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1992 Vol. 9, No. 3

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Study on Cloud-Radiation Effect on Climate in Eastern Asia
Zhao Bolin, Zhang Xiaoli, Zhu Yuanjing
1992, 9(3): 257-268. doi: 10.1007/BF02656936
In this paper, the decade data of meteorological satellite and surface meteorological observation of China have been analysed. The relationship between cloud and radiation has been studied. A set of empirical formulae of the relationships between the albedo and cloud amount, the outgoing longwave radiation and cloud amount in Chinese different districts and different seasons has been deduced. They express simply the response of both planet reflectivity and earth-atmosphere outgoing longwave radiation to the change of cloud amount. So that the sensitivity of net ra-diation of the earth-atmosphere system to the change of cloud amount and the ratio of cloud reflective effect to greenhouse effect can be estimated. In this paper, the radiative process of the earth-atmosphere system, cloud and radiative balance and its effect on climate have been synthetically studied.
An Impact of Hydrostatic Extraction Scheme on BMRC’s Global Spectral Model
Sheng Hua, William Bourke, Terry Hart
1992, 9(3): 269-278. doi: 10.1007/BF02656937
There are two important features in geophysical fluid dynamics. One is that the atmospheric and oceanic equa-tions of motion include the Coriolis force; another is that they describe a stratified fluid. The hydrostatic extraction scheme, or standard stratification approximation, posed by Zeng (1979), reflects the second aspect of geophysical flu-id dynamics. There exist two major advantages in this scheme; accurate computation of the pressure gradient force can be obtained over steep mountain slopes, and the accumulation error in vertical finite differencing can be reduced, especially near the tropopause.Chen et al (1987) introduced the hydrostatic extraction scheme into a global spectral model, which attained pre-liminary success at low resolution. Zhang and Sheng et al (1990) developed and improved the hydrostatic extraction scheme in a global spectral model, in which C0, the parameter that represents the stratification of the reference at-mosphere, changes not only with height, but also with latitude. The scheme has been incorporated BMRC’s global spectral model (IAPB). Four 5-day forecasts have been performed to test the IAPB with the hydrostatic extraction scheme. Objective verifications demonstrate a positive effect of the hydrostatic extration scheme on BMRC’s model, particularly at upper levels, over the tropics and the Antartic region.
Past, Present and Future Climatic Forcing due to Greenhouse Gases
Shi Guangyu, Fan Xiaobiao
1992, 9(3): 279-286. doi: 10.1007/BF02656938
An advanced one-dimensional radiative-convective model (RCM) is used to estimate the past, present and fu-ture climatic forcings induced by greenhouse gases of anthropogenic origin, such as CO2, CH4, N2O and CFCs, in this paper. The results show that the decadal climatic forcing for the last decade is one-order bigger than that prior to the year 1900, and in the case of no control on the emission of the greenhouse gases the climatic forcing for the year 2100 will be almost 4 times as much as now.
Spectral and Anisotropic Corrections for GMS Satellite Data
Fang Xianjin
1992, 9(3): 287-298. doi: 10.1007/BF02656939
Using the radiative transfer simulation, the sampling study about the spectral and anisotropic corrections for GMS satellite data is carried out. The conversion factor and the anisotropic reflectance factor in inversion process of broadband radiation fluxes have been obtained for various underlying surface scenes in clear sky and for the case of overcast sky. The results demonstrate that the consideration of spectral and anisotropic corrections is essential for the earth radiation budget research using satellite data. The mean conversion factors for GMS are between 2.54 and 5.30. The values of the conversion factor are different for various observation angles, especially in cases of ocean, vegeta-tion cover and wet soil surface. The error of retrieving broadband radiance without considering the difference of ob-servation geometry is about 5.5%-15% for ocean, 4.5%-10% for various land surfaces. The calculated anisotropic factors for ocean and cloud scenes are in good agreement with those estimated from Nimbus-7. For Land, desert and snow scenes, the calculated values in backward scattering direction are smaller than the measured.
