SGER: Water Vapor Measurements from the G-V VCSEL Hygrometer during START08/PreHIPPO

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The Principal Investigator (PI) will conduct the necessary spectroscopic studies and calibrations to post-process the vertical-cavity surface-emitting laser (VCSEL) water vapor data from the START(Stratosphere-Troposphere Analyses of Regional Transport)08/PreHIPPO field campaign that took place in spring 2008 onboard the National Science Foundation (NSF) G-V research aircraft. The VCSEL hygrometer shows the best precision and lowest limit of detection in upper tropospheric and lower stratospheric conditions of all the water vapor instruments onboard the NSF G-V. Water vapor is the most important trace gas species in the tropopause region from climate, chemistry, and dynamics perspectives, and accurate measurements will be critical towards assessing the START08/PreHIPPO science objectives. These studies will occur through the use of novel constant-temperature, phase-change, organic slush baths which exploit the small size of the VCSEL hygrometer. Initial studies in the laboratory and at an international water vapor instrument intercomparison study showed that this method of calibration is accurate and minimizes residual water vapor and outgassing common in other calibration techniques. The goal of this project is to provide a quality-controlled dataset for START08/PreHIPPO and to prepare the instrument for HIPPO (HIAPER Pole-to-Pole Observations) in January 2009 that can be used by the PI and others in the Science Team to address chemical, dynamic, and microphysical properties of the tropopause region. The VCSEL dataset, when combined with other measurements from other hygrometers, trace gas species, and modeling analyses, will help in the understanding of global climate change and atmospheric dynamics. The work will involve one REU (Research Experience for Undergraduates) student in the laboratory studies and data analysis during the summer of 2008, and there is a strong likelihood of another undergraduate student working on this project part-time in the 2008-2009 school year. In addition, one female graduate student will also be involved in the analysis of this data during the 2008-2009 academic year.