ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 43,Issue 8,2017 Table of Contents
2017, 43(8):901-911.
DOI: 10.7519/j.issn.1000-0526.2017.08.001
Abstract:
Using SMS-WARR and rapid refresh technique, the sensitivity of surface observation data (surface conventional observation data, automatic weather station data) to the numerical simulation of the severe convection event which occurred in Shanghai on July 31 2011 was analyzed. Four comparison experiments were designed to study the assimilation of surface observation data. The results showed that the adjustment of model initial fields varies with assimilating different surface observation data. The density of surface observation data has impacts on initial fields. The initial temperature and wind fields are obviously affected by assimilating the automatic weather station data. After assimilating conventional surface observation data and automatic weather station data, we found that the model can not only well simulate the process of this severe convection, but also simulate the surface temperature, wind field and evolution of convergence line which is more consistent with the observation. Through the analysis and comparison of the initial fileds and simulation results, we also found that the assimilation of all the observation data can improve the initial values of the model, and the observation data are integrated into the model by the mode of rapid refresh, which enhances the characterization of mesoscale structure of server convection, and improved simulation capacity of the local severe convective systems.
Using SMS-WARR and rapid refresh technique, the sensitivity of surface observation data (surface conventional observation data, automatic weather station data) to the numerical simulation of the severe convection event which occurred in Shanghai on July 31 2011 was analyzed. Four comparison experiments were designed to study the assimilation of surface observation data. The results showed that the adjustment of model initial fields varies with assimilating different surface observation data. The density of surface observation data has impacts on initial fields. The initial temperature and wind fields are obviously affected by assimilating the automatic weather station data. After assimilating conventional surface observation data and automatic weather station data, we found that the model can not only well simulate the process of this severe convection, but also simulate the surface temperature, wind field and evolution of convergence line which is more consistent with the observation. Through the analysis and comparison of the initial fileds and simulation results, we also found that the assimilation of all the observation data can improve the initial values of the model, and the observation data are integrated into the model by the mode of rapid refresh, which enhances the characterization of mesoscale structure of server convection, and improved simulation capacity of the local severe convective systems.
2 Contrastive Analysis of Inland PreTC Squall Line Accompanied by Typhoons with Different Intensities
2017, 43(8):912-923.
DOI: 10.7519/j.issn.1000-0526.2017.08.002
Abstract:
Based on conventional and unconventional observation data, and with squall lines preceding tropical cyclone caused by two typhoons (Typhoon 201409 Rammasun and Typhoon 200606 Prapiroon) of great intensity differences in inland (Hunan Province and Jiangxi Province) as analysis objects, we diagnosed reasons of differences from the aspects of observation, largescale circulation background and difference stages of squall line. Our contrastive analysis focused on environmental circumstances of initial stage, surface mesoscale characteristics and vertical structure of mature stage. The results show that inverted typhoon trough and subtropical high lead to the squall line preceding Rammasun, while squall line preceding Prapiroon is caused by the inverted typhoon trough, subtropical high and westerly trough; the different locations of subtropical high bring about the difference between positions of southeast jet surrounding these two typhoons, and the southeast jet surrounding Prapiroon is more favorable to the maintenance of squall line. In the initial stage, abundant vapor source, distinct convective instability, accumulation of instable energy and decrease of convective inhibition provide beneficial conditions, and the scattered convective cells are organized into squall lines by the surface convergence line; the different vapor conditions and locations of surface convergence line lead to different positions of two squall lines initially; potential instability of conditional unstable air layer, CAPE (convective available potential energy) and CIN (convective inhibition) indicate the convective development potential of squall line Prapiroon is more intense than the squall line Rammasun. The temperature characteristics of squall line preceding Prapiroon is more evident than that of Rammasun; vertical dynamic structure benefits the generation and development of severe convection; compared with previous research on westerly squall lines, thunderstorm high and positive variation of pressure are not found in these two squall line processes, but cold pool, distinct temperature gradient and pressure gradient have been detected, and vertical wind shear in the bottom layer relies mainly on the wind vector difference. When the bottom of westerly trough and the top of inverted typhoon trough are combined in the north of Hunan Province, convective cells strengthen and form the squall line of later stage. Compared with previous westerly squall line, during the two squall line processes, strong thunderstorm high pressure and positive pressure are not fingered out instead of cold pool, obvious temperature gradient and pressure gradient, and the lower vertical wind shear is given by the wind vector difference.
