Abstract:In the context of high-resolution TBB data, every 6h NCEP/NCAR reanalysis data sets and daily rain data, the mechanisms for the regional torrential rain development over the mid-Yangtze River basins are investigated by means of composite analysis. The results show that the heavy rainfall event often occurs in the area where the upper level diverging flow appears, and heavy rainfall is also related to East Asian Subtropical monsoon surge. Result further indicates that the ageostrophic inertial advection divergence makes the major contribution to the total upper level divergence fields. Due to the role of NW-SE oriented upper tropospheric jet axis, the distribution of horizontal wind field will be inhomogeneous on the jet exit area, and results in strong convergence over the right side of the upper level jet. The incline jet axis and strengthened convergence happen earlier than the rainfall does.

Abstract:The relationship between autumn sea-ice anomaly and winter atmospheric circulation as well as east Asia regional climate is investigated by means of correlation and composite analysis. It bears evident connection between the autumn sea-ice anomaly and winter atmospheric circulation as well as winter monsoon with heavy (light) sea-ice corresponding to strong(weak) East Asia monsoon. Further study shows that autumn heavy(light) sea-ice extent is followed by low (high) winter temperature in most of China.

Abstract:Mechanism is compared for two rainstorm processes in different places of the Yangtze River valley in Jul. 21,1998. The torrential rain in Sinan area of Guizhou Province in the upper valleys of the Yangtze River is under the influence of southwest vortex,low-level westerly jet and south Asia high. Rainbelt locates on the left-mid-hand side of the low level jet and the main vapour source is from the Bay of Bengal. But the torrential rain in Wuhan in the mid valleys of the Yangtze River is principally resulted from the coupling of boundary-layer southerly jet,low-level westerly jet and high level westerly jet. Its major vapour source is from South China Sea. Non-thermal wind convective instability at low level and non-thermal wind symmetric instability at high level are the mechanism of torrential rain.

Abstract:The surface albedo over the Yangtze Delta is derived from CH1 and CH2 data of NOAA-AVHRR. The comparison between the derived and the observed surface albedos shows that the retrieval method is reasonable. Moreover,a technique is presented to estimate the surface albedo at any time of a day by the use of the surface albedo at a single time. The influence of the solar altitude and surface conditions on the surface albedo is also investigated, indicating that they are in the same order. It is suggested that both factors must be included in the development of nowcasting and short-range numerical model.

Abstract:Based on adjoint code technique, the adjoint assimilation system of MM4 model is developed, and the assimilation experiments of conventional and non-conventional data are carried out. The results indicate that the adding of conventional and non-conventional observations into adjoint model system can improve the quality of initial field,thereof improve the result of forecasting.

Abstract:The relationship between summer precipitation anomalies in the Huaihe Basin and SSTA over the North Pacific is researched in this paper. Possible mechanisms of the effects of SSTA over the North Pacific on summer precipitation anomalies in the Huaihe Basin are primarily discussed. The main results may be concluded as follows; (1) The key area of SSTA over the North Pacific locates in 162.5~177.5°W, 36.5~41.5°N in which the mean SSTA from the preceding August to October has the largest positive correlation with the summer precipitation in the Huaihe Basin. (2) By the use of the SVD analysis technique,it is found that summer precipitation anomalies in the Huaihe Basin correspond to a large scale SSTA distribution pattern over the North Pacific and the key SSTA area is just located in the center. (3) It is the circulation anomalies in the following summer induced by the large area SSTA distribution pattern over the North Pacific that result in the summer precipitation anomaly in the Huaihe Basin. It is also the inner cause of the good correlation between the precipitation and the SSTA.

Abstract:Based on summer rain patterns of east China for nearly one century,precursors in North Hemisphere SLP and SSTA fields for every rain patterns are studied. The strong signals are found which are well indicative of rain pattern forecast.

Abstract:Based on the NCEP/NCAR 40-year reanalysis dataset, analysed is the relationship between vertical shear of zonal wind in equatorial lower stratosphere and ENSO variability. It's found that vertical shear of zonal wind in equatorial lower stratosphere bears the features of QBO. The vertical zonal wind shear is opposite to southern oscillation index (SOI) in phase and is in agreement with the SSTA in Nino3 area in phase. During the westerly (easterly) shear phase in equatorial lower stratosphere, the distributions of OLR,1 000 hPa and 200 hPa height fields, 200 hPa and 850 hPa temperature fields are similar to that in El Nino (La Nina) episode.

Abstract:A 3-dimentional nonhydrostatic PBL model with the 2nd-closure is developed and used to simulate the boundary layer on complex terrain in Beijing area. A comparison between the observed data and the simulated result is made. It is shown that this model can reasonably simulate wind ,temperature and turbulent fields in PBL atmosphere.

