Abstract:Based on the cloud structural characteristic parameters retrieved by FY2C satellite and radio sounding data, combined with precipitation on ground, the relationship between cloud parameters(including cloud top height, optical thickness, particle effective radius, depth of cloud, etc) and precipitation was studied.The relationship between frequency distribution of cloud parameters and precipitation during stratiform cloud precipitation process and convective cloud precipitation process was researched further.Results show that precipitation is usually easy on the ground when cloud depth is thicker than 5 km, cloud base is low, and effective cloud particle radius is large.When cloud top height is greater than 10 km, optical thickness exceeds 20, and there is no or very thin interlayer in cloud, the surface precipitation intensity is usually more than 1 mm/h.For the stratiform cloud precipitation, if cloud optical thickness value exceeds 17, the probability of precipitation on ground will be higher.With the increase of optical thickness, surface rainfall intensity shows an increase tendency.For the convective cloud precipitation, there is a good correlation between cloud top height and optical thickness.While optical thickness value exceeds 17 and cloud top is higher than 7 km, the probability of precipitation on the ground is greater.If the cloud optical thickness exceeds 20, surface precipitation intensity will increase significantly.Both the precipitation probability of stratiform cloud and convective cloud increases with cloud top height and optical thickness.The probability of precipitation is more related to optical thickness.Clouds of optical thickness value less than 10 are difficult to precipitate.If cloud optical thickness exceeds 20, precipitation probability of stratifo rm clouds and convective clouds will increase evidently.Comprehensive analysis of cloud top height, cloud thickness, optical thickness and other cloud parameters could be more effective to determine precipitation region and intensity on the ground.

Abstract:In a "water-hosing experiment" by using model CCSM3, different seasonal responses of the climate to the weakening of thermohaine circulation(THC) in China are studied.Results show that CCSM3 can reasonably represent the magnitude and pattern of the surface air temperature(SAT) and precipitation in China.Both SAT and precipitation decrease significantly in winter and summer after reducing annual mean THC intensity by 80%, but the magnitude and pattern of decreased SAT and precipitation are quite different in summer and in winter.The maginitude of reduced winter SAT is more robust and its cooling distribution is more homogenous than that of summer.The averaged cooling magnitude in winter is about 2.2℃ with a maximum of 4℃.The averaged cooling magnitude in summer is about 1.3℃ with a maximum of 3℃.The magintude of reduced winter/summer precipitation are all around 6%, but the anomaly patterns and the causes are significantly different.

Abstract:The amplifying of the torrential rainfall of the landing Tropical Storm Bilis (0604) and moisture budget around the typhoon vortex are studied with the dataset of CMA-STI Tropical Cyclone Optimal Tracks, the NCEP/NCAR reanalysis data and the intensive surface observations.Results show that the southwest monsoon provides abundant water vapor for torrential rainfall during the landfall of Bilis, and has important influence on the long time maintenance and torrential rainfall increament of the landing typhoon.The rainfall of Bilis after landfall is simulated by WRF(weather research and forecasting) model, showing that the model can preferably simulate the rainfall intensity and torrential rain area.The simulated path is mainly coincident with the observed path, although there is some difference between them.Rainfall is significantly increased on the south side of the typhoon centre at the onset of the monsoon surge.Results of the sensitive experiments show that the typhoon rainfall intensity is closely associated with the moisture transport, and the decrease of water vapor can remarkably weaken the rainfall, indicating that the moisture transport of southwest monsoon plays an important role in the torrential rainfall of landing typhoon.

