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Active/Passive REmote Sensing of Snow (APRESS)

English title Active/Passive REmote Sensing of Snow (APRESS)
Applicant Schwank Mike
Number 182049
Funding scheme Project funding (Div. I-III)
Research institution Swiss Federal Research Inst. WSL Direktion
Institution of higher education Swiss Federal Institute for Forest, Snow and Landscape Research - WSL
Main discipline Other disciplines of Environmental Sciences
Start/End 01.05.2019 - 30.04.2021
Approved amount 256'780.00
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Keywords (7)

scatterometry; Cryosphere; radiometry; microwave remote sensing; information retrieval; snow-ground-system; microwave radiative transfer

Lay Summary (German)

Das Projekt „Active/Passive REmote Sensing of Snow“ (APRESS) ist auf zwei Jahre angelegt. Der Antragssteller ist Mike Schwank (WSL-Birmensdorf), Projektpartner sind Martin Schneebeli (SLF Davos), Andreas Wiesmann (Gamma Remote Sensing AG), und Juha Lemmetyinen (FMI). Reza Naderpour wird den Grossteil der eigentlichen Forschungsarbeit durchführen, mit Unterstützung des Antragsstellers. Der experimentelle Teil von APRESS erfolgt in Davos (Schweiz) und am Finnischen Meteorologischen Institut (FMI) in Sodankylä (Finnland).
Lay summary
Mit dem Projekt „Active/Passive REmote Sensing of Snow“ (APRESS) verfolgen wir die Erforschung der Wechselwirkung zwischen Mikrowellen und schneebedeckten Böden. Die zu erwartenden Resultate sind für das Verständnis von Mikrowellen Signaturen wesentlich, wie sie von Satelliten gestützten Sensoren zur Fernerkundung der Erdoberfläche gemessen werden. Die Kombination aus turm-gestützten Mikrowellen Experimenten, gleichzeitigen in-situ Messungen, sowie der Modellierung von Mikrowellen Rückstreuung und Emission, ermöglicht ein tieferes Verständnis der relevanten Strahlungstransport Prozesse. Das APRESS Projekt trägt somit dazu bei, optimale Kombinationen von Messkonfigurationen (z.B. Frequenz, aktiv (Radar)/passive (Radiometer), Polarisation, Beobachtungswinkel) zukünftiger Satelliten Missionen zu definieren. Darüber hinaus verbessern und entwickeln wir Methoden zur Fernerkundung der Kryosphäre. Auf dieser Forschung basierende „Retrieval Algorithmen“ sind die Grundlage für entsprechende globale Datenprodukte. Diese ermöglichen es beispielsweise klimatisch bedingte Änderungen der Kryosphäre zu erkennen, und entsprechende Massnahmen einzuleiten.
Direct link to Lay Summary Last update: 28.09.2018

Responsible applicant and co-applicants


Name Institute

Project partner

Associated projects

Number Title Start Funding scheme
156111 Active/Passive Microwave Remote Sensing in Application to ”Vegetation & Soil” and “Snow & Soil” (MicroVegSnow) 01.05.2015 Project funding (Div. I-III)
156111 Active/Passive Microwave Remote Sensing in Application to ”Vegetation & Soil” and “Snow & Soil” (MicroVegSnow) 01.05.2015 Project funding (Div. I-III)


The Earth’s climate evolution is significantly influenced by feedbacks driven by conditions of the cryosphere. Accordingly, quantification of cryosphere state parameters is vital for monitoring ongoing climate evolution, and for achieving reliable forecast models. They are crucial for developing adequate climate-change mitigation and adaptation strategies. Especially, properties of snow and soil (such as Freeze/Thaw (F/T) status, snow water equivalent (SWE), snow density/liquid water) in vast Polar Regions play key roles in climate evolution, since they influence the release of greenhouse gases, such as CH4 and CO2, which heavily influence the Earth’s energy budget. Because microwave remote sensing does not rely on sunlight and is not much affected by atmospheric conditions, it is the method of choice to assess Essential Climate Variables (ECVs - such as ground- and snow parameters) at northern latitudes.Microwave remote sensing is a relatively young discipline, and hence its potential has not yet been fully utilized. The overall objectives of the proposed APRESS project is to fill methodical gaps still obstructing full exploitation of microwave remote sensing for quantitative assessments of state parameters of snow-covered grounds. Accordingly, the APRESS project Multi-Frequency Active & Passive (M-F A&P) microwave signatures, measured by radars and radiometers over snow-covered ground, are explored to develop and improve physical methods (retrieval approaches) for the remote estimation of Snow-Ground-System (S-G-S) parameters. To this end, the experimental part of the project foresees a field campaign during Winter 2019/20 at the remote sensing field laboratory in Davos-Laret, Switzerland, and a second one during Winter 2020/21 at the Finnish Meteorological Institute’s Arctic Research Center (FMI-ARC-Sodankylä, Finland). These campaigns are designed to perform tower-based (close-range) M-F A&P microwave measurements accompanied by in-situ snow and ground characterizations under different climatological conditions. The special feature common to the two campaigns is the implementation of two artificial target areas with an absorber and a reflector beneath the accumulating snowpack. The quasi-simultaneous M-F A&P microwave measurements over the “absorber area”, the “reflector area” and the natural snow-covered ground represent the APRESS project’s key experimental approach to assess “effective” electromagnetic properties (absorption and scattering) of naturally developing snowpacks. Microwave Radiative Transfer (RT) models for these “effective” snow electromagnetic properties are validated against M-F A&P measurements performed over the “natural area” and used in inversion schemes to retrieve S-G-S parameters. The targeted quantities to be retrieved from the microwave measurements are: SWE, snow-liquid-water content, ground F/T status, and snow-structure parameters. A further aspect considered in APRESS concerns the advancement of generic microwave resonators for accurate in-situ measurements of snow complex dielectric permittivity, which is highly relevant for microwave RT in wet snow.The APRESS project’s research is of great use for the remote sensing community as well as for space agencies with respect to the definition of future space missions with a focus on the cryosphere. Furthermore, our project brings together international experts in the remote sensing of snow and hence promotes the importance of Switzerland as a center of science in the field of microwave remote sensing.