UNIVERSITY OF CALIFORNIA, SAN DIEGO Stratocumulus-Topped Boundary Layers over Coastal Land A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Engineering Sciences (Mechanical Engineering) by Mohamed Sherif Ghonima Committee in charge, Jan Kleissel, Chair Carlos Coimbra Thijs Heus Joel Norris Lynn Russell Sutanu Sarkar 2016 The dissertation of Mohamed Sherif Ghonima is approved, and it is acceptable in quality and form for publication on microfilm and electronically: Chair University of California, San Diego 2016 iii DEDICATION I dedicate this work to my parents, Sherif and Amany Ghonima, for their continuous support and belief in me. iv TABLE OF CONTENTS Signature Page ................................................................................................................... iii Dedication .......................................................................................................................... iv Table of Contents ................................................................................................................ v List of Figures .................................................................................................................. viii List of Tables ...................................................................................................................... x Acknowledgments.............................................................................................................. xi Vita ................................................................................................................................. xiii Abstract of the Dissertation .............................................................................................. xv Chapter 1. Introduction ................................................................................................. 1 1.1 Motivation and Research Objectives .................................................................. 1 1.2 Literature Review................................................................................................ 3 1.3 Characterization of Coastal Stratocumulus ......................................................... 8 1.4 Thesis Outline ................................................................................................... 13 Chapter 2. Description of the Large Eddy Simulation Model .................................... 14 2.1 Model Equations ............................................................................................... 14 2.1.1 Anelastic and Boussinesq approximation ..................................................... 15 2.2 Sub-grid Parameterization ................................................................................ 17 2.3 Numerics ........................................................................................................... 18 2.4 Radiation ........................................................................................................... 18 2.5 Microphysics ..................................................................................................... 20 2.6 Surface Model ................................................................................................... 20 2.6.1 Ocean Surface Model .................................................................................... 21 v 2.6.2 Land Surface Model ...................................................................................... 21 2.7 Validation of Land Surface Model ................................................................... 23 2.8 Large-scale Horizontal Advection .................................................................... 25 2.9 Acknowledgement ............................................................................................ 27 Chapter 3. Turbulent and thermodynamic structure of STBL over coastal lands ...... 28 3.1 Initial Profiles and Domain Setup ..................................................................... 28 3.2 Turbulent and Thermodynamic Structures of STBL ........................................ 30 3.2.1 Ocean case – baseline analysis ..................................................................... 30 3.2.2 Land cases without advection ....................................................................... 31 3.2.3 Land case with advection of oceanic air ....................................................... 32 3.3 Effect of Aerosols on Stratocumulus Dissipation ............................................. 37 3.4 Acknowledgment .............................................................................................. 39 Chapter 4. Description of the Mixed Layer Model .................................................... 40 4.1 Governing Equations ........................................................................................ 40 4.2 Radiation Parameterization ............................................................................... 43 4.3 Entrainment Parametrization ............................................................................ 46 4.4 Cloud Thickness and Liquid Water Tendencies ............................................... 50 4.4.1 Response of Cloud Base Height to Changes in Boundary Layer Moisture Content ...................................................................................................................... 52 4.4.2 Response of Cloud Base Height to Changes in Boundary Layer Heat Content. ..................................................................................................................... 55 4.5 Factors Contributing to Cloud dissipation ........................................................ 56 4.6 Acknowledgment .............................................................................................. 58 Chapter 5. Factors Controlling Stratocumulus Cloud Lifetime .................................. 59 5.1 Effects of surface flux, entrainment, subsidence, and radiation on cloud lifetime. ......................................................................................................................... 62 5.2 Effect of large-scale horizontal advection on cloud lifetime ............................ 62 vi 5.3 Effects of initial conditions on cloud lifetime................................................... 64 5.4 STBL feedback loops ........................................................................................ 67 5.5 Acknowledgement ............................................................................................ 70 Chapter 6. Description of PBL Schemes .................................................................... 71 6.1 First-Order Closure ........................................................................................... 72 6.2 TKE Closure ..................................................................................................... 73 Chapter 7. Evaluation of WRF SCM Simulations of STBL and Proposed Correction to Improve Turbulence and Entrainment Parameterizations ............................................ 75 7.1 Model setup ....................................................................................................... 76 7.2 SCM Inversion Height determination ............................................................... 77 7.3 PBL formulation ............................................................................................... 80 7.3.1 YSU............................................................................................................... 80 7.3.2 ACM2 ........................................................................................................... 81 7.3.3 MYNN .......................................................................................................... 81 7.4 PBL evaluation.................................................................................................. 82 7.5 Microphysics scheme evaluation ...................................................................... 87 7.6 Proposed PBL correction and validation against LES ...................................... 90 7.7 Acknowledgement ............................................................................................ 98 Chapter 8. Conclusions and Outlook .......................................................................... 99 References ................................................................................................................... 104 vii LIST OF FIGURES Figure 1.1. Stratocumulus cloud deck off the coast of California, captured by NASA’s MODIS Terra satellite on April 14 2013. ........................................................................... 3 Figure 1.2. (a) Normalized GHI observations (b) Averaged cloud dissipation time derived from satellite solar resource data for June 2-9 2014 (SolarAnywhere 2014) for the state of California. ......................................................................................................................... 10 Figure 1.3. Schematic description of stratocumulus cloud dissipation. ............................ 12 Figure 2.1 (a) Surface sensible heat flux and b) latent heat flux time series. ................... 25 Figure 2.2. Surface wind speed magnitude (a) and direction (b) collected from METAR stations along the coast of California (117 -118°W, 32.5 - 33.3°N, see Fig. 1.2 (b)). ..... 27 Figure 3.1. (a) Liquid potential temperature and (b) total water mixing ratio for CGILS S12 (black lines) and DYCOMS (grey lines)