Abstract:Based on the conventional sounding observation data, Doppler radar data and windprofiling radar data, a thunderstorm gale process that occurred in Hunan and Guangdong from the night of 19 to the morning of 20 March 2013 is analyzed. The results show that the background of this strong convective weather process is the collapse of the northern branch ridge and the establishment of the southern branch trough. Strong lowlevel jet and the shear line appear before the trough, which causes the dry and cold air above the level of the warm and humid air and makes the convection develop strongly. The automatic observation shows that the convective cell is triggered when the north wind enters into Huangping Guizhou (where the dew point temperature is higher than the surrounding areas) and forms wind convergence. After that, the convective cells moves into the south region of Hunan where there is a convergence line matching a dew point front and strengthens to a severe convective zone while it is extremely cold and dry at 500 hPa. Over the night of the 19th many convective cells emerge in the western Hunan, forming a squal line at last. There are many supercells in the squal line. By comparing the mesocyclone product of the radar with the time of the thunderstorm gale, it is found that the bottom of the mesocyclones continues droping to below 2 km about 2-3 volume scans before the appearance of the most thunderstorm winds resulting from the mesocyclone, and the strongest shear height drops to the bottom height of mesocyclone about 1-2 volume scans before the appearance of the thunderstorm gale. In addition, after comparing the wind profiler radar data with the time of thunderstorm gale, we also get conclusion that a substantial jump of the bottom refraction index structure constant (C2n) always appears about 10-15 min before the time of thunderstorm wind, which is probably indicative to the appearance of wind.

Abstract:By using the data from 156 meteorological stations in Sichuan Province, the GDAS (Global Data Assimilation System) data and the HYSPLIT4 model, the water vapor transportation of the rainstorm occurring in western Sichuan Basin in 7-11 July 2013 are analyzed quantitatively. The results show that the water vapor mainly comes from the level of 950 hPa and 850 hPa, and the paths and the sources are significantly different. Backtracking one day, the bigvalue zones of water vapor sources at 950 hPa and 850 hPa both are found in the Sichuan Basin area. Backtracking three days, that of water vapor source at 950 hPa is seen still in the vicinity of the Sichuan Basin, but at the level of 850 hPa, the source is tracked to the east of the Bay of Bengal. The main water vapor sources at 950 hPa appear in the Arabian Sea and the South China Sea region, but in the east of Somalia Peninsula at 850 hPa by backtracking nine days. In general, there are five moisture transport paths at the level of 950 hPa, including two in the north and another three in south. There are two paths at the level of 850 hPa in the north and south. Four water vapor sources have been found at 950 hPa. Water vapor coming from the region of Arabian Sea to Bay of Bengal has the maximum contribution rate (44.1%), followed by the IndoChina Peninsula to South China Sea region (33.1%). The Balkhash Lake (15.7%) and the Baikal region (7.1%) contribute less relatively. There are four water vapor sources at the level of 850 hPa， of which the water vapor from the Arabian Sea region (89.4%) along the path of Indian summer monsoon is the most important. The contribution rate of the dry and cold air from the Balkhash Lake to Baikal Region is 6.3%, and water vapor contribution rates from the Bay of Bengal (3%) and local area (1.3%) are the least.

