Abstract:Coupled ocean-land-atmospheric general circulation models are the only tools to quantitatively attribute past climate change in response to human activities and to predict the magnitude of future climate change.These models are known to differ considerably in their equilibrium sensitivities to external forcing, largely because of differences in atmospheric feedbacks, especially in cloud-climate feedbacks.Yet, all models that participated in the IPCC(Inter-governmental Panel on Climate Change) Assessment Report(AR4) showed very similar simulations of the 20th century climate by these models.This paper investigates the causes and implications of this similarity.It shows three equally important physical mechanisms acting together to reduce the sensitivity of transient climate change to model differences.These include the longer time delay of climate response to forcing, more heat exchange with the deep ocean, and larger impact of oceanic upwelling in models with larger atmospheric feedbacks, but inter-model differences will show up at longer time scales.

Abstract:By using NCEP GODAS monthly sea surface height(SSH) and 160-station monthly precipitation data in China, the seasonal and interannual characteristics of SSH are analyzed over the tropical Pacific, along with the correlation relationships between SSH and summer rainfall discussed.The results show that:1) The tropical Pacific SSH takes on "V" pattern in the climatic field on the whole, it is higher in the western part than in the eastern part, and higher in the northwest part than in the southwestern part.The high value area is more stable in the northwest, the value(greater than 0.8 m) range is larger in spring and summer than in autumn and winter.The high value area in the southwestern part is largest (smallest) and northerly(southerly) in spring(summer).The SSH is higher in spring and autumn than in summer and winter over the equatorial zone.2) The SSH interannual anomalies are strongest over the tropical western and southwest Pacific, and stronger in winter and spring than in summer and autumn.The interannual anomalies are also strong over the equatorial middle and eastern Pacific, which are stronger in the autumn and winter and are unusual of the greater intensity and scope.There is closely relationship between the SSH interannual anomaly and ENSO events in the autumn, winter and spring.3) When ENSO event takes place in the winter, according to the simultaneous relationship between the tropic Pacific SSH and the summer precipitation of China, it can be predicted that the precipitation will significantly be more than normal value over the south of the Yangtze River, especially Dongting Lake and Poyang Lake region, eastern Qinghai-Tibet Plateau, Yangtze-Huai River Valley, eastern part of Neimen, while less than normal over the He Tao area, the North China and the South China in the coming year summer.

Abstract:The ensemble experiments composed of 8 members have been preformed from 1979 to 2000 by the National Center for Atmospheric Research (NCAR) Community Atmosphere Model Version 3(CAM3).Each experiment is forced by the observed sea surface temperature(SST).The analysis of variance is applied to investigate the potential predictability of East Asian summer atmospheric circulation.Results show that the potential predictability of summer sea level pressure is low in East Asia as a whole, and is high(low) in Southeast(Northwest) China.The potential predictability of East Asian summer 850 hPa zonal wind, tropospheric temperature averaged from 500 to 200 hPa, and 500 hPa geopotential height is higher in low latitudes than that in mid-high latitudes.The potential predictability of summer 500 hPa geopotential height is high, which is greater than 0.5 in the East Asia, especially larger than 0.7 over South China.It is found that the potential predictability of East Asian summer 500 hPa geopotential height exhibits distinct interannual variability, which is closely related with sea surface temperature anomaly (SST) in South China Sea in summer.Compared with that in the normal SST years, the potential predictability of East Asian summer 500 hPa geopotential height is higher in the warmer or colder SST years.