Based on conventional and unconventional observation data, and with squall lines preceding tropical cyclone caused by two typhoons (Typhoon 201409 Rammasun and Typhoon 200606 Prapiroon) of great intensity differences in inland (Hunan Province and Jiangxi Province) as analysis objects, we diagnosed reasons of differences from the aspects of observation, largescale circulation background and difference stages of squall line. Our contrastive analysis focused on environmental circumstances of initial stage, surface mesoscale characteristics and vertical structure of mature stage. The results show that inverted typhoon trough and subtropical high lead to the squall line preceding Rammasun, while squall line preceding Prapiroon is caused by the inverted typhoon trough, subtropical high and westerly trough; the different locations of subtropical high bring about the difference between positions of southeast jet surrounding these two typhoons, and the southeast jet surrounding Prapiroon is more favorable to the maintenance of squall line. In the initial stage, abundant vapor source, distinct convective instability, accumulation of instable energy and decrease of convective inhibition provide beneficial conditions, and the scattered convective cells are organized into squall lines by the surface convergence line; the different vapor conditions and locations of surface convergence line lead to different positions of two squall lines initially; potential instability of conditional unstable air layer, CAPE (convective available potential energy) and CIN (convective inhibition) indicate the convective development potential of squall line Prapiroon is more intense than the squall line Rammasun. The temperature characteristics of squall line preceding Prapiroon is more evident than that of Rammasun; vertical dynamic structure benefits the generation and development of severe convection; compared with previous research on westerly squall lines, thunderstorm high and positive variation of pressure are not found in these two squall line processes, but cold pool, distinct temperature gradient and pressure gradient have been detected, and vertical wind shear in the bottom layer relies mainly on the wind vector difference. When the bottom of westerly trough and the top of inverted typhoon trough are combined in the north of Hunan Province, convective cells strengthen and form the squall line of later stage. Compared with previous westerly squall line, during the two squall line processes, strong thunderstorm high pressure and positive pressure are not fingered out instead of cold pool, obvious temperature gradient and pressure gradient, and the lower vertical wind shear is given by the wind vector difference.
2017, 43(8):924-935.
DOI: 10.7519/j.issn.1000-0526.2017.08.003
Abstract:
Using conventional observation data, automatic weather station data, the high resolution model of ECMWF data, and FY2E TBB data, 1 km and FNL data, the reason for regional rainstorm in Northern Xinjiang in 20-21 June 2013 was analyzed and compared with the early analysis of rainstorm that had happened in Southern Xinjiang. The results showed that the Central Asian vortex was the main influencing system. The rainstorm was directly caused by in the middle and lower troposphere and the ground mesoscale system. Mesoγ convection system was monitored by both the cloud image and the automatic station wind field. Affected by the terrain of the Altai Mountains and Sharbasitao, the mesoscale low vortex and the cyclonic vortex along the piedmont from the southeast to the northwest at 850 hPa rotated, stranded and enhanced, making the divergence structure of lowlevel convergence and highlevel divergence formed and the strongest vertical upward movement at the same time enhanced rainstorm to increase. This heavy rain process was different from the heavy rain in Southern Xinjiang.
Using conventional observation data, automatic weather station data, the high resolution model of ECMWF data, and FY2E TBB data, 1 km and FNL data, the reason for regional rainstorm in Northern Xinjiang in 20-21 June 2013 was analyzed and compared with the early analysis of rainstorm that had happened in Southern Xinjiang. The results showed that the Central Asian vortex was the main influencing system. The rainstorm was directly caused by in the middle and lower troposphere and the ground mesoscale system. Mesoγ convection system was monitored by both the cloud image and the automatic station wind field. Affected by the terrain of the Altai Mountains and Sharbasitao, the mesoscale low vortex and the cyclonic vortex along the piedmont from the southeast to the northwest at 850 hPa rotated, stranded and enhanced, making the divergence structure of lowlevel convergence and highlevel divergence formed and the strongest vertical upward movement at the same time enhanced rainstorm to increase. This heavy rain process was different from the heavy rain in Southern Xinjiang.
2017, 43(8):936-942.
