ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 39,Issue 2,2013 Table of Contents
2013, 39(2):129-136.
DOI: 10.7519/j.issn.1000-0526.2013.02.001
Abstract:
Utilizing the NCEP/NCAR reanalysis data, the characteristics of annual south wind over East Asia are investigated. And it is discovered that a key area (22.5°-30°N,105°-110°E) where the south wind prevails all the year is over the southeast of the Tibetan Plateau. The south wind is strong in summer and weak in winter, showing a double peak. A peak occurs in the 15th pentad and the other peak occurs in the 37th pentad. Further research found that there is a good relationship between the south wind on the southeast of Tibetan Plateau and the spring precipitation in southern China. In the 15th pentad, the south wind on the southeast of Tibetan Plateau becomes stronger and expands eastwardly, and then the rainfall in the south of China becomes heavy. The occurring reason for the two peaks of the south wind is different. The south wind peak occurring in the 15th pentad is for a low level cyclone caused by the Tibetan Plateau heating superimposed over the south wind. It causes the south wind stronger, and then South China comes into rainy period. The south wind peak occurring in the 37th pentad is while the South China Sea monsoon broke out, the southwest wind in front of the Bay of Bengal trough intensifies the south wind. And then it brings about the rain over the Yangtze River.
Utilizing the NCEP/NCAR reanalysis data, the characteristics of annual south wind over East Asia are investigated. And it is discovered that a key area (22.5°-30°N,105°-110°E) where the south wind prevails all the year is over the southeast of the Tibetan Plateau. The south wind is strong in summer and weak in winter, showing a double peak. A peak occurs in the 15th pentad and the other peak occurs in the 37th pentad. Further research found that there is a good relationship between the south wind on the southeast of Tibetan Plateau and the spring precipitation in southern China. In the 15th pentad, the south wind on the southeast of Tibetan Plateau becomes stronger and expands eastwardly, and then the rainfall in the south of China becomes heavy. The occurring reason for the two peaks of the south wind is different. The south wind peak occurring in the 15th pentad is for a low level cyclone caused by the Tibetan Plateau heating superimposed over the south wind. It causes the south wind stronger, and then South China comes into rainy period. The south wind peak occurring in the 37th pentad is while the South China Sea monsoon broke out, the southwest wind in front of the Bay of Bengal trough intensifies the south wind. And then it brings about the rain over the Yangtze River.
2013, 39(2):137-145.
DOI: 10.7519/j.issn.1000-0526.2013.02.002
Abstract:
The tropical cyclogenesis features over the Northwestern Pacific simulated by Regional Climate Model Version 3.1 (RegCM3) with 15 km, 30 km, 45 km and 60 km resolutions are compared. It is found that the capability of RegCM3 on tropical cyclogenesis simulation over the Northwestern Pacific is influenced by resolution. The increase of resolution cannot always lead to the improvement of the simulation result. RegCM3 with 30 km resolution has the best capability of simulation on tropical cyclone (TC) genesis number and its variation. The capability of simulation by RegCM3 with 45 km resolution on TC genesis number and its variation is a little worse than RegCM3 with 30 km resolution. RegCM3 with 60 km resolution has the best capability of simulation on TC genesis position. RegCM3 with 15 km resolution has the worst capability of simulation on TC genesis number, TC genesis position and the variation of TC genesis number. The processes of TC genesis simulated by RegCM3 with different resolutions are compared. The results are as follows: The vortices cannot merger because of the small scale of them and the far distance between them. It may result in the decrease of TC genesis number in the simulation of RegCM3 with 15 km resolution. Much dry air involves in wet air before TC genesis and then reduces the water vapor and condensation latent heat release in the mid and lower troposphere. It may also result in the reduction of TC genesis number in the simulation of RegCM3 with 15 km resolution.
The tropical cyclogenesis features over the Northwestern Pacific simulated by Regional Climate Model Version 3.1 (RegCM3) with 15 km, 30 km, 45 km and 60 km resolutions are compared. It is found that the capability of RegCM3 on tropical cyclogenesis simulation over the Northwestern Pacific is influenced by resolution. The increase of resolution cannot always lead to the improvement of the simulation result. RegCM3 with 30 km resolution has the best capability of simulation on tropical cyclone (TC) genesis number and its variation. The capability of simulation by RegCM3 with 45 km resolution on TC genesis number and its variation is a little worse than RegCM3 with 30 km resolution. RegCM3 with 60 km resolution has the best capability of simulation on TC genesis position. RegCM3 with 15 km resolution has the worst capability of simulation on TC genesis number, TC genesis position and the variation of TC genesis number. The processes of TC genesis simulated by RegCM3 with different resolutions are compared. The results are as follows: The vortices cannot merger because of the small scale of them and the far distance between them. It may result in the decrease of TC genesis number in the simulation of RegCM3 with 15 km resolution. Much dry air involves in wet air before TC genesis and then reduces the water vapor and condensation latent heat release in the mid and lower troposphere. It may also result in the reduction of TC genesis number in the simulation of RegCM3 with 15 km resolution.
