homogeneity of the eca temperature data
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HOMOGENEITY OF THE ECA TEMPERATURE DATA
Janet Wijngaard
Albert Klein Tank
BUDAPEST, 25-29 SEPTEMBER
HomogeneityTests
• Standard Normal Homogeneity Test
(SNHT, Alexandersson)
• Range test (Buishand)
• Von Neumann ratio
Testing method
• No reference stations used
- stations are diverse
• Annual DTR series tested
- artificial changes opposite
effect - natural changes
same effect
CONCLUSIONS
• Test results for the examples are satisfactory
• Summarised results for SNHT, Range-test and Von Neumann Ratio
overview of homogeneity
• Meta data should be used to take full advantage of the ECA data set
Von Neumann Ratiofor Eelde Groningen
• N= 0.55 period: 1910-1998
• N=1.85 period: 1958-1998
0T=na1max)(aT=na1max{
2
2
2
1 )(zanza} na,......1
sYYza
iia/)(
1
11
sYYzn
aiian/)(
1
12
where Y is the mean and s the standard deviation of the sample
*kS= )(1
k
iiYY nk,.....1 and *0S
=0
sSSR knk
knk
/)min(max *
0
*
0
n
iii
n
ii YYYYN
1
221
1
1
)(/)(
SNHT
Range test
Von Neumann Ratio
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