RELAMPAGO Hydrometeorology Component: Land Surface Controls on Heavy Precipitation and Flooding in the Carcarana River Basin, Argentina

有组织的大陆暖季对流造成的水文气象影响是与天气有关的一些最灾难性和代价最高的影响。在全球范围内，每年这些恶劣天气事件都会导致强降雨、冰雹、龙卷风、山洪暴发和山体滑坡，进而导致严重的农作物损失、财产损失、城市灾害和生命损失。尽管这些事件对社会产生了巨大影响，但推动强烈、有组织的对流的机制以及这些事件所产生的水文反应还没有得到很好的理解。在这项工作中，我们将利用阿根廷CarcarañáRiver流域的暖季对流进行观测和耦合模拟研究。对这一区域的地理关注源于这样一个事实，即世界上一些最深和最大的对流风暴是在科尔多瓦山脉的山脚下形成的，这是安第斯山脉以东的山脉，是卡拉尼亚山脉的源头。与美国大平原相比，南美洲亚热带地区的对流组织和传播更加频繁，而且局限在一个小得多的区域--这导致卡拉尼亚河流域持续受到这些严重风暴的影响，限制了观测研究的空间范围，并增加了在野外活动中捕捉到极端事件的可能性。观测和模拟工作从两个角度进行。第一部分研究陆地表面如何影响对流降水的产生和发展(大气视角)。第二项研究调查土地覆盖的变化是否影响了流域的水文循环和发生洪水的可能性(从水文学角度看)。这项工作的影响有三个方面：它解决了水文气象学中的基本科学问题，推动了完全耦合的水文气象模式的改进，并最终提高了对高影响天气事件的预测技能。这项工作结合了综合水文气象实地活动和使用WRF/WRF-Hydro系统的耦合模拟研究，重点是阿根廷的CarcarañáRiver流域。这个盆地从安第斯山脉以东的中尺度山脉西拉斯德科尔多瓦向东向平原排放。Carcarañá盆地经常受到严重的有组织对流的影响，非常适合进行观测和模拟研究，目的是了解陆地表面在调节观测到的强对流系统和相关降水和洪水的可变性方面的作用。这项工作的首要科学问题是：陆地表面在调节CarcarañáRiver流域观测到的强降水和洪水的可变性方面起什么作用？我们通过两个附属问题来解决这一首要问题：1.土地覆盖的异质性(包括人为改变的土地覆盖)如何通过水分和能量的陆地-大气交换影响局地和中尺度对流降水的启动和增长？2.土地覆盖的变化如何影响降雨在渗透/径流之间的分配以及土壤水分和地下水在卡拉尼亚盆地陆地系统中的停留时间？我们将使用的工具是：a)现有的当地对降水、地下水位和水流的观测，b)我们的团队在Relampago活动期间测量的降水、水流、土壤湿度、温度和地表通量的观测，C)使用完全耦合的WRF/WRF-HYDRO模拟系统在离线模式(即，仅WRF-HELDRO，由观测到的气象条件驱动)和耦合(WRF/WRF-HYDRO)模式下进行数值模拟。我们的研究区域与美国大平原在陆地-大气相互作用的重要性、MCSs的启动和高层发展以及低空急流水汽输送的重要性方面有许多相似之处。因此，增进对MCSs水文气象学的了解将产生除阿根廷以外的深远好处。

Hydrometeorological impacts from organized, continental warm season convection are some of the most disastrous and costly of weather-related impacts. Globally, each year, these severe weather events cause intense rainfall, hailstorms, tornadoes, flash floods, and landslides which in turn result in significant crop losses, property damage, urban hazards and loss of human life. Despite the enormous impact such events have on society, the mechanisms driving intense, organized convection and the coupled hydrological responses from those events are not well understood. In this work, we will perform an observational field campaign and coupled modeling study using focused on warm season convection in the Carcarañá River basin in Argentina. The geographical focus on this region stems from the fact that some of the world's deepest and largest convective storms develop at the foothills of the Sierras de Córdoba - a mountain range east of the Andes which is the headwaters of the Carcarañá. Compared to the Great Plains of the United States, convective organization and propagation in subtropical South America is more frequent and confined to a much smaller region - which causes the Carcarañá river basin to be continuously affected by these severe storms, confines the spatial extent of the observational studies and increases the probability of capturing extreme events during a field campaign.The study leverages from and complements the multi-institutional RELAMPAGO/CACTI effort. The observational and modeling work is approached from two perspectives. The first investigates how the land surface impacts the initiation and growth of convective precipitation (atmospheric perspective). The second investigates if changes in land cover have affected the hydrologic cycle and the probability of flooding in the basin (hydrology perspective). The impact of this work is threefold: it addresses fundamental scientific questions in hydrometeorology, drives improvements in fully-coupled hydrometeorological models and ultimately improves predictive skill of high impact weather events.This work combines an integrated hydrometeorological field campaign and coupled modeling study using the WRF/WRF-Hydro system focused on the Carcarañá River basin in Argentina. This basin drains east from the Sierras de Cordoba, a mesoscale mountain range east of the Andes, toward the plains. Frequently impacted by severe, organized convection, the Carcarañá basin is ideally suited to perform observational and modeling studies aimed at understanding the role of the land surface in modulating the observed variability of intense convective systems and associated precipitation and flooding.The overarching science question of this work is: What is the role of the land surface in modulating the observed variability of heavy precipitation and flooding in the Carcarañá River Basin? We address this overarching question with two subsidiary questions: 1. How does land cover heterogeneity (including human-modified land cover) impact initiation and growth of convective precipitation at the local and meso-scale through land-atmosphere exchanges of moisture and energy?2. How have changes in land cover affected the partitioning of rainfall between infiltration/runoff and the residence times of soil moisture and groundwater in the Carcarañá Basin's terrestrial system?The tools we will use are: a) Existing local observations of precipitation, water table depths and streamflow, b) Observations of precipitation, streamflow, soil moisture, temperature and surface fluxes measured by our team during the RELAMPAGO field campaign, c) Numerical simulations using the fully-coupled WRF/WRF-hydro modeling system both in offline mode (i.e. WRF-Hydro only, driven by observed meteorological conditions) and coupled (WRF/WRF-Hydro) modes. Our study region has many similarities with the Great Plains of the United States in terms of the importance of land-atmosphere interactions, the initiation and upscale growth of MCSs and the importance of low-level jet moisture transport. Hence, improved understanding of the hydrometeorology of MCSs will have far-reaching benefits beyond Argentina.