Atmospheric physics 801420 224522414 2008-07-09T06:23:59Z 98.210.54.36 formatting {{Atmospheric sciences| atmophys=true}} '''Atmospheric physics''' is the application of [[physics]] to the study of the [[Earth's atmosphere|atmosphere]]. Atmospheric physicists attempt to model [[Earth's atmosphere]] and the atmospheres of the other [[planet]]s using [[fluid dynamics|fluid flow]] equations, [[chemistry|chemical]] models, radiation balancing, and energy transfer processes in the atmosphere (as well as how these tie in to other systems such as the oceans). In order to model weather systems, atmospheric physicists employ elements of scattering theory, wave propagation models, [[cloud physics]], [[statistical mechanics]] and [[spatial statistics]] which are highly mathematical and related to physics. It has close links to meteorology and climatology and also covers the design and construction of instruments for studying the atmosphere and the interpretation of the data they provide, including [[remote sensing]] instruments. == Radiation == [[Image:seasons.svg|frame|right|This is a diagram of the seasons. In addition to the density of incident light, the [[dissipation]] of light in the [[Earth's atmosphere|atmosphere]] is greater when it falls at a shallow angle.]] {{seealso|Radiation|Effect of sun angle on climate}} The sun emits radiation as a variety of wavelengths. Visible light has wavelengths between 0.4 and 0.7&nbsp;micrometers.<ref>Atmospheric Science Data Center. [http://eosweb.larc.nasa.gov/EDDOCS/Wavelengths_for_Colors.html What Wavelength Goes With a Color?] Retrieved on [[2008-04-15]].</ref> Shorter wavelengths are known as the [[ultraviolet]] (UV) part of the spectrum, while longer wavelengths are grouped into the [[infrared]] portion of the spectrum.<ref>Windows to the Universe. [http://www.windows.ucar.edu/tour/link=/earth/Atmosphere/earth_atmosph_radiation_budget.html Solar Energy in Earth's Atmosphere.] Retrieved on [[2008-04-15]].</ref> Ozone is most effective in absorbing radiation around 0.25&nbsp;micrometers,<ref name="UDE">[[University of Delaware]]. [http://www.udel.edu/Geography/DeLiberty/Geog474/geog474_energy_interact.html Geog 474: Energy Interactions with the Atmosphere and at the Surface.] Retrieved on [[2008-04-15]].</ref> where UV-c rays lie in the spectrum. This increases the temperature of the nearby [[stratosphere]]. Snow reflects 88% of UV rays,<ref name="UDE">[[University of Delaware]]. [http://www.udel.edu/Geography/DeLiberty/Geog474/geog474_energy_interact.html Geog 474: Energy Interactions with the Atmosphere and at the Surface.] Retrieved on [[2008-04-15]].</ref> while sand reflects 12%, and water reflects only 4% of incoming UV radiation.<ref name="UDE">[[University of Delaware]]. [http://www.udel.edu/Geography/DeLiberty/Geog474/geog474_energy_interact.html Geog 474: Energy Interactions with the Atmosphere and at the Surface.] Retrieved on [[2008-04-15]].</ref> The more glancing the angle is between the atmosphere and the [[sun]]'s rays, the more likely that energy will be reflected or absorbed by the [[atmosphere]].<ref>Wheeling Jesuit University. [http://www.cet.edu/ete/modules/ozone/ozatmo.html Exploring the Environment: UV Menace.] Retrieved on [[2007-06-01]].</ref> == Cloud physics == {{Main article|Cloud physics}} Cloud physics is the study of the physical processes that lead to the formation, growth and precipitation of [[cloud]]s. Clouds are composed of microscopic droplets of water (warm clouds), tiny crystals of ice, or both (mixed phase clouds). Under suitable conditions, the droplets combine to form [[precipitation]], where they may fall to the earth.<ref>Oklahoma Weather Modification Demonstration Program. [http://www.evac.ou.edu/okwmdp/physics.html CLOUD PHYSICS.] Retrieved on [[2008-04-15]].</ref> The precise mechanics of how a cloud forms and grows is not completely understood, but scientists have developed theories explaining the structure of clouds by studying the microphysics of individual droplets. Advances in radar and satellite technology have also allowed the precise study of clouds on a large scale. == Atmospheric electricity == [[Image:Lightning over Oradea Romania 2.jpg|thumb|150px|right|Cloud to ground [[Lightning]] in the global atmospheric electrical circuit.]] {{Main article|Atmospheric electricity}} Atmospheric electricity is the regular [[Diurnal phase shift|diurnal]] variations of the [[Earth]]'s [[Earth's atmosphere|atmospheric]] [[Electromagnetism|electromagnetic]] [[electrical network|network]] (or, more broadly, any [[planet]]'s electrical system in its [[celestial body atmosphere|layer of gases]]). The [[Continent|Earth’s surface]], the [[ionosphere]], and the atmosphere is known as the '''global atmospheric electrical circuit'''.<ref>Dr. Hugh J. Christian and Melanie A. McCook. [http://thunder.msfc.nasa.gov/primer/primer3.html Lightning Detection From Space: A Lightning Primer.] Retrieved on [[2008-04-17]].</ref> Lightning discharges 30,000 [[ampere]]s, at up to 100 million [[volt]]s, and emits light, radio waves, [[x-ray]]s and even [[gamma ray]]s.<ref>NASA. [http://www.nasa.gov/vision/universe/solarsystem/rhessi_tgf.html Flashes in the Sky: Earth's Gamma-Ray Bursts Triggered by Lightning.] Retrieved on [[2007-06-01]].</ref> Plasma temperatures in lightning can approach 28,000 [[kelvin]]s and [[electron]] densities may exceed 10<sup>24</sup>/m³.<ref>Fusion Energy Education.[http://fusedweb.llnl.gov/CPEP/Chart_Pages/5.Plasmas/Lightning.html Lightning! Sound and Fury.] Retrieved on [[2008-04-17]].</ref> == Atmospheric tide == {{Main article|Atmospheric tide}} The largest-amplitude atmospheric tides are mostly generated in the [[troposphere]] and [[stratosphere]] when the atmosphere is periodically heated as water vapour and ozone absorb solar radiation during the day. The tides generated are then able to propagate away from these source regions and ascend into the [[mesosphere]] and [[thermosphere]]. Atmospheric tides can be measured as regular fluctuations in wind, temperature, density and pressure. Although atmospheric tides share much in common with ocean tides they have two key distinguishing features: i) Atmospheric tides are primarily excited by the Sun's heating of the atmosphere whereas ocean tides are primarily excited by the Moon's gravitational field. This means that most atmospheric tides have periods of oscillation related to the 24-hour length of the solar day whereas ocean tides have longer periods of oscillation related to the lunar day (time between successive lunar transits) of about 24 hours 51 minutes.<ref>Glossary of Meteorology. [http://amsglossary.allenpress.com/glossary/search?id=atmospheric-tide1 Atmospheric Tide.] Retrieved on [[2008-04-15]].</ref> ii) Atmospheric tides propagate in an atmosphere where density varies significantly with height. A consequence of this is that their amplitudes naturally increase exponentially as the tide ascends into progressively more rarefied regions of the atmosphere (for an explanation of this phenomenon, see below). In contrast, the density of the oceans varies only slightly with depth and so there the tides do not necessarily vary in amplitude with depth. Note that although solar heating is responsible for the largest-amplitude atmospheric tides, the gravitational fields of the Sun and Moon also raise tides in the atmosphere, with the lunar gravitational atmospheric tidal effect being significantly greater than its solar counterpart.<ref>Scientific American. [http://www.sciam.com/article.cfm?id=does-the-moon-have-a-tida Does the Moon have a tidal effect on the atmosphere as well as the oceans?.] Retrieved on [[2008-07-08]].</ref> At ground level, atmospheric tides can be detected as regular but small oscillations in surface pressure with periods of 24 and 12 hours. Daily pressure maxima occur at 10 a.m. and 10 p.m. local time, while minima occur at 4 a.m. and 4 p.m. local time. The absolute maximum occurs at 10 a.m. while the absolute minimum occurs at 4 p.m.<ref>Dr James B. Calvert. [http://mysite.du.edu/~jcalvert/geol/tides.htm Tidal Observations.] Retrieved on [[2008-04-15]].</ref> However, at greater heights the amplitudes of the tides can become very large. In the [[mesosphere]] (heights of ~ 50 - 100 km) atmospheric tides can reach amplitudes of more than 50 m/s and are often the most significant part of the motion of the atmosphere. == Centers of research == In the UK, atmospheric studies are underpinned by the [[Met Office]], the [[Natural Environment Research Council]] and the [[Science and Technology Facilities Council]]. Divisions of the U.S. [[NOAA|National Oceanic and Atmospheric Administration (NOAA)]] oversee research projects and [[weather]] modeling involving atmospheric physics. The US [[Arecibo Observatory|National Astronomy and Ionosphere Center]] also carries out studies of the high atmosphere. In [[Belgium]], the [[Belgian Institute for Space Aeronomy]] studies the atmosphere and [[outer space]]. == See also == <!-- kinematic and dynamical meteorology (distinct) require articles --> {{col-start}} {{col-break}} *[[Adiabatic lapse rate]] *[[Atmospheric thermodynamics]] *[[Baroclinic instability]] *[[Barotropic instability]] *[[Barotropic vorticity equation]] *[[David Bates (physicist)]] *[[Convective instability]] {{col-break}} *[[Coriolis effect]] *[[Euler equations]] *[[Geostrophic wind]] *[[Gravity wave]] *[[Hydrostatic balance]] *[[Kelvin-Helmholtz instability]] *[[Madden-Julian oscillation]] {{col-break}} *[[Navier–Stokes equations]] *[[Potential vorticity]] *[[Pressure gradient force]] *[[Primitive equations]] *[[Rossby number]] *[[Rossby radius of deformation]] *[[Space weather]] {{col-break}} *[[Thermal wind]] *[[Vorticity equation]] {{col-end}} == References == {{reflist}} [[Category:Atmospheric sciences|Physics]] [[Category:Meteorology| ]] [[Category:Fluid dynamics]] [[ar:فيزياء الغلاف الجوي]] [[cs:Aeronomie]] [[de:Aeronomie]] [[et:Atmosfäärifüüsika]] [[it:Fisica dell'atmosfera]] [[ms:Fizik atmosfera]] [[pl:Fizyka atmosfery]] [[pt:Aeronomia]] [[ru:Физика атмосферы]] [[zh:大气物理学]]