Thursday, January 1, 2015

Survey on national homogenised temperature data sets

I've recently run a survey on national homogenised temperature data sets. Whilst this was not an exhaustive survey (as indicated by the number of responses), it is an indication of what's out there and what resources various countries are putting into this work.

Survey reports were received from 18 countries (CHN, CAN, ISR, IRL, SUI, SLO, NOR, HUN, NED, ROM, GBR, AUT, SRB, ESP, CZE, SWE, UKR, AUS) and 1 region (Catalonia). Summary results were as follows:

1. Number of staff involved in homogenisation (full-time equivalent)

Less than 1                                          2 countries
1-2                                                       9
2-4                                                       5
4 or more                                             3

(global and continental data sets are excluded from this - for example, the UK have several people working on the HadCRUT data sets, and the Netherlands on ECA&D and associated projects)

2. Existence of a national homogenised data set

Yes                                                                                         16
Yes but not yet released                                                         1
No national set but a station/regional set                              1
No                                                                                          1

3. Time resolution of data set

Daily                                                                                      8
Monthly                                                                                 7
Mix depending on element                                                    1
Monthly for early data, daily for later                                   1

4. Time resolution of adjustment

Results from this are a little unclear – several responses indicated use of the Vincent methodology, which interpolates adjustments based on monthly values to daily timescales.

Daily                                                                                      4
Monthly                                                                                 11
Monthly for detection, daily for adjustment                          2

5. Elements included

Maximum, minimum and mean temperature                        8
Maximum and minimum temperature                                   5
Mean temperature only                                                          4

(note that ‘maximum and minimum temperature’ implies mean temperature is not homogenised independently – in most cases it can still be calculated based on max/min)

6. Frequency of updating/reassessing homogeneity

Not updated                                                                      6 (in 2 cases, the first data set has only just
                                                                                              been completed)
Appended with unadjusted data only                               2
Irregularly                                                                         1
Annually or near-annually                                                4
Intervals longer than 2 years                                            4 (ranging from every 3 to every 10 years)

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