Weather radars bounce microwave energy off things in the air. They are designed to detect meteorological phenomena like rain, hail, and snow. But they also bounce signals off aircraft, birds, ski lifts, and more1.
Usually, meteorologists aim to filter out signals unrelated to weather to focus on those that can be used for forecasts. Smart algorithms help remove as much extraneous data as possible. For instance, one method involves filtering out stationary signals assuming they are ground-based. However, it's not always that easy. Radar signals are affected by numerous environmental variables. A signal sent from the same transmitter, at the same wavelength and energy level, and bouncing off the same structure can appear differently over time due to atmospheric changes, transient obstacles, the swaying of structures, and other factors. It can get very complex. The AMS hosts entire research conferences dedicated to the sole topic of radar meteorology.
But one person’s noise is another person’s signal. These non-meteorological signals can be valuable data to people interested in those objects not related to weather. In the United States, the meteorological radar system (NEXRAD) is funded by the U.S. government. So all of its data is publicly available through various platforms, including:
NOAA's National Centers for Environmental Information (NCEI) - NCEI archives and provides access to historical radar data.
The Radar Operations Center (ROC) - ROC offers access to near-real-time radar data and products.
Integrated Dissemination Program (IDP) - This includes the NOAA Weather and Climate Operational Supercomputing System, which distributes real-time radar data.
These sources cater to both the general public and specialized users such as researchers and meteorologists, providing tools and resources for accessing and analyzing radar data for weather monitoring and research purposes.
Birds on Radar
The Cornell Lab of Ornithology operates one of the most successful citizen science projects in history. Working with scientists at Colorado State University and the University of Massachusetts, Amherst, they developed BirdCast - a system to predict the migration of birds in North America.
Meteorological radars provide core data behind their predictions (I hope I didn’t bury the lede too far). While birds have been tracked by radar for quite some time, a recent upgrade to the NEXRAD radar system made it easier to distinguish birds from other flying creatures, such as insect swarms.
The upgrade is called “dual polarization” (a.k.a. dual-pol). Dual-pol signals give information on both the vertical and horizontal sizes of the reflected objects, allowing scientists to get a sense of the shape and size of what they are seeing on the radar.
Dual-pol was designed to allow meteorologists to better identify the type of precipitation they were seeing on the radar, especially in regards to differentiation between liquid and frozen precipitation. Among other advances, this upgrade has greatly increased the accuracy of forecasts for hail in thunderstorms and the rain/snow line in winter weather.
The new radar data came along at the right time. As computing power increased, BirdCast scientists finally had both the data and the computing horsepower they needed to analyze it quickly enough to make near-live forecasts. The results are insanely beautiful and interesting forecasts for bird migrations across North America, published every six hours. This recently published article describes how their system works.
There are all sorts of scientific and ecological uses of this data. Not least of which are programs to coordinate the dimming of skyscraper lights when migrations are expected to pass by a particular city. You’d think it’d be the other way around - bright lights would warn the birds to stay away. But it doesn’t work that way. They are attracted to the doom of bright lights the same way we are attracted to the bright lights of fame.
The Mark I Eyeball
One of the first things my statistical mentor taught me was that all data analysis begins and ends with the human eye. He advocated looking at the data visually when possible and thinking about what it means in a common sensical manner2.
In addition to radar data, BirdCast also needs data from your eyes. They use citizen scientist birders to “ground truth” what they see on the radar. This allows them to confirm what they detect and improve the system. Ultimately, they want to better distinguish between bird species. You can help out by adding your eyeballs to their eBird project.
Thank you to Bryan Pfeiffer of the Chasing Nature newsletter for introducing us to the concept of radar ornithology.
We acknowledge additional scientific contributions from Dr. Swarndeep Gill.
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Sometimes things on the ground like buildings, mountains, trains, and very large egos can also get in the way.
Amateur astronomers often refer to the human eye as the “Mark I Eyeball”. It’s been a lighthearted point of contention between them and professional astronomers lately. The latter often have little to no experience looking through telescopes with their eyes, as professional astronomy has become completely digitized. So it’s an area where amateurs can show some professional pride of their own.