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Detecting drought before the next health, water, and food catastrophe

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Detecting drought before it causes more catastrophe is big news in the science world. Food quality will suffer because of rising C)2 levels. And such an application that could allow researchers to detect drought before it causes more damage could go down like a cool drink of water for regions feeling the heat.

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Currently, University of Cincinnati researchers are at work tracking drought patterns across the United States. Qiusheng Wu, a doctoral student and research assistant for the UC Department of Geography, and Hongxing Liu, a UC professor and head of the Department of Geography, will present details this week at the annual meeting of the Association of American Geographers (AAG) in Tampa, Florida.

To trace the dynamics around agricultural drought, the University of Cincinnati researchers implemented an Event-based Spatial-Temporal Data Model (ESTDM) to detect, track and monitor conditions

The framework organizes data into objects, sequences, processes and events. The data was collected from the European Space Agency’s (ESA) Soil Moisture and Ocean Salinity (SMOS) satellite, which was the first of its kind dedicated to measure moisture near the surface of the soil. The study focused on four years of data (2010-2014), which included the devastating Texas drought in 2011 and the 2014 California drought.

The satellite uses an L-band (1.4 Ghz) passive microwave radiometer to analyze the spatial and temporal variations of soil moisture and ocean salinity. “Recent studies have shown that many historical drought events in the U.S. are closely related to La Niña, a phenomenon known for its periodic cooling of sea surface temperatures in the tropical Pacific Ocean. So in addition to measuring soil moisture for drought monitoring, it is also important to measure ocean salinity,” explains Wu, according to an April 8, 2014 news release by Dawn Fuller, "UC geographers develop a system to track the dynamics of drought." The satellite can penetrate the Earth’s surface up to 5 centimeters, providing a soil variable for each pixel, which represents 25 kilometers. The satellite’s data collection occurred over a three-day rotation.

The researchers were examining patterns of spreading drought to develop predictions for future drought events

“Soil moisture is defined as the ratio between volume of water and volume of soil holding the water, which is expressed in percentages, so high soil moisture indicates wet while low soil moisture indicates dry. By studying the soil moisture data from the satellite, we can see where the droughts begin and end, and what might indicate patterns of how it can spread over one large area. The pattern might be used to predict the drought in another location, so that those areas could take precautions to avoid the impact of an oncoming drought,” says Wu, according to an April 8, 2014 news release by Dawn Fuller, "UC geographers develop a system to track the dynamics of drought."

The Intergovernmental Panel on Climate Change (IPCC) – known as the leading international organization for the assessment of climate change – predicted in 2012 that droughts would intensify in some seasons and in many regions worldwide in the future due to reduced precipitation and/or increased evapotranspiration.

“Drought ranks among the most costly of all natural disasters. It has wide-ranging impacts on many sectors of society, affecting agriculture, economics, ecosystems services, energy, human health, recreation and water resources. By predicting the timing, severity and movement of drought events, we can provide fundamental information for planning and management in developing a response plan,” says Wu, according to the news release.

Future research will involve data gathered from a satellite that NASA is launching toward the end of the year, the Soil Moisture Active Passive (SMAP) satellite

The SMAP satellite integrates an L-band radar (1.26 GHz) and an L-band (1.41 GHz) radiometer as a single observation system combining the relative strengths of active and passive remote sensing for enhances soil moisture mapping. The combined radar-radiometer-based soil moisture product will be generated at about an intermediate 9-km resolution with three-day global revisit frequency.

Wu says, according to the news release, that the accuracy, resolution and global coverage of SMAP soil moisture and freeze/thaw measurements would be invaluable across many science and applications disciplines including hydrology, climate and carbon cycle, and the meteorological, environmental and ecology applications communities, according to the news release. If drying is predicted to spread to a third of the Earth, it's necessary to find out where the drought will be headed next so measures can be taken.

The Association of American Geographers (AAG) is a nonprofit scientific and educational society that is dedicated to the advancement of geography. The meeting will feature more than 4,500 presentations, posters, workshops and field trips by leading scholars, experts and researchers. The AAG annual meeting has been held every year since the association's founding in 1904.

