final Flashcards
define weather
current state of the atmosphere
define climate
collective state of the atmosphere over a long period of time (30 years)
define meteorology
study of the Earth’s atmosphere
Ever changing; not a perfect science
define atmosphere
the gases that surround earth and the other planets
**10-15 mile zone contains all weather
what are the elements of weather?
- air temperature
- humidity
- clouds
- precipitation
- wind direction
- wind speed
- visibility
- air pressure
define air temperature
how hot or cold the air is, molecular motion
define humidity
Moisture in the air, invisible ; refers to any one of a number of different ways of specifying the amount of water vapor in the air
define clouds
The visible part of the moisture; 10 types, only 2 of the 10 produce precipitation
define wind speed
Speed of the molecules in the air
define visibility
How far we can see; restricted by fog, pollution, etc.
define air pressure
Pressure of the atmosphere; We (at this age) cannot see it or feel it; Pressure falls as the storm approaches; Older people feel it more…also you can feel it more if you are injured
pressure __________ (rises/falls) as a storm approaches
falls
what is a surface map
what the weather is like AT THE GROUND; fronts are only shown on these
what are the 2 types of weather maps?
- surface map
2. upper air map
on a surface station model…
the circle represents
clouds; the more filled in the circle is, the more cloud coverage there is
on a surface station model…
the flag represents
wind speed
on a surface station model…
the bar represents
wind direction
**same for upper air station model
on a surface station model…
the full / half flags represent
full flag : 10 knots
half flag : 5 knots
- *pendant is 50 knots
- *same for upper air station model
on a surface station model…
the upper number on the left side represents
air temperature (in degrees Fahrenheit)
on a surface station model…
the lower number on the left side represents
dew point (in degrees Fahrenheit)
on a surface station model…
the upper number on the right side represents
air pressure (millibars)
**add a decimal to the tenths place and add either a 9 or 10 in front (whichever brings the # closer to 1000)
on a surface station model…
the lower number on the right side represents
change in air pressure (millibars)
**put a decimal point at the front
on an upper air station model…
the upper number on the left side represents…
temperature (in degrees Celsius)
on an upper air station model…
the lower number on the left side represents…
dew point depression (in degrees Celsius)
**how much the dew point temperature is away from the actual temperature
on an upper air station model…
the circle is…
shaded if the dew point depression is 5 or less
on an upper air station model…
the top right number represents…
the height of where the measurements are taken (in meters)
**add a zero to the number given
define isolines
lines of equal or constant values of a given property with respect to place and time
isobar
lines of equal atmospheric pressure
isotherm
lines of equal air temperature
isohyet
lines of equal rain fall amounts
isallobar
measures equal pressure change over time
isodrosotherm
lines of equal dew point temperature
isotach
lines of equal wind speed
Stanley Gedzelman’s (CCNY) Seven Causes of Weather
- Sun’s heating varies over Earth and with Seasons
- Difference in air temperatures over Earth causes winds
- Rotation of Earth destroys wind patterns … twisting the wind, produces spirals … high / low pressure
- Since less moisture can coexist in colder air, precipitation is generally caused by cooling the air
* ** Pressure in the atmosphere ALWAYS decreases with height *** - The process of decreasing air pressure … temperatures drop
- The process of increasing air pressure … temperature rise
- Clouds / precipitation are caused by rising air (lows) clear skies are caused by sinking air (highs)
hydrosphere
water part of the planet; affects the humidity
lithosphere
land part of the planet
biosphere
living part of the planet; brings moisture to the atmosphere
permanent gases and their percentages
Permanent Gases (98% volume)
Nitrogen (N) - 78.07%
Oxygen (O) - 20.95%
Argon (A) - .93%
Neon (Ne) - .001%
variable gases and their percentages
Variable Gases (2% volume) (greenhouse gases)
Water Vapor (H20) Methane (CH4) Carbon Dioxide (CO2) Nitrous Oxide (N20) Ozone (03) CFC's Aerosols / Particulates
outgassing
the atmospheric release of gas (including water vapor); contributed to the formation of the atmosphere
how did oxygen mostly form?
photosynthesis
troposphere
- first layer of the “thermal-structured” atmosphere
- surface to 10/15 miles up
- deeper near the equator shallower near the poles
- weather producing layer
- temperature generally decreases with height; because the sun’s rays heat from the earth’s surface up
stratosphere
- 15-30 miles up
- temperature generally increases with height in upper 2/3 levels of this layer because the ozone is absorbing UV radiation
mesosphere range of distance
30-55 miles up
thermosphere
about 55 miles and up
what layers make up the thermal structure of the atmosphere? (from bottom to the top)
troposphere, stratosphere, mesosphere, thermosphere
what are the atmospheric layers by composition?
homosphere and heterosphere
what is the atmospheric layer organized by electrical properties?
ionosphere
ionosphere
- 45/50 miles and higher
- not really a layer, but electrified region
- molecules (nitrogen) and atoms (oxygen) are readily ionized with high energy SW radiation
- D, E, F layers (lowest to highest)
- Daytime - all layers present
- Nighttime - D & E largely disappear…F remains…very reflective
- –(Aurora Borealis)
homosphere
- surface to 55/60 miles up
- well mixed region
heterosphere
- small number of atoms/molecules causes layering with heavier on bottom (oxygen&nitrogen) and lighter above (hydrogen&helium)
the earth intercepts less than ___________ of all the sun’s energy; however, solar energy represents ______% of the energy that heats the earth’s surface
2 billionths; 99.9%
Vernal Equinox date (in northern hemisphere)
march 21
Summer Solstice date (in northern hemisphere)
june 21
Autumnal Equinox date (in northern hemisphere)
september 21
Winter Solstice (in northern hemisphere)
december 21
1 “atmosphere”
90 degrees overhead
2 “atmospheres”
30 degrees above horizon
11 “atmospheres”
5-10 degrees above horizon
Tropic of Cancer
23.5 degrees north of equator
Tropic of Capricorn
23.5 degrees south of equator
explain what a lag or march of temperature is?
when a high/low temperature occurs before predicted time (march); annually and daily
when a high/low temperature occurs after predicted time (lag); annually and daily
Circle of Illumination
- boundary separating light part of the planet from the dark part
- hits ATX (or anywhere) 1x/day
of 100% of incoming solar radiation…
how much is absorbed by the earth?
