|Wednesday, June 02|
Development of a new satellite radar mission for seasonal snow mass
* Chris Derksen, Environment and Climate Change Canada, Canada
J. King, Canada
J. Lemmetyinen, Canada
V. Vionet, Canada
S. Belair, Canada
C. Garnaud, Canada
V. Fortin, Canada
Y. Crevier, Canada
P. Plourde, Canada
B. Lawrence, Canada
G. Burbidge, Canada
"Current satellite observing systems lack the capability to derive terrestrial snow water equivalent (SWE, the amount of liquid water stored by snow) at the spatial resolution, synoptic sensitivity, global coverage, and accuracy required for operational environmental monitoring, services, and prediction. The required combination of revisit time, spatial coverage, measurement resolution, and sensitivity to the mass of snow on the ground necessitates a new spaceborne observing concept. To address this observing gap, Environment and Climate Change Canada (ECCC), the Canadian Space Agency (CSA), industrial partners at Airbus, and international scientific collaborators are developing a new satellite radar mission concept primarily focused on seasonal snow, but of high relevance to other variables such as freshwater ice, glaciers, frozen ground, and ocean winds. Following technical trade-off studies, a concept capable of providing dual-polarization (VV/VH), moderate resolution (500 m), wide swath (~250 km), and high duty cycle (~25% SAR-on time) Ku-band radar measurements at two frequencies (13.5; 17.25 GHz) was identified. Ku-band radar is a viable approach for a terrestrial snow mass mission because these measurements are sensitive to (1) SWE through the volume scattering properties of dry snow and (2) the wet/dry state of snow cover. These two parameters characterize the key aspects of snow relevant to hydro-climatological applications. Analysis of data from recent field campaigns has focused on identifying the physical drivers of the radar response to SWE at Ku-band, particularly the influence of snow microstructure which complicates the relationship between radar backscatter and SWE. Analysis of tower-based Ku-band radar measurements from Finland show that applying a single, seasonally optimized radar-derived estimate of snow microstructure was sufficient to parameterize radar retrievals of SWE to an accuracy of ~26 mm (unbiased) RMSE with a coefficient of determination of 0.74. An airborne 13.5 GHz synthetic aperture radar deployed within the Trail Valley Creek (TVC) research basin (Northwest Territories, Canada) collected measurements over three periods (December 2018, January 2019, March 2019) to characterize interactions with snow, soil, and vegetation. Distributed snow property measurements including SWE and microstructure were completed during each flight campaign. These collective datasets were used to parametrize the Snow Microwave Radiative Transfer (SMRT) model. Electromagnetic models such as SMRT and snow microstructure simulations from physical snow models can constrain the forward simulations required for the inversion of SWE, and facilitate the direct ingestion of Ku-band backscatter into land surface data assimilation systems, analogous to how L-band brightness temperatures are assimilated for soil moisture. This presentation will provide an overview of the Ku-band radar mission technical concept, and ongoing science activities in support of the mission development. "
A Fully Lagrangian model for river ice dynamics
* Andrea Nicole Mellado Cusicahua, École Polytechnique de Montréal, Canada
"Every year in spring, triggered by the temperature and flow increase, the ice cover breaks up and the resulting ice floes are carried downstream. Along the way, they slide, roll, collide, and jam, and may pose a major threat to the ecosystem, to riverside communities and to infrastructures. Understanding the processes and mechanisms involved in the dynamics of river ice is a key role in the assessments of the potential impacts, which in turn, will promote adequate and reliable management decisions. Due to the intrinsic complexity, simplified theoretical models of river ice dynamics are not able to describe the complete problem. The experimental and field studies of river ice dynamics have also been restricted, due to the common issues such as instrumental limitations, lack of conventional access to the field, and cost effectiveness. Compared to theoretical solutions and experiments, numerical simulations have caught the researchers’ attention due to its convenience and computational efficiency. A two and three-dimensional fully Lagrangian numerical model based on the coupling of the discrete element method (DEM) and the