Recent Warming of Landfalling Atmospheric Rivers Along the West Coast of the United States
Recent Warming of Landfalling Atmospheric Rivers Along the West Coast of the United States
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DOI：
10.1029/2018jd029860
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发表时间：
2019-07-16
影响因子：
4.4
通讯作者：
Diffenbaugh, Noah S.
中科院分区：
文献类型：
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作者：
Gonzales, Katerina R.;Swain, Daniel L.;Diffenbaugh, Noah S.
大气河流（AR）经常产生极端降水，AR温度通过改变径流的时间和大小强烈影响水文影响。因此，AR温度的长期变化对区域水文气候具有重要影响，特别是在转向更多降雨主导的AR降水可能影响洪水风险和/或积雪蓄水的地方。在这项研究中，我们提供了美国西海岸五个次区域的AR温度的第一个气候学。然后，我们使用三种再分析产品评估了1980年至2016年每个子区域的登陆AR温度趋势。我们发现AR在季节和月尺度上变暖。在研究期间，冷季变暖范围为0.69至1.65摄氏度。我们检测到每月变暖>2摄氏度，最广泛的变暖发生在11月和3月。为了了解AR变暖的原因，我们量化了从发生到登陆的AR轨迹密度，并分析了每个月和登陆区域的沿轨迹AR温度。我们调查了三种可能的影响AR温度趋势在登陆：沿轨道温度登陆前，在登陆区域的背景温度，和AR温度在沿海海洋附近的区域登陆。一般来说，AR温度在登陆更紧密地匹配沿海和背景温度的趋势比沿轨道AR温度的趋势。AR变暖的季节不对称性和影响的异质性对区域水储存和洪水风险具有重要意义-表明AR特征的变化是复杂的，可能无法直接从背景气候的变化中推断出来。简明语言摘要大气河流（AR）风暴以其积累积雪，缓解干旱，并在美国西海岸沿着产生极端降水和洪水。AR温度是确定给定事件对水资源影响的重要变量，例如单个风暴带来的雨雪比例。因此，AR温度的变化对蓄水和洪水风险都有影响。我们发现，在季节和月度尺度上，AR都有显著的变暖，以及美国西海岸沿着变暖量的季节性和区域性变化。要了解变暖的AR在登陆地区，我们比较这些趋势与温度的趋势沿着AR轨道，背景温度在登陆地区，和温度在沿海海洋邻近的登陆地区。最强烈的变暖发生在11月和3月，这对区域洪水风险增加和蓄水量减少具有重要影响，并促使在地球仪的其他AR易发区域进行进一步调查。
Atmospheric rivers (ARs) often generate extreme precipitation, with AR temperature strongly influencing hydrologic impacts by altering the timing and magnitude of runoff. Long-term changes in AR temperatures therefore have important implications for regional hydroclimate-especially in locations where a shift to more rain-dominated AR precipitation could affect flood risk and/or water storage in snowpack. In this study, we provide the first climatology of AR temperature across five U.S. West Coast subregions. We then assess trends in landfalling AR temperatures for each subregion from 1980 to 2016 using three reanalysis products. We find AR warming at seasonal and monthly scales. Cool-season warming ranges from 0.69 to 1.65 degrees C over the study period. We detect monthly scale warming of >2 degrees C, with the most widespread warming occurring in November and March. To understand the causes of AR warming, we quantify the density of AR tracks from genesis to landfall and analyze along-track AR temperature for each month and landfall region. We investigate three possible influences on AR temperature trends at landfall: along-track temperatures prior to landfall, background temperatures over the landfall region, and AR temperature over the coastal ocean adjacent to the region of landfall. Generally, AR temperatures at landfall more closely match coastal and background temperature trends than along-track AR temperature trends. The seasonal asymmetry of the AR warming and the heterogeneity of influences have important implications for regional water storage and flood risk-demonstrating that changes in AR characteristics are complex and may not be directly inferred from changes in the background climate.Plain Language Summary Atmospheric river (AR) storms are well known for their ability to accumulate snowpack, provide drought relief, and generate extreme precipitation and flooding along the West Coast of the United States. AR temperature is an important variable for determining the water resource impacts of a given event, such as the ratio of rain to snow delivered by an individual storm. As a result, changes in AR temperature have implications for both water storage and flood risk. We find substantial warming in ARs at both the seasonal and monthly scales, as well as seasonal and regional variations in the amount of warming along the U.S. West Coast. To understand the warming of ARs at the landfall regions, we compare these trends with trends in temperature along the AR tracks, background temperature over the landfall region, and temperature over the coastal ocean adjacent to the landfall region. The most robust warming occurs in November and March, which has important implications for increased regional flood risk and decreased water storage, and motivates further investigation in other AR-prone regions around the globe.