ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 39,Issue 5,2013 Table of Contents
2013, 39(5):537-542.
DOI: 10.7519/j.issn.1000-0526.2013.05.001
Abstract:
The global atmospheric variables of observations can be decomposed physically into four components, namely zonal mean symmetric climate, asymmetric climate, zonal mean instantaneous symmetric anomaly and instantaneous asymmetric anomaly. Based on the latest ECMWF global atmospheric reanalysis ERA Interim data with 0.75°×0.75° resolution, the physical decomposition method of atmospheric winds and its application in the regional rainstorms are introduced. The result showed that the physical decomposition of ERA Interim data can better reflect the location of regional rainstorms and the relations between wind and rain. For example, the rainfall band is located along the convergence line of anomalous airflow in the lower troposphere and the anomalous airflows on both sides of a stable rainstorm band present a confrontational convergent pattern.
The global atmospheric variables of observations can be decomposed physically into four components, namely zonal mean symmetric climate, asymmetric climate, zonal mean instantaneous symmetric anomaly and instantaneous asymmetric anomaly. Based on the latest ECMWF global atmospheric reanalysis ERA Interim data with 0.75°×0.75° resolution, the physical decomposition method of atmospheric winds and its application in the regional rainstorms are introduced. The result showed that the physical decomposition of ERA Interim data can better reflect the location of regional rainstorms and the relations between wind and rain. For example, the rainfall band is located along the convergence line of anomalous airflow in the lower troposphere and the anomalous airflows on both sides of a stable rainstorm band present a confrontational convergent pattern.
2013, 39(5):543-555.
DOI: 10.7519/j.issn.1000-0526.2013.05.002
Abstract:
Based on the CMA T213 global ensemble forecast system, two different schemes of model stochastic perturbation are designed in this paper. The first scheme imposes the perturbation on the total tendency of physical process and dynamical process (STPS). The second scheme perturbates the parameterized physical process (SPPS). We separately introduce the two schemes into model to perform numerical tests. Then we evaluate the performance of ensemble forecast, analyze the characteristics of stochastic perturbation and understand the perturbation propagation mechanism. The result shows that both schemes of stochastic perturbation significantly influence the T213 model forecast variables. Perturbation values in vertical direction and horizontal direction increase along with the increase of integration time, especially in the region of middle and high latitudes. The difference between the two schemes is that the forecast variable of STPS scheme is more disturbed than SPPS scheme at the total stage of integration. The forecast variable of SPPS is more reasonable compared with STPS. The center of SPPS maximum perturbation value propagates from low latitudes to high latitudes with the increase of integration time. The total perturbation energy has the characteristics of propagating from small scale to large scale. Compared with STPS, SPPS ensemble forecast has advantages on the aspects of ensemble forecast dispersion and root mean square error of ensemble at the late stage of integration, improving the accuracy in forecasting the geopotential height field and wind field, and the techniques in forecasting precipitation. Finally， this paper proves that SPPS scheme can more reasonably reflect the uncertainty of the model physical process and it enhances the forecast ability of the ensemble forecast system at a certain degree.
Based on the CMA T213 global ensemble forecast system, two different schemes of model stochastic perturbation are designed in this paper. The first scheme imposes the perturbation on the total tendency of physical process and dynamical process (STPS). The second scheme perturbates the parameterized physical process (SPPS). We separately introduce the two schemes into model to perform numerical tests. Then we evaluate the performance of ensemble forecast, analyze the characteristics of stochastic perturbation and understand the perturbation propagation mechanism. The result shows that both schemes of stochastic perturbation significantly influence the T213 model forecast variables. Perturbation values in vertical direction and horizontal direction increase along with the increase of integration time, especially in the region of middle and high latitudes. The difference between the two schemes is that the forecast variable of STPS scheme is more disturbed than SPPS scheme at the total stage of integration. The forecast variable of SPPS is more reasonable compared with STPS. The center of SPPS maximum perturbation value propagates from low latitudes to high latitudes with the increase of integration time. The total perturbation energy has the characteristics of propagating from small scale to large scale. Compared with STPS, SPPS ensemble forecast has advantages on the aspects of ensemble forecast dispersion and root mean square error of ensemble at the late stage of integration, improving the accuracy in forecasting the geopotential height field and wind field, and the techniques in forecasting precipitation. Finally， this paper proves that SPPS scheme can more reasonably reflect the uncertainty of the model physical process and it enhances the forecast ability of the ensemble forecast system at a certain degree.
