Authors :
Nicoleta IONAC 1 *, Elena GRIGORE 1, Dana OPREA-CONSTANTIN 1, Raul ILEA 1, Alexandru DUMITRESCU 2
1 University of Bucharest- Faculty of Geography, Bucharest, Romania
2 National Administration of Meteorology, Bucharest, Romania
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Abstract
Degree-days (DDs), generically representing the sum of temperature differences between the ambient or outdoor air-temperature and a reference (base) temperature (Tb), may be expressive and useful quantitative tools in assessing the impact of climatic factors on various domains of activity, especially in the context of ongoing climate change processes. Depending on the domain they are applied to, there are four basic types of DDs, out of which the heating (HDDs) and cooling (CDDs) degree-days are used on a large scale as they best reflect the energy needs either for heating or for air-cooling processes in any area. Their practical use mainly derives from how they are calculated; the wide differences between the current calculation techniques showing that hourly (outdoor) air-temperatures produce better estimates, especially if applied for distinct heating or cooling seasons, depending on the thermal response of buildings, but these values are often unavailable. Based on an essentialized review of the existing literature and practice regarding both the calculation methods of HDD and/or CDD values and the types of base temperatures being taken into consideration, this paper presents an experimental case-study carried out for Bucharest town area. It is based on hourly air-temperature values, which were recorded at the four daily measurements hours (01.00, 07.00, 13.00 and 19.00 EET), at the two weather stations located in Bucharest’s town area, namely at Bucharest-Filaret (BF – urban), and Bucharest-Baneasa (BB – extra-urban), during the 1981-2010 period. The resulting annual and monthly degree-days (DDs) below or above several specified base temperatures (0ºC, +10ºC, +17ºC, +19ºC, +21ºC and +23ºC) and the corresponding number of days with daily mean air-temperatures lower or higher than the previously-mentioned base temperatures show that energy demands are greater for indoor cooling in summer than for heating-up in winter, meaning that local authorities and main energy suppliers may thus better plan the seasonal needs for domestic use.
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