Abstract:This paper summarizes the research results about gust fronts in China in recent years, illustrates their spatial structures, types and characteristics, discusses formation mechanisms for narrowband echoes of gust fronts, proposes the subjective recognition methods to gust fronts. The results show that based on the radar data analysis, gust fronts can be divided into two types: The static gust front and the sport gust front of the original thunderstorm, and the former can be divided further into two subtypes. The feedback effect of gust fronts for the original thunderstorm is completely different because of their different types. The formation mechanism for narrowband echoes of gust fronts can be briefed as two categories: The first is Bragg Scattering caused by the pulsation of atmospheric refraction index gradient, and the second is Particle Scattering caused by insects. Using the characteristics of reflectivity factor and radial velocity, we can identify the location and scope of gust fronts and can forecast their extrapolation. Because gust fronts are close to the ground in the lower atmosphere, we should use a lower elevation of radar data to identify them. Using the radar echo characteristics of gust fronts, the formation, development and dissipation can be comprehensively identified, matching up the variation of mesoscale convective clouds and arcus cloud lines of the high resolution satellite visible cloud images and combined with surface mesoscale observation data.

Abstract:With daily precipitation observation data in Hainan compiled by National Climate Centre of CMA and NCEP/NCAR reanalysis data, the atmospheric circulation of extreme rainstorm and its anomalous characteristics during post flood period late rainy season in Hainan Island in the last ten years are investigated. Results show that the circulation configurations of extreme rainstorm cases have many similar characteristics. In the upper level, South Asia high is located in the north of South China Sea (SCS) and provides strong divergence. In the middle and lower levels, increasing pressure gradient induced by the interactions among tropical disturbances, the Northwest Pacific subtropical high (NWPSH) and East Asia middle latitude trough are helpful to the formation of frontal zone, maintenance and reinforcement of tropical disturbance and induction of easterly low level jet. The presence of strong low level jet in north central South China Sea is the most significant feature of extreme rainstorm cases in late rainy season, which consists of the southeast wind from the northeast side of tropical disturbance, the northeast wind from the front of cold high and the easterly wind from the south side of NWPSH. The core of low leve jet shows three obvious characteristics of moving from east to west, daily gradual rising and strong wind speed fluctuation before the torrential rain occurs. The distinct characteristics are also manifested mainly in the anomalies of synoptic scale circulation of extreme rainstorm cases in comparison with the same period climatological mean: the Pacific intertropical convergence zone (ITCZ) is exceptionally active, SCS summer monsoon trough and Indian summer monsoon trough are stronger and retreat more slowly in comparison with the normal climatological means. The location of South Asia high is abnormally eastern and southern, and the intensities of middle latitude trough and NWPSH are stronger than usual. The water vapor causing the enhancement of precipitation is transported by the northeast wind from the front of cold high and the easterly wind from the south side of NWPSH.

Abstract:Using the NCEP/NCAR reanalysis data and the Tibetan Plateau meteorological stations daily precipitation data from May to September 1980-2011, 967 cases of Iranian high eastward stretching effecting Tibetan Plateau are analyzed. Precipitation over Tibetan Plateau is classified into 4 types, which are heavy rain pattern, moderate rain pattern, light rain pattern and non rain pattern with corresponding total days of 158 d,516 d,165 d and 128 d. As Iran high ridge line is more northerly (southerly), 500 hPa north south flow convergence is stronger (weaker) and 200 hPa divergence is larger (smaller) so that greater (smaller) precipitation occurs on the plateau. In addition to the direct impact of Iran high impacting on general circulation over Tibetan Plateau, its ridge line is northerly (southerly), Somali jet is stronger (weaker), the Bay of Bengal water vapor transport is stronger (weaker), indirectly leading to more (less) precipitation over Tibetan Plateau.

Abstract:Using the cloud to ground lightning data from 2009 to 2012 probed by ADTD Lightning Location Monitoring System, we analyze the spatio temporal distribution characteristics of flashes. The results show that: the negative lightning flashes are over 94% of the total, but the positive lightning accounts for about 5%. Lightning is prone to occur from May to September, most frequently seen in July and August, which is correspondent to rainfall belts. With the advance of monsoons, lightning flashes gradually increase from south to north and from east to west. Summer has lightnings the most, followed by spring and autumn, and in winter almost none. The diurnal distributions of lightnings show the single peak characteristic, and most of them occur in 16:00-17:00 BT, corresponding to the time periods of severe convective weather events. The overall distribution of lightning is that there are more in Eastern coast and the South than in western inland and the North. The lightning density distribution has obvious regional differences. The central and eastern regions, South China and the Sichuan Basin are the high lightning density area. The daytime lightning mainly occurs in the coastal areas of Jiangsu, Zhejiang and Guangdong while the night lightning usually appears in inland areas of Yunnan, Sichuan and Chongqing. The lightning in the afternoon (14:00-20:00 BT) is most active, but less active from 08:00 to 14:00 BT. The lightning high value areas in different regions appear in different months. The high lightning value of South China is in June, Sichuan Basin in July and the central and eastern parts in August. Spring lightning of southern China is most active, which is closely related to the pre rainy season in the region. The positive and negative lightning intensity is mainly concentrated in the 10 to 40 kA. The positive and negative ground lightning intensities with cumulative probability of more than 60% are less than 60 kA, 35 kA respectively. The positive and negative lightning intensities with cumulative probability of more than 90% are less than 140 kA, 65 kA respectively. Lightning intensity low value areas mainly distribute in negative lightnings while the high value areas often appear in positive lightnings.