Abstract:Using conventional meteorological observations, regional dense automatic weather station data, NCEP/NCAR 1°× 1° reanalysis data with 6 h interval and Doppler radar data, this paper analyzed environmental conditions, echo characteristics and causes of three severe convective weather processes of southwest flow type in Henan in August 2013. The results show that: (1) Three severe convections all occur in the interactions between midlatitude trough and subtropical high. Under the effect of southwest flows from low to high levels, there are temperature and dewpoint gradients and convergence line on the surface. The dynamic effect of highlevel trough and the trigger of convergence line on the surface lead to the convective weather. (2) There are unstable stratifications which are warm and wet in high level and dry and cold in low level. Strong vertical wind shear in the lower troposphere, and the large CAPE and lifting conditions are conducive to occurrence and development of squall lines and super cells. The conditions for the three events are the best on 1 August, better on 11 August and the worst on 7 August. There is a relationship between structure of convective system and the strength of convection forming condition. (3) Monitoring data from radar and dense automatic weather station show that in the initial stage multicell echo structures are dominant, and then gradually strengthen and form multicell echo groups. In the mature stage, they all develop into linear convective systems and even form organized squall lines. The interaction of updraft and downdraft is the main cause for the development and maintenance of squall lines. (4) The deep warm and moist stratification in the lower and the dry layer above that is important to the forecast of severe convective weather in summer in Henan. The indexes such as CAPE, Δθse(850-500), ΔT850-500, K index, and vertical wind shear in the lower troposphere have good indication for southwest flow super cell, squall lines and other severe storms to develop and form.

Abstract:Artificial cloud seeding was carried out by Weather Modification Office of Hebei Province on clouds in a reflux and westerly synoptic system over central and southern region of Hebei on 19 April 2013. The cloud seeding and detection site was located in the updraft airflow in front of the trough and in the reflux. The characteristics of the precipitation are: (1) the precipitation structure is characterized by pretrough cloud and reflux cloud, where large particles grew mainly in the upper front of trough; (2) both the temperatures of pretrough cloud and the according cloud top were higher while the reflux cloud was colder, causing the solid precipitation particles to block together and resulting in the enhancement of surface snow; (3) the number concentration of big cloud particles and precipitation cloud particles was high. Moreover, there were abundant small cloud particles. The value of the intercept of the full spectrum fitting curve exceeded 2 (b>2), suggesting it is suitable for seeding operation. In addition, application of airborne measured microphysical parameters, satellite, radar and airsounding data in refined operations were analyzed. The results suggest that variations in microstructure, satellite and radar parameters within cloud are significant after the operation work. The regional variation of surface precipitation has passed the analysis on significance, but whether the difference before and after the affected area is the catalytic effect needs further verification.

Abstract:Wide range of high temperature and drought occurred in South China in the summer of 2013. From 1 to 22 August, Weather Modification Center of CMA carried out the work of cloud structure forecast and seeding conditions analysis using weather modification models. This paper briefly reviews drought and weather and analyzes cloud structure forecast and seeding conditions. Three types of cloud system precipitation happened during 1-22 August in the drought region. Type I is precipitation of typhoon periphery cloud system from 1 to 4 August, Type II is precipitation of local convective cloud controlled by subtropical high from 5 to 13 August, and Type III is low pressure cloud system from 14 to 22 August after typhoon landing. The precipitation forecasts of weather modification model are basically correct with observations of Types I and III, but a bit different from Type II. The forecast results are validated by the observations of satellite, radar and precipitation. The distribution of large cloud system coincides with the retrieval result of satellite. The model can forecast the development of local convective cloud. The cloud property and vertical structure are basically consistent with radar observations. The seeding conditions are analyzed through the products of cloud band, supercooled water, vertical structure of cloud, precipitation etc. There is not only warm cloud but also mixed phase cloud of precipitation of Types I and III. The mixed phase cloud has supercooled water with the maximum of 0.3 g·kg-1 and less ice crystals between 0 and -10℃, which is suitable for cold cloud seeding. In the beginning stage there is the supercooled water with maximum value 1 g·kg-1, which is good for cold cloud seeding. A lot of work needs to do about the microphysical and seeding conditions of model forecasts for mixed phase cloud and precipitation in South China.

