Subscribe to our free daily newsletters
. Earth Science News .




Subscribe to our free daily newsletters



WATER WORLD
A 50-year Indian dry spell has reversed, with more rain to come
by Staff Writers
Boston MA (SPX) Jul 25, 2017


"There's this idea in people's minds that India is going to dry up," Wang says. "The Indian monsoon season is undergoing a longer drying than all other systems, and this created a hypothesis that, since India is heavily polluted by manmade aerosols and is also heavily deforested, these may be factors that cause this drying. Modeling studies also projected that this drying would continue to this century."

An MIT study published in Nature Climate Change finds that the Indian summer monsoons, which bring rainfall to the country each year between June and September, have strengthened in the last 15 years over north central India.

This heightened monsoon activity has reversed a 50-year drying period during which the monsoon season brought relatively little rain to northern and central India. Since 2002, the researchers have found, this drying trend has given way to a much wetter pattern, with stronger monsoons supplying much-needed rain, along with powerful, damaging floods, to the populous north central region of India.

A shift in India's land and sea temperatures may partially explain this increase in monsoon rainfall. The researchers note that starting in 2002, nearly the entire Indian subcontinent has experienced very strong warming, reaching between 0.1 and 1 degree Celsius per year. Meanwhile, a rise in temperatures over the Indian Ocean has slowed significantly.

Chien Wang, a senior research scientist in MIT's Department of Earth, Atmospheric and Planetary Sciences, the Center for Global Change Science, and the Joint Program for the Science and Policy of Global Change, says this sharp gradient in temperatures - high over land, and low over surrounding waters - is a perfect recipe for whipping up stronger monsoons.

"Climatologically, India went through a sudden, drastic warming, while the Indian Ocean, which used to be warm, all of a sudden slowed its warming," Wang says. "This may have been from a combination of natural variability and anthropogenic influences, and we're still trying to get to the bottom of the physical processes that caused this reversal."

Wang's co-author is Qinjian Jin, a postdoc in the Joint Program for the Science and Policy of Global Change.

A theory drying up
The Indian monsoon phenomenon is the longest recorded monsoon system in meteorology. Measurements of its rainfall date back to the late 18th century, when British colonists established the country's first weather observatories to record the seasonal phenomenon. Since then, the Indian government has set up several thousand rain gauges across the country to record precipitation levels during the monsoon season, which can bring little or no rain to some areas while deluging other parts of the country.

From these yearly measurements, scientists had observed that, since the 1950s, the Indian monsoons were bringing less rain to north central India - a drying period that didn't seem to let up, compared to a similar monsoon system over Africa and East Asia, which appeared to reverse its drying trend in the 1980s.

"There's this idea in people's minds that India is going to dry up," Wang says. "The Indian monsoon season is undergoing a longer drying than all other systems, and this created a hypothesis that, since India is heavily polluted by manmade aerosols and is also heavily deforested, these may be factors that cause this drying. Modeling studies also projected that this drying would continue to this century."

A persistent revival
However, Wang and Jin found that India has already begun to reverse its dry spell. The team tracked India's average daily monsoon rainfall from 1950 to the present day, using six global precipitation datasets, each of which aggregate measurements from the thousands of rain gauges in India, as well as measurements of rainfall and temperature from satellites monitoring land and sea surfaces.

Between 1950 and 2002, they found that north central India experienced a decrease in daily rainfall average, of 0.18 millimeters per decade, during the monsoon season. To their surprise, they discovered that since 2002, precipitation in the region has revived, increasing daily rainfall average by 1.34 millimeters per decade.

"The Indian monsoon is considered a textbook, clearly defined phenomenon, and we think we know a lot about it, but we don't," Wang says. "Here, we identify a phenomenon that was mostly overlooked."

The researchers did note a brief drying period during the 2015 monsoon season that caused widespread droughts throughout the subcontinent. They attribute this blip in the trend to a severe El Nino season, where ocean temperatures temporarily rise, causing a shift in atmospheric circulation, leading to decreased rainfall in India and elsewhere.

"But even counting that dry year, the long-term [wetting] trend is still pretty steady," Wang says.

More questions ahead
The team believes the current strong monsoon trend is a result of higher land temperatures in combination with lower ocean temperatures. While it's unclear what is causing India to heat up while its oceans cool down, the researchers have some guesses.

For example, Wang says ocean cooling could be a result of the natural ebb and flow of long-term sea temperatures. India's land warming on the other hand, could trace back to reduced cloud cover, particularly at low altitudes.

Normally, clouds act to reflect incoming sunlight. But Wang and others have observed that in recent years, India has experienced a reduction in low clouds, perhaps in response to an increase in anthropogenic aerosols such as black carbon or soot, which can simultaneously absorb and heat the surrounding air, and prevent clouds from forming.

"But these aerosols have been around even during the drying period, so there must be something else at work," Wang says. "This raises a lot more questions than answers, and that's why we're so excited to figure this out."

WATER WORLD
Mountain glaciers recharge vital aquifers
Fairbanks AK (SPX) Jul 24, 2017
Small mountain glaciers play a big role in recharging vital aquifers and in keeping rivers flowing during the winter, according to a new study published in Geophysical Research Letters, a journal of the American Geophysical Union. The study also suggests that the accelerated melting of mountain glaciers in recent decades may explain a phenomenon that has long puzzled scientists - why Arcti ... read more

Related Links
Massachusetts Institute of Technology
Water News - Science, Technology and Politics


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only

Comment using your Disqus, Facebook, Google or Twitter login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

WATER WORLD
Cheap 3D printed prosthetics could be game changer for Nepal

Separated by war, Iraqi children wait for parents

The last survivors on Earth

Haiti's army reborn 20 years after it was demobilized

WATER WORLD
A plastic planet

Using water displacement as the 3-D shape sensor for complex objects

Japanese engineers develop headset-less VR system

Spacepath Communications Announces Innovative Frequency Converter Systems

WATER WORLD
New algorithm, metrics improve autonomous underwater vehicles' energy efficiency

MH370 search reveals hidden undersea world

A super-algae to save our seas

Mountain glaciers recharge vital aquifers

WATER WORLD
Thawing permafrost releases old greenhouse gas

Sentinel satellite captures birth of behemoth iceberg

Massive iceberg

US need for four polar icebreakers 'critical,' warns report

WATER WORLD
French grape harvest heading to historic low

Kenyan cattle herders defend 'necessary' land invasions

Disneyland China falls a-fowl of huge turkey leg demand

Using treated graywater for irrigation is better for arid environments

WATER WORLD
Crustal limestone platforms feed carbon to many of Earth's arc volcanoes

Flood-hit New Zealand braces for more rain

Greek holiday island battles to recover from deadly quake

Two killed in 6.7-magnitude quake off Greece and Turkey resorts

WATER WORLD
Peace deal eludes Senegal's Casamance, 35 years on

Rwandan forces killing suspects without trial: HRW

AU chair questions US stance on African peacekeeping

3 killed in north Mali clashes as UN condemns violence

WATER WORLD
Artifacts suggest humans arrived in Australia earlier than thought

Father's presence encourages sibling bonding among baboons

Startup touts neuro-stimulation as 'medicine for the brain'

Towards a High-Resolution, Implantable Neural Interface




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News






The content herein, unless otherwise known to be public domain, are Copyright 1995-2017 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement