Assessing Change-Points in Surface Air Temperature Over Alaska

Elena A Khapalova,Venkata K Jandhyala,James E Overland,Stergios B Fotopoulos

doi:10.3389/fenvs.2018.00121

Abstract

An understanding of low frequency climatic variations is important for climatologists and planning by broader populations. This study applies recent advances in statistical change-point methodology to the variability of temperatures from seven stations in Alaska and the Pacific Decadal Oscillation (PDO) climate index. We allow for the presence of multiple change-points in any given data series and provide confidence intervals for the identified change-points. We analyze the multiple station data based on season and temperature means and extremes. Physical processes that correlate with specific identified temperature changes have been explored through geopotential height field maps and sea level pressure (SLP) maps. Predominantly, temperature and PDO shifts were observed during winter and spring in the 1940s and 1970s. However, as an anomaly, this study also identifies that changes in summer have occurred either in 60s or in the 80s, deviating substantively from the 40s and 70s changes that were observed during winter and spring. We also note that there is lack of clear low frequency cyclic variability in the northern North Pacific region.

Highlights

Climate scientists are concerned with identifying low frequency variability in regional as well as global climatic conditions
We have identified changes in temperature series at seven Alaskan weather stations and in Pacific Decadal Oscillation (PDO) series
There were no significant changes in the mid-1970s during summer, there were early or late changes in summer, an anomaly that has not been identified earlier in climatological studies

Summary

Introduction

Climate scientists are concerned with identifying low frequency variability in regional as well as global climatic conditions. They are interested in attributing the causes of climate change relative to internal climate variability, and the ways by which governments can mitigate the effects of climate change. Dai et al (2015) showed that the PDO is associated with large temperature anomalies over both ocean and land. Other indices that have been associated with temperature anomalies in the North Pacific include Pacific North American pattern (PNA) (Liu et al, 2017), Arctic Oscillation (AO) (Thompson and Wallace, 1998), and others

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