the continental and marine background air masses (CB and MB) are positively correlated for the reason that they are well mixed over the long range transport before arriving at the site.The negative correlation between 03 and CO in air mass LP is believed to be associated with heavy anthropogenic influence,which results from the enhancement by local sources as indicated by high CO and NOx and depletion of 03 when mixed with fresh emissions.The positive correlation in the perturbed marine air mass P*M favors the low photochemical production of 03.The negative,correlation found in the regional polluted continental air mass RPC is different from the observations at Oki Island in Japan due to the more complex 03 chemistry at Cape D'Aguilar.