Persistence of atmospheric dust, Novarupta, Mt Katmai eruption 1912

Posted: May 27, 2013 by tchannon in atmosphere, climate, general circulation, Measurement, volcanos


Remains of Mt Katmai, Katmai Caldera taken from the air.
Image courtesy Pam McPherson (enhanced TNC)

The most massive volcanic eruption of the 20th century came during June 1912 in Alaska, explosive, heard 1,500 miles away. A good deal of the mountain vanished.

Mt Katmai is one of several peaks making up the Novarupta.


AVO geologist Tina Neal shows the thickness of ash from the 1912 eruption of Novarupta at Brooks Camp in Katmai National Park, 50 km (30 miles) upwind of the vent.
Image courtesty Pam McPherson

“Description: Fierstein and Hildreth (2001) provide information about the magitude of the 1912 eruption at Novarupta and Katmai: “The world’s largest volcanic eruption of the 20th century broke out at Novarupta [see fig. 1 in original text] in June 1912, filling with hot ash what came to be called the Valley of Ten Thousand Smokes and spreading downwind more fallout than all other historical Alaskan eruptions combined. Although almost all the magma vented at Novarupta, most of it had been stored beneath Mount Katmai 10 km away, which collapsed during the eruption. Airborne ash from the 3-day event blanketed all of southern Alaska, and its gritty fallout was reported as far away as Dawson, Ketchikan, and Puget Sound [see fig. 21 in original text]. Volcanic dust and sulfurous aerosol were detected within days over Wisconsin and Virginia; within 2 weeks over California, Europe, and North Africa; and in latter-day ice cores recently drilled on the Greenland ice cap.”
Alaska Volcano Observatory (opens new window, a great deal of information)

A question has arisen on the degree and duration of the solar obscuration by dust lofted into the atmosphere. Quoted above does not mention crossing the equator.

By chance I have references to the Mt Kamai eruption in contemporary scientific papers dealing in solar radiation and atmospheric transparency.

Both of these are in Smithsonian Institution collections available online but are difficult to work with, are scans of old material.


Image courtesy Alex Noriega, Wikipedia, click image for details

Los Angeles from Mount Wilson, near the observatory.


Annotated polar view of the volcano and observatory locations

There is brief mention in a work on solar periodicity in TSI data (solar constant), which is hardly surprising since it led to 1912 being omitted from the work at Mt Wilson, USA by Abbot, the data was too variable (no mention of too obscuring, nor of low light levels)

These pioneers could measure accurately enough to see periodic solar variation but is not the subject here.

Work was also being done by Fowle: – “THE ATMOSPHERIC SCATTERING OF LIGHT
By Frederick E. Fowle” — Smithsonian Miscellaneous Collections, Vol 69, No. 3

This commences

Rayleigh has indicated how the amount of energy scattered from a beam of light within a gaseous medium may be used to determine the number of molecules in that medium. It will be shown in what follows that, whereas the application of the process to the enumeration of the number of molecules in dry air leads to normal results, its application to atmospheric aqueous vapor leads to an anomaly.


It will first be assumed that the composition of dry atmospheric air remains in general practically unchanged from day to day above an altitude like that of Mount Wilson
(1,730 meters) where the air is nearly free from dust contamination. The amount of aqueous vapor, however, changes many-fold.

And when this work was done

The observations taken each year at Mount Wilson (generally during the months from June to November, inclusive) have been subjected, year by year, to this refining process.

Data runs 1910, 1911, 1913..1916, with no 1912.

During 1912 owing to volcanic dust, this scattering by dust particles increased to about 25per cent on the haziest days. It had decreased, on the average, to 2.6 per cent during 1913, and 1 per cent during 1914 and 1915. During 1916 it increased again to an average value of 3.2 per cent producing a marked streakiness in the sky as seen at dawn at Mount Wilson.

Later, on page 11

There is to be expected above the altitude of Mount Wilson (1,730 meters) a certain amount of what has been called “dry haziness” to distinguish it from a similar haziness associated with aqueous vapor. Before the Mount Katmai eruption of 1912, during 1910 and 1911. this caused a loss of only about half of one per cent from the incoming solar radiation when the sun was in the zenith. The mean of the coefficients for these two years ( table 1 ), given in the lower line of that table [omitted, not the subject here], may be taken as a close approximation to the transparency of dry. dust-free air. During 1913, this loss due to dry haziness decreased from its enormous value of 25 per cent just subsequent to the Mount Katmai eruption to about 3 per cent and during 1914-15 to about 1 per cent, but it increased again to 3 per cent during 1916.

Ends with

Astrophysical Observatory,
Smithsonian Institution,
Washington, D. C,

So there is something contemporary from the 1910s. There was a heavy dust cloud at Mt Wilson south of Alaska but it had largely vanished a year later. Given Alaska is in the far north the effect will be most visible as far as air temperatures are concerned in the heavily monitored northern temperate zone but I wonder whether there was much dust south of the equator where also there were relatively few monitoring stations.

In addition, occurring during June an effect would take a bite out of summer sun where this is about to start to diminish into autumn, with I suppose little northern effect during the cloudy cold winter.

Post by Tim Channon

  1. craigm350 says:

    Reblogged this on CraigM350.

  2. craigm350 says:

    Tim, re: your comment on the Murray Salby thread
    Volcanic effects seem dubious and is part of what I am looking at in detail.
    I had the same nagging thought reading comments (the same pause came over me reading a recent WUWT post) as this post definitely didn’t pass me by 😉
    Wonder if Tolbachik in Kamchatka, going since Jan, may provide any data to see what comes up in temp/cloud/emissions figures (if any)…unless Vuk has something already? 🙂

  3. tchannon says:

    What is nagging at me on this is whether the eruptions are an excuse to explain away otherwise unexplained wiggles.The 1912 eruption was not that dire in the north and there is mention it did not cross the equator at all, yet global effect is claimed for a number of years isn’t it?

    I’d not looked at any time series. Since I have the facility here, already on disk,.

    Oh dear.

  4. […] few days ago I posted an article on Mt Katmai which shows the minor effect on turbidity (clarity of the atmosphere). I hadn’t looked at […]

  5. tchannon says:

    I was wrong, I have had Mt Wilson atmospheric data right through the eruption on disk here for nearly 4 years!

    The data is not formatted as described, guesswork stuff. Anyway, yes there does seem to be a dip, which is I think for a spectrobolometer and if so we have from near UV through 1.6micron, except the number of columns is wrong.