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On the Interaction Between Gravity Waves and Atmospheric Thermal Tides

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On the Interaction Between Gravity Waves and Atmospheric Thermal Tides Dissertations and Theses 2017 On the Interaction between Gravity Waves and Atmospheric Thermal Tides Ryan Matthew Agner Follow this and additional works at: https://commons.erau.edu/edt Part of the Atmospheric Sciences Commons Scholarly Commons Citation Agner, Ryan Matthew, "On the Interaction between Gravity Waves and Atmospheric Thermal Tides" (2017). Dissertations and Theses. 318. https://commons.erau.edu/edt/318 This Dissertation - Open Access is brought to you for free and open access by Scholarly Commons. It has been accepted for inclusion in Dissertations and Theses by an authorized administrator of Scholarly Commons. For more information, please contact [email protected]. ON THE INTERACTION BETWEEN GRAVITY WAVES AND ATMOSPHERIC THERMAL TIDES BY RYAN MATTHEW AGNER A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy of Engineering Physics at Embry-Riddle Aeronautical University, 2017 Copyright by Ryan Matthew Agner 2017 All Rights Reserved iii Acknowledgements I would first like to thank my wife of 8 years, Nikisha. She is one of the major reasons that I chose to pursue my Ph.D. and has been a constant source of love and support in the entire time I have known her. You are my life, thank You for everything. I also want to send my love to our 2 year old daughter Nora. I would like to thank Dr. Alan Liu for providing the guidance throughout the dissertation work and writing. Your ideas and suggestions were invaluable to my effort of this entire project. Many thanks to you for allowing me to be with my family while completing this degree. To my committee members Dr. Hickey, Dr. Snively and Dr. Swenson, thank you for lending your time and expertise in reviewing this body of work. Thanks go to my Mother, Carole Rogers and my Father, Samuel Agner Jr. for your unconditional love and support throughout my entire life and for instilling in me your values, morals and ethics that guide me. Thanks also go to my older sister, Amanda and my younger sister, Sarah. We have all been through good times and bad times and have emerged from them with stronger bonds than before. To my mother-in-law and sister-in-law I would like to express my gratitude for everything you have given both of us, from coming all the way from India to help take care of Nora while I finished this degree and for your love. Thanks are given to my entire family for everything you have given me throughout my life. iv Abstract Gravity waves and thermal tides are two of the most important dynamical features of the atmosphere. They are both generated in the lower atmosphere and propagate upward transporting energy and momentum to the upper atmosphere. This dissertation focuses on the interaction of these waves in the Mesosphere and Lower Thermosphere (MLT) region of the atmosphere using both observational data and Global Circulation Model (GCMs). The first part of this work focuses on observations of gravity wave interactions with the tides using both LIDAR data at the Star Fire Optical Range (SOR, 35◦N, 106.5◦W) and a meteor radar data at the Andes LIDAR Observatory (ALO, 30.3◦S, 70.7◦W). At SOR, the gravity waves are shown to enhance or damp the amplitude of the diurnal variations dependent on altitude while the phase is always delayed. The results compare well with previous mechanistic model results and with the Japanese Atmospheric General circulation model for Upper Atmosphere Research (JAGUAR) high resolution global circulation model. The meteor radar observed the GWs to almost always enhance the tidal amplitudes and either delay or advance the phase depending on the altitude. When compared to previous radar results from the same meteor radar when it was located in Maui, Hawaii, the Chile results are very similar while the LIDAR results show significant differences. This is because of several instrument biases when calculating GW momentum fluxes that is not significant when determining the winds. The radar needs to perform large amounts of all-sky averaging across many weeks, while the LIDAR directly detects waves in a small section of sky. The second part of this work focuses on gravity wave parameterization scheme effects on the tides in GCMs. The Specified Dynamics Whole Atmosphere Community Climate v Model (SD-WACCM) and the extended Canadian Middle Atmosphere Model (eCMAM) are used for this analysis. The gravity wave parameterization schemes in the eCMAM (Hines scheme) have been shown to enhance the tidal amplitudes compared to observations while the parameterization scheme in SD-WACCM (Lindzen scheme) overdamps the tides. It is shown here that the Hines scheme assumption that only small scale gravity waves force the atmosphere do