The airplanes went home in December. The radars pulled out in January. So what is going on with OLYMPEX in February and March? In our past blogs we stressed how during OLYMPEX we measured the structure of precipitation as winter cyclones passed from the Pacific Ocean across the Olympic Peninsula and the Olympic Mountains. And most of our focus was on measuring rain. But OLYMPEX is also tasked to measure snow, both the structure of falling snow crystals and the building of the snowpack throughout the entire winter season. Snow is one of the most difficult things to measure – both from space and on the ground. In this blog post I will highlight how it takes Olympic efforts to measure snow during this extended field phase of OLYMPEX.
Some of the key quantities that we need to measure are the snow characteristics, i.e. the shapes, sizes and water content of falling snowflakes. In order to do that, instruments that measure these characteristics needed to be placed at elevations that frequently experience snow. The best location we found is on the north side of the Olympic Mountains at Hurricane Ridge within the Olympic National Park. We installed a Micro Rain Radar (MRR), a Parsivel Disdrometer and a Precipitation Imaging Package (PIP) which are shown below. The PIP works especially well in this environment as it can accurately collect data in strong winds, such as the 80mph winds that frequently accompany the winter storms as they assault the aptly named Hurricane Ridge.
However, none of the instruments could quite handle the major snow dump we experienced in late December! Snow continues to accumulate and right now there is approximately 240 cm, or close to 8 feet of snow on the ground at Hurricane Ridge (luckily not covering our instruments!).
Another way we are measuring snow and rain is with an instrumented trailer. The trailer is parked for the winter just outside the National Park at location at 3000’ elevation, where both rain and snow can fall any time throughout the winter.
The trailer has a Pluvio type of rain gauge and a Parsivel Disdrometer. The Pluvio is a very sensitive weighing type rain gauge that has a glycol mixture in it so falling precipitation, either liquid or frozen, will melt and the liquid equivalent is measured. The Parsivel Disdrometer measures the sizes of the falling drops or snowflakes and has a thermometer so we can tell if it is below freezing. Earlier in the project when the radars and airplanes were flying in storms, this trailer mostly experienced rain. However starting in mid December, the storms became colder and the trailer frequently experienced snow. Sometimes a bit too much snow.
A team of National Park rangers and our own graduate students often had to hike, ski or snowshoe to the trailer to dig it out, empty the Pluvio or recharge the batteries. In one 10 day period in early December, the trailer recorded over 40” of precipitation. That is more than the average annual precipitation in ‘rainy’ Seattle. So far, it has recorded over 200” of precipitation (liquid – Snow Water Equivalent, SWE) since October 1, and during the latest visit to the trailer around March 7, there was a foot of new snow.
Another important part of measuring snow is measuring the snowpack. Currently there are only 4 SNOw TELemetry or SNOTEL locations in the Olympic Mountains. These are permanent installations that make long term measurements of snow depth, total precipitation and other meteorological measurements (http://www.wcc.nrcs.usda.gov/snow/). In the Olympics Mountains, these are located mostly in the northeastern section. However, our focus was on the south and southwestern sides where there are no SNOTEL sites. In order to document the accumulating snowpack and the eventual melt-off, Dr. Jessica Lundquist of the Civil and Environmental Engineering Department at the University of Washington and her team of hardy graduate and undergraduate students installed snow stakes and remote cameras at 18 locations within the higher terrain on the southwestern side of the Olympic Mountains. Each site was installed in the summer in a series of backpacking trips deep into the wilderness areas.
The cameras are installed in trees and take pictures of the stakes (with marks every 10 cm) several times a day. As the snow falls, the total on the ground is measured by the snow stake and photographed by the camera. Then the following summer the memory card from the camera is retrieved and analyzed.
Sometimes the students found that the stakes were mysteriously bent. They speculated that either wind or avalanches caused these problems. However at one site, the local inhabitants appeared to want to have a say in the new decorations of their meadow.
A key component to interpreting the data from snow cameras is to have measurements of the density of the snow pack. That way the snow depth as photographed by the cameras can be converted to SWE, which tells how much water is stored as snow. That can only be done through direct measurements of the snowpack through snow surveys. For OLYMPEX, there will be two snow surveys, one in midwinter and one at the peak snowpack in April. The midwinter snow survey took place last February and is shown below. Here they are weighing the snow collected by the tube in order to calculate the density of the snowpack.
