Long‐term changes in drought indices in eastern and central Europe (original) (raw)
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Meteorology and Atmospheric Physics
One of the negative consequences of climate change is the also increase in the severity, frequency and length of droughts appearing in Europe. The effects of meteorological drought are often substantial, not only for the natural environment but also for humans. Hence, the main purpose of this research was to determine the trends in the severity and occurrence of droughts in Europe during the period 1951–2015 using the standardized precipitation index and the standardized precipitation and evapotranspiration index (SPEI). For six European sites located in mid latitudes, the number of dry months was determined and the trend of their occurrence was examined. Moreover, for the summer months in which the indicators fell below 0, the trend related to the severity of the drought was determined for each site. Despite the absence of a statistically significant trend of an increase in the occurrence of dry months in general, an increase in the severity of droughts occurring in summer was obse...
Assessing seasonal drought variations and trends over Central Europe
Advances in Water Resources
The relevance of drought is still often underestimated for temperate climate regions like Central Europe that are characterized by on average ample precipitation. Nonetheless, several drought events in recent years (e.g. 1992, 2003, 2015 and 2018) demonstrated that droughts are a relevant factor for several economic activities (e.g., agriculture, water dependent industries, energy supply, etc.) in Central Europe. This is particularly true for the vegetation period, where increasing evapotranspiration rates due to rising atmospheric temperatures are intensifying existing drought conditions that originally developed from rainfalls deficits. The contribution of this study is an assessment of the long-term variability of drought conditions and seasonal climate trends within 1951-2015 based on a collective of 91 climate stations from the national meteorological services of Germany, Poland and the Czech Republic. Using a set of eight drought and three heavy precipitation indices an aggregated evaluation of seasonal precipitation characteristics is done and the driest seasons are identified for the entire study area as well as for four sub-regions. It is shown that the choice of the study period matters (1951-2015 vs. 1961-2015) as the pronounced (multi-)decadal variability of drought conditions restricts the temporal stability of computed trends. The drought trends computed for 1951-2015 are similar in direction, but generally smaller in magnitude than those of the ten year shorter period 1961-2015, as the 1950s have been a very dry decade in Central Europe. Seasonally, drying trends were observed for spring and less pronounced for summer, while autumn and winter show wetting trends. The seasonal trends are sensitive to shifts in the season definition by one month. Vegetation period I (VP-I) shows stronger drying trends, but less increases in heavy precipitation than spring, while the drought trends are less pronounced in vegetation period II (VP-II) as compared to the summer season, but more trends towards heavy precipitation increases occur in VP-II. These differences are explained by the daily trends in the seasonal cycle that show the strongest drying in April, June and the beginning of August and the strongest wetting in March and September. Generally, heavy precipitation increases prevail over decreasing trends in all seasons, whereby stations with strong drought trends generally have smaller positive or even negative heavy precipitation trends. A simultaneous occurrence of drought and heavy precipitation increases is observed in spring at several stations, particularly in sub-region West.
This paper analyzes the observed spatio-temporal characteristics of drought over the Czech Republic during the growing season (April to September), as quantified by the Standardized Precipitation Evapotranspiration Index (SPEI) on various time scales. The SPEI was calculated for various lags (1, 3, 6, 12 and 24 months) from monthly records of mean temperature and precipitation totals using a dense network of 184 climatological stations for the period 1961-2010. The characteristics of drought were analyzed in terms of temporal evolution of SPEI, frequency distribution and duration of drought at country level and for three regions delimited on station altitude. The driest and the wettest years during the growing season were identified. The frequency distribution of the SPEI values in 7 classes of drought category (%) show that normal moisture conditions represent around 65% out of the total values of SPEI for all times scales, in all three regions, while moderate drought and moderate ...
