ATMO 336 1st Edition Lecture 14Outline of Last Lecture II. Temp, humidity, wind, and human comforta. Core tempb. Thermalneutral zonec. ThermoregulationIII. Biological control systemsa. Human body response to cold core tempb. Human body respnse to warm core tempIV. HypothermiaV. HyperthermiaVI. Influence of weather conditions on heat lossa. Heat indexb. Wind chill indexVII. Clouds and their formationVIII. Why does rising parcel of air cool?a. Air pressure surrounding parcel is different than air pressure in parcel= pressure forces on the parcel surface are not balanced = forced to change shape (expand or condense in volume)Outline of Current Lecture IX. Rising air cools and expands as It risesX. Conditions for cloud formation (forcing air to rise) 4 basic conditionsa. Surface heating and free convectionb. Horizontal convergence of surface air and/or horizontal divergence of air at top of tropospherec. Topography (mountains)d. Uplift along weather frontsXI. Precipitationa. Collision and coalescenceb. Bergeron processc. Cloud seedingd. VirgaXII. Types of precipitationa. Rainb. Snowc. Freezing raind. SleetThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.XIII. Moving air parcels up and down in atmospherea. Rulesb. How to fill in the chartCurrent Lecture- Rising air cools and expands as it rises (expands to match the surrounding pressure)oo air compresses and warms when it moves downo when air under high pressure (like in a aerosol spray can or bicycle tire), it is released and is coldo when air is compressed (bicycle pump) air feels warm- conditions for cloud formation ( forcing air to rise)o 4 basic mechanisms that force air to move upward 1. Surface heating and free convection 2. horizontal convergence of surface air and/or horizontal divergence of air near the top of the troposphere 3. Topography (mountains) 4. Uplift along weather fronts- surface heating and free convectiono surface of hearth is not heated evenly by the sun (some surfaces absorb heat better thanothers)  blacktop surface will be warmer than a grass covered surfaceo thermals= hot air form above heated surfaces called “hot spots” and begin to rise upward. The thermals then cool by expansiono morning= parcels don’t rise very high because they quickly become colder than the surrounding air.o mid-day= deeper and deeper layer of air near the ground warms up= parcels get hotter and are able to rise higher as the day progresseso thermal rises high enough to saturation point= water vapor condenses and becomes visible as a cloud thunder storms on summer days= sunny in the morning, but parcels able to rise higher and higher later in the day- surface convergence and/or upper-level divergenceo convergence= horizontal net inflow of air into a region= air forced to rise (marked by surface lows)o divergence= horizontal net outflow of air from a region tropospheric divergences leads to rising air just DOWNSTREAM of 500mb troughso dynamic lifting= rising air is forced due to the dynamics of movement or pattern of the horizontal air flow- lifting due to topographyo air confronted by mountain= forced up and over= cools and rises (until its saturation points= clouds form)o orographic clouds= heating of mountain slows by sun causes air to rise upward through surface heating and free convectiono windward side of mountain= air forced to rise= clouds and precipitationo leeward side= warm and dry conditions (“rain shadow”= because clouds do not form where air is sinking) ex: great basin area of the US- lifting along frontal boundarieso front= transition zone between two air masses of different density warmer air= less dense colder air= more dense warmer air mass sits on top of colder air masso fronts extend horizontally and vertically= frontal zoneo weather common at frontso if atmosphere is STABLE= large area of clouds and steady precipitation commono if atmosphere is UNSTABLE= numerous thunderstorms (sometimes severe)- precipitationo takes 1 million cloud droplets to make an average raindropo collision and coalescence= colliding droplets grow by merging together or coalescencing (larger droplets fall faster than smaller ones)o Bergeron process= in cold clouds, precipitation-sized particles form by this process whentemp is between 0= -40 degrees C o Cloud seeding= inject material into clouds to get clouds to form precipitation (alleviate droughts possibly) Inject ice condensation nuclei into a cloud via aircraft or rocketo Virga= air below the cloud dry= precipitation particles may completely evaporate before hitting the ground (low relative humidity). Common in the desert. Seen as ragged cloud bottoms or streaks coming form the bottom of clouds that fade away before reaching the ground- Types of precipitationo Rain= liquid water drops. Air in clouds is very cold, precipitation usually leaves cloud as ice crystals and warms as approaching the ground (can be observed in mountains) Raindrops vary from .1 mm in diameter (drizzle) to over 5mm in diametero Snow=aggregates of ice crystals that collect as falling towards surfaceo Freezing rain= ice storm which is the most devastating of winter weather (cause of automobile accidents, power outages, personal injury). Rain becomes super-cooled and freezes upon impact with cold surfaces. Develops as a layer of warm air deep enough for the snow to melt and become rain, but as it continues to fall, it passes through a thin layer of cold air just above surface and cools to a temp. below freezing (droplets themselves do not freeze)o Sleet= less prevalent than freezing rain and is defined as frozen raindrops that bounce onimpact with ground. Melted or partially melted snowflakes fall through much deeper layer of below freezing air near ground and freeze into little balls of ice before hitting ground More difficult to forecast= develops under more specialized conditions Much less dangerous than freezing rain and is easy to see - Moving air parcels up and down in atmosphereo Rules Starting temp of water vapor in parcel is measured at ground level with focusing on the dew point As long as parcel is unsaturated (relativity humidity less than 100 %) the rate of cooling is 10 degrees C for every 1000 meters the parcel is lifted (temp deceases as it rises) As rising parcel cools, relative humidity increases (dew point will