2013, 39(2):146-155.
DOI: 10.7519/j.issn.1000-0526.2013.02.003
Abstract:
Climatic characteristics and life characteristics of southwest heat low are analyzed through survey from March to May of 1997-2006. In view of synoptic point, it can be divided into four developing stages: primary, mature, maintenance and decay. Based on the station observational data as well as NCEP reanalysis data, the typical southwest heat lows in spring are analyzed and the structural characteristics are revealed. The diagnostic results show that under the control of southwest heat low in spring, pressure decreasing and temperature increasing are significant, and meteorological elements have obviously diurnal variations. Southwest heat low is a shallow warm low, but with deep dry zone. The low zone is characterized by convergence and positive vorticity. This system is of convective instability.
Climatic characteristics and life characteristics of southwest heat low are analyzed through survey from March to May of 1997-2006. In view of synoptic point, it can be divided into four developing stages: primary, mature, maintenance and decay. Based on the station observational data as well as NCEP reanalysis data, the typical southwest heat lows in spring are analyzed and the structural characteristics are revealed. The diagnostic results show that under the control of southwest heat low in spring, pressure decreasing and temperature increasing are significant, and meteorological elements have obviously diurnal variations. Southwest heat low is a shallow warm low, but with deep dry zone. The low zone is characterized by convergence and positive vorticity. This system is of convective instability.
2013, 39(2):156-165.
DOI: 10.7519/j.issn.1000-0526.2013.02.004
Abstract:
Large amount of satellite observations have been used in numerical weather prediction and improving the forecasts greatly. Most works focus on the case study for influence of microwave satellite data on regional numerical weather prediction, while the study for long time is very little. The motivation of this paper is to improve the utilization of microwave satellite data in assimilation system and validating the influence of satellite microwave data on regional numerical prediction. In this paper, the study time of numerical prediction is from 1st to 31st August, 2008. Rapid Update Cycle (RUC) assimilation system of microwave satellite data is designed and constructed, which is based on the regional mesoscale model WRF and WRF 3DVAR system. Therefore the improvement effect of RUC assimilation system on the regional numerical prediction can be analyzed. The results show that, the RUC assimilation scheme is better than single time assimilation scheme. Compared with the former, the RUC assimilation scheme can improve the correlation coefficient of every forecast element to a certain extent. The correlation coefficients of wind field, temperature field and potential height field on the bottom level are improved remarkably. Except the 400 hPa humidity field correlation coefficient is reduced, other various levels of humidity field correlation coefficients are increased, especially in the 700 hPa and 200 hPa, the humidity field increased significantly. RUC assimilation scheme can also reduce the average square errors on the most levels. The forecast effect of microwave satellite data application on land and sea area is consistent with the characteristics; There are slightly differences in detail. On the whole, the improvement on sea area is better than the land surface area, because the surface effect is more complex. Furthermore, in the case of heavy rain and typhoon, the analyses reveal that, RUC assimilation of satellite data scheme can improve the simulation of the precipitation and typhoon track, and can simulate the attribution of heavy rainfall better, especially to improve the strong precipitation center in the simulation, and can also improve the typhoon path prediction to some extent, especially the path trend after the typhoon landing. Overall, it shows that on regional numerical weather prediction, RUC assimilation system can fully use the assimilation of microwave satellite data, and is a useful and necessary method to improve the forecast accuracy.
