Friday, November 30, 2012

Flash Drought ~ Jeffrey Basara

Figure - Extended periods of drought can lead to other hazards including wild fires.

Photos and images provided by Dr. Jeffrey Basara.

The U.S. heat wave of June 2012 saw 2,284 record-breaking temperatures. In October, the New York Times reported that the worst drought in 50 years is currently gripping the Corn Belt from Nebraska to Illinois, driving up food prices. Texas wildfires ravage that state in 2011 and 2012. Oklahoma is presently experiencing exceptional drought.

How do these events compare to the climatic events of the Dust Bowl during the Great Depression years when a heat wave gripped the country in 1936 and impacted Texas, Oklahoma, Kansas, Arkansas, Missouri, Iowa, Colorado, and New Mexico causing crops to fail?

This and other questions are of interest to hydrologist/ hydrometeorologist Jeffrey Basara, Director of Research for the Oklahoma Climatological Survey and Associate Professor in the School of Meteorology at the University of Oklahoma. In his work, Dr. Basara looks at real time data for the Great Plains and Oklahoma, in particular. While meteorologists primarily look at atmospheric conditions, hydrologists examine the complex interactions of water between the surface and the atmosphere and how the processes relate to weather and climate.

SHAN: What attracted you to the field of hydrology?

JEFF: It was not my first choice. My education was in meteorology. When I was a graduate student working for Ken Crawford, Director of the Oklahoma Climatalogical Survey, we were installing soil moisture sensors into the Oklahoma Mesonetwork. I was asked to attend an American Meteorological Society Hydrology Conference in Long Beach, California in 1997, and it seemed as if the entire symposium was focused on how soil moisture effects climate. Everything was about modeling. Every presentation.  They didn’t have a way to validate the results, which we did because of our network of sensing stations.

It was then that I realized how fortunate I was to have this opportunity to work in hydrology. Ken Crawford was my Master and Ph.D. advisor and he said to me, “You will be an expert in your field.” He was right. He has a legacy of providing opportunities to young researchers that turn into great careers.

Flux Tower Figure - Instrumentation deployed near Marena, Oklahoma, used to collect observations of soil, vegetation, and atmospheric conditions valuable in land-atmosphere interactions and drought research.

SHAN: How have deliberate man-made changes improved weather and climate in some regions – as for example, the building of man-made lakes?

JEFF: There is little doubt that a reservoir can effect soil moisture and weather. However, there are other examples. The winter wheat belt in Oklahoma creates a mesoscale atmospheric phenomena. It effects moisture content in the boundary layer and actually makes the weather cooler and more moist during the spring. One of my favorite thunderstorm/atmospheric events occurs along the wheat belt. We actually know squall lines form in the winter wheat belt area, which then impacts precipitation for the whole region.

There are other examples that have the opposite effect. The urban area of Oklahoma City shows a man-made heat element – an urban heat island. It is hotter and dryer than the surrounding areas. This doesn’t just effect the urban area itself, but also produces a warmer, dryer impact downstream.

We are using the Mesonetwork for studying land-atmosphere interactions, feedback mechanisms that can impact moisture above and below ground. These measurements from the Mesonetwork are not only important for understanding the real-time weather, but also showing climate impacts. When you think about hydrological events – none are more devastating than drought and now we have data like never before.

One topic we are now studying is called “flash drought,” the rapid onset of drought in certain areas. In 2005-2006, and then again in 2010-2011, it was dry in the spring, summer and through the winter - over three seasons. But there are times when drought occurs in a very rapid way, in a matter of weeks, and that is called flash drought.

Marena Figure July 1, 2012 - Vegetation conditions at the Marena, Oklahoma, research site.

In 2011, we came out of that drought with a very wet fall and winter season that took us completely out of the exceptional drought category. In fact, most of Oklahoma was removed from drought classification of any kind. But then we had a warm spring with limited rain and within 45-60 days during the summer, we were in exceptional drought again. What had taken months before – we experienced in 6-8 weeks.

Marena Figure August 17, 2012 - Vegetation conditions at the Marena, Oklahoma, research site following the rapid development of flash drought in the region.

Using the network sensors, we were able to see in May that a flash drought might be occurring. Monitoring the weather and soil moisture, the soil moisture was telling an interesting story. We had real time data information, where as in the past it was nearly impossible to predict. We were able to alert people that needed to know, like farmers and producers.


SHAN: What are the present areas of your greatest concern and focus with regards to weather and climate?

JEFF: The biggest concern is drought and its impacts. The Southern Great Plains, which is comprised of Nebraska, Kansas, Oklahoma, and Texas, is an area of drought concern. The precipitation is never normal. It’s more like a pendulum that swings back and forth between periods of drought and above normal precipitation (pluvials). There are reasons for this – storm tracks, ocean currents, and land-atmosphere patterns – that develop and persist.

In this region there are also large urban areas with a growing population base – Oklahoma City, Dallas, Austin and San Antonio. How is that population going to deal with the increasing challenges of water resources? When we get into periods of drought there are socio-economic impacts that are a big concern.

I recently flew into Dallas and had the opportunity to see that the reservoirs are not at capacity. Water resources are becoming stressed due to human demand and natural drought. Another issue is the overall water budget. What changes have we seen? Evaporation, transpiration, storage changes of water have occurred. The Ogallala Aquifer (an underground water reservoir that spreads from Texas to Nebraska) is being depleted. It has been treated like a fossil resource, like oil, with no regulation for drilling and pumping. By some estimates, it is at 20% of its original capacity. Lakes that once existed have completely vanished in the region.

There is another reserve of water, the Arbuckle/Simpson reservoir, that has strong regulatory controls. It’s being used with a more conservatory fashion. But places, like Dallas and other populated areas, would like to get their hands on this water.

Figure - Land-atmosphere interactions played an important role in the redevelopment of Tropical Storm Erin over central Oklahoma and excessive rainfall during August 2007.

SHAN: What are some of the socio-economic benefits that come from improved hydrological models?

JEFF: Mark Twain once said, “Whiskey is for drinking and water is for fighting.”

Water is becoming a contentious issue. Better models, including soil moisture, are going to be critical in helping us address all the needs of the region. The Oklahoma Mesonetwork is providing a half million observations per day real time and an archive of approximately 5 billion. That is a lot of data. Along with models, this gives us a much better handle on water resources and how to address what we’re seeing now in the Southern Great Plains.

Figure - Water is a critical resource to the Southern Great Plains of the United States.

For more information contact the Oklahoma Climatological Survey:

Shän Boggs worked with Dr. Kenneth Crawford and others during the early development of the Oklahoma Mesonetwork. She is a writer and editor, and now lives in Los Angeles. Her interests include science, technology, the environment, health, multimedia, and art.