Mildura : what happened in 2000?
See ACORN Observation Practices (p13) As evident in the maximum and minimum temperature charts below, there was a warming at the Mildura weather station starting in 2000.
The table below shows maximum and minimum temperatures from 1990 to 2010 (new screen May 2000) as estimated in the homogenised ACORN 1 and ACORN 2 temperature datasets, and the unadjusted original RAW observations :
The 1990-1999 maximum averages were : ACORN 1 23.71C / ACORN 2 24.26C / RAW 23.63C The 2001-2010 maximum averages were : ACORN 1 24.57C / ACORN 2 24.91C / RAW 24.57C The 1990-1999 minimum averages were : ACORN 1 10.22C / ACORN 2 10.10C / RAW 10.17C The 2001-2010 minimum averages were : ACORN 1 10.46C / ACORN 2 10.46C / RAW 10.46C The original RAW maximum averages increased 0.94C from 1990-1999 to 2001-2010. The ACORN 1 maximum averages increased 0.86C from 1990-1999 to 2001-2010. The ACORN 2 maximum averages increased 0.65C from 1990-1999 to 2001-2010, with ACORN 2 warming 1990-1999 by 0.55C and warming 2001-2010 by 0.34C. The original RAW minimum averages increased 0.29C from 1990-1999 to 2001-2010. The ACORN 1 minimum averages increased 0.24C from 1990-1999 to 2001-2010. The ACORN 2 minimum averages increased 0.36C from 1990-1999 to 2001-2010. The Bureau of Meteorology's ACORN-SAT station catalogue reads : The current site (76031) is an automatic weather station at the Meteorological Office, in flat terrain on the grounds of Mildura Airport, south of the main terminal and 9 km southwest of the town. The ground surface in the instrument enclosure and surrounds is red soil with patchy short natural grass. History The original site (76077) was within the Mildura town area. It moved in August 1927. After this move the screen was oriented northeast, but it was realigned to face south in July 1933. There was a small site move in March 1943. Temperature observations continued until 1949. Observations have been made at the airport site (76031) since 1946. Site moves took place on 11 August 1992 (from the aerodrome apron to the Meteorological Office) and in July 1989 (only a small move). The automatic weather station was installed on 1 October 1989, and became the primary instrument on 1 November 1996. There was rapid development of irrigated agriculture in the Mildura region in the period between the two World Wars, and this appears to be associated with an anomalous cooling trend in maximum temperature at Mildura over this period (amounting to 0.3–0.4°C over 30 years). The non-ACORN-SAT site of Griffith, which has a similar history of irrigation development, shows a similar trend. There was a minor decline in Mildura rainfall from 1990-1999 to 2001-2010 (annual average 289.0mm > 250.6mm). The data above show maximum temperature increases coinciding with the installation of a small Stevenson screen at the Mildura weather station in 2000, the 0.94C increase greater than would be expected from the annual rainfall decline and with ACORN adjustments that inadequately compensate for the change. Minimum temperatures increased 0.29C in RAW from 1990-1999 to 2001-2010, despite the lesser rainfall.
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