2013, 39(5):556-566.
DOI: 10.7519/j.issn.1000-0526.2013.05.003
Abstract:
Using multiple intensified observation data and NCEP daily reanalysis data, the development mechanism of a nonlinear mesoscale convective system (MCS) that caused a short time severe rainfall in Xianning City on 14 July 2010 is analyzed. The results show that the organization of nonlinear MCS is poor during 13:00-18:00 BT 14 July 2010. The strong convective cells are disorderly distributed in big stratiform echoes, keeping the quasi stationary front staying over Xianning about 5 h, and thus leading to the short time severe precipitation in Xianning. The nonlinear MCS generates in a surface vortex circulation near Meiyu front, and the convections are triggered primarily by upper cold air and lifting motion in front of the front. The favorite ambient conditions for the nonlinear MCS to maintain and develop are the convergence and concentration of unstable warm moist airflow on the southern side of the shear line over the middle reaches of Yangtze River, the mesosacle convergence of surface local airflow and the favorable wind shear of boundary layer. In general, the high spatial temporal resolution observation data can be well applied in analyzing the MCS evolution process.
Using multiple intensified observation data and NCEP daily reanalysis data, the development mechanism of a nonlinear mesoscale convective system (MCS) that caused a short time severe rainfall in Xianning City on 14 July 2010 is analyzed. The results show that the organization of nonlinear MCS is poor during 13:00-18:00 BT 14 July 2010. The strong convective cells are disorderly distributed in big stratiform echoes, keeping the quasi stationary front staying over Xianning about 5 h, and thus leading to the short time severe precipitation in Xianning. The nonlinear MCS generates in a surface vortex circulation near Meiyu front, and the convections are triggered primarily by upper cold air and lifting motion in front of the front. The favorite ambient conditions for the nonlinear MCS to maintain and develop are the convergence and concentration of unstable warm moist airflow on the southern side of the shear line over the middle reaches of Yangtze River, the mesosacle convergence of surface local airflow and the favorable wind shear of boundary layer. In general, the high spatial temporal resolution observation data can be well applied in analyzing the MCS evolution process.
2013, 39(5):567-576.
DOI: 10.7519/j.issn.1000-0526.2013.05.004
Abstract:
Using conventional observations and data from satellite and Doppler weather radar, etc., two extremely heavy rain events that happened in Sichuan Basin in the early autumn of 2012 are compared and analyzed regarding synoptical conditions, convective activities and forecast verification. The emphasis is put on the MCS activities and ambient conditions which induced the convective torrential rains in warm sector directly. The two rain events shared some features in common such as the strong and stable West Pacific subtropical high, the active plateau trough, and the genesis of southwest vortex in the low level in Sichuan Basin, but due to the different positions of the subtropical high ridge line and the different short wave disturbing intensity of westerlies, remarkable differences of the moving speed of southwest vortex and rainfall locations were induced. The MCS in the first rain event was stable and moved relatively slowly, but during the second rain event a MCC emerged with highly intensive precipitation, moving fast. The analysis result shows that there was a deep moist layer in the first rain process which was very favorable for the heavy precipitation, but a notable dry layer in the mid high level during the second rain event which created much stronger instability, good for the forming of severe convective storms. In a word, the two rainstorm processes have clear convections in warm sector and instability, and the position of Low Level Jet is more important for deciding the initiation of the convection. Finally, the forecast verification indicates that, the numerical model has obvious bias in presenting of convection in warm sector, but by the guidance of detailed mesoscale synoptical conceptual model, some correction can be made by subjective forecasting, improving the predictability of convection in the warm sector.
