UNIVERSITY OF CALIFORNIA, SAN DIEGO Mesoscale Coupled Ocean-Atmosphere Interaction A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Oceanography by Hyodae Seo Committee in charge: Arthur Miller, Co-Chair John Roads, Co-Chair Guillermo Algaze Sarah Gille Glenn Ierley Andrew Moore Joel Norris 2007 Copyright Hyodae Seo, 2007 All rights reserved. The dissertation of Hyodae Seo is approved, and it is acceptable in quality and form for publication on microfilm: Co-Chair Co-Chair University of California, San Diego 2007 iii TABLE OF CONTENTS Signature Page.................................................................................................... iii Table of Contents................................................................................................ iv List of Figures and Tables................................................................................... vii Acknowledgments .............................................................................................. ix Vita .................................................................................................................... xi Abstract ..............................................................................................................xii Chapter 1. Introduction................................................................................................ 1 Chapter 2. The Scripps Coupled Ocean-Atmosphere Regional Model (SCOAR) Model with Applications in the Eastern Pacific Sector ........................................7 Abstract ..................................................................................................... 7 2.1 Introduction.......................................................................................... 8 2.2 Regional Coupled Modeling Background ............................................. 10 2.3 The SCOAR Model..............................................................................13 2.3.1 RSM atmospheric model...........................................................13 2.3.2 ROMS ocean model..................................................................14 2.3.3 Flux-SST Coupler..................................................................... 15 2.4 Examples of SCOAR Model Simulations ............................................. 17 2.4.1 TIWs in the ETP....................................................................... 18 2.4.1.1 Background .................................................................... 18 2.4.1.2 Results............................................................................ 19 2.4.2 Mesoscale Eddy Feedbacks in the CCS..................................... 24 2.4.2.1 Background .................................................................... 24 2.4.2.2 Results............................................................................ 25 2.4.3 Gap Winds in the CAC ............................................................. 28 2.4.3.1 Background .................................................................... 28 iv 2.4.3.2 Results............................................................................ 30 2.5 Summary and Discussion ..................................................................... 31 2.6 Acknowledgments................................................................................33 Chapter 3. Feedback of Tropical Instability Wave - induced Atmospheric Variability onto the Ocean.................................................................................................... 49 Abstract ..................................................................................................... 49 3.1 Introduction.......................................................................................... 50 3.2 Model and Experiment .........................................................................53 3.3 Results ................................................................................................. 56 3.3.1 Impact of Wind-Current Covariability on the TIWs .................. 56 3.3.2 Impact of Surface Current on Wind Stress ................................ 62 3.3.3 Implication of TIW-induced latent Heat Flux on SST ...............65 3.4 Summary and Discussion ..................................................................... 67 3.5 Acknowledgments................................................................................71 Chapter 4. Effect of Ocean Mesoscale Variability on the Mean State of Tropical Atlantic Climate..................................................................................................83 Abstract ..................................................................................................... 83 4.1 Introduction.......................................................................................... 83 4.2 Model and Experiment Setup................................................................ 84 4.3 Results ................................................................................................. 86 4.4 Summary and Discussion ..................................................................... 88 4.5 Acknowledgments................................................................................90 Chapter 5. Precipitation from African Easterly Waves in a Coupled Model of the Tropical Atlantic Ocean......................................................................................95 Abstract ..................................................................................................... 95 5.1 Introduction.......................................................................................... 96 v 5.2 Models and Experiment........................................................................99 5.3 AEW-induced Low-level Convergence and Precipitation: Sensitivity to Model Resolution....................................................................... 103 5.4 Impact on the Larger-scale Mean Precipitation and SST....................... 110 5.4.1 Mean Seasonal Cycle of the ITCZ ............................................ 110 5.4.2 Large-scale SST Distribution.................................................... 112 5.5 Conclusion and Discussion...................................................................115 5.6 Acknowledgments................................................................................117 Chapter 6. Summary and Future Plans.........................................................................131 6.1 Summary of Results ............................................................................. 131 6.2 Future Plans ......................................................................................... 135 References................................................................................................................... 138 vi LIST OF FIGURES AND TABLES Table 2.1 Model domain specification .........................................................................35 Figure 2.1 Schematic description of the Scripps Coupled Ocean-Atmosphere (SCOAR) Model ........................................................................................ 36 Figure 2.2 Model domain, bathymetry and orography Model domain, bathymetry and orography ............................................................................................37 Figure 2.3 Three-day averaged oceanic and atmospheric states.................................... 38 Figure 2.4 Spatial relationship of the SST and wind stress .........................................39 Figure 2.5 Hovmöller diagram of model SST and wind stress along 1°N .....................40 Figure 2.6 Same as Figure 2.5, except along 4°S ......................................................... 41 Figure 2.7 Binned scatter plots of wind stress and SST................................................42 Figure 2.8 Same as Figure 2.4, except latent and sensible heat flux with the SST.........43 Figure 2.9 Longitude-vertical cross-sections of atmospheric and oceanic temperature . 44 Figure 2.10 Thirty-day averaged SST and wind stress in July 2003.............................. 45 Figure 2.11 Binned scatter plots of wind stress and heat flux with SST........................ 46 Figure 2.12 Model climatology of wind stress vector and Ekman pumping.................. 47 Figure 2.13 Same as Figure 2.12 except for SST.......................................................... 48 Figure 3.1 Three-day averaged SST and 10-m winds ................................................... 72 Figure 3.2 Time-mean zonal current along 23°W and the surface eddy kinetic energy . 73 Figure 3.3 Three-day averaged model SST fields with the vectors of model surface current and the vectors of model wind stress ..............................................74 Figure 3.4 Three-day averaged highpass filtered model SST overlaid with model surface current and model wind stress ........................................................ 75 Figure 3.5 Schematic representation of the relationship between wind stress and surface current over TIW-SST.................................................................... 76 vii Figure 3.6 Map of correlation of highpass filtered model wind stress and current ........77 Figure 3.7 Zonal average of time mean barotropic conversion rate of the zonal flow and ur " # $r " averaged over 150 m.............................................................. 78 sfc z Figure 3.8 Hovmöller diagrams of the model perturbation vertical velocity and