El Nino and Algae in Chile

An unusually strong El Nino pattern this year is reportedly linked to a ‘deadly red tide’ in Chile.  The implication is that sea temperature anomalies are causing an algal bloom which renders fish and shell fish poisonous to eat.   Fishermen in Los Lagos are protesting that their government is not doing enough to mitigate the event.

MODIS Aqua imagery presented by NASA can be analysed for Chlorophyll concentration, see featured image above (chlorophyll by MODIS Aqua 26 Apr 16).  The oranges and reds indicate high chlorophyll level with blues lower.  Such analysis is only possible in cloud free skies.  Unfortunately the great southern ocean makes a ready supply of the white puffy stuff and I had to go back a couple of days to get a break in the canopy to get this image.

El Nino is one of the three stages in the El Nino-Southern Oscillation (ENSO).  El Nino is a warm anomaly, La Nina is a cold anomaly and the third stage is neutral.

The National Weather Service sea surface temperature is included below for information.  Cold up welling along the coast of Chile is a usual part of the ocean circulation and brings nutrients which feed marine life.  A warm anomaly suppresses this effect and is bad news for communities reliant on the sea for food.  The warm anomaly along the coast of South America shows up in yellows and oranges.



spiral low near Greenland, 8 Apr 16

Eyes in the sky, courtesy of Dundee Satellite Receiving Station bring this image of a spiral depression near Greenland.

Such perfectly represented spiral lows happen when the vortex is present through all layers of the atmosphere: surface streamlines as well as wind aloft trace out the same pattern circular pattern.  This is often not the case in the mid-latitudes.  See following images from Earthnullschool which show that the surface low is located at the same position as the upper low.

The trailing cold front has a marked wind veer on it.

UKMO analysis for same day follows, which shows the somewhat complicated structure of the frontal system.  Bands of airflow are sucked up from the south and gradually wind upwards and around the vortex thereby mixing warm northwards.  There is a noticeable change in air mass because behind the front we can see convective cells in the polar airflow which pours down from the Davis Straits between Greenland and Canada.


Spirals, and in particular logarithmic spirals often occur in nature.  The dynamics are complicated here so there is no simple equation; circular motion on the surface of a spinning sphere moving in an elliptical orbit.  There seems to be an undeniable approximation to the following.