A comparison of climatological observing windows and their impact on detecting daily temperature extrema
- 52 Downloads
Climatological observing window (COW) is defined as a time frame over which continuous or extreme air temperature measurements are collected. A 24-h time interval, ending at 00UTC or shifted to end at 06UTC, has been associated with difficulties in characterizing daily temperature extrema. A fixed 24-h COW used to obtain the temperature minima leads to potential misidentification due to fragmentation of “nighttime” into two subsequent nighttime periods due to the time discretization interval. The correct identification of air temperature extrema is achievable using a COW that identifies daily minimum over a single nighttime period and maximum over a single daytime period, as determined by sunrise and sunset. Due to a common absence of hourly air temperature observations, the accuracy of the mean temperature estimation is dependent on the accuracy of determination of diurnal air temperature extrema. Qualitative and quantitative criteria were used to examine the impact of the COW on detecting daily air temperature extrema. The timing of the 24-h observing window occasionally affects the determination of daily extrema through a mischaracterization of the diurnal minima and by extension can lead to errors in determining daily mean temperature. Hourly air temperature data for the time period from year 1987 to 2014, obtained from Toronto Buttonville Municipal Airport weather station, were used in analysis of COW impacts on detection of daily temperature extrema and calculation of annual temperature averages based on such extrema.
KeywordsAnnual Average Daily Minimum Cold Bias Local Standard Time Hourly Temperature
- Collison P, Tabony RC (1984) The estimation of mean temperature from daily maxima and minima. Meteorological Magazine, London 113:329–337Google Scholar
- Harris SA, Pedersen JH (1995) Comparison of three methods of calculating air temperature from electronic measurements. Z Geomorph 39:203–210Google Scholar
- Trewin B (2004) Effects of changes in algorithms used for the calculation of Australian mean temperature. Aust Meteorol Mag 53:1–11Google Scholar