Description
Calculation of the UV-Cloud modification factor (CMF) bases on a transformation of the SOL-CMF following the algorithmus of den Outer et al. (2005).
This algorithm is also the basis for the calculation of the COST UV-Index Climatology.
Transformation SOL-CMF --> CMFUV:
CMFUV=(1-exp(-0.23*ln(1+Pfac*SOL-CMF)))/(1-exp(-0.23*ln(1+Pfac)))
where
Cos(SZAmin) | Pfac
-----------------------------
0.00 - 0.15 | 6.12888
0.15 - 0.30 | 4.40254
0.30 - 0.45 | 3.03030
0.45 - 0.60 | 1.93951
0.60 - 0.75 | 1.07246
0.75 - 1.00 | 0.38325
where
SZAmin = Minimal Solar Zentih Angle for day.

The plot below shows the relation between CMF(global solar) and CMF(UV erythema) depending on solar zenith angle.

Relation: CMF (solar) versus CMF(UV erythema)

At the end of this page you can find download of this climatology.

Monthly averages
Below you can find graphics (left side) of averaged erythemal UV Cloud Modification Factor for each month of the year.
Monthly averages are calculated from the years 1958 to 2002 from daily values.
On the right side the corresponding accuracy is shown. The accuracy of monthly averages depends on the density of stations.
Calculations and graphics were provided by: H. Staiger.

	JANUARY		FEBRUARY
Average	Accuracy	Average	Accuracy
	March		APRIL
Average	Accuracy	Average	Accuracy
	MAY		JUNE
Average	Accuracy	Average	Accuracy
	JULY		AUGUST
Average	Accuracy	Average	Accuracy
	SEPTEMBER		OCTOBER
Average	Accuracy	Average	Accuracy
	NOVEMBER		DECEMBER
Average	Accuracy	Average	Accuracy

Download and data information

Data format:
The files (*.txt) contain yearly gridded (1x1 degrees in latitude and longitude) daily (or monthly) Cloud Modification Factors for UV (CMFUV) calculated based on the solar cloud modification factors from Henning Staiger.
The file format is exactly the same as the original files:
similar to the format of total ozone files i.e. the grid dimensions are 61x50 covering longitudes 25W-35E and latitudes 80N-31N in a regular lat-lon grid with 1 degree spacing. See the total ozone readme file for details. Column delimiter is one blank space, record delimiter is carriage return + line feed.

Usage
Non-commercial: This climatology is free for non-comercial use. In any application aknowledgement has to be given to the Action COST726 (www.cost726.org) and to H. Staiger. In case of publication additional reference 1 (see below) has to be citated.
In any other case: you have to contact the developer: H. Staiger

Download monthly averages (*.zip):
1958-2004 (2.6 MB)

Download monthly accuracy (*.zip):
1958-2004 (2.0 MB)

Download daily data by period (*.zip):

1958-1970(21.5)MB

1971-1980(16.5 MB)

1981-1993(21.5 MB)

1994-2002(14 MB)

2002-2004 (3 MB)

Download daily data by year (*.txt, 7.9 MB each year)

----	----	----	----	----	----	----	----	1958	1959
1960	1961	1962	1963	1964	1965	1966	1967	1968	1969
1970	1971	1972	1973	1974	1975	1976	1977	1978	1979
1980	1981	1982	1983	1984	1985	1986	1987	1988	1989
1990	1991	1992	1993	1994	1995	1996	1997	1998	1999
2000	2001	2002	2003	2004	----	----	----	----	----

References:
Den Outer, P. N., Slaper, H., and Tax, R. B. (2005)
UV radiation in the Netherlands. Assessing long-term variability and trends in relation to ozone and clouds,
J. Geophys. Res., 110, D02203, 1-11, doi: 10.1029/2004JD004824.