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Author Archives: honora
From Marco Brogioni and Giovanni Macelloni (IFAC-CNR), 27 November 2013
Spring has arrived in Antarctica and, like previous years, it’s time leave for our summer campaign.
This is an multiyear campaign called DOMEX-3 that we carry out at Dome-C in Antarctica in support of ESA’s SMOS satellite mission.[caption id="attachment_1700" align="aligncenter" width="425"] Radomex L-band radiometer on observation tower. (M. Brogioni)[/caption]
The aim of the campaign is to build up a collection of a well-calibrated, multiyear, time series of L-band brightness temperature measurements and infrared brightness temperature over two years. These data are compared with those of SMOS to verify that the satellite instrument is calibrated.[caption id="attachment_1699" align="aligncenter" width="640"] Radomex L-band microwave radiometer. (M. Brogioni)[/caption]
The experiments are conducted at the Italian–French base of Concordia. The base is situated on East Antarctica’s polar plateau (75°06’06’’S latitude, 123°23’42’’E longitude), about 1000 km from the coast. At an altitude of 3280 m, the average air temperature throughout the year is –50.8° C (–30° C in summer and –60° C in winter).
The DOMEX-3 campaign, is carried out by an Italian team from the Institute of Applied Physics ‘Nello Carrara’ in Florence led by Giovanni Macelloni. It is supported by ESA and by the Italian Programme of National Research in Antarctica (PNRA).
This year, Marco Brogioni, an IFAC researcher, arrived at Concordia for the first time. Below is an excerpt from his nice diary, describing the cold!
Theoretically, I know a lot about the such expeditions since my colleagues have been there several times and I’ve heard their tales, however, being the actor and not the spectator is really different.
The preparation for the voyage started several months ago with a two-week PNRA training course, where the instructors tried to prepare us for a unique experience. Then on 2 November my journey started.[caption id="attachment_1698" align="aligncenter" width="640"] Marco Zucchelli station. (M. Brogioni)[/caption]
Thousands of miles from home, I arrived in Antarctica at the ‘Mario Zucchelli’ station, the Italian base on the Ross Sea coast. It was quite shocking. The temperature of –10°C wasn’t a shock though, this is a common winter temperature in my country, it was the surroundings that were strange.
We are used to the sea continuously moving and here it is perfectly still. The ice covers the entire gulf in front of the base and it seems as though you are looking at a picture rather than at something real.
I felt a strange sensation that reminded me of when Michelangelo, the great artist, was supposedly seated in front of his Moses sculpture, hit it with a hammer asking, “Why you don’t speak to me?!” It was my inner feeling, “Sea, why you don’t move?”[caption id="attachment_1695" align="aligncenter" width="640"] Plateau inner Antarctica. (M. Brogioni)[/caption]
After the second leg of my journey I arrived at the Concordia base Italian-French base at Dome-C which appears as two cylindrical buildings in the middle of a flat white desert. When you get out of the Busler (the DC-3 airplane’s nickname, which bring us in the heart of Antarctica) a temperature of –45°C and a 650 mBar atmospheric pressure welcome you. It’s a real shock!
My head felt light and I struggled to breath. It’s the effect of low oxygen levels in the air. Concordia is about 3200 m high, but actually because of Earth’s rotation it is like it was at 3700-4000 m. This was just my first impression of what Antarctica is.[caption id="attachment_1697" align="aligncenter" width="640"] Marco in his ‘heated’ tent laboratory. (M. Brogioni)[/caption]
I will discover what it’s really like in the coming days. Our accommodation is in the ‘summer camp’, which is 500 m away from the base – so every morning we have to commute.
The morning temperature is –50°C, but it feels like –70°C as the wind blows at around 20 knots. It was totally shocking. Not just because the air freezes my nose and my face, but because my whole body is affected. For the first time in my life I feel pain before feeling cold.
Even if you are properly dressed for this harsh environment, nothing can stop the brute force of mother Nature. Yes, compared to her we are really nothing.
