Banana444
Well-Known Member
Gorilla with the height exstension
The far red thread
- Thread starter Rahz
- Start date
Airwalker16
Well-Known Member
That's sick. Wish I could bring myself to spend that much.
Fastslappy
Well-Known Member
Orca film , some 2 x 4's & staple gun yer set to go bro !
Just Kidding AW don't take it wrong
Airwalker16
Well-Known Member
No offense taken; )
That orca is pretty cool shit though. I researched it briefly and saw some pics.
littlejacob
Well-Known Member
Bonjour
Is secret jardin and gorilla are the same?
I thought orca was S jardin exclusivity!
Is orca really that effective?
What is the height extension?
CU
Is secret jardin and gorilla are the same?
I thought orca was S jardin exclusivity!
Is orca really that effective?
What is the height extension?
CU
Airwalker16
Well-Known Member
Not even the same at all.
Fastslappy
Well-Known Member
I like it , seems briter than a flat latex white wall in the room
it covered a uneven wall nicely but i'm not going crazy with it
covers a wall & window with removeable ease (this is the why i bought it ) the window get a A/C in the summer
paint & mylar is used as well
it covered a uneven wall nicely but i'm not going crazy with it
covers a wall & window with removeable ease (this is the why i bought it ) the window get a A/C in the summer
paint & mylar is used as well
Pretty basic diagram, and I don't know if this shows clearly what's going on or not.
Btw, a relay is a switch that can connect two wires when it is turned off (by the 12/12 timer in this case) so it' perfect to start a timer when the rest of the main power shuts down.
Btw, a relay is a switch that can connect two wires when it is turned off (by the 12/12 timer in this case) so it' perfect to start a timer when the rest of the main power shuts down.
Attachments
Banana444
Well-Known Member
I have a 5x5 secret jardin i collapsed once when i put up a 6x24 carbon filter, the gorillas you could hang from the bars. The height extension adds another ft or .3meters to the height, helps the tent stay a little cooler and gives you plenty of room to grow vertical.
testiclees
Well-Known Member
According to nasa It looks like a decent swath of earth is bathed in UVB. Where did you learn that "only a few places get UVB"?
http://m.earthobservatory.nasa.gov/Features/UVB/uvb_radiation4.php
How Much Ultraviolet (UV-B) Radiation Are We Getting?
Scientists determine UV-B exposure at the surface in two ways. The first way is by measuring it directly with instruments on the ground. These ground-based instruments can tell us the amount of UV-B radiation reaching the surface at their exact locations. Because the number of these ground-based instruments is limited by cost and by the inaccessibility of many locations around the globe, and because the amount of UV-B radiation can vary enormously from one specific location to another, we depend on data from satellites for long-term, global-scale measurements of UV-B exposure. Satellite data are greatly contributing to scientists’ understanding of the effects of UV-B radiation.
This map displays estimates of UV-B irradiance at the surface based on the abundance of ozone, as measured by NASA’s Total Ozone Mapping Spectrometer (TOMS) instrument during the month of November, 2000. Data from satellites give us a daily, global perspective on the distribution of UV-B irradiance on the Earth’s surface. (Image by Reto Stöckli, based on data from the TOMS)
The second way to determine UV-B irradiance at the surface is by making estimates based on satellite measurements of ozone, cloud cover, and the other parameters described in What Reaches Earth’s Surface. Such estimates must take into account changes in the amount of radiation coming from the sun to the top of the atmosphere. To understand how researchers arrive at estimates of UV-B radiation reaching the Earth’s surface, one must first visualize a column of air that extends from the ground to the spacecraft above the atmosphere. Instruments on satellites orbiting the Earth (such as TOMS and OMI/Aura) measure the amounts of ozone, cloud cover, and aerosols in that column. Researchers can accurately calculate how much UV-B radiation there should be at the ground based on those measurements and on other conditions described earlier in this article (elevation, angle of sunlight, etc.). These values for each satellite field of view are incorporated into a global visualization of the data.
Satellite measurements are critical to our understanding of global change such as increases in UV radiation. Their importance derives from their superior calibration over long periods, their ability to observe remote or ocean-covered regions, and their capability of providing consistent global coverage. We also need well-maintained, strategically located ground-based instruments to continue to verify the accuracy of satellite-derived estimates of surface UV exposure over the globe.
Determining very long-term global trends still remains a problem because we have little historical data available before 1978, when NASA’s TOMS was first launched. Our need for historical data to detect and understand change underscores the critical importance of monitoring the Earth’ws processes for a long period of time, an objective to which NASA has committed in its Earth Observing System (EOS) program.