DOI: 10.7519/j.issn.1000-0526.2017.08.004
Abstract:
Based on hourly ground observation data, daily sounding data for every 50 m at 08:00 and 20:00 BT in Minqin Weather Station, and the NECP reanalysis data, a rarelyseen heavy fog process in Minqin from 9 to 13 November 2015 is analyzed. The results show that the increased ground relative humidity after preprecipitation provided necessary moisture condition, stable high and lowlevel circulation configurations provided a stable stratification and light wind condition for the fog formation. The thickness and intensity of fog layer were closely related to the thickness and intensity of inversion layer near surface, boundary layer height, vertical movement of moisture and absolute value of (Ts-Ta) over night. The higher the boundary layer, the thicker the inversion layer near surface, and the thicker the fog layer. The more intensive the inversion layer, the smaller the absolute value of (Ts-Ta) at night, and the more intensive the fog layer. The stable highlevel circulation, intensive inversion layer and stable isothermal layer near surface and the longlasting saturated moist layer contributed to the rarelyseen intensity and duration of the heavy fog process this time.
Based on hourly ground observation data, daily sounding data for every 50 m at 08:00 and 20:00 BT in Minqin Weather Station, and the NECP reanalysis data, a rarelyseen heavy fog process in Minqin from 9 to 13 November 2015 is analyzed. The results show that the increased ground relative humidity after preprecipitation provided necessary moisture condition, stable high and lowlevel circulation configurations provided a stable stratification and light wind condition for the fog formation. The thickness and intensity of fog layer were closely related to the thickness and intensity of inversion layer near surface, boundary layer height, vertical movement of moisture and absolute value of (Ts-Ta) over night. The higher the boundary layer, the thicker the inversion layer near surface, and the thicker the fog layer. The more intensive the inversion layer, the smaller the absolute value of (Ts-Ta) at night, and the more intensive the fog layer. The stable highlevel circulation, intensive inversion layer and stable isothermal layer near surface and the longlasting saturated moist layer contributed to the rarelyseen intensity and duration of the heavy fog process this time.
2017, 43(8):943-952.
DOI: 10.7519/j.issn.1000-0526.2017.08.005
Abstract:
Characteristic analysis of the heat wave events over China from 1958 to 2013 based on excess heat factor (EHF) was analyzed, and some heat wave indices and aspects were recommended by the Commission for Climatology (CCl) Expert Team on Climate Risk and SectorSpecific Climate Indices (ETCRSCI) of the World Meteorological Organization (WMO) World Climate Programme and the other indices were derived in this paper. The results show that, from 1958 to 2013, the heat wave numbers in central, eastern and northwestern China were more than that in other areas. The heat wave duration and heat wave frequency were most in eastern and central China. The heat wave amplitude was higher in northern China and lower in southern China. The resemble feature could be found in the heat wave mean and the heat wave median, as well. The heat wave days and the heat wave severe days were most in eastern and central China, the heat wave extreme days were most in northern and western China. The indices of the heat waves in most areas of China showed an increasing trend for the period 1958-2013. The heat wave annual value showed a significant increasing trend and it has interannual variation mainly in quasithreeyear oscillation. The main mutation was found in 1994 by using 10 years’ moving average. The heat wave events at Deqin Station of Yunnan Province were analyzed as an example in order to explain the heat wave events in western plateau area of China, and the increasing trend in the 21st century.
Characteristic analysis of the heat wave events over China from 1958 to 2013 based on excess heat factor (EHF) was analyzed, and some heat wave indices and aspects were recommended by the Commission for Climatology (CCl) Expert Team on Climate Risk and SectorSpecific Climate Indices (ETCRSCI) of the World Meteorological Organization (WMO) World Climate Programme and the other indices were derived in this paper. The results show that, from 1958 to 2013, the heat wave numbers in central, eastern and northwestern China were more than that in other areas. The heat wave duration and heat wave frequency were most in eastern and central China. The heat wave amplitude was higher in northern China and lower in southern China. The resemble feature could be found in the heat wave mean and the heat wave median, as well. The heat wave days and the heat wave severe days were most in eastern and central China, the heat wave extreme days were most in northern and western China. The indices of the heat waves in most areas of China showed an increasing trend for the period 1958-2013. The heat wave annual value showed a significant increasing trend and it has interannual variation mainly in quasithreeyear oscillation. The main mutation was found in 1994 by using 10 years’ moving average. The heat wave events at Deqin Station of Yunnan Province were analyzed as an example in order to explain the heat wave events in western plateau area of China, and the increasing trend in the 21st century.
2017, 43(8):953-961.
