Response of Vertical Velocities in Extratropical Precipitation Extremes to Climate Change
Response of Vertical Velocities in Extratropical Precipitation Extremes to Climate Change
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DOI：
10.1175/jcli-d-19-0766.1
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发表时间：
2020-08-15
影响因子：
4.9
通讯作者：
O'Gorman, Paul A.
中科院分区：
文献类型：
--
作者：
Li, Ziwei;O'Gorman, Paul A.
在气候模式的预测中，大多数地区的极端降水会加剧。垂直速度的变化有助于极端降水强度的变化，但仍然知之甚少。在这里，我们发现，在21世纪世纪气候变化的模拟中，对流层中层垂直速度在热带外极端降水中总体加强。对于每一个极端事件，我们解决了准地转欧米茄方程分解成不同的物理贡献，这种加强。我们首先考虑干分解，其中潜热被视为向上运动的外部强迫。潜热加热增加对上升运动的积极贡献大部分被干静稳定度增加和垂直速度水平长度尺度变化的消极贡献所抵消。然而，当目的是了解降水的变化时，考虑潜热的变化是一个限制，因为潜热和降水是密切相关的。因此，我们还进行了湿分解的垂直速度的变化，其中潜热是通过湿静态稳定性表示。在湿分解中，湿静态稳定性的变化起着关键作用，其他因素的贡献，如上升运动的深度变化的重要性增加。虽然干和湿的分解是自洽的，潮湿的动力学的角度有更大的潜力，让洞察动力学的贡献，在不同地区的极端降水变化的原因。
Precipitation extremes intensify in most regions in climate model projections. Changes in vertical velocities contribute to the changes in intensity of precipitation extremes but remain poorly understood. Here, we find that midtropospheric vertical velocities in extratropical precipitation extremes strengthen overall in simulations of twenty-first-century climate change. For each extreme event, we solve the quasigeostrophic omega equation to decompose this strengthening into different physical contributions. We first consider a dry decomposition in which latent heating is treated as an external forcing of upward motion. Much of the positive contribution to upward motion from increased latent heating is offset by negative contributions from increases in dry static stability and changes in the horizontal length scale of vertical velocities. However, taking changes in latent heating as given is a limitation when the aim is to understand changes in precipitation, since latent heating and precipitation are closely linked. Therefore, we also perform a moist decomposition of the changes in vertical velocities in which latent heating is represented through a moist static stability. In the moist decomposition, changes in moist static stability play a key role and contributions from other factors such as changes in the depth of the upward motion increase in importance. While both dry and moist decompositions are self-consistent, the moist dynamical perspective has greater potential to give insights into the causes of the dynamical contributions to changes in precipitation extremes in different regions.