Abstract:Along with the rapid development of economy and urbanization, atmospheric aerosol pollution is becoming worse. It is becoming a practical matter to distinguish haze and fog, and also an urgent issue need to be solved. In the past the operational standard by using relative humidity to discern fog and haze is commonly on the low side over the southeast coastal provinces. To distinguish fog and haze should be based on the change of influencing weather system combining other influencing factors. According to the new researches on aerosol in the recent years, the main water soluble particles less than 0.1μm diameter in the atmosphere are mainly composed by vitriol ammonium, while large than 1μm diameter are sodium chloride. The relative humidity for those matters is approximately 80%, so it is suggested that the weather phenomena, the visibility deterioration caused by atmospheric turbidness resulting in blur of visual field, is determined as haze when relative humidity is less than 80%, while as fog when relative humidity is large than 90%, and as the mixture of haze and fog the main constitutes are still haze when the relative humidity is between 80% and 90%. It is also suggested that to set down as soon as possible the ash haze index and its warning method, to develop the study on method of predicting and warning ash haze weather and to construct the operational platform, to open up the field of meteorological services, putting the products of environmental meteorology into public service.

Abstract:A stratified precipitation cloud over the sea is studied with two improved parameter cloud models, it is found that precipitation mechanism for the thick stratified cloud over the sea is derived from ice melting and different stratified cloud and the continental precipitation increment is going on in the warm region under the 0℃ layer, and meanwhile there is almost no liquid water in the negative region above the 0℃ layer within the stratified cloud.

Abstract:Based on the three conditions of formed-hail, a heavy hail event in Zhengzhou area on 19 July 2002 is analysed.The results show that the severe convection weather occurs easily when the water vapor and instability and the outer rising force are all suitable. The severe vertical wind shear and an appropriate height about 0℃ layer and -20℃ layer will be advantageous to the hail augmentation, and the low-level horizontal helicity and potential temperature difference are correlation with the hail area.

Abstract:The circulation patterns and radar echo feature of the heavy rain process in Liaoning Province, 5-6 August 2003, are analyzed. The simulation with PSU/NCAR MM5 model and a diagnostic analysis are made to investigate the development causes of the major influence synoptic system (North China cyclone). It shows that the cold air moved southward from Siberia, the stable and strengthened subtropical high and low level warm-moist air flow are the major causes of the event. The dry intrusion plays an important role in the rapid development of the North China cyclone.

Abstract:Based on the data of the Drought/Flood in the northwest, the north, and the east of China for the last 530 years, the abrupt change and the periodicity of the Drought/Flood series are analyzed. The results indicate that there is a period of 22-year and 169-year respectively in Shaanxi and an obvious abrupt change in Shaanxi in 1645,which is earlier about 6～7 years than North China, about 40～50 years than East of China. There is some periodicity characters of precipitation in Shaanxi and East China in recent 5 decades, and the variation is different. The dry and warm climate will continue to 2010s in northern Shaanxi, this is the facts that the ecosystem managing project must be faced.

Abstract:General circulation features over the Northern Hemisphere in 2004 are analyzed. In the first half year of 2004, the atmosphere and ocean in the central and eastern Pacific near equator tended to be a normal state. From July 2004, SST in the equatorial middle and east Pacific became warmer than before. Subtropical high over the west Pacific Ocean continued to be strong in 2004. It located eastward to its normal position and the ridge line was northward to its normal value in summer. In the first and second dekad of June, the geopotential height was higher than its normal value over the west of Baikal. In the second dekad of July and August, the geopotential height field was higher than its normal over Baikal. The South China Sea summer monsoon outbreaked in normal time and the South Asia summer monsoon was stronger than normal. The 500hPa potential high over Tibetan in 2004 was higher than normal and the snow cover was more than normal. The convection over the warm pool was more active in the second half year than that in the first half year in 2004. The climate anomaly in 2004 was possibly caused by the SST anomalies of the tropical Pacific and atmospheric general circulation.