Irrigation and Drainage, 2007
Poland is situated in a transitory temperate climate zone; nonetheless droughts occur, posing a serious economic, social and environmental problem. The central part has the lowest precipitation in the country, where frequent meteorological and agricultural droughts occur. To estimate meteorological drought frequency in the region, the SPI methodology is used. The analysis is made using the long-term record of precipitation from 1861 to 2005 for the Bydgoszcz area, at 3-, 6-, 12-, 24-and 48-month timescales. The detailed characterization of chosen meteorological and agricultural droughts in 1991-2005 is presented in this paper. The results show that the frequency of months in which drought was identified at 3-, 6-, 12-, 24-and 48-month time scales, is about 30%. According to the equation as proposed in this study, the number of droughts of different duration in 100 years statistically is from 8 for the 48-month drought to 120 for the 3-month drought. On the basis of the analysis of the meteorological and agriculture drought in 2000, it has been shown that the 1-3 month SPI better reflects agricultural drought development than the 6-month SPI. To better understand and characterize droughts in agricultural areas additional indices should be used for the evaluation impacts of meteorological drought. Other indices need to be investigated to form a system of indices giving the best evaluation of droughts in a given region.
Theoretical and Applied Climatology, 2008
The common versions (referred to as self-calibrated here) of the Standardized Precipitation Index (SPI) and the Palmer Drought Severity Index (PDSI) are calibrated and then applied to the same weather series. Therefore, the distribution of the index values is about the same for any weather series. We introduce here the relative SPI and PDSI, abbreviated as rSPI and rPDSI. These are calibrated using a reference weather series as a first step, which is then applied to the tested series. The reference series may result from either a different station to allow for the interstation comparison or from a different period to allow for climate-change impact assessments. The PDSI and 1-24 month aggregations of the SPI are used here. In the first part, the relationships between the self-calibrated and relative indices are studied. The relative drought indices are then used to assess drought conditions for 45 Czech stations under present (1961-2000) and future (2060-2099) climates. In the present climate experiment, the drought indices are calibrated by using the reference station weather series. Of all drought indices, the PDSI exhibits the widest spectrum of drought conditions across Czechia, in part because it depends not only on precipitation (as does the SPI) but also on temperature. In our climate-change impact experiments, the future climate is represented by modifying the observed series according to scenarios based on five Global Climate Models (GCMs). Changes in the SPI-based
Agronomy
Atmospheric drought is an extremely important issue on a global, regional and local scale, especially in the context of climate change. The aim of the study was to assess the spatiotemporal variation of atmospheric (meteorological) drought in agricultural areas of east-central Poland, represented by the Lublin Voivodeship (Lublin region) in 1971–2015. Average monthly air temperatures and monthly precipitation totals recorded over the 45-year period at 25 weather stations were used in the study. The assessment of spatiotemporal variation in atmospheric drought in the study area was based on calculations of the aridity index. The analysis showed an increase in the severity of atmospheric drought in the Lublin region, with intensification of this phenomenon in the last two decades, especially in the warmer half of the year (April, June–August). The main cause of drought in the Lublin region was identified as a statistically significant increase in air temperature (on average, from 0.4 ...
Climate Variability of Drought Indices in Romania
The climate variability of drought conditions in Romania was studied by using 2 indices; a drought index based on temperature and precipitation data (DI) and the self calibrating Palmer Drought Severity Index (sc-PDSI) available on line at http://www.cru.uea.ac.uk. The drought index DI was calculated using mean seasonal values of temperature and precipitation for 25 stations in Romania for the period 1951-2003. The comparison between summer (JJA) DI at three stations (Bucuresti, Sibiu and Tg. Mures) and sc-PDSI for the same season in 3 grid points very close to the mentioned stations indicate a good concordance. The seasonal values of DI for the period 1951-2003 were decomposed in empirical orthogonal functions (EOF) and rotated EOF. The time evolution of the first principal component for each season and the spatial distribution of the first rotated component were analyzed. For spring and summer the time evolution of the first component indicates a tendency to dryness for the period 1999-2003. The investigation of the spatial distribution of the first rotated EOF component pointed out the fact that in spring, autumn and winter the homogeneous zones for the DI are in the south-east of Romania. In summer, the homogeneous zones for the DI are in the south-west of Romania. The change in the DI between the 20 th and the 21 st century is analyzed from simulations with the GCM EGMAM. The analyzed station is Drobeta Tr. Severin (situated on the Danube river side at the entry in Romania). The drought index is calculated for the periods 1950-1999, 2000-2049 and 2050-2099 and differences between the periods are shown. We can observe a tendency to dryness for the periods [2018][2019][2020][2021][2022][2023][2024][2025][2026][2027][2028][2042][2043][2044][2045][2046][2047][2048][2049][2050] and also a tendency to excess of moisture for the periods
Assessment of Meteorological Drought Trends in a Selected Coastal Basin Area in Poland—A Case Study
Water
The aim of this study is to investigate the patterns and trends of drought occurrence in the northern part of Poland on the example of the Łeba river basin in the years 1956–2015. The study of meteorological drought was conducted on the basis of the Standardized Precipitation Index (SPI) on the scale of 1, 3, 6, 9, and 12 months. Annual precipitation totals did not show significant changes in the analyzed period, except for the station in Wejherowo, which is characterized by a significant increasing trend. The analysis of the long term of the variability average annual air temperature showed its statistically significant increase in the analyzed area at the rate of about 0.2 °C per decade. During the analyzed period, 14 to 84 meteorological droughts were identified, with durations ranging from 200 to 300 months. As the period of accumulating values of SPI, the number of droughts decreased, while their total duration increased. Most droughts were mild in nature, while extreme drought...