As soon I get inside my mind goes to the great Antarctic explorers, Scott, Shackleton, Amundsen…. now I start to understand what it is written in their diaries. Now they gain my eternal maximum respect![caption id="attachment_1701" align="aligncenter" width="640"] Halo around the Concordia station in Antarctica. (M. Brogioni)[/caption]
From Bob Brewin (Plymouth Marine Laboratory, UK), 4 November – currently doing experiments for ESA aboard the RRS James Clark Ross on the 23rd Atlantic Meridional Transect
We are roughly 40 degrees south and 45 degrees west, heading for the Falkland Islands where we are due to arrive on Saturday. We have two more days of sampling left and I am very much looking forward to (for the first time in two weeks) not having to get up at 4:30 am on Thursday![caption id="attachment_1681" align="aligncenter" width="640"] Two filters that have had 1 litre of surface water (~5m depth) filtered through them. (B. Brewin)[/caption]
We are now in very productive waters. The picture above shows two 25 mm GFF filters that have had 1 litre of surface water (~5 m depth) filtered through them. The colour in the filter is caused primarily by the concentration of phytoplankton in the water.
A few days back, when we were in the very blue waters (see last post), it would probably have taken 6–8 litres of surface water (maybe more) to get anywhere near this colouration.
The yellow colour of the filter is indicative of a phytoplankton community dominated by diatoms and in the right filter you can even spot a red copepod (zooplankton) antenna.[caption id="attachment_1683" align="aligncenter" width="640"] The ‘Secchi depth’ can be related to the concentration of phytoplankton in the water. (B. Brewin)[/caption]
In a space of a day, the ‘Secchi depth’ changed from 35 m to 19 m. A Secchi disk is a 30 cm white disk that is lowered into the water until the point at which it disappears. The depth of disappearance is known as the Secchi depth.
The Secchi disk is one of the oldest bio-optical instruments and has been in use since the late 19th century. In additional to the high-tech bio-optical instrumentation we have on our optics rig (see above), we also attached a Secchi disk. This way we can continue this decadal-long time-series of observations.
The Secchi depth can be related to the concentration of phytoplankton in the water (see figure above). We have compared our Secchi depth measurements taken on this cruise with the average chlorophyll concentration estimated from satellite at the same location in an October climatology (we will use the concurrent chlorophyll concentrations once they are processed after the cruise).
Demonstrated in the figure above, as the chlorophyll concentration decreases (a pigment indicative of phytoplankton biomass) the Secchi depth typically increases. The black line shows the typical relationship between chlorophyll and Secchi depth observed elsewhere in the global ocean. These Secchi depth measurements can also be used to validate algorithms designed to estimate the Secchi depth using satellite ocean-colour data, as demonstrated using the October monthly satellite climatology (bottom right figure above).[caption id="attachment_1682" align="aligncenter" width="640"] Battling through the ‘Roaring Forties’. (B. Brewin)[/caption]
As we approached 40 degrees south, we have entered the region of the ocean known as the ‘Roaring Forties’ and have been blasted by 51 knot (Beaufort 10) winds and the ship has been rocking from side-to-side. Hopefully the wind dies down tomorrow, though I am not sure the swell will?[caption id="attachment_1685" align="aligncenter" width="635"] Strong winds (B. Brewin)[/caption]
ESA’s Craig Donlon says, “A great benefit of the AMT cruise is the wide range of ocean and atmospheric conditions encountered along the transect – allowing a suite of measurements to be made that sample the processes and conditions that we measure from space. Bon courage as you head into the wilds of our blue ocean planet Bob!”
From Bob Brewin (Plymouth Marine Laboratory, UK), 31 October – currently doing experiments for ESA aboard the RRS James Clark Ross on the 23rd Atlantic Meridional Transect
Since passing the equator and surviving the ‘crossing the line ceremony’ we have been sampling constantly for over a week. I have now filtered nearly 1500 litres of water through 25mm 0.7 micron filter-pads!
We have now crossed the South Atlantic Gyre one of the least productive regions of the ocean, it’s often referred to as an ‘oceanic desert’. Here, as the photo below shows the water is as blue as it can get.[caption id="attachment_1672" align="aligncenter" width="640"] The incredible blue waters of the South Atlantic Gyre. (B. Brewin)[/caption]
The plot below shows the AMT23 transect overlaid onto a satellite chlorophyll climatology of October. The pink dot (roughly –20 latitude and –25 longitude) highlights where this photo was taken.
