Shifting rainy weather patterns make Southwest U.S. drier as the region is already experiencing prolonged droughts.
A new open-access article published in the Geophysical Research Letters journal and titled “Running Dry: The U.S. Southwest’s drift into a drier climate state” analyzes the prospects of the Southwest U.S. becoming more arid against the background of rainy weathers patterns and pressure systems shifting in the past three decades.
Lead author of the study Andreas Prein, postdoc researcher with the National Center for Atmospheric Research (NCAR) stated that a normal year in the U.S.’s Southwest regions is clearly drier than before.
“If you have a drought nowadays, it will be more severe because our base state is drier”,
The research conducted at the National Center for Atmospheric Research supports previously developed climate global models. According to these and the newly published study, shifting rainy weather patterns make Southwest U.S. drier.
Finding a ground-based correlation between model predictions and what is happening on the ground is often challenging. However, looking at meteorological data spanning the past three decades, the research team with the NCAR managed to find the missing link.
It’s undeniable that the Southwest U.S. is becoming more arid. The root cause is the increasing lack of moisture. What happened to the moisture that used to sustain lush ecosystem? During the past three decades, common rainy weather patterns supported by a certain arrangement of low pressure systems and high pressure systems have become increasingly rare.
The team found several patterns which support certain weather patterns in the U.S. Knowing the consequences of each, the team then looked at how frequent they are in the Southwest U.S. A historical perspective offered by the meteorological data spanning three decades was key to understanding frequency.
The results suggest that the weather patterns the frequency of which is decreasing in the Southwest U.S. are those bringing the much needed moisture. The Southwest region is already the driest region in the U.S. Water resources become more and more limited, while the region is facing prolonged droughts and megadroughts.
While the research doesn’t pinpoint climate change as an underlying factor for the Southwest U.S. becoming drier, it still draws attention to the need of carefully planned water management policies. The three weather patterns which are responsible for abundant moisture in the Southwest region are based on low pressure systems manifesting in the North Pacific during the winter season.
Plotting the meterological observations from 1979 to 2014, the research team found that low pressure systems vital for precipitation formed less often. As a result, the high pressure systems drove the region into a drier state. Shifting rainy weather patterns make Southwest U.S. drier, and this patterns look like they’re here to stay.