Mesoscale Modeling of Tropical Paleoclimate

该奖项将用于开发和应用一个中尺度模拟系统，以研究非洲和南美洲在末次盛冰期（LGM）期间热带气候的过去变化。建模系统由两个模型组成。中尺度气候模式（MCM）将模拟数十公里空间尺度的气候。大气环流模式（GCM）将为中尺度模式生成风、温度和湿度的横向边界条件。 对北方非洲现今和末次盛期（约21，000年前）干旱气候的模拟将与对非洲湿润期的模拟进行对比，非洲湿润期约为6，000年前，当时萨赫勒和撒哈拉非洲支持许多湖泊和广泛的植被。研究将解决以下问题：-日照、地表条件变化、区域SST差异和大尺度气候差异（即，MCM横向边界条件）在造成北方非洲表面湿度差异之间的今天，非洲潮湿期和末次盛冰期？湿度的差异是否仅与降水量的变化有关，还是蒸发和/或地下水位的变化起着重要作用？改变大气柱水汽收支的机制是什么？- 是否有任何重要的非线性机制有助于解释该地区气候变化的速度？对未来气候变化（全球变暖）有什么影响？模拟与各种组合的横向和表面边界条件，以及其他强迫功能，如日照和大气成分，将确定的重要因素和物理机制，导致潮湿的条件和快速的气候变化，假设已经发生在亚马逊河流域在全新世。中尺度模拟系统还将用于研究末次冰期的南美气候。研究将解决以下问题：-亚马逊盆地末次冰期期间干燥和冷却的分布情况如何，以及与现代气候差异相关的机制是什么？- MCM模拟了中部安第斯山脉的干旱程度有哪些差异，是什么机制导致了与现在的差异？这两个地区的模拟差异与全球气候条件有何关系？它们之间有何联系？该模型是否支持在高中部安第斯山脉的不同地区有不同干旱趋势的观点？如果是的话，这些趋势是否提供了关于末次冰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?