Publications related to Orographic lift

The Influence of the Planetary Boundary Layer on the Atmospheric State at an Orographic Site at the Eastern Mediterranean

Athanasios Nenes, Romanos Foskinis, Kunfeng Gao

We studied the influence of the Planetary Boundary Layer (PBL) on the air masses sampled at the mountaintop Hellenic Atmospheric Aerosol and Climate Change station ((HAC) 2 ) at Mount Helmos (Greece) during the Cloud-AerosoL InteractionS in the Helmos back ...

Stockholm Univ Press2024

Turbulence in the Strongly Heterogeneous Near-Surface Boundary Layer over Patchy Snow

Michael Lehning, Dylan Stewart Reynolds, Michael Haugeneder

The near-surface boundary layer above patchy snow cover in mountainous terrain is characterized by a highly complex interplay of various flows on multiple scales. In this study, we present data from a comprehensive field campaign that cover a period of 21 ...

2024

The role of secondary ice production in mixed-phase clouds

Paraskevi Georgakaki

Clouds are omnipresent in the Earth's atmosphere. Their phase composition significantly modulates their interaction with solar and terrestrial radiation, as well as precipitation formation. Particularly for clouds containing both phases, known as mixed-pha ...

EPFL2023

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

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

Brown carbon absorption in the Mediterranean basin from local and long-range transported biomass burning air masses

Athanasios Nenes

This study examines the impact of light absorption from biomass burning (BB) brown carbon (BrC) in the Mediterranean basin from local and distant fire incidents during a typical fire season in August 2019 and under severe fire activity in August 2021. The ...

Elsevier2023

Radar processing techniques to study summer snowfall in the Sør Rondane Mountains, Antarctica

Alfonso Ferrone

Snowfall is one of the main positive contributors to the surface mass balance of the Antarctic ice sheet. There are several techniques to monitor solid precipitation on the continent. Among them, meteorological radars provide the means to characterize the ...

EPFL2022

An analytical approximation of urban heat and dry islands and their impact on convection triggering

Gabriele Manoli, Kai Wang

It is well known that cities increase air and surface temperatures compared to their rural sur-roundings, the so-called urban heat island (UHI) effect. However, the associated changes in at-mospheric humidity (also known as urban dry island, UDI) and conve ...

ELSEVIER2022

Flushing the Lake Littoral Region: The Interaction of Differential Cooling and Mild Winds

Damien Bouffard, Hugo Nicolás Ulloa Sánchez, Tomy Doda, Cintia Luz Ramon Casanas

The interaction of a uniform cooling rate at the lake surface with sloping bathymetry efficiently drives cross-shore water exchanges between the shallow littoral and deep interior regions. The faster cooling rate of the shallows results in the formation of ...

AMER GEOPHYSICAL UNION2022

Wind-tunnel experimental studies of the spatial snow distribution over grass and bush surfaces

Guang Li

The snow is one of the most important water resources in grassland in northern and western China, while the wind blowing snow due to the strong wind there is a common phenomenon, which can lead to heavy disasters to harm the local animal husbandry and tran ...

SPRINGER2022

Leveraging meteorological radars to investigate the influence of atmospheric dynamics on snowfall microphysics

Josué Etienne Gehring

Precipitation is the result of a chain of meteorological processes ranging from the large- to the micro-scale. While the transport of moisture and lifting mechanisms leading to cloud formation are mostly governed by dynamical processes, the formation and g ...

EPFL2021

PointXR: A Toolbox for Visualization and Subjective Evaluation of Point Clouds in Virtual Reality

Touradj Ebrahimi, Evangelos Alexiou, Nanyang Yang

In this study, we explore the use of virtual reality to subjectively evaluate the visual quality of point cloud contents. To this aim, we develop the PointXR toolbox, a set of Unity applications that can host experiments under variants of interactive and p ...

IEEE2020

Evaluation of GPM-era Global Satellite Precipitation Products over Multiple Complex Terrain Regions

Alexis Berne, Haonan Chen

The great success of the Tropical Rainfall Measuring Mission (TRMM) and its successor Global Precipitation Measurement (GPM) has accelerated the development of global high-resolution satellite-based precipitation products (SPP). However, the quantitative a ...

2019

The Importance of Near-Surface Winter Precipitation Processes in Complex Alpine Terrain

Michael Lehning, Franziska Gerber

In this study, near-surface snow and graupel dynamics from formation to deposition are analyzed using WRF in a large-eddy configuration. The results reveal that a horizontal grid spacing of ≤50 m is required to resolve local orographic precipitation enhanc ...

2019

Preferential Deposition of Snow and Dust Over Hills: Governing Processes and Relevant Scales

Michael Lehning, Marc Parlange, Francesco Comola, Marco Giovanni Giometto

Preferential deposition of snow and dust over complex terrain is responsible for a wide range of environmental processes and accounts for a significant source of uncertainty in the surface mass balances of cold and arid regions. Despite the growing body of ...

2019

From the clouds to the ground - Effects of flow-precipitation interactions on snow distribution in complex alpine terrain

Franziska Gerber

Knowledge about the spatial distribution of seasonal snow is essential e.g. to efficiently manage fresh water resources or for hydro-power companies. The large-scale gradient of snow accumulation over mountain ranges is mainly determined by lifting condens ...

EPFL2018

Stochastic modeling of snow transport and hydrologic response in alpine terrain

Francesco Comola

The scientific community has developed a keen interest in the processes driving the hydrologic cycle in alpine regions. The concern mainly stems from the vulnerability of snow-covered environments to the warming temperatures, such that entire ecological an ...

EPFL2017

Flow Adjustment Inside and Around Large Finite-Size Wind Farms

Fernando Porté Agel, Ka Ling Wu

In this study, large-eddy simulations are performed to investigate the flow inside and around large finite-size wind farms in conventionally-neutral atmospheric boundary layers. Special emphasis is placed on characterizing the different farm-induced flow r ...

2017

Suppressed convective rainfall by agricultural expansion in southeastern Burkina Faso

Marc Parlange, Natalie Claire Ceperley, Gabriel George Katul, Theophile Mande, Scott W. Tyler

With the green economy being promoted as a path to sustainable development and food security within the African continent, the influx of agricultural land is proliferating at a rapid pace often replacing natural savannah forests. Where agriculture is prima ...

American Geophysical Union2015

Orographic effects on snow deposition patterns in mountainous terrain

Michael Lehning, Alexis Berne, Marc Schneebeli Zeugin, Danny Eddy Scipion Castillo

Orographic lifting of air masses and other topographically modified flows induce cloud and precipitation formation at larger scales and preferential deposition of precipitation at smaller scales. In this study, we examine orographic effects on small-scale ...

Wiley-Blackwell2014

Observations, theory, and modeling of the differential accumulation of Antarctic megadunes

Michael Lehning

Antarctic megadunes are characterized by significant spatial differences in accumulation rate, with higher accumulation on the windward side and near-zero accumulation on the lee side. This leads to spatial differences in physical properties of snow and su ...

Amer Geophysical Union2013