BAMOS Vol 31 No.4 December 2018 | Page 28

28 BAMOS Dec 2018 Article An urban-centric view of the weather: which Australian cities have the most ‘nice’ days? David Martin Bureau of Meteorology Email: [email protected] 1. Introduction While farmers might get excited about a day of consistent rain, for most people living in Australia’s major cities, that same rain is often considered a nuisance, as a majority of activities and day-to-day decisions in urban areas are less complicated when it’s not too cold, hot, windy, humid, cloudy or wet. Although the Bureau of Meteorology doesn’t use subjective language such as ‘nice’ in its weather forecasts, and stopped using ‘fine’ in 2015, it is language that’s commonly used during casual conversation, and by media and social media commentators. A day with the sun shining and temperatures that aren’t too hot or too cold will often be referred to as ‘nice’ or ‘fine’. This analysis presents an urban-centric view of ‘nice’ weather. 2. Method Following criteria used by the Capital Weather Gang in its Nice Day Sun forecasts and by Brian Brettschneider in an article published in The Washington Post, this analysis combined a variety of weather elements for Australian stations. The assumption is that people living in urban areas prefer days with warm temperatures, low humidity, no rain, light winds, and at least some blue sky. Closely related to ‘nice’ days are the thermal comfort observations reported by the Bureau of Meteorology for locations around the country, which include both the ambient temperature and wet bulb globe temperature. The specific criteria used were: The list of sites considered was generally those in or close to cities with a population of at least 100,000 people (as reported by the Australian Bureau of Statistics in their report Regional Population Growth, Australia, 2016–17). Some additional smaller population centres (Esperance, Ceduna, and Broome, for example) were included to increase the spatial distribution of the analysis. The included cities are representative of about 80% of Australia’s total population, so capturing those places where most Australians live. 3. Results for urban areas The winning city, with an average of 105 ‘nice’ days per year, was Brisbane (Table 1 and Figures 1 and 2). At the other end of the scale, Darwin averages only three ‘nice’ days per year because of its consistently high temperatures and high humidity, particularly in the wet season. Of course, some might argue that the hotter days in Darwin (often with humidity) make for ideal swimming conditions, but these City State/Territory Annual average Brisbane QLD 105 Alice Springs NT 81 Mildura VIC 81 Toowoomba QLD 69 Perth WA 69 Bundaberg QLD 67 • Maximum daily temperature between 18 °C and 29 °C Sydney NSW 62 • Maximum daily dew point <= 18 °C Adelaide SA 61 • Maximum daily wind gust < 11.11 m/s (40 km/h) Ceduna SA 60 • Average daily cloud cover <= 6 Oktas • Daily rainfall < 0.2 mm Townsville QLD 58 Newcastle NSW 55 Canberra ACT 53 Melbourne VIC 41 Esperance WA 41 Hobart TAS 38 Cairns QLD 37 Mount Gambier SA 34 Launceston TAS 33 Broome WA 13 Darwin NT 3 Raw, unhomogenised data was used, generally from long-term individual sites to maximise the number of places that could be examined. Where possible, sites with data since at least 1970 were selected, however there were some sites included that had a few years less data where no nearby long-term site was available, plus a couple of composite locations consisting of data from two historical sites. A change to AWS wind measurements in the early 1990s created a discontinuity in wind measurements across Australia (see Jakob 2010), however, the assumption here is that the change in instrumentation affected all sites equally, so that a comparison between cities remains valid across those years. Table 1: Annual average count of ‘nice’ days for each city (based on data from 1970–2017).