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!

Monthly weather synopsis

A monthly summary of summit weather has been available here for many years. Beginning with October 2013 the mean values for air temperature and relative humidity will be from a different sensor, and thus are not strictly comparable with those from prior months. Although the difference is likely to be only a few tenths of a degree, users should be aware of the change.

The reason for the change is that we decided to remove the fan-aspirated sensor during October fieldwork. The radiation shield housing this sensor had known systematic errors, and our technique of intermittent aspiration created additional problems. So, after 3 years of overlap with the CRN-compatible shield and sensors (T and RH), the time had come to remove this instrument.

Fieldwork!

Fieldwork this year was conducted late - as the dry season to short-rains transition was underway. Conditions were dry and dusty on trails and in the caldera; relatively high wind speeds at temperatures below freezing made servicing the weather station difficult.

The images below provide an initial perspective on our 2013 work. Note the smooth, icy glacier surface which facilitated glacier travel and accurate ablation stake measurements, while requiring fixed ropes for those without crampons. Thanks to the hard-working crew of SENE (Summit Expeditions and Nomadic Experience) for helping us achieve our objectives while keeping everyone safe!

Ascending toward the southern glaciers; view to southwest

Heading back to camp across the dry crater

Ben enjoying the exceptionally flat surface of superimposed ice on the Northern Ice Field

AWS serviced and ready to continue autonomous operation

The October 2013 SENE team (w/o Doug; Ben barely visible)

First snow accumulation since May

Telemetry from the Northern Ice Field shows a snowfall event last month, likely associated with the seasonal increase in humidity, the transition from dry season to the short rains. This was the first noteworthy, accumulating snow since early May.

Snow sensors indicate that the event began on 19 September and continued through the 27th. Averaging two series of measurements suggests 9-10 cm of accumulation. This snow isn't likely to persist, due to densification (settling) and ablation. The climate at this time of year remains quite dry and sunny, and several centimeters of surface lowering occurred on a single day, 5 October. Nonetheless, a 10 cm snowfall is sufficient to dramatically increase albedo and thus reduce the amount of solar radiation absorbed. The net effect is a reduction in the rate of ablation - for a period of perhaps weeks.

At the Northern Ice Field site where our measurements are concentrated, there has been effectively no net change in glacier thickness (mass balance) for 2 years; accumulation has balanced ablation. This will change if the 2013 short rains are delayed, as ablation can be rapid during October - November. We will visit the glaciers later this month, and are looking forward to seeing surface conditions and assessing the spatial variability of mass balance over the past year.

Dry July

Preliminary data show July 2013 to be the driest month on record for the Northern Ice Field, as measured by relative humidity via telemetry (2004-2012). July and August are typically the driest months at the summit, with July relative humidity (RH) averaging 42 +/-4% (1 std. dev.), so last month's mean of 25% was clearly anomalous. Measurements varied by only ~1% between two sensors in two different radiation shields, aspirated and naturally-ventilated. We expect verification of these values upon the next station visit, when 5-minute data from the high-accuracy, CRN-compatible shield will be recovered.

July ablation at the AWS was only ~8 cm. No snowfall, very low humidity and slightly above-average wind speed during the month would all promote sublimation, and thus ablation closer to the 10-year average for July of 11.3 cm might be expected. One explanation for below-average ablation could be that residual snowcover remains from the 2012-13 wet seasons. If so, telemetry suggests that there cannot be much snow/superimposed ice left - and once older, bare glacier ice is exposed, ablation will likely increase dramatically. Re-positioning of the AWS tower may be necessary in October, for the first time in 2 years.

Meager long rains

Snowfall at the summit during the "long rains" season was unusually meager this year. For March through May, net accumulation amounted to only 20 cm, or less than 1/3 of that last year. The most prolonged period of accumulation occurred between mid-March and mid-April (~23 cm), some of which settled and ablated rather quickly afterward. The first half of May brought ~13 cm of additional snow, a period during which there were "crazy, torrential rains" in Moshi. Little additional accumulation has been recorded at the summit since mid-May.

So, based on preliminary data, snowfall during the month of December was roughly of the same magnitude as that for the entire "long rains" period March/April/May 2013.  The stage could be set for considerable ablation during the forthcoming, extended dry season...