In September and October over Antarctica, loss of ozone and consequent increased levels of UV-B radiation at the surface are now commonly twice as high as during other times of the year. High UV-B exposures occur in nearby regions at both poles, including some regions where people live, such as Scandinavia, most of Europe, Canada, New Zealand, Australia, South Africa, and the southern region of South America. Exposures get especially high in regions of elevated altitude, such as in the Andes Mountains, and in places that are relatively free of clouds at certain times of the year, such as South Africa and Australia during their summer (December to February). In July, very high exposures appear over the Sahara, Saudi Arabia, southwestern United States, and the Himalayan Mountain regions in northern India and southern China. The equatorial regions have their maximum exposure in the spring and autumn, with higher values during the autumn due to decreased cloud cover.
The decrease of ozone amounts in the upper atmosphere above Antarctica and nearby regions between 1980 and 2000 has caused an increase in the amount of ultraviolet radiation striking the Earth and catalyzed extensive efforts by the scientific community to understand ozone chemistry. (Image courtesy NASA GSFC Scientific Visualization Studio, based on data from TOMS)
We have no reliable long-term record of actual UV-B exposure from ground-based measurements, but we do have accurate short-term estimates of decreasing ozone, which we know leads to an increase in UV-B exposure at the surface. In Scientific Assessment of Ozone Depletion: 1998, the World Meteorological Organization states that during 1998 at mid-latitudes in the north, between 35 and 60 degrees N, average ozone abundances were about 4 percent (per satellite measurements) or 5 percent (per ground-based measurements) below values measured in 1979, with most of the change occurring at the high end of that latitude zone. That means that recent UV-B radiation doses are correspondingly higher at those latitudes than historical levels (by amounts that depend on specific wavelengths). In the tropics and mid-latitudes, between 35 degrees S and 35 degrees N, both satellite data and ground-based data indicate that total ozone does not appear to have changed significantly since 1979.
next: Predictions and Monitoring
back: What Determines UV at the Surface?
hyroot
Well-Known Member
According to nasa It looks like a decent swath of earth is bathed in UVB. Where did you learn that "only a few places get UVB"?
http://m.earthobservatory.nasa.gov/Features/UVB/uvb_radiation4.php
How Much Ultraviolet (UV-B) Radiation Are We Getting?
Scientists determine UV-B exposure at the surface in two ways. The first way is by measuring it directly with instruments on the ground. These ground-based instruments can tell us the amount of UV-B radiation reaching the surface at their exact locations. Because the number of these ground-based instruments is limited by cost and by the inaccessibility of many locations around the globe, and because the amount of UV-B radiation can vary enormously from one specific location to another, we depend on data from satellites for long-term, global-scale measurements of UV-B exposure. Satellite data are greatly contributing to scientists’ understanding of the effects of UV-B radiation.
This map displays estimates of UV-B irradiance at the surface based on the abundance of ozone, as measured by NASA’s Total Ozone Mapping Spectrometer (TOMS) instrument during the month of November, 2000. Data from satellites give us a daily, global perspective on the distribution of UV-B irradiance on the Earth’s surface. (Image by Reto Stöckli, based on data from the TOMS)
The second way to determine UV-B irradiance at the surface is by making estimates based on satellite measurements of ozone, cloud cover, and the other parameters described in What Reaches Earth’s Surface. Such estimates must take into account changes in the amount of radiation coming from the sun to the top of the atmosphere. To understand how researchers arrive at estimates of UV-B radiation reaching the Earth’s surface, one must first visualize a column of air that extends from the ground to the spacecraft above the atmosphere. Instruments on satellites orbiting the Earth (such as TOMS and OMI/Aura) measure the amounts of ozone, cloud cover, and aerosols in that column. Researchers can accurately calculate how much UV-B radiation there should be at the ground based on those measurements and on other conditions described earlier in this article (elevation, angle of sunlight, etc.). These values for each satellite field of view are incorporated into a global visualization of the data.
Satellite measurements are critical to our understanding of global change such as increases in UV radiation. Their importance derives from their superior calibration over long periods, their ability to observe remote or ocean-covered regions, and their capability of providing consistent global coverage. We also need well-maintained, strategically located ground-based instruments to continue to verify the accuracy of satellite-derived estimates of surface UV exposure over the globe.
Determining very long-term global trends still remains a problem because we have little historical data available before 1978, when NASA’s TOMS was first launched. Our need for historical data to detect and understand change underscores the critical importance of monitoring the Earth’ws processes for a long period of time, an objective to which NASA has committed in its Earth Observing System (EOS) program.
In September and October over Antarctica, loss of ozone and consequent increased levels of UV-B radiation at the surface are now commonly twice as high as during other times of the year. High UV-B exposures occur in nearby regions at both poles, including some regions where people live, such as Scandinavia, most of Europe, Canada, New Zealand, Australia, South Africa, and the southern region of South America. Exposures get especially high in regions of elevated altitude, such as in the Andes Mountains, and in places that are relatively free of clouds at certain times of the year, such as South Africa and Australia during their summer (December to February). In July, very high exposures appear over the Sahara, Saudi Arabia, southwestern United States, and the Himalayan Mountain regions in northern India and southern China. The equatorial regions have their maximum exposure in the spring and autumn, with higher values during the autumn due to decreased cloud cover.
