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UA ATMO 336 - Exam 1 Study Guide

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ATMO 336 1nd EditionExam # 1 Study Guide Lectures: 1 - 9Lecture 1 Introduction to the 500mb (millibars) height maps- 55mb heighto air pressure near sea level- 1000mb water pressure is also equal to zero at sea levelo air pressure decreases as you increase in elevation (falls to 550mb) this is the height where computers forecast weather at air pressure= 0 at top of atmosphere (this is equal to 4600-6000 meters above sea level)- contour maps= averaging the 500mb height of a specific point on the map by finding which line the point is closest to- 500mb height depends on air temperatureo the higher the temperature, the higher the height of the 500mb heighto warmer than average temps= under ridges warm air expands= ridges closed highs= centers of high heights surrounded by one or more closed contours (found at top of ridges)o colder than average temps= under troughs cold air shrinks=troughs closed low=region of low heights around which one or more closed heightcontours are drawn (found at base of troughs)- related with precipitation and colder tempsLecture 2 Estimating wind speed and likely areas for precipitation- wind direction and speed at 500mbo winds blow parallel to height contours ex: in winter, air blows west towards east, but follow wavy pattern of height contours. This 500mb height level weakens during summer months(temperature differences between tropics and arctic become weaker)o wind trajectory= traces motion of air troughs (and closed lows) air makes counter clockwise turn ridges (and closed highs) make clockwise turn in the NORTHERN hemisphereo wind speeds faster where height lines are closer together and slower when spaced further apart- estimating areas for precipitationo most likely downstream from location of troughs (after wind has passed trough and heading into the ridge)o happens where air RISESo precipitation= uncommon in closed highs (air sinking causes fair weatherLecture 3Long waves, temperature patterns, and common weather terminology- Long waves and temperature patternso Long waves= define the larger-scale weather pattern Wavelength of a long wave typically a few thousand meters (west to east)2-7 long waves encircle northern hemisphere at any given time- Convergence and divergence force air to either rise or sink, both occur in upper troposphereo Convergence= horizontal inflow of air into regiono Divergence=horizontal outflow of air way from a region Stronger winds increase divergence (closely spaced height lines)- Common weather terminology; indicators of trough strengtho Zonal pattern= average temperatures are found everywhere and that strong areas of precipitation are unlikelyo Amplified (or meridional)= more extreme weather expected (cold under deep troughs, warm under large ridges, strong areas of precipitation possible just beyond the positions of troughs)- Short waves= smaller wiggles or waves that are superimposed on the long wave patterno Indicate smaller regions of warm/cold temperature contrasts and forced rising and sinking in vertical air motion =stronger weather systems.o ½ the speed of long waves- cutoff lows= when a closed low becomes completely detached from the main westerly wind currents at 500mbo remain detached for days with little movement eastwardo can produce significant rain in AZo forms when trough “pinches off”Lecture 4Numerical forecasts and the atmosphere- Numerical modelso Very complex models that describe physics and dynamic movements in the atmosphere. They also require a large number of calculations and fast computerso Errors in these forecasts= representation of the model is not exact, simulating theatmosphere is not precise since many processes in the atmosphere are not fully understood. Errors also tend to amplify with time. Dozens of different models areproduced giving different forecasts which can often be very confusing to weatherforecasters.- Ensemble weather forecasting= each computer weather forecast model is run many times, but with slightly different initial conditions. This can be used to create a probability forecast- The atmosphereo Air density highest at the surface, thin air at high altitudeso Aerosols= dust, pollen, cloud droplets (very small but at high concentrations)o Troposphere is where all the weather occurso Meteorology= the study of the atmosphere and the processes that cause weathero Weather develops as a result of flow of heat from warmer regions near equator to colder regions near poleso Functions of the atmosphere: Oxygen for life to survive Shields from UV radiation and other high energy particles from sun and space Transports heat and moisture creating more uniform conditions around the globe Applies the greenhouse effect Influences existence of sound and smellLecture 5Gas and the relationship between 500mb and air temperature- Gas= individual molecules are not chemically bonded together and composed of the same molecules that make up liquids and solidso Kinetic model= helps us understand and visualize how matter behaves at the level of individual molecules (behavior of gases) Energy state of a gas is determined by its temperature, pressure, and densityo Ideal gas law Pressure= temp. x number density x constant Equivalent to PV=nRT Holding density constant and temperature increases= increases pressure Holding pressure constant and temperature increases= causes the gas to expand (decrease number density)- Thickness= a better estimate for air temperature near the groundo 500mb height does not depend on sea level pressureo thickness of 1000-500mb is not uniformly warm or cold. To find the surface temperature, meteorologists look at 1000-850mb thickness which is more closelyrelated to the air temp just above the groundo vertical height between any two pressure levels in atmosphere is related to the temperature of the air between two pressure levels the warmer the air, the lower the air number density and the greater the vertical distance between two pressure levelsLecture 6Layers of the atmosphere, density, and pressure- troposphere= warmest at the ground as temperature decreases with altitude (ground is heated)o 75% of total mass of atmosphereo temperature inversion= layer of air in troposphere where the air temp actually increases with altitude (common during sunrise)- tropopause= temperature stops decreasing and becomes nearly steady. Acts as a “lid” on rising air motion and separates troposphere from


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