| Paper: | TH-P2.5 |
| Session: | Atmospheric Applications of Radiometry I |
| Time: | Thursday, March 29, 17:00 - 17:20 |
| Presentation: |
Oral
|
| Topic: |
Clouds and precipitation: |
| Title: |
Overland Millimeter-wave Retrievals of Total Column Water Vapor |
| Authors: |
Alan Tanner; NASA Jet Propulsion Laboratory | | |
| | Pekka Kangaslahti; NASA Jet Propulsion Laboratory | | |
| | Steven C. Reising; Colorado State University | | |
| | Javier Bosch-Lluis; NASA Jet Propulsion Laboratory | | |
| Abstract: |
Overland retrievals of total column atmospheric water vapor are demonstrated using data collected by the NASA/Colorado State University’s High resolution Airborne Microwave and Millimeter-wave Radiometer (HAMMR) during an 11-day tour aboard a Twin Otter aircraft in November of 2014 over the western United States. The nadir viewing retrieval technique is not based on sounding, but is instead based on observations of brightness temperature contrasts within radiometric images produced by land surface features, such as physical temperature contrasts or surface scattering, and of how these contrasts fade with increasing atmospheric attenuation due to both oxygen and water vapor. By matching images which are partially attenuated by water vapor in the 130 to 180 GHz range with images comparably attenuated by oxygen in the 118 to 123 GHz frequency range, data show that it is possible to deduce the unknown amount of water vapor using the known amount of oxygen in the atmosphere. This technique has the advantage of being insensitive to uncertainties of the surface scattering and emission which otherwise obscure the direct observation of water vapor emission—especially in the lower troposphere. The technique does require adequate surface contrasts and spectral consistency of the surface emission and scattering to produce accurate measurements of column water. A method to measure this spectral consistency, signal strength, and retrieval quality is developed and demonstrated in which retrievals are tested across multiple bands in the upper wing of the oxygen line above 118 GHz and matched bands one the lower wing of the 183 GHz water line. |
