statistical description of uv climate and climatological maps second educe meeting, bordeaux 2001 h....
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Statistical description of UV climate and climatological maps
Second EDUCE Meeting, Bordeaux 2001
H. Slaper and P.N. den Outer
UV climatology: Retrieve and analyse large amounts of data, spectral and pyranometer
data.
Sets requirements on format (data format, cosine correction,….)
Construction of integrated properties: daily, monthly, annual dosesV-dat
How to deal with data gaps?
Models required since UV-data exist for limited periods only
Validation of models (ground-based and satellite-based)
QA/QC-tools on irradiance scale errors
DATA SUPPLEMENTATION
Data gaps supplemented with:•RB-measurements•fractional:
Test:35 days interchanged1. randomly2. in a row
Data used:1998, skin cancer weightedRIVM, Bilthoven, The NetherlandsRB cal.: RB = spectroradiometer
0 50 100 150 200 250 300 3500.0
0.5
1.00 50 100 150 200 250 300 350
0.0
0.5
1.00 50 100 150 200 250 300 350
0.0
0.5
1.00 50 100 150 200 250 300 350
0.0
0.5
1.00 50 100 150 200 250 300 350
0.0
0.5
1.0
T1
T5
T12
T9
T8
T7
T6
0 50 100 150 200 250 300 3500.0
0.5
1.00 50 100 150 200 250 300 350
0.0
0.5
1.0
yearmeas
measyear Model
Model
UVUV
Months Random
1 2 3 4 5 6 7 8 9 10
0.86
0.88
0.90
0.995
1.000
1.005
1.010
RB-supp fractional gapped data
Average:UVsupp/UVmeas s.d. UVsupp/UVmeas s.d.
RB-supp. 1.000 0.006 1.000 0.002Fractional 1.000 0.005 1.000 0.003
1 2 3 4 5 6 7 8 9 10 11 12
0.98
1.02
1.00
Rat
io t
o m
easu
red
year
ly s
um
Month
1.1
1.0
0.9
0.8
UV-transfer model
UV-reduction algorithm
1. Global Solar Irradiation, pyranometers, WRDC2. TOMS Reflection3. ISCCP (ρ, τCLD)
OzoneSZAStandard atmosphere
Cloudless sky UV
Cloudy sky UV
Extra terrestrial UV
UV v.s. Global Solar Irradiation:UV v.s. Global Solar Irradiation:
0,0 0,5 1,00,0
0,5
1,0
red
uce
d U
V
reduced GSI
clear sky UVmeasured UV
measured Global Solar irradiationclear sky Global Solar irradiation
0 5 10 15 20
0
5
10
15
20
Mod
elle
d do
se (
J/cm
2 )
Measured dose (J/cm2)
1980 1990 2000
140
150
160
Eff
ectie
f U
V (
J/cm
2 )
Year 1980 1990 2000
90
100
110
Modelled data Measurements
Eff
ectie
f U
V (
J/cm
2 )
Year
Trends:5±1%/decade, cloudless6±2%/decade, cloudy sky
Standard deviations in yearly sums1.00 ± 0.01, cloudless0.98 ± 0.03, cloudy sky
Monthly doses
Yearly doses
0.0 0.5 1.00.0
0.5
1.0
ground-based
ISC
CP
0.0 0.5 1.00.0
0.5
1.0
ground-based
TO
MS
Grid cell ISCCP TOMSNorthern Egypt 0.64 0.70
South-east France 0.87 0.89
South-west France 0.92 0.92
Mid-west France 0.93 0.94
Northern France 0.93 0.94
Tsjech republic. 0.93 0.93
Belgium + Neth. 0.94 0.95
Mid Germany 0.94 0.94
N.Netherlands 0.87 0.91
Ireland 0.91 0.91
Scotland 0.89 0.89
Southern Sweden 0.92 0.93
ALL 0.92 0.93
CORRELEATION WITH GROUND-BASED DATAISCCP, and TOMS versus GDFBelgium + Southern Netherlands
correlation
Cloudless sky Cloudy sky
Percent change Percent change
Cloudless sky Cloudy sky
UV v.s. Global Solar Irradiation:UV v.s. Global Solar Irradiation:
0,0 0,5 1,00,0
0,5
1,0
red
uce
d U
V
reduced GSI
clear sky UVmeasured UV
measured Global Solar irradiationclear sky Global Solar irradiation
UVB 300-310 nm
0.0 0.5 1.0 1.5 2.0 2.5 3.00
5
10
15
20
measured/modelled
% o
ccur
ence
0.0 0.5 1.0 1.5 2.0 2.5 3.00
5
10
15
20
% o
ccur
ence
measured/modelled
0.0 0.5 1.0 1.5 2.0 2.5 3.00
1
2
3
% o
ccur
ence
measured/modelled
0.0 0.5 1.0 1.5 2.0 2.5 3.00
1
2%
occ
uren
ce
reduction Global Irradiation
UVA 340-350 nm Individualmeasurements
Dialy sums
Global Irradiation
UVB 300-310 nm, summer data
Clear sky modelDirect relatedSZA-dependent
Results QA/QC-absolute irradiance
Gaussian fit 95% conf.sd sd
All UVA 0.086 0.103summer UVA 0.079 0.103All UVB 0.12 0.16summer UVB 0.103 0.13
Check thresholdUVA: 20% UVB: 35%
Thresholds apply to all weather conditions
0.0 0.5 1.0 1.5 2.0 2.5 3.00
5
10
15
20
25
d:\origin50\files\educe\freqcontratuvab350.opj
1999300-310 nm
O3 = measured values
O3 = 350 Du
% o
ccur
ence
measured/modelled
Conclusions1) data gaps can be eliminated without introducing much uncertainty: 10% loss of data adds 0.5% uncertainty
2) Use of pyranometer and ozone data is good approach to model UV. The approach yields good correlation with satellite data based models next step: validation at other locations using DB
3) Agreement of model with measurements allows for irradiance checks on the 20% level