Two recent disastrous east Atlantic storms were exacerbated by the Soufrière Hills eruption, say Wyss Yim*#, Judy Huang* and Johnny C.L. Chan*
Geoscientist 20.6 June 2010
The best time for achieving a better understanding of climate change is surely the present, because we have both instrumental records and satellite records for verification. It is therefore somewhat surprising that relatively few Earth scientists are involved in ‘modern’ climate change research.
Yim and colleagues have studied the possible connection between a volcanic eruption and successive disastrous east Atlantic winter storms during February 2010. Global warming has been argued as an important cause for the increase in intensity of tropical cyclones as the oceans warms1,2,3. Recently Bender4, in a state-of-the-art computer model study, predicted that the number of strong storms in the western Atlantic could double by the end of the century through anthropogenic warming. However, the role of natural variability through volcanic eruptions, which are difficult to predict, has not been taken into consideration, the scientists believe.
On February 11, 2010 1635 UTC/GMT the Soufrière Hills volcano (latitude 16o43’N longitude 62o11’W) on Montserrat in the eastern Caribbean Sea erupted, sending an ash plume reaching 15.2 km above sea level. On 12 February at 1200 UTC/GMT, Meteosat SEVIRI Channel 7 (8.3-9.1μm infrared, available from www.sat.dundee.ac.uk) shows the ash plume from the eruption was caught up within the warm sector of a frontal system spreading in a northeasterly direction (picture) towards Western Europe. This has provided insight into how volcanic eruption clouds become involved in generating of east Atlantic winter storms.
“During February 2010 there were two successive disastrous East Atlantic winter storms with torrential rain and high winds” says Yim. “Both were associated with active cold fronts and low-pressure areas in the southern part of the North Atlantic Ocean, moving northeastwards. These storms were bolstered by an unusually strong temperature contrast of the sea surface across the Atlantic Ocean. Abnormally warm waters were widespread off West Africa and extended into the eastern Caribbean Sea through the modification of surface wind circulation by the eruption plume. To the north of this warm surface water and air, relatively cold surface waters stretched between Western Europe and the southeastern United States.”
On the morning of February 20 a severe storm from the southwest passed over the island of Madeira (maximum elevation 1862m, total land area 741 km2). “This frontal activity was exacerbated by the orographic effect of the mountainous island, as well as by the volcanic ash and aerosols arising from the eruption about eight days earlier (which provided condensation nuclei). Between 0600 and 1100, torrential rain occurred on the southwesterly slopes of Madeira, with 165mm recorded at Pico do Areeiro. This is almost double the average rainfall for the whole of February at the weather station of the city of Funchal. Damage was confined mainly to the south of the island with widespread floods (picture) and mudslides, resulting in at least 48 fatalities and severe damage to infrastructure and property.”