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294 Cards in this Set
- Front
- Back
- 3rd side (hint)
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The revolution of the sun is NOT |
a perfect circle |
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The sun is not |
In the same place every day; due to the revolution of the earth of the sun and the earths tilt |
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Altitude of the sun |
Angle of the sun above the horizon |
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Most indirect rays at |
Horizon |
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Most direct rays at |
90 degrees overhead which means rays are traversing 1 atmosphere |
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Atmospheres as a unit of measurement measures what? |
how much of the earth's atmosphere is being traversed by the suns rays (it quantifies the energy coming in) |
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In Mexico the sun can be... |
directly overhead for a short time in the summer, which means the suns rays are traversing 1 atmosphere |
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The Sun is NEVER what in Austin? |
Directly overhead, we traverse 2 atmospheres at about 30 degrees |
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When the sun is about 30 degrees how many atmospheres does it traverse? |
2 atmospheres, which means you cant look at sun |
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at sunset, you can... |
look at the sun; because it is traversing about 10 - 11 atmospheres |
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89 degrees would mean what for traversing atmospheres? |
It would mean it's between 1 -2 atmosphere |
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What is the vernal equinox? |
the start of spring in Mar. 20-21 (in northern hemisphere). For a split second, the sun is most directly overhead of the equator. As it goes more into the northern hemisphere we enjoy spring - |
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Summer Solstice |
Start of summer on June 21-22. The sun hots the tropic of cancer and then starts to lower in the sky. (this takes time) |
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The hottest day of the year is when the sun |
has already begun to lower, because the earth takes time to warm up |
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Earth does all the work to get what? |
seasons |
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Tropic of cancer |
in the northern hemisphere at 23 and a half degrees North latitude (reference point is Mexico) Furthest point North for sun |
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Tropic of Capricorn |
23 and 1/2 degrees south. Furthest point South of sun |
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Autumnal Equinox |
in the southern hemisphere, the sun is directly overhead equator. the sun is heading south on Sept. 22-23 |
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Winter Solstice |
On Dec 21- 22, the sun appears over the Tropic of Capricorn for a split second. Sun begins to appear higher in the sky again |
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Lag and March of temperatures |
Takes time for earth to heat up |
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short wave radiation / solar radiation |
- the atmosphere does not absorb a lot of energy directly from the sun. - sun to Earth (moving from hot to cool object) |
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In the troposphere what happens to temp? |
temp. generally decreases with height |
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Earth surface warms and heats what? |
the air above it |
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Earth absorbs what |
the solar energy that is ignored by the atmosphere |
think of a parking lot |
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Largely are troposphere is heated by what? |
the earth |
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Terrestrial Radiation or Long wave radiation |
the earth absorbs sun rays and reradiates it into this, which is then absorbed by the atmosphere |
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Why does temp decrease in the troposphere? |
Heat is coming from earth so you are getting away from the source |
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Guam is 14 degrees latitude so how many times will the sun hit it in a year? |
twice |
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Circle of Elimination |
- The boundary separating the dark part of the earth from the light part of the planet - there is only one - it makes its way around the earth twice (sunset and sunrise) |
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How much of the sun's short-term radiation is scattered and reflected by clouds? |
20% (for instance think thunderstorm clouds) |
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How much of the sun's short-term radiation is scattered from the atmosphere? |
6% |
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How much of the sun's short-term radiation is absorbed by the atmosphere and clouds? |
19% (more likely by clouds) |
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How much of the sun's short-term radiation is absorbed by the EARTH? |
51% |
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How much of the sun's short-term radiation is reflected by the surface? |
4% |
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what are the 4 ways to transfer energy? |
-Conduction -Convention - Advection - Radiation |
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Conduction |
moving of heat energy from hotter to colder depending upon the nature of the material that it is moving through |
Think of metal vs. Wood |
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Convention |
The vertical transfer of heat energy (in the atmosphere) |
Think of the process of Boiling |
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Advection |
The horizontal transfer or movement of properties of air and/ or of heat energy |
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Radiation |
short wave: from sun is inbound long wave: from earth is out bound |
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Rayleigh Scattering |
the blue sky we see is because of this. solar radiation passing through gas molecules makes the blue appearance |
