ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 41,Issue 3,2015 Table of Contents
2015, 41(3):261-271.
DOI: 10.7519/j.issn.1000-0526.2015.03.001
Abstract:
The variability of seasonal mean precipitation in southern China exists in three dominant modes: the first leading mode features consistent precipitation variation nearly over the whole part of southern China. The other two leading modes describe an out of phase relationship of precipitation anomalies between the middle and lower reaches of the Yangtze River Basin and the south of the basin and between the southeast and southwest China, respectively. The regional averaged precipitation in southern China is characterized by obviously interdecadal and long term changes in all the four seasons, of which the precipitation in summer has similar interdecadal changes with that in winter but contrasts with that in autumn during 1961-2013. Additionally, the interdecadal temporal turning points of precipitation anomalies are different in different seasons in the recent three decades. The spring and autumn precipitation anomalies enter into dry phase after the early 2000s and the mid late 1980s, respectively, while the winter and summer precipitation anomalies go into wet phase after the middle 1980s and early 1990s, respectively. The summer and winter precipitation anomalies gradually become neutral since the early 2000s. Furthermore, the regional averaged precipitation in southern China shows a decreasing trend in spring and autumn, but an increasing one in summer and winter during 1961-2013. In southwest China, precipitation decreases in all the four seasons except spring, and, in particular, the decreasing trend is the most remarkable in autumn. However, the linear trends of seasonal averaged precipitation and drought/flood days are not so significant in most parts of southern China, because the interdecadal component has a relatively important contribution to the precipitation variability in southern China during this period. Finally, the results shows that interdecadal component has great (weak) contribution to the variability of total area affected by flood (drought) disaster in southern China, and in southwest China, the variability of total area affected by flood/drought disaster is mainly dominated by the interannual changes in the recent decade.
The variability of seasonal mean precipitation in southern China exists in three dominant modes: the first leading mode features consistent precipitation variation nearly over the whole part of southern China. The other two leading modes describe an out of phase relationship of precipitation anomalies between the middle and lower reaches of the Yangtze River Basin and the south of the basin and between the southeast and southwest China, respectively. The regional averaged precipitation in southern China is characterized by obviously interdecadal and long term changes in all the four seasons, of which the precipitation in summer has similar interdecadal changes with that in winter but contrasts with that in autumn during 1961-2013. Additionally, the interdecadal temporal turning points of precipitation anomalies are different in different seasons in the recent three decades. The spring and autumn precipitation anomalies enter into dry phase after the early 2000s and the mid late 1980s, respectively, while the winter and summer precipitation anomalies go into wet phase after the middle 1980s and early 1990s, respectively. The summer and winter precipitation anomalies gradually become neutral since the early 2000s. Furthermore, the regional averaged precipitation in southern China shows a decreasing trend in spring and autumn, but an increasing one in summer and winter during 1961-2013. In southwest China, precipitation decreases in all the four seasons except spring, and, in particular, the decreasing trend is the most remarkable in autumn. However, the linear trends of seasonal averaged precipitation and drought/flood days are not so significant in most parts of southern China, because the interdecadal component has a relatively important contribution to the precipitation variability in southern China during this period. Finally, the results shows that interdecadal component has great (weak) contribution to the variability of total area affected by flood (drought) disaster in southern China, and in southwest China, the variability of total area affected by flood/drought disaster is mainly dominated by the interannual changes in the recent decade.
2015, 41(3):272-285.
DOI: 10.7519/j.issn.1000-0526.2015.03.002
Abstract:
A parameterization approach of cloud droplet activation is introduced into the original two moment microphysical schemes coupled with GRAPES model. Two precipitation processes are simulated and two experiments with different aerosol concentrations are conducted for both of them. The results show that when aerosol concentration increases, the biggest change of microphysical characteristics is the apparent increase of cloud water content. This is because of the suppressed conversion from cloud droplets to rain drops when more aerosols nucleate into more but smaller cloud droplets, which results in less efficient warm rain processes. On the other hand, with more cloud water left in the air, ice phase particles, especially snow and graupel, can grow through collecting more cloud water and increased snow can also be collected by graupel. Melted snow and graupel eventually produce more rain. Meanwhile, more latent heat will be released with the increase of ice particles, which can invigorate cloud updrafts and further promote rain development. In the simulation region, aerosol effect on precipitation is spatially non uniform. In the region where warm clouds are thick, suppressed warm rain process is the main factor affecting precipitation and surface rainfall is reduced. In spite of this where warm cloud is thin and cold cloud is relatively thicker, cold rain process enhancement is dominant and surface rainfall is increased. Aerosol effects on precipitation is also temporally non uniform because the distributions of warm cloud and cold cloud change during the development of clouds and precipitation.
