Abstract:The separation between operational forecasting and research has been a serious limitation for advanced techniques to be transferred into operation. The 2013 warmseason experiment, which was carried out by National Meteorological Centre (NMC) through collaborating with Chinese Academy of Meteorological Sciences (CAMS), Nanjing University, Institute of Atmospheric Physics (IAP) of Chinese Academy of Sciences (CAS), mainly focuses on seeking a new cooperation mode between operation units and research institutions to inspire new initiatives for operationally relevant research and accelerate the transfer of promising new tools from research to operations. In this paper, the recurrence conjunctive discussion about severe weather events, the advanced techniques testing and the simulated operational environment for weather forecasting, which supports the experiment, are introduced. Based on this experiment, an operational simulation system including the realtime operational data flow and tested data flow supporting subsystem, the quantitative precipitation forecast and severe convective weather forecast platforms, the realtime model verification subsystem is built. The conjunctive discussion creates a facetoface interview platform for forecasters and researchers, pushing forecasters to learn to address operational challenges from a more scientific perspective and researchers to understand more the operational needs and become better equipped to get over the application research problems proposed in the discussion. The advanced techniques testing shows that the high resolution mesoscale models are useful for severe convective weather and heavy rainfall operational forecasting, the radar wind retrieval technology and the satellite weather application platform are useful for quick analysis on mesoscale convective weather, and the cooperation between forecasters and researchers is the key factor for techniques to be transferred into operation.

Abstract:The atmospheric circulation, sources of water vapor, mesoscale systems related to extremely heavy rainfall over the Sichuan Basin on 8 July 2013 are analyzed by using the conventional data, surface dense observation, satellite data and NECP reanalysis data. This process occurs in the background with “high pressure to the east and low pressure to the west”. A small trough moves eastward over the eastern part of plateau under the stable weather pattern of westerly trough and subtropical high over Sichuan Basin. The southwest flow from the Bay of Bengal veers to easterly in Sichuan Basin transporting the moisture to western Sichuan Basin. The surface mesoscale convergence line which developed from surface easterly and northerly winds is the favorite condition for the development and strengths of convective cloud cluster. The simulated results from WRF model show that the effect of steep terrain in western Sichuan Basin and the development of low vortex provides favorite conditions for development of the convective system. The north wind invading to the north of the surface convergence line induces to the realease of convective energy, which is also favorite for the outbreak and maintainence of convective systems.

Abstract:A few operational models predicted the Beijing “7.21” (21 July 2012) severe rainstorm with the wrong reason that the severe convective rainstorm resulted mainly from cold front. In fact, a large amount of rainfall occurred over the warm area of the southwest of Beijing before the cold front. In this paper, after assimilating the surface and sounding conventional data three times by ensemble Kalman filter (EnKF) method, a nonhydrostatic mesoscale numerical model (WRF) that has a collection of 30 members was employed to simulate the process. The comparison of a better member and a worse member reveals that the better member can successfully simulate the mesoscale convective system (MCS) in the warm sector in the central and western part of Hebei Province and the southwest of Beijing and the relatively stable system configuration, thus making the MCS fully develop over Beijing. So, it does a better simulation of the warmsector precipitation during the process of the severe rainstorm. In contrast, the worse member fails to simulate the precipitation in warm sector, and turns out to be frontal precipitation with the rain band southerly and the occurrence time lagged. The difference in these simulated results is greatly related to the corresponding simulated location of the low vortex in each ensemble member. The improvement in initial field of ensemble member by EnKF, which makes the simulated movement and development of main influence systems more accurate, is therefore the key to simulate the trigger and maintenance of the convective system in warm sector successfully.

Abstract:On the basis of NCEP CFS reanalysis data with a resolution of 0.5°×0.5°, conventional surface observation and FY2E satellite data from the China Meteorological Administration, detailed investigation was conducted to one northeast cold vortex (NECV) that caused several heavy rainfall events. The results indicate that the developing stage of the NECV is the most active period for convective activities and precipitation. Minimum TBB during the lifetime of the vortex is below -60℃, and maximum precipitation is 124 mm. The South China Sea, the Yellow Sea and the Japan Sea are main moisture sources for the heavy rainfall events associated with the NECV. The NECV is a kind of deeplydeveloped baroclinic vortex system with its strong baroclinicity and kinetic energy zones mainly located at the peripheral regions around the vortex. Cold regions associated with the vortex mainly appear in midupper troposphere and lower troposphere. Vorticity budget indicates that the vertical advection of vorticity that is closely related to convective activities dominate the formation of the NECV; the vertical advection of vorticity and the convergence effects are the most favorable factors to the rapid development of the vortex; and the divergence effects dominate the dissipation of the NECV. Kinetic energy budget indicates that the kinetic energy production by the rotational wind is the most favorable factor to the vortex during the formation stage; and during the maintaining stage, transport of kinetic energy by the rotational wind is the dominant factor to the sustainment of kinetic energy associated with the NECV.