Large amount of satellite observations have been used in numerical weather prediction and improving the forecasts greatly. Most works focus on the case study for influence of microwave satellite data on regional numerical weather prediction, while the study for long time is very little. The motivation of this paper is to improve the utilization of microwave satellite data in assimilation system and validating the influence of satellite microwave data on regional numerical prediction. In this paper, the study time of numerical prediction is from 1st to 31st August, 2008. Rapid Update Cycle (RUC) assimilation system of microwave satellite data is designed and constructed, which is based on the regional mesoscale model WRF and WRF 3DVAR system. Therefore the improvement effect of RUC assimilation system on the regional numerical prediction can be analyzed. The results show that, the RUC assimilation scheme is better than single time assimilation scheme. Compared with the former, the RUC assimilation scheme can improve the correlation coefficient of every forecast element to a certain extent. The correlation coefficients of wind field, temperature field and potential height field on the bottom level are improved remarkably. Except the 400 hPa humidity field correlation coefficient is reduced, other various levels of humidity field correlation coefficients are increased, especially in the 700 hPa and 200 hPa, the humidity field increased significantly. RUC assimilation scheme can also reduce the average square errors on the most levels. The forecast effect of microwave satellite data application on land and sea area is consistent with the characteristics; There are slightly differences in detail. On the whole, the improvement on sea area is better than the land surface area, because the surface effect is more complex. Furthermore, in the case of heavy rain and typhoon, the analyses reveal that, RUC assimilation of satellite data scheme can improve the simulation of the precipitation and typhoon track, and can simulate the attribution of heavy rainfall better, especially to improve the strong precipitation center in the simulation, and can also improve the typhoon path prediction to some extent, especially the path trend after the typhoon landing. Overall, it shows that on regional numerical weather prediction, RUC assimilation system can fully use the assimilation of microwave satellite data, and is a useful and necessary method to improve the forecast accuracy.
2013, 39(2):166-179.
DOI: 10.7519/j.issn.1000-0526.2013.02.005
Abstract:
By using the GRAPES （Global/Regional Assimilation and Prediction Enhanced System） Single Column Model and the GCSS WG4 Case 3 data, the numerical experiments were conducted to evaluate the cumulus parameterization schemes, such as BMJ, SAS and KFeta. The results show that BMJ and KFeta can simulate the precipitation that consistents with the observation, while SAS is relatively poor. The potential temperature errors of the middle and upper troposphere simulated by BMJ are smaller, but cool bias of the lower troposphere is serious, meanwhile, it has stronger ability to transport water vapor upward which leads to the lower troposphere drier, middle and high troposphere wetter, so that the atmosphere adjusted by BMJ is too stable. KFeta has a trend to be cooler and wetter at lower troposphere and mainly produces cold bias, but the magnitude of lower troposphere is smaller compared to other schemes, at upper levels serious cool bias is caused by excessive overshoot. In order to solve the problem of KFeta excessive overshoot, this paper proposes a new modified scheme in which the vertical velocity equation is modified, and the modified scheme proposed by Anderson et al. also is examined. Numerical experiments show that both modified schemes can reduce high level cold bias effectively; In general, the new modified scheme is more satisfactory.
By using the GRAPES （Global/Regional Assimilation and Prediction Enhanced System） Single Column Model and the GCSS WG4 Case 3 data, the numerical experiments were conducted to evaluate the cumulus parameterization schemes, such as BMJ, SAS and KFeta. The results show that BMJ and KFeta can simulate the precipitation that consistents with the observation, while SAS is relatively poor. The potential temperature errors of the middle and upper troposphere simulated by BMJ are smaller, but cool bias of the lower troposphere is serious, meanwhile, it has stronger ability to transport water vapor upward which leads to the lower troposphere drier, middle and high troposphere wetter, so that the atmosphere adjusted by BMJ is too stable. KFeta has a trend to be cooler and wetter at lower troposphere and mainly produces cold bias, but the magnitude of lower troposphere is smaller compared to other schemes, at upper levels serious cool bias is caused by excessive overshoot. In order to solve the problem of KFeta excessive overshoot, this paper proposes a new modified scheme in which the vertical velocity equation is modified, and the modified scheme proposed by Anderson et al. also is examined. Numerical experiments show that both modified schemes can reduce high level cold bias effectively; In general, the new modified scheme is more satisfactory.
2013, 39(2):180-185.
