geog
further growth of crystals due to
collisions between falling crystals and drops
hail
concentric layers of ice build around graupel water accreting to graupel freezes, forming a layer hail begins to fall, updraft, repeat
mixing ratio
amount of water vapor (g) relative only to mass of dry air (kg).
saturation vapor pressure
- maximum amount of vapor that can exist at a given temperature temperature dependent (warmer air can hold more water vapor non linear increase
tornadoes
100-600m last 1m to 1 hour
deposition
Water vapor (gas) can change directly into ice or snow (solid)
mesoscale convective systems
A cloud system that occurs in connection with an ensemble of thunderstorms and produces a contiguous precipitation area on the order of 100 Km or more in at least one direction, and often last for several hours to a couple of days.
cloud properties
cloud top height/pressure cloud thickness cloud coverage
cloud to ground lightning
20% electrical discharge travels between the base of the cloud and the surface
how long does it take thunder to travel 1 kilometer
3 seconds (5 sec per mile)
ocean covers what percent of the earths surface?
70%
cloud to cloud lightning
80% occurring when voltage gradient overcomes the electrical resistance of the air
multicell storm
Cool downdrafts leaving a mature and dissipating storm may offer relief from summer heat, but they may also force surrounding, low-level moist air upward. Hence, dying storms often trigger new storms
low stratocumulus clouds
Generated by convection inside boundary layer Convection is driven by cloud-top longwave cooling and evaporative cooling
lake effect
Heat and moisture fluxes from warm lake enhance snowfall in downstream regions
sublimination
Ice or snow (solid) can turn directly into water vapor (gas)
nearly 75% or tornadoes form from
March to july when humid air is overlain by cooler drier air to cause strong vertical lift
steam fog
Mixing of warm, moist air with cold air Adiabatic process (no net change of energy) e.g., common when cold air move over warm lakes/streams in autumn
during evaporation:
Molecules escape into the overlying volume as water vapor
components of global water cycle
Ocean water Land soil moisture, rivers, snow cover, ice sheet and glaciers Sea ice Atmosphere water vapor, clouds, precipitation Water in biosphere (including human beings
precipitation fog
Rain occurs and some evaporates as it falls toward Earth Sometimes this will lead to saturation near surface and cause fog Adiabatic process
during saturation
There is an equilibrium between evaporation and condensation evaporation rate equals condensation rate
during condensation
Water vapor molecules randomly collide with the water surface and bond with adjacent molecules
processes of lightning formation
charge separation stepped leader return stroke dart leader
tornadoes often evolve through
a series of stages, from dust whirl to organizing and mature stages and ending with the shrinking and decay stages
small drop has
a sphere shape
collision coalescense
collector drops collide with smaller drops and merge with them if collector drop is too big compressed air beneath forces small drops aside after collector drop becomes large, super collects
thunderstorm size
about 10 km, last 10 minutes to a couple of hours
diabatic processes
add/remove heat conduction radiation
most clouds form as
air parcels in boundary layer that are lifted and cooled to saturation
mountains
air passes over mountains and causes wave and turbulence on other side
large soggy snowflakes are
associated with moist air near freezing
sleet
begins as ice crystals which melt into rain as they fall through the atmosphere. Before reaching the surface they solidify into a frozen state
air can be cooled down by
by radiation, evaporation of raindrops, melting of snowflakes, etc.
when air temp increases with height
called an inversion sound waves are refracted as they move
fog
can be considered a cloud with base at ground level air has either been: cooled to dew point had moisture added mixed with warm moist air 5 different types radiation advection upslope precipitation steam
tornado formation
can develop in any situation that produces severe weather process not well understood
H2O is unique because
can exist in all three statesCan change from any state to any other state. Latent heat is consumed or released in a phase change
desertification
caused mainly by human activities and climate change 1 bil people under threat
formation of supercell thunderstorms
change in wind direction and speed with increasing height creates spinning effect in lower atmosphere spinning horizontal vortex tubes created by windshear turn into a mesocyclone most strong and violent tornadoes form within this area of strong rotation
development of microburst
contact outburst cushion
downdrafts
cool down the environment generally the lower troposphere can cause signif damage
collision combined with riming and aggregation allow formation of
crystals large enough to precipitate within 1/2 hour of initial formation
absolute humidity
density of water vapor expressed in g/m3
when an air parcel rises, the cooling rate of the parcel relative to the cooling rate of the surrounding atmosphere...
determines the stability of the parcel
upslope fog
develops due to adiabatic cooling occurs when air is lifted over topographic barriers, mountains air expands and cools as it rises common in region between Great Plains and Rocky Mountain foothills
wall cloud
forms underneath the mesocyclone when cold/moist downdraft air feeds into the updraft and condenses at a lower level than warm air.
condensation/deposition forms
dew, frost, fog, clouds
lightening
discharge of electricity, giant spark
saturation forms
droplets or ice crystals
what stops unstable air masses from rising indefinitely
entrainment encountering a layer of stable air
mature stage
entrainment of dry air that causes cooler air from evaporation triggering downdrafts and falling precipitation and gust fronts
1st law of thermodynamics
expanding air cools, compressed warms
tornado outbreak
families of tornados
jet streams
fast, high altitude air currents
air that is cooler than its environment tends to sink leading to
formation of downdrafts
freezing rain
forms similarly to sleet, however, the drop does not completely solidify before striking the surface
why are clouds wildcards for climate change?
