Sign inRegisterCheck connection

Weather Radar as Remote Sensing on a Personal Weather Site

Weather radar is remote sensing, not a thermometer. Reflectivity, beam height, and clutter explain why a PWS linked radar beside a rain gauge.

Back to Historical weather observations and forecasts

A rain gauge counts water that reached a funnel. Weather radar does not. It transmits microwave pulses, listens for energy scattered back from hydrometeors (and from other targets), and maps that returned power in space and time. The two instruments can sit on the same personal weather station (PWS) page because they answer related questions about precipitation. They remain different observations. This article is the evergreen science of that split: reflectivity, beam height, and ground clutter, and why a station site linked official radar next to a logger.

This URL is not a live radar loop. TNET Weather does not rehost NEXRAD imagery. For current official U.S. radar, use the National Weather Service radar site. TNET is not a warning service; watches, warnings, and life-safety decisions belong to the NWS and local emergency authorities.

Historical context

Hobby weather sites of the 2000s treated radar as a neighbor to the station table. Incoming links to /radar wanted that companion view, not a second thermometer. The original captures, third-party mosaics, and GRLevel3 exports are not restored. The job of the page is still to teach what a radar image is so a visitor does not read it as a rain-gauge time series painted in color.

Reflectivity is returned power, not rainfall at the funnel

Weather radar is radio detection and ranging. NOAA’s JetStream explanation of how radar works states the WSR-88D (Weather Surveillance Radar—1988 Doppler) as a pulsed Doppler system: a short pulse, a long listen, range from round-trip time, and a Doppler phase shift for radial motion of the target. Dual-polarization, added network-wide in 2012, transmits and receives in both horizontal and vertical orientations so the returned signals can discriminate among rain, hail, snow, and non-meteorological scatterers more clearly than reflectivity alone.

The quantity most PWS pages showed is base reflectivity, expressed in dBZ (decibels relative to a reference reflectivity Z). NCEI describes base reflectivity as echo intensity used to detect precipitation, evaluate storm structure, locate boundaries, and assess hail potential. High dBZ means a strong return. It does not mean a specific number of millimeters in your funnel. Converting reflectivity to rain rate is a derived step that depends on drop-size assumptions (a Z–R relation). The same dBZ can be light rain of many small drops or fewer large drops; hail and birds also scatter strongly. A station rain gauge remains the in-situ depth measurement. Radar remains a remote-sensing field of returned power, valid at the beam’s location and time, not at the gauge orifice.

Doppler velocity is a second base quantity: motion toward or away from the antenna. It is still not the station anemometer. The mast samples air at a point; the radar samples a pulse volume that grows with range.

The beam is not at the ground

A WSR-88D does not stare along the surface. It completes a volume scan: a set of elevation angles (a volume coverage pattern). NOAA JetStream notes as many as about 15 tilts; an example active-weather pattern finishes in roughly four and a half minutes. The lowest tilt is typically near 0.5°. Because the Earth curves, that slice is already well above the ground at modest range. JetStream’s rule of thumb: at 100 miles, the 0.5° beam is about 12,000 feet above the ground.

That geometry is why a PWS rain gauge and a radar pixel over the same town can disagree honestly:

  • Shallow rain, drizzle, or monsoon cores that stay low can pass under the beam at long range.
  • Virga can produce a strong echo aloft while the gauge stays dry because drops evaporate before reaching the surface—common in desert air.
  • The sample volume widens with range. NOAA’s radar-beam note states the beam spreads on the order of 1,000 feet of width per 10 miles of travel, so at 120 miles the beam is more than two miles across. Fine structure near the radar is not the same object as a blob at the edge of the display.

A caption that says only “rain over the county” without range, tilt, and time is incomplete. The scientific caption names the radar site, the product (base reflectivity at a stated elevation, or a composite), the valid time in UTC, and that the field is remote sensing.

Ground clutter, anomalous propagation, and filters

Not every echo is weather. Buildings, terrain, wind farms, and insects return energy. Ground clutter is the near-radar return from the surface and fixed objects, usually strongest on the lowest tilt. Anomalous propagation (AP) occurs when refraction bends the beam into the ground, producing stationary false echoes that can look like rain. NWS training notes that AP is most common on the lowest slices, disappears aloft, and will not appear on satellite imagery. Super-refraction is favored when temperature increases with height or moisture drops sharply with height—conditions a desert inversion can provide at night and in the early morning.

Clutter-suppressed products are derived displays. They are easier to read and easier to over-trust. A “clean” image is not proof that the algorithm removed only non-weather. A “scientific” image with clutter left in is not a better warning; it is a different processing choice. Either way, the product is still radar, not the station.

Why a PWS put radar next to the rain gauge

The pairing is quality control, not decoration. The gauge tells you water arrived here. Radar tells you whether a precipitating echo was nearby at a comparable time. A logger spike under a clear volume is a candidate dump or clog-clear; a dry gauge under a strong nearby echo is a candidate beam-overshoot, evaporation, or a stuck tip. One funnel is a point; radar is a field. Microwave scatter is not a tipping bucket. Agreement and disagreement are both informative if units, times, and identities stay attached.

The pairing is not a flood warning, not official QPE, and not a claim that the station measured the storm at radar resolution. NCEI archives Level-II base data and Level-III products from a network of 160 S-band Doppler radars operated jointly by NWS, FAA, and the U.S. Air Force. A PWS page that links those sources should attribute NOAA/NWS, keep timestamps, and refuse to crop the legend.

How to read a station radar panel

Use this checklist when a weather site shows radar beside rain:

  • Source. Named WSR-88D versus a mosaic versus a third-party redraw. Those are different objects; see Level III products and mosaic provenance.
  • Not satellite. Infrared or water-vapor pictures are geostationary radiance, not radar. That subject lives at GOES-West.
  • Time and tilt. Volume time in UTC; base reflectivity at 0.5° is not composite reflectivity. Echo tops are another product.
  • Range. Distance from the antenna to the station. Beam height rises with that distance.
  • Local rain. Gauge depth, interval, and units, labeled as in-situ. Do not convert dBZ to inches unless you name the Z–R relation as derived.

Local geometry—how a desert radar sees a metro area—belongs on the Phoenix NEXRAD article.

Modern relevance

Radar describes precipitation structure: where hydrometeors are, how they move, how tall the echo is. TNET groups that atmospheric family on evidence families. The brief does not treat a hobby gauge as official radar, and it does not claim that a reflectivity blob sets a connection outcome. The Horizon study review is conceptual context for why precipitation appears in connection research. It does not license a caption that says dBZ caused a speed drop at an address. Observed rain, observed radar, modelled fields, and derived scores stay labeled on how the service works.

This page does not display live radar. Current official imagery: radar.weather.gov. Historical pages: observations hub.

Sources