Midterm Flashcards
How is Temperature defined?
A measure of the average speed that molecules move in a substance
What units for temperature are used in meteorology in the United States?
Fahrenheit and Celsius
Where/when is Fahrenheit used in the United States?
For the surface
Where/When is Celsius used in the United States?
For the upper air
How does air temperature change with height in the troposphere?
decreases with hight in the troposphere.
How does air temperature change with height in the stratosphere?
Increases with the hight of the stratosphere
What is the tropopause?
Boundary layer between the troposphere and stratosphere
How does the altitude of the tropopause affect the hight of clouds in the troposphere?
It prevents vertical motions from moving into the stratosphere.
Do clouds grow any taller beyond the tropopause, into the stratosphere?
No, the tropopause is a cap/lid on the atmosphere.
How is atmospheric pressure defined?
Atmospheric pressure is the force applied by air on a unit area of surface. (Example - the pressure is higher in Chicago, than it is in Denver)
What units of pressure do meteorologists use?
Millibar (mb)
What is the value of the average sea level pressure?
1013.25
What does it mean when we say air is saturated?
The atmosphere cannot contain any more water vapor without condensation happening.
What is Relative Humidity?
Water vapor in the atmosphere, relative(along with) the atmospheres capacity for moisture, at the current temperature. (Example- The same size bucket)
What is dew point temperature?
The lowest temperature to which air can be cooled at constant pressure before saturation occurs
What is the value of Relative Humidity if the dew point temperature equals the air temperature?
100%
What is latent heat?
A “Hidden Heat” required for a phase change
What is wind?
The movement of air
What is the convention for reporting wind direction?
The direction from which the wind is blowing
In what units are wind speed reported?
Knots typically
What do wind barbs represent on a map?
Wind speed
Over what altitude range does most of Earths weather occur?
In the troposphere, the layer of the atmosphere between the ground and approximately 12 km
What are the basic properties of the atmosphere used in describing weather?
Basic properties include: Temperature Pressure Density Moisture content Wind speed and direction Visibility Cloud cover Precipitation rate
Describe how temperature can be used to define payers of the atmosphere?
Temperature varies with altitude.
What parts of the atmosphere decreases with altitude?
Troposphere
Mesosphere
What parts of the atmosphere increases with altitude?
Stratosphere
Thermosphere
How does the height of the tropopause change with latitude?
The tropopause is located at higher altitudes in the tropics and lower altitudes in the polar region
When is the tropopause higher from the surface?
In the Tropics
When is the Tropopause lower to the surface?
In the Polar Regions
What limits the depth of storm clouds?
The tropopause (Example - the storms are taller in the tropic regions than the polar regions.)
As you move upward away from the Earths surface, does the pressure increase, decrease or remain constant?
The air pressure ALWAYS decreases as you move upward away from earth.
If a map shows pressures across the contiguous United States, in that geographic location would the lowest pressures be ground?
Lowest pressures would be found at the highest elevations. In the United States this would be in the Rocky mountains
Why are maps of station pressure not very useful for meteorologists?
When meteorologists want to identify where storms are developing or occurring, A station pressure map would only indicate low pressure over mountains and not identify low pressure systems in other regions of the country.
What is it meant by sea level pressure?
Sea level is the altitude to which all station pressure measurements are corrected. (1013.25)
Define vapor pressure?
It is the force exerted by water vapor molecules on a unit area.
What is saturation vapor pressure?
The vapor pressure when that air is saturated at a given temperature.
Define Saturation?
The condition where air contains the maximum amount of water vapor for a given temperature and pressure.
What atmospheric variable determines the maximum amount of moisture that can be present in air?
Temperature (From which you can find saturation vapor pressure)
can you find the saturation vapor pressure from temperature?
Yes
What two variables describe the absolute amount of moisture in the air?
Vapor Pressure
Dew Point Temperature
How does relative humidity typically change over the course of a day?
Relative humidity is typically highest in the morning, and lowest in the afternoon.
Why is relative humidity highest in the morning?
When the temperature is the lowest (RH high percentage)
Why is relative humidity lowest in the afternoon?
When the temperature is the highest (RH Low percentage)
Describe two ways that the relative humidity of air can increase?
- Lowering the air temperature and holding dew point temperature constant
- Increasing the dew point temperature and holding the temperature constant
What is the relative humidity if the dew point temperature and the air temperature differ substantially?
The relative humidity would be low (Small percentage)
What if the temperature and the dew point temperature are close in value?
The Relative Humidity would be high (High Percentage)
Latent heat is released to the air during which phase changes?
Condensation
Freezing
Deposition
During which phase changes is latent heat removed from the air?
Evaporation
Melting
Sublimation
What is the Condensation phase change?
Vapor to Water
What is the Freezing Phase change?
Condensation to ice
What is the Deposition Phase Change?
Vapor to Ice
What is the Evaporation phase change?
Water to Vapor
What is the Melting Phase change?
Ice to Water
What is the Sublimation phase change?
Ice to Vapor
What are synoptic measurements?
Ones that are made simultaneously
How are synoptic measurements coordinated for simultaneous measurement?
UTC
What is a rawinsonde?
A Baloon-borne instrument package used to make measurements of atmospheric conditions above the surface.
How frequently does a rawinsonde provide information?
Launched twice a day (Every 12 hrs at 0000UTC and 12000UTC)
How many times a day are rawinsonde’s launched?
2 times
At what times of the day are rawinsonde’s launched?
0000UTC, and 1200UTC
What atmospheric variables does a rawinsonde measure?
Temperature
Dew-point Temperature
Wind direction
Wind Speed
What atmospheric variables does a radar monitor?
Precipitation
Elevation
Location
What atmospheric variables does a Doppler Radar monitor?
Precipitation
Elevation
Location
Wind direction, based on where the precipitation is being pushed.
How does a Radar determine rainfall rates?
The intensity of the returned microwave signal to the radar receiver is proportional to the rate the rain is falling.
In addition to rainfall rates and the elevation and location of precipitation, what els does a doppler radar measure?
The frequency shift of returned energy, which is related to the wind along the beam (Toward or away from the Radar) (Example - things coming towards you has a smaller frequency, and things going away from you have a larger waver length.)
What is a wind profiler?
Another type of doppler radar that operates in very high frequency and ultra high frequency radio bands.
What information does a wind profiler provide?
Gives measurements of the vertical variation of wind speed and direction
what conditions do wind profilers work best?
Clear sky conditions
What conditions do Doppler radars pick anything up?
Rain
Ice
Snow
Bugs
What are the three primary channels used to create weather satellite images from Geostationary satellites?
Visible Channel
Infrared Channel
Water Vapor Channel
How do commercial aircraft contribute to weather data collection?
Each aircraft send data during take off, landing, and in flight
What is it that the Commercial aircrafts measure?
The jet stream at (300mb)
What important information does the National Lightning Detection Network provide?
Maps lightning strikes across the entire US, If lightning strikes we know about it
What is it important for the National Lightning Detection Network provides the info important?
Important in forested areas to assist with forrest fire detection and control.
What is the advantage of making measurements of atmospheric properties simultaneously?
Allows for examination of large weather systems and the construction of weather maps.
How do you convert from Universal Coordinated Time to your local time?
Answers will vary. For Colorado subtract 700 from UTC during standard NON daylight savings time, and Subtract 600 during daylight savings.
When do you subtract 700 from UTC in Colorado?
During NON daylight savings, standard time.
When do you subtract 600 from UTC in Colorado?
Durning Daylight savings time.
What is a meteogram?
The Graphical display of a surface weather data for a single location over a period of time.
How long of a time frame does a Meteogram typically show?
Typically Hourly data, for several hours.
What layers of the atmosphere does a rawinsonde sample during its ascent?
Entire Troposphere
Lower Stratosphere
Typically, at how many millibars does a rawinsonde’s balloon explode?
Around 100mb
What is a sounding?
A vertical measurement of atmospheric properties
What tool is used in order to make a sounding graph?
A Rawinsonde
What does a sounding graph show about the atmosphere?
Temperatures Dew Point Temperatures Pressure Wind Speeds Wind Direction
How does a weather Radar detect precipitation?
The Radar transmitter sends out pulses of microwave energy, when the energy bounces off of something it will bounce back to the radar antenna and display as an image
What information does a radar reflectivity image provide?
