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Ocean Surface Topography from Space
Error Characterization and Intercalibration of the Wet Path Delay Measurements from the TOPEX/Poseidon, Jason-1 and OSTM Microwave Radiometers
Shannon Brown
(California Institute of Technology - JPL)

Shailen Desai
Bruce Haines
(California Institute of Technology - JPL)
TMR 18.7 GHz cycle averaged hot refrernce TB over time from original GDRs (left). Modeled
			18.7 GHz hot reference using NCEP fields versus time (right).
Larger image with caption.


We will produce a seamless 20-year climate record of global wet tropospheric content that in turn will facilitate a seamless record of altimetric global sea surface height (SSH) over the same period, by rigorously calibrating and validating the measurements from the passive microwave radiometers onboard the Topex/Poseidon (T/P), Jason-1, and Ocean Surface Topography Mission (OSTM) satellites. We will generate a homogeneous record of vapor and liquid content of the troposphere with consistent quality and stability across the T/P, Jason-1, and OSTM missions by characterizing the temporal and geographically correlated errors in the radiometer measurements, as well as errors correlated with the geophysical state of the atmosphere and surface, and mitigating those errors through the recalibration of the radiometers and the development of new geophysical algorithms. A particular focus of the error characterization will be the assessment of errors near coastlines and sea ice boundaries. Along with this error assessment, new algorithms will be developed to reduce land contamination errors.

Our research goal is to ensure that the wet path delay measurements from the TMR, JMR, and AMR maintain accuracies of better than 1 cm per sample, less than 0.3 mm/year in global averages, and better than 5 mm per month in regional averages over a few hundred kilometers. The long term stability of the wet tropospheric path delay record will be assessed using on-Earth stable brightness temperature references, such as a vicarious cold reference and the Amazon rainforest, and wet troposphere content measurements from coastal Global Positioning System (GPS) sites, the Special Sensor Microwave Imager (SSM/I), the Tropical Rainfall Measuring Mission's Microwave Imager (TMI), global radiosondes and the ECMWF numerical weather prediction model. This investigation will promptly identify anomalies in the wet path delay measurements from these radiometers, such as unexpected offsets or drifts, notify users, and recommend corrections.

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