good reflectors of solar radiation (cooling) and absorbers of longwave (warming effect) difficulty simulating clouds especially stratocumulus
ozone named after
greek word for smell
downbursts
gusts of wind that can reach speeds in excess of 270 km/hr
thermals
heat from sun makes warm air masses rise and cold sink
runaway discharges
high speed moving electrons radiate light as lightning electrons approach speed of light when a large number of these happens its a runaway breakdown
saturation specific humidity
highest specific humidity for a given temperature and pressure
graupel
ice crystals that undergo extensive riming Lose six sided shape and smooth out Either falls to the ground or provides a nucleus for hail
cloud seeding
induce precipitation, injection of dry ice or silver iodide into clouds convert super cooled droplets to ice to initiate bergeron process
for a cloud drop to fall,
its terminal velocity must exceed the vertical velocity of the upward-moving air parcel. Otherwise it will be carried up.
aggregation
joining of ice crystals through the bonding of surface water builds ice crystals producing snowflakes
effects of supercell thunderstorms
large hails Damaging winds Deadly tornadoes Flooding Dangerous cloud-to-ground lightning
nitrogen cycle
lightning breaks nitrogen moleules and enables atoms to combine with oxygen in the air forming NITROGEN OXIDES dissolve in rain, carried to earth only source of nitrogen for early life forms
dew
liquid condensation on surface occurs early morning on windless cloudless days air immediately above ground cools, reaches dew point diabatic process
riming
liquid water freezing onto ice crystals
microburst
localized column of downdraft produces damaging divergent winds at surface similar to tornados dangerous to airports wet, dry, hybrid
specific humidity
mass of water vapor (g) per mass of air (kg) (in g/kg).
saturation mixing ratio
maximum mixing ratio
air parcels can be lifted by
mountains, meeting of different air masses, surface convergence, and local convection
wake turbulence
near ground a passing plane sets up chaotic currents
wet microburst
nearly saturated layer topped by dry layer driven by entrainment and precipitation loading heavy participation rain foot visible
adiabatic processes
no addition/removal of heat add water vap to air mix warm air with cold cooling of air parcel when rises
radiation fog
occurs when near surface air chills diabatically through loss of longwave radiation reaches Dew Pt requires cloudless nights and light wind to create mixed layer 'burns' off with sunrise - evaporates from below due to surface heating
advection fog
occurs when warm moist air moves across a cooler surface air is chilled diabatically to saturation common on the U.S. west coast warm, moist air from
snow
precipitation that forms by the Bergeron process, riming, and aggregation, and reaches the surface without melting
cloud drop growth is required for
precipitation to form
nitrogen oxides produced by lightening can react with others in the presence of sunlight to produce
ozone (doesnt really add to polution)
medium drop has
parachute shape
supercell storm
producing a minimum of ) 3/4 inch hail and/or wind gusts of 50 knots and/or tornado winds, classify as severe.
tornado
rapidly rotating column of air blowing around intense low pressure with circulation reaching ground wind between 105 km and 450 km
static stability
refers to atmospheres susceptibility to being displaced related to buoyancy force determined by density difference between parcel and environment
frozen dew
results when saturation occurs slightly above 0oC liquid dew formed, when Temp drops liquid dew freezes forms thin sheet of ice, tightly bound to surface dangerous - black ice
when convection happens
rising up of air parcel formation of clouds and rain heating up the environment because parcel is warmer than environment
suction vortices
small zone of intense rotation in most violent tornadoes
large drop
spherical with flattened bottom
trigger
start to uplift
thunderstorms
storm containing lightning and thunder convective (form when warm humid air rises in conditionally unstable environment)
haboobs
strong horizontal winds over desert regions create sandstorms
dew point temperature
temperature at which saturation occurs in air (generally colder than Tair, equals to Tair when saturated)
saturation vapor pressure of ice less than
that of super cooled water at the same temperature
relative humidity
the amount of water vapor in the air relative to the possible maximum.
vapor pressure
the partial pressure exerted by water vapor
collection efficiency is greatest when
the size of collector drop is slightly larger than the size of other drops
thunder
this rapid heating of air will creates an explosive shock wave
entrainment
turbulent mixing of ambient air into parcel leads to evaporation along cloud boundaries uses latent heat, cools cloud, reduces buoyancy
developing stage
unstable atmosphere
dry microburst
very dry topped by moist cooling beneath thunderstorm little or no rain virga in sky blowing dust rings
sound waves move faster in
warm air
dissipating
weakening updrafts and loss of the fuel source after 15-30 minutes
bergeron process
when air is in saturation with supercooled water, over saturated with ice, deposition of water vap over ice ice crystals grow rapidly at the expense of super cooled drops
vertical structure of supercell thunderstorm
winds push rain away and updraft is not weakened so storm can continue maturing and maintain its structure for hours
frost
~ similar to dew BUT saturation occurs below 0oC deposits white ice crystals known as hoar frost e.g. car windshield phase change from vapor directly to solid (deposition) diabatic process