A parameterization approach of cloud droplet activation is introduced into the original two moment microphysical schemes coupled with GRAPES model. Two precipitation processes are simulated and two experiments with different aerosol concentrations are conducted for both of them. The results show that when aerosol concentration increases, the biggest change of microphysical characteristics is the apparent increase of cloud water content. This is because of the suppressed conversion from cloud droplets to rain drops when more aerosols nucleate into more but smaller cloud droplets, which results in less efficient warm rain processes. On the other hand, with more cloud water left in the air, ice phase particles, especially snow and graupel, can grow through collecting more cloud water and increased snow can also be collected by graupel. Melted snow and graupel eventually produce more rain. Meanwhile, more latent heat will be released with the increase of ice particles, which can invigorate cloud updrafts and further promote rain development. In the simulation region, aerosol effect on precipitation is spatially non uniform. In the region where warm clouds are thick, suppressed warm rain process is the main factor affecting precipitation and surface rainfall is reduced. In spite of this where warm cloud is thin and cold cloud is relatively thicker, cold rain process enhancement is dominant and surface rainfall is increased. Aerosol effects on precipitation is also temporally non uniform because the distributions of warm cloud and cold cloud change during the development of clouds and precipitation.
2015, 41(3):286-295.
DOI: 10.7519/j.issn.1000-0526.2015.03.003
Abstract:
By comparing the Western Jiangnan rainy season and the Meiyu season in Eastern China, preliminary analysis on what and how the tropical Pacific and Indian sea surface temperature anomaly (SSTA) affects the regional precipitation was performed, and then the potential mechanism was studied. The results showed that: (1) Western Jiangnan rainy season, which starts early and lasts for a longer period, is an important part of China Meiyu season. It has obvious interannual and interdecadal variations, of which, since the beginning of twenty first century, it has been into a relative dry period. (2) The SSTA in the previous winter in tropical ocean is a strong signal for more or less rainfall in Western Jiangnan rainy season. That is, when SSTA in eastern equatorial Pacific is positive (negative), SSTA in West Pacific and the subtropical area of East Pacific is negative (positive), and SSTA in tropical India Ocean is positive (negative) in north and negative (positive) in south, there will be more (less) precipitation in Western Jiangnan Region in the following rainy season, which corresponds to more (less) rainfall in South and less (more) in North in China in Meiyu season. (3) In the positive (negative) tropical SSTA years, strong easterly (westerly) wind anomalies prevail in India Ocean, and they are difficult (easy) to turn north to become southerly anomalies, that is to say, the Indian monsoon is in a weak (strong) phase. At the same time, there are strong easterly (westerly) anomalies in West Pacific equatorial regions, and an (a) anticyclone (cyclone) anomaly circulation dominates the northern part of Pacific, which means the West Pacific subtropical high extends to westward (eastward), in a stronger (weaker) state. So, it is (not) beneficial to precipitation in Western Jiangnan. (4) In the positive tropical SSTA years, the water vapor source to Western Jiangnan comes mainly from the Western Pacific Ocean and forms net water vapor convergence in this area, conducive to more precipitation; but in the negative tropical SST abnormal years, the water vapor comes from both Pacific and Indian Oceans, and Western Jiangnan is only a vapor transition zone, not easy to form the water vapor convergence there, resulting in less precipitation.