It is in a region of the Atlantic Ocean with the lowest total surface chlorophyll concentration –chlorophyll being a photosynthetic pigment in phytoplankton, indicative of its biomass.[caption id="attachment_1674" align="aligncenter" width="640"] The AMT23 transect overlaid onto a satellite chlorophyll climatology of October. The pink dot shows our current location. It is region of low surface chlorophyll concentration. The graph on the right shows remote-sensing reflectance spectra in the same region. (B. Brewin)[/caption]
Alongside the map shows a remote-sensing reflectance spectra (after an initial processing) captured using our hypersepctral radiometer (Satlantic HyperSAS) at the same location as the photo was taken.
The remote-sensing reflectance is essentially a ratio of upwelling radiance to downwelling irradiance. In simple terms it is the ratio of light coming out of the ocean to that of light coming into the ocean plotted on a linear and a logarithmic scale (y-axis) as a function of wavelength (x-axis) in the UV to visible portion of the electromagnetic spectrum.
As can be seen in the plot, at UV and blue wavelengths (300–500 nm) the reflectance is very high, whereas green and red wavelengths (500–700nm) the reflectance is much lower.
Part of the reason these waters are so blue is that the phytoplankton concentrations at the surface are very low (the chlorophyll pigment in phytoplankton absorbs blue light), such that the optical properties of pure seawater dominate the reflectance signal (pure seawater absorbs light at red and green wavelengths with a higher intensity than at blue wavelengths, and also scatters blue wavelengths with a higher intensity than red and green wavelengths).[caption id="attachment_1673" align="aligncenter" width="640"] Heading for the Falklands and the sea is getting rougher. (B. Brewin)[/caption]
We are now heading for the Falklands where we are due to arrive in a week and a half. The sea is already getting rough. However, we are heading for greener waters which essentially means two very importance things: i) we are likely to see more marine life such as whales etc … and ii) I will be filtering less water!
From Bob Brewin (Plymouth Marine Laboratory, UK), 24 October – currently doing experiments for ESA aboard the RRS James Clark Ross on the 23rd Atlantic Meridional Transect
The past week has flown by. The figure below, courtesy of Arwen Bargery, shows the ocean temperature, salinity, fluorescence (an index of phytoplankton biomass), oxygen and beam transmission. These are all derived from the vertical profiles at each station we’ve so far sampled.[caption id="attachment_1667" align="aligncenter" width="634"] Vertical profiles of ocean temperature, salinity, fluorescence, oxygen and beam transmission. (A. Bargery)[/caption]
As we moved south through the North Atlantic, we have observed a general increase in ocean temperature (especially at the surface) and salinity.
The fluorescence data indicate that at the start of the cruise we were in ‘high chlorophyll’ waters (relatively speaking). The fluorescence signal then weakened as we moved towards 30° N and the maximum concentration, often referred to the deep-chlorophyll maximum, DCM, deepened.
We then observed a shallowing of the DCM and a slight increase in the fluorescence signal as we moved toward the equator. This is likely be related to the upwelling of nutrient-rich waters associated with this region.
My daily routine, described in the previous blog post, has not deviated too much. However, a few days back I helped Giorgio Dall’Olmo deploy two Bio-Argo floats. These devices are at the cutting edge of bio-optical oceanography.[caption id="attachment_1668" align="aligncenter" width="480"] Helping Giorgio Dall’Olmo. (B. Brewin)[/caption]
Argo floats essentially consist of a floating device that supports a number of oceanographic instruments, including temperature, conductivity (from which we can derive salinity) and pressure (from which we can derive depth) sensors.
In addition to these instruments, the Bio-Argo floats contain a suite of bio-optical instruments including light sensors, fluorometers and devices that measure optical backscattering. The floats sink to around 1000 m and, once every five days or so, the device floats to the surface while measuring these oceanographic variables.[caption id="attachment_1670" align="aligncenter" width="480"] Deploying ‘Bio-Argo’ float. (B. Brewin)[/caption]
This information is then transmitted to a satellite, which relays it to the Argo network where scientists can access the data in near-realtime.
Whereas ocean-colour satellite data can only observe the surface of the ocean (40m at maximum) these Bio-Argo floats extend the synoptic capabilities of satellite remote-sensing down into and through the photic zone, which is the region of the surface ocean where light penetrates.
The synergistic use of Bio-Argo floats and satellite ocean-colour data are likely to revolutionise our understanding of marine biogeochemistry and I was very excited to help deploy two of these new floats with Giorgio.
The temperature and humidity are now soaring as we approach the equator and shortly, I will be experiencing my first ‘crossing the line ceremony’.
