Hi Everybody!!
As we are heading to the finish line for 2013, most of us in North America are experiencing Winter Weather Conditions. Here in South Texas, I am not in severe cold and I have fake snow (thanks Awesome Auto). I have created clouds by the geoengineers that have given me rain for the fall/winter season with the named winter storms. But. the most exciting winter aspect for me is the winter migration of birds. New birds are arriving daily and will be making a Blog appearance next year! A few surprises are coming your way for the rest of this year. Stay tuned in and Enjoy!

P.S.-Thank all of You for your visits and comments and plus 1s. I look forward to a New Year of learning something new everyday on Google!

https://en.wikipedia.org/wiki/Winter_solstice

Winter solstice

From Wikipedia, the free encyclopedia

Winter solstice
Lawrence Hall of Science visitors observe sunset on the day of the winter solstice using the Sunstones II
Also called	Midwinter, Yule, the Longest Night
Observed by	Various cultures, ancient and modern
Type	Cultural, seasonal, astronomical
Significance	Astronomically marks the beginning of shortening nights and lengthening days
Celebrations	Festivals, spending time with loved ones, feasting, singing, dancing, fires
Date	Between December 21 and December 22 (NH) Between June 20 and June 21 (SH)
Frequency	annual
Related to	Winter festivals and the solstice

Winter solstice is an astronomical phenomenon which for the Northern Hemisphereoccurs in December and which for the Southern Hemisphere occurs in June.

For the Northern Hemisphere, the moment of winter solstice is when the sun's elevation with respect to the North Pole is at its most negative value since the previous December. (The elevation with respect to the South Pole is at its greatest since the previous December). The hemisphere has its longest night and shortest day around the moment of solstice with the night within the Arctic being 24 hours long.

Analogous remarks hold for the Southern Hemisphere. Thus, for the Southern Hemisphere, at the moment of its winter solstice in June, the sun is at its greatest height as observed from the North Pole.^[1]^[2]

Depending on one's position on the globe, the December solstice usually occurs on the 21st and the 22nd and the June solstice usually occurs on June the 20th or 21st. However, it is sometimes possible for a solstice to coincide with three different dates. Thus the December 2016 solstice coincides with 20th of the month in American Samoa, with the 21st in London and with the 22nd at Kiritimati.

The axial tilt of Earth and gyroscopic effects of the planet's daily rotation keep the axis of rotation pointed at the same point in the sky. As the Earth follows its orbit around the Sun, the same hemisphere that faced away from the Sun, experiencing winter, will, in half a year, face towards the Sun and experience summer. Since the two hemispheres face opposite directions along the planetary pole, as one polar hemisphere experiences winter, the other experiences summer.

More evident from high latitudes, a hemisphere's winter solstice occurs on the shortest day and longest night of the year, when the sun's daily maximum elevation in the sky is the lowest.^[3] The winter solstice itself lasts only a moment in time, so other terms are used for the day on which it occurs, such as "midwinter", or "the shortest day". For the same reason, it should not be confused with "the first day of winter" or "the start of winter" (Lidong in the East Asian calendars). The seasonal significance of the winter solstice is in the reversal of the gradual lengthening of nights and shortening of days. The earliest sunset and latest sunrise dates differ from winter solstice, however, and these depend on latitude, due to the variation in the solar day throughout the year caused by the Earth's elliptical orbit (see earliest and latest sunrise and sunset).

Worldwide, interpretation of the event has varied from culture to culture, but many cultures have held a recognition of rebirth, involving holidays, festivals, gatherings, rituals or other celebrations around that time.^[4]

History and cultural significance[edit]

Japanese Sun goddess Amaterasuemerging from a cave.

The solstice itself may have been a special moment of the annual cycle of the year even during neolithic times. Astronomical events, which during ancient times controlled the mating of animals, sowing of crops and metering of winter reserves between harvests, show how various cultural mythologies and traditions have arisen. This is attested by physical remains in the layouts of late Neolithic and Bronze Age archaeological sites, such as Stonehenge in Britain and Newgrange in Ireland. The primary axes of both of these monuments seem to have been carefully aligned on a sight-line pointing to the winter solstice sunrise (Newgrange) and the winter solstice sunset (Stonehenge). Significant in respect of Stonehenge is the fact that the Great Trilithon was erected outwards from the centre of the monument, i.e., its smooth flat face was turned towards the midwinter Sun.^[5]

Neolithic site ofGoseck circle. The yellow lines are the direction the Sunrises and sets at winter solstice.

