Abstract:In the fall and winter of 2008 to 2009, a rare severe drought struck t welve provinces in East China. This severe drought is due to the lack of rainfal l for a sustained period. There was a quasistationary circulation system in th e middle latitude over the Eurasia. There was a deep trough sustained over the n ortheast of Japan. In the Tibetan Plateau there was a stationary ridge. There wa s emulous cold air outbreak over the East China. Due to the persistence of the r idge over the plateau, the perturbations from West Asia could hardly reach East Asia. At the same time, the abnormal winter monsoon prevented the water vapor fr om the ocean reaching the land. The formation mechanism of such anomalous atmosp heric circulation which lasted three months stably over Eurasia Continent is yet to be further studied.

Abstract:The characteristics of mesoscale convection systems(MCS) associated with t he remnant of the downgraded severe tropical storm Bilis are studied using vario us kinds of observation data and numerical simulation. During Bilis’s going int o inland of southern part of China, the MCS developed quickly and kept active du e to the maintenance of southwest monsoon. A high resolution simulation by ARPS model gave almost the same rainfall patterns with the observation. Analysis was carried out using modeling data for studying the 3dimension structure and evol ution of the MCS. During the downgrading process of Bilis, obvious baroclinic st ructure generated, and the secondary circulation induced by vertical shear of en vironment flow determined the MCS activities. The moist 〖WTHX〗Q〖WTBZ〗 vector was also applied for the research of vertical motion of Bilis. MCS in the southern Hunan Province almost developed in north of horizontal wind shear line, which was under constrains of the low level convective instability conditi ons and northerly jet convergence.

Abstract:The operational experiment result of Lightning Nowcasting and Warning System (wh ich is developed by Chinese Academy of Meteorological Sciences, CAMS_LNWS) in Be ijing area is reported. The comparison and evaluation between the lightning nowc asting products and lightning monitoring data show that CAMS_LNWS can work stabl y, obtain many observation data regularly, automatically generate and circularly display three types of lightning nowcasting and warning products, namely the li ghtning occurrence probability, the moving trend of lightning activity region an d the lightning risk grade of key region. The lightning occurrence probability products of CAMS_LNWS have a relatively high Probability of Detectio n (POD), and it can effectively nowcast and warn the regions that may occur ligh tning flashes within 0—30 min. However, with the extension of the nowcasting an d warning lead time, the effect of CAMS_LNWS products will deteriorate.

Abstract:By employing the NCEP/NCAR reanalysis data, the characteristics of the dry cold air activity, the dry cold air intrusion and evolution, as well as its impacts o n the torrential rain during the 2008 Meiyu period are diagnosed．It is shown th at there exists a close relationship between the evolution of the circulation ov er the midhigh latitudes and the torrential rain process, and the establishmen t and maintenance of the blocking anticyclone (pressure ridge) over Northern A sia lead to the southward movement of the westerly frontal zone and the dry co ld air. The abnormal eastward movement and the enhancement of the polar cyclone transfer the dry cold air to the Changjiang River and the Huaihe River Basins, t hus enhance the torrential rain over that area. It is also revealed that the nor therly activities are in coherence with the torrential rain process, the dry cold air comes from the midhigh latitudes and the midhigh level. The Cha ngjiang River and the Huaihe River Basins locate in the low level air convergenc e area. The north wind plays an important role in the enhancement of the converg ence in the lower level and the divergence in the upper leve1.The dry cold air i ntrusion contributes to the formation and maintenance of the dry level. The dry cold air intrusion is one of the important dynamical and thermal causes for the formation and maintenance of moist front during the Meiyu period. At last, the k eys of midrange forecast are summarized on the basis of these results.

