An overview of some of the more significant weather events of 2015, using satellite data, including data from Meteosat and Metop.
14 November 2020
31 December 2015
By Jochen Kerkmann and Sancha Lancaster (EUMETSAT)
2015 was the 39th consecutive year of above average global temperatures and the warmest on record. Combined land and ocean temperatures in 2015 averaged 0.90 °C above the long-term mean (Credit: National Centers for Environmental Information (NEIC)).
Warm and dry conditions
In Europe the above average temperatures turned into recurring heatwaves which caused droughts in central and eastern parts in Summer 2015.
The cumulative effect of persistent heatwaves, with long episodes without rain, caused serious problems for people, agriculture, and industry.
Comparing the 10 days aggregation of the NDVI (Normalised Difference Vegetation Index) product for 31 August 2014 and 31 August 2015 (Figure 1), a huge difference in vegetation cover could be seen for most of Europe. This product estimates the land surface characteristics derived from satellite data. It uses reflectances from the SEVIRI Level 1.5 image data for the VIS0.6 µm and the VIS0.8 µm channels.
In Figure 1, below, the blue areas have dense and healthy vegetation cover, while red means no vegetation or very dry vegetation.
Due to the hot summer and consequent dry soil, there were also a number of fires on the Iberian Peninsula in Spain, from 6-11 August.
On Figure 2, the Meteosat-10 High Resolution Visible and Near-Infrared composite image the number of hot spots shows that on some days there was almost simultaneous occurrence of fires at considerable distances from each other.
Weather patterns in the summer also contributed to the transport of smoke from fires in Canada to as far as Russia. Smoke started to move eastwards on 9 June, due to the heat from wildfires in western parts of Canada taking the ash high up into the atmosphere, where it got caught in upper-level winds.
The smoke travelled over parts of the US, Wisconsin, Michigan, Indiana, Ohio, and West Virginia, before reaching the Mid-Atlantic states on 10 June where it stayed in the lower atmosphere and was visible from the ground as haze.
By 13 June the smoke caught in the upper atmosphere, travelled over the Atlantic and could be seen in Meteosat-10 Natural Colour RGB imagery (Figure 3) as a blue/cyan coloured ribbon moving over northern Scotland, along the Norwegian coast, over Finland, then towards Russia.
At the end of the year the continuing drier and warmer than average conditions led to a striking lack of snow pack over the Alps. A comparison of the Meteosat-10 Natural Colour RGB from 20 December in 2015 and 2014 (Figure 4) clearly shows the lack of snow in the Dolomites and in the southern French Alps.
In 2015, for the first time, the UK Met Office and Met Éireann began naming Atlantic storms. Coincidentally, in late autumn a succession of six Atlantic storms brought exceptional rainfall to parts of the UK and Ireland, causing widespread severe flooding to many towns and cities.
Storm Desmond on 5 December set a new UK record when 341mm of rain fell in 24-hours at Honister Pass, Cumbria. There was further severe flooding in Ireland and northern UK around Christmas and New Year associated with storms Eva and Frank.
Using Meteosat imagery both weather services were able to successful track the progress of the Atlantic storms and issue timely warnings to the public and relevant authorities.
The Meteosat-10 Airmass RGB image, 04 December 00:00 UTC (Figure 5), shows Storm Desmond southwest of Iceland. At that time it had a central pressure of 976 hPa.
In early September, Menorca suffered its worst storm in 33 years when a large convective system brought severe storms to the Balearics and Italy. One of the most severe cells also brought tennis ball-sized hail to parts of Naples.
The Meteosat-10 infrared image from 05 Sept 09:00 UTC (Figure 6) shows the cold-ring-shape storm that developed over the Mediterranean Sea close to Naples.
A number of unusual Tropical Cyclones formed in the North Indian Ocean in 2015. It is more unusual for cyclones in this basin to pass along the Gulf of Eden and make landfall in Yemen.
However, first Tropical Cyclone Ashobaa made landfall in June, then in late October/early November Tropical Cyclone Chapala hit Yemen, followed days later by Tropical Cyclone Megh.
Ashobaa formed over the Indian Ocean, then headed towards Oman in early June. The island of Masirah (off the east coast of Oman) received 239.4 mm of rain during the three days that Ashobaa affected the country.
Metop has microwave instruments that are important for tropical cyclone monitoring, in particular for finding the centre of a tropical cyclone.
Figure 7 shows the Metop-A AVHRR infrared image from 9 June 05:29 UTC and compares it to the 89 GHz image from the Microwave Humidity Sounder (MHS). The centre of the cyclone is not visible on the AVHRR image, but clearly appears on the MHS image.
Later in 2015 both Tropical Cyclone Chapala and Tropical Cyclone Megh caused widespread damage, extensive flooding and more than a dozen deaths. At Category 3, Tropical Cyclone Chapala was one of the strongest cyclones to ever hit Yemen.
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