In general,clouds are good reflectors of solar radiation,only a small amount being absorbed.So,when the sky is cloudy,major part of the solar radiation is obstructed from meeting the surface due to reflection.The small amount which is absorbed raises the temperature of the cloud onlyI.If,now,the temperature of the surface is lower than that of the cloud,the cloud will emit radiation in terms of long waves which will again be reflected by the earth and this portion of radiation will thus remain almost confined in between the earth and the cloud.
As a result,clouds tend to smooth out the diurnal variation of temperature,keeing the temperature low by day and high at night.Whatever be,cloudiness will try to decrease the range of diurnal variation of temperature when compared to a clear day.Thus cloudiness acts as a blanket.
Just to add a bit more to the otherwise excellent answer from Allan, the warmer an object is, the higher the frequencies of the electromagnetic force is carried. This is why your body sends only infrareds, under the visible light spectrum, but a light bulb or a wood fire sends also frequencies in the visual light spectrum.
During the daytime, the sun heats the earth. At night, that heat radiates back into space as infrareds because the earth's average surface temperature isn't more than 15 degrees Celsius. The balance of which is called, the sun's net radiation.
Clouds do stop a good part of the electromagnetic force coming from the sun as it is scattered by the tiny water droplets. But some goes through: microwaves, visible frequency and even a bit of ultraviolet.
But when the sky is cloudy and heat radiates back into space at night, there is only infrareds and those carry less energy. When it is cloudy at night, the sun's net radiation is always positive, i.e. more gain than loss.
Remember that the higher the frequency, the greater the energy. This is what Einstein and Planck argued about and the reason the quantum physic started as light can behave as both a wave and a series of quantitative units we call, photons.
Like glass in a greenhouse, clouds allow short wavelength infrared waves through. When these waves interact with the earth, the re-radiated infrared is at a longer wavelength which cannot pass through the clouds, so the heat energy is trapped.
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In general,clouds are good reflectors of solar radiation,only a small amount being absorbed.So,when the sky is cloudy,major part of the solar radiation is obstructed from meeting the surface due to reflection.The small amount which is absorbed raises the temperature of the cloud onlyI.If,now,the temperature of the surface is lower than that of the cloud,the cloud will emit radiation in terms of long waves which will again be reflected by the earth and this portion of radiation will thus remain almost confined in between the earth and the cloud.
As a result,clouds tend to smooth out the diurnal variation of temperature,keeing the temperature low by day and high at night.Whatever be,cloudiness will try to decrease the range of diurnal variation of temperature when compared to a clear day.Thus cloudiness acts as a blanket.
Just to add a bit more to the otherwise excellent answer from Allan, the warmer an object is, the higher the frequencies of the electromagnetic force is carried. This is why your body sends only infrareds, under the visible light spectrum, but a light bulb or a wood fire sends also frequencies in the visual light spectrum.
During the daytime, the sun heats the earth. At night, that heat radiates back into space as infrareds because the earth's average surface temperature isn't more than 15 degrees Celsius. The balance of which is called, the sun's net radiation.
Clouds do stop a good part of the electromagnetic force coming from the sun as it is scattered by the tiny water droplets. But some goes through: microwaves, visible frequency and even a bit of ultraviolet.
But when the sky is cloudy and heat radiates back into space at night, there is only infrareds and those carry less energy. When it is cloudy at night, the sun's net radiation is always positive, i.e. more gain than loss.
Remember that the higher the frequency, the greater the energy. This is what Einstein and Planck argued about and the reason the quantum physic started as light can behave as both a wave and a series of quantitative units we call, photons.
Like glass in a greenhouse, clouds allow short wavelength infrared waves through. When these waves interact with the earth, the re-radiated infrared is at a longer wavelength which cannot pass through the clouds, so the heat energy is trapped.