The winter solstice may have been immensely important because communities were not certain of living through the winter, and had to be prepared during the previous nine months. Starvation was common during the first months of the winter, January to April (northern hemisphere) or July to October (southern hemisphere), also known as "the famine months". In temperate climates, the midwinter festival was the last feast celebration, before deep winter began. Most cattle were slaughtered so they would not have to be fed during the winter, so it was almost the only time of year when a supply of fresh meat was available. The majority of wine and beer made during the year was finally fermented and ready for drinking at this time. The concentration of the observances were not always on the day commencing at midnight or at dawn, but the beginning of the pre-Romanized day, which falls on the previous eve.^[6]

Since the event is seen as the reversal of the Sun's ebbing presence in the sky, concepts of the birth or rebirth of sun gods have been common and, in cultures using winter solstice based cyclic calendars, the year as reborn has been celebrated with regard to life-death-rebirth deities or new beginnings such as Hogmanay's redding, a New Year cleaning tradition. Also reversal is yet another usual theme as in Saturnalia's slave and master reversals.

Insolation

From Wikipedia, the free encyclopedia

Insolation (short for incident or incoming solar radiation) is a measure ofsolar radiation energy received on a given surface area and recorded during a given time. It is also called solar irradiation and expressed as "hourly irradiation" if recorded during an hour or "daily irradiation" if recorded during a day. The unit recommended by the World Meteorological Organization is megajoules per square metre (MJ/m²) or joules per square millimetre (J/mm²).^[1] An alternate unit of measure is the Langley (1 thermochemical calorie per square centimeter or 41,840 J/m²). Practitioners in the business of solar energy may use the unit watt-hours per square metre (Wh/m²). If this energy is divided by the recording time in hours, it is then a density of power called irradiance, expressed in watts per square metre (W/m²).

Annual mean insolation at the top of Earth's atmosphere(top) and at the planet's surface

Absorption and reflection[edit]

The object or surface that solar radiation strikes may be a planet, a terrestrial object inside the atmosphere of a planet, or an object exposed to solar rays outside of an atmosphere, such as spacecraft. Some of the radiation will be absorbed and the remainder reflected. Usually the absorbed solar radiation is converted to thermal energy, causing an increase in the object's temperature. Manmade or natural systems, however, may convert a portion of the absorbed radiation into another form, as in the case of photovoltaic cells or plants. The proportion of radiation reflected or absorbed depends on the object's reflectivity or albedo.

Projection effect[edit]

The insolation into a surface is largest when the surface directly faces the Sun. As the angle increases between the direction at a right angle to the surface and the direction of the rays of sunlight, the insolation is reduced in proportion to the cosine of the angle; see effect of sun angle on climate.

US annual average solar energy received by a latitude tilt photovoltaic cell(modeled)

Average insolation in Europe; also seeInsolation map of Europe and Africa for freer-licence map.

Direct insolation is the solar irradiance measured at a given location on Earth with a surface element perpendicular to the Sun's rays, excluding diffuse insolation (the solar radiation that is scattered or reflected by atmospheric components in the sky). Direct insolation is equal to the solar constant minus the atmospheric losses due to absorptionand scattering. While the solar constant varies with the Earth-Sun distance and solar cycles, the losses depend on the time of day (length of light's path through the atmosphere depending on the Solar elevation angle), cloud cover, moisture content, and otherimpurities. Insolation is a fundamental abiotic factor^[2] affecting the metabolism of plants and the behavior of animals.

The theory for the distribution of solar radiation at the top of the atmosphere concerns how the solar irradiance (the power of solar radiation per unit area) at the top of the atmosphere is determined by the sphericity and orbital parameters of Earth. The theory could be applied to any monodirectional beam of radiation incident onto a rotating sphere, but is most usually applied to sunlight, and in particular for application in numerical weather prediction, and theory for the seasons and the ice ages. The last application is known asMilankovitch cycles.

(Please see above link for complete page in Wikipedia)

The Sun refuses to be behind a solar cloud cover as it breaks on through to Shine!

...this is brendasue signing off from Rainbow Creek. See You next time!