VALIDATION OF WATER VAPOR MEASUREMENTS FROM COMMERCIAL AIRCRAFT ACROSS THE CONUS USING RADIOSONDES

National Weather Service (NWS) radiosondes are a significant part of the upper-level observing network; however, the limited spatial and temporal coverage of these observations create large gaps in our characterization of the atmosphere. Observations from commercial aircraft are one way to increase the number of observations and fill in data between radiosonde sites. These aircraft data are collected in real-time by the Aircraft Meteorological Data Reports (AMDAR) system and traditionally have contained observations of temperature, wind, and pressure. In the past, water vapor observations have not been collected since separate instrumentation was required and these observations were not required in-flight for aircraft observations. The development and deployment of the Water Vapor Sensing System II (WVSS-II) on select commercial aircraft have allowed water vapor measurements to be added to this data set. This sensor was designed to be lightweight, require little maintenance, and be highly reliable. Vertical profiles of moisture are provided by the WVSS-II observations during takeoff and landing, yielding complete thermodynamic and kinematic profiles of the atmosphere at higher frequencies than by radiosondes alone. Radiosonde-based validation of the WVSS-II has been limited to short-term field studies in climatologically similar regions, which limits characterization of its performance in different environments. In the present study, the WVSS-II is compared to operational NWS radiosondes throughout the continental United States, covering all seasons and multiple climate regimes. Locational and seasonal biases are explored, and the performance of the sensor in both high and low water vapor environments is determined. In general, the WVSSii II is slightly moister than the radiosondes with very little difference between aircraft type. The summertime tends to have the largest difference while winter has the least. A larger moisture difference was found when examining aircraft flying through precipitation that could be due to moisture being trapped in the air sampler. Characterizing potential biases in the WVSS-II dataset will improve data assimilation processes of this data into numerical weather prediction models and create confidence for both governmental and aviation forecasters regardless of location or time of year. iii Acknowledgements I came to Madison at the end of June of 2015 from Oklahoma where it was in the mid-upper 90’s. Madison was in the upper 60’s and I froze. All summer. All I could think was “how am I going to survive winter? ”. Well, good news for me, I survived. I survived all the coursework, research, and the cold to finish this degree but I couldn’t do it without the amazing people in my life. I would like to thank Tim Wagner, my advisor and fellow OU grad, for guiding me on this research. Thank you for throwing me into a project that I didn’t even know existed and that I came to love. I had never worked with Matlab for more than one assignment and you had so much patience with me and I’ve learned so much. Also thank you for talking OU football with me since no one here even cares. I would also like to thank Steve Ackerman, Ankur Desai, and Grant Petty for reading my thesis and giving feedback on this study. To my officemates, thank you for letting me be my goofy weird self and putting up with my shenanigans. Thank you for reading all my emails before I hit send, letting me dance, and distract you with husky and cat videos. Thank you David Loveless for starting to peel all my clementines for me. Thank you Luke Gloege for helping me make all my plots pretty and helping me with Matlab in general. Lindsey Nytes, thank you for being my partner in climb, letting me climb my stress away, and pushing me to climb things I didn’t think I could. Alex Goke, thank you for being my friend I can vent to about anything and everything, and driving to Seattle to see me give my AMS presentation. Thank you to James Simkins for introducing me to tea and having teatime nearly once a day (and sometimes twice). Speaking of tea, I appreciate all you have done for me, providing warmth on cold days, and for the caffeine to keep me awake after a late night of working. iv To my friends not at at UW, Wolfgang Hanft, Brooke Hagenhoff, Carlye Harris, and Garrett Layne, I am so grateful for you continued friendship. It’s been so great having friends just a phone call or text away to suffer through grad school with. I’m so thankful we always try to find excuses to see each other even just for a meal passing through. Wolfgang, thank you also for making our crazy adventure dreams a reality and traveling cross-country multiple times to explore the world. Gabe Bromley, thank you for being my favorite adventure buddy and for climbing mountains with me (literally but also the grad school mountains). Thank you for telling me on nearly a daily basis that I can do it and supporting me through the stressful times when I thought I wasn’t going to finish in time. Thank you to my wonderful family for supporting me from when I was young to follow my passion of weather. I would not be here without your love, hard work, patience, and motivation. Lastly, I would like to thank my cat, Lucy, for giving me snuggles after a long day of working. Madison, you’ve given me so much these last two years; my passion for climbing, lifelong friends, and lastly, this degree. I know these will all take me far in my next chapter of life in Montana.