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March 26, 2015
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By Easton Kuboushek, ISA communication specialist
Iowa’s volatile weather story
Spring"and"Summer"Rainfall"In"Iowa"(1893;2014)"
Spring & Summer Rainfall in Iowa, 1893-2014
1;in;20;yr"return"in"1893;1980"has"1;in;4;yr"return"in"1981;2014"
20"
1893;1980"
1981;2014"
Jul$Aug'Precipita0on'(inches)'
July-August
Precipitation (inches)
1893;1980"Average"
1981;2014"Average"
15"
Weather volatility in Iowa has increased
over the past 20 years and for several
reasons, augmented volatility is expected
to continue. Chris Anderson, Ph.D.,
climate risk analyst, Iowa State University
(ISU) has dedicated his research to past
and future climate trends and their effects
on soybean management practices.
2010
2014
10"
2008
5"
2013
2012
0"
0"
5"
10"
15"
May$Jun'Precipita0on'(inches)'
May-June
Precipitation (inches)
Last year had the hottest average global
temperature ever recorded – but not in
Iowa. While the media clings to the
world’s warmest year, Iowa’s story is
pouring in a different direction.
Iowa’s weather story, especially in the last
decade, has come in the form of a lot of
rain at the wrong times – especially in the
spring. According to historical data,
between 1873 and 1980 Iowa experienced
20"
an abnormally wet spring once every ten
years.
Figure 1: The data illustrated in this chart show average inches of rainfall in Iowa
from 1893-2014. Points outside the yellow circle fall above the average rainfall in
inches from 1981-2014. Since 2008, Iowa has experienced five years with above
average rainfall – a probability of 1:175,000.
Since 1980 – that number has jumped to
once every three.
“It’s not just that it’s been a little bit rainier, it’s that we’ve had more extreme springs than we have ever had in
the past,” Anderson explained.
Anderson continued to illustrate the anomaly Iowa has experienced to more than 50 farmers at the 2015 ISA
Research Conference in February. “Not only have we seen a 300 percent increase in abnormally wet springs, we
have experienced them three consecutive years,” Anderson said.
Based on historical data, that is a probability of 1:8,000.
What’s more, when years 2008 and 2010 are included, Iowa experienced an above average spring rainfall five
out of seven years – a probability of 1:175,000.
Not exactly a figures to bet the farm on. Yet growers are forced to face Mother Nature head on and adapt
management practices to address our volatile climate.
Making sense of Mother Nature
Anderson, in conjunction with the ISA On-Farm Network®, seeks to take the complex rainfall and weather terms
to usable terminology for use on the farm.
“The data that are being collected by ISA and being aggregated, can give you some clues when there is an
emerging trend like this that you have to adapt to,” Anderson said.
In his effort to describe the linkages between climate trends and soybean management practices, Anderson
worked to expand the list of weather indices and associated impacts on field management, developed field-level
rather than state-level or county-level statistical relationships and computed trends and other temporal changes
in the weather indices in 2014. His work was published in two prior Advance articles to date, How Midwest
growers are managing an increase of rainfall volatility and Weather-based N Application Probability Tools.
Anderson’s research and collaboration has been and will continue to be invaluable to ISA and the Iowa soybean
farmers.
For permission to republish articles or to request high-res photos contact Dorothy Tate, dtate@iasoybeans.com
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