This means that my first day off in nearly two weeks will involve trying to dodge, as best I can, the dreaded consequences of passing the equator for the first time on a ship (flights don’t count unfortunately). Wish me luck!
Craig Donlon, ESA’s Principal Scientist for Oceans, says, “Thanks Bob! Taking ocean measurements such as these is fundamental to understanding the data we get from satellites – all very much appreciated!”
[custom_field limit="0" between=", " /]From Bob Brewin (Plymouth Marine Laboratory, UK), 15 October – currently doing experiments for ESA aboard the RRS James Clark Ross on the 23rd Atlantic Meridional Transect
We started sampling last Wednesday following the confirmation of our route, shown in the figure below.[caption id="attachment_1658" align="aligncenter" width="449"] 23rd Atlantic Meridional Transect cruise track[/caption]
I may be a cruise, but it certainly is hard work. Over the last four days my routine has been intense. I am up at 05:00 to set up for the pre-dawn conductivity temperature and depth profile during which the first optics cast is deployed.[caption id="attachment_1659" align="aligncenter" width="596"] Pre-dawn conductivity temperature and depth profile. (B. Brewin)[/caption]
I then filter water for three hours to extract phytoplankton pigment data at different water depths, before setting up the hyperspectral radiometer as I described in the previous blog post.
The filtering datasets are then logged and I then spend the rest of the morning processing the hyperspectral data.[caption id="attachment_1660" align="aligncenter" width="480"] Giorgio setting up for the second optics cast. (B. Brewin)[/caption]
After lunch, I help Giorgio Dall’Olmo with second optics cast while the second conductivity temperature and depth is deployed.
The afternoon and early evening is spent filtering more water for pigments, particulate organic carbon and fatty acids.[caption id="attachment_1661" align="aligncenter" width="640"] Giorgio deploying second optics cast. (B. Brewin)[/caption]
After dinner I just have time to call my wife and relax before crashing to sleep with the ‘motion of the ocean’.
Stefan Hendricks (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research) 8 October 2013
There aren’t many chances to do field work on polar sea ice in the depths of winter, and even fewer opportunities in Antarctica.[caption id="attachment_1642" align="aligncenter" width="640"] Polarstern in Antarctic winter (Stefan Hendricks, Alfred Wegner Institute)[/caption]
The Antarctic Winter Ecosystem & Climate Study (AWECS) of the German Polarstern Research Icebreaker, however, provided such an occasion.[caption id="attachment_1643" align="aligncenter" width="640"] Pancake Ice (Stefan Hendricks, Alfred Wegner Institute)[/caption]
Our voyage from Cape Town, South Africa, to our main working area in the Weddell Sea in Antarctica and back to Punta Arenas in Chile took nine weeks. We were in ice-covered areas from mid-June to early August, mid-winter in Antarctica – and dark for much of the time.[caption id="attachment_1644" align="aligncenter" width="640"] Working in the polar night and in a storm (Stefan Hendricks, Alfred Wegner Institute)[/caption]
One of the goals of the campaign, called CryoVex, was to look at how ESA’s CryoSat mission can be used to understand the thickness of sea ice in Antarctica. The extent of the sea ice here in winter is currently more than normal, which could be linked to changing atmospheric patterns.
This is in contrast to what we are seeing in the Arctic where there is a trend towards declining sea-ice extent in the summer. CryoSat is showing that ice continues to thin.[caption id="attachment_1645" align="aligncenter" width="640"] Airborne sea-thickness measurements with the EM-Bird (Stefan Hendricks, Alfred Wegner Institute)[/caption]
Sea-ice thickness data for Antarctica, which covers a larger area than Arctic sea ice, is also necessary to understand and potentially predict the future behavior of the ice.
To achieve sea-ice thickness retrieval with CryoSat, we have to understand the complex remote-sensing signature of snow on Antarctic sea ice and what it means for the range measurements of the CryoSat’s SIRAL radar altimeter.[caption id="attachment_1646" align="aligncenter" width="640"] Studies of snow properties (Stefan Hendricks, Alfred Wegner Institute)[/caption]
Therefore, swapping our northern hemisphere’s summer for winter in the southern hemisphere we sailed with Polarstern to Antarctica to study the properties of snow, its evolution in winter and to measure sea-ice freeboard and thickness for later validation of CryoSat data.
