Collaborative Research: Measurement and Analysis of Nocturnal Mesoscale Convective Systems and Their Stable Boundary Layer Environment During PECAN

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The Plains Elevated Convection At Night (PECAN) experiment will investigate the evolution of nocturnal mesoscale convective systems (MCSs) and convection and their interactions with the evolving nocturnal stable boundary layer (SBL) environment. This proposal addresses two primary goals of PECAN: 1) To characterize the transition from surface-based to elevated nocturnal MCS structure and the interaction of cold pools generated by MCSs with the nocturnal SBL, and 2) to determine how the organization and evolution of surface-based and elevated MCSs are influenced by the stable boundary layer and the vertical profile of wind and stability above the nocturnal low-level jet (NLLJ). To rectify the present paucity of detailed, integrated observations of nocturnal MCSs and their SBL environments, the project will observe nocturnal MCSs and convection with mobile ground-based radars, mobile sounding systems, and mobile mesonets in concert with other ground-based and airborne observing platforms during PECAN. Multi-radar syntheses, data assimilation, and modeling will provide the integrated analyses of these combined observations to evaluate the detailed internal structure of nocturnal MCSs and the impact of static stability, pre-existing boundaries, and wind shear on nocturnal MCS evolution processes.Intellectual Merit:This project emphasizes the tightly coordinated observation of nocturnal MCSs and their SBL environments with an array of multiple mobile Doppler and dual-polarimetric radars in conjunction with mobile soundings and surface in situ observing systems. These observations will be integrated to obtain 3-D airflow syntheses, precipitation fields, and thermal structure of MCSs and newly initiated convection and their environments. Mobile radars are essential as they can provide enhanced temporal and spatial resolution and low-level observations over any area within the PECAN domain. C-band radars, with their ability to both penetrate heavy precipitation and sense clear-air inflow, are required. The mobile C- and X-band dual-polarimetric radars will provide microphysical information beyond the typical operating ranges and below base-scan altitudes of the polarimetric WSR-88D radars. The mobile sounding and surface observations complement the radar wind measurements by providing unique buoyancy and shear profiles both within and outside of precipitation, thus resolving internal MCS dynamics and characterizing the SBL environment that interacts with the MCSs. These data, in combination with other PECAN data from fixed and mobile ground-based radar, profilers, mesonets, and aircraft, are essential for interpreting nocturnal MCS evolution with respect to in situ environmental conditions and for providing input and validation of cloud dynamical-microphysical model simulations of MCSs. The scientific objectives of this project are to: (i) document the internal structure and evolution of nocturnal MCSs and convection; (ii) establish the environmental ingredients and related physical mechanisms that control nocturnal MCS evolution; and (iii) test hypotheses concerning MCS dynamical microphysical forcing and MCS-environment interactions within detailed cloud-resolving models. The research conducted here will advance fundamental knowledge of the internal MCS dynamics and interactions with the SBL and will enable better representations of both within cloud-resolving models.Broader Impacts:Characterizing the morphology of nocturnal MCSs and the vertical profiles of temperature, humidity and winds ahead of and near the convective region in the cold pool are essential to helping improve the specificity and accuracy of diagnoses and short-term predictions of the geographical extent and duration of severe weather, heavy rainfall, flash flooding, and aircraft icing conditions. Additionally, these PECAN field observations will be essential for refining data assimilation systems and improving future operational numerical predictions of nocturnal MCSs and their SBL environments. The datasets collected here will also be used in university classes through graduate level. Several undergraduate and graduate students will be trained in the execution of a large atmospheric field campaign by being integrated into the data collection and post-field phase analysis. Lastly, the data collected here will be made available to other NSF and NOAA investigators identified as part of the PECAN project.