Slow trumps fast in changing the summer monsoon

Dec 24, 2012
In South Asia, summer monsoons deliver about three quarters of the annual rainfall influencing the fresh water supply, agriculture, and energy production. Small changes in monsoons can have a very large impact on local living conditions, affecting crop yields, prolonging droughts, or fostering floods. Monsoons also affect the global circulation, producing world-wide impacts.

(Phys.org)—Researchers at Pacific Northwest National Laboratory traced the different ways pollution particles change summer monsoon rainfall in South Asia. They found that pollution's effect through "slow" processes, affecting the region over weeks to months, has a more extensive impact on the monsoon than the "fast" processes occurring in a matter of days. Monsoons are an important climatic feature of our planet, and understanding the factors that influence monsoon behavior is a fundamental challenge for climate science.  Their work was published in the Geophysical Research Letters.

"Our results show that the slower impact of aerosols-cooling down sea surface temperatures-is more profound than their faster direct impacts through atmospheric heating, changes in clouds, and cooling land surface when it comes to shaping the behavior of the ," said Dr. Dilip Ganguly, atmospheric scientist at PNNL and lead author of the study. "But both slow and fast effects are important."

Monsoons affect about half the population of the Earth. Summer monsoons deliver about three quarters of the annual rainfall to South Asia, influencing the fresh water supply, agriculture, and energy production. Small changes in monsoons can have a large impact on local living conditions, affecting crop yields, prolonging droughts, or fostering floods. Monsoons also affect the global circulation, producing world-wide impacts. That's why it's important to understand factors that may change monsoons, including emissions of pollution particles (a.k.a. aerosols). In this study, PNNL researchers delved into the different ways that pollution particles influence the South rainfall.  

PNNL researchers used the Community Earth System Model (CESM) to study the effect of human-caused pollution particles on the South Asian summer monsoon. The CESM is a three-dimensional that predicts changes in features of the atmosphere, ocean, land and ice from different climate forcing agents like greenhouse gases and pollution.

The researchers explored the climate response to aerosol particle emissions by varying the emissions between pre-industrial and present-day values and monitoring the model response to those changes.

While both fast and slow climate responses to are important, they found the slow and fast changes influence precipitation patterns differently over South Asia.

"The processes changing influence the whole of South Asia, while the aerosol processes that affect land and atmosphere temperatures have a somewhat weaker impact and shift the precipitation to the west a bit," said Ganguly.

Aerosols emissions from Asia have been increasing rapidly with the enormous regional changes in society and industry. Emissions are likely to change again from the many new technological advances and increasing local concerns about emissions' impact on health and ecosystems. Researchers are interested in comparing and assessing the impacts of emissions from Asia with those from other parts of the planet.

Explore further: NRL reveals new meteorological insight into mid-level clouds

More information: Ganguly D, PJ Rasch, H Wang, and J-H Yoon. "Fast and Slow Responses of the South Asian Monsoon System to Anthropogenic Aerosols." Geophysical Research Letters 39, L18804. DOI:10.1029/2012GL053043

Related Stories

Pollution weakens monsoon's might

Jul 25, 2012

(Phys.org) -- Over 1.5 billion people in South Asia depend on the summer monsoon rains. Now, pollution exhaust threatens this primary water source for crops and daily living, according to new research at Pacific ...

Climate change and the South Asian summer monsoon

Jun 24, 2012

The vagaries of South Asian summer monsoon rainfall impact the lives of more than one billion people. A review in Nature Climate Change (June 24 online issue) of over 100 recent research articles concludes that w ...

Desert dust intensifies summer rainfall in U.S. southwest

May 21, 2012

(Phys.org) -- Dust is more than something to be brushed off the furniture. Scientists at Pacific Northwest National Laboratory found that dust kicked up from the desert floor acts like a heat pump in the atmosphere, ...

Study projects weakened monsoon season in South Asia

Feb 27, 2009

(PhysOrg.com) -- The South Asian summer monsoon - critical to agriculture in Bangladesh, India, Nepal and Pakistan - could be weakened and delayed due to rising temperatures in the future, according to a recent ...

Arizona monsoons unpredictable

Jun 18, 2007

The Arizona monsoon season produces up to a third of the region's annual rainfall but it is tough for forecasters to predict.

Recommended for you

Jeju Island is a live volcano, study reveals

52 minutes ago

In Jeju, a place emerging as a world-famous vacation spot with natural tourism resources, a recent study revealed a volcanic eruption occurred on the island. The Korea Institute of Geoscience and Mineral ...

Has Antarctic sea ice expansion been overestimated?

1 hour ago

New research suggests that Antarctic sea ice may not be expanding as fast as previously thought. A team of scientists say much of the increase measured for Southern Hemisphere sea ice could be due to a processing ...

Antarctic lakes theory dries up

4 hours ago

(Phys.org) —Antarctica is the driest continent on Earth, and always has been, with new research showing the previous "mega-lake theory" holds no water.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

omatwankr
1 / 5 (1) Dec 24, 2012
Until the USA stops accepting gays in the military, the planet will fictitiously continue to warm as we all get closer to going to hell, fulfilling the machinations of the atheist devil worshiping Illuminuti capital-socialist misanthropist transhumanist banker elite.

fillatioistly
omatwankr