December 20th, 2018 by Adam Greeley and Kelly Brunt
Traveling to Antarctica is no joke even for veterans like Kelly, but especially for first timers like me. This isn’t your run of the mill intercontinental flight; a lot more gear is needed plus required training. There are also a lot of long flights involved. To get to the United States Antarctic Program facilities in Christchurch, New Zealand from the U.S. East Coast, it takes about three layovers, over 30 hours of flying, and some time travel (cross the international date line: lose a day. Do not pass GO. Do not collect $200).
Upon arriving in Christchurch, our first stop is the U.S. Antarctic Program, run by the National Science Foundation. After some briefings on what we will need in Antarctica, what to expect, and what not to do (no touching penguins!), it’s on to the Clothing Distribution Center. It’s probably obvious to most, but Antarctica can get really cold! The U.S. Antarctic Program wants to make sure we stay warm on the ice so they provide us with Extreme Cold Weather gear including boots, snow pants, mittens, hat, neck warmer, goggles, and of course: “big red,” an aptly named parka.
Once we have all our gear and baggage together, it’s time to fly! No 737s here. The U.S. Antarctic Program transports cargo and personnel down to the ice on various military aircraft. We transited on a New Zealand C-130. Seats face the sides of the aircraft instead of forward, and consist of canvas benches with cargo strapping for backs. You get to know your neighbors really well on these flights. Straightening your knees beyond 90 degrees involves some coordination with at least one individual sitting across from you. Weather can change at a moment’s notice down in Antarctica and sometimes that means you need to turn around and head back to Christchurch four hours into a flight. These flights are known as “boomerangs” and are not the most fun.
After a scrubbed flight, and one boomerang, we made it to Antarctica. Stepping off the airplane onto the ice runway for the first time is a breath-taking experience. The McMurdo Ice Shelf stretches toward the Ross Ice Shelf to the south, while the Mt. Discovery and the Transantarctic Mountains line the western horizon. Cold, dry air fills your nose and lungs. Your eyes blink, trying in vain to bat away the overwhelming brilliance of sunlight reflecting off the snow. Snow crunches softly under foot. The wind races by and in the distance Mt. Erebus towers, watching all beneath its feet. We’ve arrived. Terra Australis Incognita: Antarctica.
December 19th, 2018 by Kelly Brunt and Adam Greeley
It’s that time of year again: Time to conduct another 88S Traverse! We have made it to Antarctica for a second straight year, in support of NASA’s ICESat-2. You can read all of our posts, including those from the 2017-2018 88S Traverse here. And here’s a fantastic video that describes last season’s traverse in great detail.
After a quick stop in Christchurch, New Zealand, we made it to McMurdo Station, which sits on the coast of Antarctica.
The 88S Traverse is a ground-based survey intended to collect highly accurate and precise GPS elevation data for direct comparison with ICESat-2 surface height data. The traverse is conducted using 2 PistenBully tracked-vehicles that pull our camping equipment and science instrumentation along the ice sheet. ICESat-2 is a satellite laser altimeter, designed to measure the surface of the Earth to an accuracy and precision of something on the order of the width of a pencil! Our goal with the 88S Traverse is to validate that ICESat-2 is meeting that level of accuracy and precision.
This season is a bit special; ICESat-2 was launched earlier this year, making this the first 88S Traverse that will be coordinated with the satellite observations. ICESat-2 launched in the wee hours of September 15, 2018. And even though it was a super early morning for me, and I did not have enough coffee in my system, the event was spectacular. ICESat-2 is currently collecting data globally, including over our field area around 88S, with the expectation of releasing these data to the public in early 2019.
More recently, NASA’s Operation IceBridge completed their Antarctic field campaign. Their flight plans included surveying the 88S Traverse route. The actual flight over our area occurred on November 12, 2018. Our survey area doesn’t change that much over short time scales. There isn’t very much snowfall (input) and it’s very cold, so there is almost no melt (output). The processes that change the surface at a detectable level happen at much greater time scales. These include compaction of snow that falls over time on the surface (we call this firn compaction) and snow migration form the wind. Therefore, the November data collected by IceBridge will be very comparable to the data that we will collect, less than two months later.
We are currently at McMurdo, waiting for weather to clear so that we can get to the South Pole. From there, we will take about a week to build the sled platforms, and then we hit the road. And by the end of our field season, we will have ground-based, airborne, and satellite data for comparison!
December 19th, 2018 by Christopher Hiemstra and Ludovic Brucker
Ground validation measurements are an important part of working with remote sensing instruments like SWESARR. Snow is dynamic and changes occur as soon as it settles to Earth’s surface. In a dry, windy place like Colorado’s Grand Mesa, snow can move around, be packed into drifts, get intercepted in canopy, sublimate back into the atmosphere, and metamorphose into depth hoar as winter progresses.
Ludo Brucker (NASA GSFC / Universities Space Research Association) and Chris Hiemstra (Cold Regions Research and Engineering Laboratory) were on Grand Mesa preparing for NASA SnowEx 2019. During the latter half of November 2018, Grand Mesa was blanketed in 40-70 cm (about 15-27 inches) of new snow from a series of storms. Fortunately, a short break in the weather with clear skies was forecast for the last SWESARR engineering flight. Optimistic plans to take early season measurements on Grand Mesa materialized.