51%
of 100% of incoming solar radiation…
how much is absorbed by atmosphere and clouds?
19%
of 100% of incoming solar radiation…
how much is scattered and reflected by clouds?
20%
of 100% of incoming solar radiation…
how much is scattered from atmosphere?
6%
of 100% of incoming solar radiation…
how much is reflected from surface?
4%
transfer of heat from molecule to molecule within a substance
EX:
grabbing a metal pot handle and it being hot
conduction
vertical transfer of heat in our atmosphere
the transfer of heat by the mass movement of a fluid, such as water and air
EX:
billowing of clouds
convection
the emission of energy as electromagnetic waves or as moving subatomic particles, especially high-energy particles that cause ionization
EX:
shortwave (solar)
longwave (terrestrial)
radiation
horizontal transfer of energy
EX:
wind, cold/warm fronts
advection
Rayleigh scattering
shortwave (blue part of spectrum); gases cause the blue sky
Mie scattering
lower levels of the atmosphere; pollen, dust, smoke, clouds, fog
Albedo varies…
place to place / time to time
due to cloud cover / particulate matter
due to the angle of the sun
due to the nature of Earth’s atmosphere
define albedo
total fraction of total radiation that is reflected by a given surface
***higher albedo=higher reflectivity
higher albedo = ______ (lower/higher) reflectivity
higher
Average Planetary Albedo… (in percent)
30%
The Atmospheric “Greenhouse” Effect
the relatively easy transmission of shortwave (incoming /solar) radiation by the atmosphere coupled with the selective absorption of longwave (outgoing / terrestrial) radiation
If an object radiates more energy than it absorbs, the objects turns…..
cooler
If an object absorbs more energy than it radiates, the object turns….
warmer
what is a black body
a perfect absorber (all the radiation it receives is absorbed) or a perfect emitter (emits the maximum radiation possible at a given temperature)
Ex: Earth
Earth’s atmosphere is NOT a black body
define energy
the property of a system that enables it to do work (kinetic, chemical, electrical, etc.)
define heat
form of energy transferred between objects by virtue of temperature differences
Mass MATTERS
define heat capacity
ratio of heat absorbed (or released) by a system compared to the corresponding temperature rise / fall
Water has a GREATER heat capacity than land
water has a _______ (higher/lower) heat capacity than land
higher
define latent heat
the type of heat that is required for a change of state
Latent Heat is absorbed during….
- *Cooling Process
- evaporation
- melting
- sublimation
> LAMES
Latent Heat is released during…
- *Warming Process
- freezing
- condensation
- deposition
> LRCDF
Maximum Thermometers use what substance?
Mercury
Minimum Thermometers use what substance?
Alcohol
albedo of…
fresh snow
85%
albedo of…
thick clouds
70 - 80%
albedo of…
water (low sun angle)
50 - 80%
albedo of…
old snow
50 - 60%
albedo of…
thin clouds
25 - 50%
albedo of…
sand surface
20 - 30%
albedo of…
green grass
20 - 25%
albedo of…
dry earth
15 - 25%
albedo of…
wet earth
10%
albedo of…
forested areas
5 - 10%
albedo of…
water (sun overhead)
3 - 5%
Earth’s RET temperature vs. actual observed surface temperature
Earth’s RET = 0 degree F / -18 degree C
AOST = 59 degrees F / 15 degrees C
**Without gases (CO2 & H2O) the atmosphere would be like the Earth’s RET; BUT…Earth’s atmosphere
is NOT a black body and selectively absorbs & emits radiation
RET stands for…
radiated equilibrium temperature
latent heat of evaporation
Heat is “hidden away” in resulting water vapor when water evaporates
Evaporation is a COOLING process
latent heat of condensation
Sensible heat is released with the rising air parcels
Condensation is a WARMING process
what is significant about 30 - 50 latitude?
