Mesoscale Modeling of Tropical Paleoclimate

该奖项将用于开发和应用中尺度模拟系统，以研究非洲和南美洲热带气候在最后一次冰盛期(LGM)期间的过去可变性。该建模系统由两个模型组成。中尺度气候模式(MCM)将模拟几十公里空间尺度上的气候。大气环流模式(GCM)将为中尺度模式产生风、温度和水汽的侧边界条件。对今天和北非大冰川(约21,000年前)干燥气候的模拟将与大约6,000年前非洲湿润时期的模拟对比，当时萨赫勒和撒哈拉非洲支持许多湖泊和广泛的植被。这项研究将解决以下问题：--日照、陆地表面条件的变化、区域海温差异和大尺度气候差异(即MCM横向边界条件)在造成今天、非洲湿润时期和末次盛冰期北非地表湿度差异方面的单独和综合作用是什么？--湿度差异只与降水的变化有关，还是蒸发量和/或地下水位的变化起到了重要作用？--改变大气水汽收支的机制是什么？--有没有任何重要的机制是非线性的，可以帮助解释该地区气候变化的速度？对未来气候变化(全球变暖)的影响是什么？对各种侧向和地表边界条件的模拟，以及其他强迫作用，如日照和大气成分，将确定导致湿润条件和快速气候变化的重要因素和物理机制，据推测，这种变化在全新世发生在亚马逊地区。中尺度模式系统也将被用来研究大冰川的南美洲气候。研究将解决以下问题：-亚马逊盆地大冰盖期间的干燥和冷却的分布是什么，与今天的气候不同有什么机制？-用中尺度模式模拟了中央安第斯山脉的干旱差异，什么机制解释了与现在的不同？-模拟的两个地区的差异是如何与全球尺度气候条件有关的，它们是如何联系的？-模式是否支持在中央安第斯高压的不同地区有不同的干旱趋势的观点？如果是这样的话，这些趋势是否提供了有关上一次冰川周期气候变化的半球间对称性或不对称性的信息？

This award will serve to develop and apply a mesoscale modeling system for studying past variability in tropical climates of Africa and South America during the Last Glacial Maximum (LGM). The modeling system consists of two models. A mesoscale climate model (MCM) will simulate climate on space scales of tens of kilometers. A general circulation model (GCM) will generate lateral boundary conditions on wind, temperature, and moisture for the mesoscale model. Simulations of the dry climates of the present day and LGM (~21,000 years ago) over northern Africa will be contrasted with simulations for the African Humid Period, approximately 6,000 years ago when Sahelian and Saharan Africa supported numerous lakes and extensive vegetation. The research will address the following questions:-What are the individual and combined roles of insolation, changes in land surface conditions, regional SST differences, and differences in large-scale climate (i.e., MCM lateral boundary conditions) in causing differences in surface wetness over northern Africa among the present day, African Humid Period and the LGM?-Are the differences in wetness associated with changes in precipitation only, or do changes in evaporation and/or water table levels play an important role?-What mechanisms are involved in changing the atmospheric column water vapor budget? -Are any important mechanisms nonlinear in a way that helps explain the speed with which the climate can change in this region? What are the implications for future climate change (global warming)?Simulations with various combinations of lateral and surface boundary conditions, as well as other forcing functions such as insolation and atmospheric composition, will identify the important factors and physical mechanisms that lead to the wet conditions and the rapid climate change that is hypothesized to have occurred in Amazonia during the Holocene. The mesoscale modeling system will also be used to study South American climate of the LGM.The research will address the following questions:-What was the distribution of drying and cooling during the LGM in the Amazon Basin and what mechanisms are associated with the differences from the present day climate?-What differences in aridity in the Central Andes are simulated with the MCM, and what mechanisms account for differences from the present day?-How are the simulated differences in both regions related to global-scale climate conditions and how are they linked?-Does the model support the idea that there are different aridity trends in different areas of the high Central Andes? If so, are these trends providing information about inter-hemispheric symmetry or asymmetry of climate change during the last glacial cycle?