Collaborative Research: Mesoscale Structure of Boundary Layer Water Vapor Budgets and Depth during IHOP: Observations, Modeling, and Implications for Convective Initiation

预测对流云发展的时间和地点是气象学研究中的一个基本挑战。大气边界层（ABL）的非均质性，特别是ABL的水汽含量和深度，导致对流起始的首选位置。地表非均质性是造成ABL非均质性的重要原因。因此，地表通量在ABL的发展和对流起始中起着重要作用。陆地表面强迫的最小尺度导致ABL特性（如深度和水蒸气含量）的非均匀性，从而导致云形成的首选位置仍然不确定。观测和模型表明尺度从几公里到近100公里不等。该项目提出了一个观测计划，作为国际H2O项目（IHOP）的一部分。IHOP是一个大型的多机构、多研究者项目，专注于测量水蒸气和水蒸气变异性。该项目的目标是提高对对流起始的认识，提高短期降水预报技能，并测试各种仪器测量水汽四维特征的能力。这项研究的关键观测是俄克拉荷马州和堪萨斯州至少300 x 300公里区域的潜热和感热地表通量图，以及机载水汽差分吸收激光雷达（DIAL）对ABL深度和对流层低层水汽的重复观测。通量图将由一个地面通量塔网络、在大约50公里长的重复飞行轨道上对地面通量的空中测量、陆地表面温度和植被覆盖的卫星遥感以及一个陆地表面模型创建。一个机载DIAL将与机载多普勒激光雷达相结合，从而能够通过远程涡旋相关方差观测ABL通量剖面。飞行将集中在10-15个相对晴朗天气的中午时间，以便用DIAL捕捉预防对流的大气。将对观测结果进行分析，以确定ABL水汽深度和水收支的空间异质性程度及其异质性的原因，特别侧重于确定地表异质性是一个重要因素的空间尺度。将分析10到15天的数据，试图超越案例研究方法。数据同化将用于将密集的中尺度观测数据吸收到高分辨率的中尺度大气模式中，该模式包括一个复杂的陆地表面方案。该模型将被用作研究观测中捕获的中尺度地面- abl -云相互作用的分析工具。此外，该模式将用于评估DIAL观测、详细的地表通量图和一种新的浅积云参数化对ABL非均质性和对流初始化预报的影响。产品将包括ABL深度图、ABL水预算估算和模型后分析领域，其中包含所有可获得的IHOP观测结果，用于DIAL观测10-15天。预期结果包括：提高对地表非均质性在对流ABL发展和对流起始中的作用的认识；通过密集观测ABL水汽含量和地表通量，可以提高模式对ABL发展和湿对流的预测程度；以及浅对流参数化对模型性能的影响。

Predicting the timing and location of convective cloud development is a fundamental challenge in the study of meteorology. Heterogeneities in the atmospheric boundary layer (ABL) particularly in ABL water vapor content and depth, lead to preferred locations for convective initiation. Land surface heterogeneity is an important cause of heterogeneity in the ABL. Hence, land-surface fluxes play an important role in ABL development and convective initiation. The minimum scale of land surface forcing that causes heterogeneity in ABL properties such as depth and water vapor content and consequently leads to preferred locations for cloud formation remains uncertain. Observations and models suggest scales ranging from a few to nearly 100 km.This project proposes an observational plan as part of the International H2O Project (IHOP). The IHOP is a large multi-agency, multi-investigator project that focuses on the measurement of water vapor and water vapor variability. The goal of this project is to improve understanding of convective initiation, increase short-term precipitation forecast skills and test the capabilities of various instruments to measure the four dimensional characteristics of water vapor. The critical observations for the research to be performed under this award are maps of surface fluxes of latent and sensible heat over a region of at least 300 x 300 km in Oklahoma and Kansas, and repeated airborne water vapor DIfferential Absorption Lidar (DIAL) observations of ABL depth and lower tropospheric water vapor. The flux maps will be created from a network of surface flux towers, airborne measurements of surface fluxes over repeated flight tracks about 50 km in length, satellite remote sensing of land surface temperature and vegetation cover, and a land surface model. One airborne DIAL will be coupled with an airborne Doppler Lidar, yielding the ability to observe ABL flux profiles via remote eddy covariance. Flights will be focused on the midday hours of 10-15 relatively fair weather days in order to capture the preconvective atmosphere with DIAL.Observations will be analyzed to determine the degree of spatial heterogeneity in ABL water vapor depth and water budgets and the causes of this heterogeneity, focusing especially on determining the spatial scales at which land surface heterogeneity is an important factor. Ten to fifteen days of data will be analyzed in an attempt to move beyond a case study approach.Data assimilation will be used to ingest dense, mesoscale observations into a high-resolution mesoscale atmospheric model that includes a sophisticated land-surface scheme. The model will be used as an analysis tool to study mesoscale surface-ABL-cloud interactions captured in the observations. Further the model will be used to assess the impacts of the DIAL observations, detailed land surface flux maps and a new shallow cumulus parameterization on forecasts of ABL heterogeneity and convective initiation.Products will include ABL depth maps, ABL water budget estimates and model post-analysis fields incorporating all available IHOP observations for the 10-15 days of DIAL observations. Expected results include: an improved understanding of the role of land surface heterogeneity in convective ABL development and convective initiation; the degree to which model prediction of ABL development and moist convection can be improved via dense observations of ABL water vapor content and surface fluxes; and the impact of a shallow convection parameterization on model performance.