The purpose of this study is to investigate the Classification of Synoptic Circulation Patterns for Fog in the Urumqi Airport in Xinjiang, China. By using relevant climate statistical method, the hourly ground observa...The purpose of this study is to investigate the Classification of Synoptic Circulation Patterns for Fog in the Urumqi Airport in Xinjiang, China. By using relevant climate statistical method, the hourly ground observation data and four times per day and NCEP/NCAR reanalysis data (1° × 1°) from 1985 to 2014 were analyzed. The results showed that: 1) The occurrence of fog significantly increased during 1985 and 2014;There are two stages of the airport fog in the 30 years, less-fog period (1985-2002) and more-fog period (2002-2014), the fog focused occurred in November to March of the following year, most in December and least in March;2) Based on Lamb-Jenkinson method, the dominant types of fog in Urumqi Airport are C, E, SE, W, A types (Among them, A, C, E, W, SE are the circulation types. C is Cyclone, A is Anti-cyclone, E is East, W is West, SE is Southeast), and the international distribution of each type is also different;3) The dominant types of persistence fog are A, C, E, SE types, A type appears in the afternoon to the nighttime, in the morning less frequent, on the other hand, C type is just the opposite;4) Atmospheric circulation characteristics for persistence fog profile can be divided into four series: A, C, E, SE series, and climatic characteristics in different series are different.展开更多
Based on the observational hourly precipitation data and the European Centre for Medium-Range Weather Forecasts(ECMWF)Reanalysis 5(ERA5)products from 2006 to 2020,22 rainstorm processes in the eastern foot of Helan Mo...Based on the observational hourly precipitation data and the European Centre for Medium-Range Weather Forecasts(ECMWF)Reanalysis 5(ERA5)products from 2006 to 2020,22 rainstorm processes in the eastern foot of Helan Mountain are objectively classified by using the hierarchical clustering method,and the circulation characteristics of different patterns are comparatively analyzed in this study.The results show that the occurrences of rainstorm processes in the eastern foot of Helan Mountain are most closely related to three circulation patterns.PatternsⅠandⅢmainly occur in July and August,with similar zonal circulations in synoptic backgrounds.Specifically,the South Asia high and the western Pacific subtropical high are stronger and more northward than those in normal years.The frontal systems in westerlies are inactive,while the water vapor from the ocean surface in the south is mainly transported to the rainstorm area by the southerly jet stream at 700 h Pa.The dynamic lifting anomalies are relatively weak,the instability of atmospheric stratification is anomalously strong,and thus the localized severe convective rainstorm is more significant.Comparatively,rainstorm processes of patternⅠare accompanied by stronger and deeper ascending motions,and the warm-sector rainstorm is more extreme.PatternⅢshows a stronger and deeper convective instability,accompanied by larger low-level moisture.Rainstorm processes of patternⅡmainly occur in early summer and early autumn,presenting a meridional circulation pattern of high in the east and low in the west in terms of geopotential height.Moreover,the two low-level jets transporting the water vapor northward from the ocean on the east of China encounter with the frontal systems in westerlies,which makes the ascending motion in patternⅡanomalously strong and deep.The relatively weak instability of atmospheric stratification causes weak convection and long-lasting precipitation formed by the confluence of cold air and warm air.This study may help improve rainstorm forecasting in arid regions.展开更多
