Advanced Search

2002 Vol. 19, No. 1

Display Method:
The Instability of the East Asian Summer Monsoom-ENSO Relations
Wang Huijun
2002, 19(1): 1-11. doi: 10.1007/s00376-002-0029-5
The instability in the relation between the East Asian summer monsoon and the ENSO cycle in the long-term variation is found through this research. By instability, we mean that high inter-relation exists in some periods but low inter-relation may appear in some other periods. It is reveals that the interannual variation of the summer atmospheric circulation during the high correlation periods (HCP) is significantly different from that during the low correlation' periods (LCP).Larger interannual variability is found during HCP for trade wind over the tropical eastern Pacific of the Southern Hemisphere, the low-level air temperature over the tropical Pacific, the subtropical high pressure systems in the two hemispheres, and so on. The correlation between summer rainfall over China and ENSO is as well different between HCP and LCP.
Associations between the Western North Pacific Monsoon and the South China Sea Monsoon
Lu Riyu, Chan-Su Ryu, Buwen Dong
2002, 19(1): 12-24. doi: 10.1007/s00376-002-0030-z
Based on the interannual variability of convection over the tropical western North Pacific (WNP), a region of 130°-160°E, 10°-20°N, a composite analysis is performed on the fields of surface temperature,outgoing longwave radiation and 850 hPa zonal wind. The composite results show that the weaker (stronger) WNP convection is related to the El Nino (La Nina)-pattern sea surface temperature (SST)anomalies in the preceding winter and in spring. A comparison with previous results indicates that a similar spatial and temporal distribution of SST anomalies is also associated with the onsets of both the WNP and South China Sea (SCS) monsoons.The composite results also show that the weaker (stronger) convection over the WNP corresponds to the easterly (westerly) anomalies that extend westward from the WNP into the Bay of Bengal. A numerical experiment by an atmospheric general circulation model shows a similar result. In addition, during weaker (stronger) convection summer, the convection over the WNP and lower-level zonal winds over the SCS exhibit a small (large) extent of seasonal evolution.
Parameterization of Longwave Optical Properties for Water Clouds
Wang Hongqi, Zhao Gaoxiang
2002, 19(1): 25-34. doi: 10.1007/s00376-002-0031-y
Based on relationships between cloud microphysical and optical properties, three different parameterization schemes for narrow and broad band optical properties in longwave region for water clouds have been presented. The effects of different parameterization schemes and different number of broad bands used on cloud radiative properties have been investigated. The effect of scattering role of cloud drops on longwave radiation fluxes and cooling rates in cloudy atmospheres has also been analyzed.
Semi-Circle Theorem of Unstable Spectrum Distribution of Heterotropic Perturbation and the Upper Bound Estimation of Its Growth Rate
Zhang Ming, Zhang Lifeng
2002, 19(1): 35-44. doi: 10.1007/s00376-002-0032-x
Based on the theoretical analysis on the unstable spectrum distribution of heterotropic perturbation, the semi-circle theorem of such spectrum distribution is obtained -- the spectrum distributed within an upper semi-circle domain with radius R0 and taking origin as its circle center in the complex plane, and the upper bound estimation of growth rate is given simultaneously. It is found that the smaller the horizontal scale of perturbation is, the higher the model top located, the greater the estimated value of upper bound of such growth rate is. Also the increase of vertical shear of wind and latitude have the positive contribution to the increase of such growth rate. Finally when stratified stability decreases, the relative maximal growth rate increases, while the maximal growth rate decreases instead.
A Theoretical Analysis on the Local Climate Change Induced by the Change of Landuse
Zhao Ming, Zeng Xinmin
2002, 19(1): 45-63. doi: 10.1007/s00376-002-0033-9
The local climate change induced by the change of landuse, i.e., the degeneration of vegetation is studied by the consideration of the equilibrium among radiation, phase change and convection in an air column and the energy balance condition on the ground surface. The result shows that the increase of ground albedo and the change of the surface heat flux as well as the decrease of the surface roughness length may induce the decrease of precipitation and the increase of temperature in the northern China, similar to the numerical simulation. Considering advection, this conclusion is also true except the amounts of the decrease of precipi tation and the increase of temperature are changed. The decrease of precipitation and the increase of temperalure will be more serious in case of global warming.
