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76-678: The summer solstice occurs during the hemisphere's summer . In the Northern Hemisphere , this is the June solstice (20, 21 or 22 June) and in the Southern Hemisphere , this is the December solstice (20, 21, 22 or 23 of December). Since prehistory, the summer solstice has been a significant time of year in many cultures, and has been marked by festivals and rituals. Traditionally, in temperate regions (especially Europe),

152-729: A = 1 2 π − φ b = 1 2 π − δ cos ⁡ ( Θ ) = sin ⁡ ( φ ) sin ⁡ ( δ ) + cos ⁡ ( φ ) cos ⁡ ( δ ) cos ⁡ ( h ) {\displaystyle {\begin{aligned}C&=h\\c&=\Theta \\a&={\tfrac {1}{2}}\pi -\varphi \\b&={\tfrac {1}{2}}\pi -\delta \\\cos(\Theta )&=\sin(\varphi )\sin(\delta )+\cos(\varphi )\cos(\delta )\cos(h)\end{aligned}}} This equation can be also derived from

228-504: A ) sin ⁡ ( b ) cos ⁡ ( C ) {\displaystyle \cos(c)=\cos(a)\cos(b)+\sin(a)\sin(b)\cos(C)} where a , b and c are arc lengths, in radians, of the sides of a spherical triangle. C is the angle in the vertex opposite the side which has arc length c . Applied to the calculation of solar zenith angle Θ , the following applies to the spherical law of cosines: C = h c = Θ

304-481: A clear day. When 1361 W/m is arriving above the atmosphere (when the Sun is at the zenith in a cloudless sky), direct sun is about 1050 W/m , and global radiation on a horizontal surface at ground level is about 1120 W/m . The latter figure includes radiation scattered or reemitted by the atmosphere and surroundings. The actual figure varies with the Sun's angle and atmospheric circumstances. Ignoring clouds,

380-464: A consensus of observations or theory, Q ¯ day {\displaystyle {\overline {Q}}^{\text{day}}} can be calculated for any latitude φ and θ . Because of the elliptical orbit, and as a consequence of Kepler's second law , θ does not progress uniformly with time. Nevertheless, θ  = 0° is exactly the time of the March equinox, θ  = 90°

456-421: A day is the average of Q over one rotation, or the hour angle progressing from h = π to h = −π : Q ¯ day = − 1 2 π ∫ π − π Q d h {\displaystyle {\overline {Q}}^{\text{day}}=-{\frac {1}{2\pi }}{\int _{\pi }^{-\pi }Q\,dh}} Let h 0 be

532-404: A decrease thereafter. PMOD instead presents a steady decrease since 1978. Significant differences can also be seen during the peak of solar cycles 21 and 22. These arise from the fact that ACRIM uses the original TSI results published by the satellite experiment teams while PMOD significantly modifies some results to conform them to specific TSI proxy models. The implications of increasing TSI during

608-407: A deep solar minimum of 2005–2010) to be +0.58 ± 0.15 W/m , +0.60 ± 0.17 W/m and +0.85 W/m . Estimates from space-based measurements range +3–7   W/m . SORCE/TIM's lower TSI value reduces this discrepancy by 1   W/m . This difference between the new lower TIM value and earlier TSI measurements corresponds to a climate forcing of −0.8   W/m , which is comparable to

684-709: A minimum in February and March and a peak in early September. In the North Indian basin, storms are most common from April to December, with peaks in May and November. In the Southern Hemisphere , the tropical cyclone season runs from the start of November until the end of April with peaks in mid-February to early March. Thunderstorm season in the United States and Canada runs in the spring through summer but sometimes can run as late as October or even November in

