exam 2 Flashcards
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
units of measure ; developed in the early 20th century ; a method of evaluating energy demand and consumption
Heating/Cooling Degree Days
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
latent heat absorbed…
- *Cooling Process
- evaporation
- melting
- sublimation
> LAMES
latent heat released…
- *Warming Process
- freezing
- condensation
- deposition
> LRCDF
humidity
refers to any one of a number of different ways of specifying the amount of water vapor in the air
(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
warmer
ELR
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
water going through the roots and out through the leaves of the plants
transpiration
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
