I'm a professor at U Michigan and lead a course on climate change problem solving. These articles often come from and contribute to the course.
By: Dr. Ricky Rood , 1:27 PM GMT on October 24, 2007
Drought in the South
The Atlanta Journal Constitution recently reported that Georgia was losing billions of dollars because of the continuing drought in the Southeast. The governor of Georgia has asked for federal aid, and in his remarks he talks about this being, at least in part, a man-made crisis. The man-made part is not due to climate change; it is due to water policy.
The severity of the situation highlights our stress on water resources. There are agreements about the release of water from North Georgia reservoirs to communities downstream in Alabama and Florida. Some of these releases are for the protection of endangered species - a cause that always comes under pressure when in conflict with the economy or human welfare. What I find most portending is the release of water from reservoirs to cool the rivers after the river water has been used to cool power plants. Energy production requires vast amounts of water.
What is the relation of climate change to this drought its impact? I have written previously that because of consumption and population pressure, we have already stressed our environment. In many cases, the projected climate change amplifies these stresses. What is happening in the Southeast (and the Southwest) is the type of crisis that we are likely to see more of. There is a need for water policy, efficient use of water, and anticipation of how climate change will impact water resouces.
Exactly two months ago I first wrote about this drought. There had been, at that time, sustained localized drought, especially in North Alabama. It has grown since then. In the figure, below, the drought in the Southeast and the continued wetness in Texas form an interesting couplet. Much of Texas had been in a major drought prior for the past few years.
Figure 1: Palmer Drought Index from National Climatic Data Center. ( Here’s an animation of the last few months. )
A basic requirement for climate models should be the ability to simulate the processes which maintain the moisture budgets over the continents. For the eastern United States, in the summer, the high pressure system, known as the Bermuda High, is one of the critical features. The Bermuda High is of different intensities and stubbornness from year to year. This year, the Bermuda High has pushed into the Southeast, and it has been very stable. In the center of a high pressure system there is usually the downward movement of air, and therefore, no rain. When a system like this is stuck over a region there is drought.
More generally, the summertime moisture budget of the United States, east of the Rockies, is strongly related to the Bermuda High and the Rockies. Moist streams of air move northward from the Gulf of Mexico. These rivers or air are often close to the surface. On their westward edge, they are guided by the elevation of the land and, ultimately, channeled by the Rockies. The impact of the stubborn Bermuda High steering moisture over Texas and the lower Midwest is clear in the figure. In a year where the Bermuda High is more variable, the moisture flux fans out over the southern coast of the U.S.
Often droughts in the Southeast of the U.S. are broken with a hurricane or two. This has not happened this year. The Bermuda High helped to steer the hurricanes into Central America and Mexico. There is not much chance of a hurricane breaking the drought this year – the drought is likely to continue.
Here’s a link to a couple of related blogs ...
The persistence of patterns and climate change.
Droughts, heat waves and fires.
In the past two days I have been called by CNN and ABC about whether or not the wildfires in California are part of climate change. Exactly how they decided to call me is an algorithm that I am not sure I could figure out, but I blog, so I clearly will talk about anything.
The Santa Ana winds are not being caused by climate change. They’ve been around longer than Santa Ana. It’s wind falling down a hill, which warms the air, lowers the relative humidity, and sucks up moisture from the ground. Bad stuff for fire fighters. The fact that the fires are so damaging is that they are in places where people have built in very dry and very vulnerable places. And for the most part, people seem to set the fires one way or another. It’s mostly a land-use and land-management issue.
If, if, if there is anything to do with climate change it would be that the extended drought has warmer temperatures than similar droughts in the past, and hence, drying is worse. I cited some research earlier that made such a argument in a way that has some substance. (Droughts, heat waves and fires.)
In answering the question, I did come across two recent papers. One that showed that there is an El Nino – La Nina cycle in Santa Ana winds in March. The other showed that in a global warming forecast, the frequency and the seasonality of the Santa Ana winds would change. Here are the links to those titles.
Finley and Raphael, Santa Ana winds and El Nino (Professional Geographer) or Finley and Raphael, Santa Ana winds and El Nino
Miller and Schlegel, Santa Ana winds and climate change (Geophysical Research Letters) and Miller and Schlegel, Santa Ana winds and climate change (Lawrence Berkley National Laboratory)
Figure 2: Smoke from multiple wildfires burning in Southern California, together with dust in Southern California, Baja California and mainland Mexico, swirl out into the Pacific and Gulf of California, respectively, in this false-color visible image from the Atmospheric Infrared Sounder on NASA's Aqua satellite, acquired at about 7 p.m. Eastern Time on October 22.
More pictures of the SoCal fires from NASA’s Earth Observatory
Comments will take a few seconds to appear.