- Location at which most heat transfer occurs
- Areas of Stormy weatherf
at 36 degrees latitude or below, _______ (more/less) shortwave radiation is received than lost
more
above 36 degrees latitude, _______ (more/less) shortwave radiation is lost than received
more
what are the three main temperature scales
fahrenheit, celsius, kelvin
who developed the Fahrenheit scale and in what year
Gabriel Daniel Fahrenheit ; 1714
based on mercury-in-glass thermometer based upon a “zero point” ; only in US
Fahrenheit Scale
what are the three significant temperatures on the Fahrenheit scale
98.6 - human body temperature
212 - water’s boiling/steam point
32 - freezing/”zero” point
who developed the Celsius scale and in what year
Anders Celsius ; 1742
devised using the decimal scale and a “zero” point; used widely worldwide (except US)
Celsius Scale
a degree of celsius is ________ (smaller/larger) than a degree of Fahrenheit by a factor of _____
larger ; 1.8
what are the three significant temperatures on the Celsius scale
37 - human body temperature
100 - water’s boiling/steam point
0 - freezing point
who developed the Kelvin scale and in what year
Lord Kelvin (William Thompson) ; 1848
used in scientific formulas/applications ; no negatives on this scale ; the “zero” point is the cessation of molecular motion
Kelvin Scale
what are the significant temperatures on the Kelvin scale
273 - freezing point of water
373 - water’s boiling/steam point
temperature scale conversion: Fahrenheit to Celsius
(F - 32) / 1.8 = C
EX: 50 F = 10 C
(50 F - 32) / 1.8 = 18 / 1.8 = 10C
temperature scale conversion: Celsius to Fahrenheit
C x 1.8 + 32 = F
EX: 30 C = 86 F
(30 C x 1.8) + 32 = 86 F
what are heating/cooling degree days
units of measure ; developed in the early 20th century ; a method of evaluating energy demand and consumption
what is the daily mean temperature that marks/determines when to be heating or cooling
65 F / 18.3 C
if the average temperature is >65…
CDD
if the average temperature is
HDD
the degree difference between the average temperature and 65 F tells you…
the number of HDD or CDD
EX: high temp is 90 F , low temp is 60 F ; therefore the average temp is 75 F ; this is 10 F > 65 F ; therefore, it would be a 10 CDD observed for the day
CDD season
Jan - Dec
HDD season
July 1 - June 30
what are the 2 factors of the heat stress index
temperature and humidity
85% of body heat loss is from…
top of head to neck/shoulders
what are the 2 main factors of the wind chill index
air temperature and wind speed
what is the most important compound in the atmosphere
water vapor
the amount of water vapor (gas) in the atmosphere is _____ (higher/lower) in the polar regions and _____ (higher/lower) near the equator/tropical regions
lower (near 0%) ; higher (near 4%)
water vapor is very important when considering…
atmospheric stability
(AKA-water vapor density) ; the weight/mass of the water vapor per volume of air parcel
absolute humidity
comparing the weight/mass of the water vapor per volume of air parcel with the total weight/mass of the air in the parcel including the water vapor
specific humidity
comparing the weight/mass of the water vapor per volume of air parcel with the weight/mass of the remaining dry air
mixing ratio
ratio of the air’s actual water vapor content compared with the amount of water vapor required for saturation at a given temp
relative humidity
relative humidity can be influenced, or changed, by…
- adding/subtracting moisture to air
- changing given air temp
relative humidity has _______ relationship to temperature
inverse ; so if temperature is getting higher throughout the day, RH is getting low
the temperature to which a parcel of air would need to be cooled to (assuming no change in air pressure or moisture content) in order for the given parcel of air to reach saturation
dew point temperature
dew point temperature is always __________ air temperature
less than or equal to
when dew point temp = air temp…
air is saturated (relative humidity = 100%)
relative humidity is lowest when…
there is a greater difference between dew point temp and air temp
relative humidity is highest when…
there is a smaller difference between dew point temp and air temp
a lower dew point temperature means…
less moisture in air (cold air can hold less water)
a higher dew point temperature means…
more moisture in air
dew cell
directly measures the air’s actual water vapor pressure (used in ASOS/AWOS sensor systems)
atmospheric stability refers to…
a state of equilibrium of the atmosphere
in order to determine atmospheric stability, we look at…
the temperature of a parcel of air as it rise and/or sinks in the atmosphere and compare that temperature to the temperature of surrounding air
when you force a parcel of air to rise…
it expands and cools
when you force a parcel of air to sink
it compresses and warms
when a given parcel of air expands/cools or compresses/warms with NO interchange of heat with its outside environment
adiabatic process
in unsaturated air, air cools/heats at a rate of…
5.5 F / 1000 Ft
in saturated air, air cools/heats at a rate of…
3.3 F / 1000 Ft
when the ELR is greater than the DALR, the atmosphere is said to be
absolutely unstable
when the ELR is greater than the MALR, but less than the DALR, the atmosphere is said to be
conditionally unstable
when the ELR is less than the MALR, the atmosphere is said to be
absolutely stable
stability is enhanced by…
- radiational cooling of the earth’s surface after sunset
- cooling of air mass from below as it moves over a colder surface
- subsidence of an air column
instability is enhanced by…
- intense solar heating
- heating of air mass from below as moves over a warmer surface
- forceful lifting of air (orographic and frontal)
- upward motion with surface air convergence
- radiational cooling from nocturnal thunderstorm cloudtops
parcels rise in _____ (warmer/colder) air
Environmental Lapse Rate ; rate at which air cools with height
water that has condensed onto objects near the ground when the temperature of those objects has cooled below the dew point temperature of the surrounding air ; not a form of precipitation, but still an important source of moisture
dew
what happens when the air temperature falls below freezing after dew has formed?
frozen dew ; NOT CALLED FROST (frost is produced by deposition - meaning it does not pass through a liquid state)
a covering of ice crystals produced by deposition on exposed surfaces when the air temperature falls below the freezing point and the temperature of the exposed objects falls below the surrounding air’s dew point temperature
frost
what kills more people annually than any other weather-related factors
heat
what are the four phases of the hydrologic cycle
evaporation, condensation, transpiration, infiltration
hydrolic cycle:
water going through the roots and out through the leaves of the plants
transpiration
hydrolic cycle:
soaking into the soil ; aquifer?
