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1

Synoptic meteorology

meteorology traditionally involves the study of weather systems, such as - extratropical high and low pressure systems, - jet streams - associated waves - fronts.

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mesoscale meteorology

the study of convective storms, land–sea breezes, gap winds, and mountain waves

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Weather forecasting

forecasting necessitates understanding a wide range of processes and phenomena acting on a variety of spatial and temporal scales.

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forecasting for a coastal location requires information concerning:

- The near-shore water temperature

- The potential for land–sea breeze circulations

- The strength and orientation of the prevailing synoptic-scale wind flow.

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The prediction of precipitation type can benefit from knowledge of:

- Atmospheric thermodynamics - Cloud physics.

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quasigeostrophic (QG) equations

simplified version of the full primitive equations

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Momentum equations

  • continuous
  • ideal gas
  • hydrostatic

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scale analysis

systematic strategy to determine which terms in the equations, often associated with specific physical processes, are most important and which are negligible in a given meteorological setting. By characterizing the temporal and spatial scales associated with specific weather systems, we can systematically neglect “small” terms in the governing equations in the study of those systems.

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The length scale

related to the size of a weather system, or how far an air parcel would travel within the system during a given time interval.

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The time scale

how long it would take an air parcel to circulate within the system

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rawinsonde can measure pressure with

baroswitch

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length scale of microscale

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time scale of microscale

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Example phenomena of microscale

turbulence, PBL

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length scale of mesoscale

1-1,000 km

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time scale of mesoscale

1h - 1day

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example phenomena of mesoscale

thunderstorm and, land sea breeze

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length scale of synoptic scale

1,000-4,000 km

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time scale of synoptic scale

1 day - 1 week

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Example phenomena of synoptic scale

Upper- level troughs, ridges. surface low and high

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length scale of planetary scale

>4,000 km

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time scale of planetary scale

>1 week

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Example phenomena of planetary scale

polar front jet stream, trade winds

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what are the variables in the system?

Four independent variables: three spatial directions (x,y,z) and time (t)

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a variety of vertical coordinates measures are used in place of the ..........

vertical distance z

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a variety of vertical coordinate measures are used in place of the vertical distance z to determine .....

determine position along the vertical coordinate axis

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popular choice of vertical coordinates

pressure, sigma (a terrain-following ratio of pressure to surface pressure), potential temperature, or a hybrid among these

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the k unit vector maintains

right angles with the horizontal unit vectors.

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vertical coordinates are known as......

isobaric coordinates

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what is the method pilots use to fly?

aircraft's measure pressure and fly along surfaces of constant pressure

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The wind velocity components are based on

the time rate of change in the distance along the respective coordinate axes following the airflow

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omega (ω), is defined as

the vertical motion in isobaric coordinates

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The pressure-coordinate vertical velocity is negative for .....

upward motion because pressure decrease with height

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The Coriolis parameter is related to

the projection of the earth’s rotation onto the vertical (kˆ) axis and is given by f = 2Ωsin ϕ

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ϕ is

latitude

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Ω is

the earth’s rate of angular rotation, 2π radians day–1 7.292x10−5 rads−1

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sidereal day

23 h 56 min

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Other basic variables

pressure (p), temperature (T), density (ρ), and specific volume a=1/p

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Td

dew point: measure of absolute water vapor content

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RH

relative humidity: measure of the degree of saturation

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The ideal gas law, or equation of state, provides a useful relation between

the pressure, temperature, and density

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Tv

virtual temperature Tv= T (1+0.61q)

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Rd

dry- air gas constant Rd = 287 J/ kg.K

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