Abstract
Impacts of the Indian Ocean Dipole (IOD), two different types of El Niño/Southern Oscillation (ENSO): canonical ENSO and ENSO Modoki, on the year-to-year winter wheat yield variations in Australia have been investigated. It is found that IOD plays a dominant role in the recent three decades; the wheat yield is reduced (increased) by −28.4% (12.8%) in the positive (negative) IOD years. Although the canonical ENSO appears to be responsible for the wheat yield variations, its influences are largely counted by IOD owing to their frequent co-occurrence. In contrast, the ENSO Modoki may have its distinct impacts on the wheat yield variations, but they are much smaller compared to those of IOD. Both the observed April-May and the predicted September-November IOD indices by the SINTEX-F ocean-atmosphere coupled model initialized on April 1st just before the sowing season explain ~15% of the observed year-to-year wheat yield variances. The present study may lead to a possible scheme for predicting wheat yield variations in Australia in advance by use of simple climate mode indices.
Highlights
Australia is one of the major wheat exporting countries in the world and accounts for 10–15% of the global wheat trades
The seasons of SON, NDJ and JJA are selected here not because Indian Ocean Dipole (IOD) and El Niño/Southern Oscillation (ENSO) have the strongest influences in these specific seasons, but because the indices in these specific seasons may represent the integrated impacts of the tropical climate modes on the wheat yields
The present study has focused on the wheat yield variations at the national level, we note that IOD shows higher correlation coefficients than ENSO at the provincial levels (Supplementary Figs 1–2)
Summary
Australia is one of the major wheat exporting countries in the world and accounts for 10–15% of the global wheat trades. Understanding and estimating the climate-related wheat yield variations is highly important for the world food management and security. Tropical climate modes such as El Niño/Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) catalogued in 19992 are known to be responsible for the climate variations in Australia[3,4]. It is important to examine impacts of the tropical climate modes on the Australian wheat yields by addressing the new climate modes This will provide useful information to farmers and decision makers for the crop management. We compare the impacts of IOD, canonical ENSO and ENSO Modoki on the Australian year-to-year winter wheat yield variations at the national level in the recent three decades by using linear correlation, regression and composite analyses. We examine the seasonal predictions of the wheat yield variations based on the observed tropical climate mode indices or the predicted ones by the SINTEX ocean-atmosphere coupled model right before the sowing date
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