Abstract:By using the rainfall data from NMC, the reanalysis data from NCEP/NC AR and OLR data from NOAA, the features of Asian summer monsoon, the western Nor th Pacific subtropical anticyclone (WPSA), ITCZ, Somalia Surges, Indian monsoo n and the heat sources in Asia Pacific area around the period of Jianghuai Valle y rainfall in 2008 are analyzed here to reveal the reasons for the anomalous features of Asian summer monsoon an d their influence on the beginning and ending of the rainfall and rainfall stren gth. The results show that forces of the monsoon members are complexly variable, decreasing or increasing by interacting with each other, so that no single memb er can play a predominant role, which is an important reason for the variable an d weaker rain belt of Jianghuai Valley. The movement of ITCZ is an important fac tor for the rainfall forecasting, it affects and precedes the WPSA by thermal an d dynamical mechanisms. Its abrupt strengthening at beginning of June is crucia l to bursting out of Jianghuai Valley rainy season and its strengthening and sur ging northwards with a typhoon landing at South China at the 5th pentad in the s ame month leads to the ending of Jianghuai Valley rainy season. So it is a criti cal forecasting index. Somali surges’ bursting out abruptly earlier than usual is also beneficial to the earlier onset of Indian monsoon and the beginning of J ianghuai Valley rainy season, and their persistence and recession have some infl uence on the position and intensity of rain belt. The onset of Indian monsoo n and the changing characteristics afterwards affect the position of IndiaBurm a monsoon trough, which affect Jianghuai Valley rain belt by changing the st rength and distribution of heat sources over southern QinghaiXizang Plateau an d Bay of Bengal.

Abstract:Guangdong suffered the heaviest rainfall during late May to mid June 2008 (soc alled “dragonboat” precipitation), according to records since 1951. Result o f diagnostic analysis shows that in this case the circulation situations of the middle and high levels in Asia and Europe are two trough and one ridge circulation pattern and the western Pacific subtropical high is weaker t han normal and expands eastward. Four main heavy rain periods in this case are a ssociated with the influence of westerly trough and southward movement of low level shear line . The variance of lowlevel jet has a close relationship with the occurrence of the rainstorm. The cold air moving down from the midlatitude areas and joinin g up against moist southerly from the Bay of Bengal and the South China Sea prod uces the vapor convergence at southern China coastal areas and the anomalous loc al meridional circulation, which causes the continuous heavy rainfall. Three of four heavy rainfall periods are associated with the instable stratification.

Abstract:Based on the conventional and nonconventional observations, reanalysis data, P WV potential water vapor data, and satellite images, the convective rainstorm oc curried in Shanghai on 25th Aug, 2008 is analyzed. The results show that a sub synoptic vorte x is developed by three strengthening flows from South China, over sea and highe r latitude area, respectively, which can explain the convergence of moisture tra nsportation, the accumulation of high energy in previous 12-24 hours, and th e trigger of vertical velocity and energy release. A series of satellite picture show the merging of cloud clusters to induce a burst of precipitation. A nd the slow movement could partly explain the significant accumulation of rainfall in a short time. GPS/PW V images display the enriching process of moisture.

Abstract:Using NCEP global 1°×1° finalanalysis data and the conventional highaltit ude and surface data，the formation mechanism of the continuous rainstorm in the northwest side of subtropical high is discussed. The results show that the he avy rain happened in the background of the exceptionally powerful subtropical h igh and the strong Typhoon “Hagupit” landing westward, and there is no lowva lue system impact on 500hPa during the course. The main trigger systems are the subtropical high and continued strong southeast wind of lowlevel jet out of the typhoon. Continuous southeast wind of lowlevel jet provides rainstorm area the continuous water vapor and instability energy. The largest rapid zonal convergence speed and terrain elevation for the formation of rainstorm provide a driving force for increasing convergence conditions. The heavy rain district is located in a stable branch of ascendant circulation. In addition, the cold air in the proc ess played an important role.

