Control of Storminess over the Pacific and North America by Circulation Regimes
Control of Storminess over the Pacific and North America by Circulation Regimes
复制标题
通过环流机制控制太平洋和北美的暴风雨
作者：
S. Amini;D. Straus
环流状况是通过对从 ERA 中期再分析中获得的太平洋-北美扩展区域上 500 hPa 位势高度和 250 hPa 纬向风的 5 天综合异常平均值进行聚类分析来确定的。确定了五个区域：北极低压 (AL)、太平洋波列 (WT)、阿拉斯加海脊 (AR)、太平洋海槽 (PT) 和北极高压 (AH)。大气河流频率和风暴路径测量的与制度相关的异常（高通滤波经向风和温度之间的 850 hPa 协方差和高通滤波经向风的 300 hPa 方差）被证明是显着的。环流状况提供了观测降水的统计显着调节（从多源加权集合数据集获得）。我们检查特定区域的异常、标准化异常和降水极值的出现。我们确定了每个区域中极端事件发生频率（第 5 个和第 95 个百分位数）与气候频率之比显着较高的区域。 AL体系中太平洋西北地区降水量减少，但美国中部和东部地区降水量增加，极端降水发生概率大幅增加，大气河流发生率增强，风暴路径更强。在WT模式下，太平洋大气河流向阿拉斯加转移，同时北太平洋东部风暴路径强度减小。 AR 状况的特点是进入西南部的湿气通量增加、极端降水以及与大气河流和风暴路径相关的热传输增加。 PT 系统中西南海岸的降水量和大气河流有所增加，德克萨斯州和佛罗里达州的降水量也有所增加。东北地区极度干旱的情况有所增加。美国中西部地区出现严重干旱。在AH期间，西北大片地区的降水量显着增加。
Circulation regimes are identified from a cluster analysis applied to 5-day means of the combined anomalies of 500 hPa geopotential height and the 250 hPa zonal wind over the extended Pacific-North America region obtained from ERA-Interim reanalyses. Five regimes are identified: the Arctic Low (AL), Pacific wavetrain (WT), Alaskan Ridge (AR) and Pacific Trough (PT) and Arctic High (AH). Regime dependent anomalies of the frequency of atmospheric rivers and measures of the storm tracks (850 hPa covariance between high pass filtered meridional wind and temperature and 300 hPa variance of high pass filtered meridional wind) are shown to be significant. The circulation regimes provide statistically significant modulation of observed precipitation (obtained from the Multi-Source Weighted-Ensemble data set). We examine regime-specific anomalies, normalized anomalies and the occurrence of extreme values of precipitation. We identify regions in which the ratio of frequency of occurrence of extremes (5th and 95th percentile) to the climatological frequency in each regime is significantly high. Precipitation is decreased over the Pacific Northwest in the AL regime, but is increased over the central and Eastern US, with a large increase in the probability of extreme precipitation, enhanced atmospheric river occurrence and stronger storm tracks. In the WT regime, Pacific atmospheric rivers are shifted towards Alaska, accompanied by a decrease in storm track magnitude over the Eastern North Pacific. The AR regime is characterized by an increase in moisture flux into the Southwest, increases in extreme precipitation and atmospheric rivers and storm track related heat transport. Increases in precipitation, and atmospheric rivers along the Southwest coast are noted in the PT regime, along with increased precipitation over Texas and Florida. The Northeastern region experiences increases in extremely dry conditions. Significant drought conditions occur over the Midwest US. Significant increases in precipitation over a broad region of the Northwest occur during the AH regime.
影响因子：
4.6
作者：
Dawson, Andrew;Palmer, T. N.
通讯作者：
Palmer, T. N.