Precision Atmospheric Marine Boundary Layer Experiment (PREAMBLE)

University Of Wyoming, Laramie WY

Investigators

Abstract

A field project will be conducted from 20 May - 20 June 2011 near the Point Conception, California. The fundamental goal of this field experiment is to directly measure the dynamic forcing responsible for the wind field within the marine atmospheric boundary layer (MABL). The study will focus on dynamics associated with the northerly low-level coastal jet that is commonplace in the California coasts during summer. Because there are many potentially non-linear interactions occurring at the interface of the strong northerly (thus potentially difficult to simulate), along-shore wind regime with the cyclonic circulation within the California Bight, direct measurements of meteorological variables in this region are necessary to pars out the important components and their interactions at MABL. If a Catalina eddy and/or coastally-trapped wind reversal should occur, dedicated flights will be conducted to explore the dynamics and thermodynamics associated with those events. Intellectual merit. The University of Wyoming King Air aircraft (UWKA) will be deployed in the California coasts, which has been used in previous research projects. A total of 50 flight hours are planned. This project will build on recently developed airborne technology that enables detection of small horizontal pressure signals using differential correction of GPS heights of an airborne platform. Such measurements will allow fine-scale assessment of the horizontal pressure gradient at levels within the MABL, and thus permit analysis of the forcing terms in the horizontal equations of motion. Determination of ageostrophic winds and accelerations of the MABL flows will be possible from the airborne sampling. In addition, a request has been made for inclusion of the University of Wyoming Cloud Radar and Cloud Lidar as part of the instrumentation onboard the UWKA. Such instrumentation will enable measurements of attendant cloud properties, such as cloud height and microphysical parameters. The standard cloud physics probes on the UWKA will also allow a host of other cloud and microphysical measurements. A critical measurement for dynamics of the MABL under conditions of a Catalina eddy or coastally trapped wind reversal is the height of the MABL stratus. Detailed information regarding the vertical structure of humidity and temperature within the MABL from the airborne missions will enable fine-scale determination of microwave refractivity profiles in this strategically sensitive region. The airborne observational dataset will be supplemented with the considerable body of surface-based instrumentation including a host of buoys surrounding Point Conception. Data collected will provide the basis for comparison with high-resolution (~ 1 km) numerical simulations with the Weather Research and Forecasting Model (WRF). Broader impacts. The Point Conception area is of strategic importance and national security interests. Meteorological phenomena in the coastal environment have prompted several major research efforts during the past two decades. Data collected as part of this field experiment will provide unique and unprecedented measurements that will be useful for validation of previous conceptual models and efforts to numerically simulate detailed MABL dynamics. This project will offer an opportunity for graduate student training in the observational aspects of atmospheric science, a focus from that was identified as a key element for the June 2009 Advanced Study Program Colloquium. As with previous field experiments, graduate students will have an opportunity to plan a research mission and serve as flight scientist on the UWKA. A new academic program, Earth System Science, has been initiated at the University of Wyoming and data from this project will be used in a research project as part of an atmospheric dynamics project.