infiltration
if air temperature and dew point temperature are one degree apart, what is the RH
96%
there is a _______ (direct/indirect) relationship between dew point temp and moisture in air
direct ; more moisture in air at higher dew points, and less moisture in air at lower dew points
sling psychrometer : dry bulb records
actual air temperature
sling psychrometer : wet bulb records
NOT dew point temperature ; after wetting the shoestring and slinging it, the evaporative cooling yields a wet bulb temperature
through this we can determine RH & Dew Point Temp using dry and wet bulb temps and psychometric tables
sling psychrometer
electronic hygrometer
electrical conductors coated with moisture absorbing chemical (usually carbon); Passage of current varies as Relative Humidity varies; used in Radiosondes / Rawinsondes
infrared hygrometer
measures the amount of infrared energy absorbed by water vapor in a given sample of air; used in weather satellites (water vapor imagery)
hair hygrometer
based on a hair strand lengthening with higher RH; hair strands attached to an index dial
most clouds form as air _____, _______, & _______
rises, expands, and cools
a cloud with its base at the earth’s surface
fog
most common type of fog we see in south central texas ; radiates heat away then cool to dew point temp ; fog forms because air becomes saturated ; little to no wind
radiation fog
most common type of fog along west coast ; horizontal wind/movement ; can occur with little wind ;
advection fog
latin root : stratus means…
“layer”
latin root : nimbus means…
“violent rain”
latin root : cumulus means…
“heap”
latin root : cirrus means…
“curl of hair”
if a parcel is colder than the air temp, what will happen
it will sink to get warmer/compress
if a parcel is warmer than the air temp, what will happen
it will rise to get colder/expand
when the parcel expands / cools or compresses / warms with interchange of heat with the outside environment
diabatic process ; but we assume adiabatic process
thermodynamic diagram : the yellow line is the…
parcel line
thermodynamic diagram : compare the yellow line to the…
air temperature line (NOT the dew point temp line)
thermodynamic diagram : when the parcel (yellow) line is left of the air temperature line, the atmosphere is…
stable
thermodynamic diagram : when the parcel (yellow) line is right of the air temperature line, the atmosphere is…
unstable
the quicker it gets colder with height the more ______ (stable/unstable) the parcel is
unstable
the slower it gets colder with height or if there are temperature inversions the more _____ (stable/unstable) the parcel is
stable
cloud formation process:
- surface heating and free convection
- topographic lift
- widespread lifting (ascent) due to surface convergence
- uplift along weather fronts (tornado capital causer)
Adding more moisture to the air than it can hold (you can see your breath when it is cold)
evaporation/mixing fog
Fog that forms when air is forced to move up slowly ; associated with topographic lift
upslope fog
cloud classification schemes : who made the first classification and in what year
Lamarck , 1802
cloud classification schemes : who made the second modification to the classification and in what year
Howard , 1803
cloud classification schemes : who made the last expansion to the classification and in what year
Abercromby & Hildebransson , 1887
cloud coverage is measure in what
octas
cloud coverage : 0/8
clear sky (CLR/SKC)
cloud coverage : 1/8 - 2/8
few clouds (FEW)
cloud coverage : 3/8 - 4/8
scattered (SCT)
cloud coverage : 5/8 - 7/8
broken (BKN)
cloud coverage : 8/8
overcast (OVC)
precipitation types
rain, freezing rain, drizzle, freezing drizzle, sleet, hail, snow
geostationary satellites
22,500 miles above ground ; images of same geographic area continuously
polar orbiting satellites
532 miles above ground ; closely parallel the earth’s meridian lines ; they pass over the north and south polar regions with each pass
precipitation formation process : collision - coalescence process
warmer temperature process
precipitation formation process : bergeron process
colder temperature process
what is the water equivalent of snowfall
1” liquid rainfall = 10” snow
water equivalent of wet snowfall
1” liquid rainfall = 5” snow
water equivalent of dry powdery snow
1” liquid rainfall = 15” snow
what are the three types of precipitation measurement
standard rain gauge ; tipping bucket rain gauge ; weighing type rain gauge
what are things to remember when measuring snowfall
- avoid areas with drifting/blowing snow
- away from trees/buildings
- measure in 3 places with a ruler and average
CLOUD ID: wispy streamers ; lower/shallower near poles ; “mares tales” ; fair weather
cirrus
precipitation that does not reach the ground
virga
what are the high clouds
cirrus, cirrocumulus, cirrostratus (all at or above 20,000 feet)
CLOUD ID: occasional precipitation that doesn’t hit the ground (virga); always white ; scales of fish ; small puffs
cirrocumulus
CLOUD ID: “halo” -usually transparent to sunlight; shadows are cast ; thin sheet like layer
cirrostratus
what are the middle clouds
altocumulus ; altostratus (6,500 - 20,000 ft)
CLOUD ID: gray base-distinguishable ; “rising castles” ; common on mornings of severe weather days ;
altocumulus
CLOUD ID: gray-blue/gray (NEVER white) ; no shadows cast ;
altostratus
what are the low clouds
stratus ; stratocumulus ; nimbostratus
CLOUD ID: uniform grey stratified layer ; light drizzle or light snow possible ; very uniform cloud bases
stratus
CLOUD ID: lumpy cloud layer ; blue sky visible between cloud elelments
stratocumulus
CLOUD ID: dark grey wet-looking cloud ; light to moderate rain (never heavy precipitation) ; bases are normally impossible to identify ; no sun or moon visible through cloud mass
nimbostratus
what are the clouds of vertical extent
cumulus ; cumulonimbus
CLOUD ID: only out when the sun is ; when they have a flat base, air has reached dew point temp ; dense and well defined ; cotton puffs
cumulus
more cloud towering means…
more instability
CLOUD ID: large, towering, precipitating ; thunder, lightning and rain ; severe storms
cumulonimbus
CLOUD SUBTYPES: lenticularis
lens like
CLOUD SUBTYPES: fractus
broken or fractured
CLOUD SUBTYPES: humilis
of small size
CLOUD SUBTYPES: congestus
to pile up/become congested
CLOUD SUBTYPES: undulatus
having waves
CLOUD SUBTYPES: translucidus
to shine through
CLOUD SUBTYPES: mammatus
bag/pouch like ; mammary (extreme turbulence)
CLOUD SUBTYPES: pileus
cap
CLOUD SUBTYPES: castellanus
small castles
CLOUD SUBTYPES: contrails
condensation trails (behind jets)
FORMS OF PRECIPITATION: falls from low stratus clouds ; drops are less than 0.02” ; trace amounts of rainfall
drizzle
FORMS OF PRECIPITATION: diameters greater than 0.02”; generally produced by nimbostratus or cumulonimbus clouds; ***intensity is based upon rate of fall
rain
what does trace mean
not measurable, but occurs
