Thursday, December 22, 2011

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.]

Tuesday, December 20, 2011

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.

Wednesday, October 19, 2011

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."

Tuesday, October 11, 2011

Fieldwork!

We are just back from a productive trip to the mountain, spending 6 days at the summit glaciers. Typically, the dry season extends into October, but this year, rain and snow were a near-daily occurrence. One evening, snowfall accompanied by lightning and thunder collapsed our dining tent. Such variability keeps the work interesting!

Our primary objective was recovering data, changing-out instruments, and servicing the weather stations for another year of autonomous operation. For example, surface lowering of the ice (due ablation) required us to lower one of the stations further into the glacier. This was accomplished by considerable chiseling of ice, to create a one-meter deep hole. We also measured and re-drilled mass balance stakes, conducted GPS surveys, and re-photographed glaciers. This year we recovered 48 additional ice cores, which were kept frozen until reaching the laboratory freezer.

A selection of images from the fieldwork is below. For a day-by-day account of the adventure, check the "Kibo2011" group on Facebook. Additional images can be seen here.

Special thanks this year to Carsten Braun (Westfield State University), Tanzania National Parks, the Tanzania Wildlife Research Institute, and to Simon and crew at Summit Expeditions and Nomadic Experience (SENE). All were extremely helpful, for which we are most grateful.

Image #1 (above).  Northern Ice Field margin.

Image #2.  Kersten Glacier, just below Uhuru Peak. One year ago the upper and lower sections were still connected!

Image #3.  Little Penck Glacier, continuing to retreat and now clearly separated into two parts.

Image #4.  Northern Ice Field (distant) and the two sections of Furtw√§ngler Glacier (foreground). Compare the Furtw√§ngler image with that from 2002 (click here).

Image #5.  One component of the UMass station, including instruments compatible with the U.S. Climate Reference Network (CRN). Note mass balance stake to left.

Image #6.  The original UMass AWS, with Uhuru Peak in distance. Barely visible against the rock background is the "RimeCam" - acquiring 3-hourly images to help assess measurement quality.

Image #7.  Swiss collaborators from Paul Scherrer Institute working through heavy snowfall, coring the Northern Ice Field's vertical wall. Our objective here is refining the history (chronology) of glaciers on Kilimanjaro.

Image #8.  A less-fortunate visitor to Kibo's glaciers... reminding us how important safety is at nearly 6,000 meters elevation.

Friday, August 19, 2011

August Update

This pair of images provides a glimpse of how the Northern Ice Field has changed over the past ten months. Last week the surface was relatively flat (left), and ~70 cm lower than when penitentes covered the glacier in October of last year (right).
October's penitentes were the result of sublimating snow from the previous wet season (i.e., masika or long rains, March-May 2010). Subsequently, little snow accumulated during either the 2010 short rains or the 2011 long rains (although there was an important event in February, see details). Less snow results in higher net radiation at the glacier surface, leading to ablation.

The right-hand image shows the AWS after repositioning the tower into the ice; note the lowest of the three enclosures, gray in color with the blue strap barely visible. Ten months later the same enclosure is well above the surface, with nearly half the tower base section exposed.

Paradoxically, the glacier surface appears relatively bright in the August image (i.e., high albedo). Two observations help account for this, and indicate why there hasn't been even more than 70 cm ablation. The first is a SPOT satellite image from 17 June (courtesy Nicolas Cullen) showing partial snow cover within the crater. This snowcover - likely to an even greater depth on the glacier - may have been residual from the long rains and/or the result of snowfall only 8 days earlier, a relatively uncommon event in June. The second observation is from the photographer of the left-hand image, Dr. Clavery Tungaraza (Faculty of Science, Sokoine University of Agriculture in Morogoro, Tanzania). In crossing the crater on 8 August, he reported walking through ~15 cm of snow showing no signs of melting, in dry, very cold weather. Again, some of this snow may have been residual, and some may have been associated with a couple small snowfall events during July. The very next day, as Clavery was desending, telemetry from the AWS indicates a multiday snowfall event began!

Nonetheless, dark old ice is just beneath the mantle of snow or superimposed ice creating the bright appearance in last week's image. In another two or three months, it is quite possible that the one-year net loss of ice from the Northern Ice Field surface may amount to a meter or more. This would make 2010-11 among the most negative years since 2000, perhaps not surprising in the context of drought impacting the Horn of Africa just to the north.

[UPDATE 9/4:  The snowfall event mentioned above continued from 9 to 15 August and resulted in net accumulation of ~5 cm. This brightened the glacier surface and temporarily suppressed ablation for a week. Net surface lowering for the month was similar to July at ~8 cm.]

Friday, August 5, 2011

Kilimanjaro Glaciers

Just over a century ago, glacier ice encircled the summit crater of Kilimanjaro, with perhaps only the inner Reusch Crater free of ice. (On the image above, the Reusch Crater is the middle, or second largest, of the three depicted. For scale, it is ~800 m in diameter.) Although their areal extent is now greatly reduced, as evident on this July 2009 image, the glaciers remain both beautiful and scientifically fascinating.

