Application of relative drought indices in assessing climate-change impacts on drought conditions in Czechia

Abstract

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 (1961Czech stations under present ( -2000 and future 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-based2 drought risk closely follow the modeled changes in precipitation, which is predicted to decrease in summer and increase in both winter and spring. Changes in the PDSI indicate an increased drought risk at all stations under all climate-change scenarios, which relates to temperature increases predicted by all of the GCMs throughout the whole year. As drought depends on both precipitation and temperature, we conclude that the PDSI is more appropriate (when compared to the SPI) for use in assessing the potential impact of climate change on future droughts.

The impact of droughts and water management on various hydrological systems in the headwaters of the Tagus River (central Spain)

“…Although precipitation is the main variable explaining the frequency, duration and severity of 286 droughts (Chang and Cleopa, 1991;Heim, 2002), recent studies have shown that the effect of 287 temperature (or evapotranspiration) is significant (Hu and Willson, 2000), particularly under global 288 warming scenarios (Dubrovsky et al, 2008). Abramopoulos et al (1988) showed that evaporation 289 and transpiration can consume up to 80% of rainfall, and found that the efficiency of drying due to 290 temperature anomalies is as high as that due to rainfall shortage.…”

Drought episodes in the Czech Republic and their potential effects in agriculture

“…In this research, the self-calibrated SPI (scSPI) was used for the Czech drought conditions. Being inspired by Dubrovsky et al (2008), we applied a similar original algorithm to calculate SPI for a single reference station or an aggregated SPI for all stations (in our case Zatec and 56 aggregate stations). For more details regarding the methodology, see Dubrovsky et al (2008).…”

“…Being inspired by Dubrovsky et al (2008), we applied a similar original algorithm to calculate SPI for a single reference station or an aggregated SPI for all stations (in our case Zatec and 56 aggregate stations). For more details regarding the methodology, see Dubrovsky et al (2008). The present version of SPI uses a gamma distribution whose parameters are estimated separately for each of the 6 months of the warm period and/or values for different time scales: 1, 2, 3, and 6 months.…”

“…In respect to the studies of the drought episodes pattern in the Czech Republic, over the past decade, many climatologists have studied the frequency and intensity of this event (Dubrovsky et al 2000(Dubrovsky et al , 2008Brazdil et al 2003) and the relationships between agriculture and crops . A group of Czech climatologists (Brazdil et al 2008) basing their study on both Z index and PDSI indices have concluded that droughts in Czechia have an increasing tendency toward longer and more intensive dry episodes in which, for example, droughts that occurred in the mid-1930s, late 1940s to early 1950s, late 1980s to early 1990s, and early 2000s were the most severe.…”

A hybrid downscaling approach for the estimation of climate change effects on droughts using a geo-information tool. Case study: Thessaly, Central Greece

“…These conditions inversely affect both the natural vegetation and the agriculture of the region as well as the water resources. Severe and extremely dry conditions result in irrigation cutbacks, overexploitation of groundwater and significant losses of crop yields [19]. In Greece, especially in Central Thessaly, the major methodological drawback for a long-term assessment of regional climate and its variability results from the lack of suitable observations or simulated data.…”