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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 Ratio for Eelde Groningen • N= 0.55 period: 1910-1998 • N=1.85 period: 1958-1998 SNHT 2 2 T0 = max T (a) = max { a z1 (n a) z 2 } a 1,......n 1 a n 1 a n a n z 1 1 (Yi Y ) / s a where Y is the mean ands z 2 i 1 1 na (Y i a 1 i Y) / s the standard deviation of the sample Range test k S k* = (Y i 1 i Y) S 0* k 1,.....n and R (max S k* min S k* ) / s 0 k n 0 k n Von Neumann Ratio n 1 n i 1 i 1 N (Yi Yi 1 ) 2 / (Yi Y ) 2 =0