Thursday, December 13, 2012

10 years for the US Climate Reference Network

Congratulations to the USCRN program on the first decade of operations!

Some of the equipment on the UMass Quelccaya weather station is compatible with that of the U.S. Climate Reference Network (USCRN), which NOAA's National Climatic Data Center (NCDC) began 10 years ago. We chose to incorporate elements of their system at our site as a result of the extensive testing and characterization they carried out. A nice overview of all USCRN aspects and prospects is contained in the Early Online Release of a paper titled "U.S. Climate Reference Network after One Decade of Operations: Status and Assessment." The paper will appear in a future issue of the Bulletin of the American Meteorological Society, and is freely available now from this link.

To stay updated on further developments of the USCRN, follow NCDC on Twitter:  @NOAANCDC

Tuesday, August 14, 2012

Fieldwork photos

Photos from this year's fieldwork are in 3 different galleries:
  1. At the summit our efforts were focused on the weather station (AWS), and in a snowpit as time permitted. Photos here
  2. Working at an elevation of nearly 6,000 meters requires adapting to less oxygen (lower partial pressure), providing time to make other observations. Photos from travel to the ice cap and at the margin are here. For several locations - including outlet glacier Qori Kalis - photos from previous years have been mixed in to illustrate ice recession and thinning.
  3. Among other observations possible while acclimatizing is documenting the elevation and habitats of various bird species living at this high elevation; the Quelccaya margin (~5,200 m or 17,000 ft) represents the upper end of most species' range. Photos of birds seen in 2012 are here (Additional Vilcanota birds can be seen here and here, or this link for more on Diuca speculifera.)
Please get in touch with any questions or comments!

Wednesday, August 1, 2012

Fieldwork weather

The figure above depicts summit weather at Quelccaya prior to and during our 2012 fieldwork. The short synopsis is that during our time at Moraine Camp and the AWS we experienced clear sky, low humidity, and low wind speeds. Just prior was an interval of high humidity, snowfall, moderately-high wind speeds, and lower temperatures.

Here are some details shown in the graph, and implications (click the graphic to see a larger version). Some measurement are presented only through the 11th due to sensor changes and service. We were at the summit from the 9th through the 15th, and near the ice cap 6-16 July:
  1. Hourly incoming solar radiation is shown in orange. Clear sky continued from the 9th through until the 15th (not shown).
  2. Blue squares are average daily relative humidity, which increased during our time in Cusco and then dropped abruptly on the day we first reached the summit.
  3. Snow accumulation & ablation is depicted as the dashed blue line. This is actually a smoothed recording of changes in surface height, where decreasing distance represents snowfall and increasing distance is a combined record of melting, sublimation, wind scour and settling. The measurements are hourly, yet must be smoothed to remove a spurious diurnal cycle due to the impact of air path temperature on the speed of sound - since acoustic sensors are used. Anyway, processes were less continuous than the smoothed plot indicates, suggesting:  a) about 1.5 cm of snowfall during the afternoon of July 4th, b) another ~1.5 cm of snowfall late on the 5th, and c) ~1.5 cm of sublimation on the 9th. Note perfect conditions for sublimation on the 9th, including clear sky and high radiation, decreasing humidity, high wind speeds and lowest temperatures of the interval.
  4. Average wind speed (red diamonds) parallels the humidity pattern, reaching a maximum on the day gear was carried to the summit and then dropping. For several 24-hour periods, it averaged < 3 m/s, and on our 'hottest' day of work at the station the average wind speed was <2 m/s - or <5 miles/hour. Very calm, especially at nearly 6,000 m elevation in the Andes.
  5. Two different measurements of temperatures are represented on the graph, both as triangles and both as the maximum hourly values each day. The pink values are measurements in a naturally-ventilated, multiplate radiation shield whereas the cyan symbols depict measurements in a sophisticated, fan-aspirated shield compatible with the US CRN system (Climate Reference Network). Note that radiation shield differences can yield huge differences in measured temperature:  on 2 days in this interval the difference is >6°C. If data were available from the multiplate shield on the 13th (sensor was being replaced) a 10+ degree difference would not be surprising. Wind speed and solar radiation critically influence temperature measurement!
Photos of fieldwork activity will be posted shortly to illustrate the weather depicted above, so stay tuned! Measurements now continue autonomously at the station, transmitted hourly to us via telemetry.

Tuesday, July 24, 2012

Un gigapan muy grande

As previous posts have indicated, Quelccaya is a large, relatively-flat ice cap. From the summit area, ice flows down and out toward the margins with much of the flow taking place via outlet glaciers such as Qori Kalis. We shot several GigaPans at Qori Kalis this month, including the broad panorama below. Additional details about Qori Kalis and the composite panorama can be seen in a new tab by clicking on the image caption (or here for those w/o Flash). Details of the glacier are best seen in the second GigaPan below (or here). Several others will be posted shortly, illustrating details of the lake/moraines as well as areas nearby.