Abstract:Based on data of the precipitation, temperature and cloud cover of 25 stations in Hangzhou Bay region and the global annual volume fraction of CO₂ from 1971 to 2006, the annual vegetation net primary productivity (ANPP) is simulated by the LPJ model (Lund-Potsdam-Jena dynamic global vegetation model).The temporal and spatial characters of the ANPP in the region are analyzed and the driving fa ctors of ANPP are further investigated.Results show that:1) The average increasing rate of ANPP is 1.5243 g·m^-2·a^-2 in the whole region.However, ANPP spatially show different increasing rates fr om 1971 to 2006, with the significant rate in the north of Jiaxing and the east of Shaoxing.2) The multiple linear regression analysis shows that there is a close relationship between cloud cover and ANPP with-0.5175 partial correlation coefficient.However, the correlation between ANPP and temperature (precipitation) is inconspicuous.Response of ANPP to climate change shows a certain geographical distribution for the different hydro-thermal conditions.3) In the whole region around Hangzhou Bay, the average trends caused by decline of temperature, increase of precipitation, reduction of cloud cover and enhancement of volume fraction of CO₂ are -0.0813, -0.0171, 0.7601, and 0.8673 g·m^-2·a^-2, and their attributions to the change of ANPP are -5.18%, -1.09%, 48.38% and 55.21%, respectively.Therefore, the changes of volume fraction of CO₂ and cloud cover play important roles to affect the change of ANPP, however, change of precipitation has little action to the ANNP.

Abstract:Aerosols are sampled at Institute of Atmospheric Physics, Chinese Academy of Sciences from July to October 2008.The mass concentrations of water-soluble inorganic ions are determined with ion chromatogram(IC).This aims to investigate the composition, characteristics of mass concentration variation, relevance and form of the main water-soluble inorganic ions and their sources.The results show that SO₄^2-, NO₃^- and NO₄⁺ are the main water-soluble inorganic ions in the aerosol samples, and they are mainly in the form of (NH4) 2SO₄ and NH₄NO₃ in aerosol particles.The correlation coefficients between SO₄^2-, NO₃^- and NO₄⁺, Ca²⁺ and Mg²⁺ are high, showing a good homology among these ions.Mass concentration ratio of NO₃^-/SO₄^2- indicates that, before 2008 Beijing Olympics, the stationary source(coal burning) is the main pollution source for water-soluble species compared to the mobile source(vehicle), which is opposite to those during the Olympics and after it.Factor analysis shows that vehicle, coal combustion, soil, building dust and biomass burning are the main sources for Beijing air pollution during the sampling period.

Abstract:The strong convective precipitation is one of disastrous weathers in Tianjin area.Based on the NCEP/NCAR reanalysis data and FY-2C TBB data, a heavy rainfall process in Tianjin area on 25 June 2008 is analyzed and simulated by the WRF(weather research and forecasting) model.The high spatialtemporal resolution data from model output are used to analyze the process.Results show that the movement of mesoscale dew-point front might be an important mechanism for the strong convective precipitation process.The low-level convergence airflow plays a crucial role in the formation and development of mesoscale convective clouds, which is the directly influencing system of the heavy rainfall process.CAPE (convective available potential energy) and another thermodynamical parameter can perfectly reflect the fo rmation and development of the heavy rain process.It is found that the heavy rainstorm area has a better corresponding to higher storm relative helicity(SRH).The frontogenesis of mesoscale dew-point front is the most important mechanism of the strong convective precipitation.

Abstract:Based on the airborne Particle Measuring Systems (PMS), the aerosol and cloud particle observation data over Shijiazhuang during a cold-front precipitation cloud system on 4-5 October 2008 are analyzed.Results show that the aerosol distribution is obviously different before and after precipitation.Befo re precipitation, the average number concentration of aerosol is about 10³ cm^-3 with mean diameter of 0.95μm.The aerosol particles are mainly concentrated on the low troposphere below 3000 m and the aerosol concentration obviously decreases in cloud.After precipitation, the average number concentration of aerosol is about 10² cm^-3 with mean diameter of 1.28μm, and the number concentration is about one order of magnitude smaller than that before precipitation.The aerosol particles are mainly concentrated near the surface layer below 1200 m, and the number concentration decrease with height.Horizontal fluctuation of the aerosol number concentration is smaller (larger) in lower level cloud area (in no cloud area or near the surface layer below cloud area).The mean number concentration of cloud particle is one or two orders of magnitude smaller than that of aerosol.The average aerosol spectrum is bimodal and the average cloud particle spectrum is unimodal.

