Summer School on “Trends, Rhythms and Events in the Earth’s Climate System – Past, Present and Future”

The Volkswagen Foundation is funding our 5th summer school on “Trends, Rhythms and Events in the Earth’s Climate System – Past, Present and Future” in 2021. After summer schools in Africa and Europe, this one will be taught entirely online. Continue reading “Summer School on “Trends, Rhythms and Events in the Earth’s Climate System – Past, Present and Future””

Using RGB Cameras to Classify Minerals in Rocks

Color is an uncertain characteristic for the determination of minerals. Many minerals occur in a variety of different colors. Examples are quartz with its color variants amethyst, rose quartz or smoky quartz or feldspar with color variants like amazonite. However, if the minerals in a rock are reliably determined, their different coloring can be used to quantify them. In this example we use a simple RGB photo taken with a smartphone to determine the amounts of quartz, plagioclase, alkali feldspar and dark minerals such as biotite and hornblende in granite. To facilitate the differentiation of minerals, we use a principal component analysis (PCA), which is also used to unmix and classify spectral images such as satellite images (Trauth, 2020).

Evolutionary Lomb-Scargle Power Spectral Analysis with MATLAB

In paleoclimate time series amplitude of spectral peaks usually varies with time. Evolutionary power spectral analysis such as the FFT-based spectrogram and wavelet power spectral analysis helps. These methods, however, require interpolation of the time series to a grid of evenly-spaced times. Instead we can use the Lomb-Scargle Method for unevenly-spaced spectral analysis, computed for a sliding window, to map changes of the cyclicities through time.

Continue reading “Evolutionary Lomb-Scargle Power Spectral Analysis with MATLAB”