Evaluating the large-scale hydrological cycle response within the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) ensemble
Evaluating the large-scale hydrological cycle response within the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) ensemble
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DOI：
10.5194/cp-17-2537-2021
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发表时间：
2021-12
影响因子：
4.3
通讯作者：
Zixuan Han;Qiong Zhang;Qiang Li;R. Feng;A. Haywood;J. Tindall;S. Hunter;B. Otto‐Bliesner;
中科院分区：
文献类型：
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作者：
Zixuan Han;Qiong Zhang;Qiang Li;R. Feng;A. Haywood;J. Tindall;S. Hunter;B. Otto‐Bliesner;
抽象的。上新世中期(∼3 Ma)是最近的暖期之一，大气中二氧化碳浓度高，导致高温，经常被认为是对近期未来气候变化的类比。在这里，我们应用水分收支分析来研究上新世模式对比项目第二阶段(PlioMIP2)的13个模式集合内低纬大尺度水文循环的响应。结果表明，上新世中期大气水汽含量的增加(由于热力作用)导致太平洋热带辐合带(ITCZ)和海洋大陆等深热带地区湿润，而副热带地区干燥。值得注意的是，在区域降水减去蒸发(PME)变化(即ITCZ北移和北印度洋增湿)中，动力效应比热力学效应起到更重要的作用。这种热力学效应在一定程度上被哈德利环流北移的动力效应所抵消，哈德利环流使北半球(即副热带太平洋)的深层热带变干，而使副热带变湿。从地球能量收支的角度看，大气能量的半球不对称引起的越赤道大气南下输送的增强(0.22PW)有利于ITCZ向北移动约1∘。ITCZ的转移重新组织了大气环流，有利于哈德利环流的北移。此外，在PlioMIP2模式中，沃克环流不断向西移动，导致北印度洋的条件更加潮湿。PlioMIP2组合突出表明，上新世中期期间半球间大气能量的不平衡可能导致动力效应的变化，抵消了热力学效应，从而改变了上新世中期的水文气候。
Abstract. The mid-Pliocene (∼3 Ma) is one of the most recent warm periods with high CO2 concentrations in the atmosphere and resulting high temperatures, and it is often cited as an analog for near-term future climate change. Here, we apply a moisture budget analysis to investigate the response of the large-scale hydrological cycle at low latitudes within a 13-model ensemble from the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2). The results show that increased atmospheric moisture content within the mid-Pliocene ensemble (due to the thermodynamic effect) results in wetter conditions over the deep tropics, i.e., the Pacific intertropical convergence zone (ITCZ) and the Maritime Continent, and drier conditions over the subtropics. Note that the dynamic effect plays a more important role than the thermodynamic effect in regional precipitation minus evaporation (PmE) changes (i.e., northward ITCZ shift and wetter northern Indian Ocean). The thermodynamic effect is offset to some extent by a dynamic effect involving a northward shift of the Hadley circulation that dries the deep tropics and moistens the subtropics in the Northern Hemisphere (i.e., the subtropical Pacific). From the perspective of Earth's energy budget, the enhanced southward cross-equatorial atmospheric transport (0.22 PW), induced by the hemispheric asymmetries of the atmospheric energy, favors an approximately 1∘ northward shift of the ITCZ. The shift of the ITCZ reorganizes atmospheric circulation, favoring a northward shift of the Hadley circulation. In addition, the Walker circulation consistently shifts westward within PlioMIP2 models, leading to wetter conditions over the northern Indian Ocean. The PlioMIP2 ensemble highlights that an imbalance of interhemispheric atmospheric energy during the mid-Pliocene could have led to changes in the dynamic effect, offsetting the thermodynamic effect and, hence, altering mid-Pliocene hydroclimate.