The data was captured during overnight hours (around 2 a.m.) on several days in July by an instrument called the Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the NOAA-NASA Suomi National Polar-orbiting Partnership (Suomi NPP) satellite managed by the National Oceanic and Atmospheric Administration and NASA. The images show how built surfaces - roads, buildings, airport runways, and the like - retain heat, sometimes hovering around 100 degrees Fahrenheit (38 degrees Celsius) for hours after sunset.
From July 1 to July 19, the built surfaces in the maps grew progressively hotter, likely the combined effect of the heat wave intensifying and the cumulative heating of those human-made structures. Due to their high heat capacity, these surfaces didn't fully cool overnight before the onset of the next day's heat, said Glynn Hulley, the JPL climate scientist who produced the series.
At the center of the images is Phoenix's Sky Harbor International Airport, where VIIRS measured the hottest land-surface temperature within the city. The airport is also where Phoenix takes its official air temperature. By those measurements, the city experienced the hottest month on record in July, including a record 31 consecutive days in which the temperature exceeded 110 degrees Fahrenheit (43.3 degrees Celsius). The previous record was 18 days.
Land-surface temperatures in cities are usually warmer than in rural and undeveloped areas because of human activities and the materials used for building. Streets - seen in these maps as a grid pattern - are often the hottest part of the built environment due to dark asphalt paving that absorbs more sunlight than lighter-colored surfaces; asphalt absorbs up to 95% of solar radiation. In the images, the mountains near Phoenix are also notably hot due to their angle to the Sun and greater soil exposure from lack of vegetation.
"Dark asphalt and concrete have a high heat capacity, so most of the heat they absorb during the day goes into storage below the ground," Hulley said. "That heat gets released slowly at night, making air temperatures much warmer during the nighttime in dense urban areas, creating the classic urban heat island effect."
The hot surfaces in and around the city stand in contrast to nearby irrigated surfaces such as agricultural fields, golf courses, and parks, which fell as low as 68 degrees Fahrenheit (18.9 degrees Celsius) during the night. The Verde River and other nearby waterways also were significantly cooler.
VIIRS is one of five instruments aboard the NOAA-NASA Suomi NPP satellite. Short for Suomi National Polar-orbiting Partnership, the spacecraft is one of several in the Joint Polar Satellite System. The images were produced from the VNP21IMG Land Surface Temperature product, which is available at NASA's Land, Atmosphere Near-real-time Capability for EOS (LANCE).
Spanish city shatters heat record
Madrid (AFP) Aug 10, 2023 -
Spain's eastern city of Valencia set a new temperature record on Thursday as the country baked under its third heatwave of the summer.
The mercury soared to 46.8 degrees Celsius (116.2 Fahrenheit) at Valencia airport, shattering the previous record of 43.4 Celsius set on July 6, 1986, state weather agency Aemet said on social media.
The centre of the Mediterranean port city was emptier than usual as many people stayed indoors to shelter from the heat, or escaped to the countryside or nearby beaches.
Those who did venture outside used fans and umbrellas to guard themselves against the scorching sun, or cooled themselves with water from fountains.
"This summer has been horrible... we cannot live in our apartment," Valencia resident Nazim Ali told AFPTV.
The local government opened an air-conditioned shelter to allow homeless people to escape the heat and access water, food and showers.
"At night we use the air-conditioning and a fan," said Roberto Gimenez, another resident.
"During the day we try to leave the house as late as we can if we don't have work to do, and go to the beach."
The record for the highest temperature in Spain -- 47.6 degrees Celsius --- was registered on August 14, 2021, at Aemet's weather station in La Rambla in the southern province of Cordoba.
The heatwave affecting most of central, southern and eastern Spain is expected to ease on Friday.
Scientists say heatwaves have become more likely due to climate change.
As global temperatures rise over time, heatwaves are predicted to become more frequent and intense, and their impacts more widespread.
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