Abstract:Using 35 meteorological stations observation data and rice yield data during 1961-2014, and the ArcGis software technology, we analyzed the spatiotemporal variation characteristics and sensitivity during the key growth period of rice when chilling injury events occur. The results show that (1) the total chilling injuries number presents a “north more south less” distribution, and the largest number of chilling injuries appears in the 1970s, then the second largest in the 2000s. (2) Most chilling injury events last three to six days, mostly three days, standing for about 50% of the total events. Some chilling injuries lasting longer than six days occur in Huaibei (the area to the north of Huaihe River), with proportion below 10%. Usually Huaibei suffers chilling injuries earlier than Huainan (the area to the south of Huaihe River), most in early September. (3) Basically, the probability of the chilling injuries also presents a “north more south less” feature and significant decadal fluctuations. The largest occurrence probability appears in the 1970s, followed by the 2000s, and the lowest during 1980s to 1990s. (4) The intensity of chilling injuries is the highest in the northwest of Jiangsu, where the most intensive chilling injuries happen in the 2000s, followed by the 1970s, and the weakest in the 1980s and the 1990s. (5) The highest sensitivity area of rice to chilling injuries is the central part of Jiangsu.

Abstract:Using the PMTred method developed by the Environment Canada, ERAinterim reanalysis data as reference series and the detailed metadata of each radiosonde station in China, the inhomogeneity test and corrections are carried out on the monthly relative humidity data at mandatory levels at 125 radiosonde stations in China. Combining with the detailed metadata we analyze the main causes for the inhomogeneity problem of the radiosonde relative humidity data in China. The results show that the shifts of instruments, the changes of data calculating methods and radiation correction method in sounding system and the update of sounding systems are the main reasons for the inhomogeneity in Chinese sounding relative humidity data. The earlier relative humidity data are obviously discontinuous because the 59701 radiosonde sensors carry more water vapor when they pass through clouds. Therefore, the changes for Lband radarsounding system after 2002 lead to the big discontinuous problem in our radiosonde relative humidity data. With the height increasing, both the number of the inhomogeneous stations and break points increase significantly. Also, the mean magnitude of correction increases with height and the correction values are negative at all mandatory levels, which indicates the radiosonde relative humidity data in China are systematically higher. The raw monthly mean relative humidity series of the 125 radiosonde stations in 850-300 hPa mandatory levels from 1979 to 2012 present decreasing trends. After the adjustments, the trends change to insignificant trends.

Abstract:Based on the satellite GMS data, FY satellite data and the hourly precipitation data of Guangxi from 1984 to 2013 and using the statistical analysis, the comprehensive analysis and the typical case study methods, the evolution characteristics and propagating mechanism of the convection over the Bay of Bengal before continuous torrential rain occurs in Guangxi are investigated. The results show that the convection over the Bay of Bengal is enhanced abnormally 2-3 d before the occurrence of continuous torrential rains. So the strong convection over the Bay of Bengal is a precursory signal to the vortex shear continuous torrential rain in Guangxi. This precursory signal can guide the short and medium term forecasting of torrential rain in Guangxi. This study conclusion shows that the convections over Guangxi are highly correlated to the convections over the Bay of Bengal. The strong convection eastward propagation channel exits between the Bay of Bengal and Guangxi.

Abstract:CINRAD WSR98D SA / SB and part of C band Doppler algorithm default parameters are same as WSR88D in U.S. The hail index products based on hail detection algorithm usually overestimate probability of hail, severe hail, and hail size in actual operational application. This paper first illustrates that probability of severe hail and hail size in WSR98D algorithm default parameter is from the dataset of 10 severe hail cases during 1992 in Oklahoma and Florida of U.S. The algorithm parameters based on this data overestimate probability of severe hail and hail size, i.e. over forecasting hail occurrence is caused by limitation of the algorithm itself. Without changing the set of hail detection algorithm parameters, combined with early hail algorithm, some environmental parameters and Doppler radar detection characteristics can be used as auxiliary criterion, such as VIL, VIL density, TBSS, etc. According to the physical process of severe hail formation, and under the assumption without losing generality we propose that the 55 dBz range exceeding 100 m2 on the -20℃ layer CAPPI products can be used as supplemental threshold for judging quickly the formation of severe hails.

