Meteorology Today 2 Flashcards

Terms Definitions
Frontal fog
removes nitrogen
water vapor
forms clouds
micro-scale motion
short-lived eddies (smallest)
The horizontal movement of air
A balloon-borne instrument that measures and transmits pressure, temperature, and humidity to a ground-based receiving station.
layer containing weather, highest pressure
Forms an hygroscopic condensation nuclei
Temperatures are usually higher (warmer) on the _________ side of a mountain range.
Weather element that always decrease with increasing height
The horizontal distance between two wave crests
Sunlight deflected in all directions after striking very small objects is said to be_____.
The boundary between the troposphere and the stratosphere.
A condition whereby the atmosphere contains more water vapor than is needed to produce saturation with respect to a flat surface of pure water or ice, and the relative humidity is greater than 100 percent.
Middle altitude clouds that consists of gray puffy masses
Maritime air masses
humid, indicated by "m"
Hygroscopic Nuclei
water-attracting particles, like salt, that allow condensation to begin in unsaturated air
friction of fluid flow (like air)
Over the last 100 years, the concentration CO2 in the earth's atmosphere has been increasing.
A measured increase in air temperature with increasing height.
Clouds are poor absorbers and emitters of infrared radiation
The sun emits radiation with greatest intensity in this region of the spectrum
An intense, rotating column of air that often protrudes from a cumuliform cloud in the shape of a funnel or a rope whose circulation is present on the ground.
Aurora australis
Occurring in the Southern Hemisphere, a glowing light display in the nighttime sky caused by excited gases in the upper atmosphere giving off light.
The property of a system that generally enables it to do work. Some forms of energy are kinetic, radiant, potential, chemical, electric, and magnetic.
Saturated (air)
An atmospheric condition whereby the level of water vapor is the maximum possible at the existing temperature and pressure.
The deterioration in one's mental and physical condition brought on by a rapid lowering of human temperature.
when small liquid cloud or fog droplets land on frozen objects and freeze on contact (milky ice)
What produces instability?
Cold air over warm air
a.k.a. rime or snow pellets: icy matter that forms from accretion
Prevailing Wind
the wind direction most commonly observed in a given location over a certain time period.
Thermal turbulence
eddy motions due to thermals (convection causes vertical motion, increasing with heat and as the atmosphere destabilizes)
Friction of air is due to...
mostly turbulence
Liquid water drops larger than .5mm that fall to the earth.
Air remains ________ when the air temperature decreases rapidly (11C for every 1000 meters) as we move upward in the atmosphere.
If the environment lapse rate declines at 12C per 1000 meters, the rising air parcel will be ________.
Hygroscopic condensation nuclei
Enabled condensation at relative humidities less than 100%
An ___________ air parcel cool off more rapidly as it rises and expands.
The most abundant greenhouse gas in the earth's atmosphere.
water vapor
In the Northern Hemisphere, surface winds tend to blow this way around an area of surface low pressure.
counterclockwise and inward
UVB radiation is more likely to cause a sunburn than is UVA radiation.
As the average speed of air molecules decreases, the temperature of the air:
Air in motion relative to the earth's surface.
A discrete quantity of energy that can be thought of a packet of electromagnetic radiation traveling at the speed of light.
Reflected light
The process whereby a surface turns back a portion of the radiation that strikes it. When the radiation that is turned back (reflected) from the surface is visible light, the radiation is referred to as reflected light.
Frost point
The temperature at which the air becomes saturated with respect to ice when cooled at constant pressure and constant water vapor content.
Vernal equinox
The equinox at which the sun approaches the Northern Hemisphere and passes directly over the equator. Occurs around March 20.
Indian summer
An unreasonably warm spell with clear skies near the middle of autumn. Usually follows a substantial period of cool weather.
Central Pressure
junction between two fronts in a frontal wave
Mountain wave eddies
form on leeward side of mountains
Radiational cooling
clouds or air emits infrared radiation into space, cooling the environment
Ice Nuclei
Same geometry as ice, small particles around which ice crystals form
mean sea level
the level representing the average surface of the ocean, 0m
The altitude at which the relative humidity reaches 100% is the ___________ ___________.
Condensation level
Orographic uplift
forced lifting of air along a topographic barrier
A condition caused by a lack of oxygen to the brain.
Air Pressure
The pressure exerted by the mass of air above a given point, usually expressed in milibars , inches of mercury, or hectopascals.
Radiant energy (Radiation)
Energy propagated in the form of electromagnetic waves. These waves do not need molecules to propagate them, and in a vacuum they travel at nearly 300,000 km per sec.
Actual Vapor Pressure
The pressure exerted by the water vapor molecules in a given volume of air.
What does ARINC stand for?
Aeronautical Radio, Inc., Annapolis, Maryland
When are radiosondes launched in the United States?
00z and 12z
What does a radiosonde measure?
Temperature, humidity, winds, and pressure up to about 30 km.
What can be converted to point upwards to measure wind speed and direction up to 16 km?
Doppler radar
curvature effect
the smaller a droplet is, the greater the curvature it has, which makes it easier for water to evaporate because of weak bonds
What models are designed to mimic the physical processes in the atmosphere?
Atmospheric models
Dew is more likely to form when the sky is ______.
Centripetal Force effects _____ but not _____.
wind direction, wind magnitude
Rainfall Intensity
is the amount of rain measured in inches per hour
Temperature declines at 6C per 1000 meters when the rising air parcel is _________, at a relative humidity of _______.
