Abstract:In the context of the 2-L AGCM of Institute of Atmospheric Physics,Academia Sinica,numerical study is performed on the influence of the western Pacific warming pool(WPWP) upon summer general circulation and monsoon LFO.Evidence suggests that the WPWP SSTA gives rise to great change in the atmospheric circulation LFO,resulting in enhancement of lowfrequency variance of sea level pressure in the monsoon region,intensification of low-frequency signal of temperature variation in the mid-upper troposphere,modification in the space pattern of low-frequency disturbance,displaying more clearly a wavetrain ranging north out of the WPWP, change in LFO phase(time domain)and revealing even more evidently the cross-equatorial propagation of low-frequency variation from the Southern Hemisphere.

Abstract:Numerical study is carried out of tropical high frequency temperature anomaly in the context of the IAP model developed by the Institute of Atmospheric Physics,Beijing.Comparison of the findings to those from a control experiment shows that the intraseasonal and biweekly oscillations are properties inherent in the atmosphere;high-frequency anomaly in tropical temperature will give rise to change in physical quantity fields,particularly in the context of intraseasonal oscillation,with primary alterations in weakening the original intraseasonal and intensifying the high-frequency portion of the oscillation at extratropics;the response is displayed tropically by the travel at great pace to the east,predominantly,and west,to less degree,in the mid and upper level atmosphere so that a teleconnection pattern is generated at low latitudes between the disturbance source and a place 20000 km away.It is noted that the perturbation resembles a type of mixed Rossby-gravity waves as regards velocity. The response takes the form of east-to-west propagation in high latitudes and dominantly eastward shift over mid-low latitudes,with meridional,chiefly equatorward,migration in some particular areas.

Abstract:Defined are East Asian winter/summer monsoon intensity indices and calculated 1873 ～1989 winter/summer and monthly(JJA/DJF)indices with the secular climatic change investigated.Evidence suggests that the summer monsoon was greatly enhanced for the study period with little change or even slightly enfeebled for the winter wind.Also,analysis shows that the summer monsoon displayed enhamced sudden change around 1918 concurrently with the abrupt rise in northern summer surface temperature,and,in contrast,the winter monsoon showed less noticeable abrupt change in 1958.Finally,sliding correlation analysis was made to investigate the relation between the winter/summer monsoons and northern surface temperature,indicating an interdecadal variation in their correlation.

Abstract:Based on analysis of pentad averaged vertical sections through 120°E,study is conducted of the structure of east Asian subtropical frontal zone at various phases of the 1991 Meiyu period alongside the documentation of the dynamic features in the context of geopotential vorticity analysis and frontogenesis theory.Evidence suggests that i)the first Meiyu phase differs in structure from the typical one in that it emerges due to a locally anomalous circulation pattern during the winter-to-summer transition;ii)the structres of the frontal zone for the three stages in the Meiyu period fall,in order,into a shallow,a deep-Ⅰ and a deep-Ⅱ type,of which the first is marked by a nearly vertical positive vorticity axis at lower levels and the others by northward tilt all the way from top to bottom,corresponding,respectively,to an equivalent barotropical and a baroclinic structure;iii)the deep types correspond,on the south side,to a complete monsoon cell,with cold(warm and moist)air as the main driving factor for the zone of the deep Ⅰ(Ⅱ)type,and iv)the low-tropospheric high potential vorticity perturbation and the warm sector in the neighborhood of a rainband play an important role in the formation and maintenance of such a structure,and the structure along with dynamic properties resembling in many ways that given by a semigeostrophic frontogenesis model incorprating latent heat release.

Abstract:Research is conducted of the distribution features of flow and divergence fields under the stress of ununiform and unsteady wind at Meiliang on Lake Taihu in terms of a 3D boundary layer model and a 2D hydrodynamic model for the area of the lake,arriving at some meaningful results.

Abstract:For comparison,numerical simulations are conducted of influence on stationary waves of anomalous heat sources at high/low levels over the Tibetan plateau and western Pacific in terms of a 3D steady primitive equation spectral model.Results show that with low(high)level heating anomaly available in the highland,the maximal circulation anomaly centers shift to the anomaly centers for all levels whilst the high/low level heating anomalies over the western Pacific make the maximal circulation anomaly centers 10～20 deg of latitude northward of the heating anomalies.The high/low level heating anomalies under study have greatly differing effects on south Asian highs and western Pacific subtropical highs.

