How is data processed at each radar site weather services use?

More about RADAR.

Radar Site Weather

By using data from the radar site weather forecasters can make quick forecasts. Let's get technical. They use computers to help them interpret the data retrieved by the radar equipment. How? You might ask...

They get a more complete convection picture, detect violent systems and update warnings when time is of the essence. But how do they make sense of these illustrations and radar system weather images?

After coming out of the radar site, signals are normally reflected by dense things in the air. Targets such as falling precipitation, airplanes, swarms of insects or birds and so forth.

We care mostly about precipitation which gives us these weather pictures. And radar processing systems have advanced algorithms to convert returned signal strength to precipitation intensity.

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radar site weather - math conversions.

The processor uses a few technical assumptions about the physical characteristics of the beam and the target(s). Then a crude mathematical relationship translates reflectivity to precipitation rate.

The weather-radar-conversion mathematics formula looks at the reflectivity. That is, ratio of reflected to broadcast signal.

Then the computer applies an exponential algorithm. The math used depends on whether we expect rain, hail or snow. But usually we raise it to a power between 1.5 and 2.5.

The reflectivity, given in decibels (dBZ), is the ratio of the incoming reflected power flux to the initial power sent out. Flux is power per unit area, the amount of energy passing through a certain area in a specified amount of time.

After that, the program multiplies by a scaling constant. Its value depends on a multitude of factors. Often, these formulae carry the names of the researchers who devised them, such as Marshall-Palmer (where perceived reflectivity is proportional to droplet diameter to the 6th power and the dielectric constant of the targets squared, weighted by a drop size distribution) and Srivastave. They are not deadly accurate, but useful nonetheless.

Radar Information


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Definition mathematics...

Here is a list of values used by the U.S. Government (NOAA) to convert radar site weather data to meaningful rainfall rates. 25 mm is about one inch.

Conversion table

One thing to note. An increase of 10 on ANY decibel scale, where the units start with dB means the intensity of the reflected radiation is TEN TIMES more powerful. That does not mean the storm is 10x stronger, just the incoming power.

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At least that's what some people think. Do you think math helps us to understand our world? Succeed at work? Use a computer?

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What Other Great Mathemeticians Have Said...

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Producing Weather Forecasts Not rated yet
The literature gives a good description as to the systems used in monitoring the incoming weather. I do not believe that the information content is too …

MAthematical Precitions of Weather Not rated yet
I think the article is overly technical. It jumps straight into formulas or jargon right away and doesn't do an especially good job of giving these terms …

Interesting Not rated yet
This article was very interesting. It does get a little technical for lower grade levels, but anyone interested in Math from the higher high school grades …

Math's Pluses and Minuses Not rated yet
Well, math helps with a lot of things. For instance, it helps a mind more able to solve problems if it can convert a problem into a math problem. Different …

Very technical, a litle difficult to understand Not rated yet
This article is very technical. It talks about math but doesn't give very much information about the actual math involved. It talks about the formulae …

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What happens if there are two storms in a line? We call it attenuation. The closer cell makes it difficult, even impossible, for the storm chasers to see the further one clearly on the weather radar. See the example circled below.

Problem Radar

Enhanced absorption and scattering here cause us to lose more power. In this case, the radar site weather information becomes reduced or even totally obscured.

Go back from Radar Site Weather to the Radar Real Time Weather webpage, or visit the Stuff in the Air homepage. It's free to get monthly weather science articles.

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