Atmospheric Moisture and Humidity Registration is NEXT WEEK Wake up Time to see your advisor Consider a minor in Earth Science Credits count for LACC and minor Latent Heat of Water Heat energy that water releases or absorbs when it changes phase Gains it from environment as it melts or evaporates So it cools the environment Loses it when it freezes or condenses So it warms the environment Latent heat of water Frost on window Humidity Description of how much water air contains Relative Humidity compares how much moisture is in the air to how much moisture the air could hold The amount of water that air can hold is a function of temperature Relative humidity lowering temperature Dew Point Temperature The air cools to the temperature that it has 100 relative humidity Air is SATURATED at 100 RH This temperature is the DEW POINT TEMPERATURE Humidity temperature daily trend Dew on spiderweb Changes of humidity Can warm or cool air and not change water content Will result in different relative humidity Can increase or decrease water content of air without change in temperature Relative humidity constant temperature Sling psychrometer Dry bulb is air temperature Wet bulb has lower temperature due to evaporation Temperature of wet bulb depends on how much moisture is in the atmosphere Relative Humidity Can calculate the amount of water in the air from the relative humidity if you know the air temperature and the amount of water the air could hold at that temperature RH amount of water amount of water 100 the air could hold the air has Changes in temperature with change in elevation Two different mechanisms Earth s atmosphere is heated from below Gases cool as they expand Gases cool as they expand Still have same heat energy Take up larger volume Increase in volume at lower pressure Atmospheric pressure declines with altitude Temperature change due to change in volume called Adiabatic lapse rate Adiabatic lapse rate Temperature declines with lowering pressure as air moves to higher altitude Temperature increases with increasing pressure as air moves to lower altitude Adiabatic lapse rate Rate of temperature change depends on saturation Saturated air has condensation of water which releases heat warms environment 10o C 1000 m if not saturated 5o C 1000 m if condensation is occurring Cooling by lifting adiabatics Orographic lifting Rain shadow Warm front lifting Convergent lifting Convective lifting Hot air balloons Environmental Lapse Rate Earth s atmosphere is heated from below Regularly cooler at greater distances from Earth s surface Varies with moisture temperature cloud cover and other local conditions Stability of Atmosphere Air rises due to a number of factors Expands as it rises cools as it does so Can calculate the new temperature with the adiabatic lapse rate Dry for unsaturated Wet for saturated Compare the temperature of the air that has risen to the temperature of the air at that height Higher density air that has risen is stable cooler Lower density air that has risen is unstable warmer Stable conditions Conditional stability Stable conditions Absolute instability Conditional stability Surface inversion Inversion aloft LA Basin Inversion Inversion Layer Los Angeles
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