Analysis of spatial distribution and evolution of terrestrial precipitation

Abstract

Monthly terrestrial precipitation was studied based on a dataset of 118 years covering the world. Different statistical indicators such as the median, the interquartile range, the Yule-Kendall index and the robust kurtosis were analysed taking into account time and latitudes in order to reach conclusions about the evolution of precipitation depending on its location around the world and also to observe its yearly variation due to temperature increases on the planet. The study enabled some of the effects of climate change to be seen, such as the trend towards more extreme phenomena. Distribution of precipitation depending on latitude, volume of water and rainfall frequency were also determined. As a result, the heaviest precipitation occurrences –with median values up to 2250 mm– were found over equatorial areas, whereas middle latitudes were characterised by moderate rainfall amounts, reaching 500 mm. Areas of the southern hemisphere at similar latitudes presented precipitation regimes with values ranging from 250 to 1000 mm dependent upon by the orography and, particularly, by weather events. The interquartile range showed a maximum at −40° due a to higher variability of precipitation. In general, high values of the Yule-Kendall index were found for deserts, whereas the equatorial area presented low values. Robust kurtosis values mainly ranged between 0.2 and 0.3 following a Gaussian distribution. Latitudinal distribution of the trend using the linear fit of the median of precipitation revealed its decrease in the equatorial area and at high latitudes in the southern hemisphere. However, an increase in the trend was found between 60 and 80° latitude. Finally, the trend of the whole median of precipitation in the long study period showed the combined effect of extreme rainfall occurrences with only a slight variation.