Abstract:Not long ago, the U.S. National Research Council (NRC) published a study report about the uncertainty in weather, climate and hydrological forecasts. The report emphasizes the importance of communicating uncertainties associated with these forecasts to users in their specific applications. Otherwise, without quantifying its uncertainty, a forecast is incomplete. The publishing of a Chinese translation of this book is currently under the way. At the moment before the Chinese version is released, this paper would like to take this occasion to contribute a comprehensive review as well as some discussions to readers, which cover the following four aspects: (1) Why is uncertainty in all hydrometeorological forecasts inherited to be intrinsic? (2) What general goals should be set to successfully deal with the uncertainty in solving real world problems? (3) To accomplish these goals, what efforts have to be made and coordinated within the entire weatherrelated enterprise including government, research community and industries or endusers. (4) Finally, the efforts and roadmaps planned so far by the American Meteorological Society and NOAA in dealing with the forecast uncertainty are briefly introduced for reference. Via this paper, it is hoped that more people will pay attention to the importance of communicating the forecast uncertainty and work toward reforming and improving weatherrelated forecasts and services to benefit the entire society.

Abstract:A heavy rainfall is simulated by GRAPESMESO model， occurring in Huanghuai area on 22 July 2008 to study the forecast uncertainty and the initial perturbation method when establishing GRAPESMESO ensemble prediction system (called GRAPESMEPS) based on TIGGE data. The results suggest that the initial perturbation structure can reflect some information of initial uncertainty. The GRAPESMEPS has the ability to capture the extreme rainfall event and can significantly improve the forecast skill of heavy rainfall. The ensemble mean can capture some characteristics of the mesoscale heavy rainfall validly. The probability forecast gives the high probability area, where the heavy rainfall occurred actually. The ensemble verification results indicate that the relation between the spread and RMSE demonstrates the rationality of the GRAPESMEPS during the early integral period, but the impact of the initial perturbation decreases in the subsequent integral period owing to the model dynamic adjustment.

Abstract:In this paper, four cases on the YangtzeHuaihe River Valley (Jianghuai for short) during continuous rainstorm process in July 2007 are chosen for numerical prediction experiments using the GRAPES3Dvar model with radar direct assimilation function. The results have shown that the direct assimilation of the Doppler radial velocity, as well as the basic reflectivity factor can effectively improve the numerical prediction effects of mesoscale precipitation. The further analysis of the joint and the separate assimilation of radar data assimilation on July 3 shows that: Joint assimilation can improve the initial analysis of the wind field and humidity information, stimulate model precipitation, reduce the spinup phenomenon. Hence the mesoscale precipitation’s occurrence and development as well as the strength, movements and distribution are more accurately forecasted, and the effects of mesoscale numerical forecast of heavy precipitation are significantly improved. The main contribution of radial velocity direct assimilation is in the wind field, which can increase small and mediumscale wind information such as cyclonic vortex in the initial field, improve the analysis of threedimensional wind field. The main impact of reflectivity’s direct assimilation is in the humidity field, which improves the initial humidity field parameters, and impacts significantly the precipitation forecast. 

Abstract:Using the physical parameters calculated from data of conventional sounding, model forecast sounding of Beijing rapid update cycle forecast system (BJRUC) and the special sounding constructed from the data detected by microwave radiometer and wind profiler during May to September 2007 and 2008, the difference of the physical parameters between the conventional sounding and the special sounding in the various severe convective weather processes was compared in detail. The availability of the special sounding to discriminate the various convective weather processes was discussed. Finally, the evolution trend of the physical parameters of three kinds of soundings in the hail, thunderstorm, heavy rainfall weather process was analyzed. Through the detailed analysis, some meaningful conclusions have been drawn. Firstly, the physical parameters from special sounding has a same evolution trend as the conventional sounding in different convective weather processes. Moreover, the characteristics of parameters of special sounding are more significant than that of conventional sounding. Therefore it could give a more detailed description of the atmospheric stratification in the convective weather process. Secondly, there has an obvious difference of the parameters of special sounding in the process of various severe weather brewing and development, and it is significant especially during three to six hours before weather occurs. Thus the special sounding has a clear sense to the shortterm nowcasting of various severe weather. Thirdly, in most cases, special sounding could show the evolution of the parameters before and after the severe weather occurs. Model forecast sounding has a better performance, but the evolution of the parameters has a time difference with the observations. The parameters of convectional sounding could not well capture the characteristics evolution during the process of severe weather because of the low temporal resolution. Fourthly, to the thermal parameters, in most cases, there have similar values and the same trends between the model forecast sounding and the special sounding. Therefore, it is needed to revise the quantitative thresholds of the various parameters and then to summarize the screening criteria for severe weather discrimination, which can be used in BJRUC forecast system to give the convective weather classification forecast.