Wintertime Stratospheric Anomalies-Part I: Warm Pools
Y. L. McHall
1992, 9(3): 299-310. doi: 10.1007/BF02656940
The stratospheric worm pools, called the 4-day wave also, are mainly the temperature anomalies in the polar re-gions of winter hemisphere. It will be shown that their occurrence, propagation speed and specific structure can be explained by the lower frequency coherent heating resulting from the wave interaction in the breaking layers of the stratosphere. Although their vertical phase slope is negligibly small, the warm pools cannot be considered as a barotropic anomaly.
Wintertime Stratospheric Anomalies-Part II: Sudden Warmings
Y. L. McHall
1992, 9(3): 311-322. doi: 10.1007/BF02656941
The process of stratospheric sudden warmings from development of planetary waves to the sudden cooling after reversal of mean zonal circulation will be studied with the primitive equations of heat and momentum balances. It will be explained that the sudden warmings may occur only in the polar regions of winter stratosphere where zonal mean temperature decreases poleward. The heating rate in the order of major warmings is produced by developed planetary waves in the stratospheric breaking layers. The particular perturbation structure characterized by large amplitude of wave 1 together with minimum of wave 2 discovered by Labitzke (1977) is crucial for initiation of major warmings. The cooling by the same mechanism can be produced in the regions with reversed mean temperature gradient.
The Characteristics of 30-60 Day Oscillation and Its Relations to the Interannual Oscillations
Song Yi, Chen Longxun
1992, 9(3): 323-336. doi: 10.1007/BF02656942
The characteristics of 30-60 day oscillation (hereafter called LFO ) of the outgoing longwave radiation data (OLR) and its relations to the interannual oscillations of the sea surface temperature (SST) are investigated by using the daily OLR data for the period from January, 1979 to December, 1987 and the corresponding monthly SST data. II is found that the LFO the band the interannual oscillations of the SST monthly anomaly (SSTA) interact each oth-er and they all relate to the occurrence and development of El Nino events closely. Before El Nino event happens, it contributes to the SST’s warming up and to the SST’s quasi-biennial oscillation (called QBO for brevity) and three and half years oscillation (called SO for short) being in warm water phase in the equatorial central and eastern Pacific (ECP and EEP) that the LFO in the equatorial western Pacific (EWP) enhances and propagates eastward; When El Nino event takes place, the LFO, SSTA and SSTA’s QBO and SO in the EEP interact and strengthen each other; But the warmer SST and the SSTA’s QBO and SO in the warm water phase in the EEP contribute to the LFO's weak-ening in the equatorial Pacific. Moreover, these contribute to the SST in the EEP becoming cold and the SSTA’s QBO and SO in the EWP being in cold water phase and then impel the El Nino event to end.
A Problem Related to Nonlinear Stability Criteria for Multi-layer Quasi-geostrophic Flow
Liu Yongming, Mu Mu
1992, 9(3): 337-345. doi: 10.1007/BF02656943
The second author studied the nonlinear stability of N-layer quasi-geostrophic flow subject to perturbations of parameters and initial data, and established the stability criteria for the flow in question, which involve finding out the lowest eigenvalue of an elliptic boundary value problem.In this paper when the domain is a periodic zonal channel, a formula of the lowest eigenvalue is established, which is useful for further studies and practical applications.