Abstract:Two convectionpermitting numerical experiments were conducted with the WRF model to examine the impact of assimilating sounding data by using an EnKF method for deterministic prediction of a torrential rainfall event over southern China during 15-16 May 2013. The initial and lateral boundary conditions were based on the NCEP GFS 1°×1° 60 h gridded forecast data which were available every 6 h from 08:00 BT 14 May to 20:00 BT 16 May 2013. The two experiments, NODA and DA, differed only in the initial conditions: while NODA was initialized from the NCEP GFS data at 08:00 BT 14 May, DA was from an ensemble mean of 30 analysismembers at 08:00 BT 15 May, which was generated using the WRFEnKF system with conventional sounding data at 20:00 BT 14 May, 02:00 BT and 08:00 BT 15 May assimilated. The results show that, compared to NODA, not only the initial conditions of DA are much closer to the observed fields, but also the DA predicted physical parameters are improved in terms of both biases and rootmeansquare errors, leading to a more accurate prediction of the location and magnitude of precipitation from DA.

Abstract:MRR is a vertically pointing Micro Rain Radar which can measure vertical profiles of radar reflectivity and drop size distribution (DSD). It plays an important role in understanding precipitation microphysical structure and improving quantitative precipitation estimation. In this study, the observations from an Sband Doppler radar, a 2DVideoDisdrometer and a rain gauge during two summer precipitation events in Nanjing are used to assess the performance of MRR. The intercomparison analyses of these four instruments in stratiform and convective precipitation are also performed. The results show that, the vertical profile of reflectivity measured by MRR and Sband radar has a good agreement below 4 km with the mean difference less than 1 dB. Above 4 km, however, MRR tends to underestimate the reflectivity due to the precipitation attenuation. The difference of reflectivity between MRR and Sband radar increases with the height. Furthermore, MRR can accurately estimate the rain rate with the reflectivity below 35 dBz, but underestimate the rain rate with the reflectivity above 35 dBz. The rainfall estimation for stratiform clouds is more accurate than that for convective clouds. Especially, MRR exhibits good performance for the weak rainfall below 0.1 mm·h-1, which cannot be measured by rain gauge. Due to the inherent limitation of MRR and the precipitation attenuation, MRR shows high consistency with 2DVD for raindrops with size from 1 mm to 5 mm, but underestimates the concentration of drops larger than 5 mm and overestimates the concentration of drops smaller than 1 mm. Overall, MRR is an effective instrument for the precipitation measurements, especially suitable for quantitative estimation of stratiform.

Abstract:This study examines the environmental conditions of bow echoes and the related damaging thunderstorm characteristics in Jianghuai Region (30°-36°N, 115°-122°E) by using the sounding data, surface observations, reanalysis data as well as the severe weather reports in 2009-2012. The Doppler weather radar data are also used to investigate the spatial and temporal distribution of bow echoes, as well as their threedimensional structures and possible mechanisms in causing damaging gales. Statistical results show that bow echoes in Jianghuai Region preferentially occur in northwestern Anhui, southeastern Jiangsu, southeastern Shandong to southwestern Jiangsu, and the plain between two mountains in southern Anhui with the frequency maximum in the late afternoon. The extreme damaging gales (>24.5 m·s-1) induced by bow echoes account for 30% of all the extreme damaging wind events. The typical synoptic systems associated with the bow echo are the northeast cold vortex (NECV) and upperlevel trough, the moderate convective available potential energy (CAPE, 1780 J·kg-1) and vertical wind shear (11.6 m·s-1 between 1000 and 700 hPa), as well as a remarkable dry layer in the middle level. Compared with the environmental conditions affected by the upperlevel trough systems, NECV is usually accompanied with a larger DCAPE and stronger cold pool on the surface. According to the structure of radar observations, bow echoes in Jianghuai Region are divided into three categories, including classic bow echo (BE), bow echo complex (BEC), and squall line bow echo (SLBE), which account for 28.6%, 14.3%, and 57.1%, respectively.

Abstract:Effective and smooth transitions from research and development to operational implementation play important parts in promoting the development of meteorological enterprise. Since 2000, the National Oceanic and Atmospheric Administration (NOAA) of the United States of America has begun to organize several test beds to implement the transitions from research and development to operations, and the test beds have become an integral part of the weather enterprise, bridging research and forecast services. This paper briefly introduces an overview of the different test beds of NOAA and their main achievements, and highlights organization and Spring Experiment of the HWT (Hazadous Weather Testbed). By forecasting experiments in severe convective weather, quantitative precipitation forecast, hurricanes, and aviation weather, we can see that developing the probabilistic forecast products of different types of severe convective weather, quantitative precipitation forecast, and the tropical storm force winds is an important development goal of the U.S. weather service. The Spring Experiment of HWT showed that highresolution “convection allowing” numerical weather prediction (NWP) models ［hereafter convectionallowing models (CAMs)］ are the technical foundation for developing fine probabilistic forecasting operation, and the development of CAMs and data assimilation, testing and application of CAMs forecasts can provide objective technical support for probabilistic forecasts of severe convective weather and quantitative precipitation. The achievements and organization of GOESR (Geostationary Operational Environmental Satellite R series) Proving Ground can also provide a reference for the application of FY4 (Fengyun4) satellite data.