760-1331: A more general formula: cos ⁡ ( Θ ) = sin ⁡ ( φ ) sin ⁡ ( δ ) cos ⁡ ( β ) + sin ⁡ ( δ ) cos ⁡ ( φ ) sin ⁡ ( β ) cos ⁡ ( γ ) + cos ⁡ ( φ ) cos ⁡ ( δ ) cos ⁡ ( β ) cos ⁡ ( h ) − cos ⁡ ( δ ) sin ⁡ ( φ ) sin ⁡ ( β ) cos ⁡ ( γ ) cos ⁡ ( h ) − cos ⁡ ( δ ) sin ⁡ ( β ) sin ⁡ ( γ ) sin ⁡ ( h ) {\displaystyle {\begin{aligned}\cos(\Theta )=\sin(\varphi )\sin(\delta )\cos(\beta )&+\sin(\delta )\cos(\varphi )\sin(\beta )\cos(\gamma )+\cos(\varphi )\cos(\delta )\cos(\beta )\cos(h)\\&-\cos(\delta )\sin(\varphi )\sin(\beta )\cos(\gamma )\cos(h)-\cos(\delta )\sin(\beta )\sin(\gamma )\sin(h)\end{aligned}}} where β

836-450: A rotating sphere. Insolation is essential for numerical weather prediction and understanding seasons and climatic change . Application to ice ages is known as Milankovitch cycles . Distribution is based on a fundamental identity from spherical trigonometry , the spherical law of cosines : cos ⁡ ( c ) = cos ⁡ ( a ) cos ⁡ ( b ) + sin ⁡ (

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912-809: A season or more is common, reckoning based on astronomical markers is shifted half a season. By this method, in North America, summer is the period from the summer solstice (usually 20 or 21 June in the Northern Hemisphere) to the autumn equinox . Reckoning by cultural festivals, the summer season in the United States is traditionally regarded as beginning on Memorial Day weekend (the last weekend in May) and ending on Labor Day (the first Monday in September), more closely in line with

988-528: A seasonal shift in the prevailing winds , it is known as a monsoon. In the northern Atlantic Ocean, a distinct tropical cyclone season occurs from 1 June to 30 November. The statistical peak of the Atlantic hurricane season is 10 September. The Northeast Pacific Ocean has a broader period of activity, but in a similar timeframe to the Atlantic. The Northwest Pacific sees tropical cyclones year-round, with

1064-415: A solar cell on the surface of the earth facing straight up, and had DNI in units of W/m^2 per nm, graphed as a function of wavelength (in nm). Then, the unit of the integral (W/m^2) is the product of those two units. The SI unit of irradiance is watts per square metre (W/m = Wm ). The unit of insolation often used in the solar power industry is kilowatt hours per square metre (kWh/m ). The Langley

1140-732: A summer vacation in mid-July and resume in the later weeks of September or the first week of October. A wide range of public holidays fall during summer, including: People generally take advantage of the high temperatures by spending more time outdoors during summer. Activities such as travelling to the beach and picnics occur during the summer months. Sports including cricket , association football (soccer), horse racing , basketball , American football , volleyball , skateboarding , baseball , softball , tennis and golf are played. Water sports also occur. These include water skiing , wakeboarding , swimming , surfing , tubing and water polo . The modern Olympics have been held during

1216-401: A surface is largest when the surface directly faces (is normal to) the sun. As the angle between the surface and the Sun moves from normal, the insolation is reduced in proportion to the angle's cosine ; see effect of Sun angle on climate . In the figure, the angle shown is between the ground and the sunbeam rather than between the vertical direction and the sunbeam; hence the sine rather than

1292-879: A time series for a Q ¯ d a y {\displaystyle {\overline {Q}}^{\mathrm {day} }} for a particular time of year, and particular latitude, is a useful application in the theory of Milankovitch cycles. For example, at the summer solstice, the declination δ is equal to the obliquity  ε . The distance from the Sun is R o R E = 1 + e cos ⁡ ( θ − ϖ ) = 1 + e cos ⁡ ( π 2 − ϖ ) = 1 + e sin ⁡ ( ϖ ) {\displaystyle {\frac {R_{o}}{R_{E}}}=1+e\cos(\theta -\varpi )=1+e\cos \left({\frac {\pi }{2}}-\varpi \right)=1+e\sin(\varpi )} For this summer solstice calculation,

