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Albédo

Publications associées (21)

Influence of sun cups on surface albedo of wet Alpine snowpack

Michael Lehning, Loïc Marcel Louis Brouet

In high elevation Alpine areas, characterised by high snow accumulation and radiation-driven melt processes, the formation of peculiar ablation features called sun cups can be observed. Sun cups likely influence the energy and mass balance of the wet snowp ...

2024

New Particle Formation Events Can Reduce Cloud Droplets in Boundary Layer Clouds at the Continental Scale

Athanasios Nenes

New particle formation (NPF) substantially contributes to global cloud condensation nuclei (CCN), and their climate impacts. Individual NPF events are also thought to increase local CCN, cloud droplet number (CDN), and cloud albedo. High resolution simulat ...

Amer Geophysical Union2024

Shape Models of Lucy Targets (3548) Eurybates and (21900) Orus from Disk-integrated Photometry

Stephan Hellmich

We use our new light curves, along with historical data, to determine the rotation state, photometric properties, and convex shape models of the targets of the Lucy mission (3548) Eurybates and (21900) Orus. We determine a retrograde spin for both targets, ...

IOP Publishing Ltd2023

Investigation of the effects of the Greek extreme wildfires of August 2021 on air quality and spectral solar irradiance

Alexandros Papagiannis

In August 2021, a historic heatwave was recorded in Greece which resulted in extreme wildfire events that strongly affected the air quality over the city of Athens. Saharan dust was also transferred over Greece on certain days of the same period due to the ...

Copernicus Publications2023

Calibration of ground surface albedo models

Christophe Ballif, Arttu Matias Tuomiranta

The emergence of bifacial photovoltaics as a serious option for large-scale power generation makes the accuracy of the in-situ estimation of ground surface albedo increasingly critical. Recent studies have evaluated the performance of different models but ...

PERGAMON-ELSEVIER SCIENCE LTD2022

Observing the Central Arctic Atmosphere and Surface with University of Colorado uncrewed aircraft systems

Julia Schmale, Radiance Flore Aurore Calmer

Over a five-month time window between March and July 2020, scientists deployed two small uncrewed aircraft systems (sUAS) to the central Arctic Ocean as part of legs three and four of the MOSAiC expedition. These sUAS were flown to measure the thermodynami ...

NATURE PORTFOLIO2022

Comparison of particle number size distribution trends in ground measurements and climate models

Jakob Boyd Pernov

Despite a large number of studies, out of all drivers of radiative forcing, the effect of aerosols has the largest uncertainty in global climate model radiative forcing estimates. There have been studies of aerosol optical properties in climate models, but ...

Copernicus Publications2022

Black carbon and dust in the Third Pole glaciers: revaluated concentrations, mass absorption cross-sections and contributions to glacier ablation

Julia Schmale

In snow and ice, light-absorbing particles (LAPs), such as black carbon (BC) and dust, accelerate the melting of Third Pole glaciers (TPGs). In this study, we revaluated LAP concentrations in the snow pits of TPGs (SP-TPGs), measured LAP mass absorption cr ...

2021

How Forward-Scattering Snow and Terrain Change the Alpine Radiation Balance With Application to Solar Panels

Michael Lehning, Annelen Kahl

Rough terrain in mid- and high latitudes is often covered with highly reflective snow, giving rise to a very complex transfer of incident sunlight. In order to simplify the radiative transfer in weather and climate models, snow is generally treated as an i ...

2021

Emittance growth suppression with a multibunch feedback in high-energy hadron colliders: Numerical optimization of the gain and bandwidth

Xavier Buffat, Sondre Vik Furuseth

A transverse feedback system can effectively mitigate the emittance growth caused by injection oscillations and machine noise in hadron beams. However, as its action on the beam depends on beam position measurements of finite accuracy, it introduces additi ...

