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Jason 1

To monitor the stability of Jason Microwave Radiometer (JMR) on Jason1 satellite, the JMR measurements are compared with measurements from the Advanced Microwave Sounding Unit (AMSU) on NOAA-18 satellite. Using the same SNOs and coldest BT methods as what are applied for monitoring Jason2 AMR, JMR's stability is monitored with AMSU's nadir view measurements at 23.8GHz and 31GHz.

Monitoring at satellite SNOs
SNOs between Jason1 satellite and the NOAA-18 satellite happens a couple of times daily. Using all SNO events over the ocean, the JMR measurements at 23.8GHz and 34.0GHz are compared with the AMSU nadir-view measurements at 23.8GHz and 31.0 GHz respectively. The long-term trend of JMR's stability is shown by applying three statistical methods to the differences between ANR and AMSU at SNOs, i.e. monthly mean, cumulative mean, and running mean.

Monitoring at the coldest part of the ocean with the coldest BT
The monitoring of JMR at the coldest part of the ocean is based on the coldest BTs, which are calculated from the cumulative distributions of BT measurements during each 10 day cyle(Ruf, 2000, IEEE Geosci., Scharroo and Schrama, 2004, Marine Geodesy). To isolate the impact of possible natural trend of coldest BT, the coldest BT trend of nadir AMSU measurements at 23.8GHz and 31.0 GHZ is also displayed for comparison.