The decrease of ozone amounts in the upper atmosphere above Antarctica and nearby regions between 1980 and 2000 has caused an increase in the amount of ultraviolet radiation striking the Earth and catalyzed extensive efforts by the scientific community to understand ozone chemistry. (Image courtesy NASA GSFC Scientific Visualization Studio, based on data from TOMS)
We have no reliable long-term record of actual UV-B exposure from ground-based measurements, but we do have accurate short-term estimates of decreasing ozone, which we know leads to an increase in UV-B exposure at the surface. In Scientific Assessment of Ozone Depletion: 1998, the World Meteorological Organization states that during 1998 at mid-latitudes in the north, between 35 and 60 degrees N, average ozone abundances were about 4 percent (per satellite measurements) or 5 percent (per ground-based measurements) below values measured in 1979, with most of the change occurring at the high end of that latitude zone. That means that recent UV-B radiation doses are correspondingly higher at those latitudes than historical levels (by amounts that depend on specific wavelengths). In the tropics and mid-latitudes, between 35 degrees S and 35 degrees N, both satellite data and ground-based data indicate that total ozone does not appear to have changed significantly since 1979.
next: Predictions and Monitoring
back: What Determines UV at the Surface?
Reread what you just posted.
testiclees
Well-Known Member
This part ?"High UV-B exposures occur in nearby regions at both poles, including some regions where people live, such as Scandinavia, most of Europe, Canada, New Zealand, Australia, South Africa, and the southern region of South America. Exposures get especially high in regions of elevated altitude, such as in the Andes Mountains, and in places that are relatively free of clouds at certain times of the year, such as South Africa and Australia during their summer (December to February). In July, very high exposures appear over the Sahara, Saudi Arabia, southwestern United States, and the Himalayan Mountain regions in northern India and southern China. The equatorial regions have their maximum exposure in the spring and autumn, with higher values during the autumn due to decreased cloud cover."
Thats just "high uvb"
The colored gradient map shows considerable USB radiation in all of the southern hemisphere
In this model UV in July is "high" well past 40N.
Last edited:
testiclees
Well-Known Member
. You said "Only a few place in the world will plants actually get uvb outside" if you're talking about planet Earth you're mistaken.
UV-B in sunlight actively promotes plant survival
UV-B radiation is an integral component of sunlight that has wide-ranging effects on organisms. Most of the UV-B that reaches the earth is absorbed by the stratospheric ozone layer and therefore UV-B wavelengths are only a small fraction of sunlight at the earth's surface. Nevertheless, since UV-B is the most energetic part of the daylight spectrum it has the potential to damage macromolecules such as DNA and proteins, generate reactive oxygen species (ROS) and impair cellular processes.
However, UV-B is not solely an agent of damage and has an important role as a regulatory signal. In particular, the perception of low levels of UV-B by plants actively promotes survival because it stimulates responses that help to protect against and repair UV-damage. Plants are unavoidably exposed to UV-B because they need to capture sunlight for photosynthesis. The fact that plants rarely display signs of UV-damage in the natural environment demonstrates that they have evolved very effective mechanisms for UV-protection and repair. The protective mechanisms include the deposition of UV-absorbing phenolic compounds in the outer epidermal tissues and the production of anti-oxidant systems. Repair of UV-damage involves enzymes such as DNA photolyases. Furthermore, responses to UV-B modify the biochemical composition of plants, influence plant morphology and help to deter pests and pathogens. It is well established that many plant responses to UV-B involve the regulation of gene expression. UV-B exposure stimulates the expression of hundreds of genes, including those involved in UV-protection and repair.
It is important to understand how plants respond to UV-B and to determine the contribution of UV-B responses to normal plant growth and development. In fact, it will not be possible to obtain a complete understanding of the role of light in controlling plant development without knowledge of the regulatory effects of UV-B. Much remains to be learnt about the cellular and molecular mechanisms of UV-B perception and signal transduction leading to the control of gene expression. Understanding these processes is the aim of our research and the present focus is the role of the UVR8 (UV RESISTANCE LOCUS
protein.
For more background information see Jenkins (2009).
http://www.gla.ac.uk/researchinstitutes/biology/staff/garethjenkins/researchinterests/plantresponsestouv-8/
UV-B in sunlight actively promotes plant survival
UV-B radiation is an integral component of sunlight that has wide-ranging effects on organisms. Most of the UV-B that reaches the earth is absorbed by the stratospheric ozone layer and therefore UV-B wavelengths are only a small fraction of sunlight at the earth's surface. Nevertheless, since UV-B is the most energetic part of the daylight spectrum it has the potential to damage macromolecules such as DNA and proteins, generate reactive oxygen species (ROS) and impair cellular processes.
