A SATELLITE AND ASH TRANSPORT MODEL AIDED APPROACH TO ASSESS THE RADIATIVE IMPACTS OF VOLCANIC AEROSOL IN THE ARCTIC A Dissertation Presented to The Academic Faculty by Cindy L. Young In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the School of Earth and Atmospheric Sciences Georgia Institute of Technology May 2014 COPYRIGHT 2014 BY CINDY L. YOUNG A SATELLITE AND ASH TRANSPORT MODEL AIDED APPROACH TO ASSESS THE RADIATIVE IMPACTS OF VOLCANIC AEROSOL IN THE ARCTIC Approved by: Dr. Josef Dufek, Advisor Dr. James Wray School of Earth and Atmospheric Sciences School of Earth and Atmospheric Georgia Institute of Technology Sciences Georgia Institute of Technology Dr. Irina Sokolik Dr. Athanasios Nenes School of Earth and Atmospheric Sciences School of Chemical and Biomolecular Georgia Institute of Technology Engineering Georgia Institute of Technology Dr. Christian Huber Dr. Judith Curry School of Earth and Atmospheric Sciences School of Earth and Atmospheric Georgia Institute of Technology Sciences Georgia Institute of Technology Date Approved: 1/6/2014 To all of my teachers, both in academics and in life. “You cannot teach a man anything; you can only help him find it within himself.” --Galileo Galilei “Listen to the mustn'ts, child. Listen to the don'ts. Listen to the shouldn'ts, the impossibles, the won'ts. Listen to the never haves, then listen close to me... Anything can happen, child. Anything can be.” --Shel Silverstein ACKNOWLEDGEMENTS I would like to thank my academic advisors, Dr. Irina Sokolik and Dr. Josef Dufek, for their support and guidance. I thank the faculty and staff of the Department of Earth and Atmospheric Sciences, especially: Dr. Ellery Ingall and Ms. Meg Grantham for their mentorship over the years, Dr. Carol Paty for sound advice, Dr. James Wray for allowing my mind to travel to distant moons sometimes, Dr. Judith Curry for her help and support, and all of the committee members who helped review this dissertation. I also thank the students I have taught over the years for helping me to become a better teacher, and I acknowledge Dr. Mark Flanner at the University of Michigan for the use of the SNICAR model. I give a special thanks to my fellow graduate students, both current and past, and to my group mates: Jennifer Telling, Ozge Karakas, Mary Benage, Xin Xi, Zheng Lu, Joe Estep, Josh Mendez, Taryn Black, Wim Degruyter, and Leah Courtland. To Dr. Jennifer Telling, I extend the warmest of thanks. I am not sure where I would be without her love and friendship, which keeps my life balanced and bearable. Mr. John Bumgarner, who fed me dinner and bubble tea while writing this document, I thank for loving and supporting me in so many ways throughout the years. I do not know what I would have done without it. I would also like to thank my family and John’s family for their encouragement and understanding. I especially would like to remember my grandparents who have passed away: Ms. Betty Henderson and Mr. Pat Young. I would like to honor the grandparents I have who are still living: Mr. George Henderson and Ms. Opal Young. It has been through their loving-kindness and continued faith in me that I have been able to achieve my goals. iv My K-12 teachers deserve my eternal gratitude. From the DoD schools in the Far East, to Union County School Systems in Georgia, to Young Harris College and Piedmont College, I received excellent instruction and was inspired. For my K-12 friends, I am forever grateful, for they helped foster in me the audacity to follow my dreams. I also thank all of my friends in the Shaolin Tai Chi and Kung Fu Club, both present and past members, especially Dr. Tracy Westeyn Brown and Master Tremayne Brown. Additionally, I thank all of my friends in the Yellow Jacket Flying Club and the friends and family I have been blessed to know at Many Forks Baptist Church. Not to be forgotten are my cats: Marlee, Kyra, Sven, Skyler, Sylvan, Stella, Oliver, and Sage (passed), who are rock stars. Their daily companionship and love has kept me grounded throughout the years. Finally, I am thankful for the promise that I can do all things through Christ who strengthens me. v TABLE OF CONTENTS Page ACKNOWLEDGEMENTS iv LIST OF TABLES ix LIST OF FIGURES x LIST OF ABBREVIATIONS xiv LIST OF SYMBOLS xvi SUMMARY xix CHAPTER 1 INTRODUCTION 1 1.1 Background and motivation 1 1.2 Outline of Dissertation 9 2 REGIONAL RADIATIVE IMPACT OF VOLCANIC AEROSOL FROM THE 2009 ERUPTION OF MT. REDOUBT 