ABSTRACT FARRINGTON, NATHANAEL CHRISTIAN. Numerical Weather Prediction of Stratus: Sensitivity to Aerosol Aware Microphysics. (Under the direction of Dr. Gary Lackmann.) Operational numerical weather prediction microphysics schemes commonly hold cloud droplet number concentration fixed domain-wide to increase computational efficiency. However, observations indicate wide variability of this quantity. Particularly, cloud condensation nucleus concentration has been observed to influence cloud droplet size, leading to changes in cloud radiative and microphysical properties. These changes have been shown to alter cloud depth, lifetime, and other characteristics of importance to operational forecasters. The advent of the Weather Research and Forecasting model version 3.6 includes the Thompson and Eidhammer radiation-coupled microphysics option which is double- moment for cloud water, accounts for some aerosol influences, and is designed for operational efficiency. Tests conducted here show that the new scheme successfully varies aerosol and cloud droplet number concentration temporally and spatially, while significantly altering the radiative properties and coverage of inland coastal stratus in the Pacific Northwest. However, tests also show that several other factors exercise greater sway over stratus coverage and lifetime relative to CCN concentration. © Copyright 2015 Nathanael C. Farrington All Rights Reserved Numerical Weather Prediction of Stratus: Sensitivity to Aerosol Aware Microphysics. by Nathanael C. Farrington A thesis submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Master of Science Marine, Earth and Atmospheric Sciences Raleigh, North Carolina 2015 APPROVED BY: _______________________________ _______________________________ Dr. Gary Lackmann Dr. Walter Robinson Committee Chair _______________________________ Dr. Anantha Aiyyer DEDICATION I dedicate this work to my wife, Kristen, who continues to set aside her dreams to chase a life with me, and to my Father, brothers, and sisters. You carry me when I am too weak to walk and without you I would not be where I am today. ii BIOGRAPHY Nate Farrington is originally from Scottsdale, Arizona. He grew up amazed at the power, in awe of the lightning, humbled by the bone-rattling thunder, and intrigued by the ominous haboobs of North American Monsoon thunderstorms. Nate has been a forecaster in the Air Force weather community for over 15 years. During his career, he has issued operational aviation forecasts for airspace over every continent and every ocean on the planet except the Arctic, served tours to Iraq and Afghanistan, supported the Special Operations community, and even broadcasted weather forecasts to 1.1 million Defense and State department viewers worldwide for the American Forces Network. Nate has a wonderful family, including three beautiful children and a lovely and talented wife of almost 16 years. Nate and his family have lived and worked in Germany and six different U.S. states. Nate assembled his undergraduate degree from five different brick and mortar institutions over ten years of rotating shift work and raising a family, culminating in a degree in Natural Science and Mathematics from Thomas Edison State College in 2010. He enrolled in the Atmospheric Science graduate program at North Carolina State University in fall of 2013 where he has been working under the guidance of Dr. Gary Lackmann. Upon finishing his Master’s degree, Nate will join the 16th Weather Squadron, part of the Air Force Weather Agency, where he will help the Air Force exploit the latest in science and technology to provide responsive, accurate, and relevant weather information to the warfighter, the intelligence community, and other national agencies. iii ACKNOWLEDGMENTS I would like express gratitude to my advisor, Dr. Gary Lackmann, for the vision and patience to conduct this project with me. His calm and steady hand guided this endeavor through storm and drought; I am indebted to him for his kindness and understanding. I would also like to thank my thesis committee members, Dr. Walter Robinson and Dr. Anantha Aiyyer, for keeping the project soundly grounded in the scientific and meteorological principles to which this thesis’ processes are subject. I would also like to thank Dr. Sandra Yuter and Dr. Matt Miller for giving me their honesty, time, and technical expertise. I thank the United States Air Force and the Air Force Institute of Technology, Civilian Institutions Program for funding this assignment. A very responsive Technical Sergeant Precious Monk at the 14th Weather Squadron (14WS) provided tens of thousands of observations crucial to this analysis. I extend a special thank you to Dr. Neil Jacobs and his team at Panasonic AirDat for gracious access to their proprietary aircraft observations and software. The National Climatic Data Center provided North American Mesoscale Model analyses. The National Center for Atmospheric Research made the Weather Research and Forecasting model available to the public. I am grateful to Unidata for the incredibly user friendly Integrated Data Viewer platform and University of Wisconsin’s Cooperative Institute for Meteorological Satellite Studies for their imagery. I particularly want to express my gratitude to Dr. Greg Thompson and Trude Eidhammer for their vision and work to modernize the microphysics of operational Numerical Weather Prediction. My lab mates, Xiaoyu Long, Chris Marciano, Allison Michaelis, Jennifer Tate, Lindsay Blank, and colleagues, Matthew Morriss, Dianna Francisco, Jeffery Willison, Andy iv Meier, Josh Tobias, and Maj Adam DeMarco provided technical assistance and friendship which made this great task easier to bear. My friend, Suchit Mehrotra, aided greatly with statistical analysis software. I would also like to thank Air Force Reserve Officer Training Corps Detachment 595 Commander, Lt Col Jay Allen, for the motivation, competition, mentorship, and friendship with which he led me. I humbly acknowledge Air Force and Army Special Operations aviators who, with weather bubbas Mr. John White and Mr. Jerry Gaunt, inspired this project and perpetually inspire me. Special operator Chief Warrant Officer 4 Paul Dulfer provided helpful maps and information. I would like to extend thanks to Mr. Randall Kallenbach and Mr. Stephen Chesser for their mentorship and friendship throughout the years, and for encouraging me to do this. Finally, I thank my family who have supported and believed in me. I want to thank my dad and mom, Tim and Linda, whose dedication to God, each other, and their professions have helped make me who I am, and whose long arm of love I felt through many valleys. I want to thank my younger brother, Phil, for wisely teaching and admonishing me with psalms and hymns and spiritual songs. I would like to thank my children, Riley, Parker, and Madison, for their resilience and love when my work robbed them of my best time and energy. Above these, I pour out my profound gratitude to my stunning wife, Kristen. I have built my career and life upon the confidence of her selfless support, tireless friendship, and skillful encouragement. Ultimately, I give thanks for all trials and success in the name of my hope, the Lord Jesus Christ, to God the Father and Creator from whose “counsel and dominion” this “most beautiful system” proceeds (Newton 1687). v TABLE OF CONTENTS LIST OF TABLES ............................................................................................................... viii LIST OF FIGURES ............................................................................................................... ix 1. Introduction ..........................................................................................................................1 1.1. Motivation ..........................................................................................................................1 1.1.1. Low Cloud Impacts on Military Aviation ....................................................................1 1.1.2. Low Cloud Impacts on Civilian Aviation ....................................................................4 1.1.3. Impacts of Low Clouds on Radiation ...........................................................................4 1.2 Background ........................................................................................................................6 1.2.1 Stratus Formation and Dissipation Processes ..............................................................6 1.2.2 Cloud Droplet Formation ...............................................................................................7 1.2.3 Cloud-Aerosol Interactions and Radiation ...................................................................8 1.2.4 Model Cloud-Aerosol Interactions and Radiation .....................................................10 1.2.4.1 Model Physics Parameterizations .............................................................................12 1.2.5 Thompson and Eidhammer (2014) Microphysics ......................................................16 1.2.5.1 Aerosol Input ..............................................................................................................17 1.2.5.2 Explicit Calculation of Aerosols ...............................................................................17 1.3 Science Questions .............................................................................................................19