Abstract:This paper reviews the existing different types of wind speed scales, and rates in detail the intensity of the tornado causing heavy casualties on June 23, 2016 in Funing County of Jiangsu Province, and the intensity of the downburst on June 1, 2015, causing the “Dongfangzhixing (Eastern Star)” cruise ship overturn. Furthermore, issues of the existing wind speed scales are discussed, and future work is presented. Based on detailed damage survey data, the Funing tornado intensity is rated EF4, and the downburst causing the cruise ship overturn is only EF1. Also, the intensity rating of the two catastrophic events clearly shows the differences between EFscale and Fscale. However, the damage at each site caused by the Funing tornado still need further rate. Due to the structure and conditions of different buildings and vegetation, the corresponding environments and the complexity of the mechanism causing damage, there must be an amount of uncertainties in the tornado or downburst intensity rating. Tornado intensity rating has more uncertainties than downburst because of the complex vortex structure and spatial distribution of air pressure of tornado, and impacts of winddriven debris caused by tornado. Improving objectivity, applicability, accuracy, consistency, and convenience of wind speed scale is an inevitable demand of future work for intensity rating of tornado or downburst. Comprehensive wind damage scale in future also need be developed to integrate intensity distribution, path length and width, movement speeds and duration， so as to provide the basis for rating comprehensive impacts of tornado or downburst.

Abstract:An extremely severe EF4 tornado struck Funing County, Jiangsu Province on 23 June 2016. The tornado killed 99 people, injured 846 others, and damaged many buildings. This paper focuses on the synoptic environment and mesoscale characteristics of the tornado by using all kinds of observation data. The tornado occurred in the most sensitive area and season with highest tornado occurrence frequency in East China. The synoptic environment for the tornado was the typical rainstorm circulation in Meiyu season. The tornadoproduced mesoscale convective system occurred in the south side of the surface warm front where the highlevel jet coupled with the lowlevel jet. The strong deeplevel dynamical forcing characteristics are significant accompanied by highlevel jet, and the thermaldynamic unstable condition is moderately strong. The tornadoproduced mesoscale convective system was a discrete cell with elliptically shaped region of reflectivity which is the most favorable convective mode for significant tornado in the United States continent. The structure of cell is the same as the typical super cell with bow echo， severe mesocyclone and tornado vortex signature (TVS). Funing tornado was in the top of the bow echo and occurred during the period when the height of the mesocyclones was lower than 1 km.

Abstract:Based on Multiplatform Tropical Cyclone Surface Wind Analysis (MTCSWA) data from NOAA/NESDIS during 2007-2014, statistic characteristics of 210 named TCs’structures in the North Western Pacific and the South China Sea are analyzed. Compared with the maximum wind speed (VMAX) from CMAbest tracks, the VMAX from MTCSWA is 10%-15 % smaller on average. Overestimation, especially for weaker TCs, is observed. Statistical relationship is provided between radius of maximum wind speed (RMAX) and VMAX, and the density distributions of RMAX in different regions are calculated. For those TCs stronger than STS, the density distributions show no regional differences while the less intensified groups show obvious structure distributions in the North Western Pacific, the Northern and Eastern China Seas and the South China Sea. Especially, in the South China Sea, the distribution difference gets much broadly from 50 to 100 km. By analyzing the distributions of four quadrants, the eastern parts of R34 is comparably larger than that in western parts, but there is no such a character in both R50 and R65. From the case study of SuperTY Bolavan (1215), an eyewall replacement and innercore structure change can be observed. During that ERC period, the distance between inner and outer eyewall (R2-R1) is reduced along with V1’s decreasing and V2’s increasing. Meanwhile the original intensity shows temporary fluctuation.

