NP
Nonlinear Processes in Geosciences

Mathematics

ECS SpotLight: The link between European warm-temperature extremes and atmospheric persistence

September 11, 2023
ECS SpotLight: The link between European warm-temperature extremes and atmospheric persistence
Credit: ESA, CC BY-SA IGO 3.0

Persistent atmospheric circulation patterns are not a necessary requirement for warm temperature extremes in Europe. This key finding from a recent study led by Emma Holmberg challenges a more traditional meteorological view of persistence, which typically considers summertime heatwaves, especially in northern regions of Europe, to be synonymous with persistent atmospheric flow patterns. Furthermo ...[Read More]

Exploring the multistable and multiscale climate system via noise

December 7, 2021

Could our present day “warm” climate turn into a frozen fully glaciated one, as if the whole Earth is a huge “snowball”? That was a question put forward independently by Mikhail Budyko and William Sellers in the late 60s [1,2] who made a first estimate of the necessary changes of incoming solar radiation, such that either the Arctic ice sheet completely melts, or the planet gets fully frozen. Base ...[Read More]

NPG Paper of the Month: “Empirical evidence of a fluctuation theorem for the wind mechanical power input into the ocean”

November 4, 2021
NPG Paper of the Month: “Empirical evidence of a fluctuation theorem for the wind mechanical power input into the ocean”
The pdf p(z,τ) (left) and the symmetry function normalised by the averaging time S(z,τ)/τ (right) as a function of the power input z for different averaging times τ (see caption). The variable τ gives the length of the averaging interval in terms of observations done every 6 hours. Data are for the recirculation area of the Atlantic subtropical gyre at a resolution of 0.5o in space and 6 hours in time for the period of 1993–2016. Note that the pdfs differ from Gaussian. The symmetry function converges to a straight line for increasing averaging periods, showing evidence of a FT. License: “Empirical evidence of a fluctuation theorem for the wind mechanical power input into the ocean".

This month the NPG Paper of the Month award is achieved by Achim Wirth for his paper “Empirical evidence of a fluctuation theorem for the wind mechanical power input into the ocean“. Achim obtained his PhD at the University of Nice (Franc), doing research on turbulence theory. He then moved to oceanography working at UCLA (USA) and Geomar (Germany). Since 2005 he holds a permanent position a ...[Read More]

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]