Abstract:Tornadoes occurred in front of typhoon in Jiangsu Province on 29 to 30 July, 200 8. A detailed analysis of the environmental conditions, structure and evolution of tornado is made based on the Doppler weather radar data, routine upperair a nd surface observations, and intensive automatic weather station observations. T he main results are as follows: The tornadoes occurred in the area with high val ue of low level vertical wind shear. The low lifting condensation level, unstabl e stratification and deeper positive vorticity all these factors supplied the th ermodynamic and dynamical conditions for the occurrence of tornadoes. The tornad o occurred at Dongtai is associated with a mesoscale squallline, whereas the t ornadoes occurred at Gaoyou and Baoying are associated with multicell convective storm. The rear part of the storm cell ha s a large reflectivity gradient, which is often accompanied by the weak echo str ucture and backflank notch in the low level. Not all the tornadoes occurred i n the stormcell with mesocyclone and tornado vortex signature. Some tornadoe s happened in the stormcell with weak cyclone vortex in the low level. When th e altitude of strong echo center and the vertical cumulative liquid water falls suddenly and cyclone vortex develops rapidly, the tornado will occur very soon. In operational work, we shouldn’t alert the occurrence of tornadoes only de pending on the mesocyclone signature and tornado vortex signature. We should a lso combine the other products, for example, reflectivity, average radial vel ocity, storm structure, etc. It is possible to greatly enhance weather radar’s capability to detect the tornadoes.

Abstract:Based on 1°×1°NCEP reanalysis data of 2008, conventional meteorological data, automatic station data, surface intensive observations and Doppler radar echo, the influences of circulation background on the track and precipitation of stron g typhoon Hagupit are synthetically analyzed, and the physical characteristi cs are also diagnostic analyzed. The results are as follows: (1) The main reason why typhoon move westnorthwest steadily is that on 500hPa level, the z onalsubtropical high on the north strengthens the east flow and rear southeast flow, and the differences between maximum east wind on the north and maximum west wind on the south increase; (2) Analysis of Doppler radar base reflectivity products show s that the convective echo in rain belt develops on the upstream sea, but quickl y weakens when it moves downstream towards to the land. The vertical integrated liquid water (VIL) is a good indicator to the estimate of precipitation both on amount and area. In the typhoon rainfall system, the different density of liquid water in cloud can make big difference in precipitation with same VIL, sometime s the difference may reach 2.5 times or more. Doppler radar product OHP (one hou r precipitation) is consistent with actual precipitation area and amount very we ll, especially with precipitation area, and OHP has a good corresponding relatio nship with both R and VIL products; (3) Physical characteristics, such as vertic al motion, vorticity and water vapor flux divergence, all are in favor of precip itation increase when “Hagupit” moves westnorthwest.

Abstract:From middle January to the beginning of February in 2008, the extremely icy rain and snow weather processes occurred in most areas of South China. Using the NOA A18 OLR data in National Satellite Meteorological Center, the extremely icy ra in and snow processes in the beginning of 2008 is tried to analyzed. The results show that the relationship between fiveday [JP2]OLR anomaly and fiveday pre cipitating amount is as follows: Y=A+B×OLR The correlation coeffic ient of the equation is 0.60525 in South China. The standard deviation of monthly OLR in China during 1989-2008 is higher than the standard deviation during 1989 -2000, which indicates the increasing of the extremely weather events in recent years; The location and intensity of the abnormal precipitation processes are we ll reflected by the OLR isogram and OLR anomaly isogram. On daily OLR isogram, t he lower the OLR is, the higher the cloud is, and the more intense precipitation is. On five and tenday average OLR isogram, the lower the OLR value is, the l onger the sustained time of clouds is. On five and tenday anomalous OLR isogra m, the lower the anomaly is, the stronger the precipitation processes are and th e longer the sustained time of the processes are. Finally it is noted that the p recipitation process produced by stratus clouds with inverse temperature is not well reflected by OLR data. This is because that the temperature of the stratus cloud is nearly the same as surface, OLR value of the clouds is high and anomaly of OLR is not negative. It is a disadvantage of application of OLR to analyzing disastrous precipitation weather process.