Abstract:To investigate the phase features of atmospheric particles detected by the Ka band cloud radar of State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, on the basis of Shupe’s summary about the characteristic values of different cloud particle phases, including reflectivity, Doppler radial velocity and linear depolarization ratio of cloud radar and temperature of rawinsonde. By using the asymmetric T type functions, which are reflectivity, Doppler radial velocity, linear depolarization ratio and verticle temperature profile, six different phases of cloud particles are retrieved, i.e., snow, ice crystal, mixed phase, liquid, drizzle and rain. By means of joint analysis between cloud radar data and sounding data at the same time and places, the following conclusion is drawn: the particle phases retrived by fuzzy logic method shows good consistency with real time sounding data, and may play a directive role in weather forecasting, weather modification and effect evalution.

Abstract:Based on the Fuyang Doppler weather radar data, the tornado that occurred in Yingshang County, Anhui Province on 23 July 2008 is analyzed in detail. It is shown that the storm is intensified rapidly after the continuous merging of storm cells, and becomes a supercell. The merger and interaction between the storm cells may be instructive for tornado warning for they are highly correlated to the time and location of the tornado. The mesocyclone and tornado vortex signature products with default parameters setting in CINRAD/SA radar system are indicative to tornado warning. When the two kinds of products are detected for the same storm simultaneously along with the observed bounded weak echo areas, the probability of tornado becomes even higher.

Abstract:Taking the rainstorm that occurred in Shandong Province on 29 July 2013 as an example, microphysical properties of cloud and precipitation were investigated by using the microphysical analysis method developed by Rosenfeld and the high spatial resolution data of MODIS polar satellite and the precipitation particle spectrum data collected by the THIES laser rain droplet collector in Zhangqiu. The analyses show that the cloud cluster for the rainstorm is composed of various clouds with different heights. Deep mixed phase growth and glaciation zones exist in the convective cloud above -10℃ and the initial temperature of glaciation growth is about -20℃. There is condensation growth, coalescence growth and mixed phase growth in systematic stratus clouds but no glaciations growth. The high rainfall intensity greater than 100 mm·h-1 occurs several times with maximum rain droplet concentration up to 104, and the extremely big drop is close to 8 mm. So, there is a close relationship between rainfall intensity and rain droplet number concentration. The diameter of raindrops bigger than 2 mm is less than 1% of total concentration, but it is the vast majority of contribution to rain intensity. From the types of spectrum distribution, it can be seen that exponential distribution is less frequent, and multi peak structure has the largest proportion.

Abstract:The paper first proposes a sicentific grouping method for the data of dense rainfall station network by using high density surface rainfall station network data and volume scanning data continuously gathered by radar, which were collected from the experiment of the project “the Rainstorm Flood Forecasting System in the Huang Huai River Basin”. Moreover, more than ten calibration methods which use radar and rain gauge are objectively tested and assessed with multi parameters by using grouped data. This study results show that: (1) The grouping method of rainfall station is scientific and reasonable, satisfying the request of assessment. (2) The integration method for regional rainfall estimation is better than the other 8 methods without integration. (3) Estimation accuracy by using radar features three phase distribution. (4) The range 50-100 km is the ideal for precipitation estimation while the range between 150 and 200 km is poor. (5) Accuracy and stability of region precipitation estimation method can be improved through long time practice.

Abstract:From 1 May to 8 June 2013 CMA Meteorological Observation Centre conducted an experiment of cloud height observations by using cloud radar (35 GHz), whose observation data are the echo power value and temporal resolution is 1 min and a ceilometer whose observation data are the back scattering intens data with 1 min temporal resolution. The result of analyzing the data observed from the 39 d experiment indicates that: (1) the data acquisition ratio of cloud radar is 26% larger than that of ceilometer; (2) the ratio is 51% in fog haze weather; (3) relatively, precipitation has more significant effect on cloud base height measured by laser ceilometer than that by cloud radar; (4) height of cloud base measured by cloud radar is almost consistent with the height by ceilometer because their average deviation is less than 300 m.

Abstract:Based on conventional observational data, MICAPS data and NECP/NCAR Reanalysis data, together with the Gaussian simulation method, snow enhancement operation conditions on 10 November 2012 by the ground based silver iodide (AgI) generator over Mountain Damao of Tangxian were analyzed. The result showed that the weather condition is cold vortex system moving from southwest to northeast. According to Pasquill stability classification, the atmospheric stratification is neutral during the operation process. The Gaussian simulation results showed that the effective concentration of AgI can diffuse up to 3.0 km. Moreover, the atmosphere is in the updraft from the surface to 3.2 km through the operation procedure. The atmospheric temperature at the height of the generator outlet is 1.0℃ by calculation. The cloud base height in winter by manual observation is between 2.5-3.0 km. Therefore, it is concluded that the position of operation site is appropriate and the operating conditions are suitable to deliver the AgI catalyst to the cloud as well.

