Climate Patterns Viewer

Connect global climate conditions to local climate impacts with the Climate Patterns Viewer tool. This product provides a historical look at how the El Niño Southern Oscillation (ENSO) and Arctic Oscillation (AO) can influence local climate conditions and corn yield across the Corn Belt. You can use these simple maps and charts to show when and where specific phases of ENSO or AO have influenced: This tool is not intended to be a forecast. Rather, this tool uses historical data (1981-2010) to highlight locations where ENSO and AO can potentially impact climate conditions over the course of the year, which can help you make more informed farm management decisions.

ENSO: El Niño
AO: Negative (October)

El Niño Advisory
Click on the map to view a chart of the data for that location; chart will appear below the maps.
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Jeff Andresen, Jim Angel, Beth Hall, Larry Biehl, Pat Guinan, Chad Hart, Olivia Kellner, Dev Niyogi, Chris Panza, Tapan Pathak, Dennis Todey, Melissa Widhalm


The Climate Patterns Viewer (CPV) provides a historical look at how two teleconnections, the El Niño Southern Oscillation (ENSO) and the Arctic Oscillation (AO), have affected local climate conditions across the Corn Belt. A teleconnection is simply an atmospheric circulation or pressure pattern in one part of the world that can alter weather conditions in another part of the world. Impacts can be immediate or have a delayed onset, and can last for weeks or months at a time. Different configurations of a teleconnection (also called “phase”) result in different types of impacts, and knowledge about the relationship between phase and impact can help corn farmers make more informed management decisions. The effects of ENSO and AO on local temperatures, precipitation, and crop yields in the U.S. Corn Belt are less uniform and less predictable than in other parts of the world. CPV helps Corn Belt farmers and advisors identify those locations where specific ENSO and AO phases have historically resulted in notable local impacts throughout the year.

Data Sources and Calculations


Teleconnection data for ENSO and AO are from 1981-2010 and obtained from the National Oceanic Atmospheric Administration (NOAA) Climate Prediction Center (CPC).

Climate Patterns Viewer uses the Oceanic Niño Index (ONI) to determine ENSO events. ONI is based on the three-month running mean of sea surface temperature (SST) in the Niño 3.4 region (5oN-5oS, 120o-170oW). The dataset of historic ONI phases for this product were collected in 2011/2012, prior to the ENSO reclassification scheme developed by Lindsey (2013), and our dataset has not been updated to reflect those changes. Classification of months as El Niño, La Niña, or neutral in the Climate Patterns Viewer are based on the 0.5 or greater and -0.5 or less cold and warm thresholds, respectively, with neutral events ranging from -0.4 to 0.4. Events where not further classified as weak, moderate, or strong events. The same classification scheme is applied to the AO.

Precipitation and Temperature Data

The observed monthly precipitation and temperature data used in this analysis are from the Applied Climate Information System (ACIS) through the Midwestern Regional Climate Center (MRCC) cli-MATE user interface. Data are from the DRD964x climate observations dataset (1980-2010) as opposed to the current nClimDiv dataset in ACIS (NCDC 2014), which was not yet available at the time of analysis for this product. Data are for the climate division level for the North Central Region (domain of the U2U research project: North Dakota, South Dakota, Nebraska, Kansas, Missouri, Iowa, Minnesota, Wisconsin, Illinois, Indiana, Michigan, and Ohio). Climate normals, or averages, are calculated at the climate division level based on 30 years of observations (1981-2010), which is consistent with the time periods used by the World Meteorological Organization.

Additional information about ACIS is available at

Crop Yield Data

Observed Crop Reporting District (CRD)-level corn yield data from 1981-2010 were obtained from the USDA National Agricultural Statistics Service (NASS) Quick Stats Database. Maps of Crop Reporting District boundaries are available through NASS.

Corn yields in the Climate Patterns Viewer have been adjusted, or detrended, to remove the effect of improved technology on yield over time. You can think of it like an inflation adjustment. For decades farmers in the Midwestern U.S. have observed a 1-3 bushel/acre yield increase annually due to better seed traits, better equipment, and more efficient farming practices. This annual upward trend makes it difficult to detect the impact of weather and climate on crop yields, and it creates challenges for comparing yields in the 1980s and 1990s with yields today. By adjusting historical yields to current-day levels of technology we can avoid these issues and more clearly identify the impacts of ENSO and AO on Midwestern crop production. The Climate Patterns Viewer uses 2010 yield trend data as the baseline adjustment value.