Abstract:A mesoγ scale and mesoβ scale downpour took place at Niutouya town of Funi ng County that located in the western bank of Bohai Sea from 5:00 to 6:00, o n 11 August, 2008. The same thing also happened in Tanghai County， and their pr ecipitations all exceed 100 mm per hour. Using CINRAD/SA radar data in Qinhuangd ao and in Tianjin, the physical quantity field of the mesoscale meteorology, MM5 model output, in Shanhaiguan, the synchronous data of the dense observations recorded once per minute, the relationship between mesoβ scale echo band and the peak value of the precipitation was analyzed. The tentative result shows that the downpour is resulted from the mutual perturbation between the mes oβ scale system and the mesoγ scale system under the background of the mes os cale echo band in the same matrix at different time. The former is the common mu lticell storm with the distance of 100km away from the matrix of echo band. It can spread in wave form on the space profile of 300km, and is related to stirri ng of gravity wave. The latter is the strong multicell storm, which would emer ge later on the bottom of the matrix of a weakening echo band, involved in the p erturbation of weak shear and the thermodynamic factor. The scaledefined is fo und on radar GPS positioning of the centroid and GIS information proofing in the dense observational network. The predictable factors of mesosmall scale syste m on disastrous downpour have been explored 0—1 hour before its occurring in th e coastal zone, so that they can provide some prediction basis for early warning .

Abstract:The automated contour system based on observation data was introduced. The cont our method in IDL was applied and real time data of local automation weather station (AWS) data, including temperature, precipitation, wind speed and wind direction, and air pressure, was processed and contour plot maps from them was generated then transferred to the WEB page, animation was played and the ma ps can be queried. The system was used widely during the 29th Olympic Games to provide decision support for weather forecasting, and also as an effective tool to monitor the weather. Forecasters can conveniently use the system to perform c ase study analysis.

Abstract:2008 was the tenth warmest year on record. In early 2008, snow storms, cold wave s, extreme low temperature and freezing weather blanketed the regions from south eastern Europe to China through West Asia; and consecutive snow storms hit North America. Severe drought persisted in northern China from boreal winter to sprin g. During summer, rain storms and floods raided East Asia, South Asia, mideast Europe and the Mississippi River and its tributaries. During 2008, severe droug ht condition maintained in Australia. The La Nina event came to the end in May. The Northern Hemisphere snow cover extent in January was the largest on record. During the year, tropical cyclone activities were weaker than normal in the Nort hwest Pacific while those were near normal in the Atlantic Ocean.

Abstract:Although overall in 2008, there are not serious persistent drought and flood d isasters happened over countrywide due to the week anomalies of climate, some si gnificant anomalies of synoptic and climatic features occurred in China such as annual mean precipitation is above normal and ranked first among recent 10 years ,significant wet in South China and wet again in Huanghuai region during summe r, annual mean temperature is above normal while cold in winter with rare snow s torm and icefreeze disasters in south part of China in the beginning of the y ear,significant less than normal of typhoon generated over South China Sea and West Pacific. However， more than normal of typhoon landing China, as well as firs t naming typhoon occurred very early than normal. It is shown by diagnostic anal y sis that belownormal Sea Surface Temperature Anomalies (SSTa) are observed ove r the central and eastern Pacific in 2008 followed a cold phase of ENSO occurred in summer of 2007. Due to influence forced by SSTa and interaction between ocea n and atmosphere, general circulation over the Northern Hemisphere shown the do minant anomalies which have been characterized as respond as follows: the inten sity and position of subtropical high over the West Pacific varied frequently th an normal; East Asian monsoon was more strong than normal both in winter and sum mer; the tropical convective activities in warm pool of West Pacific were more a ctive from winter to spring and week from summer to fall of 2008 than normal; th e meridional circulation develop strongly in January and the zonal circulation develop strongly instead from February to April over midhigh latitude area of Asia, and the transition between meridional and zonal circulation was carried ou t frequently from latter spring to fall indicated the week persistence of circul ation. These may be the main factors that influence climate anomalies in China i n 2008.