Abstract:Based on the Xingyi Doppler weather radar data, routine upperair and surface observations, a detailed analysis of the atmospheric environmental conditions and radar echo structure of a strong hailstorm which occurred in Anlong, Xingyi and Xingren of the Southwest Prefecture of Guizhou on 14 April 2009 is made, and also the echo structure of the mesoanticyclone that embedded in the left moving supercell is analyzed in detail. The backgrounds for occurrence of the hail storm are intense heatingup of the surface, which leads to the development of thermal depression in the lower atmosphere, the developing eastward mesoα scale trough in the midlevel, and an upperlevel jet stream above the convective location. The eastward convective clouds triggered by the mesoα scale trough evolve into supercells under the influence of the unstable stratification and significant vertical wind shear. The strong hailstorm splitted into a right moving supercell and a left moving supercell at 18:36 BT 14 April 2009, the left moving supercell developed into a strong one, accompanied by a mesoanticyclone with a diameter of 3 km, rotational speed once reaching 30 m·s-1 in average, and travelling leftward along the mean wind (northwest wind) towards the southeast direction, it is a rare but very strong anticyclone supercell; this supercell produced hails up to 40 mm in size. The right moving supercell is accompanied with a weak mesocyclone producing hails of 20 mm in size. The radar echoes displayed the characteristics of supercell: the strong reflectivity echo gradient in low levels, weak echo region and bounded weak echo region, front inflow and rear inflow, hookshaped echo, strong mesoanticyclone and weak mesocyclone, all these lasted for 3 to 4 hours. This article also gives an analysis on the structure of the mesoanticyclone in the strongest stage of hailstorm, and a discussion of the application of VIL (vertically integrated liquid) value in the forecast of hailstorm.

Abstract:In this paper, a most severe Meiyu front heavy rainfall was analyzed by use of the satellite imagery, Doppler radar and groundbased observations data, and the characteristics at different scales of the this weather system were revealed.The results are summarized as follows: (1) This process is an atypical Meiyu front convective storm, with the Baikal blocking high as background conditions. (2) Synoptic scale highaltitude trough, southwest vortex, lowlevel jet and ground cyclone provided the heavy rainfall with strong impetus and moisture conditions. (3) On mesoα scale, the vertical structure of the storm system was the strong lowlevel convergence and upperlevel divergence, with a strong updraft in its center. At the same time, in the highlevel, on the north side of the system there was a highaltitude jet which forces to produce a secondary circulation. And the secondary circulation of ascending branch, caused by jetstream of many mesoscale vortices on ground, provides the heavy rainfall with persistently necessary power, water vapor and unstable conditions. (4) There was an evolution of MCS on the cloud imagery. The “counterwind zone” and mesocyclone on the speed map corresponding to the bow echo of radar were just the mesoγ system of tornadoes leading to the shortterm heavy rainfall.