Abstract:By using ECWMF(European Centre for Medium-Range Weather Forecasts) analysis data, conventional observations, FY-2C satellites, radar stations and automatic weather station data, the heavy rain occurred on the night of 28 June 2009 in Fa'er Village, Shuicheng County in Guizhou Province is analyzed.The results show that the occurrence of the heavy rain on 28 June 2009 in Fa'er Village, Shuicheng County of Guizhou Province was the result of the southern branch trough, low shear and strong southwest warm air.Area of strong precipitation was in accord with middle-γ scale cloud.The movement, mergence, development, stagnation and decline of the clouds can well indicate the rainfall area and intensity.The strong convective echoes monomer resulted from the low -level convergence zone lingered around the Wumeng mountains(highest peak 2901 m) to northwest of Shuicheng County, which merged the rain clouds to the south of the county and thus caused the heavy torrential rain.The air flow field near Fa'er was changed because of its special terrain.It did not only strengthen and maintain terrain vertical velocity but also included more water vapor into the clouds and thus prolonged the duration time of the rainstorm cloud above Fa'er.The trumpet shape of the terrain also strengthened the convergence upward movement.The regional AWS data shows that the small and medium-scale weather system exerted important influence on the rain in Fa'er Village and nearby areas.It is also significant for the short-term forecast of this heavy torrential rain.

Abstract:Based on the percentile method, a distinction method for the extreme weather events is proposed by the construction of the climatologically equally likely intervals firstly.Then, the corresponding forecasting evaluation on extreme weather events is performed for 500 hPa geopotential height over Eurasian area in summer 2003.The results are as follows:1) In the analyzed period and region, the frequency of the extreme events is slightly higher than the climatological average situation.In NCEP-EPS, the forecast frequency is easy to become higher for the lower extreme events, but relatively reliable, whereas it is decreased with the extension of lead-time for the higher extreme events.When the lead-time is less than 3 d (more than 5 d), the forecast frequency is higher(lower) with relatively less reliability.2) EV(economic value) analysis shows that the performance of NCEP-EPS probabilistic forecast for the higher(lower) extreme events is better than that for the normal weather events.3) Forecast hit rate analysis shows that the hit rate is lower in the high-probability threshold.Further analysis points out that it is perhaps related with the lower ensemble spread in some cases.With the decrease of probability threshold, the hit rate steadily increases.It means that the spread of ensemble members can make them to cover all possible region of observation value, thereby to get the better forecasting results.

Abstract:By using the synoptic data such as satellite image, Doppler radar and upper wind, a rainstorm occurring in Guangxi and Guizhou as well as the southwest area of Hunan province on June 8-9, 2009 is analyzed.The results show that the storm was caused by the eastward moving MCC(mesoscale convective complex) and the development of β mesoscale strong convective cloud cluster and the mergence of them.The α mesoscale low pressure belt, together with the α mesoscale shear line on the ground surface, provided the conditions for MCC's movement to the east and β mesoscale strong convective cloud cluster's development and their mergence.The low tongue of the surface energy ratio was one of the triggers of the generation and development of MCC and β mesoscale strong convective cloud cluster.In the Doppler Radar vertical velocity diagram, the generation and development of MCC was accompanied by the establishment and maintenance of the southeast low jet stream and the generation of wide range of dead wind area.The MCC's extinction together with the weakening and vanishing southeast low jet stream, were in accordance with the generation and eastward movement of the northwest air stream.Studies also show that the budget of vorticity and the equilibrium of heat and vapour were very different during the development and vanishing periods of MCC and β mesoscale strong convective.

