UVLaser
Enlightened
Why is it when its winter or when it snow the sky turns red?
Thanks /ubbthreads/images/graemlins/grin.gif
Thanks /ubbthreads/images/graemlins/grin.gif
The sky is red?
- Thread starter UVLaser
- Start date
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BlindedByTheLite
Flashlight Enthusiast
city glow?
jtr1962
Flashaholic
The reddish-orange light from all the sodium vapor streetlights is scattered whenever there's snow. Yet another reason I hope we switch to nice white LED streetlights sometime soon. White or bluish-white skyglow would be much prettier.
B@rt
Flashaholic
Everyday mysteries
[ QUOTE ]
... In order to understand why "Red sky at night, sailor's delight. Red sky in morning, sailor's warning" can predict the weather, we must understand more about weather and the colors in the sky.
Usually, weather moves from west to east, blown by the westerly trade winds. This means storm systems generally move in from the West.
The colors we see in the sky are due to the rays of sunlight being split into colors of the spectrum as they pass through the atmosphere and ricochet off the water vapor and particles in the atmosphere. The amounts of water vapor and dust particles in the atmosphere are good indicators of weather conditions. They also determine which colors we will see in the sky.
During sunrise and sunset the sun is low in the sky, and it transmits light through the thickest part of the atmosphere. A red sky suggests an atmosphere loaded with dust and moisture particles. We see the red, because red wavelengths (the longest in the color spectrum) are breaking through the atmosphere. The shorter wavelengths, such as blue, are scattered and broken up.
Red sky at night, sailors delight.
When we see a red sky at night, this means that the setting sun is sending its light through a high concentration of dust particles. This usually indicates high pressure and stable air coming in from the west. Basically good weather will follow.
Red sky in morning, sailor's warning.
A red sunrise reflects the dust particles of a system that has just passed from the west. This indicates that a storm system may be moving to the east. If the morning sky is a deep fiery red, it means a high water content in the atmosphere. So, rain is on its way....
[/ QUOTE ] /ubbthreads/images/graemlins/wink.gif
[ QUOTE ]
... In order to understand why "Red sky at night, sailor's delight. Red sky in morning, sailor's warning" can predict the weather, we must understand more about weather and the colors in the sky.
Usually, weather moves from west to east, blown by the westerly trade winds. This means storm systems generally move in from the West.
The colors we see in the sky are due to the rays of sunlight being split into colors of the spectrum as they pass through the atmosphere and ricochet off the water vapor and particles in the atmosphere. The amounts of water vapor and dust particles in the atmosphere are good indicators of weather conditions. They also determine which colors we will see in the sky.
During sunrise and sunset the sun is low in the sky, and it transmits light through the thickest part of the atmosphere. A red sky suggests an atmosphere loaded with dust and moisture particles. We see the red, because red wavelengths (the longest in the color spectrum) are breaking through the atmosphere. The shorter wavelengths, such as blue, are scattered and broken up.
Red sky at night, sailors delight.
When we see a red sky at night, this means that the setting sun is sending its light through a high concentration of dust particles. This usually indicates high pressure and stable air coming in from the west. Basically good weather will follow.
Red sky in morning, sailor's warning.
A red sunrise reflects the dust particles of a system that has just passed from the west. This indicates that a storm system may be moving to the east. If the morning sky is a deep fiery red, it means a high water content in the atmosphere. So, rain is on its way....
[/ QUOTE ] /ubbthreads/images/graemlins/wink.gif
bindibadgi
Flashlight Enthusiast
As an astronomer (hobby - not profession) I will here put in my spoke and defend sodium vapour lamps. They cause far less of an issue for spectrometry since they are easy to filter out. the old mercure vapur lamps (the white ones) are a nightmare!
glenthemole
Newly Enlightened
In some towns near large observatories, they have special reflectors over the streetlights to angle the light down and cut down the light pollution. Think it's one of the major cities in US. Another useless bit of information from having a dad who's an astonomer, thoug hes pretty much on the instrumentation side now.
PhotonWrangler
Flashaholic
[ QUOTE ]
glenthemole said:
In some towns near large observatories, they have special reflectors over the streetlights to angle the light down and cut down the light pollution. Think it's one of the major cities in US. Another useless bit of information from having a dad who's an astonomer, thoug hes pretty much on the instrumentation side now.
