Advanced Search

1994 Vol. 11, No. 2

Display Method:
article
A Note on Some Methods Suitable for Verifying and Correcting the Prediction of Climatic Anomaly
Zeng Qingcun, Zhang Banglin, Yuan Chongguang, Lu Peisheng, Yang Fanglin, Li Xu, Wang Huijun
1994, 11(2): 121-127. doi: 10.1007/BF02666540
Abstract:
The weighted correlation coefficient of the predicted and observed anomalies and the ratio of the weighted norm of predicted anomaly to the observed one, both together, are suggested to be suitable for the estimating of the correctness of climate prediction. The former shows the similarity of the two patterns, and the later indicates the correctness of the predicted intensity of the anomaly. The weighting function can be different for different emphasis, for example, a constant weight means that the correlation coefficient is the conventional one, but same non-uniform weight leads to the ratio of correct sign of the anomaly, the stepwise weight leads lo the formulation of correctness of prediction represented by grades of the anomaly, and so on.Three methods for making correction to the prediction are given in this paper. After subtracting lie mean error of the prediction, one method is developed for maximizing the similarity between the predicted and observed patterns, based on the transformation of the spatial coordinates. Another method is to minimize the mean difference between the two fields. This method can also be simplified as similar to the “optimum interpolation” in the objective analysis of weather chart. The third method is based on the expansion of the anomaly into series or EOF, where the coefficients are the predicted but the EOFs are taken as the “observed” calculated from historical samples.
Simultaneous Non-linear Retrieval of Atmospheric Temperature and Absorbing Constituent Profiles from Satellite Infrared Sounder Radiances
Li Jun, Zhou Fengxian, Zeng Qingcun
1994, 11(2): 128-138. doi: 10.1007/BF02666541
Abstract:
Based on Zeng’s theory (1974), a successive linearized form of radiative transfer equation (RTE) is derived for simultaneous retrieval of atmospheric temperature and absorbing constituent profiles from satellite infrared observa-tions. It contains the temperature component weighting function and absorbing constituent (H2O, O3, CH4 etc.) com-ponent weighting functions. All these weighting functions reach maximum at their own “optimum information levels”, and make the remote sensing equations well-conditional. Then the atmospheric profiles are derived by Newton’s non-linear iteration method. Experiments of retrieval from both TIROS-N operational High Resolution Infrared Sounder (HIRS) and the simulated Atmospheric infRared Sounder (AIRS) show an significant improvement.
The Influence of Changes in Vegetation Type on the Surface Energy Budget
Runkua Yang, J. Shukla, P.J. Sellers
1994, 11(2): 139-161. doi: 10.1007/BF02666542
Abstract:
The influence of changes in vegetation type on the surface energy budget was studied using the Simple Biosphere Model (SiB) of Sellers et al. (1986). The modeled energy budget response to the conversion of forest to short vegeta-tion or bare soil (deforestation) was investigated with SiB forced by three time-series of atmospheric boundary condi-tions collected at three different climatic sites: an Amazonian tropical forest, a. U.S. Great Plains grassland, and a cen-tral Wales spruce forest. The results show that SiB can simulate realistic surface energy budgets and surface tempera-tures, and that deforestation may have a significant influence on the local surface energy budget and surface weather. The influence is especially prominent at the Amazonian and U.S. Great Plains sites, and greater in summer than in other seasons.It was found that atmospheric boundary conditions play a dominant role in determining the degree of changes in the surface fluxes and temperature induced by deforestation; the largest change in latent heat flux appeared at the Amazon site, the largest change in sensible heat flux appeared at the Spruce forest site, and the largest change in sur-face temperature appeared at the Great Plains site. The Bowen ratios of the SiB sensitivity integrations for each site are comparable with observations. The values of the Bowen ratio and the ratio of latent heat flux to net radiation vary distinctly from site to site, implying that local atmospheric conditions limit the range of changes caused by the vegeta-tion change.
A Model Study of Three Dimensional Wind Field Analysis from Dual-Doppler Radar Data
Kong Fanyou, Mao jietai
1994, 11(2): 162-174. doi: 10.1007/BF02666543
Abstract:
A three-dimensional wind field analysis software based on the Beijing-Gucheng dual-Doppler weather radar system has been built, and evaluated by using the numerical cloud model producing storm flow and hydrometer fields. The effects of observation noise and the spatial distribution of wind field analysis error are also investigated.
