14, November 2020
Multi-frequency scatterometer measurements are being collected during the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) campaign in the Central Arctic from October 2019 to October 2020.
The MOSAiC campaign offers an unprecedented opportunity to obtain fiducial reference measurements of snow and sea ice properties over a complete annual cycle required for the development and validation of satellite-based retrieval algorithms, as well as the improvement of microwave radiative transfer models.
Such an extensive dataset has not been available to date, and will contribute towards the validation of several EUMETSAT, EU Copernicus and ESA missions. Figure 1 shows the potential movement of the observatory (RV Polarstern icebreaker) along the Transpolar Drift during the course of the expedition.
Remote sensing instruments in the Central Observatory
| Instrument | Details | PI | Institution | Leg 1 responsible |
|---|---|---|---|---|
| Ku/Ka radar | Dual-frequency scanning radar: 12-18 GHz (Ku) and 3040 GHz | J. Stroeve | University of Manitoba | S. Hendricks |
| L-band Scatterometer | 1.26 GHz scanning radar | R. Scharien | University of Victoria | G. Spreen |
| C-band Scatterometer | C-band (~5 GHz) scanning radar | J. Yackel | University of Calgary | G. Spreen |
| X-band Scatterometer | 9.6 GHz scanning radar | C. Duguay | University of Waterloo | G. Spreen |
| MW Radiometer UWBRAD | Ultra-wideband 0.5-2 GHz radiometer (P to L-band) | J. Johnson | Ohio State University | O. Demir |
| MW Radiometer ELBARA | 1.4 GHz (L-band) | M. Schwank T. Casal |
WSL/ESA | G. Spreen |
| MW Radiometer 19-37-89-GHz | 19, 37, 89 GHz (K, Ka, W-band) | J. Stroeve | University of Manitoba | G. Spreen |
| MW Radiometer ARIEL | 1.4 GHz (L-band) | C. Cabarro | ICM-CSIC | G. Spreen |
| GNSS-R | Reflected GNSS signals from snow/ice | E. Cardellach T. Casal |
ICE-CSIC ESA |
G. Spreen |
| Infrared Camera | Surface temperature | G. Spreen | University of Bremen | G. Spreen |
| Video Camera | Visual overview of RS site | G. Spreen | University of Bremen | G. Spreen |
| Ku/Ka radar | Dual-frequency scanning radar: 12-18 GHz (Ku) and 3040 GHz | J. Stroeve | University of Manitoba | S. Hendricks |
Objectives
The scatterometer measurements are being acquired to investigate the temporal evolution of signals caused by environmental changes such as:
- snow accumulation and metamorphism;
- temperature changes;
- ice growth and melting;
- desalination;
- ice crusts and wind-packed snow formation.
These environmental changes are effective on a satellite footprint scale, which will allow comparison to the temporal evolution of the ground-based and satellite scatterometer/radar measurements.
Improved forward models of the radiative transfer in the snow and sea ice are needed to better understand the electromagnetic interaction with snow and sea-ice, and, thus, the signal measured by radar satellites, and to develop retrieval methods of snow and ice properties from these measurements.
As a fundamental prerequisite to develop and validate such models, joint ground-based scatterometer measurements, with coincident in-situ measurements of all relevant variables, are being acquired. MOSAiC offers the opportunity to perform such joint measurements under different environmental conditions, starting with the ice freeze-up and first snow accumulation throughout the winter until spring and summer, when the snow and sea ice start to melt and strong radiometric changes occur.
Overview
Sea ice is an integral part of the climate system, and an obstacle for the shipping and offshore industry. Satellite remote sensing is the method of choice to obtain hemispheric-scale information about sea ice and the snow cover on top. Microwave frequencies are ideally suited to observe sea ice/snow because they are largely independent of clouds and penetrate into the snow and sea ice.
The team is operating a ground-based multi-frequency scatterometer setup (systems operating at L-, C-, X-, Ku- and Ka-band frequencies) during the MOSAiC campaign (2019–2020) in the Central Arctic. The scatterometer observations are complemented by detailed in-situ measurements of snow and sea ice properties, and microwave radiometer measurements (P-, L-, C-, X-, K- and Ka-band).
To better interpret the measurements of current and future EUMETSAT/ESA/EU Copernicus satellite missions, validation with in-situ observations is needed. Furthermore, microwave radiative transfer (MRT) models of snow and sea ice need to be improved using coincident observations of ice/snow properties, along with scatterometer measurements. MRT models are required for the retrieval of sea ice and snow properties (e.g. ice thickness and snow depth on sea ice) from satellite missions such as Sentinel-3 and EPS-SG.
The scatterometer installation will be set up at one of the distributed monitoring stations surrounding Polarstern, as shown in Figures 2 and 3.
Status Update – August 2020
COVID-19 has had a significant impact on project logistics, causing an interruption in ground based measurements from mid-May to mid-June 2020. After drifting with the MOSAiC ice floe for many months, on 29th July 2020, the research camp was dismantled and the floe evacuated. Shortly after, the floe broke into several fragments.
The MOSAiC campaign will now focus on the start of the ice formation process and set course further north for the final leg of the expedition where the freezing phase will soon begin, reaching the North Pole on 19 August 2020. To date, team members and collaborators have submitted two abstracts for presentation at the AGU 2020 Fall Meeting.
