The Aquarius Salinity Retrieval Algorithm Beyond Version 3.0
[13-Nov-2014] Wentz, F., Meissner, T., Scott, J., and Hilburn, K.
Presented at the 2014 Aquarius/SAC-D Science Team Meeting
Our presentation will first give an overview of updates and improvements that we plan to make in the Aquarius salinity retrieval algorithm for the next major release. Then we will describe in more detail the following two improvements:
- Repeat of On-Orbit Simulations using antenna pattern with proper spillover value: Analysis of Aquarius observations have shown that the true spillover of the Aquarius antenna pattern is between 1 and 1.5% less than the GRASP 2012 simulations, which were used for the previous On-Orbit Simulations. These simulations are used to specify a number of tables used by the Aquarius Operational Processor. We will repeat the simulations using revised antenna patterns having the correct spillover.
- Improvement of land correction: The sidelobe land correction that is used in V3.0 estimates the increase in the brightness temperature of Aquarius footprints close to the coast due to emission from land that enters the antenna sidelobes. The estimate is based on land emission radiative transfer model that uses auxiliary input for soil type, vegetation type, soil moisture and land surface temperature. We have compared this land emission RTM to measured Aquarius TB over land and found discrepancies that exceed ± 20 K over large areas. We therefore expect that the use of this land emission model will result in significant errors in the land correction algorithm and that it can be improved by using a land emission model that is based on measured Aquarius rather than RTM TB. We have derived such a model. For deriving the land emission correction it is necessary to know the land emission far off boresight and therefore it is necessary to extrapolate the measured Aquarius land TB to the full range of Earth incidence angles between 0 and 90 deg. We have also adjusted the antenna gain pattern for calculating the TB contribution from the sidelobe. We will recomputed the land-correction tables using the new land TB model in conjunction with the new antenna patterns discussed in Item 1.