ABSTRACT:Rainfall records for 23 countries and territories in the western Pacific have been collated for the purpose of examining trends in total and extreme rainfall since 1951. For some countries this is the first time that their data have been included in this type of analysis and for others the number of stations examined is more than twice that available in the current literature. Station trends in annual total and extreme rainfall for 1961-2011 are spatially heterogeneous and largely not statistically significant. This differs with the results of earlier studies that show spatially coherent trends that tended to reverse in the vicinity of the South Pacific Convergence Zone (SPCZ). We infer that the difference is due to the Interdecadal Pacific Oscillation switching to a negative phase from about 1999, largely reversing earlier rainfall changes. Trend analyses for 1981-2011 show wetter conditions in the West Pacific Monsoon (WPM) region and southwest of the mean SPCZ position. In the tropical North Pacific it has become wetter west of 160 • E with the Intertropical Convergence Zone/WPM expanding northwards west of 140 • E. Northeast of the SPCZ and in the central tropical Pacific east of about 160 • E it has become drier. Our findings for the South Pacific subtropics are consistent with broader trends seen in parts of southern and eastern Australia towards reduced rainfall. The relationship between total and extreme rainfall and Pacific basin sea surface temperatures (SSTs) has been investigated with a focus on the influence of the El Niño-Southern Oscillation (ENSO). We substantiate a strong relationship between ENSO and total rainfall and establish similar relationships for the threshold extreme indices. The percentile-based and absolute extreme indices are influenced by ENSO to a lesser extent and in some cases the influence is marginal. Undoubtedly, larger-scale SST variability is not the only influence on these indices.

ABSTRACT:A new high-quality daily and monthly temperature station dataset was prepared for the tropical Western Pacific through a quality control and homogenization process. The homogeneity of 46 temperature stations, collected at a workshop conducted as part of the Pacific-Australia Climate Change Science and Adaptation Planning program, was assessed and the non-climatic step changes were removed. Here we present trends in mean and extreme temperature for the Western Pacific, covering an extended time period and larger geographical area compared with previous analyses. We discuss five main conclusions: (1) There is a significant warming trend in annual mean temperature over the past 50 years , of between 0.05 and 0.34 • C per decade. (2) Significant and spatially homogeneous warming trends are evident at the station level over 1961-2011 for the warm and cool extremes of both maximum and minimum temperatures. (3) Sub-regional trends, over the period 1951-2011, are spatially coherent, with the largest warming trends in the hottest day and night of the year and the coolest night of the year. (4) This analysis highlights the role of decadal variability in the number of days exceeding extreme temperature thresholds, with the upper (lower) tails of the distribution warming more (less) in recent decades. (5) We show that strong relationships exist between local and remote sea-surface temperature anomalies and all indices of extreme temperature, particularly with minimum temperature extremes.

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East Coast Lows are an important weather system that can produce severe wind, wave and rainfall events along the eastern seaboard of Australia. While a number of databases of these systems have been produced, this information has historically not been readily accessible to potential users outside the research sec-tor. This paper details the development of a new product, Maps and Tables of Climate Hazards on the Eastern Seaboard (MATCHES), that bridges this gap. It combines a new database of East Coast Lows with weather impacts across the eastern seaboard. Through use of user-defined impacts thresholds and an intuitive front-end interface, this new tool provides an easy way to link East Coast Lows with their weather impacts.