The NOAA-N Polar Orbiting Weather Satellite
There have been some questions posed recently about how the satellite global temperature record is created by UAH and RSS from the MSU (Microwave Sounder Unit) on weather satellites. For example, Andrew recently posted this comment:
“I keep hearing rumors that the satellite data was “adjusted” to match the surface data better. Is that true? If so, that would be disturbing.”
It is always best to ask the source, so I put the question to Dr. John Christy, who is the lead scientist at UAH that produces this dataset:
“I’ve had some queries on my blog recently that are suggesting that the UAH and RSS satellite data is somehow “tuned” to the surface data, or that the surface data is used to provide some offset function. Given that the MSU looks at microwave emissions from oxygen, essentially a first principles measurement, I don’t see any reason that surface data would be used in any way to adjust the MSU data.
But I figured I’d ask the source, if you’d care to elaborate. If not, no worries.”
To which Dr. Christy graciously responded within a couple of hours:
“No other data are used in the construction. That is why we can do comparison studies without any interdependence.”
So from Dr. Christy’s response it is clear that there is no data sharing or comparative adjustment of any kind between that satellite global temperature record and the land-ocean global temperature record such as is produced by HadCRUT and GISS.
The Advanced Microwave Sounder Unit on NOAA-N satellites
UPDATE: An additional question has been brought up related to why the data seems to be missing from the poles. Dr. Christy also responded:
As the spacecraft rolls over the pole it does so at an inclined orbit so
that the highest nadir latitude is about 82 deg with the scanner looking
out a bit closer to the pole. Since we apply the scan line data mostly to
the nadir area directly below the satellite, the actual data only go to
about 83 deg. In the gridded data I interpolate over the pole, but I
wouldn’t trust the data too much beyond 85 deg.