Interhemispheric Aerosol Radiative Forcing and Tropical Precipitation Shifts during the Late Twentieth Century
Interhemispheric Aerosol Radiative Forcing and Tropical Precipitation Shifts during the Late Twentieth Century
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DOI：
10.1175/jcli-d-15-0148.1
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发表时间：
2015-10-01
影响因子：
4.9
通讯作者：
Booth, Ben B. B.
中科院分区：
文献类型：
--
作者：
Allen, Robert J.;Evan, Amato T.;Booth, Ben B. B.
在整个世纪后半叶，热带降水量的南北向变化与严重干旱有关。虽然与各种原因有关，但这些变化的根源仍然难以捉摸。在这里，它表明，它们不太可能单独从气候系统的内部变率，如耦合的海洋-大气气候模式模拟。与以前的工作类似，作者发现人为和火山气溶胶是模拟的20世纪热带降水变化的主要驱动因素。模型，包括cloud-clouddo和寿命气溶胶间接效应产生显着较大的变化比模型，缺乏气溶胶间接效应，也重现了大部分的南太平洋热带降水转移。然而，所有的模型都大大低估了大西洋板块观测到的变化幅度，除非是由观测到的SST驱动的。从机制上讲，热带降水的变化是由半球间的海面温度变化，这是与半球不对称的变化，低纬度的表面压力，风，低云，以及强度，位置和跨赤道的能量输送的哈德利细胞。具有较大半球气溶胶辐射强迫梯度的模型产生较大的半球温度对比，反过来，较大的纬向降水变化。作者得出结论，气溶胶可能是观测到的太平洋热带降水南移的主要驱动因素。气溶胶也是大西洋变化的重要驱动因素，尽管人们不能排除自然变化的贡献，以解释观测到的变化幅度。
Through the latter half of the twentieth century, meridional shifts in tropical precipitation have been associated with severe droughts. Although linked to a variety of causes, the origin of these shifts remains elusive. Here, it is shown that they are unlikely to arise from internal variability of the climate system alone, as simulated by coupled ocean-atmosphere climate models. Similar to previous work, the authors find that anthropogenic and volcanic aerosols are the dominant drivers of simulated twentieth-century tropical precipitation shifts. Models that include the cloud-albedo and lifetime aerosol indirect effects yield significantly larger shifts than models that lack aerosol indirect effects and also reproduce most of the southward tropical precipitation shift in the Pacific. However, all models significantly underestimate the magnitude of the observed shifts in the Atlantic sector, unless driven by observed SSTs. Mechanistically, tropical precipitation shifts are driven by interhemispheric sea surface temperature variations, which are associated with hemispherically asymmetric changes in low-latitude surface pressure, winds, and low clouds, as well as the strength, location, and cross-equatorial energy transport of the Hadley cells. Models with a larger hemispheric aerosol radiative forcing gradient yield larger hemispheric temperature contrasts and, in turn, larger meridional precipitation shifts. The authors conclude that aerosols are likely the dominant driver of the observed southward tropical precipitation shift in the Pacific. Aerosols are also significant drivers of the Atlantic shifts, although one cannot rule out a contribution from natural variability to account for the magnitude of the observed shifts.