CFSR: number of days/year with Tmax >= 30C
The Climate Forecast System Reanalysis (CFSR) creates analyses of many
fields including the 2 meter temperature. The CFSR analyses were
used to find the average number of days / year with Tmax (maximum daily
temperature) >= 30C.
The American Horticultural Society describes this parameter as another
factor for determining whether plants will thrive and created a
heat zone map.
Of course, other factors determine whether a plant will thrive includeing
the winter chill (ex USDA plant zones), sunlight, water, soil and my
personal biggie, the local deer population.
- Get the 2-meter maximum temperatures from the 0-6 hour CFSR forecasts.
- Find the daily Tmax from the above files.
- Count the number of days with temperatures >= 30C for each year (1979-2008)
- Average the 30 years.
Details and Caveats
The CFSR uses a system very similar to those run by the National Weather Service to
produce the 1-6 day weather forecasts that you see on TV. (Other countries run
similar systems for their 1-6 day forecasts.) As part of producing a weather forecast,
an analysis of the current atmospheric state is created. This analysis is made
using data from satellites, aircraft, weather ballons and other sources but surprising no
2-meter temperature observations. The 2-m temperature is model derived product which
depends on the land-surface model, the model physics, the model parameterizations and the
analyses of the winds, temperatures and humidity at the model levels. There
are many reasons why the analyses will differ from observations. For example,
you make your temperature observation on a patch of grass and the model is using
a forest. (The land surface is suppose to be representative of the average conditions
in a 35x35 km grid box.) Yes, grass vs. forest can be a big difference. Another
problem is model uses the average height of the grid box. Your measurement will
be at a different elevation. An other problem is the model doesn't know the
local orography. You could be on an exposed peak or in a sheltered valley.
These features are not resolved within a 35-km grid used by the CFSR model.
One way to view the CFSR temperature is they are a model estimate of average
temperature of a 35km x 35km grid box. It will not give you the same
number as an observation.
American Horticultural Society, Heat zones
CFSR based plots
Please send comments to: Wesley.Ebisuzaki@noaa.gov