TITLE:
Extremely Cold and Warm Days in the Spanish Central Plateau: Analysis of Its Evolution from 1961 to 2010
AUTHORS:
Angel L. Labajo, Quintín Martín, Juan Labajo, Moises Egido, José L. Labajo
KEYWORDS:
Cold Day; Warm Day; Frequency; Trend; Linear Model
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.4 No.2,
April
10,
2014
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.