Abstract:Based on the WRF(weather research and forecasting) model output data with high spatial and temporal resolutions, the NCEP/NCAR 1°×1° reanalysis data, and the ground station precipitation data, this paper analyses a heavy rainstorm event in Sichuan Province from 31 July to 1 August 2009.Results show that the rainstorm bands approximately locate along the water vapor convergence regions, and the divergence field, water vapor flux and its divergence have excellent indicative function in the rainfall event.However, the atmospheric stratification is weakly stable for six hours before precipitation occurrence, which is not conductive to the occurrence and development of convection.But the analysis of the divergence field, the nonlinear balance equation and Richardson number shows that the mesoscale gravity waves exist before the rain begins, which induce the development of convective motion, while the convection plays a major role in stimulating the development of the rainstorm.Therefore, during the process, we must consider the interaction between the mesoscale gravity waves and convective motion, in order to explain the reason why the rain bands develop and maintain reasonably.

Abstract:Based on 1979-2007 seasonal NCEP/NCAR reanalysis data, relationships among Interhemispheric Oscillation (IHO), Arctic Oscillation (AO) and Antarctic Oscillation (AAO) are investigated.The results are shown as follows:1) Both AO and AAO have close relationship with mid-high latitude surfa ce pressure changes in their own hemispheres.AO in boreal winter emerge as strongest magnitude and influence broadly in both boreal spring and winter.AAO, on the other hand, exhibits most active in both austral summer and winter, and has notable impact on mid-high latitudes, especially in austral summer.2) IHO and AAO show significant positive correlation and AAO can partly explain the formation of IHO.IHO and AO exhibit insignificant negative correlations in all the four seasons.The relationships indicate that atmospheric circulation in mid-high latitudes in both the northern hemisphere (NH) and the southern hemisphere(SH) is relatively independent.3) IHO makes contributions to large scale surface pressure variation.With AAO signals removed, the significant area in SH polar region shrinks obviously.AAO has a close relation with IHO in summer.4) IHO bears a close relation to synchronous surface air temperature abnormally in Asia and north of Europe in boreal autumn, spring and winter.IHO has little relationship with surface temperature.It seems plausible that diabatic heating in northern European and Asian mainland can partly explain the formation of IHO.

Abstract:Based on daily precipitation data from 91 stations in Northeast China during the flood period fr om 1961 to 2010, the non-uniformity characteristic of extreme precipitation is analyzed.The main results are summarized as follows:the extreme precipitation amount gradually decreases from south to north and extreme precipitation mainly occurs in July; the extreme precipitation in central northeast is relatively dispersed whereas that in other areas is more concentrated; extreme precipitation amount of the lower-latitude regions is above the normal value and extreme precipitation occurs later and more intensively while it is the opposite situation in higher-latitude regions; there is a significant negative correlation between the amount and the concentration degree of extreme precipitation, which means the larger the extreme precipitation amount is, the more concentrated the extreme precipitation is, especially in the valley of Nen River and Songhua River.

Abstract:The tornado, short-term heavy precipitation and other convective weather in Yancheng City on 3 July 2006 are analyzed based on the data of dense surface automatic meteorological stations and Doppler weather radar.Results show that the weather background of the convective weather is Changjiang-Huaihe storm weather situation of the Meiyu, including the westerly trough eastward in upper levels, southwest jet stream in low-mid levels and strong convective instability.The development and maintenance of surface mesoscale vortex cause a continued strong upward motion for the convective weather.The tornado occurs in the large reflectivity gradient region in low-mid levels of the non-supercell storm, with a marked small scale vortex feature in the average radial velocity.In addition, three tropical systems in the western Pacific subtropical high and the ITCZ provide abundant moisture for the short-term heavy rainfall.There is a close relationship between the short-term heavy rainfall (occuring in a period of the increasing to the strongest, and to the beginning of decrease for the jet stream in low-mid levels) and the strong echo area larger than 50 dBZ.