DOI: 10.7519/j.issn.1000-0526.2017.08.006
Abstract:
Based on the hourly precipitation data from 74 meteorological stations in Shandong Province during 1961-2012, the spatiotemporal and diurnal variation characteristics of hourly extreme rainfalls in Shandong during the flood season (May to September) were analyzed. The results show that the hourly extreme rainfall amount and frequency in Shandong are roughly in zonal distributions, decreasing from the southeast to the northwest inland. The intensity of hourly extreme precipitation in the west central part is larger than that in other parts of Shandong. The precipitation in the west, northwest, southwest and western peninsula accounts for a higher proportion. The regional average extreme precipitation, precipitation frequency and intensity show no significant upward trends. The increasing trend of precipitation in the south, northwest, northeast and northeastern peninsula is evident, and the precipitation intensity in the south, southeast, west and eastern central part of the peninsula rises obviously. The period from 15:00 to 20:00 BT is the main occurrence period of hourly extreme precipitation in Shandong Province. The amount and frequency of precipitation decline during the period from 11:00 to 18:00 BT, while in other periods the trends are upward. Precipitation intensity in the morning shows a downward trend while at other times it is in an opposite way. The hourly precipitation and frequency are the largest in July with two highvalue centers in the day time. During the two periods of 21:00-02:00 BT and 03:00-08:00 BT, the average extreme precipitation and rainfall at most of the stations show ascending trends.
Based on the hourly precipitation data from 74 meteorological stations in Shandong Province during 1961-2012, the spatiotemporal and diurnal variation characteristics of hourly extreme rainfalls in Shandong during the flood season (May to September) were analyzed. The results show that the hourly extreme rainfall amount and frequency in Shandong are roughly in zonal distributions, decreasing from the southeast to the northwest inland. The intensity of hourly extreme precipitation in the west central part is larger than that in other parts of Shandong. The precipitation in the west, northwest, southwest and western peninsula accounts for a higher proportion. The regional average extreme precipitation, precipitation frequency and intensity show no significant upward trends. The increasing trend of precipitation in the south, northwest, northeast and northeastern peninsula is evident, and the precipitation intensity in the south, southeast, west and eastern central part of the peninsula rises obviously. The period from 15:00 to 20:00 BT is the main occurrence period of hourly extreme precipitation in Shandong Province. The amount and frequency of precipitation decline during the period from 11:00 to 18:00 BT, while in other periods the trends are upward. Precipitation intensity in the morning shows a downward trend while at other times it is in an opposite way. The hourly precipitation and frequency are the largest in July with two highvalue centers in the day time. During the two periods of 21:00-02:00 BT and 03:00-08:00 BT, the average extreme precipitation and rainfall at most of the stations show ascending trends.
2017, 43(8):962-972.
DOI: 10.7519/j.issn.1000-0526.2017.08.007
Abstract:
Based on the rainfall data from 722 stations in China, NCEP/NCAR reanalysis data, and the daily rainfall data from 7 stations in Qingdao from January 1961 to December 2011, the precipitation phases of flood season in Qingdao and the corresponding climatic circulation background are analyzed. The results show that 5 stages could be identified in the Qingdao summer flood season, including the initial stage of the main rainy season (29 June to 3 July), the stage of the Yellow RiverHuaihe River rainy season (9-25 July), the stage of North China rainy season (27 July to 6 August), the stage of tropical depression (11-20 August), and the end stage of the main rainy season (29 August to 4 September), respectively. In each stage, the corresponding climatic circulation background and the impact systems are relatively stable. The stage of the Yellow RiverHuaihe River rainy season and the stage of tropical depression are two major precipitation stages with strong intensity and longer duration. The main reasons for the formation of the stages in flood season in Qingdao are the seasonal movement of subtropical high and the circulation configuration in high and low levels. The circulation between different stages shows clearly the phenomenon of abrupt changes.
Based on the rainfall data from 722 stations in China, NCEP/NCAR reanalysis data, and the daily rainfall data from 7 stations in Qingdao from January 1961 to December 2011, the precipitation phases of flood season in Qingdao and the corresponding climatic circulation background are analyzed. The results show that 5 stages could be identified in the Qingdao summer flood season, including the initial stage of the main rainy season (29 June to 3 July), the stage of the Yellow RiverHuaihe River rainy season (9-25 July), the stage of North China rainy season (27 July to 6 August), the stage of tropical depression (11-20 August), and the end stage of the main rainy season (29 August to 4 September), respectively. In each stage, the corresponding climatic circulation background and the impact systems are relatively stable. The stage of the Yellow RiverHuaihe River rainy season and the stage of tropical depression are two major precipitation stages with strong intensity and longer duration. The main reasons for the formation of the stages in flood season in Qingdao are the seasonal movement of subtropical high and the circulation configuration in high and low levels. The circulation between different stages shows clearly the phenomenon of abrupt changes.
