Abstract:Based on FNL reanalysis data and hourly precipitation data converted from both regional meteorological station and CMORPH and using the method of high resolution WRF numerical simulation, this paper analyzes a typical shorttime local heavy rain process triggered by easterly mobile southwest vortex and complex terrain located in the northeast of Hubei in 22-24 July 2015. Further study is made on possible effect mechanism of how the mesoscale topography affects the increment of local rainfall. The result shows that the increment process of local rainfall was under the influence of the special topography in the middlelower reaches of Yangtze River, coupled with the effect of transportation of moist air in the front of southwest vortex. The two items worked together, triggering the weather process. The duration of local rainfall was short, but the increment was obvious. By researching the effect mechanism of single terrain on the local rainfall, we found that the Dabie Mountain’s terrain height impacted increment and scope of local severe rainfall positively, while the Mufu Mountain’s terrain height influenced the increment and scope of local rainfall negatively. As for the effect of Dabie Mountain’s terrain on the rainfall, the terrain was advantageous to reinforcement of convective instability, reinforcement of wind convergence and vertical shear, as well as maintenance and reinforcement of cold pool in lower troposphere. Different from Dabie Mountain’s terrain, Mufu Mountain’s terrain obstructed southerly moisture flow, then decreased the transportation of vapor flux above the rainfall area, which was unfavorable for increment of local rainfall. In addition, by researching the effect mechanism of the combined terrain on the local rainfall, we found the trumpetshaped topography consisting of Dabie Mountain’s terrain, Mufu Mountain’s terrain, Wannan Mountain’s terrain, and river valley between Mufu Mountain and Wannan Mountain, which forced the southerly airflow into terrain area to converge. What’s more, the river valley between Mufu Mountain and Dabie Moutain acted as an important channel for the southerly airflow to flow back into the Jianghan Plain from the east of Mufu Mountain, which effectively guaranteed the positive vorticity advection to be transported into the heavy precipitation area. In a word, the above favorable terrain configuration resulted in the increment of local severe rainfall.

Abstract:An extremely severe rainfall event occurred in Henan in 18-20 July 2016 (the “7·19” rainstorm) under the influence of vortex and cyclone. The precipitation was mainly concentrated in northern Henan, and the maximum accumulated rainfall was 732 mm observed at Dongmaan Station in Anyang. This paper analyzes the fundamental features of precipitation, largescale circulation and mesoscale system of the “7·19” rainstorm based on the hourly rainfall and surface wind data of automatic weather stations, the composite reflectivity data of SA radar, the conventional sounding data and ECMWF (European Centre of MediumRange Weather Forecasts) reanalysis data. At the same time, this paper also analyzes the physical quantity properties of 71 extreme rain events, which are defined as precipitation ≥100 mm·(24 h)-1 at any representative weather station within selected areas. These severe rainfall events took place in the east of Taihang Mountain in northern Henan. The results show that the topography of Taihang Mountain and favorable largescale circulation under the background of vortex and cyclone provided abundant water vapor and better convergent lifting conditions for the “7·19” rainstorm. The train effect produced by the generation, development and maintenance of mesoscale terrain convergence lines and the movement of multiple surface cyclones are the main cause for the “7·19” severe torrential rain in northern Henan. Compared to the physical characteristics of various extreme rain events, the dynamic factors of “7·19” have obvious features of extremity.

Abstract:This study verified the whole 2016 year realtime forecast and parts of 2013-2015 reforecast of heavy rain events and compared them with EC model and T639 model forecasts by using synoptic verification method. After summarizing up all verification results into several systematic biases, some conclusions were excavated to help improve the GRAPESGFS developments and operational applications. 38 heavy rainfall events were verified. Starting from the forecast quality of precipitation, synoptic weather systems and atmospheric physical factors were checked to find the direct causes of the precipitation biases and differences between other operational models. The results showed that some advances have been made in shortrange precipitation forecast, but still north bias exists in some convective rainband forecasts. Precipitation forecasts are weaker than observation in some convective cases which are under weak high level synoptic system background. Wet bias northern to the rainband and strong bias of subtropical vortex were also found in some cases while the precipitation was not over estimated.