Using conventional observations and data from satellite and Doppler weather radar, etc., two extremely heavy rain events that happened in Sichuan Basin in the early autumn of 2012 are compared and analyzed regarding synoptical conditions, convective activities and forecast verification. The emphasis is put on the MCS activities and ambient conditions which induced the convective torrential rains in warm sector directly. The two rain events shared some features in common such as the strong and stable West Pacific subtropical high, the active plateau trough, and the genesis of southwest vortex in the low level in Sichuan Basin, but due to the different positions of the subtropical high ridge line and the different short wave disturbing intensity of westerlies, remarkable differences of the moving speed of southwest vortex and rainfall locations were induced. The MCS in the first rain event was stable and moved relatively slowly, but during the second rain event a MCC emerged with highly intensive precipitation, moving fast. The analysis result shows that there was a deep moist layer in the first rain process which was very favorable for the heavy precipitation, but a notable dry layer in the mid high level during the second rain event which created much stronger instability, good for the forming of severe convective storms. In a word, the two rainstorm processes have clear convections in warm sector and instability, and the position of Low Level Jet is more important for deciding the initiation of the convection. Finally, the forecast verification indicates that, the numerical model has obvious bias in presenting of convection in warm sector, but by the guidance of detailed mesoscale synoptical conceptual model, some correction can be made by subjective forecasting, improving the predictability of convection in the warm sector.
2013, 39(5):577-584.
DOI: 10.7519/j.issn.1000-0526.2013.05.005
Abstract:
Based on the meteorological data recorded from 1971 to 2006, and the precipitation data during 1999-2009 in Jiangsu Province, Zhejiang Province and Shanghai, temporal and spatial distributions of severe convective weather are analyzed. The composite conceptual pattern of regional hail and rainfall events above 100 mm·(3 h)-1 caused by the North China cold vortex is also analyzed. Several physical parameters of the two kinds of convective weathers are calculated as well. Results show that the frequency of hail storm has a decreasing trend in the 30 years from 1971 to 2001 but a slight increase trend in the later 5 years. Hail and heavy rainfall events take place most in north of Jiangsu Province. The cold vortex is much stronger and lies further north in hailstorm than that in convective rainstorm weather. The high level jet lies north in torrential rain weather, and in hailstorm it lies right underneath the hail hit area. Moist tongue is often found at low level in the both weather conditions and dry tongue lies right above the wet area in high level during hailstorm while in torrential rain it is not. Statistics indicate that the 0℃ height, the temperature difference between 500 hPa and 850 hPa, K index, precipitable water, and high level wind shear,etc.can distinguish the category of the rainstorm and hailstorm well and the differences between them are -1700 m, 7℃, 8℃, -37 mm and 1.63×10-3s-1 respectively.
Based on the meteorological data recorded from 1971 to 2006, and the precipitation data during 1999-2009 in Jiangsu Province, Zhejiang Province and Shanghai, temporal and spatial distributions of severe convective weather are analyzed. The composite conceptual pattern of regional hail and rainfall events above 100 mm·(3 h)-1 caused by the North China cold vortex is also analyzed. Several physical parameters of the two kinds of convective weathers are calculated as well. Results show that the frequency of hail storm has a decreasing trend in the 30 years from 1971 to 2001 but a slight increase trend in the later 5 years. Hail and heavy rainfall events take place most in north of Jiangsu Province. The cold vortex is much stronger and lies further north in hailstorm than that in convective rainstorm weather. The high level jet lies north in torrential rain weather, and in hailstorm it lies right underneath the hail hit area. Moist tongue is often found at low level in the both weather conditions and dry tongue lies right above the wet area in high level during hailstorm while in torrential rain it is not. Statistics indicate that the 0℃ height, the temperature difference between 500 hPa and 850 hPa, K index, precipitable water, and high level wind shear,etc.can distinguish the category of the rainstorm and hailstorm well and the differences between them are -1700 m, 7℃, 8℃, -37 mm and 1.63×10-3s-1 respectively.
2013, 39(5):585-591.
DOI: 10.7519/j.issn.1000-0526.2013.05.006
Abstract:
Based on the conventional observation data from 542 stations in China in 1960-2008, evaluation indicators are selected from the aspect of disaster causes and the risk assessment of meteorological index system is built. The risks of low temperature, rain/snow and freezing disaster are assessed and zoned in China by using the comprehensive hazardous index which is built on the assessment philosophy of different intensity frequencies. The result shows that most parts of China are in the low risk regions. The high risk areas are mainly located in Heilongjiang, Jilin, the east of Liaoning, the east of Inner Mongolia, the north of Xinjiang, the south of Qinghai, the northeast of Tibet, and the south of Gansu. Much of South China is located in the areas with the lowest risks, and some relatively high risk areas in South China are found in central and southern part of Sichuan, the northeast of Yunnan, the west of Guizhou, the east of Hunan, the south of Anhui, the north of Jiangxi, and the north of Henan. The distribution of the high risk areas is closely related to the topography and latitudes of these regions.
Based on the conventional observation data from 542 stations in China in 1960-2008, evaluation indicators are selected from the aspect of disaster causes and the risk assessment of meteorological index system is built. The risks of low temperature, rain/snow and freezing disaster are assessed and zoned in China by using the comprehensive hazardous index which is built on the assessment philosophy of different intensity frequencies. The result shows that most parts of China are in the low risk regions. The high risk areas are mainly located in Heilongjiang, Jilin, the east of Liaoning, the east of Inner Mongolia, the north of Xinjiang, the south of Qinghai, the northeast of Tibet, and the south of Gansu. Much of South China is located in the areas with the lowest risks, and some relatively high risk areas in South China are found in central and southern part of Sichuan, the northeast of Yunnan, the west of Guizhou, the east of Hunan, the south of Anhui, the north of Jiangxi, and the north of Henan. The distribution of the high risk areas is closely related to the topography and latitudes of these regions.
2013, 39(5):592-599.
DOI: 10.7519/j.issn.1000-0526.2013.05.007
Abstract:
Daily meteorological observation data of 17 stations and yearly statistical data of Chongqing were employed to diagnose the influence of urbanization on the spatial distribution of rainfall over Chongqing metropolitan region by adopting the method of spatial standardization of precipitation. The results showed that the period of 1970-2009 was divided into two stages by the year 1997, that is the slow developing stage of urbanization and the quick developing stage of urbanization, and spatial difference of annual rainfall over the metropolitan region has relations with the acceleration of urbanization. Comparing the difference of the two stages, it is found that with the fast development of urbanization, the annual rainfall amount, rainfall intensity and the frequency of moderate and torrential rains has got increased, showing the distinct feature of urban “rain island”. In addition, as far as seasonal difference is concerned, urbanization has exerted different influence on spatial distribution of precipitation over the metropolitan region in Chongqing in summer and winter. The urban areas and the suburb in the north of the city see more rains over summer time while the increase of precipitation happens in the urban areas and its suburb in the south in winter. Such spatial distribution of rainfall in different seasons is possibly caused by the interaction between seasonal prevailing wind and the temperature gradient of urban areas and suburbs so that the rainfall in the urban and its downwind areas has increased significantly， especially in the downwind areas.
