Abstract
From anomalies of daily data of maximum and minimum temperatures, that have been obtained as difference between the real data of every day and the average data of the corresponding day of the year in each of the 14 observatories of the Spanish Central Plateau (8 in North subplateau and 6 in the South subplateau) between 1961-2010, the extremely cold and warm days are determined, throughout all the year, in all the study area and the two different sub areas. We consider a day as an extremely cold day (ECD) if achieves simultaneously the following conditions: the anomaly of minimum temperature of the day is lower than the value of the P05 percentile of the series of daily anomalies of minimum temperature, and the value of the anomaly of daily maximum temperature is lower, as well, than the P05 percentile of the corresponding series of anomalies. The values of the thresholds determined by these percentiles are obtained considering the complete anomalies daily series of temperature for all the study regions. In order to establish the extremely warm days the methodology is the same but the conditions are: the anomaly of minimum temperature of the day is greater than the value of the P95 percentile of the series of daily anomalies of minimum temperature, and the value of the anomaly of daily maximum temperature is greater as well than the P95 percentile of the corresponding anomalies series. Once the extremely warm and cold days are determined, throughout the year in the period of time considered, for each zone, the corresponding series of annual frequencies are obtained. The analysis of tendency of these series indicates that in all the cases the tendency of the frequency of the extremely cold days is decreasing. Considering a linear model for the temporary behavior of the frequency, the reduce is of the order of 1 day every 10 years. In the case of the extremely warm days its annual frequency presents an increasing tendency, which indicates that the number of extremely warm days per year has been increased during the studied time interval. In agreement with the linear model of behavior, the increase is, approximately, of the order of 1 day per decade.
Highlights
Extreme weather events like hurricanes, heavy rains that cause serious floods, the extremely high and extremely low values of temperature have taken place in all the times, having a negative effect on the normal development of human activities
In the case of the temperature, as the study of the behavior of the extreme warm and cold events has an especial importance concerning to the environments in which the human activity is developed, the incidence of the extreme events of temperature could be established by the temporary evolution of the annual frequency of daily maximum and minimum temperatures
From the thresholds obtained before and those corresponding to regional series of daily anomalies of maximum and minimum temperatures, are the anomalies for maximum daily temperature (ATMAD) and ATMID, in the Spanish Central Plateau and in each sub plateau, the extremely cold days and warm days series are obtained in each zone
Summary
Extreme weather events like hurricanes, heavy rains that cause serious floods, the extremely high and extremely low values of temperature have taken place in all the times, having a negative effect on the normal development of human activities. In the case of the temperature, as the study of the behavior of the extreme warm and cold events has an especial importance concerning to the environments in which the human activity is developed, the incidence of the extreme events of temperature could be established by the temporary evolution of the annual frequency of daily maximum and minimum temperatures. In this sense, several researches have been developed on different space scales [13]-[18]. In this work we will try to establish, by using maximum and minimum temperature anomalies, the annual frequency trend of the extremely cold and warm days obtained in the Spanish Central Plateau between 1961 and 2010
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