Simultaneous MSMR and SSM/I observations and analysis of sea-ice characteristics over the Antarctic region
Polar sea ice has been monitored quasi-continuously over the last 30 years using passive microwave radiometers onboard three satellites in polar orbit, namely Nimbus-5, Nimbus-7 and Defense Meteorological Satellite Program (DMSP) series. A short overlap between Scanning Multichannel Microwave Radiom...
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Veröffentlicht in: | International journal of remote sensing 2005-08, Vol.26 (15), p.3123-3136 |
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Zusammenfassung: | Polar sea ice has been monitored quasi-continuously over the last 30 years using passive microwave radiometers onboard three satellites in polar orbit, namely Nimbus-5, Nimbus-7 and Defense Meteorological Satellite Program (DMSP) series. A short overlap between Scanning Multichannel Microwave Radiometer (SMMR) on Nimbus-7 and Special Sensor Microwave Imager (SSM/I) onboard DMSP allowed inter-calibration of the two sensors leading to a consistent series of long-term sea-ice measurements since 1978. With the launch of Multifrequency Scanning Microwave Radiometer (MSMR) onboard OCEANSAT-1 in the polar sun-synchronous orbit during 1999, India developed the capability to monitor the polar sea ice on a regular basis. The concurrent availability of SSM/I and MSMR over the last few years presents a valuable opportunity to attempt an inter-comparison of MSMR with SSM/I measurements and derived sea-ice parameters.
In this paper, we present an indirect validation of the brightness temperatures (T
b
) observed by MSMR with near-simultaneous measurements from SSM/I over the Antarctic and Southern Polar Ocean regions. Simultaneous MSMR and SSM/I data from two contrasting seasons-summer and winter-for the 1999-2000 period have been used. Analysis includes a comparison of T
b
scatterograms to achieve confidence in the quantitative use of the T
b
data to derive various geophysical parameters, e.g. sea-ice concentration and extent. Additionally, the T
b
images produced by the two sensors are compared to establish the capability of MSMR in reliable two-dimensional portrayal of all the sea and continental ice features over the Antarctic Region. Based on a regression analysis between MSMR observed T
b
in different frequency channels and polarizations, and SSM/I-derived sea-ice concentration (SIC) values, we have developed algorithms to estimate SIC over the Southern Polar Ocean from MSMR data. The MSMR algorithms allow estimation of SIC with better than 10% rms error. MSMR SIC images faithfully capture the observed distribution of sea ice in all the sectors of the Southern Ocean both during summer and winter periods. Using the MSMR-derived SIC, we have also derived monthly sea-ice extent (SIE) estimates for a period extending for about 20 months from the beginning of the launch of MSMR. These estimates show excellent agreement with values derived from SSM/I. These analyses bring out the very high level of compatibility in the measurements and derived sea-ice parameters produce |
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ISSN: | 0143-1161 1366-5901 |
DOI: | 10.1080/01431160500104376 |