New radar method makes weather forecasts right as rain

New method makes weather forecasts right as rain

MU researchers harness modern radar capabilities to account for evaporation, create more accurate rain forecasts

COLUMBIA, Mo. – Meteorologists have known for some time that rainfall forecasts have flaws, as failure to take into account factors such as evaporation can affect their accuracy. Now, researchers from the University of Missouri have developed a system that improves the precision of forecasts by accounting for evaporation in rainfall estimates, particularly for locations 30 miles or more from the nearest National Weather Service radar.

“Right now, forecasts are generally not accounting for what happens to a raindrop after it is picked up by radar,” said Neil Fox, associate professor of atmospheric science in the School of Natural Resources at MU. “Evaporation has a substantial impact on the amount of rainfall that actually reaches the ground. By measuring that impact, we can produce more accurate forecasts that give farmers, agriculture specialists and the public the information they need.”

Mizzou Makes Rainfall Forecasts More Accurate from MU News Bureau on Vimeo.

Fox and doctoral student Quinn Pallardy used dual-polarization radar, which sends out two radar beams polarized horizontally and vertically, to differentiate between the sizes of raindrops. The size of a raindrop affects both its evaporation rate and its motion, with smaller raindrops evaporating more quickly but encountering less air resistance. By combining this information with a model that assessed the humidity of the atmosphere, the researchers were able to develop a tracing method that followed raindrops from the point when they were observed by the radar to when they hit the ground, precisely determining how much evaporation would occur for any given raindrop.

Researchers found that this method significantly improved the accuracy of rainfall estimates, especially in locations at least 30 miles from the nearest National Weather Service radar. Radar beams rise higher into the atmosphere as they travel, and as a result, radar that does not account for evaporation becomes less accurate at greater distances because it observes raindrops that have not yet evaporated.

“Many of the areas that are further from the radar have a lot of agriculture,” Fox said. “Farmers depend on rainfall estimates to help them manage their crops, so the more accurate we can make forecasts, the more those forecasts can benefit the people who rely on them.”

Fox said more accurate rainfall estimates also contribute to better weather forecasts in general, as rainfall can affect storm behavior, air quality and a variety of other weather factors.

The study, “Accounting for rainfall evaporation using dual-polarization radar and mesoscale model data,” was published in the Journal of Hydrology. Funding was provide by the National Science Foundation (Award Numbers IIA-1355406 and AGS-1258358). The content is solely the responsibility of the authors and does not necessarily represent the official views of the funding agency. The School of Natural Resources is located in the College of Agriculture, Food and Natural Resources.

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June 12, 2018 12:16 pm

A Real-Time Evaporation Correction Scheme for Radar-Derived Mosaicked Precipitation Estimations
Runs operationally at NCEP

Tom in Florida
June 12, 2018 12:34 pm

It would seem to me that this is only effective when it is already raining or about to rain nearby. No way they can forecast that out a day or two.

June 12, 2018 12:36 pm

Who knows what advances might have been made but for the trillions squandered on worse than worthless “climate change research” and “renewable energy”?

Not to mention deficits and debt reduced.

June 12, 2018 1:25 pm

Might work in the USA, but here in Australia ,the Bureau of Meteorology will still probably continue to fudge the figures as they have done for years.

Robert of Texas
June 12, 2018 1:26 pm

If I am a farmer, and I want to know how much rain I get, I’ll buy a rain gauge… I don’t NEED to know how much rain I might get in the next hour, I need to know how much I GOT after it rained. These people really need to leave the computer lab and look up…the sky is beautiful.

Reply to  Robert of Texas
June 12, 2018 4:29 pm

Robert, a rain gauge would certainly work on a small farm. However for larger farms it would be nice to know how much rain each area of my farm got or is getting. I live in Florida. It can be rain across the street and not it my yard. I am the first generation in my family’s history that didn’t farm. I have walked fields in the SE while it was raining where areas were getting soaked and muddy and other area barely damp. Modern farmer can and do use all the data they can get. GPS alone has saved them millions in fertilizer and pesticide applications.

June 12, 2018 1:37 pm

It’s good to know MU still has staff to do something. Their $1.3 M PR image recovery effort is still a work in progress.

June 12, 2018 2:16 pm

How did this get published? I didn’t see anything about climate change. Did I overlook it.

June 12, 2018 2:48 pm

‘Fox and doctoral student Quinn Pallardy used dual-polarization radar’

Alarm! Credential escalation. Pallardy is a graduate student. It is inappropriate to use doctor with his name until he has actually earned it.

June 12, 2018 3:22 pm

Some pilots I know call the rain we can see falling in the distance that never hits the ground here in the high desert, filigree. Like the post above notes, not much use that I can see in this “forecasting”. You either get the rain or you don’t and the rain guage is the best tool if you’re farming or gardening.

Steve R
Reply to  JimG1
June 12, 2018 3:58 pm

We used to call that Virga.

Linda E
June 12, 2018 4:02 pm

How about using the rain data that is already available, e.g., COCORaHS reports

Dr. S. Jeevananda Reddy
June 12, 2018 4:34 pm

When I was working in Africa/Mozambique, I was asked by FAO HQ to calibrate radar based rainfall estimates. I found the low rainfall spells presented closer to ground observations over a network of stations. As the rainfall intensity [amount] increased the deviations are non-linearly higher.

Dr. S. Jeevananda Reddy

Dr. S. Jeevananda Reddy
Reply to  Dr. S. Jeevananda Reddy
June 12, 2018 4:59 pm

Rainfall collected in a raingauge is also affected by evaporation.

Dr. S. Jeevananda Reddy

David Dibbell
June 12, 2018 6:04 pm

The concept that raindrops partly or even completely evaporate on the way down is one reason why the climate models are so pointless and wrong. The atmosphere works much better than the models to move just enough heat upward. The models have no ability to numerically simulate obviously important processes like this.

Jeff Alberts
June 12, 2018 6:35 pm

I thought the science was settled.

June 13, 2018 3:50 am

Radar relies on its own transmissions rather than light from the Sun or the Moon, or from electromagnetic waves emitted by the objects themselves, such as infrared wavelengths (heat). This process of directing artificial radio waves towards objects is called illumination, although radio waves are invisible to the human eye or optical cameras.”

Inside of those golf ball looking towers is a parabolic dish, like the one that they used for this wireless power transmission back in 1974 . The power beam pointed skywards creates a dipole moment in the water molecule .
” The water molecule in Figure 1.1 can be used to determine the direction and magnitude of the dipole moment. From the electronegativities of oxygen and hydrogen, the difference is 1.2e for each of the hydrogen-oxygen bonds. Next, because the oxygen is the more electronegative atom, it exerts a greater pull on the shared electrons; ”

Tom Andersen
June 14, 2018 3:05 pm

Wind turbines are unfortunately greatly harming weather radar in many areas of the world. Read and . Then again wind turbines also waste money and interfere with aviation.

June 17, 2018 6:10 pm

I think this is pretty good gee-whiz science. I have often wondered if the radar-reported rainfall amounts had any basis in reality, and had some clues they didn’t. So here we see attempts to make it better. Now what this has to do with “forecasting” I couldn’t tell you. I see nothing in the report explaining how this technique improves a forecast, though it does look like it may have some value improving weather recording. “sarc” Oh that’s right, model forecasts are data, so I guess data can be forecasts. “/sarc”

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