Abstract:Straw mulching and residue practices have great influence on growth and water consumption of summer corn.It can reduce soil water evaporation in early stages and increase crop transpiration in late stages.These are benefits to dry matter accumulation and yield increasing and water use efficiency of corn.The effects of straw mulching and residue are different under different soil water conditions.The increasing of yield and water use efficiency reduce with increasing of soil water content.It demonstrates that straw mulching and residue practices are applicable in arid and semi arid regions.It is significant for developing dry land farming in North China.

Abstract:By using the ETA model,a numerical simulation and experiment was conducted for a torrential rain in the northenwest of Sichuan basin on 19 August,1998.The results show that the ETA model is of better abilities on the presage of the system movement,the intensity and area of precipitation.During the torrential rain,low vortex over the plateau has the greater effect on the intensity and area of precipitation.Topograply has a close relation with the area of the torrential rain.The existence of small high pressure between Gashu and Shaanxi avails increment of the intensity of precipitation.

Abstract:General circulation features over the Northern Hemisphere in 1999 were analysed.It is shown that the 500hPa subtropical high over the west Pacific was weaker than that of last year.Its ridge point is anomaly to the east in spring and summer.At 500hPa,zonal and meridional circulation take place by turn,cold air is weaker than normal in winter.Monsoon is stronger during summer.The convection activity is strong during winter and spring,and it is weaker in tropics in summer.A strange La-Nina event is persisting in the tropical Pacific region in 1999.The anomaly of both the tropical Pacific and atmosphere circulation exerted a significant impact on weather and climate in China.

Abstract:During 1999,global climate has been warming persistently.The strong La Nina event continued in the central and eastern Pacific and it impacted on world climate,especially in the tropical region.In Europe and North America,cold and snow weather was experienced during winter,while hot weather occurred in summer.Severe floods occurred in south Asia,central Europe,southern North America and northern South America.Drought appeared in West Asia and central North America.South Asia,North America and the northeastern Australia were hit by rare tropical storms,which resulted in severe disasters.

Abstract:The features of weather/climate over China in 1999 were summarized as follows.Rainfall in most parts of north China was below normal in 1999,while the situation in south China was distinctly opposite.As a result of precipitation deficits,a long-running drought continued in most parts of the country during January—April.Then,droughts occurred again in most northern areas to the Yangtz River in summer.By contrast,most southern area to the Yangtz River experienced the excessive rainfall.Droughts in combination with waterlogging were due to the uneven distribution of rainfall in autumn and precipitation was below average again in December. The 1999 climate was still in the warming phase with annual temperature evidently higher than normal but slightly lower than 1998.The temperature also featured episodic changes with the periodic occurrence of heat wave and cold wave in some regions.The number of tropical cyclones both forming in Northwest Pacific and South China Sea and landing on China was below average during 1999.And a very early sand and dust storm hit Northwest China in late January.Moreover,there were totally more than 600 counties(times)in 29 Provinces hit by hail and tornado,with reduced areas,times and economic loss compared to normal.In addition,the thick fog weather was more frequent than usual with large area affected.

Abstract:By using the radiosonde and surface observation data of Fuzhou,eleven surface meteorological elements and nine atmospheric stratification parameters which affect the density of atmospheric pollutant were calculated.A series of regression equations were built with them and the density of SO₂、NO_x and TSP during the period between 1995 and 1998,and then the grade of pollutant′s density was forecasted daily by using the equations from Feburary to August of 1999.

Abstract:A spatial and temporal distribution features of SO₂ concentration and its possible causes were analyzed according to the data of SO₂ concentration and meteorological data in Urumqi city in 1994-1997 from routine air monitoring stations.Also,pollution assessment of every station was given.

Abstract:The climate general situation of the highest temperature,relative humidity and wind speed in relation to the body feeling temperature from June to September in Qingdao city was analysed statistically.According to the calculating model of body feeling temperature and distribution characteristic of relative meteorology elements,an empirical formula was derived.The body feeling temperature distribution in different scopes corresponds to different hotness index and comfortable feeling of outdoor people.

Abstract:By using of a simulation test with a non-randomize area control,the effect assessment of airplane rain enhancement over Zheling Reservoir of Jiangxi province from 1979 to 1982 was conducted and compared with other non-randomize tests.It is shown that the area control test is an objective assessment method better than others.Mean rain enhancement of every airplane operation is 1.37mm per four hours,and the relative rate of rain enhancement is 24.92%.By comparing accuracy of every method,the false effect of area control test is 0.53%,but the falso effect of sequence test,area contrast test and historical regression test is 9.89%,-19.52% and 19.58% respectively.

Abstract:By using of the T106 analysis data of National Meteorological Center during January 1995-December 1997,factors grouped and correlation analysis the physical factors close correlation with precipitation and definitely differentiating precipitation were defined.Every factor in sample is arranged from low to high order,then divided in section,and calculated precipitation frequency in every section.According to every facter contribution to precipitation,the weighing coefficient of every factor was calculated.The precipitation frequency of every section of every facter of every sample are weighed,and then added.A composite precipitation frequency value is given by history sample fitting.The TS score maximum value of the precipitation is defined as composite forecast index.The composite index of short-range forecast about light rain,moderate rain,heavy rain and storm rain were derived respectively.Precipitation categorical forecasts were conducted by using the method and the forecast effect was analysed.

Abstract:The climatic factors in different growth stages of late-seeded and filmed winter wheat were discussed with the application of the field test data.The agricultural climate cause of late seeded and filmed winter wheat with high yield and water-saving was analysed.The species of late-seeded and filmed winter wheat corresponding to multi-cropping cotton was selected.

Abstract:The weather system,thermal and dynamical features of the continued hail shooting weather process over a large area in Shandong Province on 28-29 April 1997 were analyzed.It is shown that the continued hail shooting process is caused by a cold vortex.The cold front triggered off convective instability energy and a stronger convection produced.Hail shooting located in the area with convective instability,high energy tongue at the middle-low level,warm advection and convergence in low level and cold advection and divergence at the high level,and ascending motion.CAPE and stronger positive vorticity advection affected importantly the hail shooting.

Abstract:The surface and upper synoptic situation and main influential systems of a rare torrential rain over Shangluo District in Shaanxi Province were analysed.The flow field,meteorologram at one station,hourly GMS-5 images and topographic features were also studied.The occurrence cause of the rare torrential rain in Shangluo District on 9 July,1998 was given.