Tuesday, September 29, 2015

Clouds and humidity

Here is another view of the constantly-changing clouds we watched September 13th on Kibo, ascending from Karanga to Barafu Camp (see below or here for the image posted last week).

According to our Northern Ice Field AWS measurements that morning, wind speeds were rather modest at the time (~7 m/s); data from NCEP (see below) agree reasonably well. The image above suggests a sharp boundary between small parcels of air with contrasting moisture content, and as shown by the image below - with Kibo's location indicated by the green circle - humidity at 500 hPa (summit level) was variable that morning. The humidity contrast is even more pronounced at the 700 hPa level (see image; brown color is less than approx. 20%, cyan blue is greater than ~95%).  Although wind speeds were low by all measures, direction varied with altitude. We were watching cream be added to coffee, in slow motion.

 The spell-binding display we witnessed was no doubt the result of numerous interacting factors, in addition to these. Mountain fieldwork is always interesting!

One additional image showing NCEP humidity data follows. Note the high humidity (blue) at 500 hPa over a broad area around Kilimanjaro. Interestingly, my field notes early that morning read: "Humidity increased during the night; the air feels and smells different, and both sides of the tent fly are frosty. Sky clear." Later that afternoon we experienced a snow squall which blanketed the summit crater with ~5 cm of new snow (image 5, previous post), our only precipitation of the expedition.

Wednesday, September 23, 2015

Fieldwork: routine tasks & new measurements

Our group has just returned from a 3-day intensive period of fieldwork on the summit glaciers of Kilimanjaro. Despite loosing one day due to a tragic accident on the mountain, hard work by all rendered our efforts largely successful.

Dry and stable weather prevailed through most of our 12 days on the mountain, but during our final afternoon of fieldwork we worked through intensive snowfall followed by colder (-6.6° C) and windier (8.0 m/s) conditions. Leo inspired us by being either entirely undaunted, or so focused on his work that he didn't notice!

Among the exciting new results is a tremendous dataset resulting from a dense network of Northern Ice Field radar profiles. Two different systems and multiple different antennas yielded beautiful data which will aid in understanding the variability of ice thickness, stratigraphic patterns, and water content within the ice. To our knowledge these were the first efforts to deploy radar equipment on Kilimanjaro glaciers, and we thank those who entrusted us with their instruments. In addition, two boxes of ice samples were collected and safely transported to Heidelberg University. There we will hopefully obtain additional radiocarbon dates from the ice, and other analyses will be conducted in conjunction with the University of Maine.

Additional images and details will be forthcoming. Here we would like to acknowledge tremendous support for this equipment-intensive effort from our entire SENE crew. Our guides Jackson, Augustino and John did a great job, Godlisten's food was outstanding, and we would especially like to thank all of our porters - who remained invariably cheerful despite some large, cumbersome loads. We also acknowledge partial financial support for this work from the National Geographic Society's Global Exploration Fund - Northern Europe, and the University of Maine's Climate Change Institute.

Image 1 (above):   Loading some of our gear at Mbahe, for transport to Umbwe Gate. Note barely-visible large metal case on the rear roof; although weighing less than 23 kg, carrying this up 4000 m was far from trivial. Thank you Daruesh!

Image 2:  Rapidly-changing, "gossamer thin" clouds engrossed us during our ascent from Karanga to Birafu camps (13 Sep.). The slight decrease in mid-tropospheric stability was probably associated with a seasonal change in regional circulation. Part of the Rebmann Glacier is visible at the crater rim.

Image 3:  Helene and Pascal heading north on a radar transect from the AWS.

Image 4:  Leo and an assistant returning from an east-west radar transect.

Image 5:  Fresh snow and clearing sky to the east, following the afternoon snowstorm of 17 September. Reusch Crater slope is visible to the right.