“Solar Radiation and its Effects on Planet Earth” The Sun emits a tremendous amount of energy, in the form of electromagnetic radiation, into space. If we could somehow build a gigantic ball around the Sun that completely enclosed it, and lined that ball with perfectly efficient photovoltaic solar panels, we could capture all of that energy and convert it to electricity and be set in terms of Earth’s energy needs for a very long time. Lacking such a fanciful sphere, most of the Sun’s energy flows out of our solar system into interstellar space without ever colliding with anything.However, a very small fraction of that energy collides with planets, including our humble Earth, before it can escape into the interstellar void.
The fraction of a fraction that Earth intercepts is sufficient to warm our planet and drive its climate system. The Sun is the star located at the center of our planetary system. It is composed mainly of hydrogen and helium. In the Sun’s interior, a thermonuclear fusion reaction converts the hydrogen into helium releasing huge amounts of energy.The energy created by the fusion reaction is converted into thermal energy (heat) and raises the temperature of the Sun to levels that are about twenty times larger that of the Earth’s surface. The solar heat energy travels through space in the form of electromagnetic waves enabling the transfer of heat through a process known as radiation (Stickler 1).
The energy that drives the climate system comes from the Sun in the form of solar flares and radiation. The Sun frequently spews plumes of energy, essentially bursts of solar wind. These solar flares contain Gamma rays and X-rays, plus energized particles (protons and electrons).
Energy equal to a billion megatons of TNT is released in a matter of minutes. Flare activity picks up as sunspots (cool areas appearing as dark spots on the sun) increase (Brit 1). When the Sun’s energy reaches the Earth it is partially absorbed in different parts of the climate system. The absorbed energy is converted back to heat, which causes the Earth to warm up and makes it habitable.
Solar radiation absorption is uneven in both space and time and this gives rise to the intricate pattern and seasonal variation of our climate.To understand the complex patterns of Earth’s radiative heating one must examine the relationship between solar radiation and the Earth’s temperature and study the role of the atmosphere and its constituents in that interaction to develop an understanding of the topics such as the “seasonal cycle” and the “greenhouse effect” (Kushnir 1). If the axis of Earth was perpendicular to the plane of its orbit (and the direction of incoming rays of sunlight), then the radiative energy flux would drop as the cosine of latitude as we move from equator to pole.However, the Earth axis tilts at an angle of 23. 5° with respect to its plane of orbit, pointing towards a fix point in space as it travels around the sun. Once a year, on the Summer Solstice (on or about the 21st of June), the North Pole points directly towards the Sun and the South Pole is entirely hidden from the incoming radiation. Half a year from that day, on the Winter Solstice (on or about the 21st of December) the North Pole points away from the Sun and does not receive any sunlight while the South Pole receives 24 hours of continued sunlight.
During Solstices, incoming radiation is perpendicular to the Earth surface on either the latitude of Cancer or the latitude of Capricorn, 23. 5° north or south of the equator, depending on whether it is summer or winter in the Northern Hemisphere, respectively (Kushnir 1). During the spring and fall (on the Equinox days, the 21st of March and 23rd of September) the Earth’s axis tilts in parallel to the Sun and both Polar Regions get the same amount of light.
At that time the radiation is largest at the true equator. Averaged over a full 24-hour period, the amount of incoming radiation varies with latitude and season.At the poles, during solstice, the earth is either exposed to sunlight over the entire (24-hours) day or is completely hidden from the Sun throughout the entire day. This is why the poles get no incoming radiation during their respective winter or more than the maximum radiation at the equator during their respective summer (Pidwirny 1). By absorbing the incoming solar radiation, the Earth warms up, like a black body (a hypothetical body that absorbs without reflection the entire electromagnetic radiation incident on its surface) and its temperature rises.
If the Earth would have had no atmosphere or ocean, as is the case for example on the moon, it would get very warm on the sunlit face of the planet and much colder than we experience presently, on the dark side (the little warmth on the dark side would come from the limited amount of heat stored in the ground from the previous daytime – this is, to some extent, what we experience in a cloud-free, land locked desert climate) (Kushnir 1). The Goldilocks Principle can be summed up neatly as “Venus is too hot, Mars is too cold, and Earth is just right. The fact that Earth has an average surface temperature comfortably between the boiling point and freezing point of water, and thus is suitable for our sort of life, cannot be explained by simply suggesting that our planet orbits at just the right distance from the sun to absorb just the right amount of solar radiation. Our moderate temperatures are also the result of having just the right kind of atmosphere.
A Venus-type atmosphere would produce hellish, Venus-like conditions on our planet; a Mars atmosphere would leave us shivering in a Martian-type deep freeze.Instead, parts of our atmosphere act as an insulating blanket of just the right thickness, trapping sufficient solar energy to keep the global average temperature in a pleasant range. The Martian blanket is too thin, and the Venusian blanket is way too thick. The ‘blanket’ here is a collection of atmospheric gases called ‘greenhouse gases’ based on the idea that the gases also ‘trap’ heat like the glass walls of a greenhouse do. These gases, mainly water vapor (), carbon dioxide (), methane (), and nitrous oxide (), all act as effective global insulators (Comet 1).
Carbon dioxide consists of one carbon atom with an oxygen atom bonded to each side. When its atoms are bonded tightly together, the carbon dioxide molecule can absorb infrared radiation and the molecule starts to vibrate. Eventually, the vibrating molecule will emit the radiation again, and it will likely be absorbed by yet another greenhouse gas molecule. This absorption-emission-absorption cycle serves to keep the heat near the surface, effectively insulating the surface from the cold of space (Kushnir 1).In the atmospheric greenhouse effect, the type of surface that sunlight first encounters is the most important factor.
Forests, grasslands, ocean surfaces, ice caps, deserts, and cities all absorb, reflect, and radiate radiation differently. Sunlight falling on a white glacier surface strongly reflects back into space, resulting in minimal heating of the surface and lower atmosphere. Sunlight falling on a dark desert soil is strongly absorbed, on the other hand, and contributes to significant heating of the surface and lower atmosphere.Cloud cover also affects greenhouse warming by both reducing the amount of solar radiation reaching the earth’s surface and by reducing the amount of radiation energy emitted into space. Scientists use the term albedo to define the percentage of solar energy reflected back by a surface.
Understanding local, regional, and global albedo effects is critical to predicting global climate change (Kushnir 2). While solar radiation does possess the possibility of being quite devastating it is one of the driving forces that allows planet Earth to exist in its current habitable state.Having a good understanding of how it affects our planet is a great way to keep a watchful eye over changes that can drastically affect the quality of life we have in our environment.Bibliography Brirt, Rob. “Solar Data Shee. t” http://www. ucar.
edu/learn/1_3_1. htm. Kuahnie, Yochanan. “Solar Radiation and the Earth’s Energy. ”