My last blog post looked at whether Africa would be a region worse off due to (human-induced) climate change, and used an IPCC report on different phenomena that causes climate variability. Whilst the blog post was quite broad, one thing that has garnered popular attention in recent weeks is the phenomenon of the El Niño Southern Oscillation (ENSO). I've decided therefore to focus on this particular phenomena for the next few blog posts to see what effects ENSO could really have, particularly for Africa.
This blog post is therefore a quick introduction on the El Niño Southern Oscillation, for both my sake, and also the sake of (any) readers.
What is the El Niño Southern Oscillation?
El Niño Southern Oscillation has two parts: El Niño and La Niña, or the warming and cooling phases. As we're looking at climate changes leading to warming, we'll be focusing on El Niño more than La Niña. In Spanish, el niño means "the little boy", but when capitalised as El Niño, it means the Christ Child, as the phenomenon tended to arrive around Christmas time.
The National Oceanic and Atmospheric Administration (NOAA) defines El Niño Southern Oscillation as "a disruption of the ocean-atmosphere system in the Tropical Pacific having important consequences for weather and climate around the globe". The oscillation, or cycle, describes fluctuations in the temperature between the ocean (specifically the Pacific Ocean) and the atmosphere (sea surface temperature therefore plays a hugely important role). Although ENSO occurs in the Pacific Ocean, it can affect weather around the world and is of large interest regarding future climate.
El Niño is also more well known that La Niña, due to the fact that El Niño and El Niño Southern Oscillation are used almost interchangeably. The "Southern Oscillation" bit refers to the changing in atmospheric pressure that occurs, while El Niño and La Niña refer to the changes in ocean temperature. These two processes of the ocean temperature and atmospheric pressure are highly linked as atmospheric and air pressure changes can be a direct result of changing water temperature, which is why the phenomenon includes both. El Niño is also seen more often that La Niña, probably because the phenomenon is usually associated with warming more than cooling.
ENSO is described as a phenomenon as it isn't the "normal" conditions of the Pacific Ocean. Normally, trade winds blow strongly from east to west across the Tropical Pacific, which pushes warm surface water towards Eastern Asia, particularly areas like Indonesia. This creates upwelling of cold water in the east side of the Pacific, and therefore a temperature gradient. The sea surface is normally about 0.5 m higher and 8°C warmer in Indonesia than Ecuador. Warmer waters will then affect weather such as increased precipitation due to higher air pressure as it warms.
During El Niño, the trade winds aren't as strong as normal, or may even reverse. This means there is less or no upwelling of cold water in the Eastern Pacific and no temperature gradient forms. The effects of El Niño can vary widely but usually, precipitation and temperature changes are expected. For example, unusually warm waters can be found in South America, from the warm winds of El Niño, which can lead to flooding in places such as Peru. Conversely, the western side of the Pacific can face drought. More importantly, the change in atmospheric heat can alter global atmospheric circulation and affect places far beyond the Equatorial Pacific region.
This basic introduction and understanding of El Niño comes from the NOAA. I'd recommend having a look at this easy and clear introduction video to El Niño from the Met Office for a visualisation of the processes I have explained and I'll explore more El Niño effects in my next blog post!
This post does well to insert the MetOffice video describing El Nino. Have a look at this story:
ReplyDeletehttp://grofutures.org/article/el-nino-monitoring-in-tanzania/
that describes some UCL-led research seeking to assess the influence of El Nino on the replenishment of a wellfield in Tanzania.
Your blog is developing well as you explore this vast area as your first blogpost recognises. I encourage you to try to narrow/sharpen your focus from now on and delve a little deeper into a specific issue or two such as El Nino influences on water resources and perhaps how spatially variable this influence is in Africa. Nice to see some interactions on this blog but try to promote this further! It certainly helps to test your conceptual understanding.
Very interesting post! Why do you think La Nina receives less attention if it is still a threat? Would be interested to hear your view on such a topic?
ReplyDeleteGreat idea! I'll try and address your question in an upcoming blog post :)
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