Drought Explained

Drought was on the minds of millions of Midwesterners this summer.

In some areas, the lack of rain caused record-breaking dryness. Crops suffered; rivers ran low. Without proper watering, lawns turned brown and arid. Derrick Snyder

Though recent rain has spelled some worry, we are not out of the drought yet, according to Purdue University graduate student Derrick Snyder and his colleagues in the Department of Earth, Atmospheric, and Planetary Sciences.

In the Atmospheric Studies track, Snyder, a Frankfort, Ind., native, has access to the latest weather maps and models. The Midwest will need a lot of rain - and eventually snow - to put the drought behind it.

Question: How historic has this drought been?

Answer: What we went through in the early summer to the first part of August was a pretty historic bout of dryness. I would say, nationwide, it was the driest summer since 1956. Locally, some of the areasaround here were dryer than they were in the 1930s during the Dust Bowl years. Some places had the all-time record for dryness.

The impact was really apparent in the rivers and some people had their wells go dry up north of Lafayette. You can see it in the trees. A lot of trees are turning colors a lot earlier than usual.

Even though we had a lot of rain the last couple of weeks, it takes a long time. The amount of rain to end the drought in some places is a foot of rain. Obviously, you don't want it all to fall at once. It takes a long time of steady rainfall. We had that the last couple of weeks and I hope we are turning a corner and will make a recovery this fall. But it's definitely possible that next spring we'll be in some form of drought. It takes a long time to recover from a dry event like this.

Q: What caused this drought? Why did it occur?

A: What we sort of had was this really persistent ridge of high pressure. It sort of diverted the storm track to the north of us. We saw a lot of severe weather in Canada this year that would normally be closer to home. We didn't get a lot thunderstorms and really heavy rainfall events when we got severe weather season.

What happens when the soil gets really dry, it starts to heat up the lower atmosphere and creates this feedback loop. The hot soil warms the atmosphere and feeds itself into more high pressure and it creates thisdome of heat. Stable air doesn't want to form thunderstorms and keeps the main storm track away from this area.

Q: Will it be a long while until the next major drought like this summer's?

A: It's hard to say, really. It's hard to look into a crystal ball. If you're e in a pattern like the Dust Bowl years, those years' came in a bunch then you had a nice, wet, cooler summers for a long time and then you had a bunch in the mid '50s where it was dry, too. Every drought is different. Sometimes it's a flash drought like this one where you go from no drought to severe drought and then it takes a few weeks to clear up and then you're back to normal.

Q: Do you foresee a dry winter like last winter?

A: You can probably say the drought is an extension of the dryness from last year. Last year in Texas, they had a lot of rain after their drought once you got into November and December. Hopefully, fingers crossed, something like that will happen here. What we really need is a wet winter. It doesn't have to be cold. We need a lot of rain or heavy, wet snow because that moisture has to be in the soil comeplanting time next spring. I think right now they are calling for an El Nino forecast - warm and dry. The way the pattern's been, it's been so warm and dry. I think every month since last September bas been above normal in terms of temperature because of the inertia of the atmosphere.