hygroscopic nuclei - ● water seeking ● condensation can begin on these when relative humidity is less than 100 percent cloud formation ● rising, cooling air ● condensation nuclei ● adequate water vapor content rising and expanding - The most common way for air to be cooled in order that a cloud may form is by: air being cooled as it rises. - Clouds and precipitation form in the air primarily due to: Condensation ● The process by which a cloud droplet first forms is ● requires the greatest release of latent heat energy into the atmosphere about equal to the dew point - Dew point is the temperature at which water vapor in the air begins to condense. The temperature inside a cloud would therefore be: the air being cooled - Clouds, dew and frost all form because air has become saturated. This condition of saturation is usually caused by: alto - The cloud form that is best described as sheets or layers that cover much or all of the sky is termed ascent of air - Which factor is most significant in the formation of clouds in the atmosphere? advection - when warm moist air moves over a cold surface, ________ fog may result. evaporation fog - They are created when water vapor is added to the air. fog supercooled ● When liquid cloud droplets exist at temperatures below freezing ● still liquid at temperatures below 0°C. ● Water can exist in this supercooled state because of lack of "freezing nuclei" in the atmosphere ● The completely frozen region of the cloud (temps less than -40C) -40°C - Pure water suspended in the atmosphere will freeze at a temperature of: collision and coalescence. ● The growth of a cloud droplet into a rain drop large enough to fall to Earth in a warm cloud is accomplished primarily through: ● cloud above freezing ● warm cloud ice-crystal process. ● Most of the precipitation that falls in the middle latitudes is formed by: ● Major method of precipitation formation in the middle and high latitudes ● Cloud below freezing condensation nuclei - The cloud droplets in a cloud are formed by water vapor molecules and: absorbed by the evaporating water - as liquid water is evaporated into the atmosphere, heat energy is deposition - frost that forms on cold glass is created by 0-4 percent - water vapor constitutes about this much of the atmosphere by volume Specific humidity - mass of water vapor in the air/ TOTAL mass of air mixing ratio - mass of water vapor/mass of DRY air Atmospheric Humidity - mass of water vapor in the air/volume of air Dew point temperature ● The temperature to which the atmosphere must be cooled for saturation to occur (with no pressure change or change in moisture content) ● The only way to change the dew point temperature is to change the amount of water vapor in the air ● Air temp is never lower than dew point ● Best single measure of weather comfortability Vapor pressure ● mass of water vapor/volume of air ● The total pressure exerted by a mixture of gases is equal to the sum of the partial pressure exerted by each gas with an increase in temperature - the capacity of the air to hold water increases air temperature remains constant - evaporating water into the air will increase the dew point and increase the relative humidity. relative humidity ● tells you the percent of water vapor the air is holding compared to the amount it could hold ● Lower ____ leads to higher evaporation rates ● Higher____ leads to lower evaporation rates ● indicates the nearness to saturation for the air. ● to change it: change the temp, or the amount if water vapor relative humidity equation - the Amount of water vapor in the air/ the amount of water vapor the air could hold at a given temp x 100 percent dew - Temperatures of the objects near the ground often cool below the dew point at night. condensation - As the temperature of air is reduced to its dew point, which of these is most likely to occur? expanded - During the process of adiabatic cooling, the temperature decreases because the air has: cooling by expansion of air - The most important process of cloud formation in the atmosphere is: air parcels - The temperature decreases as they move upward. lifting condensation level - the location of the first place where the air becomes saturated air parcel sinks - it is compressed and warmed. dry adiabatic rate ● the rate of adiabatic cooling or warming in unsaturated air; the rate of temperature change is 1°C per 100 meters ● always will be higher than the wet ● wet adiabatic rate - the rate of adiabatic temperature change in saturated air; the rate of temperature change is variable, but it is always less than the dry adiabatic rate condition for cloud formation - A rising parcel of air reaches its dew-point temperature. air parcel moves upward ● The air in the parcel expands and is cooled adiabatically. ● decrease in the atmospheric pressure ● air parcel moves ___ orographic lifting - An air parcel rises over a mountain and cools adiabatically. Which lifting mechanism has acted on this parcel? frontal wedging - Which type of lifting mechanism results from warm air lifting over cold air? forces the air to rise. - A convergence of winds near the surface is associated with cloud production because it: Rain shadow deserts - form on the leeward sides of mountain ranges convection. - The vertical motions that occur when the air is unstable are termed: environmental lapse rate. - The change in the actual air temperature as you go up into the atmosphere stable atmosphere - upward vertical motions are resisted. rise - If an air parcel is warmer than the surrounding environment, then it will unstable atmosphere - warm the surface and cool the air aloft clear skies - subsidence or sinking motion. adiabatic process - One in which no heat transfer takes place between a parcel and the environment adiabatic expansion and cooling - Fastest molecules and highest temperature rises and increases to slowest molecules and lowest temperature adiabatic contraction and warming - Slowest molecules and lowest temp decreases and goes to fastest molecules and highest temps contraction - The environment does work on the