Distant Weather Drums
Image above of the rare sight of the Namib in bloom - a once in a decade occurrence
Namibia’s weather is influenced by the beating of very distant weather drums, as distant as the mid Pacific Ocean along the equator. The drumming speak of an alteration between the warm current known as El Niño Southern Oscillation (ENSO) and La Niña, the colder opposite. Fishermen, encountering the warm currents at Christmas time along the south American coast, named it after the Christ child, El Niño. The opposite was nicknamed La Niña - little girl. While neither are necessarily forecasts for rain, Namibian’s love hearing that the little girl might be on her way across the southern African sub-continent.
Often resulting in an intensity of rain absent during a Le Niño event, La Niña speaks of a time of plenty with the desert blooming in grand profusion. The drumming of El Niño on the other hand often tell of the possibility of early rains - as early as August, two months before the ‘small’ rainy season which generally arrives in October. However it can also tell of long dry periods between rain events, especially in the peak rainy season when up to 70% of Namibia’s rain should be falling.
Graph below: Mean seasonal cycle of sea surface temperatures in equatorial Pacific Ocean indicating warm (red) and cold (blue) phases….there is a complexity of science involved here which is too complex to cover in so short an article.
Left box: An eastward expansion of warm water (red) indicates an El Niño oscillation.
Looking at the right hand column of the graph, the blue scallops or ‘cold tongues’ of La Niña events coincide with Namibia’s great rainfall years: 2000, 2008/9, 2010/11 with 2012 being the strongest on record.
It isn’t necessarily a unanimous agreement on what constitutes these events, and each region has a different relationship with ENSO. While some areas may receive a lower than normal rainfall during an El Niño event, other areas receive high rainfall due to moist air imported from the Indian Ocean. Generally however, El Niño oscillation results in below average rainfall.
The length of events can vary from a few months to a few years. El Niño tends to last 9 to 12 months while a La Niña event can last up to 3 years, as is evidenced by the 2010 - 2012 event. Since 2012 and until 2020 Namibia underwent a strong El Niño oscillation with very dry conditions prevailing.
Image left - taken in 2022 of the poster child of the wild horses, Zohra almost 4 when the image was taken showing the results of good grazing on the condition of a horse. Few wild horses get to look this good!
Namibia’s general aridity stems from its location on the rain shadow side of the African continent where rainfall is far less than on the more tropical eastern side. Added to this, the sub-tropical belt of high pressure encircling the earth tends to shed its moisture further north over equatorial Africa.
Circulation at a great height, the moisture sinks into the high pressure cells (anticyclones) centred over the tropics of Capricorn and Cancer. There are layers of dry air far above ground which thirstily absorb the moisture so that the intensity of showers is limited and little actually falls to earth as rain.
The Central Namib after 8 years of no rain - no less beautiful for all that aridity.
In 2012 namibia experienced the addition of another event known as the Benguela Niño where warm water intrusions in the Atlantic, in tandem with a La Niña event, increased the intensity of the rains. Some areas bordering on the Namib received an unprecedented 1000mm of rain during that summer.
Several of Namibia ephemeral rivers (see blog) reached the sea - including the Swakop river (image below) this would put a damper on our beach gallop in Swakop!
The music group Toto were right to “bless the rains down in Africa” in their song entitled “Africa” - there are few sensual pleasure quite so exhilarating as the sensation of copious rain on hot, parched earth. It is something everyone should experience at least one in a lifetime. See blog on Petrichor - The intoxicating scent of rain…