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Why are the surface temps too cold.


Why is the surface air temperature too cold?

If one compares the surface temperatures obtained from this page with those obtained from station data, they will appear to be too cold. There are a few reasons for this. The most important one is that the surface temperature data here are really at .995sigma level (.995 sigma = about 5mb above surface) and not at the standard 3 meters for surface temperature. Another difference is that the daily data here are the average of 0Z and 12Z values. 0Z and 12Z occur at different local times over the globe. For Colorado in the US, they occur at 5pm and 5am MST. Mean daily temperatures for station data are defined as the (max+min)/2. The maximum generally occurs at 1-2pm. So, the temperature will NOT be defined at the same time. In some regions (eastern US), that will make the surface temperatures too cold. In other regions, it may act to increase them relative to the station definition.

Obtaining actual surface temperatures maps isn't straightforward. You can try:

http://www.esrl.noaa.gov/psd/USclimate/ (monthly data)

NCDC: http://www.ncdc.noaa.gov

or CPC: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/regional_monitoring/

For data, try:
http://www.esrl.noaa.gov/psd/data/data_faq.html.