Helicity Dynamics of Atmospheric Flow
Tan Zhemin, Wu Rongsheng
1994, 11(2): 175-188. doi: 10.1007/BF02666544
Abstract:
Helicity is an important physical variable which is similar to the energy and enstrophy in three-dimensional fluid. It can be used to describe the motion in the direction of fluid rotation and also can be regarded as a new physi-cal variable in turbulence theory. In recent years, it has been used in atmospheric dynamics. In this paper, helicity of atmospheric flow, especially helicity in the boundary layer and in the vicinity of front was discussed. These results show that helicity is usually positive in the boundary layer due to the effect of friction. The helicity of boundary layer flow is larger in anticyclone than that in cyclone, resulting from the different wind structures of boundary layers in an-ticyclone and cyclone under the geostrophic momentum approximation. It is possible that the helicity is negative at certain height in the baroclinic boundary layer. The influences of nonlinearity and baroclinity on the helicity are im-portant. The so called “Cloud Street” in the boundary layer is related to the dynamics of helicity. Helicity in the at-mosphere can be expressed as the temperature advection under some conditions, so helicity would be allowed to des-cribe the frontogenesis and development of frontal structure. The amplitude of helicity increases with time in the frontogenesis. A large gradient of helicity is generated in the region located to the northeast of the surface low and in which the front is formed. In warm frontal region, as well as behind the trough of temperature, the helicity is positive, while the helicity is negative in cold frontal sector and in the ahead ridge of temperature. The largest helicity occurs in the boundary.
A Comparison Study of the Climatological Air-Sea Heat Fluxes Estimated by Different Computational Schemes of Bulk Formula
Fu Congbin, Robert Pyle, Fan Huijun
1994, 11(2): 189-200. doi: 10.1007/BF02666545
Abstract:
In this paper the different results of estimated air-sea heat fluxes by different computational schemes of bulk formula are researched. The varying results may bring another source of the uncertainties of flux climatology.In addition to the classical scheme and the sampling scheme, a revised sampling scheme named semi-sampling scheme is proposed in this paper. In this revised version, the monthly means of and are cal?culated from each simultaneous measurement as that in the sampling method. But the transfer coefficients in this version are defined based on monthly means of and instead of those in each measurement in older to use the files of monthly mean variables and in COADS (Woodruff et al. 1987).The results of a comparison study show that the covariance between and and that between and are less than 2 W / m2 and 5 W / m2 respectively in most areas, which are about one order of magni?tude less than the standard deviation of the fluxes. Therefore the difference between two schemes is not statistically significant on average. However, in the regions off coast of Asian and North American continents, the contribution of covariance between and can be as large as 15 W / m2, which is about one third to a half of the standard deviation. Since there are files of monthly mean and for each year in the COADS, we pro?pose to use these files directly in calculation of climatology. It is not necessary to use every individual report.The flux climatology calculated directly from the long-term mean values of basic meteorological elements shows an significant difference from that calculated from the mean of each year’s flux, particularly for the latent heat flux which is on the order of 10 to 15 W / m2, about 3-4 times of the difference between semi-sampling and classical schemes and about one third of the standard deviation. Therefore it indicates that the time interval of months is per?haps a better one in the calculation of flux climatology. It is not recommended to use the long-term means of the me?teorological variables.
Numerical Modelling of the Effects of Ozone on the Summer Atmospheric Circulation
Wang Qianqian, Wang Yinhui, Song Yu, Qian Yongfu
1994, 11(2): 201-211. doi: 10.1007/BF02666546
Abstract:
The effects of ozone on the summer atmospheric general circulation are simulated by use of a zonal model with the p-sigma coordinate system. Results show that the simulated properties at the upper levels are remarkably im-proved after the ozone effects are introduced to the model. The direct effect of ozone is to enhance the heating rates at the upper levels. In the lower atmosphere, this effect is very little. Furthermore, the ozone can change the distributions and values of other components of heating fields, resulting in the change of the total heating rates, and meanwhile induce evident variation of atmospheric circulation at the lower levels.
