Abstract
The spatial-temporal variability of drought occurrence over Bulgaria is characterized based on long-term records (2007–2018) of Meteosat information and the SVAT model-derived soil moisture availability index (referred to root zone depth, SMAI). Land surface temperature according to the satellite-derived Land Surface Analysis Satellite Application Facility Land Surface Temperature (LSASAF LST) product and SMAI were used to designate land surface state dry anomalies. The utility of LST for drought assessment is tested by statistical comparative analyses, applying two approaches, site-scale quantitative comparison, and evaluation of spatial-temporal consistency between SMAI and LST variability. Pearson correlation and regression modeling techniques were applied. The main results indicate for a synchronized behavior between SMAI and LST during dry spells, as follows: opposite mean seasonal course (March–October); high to strong negative monthly correlation for different microclimate regimes. Negative linear regressions between the anomalies of SMAI and LST (monthly mean), with a strong correlation in their spatial-temporal variability. Qualitative evaluation of spatial-temporal variability dynamics is analyzed using color maps. Drought-prone areas were identified on the bases of LST maps (monthly mean), and it is illustrated they are more vulnerable to vegetation burning as detected by the Meteosat FRP-PIXEL product. The current study provides an advanced framework for using LST retrievals based on IR satellite observations from the geostationary MSG satellite as an alternative tool to SMAI, whose calculation requires the input of many parameters that are not always available.
Highlights
Drought is determined by multiple climate variables on multiple time scales
We identify that the relationship between soil moisture and land surface temperature can only be regionally and temporally understood by considering regional and temporal variations of their anomalies, taking into account the main drivers of evapotranspiration and their seasonal changes
The results obtained from the use of satellite land surface temperature (LST) data as a drought indicator, providing climatic information of drought occurrence and severity, encourages their use in other applications
Summary
Drought is determined by multiple climate variables on multiple time scales It can feed back upon the atmosphere via biogeophysical and biogeochemical land-atmosphere interactions, potentially affecting the extremes of temperature, precipitation, and other variables [1,2]. There is wide scientific consensus that southern Europe, and in particular, the Mediterranean region, can be considered as a climate change hotspot, both in the recent, past, and upcoming future [5,6]. This area has experienced a broad increase in drought frequency and severity [7], especially in summer [8,9,10]
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