Representing Climate Data continued Weather Radar radar Radio

Representing Climate Data (continued) Weather Radar

radar (Radio Detection and Ranging) Allows us to look inside of clouds and “see” types of precipitation.

• A transmitter sends microwave pulses. • “Targets” scatter energy back to receiver. • Amplified and displayed as echo • Time between emitting energy and receiving it back from target tells distance to target.

• Shorter microwavelengths (~1 cm) • detect small targets • (e. g. , tiny droplets of water in clouds) • Longer micro-wavelengths (3 -10 cm) • detect larger targets • (e. g. , precipitation) • Brightness of echo • Amount of precipitation

Reflectivity units d. BZ : decibels of Z • “Z” is energy reflected back to radar • Values increase with strength of signal and intensity of ppt Two Modes: 1. Clear air 2. Precipitation • d. BZ equate to approximate rainfall rates

Clear Air Mode

Precipitation Mode

• Makes repeated 360˚scans of atmosphere at increasing elevation angles. • 2 modes: • Clear Air mode • No rain • Dust, light snow • VCP 31, 32, 35 (volume coverage pattern) • Precipitation mode • Rain or snow • VCP 12, 215

Ground clutter • Ground, buildings, trees, cars • Within 25 km of radar • Not moving with respect to radar, so can be detected by radial velocity • Insects • Birds • Turbulence • Effects density • Particulate Matter

Doppler Radar • Based on principle of Doppler shift: • Waves moving towards observer have different frequencies than waves moving away from observer. • e. g. , sound from approaching vs. leaving ambulance • Doppler radar can measure direction • Knowing wind speeds and directions within clouds gives info about vorticity (spin)

Velocity units • Radial velocities in knots • Red: wind moving AWAY • Green: TOWARD radar • Need to know where radar is!

Base reflectivity • Reflectivity in lowest elevation “slice” • Used to survey area close to radar

Composite reflectivity • Combines all elevation scans • Shows highest reflectivity

Dual-Polarization radar • Conventional radar receives pulses in horizontal directions. • Dual-pole : horizontal and vertical • Get a better picture of what exactly the targets are: hail, rain, snow, melting snow, insects!

Example of use of dual pole radar: can detect hail

Example of tornadic debris ball using dual pole

RIDGE (Radar Integrated Display with Geospatial Elements) • Combine radar with topography, roads, county lines, rivers, warnings • Overlay maps as layers • Toggle layers on or off • GIS compatible NWS Duluth

Links to interesting and helpful short videos: 1. BATS in Texas were detected on weather radar: Check this out! Full link: https: //weather. com/science/weather-explainers/news/2020 -03 -20 radar-strange-cool-things-bats 2. Take a tour inside the “giant soccer ball” to see what’s inside: Tour the radome! Full link: http: //hot 1047. com/go-inside-a-doppler-radar-with-the-national-weather -service-video/ 3. Have a look at the latest radar technology: dual pole Dual pole Full link: https: //www. youtube. com/watch? v=Qdv. AODg-lts

REVIEW • Geostationary and polar-orbiting satellites • Visible satellite imagery: • • • Records albedo Only useful during daylight hours Shows all cloud cover, land/water, frontal systems, snow surfaces Transmitted through shortwave window NEW GOES bands: • BLUE (0. 47µm): good for aerosols • RED (0. 64 µm) : good for snow/ice • Infrared satellite imagery: • Thermal IR • • • Records emitted IR Records day and night Detects temperature Reads cloud height NEW GOES bands: • CLOUD TOP PHASE ( 8. 4 µm): good for cloud composition • CLEAN IR WINDOW (10. 3µm): good for cloud heights

• Near IR Solar; Daytime only Veggie Band (0. 86µm): good for flooding, burn scars, types of vegetation, fog cirrus (not lower troposphere because water vapor absorption) Cirrus Band (1. 37 µm) : good for cirrus clouds, volcanic ash Water vapor satellite imagery: Records infrared at 6. 2 – 7. 3 µ emitted by water vapor Upper, middle, lower troposphere Tracks moisture Shows storm (low) centers Shows jet streams and sinking air Good for observing structure of storms

RADAR: Is an active form of remote sensing because it sends out energy. “target” (precipitation) scatters energy, some back to receiver, which displays it as “echo”. Brightness is intensity of precipitation Two Modes: Clear Air (can pick up ground clutter) and Precipitation d. BZ values: decibels of Z = strength of return signal Doppler : provides direction of targets toward or away from radar. Velocity image : used to identify rotation Dual polarization: can decipher and identify targets better RIDGE: GIS compatible