Abstract:The spatial seesaw structures and climate features of April to September precipitation in east China are studied month by month and season by season in this paper,and the results show that the position and intensity of the seesaw were different in different periods.The seesaw feature of precipitation between south and north areas were more obviously when the time scale became large.The index of southern-drought(flood)-northern-flood(drought) is defined as the difference of the normalized anomaly of rainfall between south and north areas,and the index from 1951 to 2003 calculated.The difference t test of typical southern-drought(flood)-northern-flood(drought) years of summer and August precipitation confirms that the drought/flood years we have identified are reasonable.The secular trend and interdecadal variations of the seesaw features of precipitation during 1951—2003,and its relation with the cold/warm events are also studied.The results show that cold/warm events had effect on the large scale precipitation seesaw in June,June to July and summer.There were more droughts in north area and floods in south area when warm events happened,and vice versa.Study also points out that the cold/warm event is only one of factors that determine the distribution of precipitation over East China.

Abstract:From a group of simple air-sea coupled equations,introducing a new heating function of oceans to the air,we get an analytical solution of the air-sea coupled equations.The analytical solution shows that the air-sea coupled interaction is able to excite unstable coupled waves,and the unstable degree of the waves varies with the change of the coefficient of air-sea coupled interaction and the effect of the deep-sea on the mixed layer.The e-folding time exists the minimum point with the change of the coefficient of air-sea coupled interaction,and the minimum point corresponds to the period of the most unstable coupled wave.The air-sea coupled interaction can excite the most unstable coupled wave with the period of 18-year in the middle latitudes,and it is 3.5-year in the low latitudes and 35-year in the high latitudes.This might be one of the possible mechanisms to drive the quasi-decadal oscillation of the air-sea system.

Abstract:Using the three-layer variable infiltration capacity(VIC-3L) hydrological model and the successive interpolation approach(SIA) of climate factors,we study the effect of different landcover types on the surface hydrological cycle.Daily climate data from 1992 to 2001 and remotely sensed leaf area index(LAI) are used in the model.The model is applied to a Baohe River basin,a subbaisn of the Yangtze River basin,China,with a area of 2 500 km²2.The vegetation cover types are mostly mixed forests,which covers 85% fraction of the Baohe River basin.Comparison of the simulation results with observed discharge data suggests that:1) Daily discharges over the period of 1992—2001 simulated with inputs of remotely sensed land cover data and LAI data can generally follow observed discharge variations,and the modeled annual total discharge agrees with observations with a mean difference of 1.4%.The use of remote sensing images also makes modeled spatial distributions of evapotranspiration physically meaningful.2) The relative computing error(RCE) of the annual average discharge is-24.8% when the homogeneous broadleaf deciduous forestry cover is assumed for the watershed.The error is 21.8% when a homogeneous cropland cover is assumed and-14.32 when a REDC(the resource and environment database of China) land cover map is used.The error is reduced to 1.4% when the remotely sensed land cover at 1 000 m×1 000 m resolution is used.

Abstract:The spatial and temporal features and circulation characteristics of summer precipitation anomaly in Xinjiang are investigated on the basis of the monthly rainfall data at 160 stations from 1951 to 2000 in China.The whole Xinjiang are divided into the south and north parts according to the complex topography of Xinjiang.Results show that the rainy season in the north began one month earlier than that in the south,and in addition to May and June there was another rainy period in October and November.The summer precipitation in Xinjiang has on the whole increased in the last 50 years,and the in crease in south was more obvious than that in north.There were quasi-three-year,quasi-five-to-six-year and quasi-ten-to-thirteen-year periodic oscillations in summer precipitation,and a sudden change in the year of 1985.In addition,the south had another quasi-twenty-to-twenty-two-year periodic oscillation whereas the north had not.The above results indicate that the wet/dry phase of climate in Xinjiang is close related with the 500 hPa height field and the location and intensity of the south asian high.

