meteorology for airborne scientists

8/9/2019 Meteorology for Airborne Scientists

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Meteorology for

Airborne Scien1sts

Henry Fuelberg

Department of MeteorologyFlorida State University


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Avia1on Related Parameters

to Forecast

Cloud Cover and Fog Precipita1on WindsSurface and Alo

Temperature

Humidity


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FirstA Few Basics

P = RT


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Atmospheric Pressure

Pressure = Force/Area

Decreases with al1tude

Pascal = Newton m2

millibar (mb) =

hectoPascal (hPa)

Mean sea level pressure =

03.25 mb (or hPa)


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Dry Adiaba1c Process

st Law dh = cv dT + p d OR dh = cp dT dp Consider an unsaturated parcel, let dq = 0 0 = cp dT dp Parcels s1ll can change temperature due to expansion

and contrac1on Exampleparcel expands, expends energy, T gets cooler Make subs1tu1ons and solve for dT/dz dT/dz = g/cp = 9.8 oC/km = d (dry adiaba1c lapse rate) d is posi1ve if T decreases with height, nega1ve forinversions Unsat. parcels always follow d Away from clouds and radia1ve processes, parcels

~ adiaba1c for several days


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Rising air cools, Subsiding air warms


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Poten1al Temperature ()Have a parcel at T and p

is temp. parcel would have if taken dry

adiaba1cally to p = 000 mb

If p = 000 mb, = T

= T (000 mb/ p) R/cp R/cp = 0.286

Parcels conserve during ascent, descent, etc. as

long as condi1ons are adiaba1cT is not conserved, it changes at d

Therefore, can serve as a tracer for parcels


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Water Vapor

Vapor pressure = par1al pressure of vapor (mb) Mixing ra1o = mass vapor/mass dry air (g/kg) Concept of satura1on Dew point temperature = temp to which air must

be cooled to become saturated (oC)

Rela1ve humidity = mixing ra1o / sat. mixing ra1o( how chose to sat. is parcel?)


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Saturated Adiaba1c Process

Parcel is saturated Li parcel, condensa1on occurs, latent heat

released, dq 0

dq = cp dT dp Let dq = latent heat release Perform some magic, get a complicated equa1on s d not a constant, depends on how muchvapor is in the air s 6 oC/km


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Radiosondes


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Hydrosta1c Stability

Displace parcel upward (could go downward)

Will displacement be

Suppressed = Stable

Layered clouds, steady precipita1on

Enhanced = Unstable

Towering clouds, showers or Tstorms

Neither = NeutralParcel moves only to where pushed


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Absolute Instability

Environ. Lapse Rate greater than Dry Adiaba1c Rate (> 0 deg/km)


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Condi1onal Instability

Environmental Lapse Rate between the Dry and Wet

Adiaba1c Rates (between 60 deg/km)


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What Causes Wind to Blow ??

It is acted on by forcesmostof which we cant see


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Straight IsobarsAbove Surface

Isobars


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Flow Around Circular Low

Include Centripetal Accelera1on


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Flow Around Circular High

Include Centripetal Accelera1on


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Upper Level Charts

Pressure is Ver1cal Coordinate (Not Z)


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500 mb Chart 8,000 or 5.5 km

Height Contours Replace Isobars


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Surface MapIsobars = Lines of constant pressure


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Straight IsobarsNear Surface


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Planetary Boundary Layer (PBL) Lowest layer of atmosdirectly influenced by thesurface PBL vs. Free Atmosphere What happens in PBL? Air is heated/cooled from belowradia1on Inversions (stable) at nightsuppress mixing Big lapse rate during dayless stablelots of mixing

Mechanical Turbulenceroughness (day or night) Thermal Turbulencethermals (day) You can bounce around a lot!!


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Wind Speed goes to zero at surface (no slip) Speed increases with height according to Ekman

Theorydirec1on also changes The more mixing the more is constant with height the more mixing ra1o constant with height Height of PBL deep during day, shallow at night Depth determined by

TemperatureWind SpeedOthers


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Marine Layer

Strong subsidence due to high pressure

Warm, dry sinking air

Cool moist air

Cold water

T inversion


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Weaker High Pressure

Clouds near top of marine layer


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Low pressure allows marine layer to

deepen as much as 6,000 .


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Smaller Scale Circula1ons

Are Superimposed onLarger Scale Flow


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Sea/Land Breezes


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Mountain/Valley Breezes


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Clouds

Most clouds are due to rising air

All precipita1on is due to rising air


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0 Basic Cloud Types


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FOG

. Cooling air to satura1on

2. Increasing Water Vapor

content to reach satura1on


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Radia1on Fog


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History or Future of Air

Trajectories

Backward in 1mewhere did air come from?

What path did it take?

Forward in 1mewhere is air going to?What path will it take?

Kinema1c methodmove parcels using

threedimensional winds


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WRF Nested Grid 45 km, 5 km, 5 km


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Procedure for Forward Trajectories

Start with 4D grid of 3D wind componentshope dataevery few hours

Move parcel one 1me step by these winds

Now at a new 3D loca1on and a new 1me

Take winds at new loca1on and 1me and move parcelanother 1me step Repeat the process un1l you reach desired ending 1me Limit is usually 50 days

Aer that uncertain1es are too great If backward trajectories, process goes in reverse


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Par1cle Dispersion Models

Establish loca1ons of emissions and rates of emissionRelease par1cles to simulate emission ratePar1cles have specified mass and are released at

specified rate

Threedimensional winds move the par1clesCan then watch the transport of the emissions


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Fire loca1ons July 2008


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Sources of Real Time Informa1on

Surface

RadiosondesSatellite

Radar

hp://www.rap.ucar.edu/weather/


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Surface Plot


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GOESYesterday PM


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Edwards AFB Sounding


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Forecast Products

All types of input data combined (assimilated) toproduce best 3D ini1al condi1ons for model

Models iterate forward in 1me

Various groups run models NWS, USAF, Navy,Europeans, etc.

Model forecast surface and alo at each itera1on Different models give different solu1ons Meteorologist decides on the most likely forecast


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Your Local NWS Office

hp://www.srh.noaa.gov


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Other Interes1ng Sites

Storm Predic1on Center

hp://www.spc.noaa.gov

Na1onal Hurricane Center

hp://www.nhc.noaa.gov


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NWS Forecast for Palmdale

Friday Night: Clear, with a low around 6.Breezy, with a southwest wind 20 to 25 mph

decreasing to between 0 and 5 mph. Winds

could gust as high as 30 mph.

Saturday: Sunny, with a high near 94.

Southwest wind around 0 mph.

Saturday Night: Clear, with a low around 63.

Southwest wind between 0 and 5 mph, withgusts as high as 25 mph.

Sunday: Sunny and hot, with a high near 98.

Sunday Night: Clear, with a low around 63.

Monday: Sunny, with a high near 95

Monday Night: Clear, with a low around 60.

Tuesday: Sunny, with a high near 94.Tuesday Night: Clear, with a low around 59.

Wednesday: Sunny, with a high near 94.

Wednesday Night: Clear, with a low around 59.

Thursday: Sunny, with a high near 94.


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Santa Barbara Channel

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