The validation activities continue with another Polarstern cruise-leg from August to October and an aircraft experiment in November at the Antarctic Peninsula. This specifically looks at how the satellite radar penetrates the snow overlying the sea ice.[caption id="attachment_1647" align="aligncenter" width="640"] Snow crystal (Stefan Hendricks, Alfred Wegner Institute)[/caption]
In the beginning of the cruise in mid-June we observed the main sea-ice growth phase of winter.
Sea ice in Antarctic very often forms as pancakes owing to the ever-present ocean swell. These pancakes solidify with time and get increasingly covered with snow.[caption id="attachment_1648" align="aligncenter" width="640"] Ice station (Stefan Hendricks, Alfred Wegner Institute)[/caption]
Since there is more snow fall in Antarctica then in the Arctic, the snow can push the ice surface 10–20 cm below the water layer.
This means wet shoes and complications when interpreting CryoSat range retrievals.
We measured snow depth and stratigraphy, freeboard and thickness at several ice stations where Polarstern was anchored to an ice floe. This had to happen in the dark and often in stormy conditions and we were grateful for the wind shadow and the lights of the ship.[caption id="attachment_1649" align="aligncenter" width="640"] Ocean heat (Stefan Hendricks, Alfred Wegner Institute)[/caption]
In the short hours of daylight and twilight, we used our onboard helicopters to obtain the regional sea-ice thickness distribution by our airborne sensor, the EM-Bird.[caption id="attachment_1650" align="aligncenter" width="640"] Aurora Australis (Stefan Hendricks, Alfred Wegner Institute)[/caption]
We have to understand the impact of the snow layer on the Antarctic sea-ice thickness retrieval with CryoSat first, but this data will serve as a benchmark for a possible sea-ice thickness data product.
Check out the AWI website for more information about the campaign.
From Bob Brewin (Plymouth Marine Laboratory, UK) 7 October 2013
After a five-day delay in departure, we finally got underway and left Immingham, UK, on 5 October. We first dropped in at Portsmouth where we arrived today to re-fuel, before eventually setting off for the Falkland Islands.[caption id="attachment_1638" align="aligncenter" width="640"] Leaving Immingham on AMT23 (B. Brewin)[/caption]
As part of the 23rd Atlantic Meridional Transect we will be taking oceanographic measurements over the six weeks it takes to arrive at the Falklands.
These measurements will be used to help validate and parameterise a new bio-optical model being developed within an ESA project.[caption id="attachment_1639" align="aligncenter" width="640"] Setting up the hyperspectral radiometers. (B. Brewin)[/caption]
Radiometric equipment is now set-up, and with the exception of a few teething issues, data are now coming in from the hyperspectral radiometer.
Setting up the radiometer was fun, it involved being hoisted up in a crane and attaching the ‘downwelling irradiance sensor’ to the front mast. We also set up the ‘sky and water radiance sensors’ on the front of the ship with the ‘tilt and roll sensor’.[caption id="attachment_1640" align="aligncenter" width="480"] Tilt and roll sensor. (B. Brewin)[/caption]
Filtration rigs are also set up and we are hoping to sample at our first cruise station on Wednesday.
From Bob Brewin (Plymouth Marine Laboratory, UK) 3 October 2013
Between the 3 October and the 4 November, I will be participating in the 23rd Atlantic Meridional Transect (AMT) cruise. Travelling on-board the RRS James Clark Ross, myself and other marine scientists depart from Immingham, UK, and take oceanographic measurements in the Atlantic Ocean for six weeks before arriving at the Falkland Islands.[caption id="attachment_1633" align="aligncenter" width="640"] RRS James Clark Ross (© NCEO)[/caption]
These measurements will be used to help validate and parameterise a new bio-optical model being developed within the ESA STSE DECIPHER project.
The project that aims to better quantify marine-ecosystem variability, and its natural and anthropogenic physical, biological and geochemical forcing, using remote-sensing observations.
AMT is a unique time-series of data (1995–2013) taken along a meridional transect in the Atlantic Ocean It is one of the only spatially extensive and internally consistent datasets on the structure and biogeochemical properties of planktonic ecosystems in the Atlantic Ocean.[caption id="attachment_1632" align="aligncenter" width="480"] Cruse track from AMT 19, colours represent low (blue) to high (red) chlorophyll-a concentrations (Taken from Hardman-Mountford et al. (2008) Remote Sensing of Environment 112 (2008) 3341-3352).[/caption]
So far, there have been 23 cruises, involving 223 scientists, supported over 200 publications and over 70 PhD theses.
