Ocean Surface Salinity Response to Atmospheric River Precipitation in the California Current System
Ocean Surface Salinity Response to Atmospheric River Precipitation in the California Current System
复制标题
加州洋流系统中海洋表面盐度对大气河流降水的响应
DOI：
10.1175/jpo-d-21-0272.1
复制
发表时间：
2022
影响因子：
3.5
通讯作者：
Varadarajan, Aniruddh
中科院分区：
文献类型：
--
作者：
Hoffman, Lauren;Mazloff, Matthew R.;Gille, Sarah T.;Giglio, Donata;Varadarajan, Aniruddh
大气河流（ARs）导致陆地和海洋的降水。海洋上的降雨可以产生一个漂浮的淡水层，影响表面和混合层之间的交换。这些“新鲜的透镜体”对天气和气候很重要，因为它们可能在所有时间尺度上影响海洋分层。在这里，我们使用原位海洋数据，搭配AR事件，和一维配置的大气环流模型，调查AR降水对表面海洋盐度的影响，在加州电流系统（CCS）的季节性和基于事件的时间尺度。我们发现，在沿海和陆上位置的CCS刷新通过雨季由于AR事件，和AR活动较高的年份与更强的刷新信号。在较短的时间尺度上，模型模拟表明，CCS AR的事件特征可以产生海洋仪器可检测到的盐度变化（≥0.01 psu）。在这里，表面盐度的变化与降雨率成线性关系，与风速成反比。更高的风速（U> 8 m s−1）导致混合，将淡水输入分配到超过20 m的深度。较低的风速（U≤ 8 m s−1）允许淡水透镜体留在地表。结果表明，当地的降水是重要的，在设置的CCS的淡水季节性循环和淡水透镜体的形成应被考虑用于识别大气变化的影响上海洋的CCS上的天气事件的时间scales.Significance StatementAtmospheric河流产生大量的降雨。本研究的目的是了解这场雨如何影响表面海洋在加州电流系统的季节和事件的时间尺度。我们的研究结果表明，在雨季的降水量较大，导致随着时间的推移，在盐度下降较大。在较短的时间尺度上，这些大气河流降水事件通常会产生海洋仪器可检测到的表面盐度响应。这种盐度响应取决于降雨量和风速。一般来说，较高的风速会导致雨水输入的淡水混合得更深，而较低的风速会减少混合，从而使一层淡水在地表持续存在。
Atmospheric rivers (ARs) result in precipitation over land and ocean. Rainfall on the ocean can generate a buoyant layer of freshwater that impacts exchanges between the surface and the mixed layer. These “fresh lenses” are important for weather and climate because they may impact the ocean stratification at all time scales. Here we use in situ ocean data, collocated with AR events, and a one-dimensional configuration of a general circulation model, to investigate the impact of AR precipitation on surface ocean salinity in the California Current System (CCS) on seasonal and event-based time scales. We find that at coastal and onshore locations the CCS freshens through the rainy season due to AR events, and years with higher AR activity are associated with a stronger freshening signal. On shorter time scales, model simulations suggest that events characteristic of CCS ARs can produce salinity changes that are detectable by ocean instruments (≥0.01 psu). Here, the surface salinity change depends linearly on rain rate and inversely on wind speed. Higher wind speeds (U> 8 m s−1) induce mixing, distributing freshwater inputs to depths greater than 20 m. Lower wind speeds (U≤ 8 m s−1) allow freshwater lenses to remain at the surface. Results suggest that local precipitation is important in setting the freshwater seasonal cycle of the CCS and that the formation of freshwater lenses should be considered for identifying impacts of atmospheric variability on the upper ocean in the CCS on weather event time scales.Significance StatementAtmospheric rivers produce large amounts of rainfall. The purpose of this study is to understand how this rain impacts the surface ocean in the California Current System on seasonal and event time scales. Our results show that a greater precipitation over the rainy season leads to a larger decrease in salinity over time. On shorter time scales, these atmospheric river precipitation events commonly produce a surface salinity response that is detectable by ocean instruments. This salinity response depends on the amount of rainfall and the wind speed. In general, higher wind speeds will cause the freshwater input from rain to mix deeper, while lower wind speeds will have reduced mixing, allowing a layer of freshwater to persist at the surface.