Abstract:Using the 100 m tower atmospheric turbulence observation data offered by National Climate Centre, wind shear exponents in different underlying surfaces and different atmospheric stabilities are analyzed. The experiments were carried out in Xilinhot City in Inner Mongolia, Huanghua City in Hebei, Hukou County and Xingzi County in Jiangxi during 2009-2011. The results show that (1) in inland simple terrain, the overall wind shear exponent >0.3 appears only in stable and very stable stratification, and the frequency of stratified shear exponent >0.4 is 2.95%. (2) In the coastal flat terrain, atmospheric stratification is more stable, the overall wind shear exponent has higher value, and the frequency of stratified shear exponent >0.4 is 4.2%. (3) Although Xingzi and Hukou both belong to the inland lake complex terrain, the terrain of Xingzi is more complex. The overall wind shear exponent >0.3 has high frequency, and stratified wind shear exponent >0.4 has the frequency up to 10%. However, in Hukou, the local lakeland air circulation has a bigger effect. The overall wind shear exponent value >0.3 has lower frequency, and the frequency of stratified wind shear exponent >0.4 is 3.37%. (4) According to the design requirements for wind turbine generator systems, wind shear exponent is 0.2, which may overestimate the wind speed of hub height.

Abstract:In this paper, the cluster regional drought events in Yunnan from 1961 to 2015 are examined by using a simplified identifying method. Based on the identified drought events, we construct a comprehensive evaluation model of the regional drought event to classify the drought grade using lasting days, stations, the average strength, accumulated strength and extreme strength of drought events. The results further show that frequency, accumulated intensity and accumulated impact of regional droughts display an increasing trend in Yunnan. Regional drought events frequently occur in December, January and March, but less in July and August. The drought events mainly persist 15-45 d, with the longest up to 222 d. Droughts often spread over whole Yunnan Province and influences seriously. In central Yunnan, drought is more frequent and serious. Especially, among the severe drought events, the middle pattern drought occurs most frequently.

Abstract:Based on a variety of test indicators from June 2015 to February 2016, the six kinds of forecast pollutants (PM10,PM2.5,SO2,NO2,CO,O3) and the AQI index of Air Quality Numerical Forecasting System in Central China were verified. Then the impact of aerosol radiation effect on surface meteorological factors was studied by sensitivity experiments. The results show that the Air Quality Numerical Forecasting System in Central China has stable and good forecasting effect on the six pollutants and AQI in Hubei Province, but the forecast error of O3 is larger and forecast value is higher than the observation. The error could be reduced by the error correction in future. Compared with the CUACE forecasting model, the 24-48 h forecast is better than that of CUACE and the 72 h effect of the two models are similar. The aerosol radiation effect has affected the distribution of surface meteorological field to a certain extent. During this process, the total radiation effect of aerosols reduced the solar radiation by 7.740 W·m-2, 2 m temperature decreased by 0.162℃, plantary boundary layer height decreased by 16.457 m, relative humidity increased by 0.557%, and 10 m wind speed decreased by 0.011 m·s-1. The effect of aerosols on meteorological elements in the daytime is greater than that over night. The reduction of solar radiation, 2 m temperature, boundary layer height, 10 m wind speed and the increase of humidity are not conducive to the spread of pollutants. The increase of pollutants concentration also contributes to the above changes of meteorological conditions, resulting in a bidirectional feedback between meteorological conditions and atmospheric pollution.

Abstract:Based on the meteorological data from 113 surface and 24 radiosonde stations in Northwest China from 1960 to 2015, the empirical formula was established between precipitable water (PWV) and surface vapor pressure, and the PWV in Northwest China was calculated. With the methods such as inverse distance weighted, MannKendall test and Morlet wavelets, the temporal and spatial distribution of PWV and its relations with other meteorological elements were analyzed. The results showed that PWV has increased in last 56 years with the increasing rate of 0.11 mm per decade, and the obviously unimodal types can be examined for the monthly variations. The high PWV area is mainly in the east of Northwest China, and the middle area of Northwest China usually presents a low value. The PWV in most parts of Northwest China has increased, which is obvious in southern Shaanxi, southeastern Gansu, northwestern Qinghai and Xinjiang. The annual average PWV in Northwest China shows an obvious mutation around 1983 and a periodical change with primary period of approximately 4 years. PWV in Northwest China shows a positive correlation with mean air temperature and relative humidity, and a negative correlation with wind speed.