My role on AMT 23 is to work on marine optics. I will be working alongside Dr Giorgio Dall’Olmo making the following measurements:
- Continuous ship measurements of above-water remote-sensing reflectance (ocean colour)
- Continuous under-way measurements of inherent optical properties (IOPs) including particle absorption and backscattering, and chlorophyll-a concentration.
- Water column profile measurements of IOPs (particle absorption, detrital absorption and particle backscattering) at 2 stations per day.
- Filtering water for measurements of phytoplankton pigments (using High Performance Liquid Chromatography); size-fractionated chlorophyll-a using fluorometry; Particulate Organic Carbon; fatty acids and suspended particulate matter.
- Measurements of atmospheric aerosol optical depth.
From Chris Derksen (Environment Canada) 22 April 2013
Following completion of the SnowSAR flights and ground measurements near Inuvik, the entire operation transferred to Alaska.
This included a rather complicated effort to ship the SnowSAR and aircraft installation (modified aft baggage doors for the Cessna-208 Grand Caravan) fromInuvik,Northwest Territoriesacross the border toFairbanks, Alaska.
Although these two communities are only separated by about 500 km by air, they are not efficiently connected either by air or ground. TheAlaskaand Environment Canada field crews made the nearly 3000 km road trip, starting with a southbound drive on the infamous Dempster highway to DawsonCity.
The Dempster, with its rough gravel surface, is known for eating tires, and the Environment Canada truck did not emerge unscathed.[caption id="attachment_1613" align="aligncenter" width="640"] Wrecked tire (Environment Canada)[/caption]
Nevertheless, three days after leaving Inuvik we crossed the Atigun Pass, through to the north slope ofAlaska, and arrived at theToolikLakefield station, operated by theUniversityofAlaska–Fairbanks.
Unfortunately, the shipping of the radar and aircraft doors toFairbanksdid not go smoothly. Owing to a series of missed steps beyond our control, the projected timeline for conducting the SnowSAR flights continued to slip.
Fortunately, our luck turned and thanks to some quick processing of our shipment by United States Customs. The SnowSAR instrumentation arrived safely inFairbanks, where the MetaSensing operator was waiting for the installation onboard a Cessna 208. The customised cargo doors for the SnowSAR antennas (X-band on the top window, and Ku-band on the bottom) can be readily interchanged among different C208 aircraft platforms, so we were ready for science flights on 18 and 19 April.[caption id="attachment_1614" align="aligncenter" width="640"] Customised doors (Environment Canada)[/caption]
The acquisition site was 600 km north ofFairbanks, and was reached with a 1.5 hour ferry flight. Before beginning the radar acquisitions, a short stop and go was performed at a small landing strip (nearGalbraithLake, at the north end of theBrooks Range) for coordination with the ground team.
The SnowSAR acquisitions began overToolikLake, where 12 corner reflectors were placed for radiometric calibration.[caption id="attachment_1616" align="aligncenter" width="427"] Caravan approach (Environment Canada)[/caption]
The tracks left by the snowmobiles reveal the locations of the targets in three parallel lines, one for the co-pol corners, one for the cross-pol at X band, and one for the cross-pol at Ku-band. The field station facilities can be seen in the bottom right of the aerial image.[caption id="attachment_1617" align="aligncenter" width="640"] Snow survey lines (Environment Canada)[/caption]
Our American colleagues had already started the snow measurements in the Imnaviat Creek watershed, which included an intensive 1 km by 1 km grid of snow survey lines.[caption id="attachment_1618" align="aligncenter" width="640"] ‘Crop circle’ patterns (Environment Canada)[/caption]
One unique aspect of these ground measurements was a FMCW radar (designed, built, and operated by Dr. H-P Marshall,BoiseStateUniversity) operating in the same frequencies as the SnowSAR. This instrument was also deployed during SnowSAR flights inAustriain February. In the photos below, you can see 1 km snow survey lines (separated by 100 m) and ‘crop circle’ patterns where the FMCW acquired measurements in a spiral pattern.