I wrote an overview of the mountain's glaciers that has just been published by Springer, as a contribution to their new Encyclopedia of Snow, Ice and Glaciers. The Kilimanjaro chapter briefly describes the history of glacier research on the mountain, and describes what makes these ice masses unique. It is available here.

Friday, July 29, 2011

Dry Season Ablation

Dry conditions continue at the summit, likely reflecting dryness on larger and longer time/space scales. Telemetry from the weather station reveals only 3-4 snowfall events since October, with the largest being that in mid-February as previously noted. One minor snowfall of a few centimeters in June served to brighten the surface slightly, enhancing reflection of solar radiation. Nonetheless, the surface lowered by ~5 cm during June and has increased this month.

Just north of the Kilimanjaro region, drought conditions are contributing to severe famine, with over 10 million people in need of humanitarian assistance. Although suffering and displacement are greatest in Somalia, large areas of Ethiopia and Kenya are struggling with food insecurity. A map posted on the Reliefweb site shows the geography of the problem as of mid-July; Kilimanjaro is just south of Kenya's southernmost Emergency Zone on the map. Another graphic from the Famine Early Warning Systems Network provides further details.

[UPDATE 8/8:  NASA's Earth Observatory website has been covering the developing drought since last autumn when rainfall was below normal, and has posted a series of SPOT and other images. There is also an overview discussion on how the tropical Pacific is involved, through La Nina teleconnections.]

Thursday, June 2, 2011

Synopsis of 2010-11 wet seasons

By the first of June an extended dry season is typically underway at the summit of Kilimanjaro, one of the most reliable features of a climate with considerable interannual variability. In a regional context, this dry season follows the "long rains" (Masika) which generally encompass much of the 3-month interval March through May. A second, shorter wet season (Vuli) happens in November-December and is somewhat more variable in magnitude and timing.

This year, neither Vuli nor Masika resulted in net accumulation, which will likely result in tremendous ablation on Kilimanjaro's horizontal glacier surfaces during the next 5-6 months. Just how little accumulation was there? Well, between 1 Nov. and 1 June (encompassing both accumulation seasons), a 30 cm net lowering of the Northern Ice Field was very consistent between the two sensors (i.e., -28 and -32 cm). For the same interval of 2009-10, the surface increased by over 60 cm.

During the brief dry interval between Vuli and Masika (usually occurring during January and/or February), ablation also predominated, except for one snowfall event detailed earlier that turned out to be the largest snowfall event of either 2010-11 wet season, and the largest since the previous May.

Tuesday, April 5, 2011

More humid... but no accumulation for March

During March, there was no snow accumulation on the Northern Ice Field. Telemetry indicates a couple minor snowfalls which weren't recorded by both of the ultrasonic sensors, and then an event of 5-10 cm on 18 and 19 March. Nonetheless, the average net change in surface height amounted to 0.0 cm.

Atmospheric humidity increased during the month however, so accumulation during April and May is more likely. This is the typical pattern, as the long rains (Masika) get underway with passage of the ITCZ over the region (see here, for example). February is rather dry on average, relative to the prior 3 months (NDJ), with the mean vapor pressure increasing 0.2-0.3 hPa from February into March. This year, the mean relative humidity increased by 20 percent; vapor pressure data are not yet available.

Monday, March 21, 2011

new video

Here is a new video produced by Caleb Medders at NBC Learn about glacier recession in general, including some brief thoughts on Kilimanjaro.

Monday, February 21, 2011

Snow!

A 3-day snowy interval was underway at this time last week, bringing over 50 cm of snow on Tuesday to Lava Tower camp at the 4,600m level - and ending an extended dry period. This snow required some climbers to turn back, according to Simon Mtuy at Summit Expeditions, as continuing up the mountain became too difficult. We hope to post photos of the event here shortly.

At the summit, snow began accumulating on Sunday the 13th and continued into the 16th. Telemetry indicates that the event brought somewhere between ~19 and 28cm to the glaciers. Through noon today (local time) the new snow had settled and ablated by 5-10cm, over the past ~5 days.

Hopefully this snowfall brought much-needed rainfall to northern Tanzania. Perhaps the "long rains" are beginning, a bit early?

[UPDATE 3/4:  Below are a couple images as the event was beginning. The first illustrates slight accumulation around the two stations on the first day of snowfall. The lower image is a view of Birafu Camp on the second day. The heaviest snowfall came the next day, which some guides describe as the most they can recall in ~4 years. Both images courtesy of Clavery Tungaraza]

Thursday, January 20, 2011

Weather station images

Here is a link to October images of Kilimanjaro's weather stations. Penitentes were present at the time on most glacier surfaces, and these appear in the images. Depending upon their size, penitentes can make glacier travel rather difficult. On Kibo it is unusual to find them greater than about 0.5m in height, but in the dry Andes they develop to heights of several meters. Currently the glacier surface is likely to be much flatter, as ablation continued through what normally are the wet months of November and December.