Climate Variability of Drought Indices in Romania in the 20 th and 21 st Centuries
2010
The climate variability of drought conditions in Romania was studied by using 2 indices; a drought index based on temperature and precipitation data (DI) and the self calibrating Palmer Drought Severity Index (sc-PDSI) available on line at http://www.cru.uea.ac.uk. The drought index DI was calculated using mean seasonal values of temperature and precipitation for 25 stations in Romania for the period 1951-2003. The comparison between summer (JJA) DI at three stations (Bucuresti, Sibiu and Tg. Mures) and sc-PDSI for the same season in 3 grid points very close to the mentioned stations indicate a good concordance. The seasonal values of DI for the period 1951-2003 were decomposed in empirical orthogonal functions (EOF) and rotated EOF. The time evolution of the first principal component for each season and the spatial distribution of the first rotated component were analyzed. For spring and summer the time evolution of the first component indicates a tendency to dryness for the period 1999-2003. The investigation of the spatial distribution of the first rotated EOF component pointed out the fact that in spring, autumn and winter the homogeneous zones for the DI are in the south-east of Romania. In summer, the homogeneous zones for the DI are in the south-west of Romania. The change in the DI between the 20 th and the 21 st century is analyzed from simulations with the GCM EGMAM. The analyzed station is Drobeta Tr. Severin (situated on the Danube river side at the entry in Romania). The drought index is calculated for the periods 1950-1999, 2000-2049 and 2050-2099 and differences between the periods are shown. We can observe a tendency to dryness for the periods [2018][2019][2020][2021][2022][2023][2024][2025][2026][2027][2028][2042][2043][2044][2045][2046][2047][2048][2049][2050] and also a tendency to excess of moisture for the periods
A drought climatology for Europe
International Journal of Climatology, 2002
We present a high spatial resolution, multi-temporal climatology for the incidence of 20th century European drought. The climatology provides, for a given location or region, the time series of drought strength, the number, the mean duration, and the maximum duration of droughts of a given intensity, and the trend in drought incidence. The drought climatology is based on monthly standardized precipitation indices (SPIs) calculated on a 0.5°grid over the European region 35-70°N and 35°E-10°W at time scales of 3, 6, 9, 12, 18, and 24 months for the period 1901-99. The standardized property facilitates the quantitative comparison of drought incidence at different locations and over different time scales. The standardization procedure (probability transformation) has been tested rigorously assuming normal, log-normal, and gamma statistics for precipitation. Near equivalence is demonstrated between the Palmer drought severity index (PDSI) and SPIs on time scales of 9 to 12 months. The mean number and duration by grid cell of extreme European drought events (SPI −2) on a time scale of 12 months is 6 ± 2 months and 27 ± 8 months respectively. The mean maximum drought duration is 48 ± 17 months. Trends in SPI and PDSI values indicate that the proportion of Europe experiencing extreme and/or moderate drought conditions has changed insignificantly during the 20th century. We hope the climatology will provide a useful resource for assessing both the regional vulnerability to drought and the seasonal predictability of the phenomenon.