NP
Nonlinear Processes in Geosciences

NP Division

NPG Paper of the Month: “Ordering of trajectories reveals hierarchical finite-time coherent sets in Lagrangian particle data: detecting Agulhas rings in the South Atlantic Ocean”

March 16, 2021
NPG Paper of the Month: “Ordering of trajectories reveals hierarchical finite-time coherent sets in Lagrangian particle data: detecting Agulhas rings in the South Atlantic Ocean”
Result of the OPTICS algorithm applied to the trajectories modelled in the Bickley Jet model flow. (a), (d) and (g) show the reachability plot with different DBSCAN clustering results, indicated by the black horizontal line. The corresponding clustering results of each choice of DBSCAN parameter is shown on the right of the reachability plots for different times. Grey particles correspond to noise. Axis units in the centre and right column are in 1000 km.

The February 2021 NPG Paper of the Month award goes David Wichmann and his co-authors for their paper “Ordering of trajectories reveals hierarchical finite-time coherent sets in Lagrangian particle data: detecting Agulhas rings in the South Atlantic Ocean“. Understanding the transport of tracers and particulates is an important topic in oceanography and in fluid dynamics in general. Th ...[Read More]

NPG Paper of the Month: “A methodology to obtain model-error covariances due to the discretization scheme from the parametric Kalman filter perspective”

March 11, 2021
NPG Paper of the Month: “A methodology to obtain model-error covariances due to the discretization scheme from the parametric Kalman filter perspective”
Illustration of the transport of a chemical specy by a heterogeneous wind field over a 1D domain (a) and the numerical simulation from a simple discretization scheme (b). The loss of variance due to the spurious numerical diffusion involves an increase of the model-error variance (c) which is coupled with the anisotropy (the correlation length-scale in 1D domain, in panel d).

The January 2021 NPG Paper of the Month award goes to Olivier Pannekoucke and his co-authors for the paper “A methodology to obtain model-error covariances due to the discretization scheme from the parametric Kalman filter perspective“. In geophysics, forecasting is based on solving the equations of physics with the help of a computer. To calculate a forecast we need an initial conditi ...[Read More]

The most-read NPG 2020 paper: “Effects of upwelling duration and phytoplankton growth regime on dissolved-oxygen levels in an idealized Iberian Peninsula upwelling system”

January 29, 2021
The most-read NPG 2020 paper: “Effects of upwelling duration and phytoplankton growth regime on dissolved-oxygen levels in an idealized Iberian Peninsula upwelling system”
(a) Snapshot of dissolved oxygen distribution in the upwelling front instabilities for the ECS simulation (γ is the Okubo-Weiss criterion). (b) Dissolved Oxygen budget in the idealized Iberian Peninsula Upwelling System. Net value is the sum of Physical, Biological and Atmospheric processes that change oxygen concentration levels. Physics accounts for the effect of upwelled subsurface waters and offshore transport by upwelling front instabilities. Biology term accounts for oxygen photosynthetic production and community respiration. Simulations performed are ECS (short upwelling season with enhanced phytoplankton growth), ECC (long upwelling season with enhanced phytoplankton growth), NCC (long upwelling season with neutral phytoplankton growth) and LCC (long upwelling season with limited phytoplankton growth). License: Effects of upwelling duration and phytoplankton growth regime on dissolved-oxygen levels in an idealized Iberian Peninsula upwelling system.

An emerging problem brought by climate change is the on-going deoxygenation of the world’s oceans. The fact that concentrations of dissolved oxygen have been/are declining in both open-ocean and coastal waters is becoming a major scientific and societal concern raised in the Kiel Declaration and in the IUCN (International Union for Conservation of Nature) 2019 report. Lower levels of dissolved oxy ...[Read More]

NP Campfire: “Perspectives on Climate Science: from historical developments to research frontiers”

January 19, 2021
NP Campfire: “Perspectives on Climate Science: from historical developments to research frontiers”

Recently, the European Geosciences Union (EGU) started to support a new type of event called ‘Campfires’ that will give the Divisions the freedom to run online interactive events in a way that suits their needs. This allows the EGU Divisions to encourage interactions in their research communities through virtual informal meetings. In this framework, and thanks to a group of young and established s ...[Read More]