October 6, 2012
Ocean-Based High-Pressure Systems To Strengthen, Say Researchers
redOrbit Staff & Wire Reports - Your Universe Online
The subtropical highs, or the high-pressure systems over oceans which influence atmospheric circulation and global climate, are expected to become more intense over the next century, according to a new study published online this week in the journal Nature Geoscience.The study, which was led by Duke University assistant professor of earth and ocean sciences Wenhong Li, found that these high-pressure systems, which "largely determine the tracks of tropical cyclones and hydrological extremes in much of the northern hemisphere," could strengthen during the summer over the northern Pacific and Atlantic Oceans, the North Carolina-based school said in a statement.
As a result, these systems "could play an increasingly important role in shaping regional climate, particularly the occurrence of drought and extreme summer rainfall, in coming years," the researchers discovered. That conclusion comes following an analysis of climate model simulations, which Li and colleagues from Columbia University and the Chinese Academy of Sciences used to predict future changes in their strength.
"According to the simulations, these high-pressure systems will intensify over the 21st century as a result of increasing greenhouse-gas concentrations," the university explained. "The simulations suggest that an increase in the land-sea thermal contrast — the difference between ocean and land heating, as Earth´s climate warms -- will fuel the systems´ intensification."
Li's team used climate model simulations from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report, as well as four decades worth of atmospheric circulation records for the months of June, July, and August, which was obtained from the European Centre for Medium-Range Weather Forecasts (ECMWF).
"The simulations suggest that these summertime highs will intensify in the twenty-first century as a result of an increase in atmospheric greenhouse-gas concentrations," Li and his co-authors wrote in the abstract of their study. "We further show that the intensification of subtropical highs is predominantly caused by an increase in thermal contrast between the land and ocean. We suggest that summertime near-surface subtropical highs could play an increasingly important role in regional climate and hydrological extremes in the future."