Changes in the Global Climate: Atmospheric Angular Momentum and Pacific Ocean Temperatures
Changes in the Global Climate: Atmospheric Angular Momentum and Pacific Ocean Temperatures
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DOI：
10.1175/jcli-d-22-0322.1
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发表时间：
2023-10
影响因子：
4.9
通讯作者：
K. Weickmann;Edward Berry;Victor Gensini;David Gold;Thomas Petroski
中科院分区：
文献类型：
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作者：
K. Weickmann;Edward Berry;Victor Gensini;David Gold;Thomas Petroski
大气角动量（AAM）用于研究过去45年来地球大气环流的变化，这是一个相当大的气候变化时期。利用全球AAM，定义了1977-98年（以下简称P1）和1999-2022年（P2）两个年代际状态。全球AAM从P1下降到P2，并伴随着减弱的副热带急流在两个半球，强对流周围的北方海洋大陆，加强海表温度（SST）梯度在热带太平洋。周期差异的项目1）内部的年代际太平洋变化（IPV），2）一个假设的瞬态海洋恒温器响应温室气体和气溶胶排放，和3）与臭氧洞有关的环流异常。在1977-2023年期间，前两个过程迫使气候朝着更大的太平洋SST梯度和印度太平洋暖池（IPWP）的向极扩展，特别是进入北方半球。臭氧洞在南半球产生了其独特的异常模式，这种模式往往在1990年代初持续存在。P1期间纬向和垂直平均AAM的变化在40°N ~ 40°S之间具有频繁的西风异常，并在年际时间尺度上向极向传播。在P2期间，环流主要由副热带东风异常，极移急流和较弱的传播。在局部地区，纬向平均异常表现为中纬度脊，导致大陆干旱。案例研究说明了P2减弱的副热带急流，并研究了2020年初向拉尼娜转变的因素，并维持了P2模式。
Atmospheric angular momentum (AAM) is used to study the variability of Earth’s atmospheric circulation during the past 45 years, a time of considerable climate change. Using global AAM, two interdecadal states are defined covering the periods 1977–98 (hereinafter P1) and 1999–2022 (P2). Global AAM decreased from P1 to P2 and was accompanied by weakened subtropical jet streams in both hemispheres, strong convection around the northern Maritime Continent, and a strengthened sea surface temperature (SST) gradient across the tropical Pacific Ocean. The period differences project onto 1) internal interdecadal Pacific variability (IPV), 2) a postulated transient ocean thermostat response to greenhouse gas and aerosol emissions, and 3) circulation anomalies related to the ozone hole. During 1977–2023, the first two processes are forcing the climate toward larger Pacific Ocean SST gradients and a poleward expansion of the Indo-Pacific warm pool (IPWP), especially into the Northern Hemisphere. The ozone hole produces its own distinct pattern of anomalies in the Southern Hemisphere that tend to become persistent in the early 1990s. The zonal and vertical mean AAM variations during P1 have frequent westerly wind anomalies between 40°N and 40°S with poleward propagation on interannual time scales. During P2, the circulation is dominated by subtropical easterly wind anomalies, poleward-shifted jets, and weaker propagation. Locally, the zonal mean anomalies manifest as midlatitude ridges that lead to continental droughts. Case studies illustrate the weakened subtropical jet streams of P2 and examine the factors behind a transition to La Niña in early 2020 that maintains the P2 pattern.