What rule do we use to adjust the station pressure to the mean sea level pressure? Pressure decreases by 10mb per 100m increase in altitude in the lower atmosphereWhat is the force that initially sets air in motion? Pressure gradient forceWhat does Coriolis force do to moving air in the northern hemisphere? Deflects it to the rightHow each of the following influence Coriolis force? Both are directly proportional. wind speedFaster wind speed = larger Coriolis force latitude Higher latitude = larger Coriolis forceWhy on a map, closely spaced isobars indicate strong winds and widely spaced isobars indicate weak winds? Closer isobars = higher PGF = greater wind speedWhat is geostrophic wind? Why would you not expect to observe geostrophic wind at equator? A geostrophic wind is a wind that results from a balance between the Coriolis force and the pressure gradient force. At the equator there is no Coriolis force, thus there cannot be a geostrophic wind. Why do upper-level winds in mid-latitude generally blow from the west? Because winds at these altitudes are approximately geostrophic, with higher pressures (warmer temperatures) to the south and lower pressures (colder temperatures) to the north. (Buys-Ballot Law). How do winds blow around a low and a high aloft and near the surface in the Northern Hemisphere? Counterclockwise around low (into low near surface), clockwise around high (out from high nearsurface)What are the forces that affect horizontal movement of air? Pressure gradient force, Coriolis force, frictional force, centripetal forceHow does Buys-Ballot law help to locate regions of high and low pressure aloft and at surface? you can tell which direction the wind is coming from and then determine pressure (B-B: back to wind, low pressure is on left)What is the effect of surface friction on wind speed and direction? As air moves from a rough to a smooth surface, how do the speed and direction change as a result of reduced friction?Friction = slower speed, 30-degree discrepancy to L/H pressure centersDescribe various scales of motion, and give an example of eachMicroscale: < 1kmLifetime: seconds to minutesi.e. turbulent eddiesMesoscale: 1km to 200kmLifetime: hours, up to one dayi.e. land/sea breezes, mountain/valley winds, thunderstorms, tornadoes/waterspouts/dust devilsDivided into mesoalpha/gamma/betascale based upon life spanSynoptic scale: 200km to 2000kmLifetime: days to weeksi.e. hurricanes, tropical storms, lows/highs, fronts, everyday weatherCovers region about the size of a statePlanetary scale: > 2000kmLifetime: weeks or longeri.e. longwaves in westerliesA friend has just returned from a trans-Atlantic jet flight and reported that the plane dropped about 1000 m when it entered an ‘air pocket’. Explain to your friend what apparently happened to cause this drop? Increased wind shear causes waves to appear; turbulent eddies break, causing pockets of air; plane flies over it into a zone of descending air, giving the feeling that there is no air below the planeWhat is wind shear and how does it relate to clear air turbulence? See aboveYou are fly fishing in a mountain stream during the early morning; would you expect the wind to be blowing up-stream or downstream? Upstream (valley breeze)What is Chinook winds and why they are warm and dry? Chinook (Foehn) wind: warm, dry wind that descends leeward slopes of high mountainsWhat atmospheric conditions contribute to the development of a strong Santa Ana condition? Why is a Santa Ana wind warm? As air descends from the elevated desert plateau, it funnels through mountain canyons in the San Gabriel and San Bernardino Mountains, finally spreading over the Los Angeles basin and San Fernando Valley. The wind often blows with exceptional speed in the Santa Ana Canyon (the canyon from which it derives its name). These warm, dry winds develop as a region of high pressure builds over the Great Basin. The clockwise circulation around the anticyclone forces air downslope from the high plateau. Santa Ana winds are warm because of compression heating of the already warm, dry desert air.Explain the following concepts: • single Cell model• Earth’s surface is evenly covered by water• Sun is always directly over equator• Earth does not rotate (ignores all forces but PGF)• three cell model• Earth spins, creating Hadley/Ferrel/Polar cells• Doldrums• regions near the equator characterized by weak winds, strong rising motion, towering convective clouds and thunderstorms• subtropical highs, horse latitude• Subtropical highs: belt of high pressure near 30o (horse latitude) caused by cooling of equatorial air as it moves northward, convergence (pile up) of air aloft; characterized by sinking motion, clear sky, major deserts, and warm surface temperature• Horse latitudes: latitudes near 30 degrees with weak winds (horses were thrown overboard due to dwindling food)• trade winds, intertropical convergence zone (ITCZ)• Trade winds: low-level northeasterly winds (southeasterly in SH) that occupy most of the tropics as the Coriolis force deflects the air flowing back from the horse latitudes towards equator• Intertropical convergence zone (ITCZ): the boundary where the northeasterly trade winds in NH converge with the southeasterly trade winds in the SH • Most stormy region due to converging fronts• Westerlies • Winds that blow more or less westerly• polar front, subpolar low, polar easterlies• Polar front: a semi-permanent front that separates tropical air masses from polar air masses • Subpolar low: a zone of low pressure near the polar front • Polar Easterlies: shallow layer of northeasterly flows formed when the southward moving cold polar air behind the polar front is deflected by the Coriolis force to the rightof its path. • jet stream• very strong winds concentrated within narrow band in atmosphere• El Nino and La Nina• El Niño: warmer than normal temperature over eastern tropical Pacific• La Niña: colder than normal surface water moves over central and eastern Pacific• Along a meridian line running from the equator to the poles, how does the general circulation help to explain zones of abundant and sparse precipitation? How does the polar front influence the development of the polar front jet stream? What is a major El Nino event?What are the conditions over the tropical eastern and central Pacific Ocean during the phenomenon called La