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Mie Scattering |
pollution that creates the haze that may be seen on city skylines |
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Albedo |
the total fraction of total radiation that is reflected away by a given surface |
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Is the atmosphere a good conductor |
No, it's not. Conduction from the earth's surface is only important for a couple of inches |
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what is an example of convention in weather? |
- A thunderstorm (its like boiling water) - and the air around you (heat is rising) |
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what is an example of advection in weather? |
A cold or warm front; dry air at night(or longer nights) avects warm air to a cooler morning |
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With a white shirt more |
light will be reflected away because it has a high albedo |
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Albedo varies |
place to place and time to time |
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Where is albedo on a cloud? |
top of a cloud reflects radiation away and casts a shadow |
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Does albedo care about the angle of the sun rays? |
Yes, lower angle, and the radiation is reflected. Explains why we have the poles |
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Average Planetary Albedo on the face of the earth |
About 30% would reflected away |
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On the surface of the earth, what thing produces the highest albedo? |
Snow |
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Can Snow give you sunburns? |
- Reflects radiation at you which can cause sunburns |
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Why does snow melt off trees? |
Bark has a low albedo which causes snow to melt off of it |
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Freshly Fallen Snow |
Albedo of 80-85% (not much energy getting to ground) |
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Dirty, Dark Snow |
- Albedo is lower, which causes it to be slushy-like. - Albedo is 50 - 60% |
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Thick Cloud during a thunderstorm |
Not much of Sun rays are getting through. Albedo is 70 - 80% on the top of the clouds |
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Low clouds that are not causing shadow |
Albedo 25 - 50% |
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High level cloud that sun shines through |
Albedo is about 10% |
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Regular Sand |
Albedo is 20 - 30% |
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Dark Sand |
Lowe than regular sand surface and is warmer |
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forested areas (very vegetative) |
Lowest Albedo of 5 - 10%, a lot of heat energy is being retained |
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unforested areas that are grassy |
Albedo 20-25% |
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An agricultural area that is empty and dry |
Albedo is 15 - 25% |
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An agricultural area that is empty and moist |
Albedo is about 10%; lower than dry earth |
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Water covers how much of the earth's surface? |
70- 75% |
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Direct Rays on the Ocean |
Albedo is low at 3-5%; water is warm because it absorbs the sun rays |
will be closer to the equator and traversing 1 atmosphere |
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Sun rays at an angle on the ocean |
Albedo is 50-80%, because rays get reflected away due to its low angle; this explains why we have ice caps at poles |
Low sun angles at the poles |
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Atmospheric Greenhouse Effect |
-We have a layer of gases - short wave radiation is passed up by the atmosphere (solar radiation) - Solar radiation turns into Terrestrial radiation - Terrestrial Radiation is absorbed by the atmosphere - Variable Gasses trap heat, keeping the earth warm - warmer air allows for more moisture to coexist, which causes more greenhouse gasses |
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Variable gasses are also called |
Greenhouse Gasses |
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Variable Gasses |
- Co^2 - Water Vapor - Methane - Nitrous Oxide - CFC's - Ozone |
Can Very Much Not Contain Oxygen |
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If an object radiates more energy away than it absorbs |
temp. of object will cool |
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If you absorb more energy than you radiate away |
Temp. will get hotter |
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Does earth do more emission or absorption? |
both |
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What matters with albedo? |
color and texture |
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Black Body Object |
- does not mean it is black - Object that it is a perfect emitter and/or a perfect absorber - can be both |
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Is the Sun an emitter? |
It is a perfect emitter |
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Is the sun a black body object? |
Yes, it is a perfect emitter |
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Is the earth a good emitter or absorber? |
It is both. During the day it absorbs and at night it emitts |
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Is the earth a black body object? |
Yes because it is a good emitter and absorber |
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Earths Radiative equilibrium Temperature (RET) |
-The surface of the earth's temperature on average is 0 degrees Fahrenheit - Ignores the atmosphere - We are actually 59 degrees Fahrenheit |
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Is the earth's atmosphere a black body object? |
- no; earth warms us and the atmosphere absorbs the greenhouse gasses. - Very selective |
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Energy |
- Property of a system that enables it to go to work - Different types of energy |
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Temperature |
