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A recent analysis has shown that wind speed in major Indian cities has been slowing down consistently and significantly over several decades. The average wind speed has fallen by 47% in Hyderabad, 47% in Bengaluru, 46% in Kolkata
What are the causes of this decrease?
While the exact explanation of this phenomenon is not clear, some scientists say it is happening (along with other atmospheric changes) as a result of an increase in surface roughness, attributed to land-use changes. This they claim can be due to urbanization, or even forest growth.
Most global studies indicate that urbanization is the major factor that can explain weakening winds in urban regions.
Why is urbanization a major reason?
Urban areas are characterized by urban ‘heat islands’, altered rainfall patterns, increased fog, haze and reduced evaporative cooling. This explains why urbanization may well be the main driver of falling wind speeds.
This is also supported by the fact that the rate of wind speed fall in some of the less-rapidly urbanizing districts is relatively slow.
Although it may yet turn out not be the main factor behind reduced wind speeds, urbanization is certainly a compounding factor.
What are the implications of Slowing wind speed?
Slow winds cannot carry moisture for long which will result in altered rainfall patterns.
Agriculture depends crucially on transpiration (a plant’s exhalation of water vapour), which in turn needs evaporation which is dependent on wind speed.
Wind-dispersed plant species also depend on wind speeds for survival. They also affect natural disasters and ocean dynamics.
This also means that air pollution in cities will take longer to get dispersed, exacerbating public-health problems.
Falling wind speed also has huge implications for the wind-energy sector and thus for the clean energy sector. Typically, a 5% fall in wind speed can lead to an almost 17% fall in wind energy in an average turbine.
What has been the global trend?
Scientists have found that wind speeds have been declining globally since the 1960s which they refer to as “global terrestrial stilling“. Although this drop may not seem like much but over long periods of time, it can have significant consequences.
What is the way forward?
Natural phenomena need to be scientifically investigated for their implications to broader socio-economic and cultural outcomes. There is a need for an informed understanding of these winds of change so that we can formulate adaptation strategies.
Source– This post is based on the article “Winds of Change in Urban India that demand close investigation” published in Live Mint on 26th Feb 2022.