Abstract:In 2010, the annual mean temperature was 0.7 ℃ higher than normal, which ranked the 10th warmest year since 1961. And it was the warmest summer mean temperature since 1961. Annual precipitation in China was 681 mm, 11.1% more than normal, which ranked the second most since 1961. During this year, extreme weather and climate events happened frequently. Southwest China experienced the rare severe autumn-winter-spring drought. In winter and spring, unusual persistent low temperature hit Northeast and North China. The most serious snowstorm attacked northern Xinjiang, which broke the historical record. From May to July, heavy rainstorm attacked southern China 14 times. From mid July to early September, severe rainstorm and induced flood attacked northern and western China 10 times. In early and mid October, seldom consecutive heavy rainstorm appeared in Hainan Province. Serious geological hazards such as mountain torrents, mudrock flow and mudslide happened in Zhugqu of Gansu Province and other sporadic places. In summer, frequent hot waves happened widely and intensely. In early summer, the weather in Northeast China was very hot and the maximum temperature in many areas broke historical records. The number of tropical cyclones was below normal, while the proportion of landing was high. The affected regions concentrated in South China. Typhoons Chanthu and Fanapi brought serious losses. The worst strong wind and hail hazards in recent 20 years occurred in Chongqing and caused heavy casualties. In spring, the strong dust storm affected 21 provinces. In general, in 2010, the losses caused by meteorological hazards were the most since 2000. The direct economic losses and mortalities or the missing caused by meteorological hazards were the most in recent 10 years.

Abstract:In order to conclude the reasons of climatic anomaly and improve the skill of climatic prediction, the observation data and physical mechanism diagnostic method were used to analyze the climatic anomaly reasons in 2010. Results showed that the climatic anomaly in 2010 ranked the first within recent 10 years and the abnormity of ocean and atmospheric circulation features may lead to that. A moderate El Nino event occurred from June of 2009 to April of 2010 and followed by La Nina event from July of 2010. The tropical Indian Ocean sea surface temperature anomaly (SSTA) experienced two important periods: from basinwide warming to negative Indian Ocean Dipole (IOD) mode, and North Atlantic SSTA was characterized as triple mode in the same period. Due to the influences forced by SSTA and interaction between ocean and atmosphere， the atmospheric circulation over the Northern Hemisphere showed the dominant anomalies which have been featured as response as follows: subtropical high over the West Pacific (SHWP) was stronger than normal and further west to its normal position because of El Nino event before October of 2010， and afterwards it was weaker than normal and further east to its normal position due to La Nina event, and the location of its ridge line also showed significant stage characteristics. The strength of the South China Sea summer monsoon was the weakest since 1951 and East Asian monsoon was weaker than normal； Blocking highs were located over middlehigh latitudes in Boreal summer. Furthermore， the Arctic Oscillation ranked the extreme negative phase in 2009/2010 winter within 60 years. SSTA forcing and internal atmospheric dynamic processes may lead to the climatic anomaly in China in 2010.

Abstract:Only 23 tropical storms occurred over the western North Pacific and the South China Sea during the tropical cyclone (TC) season 2009. Although the frequency of TCs is less than normal years, there are more TCs, ten out of twenty three, making landfall in China, typhoons are also more active than normal. The region of TC formation seems to be further west to the normal and shifts eastward from the beginning to the end of season. More TCs, about 26.1%, were formed in the South China Sea. Most of these TCs moved westward or northwestward, and the primary area attached by the landfall TCs is the South China. Landfall TCs bring extreme heavy rains. Further analysis shows that the TC genesis area and its migration are closely related to the evolution of the coupled airsea system of the tropics, that is, the updraft leg of Walker circulation shifts eastward together with the area of enhanced turbulent kinetic energy in both lower and upper troposphere and southerly surge. The primary tendency of TC tracks, as well as the high frequency of TCs’ making landfall on South China, is dominated by the local pattern of general circulation, especially the dominant beltlike subtropical high. Meanwhile, the intense activity of individual storm is closely related to the enhanced regional turbulent kinetic energy in low levels and divergence in 200 hPa.

