Downslope Winds and Dust Storms in the Salton Basin
Downslope Winds and Dust Storms in the Salton Basin
复制标题
DOI：
10.1175/mwr-d-18-0357.1
复制
发表时间：
2019-06
影响因子：
3.2
通讯作者：
A. Evan
中科院分区：
文献类型：
--
作者：
A. Evan
索尔顿盆地是位于加州东南端的一个封闭的海底水平盆地。在盆地的中心是索尔顿海，该州最大的内陆湖，周围是沙漠景观，其特点是古湖床表面，干洗，冲积扇和沙丘间。这个地区经常发生沙尘暴.然而，尽管这里的沙尘暴爆发是有规律的，但人们对造成这些风暴的气象过程知之甚少。在这里，我使用再分析的观测和输出来阐明2015-18年索尔顿盆地沙尘排放事件的气象控制。对地面和高空观测、卫星数据和再分析的分析表明，该地区最大的沙尘暴与加拿大西部海岸线附近的上层低气压有关，该低气压引导着该地区的纬向低空急流。气流被海岸山脉阻挡，导致这些山脉背风面的空气等熵下降。一旦索尔顿盆地底部的地表变暖足够，使得下降空气的密度大于地表环境空气的密度，下坡风暴就会到达沙漠底部并引发粉尘排放。这个过程也可能伴随着顺风传播的水跃。这些过程似乎是相似的，负责最强的沙尘暴事件在欧文斯谷，并可能代表其他封闭的盆地排放的主要机制。
The Salton basin is a closed, subsea level basin located in extreme southeastern California. At the center of the basin lies the Salton Sea, the state’s largest inland lake, which is surrounded by a desert landscape characterized by paleo lakebed surfaces, dry washes, alluvial fans, and interdunes. Dust storms are common occurrence in this region. However, despite the regularity of dust outbreaks here, little is known about the meteorological processes responsible for these storms. Here I use observations and output from reanalysis to elucidate the meteorological controls on dust emission events in the Salton basin during 2015–18. Analysis of surface and upper-air observations, satellite data, and reanalysis, suggest that the largest dust storms in the region are associated with an upper-level low centered near the coastline of western Canada, which directs a zonal low-level jet over the region. Flow blocking by a coastal mountain range results in isentropic drawdown of air in the lee of these mountains. Once surface warming at the floor of the Salton basin is sufficient such that the density of the descending air is greater than that of the ambient air at the surface, the downslope windstorm reaches the desert floor and initiates dust emission. This process may also be accompanied by a downwind propagating hydraulic jump. These processes appear to be similar to those responsible for the strongest dust events in the Owens Valley, and may represent the main mechanisms for emission from other closed basins.