The only problem was that the flight lines were well out into the west end of Grand Mesa and the early season snow was new and deep. Chances of getting stuck on the way out there were high, especially as the route went uphill from Grand Mesa Lodge perched on the south side of Crag Crest. Fortunately, Grand Mesa Lodge owner Mike Renner grooms Grand Mesa snowmobile trails throughout the winter season and he groomed a route out to the west side of the Mesa the previous evening. On the morning of December 4, Ludo and Chris rode 11 miles to the west end of the Mesa.
Just as they arrived in the blazing sun, the drone of the Twin Otter carrying SWESARR and flying one of the lines could be heard. They cleaned out the radar reflectors, then set about collecting snow data. The corner reflectors are used to assess the airborne radar observations.
In all, five snow pits were performed and over 1500 snow depths were measured at various points along several pre-determined flight lines.
After a week of snowfall, welcome clear and calm conditions resulted in an outstanding day collecting ground-truth data useful for assessing instruments and algorithms for the early-season snowpack.
The constellation of eight CYGNSS microsatellites reached a milestone today, completing its second year on-orbit. The first year had focused primarily on engineering commissioning, calibration and early validation of the science data products. The second year was spent continuing to refine and improve the quality of the science data products, while also applying the measurements to a number of scientific investigations. Some examples of the refined wind speed measurements are shown below for three overpasses of Hurricane Maria, on 23 Sep 2017 at 00:18 (top), 23 Sep 2017 at 00:23 (mid), and 24 Sep 2017 at 00:18 (bot).
Coincident hurricane overpasses by CYGNSS and NOAA hurricane hunter aircraft
In the figure, the green trace shows the measurements made by CYGNSS while the blue trace shows measurements made by SFMR instruments on the NOAA hurricane hunter aircraft that flew into the storms while CYGNSS was passing overhead. The CYGNSS and SFMR measurements can be seen to agree quite well. Quantitative results of the calibration and validation of CYGNSS science data products are described in a Special Issue of the IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing.
Measurements by CYGNSS of Typhoon Trami in Sep 2018, shown below, illustrate its ability to track the evolution of a storm over its full life cycle. In the figure, the lower left image is a composite over the period 20-30 Sep 2018 of all wind speed measurements made at one phase of the constellation’s orbit. The upper right insert shows all measurements made on 28 Sep 2018, with the measurements re-gridded to a storm-centric coordinate system to illustrate the wind speed structure in the inner core region.
CYGNSS wind speed measurements of Typhoon Trami
Science investigations have expanded beyond the primary mission objective to measure wind speed in tropical cyclones. The measurements are being introduced into numerical weather prediction models to assess their impact on the skill in forecasting hurricane track, intensity and structure. Early results look quite promising, with clear signs of a positive impact on forecast skill. The results will be presented in a series of talks at the annual meeting of the American Meteorological Society in January 2019.
In parallel with the activity over ocean, new science investigations are examining data over land as well. CYGNSS measurements have been found to be sensitive to the surface soil moisture, and to the presence of inland water bodies. Good examples of this are documented in recent publications. Kim and Lakshmi (2018) [doi:10.1029/2018GL078923] estimate soil moisture at numerous sites in the continental U.S. over a 12 month period and find close agreement with independent measurements made by ground sensors and another satellite. Jensen et al. (2018) [doi:10.3390/RS10091431] demonstrate the ability of CYGNSS to detect and map the extent of flood inundation under dense forest canopies. Chew et al. (2018) [doi:10.1038/S41598-018-27673-3] use this capability to produce time lapse images of flooding in and around Houston and Havana after landfalls by Hurricanes Maria and Irma, respectively. These results demonstrate the wide range of future applications of CYGNSS data as the mission moves forward into its third year.
December 10th, 2018 by Batu Osmanoglu, Ludo Brucker, and the SWESARR Team
SWESARR flew two more flights before coming home. The second-ever SWESARR flight was on December 3, 2018, and the third flight was on December 4. The weather conditions on December 3 did not allow the aircraft to fly over Colorado’s Grand Mesa, so we used that flight opportunity to update the instrument parameters and nail down the settings before a flight to the mesa.
On December 3, we also changed the flight crew a little bit. Quenton Bonds, Rafael Rincon and Chase Kielbasa flew on the aircraft collecting data around the airport. The main difference between these flights and the first flight was that the roll compensation sensitivity was reduced by 20 percent to compensate for the aircraft roll without being sensitive to the aircraft vibration. Also it snowed between Sunday and Monday, making the imagery a bit more scenic and relevant to SWESARR.
Using the data from December 3, Tobias Bollian was able to generate first geocoded and first-cut motion compensated images from SWESARR. Without the precise GPS clocks the accuracy of the motion compensation and geocoding are not ideal, but they confirm that the instrument parameters are reasonably well defined. For these images, the resolution is kept at 2.5 meters, even though the instrument’s native resolution can support about 1-meter resolution.
The next day, the weather was good and team was ready for a flight over the Grand Mesa. SWESARR team member Ludo Brucker, and SnowEx team member Chris Hiemstra were also on the ground to support SWESARR flights over the Mesa. Flight lines were coordinated in advance so that ground and air teams could collect data over the same areas.
Preliminary images over Grand Mesa around the intersection of Forest Service (FS) 100 Rd and FS 44 5/10 Rd show a partially frozen lake in these radar images from December 4, 2018. The areas where liquid water remains appear dark, while most of the lake has a much brighter backscatter. Because a single antenna is used for three different frequencies, the illuminated swath changes from about 600 meters to about 300 meters from X to KuHbands from an altitude of 1500 meters above the ground level.