Daily meteorological observation data of 17 stations and yearly statistical data of Chongqing were employed to diagnose the influence of urbanization on the spatial distribution of rainfall over Chongqing metropolitan region by adopting the method of spatial standardization of precipitation. The results showed that the period of 1970-2009 was divided into two stages by the year 1997, that is the slow developing stage of urbanization and the quick developing stage of urbanization, and spatial difference of annual rainfall over the metropolitan region has relations with the acceleration of urbanization. Comparing the difference of the two stages, it is found that with the fast development of urbanization, the annual rainfall amount, rainfall intensity and the frequency of moderate and torrential rains has got increased, showing the distinct feature of urban “rain island”. In addition, as far as seasonal difference is concerned, urbanization has exerted different influence on spatial distribution of precipitation over the metropolitan region in Chongqing in summer and winter. The urban areas and the suburb in the north of the city see more rains over summer time while the increase of precipitation happens in the urban areas and its suburb in the south in winter. Such spatial distribution of rainfall in different seasons is possibly caused by the interaction between seasonal prevailing wind and the temperature gradient of urban areas and suburbs so that the rainfall in the urban and its downwind areas has increased significantly， especially in the downwind areas.
2013, 39(5):600-607.
DOI: 10.7519/j.issn.1000-0526.2013.05.008
Abstract:
Based on the Weighted Average Precipitation (WAP), an improvement study on drought index was carried out in two aspects. After determining the two parameters of the WAP index and removing regional and seasonal differences, an improved WAP drought index named IWAP index was developed. Then, comparison analysis between IWAP index and Ci index was done. The results show that: IWAP index has a good correlation with Ci index in most of China especially in mid eastern China with correlation coefficients above 0.7 in most of Central China, most of Guizhou, southern Yunnan and southern Xinjiang. In identifying regional meteorological drought events, IWAP index also shows good consistency with Ci index on beginning time, ending time, impacted area and drought center. Further comparison of IWAP index, Ci index and anomaly percentage Pa index on drought processes for individual station shows that IWAP index is consistent with Ci index on beginning time while Pa index generally shows a delayed beginning time. However, the three indices all show good consistency on ending time. In addition, IWAP index shows a stable ability during a drought process while Ci index and Pa index tend to show unreasonable instability due to their algorithms. IWAP index also has some limitations, unsuitable to be applied in most of the Tibet Plateau and the regions with annual average precipitation less than 300 mm. IWAP index can be calculated in simple way and has clear physical meanings. Considering the nature that the index is only based on precipitation, IWAP index is not only convenient for meteorological operation, but also has obvious potential advantages in drought simulation and prediction in the case of limited output elements from current available climate models.
Based on the Weighted Average Precipitation (WAP), an improvement study on drought index was carried out in two aspects. After determining the two parameters of the WAP index and removing regional and seasonal differences, an improved WAP drought index named IWAP index was developed. Then, comparison analysis between IWAP index and Ci index was done. The results show that: IWAP index has a good correlation with Ci index in most of China especially in mid eastern China with correlation coefficients above 0.7 in most of Central China, most of Guizhou, southern Yunnan and southern Xinjiang. In identifying regional meteorological drought events, IWAP index also shows good consistency with Ci index on beginning time, ending time, impacted area and drought center. Further comparison of IWAP index, Ci index and anomaly percentage Pa index on drought processes for individual station shows that IWAP index is consistent with Ci index on beginning time while Pa index generally shows a delayed beginning time. However, the three indices all show good consistency on ending time. In addition, IWAP index shows a stable ability during a drought process while Ci index and Pa index tend to show unreasonable instability due to their algorithms. IWAP index also has some limitations, unsuitable to be applied in most of the Tibet Plateau and the regions with annual average precipitation less than 300 mm. IWAP index can be calculated in simple way and has clear physical meanings. Considering the nature that the index is only based on precipitation, IWAP index is not only convenient for meteorological operation, but also has obvious potential advantages in drought simulation and prediction in the case of limited output elements from current available climate models.
2013, 39(5):608-615.