Abstract:Global climate was persistently warmer in 2004. In early this year, snowstorms occurred in some countries in Europe and a heavy snow attacked America. Extreme cold and extreme low temperature events occurred in South Asia and Mexico. During the summer and autumn, tropical storms in the Pacific and the Atlantic Ocean brought huge damage to Japan, Philippines, U.S.A and etc. During 2004, drought conditions continued to affect parts of South Africa and Asia. Wetter-than-average conditions prevailed in South Asia, part of South America and some countries in southern Africa. Heatwaves affected Iberian Peninsula, Japan and Australia respectively.

Abstract:As for 2004, the annual total precipitation mean by whole country is less than usually annual quantity and uneven in spatial and temporal distribution. From the spring to the beginning of the summer, the heaviest drought occurred in the area of the west of Northeast and the east of inner-Mongolia in 2004 of the last 50 years, while as to the autumn, the heaviest drought on a large scale occurred in the south of China and the middle and lower reaches of Yangtze River. In the flood season, there was no heavy flood disaster in a valley scale in the main river of our country, but heavy rain, flood, surged slope, and mud-stone flow caused by locally heavy rain occurred very frequently. The loss caused by these disasters was serious in Sichuan, Chongqing, Yunnan, Henan, Hubei, Hunan provinces, and so on. Annual mean temperature on the whole country scale was on the obvious higher than usually annual mean temperature, but staggered undulation of temperature was obvious. Parts of area encountered low temperature disaster or snow disaster in the winter, the spring and the fall. The south maintained durative high temperature in the summer. Eight typhoons (tropical storm) landed in 2004. Thereinto, the typhoon named Yunna caused serious damage in Zhejiang Province. The locally strong convective weather such as thunder rain and heavy wind as well as hailstone and lightning strike occurred frequently. The dust weather increased compared with the corresponding period of last year. As a whole, the climate in 2004 is natural, and the meteorological disaster is less. In short, 2004 is a better meteorological year.

Abstract:The theory and method of duststorm monitoring by using NOAA, FY-1C, GMS-5 and FY-2B satellite, the calculation of the DDI, and the application of GIS technology are discussed. Multi-channel information of meteorological satellite was used in monitoring the severe sandstorm event occurred on 18-21 March 2002. The origin area, track of transportation and the affected area of the sandstorm are investigated.

Abstract:The atmospheric humidity are estimated with Doppler radar echo intensity. The relative humidity values are equaled to 100% in the areas of the echo intensity greater than 40dBz and relative humidity values are equaled to 90% in the areas of the echo intensity less than 20dBz, the relative humidity values are kept to linear correlation with the echo intensity in the areas of 20dBz-40dBz. The corresponding temperature values are gained by the control experimentation. Then the correspond dew point temperature values are calculated with iteration method from the humidity and temperature. Through these processes, radar echo intensity values are transformed to the variable values of the numerical model MM5 and are use in the MM5. The simulation experimentations are made to validate the method, the example is a heavy rainfall event in Quanjiao area, Anhui Province on the 13 July 2001.The background fields use the T213 data. The initial fields of control experimentation are evolved by the analysis from routine sounding and surface data. The echo intensity data of Hefei Doppler radar observations come into being the initial fields of MM5 sensitive experimentation. In this test the horizontal grids are 103×103,the distance is 10km, There are 33 levels at Perpendicularity, the central position is located at the point (31.00°N,117.66°E). The result shows that predicating precipitation areas are improved obviously and indicates that this method is feasible.

Abstract:The results between the GPS/PWV data during 10-20 September 2002 and the actual surface rainfall are analyzed. It shows that the consecutive observation data of precipitable water vapor per 30 minutes would be instructive for the forecasting of actual rainfall. First,the first arrival of PWV and last appearance of 50mm PWV would correspond well to the beginning and end of actual precipitation. When the precipitable water vapor larger than 50mm lasts longer, the actual rainfall will be more. Whereas the result will be contrary. Next, the change of rainfall within 3 and 24 hours would be instructive to forecast the future rainfall region and rainfall distribution. Finally, the trend of precipitable water vapor in the various stages can reflect the change of 500hPa field and 700hPa vapor field. It has shown us more useful basis to clarify the vapor source and transmission in actual rainfall forecast.

