More on the SAMSON Dataset
The wind roses presented by the National Water and Climate Center are based on hourly data from the Solar and Meteorological Surface Observation Network (SAMSON) dataset, available from NOAA's National Climatic Data Center (NCDC). The period of record is for 1961-1990.
SAMSON is a 3-volume CD set and is divided geographically into regions: Eastern, Central, and Western U.S. It contains hourly solar radiation data along with selected meteorological elements for the period 1961-1990. It encompasses 237 National Weather Service stations in the United States, plus offices in Guam and Puerto Rico.
The dataset includes both observational and modeled data. The hourly solar elements are:
- Extraterrestrial horizontal and extraterrestrial direct normal radiation
- Global, diffuse, and direct normal radiation.
Meteorological elements are:
- Total and opaque sky cover
- Temperature and dew point
- Relative humidity
- Wind direction (true north) and speed
- Ceiling height
- Present weather
- Precipitable water
- Aerosol optical depth
- Snow depth
- Days since last snowfall
- Hourly precipitation
The hourly winds measured at airports are normally 2- or 3-minute averages of 3- or 5-second samples at the top of every hour. These are not gusts. Newer equipment, particularly the Automated Surface Observation System (ASOS) used at most locations since 1996, automatically records these values from cup anemometer values. Older observations (generally prior to 1996) represent data recorded by personnel working at weather stations who manually observed wind speed and direction at the top of every hour, and made an estimation of hourly winds over some time period, typically 2 to 5 minutes in length.