not create enough drag to properly constrain the tidal amplitudes. The Lindzen scheme produces too much drag because all wave scales are assumed to be saturated thus continuing to provide forcing on the atmosphere above the breaking altitude. The final part of this work investigates GWs, tides and their interactions on a local time scale instead of a global scale in the two GCMs. The local time GWs in eCMAM are found to have a strong seasonal dependence, with the majority of the forcings at the winter pole at latitudes where the diurnal variations are weak limiting their interactions. In SD-WACCM, the largest local GW forcings are located at mid latitudes near where the diurnal variations peak causing them to dampen the diurnal amplitudes. On a local time level the diurnal variations may be a summation of many tidal modes. The analysis reveals that in eCMAM the DW1 tidal mode is by far the dominant mode accounting for the local time variations. The high amount of modulation of GWs by the DW1 tidal winds does not allow it to be properly constrained, causing it to dominate the local time diurnal variations. Similarly, the DW1 projection of GW forcing is dominant over all other other modes and contributes the most to the local time diurnal GW variations. The local time wind variations in SD-WACCM are influenced by several tidal modes because the DW1 tide is of compatible amplitudes to other modes. This is because of the increased damping on the tide by the GWs. It is also found that the local GW diurnal variations have significant contributions from all tidal modes due to the time and location of the forcing being dependent only on the tropospheric source regions and not the at altitude tidal winds. vi Contents List of Figuresx List of Tables xix 1 Introduction1 1.1 Motivation and Outline..............................2 2 Thermal Tide and Gravity Waves5 2.1 Atmospheric Thermal Tides...........................5 2.1.1 Introduction................................5 2.1.2 Classical Tidal Theory..........................8 2.1.3 Thermal Tidal Heating.......................... 15 2.2 Gravity Waves................................... 17 2.2.1 Introduction................................ 17 2.2.2 Linear Theory............................... 23 2.2.3 GW Momentum Flux........................... 28 2.3 GW-Tidal Interactions.............................. 31 2.3.1 Introduction................................ 31 2.3.2 Tidal Modulation of Gravity Waves................... 32 2.3.3 Gravity Wave influences on the Tides.................. 34 3 Observations of Gravity Wave - Tidal Interactions 37 vii 3.1 LIDAR Observations............................... 37 3.1.1 Introduction................................ 37 3.1.2 Data and Method............................. 38 3.1.3 Background Wind, Momentum Flux and Gravity Wave Forcing... 42 3.1.4 Results................................... 44 3.1.5 Discussion and Conclusion........................ 47 3.2 Meteor Radar Observations........................... 49 3.2.1 Introduction................................ 49 3.2.2 Data and Method............................. 50 3.2.3 ALO Results............................... 54 3.2.4 Location and Instrument Comparisons................. 57 3.2.5 Conclusions................................ 63 4 GCM analysis of Tidal Mode GW interactions 65 4.1 Introduction.................................... 65 4.2 Global Circulation Model Descriptions..................... 66 4.2.1 The extended Canadian Middle Atmosphere Model.......... 67 4.2.2 The Whole Atmosphere Community Climate Model.......... 68 4.2.3 Gravity Wave Parameterizations..................... 69 4.3 Method...................................... 72 4.4 Results and Analysis............................... 74 4.4.1 Tidal Component Amplitudes...................... 74 4.4.2 Tidal Component of Gravity Wave Effects on the Tidal Winds.... 77 4.4.3 Non-Tidal Winds and GW Forcing................... 81 4.5 Summary and Conclusions............................ 88 5 GCM Analysis of Local Time Diurnal Variations - GW Interactions 90 5.1 Introduction.................................... 90 viii 5.2 Method...................................... 91 5.3 Results....................................... 92 5.3.1 Horizontal Structure of Local Time Diurnal Variations and Diurnal GW Forcing................................ 92 5.3.2 Tidal Mode Contributions to Local Time Diurnal Variations: Winds. 96 5.3.3 Tidal Mode Contributions to Local Time Diurnal Variations: GW Forcing................................... 101 5.4 Conclusion..................................... 104 6 Summary and Conclusions 106 6.1 Future Work.................................... 109 Appendix A Chapter 4 Supplemental Figures 110 Appendix B Chapter 6 Supplemental Figures 115 Bibliography 128 ix List of Figures 2.1 Zonal wind (m/s) for the first 10 days of March
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