2017, 43(8):973-986.
DOI: 10.7519/j.issn.1000-0526.2017.08.008
Abstract:
A surface urban energy (water) balance model (SUEWS/LUMPS) was driven by 1yr field observations to evaluate the model capability in Shanghai urban area. The model input parameters were partly localized by field survey. The results show that the model can well reproduce the diurnal pattern of radiation components, the daily peak of net allwave radiation flux (Q*) was underestimated by about 25 W·m-2， the amplitude of the diurnal variation of the downward longwave radiation flux (L↓) was underestimated for all seasons, and the performance for upward longwave radiation flux (L↑) was much better than L↓. The occurrence time of the daily peak of sensible heat flux (QH) for each season (except spring) was simulated well by SUEWS, while the magnitude of QH for each season was underestimated. The performance of SUEWS model for latent heat flux (QE) in summer and autumn was better than LUMPS, but they were very similar during winter and spring. SUEWS model successfully reproduced the transition time of the sign of the storage heat flux (ΔQS) in winter, spring and autumn, but had a lag about 2 h in summer. The seasonal variation of the model performance for ΔQS was relatively large. Analysis of the model error dependency on a set of meteorological variables indicates that there was an increased underestimation of QH and QE and increased overestimation of ΔQS under higher air temperature or stronger wind speed conditions. The QH had an obvious underestimation by about -50 W·m-2 for easterly wind while overestimation by about 15 W·m-2 for the westerly wind was mainly the dense buildings over the east side and the green park over the west side was not considered by the model.
A surface urban energy (water) balance model (SUEWS/LUMPS) was driven by 1yr field observations to evaluate the model capability in Shanghai urban area. The model input parameters were partly localized by field survey. The results show that the model can well reproduce the diurnal pattern of radiation components, the daily peak of net allwave radiation flux (Q*) was underestimated by about 25 W·m-2， the amplitude of the diurnal variation of the downward longwave radiation flux (L↓) was underestimated for all seasons, and the performance for upward longwave radiation flux (L↑) was much better than L↓. The occurrence time of the daily peak of sensible heat flux (QH) for each season (except spring) was simulated well by SUEWS, while the magnitude of QH for each season was underestimated. The performance of SUEWS model for latent heat flux (QE) in summer and autumn was better than LUMPS, but they were very similar during winter and spring. SUEWS model successfully reproduced the transition time of the sign of the storage heat flux (ΔQS) in winter, spring and autumn, but had a lag about 2 h in summer. The seasonal variation of the model performance for ΔQS was relatively large. Analysis of the model error dependency on a set of meteorological variables indicates that there was an increased underestimation of QH and QE and increased overestimation of ΔQS under higher air temperature or stronger wind speed conditions. The QH had an obvious underestimation by about -50 W·m-2 for easterly wind while overestimation by about 15 W·m-2 for the westerly wind was mainly the dense buildings over the east side and the green park over the west side was not considered by the model.
2017, 43(8):987-997.
DOI: 10.7519/j.issn.1000-0526.2017.08.009
Abstract:
The relatively conventional pattern forecast method of local shorttime rainfall is mainly based on satellite images and radar echo extrapolation, but it is also worth finding a better method which can make good use of ground observation data to effectively test the radar forecast products. In the actual weather forecast, rainfall is often characteristiced regional and planar spatial distribution. So the test about shape of rainfall area is more important and more significant. In order to solve the problem in shape test with variety of difficulties and characteristics. This paper proposed a comprehensive evaluating method of 0-3 h QPF (quantitative precipitation forecast) radar rainfall forecast and quantitative indexes of shape test. We also did some experiments including grading test and error analysis on a typical radar forecast of continuous raining process in Guangdong Province in 08:30-11:24 BT 22 April 2016. To some extent, this method also has a good solution of poor data quality and accuracy control in temporal and spatial scale. The TSshape, PODshape, FARshape, Ratiop, Ratiot, Jaccard of a half hour and 1 h radar rainfall forecast shape test are above 40%, above 40%, below 30%, above 40%, above 80%, above 40% respectively. The experimental results reflect the effect of radar rainfall forecast well and show that the indexes of shape test are basically consistent with conventional quantitative indexes.