Each corn yield map in the Climate Patterns Viewer tool will list the calendar years associated with the selected ENSO or AO phase in the lower left corner of the map. As you interpret these maps, please be aware that some phases will include more years than other phases. A calendar year is classified in the appropriate phase based on the growing season (April-October) average of the climate pattern. For example, if the growing season average of the AO index is above 0.5, that calendar year would be classified as AO-Positive for purpose of the CPV yield map.

Current Climate Patterns

The current ENSO phase information comes from NOAA Climate Predication Center (CPC):

The current AO phase information comes from NOAA Climate Predication Center (CPC):

Additional References

Lindsey, R. 2013. In Watching for El Niño and La Niña, NOAA Adapts to Global Warming. National Oceanic and Atmospheric Administration. ClimateWatch Magazine. (Accessed 21 May 2014.)

National Climatic Data Center (NCDC), 2014: Transitioning to a gridded climate divisional dataset. National Oceanic and Atmospheric Administration, Silverspring, Maryland. (Accessed 4 June 2014.)

Trewin, B. O. Baddour and H. Kontongomde (Eds.), 2007. The role of climatological normals in a changing climate. World Meteorological Organization WCDMP-No. 61. WMO-TD No. 1377. (Accessed 16 June 2014.)

El Niño Southern Oscillation

The El Niño Southern Oscillation (ENSO) describes the differences in air pressure, ocean temperature, and wind patterns across the equatorial Pacific Ocean. There are three phase of ENSO (El Niño, La Niña, and Neutral) each resulting in different impacts on global and local climate patterns. The effects of ENSO tend to be stronger in the spring, fall and winter months, and it typically takes several months after the onset of an ENSO event before temperature and precipitation changes occur. These changes ultimately stem from shifts in the location of the Polar Jet Stream.

To learn more, please visit the U.S. Climate Predication Center El Niño Southern Oscillation information page.


Arctic Oscillation

The Arctic Oscillation (AO) describes the difference in air pressure between the polar region and 20 degrees south latitude (subtropics). The strength of this pressure difference changes with the AO phase (positive, negative, or neutral), which in turn effects the Polar Jet Stream. It is the strength of the Polar Jet Steam that determines where low pressure systems track across the U.S. and the likelihood of cold air outbreak events. Changes in AO phases typically occur on monthly time scales. The impacts of the AO on local climate conditions tend to have immediate onset and are most commonly seen in the fall, spring, and winter months.

To learn more, please visit the U.S. Climate Predication Center Arctic Oscillation information page.


Left: Positive AO Phase. Right: Negative AO Phase

Frequently Asked Questions

When was the last El Niño?

The NOAA Climate Predication Center (CPC) maintains a list showing the current and historical phase of El Niño Southern Oscillation (ENSO) dating back to 1950. According to this list the last El Niño period occurred in mid-2009 through early 2010. In early March 2015, scientists at NOAA indicated that El Niño conditions have again onset. Monitor the latest conditions and advisories on the CPC website.

How might someone use the information provide in the Climate Patterns Viewer?

Early Planting, Marketing Decisions in a La Niña Phase

You are reaching the beginning of the planting season. A recent ag-weather outlet mentions the La Niña that developed over the winter in the Pacific is expected to continue. You are starting to think about what your marketing strategy might mean for you during the growing season based on La Niña influences you see in CPV. Looking at the temperature and precipitation deviations in CPV, you can see what a La Niña could mean for your growing season conditions and ultimately crop yields.

Late Planting, End of Season Decisions in an El Niño Phase

You are late getting your crops in during the spring because of cool conditions in southern Minnesota. You have forward marketed some of your crop, but you are concerned about crop development throughout the growing season. Looking at the temperature information for El Niño conditions in CPV, you see that if El Niño persists the growing season tends to lean a little cooler than average. In this case you can adapt your marketing or lock in a propane price because of the additional drying expected from a crop that will be slow to mature.

Dry Conditions in an El Niño

You have some soils in Indiana that were essentially tapped out of soil moisture through the season. The fall provided a little recharge, but still left soils quite dry. You are currently in an El Niño. Looking at the precipitation composites for the winter in CPV, you see that precipitation during an El Niño winter and spring is drier than average. You can market and plan, knowing that going in to planting you have a better chance of still being dry. This will allow probably earlier field access, but also leave you needing additional precipitation in the spring.

Slow Development, Harvest Decisions in a Negative AO Phase

It’s September and your central Illinois corn crop is behind schedule. Your past experience tells you the crop won’t be optimal for harvesting for several more weeks. You hear from your local Extension specialist the AO is in a negative phase, and scientists expect this pattern to continue. Using the CPV tool you see that temperatures tend to be below average in the fall, meaning slow crop development could continue with an increased risk of frost damage before maturity. With this information you can prioritize developing a back-up harvest plan and line up the resources you might need for these late season adjustments.