Good read

Anyone with an interest in "animals, adventure and discovery in the wild places of Africa" will enjoy reading Alan Root's memoir Ivory, Apes and Peacocks. The book was published last year in London by Chatto & Windus, an imprint of Random House Group Limited (UK), and although not yet available in America it is easily available from English booksellers.

One of many fascinating stories in the book details the flight Alan made with his wife Joan over Kilimanjaro. Root does not specify a date for the flight, which based on other information was likely 10 March 1974. Launching from the eastern flank, they flew as high as 7,500 meters. He writes that "we gazed down from our gossamer craft as the dome of Kibo, the highest point in Africa, slid slowly by -- almost a mile below us."

Then, as today, Root notes that "any snow falling on it soon melts." The image above with the balloon shows the incipient hole developing in the Northern Ice Field, which Hastenrath & Geischar observed on a 1989 Landsat scene and discuss in their 1997 Journal of Glaciology paper. Enlargement of the hole eventually split the ice cap into two parts last year (2012).

Once past Kibo they started dropping towards the Shira plateau and encountered a dead spot where "the balloon came slowly to a halt." Evidently they were in a zone of converging horizontal airflow, coming around both sides of the mountain, and before afternoon convection was well developed.

Root landed the balloon in Moshi. As might easily happen today upon such a landing, they "were quickly surrounded by a crowd of curious and laughing Africans". Less likely to happen today, fortunately, Alan next heard automatic weapons being cocked. Along with his wife and ground crew, they were arrested, accused of spying, and hauled off to the Moshi police station for 2 days of interrogation.

This is the only portion of the book pertaining to Kilimanjaro, yet every page offers fascinating observations and accounts of his African experience. Numerous reviews have been written on the book; here is one from The Economist.

Delay in telemetry processing

[UPDATE 2 Apr. 13:30 GMT]  The 2 recent images above are offered as consolation for the delay in posting the monthly weather summary. Both views are from Moshi, looking up 5,000 m to the summit. The upper photo with early-morning light is from 22 March, with new snow down to perhaps 4,500 m elevation. The lower image was taken yesterday evening.

Typically in the first few days of each month, we post a synopsis of the previous month's weather at the summit (here). For March, the summary will be delayed by a week or so due travel by our data manager.

Widespread rain is being reported from Tanzania, so check back next week to learn how much snowfall the summit glaciers are receiving!

long-duration climate observations

PNAS recently published an important opinion piece by Carl Wunsch et al. that is well worth a read. It is freely available in HTML and PDF format from the Academy website, and less than a page and a half in length. They argue convincingly that "understanding of climate change is a problem for multiple generations" - stressing that an increased emphasis must be placed on long-duration observations of the climate system.

My favorite sentence takes nothing away from the value of modeling, yet emphasizes their key point:  "Today's climate models will likely prove of little interest in 100 years. But adequately sampled, carefully calibrated, quality controlled, and archived data for key elements of the climate system will be useful indefinitely."

Wunsch et al. point out numerous obstacles to obtaining adequate observations, lamenting that "governments have not done well in sustaining long-term observations." Some of us are all too familiar with this problem, yet this is not universally the case. One of NOAA's most far-sighted undertakings - the U.S. Climate Reference Network - has just achieved a decade of operation, thanks to staff and managers at NOAA whose vision has been laser-sharp. A paper reviewing this program is about to be published by the American Meteorological Society, and available here now.

The USCRN program can be a model for measurements of other climate system elements, domestically and internationally. Broadly implementing the USCRN approach would be an excellent way to address the intergenerational problem highlighted by Wunsch et al.

New aerial images

During the Wings of Kilimanjaro (WoK) expedition in early February, a helicopter flew to the summit with supplies for the group. The pilot was Ben Simpson of Tropic Air, a company based at the foot of Mt. Kenya and experienced in carrying out rescues there. Tropic Air uses the French-made Eurocopter AS 350 B3, from which WoK videographer Anika Craney got some great footage. A 12.5-minute clip of the flight is posted on the WoK FaceBook page, available here.