Abstract:Nondefault inconsistent hourly precipitation data are an abnormal status in automatic weather station (AWS) observation, which can be often met as hourly precipitation data are transmitted and recorded in 2 sources. Three groups of related instances are listed first, and the direct reasons that deeply hidden are found out manually. To solve this problem, Inter VerificationSequence Alignment (IVSA) model in smaller time scale is raised in this article. When nondefault inconsistent data from same station appears at the same time, verification with smaller time scale data (minute precipitation) is made respectively. If both data cannot be proved wrong with inner verification step, then unit error possibility is added into sequence alignment method. Correlation credibility is calculated and more reliable data can be selected accordingly. After then, monthly data in May 2012 (1360 pairs of instances) are used to train the parameters, and the data (4017 pairs of instances) from 1 June to 31 July 2012 are input to verify the efficiency of applying IVSA in real time data environment, getting an accuracy of 99.65%. It is concluded that IVSA model can eliminate nondefault inconsistence in hourly precipitation data under running rules.

Abstract:When the automatic weather station instrument malfunctions or its operating performance declines, special equipment for maintenance and calibration is often used, but it is more difficult for routine maintenance of the wind observation instruments installed at the height of more than ten meters or dozens of meters. In order to improve maintenance capabilities, for the wind observation instruments this paper puts forward fault detection method for wind direction sensors based on the observation data. Using the observation data of hourly extreme maximum wind direction and instantaneous wind direction from 2420 automatic weather stations in China, during 2009-2011 and based on the coding theory of Gray code disk of wind direction sensors, we design the fault detection method of Gray code for wind direction sensors. Through quality control on the national wind observation data, and the simulation of wind direction changes caused by the faulty of Gray code, we assess the impact of the Gray code failure. The analysis results show that: (1) By using the observation data of hourly extreme maximum wind direction and instantaneous wind direction, Gray code failure can be detected. (2) Throughout the country, the automatic weather stations seeing faults on the bits from 2 to 7 of the Gray code, takes up the proportion of 0.4%-0.8%. The occurrence proportion of the first bit of Gray code failure is 2.6%. (3) Gray code failure impacts the quality of wind observation data, and even causes the distribution of the wind direction frequency completely distorted, especially the fault of Gray code bit from 4 to 7.

Abstract: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. The ECMWF model has a good performance in predicting the activity of western Pacific subtropical high, while the prediction of T639 model shows some biases compared with the observation. The three models can predict the persistent hightemperature in Xinjiang in July 2015 well and the prediction for 850 hPa temperature is a little higher than observation in Northern China. For Southern China, the three models have smaller biases in temperature prediction than for Northern China, and the ECMWF model has better performance than T639 and Japan model. As far as Typhoon Soudelor (No.1513) in concerned, T639 model performs better in predicting its track and landing position, although the predicted intensity is a little higher. The predicted landing time of Soudelor by ECMWF model is earlier than the observation.

Abstract:The main characteristics of the general atmospheric circulation in August 2015 are as follows: The polar vortex takes the form of eccentric pattern in the Northern Hemisphere.In the midhigh latitudes of Asia, the circulation presents a twotrough and oneridge pattern, and all of those are more intense than their climatological means.The subtropical high lies westwards and southwards, and its intensity is equivalent to or a little stronger than its average state during the corresponding time of the normal years. Meanwhile, the monthly mean precipitation amount is 105.1 mm, which is almost close to the normal value (105.3 mm). The monthly mean temperature is 21.1℃, higher than its climatological mean (20.8℃). In the first dekad of August, longlasting and largescale high temperature events occur around Jianghuai region. Five regional torrential rainfall events mainly happen in August.Four tropical cyclones are active over the Northwest Pacific Ocean and the South China Sea, but only one of them lands China. Drought continuously is found in North China, eastern part of northwestern China and central Inner Mongolia. In addition, many cities suffer from strong wind and hail disaster.