Abstract:The impacts of temperature, sunshine and precipitation climatic suitabilities on rice meteorological output are determined based on the meteorological data and agricultural data from 1961 to 2016 by using the statistical analysis and the climate suitability model, whose parameters have been improved. The comprehensive index of annual agricultural climate status and its prediction model are constructed. The results show that there is a significant correlation between sunshine and precipitation suitabilities and relative meteorological output. The influence weights about sunshine and precipitation suitabilities are 0.460 and 0.428, respectively. Due to sufficient heat resources, the temperature suitability has a small influence on meteorological output (0.112). The correlation coefficient of the composite index of annual agricultural climate status and relative meteorological output based on climate suitability is 0.411, which indicates that the index can better characterize the comprehensive effect of climatic conditions on yield formation. Prediction model of composite index of annual agricultural climate is established by largescale predictors such as atmospheric circulation characteristics and Pacific SST using optimal correlation and stepwise regression. Through historic matching and trying test, the effect of prediction model is ideal and can be put into operation. The prediction results would provide scientific basis for the analysis and prediction of rice yield.

Abstract:Using the high spatiotemporal meteorological observation data from 339 traffic weather stations along highway, and 72 conventional observation stations, four heavy fog events during 1-9 December 2013, on 23 October 2015, 22 December 2015 and 12 February 2016 are analyzed. Based on 194 cases, climatic characteristics of extremely heavy fog in initiation and disappearance, microphysical characteristics of explosive enhancement and the triggering factors of heavy fogs are analyzed. The results show that visibility dropped sharply within very short time (in 30 min) because fog droplet number concentration, water content and droplet size increased remarkably, and fog droplet spectrum became broader. In addition, the sharp drop of temperature resulted from radiation reinforcement at night, the weak cold advection of underlying layer, the increase of evaporation after sunrise, and the lakeland wind effect made fog reinforce eruptively.

Abstract:By comparing the ERAInterim temperature reanalysis data and observations at 08:00 BT and 20:00 BT over Jianghuai Region from 1992 to 2016, we found the deviations between them decrease first and then increase vertically from low level to top level. The spatial differences are obvious in lower tropos phere and tend to be consistent in middle and higher levels. The reanalysis data at 500 hPa and above have transition from lower (before the year 2000) to higher (after the year 2000) deviations. Except for surface, the average absolute deviations of these two kinds of data show significant decreasing tendencies at other pressure levels. In monthly distribution of deviations, reanalysis data at surface and above 500 hPa are generally higher than sounding data, and the absolute deviations at all pressure levels are the smallest around August and September. Further researches showed that under the weather phenomena of snow, sleet, freezing rain and ice particles, deviations of reanalysis data from surface to 1000 hPa and 850 hPa are generally higher than sounding data. However, the higher amplitudes of reanalysis data minus sounding data at 1000 hPa are significantly larger than surface in foggy weather, and under all abovementioned phenomena deviations of reanalysis data are higher above 500 hPa. So, the 850 hPa temperature data should be used carefully when using ERAInterim to distinguish precipitation phase. The false temperature inversion in the nearsurface layer will have a great influence on the identification of fog.

Abstract:Referring to the method presented by Mecikalski et al (2010a; 2010b), which was based on GOES satellite data to forecast convective initiation (CI), this paper proposes a method for forecasting summer CI by using Himawari8 satellite data in Shanghai. By this method, a specific convective weather event, which occurred in Shanghai on 28 July 2016, is analyzed. Moreover, an experiment for forecasting 12 CI events in Shanghai during July-August of 2016 is implemented to validate the proposed method. The results show that the development of convective cloud cluster can be well reflected by the indicators in the method, and the interference caused by the edges of mature convective clouds can be eliminated. Of the 12 CI events, 11 are forecasted and the average lead time can be about 30 min. However, CI forecasting may be missed by this method if convection is weak.

Abstract:The main characteristics of the general atmospheric circulation in June 2018 are listed as follows. The polar vortex took the shape of a single pole in the Northern Hemisphere, stronger than in the normal years. In the midhigh latitudes of Asia, the circulation presented a twotroughs and oneridge pattern, and the troughs and ridge were stronger than their climatological means. The subtropical high lay eastwards obviously, and its intensity was a little stronger than its average state during the corresponding time of the normal years. The South China Sea monsoon bursted in the second pentad of June, three pentads later than usual. Also the strength of monsoon trough was weaker than in normal years. Meanwhile, monthly mean precipitation amount was 92.9 mm, which is 6% less than the normal (99.3 mm). Monthly mean temperature was 20.9℃, 0.9℃ higher than its climatological mean (20.0℃). There were four regional rainfall events during this month. Three tropical cyclones were active over the Northwest Pacific Ocean and the South China Sea, and the Fourth Typhoon “Ewiniar” landed in China for three times. Drought condition continued in Inner Mongolia, Liaoning and the north of Hebei Province. Extreme high temperature weather hit the BeijingTianjinHebei Region in late June. Many cities suffered from blustery weather and hailstorm.