Global Trends in the Occurrence and Characteristics of Blocking Anticylones using Sen Innovative Trend Analysis

Atmospheric blocking plays an important role in modulating mid-latitude weather, in particular in the Northern Hemisphere (NH). Trend analysis of atmospheric blocking for both hemispheres by using Şen’s Innovative Trend Analysis (ITA) is performed in this study. The blocking data archived in University of Missouri covers period of 1968 – 2019 for NH and 1970 – 2019 for Southern Hemisphere is used in the study. Block occurrence, duration and blocking intensity (BI) is analysed by classifying the NH (SH) into three groups according to the preferred blocking locations: Atlantic, Pacific and Continental (Atlantic, Pacific and Indian). In NH, blocking intensity showed mixed results. It has decreasing trend for the entire hemisphere and Atlantic Region whilst different trend for different BI clusters. For blocking numbers and duration, the entire hemisphere and regions showed increasing trends. These increasing trend values are also statistically significant. In SH, blocking intensity shows a decreasing trend for low cluster whilst medium and high cluster for the entire hemisphere. Block duration has an increasing trend for the entire SH. Block numbers have increasing trend except one point in low cluster. Blocking characteristics show different trends for different preferred blocking locations. Increasing trends of blocking numbers for overall SH and Pacific region are statistically significant at 95% level. Increasing trends of blocking duration for overall SH, Atlantic and Pacific region are statistically significant at 90%, 95% and 95% level, respectively.