Air Force Institute of Technology AFIT Scholar Theses and Dissertations Student Graduate Works 3-22-2019 Analysis of the Gálvez-Davison Index for Convective Forecasting Over Africa Using the GALWEM William A. Hanson Follow this and additional works at: https://scholar.afit.edu/etd Part of the Atmospheric Sciences Commons, and the Climate Commons Recommended Citation Hanson, William A., "Analysis of the Gálvez-Davison Index for Convective Forecasting Over Africa Using the GALWEM" (2019). Theses and Dissertations. 2202. https://scholar.afit.edu/etd/2202 This Thesis is brought to you for free and open access by the Student Graduate Works at AFIT Scholar. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of AFIT Scholar. For more information, please contact [email protected]. ANALYSIS OF THE GÁLVEZ-DAVISON INDEX FOR CONVECTIVE FORECASTS OVER AFRICA USING THE GALWEM THESIS William A. Hanson, 1Lt, USAF AFIT-ENP-MS-19-M-81 DEPARTMENT OF THE AIR FORCE AIR UNIVERSITY AIR FORCE INSTITUTE OF TECHNOLOGY Wright-Patterson Air Force Base, Ohio DISTRIBUTION STATEMENT A. APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED. The views expressed in this thesis are those of the author and do not reflect the official policy or position of the United States Air Force, Department of Defense, or the United States Government. This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. AFIT-ENP-MS-19-M-81 ANALYSIS OF THE GÁLVEZ-DAVISON INDEX FOR CONVECTIVE FORECASTS OVER AFRICA USING THE GALWEM THESIS Presented to the Faculty Department of Engineering and Physics Graduate School of Engineering and Management Air Force Institute of Technology Air Univers ity Air Education and Training Command In Partial Fulfillment of the Requirements for the Degree of Master of Science in Atmospheric Science William A. Hanson, BS 1 LT, USAF March 2019 DISTRIBUTION STATEMENT A. APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED AFIT-ENP-MS-19-M-81 ANALYSIS OF THE GÁLVEZ-DAVISON INDEX FOR CONVECTIVE FORECASTS OVER AFRICA USING THE GALWEM William A. Hanson, BS 1 LT, USAF Committee Membership: Maj. H.R. Tseng, PhD Chair Maj. Omar Nava, PhD Member Capt. Gabriel Donndelinger Member AFIT-ENP-MS-19-M-81 ABSTRACT From the hot, arid Sahara Desert to the humid, West African monsoon, Africa is a continent with vastly different weather and climate patterns from one region to the next. For this reason, thunderstorm forecasting over Africa has presented significant difficulty. The Gálvez-Davison Index (GDI) was developed for the Americas and provides a more accurate convective forecasting index than the conventional indices for thunderstorm forecasting, including the K, Total Totals, Showalter, and Lifted indices. Previous research using the GDI via the Global Forecasting System (GFS) model data over Africa showed promising results for areal coverage (Donndelinger 2018), especially during the spring through fall months. This study will look to test the GDI via the Global Air Land Weather Exploitation Model (GALWEM) to determine if the GALWEM GDI forecast is able to more accurately forecast the location and areal coverage, as well as resolve airmass thunderstorms, when compared to the GALWEM K Index (KI) and GFS GDI forecast. Results from this study show the GDI and KI have simila r location error at the 95% confidence level across the monthly, Zulu time, convective regime, and regional studies. GDI consistently outperforms the KI in terms of areal convection coverage in every study analyzed at the 95% confidence level. The GDI proves to perform best when convection is primarily airmass-based, while the KI performs best when convection is primarily from Mesoscale Convective Systems (MCSs). Furthermore, Kelvin waves and outgoing longwave radiation (OLR) show promise as additional convective forecast tools for Africa. This study contains important information for furthering meteorological understanding of convection and precipitation over the African continent v Acknowledgments Major Rose Tseng (USAF) for taking me on as her thesis student and pushing me in her own way to produce a more thorough and significant product than I thought possible. Captain Gabriel Donndelinger (USAF) for allowing me to continue his research on the GDI and KI over Africa and providing the framework of the code for plotting and analyzing the GDI. Major Omar Nava (USAF) for his help with some coding issues and talks on clustering analysis and lightning data. Dr. Jose Gálvez and Mr. Michel Davison (NOAA) for allowing me to use their index and for setting time aside to meet with me regarding this specific research. 14th Weather Squadron (USAF) for providing the lightning data used in this project for multip le differe nt regions in a timely manner. 16th Weather Squadron (USAF) for tirelessly providing GALWEM data each week; this specific project would not have been possible without you. Naval Research Laboratory (NRL) and Weather.us for providing satellite imagery. University Corporation for Atmospheric Research (UCAR) Research Data Archive (RDA) for their GFS analysis data. My classmates for all of your help and keeping me grounded. Thank you for being awesome! My amazing wife for her constant support and encouragement through the entire process. I cannot thank her enough. Thank you to my friends and siblings for pushing me to better myself and escape at times! Thank you to my parents for instilling in me a good work ethic and extreme stubbornness. Lastly, this thesis is dedicated to my grandfather who passed away this fall; you set the example of humility and hard work for me to follow. vi Table of Contents Abstract...............................................................................................................................v Table of Contents .............................................................................................................vii 1. INTRODUCTION.........................................................................................................1 General Issue..................................................................................................................1 Prob le m S tate ment .........................................................................................................3 Hypothesis......................................................................................................................3 Research Objectives, Focus Q uestions ..........................................................................4 Assumptions/Limitations ...............................................................................................5 Implications....................................................................................................................7 Preview...........................................................................................................................7 II. BACKGROUND AND LITERATURE R EVIEW ....................................................8 Chapter Overview ..........................................................................................................8 African Thunderstorms .................................................................................................8 Relevant Research........................................................................................................14 The K Index .................................................................................................................14 The Gálvez-Davison Index ..........................................................................................16 III. METHODOLOGY ....................................................................................................24 Chapter Overview ........................................................................................................24 NCEP GFS Analysis Data, GALWEM Data, and GDI Calculation............................24 K Index (KI) Calculation .............................................................................................29 Plotting ATDNET Lightning Data...............................................................................30 NRL and Weather.us IR Satellite Images ....................................................................31 vii Methods for Comparing Index Forecasts.....................................................................34 Summary ......................................................................................................................43 IV. RESULTS AND ANALYSIS ....................................................................................44 Chapter Overview ........................................................................................................44 Monthly Study .............................................................................................................44 Zulu Time Study ..........................................................................................................47 Convective Regime Study............................................................................................48 Regional Study .............................................................................................................51 Model Comparison Study ............................................................................................55 GDI-A S tudy ................................................................................................................57