DOI: 10.7519/j.issn.1000-0526.2013.02.006
Abstract:
There are less classification studies on mesoscale convective system (MCS) at present. Based on the FY 2 geostationary satellite infrared digital cloud images during summer time （June-August） of 2008-2010, the space and time characteristics of MCS were investigated in central eastern China (27°-40°N, 110°-124°E). According to the size, the classification scheme used for this study includes two previously defined categories: meso α scale convective system (MαCS) and meso β scale convective system (MβCS). Then on the basis of the shape, MαCS can be classified into mesoscale convective complex (MCC) and persistent elongated convective system (PECS), and MβCS can be classified into meso β circular convective system (MβCCS) and meso β elongated convective system (MβECS). The results have revealed that there are 208 MCSs in summer during the three years, including 68 MαCSs and 140 MβCSs. Elongated systems accounted for 79.3% of the total MCS sample that indicates the elongated system is the most common type of MCS in summer in this region. On monthly variation view, there are most MCSs in July, the second in August, and the least in June. On the whole, most MCSs move from the west to the east and some from the south to the north or the north to the south. There is also the least path of the east to the west. The peak time of MCS initiation is between 09:00 and 10:00 UTC, and the MCSs reach their maximum size mainly between 10:00 and 11:00 UTC. Most of the system dissipate between 12:00 and 13:00 UTC. The life scale of MCS is about 6.5 hours. MαCSs from the initiation to mature stage need about three to four hours, while from mature to termination phase should last for about four to five hours. And for MβCSs, the development and weakening stages have the same time about two to three hours.
There are less classification studies on mesoscale convective system (MCS) at present. Based on the FY 2 geostationary satellite infrared digital cloud images during summer time （June-August） of 2008-2010, the space and time characteristics of MCS were investigated in central eastern China (27°-40°N, 110°-124°E). According to the size, the classification scheme used for this study includes two previously defined categories: meso α scale convective system (MαCS) and meso β scale convective system (MβCS). Then on the basis of the shape, MαCS can be classified into mesoscale convective complex (MCC) and persistent elongated convective system (PECS), and MβCS can be classified into meso β circular convective system (MβCCS) and meso β elongated convective system (MβECS). The results have revealed that there are 208 MCSs in summer during the three years, including 68 MαCSs and 140 MβCSs. Elongated systems accounted for 79.3% of the total MCS sample that indicates the elongated system is the most common type of MCS in summer in this region. On monthly variation view, there are most MCSs in July, the second in August, and the least in June. On the whole, most MCSs move from the west to the east and some from the south to the north or the north to the south. There is also the least path of the east to the west. The peak time of MCS initiation is between 09:00 and 10:00 UTC, and the MCSs reach their maximum size mainly between 10:00 and 11:00 UTC. Most of the system dissipate between 12:00 and 13:00 UTC. The life scale of MCS is about 6.5 hours. MαCSs from the initiation to mature stage need about three to four hours, while from mature to termination phase should last for about four to five hours. And for MβCSs, the development and weakening stages have the same time about two to three hours.
2013, 39(2):186-193.
DOI: 10.7519/j.issn.1000-0526.2013.02.007
Abstract:
Sea land breeze is a mesoscale weather system due to the different heating between sea and land, with important influence in air quality, weather and climate of coastal areas. This paper describes the study of sea land breeze on observation, theory and numerical simulation, and in addition the characteristics of sea land breeze in three coastal areas in China. Sea land breeze is a common phenomenon in coastal area. It has been observed in mid latitudes, also high and low latitudes by field experiments since the 1960s. Theoretical studies can be divided into the analytical and the numerical studies. The analytical studies began from analyzing the force balance in the 1920s, and went into thermodynamic equilibrium and nonlinear dynamic characteristics of sea land breeze, combined with numerical simulation at last. The numerical studies have gone into practical application. Studies have shown that sea breeze begins in the late morning, ends in different time in regions. Land breeze begins in midnight, ends in the morning. Sea land breeze may cause the accumulation of pollutants, making the air quality worse. It should be paid attention.
Sea land breeze is a mesoscale weather system due to the different heating between sea and land, with important influence in air quality, weather and climate of coastal areas. This paper describes the study of sea land breeze on observation, theory and numerical simulation, and in addition the characteristics of sea land breeze in three coastal areas in China. Sea land breeze is a common phenomenon in coastal area. It has been observed in mid latitudes, also high and low latitudes by field experiments since the 1960s. Theoretical studies can be divided into the analytical and the numerical studies. The analytical studies began from analyzing the force balance in the 1920s, and went into thermodynamic equilibrium and nonlinear dynamic characteristics of sea land breeze, combined with numerical simulation at last. The numerical studies have gone into practical application. Studies have shown that sea breeze begins in the late morning, ends in different time in regions. Land breeze begins in midnight, ends in the morning. Sea land breeze may cause the accumulation of pollutants, making the air quality worse. It should be paid attention.
2013, 39(2):194-202.
