Winter orographic precipitation ratios in the Sierra Nevada - Large-scale atmospheric circulations and hydrologic consequences
Winter orographic precipitation ratios in the Sierra Nevada - Large-scale atmospheric circulations and hydrologic consequences
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DOI：
10.1175/jhm-390.1
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发表时间：
2004-12-01
影响因子：
3.8
通讯作者：
Cayan, D
中科院分区：
文献类型：
--
作者：
Dettinger, M;Redmond, K;Cayan, D
加利福尼亚州内华达山脉冬季降水在地形上增强的程度因风暴和季节而异，从低海拔和高海拔降水率几乎相同的情况到中海拔（此处考虑）降水率可能比该范围底部高出 30 倍之多的情况。对 1954 年至 1999 年风暴和季节期间与地形降水变化相关的大尺度条件的分析表明，与较少地形风暴期间和最大整体风暴期间相比，强烈地形风暴最常具有从更近西方向输送水汽的风，并且通常强烈地形风暴的对流稳定性较差。强烈的地形条件通常伴随着强降水事件，因为这两种风力条件都存在于形成许多内华达山脉风暴核心的中纬度气旋中。拉尼娜冬季期间的风暴往往会比厄尔尼诺期间的风暴产生更大的地形比（OR）。对内华达山脉中部流域的水流模型进行的简单实验表明，对于固定的流域总降水量，OR 的减少会导致冬季洪水峰值增大和春季流量减小，从而导致径流季节总体加速。
The extent to which winter precipitation is orographically enhanced within the Sierra Nevada of California varies from storm to storm, and season to season, from occasions when precipitation rates at low and high altitudes are almost the same to instances when precipitation rates at middle elevations ( considered here) can be as much as 30 times more than at the base of the range. Analyses of large-scale conditions associated with orographic precipitation variations during storms and seasons from 1954 to 1999 show that strongly orographic storms most commonly have winds that transport water vapor across the range from a more nearly westerly direction than during less orographic storms and than during the largest overall storms, and generally the strongly orographic storms are less convectively stable. Strongly orographic conditions often follow heavy precipitation events because both of these wind conditions are present in midlatitude cyclones that form the cores of many Sierra Nevada storms. Storms during La Nina winters tend to yield larger orographic ratios (ORs) than do those during El Ninos. A simple experiment with a model of streamflows from a river basin draining the central Sierra Nevada indicates that, for a fixed overall basin-precipitation amount, a decrease in OR contributes to larger winter flood peaks and smaller springtime flows, and thus to an overall hastening of the runoff season.