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87-509: A cloud forest , also called a water forest , primas forest , or tropical montane cloud forest , is a generally tropical or subtropical , evergreen, montane , moist forest characterized by a persistent, frequent or seasonal low-level cloud cover, usually at the canopy level, formally described in the International Cloud Atlas (2017) as silvagenitus . Cloud forests often exhibit an abundance of mosses covering

174-729: 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

261-504: 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

348-599: A 35-metre (115 ft)-high artificial mountain clad in epiphytes such as orchids , ferns, clubmosses , bromeliads and others. Due to a relatively mild climate and summer fog, the San Francisco Botanical Garden has three outdoor cloud forest collections, including a 2-acre Mesoamerican Cloud Forest established in 1985. The Buffalo and Erie County Botanical Gardens contains a " Panama Cloud Forest" garden in House 11. Tropical Due to

435-511: A break in rainfall during mid-season when the Intertropical Convergence Zone or monsoon trough moves poleward of their location during the middle of the warm season; Typical vegetation in these areas ranges from moist seasonal tropical forests to savannahs . When the wet season occurs during the warm season, or summer , precipitation falls mainly during the late afternoon and early evening hours. The wet season

522-481: 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,

609-464: 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°

696-421: 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

783-404: 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

870-407: 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

957-477: A large proportion of loss in TCF cover is still occurring despite formal protection. Although far from being universally accepted as true cloud forests, several forests in temperate regions have strong similarities with tropical cloud forests. The term is further confused by occasional reference to cloud forests in tropical countries as "temperate" due to the cooler climate associated with these misty forests. In 1970,

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1044-476: A moderately dense canopy and a forest floor of feathermosses , including Hylocomium splendens , Pleurozium schreberi , and Ptilium crista-castrensis . These weft-form mosses grow in boreal moss forests. The presence of cloud forests is dependent on local climate (which is affected by the distance to the sea), the exposition and the latitude (typically from 25°N to 25°S), and the elevation (which varies from 500 m to 4000 m above sea level). Typically, there

1131-1331: 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

1218-403: A reduced tree stature combined with increased stem density and generally, a lower diversity of woody plants. Trees in these regions are generally shorter and more heavily stemmed than in lower-altitude forests in the same regions, often with gnarled trunks and branches, forming dense, compact crowns. Their leaves become smaller, thicker and harder with increasing altitude. The high moisture promotes

1305-450: 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 ⁡ (

1392-415: 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

1479-401: 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

1566-879: 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,

1653-1003: 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

1740-447: 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

1827-403: 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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1914-420: Is a relatively small band of elevation in which the atmospheric environment is suitable for cloud forest development. This is characterized by persistent fog at the vegetation level, resulting in the reduction of direct sunlight and thus of evapotranspiration . Within cloud forests, much of the moisture available to plants arrives in the form of fog drip , where fog condenses on tree leaves and then drips onto

2001-500: Is a time when air quality improves, freshwater quality improves and vegetation grows significantly due to the wet season supplementing flora, leading to crop yields late in the season. Floods and rains cause rivers to overflow their banks, and some animals to retreat to higher ground. Soil nutrients are washed away and erosion increases. The incidence of malaria increases in areas where the rainy season coincides with high temperatures. Animals have adaptation and survival strategies for

2088-438: 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

2175-480: 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

2262-916: 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

2349-454: 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,

2436-680: 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

2523-2450: 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

2610-585: Is that the tropics represent a ' Garden of Eden ', a heaven on Earth, a land of rich biodiversity or a tropical paradise. The alternative is that the tropics consist of wild, unconquerable nature. The latter view was often discussed in old Western literature more so than the first. Evidence suggests over time that the view of the tropics as such in popular literature has been supplanted by more well-rounded and sophisticated interpretations. Western scholars tried to theorise why tropical areas were relatively more inhospitable to human civilisations than colder regions of

2697-593: 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

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2784-605: The Andes as far south as the northernmost parts of Chile and Perú . The climate is changing in the tropics, as it is in the rest of the world. The effects of steadily rising concentrations of greenhouse gases on the climate may be less obvious to tropical residents, however, because they are overlain by considerable natural variability. Much of this variability is driven by the El Niño-Southern Oscillation (ENSO) . The Tropics has warmed by 0.7–0.8 °C over