However, UV-B is not solely an agent of damage and has an important role as a regulatory signal. In particular, the perception of low levels of UV-B by plants actively promotes survival because it stimulates responses that help to protect against and repair UV-damage. Plants are unavoidably exposed to UV-B because they need to capture sunlight for photosynthesis. The fact that plants rarely display signs of UV-damage in the natural environment demonstrates that they have evolved very effective mechanisms for UV-protection and repair. The protective mechanisms include the deposition of UV-absorbing phenolic compounds in the outer epidermal tissues and the production of anti-oxidant systems. Repair of UV-damage involves enzymes such as DNA photolyases. Furthermore, responses to UV-B modify the biochemical composition of plants, influence plant morphology and help to deter pests and pathogens. It is well established that many plant responses to UV-B involve the regulation of gene expression. UV-B exposure stimulates the expression of hundreds of genes, including those involved in UV-protection and repair.
It is important to understand how plants respond to UV-B and to determine the contribution of UV-B responses to normal plant growth and development. In fact, it will not be possible to obtain a complete understanding of the role of light in controlling plant development without knowledge of the regulatory effects of UV-B. Much remains to be learnt about the cellular and molecular mechanisms of UV-B perception and signal transduction leading to the control of gene expression. Understanding these processes is the aim of our research and the present focus is the role of the UVR8 (UV RESISTANCE LOCUS
protein.For more background information see Jenkins (2009).
http://www.gla.ac.uk/researchinstitutes/biology/staff/garethjenkins/researchinterests/plantresponsestouv-8/
hyroot
Well-Known Member
http://www.schoolphysics.co.uk/age14-16/Wave properties/text/Ozone_layer/index.html
The ozone layer and its effect on ultraviolet light
The Earth is surrounded by a thick atmosphere which provides us with the air we beathe, keeps the planet warm and also protects us from harmful radiation from space. One of the most important types of damaging radiation is ultra violet radiation from the Sun.
The part of the atmosphere that filters out a lot of the ultra violet radiation is called the ozone layer – a region of the atmosphere between about 15 and 40 km above the Earth's surface.
The ultra violet radiation from the Sun is divided into three regions depending on the wavelength of the radiation. These are known as UVA, UVB and UVC. Some of the properties of these three types are decribed below.
UVA(a) UVA accounts for about 90% of the ultra violet radiation reaching the Earth's surface
(b) it has a wavelength range from 320 nm to 400 nm
(c) about 5% of the Sun's radiation is UVA
(d) it can pass through ordinary window glass
(e) the intensity of UVA radiation reaching the Earth's surface does not change with altitude, weather conditions or the time of year
(f) UVA can penetrate deep into the skin affecting underlying tissues
(g) prolonged exposure to UVA can cause long term skin damage.
UVB(a) UVB has a wavelength range from 290 nm to 320 nm
(b) because its wavelength is shorter than UVA it cannot pass through window glass.
(c) it causes tanning and is roughly 1000 times more likely than UVA to cause sunburn.
(d) however it does helps the body with normal vitamin D production.
(e) the ozone layer is very effective at screening out UVB. For radiation with a wavelength of 290 nm, the intensity at Earth's surface is 350 million times weaker than at the top of the atmosphere
(f) unlike UVA the intensity of UVB reaching the Earth's surface varies with the season. It is more intense in the summer than in the winter.
(g) its intensity varies with weather conditions and the time of day. It is more intense at midday than in the morning or late afternoon.
(h) it is also more intense at high altitudes and near the equator.
(i) it is known to be an important factor in the development ofcataracts and the growth of 90% of skin cancers
(j) you can protect yourself againt the effects of UVB by usingsunscreens containg a sun protection factor
UVC(a) UVC has a wavelength range from 200 nm to 290 nm
(b) it is absorbed in the upper atmosphere at around 35 km
(c) because of its short wavelength and high energy it would cause severe damage to living cells in both plants and animals if reached the Earth's surface
Damage to the ozone layer
A reduction in the amount of ozone in the ozone layer would allow more ultra violet radiation, especially UVC, to reach the planet's surface and this increase would have a damaging effect on both plants and animals. In the latter part of the twentieth century scientists discovered that the amount of ozone in the ozone layer was being reduced by the emission of chemicals by industrial processes on Earth. This effect was so severe that a hole appeared in the ozone layer above Antarctica.
Their studies showed that the ozone layer was being reduced in certain areas by chlorofluorocarbons (CFCs) chiefly used in refrigerators, air conditioners, propellants in some aerosol sprays and Styrofoam insulation. The damge to the ozone layer due to CFCs begins when sunlight breaks down these molecules releasing atomic chlorine. Atomic chlorine destroys the ozone which then increases the intensity of ultra violet radiation reaching the Earth's surface.Other gases that can affect the ozone layer are CH2, nitrous oxide (N2O), and sulphur dioxide (SO2).
