Using NEXRAD

NEXRAD is an active remote sensing system.

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NEXRAD is an acronym for next generation radar.

 

NEXRAD is also known as WSR88D which stands for Weather Surveillance Radar 1988 Doppler.

 

NEXRAD is a system of Doppler radar sites installed by the National Oceanographic and Atmospheric Administration (NOAA).

 

NEXRAD's purpose is to track precipitation and weather systems in the United States.

 

NEXRAD can also be used to track other objects in the atmosphere such as smog, pollen, insects, bats and birds.

Radar is an acronym for radio detecting and ranging system.

 

Radar uses the process of transmitting short bursts or microwave energy in the direction of the object of interest.

 

The energy is scattered and some of the energy comes back to be measured by the radar receiver.

 

Reflectivity is the term used to describe the energy returned to the radar receiver.

 

Reflectivity is measured in decibels, dBZ.

Radar was originally used during World War II to detect enemy aircraft.

 

Radar operators noted small blips on their screens which they referred to as angels.

Radar today has many application such as weather tracking, animal tracking, smog and pollen counts and wind direction.

 

Data from radar provides insights into migration and important stop over sights.

Microwave energy is emitted through an antenna of a radar station.

 

Energy moves toward the object of interest.

 

When energy reaches the object the energy scatters.

 

The bigger the object or group of objects the stronger the scattered signal.

 

The radar then receives the returned signal (reflectivity).

 

Data (images) can be viewed on a radar screen or stored in a computer for further analysis.

 

Data is recorded 24/7.

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NEXRAD operates in two modes: Precipitation and Clear Air.

 

When birds are the object of interest or target, the Clear Air mode is used.

 

Clear Air mode has a longer dwell time and is more sensitive to scattered energy, it picks up lower decibels.

 

Observations have shown that birds register in the decibel (dBZ) range of 30-35 dBZ.

 

When using radar to detect birds there are other factors to consider when analyzing the data:

Radar is useful to track birds that fly at night or at high altitudes.

 

Radar images can be used with bioacoustic records, satellite thermal imagery, counting birds by sight and identifying species by sight (ground truth).

 

The best time to monitor birds is at dusk.

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	Researcher cannot tell which bird species are migrating from image alone.
	Bird migration can not be tracked during heavy rainfall.
	Since birds migrate only twice per year, researchers are limited to the time of year they can track migration.