Rainfall Rate
Different Intensities
Where its occurring
What do the hot colors (reds, yellows) typically represent on a radar reflectivity image when the radar is in precipitation mode?
Hot Colors on the radar reflectivity image indicates intense rain or hail
What information does a radar radial velocity image provide?
Shows wind (along the beam…towards or away from the radar)
What four characteristics of precipitation can Doppler radar detect?
Distance to precipitation Altitude Geographic Location of precipitation Intensity and accumulated totals of precipitation Speed of wind toward or away radar
For a Doppler Radar, can it depict if something is going side to side?
No, it can only depict if something is going away or toward it.
What does a Wind profiler detect?
Measures wind speeds and direction
In what conditions does a Wind Profiler work best?
Clear sky conditions
How high up can a wind profiler measure?
around 10 miles high
How have Doppler Radars and wind profilers revolutionized our ability to observe winds aloft?
Prior to Doppler Radars and Wind Profillers, the only way to obtain winds aloft was rawinsonde.
Why is it not preferred to use a rawinsonde to observe winds aloft?
Because rawinsonde’s are very expensive and infrequent
Why is it better to use Doppler Radars, and Wind Profilers to observe winds aloft?
Because they provide the data more frequently and continually.
What is a vertical Wind Profile?
Depiction of the wind speed and direction at various altitudes in the atmosphere over a single location.
What is a Geostationary Orbit?
When a satellite has the same rotational velocity as Earth on Earth equatorial plane, Thus it looks at the same spot on Earth continuously.
What is a weather satellite measuring when it creates a Visible image?
It measures reflected light.
What is a weather satellite measuring when it creates a Infrared image?
The Infrared radiation emitted from Earth surface and cloud tops.
What is a weather satellite measuring when it creates a Water Vapor Image?
It measures Radiation measured from water vapor
If a cloud is dark on an infrared image but bright on a visible image, is this a high or low cloud?
This would be a low cloud, because lower clouds are warmer. For a visible image the cloud would be brighter because of the reflected Sun light.
Where is temperature on a Surface Station Model?
Upper left
What type of temperature measurements are used for a Surface Station Model?
(F)
Where is the Dew point Temperature on a Surface Station Model?
Lower Left
Where is the Wind Speed on a Surface Station Model?
Indicated by the barbs on the end of the staff.
How do you know the wind direction on a Surface Station Model?
However the wind Barb is pointed at.
On a Wind barb what does the long line mean?
10 Knots
On a Wind Barb, What does a short line mean?
5 knots
On a wind barb, what does a triangle indicate?
50 Knots
Where is the Sea Level Pressure on a surface Station Model?
On the upper right
What is contouring?
The act of drawing lines of constant value for a variable on a map.
How does Contouring simplify the reading of Weather Maps?
Countered maps readily show areas of high and low values making it easy to see patterns, maximum and minimum values in the variable field.
What are contour lines of constant pressure called?
Isobars
What are contour lines of Constant Temperature called?
Isotherms
What are contour lines of Constant Dew Point Temperature called?
Isodrosotherms
How are topographic maps of Earths surface similar to constant pressure maps of the upper atmosphere?
Both depict a three dimensional surface on a two dimensional plane.
How does the upper air station model differ from the surface station model?
The Temperature is in Celsius
Dew point depression is in Celsius (Not Dew Point Tempo)
How is the Temperature different in a Upper air Station Model, than a Surface Station Model?
The Temp is in Celsius, NOT F
How is the Dew point different in a Upper Air Station Model, vs a Surface Station Model?
The Dew point depression is used, NOT the Dew point Temperature.
What constant pressure maps might you examine to locate the jet stream?
300mb
250mb
200mb
What constant pressure maps might you examine to locate Fronts?
850mb
What information does a cross section provide that is different from an upper level map or a surface map?
A cross section shows conditions from the surface upwards for a slice of the atmosphere, rather than conditions at one level.
How would you identify a strong temperature gradient on a surface map?
Where the contour lines are closely spaced together
How would you identify a strong pressure gradient on a surface map?
Where the contour lines are closely spaced together
Is it true, that if your looking for a strong temperature, and pressure gradient, you would find them both where the contour lines are closely spaced together.
This is true
What is a staff for a Station Model?
the line the Wind Barbs are on.