Analyzing Method on Biogenic Volatile Organic Compounds
Bai Jianhui, Wang Mingxing, Hu Fei, James P. Greenberg, Alex B. Guenther
2002, 19(1): 64-72. doi: 10.1007/s00376-002-0034-8
In order to analyze biogenic volatile organic compounds in the atmosphere, an automated gas chromatography is developed and employed at the laboratory of National Center for Atmospheric Research (NCAR) during January to July, 2000. A small refrigerator was used so as to remove water in the air sample from gas line. and get accurate concentrations of volatile organic compounds. At 5°C, good water removing efficiency can be obtained at controlled flow rate. Air samples were collected around the building of Mesa Lab. of NCAR and analyzed by this gas chromatography system. This paper reports this gas chromatography system and results of air samples. The experimental results show that this gas chromatography system has a good reproducibility and stability, andmain interesting volatile organic compounds such as isoprene, monoterpenes have an evident diurnal variation.
Characteristics of Micrometeorology in the Surface Layer in the Tibetan Plateau
Liu Huizhi, Zhang Hongsheng, Bian Lin'gen, Chen Jiayi, Zhou Mingyu, Xu Xiangde, Li Shiming, Zhao Yijun
2002, 19(1): 73-88. doi: 10.1007/s00376-002-0035-7
The data of the meteorological elements in the surface layer have been analyzed which were obtained during the IOP of TIPEX fiom May to July 1998 in Gerze, Damxung and Qamdo. The characteristics of the diurnal variations and the vertical profiles of the wind velocity, temperature and humidity in the surface layer have been investigated. Some interesting results have been obtained. The moisture inversion phenomena occured during the daytime in the surface layer have also been discussed.
Land Surface Hydrology Parameterization over Heterogeneous Surface for the Study of Regional Mean Runoff Ratio with Its Simulations
Liu Jingmiao, Ding Yuguo, Zhou Xiuji, Wang Jijun
2002, 19(1): 89-102. doi: 10.1007/s00376-002-0036-6
An analytical expression for subgrid-scale inhomogeneous runoff ratios generated by heterogeneoussoil moisture content and climatic precipitation forcing is presented based on physical mechanisms for land surface hydrology and theory of statistical probability distribution. Thereby the commonly used mosaic parameterization of subgrid runoff ratio was integrated into a statistical-dynamic scheme with the bulk heterogeneity of a grid area included. Furthermore, a series of numerical experiments evaluating the reliability of the parameterization were conducted using the data generated by the emulated simulation method. All the experimental results demonstrate that the proposed scheme is feasible and practical.
Recent Progress on Tropical Cyclone Research in China
Meng Zhiyong, Chen Lianshou, Xu Xiangde
2002, 19(1): 103-110. doi: 10.1007/s00376-002-0037-5
This paper summarizes main progresses made in tropical cyclone research field in China in the past few years after the 8th five year program of China. New achievements have been made on tropical cyclone (hereafter referred as TC) structure, numerical prediction, evaluation of operational numerical model,TC-caused heavy rain, TC climate features and disasters, etc.
Effects of Nested Area Size upon Regional Climate Model Simulations
Liu Huaqiang, Qian Yongfu, Zheng Yiqun
2002, 19(1): 111-120. doi: 10.1007/s00376-002-0038-4
This paper presents a numerical study on the 1998 summer rainfall over the Yangtze River valley in central and eastern China, addressing effect of a nested area size on simulations in terms of the technique of nesting a regional climate model (RCM) upon a general circulation model (GCM). Evidence suggests that the size exerts greater impacts upon regional climate of the country, revealing that a larger nested size is su perior to a small one for simulation in mitigating errors of GCM-provided lateral boundary forcing. Also,simulations show that the RCM should incorporate regions of climate systems of great importance into study and a low-resolution GCM yields more pronounced errors as a rule when used in the research of the Tibetan Plateau, and, in contrast, our PσRCM can do a good job in describing the plateau′s role in a more realistic and accurate way. It is for this reason that the tableland should be included in the nested area when the RCM is employed to investigate the regional climate. Our PσRCM nesting upon a GCM reaches morerealistic results compared to a single GCM used.
Observation and Study of Land Surface Parameters over Gobi in Typical Arid Region
Zhang Qiang, Cao Xiaoyan, Wei Guoan, Huang Ronghui
2002, 19(1): 121-135. doi: 10.1007/s00376-002-0039-3
According to the need of popular land surface process models, characteristics and rules of some key land surface process and soil parameters over Gobi in typical arid region of Northwest China are analyzed by using the data observed during the intensive observation period of the Dunhuang Land-Surface Process Field Experiment (DLSPFE) (May-June 2000). Using the relative reflection as weighting factor, the weighted mean of the surface albedo over Dunhuang Gobi in typical arid region is calculated and its values are 0.255 -+ 0.021. After canceling the interference of the buildings, the mean values of the roughness length averaged with logarithm is 0.0019-+ 0.00071 m. After removing the influence of the oasis, the soil wetness factor computed with data under condition of no precipitation is 0.0045. After removing the influence of the precipitation, the mean values of the soil heat capacity over Dunhuang Gobi in typical arid region is 1.12 ×l06 J m -3K-1, a bit smaller than the values observed in HEIFE. But the soil heat diffusivity and conductivity are about one of those observed in HEIFE. The soil water content over Dunhuang Gobi in typical synoptic condition is very little and does not exceed 1% basically.
