Met 421 Final Exam

Question 1

What does the acronym RADAR stand for?

Answer 1

Radio Detection And Ranging

Question 2

The 2 types of radar images?

Answer 2

Plane Position Indicator: horizontal cross section

Range Height Indicator: Vertical cross structure

Question 3

NEXRAD

Answer 3

Next generation radar

WSR-88D

Question 4

What can WSR-88D measure?

Answer 4

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

Question 5

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

Answer 5

• Azimuth angle
• Elevation angle
• Distance to target

Question 6

Azimuth Angle

Answer 6

Angle of beam with respect to north

Question 7

Elevation Angle

Answer 7

Angle of beam with respect to ground

Question 8

Cone of Silence

Answer 8

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

Question 9

Clear air mode

Answer 9

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

Question 10

Precipitation mode

Answer 10

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

Question 11

Base Reflectivity

Answer 11

• shows reflectivity over Single elevation scan

- Useful for precip detection

Question 12

Composite Reflectivity

Answer 12

• Shows reflectivity over all elevation scans

- Good for thunderstorm

Question 13

2 types of precipitation estimate

Answer 13

• 1-3 hour precipitation

- Storm total precipitation

Question 14

Doppler Effect

Answer 14

-Frequency changes because objects are moving away or towards radar

Question 15

Radial Velocity

Answer 15

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.

Question 16

Zero Isodop Prolem

Answer 16

Radar cant detect movement when directly perpendicular to object.

Question 17

Echo Tops

Answer 17

Top of the precipitation core is located

Question 18

Vertical Integrated Liquid (VIL)

Answer 18

Used to detect hail

Converts reflectivity into liquid equivalent

Question 19

Ground Clutter

Answer 19

Trees
Mountains
Buildings
Animals

Question 20

Sun Strobes

Answer 20

Occur around dawn/dusk

E-M radiation

Question 21

Anomalous propagation (AP)

Answer 21

Beam refracted into ground

Appears similar to intense precipitation

Question 22

Phased Array

Answer 22

• 30 sec volume scans
• Very expensive
• Higher resolution

Question 23

GOES Satelite

Answer 23

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

Question 24

MTSAT Satellite

Answer 24

Japan

Question 25

INSAT Satellite

Answer 25

India

Question 26

METEOSTAT Satellite

Answer 26

European

Question 27

Wind Profilers

Answer 27

- Doppler radar that measures winds in the troposphere | - Around 30 around in the U.S.

Question 28

NWP model

Answer 28

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

Question 29

NWP Sigma coordinates

Answer 29

Sigma coordinates are terrain following

Question 30

Grid point vs Spectral Models

Answer 30

Grid Point - Regional - Deal w lateral boundary issues Spectral - Global - Provides lateral boundary info

Question 31

Parameterization

Answer 31

Expressing unknown quantities in terms of other variables Accounts for unresolved processes without introducing new unknowns

Question 32

Microphysics

Answer 32

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

Question 33

Grid size

Answer 33

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

Question 34

How do convective storms affect larger scales?

Answer 34

- Redistribute heat, moisture, and momentum - Generate precip in unsaturated model grid cells - Stabilize atmosphere

Question 35

Grid length and Convective Parameterization CP

Answer 35

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

Question 36

What is ensemble forecasting?

Answer 36

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

Question 37

Errors in NWP

Answer 37

- Errors in initial conditions - Errors in model physics - Predictability limitations - Errors are random and/or symmetric

Question 38

What is ensemble forecasting used for?

Answer 38

- Extended range forecasting - Short range forecasting - Climate prediction - Air quality forecasting

Question 39

Benefits of Ensemble forecasting

Answer 39

- Improve forecasting through average - Quantitative measure of the reliability of the forecast - Provide info for targeted observations

Question 40

Ensemble strategies

Answer 40

- Initial Conditions | - Model physics

Question 41

2 main ensemble systems used by NCEP

Answer 41

- Global ensemble (GFS) | - Short range ensemble forecast (SREF)