1368-1003: Is sin ⁡ ( δ ) = sin ⁡ ( ε ) sin ⁡ ( θ ) {\displaystyle \sin(\delta )=\sin(\varepsilon )\sin(\theta )} . ) The conventional longitude of perihelion ϖ is defined relative to the March equinox, so for the elliptical orbit: R E = R o ( 1 − e 2 ) 1 + e cos ⁡ ( θ − ϖ ) {\displaystyle R_{E}={\frac {R_{o}(1-e^{2})}{1+e\cos(\theta -\varpi )}}} or R o R E = 1 + e cos ⁡ ( θ − ϖ ) 1 − e 2 {\displaystyle {\frac {R_{o}}{R_{E}}}={\frac {1+e\cos(\theta -\varpi )}{1-e^{2}}}} With knowledge of ϖ , ε and e from astrodynamical calculations and S o from

1444-487: Is Midsummer . A variable seasonal lag means that the meteorological centre of the season, which is based on average temperature patterns, occurs several weeks after the time of maximal insolation. The meteorological convention defines summer as comprising the months of June, July, and August in the northern hemisphere and the months of December, January, and February in the southern hemisphere. Under meteorological definitions, all seasons are arbitrarily set to start at

1520-447: Is a number of a day of the year. Total solar irradiance (TSI) changes slowly on decadal and longer timescales. The variation during solar cycle 21 was about 0.1% (peak-to-peak). In contrast to older reconstructions, most recent TSI reconstructions point to an increase of only about 0.05% to 0.1% between the 17th century Maunder Minimum and the present. However, current understanding based on various lines of evidence suggests that

1596-403: Is a primary cause of the higher irradiance values measured by earlier satellites in which the precision aperture is located behind a larger, view-limiting aperture. The TIM uses a view-limiting aperture that is smaller than the precision aperture that precludes this spurious signal. The new estimate is from better measurement rather than a change in solar output. A regression model-based split of

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1672-438: Is absorbed and the remainder reflected. Usually, the absorbed radiation is converted to thermal energy , increasing the object's temperature. Humanmade or natural systems, however, can convert part of the absorbed radiation into another form such as electricity or chemical bonds , as in the case of photovoltaic cells or plants . The proportion of reflected radiation is the object's reflectivity or albedo . Insolation onto

1748-548: Is also used by many people in the United Kingdom and Canada . In Ireland , the summer months according to the national meteorological service, Met Éireann , are June, July and August. By the Irish calendar , summer begins on 1 May ( Beltane ) and ends on 31 July ( Lughnasadh ). Days continue to lengthen from equinox to solstice and summer days progressively shorten after the solstice, so meteorological summer encompasses

1824-480: Is an alternative unit of insolation. One Langley is one thermochemical calorie per square centimetre or 41,840   J/m . The average annual solar radiation arriving at the top of the Earth's atmosphere is about 1361   W/m . This represents the power per unit area of solar irradiance across the spherical surface surrounding the Sun with a radius equal to the distance to the Earth (1   AU ). This means that

1900-916: Is an angle from the horizontal and γ is an azimuth angle . The separation of Earth from the Sun can be denoted R E and the mean distance can be denoted R 0 , approximately 1 astronomical unit (AU). The solar constant is denoted S 0 . The solar flux density (insolation) onto a plane tangent to the sphere of the Earth, but above the bulk of the atmosphere (elevation 100 km or greater) is: Q = { S o R o 2 R E 2 cos ⁡ ( Θ ) cos ⁡ ( Θ ) > 0 0 cos ⁡ ( Θ ) ≤ 0 {\displaystyle Q={\begin{cases}S_{o}{\frac {R_{o}^{2}}{R_{E}^{2}}}\cos(\Theta )&\cos(\Theta )>0\\0&\cos(\Theta )\leq 0\end{cases}}} The average of Q over

1976-504: Is associated with the Christmas and New Year holidays. Many families take extended holidays for two or three weeks or longer during summer. In Australia and New Zealand , summer begins on 1 December and ends on 28 February (29 February in leap years). In Chinese astronomy , summer starts on or around 5 May, with the jiéqì ( solar term ) known as lìxià (立夏), i.e. "establishment of summer". Summer ends around 7 August, with

2052-454: Is called solar irradiation , solar exposure , solar insolation , or insolation . Irradiance may be measured in space or at the Earth's surface after atmospheric absorption and scattering . Irradiance in space is a function of distance from the Sun, the solar cycle , and cross-cycle changes. Irradiance on the Earth's surface additionally depends on the tilt of the measuring surface,