The following captures are from Anika's video, posted here to provide an update on recession of the glaciers; several of the perspectives she obtained are quite unique.

Below is the less-commonly seen half of the Northern Ice Field, with the eastern edge at left. The crater is behind the upper ice as seen here. Despite extensive snowcover (for early February) the split between the two halves is clearly visible; this did not exist and/or was not known prior to ~1989.

At the bottom edge of the image below is Stella Point. Trails to both the summit and crater camp are visible. The eastern end of the Rebmann Glacier is in the foreground. The apparent "hole" was recently observed on satellite imagery, and may have developed due to anomalous geothermal heat flux. Alternatively, it may have begun as a supraglacial pond which enhanced shortwave radiation receipt.

Fragments of the Southern Ice Field are seen in the next image. Beginning on the right-hand side, the Rebmann Glacier used to extend downslope but is primarily confined to the crater rim these days. Although partially obscured by cloud, this view provides a context for the image above. The narrow Decken Glacier becomes thinner each year, and may soon be cut off from the ice above. The largest ice body remaining is the Kersten Glacier, which is also seen in the fourth image. Within the past couple years the Kersten has become detached both from ice above and from the Decken Glacier to the right. Lastly, the Heim Glacier is the small sun-lit body of ice beyond the lower Kersten. As recently as 10 years ago the upper portion of this glacier began not far below the crater rim.  

Below is detail of the view above, showing how the Kersten Glacier has fragmented from the Decken, and into an upper and lower portion. Uhuru Peak is the high point behind the upper section and obscured by cloud in this view.

Many thanks to WoK and Anika for posting this video!

Windy [UPDATED 12 Feb.]

[UPDATE 12 Feb. 18:00 GMT] A final update to the weather graphic has been posted below (or here). Wind speeds and direction have returned to more typical, seasonal values. It was ironically the interval 3-6 February with anomalously high wind speeds, while the expedition was at the summit and prepared to fly off. Was early February a good time of year for the flight? Certainly; the longterm mean values shown in plots A and B both demonstrate that - on average - conditions at the summit at this time are very reasonable for paragliding. But, as we have learned in our decade of measurements, the interannual variability of climate on Kilimanjaro is large -- and summit weather can never be taken for granted.

[UPDATE 7 Feb. 04:00 GMT] Telemetry data from the summit as of midnight Wednesday local time have been added to the graphic below. Late yesterday the wind speed dropped, and Thursday is beginning with winds steadily from the East at a more reasonable speed of 8 m/s. However, humidity was high through the day Wednesday and approaching saturation at midnight. Note how little snow ablation occured (plot C). Looking forward, the forecasting models show a strong gradient in 500 hPa-level humidity parallel to the Tanzania-Kenya border, so exactly how the pattern becomes established may determine if tomorrow (Thursday) is flyable. Lets hope for the best.

Previously:  at 9 AM Tuesday morning, the image above shows how Kibo appeared from Moshi (courtesy my friend Simon at Summit Expeditions:  website and FaceBook). Such great clarity is the result of strong easterly wind. Very strong. Too strong for paragliding.

Check the graphic below to see a context for wind speeds since Sunday; plotted values have been updated to 8 AM local time this morning. In quantitative terms, the 4-hourly wind speed for the period 20:00 - 24:00 last night was 18.4 m/s = 36 knots = 41 mi/hr = 66 km/hr. This is more than 2 standard deviations greater than the longterm mean for this time and date, and as discussed in the 1 Feb. entry below, wind speeds over shorter intervals (e.g., 1-min average) have almost certainly been much greater. Furthermore, this 4-hourly speed equals the highest 4-hourly February value we have recorded on the glacier, which occurred 8 February 2004 (8 AM to 12 PM).

The forecast does indicate lessening wind speed, although it may be another day or two. To clarify yesterday's post concerning wind speed decreasing through the morning, this is the generalized diurnal pattern on Kilimanjaro, not a forecast. Nonetheless, the NOAA Climate Prediction Center forecast for the Kibo grid cell shows decreasing wind speeds at 500 hPa in the hours ahead. Lets hope so, for those seeking to fly down.