DOI: 10.7519/j.issn.1000-0526.2013.02.008
Abstract:
The data of numerical simulation are used to analyze the microphysical structures and the precipitation forming mechanisms for the spiral rain bands of typhoon. Two precipitation centers of different times are chosen as the cases being studied in the paper. The main microphysical characters of the spiral rain bands are as follows. The heterogeneous nucleation is very intense at altitudes 9-13 km, the ice crystal conversion ratio is several times higher than that in typhoon eyewall. However, the deposition processes of ice crystal and snow are very weak. The spiral rain bands are mainly produced by melting graupels (pgmlt). The graupel grows mainly through accretion with snow microphysical processes (dgacs).The peak value of the processes “dgacs” stays at altitude 8 km with big vertical vector. Compared with the stratiform clouds in the northern China, the deposition and accretion processes are very fierce in the typhoon spiral storms due to high moisture content. The profiles of the cloud water condensation processes in the spiral rain bands show a double peak type. The biggest peak stays at altitude 8 km in the cold cloud, and the secondary peak stays at altitudes 0.5-1.5 km in warm clouds.
The data of numerical simulation are used to analyze the microphysical structures and the precipitation forming mechanisms for the spiral rain bands of typhoon. Two precipitation centers of different times are chosen as the cases being studied in the paper. The main microphysical characters of the spiral rain bands are as follows. The heterogeneous nucleation is very intense at altitudes 9-13 km, the ice crystal conversion ratio is several times higher than that in typhoon eyewall. However, the deposition processes of ice crystal and snow are very weak. The spiral rain bands are mainly produced by melting graupels (pgmlt). The graupel grows mainly through accretion with snow microphysical processes (dgacs).The peak value of the processes “dgacs” stays at altitude 8 km with big vertical vector. Compared with the stratiform clouds in the northern China, the deposition and accretion processes are very fierce in the typhoon spiral storms due to high moisture content. The profiles of the cloud water condensation processes in the spiral rain bands show a double peak type. The biggest peak stays at altitude 8 km in the cold cloud, and the secondary peak stays at altitudes 0.5-1.5 km in warm clouds.
2013, 39(2):203-209.
DOI: 10.7519/j.issn.1000-0526.2013.02.009
Abstract:
The 3 h precipitation estimates at the 18 stations in central Yunnan were made by using the data of TBB, TBB temperature gradient, vapour cloud, total cloud cover, cloud classification, radar basic reflectivity and AWS (automatic weather station) rainfall from May to October of 2008-2010, and the analysis was made by using BP neural network modeling forecast model, traditional Z I relations and cloud classification Z I relations. Results show that the false prediction ratio and deviation have been improved by the BP neural network modeling forecast model, and the comparative study is a test on precipitation forecast by the integrated data of radar and satellite.
The 3 h precipitation estimates at the 18 stations in central Yunnan were made by using the data of TBB, TBB temperature gradient, vapour cloud, total cloud cover, cloud classification, radar basic reflectivity and AWS (automatic weather station) rainfall from May to October of 2008-2010, and the analysis was made by using BP neural network modeling forecast model, traditional Z I relations and cloud classification Z I relations. Results show that the false prediction ratio and deviation have been improved by the BP neural network modeling forecast model, and the comparative study is a test on precipitation forecast by the integrated data of radar and satellite.
2013, 39(2):210-217.
DOI: 10.7519/j.issn.1000-0526.2013.02.010
Abstract:
Using conventional observation data and NCEP reanalysis data, the causes for unstable conditions of a strong convective weather under the background of the cold vortex in Shenyang City of Liaoning Province were analyzed by studying four kinds of CAPE and the relationship of CAPE field and surface meteorological factors. The results show that the water vapor latent heat is the main part of the unstable energy. Under the background of the cold vortex, the low level warm and moist advection, and high level cold and dry advection were advantageous to unstable energy accumulation, which leads to the occurrence of strong convective weather. The convective temperature CAPE can refect the unstable energy required by the afternoon strong convective occurrence, and it has a certain significance to the forecast of strong convective weather.
Using conventional observation data and NCEP reanalysis data, the causes for unstable conditions of a strong convective weather under the background of the cold vortex in Shenyang City of Liaoning Province were analyzed by studying four kinds of CAPE and the relationship of CAPE field and surface meteorological factors. The results show that the water vapor latent heat is the main part of the unstable energy. Under the background of the cold vortex, the low level warm and moist advection, and high level cold and dry advection were advantageous to unstable energy accumulation, which leads to the occurrence of strong convective weather. The convective temperature CAPE can refect the unstable energy required by the afternoon strong convective occurrence, and it has a certain significance to the forecast of strong convective weather.
