These weather maps are generated from the
NCEP Global Forecast System (GFS) model. GFS is the chief operational model framework underlying U.S. NOAA/NWS
weather forecasting. The model is run four times daily on a global T1534 gaussian grid (~13 km) to produce 16-day
forecasts. Here, we use 0.25°x0.25° (~30 km) output grids available from
NOMADS, and calculate daily averages from eight 3-hourly timeslices starting at 0000 UTC.
- Temperature refers to air temperature at 2 meters above the surface.
- Sea surface temperaure (SST) is obtained from the skin temperature model output with land values removed.
- SST (skin temperature over ocean) and sea ice are analysis fields in GFS. Ingests for these parameters are made from bouy
(SST) and satellite measurements (SST and sea ice) from the previous day.
- Anomaly fields for both SST and 2-meter air temperature are made in reference to a 1979-2000 climatology
derived for the current day of the year from the
Climate Forecast System Forecast Reanalysis (CFSR) model.
- Why does Climate Reanalyzer not use the WMO 1981-2010 climate normal?
The Arctic and much of the Northern Hemisphere have warmed beyond historically-observed values since
about the year 2000 (see this example from the
NCEP Reanalysis; and also this summary from NCAR). A 1979-2000 period average is used here in order to avoid warm
bias inherent in 1981-2010 climate normal. CFSR begins January 1, 1979, which precludes deriving earlier
climatologies within the GFS/CFSR framework. Click
here to see how the different averagering periods compare against the NASA GISS 1880-2014 global land-ocean temperature index.