Lastly, coincident with the snow survey, measurements of the snow depth over the entire Olympic Mountains were taken by Lidar instruments aboard the NASA Airborne Snow Observatory (ASO) plane of JPL (aso.jpl.nasa.gov). A second flight will take place in April coincident with the next snow survey.
OLYMPEX– measuring rain and SNOW – over the Olympic Mountains.
The AfriSAR campaign is in its second week of collecting data over different forests of Gabon using airborne radar and laser instruments, UAVSAR and LVIS. While most of the NASA airborne crew are located in the City of Libreville supporting the data acquisitions and logistics, the science teams have been busy collecting data on the ground to compare and verify the airborne observations.
A group from the NASA team drove to the center of Gabon to visit Lope National Park, a study site well known for its diversity of forests and animals, and its attractive landscape. Lope covers an area of 4948 square kilometers; it has been a wildlife reserve since 1946 and national park since 2002. The study site for AfriSAR is an area of about 500 square kilometers located in the north of the park covered by savanna grasslands mixed with forests of different types and structure. In addition to measuring the study site with all airborne sensors, we are also mapping the entire national park for the National Park Service of Gabon (ANPN) with the UAVSAR radar.
On March 1, during the UAVSAR flights over Lope, Laura Duncanson from NASA/GSFC and Suzanne Marselis from University of Maryland (both from the NASA GEDI team), and Victoria Meyer and I from NASA/JPL (from the NISAR team) were on the ground collecting tree structure and soil moisture for both lidar and radar studies.
Before we arrived to the forest, we saw an elephant with her calf strolling along the edge of the forest and enjoying the fresh and cool hours of the morning. The sighting reminded us that unlike the tropical forests of the Americas, the large animals known as the African mega fauna are a major part of the ecosystem, shaping the forest structure and its dynamics. This time of the year, more than a month into the rainy season, most semi-deciduous trees in Lope are fruiting and flowering, providing nutrition for the forest and its animals. Before going to the field, we were advised by the park rangers to watch for the presence of elephants and gorillas in the forest feeding on fresh fruits.
The measurements in the field were collected in an existing network of biomass plots distributed in young and old forests and extending from the edge of the savanna to more than a kilometre into the forest. The GEDI team established small plots to simulate the 25-meter GEDI footprint, and recorded tree height and diameter, crown size, and forest canopy cover. The lidar sensor on GEDI will start sampling the Earth’s forests globally from the International Space Station sometime in 2018. LVIS provides similar measurements from the airborne platform giving the team an opportunity to examine the performance of GEDI before its launch in a complex forest. LVIS flew over Lope on March 2 and collected data over the study area coincident with ground measurements.
The NISAR team concentrated in taking samples of the soil moisture in areas where tree structure is measured during the UAVSAR overflights. The goal of these measurements was to quantify the effect of the moisture on the radar measurements of the above ground biomass. The radar signal penetrates into the forest canopy, bouncing back from tree stems and branches that contain almost the entire forest biomass or carbon stock. Depending on the density of the forest canopy, the radar measurements may reach the soil surface and reflect back, introducing errors in measurement of forest biomass. The NISAR mission will be launched in 2020 and is designed to cover the global vegetation wall-to-wall every 12 days to measure biomass with precision by removing the effect of soil moisture. For both GEDI and NISAR missions, Lope provides an ideal site with open and closed canopy forests, covering a range of biomass and giant trees scattered over a landscape with different slopes and moisture.
On the day of UAVSAR flight, the team encountered a giant Moabi, one of Africa’s most spectacular trees, more than 500 years old, standing tall up to 60 meters in height and with a majestic crown casting shade over a large area of the forest about half the size of a football field. Moabi trees have succulent fruits used by animals and seeds for cooking oils used by humans. Elephants swallow and disperse the seeds reinforcing the cycle of regeneration in the forest. Both the smell and the sound of falling fruits weighing about 250 grams can attract elephants to the site of the Moabi. Elephants use low frequency calls, which carry over distances of up to 5 kilometers in the forests, to communicate to others to join the feast of fruiting in the park. Moabi trees have been sought by loggers for their brown-pink and hard wood and are exploited all over Central Africa. Once the trees are cut, the chances of another one growing is slim as there are no seeds for dispersal, a scenario that may end in extinction of some of the wonders of the nature in Africa. Moreover, the loggers open the forests for poachers, who target elephants for their valuable ivory. Despite a ban on the international trade in ivory, African elephants are still being poached in large numbers.
