CASA RADAR Intro Prof Sandra CruzPol Ph D

CASA: RADAR Intro Prof. Sandra Cruz-Pol, Ph. D. Electrical and Computer Engineering UPRM

“There is insufficient knowledge about what is actually happening (or is likely to happen) at the Earth’s surface where people live. ” [NRC 1998]

Observation Limitations Single NEXRAD (TJUA) in PR Distance Cayey to Mayagüez: ~ 100 km Site Elevation: 850 m Curvature Beam Elevation (Above Site): 600 m Total Beam Elevation (Above SL): 1. 4 km NEXRAD Rainfall 1 Hour Total

This System “underneath” NEXRAD Water spout at Mayaguez, PR- Sept 2005

What is a Radar? Radio detection and ranging 1. How does a radar work? 2. Games

Light is an electromagnetic wave. Microwaves = have air wavelengths in the mm – cm scales Their frequencies in the Giga Hertz GH range

Electromagnetic Spectrum

Compare to: Acoustic Echo-location hello

Acoustic Echo-location hello

Acoustic Echo-location hello distance

Hi !! time t = 2 x range / speed of sound Example: range = 150 m Speed of sound ≈ 340 meters/second t = 2 X 150 / 340 ≈ 1 second

RADAR Echolocation (RADAR ~ RAdio Detection And Ranging) “Microwave Echo-Location” Tx Rx Microwave Transmitter Receiver

Target Range Tx Rx time t = 2 x range / speed of light measure t, then determine Range Example: t =. 001 sec Speed of light = c = 3 x 108 meters/second Range =. 001 x 3 x 108 / 2 = 150, 000 m = 150 km

We will see that Radars work by… Transmitting microwave pulses…. and measuring the … • Time delay (range) • Amplitude • Frequency • Polarization … of the microwave echo in each range gate

Polarization • Describes the way the electric field of the wave moves through space as seen from behing along time. ,

Doppler Effect

Target Radial Velocity Frequency ft Frequency f t+ f d

Target Radial Velocity Frequency ft Frequency f t+ f d

Zero Velocity for “Crossing Targets” Frequency ft Doppler Frequency f t+ f d

QPE – Quantitative Precipitation Estimation 0. 1 mm/hr 15 mm/hr 100 mm/hr >150 mm/hr

Play the games to learn the basics • http: //whyfiles. org • • • http: //meted. ucar. edu/hurrican/strike/index. htm http: //meted. ucar. edu/hurrican/strike/info_3. htm# http: //www. nws. noaa. gov/om/hurricane/index. shtml http: //www. nws. noaa. gov/om/edures. htm

More Games for Kids 4 -104 http: //www. nws. noaa. gov/om/reachout/kidspage. shtml

References t The COMET project [http: //www. comet. ucar. edu/] t NASA TRMM t NCAR (National Center for Atmospheric Research) University Corporation for Atmospheric Research (UCAR) t NOAA Educational Page [http: //www. nssl. noaa. gov/edu/ideas/radar. html] t Dave Mc. Laughlin Basics of Radars presentation t NWS [http: //www. crh. noaa. gov/fsd/soo/doppler. htm]