In a previous post, we illustrated a widely used method called principal component analysis (PCA). This method can be used as an exploratory tool to summarise a dataset made of hundreds or thousands of time series into just a few ‘summary’ time series called principal components.
The map in the figure below shows the location of 195 hydrologic stations, which can be used to explore the hydrologic regimes of Australian rivers.
The Pacific Ocean sometimes catches a fever in its Eastern tropical part (off the coasts between Central America and Peru): for extended periods of time, its surface waters are abnormally warm.
A dendrogram is a way to visualise objects organised in a hierarchy. It looks like a tree where: the leaves represent the objects of the dataset; the branches link similar leaves according to a given criterion.
Investigating the hydrologic regime of 195 rivers in Australia revealed three types of flow seasonality. At some stations, the wettest period occurs during one particular season (winter or summer), whereas at others, similar flows are observed all year round.
Plotting hydrologic regimes Most hydrologic studies start by determining the average quantity of water in rivers and how it is distributed throughout the year.