- Hotness or coldness of an object or a substance - dependent on the motion of molecules - more motion generates more heat, which leads to a higher temperature - is subjective |
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Heat |
- A form of energy transformed between objects by the virtue of their temperature differences - Remove heat that causes cooler temp. |
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Heat Capacity |
The ratio of the heat absorbed (or released) by a system compared to the corresponding temperature rise or fall |
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land ___ more quickly and ___ more quickly than ___ |
heats more quickly and cools more quickly than water |
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Latent means |
a hidden Trait |
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Latent Heat |
The Heat energy required for a change of state (atmospheric energy) |
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land and water have a |
different heat capacity |
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the water heats more ___ and cools more ___ |
heats Slowly and cools more slowly than land |
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6 Changes of State |
Evaporation, Condensation, Sublimation, deposition, melting, and freezing |
Consume My Fabulous Special Delicious Entree |
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Evaporation of Water |
- Liquid to Gas - Heat is absorbed - most active water molecules go to vapor form - is a cooling process though (ex: when you get out of a swimming pool) |
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Condensation |
- Gas to Liquid - Heat is released - EX: Clouds, water vapor - also causes turbulence when a plane goes in a cloud |
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Sublimation |
- Solid to Gas - heat is absorbed - EX: Dry Ice |
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Deposition |
- Gas to Solid - Heat is released - EX: Frost and snowflakes do not go through a liquid state |
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Melting |
- Solid to Liquid - heat absorbed |
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Freezing |
- Liquid to solid - heat released |
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Cloud is a sign of the atmosphere becoming |
Saturated; there are rising motions of water vapor that cool and expand to the dew point temperature |
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What is the important source of atmospheric energy? |
Latent heat |
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In the saturated environment, temperature decreases at a rate of... |
- 3.3 degrees Fahrenheit per thousand feet - you are adding sensible heat (used to be 5.5 degrees, so you give back 2.2) |
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A severe thunderstorm will do what to a plane? |
It will destroy it |
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Atmospheric Turbulence is caused by |
clouds releasing latent heat (most powerful in thunderstorms) |
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When Latent heat is absorbed (evaporation) |
heat is hidden away in that water vapor until condensation takes place and you release that sensible heat back within a rising air parcels - parcels will be warmer and the surrounding air will be warmer |
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Stable Atmosphere |
- resisting change - EX: consistently sunny in Texas - does not mean it will be stable forever |
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Unstable Atmosphere |
- EX: clouds rising and getting darker - different parts can be unstable |
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In a Northern hemispheric summer... |
- northern hemisphere is oriented to the sun - about when it is over the tropic of cancer - more direct rays |
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In a Northern Hemispheric Winter |
- Northern hemisphere is tilted away - low density of incident rays |
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World wide the average short wave radiation is balanced by average long wave radiation means |
that we are a black body object |
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Globally we can agree that it |
- balances; but it depends where you are |
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Difference between north and southern hemisphere |
Northern has more land |
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The Haves |
- At 36 degrees or less in the northern hemisphere (south of 36), we receive more short wave radiation than we have long wave radiation (or then we lose to terrestrial radiation) - operating at an energy surplus |
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The have nots |
- north of 36 experience a deficient - losing more than we can gain |
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Israel geopolitical situation |
separated by the haves and have nots and conflict occurs |
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atmospheric conflict |
will have more at 36 degrees because it is the boundary separating excess energy and an energy deficient |
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US and tornadoes |
The US has the most tornadoes in the world because we straddle 36 degrees and the access to moisture from the Gulf of Mexico |
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the oceans transfer what |
transfer heat and moisture from the haves to the have nots |
Fiona |
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What happens come Jan. |
Areas north of 36 get rid of the cold and send them south |
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The difference in air temperature drive |
wind, and winds are trying to get rid of the excess |
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Widen Zone of Conflict |
True battleground in North America for severe weather can be broadened to 30 - 50 degrees North |
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Tornado part of the US |
is east of the Rockies because that is where you get your moisture from the gulf |
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Temperature Measure |
- temperature mainly 15-1600s - started with mercury (became aginst OSHA standards) |
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Most accurate body temperature methods |
anal temperature readings |
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Largely doctors use what now |