Abstract:Based on the observational data of total ozone mapping spectrometer from 1979-2005 and ozone monitoring instrument from 2006-2007, the regional and seasonal distribution of tropospheric ozone residue and total ozone were analyzed.The abrupt change and period characteristics of ozone in Guangzhou were analyzed by such methods as binomial weighted average, Mann-Kandall abrupt change verification and wavelet analysis.The results show that the average tropospheric ozone residue is 35.89 DU in China and that the distribution of TOR is higher in east area than in west area.The highest value appears in eastern Sichuan and western Chongqing while the lowest value appears in Tibetan Plateau.TOR reaches the peak in summer, the second peak in spring, and the value of TOR is the minimum in winter.The average total ozone is 298.61 DU in China.The TO grows with the latitude, but Tibetan Plateau is the region with the lowest TO value.TO presents the highest value in spring and the lowest value in autumn.TOR in Guangzhou took on the trend of rising during 1979 and 2007.The increase of the annual mean TOR in Guangzhou was 0.38 DU/(10 a).The abrupt change happened in 1997.TOR in Guangzhou presented obvious period of one and two years.TO in Guangzhou took on the trend of reducing during 1979 and 2007.The decrease of the annual mean TO was 2.1 DU/(10 a).The abrupt change happened in 1993.TO in Guangzhou presented obvious period of two years.

Abstract:Based on the 740 stations'daily rainfall datasets in China from 1954 to 2005 and the NCEP/NCAR reanalysis data, we analyzed interannual variability of the Meiyu quasi-biweekly oscillation over Yangtze-Huaihe River Valley and discussed the background features of atmosphere circulation and sea surface temperature in anomaly years.We divided each rainfall circle into 8 phases.Phase 3 corresponds to the largest positive rainfall, while phase 7 corresponds to the largest negative rainfall.The results are as fo llows:1) the differences between strong and weak oscillation years showed that during phase 3, there is a Rossby wave-like train extending from South China Sea to Alaska, via the Sea of Japan, Sea of Okhotsk and Aleutian Island in lower atmosphere.The anti-cyclone over South China Sea coordinated with cyclone over Japan is conducive to rainfall over Yangtze-Huaihe River Valley.While in Phase 7, the wave train is out-of-phase, and extends in a more southern path; 2) in the higher level atmosphere, during phase 3, a significant positive anomaly of geopotential height occurred over Sea of Okhotsk.Together with the negative anomaly over Northeast China, the anomaly supplied adequate cold and dry air for the rainfall.3) The SST(sea surface temperature) of the Kuroshio and its extension zone from March to July showed a very significant positive correlation with the intensity of Meiyu quasi-biweekly oscillation.The lasting positive offshore SST anomaly strengthens Meiyu quasi-biweekly oscillation by regulating the position and intensity of the Western Pacific Subtropical High.

Abstract:Base on the observational data obtained from tower in Huangshi area along the Yangtze River, a detailed study on an ice storm process on 18-21 January 2008 is made in this paper.The unusual characteristics can provide the basis to understand the Huangshi area snowstorm's surface layer physical process.The results show that:before the precipitation, the wind direction changed, the horizontal and vertical wind speed increase obviously, the turbulent flux become active, the turbulent kinetic energy and the turbulence intensity presented obvious peak values; after the precipitation, the turbulent kinetic energy reached to another peak value and then weakened slowly.Thus, obvious changes of the physical quantity fi eld occurred before and after the snowstorm.

Abstract:The NCEP/NCAR reanalysis data have been used to check the principal modes of the South Pacific sea surface temperature(SST) anomalies through empirical orthogonal function(EOF) in DJF.The EOF1 mode of SST anomalies in the South Pacific is related to ENSO(El Ni?o-Southern Oscillation) and bears periodicities of 3-5 years.The EOF2 mode is related to Southern-Hemisphere Annual Mode(SAM) and bears the periodicities of quasi-biennial.The relationship between precipitation anomalies in China and the EOF modes of SST anomalies in the South Pacific is analyzed.When time coefficient of South Pacific EOF1 is in positive(negative) phase, the rainfall in May is more(less) than normal in North China.This scenario seems to be similar to that between rainfall and EOF1 mode of SST anomalies in the North Pacific.When the time coefficient of South Pacific EOF2 is in the positive(negative) phase, the rainfall of South China reduces(enhances) in summer.These results almost keep unchanged when the linear trend is removed separately from the SST anomalies and rainfall data.Using the time series of EOF1s of the South and North Pacific as two predictors, the rainfall in North China in May could probably be predicted.