Lastly, this nice image from Moshi clearly shows the glacier changes mentioned in the previous post. Ice extent today is quite different from that of 10 years ago shown on the Wings of Kilimanjaro FlyTrace map.

Summit weather - Monday

The graph page below reflects summit weather measurements to 04:00 local time today (East Africa); accompanying text update is in this post, rather than previous.

The Wings of Kilimanjaro group reached Crater Camp today, where they are spending the night. Their location can be seen on the FlyTrace map showing positions for many of the pilots. Note that the background image visible when "satellite" is clicked (upper right-hand corner) was acquired on 31 January 2003, so is almost exactly 10 years old. The glaciers are considerably reduced in area and volume since then, as discussed elsewhere on this blog and on this website.

Summit weather today probably provided a good indication of what conditions will be like tomorrow for the launch. Winds at the weather station have been moderately strong, yet appear to be steadily from the East. According to the NOAA NCEP GFS forecast for summit level (500 hPa), winds tomorrow will remain from the same direction, and perhaps decrease somewhat in speed. Based on our climatology and the GFS forecast, wind speed will likely decrease through the morning at summit level.

Humidity has been low since about dawn on 1 February, and continues to be low today (i.e., below 15 percent). Combined with moderate wind speeds, considerable snow sublimation appears to have taken place recently (see graph D below), and snow cover has likely decreased steadily over the past few days.

Measurements shown below suggest that tomorrow, 5 February, may be favorable weather for flying off the summit! The collective experience of the summit and landing-zone groups will have to assess all factors - some of which are not apparent looking at the situation remotely - before making a final decision. But their wealth of experience will serve them well. Best wishes to all for an amazing flight down!

Wings Weather [graphic UPDATED 12 Feb.]

[click graphic to open in a new window, or here for a PDF] 

The Wings of Kilimanjaro expedition reached Barranco Camp today (1 February), right on schedule. Their FaceBook page mentions seeing fresh snow at the summit as they traveled from Moir Camp to Barranco via Lava Tower (see graph above and discussion below). The group of 68 pilots, 16 passengers, 11 crew and 600 porters are climbing up for a paragliding event from the summit on approximately 5 February. The Tanzanian Government has sanctioned this event, which hopes to raise over USD 1,000,000 for three different East African charities.

Pilots and guides may be interested in a historical context for weather on the mountain, provided here for wind speed & direction, snowfall, pressure, and air temperature over the period 1 January to 15 February. Also shown on each graph are 2013 measurements obtained by satellite telemetry; these will be updated through the interval as time permits. Thanks to Mike Rawlins in the UMass Climate System Research Center for extra effort with data processing.

An article detailing our involvement with Wings of Kilimanjaro has just been published in the Boston Globe, and available here.

Plot A depicts 4-hourly averages of mean horizontal wind speed, in meters per second (m/s). This long averaging period is required by telemetry limitations, and actual wind speeds will ALWAYS be higher; averages shown differ from much-shorter, standard wind speed averaging times (e.g., 1-minute). In black is the average 4-hourly wind speed for the period Feb. 2000 to Sep. 2012. Values are slightly smoothed by a 3-day running average for each time (SD of the mean is ~3 m/s, not shown). Note the diurnal cycle in wind speed, typically with morning maxima. Plotted in red are 4-hourly wind speeds for 2013.

To convert wind speed to km/hr, multiply values shown by 3.6; a multiplier of 2.2 will convert values to mi/hr (MPH).

Plot B illustrates wind direction, with black circles showing mean 4-hourly resultant values (2000-2012), and 2013 4-hourly vectors as red squares. Note how consistent the mean airflow is at this time of year, from just south of East, with greater-than-normal variability lately.

Accumulation (snowfall) and ablation are depicted in Plot C, referenced to 31 December for each year shown. Blue lines show 2002 - 2012 (w/o 2009) and the red line shows 2013. Considerable interannual variability is illustrated. Note that the summit has received very little new snow between 3 and 29 January. We have a report* that on the 29th (Tuesday) it "rained a lot between Shira and Barranco camp" and that "it snowed big time at Crater Camp, Arrow Glacier Camp, and in the Western Breach." According to the AWS, summit snow accumulated for about 24 hours beginning at midday on the 30th. About 11 cm accumulated quickly, a substantial event for the arid summit. [*Thanks to Timba at Ahsante Tours for this.]

