El Niño is back in the tropical Pacific Ocean: How will it impact agriculture in the Southeast?     pdficon

A mature and strong El Niño is now present in the tropical Pacific Ocean. Most of the climate outlook models suggest that the 2015-16 El Niño is likely to strengthen further before the end of the year. Models and expert opinion suggest that surface water temperatures in the east-central tropical Pacific Ocean are likely to exceed 2° Celsius above average, potentially placing this El Niño event among the four strongest events since 1950 (1972-73, 1982-83, 1997-98).

The El Niño Southern Oscillation (ENSO) is the most important coupled ocean atmosphere phenomenon that causes global climate variability on interannual time scales. It manifests itself as changes in: (1) the sea-surface temperatures in the equatorial Pacific Ocean; (2) the sea level pressure difference between eastern Pacific high pressure and western Pacific low pressure (the “Southern Oscillation”). During El Niño events ocean surface temperatures warm in the central and eastern equatorial Pacific Ocean and easterlies are less strong. El Niño events normally bring cooler and wetter winter and springs to the Southeast USA. More information about ENSO impacts can be found at: http://agroclimate.org/fact-sheets-climate.php

El Niño is already causing conditions in the tropical Atlantic to be less conducive to tropical storm development and the systems that have formed have encountered high wind shear and struggled to survive. During the winter El Niño causes the Pacific jet stream current to dip into the Southeast. This provides cold fronts with more moisture and energy. El Nino typically leads to 40 to 50% more rainfall than normal for the Florida peninsula, and about 30% more than normal for South Georgia. El Niño's impacts on the weather in the Southeast US are usually most prominent in the winter, but given the strength of this year's event, we could begin to see its effects this fall. Many climate models are predicting a wet fall with above-normal temperatures for the Southeast.

Typical November rainfall anomalies during El Niño events. Farmers should be aware of the potential for a reduced harvesting window in the Fall and plant cover crops as soon as possible to avoid soil erosion due to heavy rains. Source: http://agroclimate.org/tools/Climate-Anomalies/

Detailed information on the effects of El Niño for selected weather stations in the Southeast can be found on AgroClimate: http://agroclimate.org/tools/climate-risk/

Seasonal Climate Forecast

The seasonal precipitation and temperature forecasts for October-November-December of 2015 produced by the International Research Institute for Climate and Society at Columbia University (http://iri.columbia.edu) are presented below. They were released in August and indicate increased probabilities for above average rainfall and temperature for the Southeast USA, reflecting the effects of El Niño in the region.

Seasonal precipitation (left) and temperature (right) forecasts showing increased probability of above average rainfall and temperatures for the Southeast USA during the months of Oct-Nov-Dec. Source: IRI, http://iri.columbia.edu/our-expertise/climate/forecasts/#Seasonal_Climate_Forecasts

Seasonal forecasts provided by NOAA for the same period indicate increased likelihood of above average temperature for most of the Southeast but increased likelihood of above average precipitation just for parts of Alabama and Georgia. NOAA and seasonal forecasts can be found on AgroClimate: http://agroclimate.org/forecasts/

Although seasonal forecasts are probabilistic and there is always a chance for weather patterns during the season not to behave as expected, it is well known that the presence of a strong El Niño or La Niña increases the “skill” of the forecast, meaning the ability of climatologists to produce a more accurate forecast.

Impacts on Agriculture in the Southeast USA

The most urgent potential impact to keep in mind is a reduced window of time for harvesting row crops in the Fall of 2015! Specific information for typical commodities grown in our region is provided below.

image010 Winter vegetables such as tomato and green peppers generally yield less during El Niño years than during Neutral or La Niña years. Most soil-borne pathogens and fruit quality problems increase in El Niño years. Fruit quality problems like gray wall and bacterial and fungal diseases that are typically associated with wet climates can be more prevalent during El Niño winters.

Nutrient management can also be affected by wetter cropping seasons as the frequency of leaching rainfall events increases, causing nutrients, mainly Nitrogen, to be washed out of the root zone, especially in fields irrigated by seepage irrigation. Recent studies demonstrated that during El Niño years, at least one leaching rainfall event of 1.0 inch or more in 1 day occurred in most locations where winter vegetables are grown in Florida and two of these events occurred in 9 out of 10 years.

image012 El Niño may also impact other commodities. In general, El Niño years are good for winter pasture such as rye due to wetter conditions. However, growth may be slower due to increased cloudiness and consequent decrease in solar radiation. In the case of forestry, El Niño plantings (wetter conditions) are generally well established. However, under such conditions, planting in very low lands might be avoided to minimize losses as excessive rains might drown seedlings. Wetter conditions may also have a negative impact on harvest operations.

image014 In the case of temperate fruits (peach, nectarine, blueberry, strawberry), El Niño conditions generally result in increased chill accumulation in the early part of the winter (Nov-Jan) and can reduce the need for oil or other dormancy-compensating sprays in peaches and blueberries. Growers can keep track of chill accumulation by checking the AgroClimate chill hours calculator tool on AgroClimate (http://agroclimate.org/tools/Chill-Hours-Calculator/).