By comparing the Western Jiangnan rainy season and the Meiyu season in Eastern China, preliminary analysis on what and how the tropical Pacific and Indian sea surface temperature anomaly (SSTA) affects the regional precipitation was performed, and then the potential mechanism was studied. The results showed that: (1) Western Jiangnan rainy season, which starts early and lasts for a longer period, is an important part of China Meiyu season. It has obvious interannual and interdecadal variations, of which, since the beginning of twenty first century, it has been into a relative dry period. (2) The SSTA in the previous winter in tropical ocean is a strong signal for more or less rainfall in Western Jiangnan rainy season. That is, when SSTA in eastern equatorial Pacific is positive (negative), SSTA in West Pacific and the subtropical area of East Pacific is negative (positive), and SSTA in tropical India Ocean is positive (negative) in north and negative (positive) in south, there will be more (less) precipitation in Western Jiangnan Region in the following rainy season, which corresponds to more (less) rainfall in South and less (more) in North in China in Meiyu season. (3) In the positive (negative) tropical SSTA years, strong easterly (westerly) wind anomalies prevail in India Ocean, and they are difficult (easy) to turn north to become southerly anomalies, that is to say, the Indian monsoon is in a weak (strong) phase. At the same time, there are strong easterly (westerly) anomalies in West Pacific equatorial regions, and an (a) anticyclone (cyclone) anomaly circulation dominates the northern part of Pacific, which means the West Pacific subtropical high extends to westward (eastward), in a stronger (weaker) state. So, it is (not) beneficial to precipitation in Western Jiangnan. (4) In the positive tropical SSTA years, the water vapor source to Western Jiangnan comes mainly from the Western Pacific Ocean and forms net water vapor convergence in this area, conducive to more precipitation; but in the negative tropical SST abnormal years, the water vapor comes from both Pacific and Indian Oceans, and Western Jiangnan is only a vapor transition zone, not easy to form the water vapor convergence there, resulting in less precipitation.
2015, 41(3):296-303.
DOI: 10.7519/j.issn.1000-0526.2015.03.004
Abstract:
Minutely rain data from the regional Automatic Weather Stations (AWSs) and composite reflectivity, the five lower angles radar reflectivity from Shijiazhuang radar second products are used to estimate radar based quantitative precipitation. Twenty nine rain processes in 2009-2012 are selected. According to the principle of the most similar intensity to radar echoes and the nearest distance to the AWSs, a new approach for radar quantitative precipitation estimate based on dynamic Z I relations varying with time and space is presented. Grid precipitation without observation is calculated from radar echo reflectivity using this method. A series of quantitative assessments ensure the quality of radar based precipitation estimates. Horizontal distribution of the hourly estimated rainfall data has been visually vertified against the corresponding AWS rainfall reports. Cross validation is used to analyze the errors. The results show high quality of the radar based precipitation estimates in terms of small errors, high correlation and hourly rainfall pattern and evolution, including rainfall extremes more than 40 mm·h-1. Therefore, the approach of dynamic Z I relations is shown valuable to be applied in meteorological operation and instructive for assessing severe rainfall disaster.
Minutely rain data from the regional Automatic Weather Stations (AWSs) and composite reflectivity, the five lower angles radar reflectivity from Shijiazhuang radar second products are used to estimate radar based quantitative precipitation. Twenty nine rain processes in 2009-2012 are selected. According to the principle of the most similar intensity to radar echoes and the nearest distance to the AWSs, a new approach for radar quantitative precipitation estimate based on dynamic Z I relations varying with time and space is presented. Grid precipitation without observation is calculated from radar echo reflectivity using this method. A series of quantitative assessments ensure the quality of radar based precipitation estimates. Horizontal distribution of the hourly estimated rainfall data has been visually vertified against the corresponding AWS rainfall reports. Cross validation is used to analyze the errors. The results show high quality of the radar based precipitation estimates in terms of small errors, high correlation and hourly rainfall pattern and evolution, including rainfall extremes more than 40 mm·h-1. Therefore, the approach of dynamic Z I relations is shown valuable to be applied in meteorological operation and instructive for assessing severe rainfall disaster.
2015, 41(3):304-310.
DOI: 10.7519/j.issn.1000-0526.2015.03.005
Abstract:
Using NCEP/NCAR reanalysis data this paper assessed the simulation capability of storm track by BCC_CSM. The results show that for the simulation of climate state the BCC_CSM model can simulate the location and intensity of the storm track in different seasons. The EOF results show that, regarding the simulation of the interannual changes of spatial and temporal distribution, eigenvectors of the BCC_CSM’s first mode and second mode are similar with that corresponding to NCEP reanalysis data. The first two modes are both the same in the whole region and north south reverse, but the third mode is different. For storm track strength and latitude index of each month, the BCC_CSM model has a nice simulation result and it can simulate the Midwinter Suppression of the Pacific storm track, and ineffective analog longitude index change. Simulations for moving trends of the storm track toward the polar region in the Pacific are not significant, while in the Atlantic Region the trend of storm axis position is simulated being toward the polar region after 1970.
