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.