I feel fascinated by volcanoes and I think that’s quite obvious, but there’s also room for other natural phenomena, like weather. In Spain, my home, volcanoes are rare. We do have a ~10,000-year-old monogenetic volcanic fissure in northern Spain, part of the Catalan Volcanic Field, a cluster of weak alkaline volcanic fields that have been episodically active for more than 10 million years. However, for the most part, volcanoes are not present in mainland Spain. I more directly experience other natural events like thunderstorms, but what I didn’t know until now is that the weather may have more volcanic in it than I thought. This year’s very anomalous weather in Spain might well be linked to a series of middle-latitude, northern hemisphere volcanic eruptions. And here I will explain why I think so. It all started in Kamchatka.
The April 11, 2023, Shiveluch eruption.
Russia’s Kamchatka Peninsula is home to an impressive bunch of volcanoes. The Klyuchevskoy Group and Shiveluch in the Central Kamchatka Depression are probably the most productive stratovolcanoes on the planet. At the northern end of the volcanic arc, towering 3 km above the Central Kamchatka depression, lies Shiveluch volcano, a mainly andesitic volcanic edifice with a volume of 1000 km3 that started to form 80,000 years ago or earlier. A double, nested landslide headwall encloses an active lava dome that has grown since 1964. The volcano effuses viscous andesite lava more often than not. The effusions frequently collapse into pyroclastic flows. For a distance of 15 kilometers to the south of its lava dome the landscape is a volcanic desolation of ash and rock, created by debris avalanches and pyroclastic flows from this very restless volcano. Shiveluch is also a prodigious source of plinian eruptions, including a VEI 5 event in 1854, a VEI 4 in 1964, and the eruption that interests us, the VEI 4 of 2023.
On April 11, 2023, Sheveluch entered a plinian eruption. A massive cloud of ash and gas spread out from the volcano to heights of 20 km, mantling nearby towns in tephra. Pyroclastic flows traveled distances of 19 km. This was probably the largest volcanic explosion this year. I’ve seen various estimates of the amount of sulphur dioxide produced by the eruption ranging from 700,000 to 100,000 tonnes of SO2. Overall the values seem to move through loading typical of VEI 4 eruptions. Volcanic SO injected into the stratosphere reacts to form H2SO4, and it is known that this sulphuric acid can act as an aerosol that reflects sunlight back to space and cools the atmosphere. Generally, the atmospheric effects are only considered for very large events. For example, there is a lot of talk on how Hunga Tonga will affect the climate although focused on the major water injection rather than the SO2. Smaller events like Shiveluch are generally ignored. Craig Heden suggested a while back in the comments that the eruption of Klyuchevskoy that happened later this year could enhance cyclogenesis over the North Pacific. I found it interesting but didn’t think much about it at the time. Now, however, I’m starting to consider the importance of minor eruptions in driving important weather changes based on what happened this year in Spain.
A showery June of 2023 in Spain
Spain had a really dry spring in 2023. Except for northwest Spain, most areas got a very small fraction of what they should have, with the worst conditions in eastern Spain. For example, Valencia in the east got just 4 % of the 1981-2010 median rainfall between March 1 and May 10. Barcelona in the northeast faced similar ghastly conditions with just 7 % of the rain median for the same period. To a lesser degree, these conditions were widespread throughout Spain in spring, which is usually an important time for rain in the country. This was just the continuation of a long-lived drought from previous years. Thankfully, the weather pattern reversed abruptly in late May.
May brought a curious episode of anomalous unseasonal rains to Spain. The onset of the unusually wet weather was on May 20. Rains were most frequent from about May 24 to June 12, and during this time given locations in mountainous areas would get showers most days. I was in a mountainous area myself and recall that noon showers would usually happen on consecutive days. I thought this weather to be strange and different from my earlier experience for this time of the year. I have checked a particular station in the Albarracin mountain range on the basis that it is one of the highest areas of the Spanish interior, which concentrates rain. This station shows some 8 storm days for the first 12 days of June 2023 but shows no storms whatsoever for the same period of the dry 2022 and 2021 years and only two storm days for 2020. After June 12 the weather got somewhat drier but continued to be unseasonally wet until July 7, after which a very dry period ensued in July and August, which is in line with the recent years’ trend of drought conditions. However, thanks to the June rains, the summer ended up having more rainfall than usual in most places, despite the very dry July and August months. The unseasonal rain complicated harvest in places but also probably averted what would have otherwise been a hellish fire season.