DOI: 10.7519/j.issn.1000-0526.2013.05.009
Abstract:
To develop the satellite cloud image interpretation skills and adequately exert the role of satellite cloud image in the forecast for regional rainstorm, some typical features of water vapor images during different phases of the rainstorm and their physical meaning are interpreted preliminarily, and satellite cloud image interpretation skills suitable for regional rainstorm in China are explored by analyzing FY2C water vapor images integrated with conventional dynamics fields and potential vorticity field for the rainstorm over Changjiang and Huaihe River Valley in 9-10 July 2007. The typical rainstorm event validates the good corresponding relations between satellite water vapor images and circulation and potential vorticity fields in the mid upper troposphere. According to these relations, 4 water vapor image indicators with certain forecasting meanings are summarized and abstracted: a “dry triangle structure” induced by jet breaking and wind shear, a large scale tundish like shape cloud system resulting from southward intrusion of dry and cold air, a leaf like cloud induced by dry intrusion of cold air, a white slender strip cloud line symbolizing the generation of a new jet core, etc. These features and indicators have definite physical meanings and good indicating roles for rainstorm forecast, and are easy to be identified and applied.
To develop the satellite cloud image interpretation skills and adequately exert the role of satellite cloud image in the forecast for regional rainstorm, some typical features of water vapor images during different phases of the rainstorm and their physical meaning are interpreted preliminarily, and satellite cloud image interpretation skills suitable for regional rainstorm in China are explored by analyzing FY2C water vapor images integrated with conventional dynamics fields and potential vorticity field for the rainstorm over Changjiang and Huaihe River Valley in 9-10 July 2007. The typical rainstorm event validates the good corresponding relations between satellite water vapor images and circulation and potential vorticity fields in the mid upper troposphere. According to these relations, 4 water vapor image indicators with certain forecasting meanings are summarized and abstracted: a “dry triangle structure” induced by jet breaking and wind shear, a large scale tundish like shape cloud system resulting from southward intrusion of dry and cold air, a leaf like cloud induced by dry intrusion of cold air, a white slender strip cloud line symbolizing the generation of a new jet core, etc. These features and indicators have definite physical meanings and good indicating roles for rainstorm forecast, and are easy to be identified and applied.
2013, 39(5):616-622.
DOI: 10.7519/j.issn.1000-0526.2013.05.010
Abstract:
Zhang Jian’s automated 2D multi pass velocity dealiasing algorithm based on the horizontal continuity of velocity fields is improved in this paper. In Zhang Jian’s method, a set of initial reference radials and gates are obtained by finding the weakest wind region, and then with these initial reference radials and gates, the continuities among adjacent gates are checked and the aliased velocity values are corrected. However, it is hard to precisely obtain reference radials and gates because real wind field is interfered by meso or small scale system, and isolated echo zone, which will influence the velocity dealiasing process greatly. Therefore, the improved algorithm is proposed for this problem. In the continuous detection processes, the aliased velocity suspected boundaries are determined, and then the aliased boundaries and velocity regions are identified. After that, an extend neighborhood scheme is applied to correct the aliased velocity gates in the aliased velocity region in the aliased velocity revision process. In addition, by lots of radar volume scan experiments, it is found that the discussed method is effective in velocity dealiasing, which is significantly better than Zhang Jian’s scheme and WSR 88D scheme.
Zhang Jian’s automated 2D multi pass velocity dealiasing algorithm based on the horizontal continuity of velocity fields is improved in this paper. In Zhang Jian’s method, a set of initial reference radials and gates are obtained by finding the weakest wind region, and then with these initial reference radials and gates, the continuities among adjacent gates are checked and the aliased velocity values are corrected. However, it is hard to precisely obtain reference radials and gates because real wind field is interfered by meso or small scale system, and isolated echo zone, which will influence the velocity dealiasing process greatly. Therefore, the improved algorithm is proposed for this problem. In the continuous detection processes, the aliased velocity suspected boundaries are determined, and then the aliased boundaries and velocity regions are identified. After that, an extend neighborhood scheme is applied to correct the aliased velocity gates in the aliased velocity region in the aliased velocity revision process. In addition, by lots of radar volume scan experiments, it is found that the discussed method is effective in velocity dealiasing, which is significantly better than Zhang Jian’s scheme and WSR 88D scheme.
