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We consider the inverse problem of estimating parameters of a driven diffusion (e.g., the underlying fluid flow, diffusion coefficient, or source terms) from point measurements of a passive scalar (e.g., the concentration of a pollutant).…

Numerical Analysis · Mathematics 2019-05-22 Jeff Borggaard , Nathan E. Glatt-Holtz , Justin A. Krometis

The rich history of observing system simulation experiments (OSSEs) does not yet include a well-established framework for using climate models. The need for a climate OSSE is triggered by the need to quantify the value of a particular…

We describe methods designed to determine the astrophysical parameters of quasars based on spectra coming from the red and blue spectrophotometers of the Gaia satellite. These methods principally rely on two already published algorithms…

Astrophysics of Galaxies · Physics 2017-09-28 L. Delchambre

A method is developed for estimating the emission rates of contaminants into the atmosphere from multiple point sources using measurements of particulate material deposited at ground level. The approach is based on a Gaussian plume type…

Atmospheric and Oceanic Physics · Physics 2010-06-11 Enkeleida Lushi , John M. Stockie

Despite recent advances, systematic quantitative treatment of the electron correlation problem in extended systems remains a formidable task. Systematically improvable Green's function methods capable of quantitatively describing weak and…

Chemical Physics · Physics 2016-11-15 Alexander A. Rusakov , Dominika Zgid

We explore possibilities of improving the spatial structure of NOx emissions employed in a continental scale chemistry transport model (CTM) by using satellite measurements of nitrogen dioxide and ground-based observations of near surface…

Atmospheric and Oceanic Physics · Physics 2007-05-23 I. B. Konovalov , M. Beekmann , A. Richter , J. P. Burrows

The knowledge of atmospheric parameters -- such as temperature, pressure, and humidity -- is very important for a proper reconstruction of air showers, especially with the fluorescence technique. The Global Data Assimilation System (GDAS)…

Instrumentation and Methods for Astrophysics · Physics 2019-08-13 Martin Will

Image restoration aims to recover high-quality images from degraded observations. When the degradation process is known, the recovery problem can be formulated as an inverse problem, and in a Bayesian context, the goal is to sample a clean…

Image and Video Processing · Electrical Eng. & Systems 2025-10-13 Darshan Thaker , Abhishek Goyal , René Vidal

In response to global concerns regarding air quality and the environmental impact of greenhouse gas emissions, detecting and quantifying sources of emissions has become critical. To understand this impact and target mitigations effectively,…

Applications · Statistics 2024-10-14 Thomas Newman , Christopher Nemeth , Matthew Jones , Philip Jonathan

Understanding the lifetime of CO2 in the atmosphere is critical for predictions regarding future climate changes. A simple mass conservation analysis presented here generates tight estimations for the atmosphere's retention time constant.…

Atmospheric and Oceanic Physics · Physics 2014-12-31 Riccardo DeSalvo

Thanks to the advances in modern instrumentation we have learned about many exoplanets that span a wide range of masses and composition. Studying their atmospheres provides insight into planetary origin, evolution, dynamics, and…

Earth and Planetary Astrophysics · Physics 2019-09-18 D. Shulyak , M. Rengel , A. Reiners , U. Seemann , F. Yan

Self-similar solutions of the coherent diffusion equation are derived and measured. The set of real similarity solutions is generalized by the introduction of a nonuniform phase surface, based on the elegant Gaussian modes of optical…

Quantum Physics · Physics 2015-05-19 O. Firstenberg , P. London , D. Yankelev , R. Pugatch , M. Shuker , N. Davidson

Parameter retrieval and model inversion are key problems in remote sensing and Earth observation. Currently, different approximations exist: a direct, yet costly, inversion of radiative transfer models (RTMs); the statistical inversion with…

Signal Processing · Electrical Eng. & Systems 2021-04-22 Daniel Heestermans Svendsen , Pablo Morales-Alvarez , Ana Belen Ruescas , Rafael Molina , Gustau Camps-Valls

Urban air quality forecasting is challenging because pollutant concentrations are nonlinear, nonstationary, spatiotemporally dependent, and often affected by anomalous observations caused by traffic congestion, industrial emissions, and…

Machine Learning · Computer Science 2026-05-06 Nourin Jahan , Madhurima Panja , Muhammed Navas T , Tanujit Chakraborty

We approximate a diffusion equation with highly oscillatory coefficients with a diffusion equation with constant coefficients. The approach is put in action in contexts where only partial information (namely the global energy stored in the…

Optimization and Control · Mathematics 2026-02-17 Claude Le Bris , Frédéric Legoll , Simon Ruget

The use of machine learning is becoming ubiquitous in astronomy, but remains rare in the study of the atmospheres of exoplanets. Given the spectrum of an exoplanetary atmosphere, a multi-parameter space is swept through in real time to find…

Earth and Planetary Astrophysics · Physics 2018-06-12 Pablo Marquez-Neila , Chloe Fisher , Raphael Sznitman , Kevin Heng

The non-uniform surface temperature distribution of rotating active stars is routinely mapped with the Doppler Imaging technique. Inhomogeneities in the surface produce features in high-resolution spectroscopic observations that shift in…

Instrumentation and Methods for Astrophysics · Physics 2022-02-23 A. Asensio Ramos , C. Diaz Baso , O. Kochukhov

We propose an extension of the GC3 streamer finding method of Johnston et al. 1996 that can be applied to the future Gaia database. The original method looks for streamers along great circles in the sky, our extension adds the kinematical…

Clouds are often considered a highly uncertain barrier for detecting biosignatures on exoplanets, especially given intuition gained from transit surveys. However, for direct imaging reflected light observations, clouds could increase the…

Earth and Planetary Astrophysics · Physics 2025-05-13 Huanzhou Yang , Michelle Hu , Dorian S. Abbot

A next generation of space-based observatories aims to detect and characterize potentially Earth-like exoplanets around Sun-like stars using reflected light spectroscopy. However, it remains unclear how such direct imaging…

Earth and Planetary Astrophysics · Physics 2025-10-28 Arnaud Salvador , Tyler D. Robinson