Abstract:The GVG system is a new solution,with the conception of sampling lineage instead of the traditional sampling point or sampling area,to extracting crop acreage information. By calculating the crop acreage proportion to total arable land within the linear sample zone, we can obtain the total acreage percentage of different crops over the same agriculture district which has the same planting patterns. The another purpose of this text is to compare the data obtained by using GVG sampling lineage over a paddy test site centered on Longdu, Jiangning County(Jiangsu Province, China) and by extracting the information from Landsat 7 ETM+ imagery acquired during the period of paddy peak biomass. Preliminary analysis on the results indicates that the GVG sampling system provides the best solution for its efficiency and economy.

Abstract:The precipitation dataset for global land area from 1900 to 1998 from Dr Mike Hulme (Climate Research Unit (CRU), East Angles University, UK ) is the longest global precipitation dataset available now. The dataset has been analyzed comprehensively in this article. The result shows that the largest variability of precipitation is located in monsoon areas, and the method of getting monsoon rainfall of several famous monsoon areas from this dataset is also presented. We also analyzed the time series of global land surface precipitation in January and July. We found that there is no apparent trend in July, but a weak increasing trend in January; there is obvious 2~7-,13-and 20-year cycle in both time series. We also test the reliability of the dataset for future work.

Abstract:Based on REOF technique and annual precipitation in Northern Hemisphere land areas in 1900-1996,division of annual precipitation field is made with the variation features of precipitation in subareas discussed. The annual precipitation in China is also divided into subareas with their correlations with the global precipitation field investigated.

Abstract:Laplace transform and B-spline are both widely used in various fields. Considering their union,B-spline is used during Laplace integral. Function with non-smooth point, is approximated by B-spline, then integrated. A set of analytic formulas are given. Experimental results show that the scheme behaves well.

Abstract:Using rotated empirical orthogonal f unction (REOF) method, the summer standardized precipitation field in Southwest China is divided objectively into 5 regions. Based on this, the long-term trend of each region summer precipitation anomaly is analyzed. It is found that the summer precipitation fields in 5 regions have distinct characteristics of interdecadal change in the recent 50 years. The long-term trend of Chuandong, Chuanxi and Guizhou's precipitation is not distinct,but that of Sichuan basin's and Yunnan's is markedly drying.

Abstract:Correlation and composite analysis are carried out to reveal the relation between Meiyu storm of 1991,1996,1998 and high level jet in this study. Results show that the stable large-scale circulation pattern is the main reason for lasting local precipitation in 1991 and 1998, and the unstable large-scale circulation pattern makes the precipitation difficult to last long in one place in 1996. It is also found that Meiyu storm has close relation with high level jet. The storm is likely to occur right to where the high level NW jet exits or SW jet enters. The high level divergence field which leads to Meiyu storm under SW jet is mainly composed of meridional wind, and NW jet composed of zonal wind which could lead to storm when working with meridional wind divergence east to the South Asia High together,a situation happening frequently in 1988. Northerly of South Asia High NW quadrant plays an important role in forming of monsoon anti-circulation south to rain zone.

Abstract:With the data published on Surface Meteorological Monthly Bulletin and Surface Chart during 1971-1996, the temporal variation of sand-dust storms invading Beijing is analyzed. Furthermore, the movement routines and source locations of sand-dust storms are determined in assistance with GIS. The results show: Sand-dust storms in Beijing occurred frequently in spring and early summer, especially in April. According to their source locations, the sand-dust storms are classified into two types, i. e. the internal and external-source sand-dust storm. For the external-source sand-dust storms, they always intrude Beijing from two major regions, one is the Wulanchabumeng, Erlianhaote and Abagaqi(western part of Xilin-guolemeng) of Inner Mongolia, the another is the Sino-Mongolia boundary from eastern part of Hami, to Alashanmeng. The source locations of internal-source sand-dust storms are mainly in Tenggeli desert and its surrounding areas.

Abstract:By the use of the meteorological satellite FY-1C/CAVHRR data .estimated are the concentrations of chlorophyll-a in Chaohu Lake. A remote sensing estimating model is proposed by analyzing the correlation of the FY-1C/CAVHRR channel data for watercolor monitoring and synchronal field survey for chlorophyll-a concentrations. The result indicates that meteorological satellite FY-1C can be used to monitor concentrations of chlorophyll-a in large lakes as a kind of important assistant means of routine water quality sampling survey with its advantages of time and spatial resolution.

Abstract:Experiment is done to make potential prediction of air pollution in Liaoning Province with non-hydrostatic mesoscale model (MM5V2) with increased levels near the ground. The T106L19 output is used as initial field and lateral boundary condition. According to American method, the potentiality of air pollution is predicted by means of judging the mixing layer height and the mixing layer average wind speed near the ground. The observation data of SO₂ is used to check the prediction.

Abstract:The interface and function of the meteorological code data automatic transformation processing software is introduced in this article that is used in the weather forecast. The design methods are illustrated in detail about the time controlling, the code merging, the control on the sub-process for code selection, the inquiry of the result of the processed meteorological codes, and the method of the data storage management, etc. The examination shows that the software is stable when in use and it meets the needs in the routine forecast operation in the meteorological stations.