Moisture and WindQ: Is the change over the annual cycle in the Northern Hemisphere larger or smaller then the annual cycle in the Southern Hemisphere?A: Northern, because there is more land mass which absorbs more heat quicklyProperties of the AtmosphereTemperaturePressureMoistureWindAtmosphere is a thin layer of air extending from the surface to 100 km90% of mass is below 12kmWeather occurs 2-5k78% nitrogen21% oxygen.00001% water vaporTemperature = the average speed of moleculesWhen object of different temperature come into contact the object with more heat shares with object of lesser heat (2nd law of thermodynamics)Absolute zero = no molecule movement-459.67 degrees F273.15 degrees CIf the temperature on the Fahrenheit scale is 100 degrees, then the corresponding temperature on the Celsius scale is greater than 100 degrees. FALSEHow does moisture exist in the atmosphere?Solid (ice crystals)Liquid (cloud droplets, fog, rain)Gas (water vapor)In clouds it exists asLiquid waterIce crystalsSeasonsWhy does the temperature change during the year and why is this change larger in middle and high latitudes than in the tropics?How does the tilt of the earth cause seasons?Length of daylightAmount of sunlight able to pass through theatmosphereArea illuminated by the sunAir Pressure: the force applied by air to a unit area of surfaceP=force/areaThe air pressure at a given point is equal to the weight of all of the air above that pointPressure decreases with altitude870 typical pressure in BoulderPressure at sea level in different units:10 tons per square meter14.7 psi (pounds per square inch)29.92 inches of mercury760 millimeters of mercurymeteorologists use: 1013.25 millibars or hPaStation pressure: the air pressure measured at a surface weather station (this is also called surface pressure)Mean sea level pressure: the pressure that would be measured if the weather station were located at sea levelSUMMARYWhy does temperature change during the year?Tilt of the Earth and Earth rotating around the SunHow are the different layers of the atmosphere defined?Name the layers and describe how and why temperature changesRole of troposphere and tropopause and how tropopause heightchanges with latitudeWhat is the difference between station and sea level pressure?What are typical pressure readings at sea-level and in Boulder? What is the typical range of sea level pressure?Why do we use sea-level pressure in weather maps?The Vapor Pressure is a measure of how much water vapor is in the atmosphereVapor pressure increases as the amount of water in the atmosphere increasesthe force per unit area applied by only the water vapor moleculesvapor pressure at normal atmospheric temperature ranges form 0 mb in a dry cold atmosphere to 60 mb in a humid tropical atmosphereVapor pressure is an absolute measure of the amount of water in the atmosphereDoesn’t depend on anything elseVapor pressure varies with season and weather systemWhere is the vapor pressure low and high?Higher vapor pressure = more water in atmosphereHow does the vapor pressure change from Winter to Summer?More evaporation in summer, water vapor increasesThe dew point temperature is another measure of absolute amount of water in the atmosphereSaturatedInvisible vapor condenses into visible cloud dropletsWhen the atmosphere can not contain any more water vapor without condensing into cloud droplets is it saturatedWhen air is near saturation our bodies cool inefficiently because water has difficulty evaporatingThe limit of how much water vapor can be in the air is determined by the saturation or equilibrium vapor pressureWater is continually condensing while liquid water is continually evaporatingWhen the rate of condensation equals the rate of evaporation the situation is in a state of equilibriumThe atmosphere is saturated when it cannot contain any more water vapor without having cloud dropletsSaturation Vapor Pressure is the vapor pressure at which at atmosphere become saturatedOnly factor for saturation is the temperatureSaturation vapor pressure increases as temperature increasesLittle capacity for moisture in coldThe Leaky Bucket AnalogyLevel of balance is determined only by rate of inflow of evaporation, which depends on temperatureThe saturation vapor pressure always increases as the air temperature increasesRelative HumidityThe amount of water vapor in the atmosphere relative to the atmosphere’s capacity for moisture at a given temperatureRelative humidity = (vapor pressure/saturation vapor pressure) x 100%Depends on two quantities 1) the absolute amount of moisture in the air (vapor pressure) 2) the amount of moisture the air can contain when it is saturated (saturation vapor pressure)When the air is saturated the relative humidity = 100%Can be roughly estimated by comparing dew point temperature and the actual temperatureEx. If the temperature is 70 and the dew point in 69, air only needs to cool 1 for saturation to occurRelative humidity fluctuates and it can be approximated by comparing temperature to dew point temperatureLocationVapor pressureTempSaturation Vapor PressureRelative HumiditySW Desert in Summer8mb35 C60 mb13%Northern Plaines in winter2 mb0 C6mb33%Which Location has higher absolute humidity? SW DesertVapor pressure is the variable you look at to determine humidityAt which location is the air closer to being saturated? NW in winter, look at relative humidity to determine this.The Dew Point Temperature is the temperature to which air must be cooled (at constant pressure) to just become saturated (dew forms)Td increases as the amount of water vapor in the atmosphere increasesTd is an absolute measure of water vapor in the atmosphereMaps often express Td as a dew point depression or T-Td1. The relative humidity is high when the different between the temperature and the dew point temperature is small2. The relative humidity is low when the different between the temperature and dew point temperature are largeWhich one of the following weather observations would tell you how close the atmosphere is to being saturated?TemperatureDew Point TemperatureRelative humidity ✔Saturation vapor pressureWhich one of the following weather observations would tell you the actual amount of water vapor in the atmosphere?TemperatureDew Point Temperature ✔Relative humiditySaturation vapor pressureLatent heat is critical for weatherThe energy associated with the phase changes of water is called latent heatLatent heat is released from the