Note on Issue with Annual Summaries for the Period 1951-1961

[Rwood]

Met Service provided an update of annual sunshine averages to 1950 by the time this was published. Unfortunately these were rather misleading (too high) for several reasons. Records prior to 1935 were included in the calculation, and in several cases these were "optimistic" - most notably in the case of Napier. Standardisation of equipment and measuring methods was not done for data prior to 1935. Also, the period 1935-1950 was sunnier than the long term records have since indicated, giving a further distortion. Finally, I suspect that there was some tightening of measurement rules from about 1951, as the occurrence of 6 consecutive years (1951-1956) of lower than average sunshine, especially in the North Island, is not easy to explain, even given the earlier factors.

The net result is that I consider the assessments of sunshine deviations for the period 1950-1961 to be too negative (from about 1962 on new averages for 1935-1960 were used, and then 30-year spans for the periods ending 1970, 1980 etc were used.


The "new" average for Napier to 1960 was more than 120 hours below the dodgy number obtained for records up to 1950.

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