Drying will spread to a third of the Earth, scientists predict, according to another recent study

The drought in Sacramento also is becoming global through the end of this century, and drought usually leads to more starvation somewhere. Increasing heat is expected to extend dry conditions to far more farmland and cities by the end of the century than changes in rainfall alone, says the new study, "Global warming and 21st century drying," published in the March 2014 issue of the journal Climate Dynamics.

Much of the concern about future drought under global warming has focused on rainfall projections. But higher evaporation rates may also play an important role as warmer temperatures wring more moisture from the soil, even in some places where rainfall is forcasted to increase, say the researchers in new research.

The study, "Global warming and 21st century drying," published in the March 2014 issue of the journal Climate Dynamics, is one of the first to use the latest climate simulations to model the effects of both changing rainfall and evaporation rates on future drought. The study estimates that 12 percent of land will be subject to drought by 2100 through rainfall changes alone. But the drying will spread to 30 percent of land if higher evaporation rates from the added energy and humidity in the atmosphere is considered. The authors also have made all their data and calculations public available on a supplementary website.

An increase in evaporative drying means that even regions expected to get more rain, including important wheat, corn and rice belts in the western United States and southeastern China, will be at risk of drought

The study excludes Antarctica. “We know from basic physics that warmer temperatures will help to dry things out,” said the study’s lead author, Benjamin Cook, according to a March 31, 2014 news release, "Warming climate may spread drying to a third of earth, says study." Cook is a climate scientist with joint appointments at Columbia University’s Lamont-Doherty Earth Observatory and the NASA Goddard Institute for Space Studies. “Even if precipitation changes in the future are uncertain, there are good reasons to be concerned about water resources.”

In its latest climate report, the International Panel on Climate Change (IPCC) warns that soil moisture is expected to decline globally and that already dry regions will be at greater risk of agricultural drought. The IPCC also predicts a strong chance of soil moisture drying in the Mediterranean, southwestern United States and southern African regions, consistent with the Climate Dynamics study.

Using two drought metric formulations, the study authors analyze projections of both rainfall and evaporative demand from the collection of climate model simulations completed for the IPCC’s 2013 climate report.

Both metrics agree that increased evaporative drying will probably tip marginally wet regions at mid-latitudes like the U.S. Great Plains and a swath of southeastern China into aridity

If precipitation were the only consideration, these great agricultural centers would not be considered at risk of drought. The researchers also say that dry zones in Central America, the Amazon and southern Africa will grow larger. In Europe, the summer aridity of Greece, Turkey, Italy and Spain is expected to extend farther north into continental Europe.

“For agriculture, the moisture balance in the soil is what really matters,” said study coauthor Jason Smerdon, according to a March 31, 2014 news release, "Warming climate may spread drying to a third of earth, says study." Smerdon is a climate scientist at Lamont-Doherty. “If rain increases slightly but temperatures also increase, drought is a potential consequence.”

Today, while bad weather periodically lowers crop yields in some places, other regions are typically able to compensate to avert food shortages. In the warmer weather of the future, however, crops in multiple regions could wither simultaneously, the authors suggest. “Food-price shocks could become far more common,” said study coauthor Richard Seager, according to the news release. Seager is a climate scientist at Lamont-Doherty. Large cities, especially in arid regions, will need to carefully manage their water supplies, he added, according to the news release.

The study builds on an emerging body of research looking at how evaporative demand influences hydroclimate. “It confirms something we’ve suspected for a long time,” said Toby Ault, in the news release. Ault is a climate scientist at Cornell University, who was not involved in the study. “Temperature alone can make drought more widespread. Studies like this give us a few new powerful tools to plan for and adapt to climate change.”

Rainfall changes do not tell the whole story, agrees University of New South Wales researcher Steven Sherwood, in a recent Perspectives piece in the leading journal Science. “Many regions will get more rain. But it appears that few will get enough to keep pace with the growing evaporative demand.”

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