Abstract:In this study, Yunnan Province was chosen as the study area.Five meteorological factors, namely, precipitation, temperature, wind speed, evaporation and relative humidity, as well as the grid of tree species and the land use distribution in Yunnan Province were taken as fire risk factors during the forest fi re prevention period.By standardization and offering different weights to each factor, area division of meteorological forest fire risk at different rankings in Yunnan Province was made with the analysis and calculation functions of ARCGIS, which was verified by historical record of forest fires.According to the result, the development trend of meteorological forest fire risk area division is consistent with the real situation in Yunnan from December to May.This result accurately reflects the regular meteorological forest fire levels in different months during the forest fire prevention period by comparing with the history of forest fire records, which shows its practical value.

Abstract:An exceptional heavy snowstorm occurred in the eastern part of Heilongjiang Province on 4-5 March 2007.The dynamical structure features are analyzed using the Doppler weather radar data in Mudanjiang.The result shows that the upper-lower jet streams, wind shear and cold-warm advection are characteristic during the process of snowstorm.The mesoscale convergence shear line and the position-change of southwest jet streams are caused by the warm south airflow and the cold northeast air current, which have important indicative significances in the process of snowstorm evolution.The radar reflectivity factor is between 15 and 27 dBZ, and the echo area is wide with the echo top of about 6 km.The cold-warm advection is obvious and the radial velocity is large.The phenomena of bull's eye squall and velocity ambiguity can be a starting point in forecasting of this kind of snowstorm.

Abstract:By using the temperature observation data of 124 stations in Yunnan Province during 1961-2008, the 1 km×1 km fine-grid temperature data was obtained after the terrain correction.The study on the climate division based on the fine mesh data and the selection of representative climate stations in Yunnan Province was carried out.The results show that there are six climate zones in Yunnan Province, namely, plateau climate zone, temperate zone, north subtropical zone, middle subtropical zone, south subtropical zone and north tropic zone.Each of them occupies an area of 3.32, 3.65, 15.65, 6.82, 8.66 and 1.31 ten-thousand square kilometers respectively.The plateau climate zone is located in the high altitude area over 3000 m in northwest of Yunnan Province.The temperate zone is mainly located in the area with altitude of 2200~3000 m in the northeast and northwest of Yunnan Province.The north subtropical zone is mainly located in the high altitude area in the middle, west and south and the low altitude area in the north of Yunnan Province.The middle subtropical zone mainly lies in the relatively high altitude area in the middle, southeast and southwest of Yunnan Province.The south subtropical zone mainly lies in the south area of Yunnan Province and the stream valley area.The north tropic zone is mainly located in the south area of Yunnan Province and the lower altitude stream valley area.Distribution of each climate zone is related with the terrain and the latitude.Compared with administrative region, the terrain feature better embodies climate characteristics of different climate zones.Through statistical analysis on consistency and deviation of the sequence of the stations and the climatic zone, representative climate stations are selected.They can better reflect the characteristics of each climate zone of Yunnan Province.

Abstract:Based on the fixed-point observation data of CCN(cloud condensation nuclei) concentration fr om DMT(Droplet Measurement Technologies), an extreme disastrous weather occurred during June 11-13, 2007 in Shijiazhuang, with the air quality and visibility being both bad, is analyzed.Results show that the extreme weather is closely related to the straw burning(one of the human activities) around Shijiazhuang City.The persistent downward flow in the middle and high troposphere forces the smog to gather near the ground layer, and makes the number of CCN particles increases.The weak exchange of vertical turbulence restrains the vertical diffusion of smog near the ground layer, which makes the visibility much worse and leads to the formation of haze weather.The thickness of temperature inversion and the low wind velocity on the ground jointly enable the smog to accumulate over the special terrain.

