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Table 1

Pan coefficients for class A pan for different pan siting and environment and different levels of mean relative humidity and wind speed (FAO Irrigation and Drainage Paper No. 56; Allen et al. 1998)

Class A panCase A: Pan placed in short green cropped
Relative humidity (%)
Low (<40)Medium (40–70)High (>70)
Wind speed (m/s)Windward side distance of green crop (m)
Light <2 0.55 0.65 0.75 
10 0.65 0.75 0.85 
100 0.7 0.8 0.85 
1,000 0.75 0.85 0.85 
Moderate 2–5 0.5 0.6 0.65 
10 0.6 0.7 0.75 
100 0.65 0.75 0.8 
1,000 0.7 0.8 0.8 
Strong 5–8 0.45 0.5 0.6 
10 0.55 0.6 0.65 
100 0.6 0.65 0.7 
1,000 0.65 0.7 0.75 
Very strong >8 0.4 0.45 0.6 
10 0.45 0.55 0.6 
100 0.5 0.6 0.65 
1,000 0.55 0.6 0.65 
Class A panCase A: Pan placed in short green cropped
Relative humidity (%)
Low (<40)Medium (40–70)High (>70)
Wind speed (m/s)Windward side distance of green crop (m)
Light <2 0.55 0.65 0.75 
10 0.65 0.75 0.85 
100 0.7 0.8 0.85 
1,000 0.75 0.85 0.85 
Moderate 2–5 0.5 0.6 0.65 
10 0.6 0.7 0.75 
100 0.65 0.75 0.8 
1,000 0.7 0.8 0.8 
Strong 5–8 0.45 0.5 0.6 
10 0.55 0.6 0.65 
100 0.6 0.65 0.7 
1,000 0.65 0.7 0.75 
Very strong >8 0.4 0.45 0.6 
10 0.45 0.55 0.6 
100 0.5 0.6 0.65 
1,000 0.55 0.6 0.65 
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