Unsettled weather continues

Kilimanjaro was visible from Moshi this morning, for the first time in awhile, following heavy rain last night. This has been a wet month on the mountain! Thanks to Simon Mtuy for sending the image and report.

Rain, snow & cyclones [updated]

For several years now, I have corresponded with Timba at Ahsante Tours & Safaris about a relationship between Kilimanjaro-region precipitation and cyclones in the south-west Indian Ocean. On Monday afternoon (10 Feb.) he wrote that it was "currently raining big time here, and has been for the past weekend".

So, here is a synopsis of what was happening in the ocean. Tropical Storm Edilson had developed by 5 Feb. Another Tropical Depression formed on the 6th, which became Tropical Storm Forbane on 8 Feb. This quickly developed from Moderate to Severe that day, by which time Edilson was rapidly moving south. Fobane became subtropical by the 10th, and also moved west. Here is a map of the storm's positions on the afternoon of 8 Feb., from the Severe Weather Information Center of the WMO (World Meteorological Organization):

At the summit of Kilimanjaro, snow accumulation was considerable over the weekend (8 & 9 Feb.). Measurable accumulation also occurred in the days prior, particularly 4 Feb. The graph below shows daily snow accumulation on the summit glaciers, with our data currently extending only until noon on 10 February.

Here is a beautiful map of regional circulation at 500 hPa (summit level) from Earth, based on NOAA data. This is a screenshot showing the situation at 15:00 local time on 8 Feb., with winds from 315° at 21 km/hr (5.9 m/s) at Kilimanjaro level (indicated by the small green circle). Data sent by telemetry from the AWS correspond remarkably well with this NCEP value, averaging 6.3 m/s from 334° for the period noon to 16:00 local time.

A snowfall total of ~20 cm through 9 Feb. is an important event at the arid summit of Kilimanjaro. This time of year is more typically associated with a brief dry interval, while the ITCZ is north of the mountain. It is probably a safe hypothesis that this - and similar snowfall events - are not associated with either the short- or long-rain seasons. Nonetheless, they are tied to regional atmospheric circulation and activity in the south-west Indian Ocean. They are very important in terms of mass balance for the glaciers, and are also to the safety and success of porters, guides, and clients on the mountain. Lastly, with further analysis the impacts of cyclones at this time of year should be relatively easy to forecast. Thanks again, Timba!

[UPDATE 2/12: Simon Mtuy of Summit Expeditions (SENE) wrote that his group was within the caldera ("Crater Camp") on the night of 8 or 9 February. As is sometimes the case, the amount of snowfall appears to have been greater within the crater than on the glacier. He writes "they have huge snow through the night, and the tents were about 1 m under the snow." To reach the summit they had to cross the crater to Stella Point and then follow the ridge to Uhuru Peak, rather than ascend directly from camp. In the text above I mention that unexpected snowfall has consequences for both humans and the glaciers. Simon writes that this event created big problems for the porters, who weren't expecting snowfall and either did not have sunglasses or had some which provided inadequate protection against the highly-reflective new snowcover.]

Short-rains synopsis

On the Northern Ice Field the 2013 "short rains" were right on schedule, with snow accumulation beginning ~5 November and continuing intermittently until ~17 December. Net accumulation of snow at the weather station was 49 cm, which is more than the glaciers typically receive during this seasonal wet period. Settling, transformation and ablation of this snow in the month following (i.e., to mid-January) lowered the surface by ~16 cm. Nonetheless, through the mini dry season before the "long rains" begin in March (typically) the glacier surface will remain relatively bright, causing much less energy absorption than that following years when the "short rains" are meager or fail altogether.

