Aquarius Algorithm Workshop March 2007 College of Engineering Department of Atmospheric, Oceanic & Space Sciences Chris Ruf Space Physics Research Laboratory Dept. of Atmospheric, Oceanic & Space Sciences University of Michigan (V), (F) Antenna Sidelobe Correction for Land Contamination

19 Mar 2008Ruf, Land Contamination, Aquarius Algo Workshoppg 2 of 10 Contributions to Antenna Temperature

19 Mar 2008Ruf, Land Contamination, Aquarius Algo Workshoppg 3 of 10 General Description of Algorithm Model T B entering antenna from Earth at all view angels –Derive model from satellite radiometer observations –Stratify by lat/lon of antenna, obs. frequency, time of year Derive sidelobe contribution to T A as antenna pattern weighted average Incorporate improved knowledge of sidelobe contribution into standard APC algorithm

19 Mar 2008Ruf, Land Contamination, Aquarius Algo Workshoppg 4 of 10 Heritage with Other Flight Projects Obligis, E., L. Eymard and N. Tran, “A new sidelobe correction algorithm for microwave radiometers: Application to the Envisat instrument,” IEEE Trans. Geosci. Remote Sens., 45(3), –Use 1 year of Envisat nadir TBs at 23.8 and 36.5 GHz –Stratify by season – 4 time bins –Use nadir TBs directly in antenna pattern weighted averages –Incorporated into Envisat Level 1B operational processing in Nov Developed with Jason Microwave Radiometer; Planned for AMR on OSTM (Jason-2); Shannon Brown lead –Use 3 year JMR nadir TBs at 18.7, 23.8 and 34.0 GHz –Derive model to estimate off-nadir TB from nadir obs by regression of simulated database of TBs at many angles from ocean/atmos data record and radiative transfer model (over ocean only)

19 Mar 2008Ruf, Land Contamination, Aquarius Algo Workshoppg 5 of 10 Brown JMR Results (1 of 3) (ref. Brown, S., “ Generate JMR TE Maps, ” JPL Tech. Memo, 4 Apr 2006) Map of the 18.7 GHz nadir brightness temperature centered at LAT=35.5 o E, LON=17 o N. Inner black circle represents 10 o off-nadir. Outer black circle is the Earth limb at 1338 km altitude, approximately 55 o off-nadir.

19 Mar 2008Ruf, Land Contamination, Aquarius Algo Workshoppg 6 of 10 Brown JMR Results (2 of 3) (ref. Brown, S., “ Generate JMR TE Maps, ” JPL Tech. Memo, 4 Apr 2006) Earth incidence angle from perspective of 1338 km altitude above ground at LAT=35.5 o E, LON=17 o N.

19 Mar 2008Ruf, Land Contamination, Aquarius Algo Workshoppg 7 of 10 Brown JMR Results (3 of 3) (ref. Brown, S., “ Generate JMR TE Maps, ” JPL Tech. Memo, 4 Apr 2006) (LEFT) Nadir TB observations at 18.7 GHz (RIGHT) Modeled upwelling TB from perspective of 1338 km altitude above ground at LAT=35.5 o E, LON=17 o N. (Note: no change from nadir for land TBs)

19 Mar 2008Ruf, Land Contamination, Aquarius Algo Workshoppg 8 of 10 Aquarius Sidelobe Land Contribution (1 of 2) (ref. Brown, S., “ Aquarius APC, ” JPL Aquarius TIM, 1 Feb 2006,) Aquarius required to retrieve salinity > 450 km from coast All points in blue > 450 km from land

19 Mar 2008Ruf, Land Contamination, Aquarius Algo Workshoppg 9 of 10 Aquarius Sidelobe Land Contribution (2 of 2) (ref. Brown, S., “ Aquarius APC, ” JPL Aquarius TIM, 1 Feb 2006,) Less than 10% of on-Earth sidelobe fraction on land at 450 km (p1V) (Assumes knowledge of T Land is better than 15 K)

19 Mar 2008Ruf, Land Contamination, Aquarius Algo Workshoppg 10 of 10 Aquarius Implementation Use SMOS observations to train T earth model –Model for incidence angle dependence of TB over ocean and land can be better constrained by obs Pre-launch simulations –Build T earth database –Assess sensitivity of correction to errors in Integrated antenna beam fractions T earth (seasonal dependence, RFI effects, other?)