All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 149 19 0
PDF Downloads 38 5 0

Aircraft-based Radiometric Imaging of Tropospheric Temperature and Precipitation Using the 118.75-GHz Oxygen Resonance

A. J. GasiewskiSchool of Electrical Engineering, Georgia Institute of Technology, Atlanta, Georgia

Search for other papers by A. J. Gasiewski in
Current site
Google Scholar
PubMed
Close
,
J. W. BarrettResearch Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts

Search for other papers by J. W. Barrett in
Current site
Google Scholar
PubMed
Close
,
P. G. BonanniResearch Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts

Search for other papers by P. G. Bonanni in
Current site
Google Scholar
PubMed
Close
, and
D. H. StaelinResearch Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts

Search for other papers by D. H. Staelin in
Current site
Google Scholar
PubMed
Close
Full access

Abstract

Passive microwave imagine of O2emissions using the 118.75-GHz(1) resonance has been investigated for tropospheric and stratosphere remote sensing of atmospheric temperature and precipitation. An imaging millimeter-wave spectrometer (MTS) using eight double-sideband channels centered around the 118.75-GHz O2 resonance, and including a fixed-beam 53.65-GHz radiometer and video camera was constructed. The MTS collected data during 33 flights of the NASA ER-2 high-altitude aircraft in 1986 during the Genesis of Atlantic Lows Experiment (GALE) and the Cooperative Huntsvilie Meteorological Experiment (COHMEX), yielding the first high spatial resolution microwave images of atmospheric O2 brightness.

The isolated 118-GHz fine offers higher spatial resolution and precipitation sensitivity than O2 lines in the 5-mm band near 60 GHz. The brightness temperature perturbations of clouds in nonprecipitating regions are typically twice as large in the 118-GHz channels relative to comparable 60-GHz channels. However, observations over cirrus anvils show that the 118-GHz brightnesses are not adversely sensitive to some optically opaque cloud cover. Thus, these channels are expected to be useful for temperature sounding in the presence of clouds, although retrieval ambiguities can result from variations in the water vapor profile and surface emissivity. The demonstration of 118-GHz temperature profile retrievals is left for a subsequent paper.

Over deep convective precipitation, 118-GHz brightness temperature images are characterized by decreases of up to 200 K due to strong scattering in the storm core. The amplitudes of the 118-GHz brightness perturbations contain information on the altitude of the cell top. The shape of the 118-GHz spectrum is also suggested to contain altitude information by virtue of the various peaking altitudes of the 118-GHz weighting functions. Precipitation cells observed by the MTS sometimes appear in bands or rows, and have been accompanied by periodic radiance structures.

Abstract

Passive microwave imagine of O2emissions using the 118.75-GHz(1) resonance has been investigated for tropospheric and stratosphere remote sensing of atmospheric temperature and precipitation. An imaging millimeter-wave spectrometer (MTS) using eight double-sideband channels centered around the 118.75-GHz O2 resonance, and including a fixed-beam 53.65-GHz radiometer and video camera was constructed. The MTS collected data during 33 flights of the NASA ER-2 high-altitude aircraft in 1986 during the Genesis of Atlantic Lows Experiment (GALE) and the Cooperative Huntsvilie Meteorological Experiment (COHMEX), yielding the first high spatial resolution microwave images of atmospheric O2 brightness.

The isolated 118-GHz fine offers higher spatial resolution and precipitation sensitivity than O2 lines in the 5-mm band near 60 GHz. The brightness temperature perturbations of clouds in nonprecipitating regions are typically twice as large in the 118-GHz channels relative to comparable 60-GHz channels. However, observations over cirrus anvils show that the 118-GHz brightnesses are not adversely sensitive to some optically opaque cloud cover. Thus, these channels are expected to be useful for temperature sounding in the presence of clouds, although retrieval ambiguities can result from variations in the water vapor profile and surface emissivity. The demonstration of 118-GHz temperature profile retrievals is left for a subsequent paper.

Over deep convective precipitation, 118-GHz brightness temperature images are characterized by decreases of up to 200 K due to strong scattering in the storm core. The amplitudes of the 118-GHz brightness perturbations contain information on the altitude of the cell top. The shape of the 118-GHz spectrum is also suggested to contain altitude information by virtue of the various peaking altitudes of the 118-GHz weighting functions. Precipitation cells observed by the MTS sometimes appear in bands or rows, and have been accompanied by periodic radiance structures.

Save