2128-467: Is called ' midsummer '. Traditionally in northern Europe midsummer was reckoned as the night of 23–24 June, with summer beginning on May Day . The summer solstice continues to be seen as the middle of summer in many European cultures, but in some cultures or calendars it is seen as summer's beginning. In Sweden , midsummer is one of the year's major holidays when the country closes down as much as during Christmas. The following tables contain information on

2204-680: Is exactly the time of the June solstice, θ  = 180° is exactly the time of the September equinox and θ  = 270° is exactly the time of the December solstice. A simplified equation for irradiance on a given day is: Q ≈ S 0 ( 1 + 0.034 cos ⁡ ( 2 π n 365.25 ) ) {\displaystyle Q\approx S_{0}\left(1+0.034\cos \left(2\pi {\frac {n}{365.25}}\right)\right)} where n

2280-2450: Is nearly constant over the course of a day, and can be taken outside the integral ∫ π − π Q d h = ∫ h o − h o Q d h = S o R o 2 R E 2 ∫ h o − h o cos ⁡ ( Θ ) d h = S o R o 2 R E 2 [ h sin ⁡ ( φ ) sin ⁡ ( δ ) + cos ⁡ ( φ ) cos ⁡ ( δ ) sin ⁡ ( h ) ] h = h o h = − h o = − 2 S o R o 2 R E 2 [ h o sin ⁡ ( φ ) sin ⁡ ( δ ) + cos ⁡ ( φ ) cos ⁡ ( δ ) sin ⁡ ( h o ) ] {\displaystyle {\begin{aligned}\int _{\pi }^{-\pi }Q\,dh&=\int _{h_{o}}^{-h_{o}}Q\,dh\\[5pt]&=S_{o}{\frac {R_{o}^{2}}{R_{E}^{2}}}\int _{h_{o}}^{-h_{o}}\cos(\Theta )\,dh\\[5pt]&=S_{o}{\frac {R_{o}^{2}}{R_{E}^{2}}}{\Bigg [}h\sin(\varphi )\sin(\delta )+\cos(\varphi )\cos(\delta )\sin(h){\Bigg ]}_{h=h_{o}}^{h=-h_{o}}\\[5pt]&=-2S_{o}{\frac {R_{o}^{2}}{R_{E}^{2}}}\left[h_{o}\sin(\varphi )\sin(\delta )+\cos(\varphi )\cos(\delta )\sin(h_{o})\right]\end{aligned}}} Therefore: Q ¯ day = S o π R o 2 R E 2 [ h o sin ⁡ ( φ ) sin ⁡ ( δ ) + cos ⁡ ( φ ) cos ⁡ ( δ ) sin ⁡ ( h o ) ] {\displaystyle {\overline {Q}}^{\text{day}}={\frac {S_{o}}{\pi }}{\frac {R_{o}^{2}}{R_{E}^{2}}}\left[h_{o}\sin(\varphi )\sin(\delta )+\cos(\varphi )\cos(\delta )\sin(h_{o})\right]} Let θ be

2356-593: Is the power per unit area ( surface power density ) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Solar irradiance is measured in watts per square metre (W/m ) in SI units . Solar irradiance is often integrated over a given time period in order to report the radiant energy emitted into the surrounding environment ( joule per square metre, J/m ) during that time period. This integrated solar irradiance

Summer solstice - Misplaced Pages Continue

2432-524: The Middle English somer , via the Old English sumor . From an astronomical view, the equinoxes and solstices would be the middle of the respective seasons, but sometimes astronomical summer is defined as starting at the solstice, the time of maximal insolation , often identified with 21 June or 21 December. By solar reckoning, summer instead starts on May Day and the summer solstice

2508-404: The fall . These storms can produce hail , strong winds and tornadoes , usually during the afternoon and evening. Schools and universities typically have a summer break to take advantage of the warmer weather and longer days. In almost all countries, children are out of school during this time of year for summer break , although dates vary. Many families will take holidays for a week or two over