Abstract:Based on the Panman-Monteith method by FAO and the weather data from 1961 to 2008 at 25 weather stations, the correlation between potential evaporation and climatic vacillation on typical grassland is analyzed.The result shows that:1) The seasonal and annual potential evaporation is on a decreasing trend on typical grassland.The potential evaporation in spring declines most at 3.71 mm/(10 a).It is followed by summer and autumn evaporation, and winter evaporation shows the least decrease.More than 80% of the annual potential evaporation occurs during the periods of grass ventilation reventilization and growth.It is the period when evaporation fluctuates most in a whole year.This might induce severe drought events, aboveground biomass decrease and grassland degradation on typical grassland.2) Potential evaporation on typical grassland is most closely related to such factors as relative humidity, precipitation, sunshine hours and average wind speed instead of temperature.From the view of energy equilibrium, this could be explained by the decline of average wind speed in the recent 50 years affe cting evaporation aerodynamically.Radiation reduces because of sunshine hour decline and humidity increase, which causes the decline of evaporation.3) The evaporation on typical grassland is low and fluctuates a lot in this century, which will probably induce severe drought disaster.It is in accordance with the conclusion from recent studies showing the ecological water consumption increases and more severe droughts and ecological degradation occur after climate warming.

Abstract:Based on the risk assessment technology, drought risk for winter wheat in Yunnan Province was studied, the pivotal period of winter wheat yield reduction caused by drought was set and such index as drought intensity, yield reduction risk, disaster resistance and drought loss comprehensive risk were calculated.Thus, Yunnan Province was divided into different winter wheat drought risk regions.The paper pointed out that from inside to outside of Yunnan Province, the risk of losses caused by drought for winter wheat gets higher.

Abstract:Based on the hourly output of WRF(weather research and forecasting model), MOS(model output statistics) prediction process of hourly solar radiation was designed, including low-pass filtering of hourly observation series which was then divided by astronomical radiation, selection and dimensionality reduction of output factors and foundation of MOS prediction functions.Judging from the results of experimental prediction of hourly solar radiation at Wuhan station in January, April, August and October 2009, it shows that this method is relatively stable in monthly forecasts and that both fitting and forecast results are satisfactory, mean absolute percentage error was controlled between 20% and 30%.Relative mean square root error was controlled between 30% and 40%.Radiation forecast was improved by 50% compared with model direct prediction.It is clear that accuracy rate of model radiation prediction can be greatly improved through interpretation and implement of model output results.Besides, 13 output factors including temperature, cloud amount, dew point, specifi ed humidity, relative humidity and surface pressure analyzed here can provide reference for other regions in fo undation of MOS functions of hourly solar radiation.

Abstract:The paper summarizes the developments of the National Centers for Environmental Prediction (NCEP), the European Centre for Medium-Range Weather Forecasts(ECMWF), and the Canadian Meteorological Centre(CMC), which are the most representative of global ensemble forecast system(GEFS).Due to the enlarging of computational resources, the model resolution and ensemble size of their GEFS subsequently increase.At the same time, for promoting the improvement of the forecast skill, they all devote to develop the initial and model perturbation methods used to simulate the effect of initial and model uncertainties.The initial perturbation methods are updated from the singular vector (SV) method(ECMWF), the breeding method (NCEP) and the perturbed observation (PO) method (CMC) to the ensemble of data assimilation and singular vector(EDA-SV) method(ECMWF), the ensemble transform with rescaling(ETR) method(NCEP) and the ensemble Kalman filter(EnKF) method(CMC).Several attempts are also made to account for model-related uncertainty.ECMWF and CMC have revised their stochastic physics parameterization tendencies(ECMWF) and multi-parameterization(CMC) schemes, and NCEP also develops stochastic total tendency perturbation to estimate the model-related uncertainty.To accelerate improvements on the accuracy of global high-impact weather forecasts, TIGGE(the THORPEX interactive grand global ensemble) was initiated to enhance international collaboration on multi-center and multi-model ensemble forecast, and NAEFS (North American ensemble fo recast system) can provide an operational framework for global multi-model ensemble forecast system.They are all helpful for developing the global interactive forecast system(GIFS).