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Assessment of apparent nonstationarity in time series of annual inflow, daily precipitation, and atmospheric circulation indices: A case study from southwest Western Australia

Bates, BC; Chandler, RE; Charles, SP; Campbell, EP; (2010) Assessment of apparent nonstationarity in time series of annual inflow, daily precipitation, and atmospheric circulation indices: A case study from southwest Western Australia. Water Resources Research , 46 , Article W00H02. 10.1029/2010WR009509. Green open access

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Abstract

The southwest region of Western Australia has experienced a sustained sequence of low annual inflows to major water supply dams over the past 30 years. Until recently, the dominant interpretation of this phenomenon has been predicated on the existence of one or more sharp breaks (change or jump points), with inflows fluctuating around relatively constant levels between them. This paper revisits this interpretation. To understand the mechanisms behind the changes, we also analyze daily precipitation series at multiple sites in the vicinity and time series for several indices of regional atmospheric circulation that may be considered as drivers of regional precipitation. We focus on the winter half-year for the region (May to October) as up to 80% of annual precipitation occurs during this "season". We find that the decline in the annual inflow is in fact more consistent with a smooth declining trend than with a sequence of sharp breaks, the decline is associated with decreases both in the frequency of daily precipitation occurrence and in wet-day amounts, and the decline in regional precipitation is strongly associated with a marked decrease in moisture content in the lower troposphere, an increase in regionally averaged sea level pressure in the first half of the season, and intraseasonal changes in the regional north-south sea level pressure gradient. Overall, our approach provides an integrated understanding of the linkages between declining dam inflows, declining precipitation, and changes in regional atmospheric circulation that favor drier conditions.

Type:Article
Title:Assessment of apparent nonstationarity in time series of annual inflow, daily precipitation, and atmospheric circulation indices: A case study from southwest Western Australia
Open access status:An open access version is available from UCL Discovery
DOI:10.1029/2010WR009509
Publisher version:http://dx.doi.org/10.1029/2010WR009509
Language:English
Additional information:Copyright 2010 by the American Geophysical Union
Keywords:Ocean climate variability, Sea-surface temperature, Water management, Winter rainfall, River-basin, Streamflow, Models, Trends, Attribution, Reanalysis
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Statistical Science

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