2013, 39(5):623-632.
DOI: 10.7519/j.issn.1000-0526.2013.05.011
Abstract:
FY 3A/VIRR cloud phase retrievals were evaluated by Terra/MODIS cloud phase products, with the single and complex cloud conditions discussed. In this study, consistency comparison, discrepancy image display as well as overlay display method for the two kinds of products were all employed. The analysis results show that the two kinds of cloud phase products have good consistency under the simple cloud condition, and the consistency rate is close to 85%, but under the complex cloud condition, the consistency between the two kinds of cloud phase products decreases because the Terra/MODIS cloud phase products have a lot of undefined phase cloud pixels. The different pixels of the FY 3A/VIRR and Terra/MODIS cloud phase products mainly distribute in the edges of clouds or the boundary parts of different cloud phases. The different cloud phase algorithm and cloud categorizing methods are the main cause for the different cloud phases between FY 3A/VIRR and Terra/MODIS.
FY 3A/VIRR cloud phase retrievals were evaluated by Terra/MODIS cloud phase products, with the single and complex cloud conditions discussed. In this study, consistency comparison, discrepancy image display as well as overlay display method for the two kinds of products were all employed. The analysis results show that the two kinds of cloud phase products have good consistency under the simple cloud condition, and the consistency rate is close to 85%, but under the complex cloud condition, the consistency between the two kinds of cloud phase products decreases because the Terra/MODIS cloud phase products have a lot of undefined phase cloud pixels. The different pixels of the FY 3A/VIRR and Terra/MODIS cloud phase products mainly distribute in the edges of clouds or the boundary parts of different cloud phases. The different cloud phase algorithm and cloud categorizing methods are the main cause for the different cloud phases between FY 3A/VIRR and Terra/MODIS.
2013, 39(5):633-644.
DOI: 10.7519/j.issn.1000-0526.2013.05.012
Abstract:
Currently the method which GRAPES 3DVar (global＼regional assimilation and prediction system) used can only detect the data of clear FOV, the whole channel data needs to be removed if the FOV is polluted by cloud. In fact, studies have shown that the data above cloud top in cloud FOV is more important to numerical prediction. Therefore, refering to McNally and Watts cloud detection schemes and, combining GRAPES 3DVar system and instrument characteristics, we built a detection scheme which is suitable for GRAPES 3DVar mode. This scheme can not only detect the field data of clear sky, but also detect the channel data above cloud top which is not influenced by cloud in cloud FOV. Besides, it can calculate the height of cloud top, and judge the cloud base of high, middle and low cloud. The detection scheme for the field view of clear sky cloud and the detection scheme for clear channel cloud are used to detect the AIRS observational data. The results show that the clear data detected by the field view of clear sky scheme stands for a 9.14% of the total and those by the clear channel cloud detection scheme the rate reaches 34.86%, 3.8 times more than the traditional cloud detection scheme.
Currently the method which GRAPES 3DVar (global＼regional assimilation and prediction system) used can only detect the data of clear FOV, the whole channel data needs to be removed if the FOV is polluted by cloud. In fact, studies have shown that the data above cloud top in cloud FOV is more important to numerical prediction. Therefore, refering to McNally and Watts cloud detection schemes and, combining GRAPES 3DVar system and instrument characteristics, we built a detection scheme which is suitable for GRAPES 3DVar mode. This scheme can not only detect the field data of clear sky, but also detect the channel data above cloud top which is not influenced by cloud in cloud FOV. Besides, it can calculate the height of cloud top, and judge the cloud base of high, middle and low cloud. The detection scheme for the field view of clear sky cloud and the detection scheme for clear channel cloud are used to detect the AIRS observational data. The results show that the clear data detected by the field view of clear sky scheme stands for a 9.14% of the total and those by the clear channel cloud detection scheme the rate reaches 34.86%, 3.8 times more than the traditional cloud detection scheme.
2013, 39(5):645-652.
