METR 121 WKU Exam 2 (Chs. 5-8)

What is an adiabatic process? - answer-Clouds moving up into the atmosphere until the dew point temperature = regular temperature, then a cloud forms, without a transfer of heat How would one normally obtain the environmental lapse rate? - answer-By releasing a radiosonde into the atmosphere What could make the air lift? - answer--Daytime Solar Heating -Advection of Warm Air -Advecting air over warm surface Why are the moist and dry adiabatic rates of cooling different? - answer-The moist adiabatic lapse rate is less than the dry adiabatic lapse rate because moist air rising condenses out its water vapor (once saturation is attained). This condensation releases heat which results in that rising parcel cooling at a slower rate than it would if no condensation took place If the atmosphere is conditionally unstable, what does this mean? - answer-This occurs when the environmental lapse rate falls between the moist and dry adiabatic lapse rate. Conditionally unstable means that, if unsaturated air could be lifted to a level where it becomes saturated, instability would result. What condition is necessary to bring on instability? - answer-If unsaturated air could be lifted to a level where it becomes saturated Explain why an inversion represents an extremely stable atmosphere? - answer-With an inversion, warm air overlies cold air; rising air is becoming colder while the air around it is getting warmer. This causes the rising air to sink Why are cumulus clouds more frequently observed during the afternoon? - answer-Because of daytime solar heating. As the Sun heats the Earth's surface, thermals are created, and air rises. There are usually large spaces of blue sky between cumulus clouds. Explain why that is - answer-Because warm air is displacing air that is already there and evaporating the clouds. Why do most thunderstorms have flat tops? - answer-Cumulonimbus clouds can grow to such a height that they encounter the bottom of the stratosphere, which is extremely stable with rising temperatures with altitude (inversion). The rising cumulonimbus cannot enter the stratosphere and hence spread out List 4 primary ways in which clouds form - answer-Surface heating and free convection- Sun comes out hits the surface and picks up temperature, then starts to rise Uplift along topography- Force to rise along mountains due to condensation and latent heat being released Widespread ascent due to convergence of surface air- Rising air will force things to condense Uplift along weather fronts- Cold fronts force warm air up where it cools, forming clouds and precipitation Explain why rain shadows form on the leeward side of mountains. - answer-Precipitation falls on the windward side of mountain What is the primary difference between a cloud droplet and a raindrop? - answer-Cloud droplets are smaller Why do typical cloud droplets seldom reach the ground as rain? - answer-Because they are so small and light that any vertical motion in the atmosphere, even very slight, is sufficient to hold them aloft. Describe how the process of collision and coalescence produces rain? - answer-Cloud droplets, produced initially through the "solute effect" grow larger by collision with other cloud droplets and sticking (coalescence). How does the ice-crystal (Bergeron) process produce precipitation? What is the main premise behind this process? - answer-In an environment of ice crystals and super-cooled cloud drops the ice will grow at the expense of the super-cooled drops, This occurs because the saturation vapor pressure required over ice is less than that required over water at the same temperature. Explain the main principle behind cloud seeding. - answer-to inject clouds with small particles to act as nuclei so the cloud particles will grow enough to fall to the surface as precipitation How does rain differ from drizzle? - answer-Difference is size of each Why is it never too cold to snow? - answer-the air always contains water vapor that could produce snow How would you be able to distinguish between virga and fallstreaks? - answer-Virga=Cumulus, Fallstreaks=Cirrus What is the difference between freezing rain and sleet? - answer-Freezing rain freezes closer to the surface while sleet starts off as snow, melts into rain, freezes again. Freezing rain is almost like a glaze How do the atmospheric conditions that produce sleet differ from those that produce hail? - answer-Sleet forms when there is a layer of above freezing temperatures below cloud base but the temperatures at the surface are below freezing. Hail is produced inside a cumulonimbus cloud by accretion of super-cooled liquid water onto a large frozen embryo caught in a strong updraft. What is doppler radar? - answer-A radar that determines the velocity of falling precipitation either toward or away from the radar unit by taking into account the doppler shift How does doppler radar measure the intensity of precipitation? - answer-Sometimes, scientists need to uses techniques to look inside the clouds or storms. One of the ways to do this remotely is through satellite images Explain why atmospheric pressure decreases with increasing altitude - answer-Gravity pushes down, which means less pressure above you What might cause the air pressure to change at the bottom of an air column? - answer-Change of temperature Why is the decrease of air pressure with increasing altitude more rapid when the air is cold? - answer-Cold air is more dense, which will sink down to the surface What is considered standard sea-level atmospheric pressure in millibars? In inches of mercury? In hectopascals? - answer-1013.25 mb 29.92 in 1013.25 hPa How does an aneroid barometer measure atmospheric pressure? - answer-Metal box in barometer, which is sealed off from the outside air How does sea-level pressure differ from station pressure? Can the two ever be the same? - answer-station pressure is a pressure measured at a given height. Where as sea level pressure is when