FORMS OF PRECIPITATION: rain that falls in liquid form but freezes upon impact; droplet size greater than 0.02”; ice storms
freezing rain
FORMS OF PRECIPITATION: drizzle that falls in liquid form but freezes upon impact; droplet size less than 0.02”; difficult to see-dangerous
freezing drizzle
FORMS OF PRECIPITATION: frozen raindrops (freeze in air, not upon impact) ; diameter is 0.2” or less; distinctive sound when hitting ground
ice pellets (sleet)
FORMS OF PRECIPITATION: produced through deposition ; up to 0.8” in diameter ; intensity is always based upon visibility
snow
FORMS OF PRECIPITATION: always produced by cumulonimbus clouds ; large liquid water contents, large cloud droplet size, and great vertical height are favorable in creating this form of precipitation ; diameter of 1” (size of quarter) or greater is one criteria that classifies a thunderstorm as being “severe”
hail
the weight of air above a given surface
air pressure
as you climb in elevation, there are fewer air molecules above you, therefore , air pressure always ______ with height
decreses
two identical columns of air (fixed width):
if we move air into the column with no temperature change…
surface pressure would increase
two identical columns of air (fixed width):
if we move air out of the column with no temperature change…
surface pressure would decrease
two identical columns of air (fixed width with same air pressure):
if we warm one column…
the molecules move faster and spread farther apart, the air becomes less dense and the column expands in height
two identical columns of air (fixed width with same air pressure):
if we cool one column…
the molecules move more slowly and crowd closer together, the air becomes more dense and the column shrinks in height
it takes a ____ (shorter/taller) column of cold, dense air to exert (less, more, same) surface pressure as taller column of warm, less dense air
shorter, same
atmospheric pressure decreases more rapidly with elevation in a ______ (warm/cold) column of air
cold
true/false: high pressure is always cold
false ; high pressure is not always hot or cold, it depends on where it is in the atmosphere
atmospheric pressure decreases more slowly with elevation in a _____ (warm/cold) column of air
warm
warmer air aloft is normally associated with ________ (higher/lower) atmospheric pressure aloft
higher (resulting in a more stable atmosphere)
colder air aloft is normally associated with _________ (higher/lower) atmospheric pressure aloft
lower (resulting in a more unstable atmosphere)
unequal heating of the Earth’s surface causes…
the wind to blow (lack of equilibrium)
how do we measure air pressure
barometers (mercurial vs. aneroid)
corrections must be made for what factors when measuring air pressure
- temperature
- instrument
- gravity
- sea level
atmospheric pressure decreases, on average, ____ inch of ______ for each ______ foot rise in altitude
one ; mercury ; 1000
what is the standard surface atmospheric pressure
- 2 mb (milibars)
- 7 lbs/inch
- 92 “ mercury
high pressure is also referred to as…
“anticyclone”
(rising/sinking) air is more stable ; is this more associated with high or low pressure?
sinking ; high pressure
a “mountain” of air above a given location
high pressure
a “valley” of air above a given location
low pressure
low pressure is also referred to as…
“cyclone”
(rising/sinking) air is more unstable ; is this more associated with high or low pressure?
rising ; low pressure
storminess is generally brought by (high/low) pressure
low pressure (rising air)
low pressure:
warm core lows
tropical ; tropical cyclones
low pressure:
cold core lows
extratropical ; frontal lows
planes should always take off or land (against/into) the wind
INTO
high pressure in the NORTHERN HEMISPHERE always rotates (clockwise/counterclockwise)
clockwise
low pressure in the NORTHERN HEMISPHERE always rotates (clockwise/counterclockwise)
counterclockwise
if you see a front drawn on a map…
it is a surface weather map
troughs = (low/high) pressure
low pressure
ridges = (low/high) pressure
high pressure
with corrections made to surface pressure readings, surface pressure charts use ______ to depicts lines of _________________________
isobars ; lines of equal surface pressure
upper air charts are also called…
constant height charts
“ASL”
“above sea level”
upper air charts are constructed to show…
height variations along a constant pressure height surface
on upper air charts, height contour lines depict…
pressure
on upper air charts, higher heights =
higher pressure @ respective height
on upper air charts, lower heights =
lower pressure @ respective height
850 mb chart
4,000 ft ASL
700 mb chart
9,800 ft ASL
500 mb chart
18,500 ft ASL
300 mb chart
30,000 ft ASL
250 mb chart
34,250 ft ASL
200 mb chart
38,500 ft ASL
Newton’s 1st Law of Motion
an object at rest will remain at rest and an object in motion will remain in motion (and will travel at a constant velocity along a straight line) as long as no force is exerted on the object
Newton’s 2nd Law of Motion
the force exerted on an object equals its mass times the acceleration produced
(F=ma)
Newton’s 3rd Law of Motion
for every action, there’s and opposite and equal reaction
hurricanes and tornadoes are (high/low) pressure systems
low pressure systems
90% of tornadoes will turn (clockwise/counterclockwise)
counterclockwise (in Northern Hemisphere; because low pressure rotates counterclockwise)
pressure gradient force
air will always move from higher to lower pressure
THINK : tire blowouts
define the coriolis force
deflection cause by a rotating object
in the northern hemisphere, deflection from the coriolis effect is towards the (left/right)
right
coriolis force is ________ at equator and ________ near poles
NEGLIGIBLE at equator and STRONGER near poles
coriolis force only affects wind __________, not wind ___________
direction ; NOT speed
the amount of deflection depends on…
- rotation of the earth
- latitude
- objects’ speed
large scale wind systems are associated with…
the coriolis effect
generally hurricanes do not form within 5 degrees of __________
the equator
because the coriolis effect is weak at equator and strong at poles; and large wind systems are associated with CF
define friction
wind blowing across Earth’s surface and against other air molecules
friction causes _____% tilt towards (high/low) pressure
33% ; low pressure
Buys-Ballot Rule
says if you stand with your back to the wind and turn to the left 30 degrees, on your right will always be high pressure and on your left low pressure
geostrophic wind generally acts in absence of…
friction (because it is found higher up)
define geostrophic wind
theoretical horizontal wind blowing in a straight path, parallel to the isobars (constant contour lines) at a constant speed
geostrophic wind is caused by an exact balance of _______________ and ___________
pressure gradient force & coriolis force
define hydrostatic balance
in the vertical, an exact balance between vertical pressure gradient force and gravity
