Analysis of recent rainfall trends and links to teleconnection patterns in California (U.S.)

Abstract

The aim of this research is to enlarge knowledge of space-time evolution of precipitation in California over the last decade on a monthly, seasonal and annual time-scale. This study also analyses the relationship between precipitation and teleconnection patterns with most influence on Californian climate. The homogeneity of the data from the selected stations was verified and finally 165 meteorological stations were used with an observation period that ranged from 1980 to 2019. In order to evaluate trends and statistical significance, both the non-parametric Mann-Kendall test and modified Sen’s slope method were used. Correlation analysis using the partial non-parametric Spearman Test (95% confidence level) was performed to find out relationships between precipitation and nine teleconnection patterns in the State of California. Spatial analysis was achieved using Empirical Bayesian Kriging (EBK). Finally, this research, as a novelty, shows regionalisation of California State as a function of significance in the correlation of precipitation with teleconnection patterns. To achieve this, Principal Component Analysis (PCA) and Agglomerative Hierarchical Cluster analysis (HCA) was performed. Results show a positive precipitation trend in winter and negative precipitation trend in late summer and autumn. The teleconnection patterns more correlated with precipitation are El Niño along Southern Oscillation (ENSO), Antarctic Oscillation (AAO) and North Atlantic Oscillation (NAO). Four areas were discerned outlining the Mojave Climate Region (Area 4) by having ENSO as the teleconnection pattern that best account precipitation.