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Thu 23rd of November 2017


IAS EXPRESS - Free Download

More aerosol in atmosphere results in heavier rainfall
  • Contrary to the general notion that pre-monsoon aerosol loading results in decrease in seasonal rainfall, a long-term (2002-2013) satellite observational study and model-based analysis by researchers from the Indian Institute of Technology (IIT) Kanpur has found that higher aerosol loading results in delayed but more rainfall over Central and Northern India. Higher aerosol loading changes cloud properties in terms of size (both height and width) and microphysics, which results in more rainfall. 

  • Fourteen microns is the agreed raindrop size, and until it reaches this size, the growth of droplets in the cloud is primarily driven by condensation. When aerosol particles are higher, the number of nucleation sites increases resulting in far too many number of droplets. Under such circumstances, it takes time for the droplets to grow in size through condensation.

  • There is an increase in the condensation of water vapour into cloud droplets as the number of aerosol particles increases. But there is a reduction in radius of the drops formed near the cloud base.

  • Although genesis of cloud systems is influenced by various meteorological parameters, aerosols are capable of strongly modifying the cloud structure, dynamics and composition during Indian summer monsoon.

  • Once cloud starts forming due to convection, the presence of more aerosol particles tend to modify the warm phase microphysics as well as ice phase microphysics.

  • Two forces - gravity and updraft (vertical velocity) - tend to act on droplets.

  • Under high aerosol loading, rather than falling down as raindrops, the smaller droplets tend to rise upwards in convective atmosphere due to updraft.

  • As the droplets are lifted up they tend to cross the freezing level and turn into ice particles. The process of water droplets turning into ice particles releases more latent heat of freezing and further invigorates the cloud. 

  • In the absence of cloud, aerosol particles tend to absorb solar radiation and this leads to warming or less decrease in temperature with height. As a result, there is suppression of convection leading to further suppression of cloud formation.

  • Till now scientists have shown that presence of more aerosol in pre-monsoon season may lead to reduction in total monsoon rainfall due to aerosol-solar radiation interactions. 


Prelims Question of the Day

With reference to 'Natural Rate of Unemployment', consider the following statements.

1. It is the level of unemployment in an economy that is just consistent with a stable rate of Inflation.

2. It is the unemployment that prevails when all markets in the economy are in equilibrium.


(a)1 and 2

(b)2 only

(c)1 only

(d)None of the above

Mains Question of the Day

1.GS-No party in power can afford to ignore Directive Principles of State Policy. Comment.(200 Words)

2.Political Science - Explain the role of non state actors, like IMF, World Bank, European Union and MNCs, in modulating and transforming the broad dynamics of international relations. (250 Words).

3.SOCIOLOGY - What is the impact of Globalization on the structure and mobilization of the working class in India? (250 Words).

Sociology - Thinkers