Abstract:Based on the conventional meteorological observation data, NCEP/NCAR 1°×1° monthly mean reanalysis data, the outgoing longwave radiation (OLR) data observed by the NOAA satellite and the data from the Typhoon Yearbook of China Meteorological Administration, this paper analyzed the causes for the no generation of tropical cyclones (TCs) in the northwestern Pacific and South China Sea (SCS) in August 2014. The results show that the invading of the polar cold air led to the further eastward and southward movement of the subtropical high in northwestern Pacific during the first twenty days in August. In the last ten days the cold air became weaker, then the subtropical high moved westward and southward, driving the convergence zone between the easterly trade wind in the south side of the subtropical high and the equatorial westerly to be located abnormally further southward than normal. The weaker Miscarene high caused the Somali jet and the crossequatorial flow over the eastern Indian Ocean to get weakened, and the low and midlevel monsoon depression or monsoon trough over the Indian Peninsula to be extremely inactive. Additionally, along with the weaker Australian high and its position deviation, the crossequatorial flow over the southern SCS became weaker too. The SST of the tropical cyclone genesis was much lower than normal during the first dekad of August, so the warm and moist air in the area with lower SST could not form. In addition, the weak convection in the northwestern Pacific and SCS, the stable atmosphere and large vertical wind shear were unfavorable for the generation and development of tropical cyclone. In the lower level over the ocean between SCS and the east of Philippines, there was positive vorticity and negative divergence, but the convergence was not strong enough for the formation or development of TC. The weak updraft at the highlevel troposphere caused by the South Asia high and the easterly disturbance south to the subtropical high could not accomplish the upperlevel divergence process, being difficult to support the maintenance and intensification of the upward flow. Hence, the four tropical disturbances in the abnormally southward ITCZ did not develop into tropical cyclones.

Abstract:The variation characteristics of precipitation in the dry season (from November to the following April) in the Southwest of China are investigated by using the observation data from 1961 to 2011. The results indicated that the precipitation during the dry season changed remarkably around 2000. The spatial distribution characteristics of the precipitation before 2000 was distinctively different from the characteristics after 2000. The rain was much less than normal and drought got worsened in the 21st century. Precipitation in Yunnan and its surrounding areas reduced significantly. The negative correlation between the rain of the dry season in Southwest and the western Pacific subtropical high (WPSH) strengthened rapidly in late 1990s. Meanwhile the feature of WPSH has shown markedly decadal enhancement since the 21st century. Its area has been growing, with intensity enhancing and position being farther western than normal. Enhancement of the relation between the rainfall during the dry season and WPSH and the decadal enhancement of WPSH, both contribute remarkably to the decline of the dryseason rainfall, and probably result in the frequent drought in the Southwest of China.

Abstract:Based on the summer precipitation data over Tibet and monthly NCEP/NCAR reanalysis data during the period from 1980 to 2013, we analyzed the intraseasonal variation of summer precipitation principal mode, especially the largescale circulation features of corresponding precipitation anomalies in July and August. The results show that obvious intraseasonal variation exists in summer rainfall over Tibet. The correlation coefficient of PC1 between June and July principal mode is significant while weak between July and August. In morerain years, the upstream zonal wind of the Tibetan Plateau is westerly anomaly in July and August but the moisture water vapours come from different regions. And the upper troposphere circulation in the midhigh latitude over Eurasia in July and August is different significantly. Further research shows a strong negative correlation between precipitation and the intensity of South Asian high (SAH) in July, which means morerain/lessrain in July, SAH is weaker/stronger. In August, there is a strong correlation between precipitation and the position of SAH. That is, SAH southward/northward to its normal position may lead to flood/drought over Tibet in August.

