ABSTRACT
The past two decades of the 20th century and the first of the 21st century have been characterized by global temperature rise and increased frequency of weather‐induced extreme events such ...as floods, droughts, heavy rainfall, and heat waves. We investigated the heat and the cold waves in the Carpathian Region, an area whose rich biosphere is endangered by extreme events. We used the daily minimum (TN) and maximum (TX) temperature data collected in the framework of the CARPATCLIM project. Such high‐resolution (0.1° × 0.1°) gridded data range from January 1961 to December 2010. In this study, a heat wave occurs when temperature is above the 90th percentile for at least five consecutive days and a cold wave occurs when temperature is below the 10th percentile for at least five consecutive days. The percentiles have been computed over the baseline period 1971–2000. We distinguish between night‐time and daytime events and we discuss heat (and cold) waves considering at least five consecutive night and days with temperature above (below) the selected percentile. For each heat or cold wave event, we assigned duration, severity, and intensity. For these parameters and for frequency, we performed linear trend analysis for the period 1961–2010. The trends have been computed on an annual and seasonal basis and tested for statistical significance. Different spatial patterns of heat and cold waves characterize the Carpathian Region: heat wave events show general increase in all the parameters considered, while cold wave events show a decrease in all the variables West to the Carpathians and an increase North–East to the Carpathians. We also compiled a list of the most relevant heat waves that hit the Carpathian Region from 1961 to 2010: out of seven events, four occurred from 2000 to 2010. Instead, the 1960s and the 1980s have been the decades most hit by severe cold waves.
ABSTRACT
The Carpathians are the longest mountain range in Europe and a geographic barrier between Central Europe, Eastern Europe, and the Balkans. To investigate the climate of the area, the ...CARPATCLIM project members collected, quality‐checked, homogenized, harmonized, and interpolated daily data for 16 meteorological variables and many derived indicators related to the period 1961–2010. The principal outcome of the project is the Climate Atlas of the Carpathian Region, hosted on a dedicated website (www.carpatclim‐eu.org) and made of high‐resolution daily grids (0.1° × 0.1°) of all variables and indicators at different time steps. In this article, we analyze the spatial and temporal variability of 10 variables: minimum, mean, and maximum temperature, daily temperature range, precipitation, cloud cover, relative sunshine duration, relative humidity, surface air pressure, and wind speed at 2 m. For each variable, we present the gridded climatologies for the period 1961–2010 and discuss the linear trends both on an annual and seasonal basis. Temperature was found to increase in every season, in particular in the last three decades, confirming the trends occurring in Europe; wind speed decreased in every season; cloud cover and relative humidity decreased in spring, summer, and winter, and increased in autumn, while relative sunshine duration behaved in the opposite way; precipitation and surface air pressure showed no significant trend, though they increased slightly on an annual basis. We also discuss the correlation between the variables and we highlight that in the Carpathian Region positive and negative sunshine duration anomalies are highly correlated to the corresponding temperature anomalies during the global dimming (1960s and 1970s) and brightening (1990s and 2000s) periods.
•We present an evaluation of the EUMETSAT LSA-SAF evapotranspiration product from for drought assessment and monitoring in Europe.•We propose the ratio between evapotranspiration (ET) and reference ...evapotranspiration (ET0) as water stress index.•In absence of time series of data long enough to characterize normal conditions, ET/ET0 gives relevant information for drought monitoring.•ET/ET0 showed a coherent behavior compared to the meteorological indices SPI, SPEI and the remote sensing estimated fAPAR anomalies.•ET/ET0 showed a high correlation with the meteorological index Sc-PDSI, related to soil moisture variability.
Evapotranspiration is a key parameter for water stress assessment as it is directly related to the moisture status of the soil-vegetation system and describes the moisture transfer from the surface to the atmosphere. With the launch of the Meteosat Second Generation geostationary satellites and the setup of the Satellite Application Facilities, it became possible to operationally produce evapotranspiration data with high spatial and temporal evolution over the entire continents of Europe and Africa. In the frame of this study we present an evaluation of the potential of the evapotranspiration (ET) product from the EUMETSAT Satellite Application Facility on Land Surface Analysis (LSA-SAF) for drought assessment and monitoring in Europe.
To assess the potential of this product, the LSA-SAF ET was used as input for the ratio of ET to reference evapotranspiration (ET0), the latter estimated from the ECMWF interim reanalysis. In the analysis two case studies were considered corresponding to the drought episodes of spring/summer 2007 and 2011. For these case studies, the ratio ET/ET0 was compared with meteorological drought indices (SPI, SPEI and Sc-PDSI for 2007 and SPI for 2011) as well as with the anomalies of the fraction of absorbed photosynthetic active radiation (fAPAR) derived from remote sensing data. The meteorological and remote sensing indicators were taken from the European Drought Observatory (EDO) and the CARPATCLIM climatological atlas.
Results show the potential of ET/ET0 to characterize soil moisture variability, and to give additional information to fAPAR and to precipitation distribution for drought assessment. The main limitations of the proposed ratio for drought characterization are discussed, including options to overcome them. These options include the use of filters to discriminate areas with a low percentage vegetation cover or areas that are not in their growing period and the use of evapotranspiration without water restriction (ETwwr), obtained as output of the LSA-SAF model instead of ET0. The ET/ETwwr ratio was tested by comparing its accumulated values per growing period with the winter wheat yield values per country published by Eurostat. The results point to the potential of using the remote sensing based LSA-SAF evapotranspiration and the ET/ETwwr ratio for vegetation monitoring at large scale, especially in areas where data is generally lacking.
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