2013, 39(2):218-225.
DOI: 10.7519/j.issn.1000-0526.2013.02.011
Abstract:
Based on the NCEP 1°×1° reanalyzed data, the circulation situation and physics fields of two heavy snowfall events in Zhejiang during the winter of 2010 were analyzed. The results have shown that: (1) The two heavy snowfalls are caused by the intersection of north cold air and southwest warm moist flow. The duration of snowfall is short when the cold air is strong, because the front zone moves southward quickly. The heavy snowfall occurred in the convergence area of wind velocity of shear lines in the middle and low levels. (2) The cold air of moderate intensity makes the cold layer and the stationary front exist for a long time. This is an important condition for long duration snowfall. The heavy snowfall occurred in the front of low level jet on the left side. (3) There is strong convergenc of vapor flux over snowfall region. The relationships between the variation of large value area of vapor flux and the snowfall process are significant. (4) It is the favorable dynamic condition for heavy snowfall that there are convergence in the lower level and divergence in the upper level. The intensity of snowfall increases with the intensity of lower level convergence and upper level divergence.
Based on the NCEP 1°×1° reanalyzed data, the circulation situation and physics fields of two heavy snowfall events in Zhejiang during the winter of 2010 were analyzed. The results have shown that: (1) The two heavy snowfalls are caused by the intersection of north cold air and southwest warm moist flow. The duration of snowfall is short when the cold air is strong, because the front zone moves southward quickly. The heavy snowfall occurred in the convergence area of wind velocity of shear lines in the middle and low levels. (2) The cold air of moderate intensity makes the cold layer and the stationary front exist for a long time. This is an important condition for long duration snowfall. The heavy snowfall occurred in the front of low level jet on the left side. (3) There is strong convergenc of vapor flux over snowfall region. The relationships between the variation of large value area of vapor flux and the snowfall process are significant. (4) It is the favorable dynamic condition for heavy snowfall that there are convergence in the lower level and divergence in the upper level. The intensity of snowfall increases with the intensity of lower level convergence and upper level divergence.
2013, 39(2):226-233.
DOI: 10.7519/j.issn.1000-0526.2013.02.012
Abstract:
After analyzing the strong randomness of the observed wind speed during January, April, July and October 2011 both in Hebei and Inner Mongolia, a nowcasting model of wind speed based on mean generation function (MGF), gray relational analysis and multivariate linear regression is presented, which is used to predict the future 0-4 h wind speed every 15 min. Taking the cycle of wind speed and the closed cycles between the predictors and predictand, the parameters of the nowcasting model based on MGF are determined. Based on the observed data from the wind tower in Hebei and Inner Mongolia, the applicability of the nowcasting model in wind speed is elaborated. The results show that the forecast accuracy of the nowcasting model based on MGF is improved significantly compared with the performance of the traditional autoregressive moving average (ARMA) model. Therefore, the model itself has a high value of practical application.
After analyzing the strong randomness of the observed wind speed during January, April, July and October 2011 both in Hebei and Inner Mongolia, a nowcasting model of wind speed based on mean generation function (MGF), gray relational analysis and multivariate linear regression is presented, which is used to predict the future 0-4 h wind speed every 15 min. Taking the cycle of wind speed and the closed cycles between the predictors and predictand, the parameters of the nowcasting model based on MGF are determined. Based on the observed data from the wind tower in Hebei and Inner Mongolia, the applicability of the nowcasting model in wind speed is elaborated. The results show that the forecast accuracy of the nowcasting model based on MGF is improved significantly compared with the performance of the traditional autoregressive moving average (ARMA) model. Therefore, the model itself has a high value of practical application.
ZHENG Yongguang
,
LIN Yinjing
,
ZHU Wenjian
,
LAN Yu
,
TANG Wenyuan
,
ZHANG Xiaoling
,
MAO Dongyan
,
ZHOU Qingliang
,
ZHANG Zhigang
2013, 39(2):234-240.