However there are some optimistic results. In 2003 scientits announced that the depletion of the ozone layer may be slowing down due to the international ban on chlorofluorocarbons. Three satellites and three ground stations confirmed that damage to the ozone layer has slowed down significantly during the past decade. It is possible that further damage may still occur due to CFCs used by nations which have not banned them, and by gases which are already in the stratosphere.
Finally remember that damage to the ozone layer and the increase in sunburn has nothing to do with global warming.
The ozone layer and its effect on ultraviolet light
The Earth is surrounded by a thick atmosphere which provides us with the air we beathe, keeps the planet warm and also protects us from harmful radiation from space. One of the most important types of damaging radiation is ultra violet radiation from the Sun.
The part of the atmosphere that filters out a lot of the ultra violet radiation is called the ozone layer – a region of the atmosphere between about 15 and 40 km above the Earth's surface.
The ultra violet radiation from the Sun is divided into three regions depending on the wavelength of the radiation. These are known as UVA, UVB and UVC. Some of the properties of these three types are decribed below.
UVA(a) UVA accounts for about 90% of the ultra violet radiation reaching the Earth's surface
(b) it has a wavelength range from 320 nm to 400 nm
(c) about 5% of the Sun's radiation is UVA
(d) it can pass through ordinary window glass
(e) the intensity of UVA radiation reaching the Earth's surface does not change with altitude, weather conditions or the time of year
(f) UVA can penetrate deep into the skin affecting underlying tissues
(g) prolonged exposure to UVA can cause long term skin damage.
UVB(a) UVB has a wavelength range from 290 nm to 320 nm
(b) because its wavelength is shorter than UVA it cannot pass through window glass.
(c) it causes tanning and is roughly 1000 times more likely than UVA to cause sunburn.
(d) however it does helps the body with normal vitamin D production.
(e) the ozone layer is very effective at screening out UVB. For radiation with a wavelength of 290 nm, the intensity at Earth's surface is 350 million times weaker than at the top of the atmosphere
(f) unlike UVA the intensity of UVB reaching the Earth's surface varies with the season. It is more intense in the summer than in the winter.
(g) its intensity varies with weather conditions and the time of day. It is more intense at midday than in the morning or late afternoon.
(h) it is also more intense at high altitudes and near the equator.
(i) it is known to be an important factor in the development ofcataracts and the growth of 90% of skin cancers
(j) you can protect yourself againt the effects of UVB by usingsunscreens containg a sun protection factor
UVC(a) UVC has a wavelength range from 200 nm to 290 nm
(b) it is absorbed in the upper atmosphere at around 35 km
(c) because of its short wavelength and high energy it would cause severe damage to living cells in both plants and animals if reached the Earth's surface
Damage to the ozone layer
A reduction in the amount of ozone in the ozone layer would allow more ultra violet radiation, especially UVC, to reach the planet's surface and this increase would have a damaging effect on both plants and animals. In the latter part of the twentieth century scientists discovered that the amount of ozone in the ozone layer was being reduced by the emission of chemicals by industrial processes on Earth. This effect was so severe that a hole appeared in the ozone layer above Antarctica.
Their studies showed that the ozone layer was being reduced in certain areas by chlorofluorocarbons (CFCs) chiefly used in refrigerators, air conditioners, propellants in some aerosol sprays and Styrofoam insulation. The damge to the ozone layer due to CFCs begins when sunlight breaks down these molecules releasing atomic chlorine. Atomic chlorine destroys the ozone which then increases the intensity of ultra violet radiation reaching the Earth's surface.Other gases that can affect the ozone layer are CH2, nitrous oxide (N2O), and sulphur dioxide (SO2).
However there are some optimistic results. In 2003 scientits announced that the depletion of the ozone layer may be slowing down due to the international ban on chlorofluorocarbons. Three satellites and three ground stations confirmed that damage to the ozone layer has slowed down significantly during the past decade. It is possible that further damage may still occur due to CFCs used by nations which have not banned them, and by gases which are already in the stratosphere.
Finally remember that damage to the ozone layer and the increase in sunburn has nothing to do with global warming.
hyroot
Well-Known Member
http://m.earthobservatory.nasa.gov/Features/UVB/uvb_radiation3.php
What Determines How Much Ultraviolet Radiation Reaches the Earth’s Surface?
The amount of UV radiation reaching the Earth’s surface varies widely around the globe and through time. Several factors account for this variation at any given location. They are discussed below in order of importance, and descriptions of their effects appear in succeeding paragraphs.
The effects of ultraviolet radiation decrease with depth in the water column. (Image courtesy of NOAA)
Cloud Cover
Cloud cover plays a highly influential role in the amount of both UV-A and UV-B radiation reaching the ground. Each water droplet in a cloud scatters some incoming UV radiation back into space, so a thick cover of clouds protects organisms and materials from almost all UV. The larger the percentage of the sky that is covered by clouds, the less UV reaches the ground. The more opaque the cloud, the less UV-B. However, thin or broken cloud cover can be deceiving to people who are sunbathing, and the result can be an unexpected and severe sunburn.
