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