2584-472: The signal-to-noise ratio , respectively. The net effect of these corrections decreased the average ACRIM3 TSI value without affecting the trending in the ACRIM Composite TSI. Differences between ACRIM and PMOD TSI composites are evident, but the most significant is the solar minimum-to-minimum trends during solar cycles 21 - 23 . ACRIM found an increase of +0.037%/decade from 1980 to 2000 and

2660-631: The ACRIM III data that is nearly in phase with the Sun-Earth distance and 90-day spikes in the VIRGO data coincident with SoHO spacecraft maneuvers that were most apparent during the 2008 solar minimum. TIM's high absolute accuracy creates new opportunities for measuring climate variables. TSI Radiometer Facility (TRF) is a cryogenic radiometer that operates in a vacuum with controlled light sources. L-1 Standards and Technology (LASP) designed and built

2736-1040: The Earth Radiometer Budget Experiment (ERBE) on the Earth Radiation Budget Satellite (ERBS), VIRGO on the Solar Heliospheric Observatory (SoHO) and the ACRIM instruments on the Solar Maximum Mission (SMM), Upper Atmosphere Research Satellite (UARS) and ACRIMSAT . Pre-launch ground calibrations relied on component rather than system-level measurements since irradiance standards at the time lacked sufficient absolute accuracies. Measurement stability involves exposing different radiometer cavities to different accumulations of solar radiation to quantify exposure-dependent degradation effects. These effects are then compensated for in

2812-463: The Earth moving between its perihelion and aphelion , or changes in the latitudinal distribution of radiation. These orbital changes or Milankovitch cycles have caused radiance variations of as much as 25% (locally; global average changes are much smaller) over long periods. The most recent significant event was an axial tilt of 24° during boreal summer near the Holocene climatic optimum . Obtaining

2888-723: The Southern Hemisphere, school summer holiday dates include the major holidays of Christmas and New Year's Day . School summer holidays in Australia, New Zealand and South Africa begin in early December and end in early February, with dates varying between states. In South Africa, the new school year usually starts during the second week of January, thus aligning the academic year with the Calendar year . In India , school ends in late April and resumes in early or mid-June. In Cameroon and Nigeria , schools usually start

2964-473: The TRF in both optical power and irradiance. The resulting high accuracy reduces the consequences of any future gap in the solar irradiance record. The most probable value of TSI representative of solar minimum is 1 360 .9 ± 0.5 W/m , lower than the earlier accepted value of 1 365 .4 ± 1.3 W/m , established in the 1990s. The new value came from SORCE/TIM and radiometric laboratory tests. Scattered light

3040-646: The TSI record is not sufficiently stable to discern solar changes on decadal time scales. Only the ACRIM composite shows irradiance increasing by ~1   W/m  between 1986 and 1996; this change is also absent in the model. Recommendations to resolve the instrument discrepancies include validating optical measurement accuracy by comparing ground-based instruments to laboratory references, such as those at National Institute of Science and Technology (NIST); NIST validation of aperture area calibrations uses spares from each instrument; and applying diffraction corrections from

3116-416: The above irradiances (e.g. spectral TSI , spectral DNI , etc.) are any of the above with units divided either by meter or nanometer (for a spectral graph as function of wavelength), or per- Hz (for a spectral function with an x-axis of frequency). When one plots such spectral distributions as a graph, the integral of the function (area under the curve) will be the (non-spectral) irradiance. e.g.: Say one had

Summer solstice - Misplaced Pages Continue

3192-409: The approximately circular disc of the Earth, as viewed from the Sun, receives a roughly stable 1361   W/m at all times. The area of this circular disc is π r , in which r is the radius of the Earth. Because the Earth is approximately spherical , it has total area 4 π r 2 {\displaystyle 4\pi r^{2}} , meaning that the solar radiation arriving at

3268-404: The beginning of a calendar month and end at the end of a month. This meteorological definition of summer also aligns with the commonly viewed notion of summer as the season with the longest (and warmest) days of the year, in which daylight predominates. The meteorological reckoning of seasons is used in countries including Australia , New Zealand , Austria , Denmark , Russia and Japan . It

3344-404: The build-up to the longest day and a diminishing thereafter, with summer having many more hours of daylight than spring. Reckoning by hours of daylight alone, summer solstice marks the midpoint, not the beginning, of the seasons. Midsummer takes place over the shortest night of the year, which is the summer solstice, or on a nearby date that varies with tradition. Where a seasonal lag of half

