American farmers haven’t needed a satellite this summer to tell them we’re in a drought. The worst dry spell in more than 20 years has had a devastating impact on U.S. crop production.
What’s amazing is that you can see the dryness below ground— from space. NASA’s GRACE mission, which uses two satellites to measure the tug of gravity with unprecedented detail, is sensitive enough to tell when stored groundwater has dried up, based on changes in the total mass of the land over which it orbits.
See the time-lapse map below, then read this fascinating article from NASA’s Earth Observatory. Ten years ago, when GRACE was launched, some hydrologists didn’t think it was possible to measure groundwater from orbit.