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Saharan Air Layer Dust Loading: Effects on Convective Strength in Tropical Cloud Clusters Randall J

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Saharan Air Layer Dust Loading: Effects on Convective Strength in Tropical Cloud Clusters Randall J University of South Florida Scholar Commons Graduate Theses and Dissertations Graduate School October 2015 Saharan Air Layer Dust Loading: Effects on Convective Strength in Tropical Cloud Clusters Randall J. Hergert University of South Florida, [email protected] Follow this and additional works at: http://scholarcommons.usf.edu/etd Part of the Environmental Sciences Commons, and the Meteorology Commons Scholar Commons Citation Hergert, Randall J., "Saharan Air Layer Dust Loading: Effects on Convective Strength in Tropical Cloud Clusters" (2015). Graduate Theses and Dissertations. http://scholarcommons.usf.edu/etd/5882 This Thesis is brought to you for free and open access by the Graduate School at Scholar Commons. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Scholar Commons. For more information, please contact [email protected]. Saharan Air Layer Dust Loading: Effects on Convective Strength in Tropical Cloud Clusters by Randall J. Hergert A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Environmental Science and Policy School of Geosciences College of Arts and Sciences University of South Florida Major Professor: Jennifer Collins, Ph.D. Lori Collins, Ph.D. Charles H. Paxton, Ph.D. Jason Dunion, M.S. Date of Approval: September 25, 2015 Keywords: SAL, cyclones, cloud condensation nuclei, aerosols Copyright © 2015, Randall J. Hergert Table of Contents List of Tables ............................................................................................................................................................................. iii List of Figures ........................................................................................................................................................................... iv Abstract ...................................................................................................................................................................................... v 1.0 Introduction ....................................................................................................................................................................... 1 1.1 Hurricane Threat ........................................................................................................................................... 2 1.2 The North Atlantic Tropical Region ........................................................................................................ 3 1.3 Tropical Cyclone Lifecycle .......................................................................................................................... 5 1.4 The Saharan Air Layer (SAL) ..................................................................................................................... 7 1.5 Sal Image and Perception .......................................................................................................................... 10 1.6 Radiative Properties and Effects on SAL Dust .................................................................................. 15 1.7 SAL Conclusion .............................................................................................................................................. 17 1.8 Purpose ............................................................................................................................................................. 18 1.9 Hypothesis ...................................................................................................................................................... 18 2.0 Methodology .................................................................................................................................................................. 19 2.1 Study Area ........................................................................................................................................................ 19 2.2 Datasets ............................................................................................................................................................. 20 2.3 Exclusions ........................................................................................................................................................ 22 2.4 Analysis ............................................................................................................................................................. 23 2.4.1 AOT vs. TPW ................................................................................................................................. 23 2.4.2 AOT vs. IR Brightness (t-min) ............................................................................................... 23 2.4.3 AOT vs. TCC: A GIS Analysis .................................................................................................... 23 3.0 Results ............................................................................................................................................................................... 25 3.1 AOT vs. TPW 1988 – 2009 ........................................................................................................................ 25 3.1.1 AOT vs. TPW Variable Analysis ........................................................................................... 25 3.1.2 AOT vs. TPW Regression Analysis ..................................................................................... 26 3.2 Monthly Analysis of AOT vs. TPW ......................................................................................................... 28 3.3 AOT vs. IR Brightness 1982 – 2009 ...................................................................................................... 32 3.3.1 AOT Dataset Analysis .............................................................................................................. 32 3.3.2 IR Brightness (t-min) Dataset Analysis ........................................................................... 33 3.3.3 AOT vs. t-min Regression Analysis .................................................................................... 34 3.4 T-min vs. AOT with TPW 1988 – 2009 ................................................................................................ 35 3.5 T-min vs. AOT: A GIS Perspective .......................................................................................................... 36 4.0 Discussion ........................................................................................................................................................................ 39 4.1 TPW vs. AOT Discussion ............................................................................................................................ 39 4.2 T-min vs. AOT Discussion .......................................................................................................................... 42 i 5.0 Conclusion and Future Work ................................................................................................................................... 44 6.0 References ........................................................................................................................................................................ 47 ii List of Tables Table 1: Brightness Temperature (Tb) threshold by basin used in Hennon et al. (2011) to identify Tropical Cloud Clusters (TCCs).................................................................... 22 Table 2: Regression Model results for TPW vs AOT.................................................................................. 28 Table 3: Geographic extent of grid boxes placed over the study area for TPW and AOT......... 29 Table 4: Regression model results for TPW vs AOT Monthly Analysis............................................... 31 Table 5: Regression Analysis Results for t-min against AOT.................................................................. 35 Table 6: Regression model results for t-min vs TPW and AOT............................................................. 35 Table 7: Regression model results found using the Ordinary Least Squares Tool within ArcGIS............................................................................................................................................ 36 iii List of Figures Figure 1: Depiction of the SAL interacting with other features over the tropical North Atlantic........................................................................................................................................... 8 Figure 2: Study Area: The study area pertains to the region outlined in black, while the Main Development Region (MDR) pertains to the area outlined in orange.......................................................................................................................................................... 19 Figure 3: AOT from 1988 – 2009, used in the AOT v TPW regression analysis............................... 26 Figure 4: Power Transformed AOT with λ=0.25........................................................................................... 26 Figure 5: Total Precipitable Water observations from 1988 – 2009................................................... 27 Figure 6: Power transformed TPW dataset with λ=1.5.............................................................................. 27 Figure 7: Locations of grid-boxes where TPW and AOT data were extracted for a month-by-month
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