Here is a clip produced by New York Times Science Times. The feature was filmed in June 2001 for broadcast on the National Geographic Channel, and recently turned up on YouTube. Director of Photography John Hazard was fun to have along, joining Georg Kaser, Tharsis Hyera, Erick Masawe and others!
Saturday, April 28, 2012
Wednesday, April 25, 2012
Snowy April
As of yesterday, 30 cm of snow has accumulated on the Northern Ice Field this month. Not since 2006 has there been this much during April.
Any photographs of snowcover in the crater or at the summit would be appreciated!
[UPDATE 5/1: See above... snowfall continued.]
Any photographs of snowcover in the crater or at the summit would be appreciated!
[UPDATE 5/1: See above... snowfall continued.]
Wednesday, April 4, 2012
6 March snowfall
For the month of March, telemetry data indicate net snow accumulation of a paltry 2.7 cm. However, a detailed examination reveals a more interesting situation.
Telemetry shows only 2 snowfall events occurring at the summit during March. Establishing the magnitude of snowfall from telemetry data is sometimes tricky because: 1) telemetry data are only 4-hourly, 2) measurements by the 2 acoustic sensors often differ due spatial variability of accumulation, and 3) acoustic sensors sometimes yield noisy data during snowfall events. However, for the event on 6 March both acoustic sensors recorded 15-20 cm of accumulation, placing this event among the top 3 in the one-day snowfall rankings since 2000. More typically, snowfall events tend to occur over longer time periods.
The weather on 6 March contrasts sharply with that of other days last month. For example, the 4 AM and 8 AM 4-hourly mean values of temperature and humidity were the highest for both times during the month, suggesting cloud cover and moisture advection. Likewise, the temperature at noon was the lowest for any day of the month, humidity was the second highest, and 12 PM minima of both incoming and reflected solar irradiance were recorded.
Through the balance of March, lowering of the glacier surface was nearly linear, suggesting a near-constant, combined rate of ~7mm/day for settling, sublimation and melt.
Telemetry shows only 2 snowfall events occurring at the summit during March. Establishing the magnitude of snowfall from telemetry data is sometimes tricky because: 1) telemetry data are only 4-hourly, 2) measurements by the 2 acoustic sensors often differ due spatial variability of accumulation, and 3) acoustic sensors sometimes yield noisy data during snowfall events. However, for the event on 6 March both acoustic sensors recorded 15-20 cm of accumulation, placing this event among the top 3 in the one-day snowfall rankings since 2000. More typically, snowfall events tend to occur over longer time periods.
The weather on 6 March contrasts sharply with that of other days last month. For example, the 4 AM and 8 AM 4-hourly mean values of temperature and humidity were the highest for both times during the month, suggesting cloud cover and moisture advection. Likewise, the temperature at noon was the lowest for any day of the month, humidity was the second highest, and 12 PM minima of both incoming and reflected solar irradiance were recorded.
Through the balance of March, lowering of the glacier surface was nearly linear, suggesting a near-constant, combined rate of ~7mm/day for settling, sublimation and melt.
Sunday, March 18, 2012
February weather variability
Below are four sets of graphs and time-lapse video clips which illustrate the interannual variability of weather and snowcover at Kilimanjaro summit during February. The graph shows the average change in snow or ice surface height on the Northern Ice Field (black line) and that relative to a height datum on January 31st for the year illustrated (in color). The video provides a daily view of the glacier, crater, and Uhuru Peak - in addition to the weather each morning through the month.
To see the camera system installation, click here, or here for an annotation of what the scene illustrates.
February 2006, with images from 10:58 AM each day:
February 2007, with images from 10:19 AM each day. The month began with the greatest crater snow depth of the decade:
February 2008, with images from 12:24 AM each day:
February 2010 (partial), with images from 10:02 AM each day:
To see the camera system installation, click here, or here for an annotation of what the scene illustrates.
February 2006, with images from 10:58 AM each day:
February 2007, with images from 10:19 AM each day. The month began with the greatest crater snow depth of the decade:
February 2008, with images from 12:24 AM each day:
February 2010 (partial), with images from 10:02 AM each day:
Wednesday, February 29, 2012
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.
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.
Wednesday, February 8, 2012
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!
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.]
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.]
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