The two sets of Landsat 8 images below depict the regional- and local-scale impacts of the "short rains". In the top set (click to enlarge), Kibo caldera can be located as the small blue area (i.e., ice and snow) just below and to the right of image center; resolution in both cases is 30 m. The first scene (30 October) was acquired shortly after our fieldwork, when virtually no seasonal snow was present at the summit (thin, high clouds partially blur the image slightly). There is little snow within the caldera in the middle scene, although remnants of the snowfall mentioned in an earlier post can be seen. In the 18 January 2014 scene, considerable snowcover can be seen in the caldera and on the flanks of Kibo - even though the short rains ended in mid-December at the summit; perhaps they continued longer at lower elevations. Finally, note the progressive response of vegetation around the mountain to short rains precipitation; an ephemeral lake is visible to the north of Kilimanjaro on 18 January.

The following images are cropped from the full Landsat scenes, providing greater detail of Kibo and the caldera (click to enlarge).

And yet more snow!

More fresh snow on Kibo this morning, after "big rains" last night in Mbahe (near Marangu gate). Thanks to Simon at SENE... better than any webcam!

More snow

Snow accumulation and the 2013 short-rains are well underway on the mountain! Simon Mtuy sent the image above, taken late yesterday after he ran home to Moshi from Millennium Camp(!) The snowline here looks to be slightly below ~4,500 m.

2013 Fieldwork Images

A gallery of images depicting our recent fieldwork is posted here. (Viewing these requires the freely-available Adobe Flash Player web browser plug-in, which usually works consistently across browsers on a broad range of devices.)

The objectives of our work all pertain to climate and glacier research at the summit:  recovering climate data from automated weather station instrumentation; inspecting, servicing, repairing and replacing equipment; and making both observations and measurements of the summit glaciers. However, other aspects of the fieldwork are disproportionately represented by the gallery - primarily because carrying out the research objectives requires staying alive and functional for several days at an elevation of 6,000 meters (19,000 feet). Doing this necessitates ascending slowly to allow both our bodies and those of our Tanzanian helpers to acclimatize (~6 days). Once on the summit glaciers we then become too busy and/or cold to spend much time taking photos!

For 2013 work - as the images illustrate - we began in Arusha, traveled to West Kilimanjaro, ascended the Lemosho Route, slept 3 nights at the summit, and descended via Millennium Camp to Mweka. Logistical support is required of all groups on the mountain, even with research permits, and ours was provided by SENE (Summit Expeditions and Nomadic Experience). This support allows us to maximize our time preparing for and carrying out the research.

As always, we would like to thank everyone at SENE for another safe and productive round of fieldwork - and for the two-way transfer of knowledge that characterizes these experiences. We would also like to acknowledge invaluable assistance from the staff at Tanzania Wildlife Research Institute (TAWIRI) who oversee and manage all wildlife and environmental research in Tanzania, the staff at Tanzania National Parks (TANAPA), and the many wardens and other staff at Kilimanjaro National Park. Asanteni!

Snow!

In an early-October entry I mentioned a late-September snowfall event which resulted in ~10 cm of accumulation on the Northern Ice Field, ending 4+ months of ablation. Prior to the September snow, surface albedo had dropped below 0.5 and net radiation receipt was increasing with the seasonal increase in solar irradiance.

Brightening of the glacier surface with the September snow prevented any further mass loss for at least 2 weeks. During this time the snow was transformed by melting and re-freezing to create the bright, icy surface we encountered upon our visit beginning 24 October, as shown in the photo above. Simultaneously, as demonstrated by other evidence, sublimation was removing some of the mass added by September snow.

The next snowfall occurred during our descent (27 October), although we received no rain low on the mountain and were not aware of the snow until the mountain emerged from clouds in the evening.

Today we received a note from Timba at Ahsante Tours & Safaris that more continuous precipitation has begun on the mountain, with fresh snow visible at the summit, and heavy rain occurring during afternoons at lower elevations. Our telemetry data confirm Timba's information, with higher humidity and snowfall especially during the interval 5-9 November. Snowfall was especially heavy on the Northern Ice Field late on 8 November into the next morning, with an average of 14 cm recorded by our 2 sensors. So the glacier-surface albedo has increased yet again, and this event may have been enough to bring thin snowcover to the crater.

As always, we welcome and encourage sharing of any photographs and/or snowcover observations!