Normally we think of droughts over South East Asia (i.e. Borneo) and north-eastern Australia (Queensland) associated with strong El Niño events. This for instance led to dramatic fires through the tropical rainforests of Borneo, during the last ‘Super El Niño’ – of 1997-1998.
This year – during the currently developing Super El Niño of 2015-2016 – we should also keep an eye on the tropical Atlantic, where the Southern Amazon and agricultural parts of northern Brazil should brace themselves for record-drought, accompanied by soaring temperatures – judging by climate model runs.
Amazon forest fires & raised corn and soy prices?
Indeed: That would create the perfect background for extra CO2 emissions from Amazon forest fires and raised corn and soy prices as a result of lowered agricultural productivity in that region – possibly influencing global food (and energy) markets.
Shown below according to NOAA NCEP model forecast much of Brazil is likely to experience both a (strong) positive temperature anomaly and a (strong) negative precipitation anomaly – so a hot and dry boreal winter (the average over December 2015 and January & February 2016).
This is an important chart to look at for everyone, anywhere. Why? Because it shows the entire world is in for a record-warm winter of 2015-2016. Clear local effects can be witnessed over Canada, Brazil, possibly also Eurasia. More to come in our specialised forecast. Credit: NOAA NCEP.
Modelled precipitation effects of the current El Niño during the 2015-2016 boreal winter. Noteworthy is a forecast drought over parts of Brazil. Typical patterns include extra rainfall in the Rift Valley of East Africa, dryer conditions along Africa’s West coast – and somewhat wetter conditions over parts of the southern US, possibly including California. Indonesian drought conditions seem to change in this forecast, influenced by possible developments in the Indian Ocean, breaking a typical El Niño pattern from the West. Queensland can expect a weaker than normal monsoon, although the anomaly in this image is drawn above sea. Credit: NOAA NCEP.
Mechanism behind forecast Brazil drought: from Pacific El Niño to ‘Atlantic La Niña’
How does this happen? Sometimes, during El Niño the mirrored effect manifests in the tropical Atlantic – meaning an opposite state, with warm water (Western Hemisphere Warm Pool) in the West (Gulf of Mexico, Carribean) and cooler water off the West coast of Africa – much like an ‘Atlantic La Niña’.
The reason is that increased convection over the East Pacific (where trade winds are blocked during El Niño) sucks in more air from the East, across Latin America. This forms an extra engine to Atlantic tropical (easterly) trade winds. As Atlantic trade winds pick up, more warm water is blown into the Gulf of Mexico, where it enters the Gulf Stream – adding heat to North American coastal waters and promoting an increase in rainfall over parts of the southern US.
Due to increased upwelling along the coast of Africa relatively cool water stabilises the atmosphere between Africa and Brazil, where a high pressure blockade forms – so the ‘Inter Tropical Convergence Zone’ (IRCZ) or ‘monsoon’ does not reach as far South in that area as it normally does during boreal winter months. Studies show this might also be the trend, as global climate warming might block the ITCZ more often, leading to returing Amazon droughts.
The result: Tropical rains get stuck across the northern margins of South America (Guyana, Surinam) and do not reach the southern Amazon and central Brazil. Due to drought and increased Sun exposure also temperatures rise – possibly worsening drought conditions.
No sign California will see return of massive El Niño rains of 1997-1998
Just look at the above model. Not every Super El Niño creates the same local climate effects. There’s good news in that if you remember the damage of the 1997-1998 El Niño (mudslides) – but ‘neutral precipitation’ is definitely not something that will alleviate current drought conditions in the south-western State.
We will get back to the matter in our specialised forecast for North America and Europe – coming soon.
© Rolf Schuttenhelm | www.bitsofscience.org