document: Some of this year 's drought in the Midwest may have been caused by ocean temperature abnormalities near the equator in the Pacific Ocean , according to a new computer study reported Thursday . Such droughts could be anticipated if the temperature abnormalities turn out to be predictable , one of the authors said in the report appearing in Friday 's issue of Science magazine . The authors are Kevin E. Trenberth and Grant W. Branstator of the National Center for Atmospheric Research in Boulder , Colo. , and Phillip A. Arkin of the Climate Analysis Center of the National Oceanic and Atmospheric Administration in Camp Springs , Md. . They noted that when asked what caused the drought that hit much of North America in 1988 , meteorologists often reply `` the jet stream was displaced northward of its usual position so that storms , which tend to track along the path of the jet stream , were similarly displaced northward . '' `` Such an answer is , however , just a brief description of the weather patterns associated with the drought but does not get at the cause . A more satisfying response would address why the jet stream was displaced northward , '' the team wrote . Their proposed answer focuses on the development in April , May and June of drought in the Midwest , where several states recorded less rain than at any time since 1895 . By July the weather pattern they studied was breaking up , and continuing dryness in the study area and elsewhere probably had other causes , Arkin said . But during the April-June period there were alternating high and low pressure centers across much of the northern half of the Western Hemisphere : A high-pressure center north of Hawaii , a low in the Gulf of Alaska , a high in central Canada extending down into the northern Great Plains states and a low on the East Coast . In this period , Pacific Ocean temperatures ranged up to 5.4 degrees Fahrenheit below normal in a narrow band extending about 4,000 miles along the equator westward from the coast of South America , with the coolest spot midway along the band . At the same time , a bit to the north of this band , surface temperatures ranged up to 0.9 degrees above normal . When this temperature pattern was fed into the computer , the pattern of stationary alternating high and low pressure systems was reproduced . The below-normal equatorial temperature by itself did not give such a result . `` We have n't proved anything ; all we 've done is shown that it 's a possibility , '' Arkin said . The global atmosphere is so complicated that repeated running of a more detailed computer model would be needed to show that these abnormal temperatures are likely to be associated with drought , he said . If the model holds up , the work will be the first demonstration of tropical sea surface temperatures affecting weather outside the tropics in the summer , Arkin said . The authors took note of computer models predicting increased frequency of drought with the buildup of the `` greenhouse effect '' global warming caused by accumulation of gases like carbon dioxide in the atmosphere . `` The greenhouse effect may tilt the balance such that conditions for droughts and heat waves are more likely , but it can not be blamed for an individual drought , '' they said .
extractive_keyphrases: droughts midwest ocean temperature abnormalities atmospheric research weather patterns pacific ocean temperatures new computer study temperature abnormalities