I have put together a table that shows rain accumulations in several important Spanish cities distributed over the whole peninsula. The data is for the May 18-July 6 interval, July 6 included. I extracted the data from AEMET graphs, and since it comes from graphs and not reported values it may not be the perfect value measured but it must be close enough. I compare it to the median rainfall over the same period for the 1981-2010 years that is reported by AEMET. Overall the whole peninsula was bathed in an abnormally high amount of rain, with the only exception of Barcelona in the NE end. There is a relationship with latitude. The rain anomaly is more strongly positive in the south of Spain whilst in the north it is more subtle. The south got up to 10-30 times the amount of rain in a normal, median period. This is in areas that don’t usually get rain for this moment of the year because they are under the influence of anticyclones that migrate northward during summer, bringing stable weather. I think what we saw was a southward migration or expansion of the mid-latitude lows, jet stream, and associated rain, bringing unusually unstable weather, particularly to the southern half of the country although also to the northeastern interior (Zaragoza or Teruel). The total amount of rain must have been greater in mountainous areas, Teruel I think is the only city here that can be considered as being mountainous, and received 200 mm, the most rain, in the time considered.
Rain accumulations for the May 18-July 6 interval
|Median rainfall for
|Percent of median precipitation for interval in 2023
|43° 25′ 26” N
|Santiago de Compostela
|42° 53′ 17” N
|42° 46′ 37” N
|41° 39′ 38” N
|41° 38′ 27” N
|41° 17′ 34” N
|40° 21′ 02” N
|39° 53′ 05” N
|39° 28′ 50” N
|39° 28′ 17” N
|38° 00′ 07” N
|37° 50′ 56” N
|37° 25′ 00” N
|36° 50′ 47” N
Now, the question is, is there a link with Shiveluch? I’ve been wondering for a while what could have caused the anomalous rains of June. Because when something happens there must be a cause, and in this case, it seems to have been quite an exceptional anomaly so must be caused by something exceptional. I first wondered about El Nino, but to my knowledge, El Nino does not strongly influence storm activity over Spain, or at least there is no precedent that I know of. In general, ENSO is not supposed to have a strong effect on Europe, though I may be wrong. Also, El Nino continued ramping up through July and August when the conditions shifted back to dry in Spain. The Quasi-biennial Oscillation was positive in 2023 but was also positive in 2021 when there was a dry June. The Solar activity was higher than in previous years but not that high above 2022 to really suspect anything. However, Shiveluch could be just right. Its eruption was on April 11. The sulfur dioxide cloud of Shiveluch reached the North Atlantic on April 20-21. Presumably, the driving mechanism would have been cooling induced by the sulphuric acid reflecting sunlight into space. The cooling may have taken some time before altering the weather patterns. There is a month that elapses between the sulfur dioxide cloud reaching the longitude of Spain on April 20 and the onset of wet weather on May 20. Overall the rain persisted over Spain for 1-3 months following the Shiveluch explosion. So I think there may be a link.
Later down the year
It doesn’t end here. 2023 has featured more explosive eruptions in middle northern latitudes and I think they have also affected Spanish weather. Shishaldin comes in. Alaska’s Mount Doom is how Jesper refers to Shishaldin, a fitting name for this basalt stratovolcano, that is large, young, and symmetrical. Subduction zone basalt can be quite dangerous, don’t be fooled by the friendly gas-poor tholeiites of Hawaii or Reykjanes. Shishaldin is in fact a capable explosive volcano. Its steep conical peak has been built by numerous subplinian eruptions with lava fountains. Roaring towers of fire shoot above the icy summit of Shishaldin as glowing snakes creep down the flank and curtains of black tephra rain from the sky. The pure white of the mountain is now ruined with volcanic waste, but not for long in the unforgiving climate of the Aleutians.
Shishaldin started to produce some activity around July 14 consisting of a minor eruption with limited SO2 cloud. This was followed by a series of remarkable eruptions all producing substantial sulfur dioxide clouds that drifted for days before fading into H2SO4 and spiraled around mid-latitude cyclones. The clouds were not as large as that of Shiveluch and did not reach too high, only about 10 km, but this is just enough to have made it into the stratosphere so far north, and maybe aided by frequent cyclones. The eruptions happened on July 26, August 4, August 15, August 25, September 5, September 15, September 24, and October 3. As you may have noticed these 8 subplinian eruptions and the smaller preceding event happened at regular intervals of about 10 days, almost like a clock. I do not know the mass of sulfur in these clouds but to my eye, from the density and size, the 15 August and 5 September events look more robust. Since they were periodic they must have had around the same size but not all may have had the same explosivity, some may have produced more lava and less plume, while others may have injected the SO2 higher up.
