TEMPORAL VARIABILITY OF DAILY CLIMATE EXTREMESOF TEMPERATURE AND PRECIPITATION IN THE MIDDLE POLABÍ (ELBELAND) LOWLAND REGION

This paper analyses a 49 year (1961–2009) average 10th and 90th percentile values of daily temperatures and precipitation in a region of the middle Polabi lowland region in order to predict extreme dry-wet and cold-warm spells risk. The extremes are described by 11 indices based on temperature and precipitation. For the temperature indices based on relative thresholds are include cold days (TX10p) for lower extremes and warm days (TX90p) for higher extremes. To examine durational characteristics of extreme temperature events, such as cold spell (CSDI), warm spell (WSDI) and heat wave duration index (HWDI). Index using fixed threshold includes frost days (t ≤ –0.1°C). In the same way for the precipitation indices based on relative thresholds, upper fifth (R95p) and first (R99p) percentile values are used to calculate the accumulation of very wet day or extremely wet day precipitation. Very heavy or intense rainfall is measured using the RX1day index. To examine durational characteristics of extreme precipitation events, as consecutive dry (CDD) and wet (CWD) days are used. The Poisson process was successfully applied in the study of extreme climatic variable values. The probability of risk assessment (λ, 1/year) of the occurrences of extreme climate events was classificated: λ. 0.2 (frequent), 0.1 λ 0.2 (probable) and 0.01 λ 0.1 (rare). The results showed statistically relatively significant variability in frequency, duration and severity of heat waves and number of tropical days. The annual occurrence of frost days are de creases, while the annual warm and tropical days are increased. However, the trend in warm and tropical days is greater in magnitude and is related to rise in these events since early 1990s