New research that examines the role of stationary low- and high-pressure systems projects that global warming will spawn more extreme wet and dry weather around the world.
Those extremes include more frequent dry spells in the northwestern, central, and southern United States and in Mexico, and more frequent heavy rainfall events in south Asia, the Indochinese Peninsula, and southern China.
One reason: subtropical stationary waves in northern summers. These planet-spanning waves are composed of persistent high-pressure systems over the North Pacific and North Atlantic and persistent low-pressure systems over Eurasia and North America, the study says. The high-pressure systems provide persistent conditions for dry weather, while the low-pressure systems fuel wet weather.
The intensity of subtropical stationary waves during northern summers increased from 1979 to 2013, and projections suggest the increase will accelerate as the climate warms, the study says.
“Increasingly strong subtropical stationary waves play an important role in explaining the increase in extremely dry weather in North America and extremely wet weather in south and southeast Asia,” says lead author Jiacan Yuan, a postdoctoral associate in the earth and planetary sciences department at Rutgers University–New Brunswick and the university’s Institute of Earth, Ocean, and Atmospheric Sciences.
Subtropical stationary waves may serve as an important link connecting regional droughts and extreme rainfall events with global warming, the study says. Such extremes, which have increased significantly in recent decades because of a warming climate, can cause enormous economic losses and threaten lives.
Examples of extreme events include catastrophic floods in South Asia during the 2017 monsoon season, which killed about 1,300 people died and affected more than 45 million people, according to a United Nations Children’s Fund report. A severe drought afflicted Texas in 2011, with the Texas AgriLife Extension Service estimating direct agricultural losses at $5.2 billion.
The findings appear in the Journal of Climate.
Scientists from Duke University and Georgia Institute of Technology also contributed to the study.
Source: Rutgers University