[/ QUOTE ]
I've seen those reflectors around Tucson because of the Kitt Peak observatory.
glenthemole said:
In some towns near large observatories, they have special reflectors over the streetlights to angle the light down and cut down the light pollution. Think it's one of the major cities in US. Another useless bit of information from having a dad who's an astonomer, thoug hes pretty much on the instrumentation side now.
[/ QUOTE ]
I've seen those reflectors around Tucson because of the Kitt Peak observatory.
jtr1962
Flashaholic
[ QUOTE ]
bindibadgi said:
As an astronomer (hobby - not profession) I will here put in my spoke and defend sodium vapour lamps. They cause far less of an issue for spectrometry since they are easy to filter out. the old mercure vapur lamps (the white ones) are a nightmare!
[/ QUOTE ]
I just want to point out here that the sodium lights which are easy to filter out are low pressue sodium which incidentally are not used in most US cities because they emit light at only one frequency, meaning no color rendering whatsoever. The high pressure sodium used in most of the US emit light at probably more frequencies than the old mercury vapor did. I'm all for designing streetlights which eliminate light directed upwards. It would be nice to see the sky in big cities for a change. However, I also like to have light which creates a pleasant ambience and is good for seeing. Sodium vapor does neither. In fact, once you correct the spectrum for scotopic visibility the efficiency is worse than even incandescents.
bindibadgi said:
As an astronomer (hobby - not profession) I will here put in my spoke and defend sodium vapour lamps. They cause far less of an issue for spectrometry since they are easy to filter out. the old mercure vapur lamps (the white ones) are a nightmare!
[/ QUOTE ]
I just want to point out here that the sodium lights which are easy to filter out are low pressue sodium which incidentally are not used in most US cities because they emit light at only one frequency, meaning no color rendering whatsoever. The high pressure sodium used in most of the US emit light at probably more frequencies than the old mercury vapor did. I'm all for designing streetlights which eliminate light directed upwards. It would be nice to see the sky in big cities for a change. However, I also like to have light which creates a pleasant ambience and is good for seeing. Sodium vapor does neither. In fact, once you correct the spectrum for scotopic visibility the efficiency is worse than even incandescents.
bindibadgi
Flashlight Enthusiast
I didn't realise that. We have the low pressure ones here and they are good. I understand that the high pressure ones are as bad as mercury vapour as a result of the Doppler broadening - the very thing that makes them seem better for street lighting. Ironic, but true.
I too wish for darker skies. I lamented when a row of lights was installed down the main road near my house (even the low pressure Na lights) but the government doesn't seem keen on forking out the money for shielding them. I really wish they would.
I also wish that people would realise that sensor lights are much better for security than huge spotlights pointed outwards. Living near a school doesn't help at all. :shake:
I too wish for darker skies. I lamented when a row of lights was installed down the main road near my house (even the low pressure Na lights) but the government doesn't seem keen on forking out the money for shielding them. I really wish they would.
I also wish that people would realise that sensor lights are much better for security than huge spotlights pointed outwards. Living near a school doesn't help at all. :shake:
greenLED
Flashaholic
Aerosols also influence sky color at night. I saw a scarlet red moon a couple of years ago in South Africa.
glenthemole
Newly Enlightened
[ QUOTE ]
PhotonWrangler said:
[ QUOTE ]
glenthemole said:
In some towns near large observatories, they have special reflectors over the streetlights to angle the light down and cut down the light pollution. Think it's one of the major cities in US. Another useless bit of information from having a dad who's an astonomer, thoug hes pretty much on the instrumentation side now.
[/ QUOTE ]
I've seen those reflectors around Tucson because of the Kitt Peak observatory.
[/ QUOTE ]
Had a feeling it was kitt peak, wasn't sure though.
PhotonWrangler said:
[ QUOTE ]
glenthemole said:
In some towns near large observatories, they have special reflectors over the streetlights to angle the light down and cut down the light pollution. Think it's one of the major cities in US. Another useless bit of information from having a dad who's an astonomer, thoug hes pretty much on the instrumentation side now.
[/ QUOTE ]
I've seen those reflectors around Tucson because of the Kitt Peak observatory.
[/ QUOTE ]
Had a feeling it was kitt peak, wasn't sure though.