The relatively conventional pattern forecast method of local shorttime rainfall is mainly based on satellite images and radar echo extrapolation, but it is also worth finding a better method which can make good use of ground observation data to effectively test the radar forecast products. In the actual weather forecast, rainfall is often characteristiced regional and planar spatial distribution. So the test about shape of rainfall area is more important and more significant. In order to solve the problem in shape test with variety of difficulties and characteristics. This paper proposed a comprehensive evaluating method of 0-3 h QPF (quantitative precipitation forecast) radar rainfall forecast and quantitative indexes of shape test. We also did some experiments including grading test and error analysis on a typical radar forecast of continuous raining process in Guangdong Province in 08:30-11:24 BT 22 April 2016. To some extent, this method also has a good solution of poor data quality and accuracy control in temporal and spatial scale. The TSshape, PODshape, FARshape, Ratiop, Ratiot, Jaccard of a half hour and 1 h radar rainfall forecast shape test are above 40%, above 40%, below 30%, above 40%, above 80%, above 40% respectively. The experimental results reflect the effect of radar rainfall forecast well and show that the indexes of shape test are basically consistent with conventional quantitative indexes.
2017, 43(8):998-1004.
DOI: 10.7519/j.issn.1000-0526.2017.08.010
Abstract:
Stable weather index (SWI) of Beijing is developed to meet the demand of quantitative description of the degree of stable weather which is conducive to the formation of fog and haze in China. During a heavily polluting process in January 2015, both the SWI and AQI (air quality index) showed consistent trend: stable growth in the developing stage and rapid decrease in the ending stage. SWI is also used to assess the effect of reduction measure of pollution source. Under the similar stable weather as described by SWI, reduction measures contained air pollution in Beijing during APEC. SWI is developed further based on meteorological data lasting 13 years. Subindex of any parameters is defined as the conditional probability of foghaze divided by the climatology probability when the threshold of the parameter is met. The top 10 stableweatherimplication parameters are chosen, of which subindexes are added up as the final SWI. The developed SWI shows better correlation with PM2.5 concentration which means better characterization of stable weather.
Stable weather index (SWI) of Beijing is developed to meet the demand of quantitative description of the degree of stable weather which is conducive to the formation of fog and haze in China. During a heavily polluting process in January 2015, both the SWI and AQI (air quality index) showed consistent trend: stable growth in the developing stage and rapid decrease in the ending stage. SWI is also used to assess the effect of reduction measure of pollution source. Under the similar stable weather as described by SWI, reduction measures contained air pollution in Beijing during APEC. SWI is developed further based on meteorological data lasting 13 years. Subindex of any parameters is defined as the conditional probability of foghaze divided by the climatology probability when the threshold of the parameter is met. The top 10 stableweatherimplication parameters are chosen, of which subindexes are added up as the final SWI. The developed SWI shows better correlation with PM2.5 concentration which means better characterization of stable weather.
2017, 43(8):1005-1015.
DOI: 10.7519/j.issn.1000-0526.2017.08.011
Abstract:
Aiming at the problem that the resolution of the current wind forecasts is not high and dynamic downscaling method is less applicated to wind forecasting, this paper used the diagnostic wind field function of CALMET model and high spatial resolution terrain data to dynamically downscaling the wind forecast data outputted by WRF model. The main theory is kinematic effect of terrain. After the largescale surface wind field was adjusted by slope flows and terrain blocking effects, the wind field became finer and showed the feature corresponding to terrain. In the experiment part, we took Guangdong Province as study region, using observation data and CLDAS (CMA land data assimilation system) data to examine the simulation result by a case. The result indicated that the resolution of wind field was more precise after downscaling and contained more sophisticated information related to terrain. Correlation coefficients between the simulation and observation results of wind speed were at a high level and the RMSE (root mean square error) was much smaller. The comparison between simulation and CLDAS showed the similar result. To sum up, the combination of WRFCALMET is an outstanding downscaling method which could effectively improve the temporalspatial resolution of wind forecast data. Meanwhile it might be able to make the result closer to observation. Thus, this method could probably be a reference for wind forecasting in the future.
