Late September into October is typically a period of transition on Kibo between the dry season and Vuli, the short rains. At this transitional time, considerable snowcover sometimes remains in the summit caldera - but in other years the mountain is bare. Hans Meyer wrote of this in 1891: "In October, when all the snowfields had disappeared, there was likewise comparatively little snow to be met with on the ice-cap".
In the past couple weeks, our friend Simon Mtuy and ultrarunner Kelly Halpin were up and down the mountain a few times and visited summit glaciers. Only very small patches of residual snow were found at the top (perfect for running). Back at the base afterwards, Simon documented a rapid transition-season change in snow cover over the course of one day, 22 October. Prior to snowfall overnight on 21-22 October, the dark volcanic rock had been absorbing a high proportion of the intense solar radiation high on the mountain, for weeks. Meyer also wrote of this: "...the dark rock is sometimes heated to such a degree that the [emitted longwave] radiation may be directly felt, and even seen in the vibration of the atmosphere over it's surface".
Simon's pair of photos nicely shows the impact of heat stored by Kibo's rocks and sand, in an otherwise extreme climate. Within the 11 hours between the photos, much of the snow evaporated and melted - while the air temperature almost certainly remained below freezing.
Thanks Simon for your observation, and for sharing the documentation!
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