Cooler rainy conditions may slow development rates in some perennial fruit crops such as strawberry. Lower levels of solar radiation resulting from cloudy conditions may also affect growth in some cultivars. Additionally, conditions may favor the development of fungal diseases such as Anthracnose and Botrytis fruit rots. Angular leaf spot (Xanthomonas fragariae) is another disease that is favored by cool wet winters (EDIS publication: http://edis.ifas.ufl.edu/PG056). Strawberry growers in Florida can monitor the risk for Anthracnose and Botrytis fruit rot diseases using the Strawberry Advisory System (SAS) available on AgroClimate: http://agroclimate.org/tools/strawberry/. More information about SAS is available in the following EDIS Publication: https://edis.ifas.ufl.edu/ae450

To help strawberry growers in Florida be more prepared for a season with potentially higher disease pressure we have recently released SAS smartphone apps: 1. Apple iOS: https://itunes.apple.com/us/app/sas-strawberry-advisory-system/id898025106?mt=8 2. Google Android: https://play.google.com/store/apps/details?id=org.agroclimate.strawberry

image016 Row crops that may be impacted by El Niño in the Southeast are mainly small grains (winter and spring wheat, oats, barley, and rye). The increased exposure to low temperatures (chill accumulation) in the early part of the winter (Nov-Jan) may accelerate flowering, specially those varieties with high vernalization requirements. The potential for rainy conditions during the Fall may delay the harvest of summer crops (corn, peanuts, and cotton) and result in delays planting winter crops.

El Niño Impacts on Agriculture around the World

El Niño impacts on global agriculture are significant, especially in the Southern hemisphere when most of the El Niño effects take place during the main summer cropping season. The figure below shows the typical global effects during December through February.

Typical El Niño global impacts during December through February http://www.pmel.noaa.gov/tao/elnino/nino-home.html

In South America we can expect improved soybean and corn production in southern Brazil, Argentina and Paraguay. Nevertheless recent studies have demonstrated a significantly higher risk for soybean rust during El Niño years. Soybean rust is a foliar fungal pathogen, which has a significant impact in soybean production in Brazil and Paraguay. Northern parts of Brazil normally experience below average precipitation during El Niño events. Implications include lower beef production since most beef cattle raised in region is grass-fed and potential implications for soybean and oil palm production. There is also an increased risk for forest fires during El Niño years. In the region of the “cerrados” there is no significant effects on rainfall but El Niño normally brings higher temperatures that can have an adverse effect on crop production. Colombia and Venezuela may experience below average rainfall with potential implications for coffee production, as Colombia's coffee regions have been drier than usual this year.

image018 El Niño is known to cause low grain production in South Asia and Australia. In southeast Australia El Niño is linked to hot and dry summers increasing the frequency and severity of bush fires and decreasing wheat exports. In Indonesia and Vietnam El Niño has been linked to reduced production of coffee, cocoa, and palm oil. A study looking at the relation between El Niño and droughts in India since 1950 concluded that of the 13 droughts that occurred, 10 were in El Niño years. It is important to highlight that not all El Niño events resulted in drought in India but it certainly increases the chances for below average precipitation in the country.

In Africa El Niño typically brings below average precipitation to the southeastern region of the continent, especially for Mozambique and Zimbabwe with negative implications for corn production. More detailed impacts of El Niño in Mozambique can be evaluated in the AgroClimate Mozambique climate information system that is currently under development with funding from the USAID: http://mz.agroclimate.org The horn of Africa (Ethiopia and Kenya) normally experiences the opposite effect during El Niño years with an increased probability for above average precipitation.

Global seasonal climate forecast for Oct-Nov-Dec 2015

image020 image022 Global precipitation (top) and temperature (bottom) seasonal forecasts for Oct-Nov-Dec 2015. Source: http://iri.columbia.edu

Date Issued: September 4, 2015
Prepared by Dr. Clyde Fraisse.

Agricultural and Biological Engineering
University of Florida - IFAS