13 2.1 Introduction 13 2.2 Data and methodology 17 2.2.1 Satellite data 17 2.2.2 Aerosol microphysical model 18 2.2.3 Radiation transfer calculations 21 2.3 Results and discussion 22 2.3.1 Optical properties of volcanic aerosol 22 2.3.2 Satellite data analysis to constrain a radiative transfer model 24 2.3.3 The effect of volcanic aerosols on the Arctic radiation balance 32 2.3.3.1 Case study of volcanic plume detected on April 2 32 vi 2.3.3.2 Examining the role of vertical structure of volcanic aerosol plumes 39 2.3.4 Comparing radiative impacts of major aerosol types in the Arctic 46 2.4 Conclusions 49 3 ASSESSMENT OF DEPOSITIONAL ASH LOADINGS FROM THE 2009 ERUPTION OF MT. REDOUBT 52 3.1 Introduction 52 3.2 Methodology, Fall3D setup, and data 55 3.2.1 The Fall3D model 57 3.2.1.1 Mass flow rate (MFR) determinations 61 3.2.1.2 Initial ash size distribution and sphericity 62 3.2.1.3 Source type 64 3.2.1.4 Diffusion coefficients 66 3.2.2 Satellite and field data 67 3.3 Investigation of model performance 68 3.3.1 Examination of Δ values and selection of best-fit case 69 3.3.2 Validation of modeled areal extent of ash plumes 70 3.4 Assessment of areal extent and amount of deposited ash 74 3.4.1 Modeled deposit loading fields and associated uncertainties 74 3.4.2 Spatial and temporal gradients of total deposit loadings 82 3.5 Conclusions 86 4 SURFACE RADIATIVE IMPACTS OF ASH DEPOSITS FROM THE 2009 ERUPTION OF MT. REDOUBT 88 4.1 Introduction 88 4.2 Methodology 90 4.3 Results and discussion 93 vii 4.4 Conclusions 105 5 CONCLUSIONS 108 5.1 Dissertation summary 108 5.2 Implications for future research 110 REFERENCES 113 VITA 125 viii LIST OF TABLES Page Table 2.1: Input parameters for SBDART. Sulfate size distribution was held constant at an effective radius of 0.5 µm and σ of 0.5 [Kearney and Watson, 2009]. For ash, σ is set to 0.59 and held constant for all simulations [Niemeier et al., 2009]. Refractive indices for sulfate from OPAC were used for 70% sulfate solution. For ash, refractive indices of andesite from Pollack et al. [1973] were used. a indicates values used for the April 2 case study. b indicates values used in sensitivity study. For both plumes, aerosol optical depth was distributed uniformly within the layer. 19 Table 2.2: Shortwave (SW) and total DARFE for a thin (~2 .5 – 7 km) plume in Wm-2AOD-1. DARFE was calculated for a range of AOD between 0.18 and 0.58. 35 Table 2.3: Shortwave (SW) and total DARFE for a thick (~3 – 20 km) plume in Wm-2AOD-1. DARFE was calculated for a range of AOD between 1 and 3. * For this case, DARFETOA was not linear at broader AOD ranges, so it was calculated in an AOD range of 1 to 1.5. 45 Table 2.4: Studies chosen for comparisons of DARF and heating rates (HR) of Arctic aerosols, along with aerosol types, surface albedo, AOD at 500 or 550 nm, ω0 (singe scattering albedo) at 550 nm, solar zenith angle (SZA), vertical plume thickness and placement within the atmosphere that were used. Boxes filled with an X indicate information was not available. a TOA SW DARF for SZA=62.6o obtained from Dr. Quinn, [personal communication, 2011]. b Vertical placement of the layer is unknown, but thickness is reported as 1 km. 48 Table 3.1: Eruption events, dates, times, durations, plume heights, and mass flow rates (MFRs) used in simulations. 56 Table 3.2: Cases selected for event 5 and Δ values. 60 Table 4.1: Dates and times (UTC) for major land depositing events from the 2009 eruption of Mt. Redoubt. 90 Table 4.2: Measured and modeled mass median radius for all particle sizes at four distances from the volcanic vent. 95 ix LIST OF FIGURES Page Figure 1.1: Broad impacts of volcanic aerosols on the Arctic environment 5 Figure 1.2: Layout and main goals of dissertation 11 Figure 2.1: (a) Spectral dependence of refractive indices of ash and sulfate. (b) Concentration normalized extinction coefficients (Ke) versus wavelength for an ash rich mixture containing an ash to sulfate ratio of 9 to 1 and an effective radius for ash Reff =5 µm compared to andesite with Reff =5 µm (right axis) and for a sulfate rich mixture containing an ash to sulfate ratio of 1 to 9 and an effective radius for ash Reff =1.5 µm compared to sulfate with Reff =0.5 µm (left axis). (c) Single scattering albedo (ω0) versus wavelength for an ash rich mixture containing an ash to sulfate ratio of 9 to 1 and Reff =5 µm and a sulfate rich mixture containing an ash to sulfate ratio of 1 to 9 and Reff =1.5 µm.