Abstract:On the basis of the daily precipitation of the Meiyu period at 44 stations in the Changjiang-Huaihe region from 1954 to 2003,the temporal evolution and spatial distribution characters of torrentialrain(≥50 mm/d) are investigated in terms of fuzzy cluster method and empirical orthogonal function(EOF) decomposition.Results show that the Changjiang-Huaihe region is divided into south and north area according to the prominent reginal difference of torrential-rain rainfall;there are prominent inter-pentadly,inter-monthly,inter-annual,inter-decadal variabilities in the torrential-rain rainfall of the Meiyu period;the peak value of torrential-rain rainfall appears in the fifth pentad of June in south area and in the first pentad of July and the fifth pentad of June in north area;the contribution rate of torrential-rain to the total rainfall of the Meiyu period in south area is higher than that in north area,while the concentration rate(the ratio of Meiyu torrential-rain rainfall to annual torrential-rain rainfall) in north area is higher than that in south area;the torrential-rain rainfall shows a remarkable long-term ascending trend in south area,but no evident trend in north area;there are different time scale oscillations in the torrential-rain in both south and north area.

Abstract:Horizontal and vertical structure of rainfall rates of Typhoon Dan’s precipitation cloud systems at three different times during its life period is studied based on the data from TRMM Precipitation Radar(PR).Results show that stratiformis precipitation occupied more area and contributed more rainfall to the total than convective precipitation at the three times.The average rainfall rate of stratiformis precipitation at the three times varied little while that of convective precipitation had a considerable increase with the intensification of typhoon.In vertical,the profiles of convective and stratiformis precipitation were obviously different while the profiles of themself at the three times had small differences.Convective profiles can be devided into three sects according to the slope,the rainfall rate decrease with altitude and the rapidest decreased occurred within the altitude range from 5 to 6 km.Stratiformis profiles can be divided into four sects,and there was a distinct bright band structure near the altitude of 4.5km.

Abstract:By using a 3D convective cloud model,a hail-producing convective weather process on 23th August 2001 in Beijing is simulated and analyzed with cloud-seeding process.The results show that no matter the seeding agent is silver iodide(AgI) or liquid carbon dioxide(LC),the seeding effect in the region of maximum supercooled water(temperature range: 0—-10℃) is better than that in the region of maximum updraft(temperature range: 8—-7℃);and the seeding effect on both rain enhancement and hail suppression in the region of maximum supercooled water by AgI is better than that by LC,while in the region of maximum updraft,the seeding effect on rain enhancement by LC is better than that by AgI,but it is worse on hail suppression.For the studied case,no matter what seeding method is used,the earlier the seeding time,the better the effect on both hail suppression and rain enhancement with an appropriate seeding dose.In addition,the seeding effect on both hail suppression and rain enhancement could be poistive before the mature stage of cloud development,and the negative effects such as hail increase and rain decrease could occur while seeding during or after the mature stage.

Abstract:Based on the DEM data of 1 km×1 km and the precipitation data of 46 base stations in the Songhuajiang River basin,the interpolation of the annual rainfall of 2000—2004 is performed in the paper using the parameter-elevation regression on independent slopes model(PRISM) methed,which mainly takes into account the weight of the distance between raster points and base stations and of the elevation changes from raster points to base stations.The spatial distribution of the annual precitation containing geographical information is output by Arcinfo at a high resolution,and cross-validation errors of the stations are small.

Abstract:Impacts of the previous winter Kuroshio SSTA on summer rainfall in China are simulated and analyzed in terms of the NCAR CCM3.Results indicate that there is a close relationship between previous winter Kuroshio SSTA and summer precipitation in China.When the previous winter Kuroshio SSTA is anomalously high,in the following summer the Western Pacific subtropical high becomes stronger and west-extending,and the Asian summer monsoon is weaker and the Meiyu front lies more southward.As a result,the summer precipitation is more than normal in the Changjiang-Huaihe River reach and in the mid-lower reaches of the Yangtze River,and less than normal in North and Northeast China;and vice versa.

