METO 621PowerPoint PresentationPurposeElectromagnetic RadiationSlide 5Electromagnetic spectrumSlide 7Schematic of a waveWAVELENGTHFREQUENCYVELOCITYSOLAR ENERGYSOLAR SPECTRUMSlide 14UV-VISIBLE SOLAR SPECTRUM OBSERVED FROM THE GROUNDUV-VISIBLE SOLAR SPECTRUM OBSERVED FROM THE GROUNDSOLAR GEOMETRYEFFECTIVE AREAINFRARED FLUX FROM EARTH SAHARAINFRARED FROM EARTH MEDITERRANEANINFRARED FROM EARTH ANTARCTICHYDROSTATIC EQUATIONHYDROSTATIC EQUATION-2HYDROSTATIC EQUATION-3Optical line-of-sight pathsSlant column massSlide 27Atmospheric compositionHeight profiles for minor speciesSlide 30METO 621LESSON 1• AOSC 621 - PHYSICS AND CHEMISTRY OF THE ATMOSPHERE II• •Texts: Radiative Transfer in the Atmosphere and Ocean, Gary E. Thomas and Knut Stamnes, Cambridge University Press•Chemistry of Atmospheres, Richard P. Wayne, Oxford University Press•Lecturer: Professor Robert D. Hudson, Room 3421, •Computer and Space Sciences Building.•Phone 301-405-5394 •E-mail [email protected]•The Department of Meteorology Web Site is www.meto.umd.edu•Lessons Tuesday 8.00 am to 9.15 am, in CSS 2428• Thursday 8.00 am to 9.15 am in CSS 2428 • •Office hours No set office hours will be posted. Students may come by my office at any time. •If you wish to make a formal appointment - send me an e-mail•______________________________________________________________________________•______________________________________________________________________________ •The two textbooks listed above cover most of the material given in this course.. However, as AOSC 621 covers both chemistry and physics the course consists of selections from the textbooks. PowerPoint presentations have been prepared for each class, these will contain any material not covered by either book. .The .ppt files may be found on my web page: http://www.atmos.umd.edu/~hudson/meto621.d/• A schedule of the classes, homework assignments, etc can also be found on the same web site - AOSC621intr.htm . This schedule gives the material to be covered in each lecture. as well as the dates of the homework assignments . The homework assignments will be posted on my web site. In addition to the homework a project will be assigned at about mid-term.. There will be two exams, a mid-term exam and a final exam. 70% of the final grade will be based on these two exams, 15% on the project, and the remaining 15% on the homework assignments.Purpose•The purpose of this course is twofold:•(1) To examine how solar radiation is transferred through the atmosphere, absorbed by the Earth, and re-emitted by the Earth and atmosphere.•(2) To examine how this radiation drives the chemistry and dynamics of the atmosphere.Electromagnetic Radiation•Basically all of the energy that drives the chemistry and dynamics of the earth’s atmosphere emanates from the sun.•This energy is in the form of electromagnetic waves. •This is especially true if we consider the particles from the sun as having wave duality.•In order to explain the ejection of electrons from a surface illuminated with light, Einstein postulated that waves could be considered as a packet of particles each particle having an energy of h (where  is the frequency of the radiation). He called each particle a photon.Electromagnetic Radiation•By analogy a stream of particles can be considered as a wave.•The chemistry of the atmosphere is dominated by radicals derived from the dissociation of atmospheric species.•It is much easier to picture this dissociation as the interaction of a photon with a molecule than as an interaction of a wave with the molecular field.•Dissociation requires a threshold of energy, i.e. a certain frequency. Only photons with an energy (frequency) above this threshold will cause dissociation.Electromagnetic spectrumElectromagnetic spectrum•Most of the energy that drives the dynamics comes from a narrow band of frequencies known as the visible spectrum - heats the ground•Most the the energy that drives the chemistry pf the atmosphere comes from the ultraviolet part of the spectrum - high energy photons.•Most of the energy that heats the atmosphere is thermal radiation from the groundSchematic of a waveWAVELENGTH•DISTANCE BETWEEN SUCCESSIVE PEAKS•GIVEN THE SYMBOL λ•MANY UNITS USED :•(A) MICRON, 10-6 METERS•(B) NANOMETER, 10-9 METERS•(C) ANGSTROM, 10-10 METERSFREQUENCY € Defined as the number of maxima that pass an observerper secondGiven the symbol νc = λνWave number is also used. It is the reciprocal of the wavelengthIn the textbook it is given the symbol ν Caution - the use of ν and ν are reversed in many textbooksVELOCITY•WAVE VELOCITY IS DEFINED AS THE DISTANCE A PEAK MOVES IN ONE SECOND. •IN VACUO THE WAVE VELOCITY OF AN ELECTROMAGNETIC WAVE IS 2.997925x108 METERS PER SECOND•FOR THOSE OF YOU WHO PREFER ENGLISH UNITS, THE VELOCITY OF LIGHT IS 1.80262x1012 FURLONGS PER FORTNIGHT.•THE WAVE VELOCITY IS GIVEN THE SYMBOL c.SOLAR ENERGY•Solar constant – energy from the sun that falls on unit surface normal to the line from the sun, per unit time, at the outside of the atmosphere at the mean solar distanceS = 1.368 Kw per meter 2•S is integrated over all wavelengths•S varies with the sunspot cycleSOLAR SPECTRUMSOLAR SPECTRUM•A blackbody curve for a temperature of 6000K matches the observed solar spectrum.•The difference between the 6000K spectrum below about 400 nm is due to absorption in the photosphere.•The structures shown below 400 nm are known as Fraunhoffer linesUV-VISIBLE SOLAR SPECTRUM OBSERVED FROM THE GROUNDUV-VISIBLE SOLAR SPECTRUM OBSERVED FROM THE GROUND •Slide shows the absorption of the solar radiation by the atmosphere.•Major absorbers are molecular oxygen (O2), ozone (O3), water vapor (H2O) and carbon dioxide (CO2).•The wavelength is in nm. 1000nm is equal to one micron.SOLAR GEOMETRYEFFECTIVE AREA•If the solar zenith angle (SZA) of the sun is θ, then the effective area is given by1/cos θ.•Hence the energy on unit area at the surface is S divided by the effective area, i.e. S.cos θ.•College Park is at a latitude of 39 degrees•At summer solstice the SZA is 17 degrees, and at the winter solstice 61 degrees•The ratio of the effective areas is 1.97, i.e. twice as much energy per unit area is incident on College Park at summer solstice than at winter solstice.INFRARED FLUX FROM EARTHSAHARAINFRARED FROM EARTHMEDITERRANEANINFRARED FROM