what allows the Earth’s atmosphere to remain in place
hydrostatic balance
REMEMBER :
outgoing pressure (geostrophic wind) is balanced by gravity, keeping us from being sucked into space! This is hydrostatic balance
wind is characterized by…
- direction
- speed
- gustiness
speed vs. gustiness
speed is always based on a two minute average
gustiness is instantaneous and a certain % above sustained wind
veering vs. backing wind
veering shifts clockwise
backing shifts counterclockwise
back wind shifts (clockwise/counterclockwise)
counterclockwise
veneering wind shifts
clockwise
what are wind roses/what do they do
graphical device to indicate frequencies of which wind direction is
**USDA and TCEQ
who uses wind roses
airport runways and architects
what is the average prevailing wind direction in ATX
south
wind instrumentation examples
wind vane anemometer ice free wind sensor aerovane wind sock rawinsonde doppler radar
***(located 30 feet above surface)
what are the scales of atmospheric motion
microscale, mesoscale, macroscale
scales of atmospheric motion:
microscale
- small area/footprint
- close to earth (turbulent flow)
- not very representative
scales of atmospheric motion:
mesoscale
- size of several state (regional view)
- big advancements have been on this scale
scales of atmospheric motion:
macroscale - synoptic
- weathermap scale
- map of US
scales of atmospheric motion:
macroscale - global
encompasses most
who invented the single cell global atmospheric circulation model and in what year
george hadley ; 1700s
describe the single cell global atmospheric circulation model
with higher pressure at the poles, sinking cold air flowed southward from the polar regions…once it got to the Equator, after warming, with lower pressure, air was lifted
**one big circulation cell ; too simple
Hadley Cell location
equator 30 degrees north or south latitude
what is the ITCZ
Intertropical Convergence Zone ; area around the equator (“Doldrums”)
in general during the WINTER in the northern hemisphere…higher pressure is over (land/water) and lower pressure over (land/water)
higher pressure is over LAND and lower pressure is over WATER
in general during the SUMMER in the northern hemisphere…higher pressure is over (land/water) and lower pressure over (land/water)
higher pressure is over WATER and lower pressure is over LAND
the troposphere is _________ (shallower/deeper) near the equator, and (shallower/deeper) near poles
DEEPER at equator, SHALLOW at poles
define jet streams
strong, mainly upper level, tropospheric steering wind
polar jet streams are found best at
300 mb height
subtropical jet streams are found best at
200 mb height
low level jet streams are found best at
850 mb to 700 mb heights ; common in central US
surface waters of oceans tend to move with the ________
surface wind (upwelling)
la nina
colder than average equatorial pacific ocean water temps
el nino
warmer than average equatorial pacific ocean water temps
notable el nino events:
1982 - 1983
strong event ; $8 billion in damage
notable el nino events:
1986 - 1987
weaker event ; ended drought in SE USA
notable el nino events:
1991 - 1992
strong event ; severe TX flooding ; 5 year drought ended in CA
what are monsoons
season wind shifts that result in heavy rain
where are monsoons most common
india/southeastern asia
**baby monsoon - southwestern usa (because of summer thermal low)
what are thermal lows
a low pressure circulation created by changes in air temperature
katabatic wind
- cold, downslope wind (gravity)
- can be quite destructive
- Greenland, Antarctica
- referred to as a “mistral” in the Alps
chinook wind
- warm downslope wind
- referred to as the “snoweater” wind by Native Americans
- eastern slopes Rockies in US/Canada
santa ana wind
- warm, dry downslope wind in California
- most common during fall months (october)
- strong surface high pressure over the Great Salt Lake Region
desert winds
- dust devils
- haboob (N. Africa/India)
wind shear
rapid change in wind direction and or wind speed in a small area
EX: tornadoes, thunderstorms, cold fronts
eddy
small whirlwind of water
air masses are characterized by
homogeneous physical properties
-temperature & humidity
A or cA
continental arctic
cP
continental polar
mP
maritime polar
mT
maritime tropical
cT
continental tropical
what air mass is best described by the following:
canada, not as cold as arctic, lake erie modifies temperature upward
continental polar (cP)
what air mass is best described by the following:
gulf of mexico, austin, houston, new orleans, ingredient in thunderstorms
maritime tropical (mT)
what air mass is best described by the following:
think arctic circle, barrow, alaska, only reached austin a couple of times
continental arctic (A or cA)
c =
land
m =
water
T =
warm
P =
cool
A =
very cool
what air mass is best described by the following:
northern desert in mexico, part of new mexico, and arizona; hot and dry
continental tropical (cT)
dry air has a (higher/lower) molecular weight
higher
fronts are found
in troughs of low pressure
**surface convergence and upper level divergence
what is cyclogenesis
low pressure developing at the surface
what causes cyclogenesis
increased surface convergence and upper level divergence (low pressure)
what is a front
a boundary between air mass
frontolysis
a weakened or dying front
frontogenesis
the birth or growth of a new front
overrunning
when less dense air mass runs up over a heavier air mass (frizzing drizzle, lots of clouds)
cold front
4 - 5 mph
- when cold air ACTIVELY advances into a region formerly occupied by warmer air
- steeper slope
- the most dynamic weather comes from the cold frontal lift
a cold front is shown by the color _____ and a line of ________ pointing in the direction that ________________
blue ; triangles ; the front is moving
warm front
- when the surface position of a front moves such that warmer air occupies territory formerly occupied by colder air
- more gentle slope
a warm front is shown by the color _____ and a line of _________pointing in the way that ____________
red ; semicircles ; the front will move
stationary front
- when little forward movement of either air mass, usually upper level winds are parallel to the surface frontal boundary
- causes the floods in TX
a stationary front is shown by a line of ___________
ALTERNATING triangles and semicircles
occluded front
- when a cold front overtakes a warm front in the vicinity of a surface low
- more common over northern US
an occluded front is shown by a line of _____________
triangles and semicircles
all on one side of the line, unlike stationary fronts where the triangles and semicircles are alternating
what do dry lines do
separate two air masses - boundary between cT (hot, dry air) and mT (warm, moist air)
true/false: dry lines are a type of front
FALSE ; dry lines are not technically a front
the molecular weight of cT air is __________(heavier/lighter) than that of the mT air…..what does this mean?