Abstract:The principal patterns of winter SST over the Kuroshio area are identified by use of EOF analysis.Then,the optimum coupling modes of East Asian summer monsoon anomaly and winter SSTA over the Kuroshio area are disclosed by SVD method.The EOF modes of winter SST show relatively consistent cold or warm anomaly distributions over the whole Kuroshio area.When the Kuroshio in winter is colder than normal,the tropical monsoon trough tends to strengthen and the Meiyu front tends to weaken,and the tropical monsoon circulation cell becomes strong in the following summer;and the southwest flow prevails over East Asia,the indensity of southeast flow is stronger but its range is smaller than normal,and the north flow becomes weak.In winter when the Kuroshio SST is warmer than normal,the situation is opposite.

Abstract:Based on the NCEP/NCAR reanalysis monthly 2.5°×2.5°500 hPa heights and the Arctic 1°×1°sea ice data,the indices for the polar vortex area and intensity,and the Arctic sea ice area are calculated,and their longitudinal distributions,and periodicity and the sudden changes of long term trends are analyzed to reveal their intrinsic relationships.It is found that the indexes of sea ice and polar vortex had evident differences in longitudinal distribution,and their relative positions were also different in the eastern and western hemispheres.They had own individual periods,respectively,in addition to the common period of 4-month,quasi-6-month,quasi-one year,4—5-year and 10-year.It is also evident that both the Arctic sea ice and polar vortex aresa have decreased slowly since the 1980s,but the time when sudden change happened was not the same.The sea ice and polar vortex area indices were positively corrlated,but the relationships between the sea ice area and the polar vortex intensity,and between the polar vortex area and the polar vortex intensity were very complicated.

Abstract:Variations of Arctic sea-ice in four sectors and their ralations with autumn temperature in China are studied in this paper by use of the monthly 1°×1°sea-ice concentration data of Hadley center from January 1953 to February 2003 and the monthly temperature data at 160 stations in China.The results show that the sea-ice concentration of various seasons all exhibited a distinctive linear dencending trend in four sectors in the last 50 year,and the decrease in sea-ice concentration was fastest in the European sector in spring and summer.The beginning time of the abrupt change of the seaice concent ration for various seasons was different,it was 1970’s for spring and summer concentrations while 1980’s for fall and winter concentrations.The sea-ice concentration of various sectors displayed an interdecadal variation as well as distinctive seasonal ans regional differences.The distinctive correlation areas between the sea-ice of sector Ⅰand the autumn temperature in China lay in the Hetao area,the mid-reach of the Yangtze River and part of Xinjiang.The sea-ice in sectors Ⅰand Ⅱ were significantly correlated with the 2-year and 1-year later autumn temperature in China,respectively.

Abstract:The dry and wet years in Southeast Asia have been identified and tested by using the Precipitation Reconstruction data set (PREC viz.Precipitation Monthly Anomalies Over Global Land & Oceans from 1948—2003) on annual and seasonal scales from 1948 to 2002.The relation between rainfall and ENSO events has been studied.The results show that in 1948—1959,except summer,wet years,springs,autumns,and winters were evidently more than dry years,springs,autumns,and winters,respectively;in the 1960’s,dry/wet years and seasons were about equal;in the 1970’s,wet years and summers were more than dry years and summers,and wet/dry springs,autumn and winters were about the same;1980—1989 was a frequent period of droughts;and 1990—2002 was a frequent period of droughts/floods with dry years more than wet years.Through calculating the precipitation trend coefficient in Southeast Asia,it was found that a decline trend occurred in annual and seasonal rainfalls except winter.

Abstract:The remote sensing data at 1.1km×1.1km resolution from the polar-orbiting weather satellite are retrieved by a range of split window algorithms to obtain ground surface temperatures,which together with minimum surface temperatures(MST) measured at a number of meteorological stations are then used to get gridded MSTs by use of regression and variational techniques.After comparison of errors from these algorithms the best one is selected for retrieving.By use of the retrieved variational corrected MSTs,injury indices and conditions for wheat’s growth stages,the regional distribution of various degree freezing injuries is plotted,thereby realizing the remote sensing monitoring of wheat’s injury and the accurate calculation of the injury areas.