DOI: 10.7519/j.issn.1000-0526.2013.02.013
Abstract:
The convective weather forecasting is based on its monitoring. The Severe Weather Prediction Centre of National Meteorological Centre constructed an operational system of severe convective weather comprehensive monitoring based on the multi source data, including conventional observation data, automatic weather station (AWS) data, lightning data, radar data and satellite data. The convective weather monitoring includes cumuli, high temperature at surface, thunderstorm, cloud ground lightning, hail, tornadoes, high winds, thunderstorm high winds, short duration heavy rain, radar reflectivity, convective storms (based on radar data), deep convective clouds, and mesoscale convective systems (MCS) based on the IR satellite data. The system gives the different distributions of different convective weather in different periods. The techniques used in the system include: The quality control of AWS data, the extracting information and statistical technique of convective weather, (Cartesian Tracking Radar Echoes by Correlation, CTREC), (Thunderstorm Identification Tracking Analysis and Nowcasting, TITAN), identification of deep convective clouds, identification and tracking of MCS, and lightning density monitoring. The system of monitoring convective weather automatically runs regularly, fully compatible with the MICAPS platform. The monitoring system at National Meteorological Centre has played an important role in real time convective weather forecasting.
The convective weather forecasting is based on its monitoring. The Severe Weather Prediction Centre of National Meteorological Centre constructed an operational system of severe convective weather comprehensive monitoring based on the multi source data, including conventional observation data, automatic weather station (AWS) data, lightning data, radar data and satellite data. The convective weather monitoring includes cumuli, high temperature at surface, thunderstorm, cloud ground lightning, hail, tornadoes, high winds, thunderstorm high winds, short duration heavy rain, radar reflectivity, convective storms (based on radar data), deep convective clouds, and mesoscale convective systems (MCS) based on the IR satellite data. The system gives the different distributions of different convective weather in different periods. The techniques used in the system include: The quality control of AWS data, the extracting information and statistical technique of convective weather, (Cartesian Tracking Radar Echoes by Correlation, CTREC), (Thunderstorm Identification Tracking Analysis and Nowcasting, TITAN), identification of deep convective clouds, identification and tracking of MCS, and lightning density monitoring. The system of monitoring convective weather automatically runs regularly, fully compatible with the MICAPS platform. The monitoring system at National Meteorological Centre has played an important role in real time convective weather forecasting.
2013, 39(2):241-248.
DOI: 10.7519/j.issn.1000-0526.2013.02.014
Abstract:
The CINRAD SA Doppler weather radar has the ability of detecting forest fires, however, the spatial scales of fire echoes are far less than rainfall’s, therefore it is hard to distinguish fire echoes from others manually. In order to make the fire detection and recognition possible by radar, a new method of fire clutter filtering was proposed and discussed in detail which reserves the fire echoes while removes the clutter echoes efficiently. Meanwhile, another new method of precipitation echo filtering was developed， which used the numbers of non zero velocity gates and reflectivity gates. Based on that, an automatic fire detection system was developed, which can recognize and identify fire echoes out of clutter and precipitation echoes automatically. During one and a half year’s real time test, the system detected nearly 100 of fire events in region of Wenzhou City, most of them confirmed by forest fire management departments. The accuracy of fire detection in terms of the probability of detection (POD), the false alarm ratio (FAR) and the critical success index (CSI) statistics is 79%, 4% and 76% respectively. Within the valid radius approximately 110 km away from radar station, the system can detect, position and alarm forest (wildland) fires automatically, as well as providing fire monitoring every 6 min continuously. It could be a brand new approach of forest fire detection, which can provide timely and accurate fire information to decision makers of forest fire management.
The CINRAD SA Doppler weather radar has the ability of detecting forest fires, however, the spatial scales of fire echoes are far less than rainfall’s, therefore it is hard to distinguish fire echoes from others manually. In order to make the fire detection and recognition possible by radar, a new method of fire clutter filtering was proposed and discussed in detail which reserves the fire echoes while removes the clutter echoes efficiently. Meanwhile, another new method of precipitation echo filtering was developed， which used the numbers of non zero velocity gates and reflectivity gates. Based on that, an automatic fire detection system was developed, which can recognize and identify fire echoes out of clutter and precipitation echoes automatically. During one and a half year’s real time test, the system detected nearly 100 of fire events in region of Wenzhou City, most of them confirmed by forest fire management departments. The accuracy of fire detection in terms of the probability of detection (POD), the false alarm ratio (FAR) and the critical success index (CSI) statistics is 79%, 4% and 76% respectively. Within the valid radius approximately 110 km away from radar station, the system can detect, position and alarm forest (wildland) fires automatically, as well as providing fire monitoring every 6 min continuously. It could be a brand new approach of forest fire detection, which can provide timely and accurate fire information to decision makers of forest fire management.
2013, 39(2):249-252.