thermal devices |
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Are all thermometer devices accurate? |
not necessarily, some have biases |
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airport observations devices |
finding out that they have a bias of +1 degree, which causes problems when trying to quantify global warming |
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All temperatures should be measured in the... |
- shade - make sure you are measuring what you want to measure |
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No temperature is better than |
bad temperature data |
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Accurate siteing |
will affect the accuracy of your record |
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Thermometer |
measures temp. |
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Hygrometer |
measures humidity |
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Thermohygrometer |
- measures temperature and humidity - used in airports - is white (high albedo) - well ventilated |
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Thermograph |
- older device in outside shelters that used ink and a pen to trace temperature (24hr to 7-day record) |
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radiometers |
measure temperature from space with satellites that are remote sensor - measures exact temp and dewpoint readings |
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Thermometer Shelter/ exposure |
- air temp should always be measured in the shade |
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Thermometers are much better energy ___ than air is |
energy absorbers (make sure you are measuring the temp of the air |
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The coke thermometer |
was facing the sun and had high albedo, which means it was measuring the temp of the coke thermometer |
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Cotton Region Shelter (CRS) |
- white - louvered so that air can move freely in (pointed up so that sun rays do not reach thermometer) - doors face north in north America so sun does not hit it |
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Are you damaging a thermometer by having it in the sun |
No, it will eventually cool down |
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Rules for measuring Temp. |
1. No direct sunlight on the thermometer sensor itself - measure the temp in the shade 2. Sensor and its shelter should be well ventilated (radiation shield) 3. Should be shielded by nearby radiated surfaces 4. All official surface air temp. readings are measured 5ft above the ground 5. Above grassy, naturally vegetative area for that geographic area 6. sometimes most accurate thermometers are inconvenient places |
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Thermometer Radiation Shields |
- more modern than TRS - is white (high Albedo) - air can go through easily - often liked by wasps |
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If you let sun rays hit the thermometer directly what are you measuring? |
the temp. of the thermometer |
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What does it mean for thermometers to be shielded away from nearby radiated surfaces? |
keep away from concrete, cement walls, black top, or roads. It should be on a naturally vegetative surface (this is dependent on location) |
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At what height do we measure air temp? |
5 ft above ground |
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In the case of a lot of weather instruments, what can we say about their location? |
accurate ones are often in inconvenient areas |
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In the case of frost, what can we assume about temperature readings? |
cold air sinks down, so this is why you may see frost (32 degrees) at air temps that are 34 or 35 |
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lower dew points do what in terms of weather comfort? |
temperature can be relitively the same, but if the air is dryer than it can be more comfortable for people. Additionally, longer means dryer/ cooler air |
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What are the temperature scales? |
Fahrenheit, Celsius, Kelvin |
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Fahrenheit scale |
- Most widely used in the US, but there are some countries that use it - developed in the 1700s by Gabriel Daniel Fahrenheit - Based on mercury in a glass tube (heat causes expansion of mercury and it raises) - Does this using the zero point
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Celsius Scale |
- widely used everywhere, but US - Made in the early 1740s by Andrew Celcius - devised using a zero point |
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Kelvin Scale |
- largely used in scientific application - made by lord kelvin and William - it's zero point is not a freezing point it is absolute zero (no negative numbers on kelvin scale) lowest you can achieve |
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What is a zero point? |
A base unit that does not have to be zero |
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On a Fahrenheit scale, what is the zero point? |
32 degrees Fahrenheit (freezing point of water) |
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Body temperature in Fahrenheit? |
98.6 degrees Fahrenheit (not consistent because you will be hot when you wake up and in the evening, but be cooler at different times). Worrying when above 99 degrees |
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What is the boiling point of water at sea level in Fahrenheit? |
212 degrees Fahrenheit |
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in the early 80s there was a movement to convert the US to celsius but... |
after a poll, they realized that it would politically be a bad idea |
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On a Celcius scale, what is the zero point? |
0 degrees, which is also the freezing point of water |
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Body temperature in Celcius? |
37 degrees Celcius |
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What is the boiling point of water at sea level in Celcius? |
100 degrees Celcius |
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What is the size comparison between a degree of Fahrenheit and celsius? |
A degree of Celcius is larger than Fahrenheit by a factor of 1.8 |
