Collaborative Research: Convective Organization and Climate

该研究小组将制定并应用一个简化的数值模式，以探索有利于湿大气对流自聚集的条件。在自然界和全物理大气数值模拟中，积云对流聚集成包含许多单独的对流单体的块状物是非常重要的。研究人员使用大气建模系统(SAM)数值模式进行了初步分析，并将对这些模拟进行扩展，以解决以下假设：对流的自聚集将导致表面温度的系统性下降，而这种下降可能反过来导致对流的解体和表面的恢复性回暖。因此，系统自然会被聚集状态和分解状态之间的相变所吸引，并将成为自组织关键系统的一个例子。这项拟议工作的目标是：(1)理解自聚集的物理学，(2)确定系统中存在多少滞后，(3)确定具有表面能量平衡的辐射-对流平衡系统是否受到自组织临界性的影响，以及(4)了解上述因素对基于理想化的辐射-对流状态以及更真实的世界条件所预测的气候的影响。这项工作的学术价值来自于对影响湿大气对流的机制的改进的基本理解，湿大气对流是气候系统的一个关键但仍未完全理解的组成部分。热带气候趋于自组织临界状态的假设得到证实，可以大大促进对对流和气候之间相互关系的理解。这项研究的更广泛影响包括在两个合作机构中的每个机构教育和培训一名研究生。这项工作还有可能通过改进适合纳入耦合气候模式的参数来改进对流的表示，这反过来又有助于改进气候预报。

This research team will formulate and apply a simplified numerical model to explore conditions favoring the self-aggregation of moist atmospheric convection. Aggregation of cumulus convection into clumps containing many individual convective cells is prominent in nature and in full-physics numerical atmospheric simulations alike. The researchers have performed preliminary analyses using the System for Atmospheric Modeling (SAM) numerical model, and will expand upon these simulations in order to address the hypothesis that self-aggregation of convection will lead to a systematic decline in the surface temperature, and that such decline may in-turn lead to disaggregation of convection and restorative re-warming of the surface. As such, the system would naturally be attracted to the phase transition between aggregated and disaggregated states and would constitute an example of a self-organized critical system. The objectives of the proposed work are to: (1) understand the physics of self-aggregation, (2) determine how much hysteresis there is in the system, (3) determine whether radiative-convective equilibrium systems with surface energy balance are subject to self-organized criticality, and (4) understand the implications of these aforementioned factors upon climates predicated on idealized radiative-convective states as well as more real-world conditions.The intellectual merit of the work derives from improved basic understanding of mechanisms influencing moist atmospheric convection, which is a critical but nonetheless not fully understood component of the climate system. A confirmation of the hypothesis that tropical climate tends toward a state of self-organized criticality could substantially advance the understanding of the interrelationship between convection and climate.The broader impacts of the study include the education and training of a graduate student at each of two collaborative institutions. The work also has potential to lead to improved representations of convection via improved parameterizations suitable for incorporation into coupled climate models, which could in turn contribute to improved climate forecasts.