Using NCEP/NCAR reanalysis data this paper assessed the simulation capability of storm track by BCC_CSM. The results show that for the simulation of climate state the BCC_CSM model can simulate the location and intensity of the storm track in different seasons. The EOF results show that, regarding the simulation of the interannual changes of spatial and temporal distribution, eigenvectors of the BCC_CSM’s first mode and second mode are similar with that corresponding to NCEP reanalysis data. The first two modes are both the same in the whole region and north south reverse, but the third mode is different. For storm track strength and latitude index of each month, the BCC_CSM model has a nice simulation result and it can simulate the Midwinter Suppression of the Pacific storm track, and ineffective analog longitude index change. Simulations for moving trends of the storm track toward the polar region in the Pacific are not significant, while in the Atlantic Region the trend of storm axis position is simulated being toward the polar region after 1970.
2015, 41(3):311-318.
DOI: 10.7519/j.issn.1000-0526.2015.03.006
Abstract:
In the context of increasing haze days in China, a significant feature is that the persistence of haze weather is enhanced. Based on the statistical haze data over the Jingjinji (a region referred to Beijing along with Tianjin and Hebei Province) during the period 1981-2013, the climatic characteristics of spatial and temporal distribution of persistent haze events, which refer to the haze events lasting for 2 or more days, are analyzed. The result shows that the increase in both the frequency and days of persistent haze events is the main reason leading to the growth of total haze events while the variation of non persistent haze days has no noticeable trend since 1981. The persistent haze events are mainly recorded in Beijing, the northern part of Tianjin and the southwest of Hebei Province, where the annual mean persistent haze days account for more than half of the total haze days in general. The areas affected by persistent haze events have expanded in an interdecadal increasing trend and the expansion has further accelerated since 2000.
In the context of increasing haze days in China, a significant feature is that the persistence of haze weather is enhanced. Based on the statistical haze data over the Jingjinji (a region referred to Beijing along with Tianjin and Hebei Province) during the period 1981-2013, the climatic characteristics of spatial and temporal distribution of persistent haze events, which refer to the haze events lasting for 2 or more days, are analyzed. The result shows that the increase in both the frequency and days of persistent haze events is the main reason leading to the growth of total haze events while the variation of non persistent haze days has no noticeable trend since 1981. The persistent haze events are mainly recorded in Beijing, the northern part of Tianjin and the southwest of Hebei Province, where the annual mean persistent haze days account for more than half of the total haze days in general. The areas affected by persistent haze events have expanded in an interdecadal increasing trend and the expansion has further accelerated since 2000.
2015, 41(3):319-327.
DOI: 10.7519/j.issn.1000-0526.2015.03.007
Abstract:
Daily meteorological observation data of 17 stations of Chongqing and NCEP/NCAR reanalysis data are employed to diagnose the influence of urbanization on the summer high temperature and sultry weather in Chongqing. Results show that high temperature days and hot days at Shapingba Station decrease with the rapidly accelerating of urbanization. Maximum temperature decrease is the main reason for the decrease of high temperature days and hot days. Correlation analysis indicates that the difference of hot days between the main urban zone and suburbs increases gradually，which indicates the decrease of high temperature days and hot days at Shapingba Station is caused by the rapidly accelerating of urbanization，not by the regional climate changes. Observation Minus Reanalysis （OMR） method is used to analyze the difference between observed temperature and NCEP/NCAR reanalysis （NNR） temperature. So, we found that along with the rapidly accelerating of urbanization, mean temperature and minimum temperature increase, especially for minimum temperature, but maximum temperature decreases.
Daily meteorological observation data of 17 stations of Chongqing and NCEP/NCAR reanalysis data are employed to diagnose the influence of urbanization on the summer high temperature and sultry weather in Chongqing. Results show that high temperature days and hot days at Shapingba Station decrease with the rapidly accelerating of urbanization. Maximum temperature decrease is the main reason for the decrease of high temperature days and hot days. Correlation analysis indicates that the difference of hot days between the main urban zone and suburbs increases gradually，which indicates the decrease of high temperature days and hot days at Shapingba Station is caused by the rapidly accelerating of urbanization，not by the regional climate changes. Observation Minus Reanalysis （OMR） method is used to analyze the difference between observed temperature and NCEP/NCAR reanalysis （NNR） temperature. So, we found that along with the rapidly accelerating of urbanization, mean temperature and minimum temperature increase, especially for minimum temperature, but maximum temperature decreases.
2015, 41(3):328-335.