2021

Evolution of stream and lake water temperature under climate change

Alfred Johny Wüest, Damien Bouffard, Bettina Schaefli, Wolf Hendrik Huwald, Adrien Michel, Carl Love Mikael Råman Vinnå

This report presents past observations and projects the future development of water temperature in Swiss lakes and rivers. Projections are made until the end of the 21st century using the CH2018 climate scenarios. Besides climate change effects on temperat ...

Federal Office for the Environment (FOEN)2021

Transverse Noise, Decoherence, and Landau Damping in High-Energy Hadron Colliders

Sondre Vik Furuseth

High-energy hadron colliders are designed to generate particle collisions within specialized detectors. A higher number of collisions is achieved with high-quality beams of low transverse emittances, meaning a small transverse cross-section, and high inten ...

EPFL2021

Improved Near-Surface Continental Climate in IPSL-CM6A-LR by Combined Evolutions of Atmospheric and Land Surface Physics

Etienne Gabriel Henri Vignon

This work is motivated by the identification of the land-atmosphere interactions as one of the key sources of uncertainty in climate change simulations. It documents new developments in related processes, namely, boundary layer/convection/clouds parameteri ...

2020

Constraining the Twomey effect from satellite observations: issues and perspectives

Athanasios Nenes

The Twomey effect describes the radiative forcing associated with a change in cloud albedo due to an increase in anthropogenic aerosol emissions. It is driven by the perturbation in cloud droplet number concentration (Delta N-d, (ant)) in liquid-water clou ...

Copernicus GmbH2020

Version 1 of a sea ice module for the physics-based, detailed, multi-layer SNOWPACK model

Michael Lehning, Katherine Colby Leonard, Nander Wever

Sea ice is an important component of the global climate system. The presence of a snowpack covering sea ice can strongly modify the thermodynamic behavior of the sea ice, due to the low thermal conductivity and high albedo of snow. The snowpack can be stra ...

COPERNICUS GESELLSCHAFT MBH2020

A new method to determine multi-angular reflectance factor from lightweight multispectral cameras with sky sensor in a target-less workflow applicable to UAV

Christoph Strecha, Manuel Simon Paul Cubero-Castan

A new physically based method to estimate hemispheric-directional reflectance factor (HDRF) from lightweight multispectral cameras that have a downwelling irradiance sensor is presented. It combines radiometry wilh photogrammetric computer vision to derive ...

ELSEVIER SCIENCE INC2019

Modeling the performance of cool pavements and the effect of their aging on outdoor surface and air temperatures

Flourentzos Flourentzou

Aiming at the improvement of a dense urban area's microclimatic conditions, this study examines by simulation means, the application of highly reflective materials as a mitigation strategy. However, as significant albedo changes may occur due to weathering ...

ELSEVIER SCIENCE BV2018

How Are Turbulent Sensible Heat Fluxes and Snow Melt Rates Affected by a Changing Snow Cover Fraction?

Michael Lehning

The complex interaction between the atmospheric boundary layer and the heterogeneous land surface is typically not resolved in numerical models approximating the turbulent heat exchange processes. In this study, we consider the effect of the land surface h ...

FRONTIERS MEDIA SA2018

Airborne hyperspectral sensor radiometric self-calibration using near-infrared properties of deep water and vegetation

Bertrand Merminod, Vincent Maurice Nouchi, Kevin Sylvain Barbieux

Retrieving the water-leaving reflectance from airborne hyperspectral data implies to deal with three steps. Firstly, the radiance recorded by an airborne sensor comes from several sources: the real radiance of the object, the atmospheric scattering, sky an ...

Spie-Int Soc Optical Engineering2016

Carbon storage versus albedo change: radiative forcing of forest expansion in temperate mountainous regions of Switzerland

Michael Lehning, Marc Schneebeli Zeugin

In this study, we assess the climate mitigation potential from afforestation in a mountainous snow-rich region (Switzerland) with strongly varying environmental conditions. Using radiative forcing calculations, we quantify both the carbon sequestration pot ...

European Geosciences Union2015