Abstract:For studying climatic characteristics and change trend of fog in Hebei Province, based on the observational data from 49 meteorological stations in Hebei Province during 1965-2006, the temporal and spatial features of fog, diurnal variational law and the longterm variation trend are analyzed by using the correlation analysis, trend analysis and MannKendall test methods. Results show that annual fog days are 15 d in Hebei Province, those in plain are more than 20 d, and in plateau, mountains and hills are less than 10 d. The fogprone season is in autumn and winter, the 15.7% of fog frequency in November is the highest. Except summer, foggy days in plain are more than other topographic regions in general. The turning point of fog in Hebei Province is in the early 1970s. First, it is less from 1965 to 1971 then, after 1972 it experiences a more-less-more variational process. Frequency that fog occurs is the highest at 05:00 BT accounting for 22.2%, and frequency that fog dissipates is the highest at 08:00 BT accounting for 18.8%. The shorttime fog within 3 hours occurs easily. Foggy days in Hebei Province hava a change trend, stations in piedmont plain show an upward trend mostly, but stations in other topographic regions show a downward trend commonly.

Abstract:Based on the intensive observations of temperature and development course during grain filling period, weight per 1000 seeds, and grain filling rate of double harvest paddy rice at different agrometeorological stations from three southern provinces of China, it was founded out that average temperatures during the reproductive growth periods of doubleharvest early paddy rice, doubleharvest late paddy rice, and singleharvest paddy rice increased by 2 ℃ in recent years. The decrease in the duration of headingmilk of early and late paddy rice was about 6 days and the duration of headingmature decreased by about 6 days for early paddy rice and 5 days for late paddy rice. Climate warming usually happened with water stress. The number of the days for grain filling was significantly negatively correlated with average temperature and positively correlated with average relative humidity, identified by regression analysis. Climate warming resulted in the decrease in the sampling numbers of weight per 1000 seeds and grain filling rate taken from the Monitoring Regulation of Agrometeorology currently used. These measurements can only indicate the status of rice at the late stage of grain filling. The results also indicated that climatic warming has caused the earlier development and shorter duration of grain filling of rice in the south of the Yangtze River. The Monitoring Regulation of Agrometeorology has to be modified. The first time for measuring the weight of per 1000 seeds and grain filling rate should be shifted to the day of universal heading or 5 days after universal heading. Thus, the observation should be taken every 5 days to enhance the applicability of the measured data and the availability of service.

Abstract:Using Enshi Doppler radar and MICAPS data, the radar product characteristics are conducted by the comparative analysis between severe hail and shorttime heavy rainfall occurring in the Enshi mountain area during 2007 to 2008. On this basis, some radar nowcasting indicators of severe hail and shorttime heavy rainfall are found and chosen which are suitable for the Enshi mountain area： the thickness of the negative temperature region echo ≥ 7 km, CR strong central echo reflectivity ≥ 55 dBz, strong echo gradient ≥ 15 dBz·km-1, 45 dBz strong echo height ≥ 7.5 km, VIL density ≥ 3.2 g·m-3, and VWP shear means ≥2.3×10-3 s-1 are selected as nowcasting indicators of approaching severe hail; while the strong central echo reflectivity, VIL density, 40 dBz strong echo height and wind profiler radar on the VWP shear means (1.8-6.1 km) are 43.7 dBz, 1.1 g·m-3, 7.0 km and 1.9×10-3 s-1, the nowcasting status of shorttime heavy rainfall to the site and the surrounding areas is very appropriate. Finally, the severe hail and shorttime heavy rainfall events occurring in 2009 are adopted to test the performance of these nowcasting indicators.

Abstract:TWR01 Weather Radar， a computerized smallscale digital radar, has the function of GIS and GPS, and it is suitable for the mobile or fixed antihail operation command and meteorological safeguard and service. The technique of the extraction of echo characteristic parameters of TWR01 Weather Radar is based on the way of the target outline extraction of images. The way plays an important role in image recognition and image analysis and is widely used in the field of measurement and remote sensing. The technique of the extraction of echo characteristic parameters of TWR01 Weather Radar is to extract and describe the geometric structure of radar echo according to its layer and intensity, thus possessing general text data connection, achieving then synchronous conservation of images and data and solving the technical problems of echo data and data analysis finished through manpower. The extraction and application of echo characteristic parameters of TWR01 Weather Radar can help quantitatively analyze the evolution trend of echo and the law of echo change, monitor the change of local weather, conduct antihail and warning operation, and assess the result of the operation. Based on this, the command system of antihail local operation warning of TWR01 Weather Radar is set up.