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Zero point for Kelvin |
absolute zero |
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Freezing point for Kelvin |
273 degrees Kelvin |
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The boiling point of water for kelvin |
373 degrees Kelvin |
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Between Kelvin and Celcius |
both have a hundred degrees that separate freezing point from boiling point |
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How to convert Fahrenheit to Celsius? |
(F - 32) / 1.8 = C |
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How to convert Celsius to Fahrenheit? |
(C * 1.8) + 32 = F |
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What are the Air temperature controls? |
1. Sun 2. Differential heating of land and water 3. Ocean Currents 4. Elevation 5. Lattitude and Geographic position |
SDOEL |
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What is the primary control for temperature? |
The sun |
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Differential heating of land and water |
- land tends to warm and cool quickly (variation between land) - Water tends to heat and cool more slowly (variety between water's mass is an important factor) - water has a higher heat capacity than land (require more heat) |
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Ocean Currents |
helps redistribute heat (less efficient than water) |
think what wind does |
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Elevation |
Mountain vs sea level |
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Lattitude and Geographic positions |
north vs south latitude (on the north side you will not see the sun if you are at 40 degrees latitude, but will on south) |
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It has never snowed in |
key west Florida (coldest it has been is about 42) - it is protected by the water around it that holds heat |
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when would you know if you are likely to get bad weather from a hurricane? |
If you are right of the line |
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Temperature is being gathered... |
- at 100s of stations worldwide hourly; and are mostly at airports; when the weather starts changing quickly in the US then it changes to every 30min (in Asia and Europe they do it every 30min always) - ship based observations |
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Climate average |
is not exact |
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How do you calculate the average of the day? |
If you have the high and low for the day |
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Ship-based meteorology |
do it on the ocean |
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Info by radars has to be |
humanly augmented (we may have to infer that there is a tornado) |
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climatological averaged |
- made over 30 yr. span - does not guarantee future temperatures |
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Air Temperature Data Uses |
- climatology - determine time of death - aviation safety - can see record extremes |
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temperature data differs |
by location |
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How do we use weather data to determine the time of death? |
if a body deceased outside in a warm environment, within 10 min. flies within 10 miles will know there is a dead body (use as host). Can also tell if the body was moved after its death |
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Heating/ Cooling Degree days are most used by... |
energy and power companies |
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heating and cooling Degree days help to calculate what? |
help us forecast what the energy requirement is needed to keep people comfortable at a given temperature (forecast energy usage) |
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Degree "Days" |
- not a 24-hour day - unit of measurement - forecast energy usage - developed in the early 20th century |
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Base number for heating/ cooling degree days |
65 degrees Fahrenheit; the system assumes that if the outside is at this temperature outside then it will require little energy to keep a building cool |
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If in a 24hr calendar day it is a high of 75 and a low of 55 then |
average is 65 degrees, so we require no heating/ cooling degree days on this day |
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If in a 24hr calendar day it is a high of 85 and a low of 65 then |
average is 75; so we will need 20 Cooling Degree Days because the average is on the high end of 65 and 85-65 = 20 |
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if the temperature is 80 - 60 degrees on Sunday and the temperature is 90 - 60 degrees on Monday how many CDD/ HDD are needed for both days? |
- First, find the averages of both day's highs and lows. (add the 2 numbers and divide by 2 for both) - then compare both averages to the base number (65). In this case the averages are 70 and 75, so they are both above the base number, which means you need CDD. - then subtract both averages by 65 to get the differences. in this case, you get 5 CDD and 10 CDD |
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you heat in the... |
winter |
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CDD season |
- time of the year you are cooling - Jan. 1 - Dec. 31 - start the season when we are doing it minimally and end the season when we are doing it minimally - want to capture the season in its totality |
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HDD Season |
- when you are heating - July 1 - June 30 - start and end when you are doing it minimally (when the sun takes care of it) - want to capture the season in its totality |
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Average annual CDD and HDD in Austin |
CDD: 3375 HDD: 1185 (Shows us that CDD are more) |
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Are CDD or HDD more worrying |
in hot climate places the CDD places are a bit more worrying because they are prepared for extreme heat, but not extreme cold. still there are sides to both |
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can you have both cooling and heating degree days |
no |
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Biometeorological Applications |
- heat stress - wind chill index - both feel like temperatures |
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What is the heat stress index reliant on? |
reliant upon air temp. and relative humidity - the higher the relative humidity and higher the air temp the heat stress increases |
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What is relative humidity? |
- always a percent - 100% is when air is completely saturated (not saying anything about water vapor content, just saying that at that temperature the air is allowing the maximum amount of water vapor to coexist at that temp.) - the ratio of the air's actual water vapor content compared with the amount of water vapor required for saturation at a given temperature |
tells you nothing about how much moisture is in the air |
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Why are the numbers 80 to 85 significant in relation to the heat stress index? |
above this temp and relative humidity is when your body is having to work harder - in this region heat sensitive and unacclimated individuals may suffer - above 95 -100 only heat-acclimated people can work for extended periods |
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What is the number one killer on the surface of the earth globally? |
heat |
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who is effected more by heat |
older people, people whose body conditions are not fit, overweight people, people with underlying medical conditions |
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with a lower relative humidity |
it will be dryer |
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What is the WBGT |
- Stands for Wet Ball Glow Temperature - something the military and athletic depts. use - it considers wind, cloudy or sunny, relative humidity, temp. - if it is sunset and cloudy then it is not much different then the heat stress index |
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Wind chill Index |
- based on air temperature and wind speed - the higher the wind and the higher the temperature can cause detrimental effects - wind moves over the body and takes away body heat |
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The wind Chill index was developed for... |
polar science, which can lead it to be misused in non- polar areas |
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The wind chill index was re- written to |
- to where it would stop at lower temperatures |
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in extreme temp. your skin will |
begin to crystalize in minutes |
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Atmospheric Moisture |
- is probably one of the most important elements in our atmosphere - also a greenhouse gas (most variable) - varies based upon air temp (how much moisture can coexist) - 0-4% - aka. water vapor |
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Atmospheric pressure is important in understanding what concept? |
atmospheric stability or instability |
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How to go from ocean water to cloud |
water has to evaporate and condensation has to happen to make visible cloud droplets |
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Do plants give off moisture |
yes through transpiration |
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Do all clouds precipitate |
no |
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what do we call it when the rain goes into the ground |
percolation or infiltration (soil type changes this) |
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80% of body heat loss is where? |
from the neck up |
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Humidity |
refers to any number of different ways of specifying the amount of water vapor in the air |
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Absolute Humidity |
the weight (or mass) of the water vapor per volume of air (Parcel of air) |
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Which two concepts of humidity are comparisons? |
specific humidity and mixing Ratio |
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Specific humidity |
when you compare the Absolute humidity, or weight or mass of the water vapor per volume of air (parcel), with the total weight or mass of the air in the parcel including the water vapor |
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Mixing Ratio |
Comparing the weight or the mass of the water vapor in a volume of air (absolute humidity) to the weight of the dry air in the parcel |
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Dew point should always be |
the same or less than the air temperature |
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If it is 100% saturated is it raining |
no, but the clouds are saturated, so it could start to rain over time |
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if you bring the temperature up 4 degrees then the relative humidity will |
decrease, because the higher temperature will allow for more moisture to coexist |
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relative humidity can be affected by what |
- cooling or heating the temp. - adding or subtracting moisture |
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How does temperature change affect relative humidity? |
If moisture (water vapor content) stays the same - as temp cools, the relative humidity goes up - as temp heats, the relative humidity goes down (a decrease in relative humidity occurs because in the warmer air the water vapor molecules are zipping about at such high speeds they are unlikely to join together and condense.) |
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Air temperature and relative humidity enjoy an ___ relationship |
inverse relationship |
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If you move a parcel of air through invention (horizontal) |
warm to cold place causes air parcel to cool and allow less moisture to coexist |
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What does a parcel do when it moves up through the convection |
it expands and cools causing less moisture to exist in water vapor form (but also allowing for clouds to form) |
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Dew point temperature |