2871-1062: The Caribbean . The 1997 version of the World Conservation Monitoring Centre's database of cloud forests found a total of 605 tropical montane cloud forest sites in 41 countries. 280 sites, or 46% of the total, were located in Latin America , known in biogeography as the Neotropical realm . Twelve countries had tropical montane cloud forest sites, with the majority in Venezuela (64 sites), Mexico (64), Ecuador (35) and Colombia (28). Southeast Asia and Australasia had 228 sites in 14 countries – 66 in Indonesia, 54 in Malaysia, 33 in Sri Lanka, 32 in

2958-732: The Pantropic . The system of biogeographic realms differs somewhat; the Neotropical realm includes both the Neotropics and temperate South America, and the Paleotropics correspond to the Afrotropical , Indomalayan , Oceanian , and tropical Australasian realms . Flora are plants found in a specific region at a specific time. Some well-known plants that are exclusively found in, originate from, or are often associated with

3045-579: The Waterberg Biosphere of South Africa , and eastern Madagascar rainforests. Often the soils of tropical forests are low in nutrient content, making them quite vulnerable to slash-and-burn deforestation techniques, which are sometimes an element of shifting cultivation agricultural systems. In biogeography , the tropics are divided into Paleotropics (Africa, Asia and Australia) and Neotropics (Caribbean, Central America, and South America). Together, they are sometimes referred to as

3132-612: The World Conservation Monitoring Centre , with 327 of them legally protected areas as of 2002. Important areas of cloud forest are in Central and South America (mainly Costa Rica , Venezuela , Honduras , Mexico , Ecuador , and Colombia ), East and Central Africa , India , Sri Lanka , Thailand , Vietnam , Indonesia , Malaysia , the Philippines , Hawaii , Papua New Guinea , and in

3219-619: The axial tilt of the Earth . The Tropic of Cancer is the Northernmost latitude from which the Sun can ever be seen directly overhead , and the Tropic of Capricorn is the Southernmost. This means that the tropical zone includes everywhere on Earth which is a subsolar point at least once during the solar year . Thus the maximum latitudes of the tropics have equal distances from the equator on either side. Likewise, they approximate

3306-472: 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

3393-405: The soil acidity is very high, with more humus and peat often forming the upper soil layer. Stadtmüller (1987) distinguishes two general types of tropical montane cloud forests: Only 1% of the global woodland consists of cloud forests. They previously comprised an estimated 11% of all tropical forests in the 1970s. A total of around 736 cloud forest sites have been identified in 59 countries by

3480-631: 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

3567-1040: 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

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3654-463: 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

3741-536: The Northern Hemisphere. A popular explanation focused on the differences in climate. Tropical jungles and rainforests have much more humid and hotter weather than colder and drier temperaments of the Northern Hemisphere, giving to a more diverse biosphere. This theme led some scholars to suggest that humid hot climates correlate to human populations lacking control over nature e.g. 'the wild Amazonian rainforests'. Solar radiation Solar irradiance

3828-745: The Philippines, and 28 in Papua New Guinea. 97 sites were recorded in 21 African countries, mostly scattered on isolated mountains. Of the 605 sites, 264 were in protected areas. Cloud forests occupied 0.4% of the global land surface in 2001 and harboured ~3,700 species of birds, mammal, amphibians and tree ferns (~15% of the global diversity of those groups), with half of those species entirely restricted to cloud forests. Worldwide, ~2.4% of cloud forests (in some regions, more than 8%) were lost between 2001 and 2018, especially in readily accessible places. While protected areas have slowed this decline,

3915-473: 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

4002-646: 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

4089-712: The United States, the Atlanta Botanical Garden has a large tropical cloud forest greenhouse with a large collection of cloud forest epiphytes from around the world. It implements a refrigeration system to decrease the temperature at night. For many years, the Singapore Botanic Gardens had a so-called coolhouse. The Gardens by the Bay features a 0.8 hectares (2.0 acres) coolhouse that is simply named " Cloud Forest ". The latter features

