Abstract:Heavy precipitation event during 4—5 July 2003 is diagnosed by using the observational data.Based on mesoscale model MM5(V3.6),the meso-β-scale system is simulated.The simulation shows that the foundamental reason for the cease of the precipitation is not change in ascending motion condition,but the gradual replacement of wet air by dry air in the low layer in the rainstorm area under influence of the mid-low level horizontal circulation and the secondary circulation of the Meiyu front.

Abstract:Using the 3-D convective storm numerical model(IAP-CSM3D),dynamical effects by means of artificial updraft restraint are introduced into some regions of modeling convective clouds during a short time period at different evolution stages and different areas of a hailstorm,to study physical processes which affect the precipitation formation of hailstorm.The results indicate that in the earlier stage of the development of a hailstorm,an artificial restraint with a common intensity can highly influence the development and precipitation of the hailstorm,increasing its surface precipitation,especially the hailfall amount,but in the later stage of the hailstorm development,the restraint has a small influence on the precipitation.When the restraint is quite strong and its range is very large,only at the vigorous stage the restraint can distinctively reduce the hailfall amount and other solid-state precipitation from the affected hailstorm.Finally,the mechanism for the effect of the updraft restraint of the hailstorm on micro-physical processes is analyzed.

Abstract:Based on the daily precipitation data of 74 observational stations in South China and the daily NCAR/NCEP reanalysis dataset in 1957—2001,the features of different precipitation periods in the pre-flood season(AMJ) in South China are compared.The main results are obtained as follow:the pre-flood season in South China is composed of the frontal precipitation period and the summer monsoon precipitation period.The former mainly appears in April,accompanied with a typical transition circulation pattern from winter to summer,where in strong subtropical westerly jet streams prevail in the high level over South China,the atmospheric stratification is stable,and the moisture is mainly originated from the westerly transport over the Arabian Sea and the easterly transport on the south side of WPSH;before the onset of SCSSM,the subtropical high dominates over the SCS and the moisture in South China mainly comes from the westerlies over the Arabian Sea,the easterlies on the south side of WPSH and the southwesterlies over the Bay of Bengal.After the onset of SCSSM,the subtropical high withdraws out of the SCS,accompanied with the strengthening of the cross-equatorial moisture transport from the Southern Hemisphere;the summer monsoon precipitation peaks in June when the South Asian High prevails over the Tibetan Plateau and South China,vigarous convection develops and the powerful cross-equatorial flow cross the Bay of Bengal and transports moisture towards South China.

Abstract:In this paper,the AgI-seeding effects for the convectional clouds in Beijing on July 5,2003 were evaluated by using the three-dimensional convective storm model (IAP-CSM3D) with an artificial seeding function module developed by the Institute of Atmospheric Physics (IAP),Chinese Academy of Sciences.Detailed simulations on rain enhancement with rockets launching at different time,elevations,distances and seeding in different positions of clouds are analyzed.The results show that a positive effect of rain enhancement can be obtained when seeding in suitable parts of the clouds.A greater benefit in the rain enhancement effect can be gotten when seeding in the developing stage of clouds.The launching elevation of rockets has a great influence on the effect.The principle for the optimal launching elevation selection is given and the mechanism of rain enhancement by AgI-loading rockets is also analyzed in this paper.The above results obtained are expected to help improving the seeding efficiencies in practice.

Abstract:By use of Mann-Kendall abrupt change test,interdecadal abrupt climatic change of North Pacific oscillations(NPO) is studied.It is indicated that an obvious abrupt climate change occurred in 1976,and both the general circulation field and the teleconnection pattern changed remarkably before and after the abrupt change.Correspondingly,characters of wintertime weather and climate in China are also studied.Results show that before(after) the abrupt change,winter temperature in China was lower(higher) with changes in northern China larger than in southern China,and winter precipitation showed an out-of-phase character with more(less) rainfall in the middle-lower reaches of the Yangtze River and less(more) rainfall in South China.Besides,it is also pointed out that 3-year and 6-~7-year periods dominated before the NPO abrupt change,while 5-year and 10-year periods have begun to dominate after the abrupt change although 3-year period still exists.

