METEOROLOGY EXAM 2 REVIEW 1 Terms and definitions for atmospheric moisture d Mixing Ratio a Vapor Pressure c Specific Humidity e Relative Humidity b Absolute Humidity the density of water vapor which is the ratio of the ratio of mass of water vapor in a given air The ratio of the amount of water vapor in the the ratio of mass of water vapor in a given air parcel pressure exerted by H2O vapor molecules in air the larger the vapor pressure is the more H2O vapor molecules in air mass of water vapor and the volume of air parcel to the total mass of air in the parcel to the total mass of dry air in the parcel air compared to the amount of required for saturation at constant pressure and constant water vapor content to become saturated obtained by evaporating water into the air air cools down heats up i Without changing the air s water vapor content as air cools the relative humidity increases and as air warms the relative humidity decreases Temperature to which air must be cooled The lowest temperature that can be h What happens to the vapor pressure and relative humidity when f Dew Point Temperature g Wet Bulb Temperature 2 Formation of Dew Frost Haze Fog and Clouds a Dew and Frost As air cools to its saturation dew point vapor molecules can adhere as dew on the ground surface or as frost when air temperature 0 C b Haze i Dry haze Small aerosol particles 1 2 abundant RH relative low 3 Some selective scattering of sunlight 4 Bluish or yellowish color ii Wet haze 1 RH above 75 condensation begins on hygroscopic particles particles grow 2 visible light scattered evenly grayish or white haze c Fog Fog formed either advection fog i through cooling of an atmospheric layer radiation fog ii through a water vapor source evaporation mixing fog d Clouds 3 Classification of Fog Types a Radiation Fog is reached by radiational cooling i occurs at the ground when dew point temperature ii iii often occurs in valleys and over water bodies iv Either no wind or low winds b Advection Fog i Warm moist air that moves above a cold surface ii May become cooled to its dew point temperature iii Advection fog often forms above the ocean when iv warm ocean air is above cooler waters v Wind needed c Evaporation Mixing Fog i mixing warm unsaturated air with cool unsaturated ii air which can occur during evaporation iii Steam fog is an example of this mixing process iv v vi e g it occurs when warm pools of water are a source for vapor that condense into the cooler air above rivers lakes or during 4 Definitions and causes of stable and unstable atmospheric air dry wet environmental lapse rate a Stable Atmospheric Conditions i Example fall 1 A morning atmosphere has a stable vertical profile keeping fog unmixed 2 Cold air below warm air is considered stable because cold air has a higher density and when displaced will gravitate back below the warm lighter air b Unstable Atmospheric Conditions i Absolutely unstable conditions indicate that a lifted parcel of air whether dry or moist will be warmer than the surrounding environmental air and hence continue to rise c Environmental Lapse Rate vertical i The actual profile of temperature in air 5 Processes that cause instability and cloud development a Absolutely unstable conditions indicate that a lifted parcel of air whether dry or moist will be warmer than the surrounding environmental air and hence continue to rise b Conditions are initially stable when the environmental lapse rate is smaller than the dry adiabatic lapse rate 6 Processes that generate falling precipitation from clouds a collisions that join together small cloud droplets b coalescence that attaches faster and larger droplets with smaller slower droplets 7 Types of precipitation and their formation a Freezing Rain b Sleet c Hailstones i cold raindrops fall through a shallow subfreezing layer and freeze upon striking the ground or the surface of a cold object i cold raindrops or partially melted snowflakes fall through a relatively deep subfreezing layer and turn back into solid ice before reaching the surface i only form in thunderstorms that have updrafts capable of keeping ice particles within the cloud long enough to acquire further coatings of ice 8 Which type of clouds produce which types of precipitation a Stratocumulus i Drizzle b Cumulonimbus i Thunderstorms Lightning Showers or Snow c Nimbostratus i Intense rain or snow