with John Maunder
Rainfalls for the month of August have been recorded in Tauranga since 1898, except for 1904, 1907, 1908 and 1909.
From January 1898 to December 1904, the observation site was described as the Tauranga Harbour, from November 1904 to April 1907 the site was described as simply ‘Tauranga'. From January 1910 to December 1923 the site was Waikareao, in Otumoetai; from January 1924 to September 1940 the site was at 148 Waihi Rd, in Judea; from October 1940 to January 1941 the site was at Te Puna; and from February 1941 to now, the site is Tauranga Airport.
The methodology use in adjusting the older sites to the current observing site is published in the ‘NZ Meteorological Service Miscellaneous Publication' No 180 in 1984.
It is considered that the homogeneous rainfall series described here is a fair and true record of what the rainfall would have been if the current observation site (Tauranga Airport) had been used since 1898. This should be coupled with the understanding that although standard accepted methodologies have been used, any adjustments are only estimates of what would have occurred if the location of the rainfall records had always been in the same place with the same surroundings and the same or similar recording gauge.
In terms of climate change (such as is it getting wetter or drier, or warmer or colder), the methodology used in computing an ‘official' set of climate observations is very important, as otherwise erroneous conclusions may be drawn.
The graph shows the range of rainfalls from an extreme high of 274 mm in 2010 to a low of only 17 mm in 1914.
The second wettest August was 1916 when 263 mm was recorded, and the second driest August was in 1982 when only 31 mm fell.
The long-term average rainfall for Tauranga for August is 124 mm. The rainfall for Tauranga for August 2019 was 74 mm.
The graph of the August rainfall shows normal variations from year-to-year.
There is a small decrease in the overall August rainfalls during the last 50 years – from 1961-2010 – from an average of 121 mm, compared with an average of 133 mm during the 50 years from 1911-1960. Since 1898, there have been 11 August months with a rainfall of 220 mm or more – with 10 occurring during 1900 to 1976 – and only one August month since then 2010, which was the highest rainfall for any August. Only five August months have had rainfalls of 50 mm or less.
Chronologically, the 11 wettest August months are 1913, 1916, 1920, 1927, 1938, 1942, 1957, 1965, 1970, 1976 and 2010.
In contrast, chronologically the five driest August months are 1914, 1921, 1982, 1983 and 2002.
For further information see: https://sites.google.com/images/climatediceandthebutterfly/