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HOME > Monitoring_and_Data > Oceanic and Atmospheric Data > Reanalysis: Atmospheric Data > CFSR plant hardiness zones

### Introduction

The Climate Forecast System Reanalysis (CFSR) creates analyses of many fields including the 2 meter temperature. The CFSR analyses were used to create a plant hardiness zone map using the same formula as used by the USDA. See http://en.wikipedia.org/wiki/Hardiness_zone. For practical use, you should use the USDA product. The CFSR based product is for reasearch on performance of the reanalysis.

For the plots, a value between 7,0 and 7.5 corresponds to zone 7a and value between 7.5 and 8.0 corresponds to a zone 7b.

### Calculation

1. Find the minimum 2m temperature (6 hour forecast) for 1979 from the CFSR.
2. Repeat the above for the years 1980 to 2008 (30 years in total).
3. Average the 30 years to produce a 30-year average annual minimum temperature
4. Convert the data from Kelvin to Fahrenheit.
5. To the temperature data, add 70, divide by 10 and set the negative values to zero.

### 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.

http://en.wikipedia.org/wiki/Hardiness_zone
CFSR based plots