Boundary Layer Quasi-equilibrium and Tropical Atmospheric Circulations

9616290雷蒙德，新墨西哥矿业与技术研究所“边界层准平衡与热带大气环流”雷蒙德博士将探讨热带海洋上的湿润对流是由大气亚云层的熵平衡控制的这一观点。这一假设被称为边界层准平衡（BLQ），将通过最近开发的积云系综模型和首席研究员的赤道β平面原始方程模型以及TOGA COARE数据分析的一系列建模实验来检验。雷蒙德博士还将探讨这一假设对热带大气环流的总体影响。简单地说，这一假设断言，边界层或亚云层迅速适应湿润熵的流入和流出，以这样一种方式，流入在半天或更长的时间尺度上平衡流出。在潮湿的热带地区，这一过程的主要因素是海气通量以及来自潮湿对流的对流和中尺度下降气流，尽管在非常干燥的空气存在于边界层上方的情况下，进入边界层的干夹带可能很重要。最终的结果是，海气通量（在某些情况下，干夹带）对对流活动施加了强有力的控制。为了实现这一假设，雷蒙德博士将重点关注三个问题：(1)BLQ适用的运动尺度；(2)中层大气湿度、风切变和相关条件的变化如何影响上升气流和下降气流的比例，从而影响边界层平衡；(3)BLQ对大尺度热带环流的影响。这项工作对处理全球气候和天气模式中的对流具有重要意义。

9616290 Raymond, New Mexico Institute of Mining and Technology "Boundary Layer Quasi-equilibrium and Tropical Atmospheric Circulations" Dr. Raymond will explore the idea that moist convection over the tropical oceans is controlled by the entropy balance of the sub-cloud layer of the atmosphere. This hypothesis, known as the boundary layer quasi- equilibrium (BLQ), will be examined through a series of modeling experiments with a recently developed cumulus ensemble model and with the principal investigator's equatorial beta plan primitive equation model as well as through analysis of TOGA COARE data. Dr. Raymond also will explore the consequences of this hypothesis for tropical atmospheric circulations in general. Simply stated, this hypothesis asserts that the boundary or sub-cloud layer rapidly adjusts to the inflow and outflow of moist entropy in such a way that inflow balances outflow on time scales of half a day or greater. In the moist tropics, the primary elements in this process are sea-air fluxes and convective and mesoscale downdrafts from moist convection, although dry entrainment into the boundary layer can be important in instances where very dry air exists just above the boundary layer. The net result is that sea-air fluxes (and in some case, dry entrainment) exert a strong control on convective activity. In pursing this hypothesis, Dr. Raymond will focus on three issues: (1) the scales of motion over which the BLQ applies, (2) how variations in middle level atmospheric moisture, wind-shear and related conditions affect the ratio of updrafts and downdrafts and thus the boundary layer balance, and (3) the implications of BLQ with respect to large-scale tropical circulations. This work has important implications for the treatment of convection in global climate and weather models.