European heatwaves in Summer 2019
June and July 2019
United Kingdom, Alps, Greece, Spain, France, Europe, Germany, Austria, Czech Republic, Switzerland, Poland, Portugal, Luxembourg, Belgium, Finland, Norway, Netherlands, Lithuania
Meteosat-11, Metop-A, Sentinel-3
SEVIRI, ASCAT, OLCI
Land Surface Temperature, ASCAT Soil Moisture Index, True Colour RGB, Evolution RGB, Brightness Temperature
Maximum temperature records were broken in many parts of Europe in June and July 2019, due to a series of heatwaves.
20 November 2020
01 June 2019
Summer 2019 in Europe echoed the summer of 2018 with periods of extremely high temperatures across Europe. Many places in Central and Western Europe saw maximum temperatures tumble more than once. The extreme temperatures started in June and returned in July.
The Evolution RGB (Figure 1) indicates thermal change (compared with uniform summer temperatures) in three periods. The colours show when 10.8 µm brightness temperatures are moderate. Blue is used to indicate normal values in the period from 24–30 June, green indicates normal values in the period from 1–18 July, and red indicates normal values in the period 19–28 July. These periods roughly correspond to the June heatwave, the interim cooler period and the July heatwave affecting western Europe in summer 2019. The limits of these periods were chosen subjectively.
Unsurprisingly, green predominates in south western and Central Europe up to the Baltic Sea, where the maximum temperatures were the highest in the June and July waves. Ireland (red) was cooler at the end of July, whereas parts of Scandinavia (blue) were not affected by the first heatwave. Also the southern Alps and eastern areas (red) did not suffer the second wave, only the first. Over northern Africa, the source of the hot air, a colourful mosaic indicates in green the common part of the corridor for the two major waves.
Central Spain shows black, that is persistent heat throughout. Opposite to that is Greece, almost unscathed by the heat.
This RGB takes the highest brightness temperature in each of the periods noted above, based on the daily image at 13:45 UTC. The method does not completely eliminate cloud, therefore, the heat on the ground might be masked to some extent.
Figure 2 shows the different areas, in fact very similar, affected by both heatwaves. It shows the maximum brightness temperatures (BT) achieved at different Meteosat-11 pixels on channel 10.8 µm, in colours for the range 30–55 °C. BT is a proxy for ground temperature, normally some degrees above the air temperature at 2 m height, which is more representative of the thermal experience.
A heatwave in large parts of Europe during the last week of June 2019, broke several historical records at single locations in France, Switzerland, Austria, Germany, the Czech Republic and Spain.
In France on 28 June, new record of 45.9 °C, more than 1.5°C above the previous record, was recorded Gallargues-le-Montueux, Gard, near the city of Nîmes. Night-time temperatures in France also set records, with minimum temperature of 25.7 °C recorded in Limoges.
In Switzerland new June records were set at more than 40 stations, and new all-time records were set at six sites. In Austria and Germany, the whole month of June 2019 was the warmest ever recorded.
The heatwave was as a result of a high pressure system bringing warm air from Africa, which remained stationary over many parts of Europe for a number of days, raising temperatures.
Figure 3 is a comparison of the Meteosat-11 Natural Colour RGB on 17 July and 27 July, showing a notable difference in the green contribution in this RGB imagery. Less green means less Sun reflection from the chlorophyll in vegetation — due to high temperatures and plenty of insolation from the Sun, the vegetation's vitality weakened considerably in less than 10 days.
New temperature records
Maximum temperature records for June were broken in numerous places across Europe:
- 26 June, Germany: 38.6 °C recorded in Berlin, beating the country's previous June record of 38.2 °C.
- 26 June, Czech Republic: 38.9 °C recorded in Doksany, the highest June temperature ever recorded.
- 26 June, Poland: 38.2 °C recorded in Radzyń, the highest June temperature ever recorded.
- 26 June, Switzerland: 35.5 °C recorded in Zürich, a new June record for the station.
- 28 June, France: A national all-time record of 46.0 °C was recorded in Vérargues.
- Five died in France, four in Germany, three in the UK, two in Spain, and one in Italy. Nine of these were drownings, as people tried to cool off.
- Intense wildfires erupted in Spain's Catalonia region, charring 16,000 acres.
Figure 4 shows the daily maximum land surface temperature (LST) anomaly for 24 June–2 July. The reference period is the 2004–2018 median. The values represent the land surface radiative temperature, which differs from the 2 m air temperature measured by conventional weather stations. Satellite land surface temperature can only be measured in clear sky conditions, since clouds are opaque to infrared radiation.