Abstract:The difference and correlation between microwave radiometer and radiosonde are presented in this paper, based on conventional sounding, MP 3000A ground based microwave radiometer and automatic station data. Result shows temperature and relative humidity differences from Suzhou ground based microwave radiometer are 3.2℃ and 29% respectively, while correlation coefficients are above 0.98 and around 0.5 accordingly. Analysis of signature for microwave radiometer observations in different weather conditions illustrates that there is a good correspondence between the vertical variations of relative humidity, liquid water content and the rainfall, severe weather, and fog. In precipitation and strong convection cases, relative humidity below 6 km increases ahead of the weather process (lead time of increase in relative humidity in rainfall case is longer than that in severe convection case), liquid water content below 3.5 km rises rapidly, especially in the height from 2.25 to 3.25 km. However, in fog cases, increase of relative humidity is below 3-3.5 km and liquid water content is below 1.5 km. A index and convective stability index may lost their indicative significance after obvious precipitation appears, but they perform well at the beginning of rainfall (especially remarkable rains) and in the fog case.

Abstract:Based on the 24 h hourly outdoor temperature forecasts from Beijing Rapid Update Cycle （BJ RUC）NWP and observed indoor temperature from Beijing Haiyuan Community during 1-15 March 2010, the relations between heat supply and loss， indoor and outdoor temperature, supply and return water temperature of heating system for buildings are established by using the principle of the energy equilibrium. A numerical simulation model of supply and return water temperature is deduced. The simulation experiment of hourly temperature forecast is carried out. Then the simulated forecast is compared to the observed temperature in Beijing Haiyuan Community. The results show that the mean square root error between simulated indoor temperature and required temperature (20℃) is 0.25℃. Comparably, the actual error of operation in Beijing Haiyuan Community is 1.53℃. The root mean square errors between simulated and observed supply water temperature and return water temperature are 3.69℃ and 3.80℃ respectively. Which is much less than the actual operation error 1.53℃ in Beijing Haiyuan Community.

Abstract:Variation characteristics of temperature difference between light louvred screen and reinforced plastic screen are explored by using the minute data from April 2012 to September 2013 in regional automatic weather station in Fengjing of Shanghai, to reveal degrees of temperature difference of the two screens. Temperature difference, daily extremes and the change characteristics of temperature difference under different cloud cover, different heating (cooling) rate, different wind speed, different rainfall intensity and the reason of temperature difference are analyzed with methods of linear analysis, linear fitting and multiple regression. Temperature correction equations for different seasons are calculated. The results show that temperature difference, dispersion of temperature difference and daily extreme difference have seasonal differences. The daily maximum temperature reference value of light louvred screen is lower in spring, summer and autumn. Reference value of high temperature days is lower. Solar radiation and infrared (cooling) radiation have great influences on the temperature difference. The more radiation, the bigger the temperature difference. Single wind condition or single rainfall condition has smaller influence on temperature difference. Under the condition of rain, strong winds and infrared cooling radiation with slow winds increase the temperature difference. The observed value of temperature in light louvred screen is more sensitive to the changes in the environmental temperature. The results show that, the different material and structure make light louvered screen have lower performance of anti radiation, which is the main cause for temperature difference.

Abstract:The performance of medium range forecast is verified and compared for the models of T639, ECMWF and Japan from September to November 2014. The results show that all the three models have good performance in predicting the variation and adjustment of atmospheric circulation over Asian middle and high latitude areas and the transition of temperature at 850 hPa. They also have good performance in predicting ridge line position of western Pacific subtropical high, but the deviation of EC is the smallest. EC is the best at forecasting the track and intensity of typhoon Fung wong among all the three models. EC and T639 can forecast fog and haze, but EC does even better than T639.

Abstract:The following are the main characteristics of the general atmospheric circulation in November 2014. There was one polar vortex center in the Northern Hemisphere. The circulation presented zonal patterns in middle high latitudes. The south baranch trough was active located near 100°E in general. The Northwest Pacific subtropical high was almost the same as the normal, lying by south and west. Meanwhile, monthly mean precipitation amount was 22.6 mm, which is 20.2% more than its climatological mean (18.8 mm). Monthly mean temperature was 3.9℃, 1.0℃ higher than its climatological mean (2.9℃). There were four major rainfall processes, and parts of the south of Changjiang River, and South China saw rains obviously, even with continued rainy day somewhere. In the month, there were four major cold air processes influencing China, resulting in the extreme drop in daily temperature at 26 stations, including three stations had new records for the daily temperature drop. In additon, there were also four wide spread fog haze events in central and eastern China during this month.