The spatio temporal analysis of drought episodes within Czech Republic in relation with the land use and vegetation stress
Abstrakt
The subjects of the research are to identify the spatial distribution and the temporal patterns of the Maximum Number of Consecutive Summer Days, data which are freely available on European Climate Assessment and Database. The chosen period was from 2000 up to 2015 and covers the territory of Czech Republic with a number of 37 meteorological stations which-are spread evenly.
The reasons for performing this analysis are connected with the multiple numbers of drought events that frequently occur within the areas influenced by continentalism features. The chosen index was computed for the summer months (June, July and August), along with the neighbor months of the hot season: May and September, in order to detect whether some drought episodes expanded or not for a larger period of time, threatening the soil moisture or the agricultural productivity.
The unique conditions of the droughts were calculated for the stations that exceeded the 90th and the 95th percentile, along with the empirical probabilities. Significant trends were found, that were greater than the corresponding global trend for temperatures, provided by the IPCC reports.
The spatial distribution of the index was examined by means of multiple regression analysis, in comparison with the elevation, latitude and longitude values of the study area and this method characterized the observed and the fitted values reasonably well, expressed through R-squared coefficients that varied from 0.4 for May and September, up to 0.8 for the summer months. Czech Republic is a country where more than 70% of its territory is used as an agricultural production area, hence we applied a remotely sensed index developed by Felix Kogan in 1997: Vegetation Condition Index, which was used for detecting and monitoring the vegetation stress, in order to validate the methodology, but also with the purpose of depicting the agricultural areas that were moderately or severely affected by droughts, particularly during the period of crop growth.