3420-442: The cavity, electronic degradation of the heater, surface degradation of the precision aperture and varying surface emissions and temperatures that alter thermal backgrounds. These calibrations require compensation to preserve consistent measurements. For various reasons, the sources do not always agree. The Solar Radiation and Climate Experiment/Total Irradiance Measurement ( SORCE /TIM) TSI values are lower than prior measurements by

3496-407: The cavity. This design admits into the front part of the instrument two to three times the amount of light intended to be measured; if not completely absorbed or scattered, this additional light produces erroneously high signals. In contrast, TIM's design places the precision aperture at the front so that only desired light enters. Variations from other sources likely include an annual systematics in

3572-451: The conventional polar angle describing a planetary orbit . Let θ  = 0 at the March equinox . The declination δ as a function of orbital position is δ = ε sin ⁡ ( θ ) {\displaystyle \delta =\varepsilon \sin(\theta )} where ε is the obliquity . (Note: The correct formula, valid for any axial tilt,

3648-426: The daily average insolation for the Earth is approximately 6 kWh/m = 21.6 MJ/m . The output of, for example, a photovoltaic panel, partly depends on the angle of the sun relative to the panel. One Sun is a unit of power flux , not a standard value for actual insolation. Sometimes this unit is referred to as a Sol, not to be confused with a sol , meaning one solar day . Part of the radiation reaching an object

3724-625: The dates of earliest sunrise and latest sunset vary by a few days. This is because Earth orbits the Sun in an ellipse, and its orbital speed varies slightly during the year. There is evidence that the summer solstice has been culturally important since the Neolithic era. Many ancient monuments in Europe especially, as well as parts of the Middle East, Asia and the Americas, are aligned with

3800-499: The electrical heating needed to maintain an absorptive blackened cavity in thermal equilibrium with the incident sunlight which passes through a precision aperture of calibrated area. The aperture is modulated via a shutter . Accuracy uncertainties of < 0.01% are required to detect long term solar irradiance variations, because expected changes are in the range 0.05–0.15   W/m per century. In orbit, radiometric calibrations drift for reasons including solar degradation of

3876-409: The energy imbalance. In 2014 a new ACRIM composite was developed using the updated ACRIM3 record. It added corrections for scattering and diffraction revealed during recent testing at TRF and two algorithm updates. The algorithm updates more accurately account for instrument thermal behavior and parsing of shutter cycle data. These corrected a component of the quasi-annual spurious signal and increased

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3952-623: The equator towards the North Pole in the Northern Hemisphere in June (around the summer solstice there), but decreases towards the South Pole in the Southern Hemisphere at the time of the southern winter solstice. Summer Summer or summertime is the hottest and brightest of the four temperate seasons , occurring after spring and before autumn . At or centred on the summer solstice , daylight hours are

4028-453: The final data. Observation overlaps permits corrections for both absolute offsets and validation of instrumental drifts. Uncertainties of individual observations exceed irradiance variability (~0.1%). Thus, instrument stability and measurement continuity are relied upon to compute real variations. Long-term radiometer drifts can potentially be mistaken for irradiance variations which can be misinterpreted as affecting climate. Examples include

4104-533: The global warming of the last two decades of the 20th century are that solar forcing may be a marginally larger factor in climate change than represented in the CMIP5 general circulation climate models . Average annual solar radiation arriving at the top of the Earth's atmosphere is roughly 1361   W/m . The Sun's rays are attenuated as they pass through the atmosphere , leaving maximum normal surface irradiance at approximately 1000   W/m at sea level on

4180-528: The height of the Sun above the horizon, and atmospheric conditions. Solar irradiance affects plant metabolism and animal behavior. The study and measurement of solar irradiance have several important applications, including the prediction of energy generation from solar power plants , the heating and cooling loads of buildings, climate modeling and weather forecasting, passive daytime radiative cooling applications, and space travel. There are several measured types of solar irradiance. Spectral versions of