DOI: 10.7519/j.issn.1000-0526.2015.03.008
Abstract:
An interannual precipitation increment forecasting model with high predictive capability for forecasting the summer rainfall in Shaanxi Province is presented by analyzing the physical mechanisms of precipitation during flood season based on the interannual increment forecasting approach. The research results show that the interannual SST increment in middle and eastern equatorial Pacific, the 500 hPa height interannual increment and rainfall during flood season in Shaanxi have very good correlations. When the distribution pattern is north south “- + -” in interannual increment of SST in middle and eastern equatorial Pacific from the previous autumn to winter, there would be more rains in the summer. Conversely it would rain less. When the distribution pattern of the interannual increment at 500 hPa height is positive, showing zonal, near the equator from the previous autumn to winter, there would be more rains in the summer. Otherwise, it would be dry. In this research, we find a good correlation between the interannual increment of 74 circulation features from National Climate Centre, soil temperature at 0 cm depth and precipitation during flood season in Shaanxi. Based on the analysis of the physical meanings of predictors, predictors are introduced via the optimal subset regression, and 40 prediction models for rainy season precipitation and each month (June, July and August) of 10 climatic regions of Shaanxi are established by using the interannual increment approach. Cross validation testing of rainy season precipitation shows that the anomaly consistency rate reaches 78.4%. It is shown by the hindcasting results during 2010-2013 that the PS score of flood season precipitation is 75.8 and 66, separately. Thus, this work demonstrates that the interannual increment approach has good predictive skill. It can improve the level of predicting rainfalls in Shaanxi flood season and can be used as an effective way in forecasting operations.
An interannual precipitation increment forecasting model with high predictive capability for forecasting the summer rainfall in Shaanxi Province is presented by analyzing the physical mechanisms of precipitation during flood season based on the interannual increment forecasting approach. The research results show that the interannual SST increment in middle and eastern equatorial Pacific, the 500 hPa height interannual increment and rainfall during flood season in Shaanxi have very good correlations. When the distribution pattern is north south “- + -” in interannual increment of SST in middle and eastern equatorial Pacific from the previous autumn to winter, there would be more rains in the summer. Conversely it would rain less. When the distribution pattern of the interannual increment at 500 hPa height is positive, showing zonal, near the equator from the previous autumn to winter, there would be more rains in the summer. Otherwise, it would be dry. In this research, we find a good correlation between the interannual increment of 74 circulation features from National Climate Centre, soil temperature at 0 cm depth and precipitation during flood season in Shaanxi. Based on the analysis of the physical meanings of predictors, predictors are introduced via the optimal subset regression, and 40 prediction models for rainy season precipitation and each month (June, July and August) of 10 climatic regions of Shaanxi are established by using the interannual increment approach. Cross validation testing of rainy season precipitation shows that the anomaly consistency rate reaches 78.4%. It is shown by the hindcasting results during 2010-2013 that the PS score of flood season precipitation is 75.8 and 66, separately. Thus, this work demonstrates that the interannual increment approach has good predictive skill. It can improve the level of predicting rainfalls in Shaanxi flood season and can be used as an effective way in forecasting operations.
9 Calculation of Rainstorm Intensity Formula for the Main Urban Areas of Chongqing and Its Application
2015, 41(3):336-345.
DOI: 10.7519/j.issn.1000-0526.2015.03.009
Abstract:
Using the minutely precipitation data during 1981-2013, which is from the stations of Shapingba, Beibei, Banan and Yubei in the main urban areas of Chongqing, the rainstorm intensity formula fitted by the Pearson Ⅲ distribution, Gumbell distribution and exponential distribution was made respectively by using the annual multisampling method and annual maximum value method. The results show that rainstorm intensity calculated by the formula using annual maximum value method is less than that calculated by the formula by annual multisampling method for the reappearing period less than 10 years. In the 10-30 years reappearing period, the difference of the two is slight, and the rainstorm intensity calculated by the formula according to annual maximum value method is more than that calculated by the formula according to annual multisampling method. The error of rainstorm intensity formula according to annual multisampling method is the least for the four stations. The rainstorm intensity formula of Beibei and Banan is made fitted by exponential distribution according to annual multisampling method based on the precipitation data from 1981 to 2013. The rainstorm intensity formula of Yubei and Shapingba is made fitted by exponential distribution according to annual multisampling method based on the precipitation data from 1991 to 2013. The applicability of new formula to calculate the rainstorm intensity in the main urban area of Chongqing is determined by analyzing the spatial distribution features of precipitation in different times.