heavier ; when it charges east a dry line lift occurs which can cause thunderstorms
define weather forecasting
predicting how the state of the atmosphere will change with time
what resources do we use to “piece together the puzzle” of weather forecasting?
- satellite
- doppler radar
- rawinsondes
- aircraft data
- lightning data
- buoy data
- weather charts/maps
- numerical weather predictions/comp model
- citizen weather observations
- surface aviation weather observations
- storm spotters/chasers
- looking outside
what air mass is best described by the following:
northern pacific/atlantic, foggy, rainy, chilly
*think Seattle
maritime polar (mP)
remember that air masses ________ as they move
modify
**meaning they can start off as one type (ex: cT) and modify into another as it travels (ex: mT)
severe weather and thunderstorms are associated most with which type of front
cold front
**need dynamic lift
define overrunning
less dense air spreading over/occupying more dense air
how does warmer air remover colder air
from the top…“eating” its way down
what type of front are floods associated with
stationary front
what type of front are clouds and fog associated with
occluded front
to be able to forecast the weather, what must be known
the current weather information over a large area
ASOS/AWOS cannot observe
- hail
- tornadoes
- sleet
- snow depth
what is one of the most reflective hydrometers
wet hail
humans augment what weather observations
- hail
- tornadoes
- sleet
- snow depth
what is the cone of silence
a single sight radar ; when a storm is near or over the radar site, data is unavailable and shows up as this black hole
what color representations on a radar are more reflective/less reflective
less reflective = green
more reflective = red
ASOS/AWOS can observe
- temperature
- pressure
- speed
how often are rawinsondes released
twice a day at hundred of locations worldwide ( 6-7 am & 6-7pm CST)
what do rawinsondes measure with ascension
- temperature
- humidity
- atmospheric pressure
- wind speed/direction
what is the average flight of a rawinsonde
60 - 90 minutes
how high do rawinsondes travel
as high as 100,00 ft (15 - 20 miles)
what are METARS
coded aviation (surface) weather observations that are transmitted globally >hourly ; it is a description of the meteorological elements observed at an airport at a specific time
what does WMO stand for
World Meteorological Organization
*it is a UN specialized agency
what is the WMO responsible for
the international exchanges of weather data and certifying that the observation process DOES NOT vary between nation since all weather observations must be comparable
where do people get their weather forecasts
- radio
- tv
- internet
- newspapers
- AMS/NWA
what does it take to be a part of AMS
AMS certified broadcast meteorologist have to pass a test ; joining the AMS/NWA is voluntary because we do not/rarely license meteorologists in the US
who issues weather watches/advisories/warnings
the National Weather Service (government)
**this is the SOLE source to issue these
which is described below: watch, advisory, or warning?
type of weather specified is imminent or is occurring and is a public inconvenience (smaller to larger geographic area)
advisory
which is described below: watch, advisory, or warning?
type of weather specified is imminent or is occurring and is an immediate threat to life and/or property (generally smaller geographic area)
warning
which is described below: watch, advisory, or warning?
