NP
Nonlinear Processes in Geosciences

NP Division

NPG Paper of the Month: “Inferring the instability of a dynamical system from the skill of data assimilation exercises”

April 25, 2022
NPG Paper of the Month: “Inferring the instability of a dynamical system from the skill of data assimilation exercises”
Scatter plots of the largest Lyapunov exponent (left) and Kolmogorov-Sinai entropy (right) against the skill of DA measured as the RMSE of the analysis. The experiments are done with model configurations displaying fully developed chaos (main panels) and with weakly chaotic configurations (insets). In all cases a strong observational constraint is applied: we measure the entire state vector at each time step. The theoretical error upper bound are also displayed (red markers).

The NPG paper of the month was awarded to “Inferring the instability of a dynamical system from the skill of data assimilation exercises” by Yumeng Chen, Alberto Carrassi, and Valerio Lucarini. Geophysical systems are usually described by a set of dynamical equations that are often non-linear and chaotic (Ghil and Lucarini, 2020). Errors about the initial state can grow, shrink, or sta ...[Read More]

When weather extremes meet climate change: how do scientists attribute single events to climate change?

February 25, 2022
When weather extremes meet climate change: how do scientists attribute single events to climate change?
Tropical Cyclone Batsirai landfalled in Madagascar on February 5-6 2022, causing extended floding, visible on February 10 (right) when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite passed over. In this comparison of false-color imagery, which uses MODIS bands 7-2-1, areas flooded with sediment-laden water appear blue. The same area is shown on January 30, between recent storms (left panel). Credits: NASA Earth Observatory.

One of the main new points of the IPCC reports AR6 with respect to the previous ones is the increased confidence that global climate change induced by anthropogenic emissions is critically affecting the dynamics of weather extremes. For summer, and specifically over Europe, the AR6 report states that we are already observing prolonged periods of extremely warm conditions with increased droughts bo ...[Read More]

NP Campfire: “Scaling and multifractals : from historical perspectives to recent developments”

, and December 20, 2021
NP Campfire: “Scaling and multifractals : from historical perspectives to recent developments”
Adapted from G. Sarma et al. (1991).

Scaling law behaviours are ubiquitous in geosciences both from a theoretical and practical point of view. They are required to better understand, analyse and simulate the underlying processes, which yields the observed variability of geophysical fields over wide ranges of spatio-temporal scales. A group of scientists within the Nonlinear Processes in Geosciences (NP) Division of the European Geosc ...[Read More]

NPG Paper of the Month: “Comparing estimation techniques for temporal scaling in palaeoclimate time series”

December 14, 2021

The NPG paper of the month of July was awarded to Comparing estimation techniques for temporal scaling in palaeoclimate time series by Raphaël Hébert, Kira Rehfeld and Thomas Laepple (https://doi.org/10.5194/npg-28-311-2021). Raphaël Hébert is currently a post-doctoral researcher at the Alfred-Wegener-Institut in Potsdam (Germany) in the Earth System Diagnostics group of Thomas Laepple, where he a ...[Read More]