Droughts and water can’t be on the same sentence, or at least that’s what we think. When we imagine a drought, we usually think about dry, hot, dusty and cracked land or dried lakes, streams or rivers due to the lack of water or less precipitation.
But recent studies suggest that droughts can now start over oceans and the bad news is, they can be a lot worse than those that start over land.
According to a September 21 study published in the journal Water Resources Research, 1 in 6 of all the droughts that affected land areas around the world from 1981 to 2018 actually started over water and moved onto land, and they did so at a high frequency along the West Coast of North America.
Stanford climate researcher and senior study author Noah Diffenbaugh and his colleague environmental engineer Julio Herrera Estrada discovered this phenomenon by following areas of low atmospheric moisture around the world, from both land and sea, through meteorological records.
Lead author Herrera said: “We normally don’t think about droughts over the ocean—it may even sound counterintuitive. But just as over land, there can be times where large regions in the ocean experience less rainfall than normal.”
Here, they were able to observe how low-moisture air masses formed, changed shape and moved over the seas sometimes taking half a year before they hit land and destroy crops.
Since this phenomenon moves at a much slower pace, both researchers said that it would allow forecasters to predict this new type of drought that could have huge impacts in vulnerable regions like the western United States.
Diffenbaugh explained: “Because they usually take a number of months to migrate onto land, there is a potential that tracking moisture deficits over the ocean could provide advance warning to help protect against at least some of the most severe droughts.” Herrera added that this discovery could hopefully open more “conversations about the benefits of monitoring and forecasting droughts beyond the continents.”
Although not as widely discussed, the United Nations Food and Agriculture Organisation reveals that droughts have actually affected more of the world’s population than earthquakes, tsunamis and other natural disasters over the last 40 years.
These disasters have killed and displaced millions and experts believe that land falling droughts are a lot more severe than conventional ones since they can be one third drier, grow four times faster and spread five times larger.
The study pointed out North America, eastern South America, eastern Asia and southwestern Africa as the hotspots for landfalling droughts that originate over oceans.
Although experts admit that forecasting can still be a challenge, Chris Funk who created drought early-warning systems for African countries is excited about this new discovery: “I’m a big fan of this work—it’s really exciting. One of the things that’s appealing about this work is that the data are already there. There’s an incredible array of satellite observations. Landfalling droughts give us a new pattern to look for. We’re going to need that because climate change is making droughts more severe.”