High winds cause waves, storm surge, erosion and physical damage to infrastructure and ecosystems. However, there have been few evaluations of wind climatologies and future changes, especially change in high-wind even...High winds cause waves, storm surge, erosion and physical damage to infrastructure and ecosystems. However, there have been few evaluations of wind climatologies and future changes, especially change in high-wind events, on a regional basis. This study uses Alaska as a regional case study of climatological wind speed and direction. Eleven first-order stations across different subregions of Alaska provide historical data (1975-2005) for the observational climatology and for the calibration of Coupled Model Inter comparison Project (CMIP5) simulations, which in turn provide projections of changes in winds through 2100. Historically, winds exceeding 25 and 35 knots are most common in the Bering Sea coastal region of Alaska, followed by northern Alaska coastal areas. Autumn and winter are the seasons of most frequent high-wind occurrences in the coastal sites, while there is no distinct seasonal peak at the interior stations where high-wind events are less frequent. An examination of the sea level pressure pattern associated with the highest-wind event at each station reveals the presence of a strong pressure gradient associated with an extratropical cyclone in most cases. Northern coastal regions of Alaska are projected to experience increased frequencies of high-wind events during the cold season, especially late autumn and early winter, when reduced sea ice cover in the late century will leave coastal regions increasingly vulnerable to flooding and erosion.展开更多
使用浙江省69个基准站2006—2015年5—9月以及同期杭州城区58个区域自动站小时降水资料,利用Gamma分布计算浙江省短时强降水的累积概率,同时综合其频率分布,揭示杭州市小时降水强度的分布特征。此外,以杭州市区为例,利用探空资料分析不...使用浙江省69个基准站2006—2015年5—9月以及同期杭州城区58个区域自动站小时降水资料,利用Gamma分布计算浙江省短时强降水的累积概率,同时综合其频率分布,揭示杭州市小时降水强度的分布特征。此外,以杭州市区为例,利用探空资料分析不同量级(≥50 mm·h-1、30~<50 mm·h-1、20~<30 mm·h-1、<20 mm·h-1)小时雨强出现的环境指标,并基于核密度估计方法提取预报指标。结果表明:杭州城区出现小于等于10 mm·h-1的降水概率高达98.4%,≥20 mm·h-1的概率仅0.05%;受杭州湾偏东气流影响,杭州市区发生短时强降水频率相对较高,尤其是余杭区的东部和西北山区;自2008年以来杭州市区每年短时强降水日数为18~28 d,其中大于等于50 mm·h-1的短时强降水日所占比例高达10%~20%(除2009年和2012年低于10%外);可用于预报杭州市区短时强降水的最佳环境因子依次为整层可降水量、K指数、最佳抬升指数、沙氏指数、925 h Pa露点温度和强天气威胁指数;在判断杭州市区短时强降水强度上表现最好的环境因子为整层可降水量,其次是850 h Pa垂直速度和925 h Pa散度。展开更多
文摘High winds cause waves, storm surge, erosion and physical damage to infrastructure and ecosystems. However, there have been few evaluations of wind climatologies and future changes, especially change in high-wind events, on a regional basis. This study uses Alaska as a regional case study of climatological wind speed and direction. Eleven first-order stations across different subregions of Alaska provide historical data (1975-2005) for the observational climatology and for the calibration of Coupled Model Inter comparison Project (CMIP5) simulations, which in turn provide projections of changes in winds through 2100. Historically, winds exceeding 25 and 35 knots are most common in the Bering Sea coastal region of Alaska, followed by northern Alaska coastal areas. Autumn and winter are the seasons of most frequent high-wind occurrences in the coastal sites, while there is no distinct seasonal peak at the interior stations where high-wind events are less frequent. An examination of the sea level pressure pattern associated with the highest-wind event at each station reveals the presence of a strong pressure gradient associated with an extratropical cyclone in most cases. Northern coastal regions of Alaska are projected to experience increased frequencies of high-wind events during the cold season, especially late autumn and early winter, when reduced sea ice cover in the late century will leave coastal regions increasingly vulnerable to flooding and erosion.
文摘使用浙江省69个基准站2006—2015年5—9月以及同期杭州城区58个区域自动站小时降水资料,利用Gamma分布计算浙江省短时强降水的累积概率,同时综合其频率分布,揭示杭州市小时降水强度的分布特征。此外,以杭州市区为例,利用探空资料分析不同量级(≥50 mm·h-1、30~<50 mm·h-1、20~<30 mm·h-1、<20 mm·h-1)小时雨强出现的环境指标,并基于核密度估计方法提取预报指标。结果表明:杭州城区出现小于等于10 mm·h-1的降水概率高达98.4%,≥20 mm·h-1的概率仅0.05%;受杭州湾偏东气流影响,杭州市区发生短时强降水频率相对较高,尤其是余杭区的东部和西北山区;自2008年以来杭州市区每年短时强降水日数为18~28 d,其中大于等于50 mm·h-1的短时强降水日所占比例高达10%~20%(除2009年和2012年低于10%外);可用于预报杭州市区短时强降水的最佳环境因子依次为整层可降水量、K指数、最佳抬升指数、沙氏指数、925 h Pa露点温度和强天气威胁指数;在判断杭州市区短时强降水强度上表现最好的环境因子为整层可降水量,其次是850 h Pa垂直速度和925 h Pa散度。
