Development, Deployment, and Validation of a Differential Abospbtion Lidar for Water Vapor Profiling in the Lower Troposphere

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Researchers at Montana State University (MSU) have developed a novel diode-laser-based differential absorption lidar (DIAL) for water vapor profiling in the lower troposphere. This instrument, which until now has been laboratory-based, utilizes external cavity diode lasers in conjunction with a tapered semiconductor optical amplifier to produce a widely tunable DIAL laser transmitter capable of accessing many water vapor lines of varying strength. This is the first diode-laser-based DIAL instrument to successfully demonstrate both nighttime and daytime water vapor profiling capabilities, and has the potential to spearhead cost-effective deployment of networks of similarly-designed sensors. The supported research will test and evaluate development of a field deployable DIAL instruments for unattended long-term data collection in a variety of geographic/meteorological settings. The semiconductor laser-based instrument, which incorporates many cost-effective off-the-shelf components, will be modified to operate over a wider temperature range. The instrument will be deployed at three field sites for data collection on the order of thirty days at each site. The long term data sets collected during these field deployments will be compared with in situ water vapor measurements for validation purposes. The intellectual merit of this effort rests is development of a more sophisticated and cost-effective DIAL instrument that can be deployed in a ground based network for climate and weather research and forecasting applications.Broader impacts of this effort include potential impacts of improved monitoring and forecasting of local and mesoscale weather effects (e.g., thunderstorm development) that are highly dependent on accurate knowledge of atmospheric water vapor content in the layer nearest the earth's surface. Close cooperation with personnel at the National Center for Atmospheric Research will speed integration of developed technologies into the suite of instruments available for NSF-supported researchers. Training of a graduate student will also be enhanced through direct involvement in this effort.