Using the minutely precipitation data during 1981-2013, which is from the stations of Shapingba, Beibei, Banan and Yubei in the main urban areas of Chongqing, the rainstorm intensity formula fitted by the Pearson Ⅲ distribution, Gumbell distribution and exponential distribution was made respectively by using the annual multisampling method and annual maximum value method. The results show that rainstorm intensity calculated by the formula using annual maximum value method is less than that calculated by the formula by annual multisampling method for the reappearing period less than 10 years. In the 10-30 years reappearing period, the difference of the two is slight, and the rainstorm intensity calculated by the formula according to annual maximum value method is more than that calculated by the formula according to annual multisampling method. The error of rainstorm intensity formula according to annual multisampling method is the least for the four stations. The rainstorm intensity formula of Beibei and Banan is made fitted by exponential distribution according to annual multisampling method based on the precipitation data from 1981 to 2013. The rainstorm intensity formula of Yubei and Shapingba is made fitted by exponential distribution according to annual multisampling method based on the precipitation data from 1991 to 2013. The applicability of new formula to calculate the rainstorm intensity in the main urban area of Chongqing is determined by analyzing the spatial distribution features of precipitation in different times.
2015, 41(3):346-352.
DOI: 10.7519/j.issn.1000-0526.2015.03.010
Abstract:
Based on the first snow date (FSD) data of Hubei from 1961/1962 to 2012/2013, we reveal the atmospheric circulation features in abnormal early/late FSD. For the late FSD years in Hubei Province, the circulation distribution of the sea surface temperature anomaly (SSTA), the height anomaly and low level wind field from November to February that year can be illustrated as follow: SSTA in Northwest Pacific and in the Southern Pacific Ocean to the east of New Zealand is abnormally higher, which is good for the weakening of Ural Mountains Ridge, and the weakening of Lake Baikal low pressure and Aleutian low. Meanwhile, East Asian trough is strengthened and Bengal Bay trough is weakened. The corresponding 500 hPa height field shows a “- + -” wave train distribution from north to south in Eurasia. In mainland China, the low level wind field is controlled by abnormal north winds. Otherwise, the FSD comes early. Typical circulation distribution in 2013/2014 agrees with the late FSD in Hubei. In addition, prediction model for FSD is established by using SSTA in the key areas, which accurately predicts the late FSD in 2013/2014 and gives a good reforecasting test with the accuracy getting to 75%. So, this is a new method for the prediction of FSD in Hubei.
Based on the first snow date (FSD) data of Hubei from 1961/1962 to 2012/2013, we reveal the atmospheric circulation features in abnormal early/late FSD. For the late FSD years in Hubei Province, the circulation distribution of the sea surface temperature anomaly (SSTA), the height anomaly and low level wind field from November to February that year can be illustrated as follow: SSTA in Northwest Pacific and in the Southern Pacific Ocean to the east of New Zealand is abnormally higher, which is good for the weakening of Ural Mountains Ridge, and the weakening of Lake Baikal low pressure and Aleutian low. Meanwhile, East Asian trough is strengthened and Bengal Bay trough is weakened. The corresponding 500 hPa height field shows a “- + -” wave train distribution from north to south in Eurasia. In mainland China, the low level wind field is controlled by abnormal north winds. Otherwise, the FSD comes early. Typical circulation distribution in 2013/2014 agrees with the late FSD in Hubei. In addition, prediction model for FSD is established by using SSTA in the key areas, which accurately predicts the late FSD in 2013/2014 and gives a good reforecasting test with the accuracy getting to 75%. So, this is a new method for the prediction of FSD in Hubei.
2015, 41(3):353-363.
DOI: 10.7519/j.issn.1000-0526.2015.03.011
Abstract:
The spatial error structure of surface precipitation derived from the latest version 7 Tropical Rainfall Measuring Mission (TRMM) Multi satellite Precipitation Analysis (TMPA) algorithms are systematically studied by comparing with the daily China precipitation analysis product (CPAP) from September 2008 to August 2012. The TMPA products include the real time product 3B42RT, the research product 3B42 (3B42V7). In terms of four year mean daily precipitation the 3B42V7 products are highly correlated with CPAP with correlation coefficient (CC) being about 0.94, relative bias (RB) about -0.11% and the root mean square error (RMSE) about 0.53 mm·d-1. The 3B42RT product has lower CC about 0.75 and higher relative bias (RB) about 39.30% and RMSE about 1.25 mm·d-1. The 3B42RT product overestimated the rainfall in the west of China with RB about 116.60 % for the whole year (104.52%、 105.73%、117.64% and 326.60% respectively for spring, summer, autumn and winter). The relative error of 3B42V7 product is only 0.82 % (2.25%, 1.24%, -5.27%, -24.64% for spring, summer, autumn and winter, respectively).
