• Login
    View Item 
    •   Home
    • UA Graduate and Undergraduate Research
    • UA Theses and Dissertations
    • Dissertations
    • View Item
    •   Home
    • UA Graduate and Undergraduate Research
    • UA Theses and Dissertations
    • Dissertations
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of UA Campus RepositoryCommunitiesTitleAuthorsIssue DateSubmit DateSubjectsPublisherJournalThis CollectionTitleAuthorsIssue DateSubmit DateSubjectsPublisherJournal

    My Account

    LoginRegister

    About

    AboutUA Faculty PublicationsUA DissertationsUA Master's ThesesUA Honors ThesesUA PressUA YearbooksUA CatalogsUA Libraries

    Statistics

    Most Popular ItemsStatistics by CountryMost Popular Authors

    Investigating the Effects of Viewing/Solar Geometry and Precipitable Water Vapor on Passive Radiometeric Cloud Detection and Property Retrievals

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    azu_etd_18805_sip1_m.pdf
    Size:
    5.473Mb
    Format:
    PDF
    Download
    Author
    McHardy, Theodore Mitchell
    Issue Date
    2021
    Keywords
    Cirrus
    Cloud
    Microphysics
    Advisor
    Dong, Xiquan
    
    Metadata
    Show full item record
    Publisher
    The University of Arizona.
    Rights
    Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction, presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
    Abstract
    Clouds are well established as a major source of uncertainty in climate and are the dominant modulators of radiation both at the surface and at the top of the atmosphere. Their impact on the Earth’s radiation budget mainly depends on the bulk cloud properties, such as cloud amount, height, and microphysical/optical characteristics. Large-scale satellite data are needed to both verify and improve general circulation model (GCM) parameterizations of clouds and radiation for climate prediction. For reliable application of satellite datasets in cloud processes and climate models, it is important to have a reasonable estimate of the bias and uncertainty in the derived cloud properties. Ideally, the calibration and evaluation of passive radiometric-based cloud products should be done via in-situ aircraft. This is often impractical; thus, satellite retrievals are often validated with long-term ground-based or space-borne active remote sensing instruments. This dissertation makes use of both types of platforms for validating passive radiometric-based cloud products. In the first study, the daytime single-layered low-level cloud properties retrieved by instruments onboard GOES are compared with ground-based observations and retrievals over the DOE ARM SCF from June 1998 through December 2006. Comparisons are made for monthly means, diurnal means, and one-to-one GOES and ARM collocated pairs. GOES cloud effective temperature (Teff) is highly correlated with ARM cloud-top temperature (Ttop), having an R2 value of 0.75, though GOES exhibits a cold bias. GOES retrieved cloud optical depth (τ) and liquid water path (LWP) have very good agreement with ARM retrievals with R2s of 0.45 and 0.47, while GOES retrieved cloud-droplet effective radius (re), on average, is about 2 µm greater than ARM re. An examination of solar and viewing geometry has shown that GOES retrieved mean re and τ values are impacted by solar zenith angle (SZA) and especially scattering angle (SCA). In the second study, a quantitative evaluation of maritime transparent cirrus cloud detection, which is based on GOES-16 data and developed with collocated CALIOP profiling, is performed. First, the relationships between the clear-sky 1.378 µm radiance, viewing/solar geometry, and precipitable water vapor (PWV) are characterized. Next, detection thresholds are computed using the Ch. 4 radiance (λ= 1.378 µm) as a function of viewing/solar geometry. In addition to bulk statistics, an example application and case study are shown for validation. The algorithm detects nearly 50% of sub-visual cirrus (COD or τ < 0.03), 80% of transparent cirrus (0.03 < COD < 0.3), and 90% of opaque cirrus (COD > 0.3). This study lays the groundwork for a more complex, operational algorithm to detect GOES transparent cirrus clouds. In the third and final study, this algorithm is modified and applied for detecting transparent cirrus clouds over land for removing some potential false-alarm pixels. Clear-sky false alarm rates over land are examined as a function of PWV, and a threshold for pixel-rejection is determined. Then, thresholds for removing pixels with low- and mid-level clouds underneath are devised by integrating the water vapor mixing ratio between the top-of-the-atmosphere (TOA) and a specific altitude. The total-column and layer PWV thresholds are applied to the full over-land sample to determine their effectiveness in reducing the number of false alarms. This study suggests that for cirrus applications, lower-tropospheric clouds are a much more significant source of contamination than the land surface, due to the difficulty of removing them without the addition of downstream or level-2 products.
    Type
    text
    Electronic Dissertation
    Degree Name
    Ph.D.
    Degree Level
    doctoral
    Degree Program
    Graduate College
    Atmospheric Sciences
    Degree Grantor
    University of Arizona
    Collections
    Dissertations

    entitlement

     
    The University of Arizona Libraries | 1510 E. University Blvd. | Tucson, AZ 85721-0055
    Tel 520-621-6442 | repository@u.library.arizona.edu
    DSpace software copyright © 2002-2017  DuraSpace
    Quick Guide | Contact Us | Send Feedback
    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.