Abstract:Two surface gale events happened in April 17-19 and May 12-14 of 2001 over Liaoning Province are simulated using MM5 model, and the results are compared with wind observation data at 13 sites (meteorological stations and wind farms). The main experiment results are as follows. The model has good quality in simulating the evolution and distribution characters of regional wind fields. The variation trends of wind speed in every hour are nearly the observations, but there are certain differences in values. When instantaneous (average) wind speed is more than 10.0m·s^-1(9.0m·s^-1), the simulation values are lower obviously than the observational data. The preliminary experiments show that MM5 model has better ability to simulate patterns of regional wind fields and local variation characters in every hour, but the intensity of heavy wind speed is decreased.

Abstract:Considering the effects of the outside factor and the periodic change of the predictand, the multivariate mixed threshold regression model with periodic components is developed. It shows that the model is better and steadier on prediction capacity in the 7-year experiments for rainy season precipitation.

Abstract:Synoptic and climatic characteristics of dense fog and associated weather conditions in Anhui Province are analyzed. A multi-regression equation is developed on the basis of factors which reflect the weather features in the formation of dense fog through correlation verification by use of 3-years T106 data. An operational forecast system used to forecast 24-72 hours dense fog is eventually confirmed through the verification of one-year T213 data. Forecast results show that the forecast system is helpful for the forecast of dense fog of the stations in Anhui Province.

Abstract:An analysis of the heavy fog which appeared in southern Hebei Province from the mid-night of 28 to the noon of 29 November in 2003 is made.The results show that the physical elements relating to stability are the indexes not only of severe convection process,but also of heavy fog.Fog is a weather phenomenon which comes forth in steady atmosphere. From the stratification and change of the atmosphere, a heavy fog appearing or not,as well as the growing or vanishing time can be decided.In addition,the humidity's accumulation is a cause affecting the heavy fog making also.

Abstract:Analysis of a heavy rainfall event at Cangzhou, Hebei Province 11-12 October 2003 is made from some aspects such as influence systems, triggering mechanism, stability and physical quantity fields, etc. It shows that the event belongs to stable rainfall, its energy accumulation is smaller than that in summer, but the jets are stronger with the high value center of the mid-low level convergence and the upper-level divergence and playing an important role in the formation of the event, providing vapor and motive terms, and the heavy rain region appears with the high value center of upshift velocity.

Abstract:Based on the NCEP/NCAR reanalysis data, the features of atmospheric circulation and meteorological factors of the 6-day continuous cloud deck appeared on January 19 to 24, 1984 in Huangshan mountain are analyzed, It shows that the event occurred under the conditions as follow. At 500hPa level, a blocking high laid in Okhotsk, the pressure ridge in Wulaershan leant towards east, a depression laid over Northeast China, and westerly flow over the Huangshan mountain. At 1000hPa, a northeasterly forward high is over the Huangshan Mountain. The cloud deck appeared after cold front and heavy rain, and then temperature and humidity droped, and the upward current turned into downward motion. During the appearance of cloud deck, the temperature, the specific humidity, and the vertical velocity are changing less, and the wind velocity is lower, but the wind direction is chaos.

Abstract:With T106 numberial products, satellite data and observations, a study of Wenzhou heavy rain associated with tropic cyclone 9909 is made. The results show that the autumn tropic cyclone landing at the east of Guangdong Province often accompanies with an inverted trough extending to the middle-south of Zhejiang coast. At the special place MCC is occured, and at the same time, it causes the heavy rain.

Abstract:Based on the synoptic routine analysis, a regression estimation of event probabilities to forecast scatter of radiation fog at Xianyang Airport is developed. An analysis is made by selecting 95 events of radiation fog at 6:00 a.m. during the period from 1992 to 2002 and thinking over the probabilities of scatter of the radiation fog in 4 hours. The regression equation is significant on the statistic F-test, and the accuracy of returning-forecast and testing-forecast are over 78%.