An Analysis of the Air Parcel Trajectories of Long-Range Transport at Shanghai
Shao Demin, Zhang Wei, Shen Aihua, Cheng Xueqing, Fu Zhemin, He Zhenzhen
1992, 9(3): 346-350. doi: 10.1007/BF02656944
Variability in Latent Heat Flux over the Tropical Pacific in Association with Recent Two ENSO Events
Fu Congbin, Henry Diaz, Fan Huijun
1992, 9(3): 351-358. doi: 10.1007/BF02656945
This paper analyzed the variations of latent heat flux (LHF) over the tropical Pacific in the period 1978-1988 by using COADS (Comprehensive Ocean and Atmospheric Data Set). It has been founded that the interannual variabili ty of LHF exhibits strong ENSO signal, with the significant increasing LHF during the recent two warm events, i.e., 1982 / 83 and 1986 / 87 and decreasing LHF in the cold episodes. However the longitudinal distribution of the LHF departures varies from event to event. In the eastern Pacific, the specific humidity difference at air-sea interface (qs -qa) makes a dominant contribution to the interannual variability of LHF ( r = 0.73 ), while in the western Pacific the surface wind speed, W and the qs - qa make nearly equal contribution to that of LHF.
Surface Pressure and Summer Monsoon Rainfall over India
B. Parthasarathy, K. Rupa Kumar, A. A. Munot
1992, 9(3): 359-366. doi: 10.1007/BF02656946
The relationship between the all-India summer monsoon rainfall and surface pressure over the Indian region has been examined to obtain a useful predictor for the monsoon rainfall. The data series of all-India monsoon rainfall and the mean pressures of three seasons before and after the monsoon season as well as the winter-to- spring pressure tendency (MAM-DJF) at 100 stations for the period 1951-1980 have been used in the analysis.The all-India monsoon rainfall is negatively correlated with the pressure of the spring (MAM) season preceding the monsoon and winter-to-spring seasonal difference as pressure tendency (MAM-DJF), at almost all the stations in India, and significantly with the pressures over central and northwestern regions. The average mean sea level pres?sure of six stations (Jodhpur, Ahmedabed, Bombay, Indore, Sagar and Akola) in the Western Central Indian (WCI) region showed highly significant (at 1% level) and consistent CCs of-0.63 for MAM and -0.56 for MAM-DJF for the period 1951-1980. Thus, the pre-monsoon seasonal pressure anomalies over WCI could provide a useful parameter for the long-range forecasting scheme of the Indian monsoon rainfall.
Weather Yield Model for the Semi Tropical Region (Pakistan)
Syed Faizan Haider, K. H. Asif, Amjad Hussain Gilani
1992, 9(3): 367-372. doi: 10.1007/BF02656947
Weather models are essential tools for checking of the effect of the weather elements in terms of their effect on the production of the crop. This research is an attempt to see the effect of only two variables i.e., temperature and rainfall for the division Faisalabad (semitropical region of Pakistan).The model fitted is of the linear form:the values of a,b, c have been found. The expected yield has been calculated by using the aridity indices (X1 and X2 ) and the result in the form of coefficient of determination R2 has been found equal to 0.166. The significance of the regression coefficient has been tested, which shows that the contribution to the yield from aridity index at germination and that at ripening is significant.The wheat yields are the results of a wide variety of variables, most of which show varying degree of relationship with one another, some positive and some negative in terms of output. These variables may be technology, fertilizers, pesticides, epidemics, kinds of seeds used, market price of crop and the area under cultivation etc, which can be the source of variation in the wheat yield. Since rainfall during germination and temperature at the ripening periods are the necessary factors for the yield of wheat, for this purpose these parameters have been studied in order to their contribution.
On Accurate Detection of Oceanic Features from Satellite IR Data Using ICSED Method
Li Jun, Zhou Fengxian
1992, 9(3): 373-382. doi: 10.1007/BF02656948
ICSED (Improved Cluster Shade Edge Detection) algorithm and other various methods to accurately and efficiently detect edges on satellite data are presented. Error rate criterion is used to statistically evaluate the perform-ances of these methods in detecting oceanic features for both noise free and noise contaminated AVHRR (Advanced Very High Resolution Radiometer) IR image with Kuroshio. Also, practical experiments in detecting the eddy of Kuroshio with these methods are carried out for comparison. Results show that the ICSED algorithm has more advantages than other methods in detecting mesoscale features of ocean. Finally, the effectiveness of window size of ICSED method to oceanic features detection is quantitatively discussed.