DOI: 10.7519/j.issn.1000-0526.2013.02.015
Abstract:
This paper mainly aims at wind speed calibration by standard wind speed measurements and its influence factor analysis. First, we find out the main influence factors, and then eliminate them, thus make the calibration results more real and reliable. The calculation formula in JJG431 86 verification regulation is used for argument analysis, and the examples are used for verification. The results show that laboratory temperature is the great factor of influence on the standard wind speed, thus it must be temperature controlling. In the calibration of an anemometer, the temperature change of the laboratory should not be more than 3℃. The air density correction coefficient in the table is too sketchy, and the influence values on standard wind speed can not be ignored, therefore we should use the formula to calculate directly and eliminate errors.
This paper mainly aims at wind speed calibration by standard wind speed measurements and its influence factor analysis. First, we find out the main influence factors, and then eliminate them, thus make the calibration results more real and reliable. The calculation formula in JJG431 86 verification regulation is used for argument analysis, and the examples are used for verification. The results show that laboratory temperature is the great factor of influence on the standard wind speed, thus it must be temperature controlling. In the calibration of an anemometer, the temperature change of the laboratory should not be more than 3℃. The air density correction coefficient in the table is too sketchy, and the influence values on standard wind speed can not be ignored, therefore we should use the formula to calculate directly and eliminate errors.
2013, 39(2):253-258.
DOI: 10.7519/j.issn.1000-0526.2013.02.016
Abstract:
In order to improve the ability to use the products of T639, some synoptic verification on its medium range forecasting in autumn 2012 are made in comparison with the NWP of ECMWF and Japan models. The results show that the three models have good performances in the aspect of predicting the large scale circulation evolution and adjustment in Asian middle and high latitude areas. As a whole, the ECMWF model is better in forecasting most weather systems compared with the T639 and Japan models. Taking tropical storm No.1223 (Son Tinh) as an example, it is found that the ECMWF model gets the most reliable results, whereas T639 and JAPAN models have large deviations in forecasting the turning track of Son Tinh.
In order to improve the ability to use the products of T639, some synoptic verification on its medium range forecasting in autumn 2012 are made in comparison with the NWP of ECMWF and Japan models. The results show that the three models have good performances in the aspect of predicting the large scale circulation evolution and adjustment in Asian middle and high latitude areas. As a whole, the ECMWF model is better in forecasting most weather systems compared with the T639 and Japan models. Taking tropical storm No.1223 (Son Tinh) as an example, it is found that the ECMWF model gets the most reliable results, whereas T639 and JAPAN models have large deviations in forecasting the turning track of Son Tinh.
2013, 39(2):259-264.
DOI: 10.7519/j.issn.1000-0526.2013.02.017
Abstract:
The following are the main characteristics of the general atmospheric circulation in November 2012. There was one polar vortex center in the Northern Hemisphere, which was located in the northern Canada. The circulation presents meridional patterns in middle high latitudes. The average south baranch trough is located at 90°E nearby and eastward shift is frequently. The subtropical high is stronger than normal years’. The monthly mean precipitation is 31.7 mm, and 68.6% more than normal (18.8 mm). The monthly mean temperature is 2.0℃, and 0.9℃ lower than normal (2.9℃). There were four cold air processes nationwide and three rainfall processes in the month. The northern areas of China suffered from a wide range of heavy snowfall and chilling weather. Most areas of North China usher in the first snowfall this year, in Beijing, Tianjin, Hebei, Inner Mongolia and other places have suffered from extreme precipitation. Meanwhile, a large scale persisting rainy weather happened in the southern China.
The following are the main characteristics of the general atmospheric circulation in November 2012. There was one polar vortex center in the Northern Hemisphere, which was located in the northern Canada. The circulation presents meridional patterns in middle high latitudes. The average south baranch trough is located at 90°E nearby and eastward shift is frequently. The subtropical high is stronger than normal years’. The monthly mean precipitation is 31.7 mm, and 68.6% more than normal (18.8 mm). The monthly mean temperature is 2.0℃, and 0.9℃ lower than normal (2.9℃). There were four cold air processes nationwide and three rainfall processes in the month. The northern areas of China suffered from a wide range of heavy snowfall and chilling weather. Most areas of North China usher in the first snowfall this year, in Beijing, Tianjin, Hebei, Inner Mongolia and other places have suffered from extreme precipitation. Meanwhile, a large scale persisting rainy weather happened in the southern China.
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ISSN:1000-0526 CN:11-2282/P