Now, the interesting thing is that once again there seems to be a weather response in Spain. I turn to Madrid, the Spanish capital because this area has been the most affected by an exceptionally wet Autumn. Autumn (here meaning September, October, and November), has been more rainy than normal in most of the country. However, the center of the peninsula takes the prize. For the entire period considered, the rain in Madrid, which has a central location in the peninsula, is 3.5 times the normal year amount of rain. More than 350 mm of rain accumulated in Madrid during these 3 months of 2023. Madrid had no rain during July or August. The first substantial rain event lasted September 4 and 5, where a series of thunderstorm systems brought some 90 mm of rain. Could have ended really badly, because an intense stationary mesoscale system that was originally forecasted to hit Madrid ended up somewhere else. Had it hit Madrid the amount of water dumped in a short amount of time would have collapsed the city and flooded many places. Assuming there is a volcano-weather link, the Shiveluch eruption would have taken 39 days to show up as an irruption of wet weather in Spain back in May. For Shishaldin, the time elapsed between the first subplinian eruption and the September 4-5 storms is about 40 days, nearly identical. Some significant rainfall events continued until September 17, when things became stable for a while.
Unstable weather resumes just before mid-October, and on October 19 an atmospheric river ahead of a cold front soaks Madrid in more than 100 mm of rain in a single day, 3 months’ worth of rain, which marks an all-time record for the city in a century of weather monitoring. Of course, the Shishaldin subplinian eruptions were ongoing a month before this happened and the, probably stronger than normal, September 5 explosion happened 44 days earlier. A subtropical storm on 22 October left some 35 mm of rain in Madrid after making its way from the south coast of the Peninsula, where it will be remembered for obliterating a substantial fraction of the trees in Huelva city, due to hurricane-force wind gusts. Unstable weather, although not overly dramatic, persisted near-continuously until mid-November whilst the second half of the month was dry until November 30. The major rain events of September and October could fit with the effects of Shishaldin’s explosions, with a 1-month lag, since these eruptions happened mostly during August and September.
The last northern volcanic explosion came from Klyuchevskoy. A basaltic-andesite stratovolcano with a bit of gigantism and hyperactivity. It is the neighbor of Shiveluch and it’s no surprise it went up in the same year since this is the Central Kamchatka Depression, the valley of giants. The eruption style is not too different from Shishaldin, although the somewhat higher viscosity of basaltic-andesite drives larger explosive events. Volcanic activity climaxed towards the end of October after many days of strombolian explosions and lava flows going down the flanks on various sides of the cone. On October 31-November 1 lava fountains were 1 km high above the mighty summit of Klyuchevskoy, and ash reached 14 km above sea level. This explosive event created a sulfur dioxide cloud that looks to me to be somewhere in between Shishaldin and Shiveluch size.
Somewhat later, across the planet, a third major rainfall event hit Madrid on November 30-December 1, and dropped some 60 mm of rain in the AEMET station that I’ve been quoting. Another 20 mm followed shortly on December 7. These two significant rainfall episodes came after the Klyuchevskoy eruption by 30 and 37 days respectively. Two is a coincidence, three is a pattern.
Initially, I was only going to talk about 2023. However, after finishing the rest of the article, the Canadian Fires of 2023 came to my mind as a possible alternative mechanism for driving the unusual weather at home, and while they do not fit the rain events as well as the eruptions I decided I needed to find a stronger correlation between eruptions and weather before publishing the article. Finding meteorological data for old years is no easy task but I tried. I chose one station near Madrid, the Madrid Airport, as a means of judging weather conditions, anything more than this would have taken too long since I do not know any open sources to download the data as an archive. I have looked in detail at the 2008-2023 years, writing down the total precipitation for each month in this period, and I have compared it to all plinian subplinian events in the Aleutians in that timeframe. I have also looked at 1999 and the Shishaldin eruption of that year, which was its last subplinian/paroxysmal event before the 2020 eruption. I haven’t looked into Kamchatka eruptions yet. Here is a list of the eruptions and the conclusions I’ve reached:
1999 Shishaldin eruption: There was a substantial eruption on 19 April this year, with a plume that rose 16 km. The effects should have kicked in around late May or early June. In Madrid Airport the month of May is slightly deficient in rain compared to May in the 2008-2023 years that I have looked up, while June is about the same as the June average of those years. As such it doesn’t look like there was any effect on Madrid. That said, there was an EF3 tornado on June 1 in northern Spain (the Navaleno tornado) that happened 43 days after the Shishaldin eruption and is among the few strongest tornadoes known in Spain for the past several decades.
2008 Kasatochi eruption: This small Aleutian island was the first that came to mind and the reason why I started looking for data this year, the eruption was an intense VEI 4 and a remarkably sulfur-rich one that was also preceded by another VEI 4 in the Aleutians from Okmok volcano. The Okmok eruption was on July 12, and the Kasatochi eruption on August 7. Wet conditions should have hit towards the end of August or the start of September. August had no rain but September was extremely wet as was October. In the 2008-2023 years for the Madrid Airport station, the wettest months of September and October are those of 2023, but the second wettest are those of 2008. September 2008 had 2.6 times as much rain as the average 2008-2023 September months, and October 2008 had 2.1 times as much. Wet conditions ensued on September 6. The strongest rain event, with 62 mm accumulated in two days, occurred 46 days after the Kasatochi eruption. November was dry and the effects must have already subsided by then.