atmospheric conditions are favorable for the type of weather specified (generally larger geographic area)
watch
time span of weather watches
longer time span: 4 - 6 hours up to 24 - 48 hours
time span of weather advisory
6 - 24 hours
time span of weather warning
.5 - 1 hour
what are the different methods of forecasting
- persistence forecasting
- steady state/trend forecasting
- analogue method forecasting
- ensemble forecasting
- climatological forecasting
- “gut” forecasting
what type of forecasting method is best described by the following:
looking at similar systems from the past
analogue method forecasting
what type of forecasting method is best described by the following:
looking at movement of system
steady state/trend forecasting
what type of forecasting method is best described by the following:
tied to numerical weather prediction; several members are run to collect data and test accuracy of model
ensemble forecasting
what type of forecasting method is best described by the following:
basing forecast on climate/previous trends of that location and season
climatological forecasting
what type of forecasting method is best described by the following:
most valuable in short term, use when pattern is stable
persistence forecasting
what type of forecasting method is best described by the following:
go with and make decisions based on your experience/instinct
“gut” forecasting
weather forecasting is a ___________ science
non-perfect
what method of weather forecasting should be used
all of them! don’t just look at one, use a combination
what does NWP stand for
Numerical Weather Prediction
what is NWP
computer atmospheric models made through programs
how often are NWP models run
1-4 times/day
what are some problems with the NWP system
- if bad data in, then bad data out
- model make certain assumptions therefore have certain biases
- data sparse areas of the world
- cannot adequately interpret many of the factors that influence surface weather
- small disturbances/errors tend to be amplified with time
what does POP forecasting stand for
probability of precipitation
true/false: POP forecasting is very misunderstood
true
how do we arrive at forecast POP
(forecaster certainty) x (areal coverage expected)
EX: 50% x 20% = 1000 or 10% POP
**it means there’s a 10% chance that it will rain AT A GIVEN LOCATION
it does not mean that it will be raining 10% of the time or 10% of the area
what is the short term forecast accuracy
80-90% (today/tonight)
what is the medium term forecast accuracy
over 80% (2-3 days out)
what is the monthly or seasonal outlook accuracy
much lower (30-90 days out)
what is the longer range forecast accuracy
70% (4-8 days out)
what percent of thunderstorms worldwide are classified as severe
less than 5%
true/false: straight line winds can cause more damage than tornadoes
true ; straight line winds diverge whereas the winds of tornadoes converge
what are the basic requirements for a thunderstorm
- lift
- instability
- moisture
how long to most thunderstorms last
about an hour
how are thunderstorms brought to an end
the down draft (cold, more dense air) cuts off the updraft and the storm commits atmospheric “suicide”
true/false: severe thunderstorms do not last as long as air mass thunderstorms
false ; severe thunderstorms are longer lasting because of an established/well developed wind structure (2 hours longer)
where do most severe thunderstorms occur
middle latitudes along cold fronts/dry lines
**cP/mP/mT/cT boundaries
what are the criteria for a US severe thunderstorm
- presence of a tornado
- 1 inch or larger diameter hail (@ surface)
- convective wind gusts of 50 knots/58mph
**this is an AND/OR list; only one criteria must be met for it to be considered severe
true/false: the presence of an initial tropospheric temperature inversion contributes to thunderstorm development
true
define squall lines
a line of thunderstorms
what is something you should always remember to look for in a squall line
always watch for the storm at the end of the line
what determines the severity of the individual thunderstorms in a squall line
the density of the storms along the line
define super cells
long lasting thunderstorms that develop a strong, internal wind structure and that control their atmospheric environment
true/false: super cells are always severe
true
define mesocyclones
a rotating updraft, usually 3 - 7 miles, within an intense cumulonimbus cloud/severe thunderstorm
what percent of mesocyclones produce tornadoes
less than 20%
what is a mesoscale convective complex/system
a number of individual thunderstorms that grow in size and arrange and organize into a long lasting convective complex
where are mesoscale convective systems commonly found
USA plains and into Mississippi Valley
how much larger can mesoscale convective systems be than average air mass thunderstorms
as much as 1000x
what does derecho mean
“straight ahead” or “direct”
what is a derecho
a widespread and usually fast moving convective wind storm
how severe is the reach and damage of a derecho
can produce damaging wind over areas hundreds of miles long and more than 100 miles across
true/false: thunderstorms are bad for the environment
false; thunderstorms are good for the environment because they help keep the Earth in electrical balance; they also serve as a great way for the atmosphere to release energy
what are the 4 different types of thunderstorms
- single cells
- multicell clusters
- multicell lines
- supercells
what are the stages of thunderstorm developement
- cumulus (updrafts dominate)
- mature (updrafts/downdrafts coexist)
- dissipating (downdrafts dominate)
lightning won’t develop until _____________ develop
downdrafts
at any given moment, how many individual thunderstorms are in progress worldwide
2000
of the 2000 individual thunderstorms in progress worldwide, what percent are severe or non-severe
over 95% non-severe ; less than 5% severe
what are the differences in hail size between severe and non severe thunderstorms
non-severe : hail less than 1” in diameter
severe: hail equal or greater than 1”
what are the differences in formation location between severe and non-severe thunderstorms
non-severe : found WITHIN mT airmass
severe : found ON boundaries of mT airmass
hail size (and thunderstorm severity) is entirely dependent on _____________
thunderstorm updraft and downdraft speed
largest hail often falls ________ (NW, NE, SW, SE) of tornadoes
NE
what is the number one weather killer in the US
summer heat
true/false: flash floods are one of the top weather killers in the US
true ; general public does not understand the power of moving water
**south central texas is considered the flash flood capital of the US
what are straight line thunderstorm winds
strong downdraft winds from thunderstorms with a divergent wind pattern
**referred to in general as downbursts
where are GOES satellites east and west located
GOES west is at 135 W longitude
GOES east is at 75 W longitude
what are the three different satellite image types
visible, infrared, and water vapor
what does the visible satellite image type display
shows what the sun light up, cannot see at night
what does the infrared satellite image type display
hotter colors denote colder cloudtops, 24 hrs a day
what does the water vapor satellite image type display
mid and upper level atmospheric moisture
reflectivity vs. velocity data
reflectivity will show levels of precipitation
velocity will show where it’s moving
what is clear air mode
when there is high certainty of no precipitation, satellites can enter this mode and not do as much work
what is dual pol
horizontal and vertical measurements/waves, this crossection allows us to capture both size and shape of hydrometers
ASOS stands for
automated surface observing system
AWOS stands for
automated weather observing system
an example of an airport that uses human augmentation
austin bergstrom
an example of an airport that does not use human augmentation
camp mabry
what are the most common lightning types
cloud to cloud & intracloud
a bolt of lightning is about the diameter of…
a pencil
within the lightning bolt, it is about ___ times the temperature of _______________
5 times the temperature of the outer surface of the sun
what about tornadoes kills most people
the flying debris
