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El Nino and Rainfall

El Nino and Rainfall

At the end of 2006, East Africa was bombarded with unusually heavy rainfall. Floods swept across the region, affecting up to 1.5 million people in Somalia, Ethiopia, Kenya, and parts of surrounding countries. At the same time, Indonesia and Australia fought back widespread fires, fueled in part by unusually dry conditions. What’s up with the weather? Part of it may be that El Niño was back, and the Eastern Hemisphere was probably feeling the impact in November and December 2006.

This image shows rainfall anomalies (difference from normal) over the South Pacific and Indian Oceans that may be related to El Niño. The image was made by comparing rainfall totals in November 2006 to the average November rainfall between 1999 and 2005. The data come in part from measurements taken by the Tropical Rainfall Measuring Mission (TRMM) satellite. Areas of dark brown over Indonesia and Southeast Asia show that these regions received much less rain than normal during November 2006, while blue over East Africa reveals higher-than-average rainfall totals. Australia is light brown, indicating shortages of a few millimeters per day. Though the country was in extreme drought at the time, the deviation from normal rainfall levels doesn’t appear exceptionally large, probably because November is already a dry month in Australia.

The rainfall patterns illustrated in this image are typical during an El Niño event. El Niño happens when trade winds weaken, and the eastern Pacific Ocean heats up. These changes in the atmosphere and the ocean set off a string of unusual weather patterns around the globe, including drought in Australia, Southeast Asia, and Indonesia, and high rainfall in East Africa and parts of North and South America. El Niño also suppresses hurricanes in the Atlantic Ocean and increases the number of typhoons that form in the Pacific.

NASA image created by Jesse Allen, Earth Observatory, using rainfall data provided courtesy of the Global Precipitation Climatology Product team at NASA Goddard Space Flight Center.

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