Abstract:The wind direction and wind speed information at 7 basic stations in Sichuan, which observed by automatic and manual in parallel, is employed to analyzed the difference between the wind direction and wind speed by automatic and manual observations, and the reasons for the differences. The parallel comparison observation results have indicated that the wind speed observed by automatic is higher than that by manual way， and the value on the high side is during 0.06-0.46 m·s-1, which falls in the deviation range of measuring accuracy of the wind speed. The 2min wind speed, 10min wind speed and maximum wind speed with automatic and manual comparison difference in the accuracy of wind speed observations (±0.5 m·s-1), are respectively within the scope of 37.72%, 55.35%, and 67.75%, and their wind direction consistent rates are 62.33%,75.84% and 43.64%. The wind speed differences between automatic and manual ways gradually become smaller with the increase in wind speed, and they have no obvious diurnal variation, seasonal changes and regional changes. However, two types of automatic and manual observation principles, accuracy, statistical methods, observation time and the different methods of observation will give rise to the difference between wind measurements.

Abstract:With the automation of surface weather observing system, the observation of wet bulb temperature has been stopped. In order to estimate the wetbulb temperature, the approximation method and multiple regression method are used. Based on the hourly observation data at 134 reference climatological stations throughout China in 2001, as well as those at 75 stations in Hubei Province from 1991 to 2000, the error analysis of two kinds of wetbulb temperature estimation methods is carried out. The results show that: (1) Using approximation method to estimate the wetbulb temperature, its error is very small, and the maximum error is 0.19 ℃; (2) Using multiple regression methods to estimate the wetbulb temperature, the frequency of error within ±0.4 ℃ is over 99%;(3) Different ventilation conditions on the estimation of wetbulb temperature have considerable influences, and they are related with the relative humidity closely. As the relative humidity increases, the impacts of ventilation condition are gradually reduced. (4) Wetbulb freezing on the estimation of wetbulb temperature has no considerable influences.

Abstract:Based on the daily temperature and precipitation data at 78 stations of Anhui Province during 1961-2008, this paper adopts a cumulative frequency method to correct the threshold of five drought indexes, and then uses the corrected indexes to analyze the drought features of the interannual variability, seasonal evolution and spatial distribution etc. in Anhui Province. The results show that the changing trends of the sum of drought days calculated in terms of drought process are basically consistent; the years with many drought days are in accordance with the typical drought years in history of Anhui Province; the seasonal changes of Z and SPI indexes are not obvious, but those of Pa, MI and CI indexes are not only obvious but also consistent; the drought in autumn ranks first, in summer second and in winter and spring least; the spatial distributions of Z and SPI indexes are not obvious, but those of Pa, MI and CI indexes are consistent and in zonal patterns; the frequency of drought descends from north to south. As to the drought monitoring in Anhui Province, the CI index is the optimum among the five drought indexes.

Abstract:The following are the main characteristics of the atmospheric circulation in January 2011. The polar vortex was located to the North America in the Northern Hemisphere. The circulation presented a threewave pattern in middlehigh latitudes. The East Asia and the North America major troughs were weaker than the troughs in average conditions, and the European trough was stronger. The frontal zone in East Asia was further south than normal. The south branch trough was located at 90°E nearby and its intensity was equivalent to normal. The subtropical high in Northwest Pacific was equivalent weaker than normal obviously. The average temperature (-8.3 ℃) was 2.4 ℃ less than the normal years and the average precipitation (8.2 mm) was 3.9 mm less than the normal years. The drought conditions in North China and Huanghuai area, etc. have been more serious. The active cold air currents resulted in severe freezing rain and snow disasters. There were three cold air processes and six rainfall processes.