jnAna means ‘knowledge’ in Sanskrit.
Under this title i will post some interesting information i gather while reading articles.. The first one is on, the most talked about topic “Global warming”. Here’s an excerpt to understand about solar radiation, infra red radiation..
Almost all incoming solar radiation, known as short-wave radiation, passes through the atmosphere and reaches the Earth’s surface. The bulk atmospheric constituents (99 per cent) – nitrogen and oxygen – are transparent to short-wave solar radiation.
On reaching surfaces, short-wave radiations undergo reflection and absorption. ‘Fractionation’ between these two is associated with the nature of the surface. That is, the surface composition’s texture and colour determine what fraction of incident radiation gets reflected and goes back.
The characteristics of shortwave solar radiation do not change when reflected, and essentially the atmosphere remains transparent on its return journey too. Albedo, or surface reflectivity, determines the fraction of radiation absorbed by the surface, and thus its temperature. Low albedo implies a larger fraction will be retained. In short, tinkering with the albedo of surfaces can help lower surface temperature by reflecting a larger fraction of incident solar short-wave radiation back.
Take the example of the surfaces amenable to albedo tinkering in a large city like Delhi. About 64 sq km (12.5 per cent of the city’s total area) is occupied by roads made of asphalt. When freshly laid, the colour is black
and the albedo 0.05. With time, the colour changes to grayish black and the albedo to 0.15. In the first case, the black surface will only reflect 5 per cent of the incident solar radiation and absorb 95 per cent. Later, the grey reflects 15 per cent and absorbs 85 per cent.
Short-wave radiation absorbed during the day transforms into heat, and this heat is sent back into the atmosphere as infra-red radiation partially trapped by green gases, the essence of the global warming problem.
This area is large enough to alter the albedo substantially by bouncing a large chunk of short-wave solar radiation back. By the simple expedient of raising the albedo from 0.15 to 0.4, an additional 25 per cent of the short-wave radiation can be reflected away from the Earth’s surface, lowering the city’s overall average temperature by about 2 degree Celsius. This decrease would send less infra-red radiation back to be trapped by green house gases.
To read more Could It Be This Easy?
Instead of talking about global warming, let’s take simple and practical steps to counter it
Arun K Attri