Ozone in the Stratosphere
Ozone is the combination of three oxygen atoms into a single molecule (O3). It is a gas produced naturally in the stratosphere where it strongly absorbs incoming UV radiation. But as stratospheric ozone decreases, UV radiation is allowed to pass through, and exposure at the Earth’s surface increases. Exposure to shorter wavelengths increases by a larger percentage than exposure to longer wavelengths. Scientists can accurately estimate the amount of UV-B radiation at the surface using global data from satellites such as NASA’s TOMS (Total Ozone Mapping Spectrometer),GOME (Global Ozone Monitoring Experiment) andAura (will open in a new window), to be launched in 2003, satellites. These satellite measurements are compared to ground-based measurements to ensure that the satellite data are valid. To calculate the reduction of UV-B by ozone, scientists consider the total ozone in a column of air from the stratosphere to the Earth’s surface. At mid-latitudes, a decrease of one percent in ozone may result in an increase of between one (310 nm) and three (305 nm) percent of potentially harmful UV-B at the surface during mid-summer when UV-B is highest.
Ozone depletion is greater at higher latitudes, (toward the North and South Poles) and negligible at lower latitudes (between 30 degrees N and 30 degrees S). This means that decreases in ozone over Toronto are likely to be greater than those over Boston, and those over Boston greater than those over Los Angeles, while Miami will typically see the least ozone depletion of the four cities. However, cities at lower latitudes generally receive more sunlight because they are nearer the equator, so UV levels are higher even in the absence of ozone depletion. If ozone were to decrease at lower latitudes, southern cities would experience a greater absolute increase in UV-B than cities in the north for the same amount of ozone depletion.
The U.S. Department of Agriculture maintains an extensive network of radiometers to monitor ultraviolet B (UV-B) radiation across the country. The one pictured above is in Beltsville, Maryland. (Photograph by Jeannie Allen)
Oblique angle of sunlight reaching the surface
At any given time, sunlight strikes most of the Earth at an oblique angle. In this way, the number of UV photons is spread over a wider surface area, lowering the amount of incoming radiation at any given spot, compared to its intensity when the sun is directly overhead. In addition, the amount of atmosphere crossed by sunlight is greater at oblique angles than when the sun is directly overhead. Thus, the light travels through more ozone before reaching the Earth’s surface, thereby increasing the amount of UV-B that is absorbed by molecules of ozone and reducing UV-B exposure at the surface.
The three images above illustrate how a change in angle between the sun and the Earth’s surface affect the intensity of sunlight (and UV-B) on the surface. When the sun is directly overhead, forming a 90° angle with the surface, sunlight is spread over the minimum area. Also, the light only has to pass through the atmosphere directly above the surface. An increased angle between the sun and the surface—due to latitude, time of day, and season—spreads the same amount of energy over a wider area, and the sunlight passes through more atmosphere, diffusing the light. Therefore, UV-B radiation is stronger at the equator than the poles, stronger at noon than evening, and stronger in summer than winter. (Illustration by Robert Simmon)
Aerosols
Unlike clouds, aerosols in the troposphere, such as dust and smoke, not only scatter but also absorb UV-B radiation. Usually the UV reduction by aerosols is only a few percent, but in regions of heavy smoke or dust, aerosol particles can absorb more than 50 percent of the radiation.
While the presence of aerosols anywhere in the atmosphere will always scatter some UV radiation back to space, in some circumstances, aerosols can contribute to an increase in UV exposure at the surface. For example, over Antarctica, cold temperatures cause ice particles (Polar Stratospheric Clouds) to form in the stratosphere. The nuclei for these particles are thought to be sulfuric acid aerosol, possibly of volcanic origin. The ice particles provide the surfaces that allow complex chemical reactions to take place in a manner than can deplete stratospheric ozone.
The eruption of Mt. Pinatubo in 1991 injected sulfate aerosols into the stratosphere, significantly though temporarily depleting stratospheric ozone and resulting in an increase of UV-B reaching the Earth’s surface. Over millions of years, the biosphere has evolved to deal with temporary increases in UV from reductions in stratospheric ozone by natural causes such as volcanic eruptions, but has not had the time required to adjust to long-term ozone reductions attributed to human activities of the last 30 years. (Photograph courtesy USGS)
Water Depth
UV-B exposure decreases rapidly at increasing depths in the water column. In other words, water and the impurities in it strongly absorb and scatter incoming UV-B radiation. Some substances that are dissolved in water, such as organic carbon from nearby land, will also absorb UV-B radiation and enhance protection of microorganisms, plants, and animals from UV-B. Different masses of water at different locations contain different amounts of such dissolved substances and other particles, making evaluation of UV damage very difficult.
