Meteo 201 Midterm

Troposphere

The lowest layer of the atmosphere where temperature decreases with height and most weather occurs.

Boundary Layer

The lower part of the troposphere affected by energy, moisture, and momentum exchanges with the ground, averaging about 1 km in depth.

Stratosphere

The layer above the troposphere, extending to ~50 km, where temperature is nearly constant in the lower part and increases with altitude.

Tropopause

The boundary between the troposphere and stratosphere, marked by an abrupt decrease in the environmental lapse rate.

Inversion

An atmospheric layer where temperature increases with height.

Environmental Lapse Rate (ELR)

The rate at which temperature decreases with height, influenced by latitude.

Diurnal Range

The difference between the highest and lowest temperature of a day.

Surface Station Model

A compact representation of weather data observed at a specific location and time on a map.

Wind Direction

The direction from which the wind is blowing, e.g., a northwest wind comes from the northwest.

Prevailing Wind

The wind direction most frequently observed during a specified period.

Air Pressure

The force exerted by air per unit area, with average sea level pressure at 1000 mb.

Trough

An elongated zone of low pressure where winds converge at the surface.

Ridge

A zone of high pressure where winds diverge at the surface.

Isopleth

A line on a map connecting points of equal value for a specific variable.

High pressure

fair weather

Low pressure

clouds and precipitation

Climatology

use the average as the forecast

persistence

what has happened will continue to happen

analog forecasting

assume weather repeats itself

Grid point model

cover the forecast area witha 3D grid, solve equations as grid point

spectral model

because atmospheric variables tend to be wavy build a model using wavy mathematical functions

why do NWP go bad

• computer models are imperfect

• observational limits

• the atmosphere is a nonlinear system

ensemble forecasting

A set of computer model forecasts rather than just one

SREF

short range ensemble forecast

GEFS

global ensemble forecasts

MOS

Model output system: a statistical forecasting technique that turns output from NWP models into local weather forecasts

NBM

National blend of models: a forecast guidance based on a blend of the output from various NWP models

Humidity

generic word used to describe moisture in atmosphere

saturation

condition at which evaporation rate = condensation rate. when condensation rate is less than the evaporation rate, condensation nuclei grow and make clouds

Latent heat

the amount of energy that is released or absorbed during a phase change at a constant temperature

condensation nuclei

microscopic particles of dust, dirt, soot, salt and other particles in the air onto which water vapor condenses to form cloud drops

wet bulb temperature

the lowest temperature to which air can be cooled by evaporating water into it

relative humidity

the measure of the amount of moisture in the air compared to the maximum amount the air can hold at a given temperature?

dew point

temperature to which air must be cooled at constant pressure for saturation to occur

orographic lifting

occurs when an air mass is forced to rise over a topographic barrier, such as a mountain range.

liquid precipitation =

rain + melted solid precipitation

Planck’s law

all matter emits radiation constantly and at all wavelengths

Wiens law

matter does not emit radiation at all wavelengths equally. the hotter the object the shorter the wavelength of maximum emission

stefan-boltzman law

the total energy emitted per unit area is proportional to the fourth power of temperature E=𝜎T⁴

Kirchoffs law

an object that absorbs radiation efficiently at a particular wavelength will also emit radiation efficiently at that wavelength

conduction

molecular collisions transfer energy

convection

blobs (parcels) of rising air transfer energy

the best absorbers of infared are

Carbon dioxide and water vapor

Low clouds

below 6500 ft

Alto (middle)

between 6500 and 20000 ft

Cirro (high)

above 20000 ft

cumulus

puffy clouds

stratus

low light or dark gray clouds that cover most of the sky

cirrus

wispy, feathery, (tufts of hair)

altocumulus

white or gray patches that look like sheeps wool

nimbus

clouds that produce precipitation

GPS

Global positioning satellites

Geostationary

• 22500 miles up over equator, provides best views of tropics and mid-latitude

• orbits at the same speed as earth

• ideal for making movies

Polar orbiting

orbit pole to pole, 500 miles up, image in swaths (so must piece together

• sees each point twice a day and provides the vast majority of satellite data for NWP models

• High resolution

remote obersvations

instrument not in direct contact with the medium it is measuring

in situ observations

instrument in direct contact with the medium it is measuring

visible imagery

radiometer measures back-scattered visible radiation

Infrared

radiometer turned to infrared wavelengths emitted by clouds and earth.. the warmer the emitter, the more radiation emitted

water vapor imagery

• water and water vapor are the dominant atmospheric emitter of radiation

• cant give information about low in the atmosphere

Hydrometer

any product of condensation or deposition of atmospheric water vapor

Clear air mode

antena scans 5 elevation angles in 10 minutes. typically used on days with no precipitation or very light precipitation. Most sensitive mo

Precipitation mode

antena scans 9-14 elevation angles in 5-6 minutes. used on days with precipitation. can miss lighter precipitation due to faster scanning

doppler effect

the pitch of sound is different depending on how the object making the sound is moving relative to the listener

if PGF was the only force acting on air, the wind would blow ____ from higher pressure toward lower pressure

Away

coriolis effect

apparent deflection imparted to moving objects that results from earths rotation

when PGF and CF are only forces acting on air, they balance to produce winds that are ____ to isobars, lower pressure to left

parallel

geostrophic wind

hypothetical flow that results from a balance between the pressure gradiant force and the coriolis force

the magnitude of the coriolis force _____ as you approach equator

decreases

conventional doppler radar

radar wave only in horizontal plane so captures only one dimension of targets

dual polarization

radio waves in both horizontal and vertical directions so it captures two dimensions of targets

Differential Reactivity (ZDR)

difference between the horizontal and vertical reflectivity, helps with target shape

Correlation coefficient

good for discriminating meteorological from non meteorological targets

convection

the vertical transport of energy by rising parcels of air

advection

the process of transporting some quality or characteristic by the movement of air

cold cloud

ice, water, and water vapor can coexist

The _____________ is the dominant precipitation producer in mixed phase clouds

bergeron findeison process (ice-crystal process)