Measuring Atmospheric and Surface Features using Microwave Radiometers
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Dr. Norman C. Grody
National Oceanic and Atmospheric Administration
Monday September 16, 2019, 12 PM
ESSIC Conference Room 4102, 5825 University Research Ct, College Park, MD 20740
Abstract:
After retiring from NOAA in 2005 I considered building microwave radiometers using information and components available through the Internet. My project became a reality when I realized how cheap the components could be. In fact the most expensive part was the test equipment needed to measure the radiometer performance. However, I was able to construct a 4, 12 and 20.5 GHz Dicke radiometer from parts costing about $100 each. The construction, measurements and analysis is summarized in an 88 page report that is available on the internet. This talk briefly outlines some main findings in the report.
Unlike infrared, the microwave emissivity over land is highly variable. Emissivity measurement is important for two reasons. It provides information on surface properties and is needed to properly derive atmospheric variables such as precipitation and water vapor over land using satellite viewing radiometers. I shall therefore also describe the anomalous emissivity found over deserts and snow/ice covered surfaces from satellite microwave radiometer measurements that have yet to be resolved. For example, deserts are found to have different emissivity and penetration depths depending on frequency, grain size and impurities. Also, compared to new snow, aged or metamorphosed snow is found to have distinct microwave signatures at high frequencies. Finally, ice on the snow and within the snow pack displays inverted microwave spectra that is yet to be fully understood.
Bio-sketch:
Beginning in the 1960’s NASA solicited scientists and engineers to develop satellite infrared and microwave radiometers for observing and measuring the atmospheric and surface properties of our solar system. After completing my PhD in Electrophysics at NYU doing plasma research, I began my government career working at NASA in 1971 at a time when the US first began carrying experimental microwave radiometers aboard satellites to view Earth from space. I then joined NOAA in 1972 working on more advanced radiometers by the Air Force, Navy, NASA and NOAA. Throughout the years, these instruments measured the low level thermal radiation (~10-12 watts) emanating from the Earth’s surface and intervening atmosphere at frequencies between 1.4 and 183 GHz. At NOAA I was mainly involved in developing algorithms to derive surface and atmospheric parameters from the radiometric measurements. These parameters are used by various organizations to help monitor, analyze and forecast the weather and climate.
Contact:
Norm can be reached out by ngantique@hotmail.com Further contact can be directed to the host of the seminar, Ralph Ferraro, ralph.r.ferraro@noaa.gov
Webinar info:
Event site: http://go.umd.edu/grody
Event number: 734 299 887
Event password: essic
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