Influence of the PNA on declining mountain snowpack in the Western United States
Influence of the PNA on declining mountain snowpack in the Western United States
复制标题
DOI：
10.1002/joc.2137
复制
发表时间：
2011-06-30
期刊：
影响因子：
--
通讯作者：
Abatzoglou, John T.
中科院分区：
文献类型：
--
作者：
Abatzoglou, John T.
美国西部山区积雪的广泛减少是区域气候变化的一个标志性指标。观测到的低海拔流域积雪减少与模式对人为气候变化的预测基本一致；然而，在喀斯喀特山脉、北落基山脉和内华达山脉的大部分地区，减少的幅度已经超过了仅仅基于20世纪后期人为变暖的预测。为了解决观测和预测之间的差异，研究了与太平洋-北美（PNA）模式相关的月内变率对冬末降雪降水百分比和融雪代理的影响。PNA对整个美国西部的冻结水平高度有重大影响，PNA的正值通常与异常高的冻结水平有关。近半个世纪以来，PNA在冬末的正趋势导致了区域冰点高度的上升、降雪率的下降以及山地和亚山地地区融雪量的增加。这种大气环流的变化加速了由人为强迫预测的山地积雪的减少。版权。(C) 2010年皇家气象学会
The widespread decrease in mountain snowpack across the Western United States is a hallmark indicator of regional climate change. Observed decreases in snowpack across lower-elevation watersheds are broadly consistent with model predictions of anthropogenic climate change; however, the magnitude of the decreases across much of the Cascades, Northern Rockies and Sierra Nevada has exceeded predictions based solely on late 20th century anthropogenic warming. To resolve the disparity between observations and predictions, the influence of intramonthly variability associated with the Pacific-North American (PNA) pattern on both the percent of precipitation falling as snow and a proxy for snowmelt during late winter is examined. The PNA is shown to have a significant influence on the elevation of the freezing level across the Western United States, with positive values of the PNA generally associated with anomalously high freezing levels. The positive tendency of the PNA during late winter over the last half-century has contributed to regional increases in the elevation of the freezing level, decreases in the percent of precipitation falling as snow, and increases in snowmelt across montane and sub-montane regions. This change in atmospheric circulation accelerated the decline in mountain snowpack predicted by anthropogenic forcing. Copyright. (C) 2010 Royal Meteorological Society