The spatial error structure of surface precipitation derived from the latest version 7 Tropical Rainfall Measuring Mission (TRMM) Multi satellite Precipitation Analysis (TMPA) algorithms are systematically studied by comparing with the daily China precipitation analysis product (CPAP) from September 2008 to August 2012. The TMPA products include the real time product 3B42RT, the research product 3B42 (3B42V7). In terms of four year mean daily precipitation the 3B42V7 products are highly correlated with CPAP with correlation coefficient (CC) being about 0.94, relative bias (RB) about -0.11% and the root mean square error (RMSE) about 0.53 mm·d-1. The 3B42RT product has lower CC about 0.75 and higher relative bias (RB) about 39.30% and RMSE about 1.25 mm·d-1. The 3B42RT product overestimated the rainfall in the west of China with RB about 116.60 % for the whole year (104.52%、 105.73%、117.64% and 326.60% respectively for spring, summer, autumn and winter). The relative error of 3B42V7 product is only 0.82 % (2.25%, 1.24%, -5.27%, -24.64% for spring, summer, autumn and winter, respectively).
2015, 41(3):364-371.
DOI: 10.7519/j.issn.1000-0526.2015.03.012
Abstract:
Using the Tropical Cyclone Yearbook，two dimensional Fengyun (FY 2E) 0.1°×0.1° cloud top brightness temperature data, hourly rainfall observations from nearly 100 automatic weather stations (AWS) , conventional observation data and the NCEP/NCAR reanalysis data, large scale circulation characteristics and mesoscale circulations were analyzed for typhoons of 1209 (Saola) and 1210 (Damrey). The results show that: (1) Northerly and stable position of subtropical high pressure (STP) provides favorable large scale circulations. The direct raining system is the mesoscale convective complex (MCC), which is generated by the development of meso β or meso γ rain clusters located in the east of typhoon and the west of STP. (2) Link of the area of Liaodong Peninsula with the channel of moisture transported by lower level jets and the formation of moisture convergence are responsible for the occurrence of heavy precipitation in the area. Standing link of water vapor transport belts for typhoons of Damrey and Saola is favorable for genesis and development of convective complex in typhoon rain belts, beneficial to the genesis of severe rainfall. (3) Near the center of Damrey, the coupling dynamical structure of positive vorticity and the negative divergence form, which causes strong upward motion in the lower troposphere, and has the convergent water vapor at the lower level lifted to the middle level, good for genesis and development of MCS. Moving northeastward along the periphery of STP, MCS rapidly develops and results in heavy precipitation. The heavy rainfalls are located at lower level jet belts of the east of Damrey and the west of STP. （4）The local vertical circulations in the south of Liaodong Peninsula are helpful for the formation and development of mesoscale convective cloud clusters.
Using the Tropical Cyclone Yearbook，two dimensional Fengyun (FY 2E) 0.1°×0.1° cloud top brightness temperature data, hourly rainfall observations from nearly 100 automatic weather stations (AWS) , conventional observation data and the NCEP/NCAR reanalysis data, large scale circulation characteristics and mesoscale circulations were analyzed for typhoons of 1209 (Saola) and 1210 (Damrey). The results show that: (1) Northerly and stable position of subtropical high pressure (STP) provides favorable large scale circulations. The direct raining system is the mesoscale convective complex (MCC), which is generated by the development of meso β or meso γ rain clusters located in the east of typhoon and the west of STP. (2) Link of the area of Liaodong Peninsula with the channel of moisture transported by lower level jets and the formation of moisture convergence are responsible for the occurrence of heavy precipitation in the area. Standing link of water vapor transport belts for typhoons of Damrey and Saola is favorable for genesis and development of convective complex in typhoon rain belts, beneficial to the genesis of severe rainfall. (3) Near the center of Damrey, the coupling dynamical structure of positive vorticity and the negative divergence form, which causes strong upward motion in the lower troposphere, and has the convergent water vapor at the lower level lifted to the middle level, good for genesis and development of MCS. Moving northeastward along the periphery of STP, MCS rapidly develops and results in heavy precipitation. The heavy rainfalls are located at lower level jet belts of the east of Damrey and the west of STP. （4）The local vertical circulations in the south of Liaodong Peninsula are helpful for the formation and development of mesoscale convective cloud clusters.