Numerical Simulation for the Impact of Deforestation on Climate in China and Its Neighboring Regions
Song Yukuan, Chen Longxun, Dong Min
1994, 11(2): 212-223. doi: 10.1007/BF02666547
Abstract:
In this paper, the CCM0B model is used to study the effect of the deforestation on the climate of China and its neighboring regions. On the assumption that the forest is China would be replaced by the vegetation (Such as grassland), the distribution of the albedo changed was calculated. The initial felds used were taken from the FGGE zonal mean data on 16 July, 1979. In the control simulation, the observed albedo data were used to modify the physi-cal parameters of the original model. The control and sensitive experiments were ran each for 210 days, in which the external forcing fields were fixed in July. As a result, we find that the East Asian Monsoon, Hadley cell and troposphere easterly jet are weakened for the deforestation in China. The precipitation and cloud amount over China are also decreased. The changes in evaporation and surface temperature are small. The results also show that the deforestation in China exerts a remarkable effect on the climate in the neighboring regions of China.
A Forecasting Model of Vector Similarity in Phase Space for Flood and Drought over the Huanghe-Huaihe-Haihe Plain in China
Zhou Jiabin, Wang Yunkuan, Yang Guiying, Wu Jinsheng
1994, 11(2): 224-229. doi: 10.1007/BF02656952
Abstract:
To represent well the characteristics of temporal and spatial distributions, chart of 3-dekad moving total precipi-tation is proposed in this paper first. Then this kind of chart is expanded in terms of Chebyshev polynomial at irregular grids, and the quantitative representation of precipitation is got. Finally the Chebyshev coefficients are fore-casted by using the forecasting method of vector similarity in phase space proposed by Zhou (1992). Using above mentioned procedures temporal and spatial distributions of precipitation over the Huaaghe-Huaihe-Haihe Plain in China are forecasted.
Modelling the Interannual Variation of Regional Precipitation over China
Wang Huijun
1994, 11(2): 230-238. doi: 10.1007/BF02666549
Abstract:
The interannual change of regional precipitation over China during 1979-1988, simulated by the IAP 2-L AGCM (the atmospheric general circulation model) developed in the Institute of Atmospheric Physics and by using the observational monthly sea surface temperature (SST) and sea ice occupations, was analysed and compared with that of observation. Results show that the abilities of the model to simulate the interannual variabilities of precipita-tion are different from one region to another in China Studies indicate that the regional precipitation interannual va-riation which is correlated to the strong sign of sea surface temperature anomalies (SSTA) could be simulated well by the model, strong SSTA is important for the seasonal and extra-seasonal climate predictions through climate models. The results also suggest that the horizontal resolution of the model should be more refined in order to give better rep-resentations of regional details.
Water Resources of the South Asian Region in a Warmer Atmosphere
M.Lal
1994, 11(2): 239-246. doi: 10.1007/BF02666550
Abstract:
The global mean surface temperature may rise by about 0.3oC per decade during the next Few decades as a result of anthropogenic greenhouse gas emissions in the earth’s atmosphere. The data generated in the greenhouse warming simulations (Business-as-Usual scenario of IPCC) with the climate models developed at Max Planck Institute for Meteorology, Hamburg have been used to assess future plausible hydrological scenario for the South Asian region. The model results indicate enhanced surface warming (2.7oC for summer and 3.6oC for winter) over the land regions of South Asia during the next hundred years. While there is no significant change in the precipitation over most of the land regions during winter, substantial increase in precipitation is likely to occur during summer. As a result, an increase in soil moisture is likely over central India, Bangladesh and South China during summer but a statistically sig-nificant decline in soil moisture is expected over central China in winter. A moderate decrease in surface runoff may occur over large areas of central China during winter while the flood prone areas of NE-India. Bangladesh and South China are likely to have an increase in surface runoff during summer by the end of next century.
Improving the Vorticity-Streamfunction Method to Solve Two-Dimensional Anelastic and Nonhydrostatic Model
Sun Litan, Huang Meiyuan
1994, 11(2): 247-249. doi: 10.1007/BF02666551
Abstract:
The potential temperature vorticity has been introduced to polish the (momentum) vorticity-streamfunction method for solving the two-dimensional and nonhydrostatic model with much accuracy but not many increments of computation. The three-step procedure introduced in the present paper can be used to solve both shallow and deep dynamic models.