Abstract:By using the 1961—2000 main meteorological element data at 51 representative observation stations in the 7 provinces of the Loess Plateau,the response of climate-productivity of crops to climatic change is studied.Results show that the climate-productivity in the Loess Plateau exhibited a decending trend,and the annual and seasonal mean temperatures increased at a rate greater than the mean warming rate over the whole China during the last 40 years.The annual and crop growing senson rainfall decreased.The warming and drying of the climate in the plateau resulted in the decending of climate-productivity.Future "warm and humid" climate will be most favorable to crops production with a mean growth range of production of 5.9%;while future "cold and humid" climate will be most unfavorable to crops production with a mean reduce range of production of 6.3%.

Abstract:By use of the meso-scale non-hydrostatic model MM5(V3),and the observational data and T213 output data,we simulate and analyze the backflow precipitation over North China on Dec.22—23,2002.The results show that the lower level Northeast airflow was dry and cold,and it acted as a cold wedge;the start and end time of precipitation were closely correlated to the wind direction,including the upper warm air flow and lower cold air flow;and the precipitation strength was correlated to the wind speed.The moisture came from the South along with the south-west air flow.

Abstract:By using the T106 data and filter method,the mesoscale precipitation systems have been found,and the characters and variations of some meteorological elements also have been analyzed.It is found that by analying and tracing the mesoscale systems,the rainstorm forecasting could be more accurate.The strong convergence of moisture corresponds to the rainstorm well in time and position.We must pay attention to the southern warm thermal advection as well as the northern cold thermal advection in the cold front shear type rainstorm process.

Abstract:In this paper,the mumerical simulation of precipitation during the period of 0000Z 5th to 1200Z 6th July 1991 is carried out by using the MM5 meso-scale model.Through the diagnostic analysis of simulated 3-hour interval results,it is found that the trend of upper level jet was close related to the motion of southwest vortex.When the northwest,west and southwest jet lay over the east of China,the southwest vortex was stationary,moved eastwards rapidly,and strengthened and moved slowly,respectively.Meanwhile,the motion of rain core was consistent with the eastward motion of the southeast vortex.At first,the rain belt was stationary,then it moved quickly eastwards,and at last,its movement became slow.Wet potential vorticity had a great contribution to the stronger baroclinicity of the southwest vortex.Before the baroclinicity of southwest vortex had not been built and in areas near the cold front,the rain belt might lie in anywhere of the left of southwest low level jet,but when the baroclinicity of low level vortex was strengthened and when the warm air came into being,the rain belts all occurred in the left front of southeast low level jet.

Abstract:Using the mesoscale model MM5V3.6 and the NCEP daily reanalysis data every 6 hours,we numerically simulate the snowstorm on March 1—2,2003 in Liaoning Province.We emphatically analyze and discuss the genesis,development and evolution characters of the mesoscale system during this course.Through the simulation we find that the MM5V3.6 has the ability to successfully simulate each factor in this mesoscale snowstorm.The results show that the convergence of low level air flows and the divergence of upper air flows resut in the strengthening of ascending motion and the genesis and maintenance of the center of low level positive vorticity,therefore the water vapor condensation in the vertical direction is the gensis mechanism of the snowstorm.

Abstract:The horizontal and vertical momentum loss caused by the shock of heavy rain in low-level wind shear of thunderstorms on the airframe and wing are analyzed,the water film thickness on the airframe and wings estimated,and the flight resistance resulted from raindrops-striking caused by the roughness of airplane when the heavy rain shocks the airplane is discussed.Study shows that the effect of the shock of heavy rain on an airplane in the low-level wind shear of thunderstorms is evident,the flight resistance resulted from the roughness of airplane is able to change the flight track and endanger the flight safety,whereas,the increase in the mass of airplane caused by the water film on the airframe and its wings in heavy rain is nigligible.

Abstract:According to the management situation of agrometeorology and eco-environment monitoring information as well as the requirement of business and research in natural reserve,the information database,which includes observations information,parameter information and products information has been established based on the Microsoft Access 2000 in the paper.The visualization developing software Visual Basic 6.0 was made use as the development tool so as to realize the automatic program of data acquiring,editing,querying,checking,statistic,analyzing,codes transmitting,reports output and data transition.