WEDNESDAY: Measuring Hail by Using Radar . . . and Satellites!

Satellites detect hail by what is called "Passive Microwave Detection". Unlike radars, their instruments are detecting microwaves that scatter from ice particles, which differs from the way they scatter from liquid water.  At certain frequencies, the amount of scattering can help scientists estimate the size of the hailstones. See how NASA is using CoCoRaHS hail reports to conduct research on how hail melts as it falls.

Polarimetric (or "dual-pol") radars can detect the presence of hail more accurately than conventional NEXRAD radar. To do this, polarimetric radars transmit and receive horizontal and vertical radio waves - resulting in a ratio that helps relay the overall shape of the object. When falling, raindrops are shaped like tiny "hamburger buns", while hailstones are larger and much rounder.

In both cases, scientists often don't get to see what landed on the ground - which is where CoCoRaHS hail photos come in!  See below for an example of how all three - satellite, radar, and ground - can be compared and studied.

Tomorrow you can learn more about research projects (NSF and NASA) that are partnering with CoCoRaHS!