NP
Nonlinear Processes in Geosciences

attractor

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]

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]

Four reasons for still observing cold spells despite the undeniable global climate change

February 18, 2021
Four reasons for still observing cold spells despite the undeniable global climate change
Stravinsky fountain, near the Centre Pompidou (Paris) frozen by the cold wave of 2021.

The winter of 2020-2021 has been characterized by various cold waves affecting – at different times – Western and Eastern Europe and North America.  The most striking pictures show Madrid covered by up to 40 cm of fresh snow, frozen Thames near London and Canal St Martin in Paris, heavy snow in Amsterdam and even on the Eolian Islands, just offshore Sicily. At first this seems contradi ...[Read More]