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.
A vigorous storm brought tornadoes and massive hail stones the central USA yesterday, 26 Apr 16.
Cloud top pressure, courtesy of EOSDIS, computed from satellite imagery shows pressure of highest cloud visible to the sensor; the lower the pressure the higher the cloud.
Desktop meteorologists can get a quick view of the tornadoes and convective storms that hit central USA yesterday, 26 Apr 16, by using NASA’s EOSDIS presented as the featured image to this blog. The purple mass in the top right hand area of the picture is very high cloud associated with this active storm system.
Visual imagery is presented below.
A look at the wind flow at 250 mb /30,000ft ish, using the Earth website, shows the region overlain by the exit of a powerful jet stream. Mathematical dynamics predict this to be aan area of strong divergence the result of which being the air is literally sucked up through the atmosphere from the surface causing these vigorous storms.
This Reuters release caught my eye. One economic benefit of climate change is the possibility of cheaper shipping routes between China and the Atlantic. It is, perhaps, a small positive in an impending global disaster.
There are some problems though. The Canadian section is claimed as ‘Internal Waters’ and the map shows why.
Sea ice still extends over these waters in winter but the National Snow and Ice Data Centre reports on 28 Mar 16, that ‘The Arctic sets yet another record low maximum extent” … of sea ice. So this story will be a theme in Geopolitics in the future.
EOSDIS sourced imagery for 20 Apr 16 shows the area north of Alaska to be fast with sea ice at the moment, so no shipping possibilities on this route at the moment. (Polar view, so north is towards the top right hand corner.)
The same area, without sea ice overlay gives an impressive view of the ice flows even if the perspective of the polar regions makes a good featured image to this blog.
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.
8 Apr 16 surface streamline
8 Apr 16 250 mb (30,000 ft) streamline
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.
One of the tricky things about meteorology is that it happens in three dimensions above the surface of a rotating sphere. In fact, if you add in time, it is four dimensional. Yet we only have two dimensional graphics from which to build our understanding of it; its rather like building the picture of a garden viewed only through the narrow gaps in boundary fence.
This featured picture has a stable south westerly jet-stream flow aloft, marked by cirrus which weaves itself across a lower level unstable north westerly from the direction of Cape Farewell, the southern tip of Greenland. Such differential motion of low and high level clouds give rise to traditional seagoing forecast rules of thumb and allow an observer to detect whether they are ahead or astern of a storm. Of course, a peek at the ships log might tell them that.
Jet stream is shown here from Earthnullschool’s 250mb streamlines. This matches the shape of the cirrus in the satellite picture above.
Whilst below the 1000mb streamlines are:
In this case, cumulus at lower levels moves from the north west whilst cirrus at high levels comes from the south west. The area does lie to the south west of the complex Atlantic low in the aftermath of storm Katie and pressure is building heralding more settled weather to come.
The meteorological event of the day, storm Katie, gives a dramatic signature on all the various meteorological graphics. MODIS channel 22 at 280230, Earthnullschool surface winds and UKMO surface analysis 280000 presented above.
Surface wind flow from Earthnullschool shows the intense wind field over SE UK, squeezed ahead of the vortex, but the NW’ly surge of air from Denmark Straits is perhaps the most striking element of this graphic.
The storm is a snag in a larger complex depression which mixes cold air from the pole to the West and warm air up to the East. By this method, the atmosphere does its job of breaking down the temperature gradient from equator to pole and illustrates one of the keys to meteorology.
NASA’s EOSDIS Worldview gives stunning pictures. This one, of polar regions north of Greenland appears to show the ice edge with cold air streaming off over the sea forming ever deepening cumulus. This edge seems almost too bold.
Check on MODIS (Dundee) Channel 6 (snow/cloud discrimination 1628-1652nm) and Channel 22 (surface cloud 3.929-3.989µm) seems to back this analysis up; temperatures of cloud tops over the sea being colder than the ice. Fractures and polynyas in ice, much loved by cold war submariners, show up with amazing clarity.
desert sands blow out of Africa on a conveyor belt of air ahead of a cold front
Cold fronts are normally identifiable from their cloud signature on satellite imagery. Of course, air mass boundaries can exist without condensation: density changes and air flows can exist without clouds particularly in dry and hot air. Summer front can cross the UK with just low strato-cumulus. In the Mediterranean, cloudless density boundaries one day give potential for fierce thunderstorms the next.
The 23 Mar 2016 was a case in point. Over the Eastern Mediterranean we note a conveyor belt of air dragging sand northwards from the African deserts. No clouds but a cold front none the less.