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Increase green cover to mitigate urban heat : NASA

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By NewsGram Staff Writer

Washington:  Providing a solution to the recent problem of rising urban heat, a recently conducted study by NASA explained how increasing the green cover can help cities to a great extent.

Cheetal_(spotted_deer)_at_Van_Vihar_National_Park

Using multiple satellites’ observations, researchers found that areas in the US covered in part by concrete surfaces had a summer temperature 1.9 degrees Celsius higher than surrounding rural areas.

In winter, the temperature difference was 1.5 degrees Celsius higher in urban areas.

At the human level, a rise of one degrees Celsius can raise energy demands for air conditioning in the summer from five to 20 percent.

“This has nothing to do with greenhouse gas emissions. It is in addition to the greenhouse gas effect. This is the land use component only,” said Lahouari Bounoua, research scientist at NASA’s Goddard Space Flight Centre in Greenbelt, Maryland.

The urban heat island effect occurs primarily during the day when urban impervious surfaces absorb more solar radiation than the surrounding vegetated areas, resulting in a few degrees temperature difference.

The urban area has also lost the trees and vegetation that naturally cool the air.

“Anywhere in the US, small cities generate less heat than mega-cities,” Bounoua said.

The reason is the effect vegetation has on keeping a lid on rising temperatures.

“The amount and type of vegetation plays a big role in how much the urbanisation changes the temperature,” added research scientist and co-author Kurtis Thome.

As a by-product of photosynthesis, leaves release water back into the atmosphere in a process called evapotranspiration, which cools the local surface temperature the same way that sweat evaporating off a person’s skin cools them off.

Trees with broad leaves have more pores to exchange water than trees with needles, and so have more of a cooling effect.

“So even though 0.3 degrees Celcius may seem like a small difference, it still may have impact on energy use,” Bounoua said, especially when urban heat island effects are exacerbated by global temperature rises due to climate change.

Understanding the tradeoffs between urban surfaces and vegetation may help city planners in the future mitigate some of the heating effects, the authors noted in a paper that appeared in the journal Environmental Research Letters.

(With inputs from IANS)

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Habitability Of Surrounding Planets Affected By Super Flares Of Red Dwarfs: NASA

Red dwarfs -- especially young red dwarfs -- are active stars, producing flares blast out energy

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NASA, space, red dwarf
Superflares from red dwarfs may affect habitability of planets Pixabay

Using NASA’s Hubble Space Telescope, astronomers have found that violent outbursts, or superflares, from red dwarf stars could affect the habitability of any planets orbiting it.

Young low-mass stars flare much more frequently and more energetically than old stars and middle-age stars like our Sun, the findings of the study published in the Astrophysical Journal showed.

The findings are based on observations of the flare frequency of 12 red dwarfs.

Hubble is observing such stars through a large programme called HAZMAT — Habitable Zones and M dwarf Activity across Time.

“M dwarf” is the astronomical term for a red dwarf star — the smallest, most abundant and longest-living type of star in our galaxy.

Hubble Telescope. red dwarf
Hubble Telescope. Flickr

The HAZMAT programme is an ultraviolet survey of red dwarfs at three different ages — young, intermediate, and old.

“The goal of the HAZMAT programme is to help understand the habitability of planets around low-mass stars,” explained the programme’s principal investigator, Evgenya Shkolnik from Arizona State University.

“These low-mass stars are critically important in understanding planetary atmospheres,” Shkolnik added.

Stellar flares from red dwarfs are particularly bright in ultraviolet wavelengths, compared with Sun-like stars.

Red dwarf  planet
Artist’s view of planets transiting red dwarf star in TRAPPIST-1 system. Flickr

Hubble’s ultraviolet sensitivity makes the telescope very valuable for observing these flares.

The flares are believed to be powered by intense magnetic fields that get tangled by the roiling motions of the stellar atmosphere.

When the tangling gets too intense, the fields break and reconnect, unleashing tremendous amounts of energy.

The team found that the flares from the youngest red dwarfs they surveyed — just about 40 million years old — are 100 to 1,000 times more energetic than when the stars are older.

This younger age is when terrestrial planets are forming around their stars.

Red dwarf
This illustration shows a red dwarf star orbited by a hypothetical exoplanet. NASA

About three-quarters of the stars in our Milky Way galaxy are red dwarfs. Most of the galaxy’s “habitable-zone” planets — planets orbiting their stars at a distance where temperatures are moderate enough for liquid water to exist on their surface — orbit red dwarfs.

In fact, the nearest star to our Sun, a red dwarf named Proxima Centauri, has an Earth-size planet in its habitable zone.

Also Read: NASA Plans For Science Payloads For Delivery To Moon

However, red dwarfs — especially young red dwarfs — are active stars, producing flares that could blast out so much energy that it disrupts and possibly strips off the atmospheres of these fledgling planets. (IANS)