Abstract:Study of the summer 1991 persistent heavy rainfall event over the Changjiang-Huaihe valleys exhibits multi-periods for rainfall intensity,revealing that the rainbelt oscillated meridionally on a daily basis;variation of short-term precipitation was associated with the short-range change in vigor of low-level southerly,low-level convergence,upper-level divergence and frontogenesis/frontolysis;the rainfall of≥5 mm·h^-1(<5 mm·h^-1)accounts for 68%(32%)of the regional precipitation;the duration and amount of intense(weak)rainfall increased(decreased)as a function of the rise in precipitation category.

Abstract:The paper concerns the causes of enhanced rainfall from Typhoon 9012(YANCY)in terms of intense observations collected in the implementation of the 1990 SPECTRUM project. Results show that the regional intense precipitation made up 64% of the total with the rainfall duration changing versus the meridional oscillation of the storm’s position;meso-α-scale torrential rainfall region was associated with northeasterly jet on the west side and an inverted trough of the tempest;the meso-β-scale heavy rain sector bore close relation to a surface vigourous easterly area,easterly perturbation,a meso convergence region,a meso cyclone,a meso frontal zone and a meso frontogenesis region.

Abstract:A soft-and hardware scheme for a circuit board is presented for the signals processing system of a 1D FSSP(forward scattering cloud-droplet spectrum prober)-100.The system is composed mainly of a special single-board microcomputer,parallel interface element 8255 and a liquid crystal indicator,and responsible for collecting FSSP signals and processing them in a designed way.Further,the range of the device can be regulated through the processing borad.

Abstract:Established is a dynamic model of paddy rice growth based on rice biology with the aid of field observations.Practice demonstrates that,other things being suitable,the model has such ability to better simulate the effect on the growth of weather/climate conditions as to be used to predict the development stage and thus to carry out field management.

Abstract:With 0800 h convenient data and numerical products as input,the element field of a key region is expanded as the Chebyshev orthogonal polynomial,whose coefficients are taken as predictors to be trained with the aid of the B-P neural network,whereupon is established an artificial rainfall fallout region forecasting network for categories 5,10 and 25 mm for 24 h in advance.Tests show that >95% of the historical events are predicted with successful operational application in summer(JJA)1994.

Abstract:Through synoptical diagnosis and numerical study of the Sichuan torrential rain events,one in the western part on July 11～14,1981 and the other in the eastern on July 26～ 29,1982,we come to the conclusion that the western event was largely related to the enhanced Tibetan vortex which migrated east to meet SW flow along the brim of a subtropical high,resulting quite easily in the event whilst the eastern event occurred due to the fact that the Plateau lowvalue system moved rather fast and the eastern Tibet was under the effect of NW flow;the huge relief affected the precipitation over the eastern highland,the genesis,development and travelling of the low-value system,and the subtropical high;the terrain east of 105°E had more influence on the eastern event;the relief in east China served as a weakening factor for the highland rainfall.

Abstract:In the context of ECMWF/WMO objectively analyzed gridded data,study is conducted of the features of atmospheric nonadiabatic heating fields in the years of plentiful and deficient Meiyu rainfall.Evidence suggests that such events bore an intimate relation to these fields;such fields showed different characteristics for different phase of the Meiyu;the fields were distinguished from each other as regards the features in the years of abundant and less Meiyu precipitation.

Abstract:Climatological calculation of surface sensible heat over China are investigated,presenting an expression based on the Bowen ratio scheme,whereby computed are monthly and annual mean sensible flux densities of 215 stations across the country along side the spatial/temporal distribution features.

Abstract:A set of single Doppler velocity models are presented for typical ambient windfields that include those of being uniform horizontally,entirely vortical and utterly divergent,which are marked by different signatures in the single Doppler velocity field.The models proposed can help users identify useful information from the Doppler velocity patterns.

Abstract:Using 1978～1987 temperature of Beijing,Taiyuan,Shanghai,Wuhan and Guangzhou located in N,E,S,and Central China and with the aid of climatologically characteristic statistics,investigation is carried out of the probability distribution of daily mean temperatures over the country.Results show that the distribution is of normal character with a limited number of stations showing negative skew nature.

Abstract:Main facts of 1928～1941 weather forecasting and other types of predictive service by Institute of Meteorology,Nanking.