SGER: Hydrodynamics of the Caribbean Low-Level Jet and Its Relationship to Drought

这是气候变异性和可预测性(CLIVAR)计划试点项目DRICOMP下的一笔赠款，用于耦合模式中的干旱项目，主要研究人员将分析大气/海洋耦合全球气候模式的输出结果和国家环境预测中心(NCEP)北美地区再分析的结果，以试图提高我们对加勒比低空急流的流体动力学及其与北美和中美洲夏季干旱的关系的理解，并评估我们在模式中捕捉这种关系的能力。过去的研究表明，美国中部的干旱与大平原低空急流从墨西哥湾向极地输送的水汽减少有关。向经的大平原急流位于向纬向的加勒比海低空急流的北部，在月平均气候学上，它们通常看起来是相连的。然而，加勒比海急流的基本流体动力学以及它在干旱期间如何变化还不是很清楚。首席调查员将对加勒比低空急流通过与大平原急流相互作用向美国中部提供湿气以及通过将气候学与干旱时期进行对比直接向中美洲供应湿气的作用进行探索性评价。大气和地表水分收支分析以及热力学平衡将在再分析和20世纪政府间气候变化专门委员会第四次评估报告(IPCC AR4)在五个模式中整合的大气环流模式(GCM)输出中进行诊断。这些分析可能导致更好地理解干旱的动态，并评估模型在多大程度上捕捉干旱机制。这项研究的更广泛影响在于，它可能揭示出与北美干旱的新的物理联系，这可能有助于干旱预测。

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 principal investigators will analyze output from coupled atmosphere/ocean global climate models and the National Center for Environmental Prediction's (NCEP's) North American regional reanalysis to try to improve our understanding of the hydrodynamics of the Caribbean low-level jet and its relationship to summer drought over North and Central America and to evaluate our ability to capture this relationship in models. Past studies suggest that drought over the central United States is associated with a decrease in the poleward transport of moisture from the Gulf of Mexico by the Great Plains low-level jet. The meridionally-oriented Great Plains jet is located just north of the zonally-oriented Caribbean low-level jet, and, in monthly mean climatologies, they often appear to be connected. The basic hydrodynamics of the Caribbean jet and how it varies during drought are, however, not well known. The principal investigators will conduct exploratory evaluations of the roles of the Caribbean low-level jet in supplying moisture to the central United States through interactions with the Great Plains jet and in supplying moisture directly to Central America, by contrasting the climatology with times of drought. Atmospheric and surface moisture budget analyses, as well as thermodynamic balances, will be diagnosed in the reanalysis and in the general circulation model (GCM) output from 20th Century Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) integrations in five models. These analyses may lead to a better understanding of the dynamics of drought and an assessment of how well models capture drought mechanisms.A broader impact of the study is in its potential to reveal a new physical link to North American drought that could contribute to drought prediction.