WEPS Climate Data (Cligen and Windgen)

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WEPS Climate Data(Cligen and Windgen)
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Climate Data

• Climate Generation by Stochastic Process

A stochastic process is one involving a randomly
determined sequence of observations each of which
is considered as a sample of one element from a
probability distribution. By stochastically
simulating a process, such as weather, one can
recreate a series of weather data that
statistically mimic the historic record.
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Consider a Normal Distribution where the Y-axis
represents the probability of some measurement
(height of people or wind speed) on the X-Axis.
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If the probabilities are cumulated, the
distribution looks like the graph above. To
stochastically simulate a measurement, one only
needs to randomly select a probability and read
the corresponding measurement (i.e., wind speed)
from the X-Axis.
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If random numbers are repeatedly selected and
measurements determined, eventually the original
historic wind speed distribution will be
recreated. Wind speeds typically follow a Weibull
Distribution.
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Climate Data

• Climate Generation by Stochastic Process

• WEPS does not use actual data.
• It uses statistically probable weather
  conditions.
• This is more appropriate than using measured data
  (saves computer space) .
• WEPS and WEPP use this type of data generation.
• The model runs for 15 years to recreate the
  historical weather distribution and get a stable
  erosion estimate.
• Two steps are used Statistics are calculated
  from historic data, then the data is
  stochastically generated.

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Climate Data

• WINDGEN Data

• WINDGEN was developed specifically for WEPS.
• The data comes from a quality-controlled hourly
  wind data sets.
• There are 1304 stations in the 48 state data set.
• Stations with less than 5 years of data were
  excluded to get a good representation of
  historical winds.

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• Wind (Windgen) Station Data

• WindsgtThreshold - 8.0 m/s or 17.9 miles/hr, Units
  are in hours for the month.
• Energy - kJ/m2/Month, stations over 1000 have
  fair risk of erosion.
• Monthly Percent - Percent of the yearly wind
  energy.
• Preponderance - Same as for WEQ
• PWED - Prevailing Wind Erosion Direction (16
  points of the compass).

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Climate Data

• Climate Generation by Stochastic Process

• Like Windgen, Cligen is a stochastic weather
  generator which produces daily estimates of
  precipitation, temperature, dewpoint, wind, and
  solar radiation for a single geographic point,
  using monthly parameters (means, SD's, skewness,
  etc.) derived from the historic measurements.

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Climate Data

• Temp, Rainfall, Radiation, Dew point are used.
• Wind, speed and direction are not used)

• CLIGEN