Ultraviolet B (UV-B) radiation reaches different depths in ocean water depending on water chemistry, the density of phytoplankton, and the presence of sediment and other particulates. The map above indicates the average depth UV-B penetrates into ocean water. At the depth indicated, only 10 percent of the UV-B radiation that was present at the water’s surface remains. The rest was absorbed or scattered back towards the ocean surface. (Image courtesy Vasilkov et al., JGR-Oceans, 2001)
Elevation
Living organisms at high elevations are generally exposed to more solar radiation and with it, more UV-B than organisms at low elevations. This is because at high elevations UV-B radiation travels through less atmosphere before it reaches the ground, and so it has fewer chances of encountering radiation-absorbing aerosols or chemical substances (such as ozone and sulfur dioxide) than it does at lower elevations.
Ecosystems at high altitudes, such as this lake in the Rocky Mountains of Colorado, receive more exposure to ultraviolet radiation than ecosystems at low altitudes. (Photo courtesy Philip Greenspun © 1994)
Reflectivity of the Earth’s Surface
As a highly reflective substance, snow dramatically increases UV-B exposure near the Earth’s surface as it reflects most of the radiation back into the atmosphere, where it is then scattered back toward the surface by aerosols and air molecules. Fresh snow can reflect much as 94 percent of the incoming UV radiation. In contrast, snow-free lands typically reflect only 2-4 percent of UV and ocean surfaces reflect about 5-8 percent (Herman and Celarier 1997).
next: How Much Are We Getting?
back: Effects on the Biosphere
Ultraviolet Radiation
Introduction
Effects on the Biosphere
What Determines UV at the Surface?
How Much Are We Getting?
Predictions and Monitoring
Ref
What Determines How Much Ultraviolet Radiation Reaches the Earth’s Surface?
The amount of UV radiation reaching the Earth’s surface varies widely around the globe and through time. Several factors account for this variation at any given location. They are discussed below in order of importance, and descriptions of their effects appear in succeeding paragraphs.
The effects of ultraviolet radiation decrease with depth in the water column. (Image courtesy of NOAA)
Cloud Cover
Cloud cover plays a highly influential role in the amount of both UV-A and UV-B radiation reaching the ground. Each water droplet in a cloud scatters some incoming UV radiation back into space, so a thick cover of clouds protects organisms and materials from almost all UV. The larger the percentage of the sky that is covered by clouds, the less UV reaches the ground. The more opaque the cloud, the less UV-B. However, thin or broken cloud cover can be deceiving to people who are sunbathing, and the result can be an unexpected and severe sunburn.
Ozone in the Stratosphere
Ozone is the combination of three oxygen atoms into a single molecule (O3). It is a gas produced naturally in the stratosphere where it strongly absorbs incoming UV radiation. But as stratospheric ozone decreases, UV radiation is allowed to pass through, and exposure at the Earth’s surface increases. Exposure to shorter wavelengths increases by a larger percentage than exposure to longer wavelengths. Scientists can accurately estimate the amount of UV-B radiation at the surface using global data from satellites such as NASA’s TOMS (Total Ozone Mapping Spectrometer),GOME (Global Ozone Monitoring Experiment) andAura (will open in a new window), to be launched in 2003, satellites. These satellite measurements are compared to ground-based measurements to ensure that the satellite data are valid. To calculate the reduction of UV-B by ozone, scientists consider the total ozone in a column of air from the stratosphere to the Earth’s surface. At mid-latitudes, a decrease of one percent in ozone may result in an increase of between one (310 nm) and three (305 nm) percent of potentially harmful UV-B at the surface during mid-summer when UV-B is highest.
Ozone depletion is greater at higher latitudes, (toward the North and South Poles) and negligible at lower latitudes (between 30 degrees N and 30 degrees S). This means that decreases in ozone over Toronto are likely to be greater than those over Boston, and those over Boston greater than those over Los Angeles, while Miami will typically see the least ozone depletion of the four cities. However, cities at lower latitudes generally receive more sunlight because they are nearer the equator, so UV levels are higher even in the absence of ozone depletion. If ozone were to decrease at lower latitudes, southern cities would experience a greater absolute increase in UV-B than cities in the north for the same amount of ozone depletion.
The U.S. Department of Agriculture maintains an extensive network of radiometers to monitor ultraviolet B (UV-B) radiation across the country. The one pictured above is in Beltsville, Maryland. (Photograph by Jeannie Allen)
Oblique angle of sunlight reaching the surface
At any given time, sunlight strikes most of the Earth at an oblique angle. In this way, the number of UV photons is spread over a wider surface area, lowering the amount of incoming radiation at any given spot, compared to its intensity when the sun is directly overhead. In addition, the amount of atmosphere crossed by sunlight is greater at oblique angles than when the sun is directly overhead. Thus, the light travels through more ozone before reaching the Earth’s surface, thereby increasing the amount of UV-B that is absorbed by molecules of ozone and reducing UV-B exposure at the surface.