The snow cover properties at Imnaviat Creek inAlaskawere markedly different from Trail Valley Creek nearInuvik. Meteorological conditions combined to create a depth hoar layer at Imnaviat that was remarkable. These large faceted grains are found at the bottom of the snowpack, and form as a result of temperature-induced vapor pressure gradients in snow. In over 30 years of snow surveys at Imnaviat, our colleague Matthew Sturm noted that he had never seen depth hoar crystals as large as what we measured this year. The grid spacing in the photo below is 2 mm, so this depth hoar crystal was approximately 14 x 12 mm in size. The impact of these large crystals on the airborne SnowSAR measurements will be important to determine.[caption id="attachment_1619" align="aligncenter" width="640"] Depth hoar crystal (Environment Canada)[/caption]
Despite some stressful moments when our timeline was slipping, in the end we managed to acquire nearly coincident airborne SnowSAR and LiDAR measurements, with detailed ground-based surveys, in harsh Arctic environments, in two countries, separated by only 8 days. More than 15 hours of SnowSAR acquisition flights were achieved inAlaskaandCanadain the last two weeks, from which more than 250 SAR strip images will be obtained.
Over the coming months we will quality control all the ground measurements, and the final SnowSAR and LiDAR datasets will be processed. These various datasets will then be utilized to improve our knowledge of X- and Ku-band radar response to snow cover properties, and our ability to retrieve snow water equivalent (the amount of water stored in solid form by the snowpack) from these measurements.
Ultimately, we will combine our work with the analysis of SnowSAR data acquired inFinlandandAustria, to maintain the current momentum behind radar remote sensing of snow. Now that the melt season is imminent, the SnowSAR will take well deserved vacation…unti the next mission of course!
The success of this ambitious data acquisition plan (as well as the campaign periods in December and March) was due to the hard work of many people and organisations. A big thanks to:
- MetaSensing for the installation and operation of the SnowSAR, particularly Alex Coccia for his flexible travel schedule;
- Pilots and staff at North-Wright (Inuvik) and Wright’s Air Services (Fairbanks);
- Lake Central Aircraft Services for the development of a flexible aircraft installation for the SnowSAR;
- Staff at the Aurora Research Institute and Toolik Lake Field Station for their logistical support;
- The large group of participants who contributed to ground data collection, often under harsh Arctic conditions;
- EnvironmentCanada, the European Space Agency, and NASA Terrestrial Hydrology Program for financial and logistical support
From Chris Derksen (Environment Canada)12 April 2013
The final phase of the Canadian SnowSAR campaign is now complete, with successful flights conducted over the Trail Valley Creek study site on 8–9 April.
There was a major addition to the experiment – an airborne LiDAR system was also flown, onboard a turbo Otter aircraft on 6–7 April.
The same flight lines were covered by both the SnowSAR and the LiDAR. So, we will have 1 m resolution snow-depth estimates from the LiDAR to compare with the SnowSAR measurements and the blowing snow model simulations that will be conducted at Environment Canada.[caption id="attachment_1603" align="aligncenter" width="640"] Otter aircraft on approach. (Environment Canada)[/caption]
The LiDAR flights, funded by NASA, were coordinated by collaborators at theUniversityof Alaska Fairbanks. Four scientists made the long drive fromFairbankstoInuvikto participate in the snow sampling during the campaign period.[caption id="attachment_1604" align="aligncenter" width="640"] Ground sampling. (Environment Canada)[/caption]
Conditions were cold and windy during most of the ground sampling period. The focus was similar to the previous measurements made in December and March: long snow-depth transects along the flight lines, and snow stratigraphy measurements to understand the layered properties of the snowpack.[caption id="attachment_1605" align="aligncenter" width="640"] Snow trench. (Environment Canada)[/caption]
Ground penetrating radar measurements were also performed. It was quite the achievement to keep all the cables untangled![caption id="attachment_1606" align="aligncenter" width="640"] Ground-penetrating radar and cables. (Environment Canada)[/caption]
The Inuvik campaign is now complete and we are in the midst of transferring the SnowSAR toFairbanks,Alaska, after which flights will be conducted near theToolikLakeresearch station.
While the radar is on its way via air, the ground team is presently waiting out a blizzard in Inuvik before making the drive toAlaska. A final blog post will be provided fromAlaskain a few days.
The final photo for this post shows the tundra landscape of the western portion of the Trail Valley Creek watershed. TheMackenzie River, surrounded by forest, can be seen in the distance. If you look closely, you can see a wide path of trampled snow, left by a reindeer herd that recently moved through.[caption id="attachment_1607" align="aligncenter" width="640"] Tundra landscape of Trail Valley Creek. (Environment Canada)[/caption]