Aiming at the problem that the resolution of the current wind forecasts is not high and dynamic downscaling method is less applicated to wind forecasting, this paper used the diagnostic wind field function of CALMET model and high spatial resolution terrain data to dynamically downscaling the wind forecast data outputted by WRF model. The main theory is kinematic effect of terrain. After the largescale surface wind field was adjusted by slope flows and terrain blocking effects, the wind field became finer and showed the feature corresponding to terrain. In the experiment part, we took Guangdong Province as study region, using observation data and CLDAS (CMA land data assimilation system) data to examine the simulation result by a case. The result indicated that the resolution of wind field was more precise after downscaling and contained more sophisticated information related to terrain. Correlation coefficients between the simulation and observation results of wind speed were at a high level and the RMSE (root mean square error) was much smaller. The comparison between simulation and CLDAS showed the similar result. To sum up, the combination of WRFCALMET is an outstanding downscaling method which could effectively improve the temporalspatial resolution of wind forecast data. Meanwhile it might be able to make the result closer to observation. Thus, this method could probably be a reference for wind forecasting in the future.
2017, 43(8):1016-1021.
DOI: 10.7519/j.issn.1000-0526.2017.08.012
Abstract:
The performance of mediumrange forecasts is verified and compared for the T639, ECMWF and Japan models from March to May 2017. The results show that T639 and ECMWF models can predict the variation and adjustment of the atmospheric circulation over Asian middle and high latitude areas well. T639 and ECMWF models perform well in predicting the transition of temperature at 850 hPa, as they all have smaller biases for Southern China than for Northern China, but ECMWF model shows a better comprehensive performance than the other one. Taking the sandstorm process seen in 3-7 May as a case, we see that ECMWF model is most effective in mediumrange forecasting of the surface high pressure system which incurred the sandstorm weather process this time.
The performance of mediumrange forecasts is verified and compared for the T639, ECMWF and Japan models from March to May 2017. The results show that T639 and ECMWF models can predict the variation and adjustment of the atmospheric circulation over Asian middle and high latitude areas well. T639 and ECMWF models perform well in predicting the transition of temperature at 850 hPa, as they all have smaller biases for Southern China than for Northern China, but ECMWF model shows a better comprehensive performance than the other one. Taking the sandstorm process seen in 3-7 May as a case, we see that ECMWF model is most effective in mediumrange forecasting of the surface high pressure system which incurred the sandstorm weather process this time.
2017, 43(8):1022-1028.
DOI: 10.7519/j.issn.1000-0526.2017.08.013
Abstract:
The main characteristics of the general atmospheric circulation in May 2017 are as follows. There was one polar vortex center in the Northern Hemisphere, stronger than usual. The 500 hPa geopotential height presented the distribution of a multiwave pattern in the high latitude of Northern Hemisphere. The strength of Western Pacific subtropical high was a little stronger than in normal years, and the south branch through was a little weaker. The monthly mean temperature was 17.1℃, 0.9℃ higher than normal, which ranks the fourth highest since 1961. The monthly mean precipitation amount was 59.4 mm, which is less than normal (69.5 mm) by 14.5%, whereas an extremely strong precipitation event that broke the historical records occurred in Guangzhou on 7 May. Five rainfall processes occurred in Southern China this month, and an extremely hightemperature event happend in Northern China. Severe droughts occurred in the west part of Northeast and North China, and two dust weather events happened in the northern part of China.
The main characteristics of the general atmospheric circulation in May 2017 are as follows. There was one polar vortex center in the Northern Hemisphere, stronger than usual. The 500 hPa geopotential height presented the distribution of a multiwave pattern in the high latitude of Northern Hemisphere. The strength of Western Pacific subtropical high was a little stronger than in normal years, and the south branch through was a little weaker. The monthly mean temperature was 17.1℃, 0.9℃ higher than normal, which ranks the fourth highest since 1961. The monthly mean precipitation amount was 59.4 mm, which is less than normal (69.5 mm) by 14.5%, whereas an extremely strong precipitation event that broke the historical records occurred in Guangzhou on 7 May. Five rainfall processes occurred in Southern China this month, and an extremely hightemperature event happend in Northern China. Severe droughts occurred in the west part of Northeast and North China, and two dust weather events happened in the northern part of China.
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ISSN:1000-0526 CN:11-2282/P