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June 1988 <br /> Climate--C <br /> I . The C factor characterizes climatic erosivity , specifically <br /> windspeed and surface soil moisture . The factor for any given <br /> location is based on long—term climatic data and is expressed <br /> as a percentage of the C factor for Garden City , Kansas , which <br /> has been assigned a value of 100. In an area with a C factor <br /> of 50, for example, the the product of IKC would be only half <br /> of the IKC for Garden City , Kansas . <br /> II . The climatic factor equation expressed as: <br /> 34. 48 V3 <br /> C = <br /> (P—E) 2 <br /> Where V is the mean annual windspeed corrected to a standard <br /> height of 30 feet. P-E is the precipitation effectiveness <br /> index of Thornthwaite . 34 .48 is the constant used to adjust <br /> local values to a common base (Garden City , Kansas) . <br /> III . The windspeed term of the climatic factor is based on the rate <br /> of soil movement being proportional to windspeed cubed . <br /> Several researchers have reported that when windspeed exceeds <br /> that required to barely move the soil (threshold velocity) , the <br /> soil movement is directly proportional to friction velocity <br /> cubed which , in turn , is related to mean windspeed cubed . <br /> IV . The soil moisture term of the climatic factor was developed on <br /> the basis that erodibility of a soil varies inversely with the <br /> equivalent surface soil moisture . Effective surface soil <br /> moisture was assumed to vary as indicated by the Thornthwaite <br /> index of precipitation effectiveness (P—E) . <br /> V. Developing local C factors . <br /> The Wind Erosion Research Unit of the Agricultural Research <br /> Service has developed benchmark C factors , and erosive wind <br /> energy distribution, and preponderance tables where data is <br /> available . ARS has not attempted to determine how far the <br /> benchmark data should be extended . <br /> In many places these benchmark data represent a large area and <br /> little change in climate is experienced as one moves away from <br /> data collection sites . However, in other areas , one or more of <br /> the important climatic parameters may change significantly <br /> within a short distance from the data site . Temperature , wind <br /> velocity , wind direction, or precipitation may change <br /> drastically a relatively short distance away from the site due <br /> to elevation , lake effect, terrain roughness, or a combination <br /> of these effects. <br /> C-1 <br /> EXHIBIT K 38 TOTHL P.02 <br /> CLIMATE INFORMATION <br />