Summit snowcover - late July

Recent posts have detailed the extent of snowfall during the 2012 Long Rains, which included a couple atypical events during June. Below are some images from the summit taken at the very end of July, snowing snowcover on the crater rim and within the crater.  Imagine the effect of this snowcover on energy exchanges at the crater surface, when perhaps only 30% of the intense incoming solar radiation is absorbed rather than roughly 80% without snow. The effect on people climbing the mountain is likewise severe, exposing skin to radiation from all directions; big sunhats offer protection only from incoming sun!

These images were shot by Peter Greig during a reconnaissance climb for the project Wings Of Kilimanjaro (WoK). In early 2013 a large number of pilots will paraglide and hang-glide off the top while raising a substantial amount of money for Tanzanian charities. Additionally, their goal is to "reinforce the universal need for humanity, compassion and generosity inherent in all of us". More photos from the reconnaissance are available on facebook.

Image captions:

1. late afternoon in the crater, with Uhuru Peak to the left and the Furtwängler Glacier to the right
2. nearing Uhuru Peak, showing snowcover on the ridge above the southern glaciers
3. morning within the crater, walking East between Furtwängler Glacier and the descent from Stella Point; note some topographic shading here
4. looking North across the crater from high on Uhuru Peak; "crater camp" is visible in the foreground by the Furtwängler Glacier fragments, with the Northern Ice Field in the distance. At this time of year, when the sun is in the northern hemisphere, north-facing slopes such as those above crater camp are the first to become snow free.

Peter Greig photo, Wings Of Kilimanjaro

Peter Greig photo, Wings Of Kilimanjaro

Peter Greig photo, Wings Of Kilimanjaro

Peter Greig photo, Wings Of Kilimanjaro

June & July weather

A summary of the previous month's weather at Kilimanjaro's summit is typically posted (here) within the first few days of each month. This year the June synopsis didn't make it in time, due to travel for other fieldwork. As usual though, the temperature fell slightly and the average humidity dropped relative to May, but two other reasons made the month noteworthy. First, June saw a net increase in the glacier surface height. Although the net change was only +4 cm, this was the first June in which accumulation was greater than ablation. In comparison - now that the dry season is underway - lowering during July amounted to ~16cm.

Also in June 2012, the daily maximum of incoming solar radiation was on average lower than in any month of the past 10 years. June irradiance is always relatively low of course, being at 3°S latitude, yet the new record this year is likely due to both greater cloud cover than normal - and to snow on the radiometer dome.

June snowfall

Don't expect to see bare glacier ice on Kilimanjaro's glaciers anytime soon - at least not on horizontal surfaces at the summit. Higher than normal snowfall has continued into June, with ~7 cm accumulation on the Northern Ice Field June 9th and 10th and another event beginning June 22nd. Snowfall this late is quite unusual, as the long rains typically finish by the end of May.

For the glaciers, additional new snow will keep albedo high and reduce the absorption of incoming solar radiation. Less absorption will result in less ablation during the forthcoming dry season. No, this does not mean that recession of Kilimanjaro glaciers has ended; 2011-12 snowfall merely demonstrates the expected interannual variability (which our measurements seek to quantify and understand). For travel on the glaciers, the amount of accumulation since November (~75 cm) will likely result in extensive penitentes towards the end of the dry season (i.e., Sep - Oct).

Telemetry data from Kilimanjaro have been examined only to June 24th due to other fieldwork obligations. Stay tuned for an update towards the end of July!

A Fairy Tale comes true!

After more than 12 years of meteorological measurements on Kibo's Northern Ice Field, the most-recent period October through May has - for the first time - followed the expected pattern:  'short rains' during November and December, a brief dry interval into February, substantial and prolonged 'long rains' in March-April-May, and then commencement of an extended dry season by June. The figure above details this pattern through increases in glacier surface height (snowfall) as well as decreases (ablation).

Typically, only a June beginning of the dry season has been reliable, as noted in an entry yesterday. In some years Masika brings only minimal accumulation to the glaciers (e.g., 2001, 2005, 2009 or 2011), sometimes it is Vuli which fails (e.g., 2005 or 2010), sometimes Vuli snowfall exceeds that of Masika (e.g. 2006-07), and sometimes nearly-constant-yet-modest accumulation occurs from November to June (e.g., 2009-10).

Variability in the seasonal timing and magnitude of precipitation at Kilimanjaro's summit is the norm, despite an annual cycle of humidity which follows the 'expected' pattern rather closely. Both small- and large-scale aspects of atmospheric circulation modulate the humidity pattern and influence snowfall, and the timing and amount of snowfall is hugely important to glacier mass balance there. Documenting the inter-annual variability of precipitation on Kilimanjaro and measuring the impact on glaciers is why we keep the AWS going!

2012 dry season begins

One of the most consistent elements of climate on the Northern Ice Field has been cessation of Masika (long rains) by the beginning of June. This year was no exception, with accumulation of snow ending ~17 May. Another extended dry season has begun on Kilimanjaro.

Don't expect to see glacier ice exposed at the surface anytime soon however, as considerable snowfall occurred in the 6+ weeks prior. This followed a notable event in early March, and a snowy short rains (especially November). Indeed, there has been 75 cm of net snow accumulation on the glacier surface since early-October fieldwork! During the forthcoming dry season this clean, relatively-bright snowcover will reflect much more solar radiation than the underlying, decades-old ice surface would, effectively reducing ablation of horizontal surfaces. As a result, large areas of the glaciers are likely to remain snow covered through the dry season.

By September, penitentes could be well developed on the glaciers. Although both beautiful and fascinating, these will render glacier travel more difficult during September fieldwork.

More on April precipitation

"The rains this year began promptly on the 1st of April." So begins a column by Gareth Jones on 11 May, titled "Kenya:  Wet in the Wild" and published by AllAfrica Global Media.

At the summit of Kilimanjaro, seasonal precipitation in the form of snow began at exactly the same time, as the screen shot below illustrates. Four-hourly data by telemetry are shown here as circles, from 2 different sensors. The red line simply smooths out a diurnal cycle, and y-axes units are meters of snow accumulation.

If snowfall on the mountain continues through the rest of May, as the Kenya Meteorological Department is forecasting for rains to the north, the 2012 long rains will be one of the snowiest on the Northern Ice Field since our measurements began in 2000.

Snowy, calm April 2012

 Snowfall continued through the final week of April, bringing total accumulation to 44 cm. This is the most snow for any April since our records began in 2000. Humidity was high, incoming solar radiation was low, and April 2012 established a new record for the lowest mean monthly wind speed, at only 10.2 km/hr! All monthly values are provided here.
[UPDATE 5/7: The photo above was taken on 1 May, clearly illustrating the late-April snow (courtesy Simon Mtuy).]