- expressed in degrees (allows it to be compared to air temperature) - the temp. to which a parcel of air would need to be cool to, assuming no change in air pressure or moisture content, in order for the given parcel of air to reach saturation - does tell you about the humidity in the air |
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If the dew point and air temperature are close together then |
the relative humidity is high |
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What is the relative humidity when there is a 1 degree difference between the air temp and dewpoint? |
96% |
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Which situation has the lowest amount of water vapor? |
Situation C is the lowest because dew point is the lowest and the question asks about moisture |
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Which has the highest amount of moisture? |
A because the dewpoint is the highest |
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Which has the lowest relative humidity? |
B because it has the greatest difference between the air temp and dew point depression |
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Which has the highest relative humidity? |
c because there is only a one-degree difference |
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Dew cell |
- a sensor coded with some type of moisture sensing material to look at water vapor pressure (measures absolute Humidity) - located at airports - modern invention |
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Hair Hydrometer |
- hair is really reactive to humidity - hair stand gets longer when air is more humid (High RH) - dry air gets the hair to shorten (low RH) - used hair to look at relative humidity depending on how it expanded or retracted |
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infrared Hygrometer |
satellites in space that tell about moisture on the earth - more remote sensing |
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Electronic Hygrometers |
- rawindodes use these - measures RH with height |
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Sling Psychrometer |
- has two thermometors - one of them just measures the air temp (dry bulb) - the other has a wet shoelace tied on it to measure evaporating cool to temp (wet bulb temp) - it is swong which causes evaporation (a cooling process) - produces the numbers to calculate dewpoint and relative humidity |
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Chilled mirror Technology |
- look at the moisture that builds up on the chilled mirror - stopped being used because mirrors got too dirty quick |
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How we measure humidity from modern to old |
- Dew Cell - Infrared hygrometer - Electronic hygrometer - Sling Psychrometer - Chilled Mirror Tech - Hair Hygrometer |
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Atmospheric Stability |
- Stable vs. Unstable - is the parcel of air-stable or unstable - equilibrium in the atmosphere |
think human stability |
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Example of an Unstable Atmosphere |
tornadoes, hurricanes |
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Is a parcel is unstable it wants to... |
rise, at least initially |
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If air is stable it wants to... |
stay in place or sink |
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When a parcel rises and the pressure falls what happens to it? |
it expands and cools as long as it doesn't reach equilibrium (then it will stay still) |
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When a parcel sinks it... |
compresses the molecules, and would cause it to create compressional heat |
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If a parcel is warmer than its surrounding area then it will |
rise to cool, until it reaches equilibrium and then it wants to sit there |
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What do we need to know to determine atmospheric stability |
the temperature of the parcel at any given level and how it will change as it compresses and sings compared to the temperature of the air surrounding the parcel (Environmental Temperature) |
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What allows us to measure temperature at various levels or environmental temperature? |
rawinsodes |
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What is Environmental Temperature |
its the temperature of the environment at various levels |
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If at 1500 ft you have a parcel of air that is 81 degrees, but the environmental temperature is 78 degrees, what will the parcel do? |
Will rise because it is hot for that given level |
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If at 2000 ft the parcel of air is 72 degrees and the environmental temperature is also 72, then what will the parcel do? |
its reached equilibrium so it will stay at that level |
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Adiabatic Process |
the process that assumes that, this parcel as it goes up and expands and cools, there is no interchange of heat across the parcel wall (no release of heat across the parcel) |
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Diabatic Process |
there is an exchange of heat across parcel walls |
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What process will we assume for this class? |
Adiabatic Process |
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Parcel rising |
it expands and cools |
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forcing a parcel to sink will |
compress and produce compressional heating - moving into more molecules as it gets closer to the earth |
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when the air expands and cools to the dew point temperature forms what |
a cloud |
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a cloud is proof of |
saturation |
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in evaporation latent heat is absorbed, but what happens in condensation |
latent heat is released as sensible measurable heat (not cooling as quickly) - its cooling less then it would in an unsaturated area |
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Everything about Atmospheric stability depends on the... |
rate at which air cools or warms with height (considering moisture) |
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DALR |
- stands for dry adiabatic lapse rate - if the air is unsaturated - more degrees ferrenheit - on average is about 5.5 degrees Fahrenheit per 1000ft |