parcel, increasing the parcel energy, increasing the speed of the molecule, increasing temperature Expansion - doing work on the environment, this uses energy, since no new energy can come in to replace that which has been expended, this loss of energy slows down the molecules humidity - a generic term for the amount of water vapor that is present in the air daltons law ● The total pressure exerted by a mixture of gases is equal to the sum of the partial pressure exerted by each gas ● warm, cold - ____water has the capacity to hold more water vapor than _____ air ● dew point temperature - The temperature to which the atmosphere must be cooled for saturation to occur (with no pressure change or change in moisture content) ● only way to change is to change the amount of water vapor in the air ● best measure air temperature - never lower than dew point Dew point depression ● T - Td (water holding capacity of atmosphere) - (amount of water in atmosphere) ● Dew point and air temp are close together the relative humidity is high and visa versa process of clouds - Air rises- temp drops- RH up clouds - Classified according to their appearance and height stratiform - sheet like, layered cumulus - vertically developed, puffy, heaped high - form above 20000 ft and are composed mainly of ice crystals cirrus - hight middle - between 6500 ft and 23000 ft and are composed of water droplets and/or ice crystals Alto - middle low - bases below 6500 ft and are composed mainly of water droplets. However during winter they may contain ice crystals and snow stratus - low vertical development clouds ● These clouds can have bases as low as 1000 ft and tops as high as 65000 ft. they are composed of both water droplets and ice crystals ● you can get precipitation Cumulus - vertical cumulonimbus ● vertical ● Thunder and lightning are associated with the ________ cloud ● formed in an unstable environment radiation inversion ● clear, calm nights ● frost - frozen dew ● gas to solid ● Areas under clouds and or trees cool down more slowly because they absorb LWR Condensation nuclei - small particles that range from less than a tenth of a micrometer to greater than a micrometer. These are usually small pieces of dust, pollen, ash, or even bacteria Hydrophobic nuclei ● repel water and resist condensation even when relative humidity is 100 percent ● When visibility decreases to less than 1 km we say that a cloud has formed that is resting on the ground radiation fog - Earth's surface cools rapidly... a radiation inversion forms Early morning, fall through spring, clear calm night advection fog - Cold surface (snow cover, cold ocean currents) with warm moist air and cooling it down upslope fog - Air rises and cools adiabatically (fog) severe weather ● west of the rockies ● A relatively warm, moist, conditionally unstable atmosphere (usually a dew point above 50 degrees) ● A mechanism to generate upward motion in the atmosphere (front, surface low pressure, upper level divergence) usually associated with a clash in air mass ● The presence of an upper level jet stream nearby.. Preferably the ascending branch (area between a trough and a ridge) of an upper level jet stream jet stream ● Currents of fast moving air. Those most important to us in meteorology are generally found near the top of the troposphere ● Cold air north, warm air south tough ● temperatures are generally below normal and you will often find unsettled weather ● ridge - temperatures are generally above normal and you will often find fair weather ● dry adiabatic lapse rate (DALR) - As long as the air in a rising or sinking parcel remains unsaturated, the rate of adiabatic cooling or warming real constant. ● 10 degrees c/1000m moist adiabatic lapse rate (MALR) ● The rate at which a saturated air parcel will cool ● always smaller than the DALR ● It varies greatly depending upon the amount of water vapor present in the air parcel. This is because a warm saturated parcel will be holding more water vapor than cold, saturated parcel ● 6 degree c/1000m parcel lapse rates - MALR and DALR Lifting condensation level - The level at which a parcel of airlifted and cooling dryadiabatically would first become stauresated (where a cloud would form) Atmospheric stability - We can determine the stability of the atmosphere by comparing the temperature off a rising parcel to the environment (its surroundings) Absolute stability ● - when the ELR is less than the MALR ● The environment is cooling more slowly than a saturated or dry air parcel Absolute instability ● The atmosphere is in a condition of absolute instability when the ELA is greater than the DALR ● The environment is cooling faster than a dry or saturated air parcel ● Occurs only in the thin layers of the atmosphere (usually close to the surface) Conditional instability ● Conditional instability occurs when he ELR is between the MALR and the DALR ● The environment is cooling slower than a dry air parcel, but faster than a saturated air parcel level of convection - environmental lapse rate 8 degree c/1000m convection - Refers to the vertical movement of the atmosphere due to density differences between an air parcel and the surrounding atmospheric environment widespread - ascent due to convergence cloud base formula ● H(meters)=125m(T-Td) (celcius) ● H(feet)=222ft (T-Td) (Fahrenheit) ● td can't be greater than t ice-crystal process (bergeron-dindeisen) ● cold clouds ● Major method of precipitation formation in the middle and high latitudes ● Cloud below freezing glaciated region ● A pure water droplet will not freeze until temperatures reach around -40C ● Ice crystals have smaller evaporation rate than a cloud droplet. thus , ice crystals will grow faster than cloud droplets in clouds that contain both freezing rain - snow to rain to sleet ● Snow to rain to freezing rain to ● forms when snowflakes melt partially then re-freeze before hitting the ground convergence ● joining of parts ● smaller, lower - the ____ the dew point depression, the ____ the height of the convective cloud base. hoar frost - ice crystals on the ground, gas to solid