Finding a Moabi tree is a rare occasion. But here in Lope, both Moabi trees and the elephants are protected. While quantifying the structure of large trees in the field, we also collected soil moisture measurements at intervals of 20 meters in the plots to compare with the radar measurements at similar resolutions. The soil measurements were collected at the depth of 15 centimeters to capture the variations of moisture near the surface. A quick look at the data showed that Lope is significantly dryer than the coastal forests of Mondah, the location of another AfriSAR study site. The average total rainfall in Lope is 1500 millimeters a year, almost half of the rainfall in Mondah and the city of Libreville. Our soil moisture measurements reflected this difference in rainfall, showing dry conditions in the forests and savanna of Lope, except, under the shade of the giant Moabi, where it was cooler and moist. The large difference in rainfall does not reflect in how tall the trees may grow in these sites, and for the same reason in most of humid tropics. With climate and other environmental variables playing a much smaller role in predicting the variations of forest structure and biomass, direct measurements from remote sensing techniques from space may be our only chance to quantify the size of trees and their carbon stocks globally.
Gabon is home to one of the most pristine rainforests on the planet—devoid of people and intact in most places, while rich in animals and plants. The Gabonese forests are representative of the Congolian tropical forests, altogether the second largest rainforest in the world after the Amazon. This makes the small Central African country the ideal field site for AfriSAR, a campaign to test technologies that will lead to future space missions to measure forests from space.
During two weeks in February and March 2016, NASA will collaborate with space agencies in Gabon and Europe to collect measurements of plant mass, distribution of trees, shrubs and ground cover, as well as diversity of plant and animal species—not only from Gabon’s rainforest but also from the country’s wetlands, mangrove forests, and savanna. The data, gathered through airborne radar and laser instruments, as well as from ground teams, will improve our understanding of the role of forests in the carbon cycle. Scientists now think that the world’s forests absorb about a quarter of all the carbon dioxide we put in the atmosphere through the burning of fossil fuels, but to confirm this they need better studies of forest structure and biomass.
To learn more about AfriSAR, read our release and watch the video here.
Field season is an exciting time for scientists – we leave behind the comforts of labs and offices to collect data in remote locations. Preparing for the field season is no easy task and requires an enormous amount of planning. Considerations such as “how many data loggers can I fit in my checked bag?” and “have I packed enough mosquito spray and Snickers bars?” are important parts of the equation. So is safety. In the field we are responsible for the well-being of ourselves and the team. We need to be prepared for exposure to cold weather, travel in rugged landscapes and any medical incidents that may arise.
To learn more about field safety, my colleagues and I recently traveled to southcentral Alaska for three days of wilderness first aid and snow machine safety training under the guidance of Dorothy Adler, a certified instructor with SOLO schools and the North American Outdoor Institute.
Day 1: Looking at the disarray in my personal first aid kit, it was apparent that I needed professional help. Fortunately Dorothy was there with detailed advice that included an extensive list of items to add to our medical packs and how to use them. SOAP (Subjective Objective Assessment Plan) Notes, a rigorous way to document patient information, were drilled into our heads. We also practiced patient assessments and exams on paper and with partners, which included obtaining and monitoring vital signs (e.g. heart and respiratory rate), ascertaining the location and condition of injury or illness, patient treatment and emergency evacuation.
Day 2: We continued to practice our SOAP Notes while learning how to properly address conditions such as shock, musculoskeletal and soft tissue injuries, including splinting, spinal cord management, wound care and cold-related injuries. A highlight was working through “real life” outdoor emergency scenarios as a team. One of these scenarios involved multiple victims having severe injuries after falling down a mountain cliff. The rescuers were faced with assessing and treating injuries ranging from a broken tibia/fibula, a ruptured spleen and head/spinal trauma. Dealing with emergencies is never easy, but it does become more manageable with preparation and ongoing training.
Day 3: We ventured outside of the classroom into the beautiful Alaskan wilderness to practice cold weather travel and snow machine (also known as a “sled”) safety. At first I was nervous to be operating a powerful Polaris, but gradually became more comfortable as we experienced driving on hard-packed snow and icy trails. A practical skills course on a frozen lake had us setting up anchors with ice screws and rope systems to tow out a stuck machine (this is not trivial, as they easily weigh over 185 kg). We also practiced correct methods for side hilling, using avalanche beacons and staying warm in a cold environment. After a long but rewarding day it was time to fire up the sled and return home (safely).
Jennifer Watts is a PhD candidate at the University of Montana and researcher with the ABoVE campaign.