Both 2018 and 2019 saw exceptionally dry, hot summers.
By Christine Träger-Chatterjee (EUMETSAT). Maps provided by: Arne Spitzer (CM SAF, sunshine duration), Joao Martins (LSA SAF, land surface temperature), David Fairbairn (H SAF, soil wetness index)
Large parts of Europe experienced an exceptionally dry and hot summer season in 2018 (see also page 14 in the Annual Report 2018). This was followed by more dry and hot spring and summer seasons in 2019. With global warming, extreme heat waves and droughts are expected more frequently in Europe.
Heatwaves associated with droughts cause many problems, such as water shortage, harvest losses, loss of human lives, damages to roads and railways, interruptions of traffic on large rivers and reduced capacity of power plants. To mitigate their impacts it is important to better understand the development and the characteristics of heatwaves and droughts (see Land–atmospheric feedbacks during droughts and heatwaves: state of the science and current challenges, Miralles et al.2019).
This case study introduces three examples of satellite-based climate data records, provided by EUMETSAT's Satellite Application Facilities (SAFs), that can be used to study heatwaves and droughts:
- Sunshine Duration, as a major driver of the development of heat and drought situations, from CM SAF.
- Land Surface Temperature, as measure of heat, from LSA SAF.
- Root Zone Soil Wetness Index, as dry soil has the potential to promote the development of heatwaves, from H SAF.
Sunshine Duration from the Climate Monitoring SAF (CM SAF)
The CM SAF provides a climate data record on sunshine duration derived from MVIRI and SEVIRI on Meteosat first and second generation satellites. The climate data record covers the time period January 1983 to December 2017. It is part of the SARAH ed 2.1. data set (DOI: https://doi.org/10.5676/EUM_SAF_CM/SARAH/V002_01), available via the CM SAF website.
The anomaly maps of sunshine duration have been calculated using the climate data record, and the interim climate data record, covering January 2018 until the last month completed.
Land Surface Temperature from the Land Surface Analysis SAF (LSA SAF)
The LSA SAF provides a climate data record of land surface temperature derived from SEVIRI on Meteosat Second Generation (MSG) satellites. The anomaly maps of land surface temperature have been calculated using the climate data record as the background climatology and near real-time product LSA-001.
Both, the climate data record (DOI: 10.15770/EUM_SAF_LSA_0001) and the near real time product are available via the LSA SAF.
Root Zone Soil Wetness Index from the Hydrology SAF (H SAF)
The H SAF provides a climate record on the soil water index in the root zone, referred to as H141, based on ERS/SCAT and Metop ASCAT assimilation, covering the time period January 1992 to December 2018. For 2019 the anomalies were created using the H SAF product H142.
Both products, H141 (DOI of H141: 10.15770/EUM_SAF_H_0008) and H142 are available via the H SAF.
It should be noted that the length of the background climatologies are different for each of the three variables. For the calculation of the anomalies, the longest available period for each of the three products was used, i.e. 35 years for sunshine duration, 11 years for land surface temperature and 27 years for soil wetness index. The exact time span of each background climatology is mentioned in the paragraphs above.
As a consequence of the different lengths of the background climatologies used to calculate the anomalies, comparisons of the anomalies between the three different variables should be treated with extreme caution, especially the relatively short background climatology of land surface temperature. It represents a period which was largely warmer than previous periods, so, the LST anomalies presented here are probably underestimated, in relation to the anomalies of the soil wetness and sunshine duration, which are based on background climatologies of 27 and 25 years, respectively.
In their paper The Exceptional 2018 European Water Seesaw Calls for Action on Adaptation, Toreti et al (2019), show that the heat and drought conditions in spring-summer 2018 were unique in the past 500 years. In the paper Concurrent 2018 Hot Extremes Across Northern Hemisphere Due to Human-Induced Climate Change, Vogel et al (2018) state that without human-induced global warming, a situation like this would have been highly unlikely.
The maps show large areas of above average Land Surface Temperatures (derived from MSG instruments), that started to appear in April and continued throughout the summer months. This correlates to the above normal sunshine duration.
The development of anomalously dry soil conditions (see the root zone soil wetness index) started in March in north-eastern and central Europe. The drought in these regions remained throughout the entire year.
The gallery below shows monthly anomalies of sunshine duration, land surface temperature, and root zone soil wetness index for spring (March, April May) and summer (June, July, August) 2018.
The remarkable features in the anomalies of 2019 are the large extent and the intensity of the above average sunshine durations, and that the warmer then normal land surface temperatures (derived from MSG SEVIRI measurements) started in February and March.
With the exception of May, the above average sunshine duration and the warmer then usual land surface temperature remained until the end of the meteorological summer season (end of September).
The soil moisture conditions show a similar development: drier than normal conditions started to develop in February. The intensity and the spatial extend of the dry conditions continuously developed until August.
The gallery below shows the monthly anomalies of sunshine duration, land surface temperature, and root zone soil water index for spring (March, April May) and summer (June, July, August) 2019.
Overall the anomalies in both years, 2018 and 2019, started in February/March and remained until at least August. Although, the intensity of the anomalies was less pronounced in 2019, the spatial extend of the anomaly was larger.
Previous case study
July 2019 European heat wave (Wikipedia)