Collaborative Research: Observational and Modeling Studies of Overshooting Convection and Stratosphere-Troposphere Exchange

穿透（超冲）对流层顶的深层对流影响温带对流层上层和平流层下层的微量气体组成，这对全球大气化学和地球辐射平衡具有重要意义。本研究将结合10多年的地面雷达观测资料和数值模式模拟，研究超冲对流的物理和化学特征。来自大约100台NEXRAD雷达的数据将被合成到具有高时空分辨率的三维区域网格中。超冲对流物理特征的气候学，如垂直范围、地理分布、年际变率、年周期和日周期，将由雷达观测计算出来。由合成雷达数据得出的过冲对流特征将与基于卫星红外观测的估计进行比较。为了研究跨对流层顶运输的机制并对平流层-对流层交换进行定量估计，将对个案研究和整个暖季进行具有明确解析对流和化学的数值模式模拟。雷达数据将与飞机上的原位微量气体观测一起使用，以评估数值模拟的性能。知识价值：众所周知，温带对流可以穿透对流层顶并延伸到平流层下层，但关于其地理分布、发生频率或穿透平流层深度的定量信息很少。本研究的雷达分析将在高时空分辨率的直接几何观测的基础上产生一种新的中纬度超冲对流区域气候学。这些结果将与卫星对超调的红外估计进行比较，后者提供了将区域结果扩展到全球领域的潜力。超调对流的高分辨率数值模拟将用于研究平流层-对流层交换机制，并对重要微量物质的输送进行定量估计。更广泛的影响：这项研究将产生一个长期的、公开的、覆盖美国大部分相邻地区的雷达反射率数据集，这些数据将适用于广泛的其他水文气象问题。由于对流在目前的全球气候模式中没有得到解决，这些研究将为发展由于对流过冲引起的平流层-对流层交换的参数化提供指导。更好地了解超调对流将有助于减少未来气候预估中的不确定性，这是一个重要的经济和社会问题。此外，诊断对流行为及其对大气化学的影响将有助于更好地了解影响空气质量和人类健康的过程，因为在超冲风暴中对流层臭氧的增加和平流层臭氧的消耗都是可能的。

Deep convection that penetrates (overshoots) the tropopause affects the trace gas composition of the extratropical upper troposphere and lower stratosphere, which is important for global atmospheric chemistry and the Earth's radiation balance. This study will combine more than 10 year data of ground-based radar observations with numerical model simulations to study the physical and chemical characteristics of overshooting convection. Data from approximately 100 NEXRAD radars will be composited onto a three-dimensional regional grid with high spatial and temporal resolution. Climatology of the physical characteristics of overshooting convection, such as vertical extent, geographic distribution, interannual variability, and annual and diurnal cycles will be computed from the radar observations. Overshooting convection characteristics derived from the composited radar data will be compared with estimates based on satellite IR observations. To investigate the mechanisms responsible for cross-tropopause transport and to make quantitative estimates of stratosphere-troposphere exchange, numerical model simulations with explicitly resolved convection and chemistry will be carried out for case studies and for an entire warm season. The radar data will be used along with in situ trace gas observations from aircraft to evaluate the performance of the numerical simulations.Intellectual Merit: It is well known that convection in the extratropics can penetrate the tropopause and extend into the lower stratosphere, but there is little quantitative information about its geographic distribution, frequency of occurrence, or depth of penetration into the stratosphere. The radar analyses in this study will lead to a new regional climatology of overshooting convection in the midlatitudes based on direct geometric observations at high spatial and temporal resolution. The results will be compared with satellite IR estimates of overshooting, which offer the potential to extend the regional results to a global domain. High-resolution numerical simulations of overshooting convection will be used to investigate stratosphere-troposphere exchange mechanisms and to make quantitative estimates of the transport of important trace species.Broader Impacts: This research will produce a long-term, public, dataset of radar reflectivity over a large portion of the contiguous U.S. These data will be applicable to a wide range of other hydrometeorological problems. Since convection is not resolved in current global climate models, these studies will provide guidance for developing parameterizations of stratosphere-troposphere exchange due to overshooting convection. A better understanding of overshooting convection will help to reduce uncertainties in future climate projections, which is an important economic and social problem. In addition, diagnosing convective behavior and its impact on atmospheric chemistry will lead to an improved understanding of processes affecting air quality and human health, as both increases in tropospheric ozone and depletion of stratospheric ozone are possible in overshooting storms.