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!