Abstract:Based on the daily temperature data of Urumqi Meteorological Station from 1 January 1951 to 31 December 2015 and using daily minimum temperature and temperature drop range as the index, database of cooling process in Urumqi City ever the past 65 years is established. The cooling process is divided into 5 grades, i.e. Ⅰ (weak), Ⅱ (medium), Ⅲ (relatively strong), Ⅳ (strong), Ⅴ (cold wave). Some climate characteristics of cooling process are analyzed, such as frequency, continuous days, temperature drop range in different periods, minimum temperature, and anomaly of minimum temperature. The results show that: (1) From 1951 to 2015, there were 5834 cooling processes， annually 89.8 processes in average, of which 78.1% is of Grade Ⅰ (weak) cooling process. The seasonal distribution of the frequency of cooling process is uniform, but the largest number of Grade Ⅳ (strong) and Ⅴ (cold wave) cooling processes is in spring. Annual mean frequency of cooling process in the seven decades is not so different. Between the years with more and less cooling processes, the largest process frequency difference is in June-August, and the smallest difference is in April and September. With the decadal increases, the average annual frequency increased in Grade Ⅰ (weak) cooling process, and decreased in Grade Ⅴ (cold wave) process. (2) The continuous days of cooling process is 1.89 days in average and 49.0 % of the process lasts one day. The highest frequency of the continuous days changes from one day to three days as the grade changes from I (weak) to Ⅴ (cold wave). The continuous days of Grade Ⅳ (strong) and Ⅴ (cold wave) cooling processes are relatively more from late autumn to winter and less in spring. (3) The drop range of temperature of process is -4.4℃ in average and the largest drop in temperature is in autumn and the smallest drop in summer. The largest drop ranges of Grade Ⅳ (strong) and Ⅴ (cold wave) processes are in June and December. The maximum drop range of temperature in 24 h, 48 h and 72 h is -3.1℃,-5.5℃ and -7.4℃ in average, respectively. For 24 h, the largest temperature drop range happens in Spring and the smallest in winter. For 48 h, the largest drop is in spring and the smallest in summer. For 72 h, the largest drop is in winter and the smallest in summer. (4) The minimum temperature of the cooling process is 0.3℃ in average, the lowest is in winter and the hightest is in summer with distinct seasonal characteristics. The maximum daily temperature anomaly is -1.9℃ in average. As the grade changes from Ⅰ (weak) to Ⅴ (cold wave), the temperature anomaly gets much lower. The maximum daily temperature anomaly of Grade Ⅴ (cold wave) is -8.5℃. (5) During the months with more cooling processes in Urumqi, the 500 hPa high level is mainly controlled by zonal westerlies in Xinjiang Region, the shortwave trough and east ridge with the stable westerlies affecting Xinjiang. In the abnormally less cooling process months, the 500 hPa high level is controlled by northwest airflow in Xinjiang Region, in the high latitudes of cold air from the north to the south channel, which is more favorable for the strong cold air to enter Xinjiang.

Abstract:Flood and drought caused by summer precipitation anomaly are the most serious disasters in Yellow River Basin, so it is very important to predict the summer precipitation in the Yellow River Basin. Based on summer precipitation observation in the River Basin, and the BCCCGCM model data, a pattern projection downscaling method is used to predict summer precipitation there. The results show that: (1) The prediction result of pattern projection downscaling method is better and more stable than model output prediction for Yellow River Basin. The monthly prediction is better than seasonal prediction. (2) The pattern projection downscaling method produces different predictions for different areas in the Yellow River Basin. In summer (JJA), the better prediction regions are dispersive. But the better prediction regions are collective in monthly prediction. The prediction capability of the method varies with month. (3) The results of independent sample test on the data from 2009 to 2013 show that the prediction of pattern projection downscaling method for Yellow River Basin is better than model output. Especially in June and July, the prediction of downscaling is greatly superior to the model output.

Abstract:Based on the wind field and vapor field at 700 hPa of NCEP/NCAR daily reanalysis dataset, and the precipitation data of 11 stations in Shanghai, this paper applies the method of the extended period rainstorm forecast in Shanghai. Based on the data of 112 rainstorm days in the past 10 years, the static prediction model of low frequency system is established. One is the type of northern lowfrequency anticyclone and the south lowfrequency cyclone, while the other is the type of northern lowfrequency cyclone and the south lowfrequency anticyclone. Further research shows that rainstorms with a daily rainfall of 100 mm or more are mainly lowfrequency cyclones, accounting for 60% of the total number of rainstorms. Lowfrequency cyclonetype mobile characteristics are very consistent in the 30 days before the occurrence of rainstorms. This consistency can be used to establish the dynamic prediction model of heavy rain. Using this method, the heaviest rainfalls in the flood season in the last 5 years are forecasted accurately, and the lead time is more than 12 days.

Abstract:Based on the daily precipitation data of stations in China and NCEP/NCAR reanalysis data and using MannKendall method and period analysis, this paper analyzes the decadal variability and intramonthly oscillation of the ridge line position of the western Pacific subtropical high (WPSH) in autumn, and the possible connection with autumn precipitation over the upper reaches of Hanjiang River. The results show abrupt change of the WPSH ridge line in autumn happened around 1997, which is very different from the WPSH strength. After the abrupt change, the WPSH ridge line in autumn obviously moved north and the days when it stayed by north were more than before. Meanwhile, stronger intramonthly oscillation of the WPSH ridge line and increasing autumn precipitation over the upper reaches of Hanjiang River were observed. When quasibiweekly period is strong, it is more likely to be rainy in autumn over the upper reaches of Hanjiang River. Conversely when quasibiweekly period is weak, it is more likely to be dry.

Abstract:According to the spetiotemporal distribution characteristics of the power equipment pollution flashover and the geographic features in Henan, duration of the contamination, temperature inversion near the ground surface, relative humidity and wind are firstly identified as import contributions to pollution flashover disaster. Then the composite thresholds of these factors are respectively assessed using the methods of spatiotemporal matching, statistical analysis of threshold and model based on the flashover hazard data and meteorological observations. The comprehensive meteorological model for pollution flashover established here considers well the atmospheric conditions that breed the disaster, including high humidity, weak wind, less rain in the early period and stable atmospheric stratification near the surface. The model established here fits the relationship between the meteorological environmental conditions and the pollution flashover events well. The validation results indicate that the model can capture the disaster events with the false alarm rate less than 10%. The spatiotemporal characteristics of the annual mean power flashover events calculated from the 30year historical observations show high frequency over the northeast of Henan during wintertime. Thus, the findings in this paper would provide a scientific support for the early warning of power equipment pollution flashover in this region.

Abstract:The evapotranspiration of the cropland is the sum of plant transpiration and soil evaporation. Assessment of actual evapotranspiration of crops is very important for the water saving technology, water resource management and reasonable irrigation plan. In this paper, the actual evapotranspiration of summer corn measured by automatic weighing lysimeter during the growing season (April to September) in 2013 is used to evaluate the applicability of PenmanMonteith (FAO PM), Hargreaves, and PriestleyTaylor methods in the Huailai Region of Hebei Province. Correlation coefficients, the root mean square error (RMSE), consistency index (d) and other indicators are applied, in monthly and daily time scales, to compare the accuracy of the three methods. The results show that: （1） compared with lysimeter measured results, summer maize monthly actual evapotranspiration calculated by the three methods have some deviations; FAO PM method and Hargreaves method show good performance and accuracy; the accuracy of PT method is the worst. （2） The main meteorological factors that affect the actual evapotranspiration calculation results are the net radiation of the sun and temperature. （3） The Hargreaves method needs fewer parameters and has a great advantage in computing, and it is credible in assessing actual evapotranspiration in Huailai.

Abstract:This paper focuses on the effect verification and analysis of artificial precipitation enhancement for a stratiform cloud precipitation event, which occurred over Dalian on 12 April 2015, by using statistical and physical verification methods. The results reveal that the relative rain enhancement rate increases by 49% (α<0.01) in 30-50 min after catalyzing the operational clouds and reaches the maximum rainfall rate by calculating the minutely rainfall of observational and fitted values in the operation and contrast area. Moreover, significant improvement exhibits in physical effects in terms of radar echo intensity and area of target cloud, precipitation duration and variation characteristics of raindrop spectra in fitting clouds.

Abstract:The performance of mediumrange forecast for the models of T639, ECMWF and Japan from June to August 2016 is verified and compared. The results show that all of the three models can predict the variation and adjustment of the atmospheric circulation over Asian middle and high latitude areas well, of which ECMWF model performs the best. Both ECMWF and T639 models have good performance in predicting the western Pacific subtropical high, and the bias of ECMWF is smaller than that of T639. The three models predict well on the sustained hightemperature process over Sichuan Basin, and also can perform well in predicting the transitions of temperature at 850 hPa. However, ECMWF model and JP model forecast temperature better for Southern China than for Northern China. Generally, ECMWF model shows a better performance than the other two models. For the Typhoon Nida, ECMWF model does best in predicting the track and intensity, while T639 shows larger errors.

Abstract:The main characteristics of the general circulation in August 2016 are as follows. The polar vortex of the Northern Hemisphere presents a single pattern. In the midhigh latitudes of Asia, the circulation presents a twotrough and oneridge pattern. The subtropical high lies eastward and northward obviously, and its intensity in northwestern Pacific Ocean is weaker than its average state during the corresponding period of normal years, and the high pressure on land is stronger than the average. Meanwhile, the monthly mean precipitation is 93.9 mm, which is 11.2% less than its normal value (105.7 mm). The monthly mean temperature is 22℃, 1.2℃ higher than its climatological mean (20.8℃), which is the highest historical record since 1961. Six regional torrential rainfall events happened in August, and four of them were caused by tropical cyclones or tropical disturbances. In August, eight tropical cyclones were active over the northwestern Pacific Ocean and the South China Sea, and Typhoons Nida (1604) and Dianmu (1608) made landfall along the coastal areas over southern China. Longlasting and largescale high temperature occurred all over the central and eastern part of China. Continuous drought happened over the western part of Northeast and eastern Inner Mongolia of China.