SGER: The Role of Land-Atmosphere Coupling in Perpetuating Drought

这是气候变率和可预测性 (CLIVAR) 计划试点项目 DRICOMP 下的一笔赠款，用于耦合模型干旱项目，该项目的重点是对全球气候模型输出中所代表的干旱机制进行初步探索，并尝试评估这些模型在模拟干旱方面的可靠性。该项目的目标是尝试了解和确定陆地-大气耦合在气候模型和观测中使干旱永久化的作用。 由于土壤湿度异常具有很大的持续性，因此具有强（正）土壤湿度-降水耦合的区域会将这种持续性赋予降水变率；这将使干旱和潮湿期持续下去。 在当前的气候模型中，土壤湿度对降水的影响差异很大。这项研究首次探索性地解决了几个重要问题：陆地-大气耦合强的气候模型是否比弱耦合的模型更有可能出现更长时间、更严重的干旱？与其他地区相比，陆地-大气耦合强的地区是否更有可能遭受长时间的干旱？针对气候变化，陆地-大气耦合大的气候模型是否更有可能经历更长时间、更严重的干旱？主要研究人员将分析气候参与政府间气候变化专门委员会 (IPCC) 第四次评估报告的模型以及属于北美区域气候评估计划 (NARCAP) 一部分的高分辨率模型数据集。 为了进行观测，他们将使用北美区域再分析（NARR）、陆地表面水文循环的回顾性可变入渗能力（VIC）模型模拟​​、来自全球陆地数据同化系统（GLDAS）项目的全球数据以及来自南部大平原大气辐射测量（ARM）站点的数据。 他们将应用滞后相关和回归分析来量化当地土壤湿度和蒸发对后期降水的影响。将根据降水量、土壤湿度或径流定义三个干旱指数。 文献中使用这三个变量作为定义“气象”、“农业”和“水文”干旱的基础。 对于每个月、每个位置和数据集，他们将计算整个记录期间的每月发生率百分位数。 他们将把陆地-大气耦合的强度与干旱的持续时间和强度联系起来。这些研究的更广泛影响在于评估气候模型在预测未来干旱方面的可靠性。 该项目将为研究生提供部分支持。

This is a grant under a Climate Variability and Predictability (CLIVAR) Program pilot project called DRICOMP, for the Drought in Coupled Models Project, which focuses on making initial explorations into the mechanisms of drought as they are represented in the output of global climate models and on attempting to assess the reliability of these models in simulating drought.The objective of this project is to attempt to understand and determine the role of land-atmosphere coupling in perpetuating drought in climate models and in observations. Because soil moisture anomalies have large persistence, regions with strong (positive) soil moisture-precipitation coupling will have this persistence imparted to the precipitation variability; this will act to perpetuate both droughts and wet spells. The effect of soil moisture on precipitation is extremely variable among current climate models.This research represents a first exploratory effort to address several important questions: are climate models with strong land-atmosphere coupling more likely to have longer and more intense droughts than models with weak coupling, are regions of strong land-atmosphere coupling more likely to suffer droughts of long duration compared to other regions, and are climate models with large land-atmosphere coupling more likely to experience longer and more intense droughts in response to climate change?The principal investigators will analyze the climate models participating in the Intergovernmental Panel on Climate Change (IPCC) fourth assessment report and the high-resolution model datasets that are part of the North American Regional Climate Assessment Program (NARCAP). For observations they will use the North American Regional Reanalysis (NARR), a retrospective Variable Infiltration Capacity (VIC) model simulation of the land surface hydrological cycle, global data from the Global Land Data Assimilation Systems (GLDAS) project and data from the Southern Great Plains Atmospheric Radiation Measurement (ARM) site. They will apply lagged correlation and regression analyses to quantify the effect of local soil moisture and evaporation on later precipitation. Three drought indices, based on precipitation, soil moisture or runoff, will be defined. These three variables are used in the literature as the basis for defining "meteorological", "agricultural" and "hydrological" droughts. For each month, location and dataset, they will calculate monthly percentiles of occurrence for the entire period of record. They will relate the strength of land-atmosphere coupling to the duration and intensity of droughts.Broader impacts of the studies are in their contribution to assessing the reliability of climate models in projecting future droughts. The project will provide partial support for a graduate student.