Plot D shows barometric pressure, with +/- 1 standard deviation of the mean 4-hourly averages shown in blue, and 2013 4-hourly values shown in red. Note that the semidiurnal pressure oscillation is apparent even in 4-hourly data! Also, pressure between 16:00 on 19 January through the 23rd was higher than measured for any of these 4-hourly intervals since June 2001. The significance of this is not entirely clear, but could reflect an interval of anomalously warm troposphere at altitudes below this level (i.e., increasing geopotential height).

Finally, plot E is air temperature as measured within our aspirated radiation shield, with 2013 values in pink. Note the early-morning minima on the 24th. The relative warmth shown on 29, 30, and 31 January is likely due to cloud cover, as humidity began increasing in the afternoon of the 29th (not shown). 

NB:  All discussion and accompanying figures on this website are for scientific purposes only, to aid in interpreting the climate on Kilimanjaro’s Northern Ice Field. All data are preliminary and not in real-time; measurements may not be representative of conditions at the summit, in the surrounding atmosphere, or elsewhere on the mountain. The author and any institutions with which the author is affiliated assume no responsibility for any application of these interpretations or these data, including but not limited to paragliding and hang-gliding. Be safe!

Christmas snow

Here is how Kibo looked at about Christmas from near one of the Shira Camps. Unsettled weather and the snowlevel at roughly 4,500m (background photo courtesy SENE).

Snow, lightning

Kilimanjaro was wet through the second half of December, "crazy wet" as characterized by Timba at Ahsante Tours. Telemetry from the Northern Ice Field provides the evidence, with high humidity and snowfall totaling 33.8 cm between 16 December and 3 January. The days of greatest accumulation were the 27th (4.9 cm), 30th (5.2 cm) and 2 January (5.5 cm). Although 5 cm is a moderate hourly rate in some mountain regions, less than 4% of all days with snowfall on Kilimanjaro are of this magnitude. Although such events do not add much mass, they are disproportionally important in terms of raising albedo and thus decreasing net radiation receipt.

Snowfall on the glaciers is often rainfall lower on the mountain, and often much heavier than summit snowfall might suggest. Kilimanjaro precipitation is frequently associated with convection, particularly at this time of year, and at 12:30 PM on Wednesday (2 January), lightning struck a group that was approaching Lava Tower. The group leader Ian McKeever was killed and several other were burned. McKeever's FaceBook post the day before from Shira 2 camp mentioned "torrential rain all day", and the group's guide Said Makacha indicated that there was heavy rain during the hike to Lava Tower.

We have learned that 2 porters have also tragically died in recent days. At the moment it is unclear whether lightning, hypothermia, or another cause was responsible; condolences to the families of all 3 victims.

Lightning is not common on Kilimanjaro itself (e.g., zoom in with this Google Earth overlay showing lightning frequency), and deaths are quite rare - especially considering the number of people camped high on the mountain most nights . An article in the Tanzanian "Daily News Online Edition" recalls the previous incident in 1999, which occurred just a couple months before we began working on the mountain. The article quotes a National Park source suggesting the terrible idea that climbers take cover in caves (above 4,000 m) during rain, evidently not aware that the 1999 death occurred at Shira Caves, a short distance from where the death occurred this week.

While strikes may be infrequent, lightning is often visible at night from high on Kilimanjaro, and thunder has been heard while camped at the summit for fieldwork on the past two trips.

Can we learn anything from summit weather on 2 January that may help explain the tragic death(s)? Maybe. Wind direction on the Northern Ice Field blew steadily from the South beginning about midnight, at a bit lower speed than normal for the day. Southerly flow is relatively uncommon at our measurement site; wind is more typically from the East, which helps suppress convection above the mountain's western slopes (up which many climbers ascend). It is possible that light winds from the south, in conjunction with regional instability, aided the development of convection which led to the lightning strike.

On 4 January humidity decreased dramatically, the wind veered back to the East, and solar radiation measurements indicate generally clear conditions.