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    Lidar and satellite studies of noctilucent clouds over Alaska

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    Author
    Alspach, Jennifer H.
    Chair
    Collins, Richard
    Committee
    Bossert, Katrina
    Thorsen, Denise
    Fochesatto, Javier
    Keyword
    noctilucent clouds
    Alaska
    optical radar
    artificial satellites in meteorological optics
    Metadata
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    URI
    http://hdl.handle.net/11122/11253
    Abstract
    This thesis presents studies of noctilucent clouds (NLCs) occurring in the summer polar mesosphere over Alaska. Lidar observations of NLCs conducted at Poker Flat Research Range in Chatanika, Alaska (65° N, 147° W) from 1998-2019 are analyzed. The NLCs detected by lidar are characterized in terms of their brightness properties and duration. NLCs were detected on ~51% of the nights when lidar observations have been conducted during NLC season. The brighter NLCs are found to exist at lower altitudes, indicating a growth-sedimentation mechanism. Cloud Imaging and Particle Size (CIPS) data from the Aeronomy of Ice in the Mesosphere (AIM) satellite is used to examine NLC occurrence and brightness over the Alaska region (60-70° N, 130-170° W). In general, high frequency and brightness in the CIPS data corresponds to positive detections of NLCs by the lidar. Microwave Limb Sounder (MLS) temperature and water vapor data from the Aura satellite is used to investigate the meteorological environment of the NLCs observed by lidar at Chatanika. The occurrence of NLCs at Chatanika is found to be driven by the temperature relative to the frost point. Low temperatures relative to the frost point (> 4 K below) correspond to observations when NLCs were present. High temperatures relative to the frost point (> 8 K above) correspond to observations when NLCs were absent. The MLS data is also used to investigate the stability of an ice cloud at different latitudes (64.7°-70.3° N) relative to the equilibrium water vapor mixing ratio. The stability study suggests that the weakest NLCs detected by lidar at Chatanika were in subsaturated conditions, and it is likely that the NLCs formed over several hundred kilometers to the north of Chatanika. The Rayleigh three-channel receiver system was used to conduct NLC measurements during 2019. A technical overview of the three-channel system and the density and temperature retrieval methods is presented at the end of the thesis using observations from the winter of 2018 and the summer of 2019.
    Description
    Thesis (M.S.) University of Alaska Fairbanks, 2020
    Table of Contents
    Chapter 1. Introduction -- 1.1. The Summer Polar Mesosphere -- 1.2. Noctilucent Clouds -- 1.2.1. Description -- 1.2.2. Noctilucent Cloud Formation -- 1.2.3. Waves and Other Impacts -- 1.2.4. Climate Change Implications -- 1.3. History of Noctilucent Cloud Research -- 1.4. Scope of This Study. Chapter 2. Lidar Measurements of Noctilucent Clouds -- 2.1. Rayleigh lidar technique -- 2.2. The Poker Flat Rayleigh lidar -- 2.3. Analysis of Noctilucent Clouds -- 2.4. Noctilucent Cloud Lidar Observations -- 2.5 Summary and Conclusions. Chapter 3. Satellite Analysis of Noctilucent Clouds -- 3.1. The Cloud Imaging and Particle Size (CIPS) Instrument -- 3.2. CIPS Analysis -- 3.3. The Microwave Limb Sounder (MLS) Instrument -- 3.4. MLS Analysis. Chapter 4. Rayleigh Three-Channel Receiver -- 4.1. The Three-Channel Receiver -- 4.2. Signal Analysis -- 4.2.1. 22-23 December 2018 Observation -- 4.2.2. 22-23 Dark Signal -- 4.2.3. 11-12 August 2019 Observation -- 4.3. Density and Temperature Retrievals -- 4.3.1. Temperature Retrieval from Relative Density -- 4.3.2. Combining Low and High Channel Data -- 4.3.3. Simultaneous RDTL and SRWTL Measurements -- 4.4. Summary and Conclusions. Chapter 5. Summary and Conclusions -- References -- Appendices.
    Date
    2020-05
    Type
    Thesis
    Collections
    Atmospheric Sciences

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