Saturated and 100%
homogeneous freezing
freezing of pure water without an ice nucleus, using an ice embryo
Trade Winds
wind from horse latitudes goes back to the equator, but is directed west by the Coriolis Force, causing Northeasterly winds
The largest storm in our atmosphere, in terms of actual size (diameter) is the
middle latitude cyclonic storm
The heat we can feel and measure with a thermometer
sensible heat
Longwave radiation
A term most often used to describe the infrared energy emitted by the earth and the atmosphere.
Mean (average) annual temperature
The average temperature at any given location for the entire year.
What is channel 2 imagery?
Responds to both emitted terrestrial radiation and reflected solar radiation.
What is a Persistence Forecast?
Tomorrow's weather will be like today's.
What type of air mass is maritime polar (mP)?
Cold and moist
Relative Humidity
Measure of how close the air is to being saturated (% age)
How is wet bulb depression determined?
By subtracting the wet-bulb temperature from the dry-bulb temperature
What type of front has a higher chance of producing bad weather?
Cold front
What model should you look at first?
GFS- Global Forecast System
The rate at which radiant energy is emitted by a body:
increases with increasing temperature
What is the next big thing in weather instruments?
Dual polarization radar
What does this model do?
It helps us fill in the gaps.
Type of front depends on
direction air mass is moving and characteristics of air mass
What are numerical weather prediction models?
They are mathematical models. Dozens of mathematical equations that describe how temperature, pressure, winds, and moisture will change with time.
Cloud and precipitation patterns of warm fronts
stratus clouds with light to moderate continuous rain ahead, clear skies behind
What is also included in the AWIPS?
Radar, satellite, and surface (ASOS) data
In ASOS, what do we use to identify the type of precipitation?
A precipitation identification sensor. Identifies precipitation as rain, snow, or precipitation undetermined. Will only report if fall rates are .01 inch per hour or greater. Categorizes as light, moderate, or heavy. Pulsed infrared is sent from the transmitter in one arm to the receiver in the other. The sensor is really only a precipitation indicator, as observations of weather such as haze are made by readings from a combination of sensors. Sometimes gets confused- sleet reported as rain, hail as rain, blowing snow as snow or rain. 1 meter between transmitter and receiver. Rain vs. snow discrimination based on fall speed. Rapid interruption of beam=rain, slower interruption of beam=snow, and another sensor decides if freezing rain is occurring.
Newton's Third Law applied to the atmosphere
The atmosphere exerts a friction on the Earth's surface driving surface currents of the ocean
What thing can measure both wind speed and direction, but only when clouds are present?
Satellite cloud drift winds (from GOES)
What is the short-range forecast?
6 hours to 60 hours. More than 12 hours- models becomes very important. NAM (North American Model).
What do air masses and fronts have?
They have both horizontal and vertical extent and we call them frontal surface or a frontal zone.
What is Super Resolution-New WSR-88D Build?
Available at or below 1.5 degree. The range gates for reflectivity decrease from 1 km to 250 m. Azimuthal resolution changes from one degree to a half degree. Improves rotation detection and the data range is extended from 230 km to 300 km. Takes a lot of computing power and only available at low angles. Current algorithms can't handle that data and we still use the legacy scale for algorithms. Forecasters will have to adjust methodologies for viewing targets. Stronger reflectivity and velocity signatures farther out.
Cloud and precipitation patterns of cold front
warm, moist air ahead of front is forced up and condenses creating squall lines ahead, cumulus clouds behind
Signs of a passing front
1. Temp change 2. Dew point change 3. Shift in wind direction 4. Pressure change 5. Clouds and precipitation patterns
What are the cons of visible imagery?
It is tough to distinguish clouds from snow-covered ground. A field of clouds smaller than the resolution will show up as a uniform gray area. Thin clouds will not show up very brightly, especially up against a highly reflective surface.
What are the names of the 3 radar scans and how long does it take each mode to complete one scan?
Clear air, 10 minutes; precipitation, 6 minutes; and severe weather, 5 minutes.
Maritime air masses are unstable because
moist air is less dense than dry air at the same temperature so it rises and evaporates, resulting in convection
What are the six steps in the polar front theory?
Stationary front, frontal wave, open wave, maturing phase, mature-occluded, and dissipated stage.
What is observation frequency and what are the values for this?
Data is collected over time to make a representative observation, thus the data is valid over a larger area. Sky conditions are taken in 30 minute intervals and it has a 3-5 mile radius. Visibility has a 10 minute processing interval and it has a 2-3 mile radius. Precipitation has a 10 minute processing interval and it has a 1-2 mile radius. Freezing rain has a 15 minute processing interval and it has a 2-3 mile radius. Temperature and dewpoint has a five minute processing interval and it has a 5 mile radius. Wind has a 2 minute processing interval and it has a 1-2 mile radius. Pressure has a 1 minute processing interval and it has a 5 mile radius.
What does a 60% chance of rain mean?
For any given random location in the forecast area, there is a 60% chance of rain. If a forecast calls for 60% chance of rain for 10 days straight, it should rain on your house 6 of those days.
When a cP air mass moves over the ocean
warm ocean surface adds heat and moisture to the air causing instability and changes designation
If a warm air mass moves over colder land
surface air cools, air above is warmer causing little vertical mixing resulting in stratiform clouds, fog, and accumulation of dust, smoke, pollutants causing low visibility
What type of imagery is not in the atmospheric window?
Water vapor imagery. It senses at the wavelength where water vapor absorbs and emits.
What is the new way that is used to determine significant levels?
It is called RRS. If the temperature or relative humidity along a straight line from one point to the next changes by 0.5 °C or 5% respectively, the point you started your line from is known as a significant level. 5 m/s departure for wind speed and 10 degrees departure for direction.
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