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Updated: March 17, 2014 01:14 IST

Aerosols can enhance monsoon rains: study

N. Gopal Raj
Comment (2)   ·   print   ·   T  T  

Interest in examining how aerosols affect climate

Monsoon rains over India could increase if desertification leads to more dust from West Asia and North Africa swirling into the air, suggests a research report being published in Nature Geoscience.

There has been growing interest in examining how fine particles in the atmosphere, known as aerosols, affect the climate.

However, much of this research has looked at particles generated by human activity, especially the role of soot.

Natural aerosols

But natural aerosols, such as sea-salt and dust, are far more abundant than human-produced ones, remarked V. Vinoj, who is currently with IIT Bhubaneswar.

The research appearing online in Nature Geoscience was carried out by him with Philip J. Rasch's group at the Pacific Northwest National Laboratory in the U.S.

Analysing observational data, Dr. Vinoj and his colleagues found that monsoon rainfall during June, July and August over central India was strongly correlated with aerosol levels over West Asia, North Africa and the Arabian Sea.

Global climate model

The scientists turned to a global climate model, the Community Atmosphere Model (CAM5), to simulate what effect different types of aerosols would have on the monsoon rains.

When dust was removed altogether, the correlations between the central Indian rains and West Asian aerosol levels disappeared.

The simulations also showed that when West Asian dust levels dropped, rains over central India decreased within a week.

The dust acted by absorbing radiation from the sun and heating the atmosphere.

High levels of dust over West Asia and North Africa lowered atmospheric pressure in land regions to the north and west of the Arabian Sea, the scientists said.

Band strengthened

That low-pressure band strengthened moisture-laden winds that fed the Indian monsoon.

“The expected expansion of desert and arid regions under global warming could enhance dust transport from the deserts of the Middle East and North Africa to the Asian monsoon regions, further enhancing monsoon rainfall,” observed William Lau of the NASA Goddard Space Flight Center in the U.S in a commentary published in the same journal.

RELATED NEWS

Managing the monsoonMay 2, 2014

Amazing it may seem, ancient Indian folk wisdom have clearly understood the direct link between aerosols and rains. Local communities over the centuries have devised weather-related customs that, they say, help bring in copious showers. Mariamman, goddess of disease and rain, predominant in the rural areas of Tamil Nadu, Karnataka and Andhra Pradesh on whose honour regular village festivals are performed before the onset of rains. The underlying idea is to create much dust (Aerosols) for good rain fall.

from:  N.G. Krishnan
Posted on: Mar 17, 2014 at 10:44 IST

The global warming due to burning of fossil fuels and the movement
of sun towards north during summer evaporates more water from sea
surface . The heated atmospheric air over the land area raises due to
lower density which creates low pressure and the moist air from the
sea is drawn over the land surface due to this low pressure .Where
ever cooler surfaces are available like forest , high mountains, etc
the moisture condenses as rain . When the warming up is more, more
water evaporates and more rain is expected .This is the correct logic
. This article is not giving reason for low pressure formation. The
dust particle forms the core for the raindrops but first cooler
temperature is required for condensation . That is why even when
silver iodide is sprayed in the clouds for giving the core particle
for the raindrops the condensation does not occur without cooler
temperature .

from:  sbalaraman
Posted on: Mar 17, 2014 at 09:52 IST
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