pressure is taken at sea level. they can be the same if the station pressure is taken at sea level. Why will Denver, Colorado, always have a lower station pressure than Chicago, Illinois? - answer-Denver is in the mountains and is considered the mile high city What are isobars? In what increment are they usually drawn on a surface weather map? - answer-Isobars are lines connecting points of equal pressure. They are usually drawn in millibars On an upper level map, is cold air aloft generally associated with low or high pressure? What about warm air aloft? - answer-Cold air is usually associated with low pressure while warm air is associated with high pressure What do Newton's first and second laws of motion tell us? - answer-1st- An object at rest will remain at rest and an object in motion will remain in motion 2- The force exerted on an object equals its mass times the acceleration produced (F=ma) What does a steep or strong pressure gradient mean? How would it appear on a surface map? - answer-A steep pressure gradient means a big change in pressure over a short distance. It would show up on the surface map with the isobars drawn close together What is the name of the force that initially sets the air in motion and, hence, causes the wind to blow? - answer-Pressure Gradient Force Explain why, on a map, closely spaced isobars (or contours) indicate strong winds, and widely spaced isobars (or contours) indicate weak winds. - answer-Closely spaced isobars means a strong pressure gradient. This results in a stronger pressure gradient force and hence a stronger wind speed. Since F=ma, the "a" will be bigger if the slope or gradient is greater - gravity will pull it down hill faster. What does Coriolis effect do to moving air? In Northern Hemisphere? In the Southern Hemisphere? - answer-Northern Hemisphere - causes the wind to veer to the right. • Southern Hemisphere - causes the wind to veer to the left. Explain how each of the following influences Coriolis force: wind speed? Latitude? - answer-• Wind speed - the stronger the wind, the greater the deflection • Latitude - zero at the equator to a maximum at the poles What is a geostrophic wind? On an upper-level air chart, how does it blow? - answer-Geostrophic wind is a wind blowing parallel to the isobars. Geostrophic winds blow parallel to the isobars. What are the forces that affect the horizontal movement of air? - answer-Pressure Gradient Force, coriolis force, and friction if in the boundary layer. Describe how the wind blows around high pressure areas and low pressure areas aloft and near the surface: Northern Hemisphere and Southern Hemisphere - answer-Aloft - parallel to isobars • NH Lo - counterclockwise • NH Hi - clockwise • SH Lo - clockwise • SH Hi -- counterclockwise Surface - across isobars • NH Lo - counterclockwise into • NH Hi - clockwise out of • SH Lo - clockwise into • SH Hi - counterclockwise out of How does zonal flow differ from meridional flow? - answer-Zonal flow is wind blowing from west to east. Meridional winds blow from north to south or along the Meridians (longitude lines). If the clouds overhead are moving from north to south, would the upper-level center of low pressure be to the east or west of you? - answer-East, with your back to the wind, the low is on the left and the high is on the On a surface map, why do surface winds tend to cross the isobars and flow from higher pressure toward lower pressure? - answer-Friction Since there is always an upward-directed pressure gradient force, why doesn't air rush off into space? - answer-The vertical motion is not strong enough to exceed the escape velocity imposed by gravity. • Called hydrostatic equilibrium List as many ways as you can of determining wind direction and wind speed - answer-trees, flags, wet finger, wind instruments Below is a list of instruments. Describe how each one is able to measure wind speed, wind direction, or both. - answer-• Wind vane - direction only; points into wind • Cup anemometer - speed only; cups spin and speed is registered • Aerovane - direction and speed; points into wind, spinning propeller measures speed. • Radiosonde - calculated geometrically from speed and direction of balloon • Satellite - measures movement of clouds • Wind profiler - measures vertical profile of wind speed and direction from movement of rain drops. Describe the various scales of motion and give an example of each - answer-• Microscale - smallest; chimney • Mesoscale - middle; thunderstorm • Macroscale - largest; frontal system What is wind shear and how does it relate to clear air turbulence? - answer-Wind shear is the sudden and unexpected change in wind speed or direction. • If the eddies form in clear air, then the shear is called clear air turbulence Why does a sea breeze at the surface blow from sea to land and a land breeze from land to sea? - answer-• Sea breeze - Pressure Gradient Force is from sea to land • Land breeze - Pressure Gradient Force is from land to sea Which wind will produce clouds: a valley breeze or a mountain breeze? Why? - answer-Valley breeze; Pressure Gradient Force is up mountain. Clouds form as air moves up the mountain, cools, condenses, and forms clouds. What are katabatic winds? How do they form? - answer-Katabatic winds are any strong downslope winds. • They form as cold dense high pressure forms. Hence, PGF is from mountain to lower elevation or a "mountain breeze." Explain why chinook winds are warm and dry - answer-Chinook winds descend eastern slopes of Rockies, warm dry adiabatically and warm through compression. Describe how dust devils usually form - answer-Dust devils form along a turbulent cold air boundary. Briefly explain how the monsoon wind system develops over eastern and southern Asia - answer-Monsoon means seasons - wind changes direction from one season to the next. In eastern and southern Asia, the change is based on the seasonal movement of the Siberian High pressure. In winter the PGF is from land to water; in summer,