The high level of local pollution is burning the fog over cities in the Indo-Gangetic Plains (IGP), with Delhi recording the maximum “fog holes” during winter, a study that analysed 17 years of satellite data from NASA shows.
The paper ‘Urban Heat Island over Delhi punches Holes in Widespread Fog in the Indo-Gangetic Plains’ by the Indian Institute of Technology Bombay (IIT-B) and University of Petroleum and Energy Studies, Dehradun, was published in the journal Geophysical Research Letters by the American Geophysical Union on January 8.
The researchers said this is the first study that shows the direct impact and evidence of urban hotspots in fog globally, and specifically over Delhi.
The two-member team found more than 90 occurrences of fog holes in Delhi, where the incidence of fog has dipped by over 50% between 2006 and 2016.
The area covers more than 700 square kilometres making it the largest in terms of frequency and extent as compared to the Po Valley in Italy, north China plains and California’s Central Valley, which experience similar phenomena.
With land surface temperatures over Delhi recorded at around four to five degrees Celsius higher compared to its rural surroundings, researchers said the formation of urban heat islands burns the base of the fog layer during mid-morning.
The urban heat island is a phenomenon when the heat gets trapped near the earth’s surface as a result of a decline in green cover, rapid urbanisation, energy-intensive activities, and concrete structures. For instance, vegetation cover in rural areas surrounding Delhi is more than 65% compared to the city.
Relative humidity, which should be about 95%, is a key factor for fog formation. When surface temperatures increase due to urban heat island effect, there is a decrease in relative humidity which is not conducive to form fog droplets,” lead investigator and senior physical scientist at Washington’s Environmental Defense Fund, Ritesh Gautam, said.
High humidity levels are important since the air has to be saturated enough with water vapour so that it can condense on pollutants or particles in the air to form fog near the ground,” Gautam, a former IITB professor, added.
Delhi witnessed more than a 50% decrease in fog cover. Between 2008 and 2016, the city recorded fog holes for 55 days, despite a 20% increase in fog at a distance of 15km to 30km from the city centre during the study period. The team also found a fourfold decrease in the thickness of the fog around the edges of the hole over Delhi as compared to its surrounding.
Across the IGP that runs across 1,800km, there was a 17% to 36% decline in fog cover across Amritsar, Jalandhar, Patiala, Ludhiana and Lahore. These five cities had 24 to 32 days of fog holes.
Fog is an important climatic feature as it affects local vegetation and weather and fog mixed with pollutants create problems.
Our study suggests that links between urbanisation and fog dynamics and its frequency should be assessed to better understand the relationships between fog, air pollution and urbanisation, and help advance the development of fog forecasting capabilities,” said Gautam.
Increasing urbanisation may make fog rarer, but there could be some benefits from the change.
We have a situation where fog is getting amplified by air pollution but urbanisation is decreasing fog. As more urban cities come up, we won’t be able to see the fog but will see holes. However, the fog over Delhi and other places is so notorious that may be urbanisation is helping to keep the polluted fog intensity over Delhi low,” said Gautam.
The findings from the study are important since dense and polluted winter fog in the IGP — with a population of more than 900 million — envelopes north India, Pakistan, Nepal and Bangladesh every year from December to January severely affecting air quality and disrupting air, rail and road traffic.
Madhavan N Rajeevan, the secretary at the Union ministry of earth sciences, said the study will be very useful in understanding the process of why fog occurs and ultimately to predict its occurrence.
Though we know the basic principles and processes by which fog occurs, its prediction is a very tricky issue. Fog occurrence may vary depending on local conditions such as different topographies or urban heat islands that play an important role in its formation,” Rajeevan said.
Buried glaciers have been spotted on Mars, offering new hints about how much water may be accessible on the Red Planet and where it is located, researchers said Thursday.
Although ice has long been known to exist on Mars, a better understanding of its depth and location could be vital to future human explorers, said the report in the US journal Science.
Astronauts could essentially just go there with a bucket and a shovel and get all the water they need," said co-author Shane Byrne of the University of Arizona Lunar and Planetary Laboratory in Tucson.
A total of eight ice sites, some as shallow as a few feet (one meter) below the surface, and going as deep as 100 meters or more, have been exposed by erosion.
These underground cliffs, or scarps, appear "to be nearly pure ice," said the report.
The discovery was possible due to images and data sent by the Mars Reconnaissance Orbiter (MRO), launched in 2005.
The probe's first find of water on Mars was published in Science in 2010.
But now, scientists realize that ice is more widespread than previously thought, said lead author Colin Dundas, a geologist at the US Geological Survey in Flagstaff, Arizona.
There is shallow ground ice under roughly a third of the Martian surface, which records the recent history of Mars," he said.
What we've seen here are cross-sections through the ice that give us a 3-D view with more detail than ever before.
The ice contains bands and color variations that suggest it was formed layer by layer, perhaps as snow accumulated over time, leading to ice sheets.
Researchers believe the ice formed relatively recently, because the sites appear smooth on the surface, unpocked by craters that would be formed by celestial debris smashing into the planet over time.
But just how and when they formed remains unclear.
The cliffs are located in the northern and southern hemispheres of Mars, at a latitude of 55 to 58 degrees, which on Earth would be similar to Scotland or the tip of South America.
These regions slip into a frigid darkness during the Martian winter and would not be a suitable site for a long-term human camp.
However, they are not as treacherous as the poles, and if a sample could be drilled from one of the glaciers, researchers could learn plenty about Mars' climate and the potential for life on Earth's neighboring planet.
If you had a mission at one of these sites, sampling the layers going down the scarp, you could get a detailed climate history of Mars," said MRO deputy project scientist Leslie Tamppari of NASA's Jet Propulsion Laboratory.
It's part of the whole story of what happens to water on Mars over time: Where does it go? When does ice accumulate? When does it recede?
NASA plans to send the first human explorers to Mars by the 2030s.
Authors: Subcontinent Times
Updated: Jan 12, 2018 12:32 IST
Mumbai (Maharashtra) [India], Jan 12 (ANI): The Indian Naval Ships Nirbhik and Nirghat have been decommissioned at Naval Dockyard, Mumbai, after a glorious 30 and 28 years respectively in the service of the nation.
The ceremony involved
Has NASA finally found evidence of alien life on Mars? A series of pictures taken by the space agency's Curiosity rover have given rise to the idea, after researchers found what looks like fossils among the rocks.
Barry DiGregorio, a research fellow at the University of Buckingham, believes these photos (taken on January 2, 2018) reveal "trace fossils" on the surface of Mars.
They look remarkably similar to Ordovician trace fossils I have studied and photographed here on Earth," he said.
If not trace fossils, what other geological explanations will NASA come up with?
NASA described the formations as "stick-like figures" with each one "about a quarter-inch long".
The space agency used the Mars Hand Lens Imager (MAHLI) camera on board the Curiosity rover to take the close-up pictures of the patterns.
Trace fossils are the name given to remains of things left behind by creatures such as dead remains, footprints or burrows.
Predictably, many on the internet believe the figures are proof that alien creatures once roamed the surface of Mars.
Interestingly, NASA said that it had originally moved past this point on the Martian surface, before wheeling back for a second look at the figures.
These were unique enough, given the fact that we didn't know they were there … [that] we thought we should go back," Ashwin Vasavada from NASA's Jet Propulsion Laboratory told Space. om.
So, does NASA believe it has found trace fossils of alien creatures on Mars? We don't rule it out," Vasavada said.
But we certainly won't jump to that as our first interpretation.
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