4176-416: 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

4263-399: The angle of the Earth's axial tilt. This angle is not perfectly fixed, mainly due to the influence of the moon, but the limits of the tropics are a geographic convention, and their variance from the true latitudes is very small. Many tropical areas have both a dry and a wet season. The wet season , rainy season or green season is the time of year, ranging from one or more months when most of

4350-409: 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

4437-459: The average annual rainfall in a region falls. Areas with wet seasons are disseminated across portions of the tropics and subtropics , some even in temperate regions. Under the Köppen climate classification , for tropical climates , a wet-season month is defined as one or more months where average precipitation is 60 mm (2.4 in) or more. Some areas with pronounced rainy seasons see

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4524-442: 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

4611-407: 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

4698-451: 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,

4785-426: 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

4872-408: The development of a high biomass and biodiversity of epiphyte , particularly bryophytes , lichens , ferns (including filmy ferns ), bromeliads and orchids . The number of endemic plants can be very high. An important feature of cloud forests is the tree crowns that intercept the wind-driven cloud moisture, part of which drips to the ground. This fog drip occurs when water droplets from

4959-499: 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

5046-409: 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

5133-452: The extent of environmentally suitable areas for cloud forest in Mexico will sharply decline in the next 70 years. A number of climate models suggest low-altitude cloudiness will be reduced, which means the optimum climate for many cloud forest habitats will increase in altitude. Linked to the reduction of cloud moisture immersion and increasing temperature, the hydrological cycle will change, so

5220-453: 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

5307-401: The fog adhere to the needles or leaves of trees or other objects, coalesce into larger drops and then drop to the ground. It can be an important contribution to the hydrologic cycle . Cloud forests are often peatlands , showcasing many classic peatland attributes. Due to the high water content of the soil, the reduced solar radiation and the low rates of decomposition and mineralization ,

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5394-460: The geographic region; these usages ought not be confused. The Earth's axial tilt is currently around 23.4° , and therefore so are the latitudes of the tropical circles , marking the boundary of the tropics: specifically, ±23°26′09.8″ (or 23.43605°). The northern one is called the Tropic of Cancer , and the southern is the Tropic of Capricorn . As the Earth's axial tilt changes, so too do

5481-533: 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

5568-453: The ground and vegetation, in which case they are also referred to as mossy forests . Mossy forests usually develop on the saddles of mountains, where moisture introduced by settling clouds is more effectively retained. Cloud forests are among the most biodiversity-rich ecosystems in the world, with a large number of species directly or indirectly depending on them. Other moss forests include black spruce / feathermoss climax forest , with

5655-429: The ground below. Annual rainfall can range from 500 to 10,000 mm/year and mean temperature between 8 and 20 °C (46.4 and 68 °F). While cloud forest today is the most widely used term, in some regions, these ecosystems or special types of cloud forests are called mossy forest, elfin forest , montane thicket, and dwarf cloud forest. The definition of cloud forest can be ambiguous, with many countries not using

5742-528: 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

5829-844: 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

5916-526: The initial cloud forest cover remains. Significant areas have been converted to plantations , or for use in agriculture and pasture . Significant crops in montane forest zones include tea and coffee , and the logging of unique species causes changes to the forest structure. In 2004, an estimated one-third of all cloud forests on the planet were protected at that time. Because of their delicate dependency on local climates, cloud forests will be strongly affected by global climate change . Results show that

6003-574: 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

6090-961: The last century—only slightly less than the global average—but a strong El Niño made 1998 the warmest year in most areas, with no significant warming since. Climate models predict a further 1–2 °C warming by 2050 and 1–4 °C by 2100. Tropical plants and animals are those species native to the tropics. Tropical ecosystems may consist of tropical rainforests , seasonal tropical forests , dry (often deciduous) forests , spiny forests, deserts , savannahs, grasslands and other habitat types. There are often wide areas of biodiversity , and species endemism present, particularly in rainforests and seasonal forests. Some examples of important biodiversity and high-endemism ecosystems are El Yunque National Forest in Puerto Rico , Costa Rican and Nicaraguan rainforests, Amazon Rainforest territories of several South American countries, Madagascar dry deciduous forests ,