4256-844: The hour angle when Q becomes positive. This could occur at sunrise when Θ = 1 2 π {\displaystyle \Theta ={\tfrac {1}{2}}\pi } , or for h 0 as a solution of sin ⁡ ( φ ) sin ⁡ ( δ ) + cos ⁡ ( φ ) cos ⁡ ( δ ) cos ⁡ ( h o ) = 0 {\displaystyle \sin(\varphi )\sin(\delta )+\cos(\varphi )\cos(\delta )\cos(h_{o})=0} or cos ⁡ ( h o ) = − tan ⁡ ( φ ) tan ⁡ ( δ ) {\displaystyle \cos(h_{o})=-\tan(\varphi )\tan(\delta )} If tan( φ ) tan( δ ) > 1 , then

4332-574: The issue of the irradiance increase between cycle minima in 1986 and 1996, evident only in the ACRIM composite (and not the model) and the low irradiance levels in the PMOD composite during the 2008 minimum. Despite the fact that ACRIM I, ACRIM II, ACRIM III, VIRGO and TIM all track degradation with redundant cavities, notable and unexplained differences remain in irradiance and the modeled influences of sunspots and faculae . Disagreement among overlapping observations indicates unresolved drifts that suggest

4408-467: The last day of February. Summer is traditionally associated with hot or warm weather. In Mediterranean climates , it is also associated with dry weather, while in other places (particularly in Eastern Asia because of the monsoon) it is associated with rainy weather. The wet season is the main period of vegetation growth within the savanna climate regime. Where the wet season is associated with

4484-550: The length of the day on 20 June 2016, close to the summer solstice of the Northern Hemisphere and winter solstice of the Southern Hemisphere . The data was collected from the website of the Finnish Meteorological Institute as well as from certain other websites. The data is arranged geographically and within the tables from the longest day to the shortest one. Times that occur the next day (21 June) are marked with . The length of day increases from

4560-448: The longest and darkness hours are the shortest, with day length decreasing as the season progresses after the solstice. The earliest sunrises and latest sunsets also occur near the date of the solstice. The date of the beginning of summer varies according to climate , tradition, and culture. When it is summer in the Northern Hemisphere , it is winter in the Southern Hemisphere , and vice versa. The modern English summer derives from

4636-508: The lower values for the secular trend are more probable. In particular, a secular trend greater than 2 Wm is considered highly unlikely. Ultraviolet irradiance (EUV) varies by approximately 1.5 percent from solar maxima to minima, for 200 to 300 nm wavelengths. However, a proxy study estimated that UV has increased by 3.0% since the Maunder Minimum. Some variations in insolation are not due to solar changes but rather due to

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4712-423: The meteorological definition for the parts of the country that have four-season weather. The similar Canadian tradition starts summer on Victoria Day one week prior (although summer conditions vary widely across Canada's expansive territory) and ends, as in the United States, on Labour Day . In some Southern Hemisphere countries such as Brazil , Argentina , South Africa , Australia and New Zealand , summer

4788-630: The reference radiometer and the instrument under test in a common vacuum system that contains a stationary, spatially uniform illuminating beam. A precision aperture with an area calibrated to 0.0031% (1 σ ) determines the beam's measured portion. The test instrument's precision aperture is positioned in the same location, without optically altering the beam, for direct comparison to the reference. Variable beam power provides linearity diagnostics, and variable beam diameter diagnoses scattering from different instrument components. The Glory/TIM and PICARD/PREMOS flight instrument absolute scales are now traceable to

4864-497: The relative proportion of sunspot and facular influences from SORCE/TIM data accounts for 92% of observed variance and tracks the observed trends to within TIM's stability band. This agreement provides further evidence that TSI variations are primarily due to solar surface magnetic activity. Instrument inaccuracies add a significant uncertainty in determining Earth's energy balance . The energy imbalance has been variously measured (during

4940-660: The role of the elliptical orbit is entirely contained within the important product e sin ⁡ ( ϖ ) {\displaystyle e\sin(\varpi )} , the precession index, whose variation dominates the variations in insolation at 65°   N when eccentricity is large. For the next 100,000 years, with variations in eccentricity being relatively small, variations in obliquity dominate. The space-based TSI record comprises measurements from more than ten radiometers and spans three solar cycles. All modern TSI satellite instruments employ active cavity electrical substitution radiometry . This technique measures

