ANNEX I - PAN COEFFICIENTS FOR CLASS A PAN AND SUNKEN COLORADO PAN

PAN COEFFICIENT (K pan) FOR CLASS A PAN FOR DIFFERENT GROUND COVER AND LEVELS OF MEAN RELATIVE HUMIDITY AND 24 HOUR WIND

Class A pan	Case A: Pan placed in short green cropped area				Case B1: Pan placed in fallow area
RH mean %		low < 40	medium 40-70	high > 70		low < 40	medium 40-70	high > 70
Wind km/day	Windward side distance of green crop m				Windward side distance of dry fallow m
Light	1	.55	.65	.75	1	.7	.8	.85
< 175	10	.65	.75	.85	10	.6	.7	.8
	100	.7	.8	.85	100	.55	.65	.75
	1000	.75	.85	.85	1000	.5	.6	.7
Moderate	1	.5	.6	.65	1	.65	.75	.8
175-425	10	.6	.7	.75	10	.55	.65	.7
	100	.65	.75	.8	100	.5	.6	.65
	1000	.7	.8	.8	1000	.45	.55	.6
Strong	1	.45	.5	.6	1	.6	.65	.7
425-700	10	.55	.6	.65	10	.5	.55	.65
	100	.6	.65	.7	100	.45	.5	.6
	1000	.65	.7	.75	1000	.4	.45	.55
Very strong	1	.4	.45	.5	1	.5	.6	.65
> 700	10	.45	.55	.6	10	.45	.5	.55
	100	.5	.6	.65	100	.4	.45	.5
	1000	.55	.6	.65	1000	.35	.4	.45

PAN COEFFICIENT (K pan) FOR SUNKEN COLORADO PAN FOR DIFFERENT GROUND COVER AND LEVELS OF MEAN RELATIVE HUMIDITY AND 24 HOUR WIND

Class A pan	Case A: Pan placed in cropped short green area				Case B1: Pan placed in fallow area
RH mean %		low < 40	medium 40-70	high > 70		low < 40	medium 40-70	high > 70
Wind km/day	Windward side distance of green crop m				Windward side distance of dry fallow
Light	1	.75	.75	.8	1	1.1	1.1	1.1
< 175	10	1.0	1.0	1.0	10	.85	.85	.85
	> 100	1.1	1.1	1.1	100	.75	.75	.8
					1000	.7	.7	.75
Moderate	1	.65	.7	.7	1	.95	.95	.95
175-425	10	.85	.85	.9	10	.75	.75	.75
	> 100	.95	.95	.95	100	.65	.65	.7
					1000	.6	.6	.65
Strong	1	.55	.6	.65	1	.8	.8	.8
425-700	10	.75	.75	.75	10	.65	.65	.65
	> 100	.8	.8	.8	100	.55	.6	.65
					1000	.5	.55	.6
Very strong	1	.5	.55	.6	1	.7	.75	.75
> 700	10	.65	.7	.7	10	.55	.6	.65
	> 100	.7	.75	.75	100	.5	.55	.6
					1000	.45	.5	.55

¹ For extensive areas of barefallow soils and no agricultural development, reduce K pan by 20% under hot, windy conditions; by 5-10% for moderate wind, temperature and humidity conditions.