Seasonal change

Most years, there is a short dry season on the mountain in between the short and long rains, typically centered on February. In addition to lower humidity, this interval is identifiable in AWS measurements as lowering of the glacier surface, due to both ablation and settling of any snow accumulating during the short rains.

This year the Northern Ice Field surface began lowering on 31 December and continued until 19 February, dropping a total of 27 cm. Very little if any snowfall occurred during this interval. Then, 3 days of meager snowfall suggested that a seasonal change was beginning. Precipitation began accumulating again on the 25th, and by the 27th it appears that a more significant snowfall was underway. However, this is our most recent telemetry. Stay tuned to learn whether the long rains are beginning a bit early this year.

January ablation

 

The 2011 short rains on Kilimanjaro summit continued until the very end of December, with most snowfall occurring during the second half of November. For the season, net snow accumulation on the Northern Ice Field amounted to ~30 cm.

The image above shows an easterly view across the crater on 28 December, just prior to the year’s final snowfall event; snowcover in the crater is often “patchier” than that on the glaciers (credit:  Rohun Gholkar). On the graph, the timing of this photograph is indicated by the light blue star. After departing the summit, Rohun’s team encountered sleet and rain, which was likely associated with 3 days and ~10 cm of snowfall on the glacier (see graph; dashed line indicates midnight on New Year’s Eve).

Very little snowfall occurred during January 2012, as shown in the lower figure, resulting in a net surface height lowering of 19 cm. Two 48-hour intervals of rapid lowering are highlighted by red lines on the graph. Based on weather station measurements received by satellite telemetry, these seem to have been intervals of enhanced sublimation. We cannot be certain, but this interpretation is based on the following, which pertains to both intervals:  air temperature was 2.0 – 2.5° C lower than normal for January, the sky remained mostly clear, wind speed was ~50% higher than normal (directly from the east), and relative humidity averaged a very low 20-25% instead of ~60% as on a typical January day. Together, these are perfect conditions for sublimation.

Any first-hand observations and/or photos from the summit area during these dry intervals (Jan. 1 & 2, Jan. 22 & 23) would be greatly appreciated!

Heavy rainfall in Dar es Salaam

Dar es Salaam experienced extremely heavy rainfall yesterday, with one source reporting a 24-hour total at the airport of 233 mm. An article in The Muslim News quotes a Tanzania Meteorological Agency (TMA) source reporting 156.4 mm. Either one is apparently the highest 24-hour amount since the mid 1950s.

Flooding and lightning strikes have killed at least 20 people according to the BBC, and left thousands homeless. The event has reportedly crippled the city of Dar, destroying considerable infrastructure. TMA forecasts the heavy rains to continue over the region.

Snowfall data and accounts from Kilimanjaro are not available yet. Being convective in nature, the heavy rainfall may not be widespread.
 
[UPDATE 12/30 & 1/3/12:  Snowfall began at the station on Wed., 28 Dec. and continued to the 31st. Telemetry indicates ~11cm of accumulation for the event, which is certainly a significant snowfall by Kilimanjaro standards. Tim from SENE was recently on the mountain, so perhaps we'll have a first-hand report soon.]

East African Drought

The Weather Underground blog has a helpful discussion of the drought which so terribly impacted East Africa this year, and author Jeff Masters points out that it was 2011's deadliest weather disaster. He annotates several figures from NOAA's Climate Prediction Center (above), showing that the drought was concentrated to the north of Kilimanjaro. Likewise, the most anomalous rainfall through the currently-underway short rains season has also been further north. On the mountain, the relative snowfall amounts are consistent with regional patterns depicted in the figures.

Masters also provides some thoughts on East Africa's future vulnerability. Considerable uncertainty exists between measured precipitation trends, and that predicted by models due to changes in Walker circulation. Kilimanjaro snowfall and glacier mass balance measurements support evidence from station data for steady drying of the climate in recent decades.

Fieldwork photos

Finally... images from September-October fieldwork have been processed, and a selection is now posted here! This trip was especially enjoyable and productive, as hopefully conveyed by the photos.

More ice sampling

In 2009 we collaborated with researchers at Paul Scherrer Institute (Switzerland) to test new techniques for dating glacier ice (more here). Encouraging results justified further investigation, which was part of our recent fieldwork. Here is a short clip illustrating this year's approach to sampling; note that September weather wasn't quite as dry as normal!

Early Short Rains?

A recent posting here discussed a multi-day August snowfall event which resulted in ~5cm of accumulation on the Northern Ice Field. The next month or so was relatively dry, as typically the case at this time of year, with only about 14cm of ablation due to relatively high albedo following the mid-August snowfall event.

At the Northern Ice Field AWS, the next snowfall event appears to have occurred on 20 September, the day our team arrived in Tanzania. More snowfall was recorded on the 23rd, when we waited - in the rain - for our final permits at park headquarters in Marangu. Ascending the mountain we encountered light precipitation on a few days. However, while setting up camp in the crater on the 29th, a snow squall brought another 3-4cm of accumulation to the glacier.

The next snowfall occurred during the night of October 1st, apparently associated with tremendous convection visible to the East and accompanied by lightning and thunder, the most we have ever seen from the summit. By morning, camp was blanketed by a uniform 6cm of new snow, with more variable accumulation on the glacier. Rather fortuitously, the AWS had been reset into the ice the previous day; disturbance of the glacier surface is unavoidable during this process. Perfect timing for a snowfall event!

Telemetry from the AWS indicates continuing accumulation since we departed on the 4th, with snowfall on the 5th and a multiday event from ~11-15 October. With net accumulation of ~5cm to mid-October, little additional ablation is likely in the next few months - especially if the Short Rains have indeed begun.

Finally, anecdotal reports from around the mountain support the idea of an early Short Rain season. For example, a note from 17 October indicated "lots of rain on Kilimanjaro" which made climbing very difficult for some clients (Ngorogoro Camp and Lodge). Also from the 17th, several reports of rain "every day" in Arusha. In the week prior, perhaps coinciding with the multiday event on Kilimanjaro, a storm over Kibwezi, Kenya (just north of Kilimanjaro) "was so intense that it prevented small aircraft from going to the coast."