The 2019 heatwave got its start in late June, when warm air masses from the Sahara first hit Spain and then spread to Central Europe. A pair of high-pressure systems was responsible for drawing in the warm air and suppressing cloud cover. The exceptional heat lasted through the month, and it could melt billions of tons of ice in Greenland.
Europe massive heat wave was on its way out - and left a slew of broken temperature records in its wake recently. Many countries were gripped by temperatures above 104 Fahrenheit (40 degrees Celsius) between June 26 and June 30. According to the World Meteorological Organization, June 2019 is now the hottest month on record for the continent as a whole.
NASA's Ecosystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) measures Earth's surface temperature from the International Space Station at different times of day. Although its primary objective is to monitor the health of plants, ECOSTRESS can also detect heat events such as the one much of Europe just experienced.
ECOSTRESS mapped the surface, or ground temperature, of four European cities - Rome, Paris, Madrid and Milan during the mornings of June 27 and June 28.In the images, hotter temperatures appear in red and cooler temperatures appear in blue. They show how the central core of each city is much hotter than the surrounding natural landscape due to the urban heat island effect - a result of urban surfaces storing and re-radiating heat throughout the day.
The fact that surface temperatures were as high as 77-86 degrees Fahrenheit (25-30 degrees Celsius) in the early morning indicates that much of the heat from previous days was stored by surfaces with high heat capacity (such as asphalt, concrete and water bodies) and unable to dissipate before the next day. The trapped heat resulted in even higher midday temperatures, in the high 40s (Celsius) in some places, as the heat wave continued.
ECOSTRESS launched to the space station last summer and began collecting its first heat data just days after installation. The instrument measures variations of ground temperatures to within a few tenths of a degree, and it does so with unprecedented detail: It's able to detect temperature changes at various times of day over areas the size of a football field. These measurements help scientists assess plant health and response to water shortages, which can be an indicator of future drought. They can also be used in observing heat trends, spotting wildfires and detecting volcanic activity.
ECOSTRESS provides a wide range of image products for studying the land surface and recently made all these products publicly available through the NASA Land Processes Distributed Active Archive Center (LPDAAC).
JPL built and manages the ECOSTRESS mission for NASA's Earth Science Division in the Science Mission Directorate at NASA Headquarters in Washington. ECOSTRESS is an Earth Venture Instrument mission; the program is managed by NASA's Earth System Science Pathfinder program at NASA's Langley Research Center in Hampton, Virginia.
The map above shows air temperatures across Europe on July 25, 2019. The map was derived from the Goddard Earth Observing System (GEOS) model and depicts air temperatures at 2 meters (about 6.5 feet) above the ground. The darkest red areas are where the model shows temperatures surpassing 40°C (104°F). Temperatures have since fallen, and rain is in the forecast for some of the countries. The GEOS model, like all weather and climate models, uses mathematical equations that represent physical processes (such as precipitation and cloud processes) to calculate what the atmosphere will do. Actual measurements of physical properties, like temperature, moisture, and winds, are routinely folded into the model to keep the simulation as close to observed reality as possible.
These record-breaking temperatures come just one month after another record-breaking heatwave. However, July temperatures soared much higher than June—about 15°C higher in some regions. The map below, created with data from the GEOS model, shows the temperature difference between June 26 and July 25, 2019. Satellites also show the ground becoming browner from June to July.
This July heatwave was caused by a massive area of high pressure positioned over the region, sometimes called a heat dome. The air mass acts as a roadblock in the sky, forcing the jet stream to travel around it in a wavy pattern that looks like the uppercase Greek letter omega. This omega block drew hot air north from the Sahara Desert.
Past research has linked rising global temperatures to more frequent and intense regional heatwaves, with researchers showing parts of Europe and North America could experience an extra 10 to 15 heatwave days for each degree of global warming. Projections from the UK Met Office also show that intense heatwaves could occur on average as regularly as every other year by the middle of the century.