2015, 41(3):372-379.
DOI: 10.7519/j.issn.1000-0526.2015.03.013
Abstract:
The features and forecast method are found by analyzing daily MICAPS data. The results indicate that: (1) Continuous wet weather happens in the condition that it warms up rapidly after the continuous cold wet weather. (2) The favorable circulations for the continuous wet weather are that the circulation at 500 hPa turns to zonal in North China, the south branch trough strengthens and moves eastward, southwesterly jet sets up at 850 hPa, the surface cold air weakens and the quasi stationary front moves to north. (3) The top of the front is below 850 hPa in curve T lnp and continuous wet weather may occur on the next day when the front goes down to the surface. (4) The warm and humid air condenses on the cold surface indoors where surface temperature is lower than dew point outdoors. (5) Continuous wet weather can be divided into heavy, moderate and light degrees based on the minimum temperature on the day before, the dew point and the heating extent on the very day. (6) Continuous wet weather has two ending ways: cold ending and warm ending. All the results above can be applied in forecasting operations.
The features and forecast method are found by analyzing daily MICAPS data. The results indicate that: (1) Continuous wet weather happens in the condition that it warms up rapidly after the continuous cold wet weather. (2) The favorable circulations for the continuous wet weather are that the circulation at 500 hPa turns to zonal in North China, the south branch trough strengthens and moves eastward, southwesterly jet sets up at 850 hPa, the surface cold air weakens and the quasi stationary front moves to north. (3) The top of the front is below 850 hPa in curve T lnp and continuous wet weather may occur on the next day when the front goes down to the surface. (4) The warm and humid air condenses on the cold surface indoors where surface temperature is lower than dew point outdoors. (5) Continuous wet weather can be divided into heavy, moderate and light degrees based on the minimum temperature on the day before, the dew point and the heating extent on the very day. (6) Continuous wet weather has two ending ways: cold ending and warm ending. All the results above can be applied in forecasting operations.
2015, 41(3):380-387.
DOI: 10.7519/j.issn.1000-0526.2015.03.014
Abstract:
The main characteristics of the general atmospheric circulation in December 2014 are as follows: The polar vortex of the Northern Hemisphere is stronger than the normal. The Eurasia mid high latitude circulation presents the trough ridge trough pattern. The East Asian major trough is stronger, causing cold airs to be very active. The south branch trough is located near 70°E, being obviously more westward than in the same period of normal years, so not favorable for the water vapor transport to eastern China. The subtropical high is stronger, located more westward and northward than in normal years. The monthly mean precipitation over China is 7.9 mm, which is 24.8% less than the normal value (10.5 mm). Especially in Huabei, Huanghuai, Jianghuai, Jianghan regions, the precipitation amounts decrease 80% of the normal. The monthly mean temperature over China is -3.4℃, 0.2℃ lower than normal (-3.2℃). The temperature changes greatly in this month showing the characteristics of being cold in early and midmonth but warm later. There are five cold air processes, four fog haze processes and one large range rainfall event over China in this month. Many places in the north experience extreme daily temperature dropping events, and some areas of northeast China suffer snow disasters. Meanwhile, wide range of fog haze weather persists in the 2nd and 3rd dekads this month.
The main characteristics of the general atmospheric circulation in December 2014 are as follows: The polar vortex of the Northern Hemisphere is stronger than the normal. The Eurasia mid high latitude circulation presents the trough ridge trough pattern. The East Asian major trough is stronger, causing cold airs to be very active. The south branch trough is located near 70°E, being obviously more westward than in the same period of normal years, so not favorable for the water vapor transport to eastern China. The subtropical high is stronger, located more westward and northward than in normal years. The monthly mean precipitation over China is 7.9 mm, which is 24.8% less than the normal value (10.5 mm). Especially in Huabei, Huanghuai, Jianghuai, Jianghan regions, the precipitation amounts decrease 80% of the normal. The monthly mean temperature over China is -3.4℃, 0.2℃ lower than normal (-3.2℃). The temperature changes greatly in this month showing the characteristics of being cold in early and midmonth but warm later. There are five cold air processes, four fog haze processes and one large range rainfall event over China in this month. Many places in the north experience extreme daily temperature dropping events, and some areas of northeast China suffer snow disasters. Meanwhile, wide range of fog haze weather persists in the 2nd and 3rd dekads this month.
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