Science of Storms Question and Answer Bank

5 Pages
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Department
Atmospheric & Oceanic Sciences
Course Code
ATOC 182
Professor
Eyad Atallah

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Description
Review Questions for Final Exam 1) What is the difference between a Colorado Cyclone and an East Coast Cyclone? Colorado Cyclones are closer to the cold air coming from the northwest than East Coast Cyclones. The lifting mechanisms (cold fronts) are stronger than they are on the East Coast. Colorado Cyclones also have a second lifting mechanism on top of the cold front, the Rockies Mountains. These mountains add to the lifting of the warm air. However, the East Coast cyclones are much more intense than the Colorado cyclones due to the fact that there is warmer air coming from the Gulf of Mexico for the east coast and not as much warm air more up north. There is more contribution from latent heat release from the condensation and more heat from the warm ocean. Also, there are stronger thermal contrasts along the coastal boundaries, hot land vs. cooler water, and there is more than one jet streak available for the cyclone’s development. 2) What is a cold wave? A cold wave is a wave of cold air, that is 2 standard deviations (or more) colder than the mean cold temperature experienced in a certain area. 3) Why are cold waves more common in Canada and the United States than in Western Europe? Cold waves are more common in Canada and US than in Western Europe because the cold air coming from the arctic (Arctic air mass) and Western Europe mostly experiences air coming from the ocean (Polar air mass). The air is colder coming from the arctic because the heat capacity of land is much less than water therefore the air stays cold. As opposed to the ocean that has a higher heat capacity therefore the temperature is regulating. 4) What are the ingredients for Lake Effect Snow? Instability: To have lake effect snow you need the atmosphere to be absolutely unstable. To get this you need the environmental lapse rate to be higher than the dry adiabatic lapse rate (10degrees/km) and the moist adiabatic lapse rate (5degrees/km). The lake temperature needs to be around 1-4 degrees and the cold air mass around -15 to -20 degrees, which makes the lapse rate at around 15 degrees/km (need at least 13degrees/km). That way the air parcel will always be warmer than the environment therefore always buoyant and rising. Fetch: Fetch is the direction and amount of time the air stays on the lake. The longer the air stays on the lake the more moisture can be evaporated into the air the stronger the lake effect snow. There are long and short axis to the lakes. If the air travels the long axis it will spend more time over the lake as opposed to the short axis. Wind shear: If there is less change in the direction of the wind it’ll create stronger wind bands, with more change the bands will weaken and so will the intensity of the storm. Winds blowing from too many different angles/directions will blow the cloud apart. Upstream Moisture: Impacts the precipitation potential, it preconditions the air mass. With a higher relative humidity there is more moisture in the air, which will give you more precipitation. If the relative humidity is low then it is difficult to get condensation, clouds and precipitation. Upstream Lakes: The effect of other lakes upstream will impact the snowfall of downwind lakes. It may increase the amount of precipitation formed at the end of the lake. Topography: Rougher terrain contributes to the convergence/lifting of the air. It forces the air to rise, which adds to more clouds and precipitation Snow/ice cover on the lake: If the lake is covered with ice there is no water that can be evaporated into the air therefore lake effect snow cannot occur. The more ice that covers the lake the less lake effect snow that you will occur. 5) In what season is Lake Effect snow most common? Lake effect snow is most common in early to mid winter. This is when the lake waters are relatively warm and the air is cold enough to create a large temperature difference between the lake and the air above. 6) How does the intensity of Lake Effect Snow compare to Cyclones in review question 1? 7) What is the typical progression of winter precipitation as a warm front approaches you and why? Be sure to keep in mind the impact of phase changes of water on the temperature of the atmosphere. The precipitation goes from snow to ice pellets to freezing rain to rain. Before the warm front passes the temperatures are below zero throughout the atmosphere thus snow forms. As a warm front approaches the temperatures at the higher levels is cold, middle level a few degrees above zero, surface level is below zero. This leads to ice pellets because the snow melts at the middle level but refreezes as it goes down. The refreezing of the ice pellets leads to latent heat release and that warms the (middle) temperatures further leading to freezing rain. Rain that is super cooled and is frozen upon contact with a surface, which also gives latent heat release and eventually leads to temperatures that are too warm for freezing (rain). 9) What are the ingredients necessary in order to get a thunderstorm? You need a source of moisture, conditionally unstable atmosphere, a mechanism to trigger the updraft and for super cell thunderstorms you need vertical wind shear. 10) What are typical thunderstorm hazards? Be sure to be able to explain how each of the hazards of a thunderstorm is formed. The downburst or microburst of the storm is a hazard for planes landing or taking off in a thunderstorm. The downburst is made by the cool dry air entering the back side of the storm, evaporation due to the updraft causes the air to be negatively buoyant and flow down rapidly. Flash floods can also be created due to a thunderstorm. The heaviest rain happens in the downburst. If it rains heavily in a valley or on a hill leading to a valley it can accumulate quickly and create a flash flood. Hail is formed with the updraft is strong enough and can carry the raindrops up into extremely cold regions of the atmosphere. It occurs when an updraft lifts an ice particle or nucleus that super cooled water can attach to and form ice around once it reaches extreme cold air temperatures. The stronger the updraft the larger the hailstones. Lightening is another hazard formed by thunderstorms. The snow and ice crystals in the thunder cloud transfer there negative charge to the heavier rain drops and hail stone which move to the
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