What are wind barbs for a Station Model?
Wind barbs are the lines and flags, on the Staff.
Why can pressure be used as a vertical coordinate in Meteorology?
Because pressure decreases with an increase in altitude. This gives us an altitude.
At What (mb) levels are constant pressure maps typically available?
850 700 500 300 250 200
How do upper level troughs and ridges appear on a constant height map compared to a constant pressure map?
They appear the same. Low heights on a constant pressure map are the same as low pressures on a constant height map.
Is the slope of the 500 mb surface steeper during the Northern Hemisphere in the Winter?
Yes, it is steeper in the winter.
Why is the slope of the 500mb surface steeper in the winter, and not summer?
Larger low level temperature gradients will result in larger height differentials for the same pressure level, leading to a greater slope of the pressure surface.
Will larger low level temperature gradients result in larger height differentials for the same pressure level?
Yes
What is the Dewpoint Depression?
The difference between the temperature and the dewpoint temperature (Exc - if the temp is 70 and dewpoint temp is 20, the dewpoint depression is 50)
What information does the dewpoint depression provide about the atmosphere?
Provides information of how nearly saturated the air is, a small dewpoint depression means high Relative Humidity.
What are the key features of interest on a 850 mb map?
locations of frontal boundaries, Low Level Jet
What are the key features of interest on a 300mb map?
Location of jetstream, jetstreaks
What is a cross section?
A diagram of the atmosphere oriented in a vertical plane. like slicing a cake and looking at the layers within.
What is a numerical weather prediction?
Way of predicting future weather, using mathematical models based on physics, and solved on a computer.
What does a computer model consist of?
Interconnected set of mathematical equations describing the atmospheres behavior.
What are the three main factors that cause Numerical Weather Prediction forecasts to degrade as the forecast range lengthens?
Inadequate to resolve small scale storms, or topography.
What is ensemble forecasting?
A model run repeatedly for the same case but with slight changes, to predict accuracy of the forecasts.
What is the main reason for improved accuracy of weather forecasts in recent decades?
More powerful computers that lead to better resolutions and equations that were more accurate.
What are some of the physical processes that numerical models must account for in order to have accurate forecasts?
Friction
Radiation passing through the atmosphere
What role do grids have in relation to observational data used to initialize a computer model?
Data that are used in a computer model must be interpolated in a grid format.
Explain how computer models can approximate complex terrain?
Computer models use a process that breaks complex terrain into blocks, estimating the average height within the block.
How are rawinsonde measurements used when a computer model makes a forecast?
Data from rawinsonde’s are used to initialize input to computer models (Observations to start your prediction from.)
Why do grids of high resolution models generally cover only a limited area, rather than the entire earth?
Because the calculations take a very long time, and would be useless by the time the computer did the entire earth.
What is the trade off of a high resolution grid computer model?
It takes a longer time, but you have better images
What is the trade off os a low resolution grid computer model?
It is much faster, but less accurate.
What is it meant by “Parameterization” in numerical models?
Means the approximation the processes in the atmosphere, rather than the exact details.
Why to operational weather predictions have worse resolution than wed like?
Because Operational Weather forecast models do not have sufficient computing capacity to predict in time for the forecast. Forecasters have limited time.
If computing capabilities were unlimited would Numerical Weather Predictions be perfect?
no, Because the initial numbers are predictions, and approximations.
What is the significance of instability with respect of thunderstorms?
Instability determines the location and intensity of convective storms in the atmosphere.
What is an adiabatic process?
When a Air Parcel does not mix with its environment or exchange heat energy with its environment.
Does the temperature of an Air Parcel change during an Adiabatic Process?
Yes, only because of pressure change.
What is the value of a Dry Adiabatic Laps Rate?
10 C/km
What is the value of a Moist Adiabatic Laps Rate?
6 C/km
Does the Dry Adiabatic Laps Rate happen under, or over the Moist Adiabatic Laps Rate?
It Happens Under the Most Adiabatic Laps Rate
When you have a descending air parcel does it remain saturated a tall?
No, They never remain saturated during decent.
What is the name of the Laps Rate obtained from rawinsonde measurements?
The Environmental Laps Rate
When looking at atmospheric stability, is warm air more or less dense than cold air?