Abstract:Using the REOF and wavelet analysis methods,the summer precipitation from 39 stations in Eastern China for the periods 1900—1999 is analyzed.The results show that South China and Southwest China,the middle and lower reaches of the Yangtze River,North China and the Southwest of Northeast China are three areas,where remarkably interannual and interdecadal variability of summer precipitation exists,separately.The relationship between them with winter SSTA over North Pacific is examined.

Abstract:In this paper,the climatic features of the spring(MAM) precipitation anomalies in Northeast China are studied using the monthly precipitation data of 93 stations during 1959—2003.The five climatic divisions for spring precipitation in Northeast China are made by applying the Rotated Empirical Orthogonal Function method.It is found that the interannual change and secular trend of the spring precipitation show obvious regional differences,i.e.a distributive character of the precipitation more in the east and less in the west;the west region is vulnerable to drought/flood,and the precipitation has been slightly increased in the past 45 years;the secular trend and periodical characteristics of the spring precipitation also exhibit regional differences.

Abstract:Vertical integrated liquid-water content(VIL) is calculated based on the voluminal scan data of Doppler weather radar.The analysis of gradually increasing initial threshold-value is employed in identifying the VIL heartland.Area-ratio dynamical forecasting method, classification method and VIL heartland area-conservation principle are employed in tracking VIL heartland.Based on the least square analysis,and integration method and linear extrapolation,the new heartland position can be predicted for a short time period.Results show that those method are able to identify,track,and forecast the VIL heartland well.

Abstract:In this paper,a summer relative comfort index (RCI) has been developed to improve upon the limitations of the current,widely used comfort indices.It includes variables not used in previous indices,such as factors that consider consecutive days of stressful weather,cloud cover,and accumulation of heat through the day,and by which the relationship between relative comfort index and heat-related mortality in summer have been analyzed.

Abstract:The question that air conditioners of split & wall-mounted type on high buildings are prone to meet the lightning strike is put forward.Then,the methods about how air conditioners can avert the lightning strike are analyzed and discussed from the characteristics of high buildings,and according to the rules of the lightning protection design,and two effective projects solving the question are put forward.One is a remedy,and the other is an advance method for the lightning protection of air conditioners of split & wall-mounted type at the design and construction stage of buildings.The analysis and comparison of the two projects show that the lightning protection of high buildings is holistic and the lightning protection of air conditioners and auxiliary equipments should be solved at the preparation stage of engineering.

Abstract:The geodesic active contour model has been wide used in image segmentation for its computational stability.Most implicit active contour models,however,are based on explicit updating schemes and therefore of limited computational efficiency.To alleviate the problem,this paper presents a fast active contour model based on the additive operator splitting(AOS) algorithm.In the new model,the time step can be set large to improve the model’s time efficiency.During constructing the coefficient matrix,regional information is used to reduce the effect of noises.The results show that the new model can get better results in an efficient way.

Abstract:Based on the NCEP/NCAR reanalyzed monthly sea surface pressure(SLP),the 160 stations monthly precipitation of China and the Met office and British atmospheric data center(BADC) monthly sea surface temperature(SST) dataset,the constitute and formation cause of the inter-decadal and inter-annual variations of summer rainfall anomalies in northeast China have been analyzed by using the periodical analysis,SVD and REOF methods.Results show that:(1)the inter-decadal and inter-annual variations of the summer rainfall anomalies in northeast China is relatively equipoise,but the local inter-annual variability in the southeast is slightly stronger than that in the northwest;(2)on the inter-decadal and inter-annual scales the strong(weak) east Asia summer monsoon corresponds to the excess(deficient) precipitation in northeast China;(3)there is no direct connection between El Nino events and the summer monsoon in northeast China,i.e. the former has no close relation with the summer rainfall in northeast China.