The three images above illustrate how a change in angle between the sun and the Earth’s surface affect the intensity of sunlight (and UV-B) on the surface. When the sun is directly overhead, forming a 90° angle with the surface, sunlight is spread over the minimum area. Also, the light only has to pass through the atmosphere directly above the surface. An increased angle between the sun and the surface—due to latitude, time of day, and season—spreads the same amount of energy over a wider area, and the sunlight passes through more atmosphere, diffusing the light. Therefore, UV-B radiation is stronger at the equator than the poles, stronger at noon than evening, and stronger in summer than winter. (Illustration by Robert Simmon)
Aerosols
Unlike clouds, aerosols in the troposphere, such as dust and smoke, not only scatter but also absorb UV-B radiation. Usually the UV reduction by aerosols is only a few percent, but in regions of heavy smoke or dust, aerosol particles can absorb more than 50 percent of the radiation.
While the presence of aerosols anywhere in the atmosphere will always scatter some UV radiation back to space, in some circumstances, aerosols can contribute to an increase in UV exposure at the surface. For example, over Antarctica, cold temperatures cause ice particles (Polar Stratospheric Clouds) to form in the stratosphere. The nuclei for these particles are thought to be sulfuric acid aerosol, possibly of volcanic origin. The ice particles provide the surfaces that allow complex chemical reactions to take place in a manner than can deplete stratospheric ozone.
The eruption of Mt. Pinatubo in 1991 injected sulfate aerosols into the stratosphere, significantly though temporarily depleting stratospheric ozone and resulting in an increase of UV-B reaching the Earth’s surface. Over millions of years, the biosphere has evolved to deal with temporary increases in UV from reductions in stratospheric ozone by natural causes such as volcanic eruptions, but has not had the time required to adjust to long-term ozone reductions attributed to human activities of the last 30 years. (Photograph courtesy USGS)
Water Depth
UV-B exposure decreases rapidly at increasing depths in the water column. In other words, water and the impurities in it strongly absorb and scatter incoming UV-B radiation. Some substances that are dissolved in water, such as organic carbon from nearby land, will also absorb UV-B radiation and enhance protection of microorganisms, plants, and animals from UV-B. Different masses of water at different locations contain different amounts of such dissolved substances and other particles, making evaluation of UV damage very difficult.
Ultraviolet B (UV-B) radiation reaches different depths in ocean water depending on water chemistry, the density of phytoplankton, and the presence of sediment and other particulates. The map above indicates the average depth UV-B penetrates into ocean water. At the depth indicated, only 10 percent of the UV-B radiation that was present at the water’s surface remains. The rest was absorbed or scattered back towards the ocean surface. (Image courtesy Vasilkov et al., JGR-Oceans, 2001)
Elevation
Living organisms at high elevations are generally exposed to more solar radiation and with it, more UV-B than organisms at low elevations. This is because at high elevations UV-B radiation travels through less atmosphere before it reaches the ground, and so it has fewer chances of encountering radiation-absorbing aerosols or chemical substances (such as ozone and sulfur dioxide) than it does at lower elevations.
Ecosystems at high altitudes, such as this lake in the Rocky Mountains of Colorado, receive more exposure to ultraviolet radiation than ecosystems at low altitudes. (Photo courtesy Philip Greenspun © 1994)
Reflectivity of the Earth’s Surface
As a highly reflective substance, snow dramatically increases UV-B exposure near the Earth’s surface as it reflects most of the radiation back into the atmosphere, where it is then scattered back toward the surface by aerosols and air molecules. Fresh snow can reflect much as 94 percent of the incoming UV radiation. In contrast, snow-free lands typically reflect only 2-4 percent of UV and ocean surfaces reflect about 5-8 percent (Herman and Celarier 1997).
next: How Much Are We Getting?
back: Effects on the Biosphere
Ultraviolet Radiation
Introduction
Effects on the Biosphere
What Determines UV at the Surface?
How Much Are We Getting?
Predictions and Monitoring
Ref
churchhaze
Well-Known Member
Isn't this thread supposed to be about far-red?
testiclees
Well-Known Member
Apologies.
I inadvertently derailed topic when I questioned "Only a few place in the world will plants actually get uvb outside". Actually the opposite seems to be true
Back on topic:
Would a pair of these 10w 730-740 chips be appropriate to trigger flower initiation (am i understanding correctly?) Or would it be overkill for a 26" x 50" layout? I am interested in an elegant, minimalist engine that i could rig separate from my light bar.
Last edited:
Abiqua
Well-Known Member
Realistically I would attempt just 1x....if the efficiency is up over 20-25% then I don't see much of difference between the LEDEngin that will supposedly cover an 8'x8' space with only 1x "10w" diode [5.7 watts? actual]