Research finds Caribbean islands particularly susceptible to flash droughts

The word “drought” typically conjures up images of parched soils, dust-swept grasslands, depleted reservoirs, and dry creek beds, all resulting from weeks or seasons of persistent, dry atmospheric conditions.

In the sunny Caribbean islands, however, drought conditions can occur much more quickly, with warning signs appearing too late for mediation strategies to limit agricultural losses or prevent strain on infrastructure systems which provide drinking water to communities.

Such phenomena, known as flash droughts, are the subject of a new paper authored by Assistant Professor Craig Ramseyer of the College of Natural Resources and Environment and published in the Journal of Hydrometeorology. The paper’s conclusion is that the Caribbean islands are particularly susceptible to flash droughts, and Ramseyer advocates alternative methodologies to more accurately measure drought conditions in the region.

“The tropics have extremely intense solar radiation, so atmospheric processes tend to accelerate,” said Ramseyer, who teaches in the Department of Geography. “Although they often receive daily precipitation, island ecosystems are particularly vulnerable to drought conditions. »

Ramseyer, whose research focuses on tropical precipitation and extreme weather impacts in the Caribbean, used a new drought index that takes into account atmospheric demand for moisture to identify drought risk conditions instead of more traditional measures of soil moisture.

“This new drought index is really being developed to try to identify the primary trigger for drought by focusing on evaporative demand,” said Ramseyer, who collaborated on the paper with Paul Miller, an assistant professor at the Louisiana State University. “Evaporative demand measures how thirsty the atmosphere is and how much moisture it can collect from soil or plant matter.”

Ramseyer emphasized that early identification of drying conditions is a key step in limiting the impacts of droughts.

“A lot of drought observations are based on soil moisture, but in tropical environments a drop in soil moisture is a response to other events that have already occurred, so you further down the chain of events,” he said. “We can mitigate many losses, for example in the agricultural sector, by being able to predict sudden and abnormal increases in evaporative demand.”

The impacts of drought conditions extend beyond agriculture: tropical ecosystems are also greatly affected by dry atmospheric conditions, and access to fresh water is a necessity both for communities in the region and for a tourism industry that is a central driver of Caribbean economies.

A new position for atmospheric research

To better understand the impact of this interaction of weather patterns on drought conditions, Ramseyer used 40 years of data from a long-term ecological research project in the El Yunque National Forest. He found that flash droughts occurred regularly in the Caribbean and that drought events were not limited to the island’s traditional dry seasons.

“In terms of climate, Puerto Rico is located at a crossroads, buffered to the west by the El Niño Southern Oscillation and the colder North Atlantic Oscillation to the east,” Ramseyer said. “For this reason, Puerto Rico has a unique geography for atmospheric change research.”

Looming concerns over global warming have only accelerated the need for meteorologists to better understand drought patterns in the Caribbean and improve monitoring of moisture conditions in the region.

“A warming planet leads to an overall increase in available moisture in the atmosphere, which means that short-term types of precipitation, common in the Caribbean, will increase in intensity,” Ramseyer said. “Meanwhile, droughts are becoming more severe, so climate change is altering both extremes. »

Ramseyer, who helped Virginia Tech become a member of the University Corporation for Atmospheric Research this year, said developing clearer criteria for flash drought conditions is an important first step toward solving infrastructure problems that Caribbean communities are likely to face.

“The main problem now and in the future for the Caribbean is finding a way to successfully capture precipitation and release it slowly to mitigate evaporation losses,” Ramseyer said. “Puerto Rico and the entire Caribbean face water infrastructure challenges that must be addressed to adapt to these trends.”

Geography Department Chairman Tom Crawford said Ramseyer’s paper reflects a use of big data to address climate and weather challenges.

“Dr. Ramseyer’s research applies advanced computing and geospatial science to make significant contributions to the problem of flash droughts and precipitation variability in general,” Crawford said. “In addition to its impact on research, its course on climate data analysis and programming trains the next generation of researchers in cutting-edge computational techniques applied to climate change.”

Ramseyer calls for additional research to understand the relationship between sudden drought events and economic losses and how future drought events can be better communicated to stakeholders and communities.