Analysis of the Aerosol Extinction Characteristics in Different Areas of China
Zhang Junhua, Mao Jietai, Wang Meihua
2002, 19(1): 136-152. doi: 10.1007/s00376-002-0040-x
The multi-wavelength aerosol optical depths and the Angstrom exponent between 450 nm and 900 nm in four locations of China (Miyun, Beijing; Xinfeng, Guangdong; Waliguan, Qinghai and Damxung, Tibet)have been observed by sun-photometers. This paper analyzes their characteristics for a one-year period from February 1998 to January 1999. The results show that in the arid and semi-arid locations like Miytun (117.12°E, 40.65°N) and Waliguan (100.90°E, 36.29°N), there is a maximum of aerosol optical depth in the spring, it is about twice as large as in any other season. In a humid region like Xinfeng (114.2°E, 24.5°N), theaerosol optical depth also has a maximum in the spring, however it is only slightly larger than in other sea sons. The Angstrom exponent shows a significant minimum at Waliguan in spring, about 0.15, indicating relatively large dust aerosol particles. Large variability of the monthly mean Angstrom exponent is also found in Miyun and Xinfeng, but there is no tendency with seasons. It means that the source of aerosol in these locations is complicated.
Observational Analyses of Baroclinic Boundary Layer Characteristics during One Frontal Winter Snowstorm
Xu Yinlong, Qian Fenlan, Chen Zhi, Li Shiming, Zhou Mingyu
2002, 19(1): 153-168. doi: 10.1007/s00376-002-0041-9
The evolution and characteristics of the baroclinic boundary layer for one frontal winter snowstorm were analyzed by using the well-documented dataset during Intensive Observation Period (IOP) 17 of STORM-FEST. It is found that when the warm moist air was lifted across the front, a great amount of la tent heat release because of snowing increased the frontal temperature contrast to intensify frontogenesis. Itis shown in the zig-zag section diagram of potential temperature that when the frontogenesis got stronger, a cold trough was formed and both low-level jet (LLJ) and upper-level jet (ULJ) emerged ahead of the front.In the strongest stage of frontogenesis, the frontal contrast of potential temperature of cold trough reached as high as 20 K. Hereafter the LLJ ahead of the front tended to weaken and the LLJ behind the front tended to strengthen. The frontal circulation system was dominated by the cold air advection behind the front,which transported the cold air behind the front forward to the warm area ahead of the front to weaken the cold trough and finally frontolysis occurred. It is shown by the analyses of turbulent characteristics of front al baroclinic boundary-layer that the vertical shear (wv) above the boundary layer was very large, and the pumping of the strong wind shear in turbulent energy budget made the characteristic variables within the PBL well mixed. Sufficient moisture carried by southerly flow from the Mexico Gulf, and the strong baroclinity of the frontal boundary layer played key roles in this frontal winter snowstorm, and the large-scale ULJ behind the cold front is also advantageous to the development of the convective boundary layer.
A Flexible Coupled Ocean-Atmosphere General Circulation Model
Yu Yongqiang, Yu Rucong, Zhang Xuehong, Liu Hailong
2002, 19(1): 169-190. doi: 10.1007/s00376-002-0042-8
Based on the National Center for Atmospheric Research (NCAR) Climate System Model version 1(CSM-1), a Flexible coupled General Circulation Model version 0 (FGCM-0) is developed in this study through replacing CSM-1's oceanic component model with IAP L30T63 global oceanic general circulation model and some necessary modifications of the other component models. After the coupled model FGCM--0 is spun up for dozens of years, it has been run for 60 years without flux correction. The model does not only show the reasonable long-term mean climatology, but also reproduce a lot of features of the interannual variability of climate, e.g. the ENSO-like events in the tropical Pacific Ocean and the dipole mode pattern in the tropical Indian Ocean. Comparing FGCM-0 with the NCAR CSM-1, some common features are found, e.g. the overestimation of sea ice in the North Pacific and the simulated double ITCZ etc.The further analyses suggest that they may be attributed to errors in the atmospheric model.