World Grain - July 2012 - 64

FEATURE

impacting crops
D
rought has evolved this year in important crop-producing regions such as the U.S. Midwest, China and portions of south-central Russia. Changing weather patterns from July through September suggest many of today’s drought-stricken areas will be relieved while new droughts form in Australia, Indonesia, Malaysia and South Africa. For the past few months the earth’s atmosphere has been trying to slip back into a more normal mode after two years of inﬂuence from La Niña. La Niña events tend to remove moisture from the atmosphere, and the longer they last the more weather patterns trend drier and sometimes temperatures become more extreme. That is exactly what has occurred in recent months. The winter season was plagued with temperature extremes. Most of northern North America and the arctic experienced a record period of warm weather while many areas in Europe and Asia experienced bitter cold conditions. In addition to the temperature extremes, many areas reported much less than usual precipitation and these symptoms are strongly associated with the persistent La Niña event. La Niña, by deﬁnition is the result of colder than usual ocean surface temperatures in the Paciﬁc Ocean between the International Dateline and the coast of South America — mostly near the equator. These cooler ocean temperatures result in less water vapor getting into the atmosphere as a result of slower evaporation rates (a direct byproduct of the cool ocean water). The most recent La Niña event lasted for two years, and over that period of time much less water vapor was released to the atmosphere and over time the air turned drier. Drier air will heat and cool more efﬁciently, and because of La Niña many areas around the world did experience unusual dryness and signiﬁcant temperature anomalies. Once the spring growing season arrived this year, dryness
64

by Drew Lerner

U.S. Midwest, China and parts of Russia dealing with drought
emerged very quickly across the European Continent and late winter and spring were notably cool, as well. A little later in spring, dryness also showed up again in south-central Russia and a part of Ukraine. In more recent weeks, Europe’s dryness abated, but a new region of signiﬁcant dryness emerged in both China and the United States. La Niña passed away three months ago, but the lingering effects of the phenomenon have been slow to abate. Dryness issues have festered signiﬁcantly in the eastern part of the U.S. Midwest, lower Mississippi River Valley and southeastern states over the past few months, and the situation has more recently been accompanied by warm to hot temperatures further exacerbating the situation. Dryness and heat have now prevailed too long and summer crop production is slipping lower as each day goes by. Much of the U.S. corn crop will reproduce during the peak of this heat and dryness resulting in some production loss. In the meantime, similar conditions have occurred in southcentral Russia, a part of Ukraine and China. Each of these areas has potential to get some relief in July and August as the atmosphere continues to evolve away from La Niña. Forecasters are predicting an El Niño event will evolve over the next few weeks. El Niño is the opposite of La Niña. The ocean temperatures in the eastern equatorial Paciﬁc Ocean will trend warmer than usual in an El Niño event. Warming the ocean
July 2012 / World Grain / www.World-Grain.com

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World Grain - July 2012

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