5016-477: The solar term of lìqiū (立秋, "establishment of autumn"). In southern and southeast Asia, where the monsoon occurs, summer is more generally defined as lasting from March, April, May and June, the warmest time of the year, ending with the onset of the monsoon rains . Because the temperature lag is shorter in the oceanic temperate southern hemisphere, most countries in this region use the meteorological definition with summer starting on 1 December and ending on

5092-480: The summer holiday begins in late June and ends in mid-to-late August. Similarly, in Canada the summer holiday starts on the last or second-last Friday in June and ends in late August or on the first Tuesday of September, with the exception of when that date falls before Labour Day , in which case, ends on the second Tuesday of the month. In Russia , the summer holiday begins at the end of May and ends on 31 August. In

5168-527: The summer months every four years since 1896. The 2000 Summer Olympics , in Sydney , were held in spring and the 2016 Summer Olympics , in Rio de Janeiro , were held in winter . In the United States, many television shows made for children are released during the summer, as children are off school. Conversely, the music and film industries generally experience higher returns during the summer than other times of

5244-409: The summer solstice is seen as the middle of summer and referred to as midsummer ; although today in some countries and calendars it is seen as the beginning of summer. On the summer solstice, Earth's maximum axial tilt toward the Sun is 23.44°. Likewise, the Sun's declination from the celestial equator is 23.44°. Although the summer solstice is the longest day of the year for that hemisphere,

5320-597: The summer, particularly in Southern Hemisphere Western countries with statutory Christmas and New Year holidays. In the United States, public schools usually end in late May in Memorial Day weekend, while colleges finish in early May. Public school traditionally resumes near Labor Day, while higher institutions often resume in mid-August. In England and Wales , school ends in mid-July and resumes again in early September. In Scotland ,

5396-392: The sun does not set and the sun is already risen at h = π , so h o = π . If tan( φ ) tan( δ ) < −1 , the sun does not rise and Q ¯ day = 0 {\displaystyle {\overline {Q}}^{\text{day}}=0} . R o 2 R E 2 {\displaystyle {\frac {R_{o}^{2}}{R_{E}^{2}}}}

5472-472: The sunrise or sunset on the summer solstice (see archaeoastronomy ). The significance of the summer solstice has varied among cultures, but most recognize the event in some way with holidays , festivals , and rituals around that time with themes of fertility. In the Roman Empire , the traditional date of the summer solstice was 24 June. In Germanic-speaking cultures, the time around the summer solstice

5548-625: The system, completed in 2008. It was calibrated for optical power against the NIST Primary Optical Watt Radiometer, a cryogenic radiometer that maintains the NIST radiant power scale to an uncertainty of 0.02% (1 σ ). As of 2011 TRF was the only facility that approached the desired <0.01% uncertainty for pre-launch validation of solar radiometers measuring irradiance (rather than merely optical power) at solar power levels and under vacuum conditions. TRF encloses both

5624-468: The top of the atmosphere, averaged over the entire surface of the Earth, is simply divided by four to get 340   W/m . In other words, averaged over the year and the day, the Earth's atmosphere receives 340   W/m from the Sun. This figure is important in radiative forcing . The distribution of solar radiation at the top of the atmosphere is determined by Earth's sphericity and orbital parameters. This applies to any unidirectional beam incident to

5700-471: The view-limiting aperture. For ACRIM, NIST determined that diffraction from the view-limiting aperture contributes a 0.13% signal not accounted for in the three ACRIM instruments. This correction lowers the reported ACRIM values, bringing ACRIM closer to TIM. In ACRIM and all other instruments but TIM, the aperture is deep inside the instrument, with a larger view-limiting aperture at the front. Depending on edge imperfections this can directly scatter light into

5776-514: The year and market their summer hits accordingly. Summer is popular for animated movies to be released theatrically in movie theaters . With many schools closed, especially in Western countries, travel and vacationing tend to peak during the summer. Teenagers and university students often take summer jobs , and business activity for the recreation, tourism, restaurant, and retail industries reach their peak. Insolation Solar irradiance

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