DOI: 10.7519/j.issn.1000-0526.2013.05.013
Abstract:
Abnormal echoes because of transmitter, receiver, and servo fault were analyzed in this article. Affection to archive data and the alarm of different fault were analyzed also. The result shows that constructing radar status information database, inspecting radar status information of archive, and forming abnormal data block including archive， status, and alarm can improve data quality, supply credibility information for users. According to statistics of Shijiazhuang radar site, 90% abnormal radar data can be eliminated. These supply reference for radar data quality control, fault diagnosing, and sounding technology improvement.
Abnormal echoes because of transmitter, receiver, and servo fault were analyzed in this article. Affection to archive data and the alarm of different fault were analyzed also. The result shows that constructing radar status information database, inspecting radar status information of archive, and forming abnormal data block including archive， status, and alarm can improve data quality, supply credibility information for users. According to statistics of Shijiazhuang radar site, 90% abnormal radar data can be eliminated. These supply reference for radar data quality control, fault diagnosing, and sounding technology improvement.
2013, 39(5):653-658.
DOI: 10.7519/j.issn.1000-0526.2013.05.014
Abstract:
The medium range forecast products of the numberical models T639, ECMWF and Japan from December 2012 to February 2013 are compared and verified. The results show that the three models have good performance in predicting the variation and adjustment of atmospheric circulation over Asian middle and high latitude areas, but all of them have systemic errors increasing with forecasting time. Comparatively speaking, EC model has better performance than T639 and JP models. For the temperature field at 850 hPa, EC model has better performance than JP in the north of China but in the South, JP plays better than EC. Comparatively, the forecast errors of T639 model are the biggest no matter in the south or the north of China. For the process of weak cold airs in the Northeast of China, JP model has the best performance, T639 model produces obvious errors in predicting the intensity and position of cold high, and EC also creates some small errors in intensity and position forecasts.
The medium range forecast products of the numberical models T639, ECMWF and Japan from December 2012 to February 2013 are compared and verified. The results show that the three models have good performance in predicting the variation and adjustment of atmospheric circulation over Asian middle and high latitude areas, but all of them have systemic errors increasing with forecasting time. Comparatively speaking, EC model has better performance than T639 and JP models. For the temperature field at 850 hPa, EC model has better performance than JP in the north of China but in the South, JP plays better than EC. Comparatively, the forecast errors of T639 model are the biggest no matter in the south or the north of China. For the process of weak cold airs in the Northeast of China, JP model has the best performance, T639 model produces obvious errors in predicting the intensity and position of cold high, and EC also creates some small errors in intensity and position forecasts.
2013, 39(5):659-664.
DOI: 10.7519/j.issn.1000-0526.2013.05.015
Abstract:
The main characteristics of the general atmospheric circulation in February 2013 are as follows: There were two polar vortex centers in the Northern Hemisphere with more stronger strength than normal years. Atmospheric circulation presented a three wave pattern in middle high latitudes. The south branch trough was to the west, which is not favorable for the transportation of water vapor. The West Pacific subtropica high was stronger than normal years. The monthly mean temperature was -1.2℃， higher than normal. The mean precipitation this month was 14.1 mm, 19.0% less than normal. Two cold air events affected China and fog and haze weather happened many times. Drought still lasted in the southwest of China, and severe snowstorms hit the south of Tibet.
The main characteristics of the general atmospheric circulation in February 2013 are as follows: There were two polar vortex centers in the Northern Hemisphere with more stronger strength than normal years. Atmospheric circulation presented a three wave pattern in middle high latitudes. The south branch trough was to the west, which is not favorable for the transportation of water vapor. The West Pacific subtropica high was stronger than normal years. The monthly mean temperature was -1.2℃， higher than normal. The mean precipitation this month was 14.1 mm, 19.0% less than normal. Two cold air events affected China and fog and haze weather happened many times. Drought still lasted in the southwest of China, and severe snowstorms hit the south of Tibet.
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ISSN:1000-0526 CN:11-2282/P