利用自动气象站观测降水、ERA5(ECMWF reanalysis version 5)再分析资料和GDAS(Global Data Assimilation System)资料,基于SOMs(self-organizing maps)算法和天气学检验方法,归纳总结2012—2021年太行山中南段75次暖季极端降水事件的...利用自动气象站观测降水、ERA5(ECMWF reanalysis version 5)再分析资料和GDAS(Global Data Assimilation System)资料,基于SOMs(self-organizing maps)算法和天气学检验方法,归纳总结2012—2021年太行山中南段75次暖季极端降水事件的环流形势,探讨不同形势下的水汽输送特征及降水差异。结果表明:影响太行山中南段暖季极端降水的环流形势可分为高空槽型、低涡型、副高纬向型、副高经向型和西北气流型5种,其中以高空槽型最为常见,西北气流型最少。低涡型存在孟加拉湾、南海和西北太平洋水汽输送通道,其日降水极值、最大小时降水强度和影响范围在所有类型中均最大,与低涡型相比,高空槽型缺少西北太平洋水汽输送通道,而副高纬向型和副高经向型缺少孟加拉湾水汽输送通道。利用HYSPLIT(hybrid single-particle Lagrangian integrated trajectory)模型追踪气团发现:低涡型和副高纬向型均以来自西北太平洋的水汽输送贡献最大,高空槽型和副高经向型分别以来自黄海沿岸和南海的水汽输送贡献最大。整层水汽收支分析表明:太行山中南段暖季极端降水最主要的水汽流入来自南边界,其他流入边界及各边界水汽流入贡献的相对大小与环流形势有关。展开更多
In this study, the classification scheme developed by Jenkinson and Collison （1977） based on a typing scheme of Lamb （1950） is applied to obtain circulation types from the mean sea-level pressure on a monthly basi...In this study, the classification scheme developed by Jenkinson and Collison （1977） based on a typing scheme of Lamb （1950） is applied to obtain circulation types from the mean sea-level pressure on a monthly basis. Monthly mean sea-level pressure data from 1951 to 2002 are used to derive six circulation indices and to provide a circulation catalogue with 27 circulation types. Five major types （N, NW, C, CSW, and SW） which occurred most frequently are analyzed to reveal their relationships with the temperature of Harbin on various time scales. Stepwise multiple regression is used to reconstruct temperature anomaly. The monthly mean rainfall of all types occurring and the composite maps of three major types （C, CSW, and SW） relevant to Harbin＇s precipitation are studied. The results show that the dominant types in winter are types N and NW. types C, CSW, and SW occur frequently in summer. Types N and NW favor a negative temperature anomaly and correspond to less rainfall, while types C, CSW, and SW often induce a positive temperature anomaly and correspond to more rainfall. Moreover, a successful statistical model can be established with only one of the six indices and large-scale mean temperature. Using the model, 77.3% of the total variance in the temperature anomaly between 1951 and 2002 can be reconstructed. Type C has a close relationship with total rainfall and type C precipitation plays a major role in determining the total rainfall of Harbin in recent years. This classification scheme is a statistical downscaling model and its relationships with temperature and precipitation can be used to forecast regional climate.展开更多
文摘The purpose of this study is to investigate the Classification of Synoptic Circulation Patterns for Fog in the Urumqi Airport in Xinjiang, China. By using relevant climate statistical method, the hourly ground observation data and four times per day and NCEP/NCAR reanalysis data (1° × 1°) from 1985 to 2014 were analyzed. The results showed that: 1) The occurrence of fog significantly increased during 1985 and 2014;There are two stages of the airport fog in the 30 years, less-fog period (1985-2002) and more-fog period (2002-2014), the fog focused occurred in November to March of the following year, most in December and least in March;2) Based on Lamb-Jenkinson method, the dominant types of fog in Urumqi Airport are C, E, SE, W, A types (Among them, A, C, E, W, SE are the circulation types. C is Cyclone, A is Anti-cyclone, E is East, W is West, SE is Southeast), and the international distribution of each type is also different;3) The dominant types of persistence fog are A, C, E, SE types, A type appears in the afternoon to the nighttime, in the morning less frequent, on the other hand, C type is just the opposite;4) Atmospheric circulation characteristics for persistence fog profile can be divided into four series: A, C, E, SE series, and climatic characteristics in different series are different.
