Amazon rainfall linked to Atlantic Ocean temperature

Amazon rainfall linked to Atlantic Ocean temperature
mongabay.com
February 25, 2008

Climate models increasingly forecast a dire future for the Amazon rainforest. These projections are partly based on recent research that has linked drought in the Amazon to sea surface temperatures in the tropical Atlantic. As the tropical Atlantic warms, the southern Amazon — the agricultural heartland of Brazil — may see higher temperatures and less rainfall.

Still the relationship between sea temperatures and precipitation is poorly understood, introducing uncertainty for models seeking to forecast future climate in the region. Now a new study, published in Philosophical Transactions of the Royal Society B by Peter Good and colleagues from the Met Office Hadley Center, attempts to devise a method for measuring how sea surface temperature gradients in the tropical Atlantic affect precipitation in the Amazon.

Using an atmospheric general circulation model (AGCM) based on observed sea surface temperatures from 1949 to 2005, Good and colleagues found that better simulations of the north-south sea surface temperature gradient would improve the accuracy of climate models for the Amazon.

"Current climate models show a large spread of projections for rainfall change over Amazonia. North-south gradients in tropical Atlantic sea-surface temperature (SST) can affect southern Amazon dry season rainfall by modifying the moisture transport into the region and the stability to convection," Good told mongabay.com. "We study how best to measure this SST gradient, to explain present-day rainfall variability. Then we show that the large model differences in future projections for dry-season rainfall in this region are largely associated with model differences in this gradient measure."

Peter Good et al (2008). An objective tropical Atlantic sea surface temperature gradient index for studies of south Amazon dry-season climate variability and change [FREE OPEN ACCESS]. Phil. Trans. R. Soc. B, DOI: 10.1098/rstb.2007.0026

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