Challenges in developing a high-quality surface wind-speed data-set for Australia

Abstract

One of the main drivers for this project is the requirement to complement other high-quality surface data-sets with surface wind data for use in climate change detection and attribution studies. The high-quality data may also be used to analyse trends in storminess. Investigations highlighted the following three issues: Over the last two decades Automatic Weather Stations (AWS) have been installed at a large number of locations over the Australian region. The majority of newly installed wind instruments are rotating cup anemometers (Synchrotac), in many cases replacing older types, such as pressure tube anemometers (Dines). The corresponding changes in instrumentation alone can significantly change the characteristics of observed wind speed. Daylight Saving Time (DST) is in effect in the majority of Australian States, typically for a period from late October to late March. During this period, observations are taken according to DST rather than Local Standard Time (LST). Observations taken one hour earlier (compared with LST) can significantly affect the measured wind speed relative to climatology at a particular time. Estimates of daily mean wind speed depend on the frequency of synoptic observations. The frequency of these observations typically increases towards the latter part of the record, in some cases from two observations (at 0900 and 1500) to eight observations a day (at three-hourly intervals). Depending on the number of synoptic observations used to derive the daily mean wind speed, the true value may be significantly over- or underestimated.