6177-508: 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

6264-438: The original extent of cloud forests on the Earth was around 50 million hectares . Population growth , poverty and uncontrolled land use have contributed to the loss of cloud forests. The 1990 Global Forest Survey found that 1.1% of tropical mountain and highland forests were lost each year, which was higher than in any other tropical forests. In Colombia, one of the countries with the largest area of cloud forests, only 10–20% of

6351-719: The overhead sun, the tropics receive the most solar energy over the course of the year, and consequently have the highest temperatures on the planet. Even when not directly overhead, the sun is still close to overhead throughout the year, therefore the tropics also have the lowest seasonal variation on the planet; "winter" and "summer" lose their contrast. Instead, seasons are more commonly divided by precipitation variations than by temperature variations. The tropics maintain wide diversity of local climates, such as rain forests , monsoons , savannahs , deserts , and high altitude snow-capped mountains . The word "tropical" can specifically refer to certain kinds of weather , rather than to

6438-630: 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

6525-497: 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

6612-604: The results of climate change will be a loss in biodiversity, altitude shifts in species ranges and community reshuffling, and, in some areas, complete loss of cloud forests. Cloud-forest conditions are hard and expensive to replicate in a glasshouse because it is necessary to maintain very high humidity. Day temperatures have to be between 70-75F while night temperatures have to be maintained between 55-60F. In most cases, sophisticated refrigeration equipment has to be used to provide night temperatures below 60F. Such displays are usually quite small, but there are some notable exceptions. In

6699-660: 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

6786-392: 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}}}}

6873-458: The system will dry out. This would lead to the wilting and the death of epiphytes, which rely on high humidity. Frogs and lizards are expected to suffer from increased drought. Calculations suggest the loss of cloud forest in Mexico would lead to extinction of up to 37 vertebrates specific to that region. In addition, climate changes can result in a higher number of hurricanes , which may increase damage to tropical montane cloud forests. All in all,

6960-625: 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

7047-560: The term (preferring such terms as Afromontane forest and upper montane rain forest, montane laurel forest , or more localised terms such as the Bolivian yungas , and the laurisilva of the Atlantic Islands), and occasionally subtropical and even temperate forests in which similar meteorological conditions occur are considered to be cloud forests. In comparison with lower-altitude tropical moist forests, cloud forests show

7134-468: 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

7221-516: The tropical and polar circles . The tropics constitute 39.8% of Earth's surface area and contain 36% of Earth's landmass . As of 2014 , the region was home also to 40% of the world's population , and this figure was then projected to reach 50% by 2050. Because of global warming , the weather conditions of the tropics are expanding with areas in the subtropics , having more extreme weather events such as heatwaves and more intense storms. These changes in weather conditions may make certain parts of

7308-469: The tropics include: Tropicality refers to the image of the tropics that people from outside the tropics have of the region, ranging from critical to verging on fetishism. Tropicality gained renewed interest in geographical discourse when French geographer Pierre Gourou published Les pays tropicaux ( The Tropical World in English), in the late 1940s. Tropicality encompassed two major images. One,

7395-568: The tropics uninhabitable. The word "tropic" comes via Latin from Ancient Greek τροπή ( tropē ), meaning "to turn" or "change direction". The tropics are defined as the region between the Tropic of Cancer in the Northern Hemisphere at 23°26′09.8″ (or 23.43605°) N and the Tropic of Capricorn in the Southern Hemisphere at 23°26′09.8″ (or 23.43605°) S; these latitudes correspond to

7482-471: 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

7569-726: The wetter regime. The previous dry season leads to food shortages into the wet season, as the crops have yet to mature. However, regions within the tropics may well not have a tropical climate. Under the Köppen climate classification, much of the area within the geographical tropics is classed not as "tropical" but as "dry" ( arid or semi-arid ), including the Sahara Desert , the Atacama Desert and Australian Outback . Also, there are alpine tundra and snow-capped peaks, including Mauna Kea , Mount Kilimanjaro , Puncak Jaya and

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