Detection of Asian dust in California orographic precipitation
Detection of Asian dust in California orographic precipitation
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DOI：
10.1029/2010jd015351
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发表时间：
2011-08-26
影响因子：
4.4
通讯作者：
Prather, Kimberly A.
中科院分区：
文献类型：
--
作者：
Ault, Andrew P.;Williams, Christopher R.;Prather, Kimberly A.
气溶胶作为云凝结核（CCN）和冰核（IN）影响云的微物理特性。通过改变云的性质，气溶胶有可能改变降水的位置和强度，但确定气溶胶引起的降水变化的幅度和可重复性仍然是对实验者和建模者的一个重大挑战。在CalWater早期启动活动期间（2009年2月22日至3月11日），在两个热带气旋期间进行了一系列独特的大气化学，降水和气象测量。这两个风暴显示出增强的综合水汽浓度和水平水汽输送，由于大气河流条件，并在一起，产生了23%的年降水量和38%的最大积雪在加州的中央塞拉利昂雪实验室（CSSL）。不溶性残留物的降水测量结果表明，在两个风暴与第一个显示主要是生物质燃烧的有机物种，而第二个风暴显示从生物质燃烧有机物的亚洲灰尘的主导地位的过渡发生非常不同的化学。如图所示，沙尘在第二次风暴期间被输送到太平洋彼岸，并与内华达州山脉上空较冷的高海拔降水地形云结合。第二场风暴产生的降水量是第一场风暴的1.4倍，CSSL的积雪量增加了1.6倍。如先前的测量和建模研究所述，灰尘可以有效地充当冰核，导致增加的霜化率和提高的降水效率，最终可能导致降水的差异。未来的建模研究将有助于解卷积的气象，微物理和气溶胶因素导致这些差异，并将使用CalWater的气象和气溶胶观测，以约束基于模型的解释。这种联合努力的最终目标是利用这些结果来改善区域气候模式中气溶胶-云对降水的影响。
Aerosols impact the microphysical properties of clouds by serving as cloud condensation nuclei (CCN) and ice nuclei (IN). By modifying cloud properties, aerosols have the potential to alter the location and intensity of precipitation, but determining the magnitude and reproducibility of aerosol-induced changes to precipitation remains a significant challenge to experimentalists and modelers. During the CalWater Early Start campaign (22 February to 11 March 2009), a uniquely comprehensive set of atmospheric chemistry, precipitation, and meteorological measurements were made during two extratropical cyclones. These two storms showed enhanced integrated water vapor concentrations and horizontal water vapor transports due to atmospheric river conditions and, together, produced 23% of the annual precipitation and 38% of the maximum snowpack at California's Central Sierra Snow Lab (CSSL). Precipitation measurements of insoluble residues showed very different chemistry occurring during the two storms with the first one showing mostly organic species from biomass burning, whereas the second storm showed a transition from biomass burning organics to the dominance of Asian dust. As shown herein, the dust was transported across the Pacific during the second storm and became incorporated into the colder high-altitude precipitating orographic clouds over the Sierra Nevada. The second storm produced 1.4 times as much precipitation and increased the snowpack by 1.6 times at CSSL relative to the first storm. As described in previous measurement and modeling studies, dust can effectively serve as ice nuclei, leading to increased riming rates and enhanced precipitation efficiency, which ultimately can contribute to differences in precipitation. Future modeling studies will help deconvolute the meteorological, microphysical, and aerosol factors leading to these differences and will use CalWater's meteorological and aerosol observations to constrain the model-based interpretations. The ultimate goal of such combined efforts is to use the results to improve aerosol-cloud impacts on precipitation in regional climate models.