Abstract:Two indices for strong SSW events are put forward in this paper,according to the WMO standards.Using the NCEP/NCAR reananysis daily temperature and height data at 30hPa level,35 strong SSW events during January to March from 1950 to 2002 are determined.The climate and its anomalous features of SSW events are given,and their formation mechanism is partly explained by the interannual change and abnormality of sunshine and ozone distribution in the mid-high latitudes in the Northern Hemisphere.

Abstract:The performance of Lanczos filter and Butterworth filter was analysed based on filtering Madden-Julian Oscillation signal from long sequences.The results indicate that Lanczos filter is better than Butterworth filter when parameter n is large enough and when n is larger than threshold value 69 day,the advantage of Lanczos is absolutely tenable.

Abstract:By utilizing of the NCEP/NCAR reanalysis grided humidity data during January 1951 to November 2000,the evolutionary feature of the whole tropospheric precipitable water over Tianshui in the east of Northwest China,is analyzed and contrasted with those in other places at the same latitude over the world.Results show that in the past 50 years,precipitable water in the troposphere over the east of Northwest China was in a desending,and its descending amplitude is the largest among those at the same latitude.This reveals a background condition for the severe droughts at Tianshui in the mid-late 1990’s.

Abstract:Based on the 1961—2000 precipitation observations at 48 selected stations,by using the ISODATA fuzzy cluster method,the summer precipitation in west China is divided into two typical precipitation patterns (characteristic distributions of precipitation).One is characteristic of more precipitation in the most areas of west China and less precipitation in the other areas,and precipitation distributive trends of the other pattern are just opposite to the first pattern.Analyses of the interannual and interdecadal changes of the two precipitation patterns show that the precipitation character in west China has been changed since the mid-1970s.It is also found that the contemporaneous 500hPa circulation and the early time equatorial Pacific SSTA field for the two patterns are remarkably different,which has good indication for the short-range climatic prediction of precipitation in west China.

Abstract:The annual extremes characteristics of daily and a continuous process rainfall are analyzed by REOF and statistical models using the daily precipitation data of 80 stations in the Yangtze River Delta.The results show that the extreme precipitation in the Yangtze River Delta mainly belongs to the following patterns:South-east difference pattern of annual extremes of daily rainfall;North-south difference pattern of annual extremes of a continuous process rainfall.The four kinds of statistical models (Gumbel,Lognormal,Weibull,and Person Ⅲ) were used to fit the annual extremes series of daily and a continuous process rainfall.Test results have showed that the Weibull distribution is more suitable to the daily rainfall,and the lognormal distribution fits the continuous process rainfall.The spatial distribution of the extremes of a continuous process rainfall is relatively concentrated,and its spatial-temporal variabilities are smaller than those of the extremes of daily rainfall.

Abstract:Using the Doppler radar data in Jilin Province in 2003—2004,the distributive characteristics of whole atmospheric layer vertically integrated liquid water(VIL) and the VIL above and below the 0℃ layer in the cases of the stratiformis continuous precipitation,and convective cloud precipitation are analyzed.It is pointed out that VIL can be used in the selection of weather modification operation region,the analysis of heavy rain processes and severe storms,and the research of precipitation mechanism,etc.

Abstract:The intraseasonal oscillation is a strong signal of the tropical atmospheric activilies and also a common phenomenon in the tropical ocean.This article depicts firstly the progresses in the research on the tropical intraseasonal oscillations,such as the studies on the observation and mechanism of the tropical atmospheric intraseasonal oscillations and on the tropical oceanic intraseasonal oscillations.And then the effects of air-sea interaction and multi-scale interaction upon the intraseasonal oscillations are discussed briefly.Prospects of further studies on the tropical intraseasonal oscillations are proposed based on those summaries.