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MALR |
- stands for moist adiabatic lapse rate - if the air is saturated - less degrees Fahrenheit - is about 3.3 degrees Fahrenheit (less than DALR because sensible heat is being released) |
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In saturated air (cloud) there is |
- release of measurable heat (condensation) - use 3.3 to figure out temp. - do not use DALR number (However if this air was very cold then this number could become closer to 5.5 because less moisture can coexist)
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If a parcel is ricing the environment is... |
unstable |
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If a parcel is sinking the environment is... |
its stable |
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If you would want an unstable environment what would you want the air up high to be? |
Extremely cold, along with some other factors |
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the colder and quicker it gets with height |
the more instability |
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the overall atmospheric temp. profile (i.e, how quickly it actually cools with height can determine |
stability |
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the more slowly it gets colder with height or if it warms then |
it is a more stable environment |
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ELR |
Environmental Lapse rate - real life temperature |
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When ELR is greater than DALR (5.5) then |
atmosphere is absolutely unstable |
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When ELR is greater than the MALR (3.3) but less than the DALR (5.5) |
with just this information you say that the atmosphere is conditionally unstable |
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When ELR is greater than the MALR (3.3) but less than the DALR (5.5) and the condition is saturated
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Absolutely unstable due to knowing the condition |
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When ELR is greater than the MALR (3.3) but less than the DALR (5.5) and the condition is unsaturated |
it is stable do to the condition |
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When ELR is less than the MALR (3.3)
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it is absolutely stable |
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A thermodynamic diagram (td/ sdgs) can tell us |
- what air temp does with height - what dew point temp does with height (will always be the line less than Air temp line) - can find the freezing level (0 degrees celsius) - If DP and AT touch there are clouds (saturation) - DP and AT lines close together means Hight Relative humidity; farther apart means low RH - info about wind (direction and speed) - It is stable when the yellow line (theoretical temp of the parcel) is to the left of the AT - DP tells us moisture content - important to remember it is a slanted diagram - only a snapshot of that time |
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on a td/ sdgs a tropical environment will show |
- parel line will be to the right of AT line - AT and DP will be close together - winds high in the atmosphere will be different from the winds closer to the ground |
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on a td/ sdgs when the parcel line is to the right of the air temperature line the atmosphere is |
unstable |
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how can we get some data for td/ sdgs for Austin? |
BSM data from FedEx website collected from airplanes going up or down |
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Assuming a clear sunny day and dew point and air temperature stay the same when would relative humidity be its highest |
the relative humidity is greatest when air temperature is the coolest, so 6 - 8 am |
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an increase in the water vapor content of the air (with no change in air temperature) increases the |
the air’s relative humidity. - As more water vapor molecules are added to the air, there is a greater likelihood that some of the vapor molecules will stick together and condense. Condensation takes place in saturated air. So, as more and more water vapor molecules are added to the air, the air gradually approaches saturation, and the relative humidity of the air increases |
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removing water vapor from the air decreases the likelihood of |
saturation, which lowers the air’s relative humidity |
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as the air temperature increases (with no change in water vapor content), the relative humidity |
decreases - The higher the temperature, the faster the molecular speed, the less likely saturation will occur, and the lower the relative humidity |
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a decrease in air temperature |
raises the relative humidity. - As the air temperature lowers, the water vapor molecules move more slowly. Condensation becomes more likely as the air approaches saturation, and the relative humidity increases. |
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Convection __ an important form of energy transfer in our earth's atmosphere |
is |
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the atmosphere greenhouse effect is produced by relatively easy transmission of ___ coupled with selective absorption of ____ |
short wave/ solar radiation; long wave/ terrestial |
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average observed temp |
earths surface is about 59 degrees F or 15 degrees c |
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very cold upper level troposhere temp often results in a more |
unstable atmosphere |
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given a mostly sunny summer day at what time of the day is the RH highest |
6- 8am |
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as humidity decreases hair strands |
contract or become shorter |
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when is the sun lowest in the sky in Austin |
around Dec. 21st |
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latent heat of evaporation does what with sensible heat |
it releases it |
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