Abstract:According to the conventional meteorological observation over the period 1981-2000 and NCEP/NCAR reanalysis data, coupled with synthetic analysis and power diagnostic analysis method, the paper illustrates the spatial distribution of coldair snowstorm and noncoldair snowstorm, atmospheric circulation, vapor transportation, stability and vertical motion and does comparative analysis. The results indicate that coldair snowstorms are meso and microscale snowfalls which occur in the northwest air flow behind trough, while the noncoldair snowstorms tend to occur in southwest air flow in front of trough, usually largescale snowfalls. Coldair snowstorms have distinct local characteristics, resulting from the response of strong cold air to the physical condition of underlying surface. In addition, this paper proposes that the unstability of atmospheric boundary caused by the strong interaction of cold and warm waters of the Bohai Sea is the nature of coldair snowfalls, and the snowfalls occurring in such unstable stratification of boundary layer is the concept of coldair snowfalls.

Abstract:Circulation situation, characteristics of surface meteorological elements, structure of atmospheric boundary layer and air pollution status of the longlasting foghaze event in Jiangsu Province during 12-16 January 2013 are analyzed by using the FNL analysis data, data on pollutant particle concentration and conventional meteorological data. The results indicate that steady upper air circulation situation, warm advection of middlelow layers and stable distribution of surface pressure field are favorable for haze to occur in terms of circulation features. Continuous and slight changes of pressure gradient, slow wind speed, increase of relative humidity as well as the PM2.5 and PM10 concentrations are beneficial to the formation and development of haze. Temperature inversion is observed in low layers during the haze event. The height of mixed layer is inversely correlated to AQI. Lower mixed layer height corresponds with higher AQI, more serious pollution and lower visibility. The increase of relative humidity and enrichment of PM2.5 concentration in contaminant particles lead to the decrease of visibility and continuous pollution while strong wind and low temperature caused by severe cold air is responsible for the important dynamic mechanism of quick erasion of particulate matter. The pollution of Nanjing mainly originates from the Yellow Sea, Anhui Province, and the pollution from the north and local atmospheric pollution.

Abstract:To evaluate quantitatively the suitability of microclimate in greenhouse for the growth and development of vegetables and increase the connotation of facility agriculture meteorological quantitative service, this paper sets up four suitabilitydegree models of inside air temperature, air relative humidity, solar radiation and three factors integrated microclimate in cucumber solar greenhouse are respectively based on the observation data and the results of previous studies and thus the correlation between cucumber actual yield and suitabilitydegree of the models are verified. It is concluded that cucumber yield increases with the increase of integrated suitabilitydegree, and they two are significant correlated. This means that the model for analyzing the suitability of microclimate for cucumber growth in greenhouse is reliable. From the application of the models it is found that the most appropriate time is May in which the microclimate in greenhouse contributes to the growth and development of cucumber well while the most unsuitable time is January. Regardless of temperature suitability, air relative humidity suitability, the received solar radiation suitability or three factors comprehensive suitability, the varying trend of its values is irregular “V”shaped during the whole observation year. The spring suitability degree is the highest, followed by the autumn, and the lowest in winter. The calculation result is in line with the local actual situation.

Abstract:Possible precursor of the summer climate in 2014 was reviewed. Its characteristics are that in early 2014 central and eastern equatorial Pacific had a normal but a little bit cold situation, and then developed to warm state. It was projected to have an El Ni〖AKn~D〗o event in the summer, the Greenland sea ice would be more in the winter, and the snow cover over the Tibetan Plateau would be a bit more than normal. These features had significant effects on the East Asian summer monsoon later. By analyzing the possible effects of these precursors, summer rainfall belt in 2014 was predicted to be in the position by north, but more southerly than that of 2013. The rainfall areas are mainly located in the region from the southern part of North China to Jianghuai Area. Comparing the observation with prediction, big differences are found. The distribution pattern with more rainfall in the South and less in the North was not predicted. However, the prediction is consistent with the observation over the Northeast, North China, the middle reaches of the Yangtze River, the west of South China, and the south of Southwest. In addition, the prediction of tropical cyclones, Meiyu and the rainy season in North China agrees with the observation. Finally, the complexity and problems of flood season climate prediction were analyzed and discussed.

Abstract:The main characteristics of the general atmospheric circulation in February 2015 are as follows. There is one polar vortex center in the Northern Hemisphere, stronger than usual. The atmospheric circulation is in a fourwave pattern over midhigh latitudes. The West Pacific subtropical high is weaker than usual and the south branch trough is almost at the same position as normal. The monthly mean temperature is -0.2℃, 1.5℃ higher than normal. The monthly mean precipitation is 16.3 mm, which is 6.3% less than normal. Two strong cold air processes are experienced in this month, and northeast of China has one heavy snowfall process. Starting from the second half of February, more rain and snow events visit wide range of Southern China, while two haze or fog events and one sand and dust weather appear in the central and eastern part of China.