A Two-plume Convective Model for Precipitation Extremes

Abstract

In the study of diagnosing climate simulations and understanding the dynamics of precipitation extremes, it is an essential step to adopt a simple model to relate water vapor condensation and precipitation, which occur at cloud-microphysical and convective scales, to large-scale variables. Several simple models have been proposed; however, improvement is still needed in both their accuracy and/or the physical basis. Here, we propose a two-plume convective model that takes into account the subgrid inhomogeneity of precipitation extremes. The convective model has three components, i.e., cloud condensation, rain evaporation, and environmental descent, and is built upon the zero-buoyancy approximation and guidance from the high-resolution reanalysis. Evaluated against the CMIP5 climate simulations, the convective model shows large improvements in reproducing precipitation extremes compared to previously proposed models. Thus, the two-plume convective model better captures the main physical processes and serves as a useful diagnostic tool for precipitation extremes.

摘要

在研究极端降水动力学或诊断气候模拟结果时, 经常需要利用简单模型对极端降水进行诊断, 从而简化物理过程并分析降水过程中的跨尺度相互作用. 之前的极端降水模型在准确度以及物理图像上还有待进一步的提高. 基于高分辨率的再分析资料, 本研究提出了极端降水的双羽流非均匀对流模型, 从而将次网格对流的非均匀性也考虑在内. 此模型建立在零浮力假设的基础上, 包含了云凝结、 降水再蒸发和环境下沉三个主要的物理过程, 并对其进行参数化. 利用CMIP5模拟结果进行评估, 此模型很好地拟合了极端降水, 其误差较于以往单羽流均匀的模型减少约一半. 研究结果表明此非均匀对流模型涵盖了极端降水的主要物理过程, 为极端降水的诊断研究提供了一个有力工具.

Electronic Supplementary Material to

A Two-plume Convective Model for Precipitation Extremes