基金National Natural Science Foundation of China(41965001)Program of Technology and Innovation for Leading Talents in Ningxia Hui Autonomous Region(2021GKLRLX05)。
文摘Based on the observational hourly precipitation data and the European Centre for Medium-Range Weather Forecasts(ECMWF)Reanalysis 5(ERA5)products from 2006 to 2020,22 rainstorm processes in the eastern foot of Helan Mountain are objectively classified by using the hierarchical clustering method,and the circulation characteristics of different patterns are comparatively analyzed in this study.The results show that the occurrences of rainstorm processes in the eastern foot of Helan Mountain are most closely related to three circulation patterns.PatternsⅠandⅢmainly occur in July and August,with similar zonal circulations in synoptic backgrounds.Specifically,the South Asia high and the western Pacific subtropical high are stronger and more northward than those in normal years.The frontal systems in westerlies are inactive,while the water vapor from the ocean surface in the south is mainly transported to the rainstorm area by the southerly jet stream at 700 h Pa.The dynamic lifting anomalies are relatively weak,the instability of atmospheric stratification is anomalously strong,and thus the localized severe convective rainstorm is more significant.Comparatively,rainstorm processes of patternⅠare accompanied by stronger and deeper ascending motions,and the warm-sector rainstorm is more extreme.PatternⅢshows a stronger and deeper convective instability,accompanied by larger low-level moisture.Rainstorm processes of patternⅡmainly occur in early summer and early autumn,presenting a meridional circulation pattern of high in the east and low in the west in terms of geopotential height.Moreover,the two low-level jets transporting the water vapor northward from the ocean on the east of China encounter with the frontal systems in westerlies,which makes the ascending motion in patternⅡanomalously strong and deep.The relatively weak instability of atmospheric stratification causes weak convection and long-lasting precipitation formed by the confluence of cold air and warm air.This study may help improve rainstorm forecasting in arid regions.
文摘利用T-mode斜交旋转主成分分析法,对湖南2021年汛期(4—9月)逐小时850 hPa风场进行环流分型,在此基础上开展同期华南快速循环同化模式(CMA-GD-R3)小时降水预报性能检验。结果表明:影响湖南2021年汛期的主要环流型为西南涡切变型、切变型、副热带高压边缘南风型和台风外围东风型4类;模式小时降水预报的晴雨准确率和分级降水TS评分日变化特征明显,晴雨准确率夜间高于白天,分级降水TS评分峰值出现在早晨,各环流型的临近时效降水预报效果较好,短时强降水发生频次最高的西南涡切变型晴雨准确率较低,副热带高压边缘南风型在较大量级降水表现相对较差;SAL(structure amplitude and location)检验显示,西南涡切变型、切变型过程模式位置预报较接近实况,强度预报表现为前弱后强,副热带高压边缘南风型过程预报落区分散,位置预报不稳定,整体强度较实况明显偏弱,台风外围东风型过程在短时预报时效落区接近实况,强度预报显著偏弱,该方法能较客观地反映模式降水预报空间偏差。
基金Supported by the National Natural Science Fundation of China under Grant No.40375025 and Programme of the Ministry of Science and Technology (2001BA611B-01).
文摘In this study, the classification scheme developed by Jenkinson and Collison （1977） based on a typing scheme of Lamb （1950） is applied to obtain circulation types from the mean sea-level pressure on a monthly basis. Monthly mean sea-level pressure data from 1951 to 2002 are used to derive six circulation indices and to provide a circulation catalogue with 27 circulation types. Five major types （N, NW, C, CSW, and SW） which occurred most frequently are analyzed to reveal their relationships with the temperature of Harbin on various time scales. Stepwise multiple regression is used to reconstruct temperature anomaly. The monthly mean rainfall of all types occurring and the composite maps of three major types （C, CSW, and SW） relevant to Harbin＇s precipitation are studied. The results show that the dominant types in winter are types N and NW. types C, CSW, and SW occur frequently in summer. Types N and NW favor a negative temperature anomaly and correspond to less rainfall, while types C, CSW, and SW often induce a positive temperature anomaly and correspond to more rainfall. Moreover, a successful statistical model can be established with only one of the six indices and large-scale mean temperature. Using the model, 77.3% of the total variance in the temperature anomaly between 1951 and 2002 can be reconstructed. Type C has a close relationship with total rainfall and type C precipitation plays a major role in determining the total rainfall of Harbin in recent years. This classification scheme is a statistical downscaling model and its relationships with temperature and precipitation can be used to forecast regional climate.