Tuesday, July 17, 2012

2012 Fieldwork Return

Back into Cusco last night after ~10 days at Quelccaya. With help from Vicencio Expeditions (Guide Felix, porters Theodoro and Hector, a cook and 8 horses), we accomplished just about all we hoped to. First up was locating the elusive 1983 survey points, a considerable relief. Then, 5 days and 4 nights were spent on top at the AWS, servicing the station and measuring snow. The weather was rather incredible, with cloudless days of no wind and very low humidity. Although at times we baked in the sun, quick checks suggested the air temperature remained below freezing every day; nights were invariably clear and cold. Ablation seems to have been minimal through the interval, due to the relatively fresh snow cover and dominance of sublimation over melting. More details will follow. Here are a few quickly-selected, unedited images.

1. From our tent just before sunrise on 12 July (Happy Birthday Elise).

2.  Carsten prepares our morning coffee, crucial task #1 each day.

 3.  Here the AWS tower has been raised, and instrument adjustments/service are underway.

 4.  Changing out one of the temperature/humidity sensors.

5.  Snowpit, part I. Eventually we went to 4.5 meters, about half again this depth. This required saws and hard effort which broke both of our steel shovels; credit for perseverance goes primarily to Theodoro and Hector (and our trusty Voilé shovel). The contact between the most recent accumulation (i.e., 2011-2012) and the 2011 dry-season surface is readily apparent.

 6.  Qori Kalis outlet glacier, as seen while waiting for a GigaPan panorama to execute (615 images). Note the adult Mountain Caracara flying by!

Monday, July 2, 2012

2012 Fieldwork Underway

Here we are yesterday at Logan Airport in Boston, days of packing and preparations behind us. Try as we might to cut down the amount of gear required for fieldwork on Quelccaya, this is about what we always end up with. Raising the tower must be done annually to keep up with accumulation and minimize the effect of changing measurement height, so that means tubing, fittings, cabling and lots of tools; living at nearly 6,000 m requires warm clothes and robust tents.

This year will be a small "team" (as shown above), but we have some exciting science planned in addition to servicing the station and recovering data. First up will be locating 2 survey points on a ridge overlooking the glacier, established in 1983. Dave Chadwell installed and used these to complete a thorough 3D survey of a transect up the glacier. Re-visiting these points is an idea he came up with last year, and the National Geographic Society has decided to support the effort. So now - nearly 30 years later - we hope to find the points and establish their position with centimeter-accuracy GPS. At Scripps, Dave will then compute positions for each point in the transect, and next year we will reoccupy these points with the GPS equipment to get precise elevations. The result will establish a profile of ice thickness change over the intervening 30 years -- how cool is that?

Meanwhile, our other goal for this year is to dig a snowpit back through 2-3 years of accumulation and measure a profile of density. Equipped with detailed density profiles from previous fieldwork, we hope to learn more about ablation processes and meltwater percolation.

We arrived in Cusco today with all our gear and have begun adjusting to life at 3,400 meters. We'll continue adapting for 3 or 4 more days before moving up.

Friday, June 1, 2012

Dry season begins

Following a snowy February, accumulation decreased steadily through March and April. Preliminary data indicate that maximum accumulation occurred on 4 May at 2.08 meters, which is an average depth for recent years. However, only when density measurements are made during fieldwork will we know the snowpack's water equivalence. This year we will make such measurements during July, when we plan to dig a very deep pit and investigate the role of vertical meltwater percolation.

Tuesday, February 28, 2012

Accumulation Update

Despite a snowy September, 2011-12 accumulation to the end of February is very close to average, at ~1.8 meters so far for the season. As previously described, October and November yielded no net accumulation, whereas an interval of a couple weeks in mid-February illustrates the near-daily snowfall typical of the wet season in the Vilcanota:  between the 10th and 26th (inclusive) there were only 3 days without accumulation, with snowfall days averaging 4.7cm and a median of 3.8cm.

2011 Fieldwork Photos

Fieldwork in 2011 was productive, interesting, and fun. We began in Cusco at the end of June, meeting up with several collaborators before departing for the Cordillera Vilcanota. Our first night out was at only 4,400m, yet accumulating snowfall began as we were putting up the tents. Although snow at lower elevations melted quickly, high wind and blowing snow during our first couple days on the glacier made work nearly impossible. Fortunately, sufficient time was budgeted to get everything done, and during 6 days at the summit we raised the weather station tower, serviced existing and added new instrumentation, and conducted snowpit measurements. Joining us in camp for some of the time were Lonnie Thompson, Henry Brecher, Keith Mountain and others, which was great.

Many aspects of the field season are depicted here, beginning in Cusco. Above photo courtesy Keith Mountain (Univ. Louisville).