2013 Pavlof eruption: This basaltic-andesite volcano had a few strong eruptions in the 2010s. An eruption on June 24 sent ash to 8.5 km. July was dry and August was average, so no obvious correlation is apparent.
2014 Pavlof eruption: On June 5 activity climaxed in an event that produced a large sulfur dioxide cloud that drifted over Siberia, some lighting accompanied the event but the height of the plume is unknown. The following July was the second rainiest of the 2008-2023 years in Madrid Airport. The culprit is a single precipitation episode on July 3. When searching the news, reports appear of a series of hailstorms that affected multiple provinces of Spain on July 2. Some of the storms were very damaging where up to half a meter of hail accumulated. On July 3, another hail storm described as being spectacular hit Madrid and surrounding areas. Since the unusual weather ensued 27 days after the Pavlof eruption I believe there may be a link. No rain fell in August.
2016 Pavlof eruption: Erupted on March 27 when ash reached 11 km. The following months of April and May were very wet in Madrid. This year had the rainiest April of the 2008-2023 years, while May nearly doubled the average amount of rain. The April rains hit as early as April 5, although being one of the rainiest months of the year this is not surprising, plus, the two largest rain episodes of April were during its last third. 40 days after the eruption there was the start of a 7-day episode of continuous rain that produced most of the accumulation of May and the largest “uninterrupted” rain event of the two months, a total of 62 mm. June was dry.
Two other strong events during this time were a November 15 2014 subplinian eruption of Pavlof, and two explosive eruptions of Shishaldin in January 2020. Neither of these two eruptions were followed by wet conditions. However, they happened close to the winter solstice, when there was little solar irradiance so far north. If there is not much sunlight to reflect into space due to the days being short and the sun’s angle low on the horizon then the extra cooling and any secondary effects on the atmosphere of the volcanic aerosols are expected to weaken.
In this article, I put together 6-7 cases of eruptions in the Aleutians and Kamchatka that preceded anomalously wet weather in Spain by about 30-40 days. The majority are VEI 3 subplinian eruptions from basaltic and basaltic-andesite stratovolcanoes, plus two andesite VEI 4 events (Kasatochi and Shiveluch). The rain was punctual in most cases, except for Kasatochi and Shiveluch where it persisted for almost two months. The volcanoes described here are more than 50 degrees north of the Equator, where the tropopause can be very low, whilst the volcanoes are tall Pavlof (2515 m), Shishaldin (2,857 m), or Klychevskoy (4,754 m). It’s easy for them to make stratospheric injections of volcanic gas, and any effect can be increased due to the aerosols staying within the northern hemisphere. I think that small transient cooling, induced by these eruptions north of the jet stream, may have triggered intrusions of mid-latitude cyclones towards more southern latitudes, affecting Spain and bringing rainy weather. Cooling of the atmosphere I think might enhance convection given how the ocean takes longer to cool, so that warm humid air over the oceans might become unstable. Temperature differences between air masses of higher and lower latitudes are associated with the jet stream speed, so another possible mechanism is that volcanic aerosols alter this balance and affect the jet stream. This speculation is just based on what has transpired in Spain and I would be very much interested to know if other places have also felt any possible effects from the eruptions of this year of the northern Ring of Fire. And of course, this is still speculative, no connection confirmed yet, but I think it looks promising.
Much attention has been given to catastrophic volcanic winters by giant explosive eruptions. However here I show evidence that smaller eruptions could be having significant effects on weather. And even beneficial effects. Spain started this year with a serious drought situation. Although the drought probably hasn’t fully subsided, the abundant rains of summer and autumn this year have brought relief to much of the country. The summer rains probably weakened this year’s fire season, which was thankfully relatively uneventful in the peninsula. Finding out about this is a fascinating surprise for me, yet another new way I will be looking at volcanoes from now on, and an elegant way for two of my passions to come together.
Links to data
I have relied on seasonal analysis of the AEMET to judge the rainfall anomalies over 2023, particularly on the May 20-July 7 rains:
Copernicus Sentinel-5P sulfur dioxide maps have been helpful in understanding the eruptions of 2023:
The following database of Spanish supercells since 2011 already shows data for hail events during the year 2023 although doesn’t yet list the supercells:
The Albarracin station data can be viewed in the following link, its location on a mountain range means it was more affected by the May 20-July 7 rains, which were often thunderstorms that developed over high areas:
I used this weather station to view the rainfall events from September to December in Madrid, since the El Retiro station seemed to have some problems during the time:
Madrid Airport station data: