Homogeneity Analysis onSurrogate Temperature Data, Network No.1

Palma 25-27 January 2010

lars.andresen@met.no

Norwegian Meteorological Institute met.no

Work tool: ProClimDB by Petr Stepanek

• Procedure– Network analysis / Length of data period /

Distance between stations / Correlations between stations

– Quality control / Finding reference stations / Detection of outliers / Correction of original data series

– Homogeneity analysis / Finding reference stations / Using SNHT method (Automatic AnClim) / Breaks and adjustments

– Adjustments of data series

Norwegian Meteorological Institute met.no

Network No.1 – analysis 1

Length of data series

Station series

0

1

2

3

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

Length of data series (5-year intervals)

Nu

mb

er

of

sta

tio

ns

Distance between stations

Distance between stations

0

20

40

60

80

100

120

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110130120150130100120150150060110100110050060150100130120150100060050150060100120150160060120100150060120100

Station id

Dis

tan

ce

(k

m)

Norwegian Meteorological Institute met.no

Network No.2 – analysis 2

Correlations between stations

Correlation between stations of Network no.1, within a radius of 200 km

0.00.10.20.30.40.50.60.70.80.91.0

150 070 160 110 120 100 060 130 110 150 070 100 160 120 130 100 110 150 130 120 160 110 150 130 160 120 150 160 120 130 150 130 160 150 160 160

050 060 070 100 110 120 130 150

Top: NeighboursBottom: Candidate station

Co

rrel

atio

n

Norwegian Meteorological Institute met.no

Settings

ProClimDB

Norwegian Meteorological Institute met.no

Quality control – 1

• Criterions for making reference series– Maximum 6 stations, – Within distance of 200 km– Maximum altitude difference is 800 m– For consecutive 5-year periods with

common data and confidence limit = 0.95– Observation values are standardized to

the altitude of candidate by regression– Outliers check on the difference between

observation and reference value (0.99)

Norwegian Meteorological Institute met.no

Quality control - 2

Loxodromes of each candidate in different 5-year periods

0.00

100.00

200.00

300.00

400.00

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600.00

700.00

050 060 070 100 110 120 130 150 160

Station id

Dis

tan

ce

(k

m)

Norwegian Meteorological Institute met.no

Homogeneity analysis 1

• Criterions for making reference series for detecting breaks– Maximum 5 stations– Correlation with neigbours above 80%– Maximum altitude difference is 800 m– For 40-year periods (10 years overlap)

with common data– Distribution of neighbour values is

standardized to the AVG and STD of candidate, for each month

– Candidate and reference series are used in the homogenization analysis (SNHT method, automatically analysed in AnClim – results transferred to ProClimDB)

Norwegian Meteorological Institute met.no

Homogeneity analysis 2

• Breaks– 38 breaks in Network No.1– For station 050 four breaks:

• 1941• 1951• 1975• 1984

– No iterations

Norwegian Meteorological Institute met.no

Homogeneity analysis 3

• Adjustments (station 050 – no

iterations)– 1.procedure

• Ref.series for breaks, weigthing on distance (1/d) (power of weights = 0.5).

• Maximum adjustment:1.3°C• Number of adjustments: 33 for 12 months

– 2.procedure• Ref.series based on up to 10 years around

break, minimum 4 years from end (or from another break), 5 nearest stations with distance below 200 km, weigthing on distance (power of weights = 0.5).

• Maximum adjustment: 1.0°C• Number of adjustments: 28 for 12 months

Norwegian Meteorological Institute met.no

Homogeneity analysis 4 – station 050 – 1(ref.series as for detect.breaks)

JAN FEB MAR APR

MAY JUN JUL AUG

SEP OCT NOV DECNotice scale for

JUN-SEP

Norwegian Meteorological Institute met.no

Homogeneity analysis 5 – station 050 -2(ref.series for making adjustm. – for this presentation only)

JAN FEB MAR APR

MAY JUN JUL AUG

SEPNotice scale for

AUG

OCT NOV DEC

1975

1985

1951

1941