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Met 421 > Met 421 Final Exam > Flashcards

Met 421 Final Exam Flashcards

1
Q

What does the acronym RADAR stand for?

A

Radio Detection And Ranging

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2
Q

The 2 types of radar images?

A

Plane Position Indicator: horizontal cross section

Range Height Indicator: Vertical cross structure

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3
Q

NEXRAD

A

Next generation radar

WSR-88D

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4
Q

What can WSR-88D measure?

A
  • Storm intensity
  • Storm movement
  • Detection of hail
  • Rainfall estimates
  • Detection of tornado
  • Wind fields within storms
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5
Q

What 3 pieces of info does a radar use to determine target location?

A
  • Azimuth angle
  • Elevation angle
  • Distance to target
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6
Q

Azimuth Angle

A

Angle of beam with respect to north

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7
Q

Elevation Angle

A

Angle of beam with respect to ground

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8
Q

Cone of Silence

A

Area directly above the radar that the radar cannot detect because of elevation limitations.

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9
Q

Clear air mode

A

5 Elevations, 10 Minutes
Used with no precipitation, can be used to detect snow.
Most sensitive mode.

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10
Q

Precipitation mode

A
  • Faster antenna
  • 9-14 scans 5-6 minutes
  • Good for precipitation
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11
Q

Base Reflectivity

A
  • shows reflectivity over Single elevation scan

- Useful for precip detection

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12
Q

Composite Reflectivity

A
  • Shows reflectivity over all elevation scans

- Good for thunderstorm

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13
Q

2 types of precipitation estimate

A
  • 1-3 hour precipitation

- Storm total precipitation

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14
Q

Doppler Effect

A

-Frequency changes because objects are moving away or towards radar

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15
Q

Radial Velocity

A

Hydrometeors moving toward/away from radar
- positive values = away (Red)
- negative values = towards (Green)
Base velocity
-Relative to ground
Storm relative velocity
-Storm motion subtracted. Used to detect motion in storm.

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16
Q

Zero Isodop Prolem

A

Radar cant detect movement when directly perpendicular to object.

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17
Q

Echo Tops

A

Top of the precipitation core is located

18
Q

Vertical Integrated Liquid (VIL)

A

Used to detect hail

Converts reflectivity into liquid equivalent

19
Q

Ground Clutter

A

Trees
Mountains
Buildings
Animals

20
Q

Sun Strobes

A

Occur around dawn/dusk

E-M radiation

21
Q

Anomalous propagation (AP)

A

Beam refracted into ground

Appears similar to intense precipitation

22
Q

Phased Array

A
  • 30 sec volume scans
  • Very expensive
  • Higher resolution
23
Q

GOES Satelite

A

U.S.
5 visible/IR channels
3 axis stabalized always facing earth

24
Q

MTSAT Satellite

A

Japan

25
Q

INSAT Satellite

A

India

26
Q

METEOSTAT Satellite

A

European

27
Q

Wind Profilers

A
  • Doppler radar that measures winds in the troposphere

- Around 30 around in the U.S.

28
Q

NWP model

A

Programs that integrate equations forward in time to predict variables for the future.

29
Q

NWP Sigma coordinates

A

Sigma coordinates are terrain following

30
Q

Grid point vs Spectral Models

A

Grid Point

  • Regional
  • Deal w lateral boundary issues

Spectral

  • Global
  • Provides lateral boundary info
31
Q

Parameterization

A

Expressing unknown quantities in terms of other variables

Accounts for unresolved processes without introducing new unknowns

32
Q

Microphysics

A

-Uses grid spacing and the weather variables within the grid for forecasting.

33
Q

Grid size

A
  • Currently 12 km in NAM model. This accounts for storms partially resolved. Requires some CP.
  • < 4 km = storm fully resolved. No CP required.
34
Q

How do convective storms affect larger scales?

A
  • Redistribute heat, moisture, and momentum
  • Generate precip in unsaturated model grid cells
  • Stabilize atmosphere
35
Q

Grid length and Convective Parameterization CP

A

-As grid length decreases -> turn off cp and use explicit convection

36
Q

What is ensemble forecasting?

A

Several model runs called members are used to provide accuracy through ensemble average

37
Q

Errors in NWP

A
  • Errors in initial conditions
  • Errors in model physics
  • Predictability limitations
  • Errors are random and/or symmetric
38
Q

What is ensemble forecasting used for?

A
  • Extended range forecasting
  • Short range forecasting
  • Climate prediction
  • Air quality forecasting
39
Q

Benefits of Ensemble forecasting

A
  • Improve forecasting through average
  • Quantitative measure of the reliability of the forecast
  • Provide info for targeted observations
40
Q

Ensemble strategies

A
  • Initial Conditions

- Model physics

41
Q

2 main ensemble systems used by NCEP

A
  • Global ensemble (GFS)

- Short range ensemble forecast (SREF)

Met 421 (3 decks)

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