weakly-compressible moving particle semi-implicit (WC-MPS) is presented in this paper to simulate the river ice and water interactions. A multi-sphere Hertzian contact dynamic model is used in the DEM to calculate the motion of ice floes caused by collisions with other solids such as ice floes, boundaries, and obstacles present in the river. The hydrodynamic properties are obtained from the WC-MPS model, where the free-surface flow continuum equations are solved. The hydrodynamic forces are added to the ice floes’ contact forces, and their final motion is determined. The mesh-free Lagrangian nature of the DEM-WC-MPS model renders it adequate to predict the highly dynamic movement of ice floes in the presence of violent free-surface flow. First, the two-dimensional DEM is validated alone using an experimental case present in the literature where piled-up cylinders collapse after the gate retaining the cylinders is opened. Next, the two-dimensional DEM-WC-MPS model is validated using a numerical test case and an experimental test case. In the numerical test case, a solid block is dropped in a steady tank containing water. The results are compared with numerical results present in the literature. The experimental case is similar to the previous one, but with water mixed with the piled-up cylinders. Finally, experiments of dam-break flow over dry and wet beds with floating blocks representing ice have been carried out to obtain high-quality data useful for the validation of the three-dimensional WC-MPS model. In each validation case, the solid floes’ positions between the numerical and experimental results are compared. The results show that the proposed model is able to numerically reproduce and predict the complex two-dimensional and three-dimensional dynamic behavior of wave-ice floes interaction. "
Ice Cover Impact Assessment on Jenpeg Operation under Climate Change
* Samantha Wilson, Department of Civil Engineering, University of Manitoba, Canada
Masoud Asadzadeh, Canada
Kevin Lees, Canada
Su Jin Kim, Canada
During winter, an ice cover creates resistance against channel flow and decreases the conveyance capacity of a river. In cold regions of Canada, for example the Lower Nelson River basin, water resources operators aim to reduce the effects of ice on the flow conveyance by promoting formation of a smooth and stable ice cover. One region of focus for ice formation is the West Channel of the Nelson River upstream of the Jenpeg Generating Station (Jenpeg). Manitoba Hydro (MH) has been closely documenting their ice stabilization program (ISP) since 2003, providing a historical dataset for analysis. In this study, the MH ISP data is used to develop a statistical model and estimate different components of the ice impact. These components focus on predicting the onset of freeze-up and the timing and magnitude of ice impacts throughout winter. This model uses air temperature as the sole independent variable because heat flux is a primary driver of ice formation, and air temperature is immediately available for future climate simulations. The model is used to identify if statistically significant changes should be expected in the impact of the ice cover in the operation of Jenpeg due to the future climate conditions.
Field observations on the effects of tributaries on downstream breakup dynamics
* Tadros Ghobrial, Laval University, Canada
Catherine Blouin, Canada
Brian Morse, Canada
Gabriel Pelchat, Canada
Jean-Robert Ladouceur, Canada
Break-up ice jams in recent years have caused significant damages in the province of Quebec. Tributaries often play an important role during the breakup season. They can provide the required thermal heat to open the ice cover downstream and thus help evacuate ice runs. They can also exaggerate the problem by releasing ice runs that congest the downstream river and increase the risk of ice jam flooding. These are complex ice processes that are site specific and depends on ice and hydrometeorological conditions. The objective of this study is to document how tributaries affect breakup dynamics at, and downstream of, major confluences of the Chaudière River during the 2019-2020 winter season. Measured parameters included air temperature as well as water temperature, depth, and near-bed turbulence. Time lapse images and GPS trackers were used to quantify ice motion. A total of 70 observation sites were instrumented: 19 sites on the Chaudière River and 51 sites on its 14 tributaries. The main processes governing breakup are identified and the spatiotemporal dynamics of ice movements between tributaries and downstream systems is described.