Both the animation and Figure 5 show that by 29 June, in some regions in France and Spain, temperatures were 12 °C above normal. While continental Portugal had below average temperatures north of the Montejunto-Estrela mountain range, while the south showed slightly above normal temperatures.
The LST is estimated from thermal infrared radiances measured by the SEVIRI instrument on board the Meteosat Second Generation satellites. The Satellite Application Facility on Land Surface Analysis, has been providing LST estimates every 15 min since 2004.
According to the World Meteorological Organization and the Copernicus Climate Change Service, July matched, and maybe broke, the record for the hottest month since analysis began.
Using data from Copernicus Climate Change Service, the WMO calculated that July 2019 was on a par with, and possibly marginally warmer than the previous warmest July, in 2016, which was also the warmest month ever.
The heat wave was caused by a strong omega block, consisting of hot, dry air from North Africa, trapped between cold storm systems. An area of high pressure stretched from the central Mediterranean to Scandinavia, and was pinned between two low-pressure areas, one over western Russia and the other over the eastern Atlantic.
The Land Surface Temperatures anomalies for 20–28 July (Figure 6) show widespread of high positive temperature anomalies, from Portugal to Poland. These anomalies turned into negative with introduction of low pressure system from the west Atlantic across central Europe, towards end of the observed period.
New temperature records
Maximum temperature records for July were broken in numerous places across Europe:
- 24 July, Belgium: highest recorded temperature of 40.2 °C, recorded in Angleur.
- 24 July, France: 41.2 °C recorded in Bordeaux, breaking the city's previous record of 40.7 °C.
- 25 July, France: 42.6 °C recorded in Paris, breaking the city's previous record of 40.4 °C.
- 25 July, Germany: 42.6 °C recorded in Lingen, Lower Saxony, beating previous the maximum temperature record of 40.5 °C, set the day before.
- 25 July, Luxembourg: 40.8 °C recorded in Steinsel, the highest recorded in the country, beating the record of 37.9 °C.
- 25 July, Netherlands: 40.7 °C recorded in Gilze en Rijen, beating the previous day's all-time record of 39.3 °C.
- 25 July, UK: 38.7 °C recorded in Cambridge, beating the all time maximum temperature record of 38.5 °C.
- 26 July, Norway: 33.4 °C recorded in Bergen, the highest recorded.
- 28 July, Finland: 33.7 °C, recorded in Emäsalo, Porvoo, a new station record.
The Sentinel-3 OLCI True Colour RGB (Figure 7) shows almost completely clear skies over parts of Western Europe on 25 July, with some small patches of fair weather cirrus.
- One death was reported in Belgium and five in France.
- The high temperatures and dry conditions caused several fires across Luxembourg during the heatwave.
- Many farm animals died because of the high temperatures, mainly due to ventilation systems failing.
- Many heat-related incidents on the UK's rail network caused widespread disruption.
The dry weather left many countries with the threat of drought.
- Two-thirds of French departments faced water restrictions. By late July more than 20 departments were in the critical red category, that restricts water use to only essential needs.
- In July, Lithuania declared an emergency, with drought expected to cut its harvests by half.
- Spain had third driest summer this century.
Dry weather also has hit parts of Germany, Poland, the Czech Republic and Scandinavian countries.
Figure 8 shows the Soil Water Index anomalies for Europe on a daily basis between 1 April and 7 July in a 1 km grid.
By filtering the ASCAT surface soil moisture time series with an exponential filter, the so-called ASCAT Soil Water Index (SWI) is derived which is an estimate of the moisture content in the soil profile down to a depth of about 0.5 m. The T-Value corresponds to the number of preceding days that are taken into account in the exponential filtering (e.g. 10 days are used to calculate the SWI -T10). The example shows SWI -T10 anomalies (the reference period is from 2007 to 2018).
Record-breaking temperatures for June (Copernicus Climate Service)
European heatwave: France hits record temperature of 45.9C (BBC)
'Today is the hottest day in the history of France': Europe's hellish heat wave is caused by a high-pressure weather system unlike any ever seen before (Business Insider)
Minimum night temperatures (MeteoFrance/Twitter)
Juni nicht nur bei Hitze Rekordmonat (ORT.at, in Austrian German)
What is causing the European heatwave? (The Guardian)
July matched, and maybe broke, the record for the hottest month since analysis began (WMO)
July sees large weather fluctuations (Daily Finland)
Another exceptional month for global average temperatures (Copernicus Climate Service)
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