Warm air is less dense than cold air.
When looking at atmospheric stability, is cold air more or less dense than cold air?
Cold air is more dense that Warm air.
When looking at atmospheric stability, When Air Parcels are displaced upward that become more dense than their environment, what happens?
They will return to their original position, indicating a stable environment.
When looking at atmospheric stability, when Air Parcels are displaces upward and become less dense than their environment, what happens?
will accelerate away from their original position indicating an unstable environment.
When an air parcel is warmer than its surrounding environment, and keeps going up, is that stable or unstable?
Unstable.
When an air parcel is cooler than its surrounding environment, and goes back to its original position, is that stable or unstable?
Stable
As the environmental lapse rate becomes larger, does the atmosphere become more stable or less stable?
Less stable, because the environmental temperature will decrease with height at a warmer rate with a large laps rate. This means that a rising parcel is more likely to be warmer than the surrounding environment and more likely to rise.
What is it meant be “Conditional Instability?”
In order to have instability, the Air Parcel has to be saturated. (Unsaturated air parcels will be stable, saturated air parcels will be unstable.)
What is the “Lifting Condensation Level” Mean?
The altitude where condensation first occurs when an air parcel is lifted from the surface. (This would be the cloud bases)
Where is the “Lifting Condensation Level” located on a cloud?
The cloud base.
What is the level of free convection?
The altitude where a rising air parcel becomes boyant
Where is the “Level Of Free Convection” compared to the “Lifting Condensation Level?”
The Level of free convection is higher than the Lifting Condensation Level.
What are the 4 ways air parcels can be lifted?
Fronts
Sea Breeze
Topography
Convergence at low levels
How does the heating of the ground by sunlight affect the stability of the lower atmosphere?
Increases the environmental laps rate, and makes the air less stable.
What does it mean if the air is Stable?
If vertically displaced air returns to its original environment
What does it mean if the air is unstable?
if vertically displaced air continues to move vertically in the direction of the displacement.
What is Convection?
Buoyant vertical air currents within the atmosphere, often resulting in the formation of cumulus clouds, or thunderstorms.
What can convection make in the environment?
Cumulus clouds or thunderstorms.
What is meant by the term Air Parcel?
a small volume of air that is assumed to retain its identity as it moves through the atmosphere. Think of it as a balloon.
What do the inflation of a tire and the descent of an air parcel have in common?
Both involve in compression which warms air.
If you compress an air parcel, does it make it warmer?
Yes
Why does an Air Parcel cool as it rises?
Because they encounter lower pressure, which cools it.
Which of the following is constant: Dry Adiabatic Laps Rate, Moist Adiabatic Laps Rate, Environmental Laps Rate?
Dry adiabatic laps rate, because its a constant 10 C/km
What does a Air Parcel do when vertically displaced in a stable environment?
Return to its original position
What does a Air Parcel do when vertically displaced in a unstable environment?
Accelerate away from its original position
What does a Air Parcel do when vertically displaces in a neutral environment?
Remain at its new position.
Why is an inversion indicative of a stable layer in the atmosphere?
At the tropopause, when the environmental temperature starts to rise, the air parcel will cool and fall back to its original position, making for a stable atmosphere.
If the environmental lapse rate in the lower troposphere is approximately 5 Ckm would you expect strong convection to develop?
No, because the saturated, or unsaturated Air Parcel will be colder than its environment, and return to its original position.
Is the atmosphere likely to be more unstable in the mid afternoon or in early morning?
Mid afternoon, because the sun will heat up the surface and make the air less buoyant,
What is the lifting condensation level?
is the altitude at which condensation first occurs in a lifted air parcel, (Where the air cooled enough to reach its dew point.
What is the level of free convection?
The level of free convection is the altitude at which a lifted air parcel first becomes buoyant and can rise on its own.
What are 5 ways an air parcel can be brought to its level of free convection?
Lifting along a cold front Lifting along a sea breeze Lifting Along topography Low level convergence Solar heating of air near the surface
Why are cumulonimbus clouds less common in the winter than in summer in the United States?
Because the surface is cooler in the winter, its harder for parcels to become buoyant, because they get cooler than the environment faster.
What does Lifted Index mean?
How fast the air parcel is going up
