The Interdecadal Pacific Oscillation (IPO) has been shown to be associated with decadal climate variability over parts of the Pacific Basin, and to modulate interannual El Niño–Southern Oscillation (ENSO)‐related climate variability over Australia. Three phases of the IPO have been identified during the 20th century: a positive phase (1922–1944), a negative phase (1946–1977) and another positive phase (1978–1998). Climate data are analysed for the two most recent periods to describe the influence of the IPO on decadal climate trends and interannual modulation of ENSO teleconnections throughout the South West Pacific region (from the equator to 55°S, and 150°E to 140°W). Data coverage was insufficient to include the earliest period in the analysis.Mean sea level pressure (SLP) in the region west of 170°W increased for the most recent positive IPO period, compared with the previous negative phase. SLP decreased to the east of 170°W, with generally more southerly quarter geostrophic flow over the region. Annual surface temperature increased significantly southwest of the South Pacific Convergence Zone (SPCZ) at a rate similar to the average Southern Hemisphere warming. Northwest of the SPCZ temperature increases were less, and northeast of the SPCZ more than the hemispheric warming in surface temperature. Increases of annual precipitation of 30% or more occurred northeast of the SPCZ, with smaller decreases to the southwest, associated with a movement in the mean location of the SPCZ northeastwards. The IPO modulates teleconnections with ENSO in a complex way, strengthening relationships in some areas and weakening them in others. For New Zealand, there is a consistent bias towards stronger teleconnections for the positive IPO period.These results demonstrate that the IPO is a significant source of climate variation on decadal time scales throughout the South West Pacific region, on a background which includes global mean surface temperature increases. The IPO also modulates interannual ENSO climate variability over the region. Copyright © 2001 Royal Meteorological Society

This study characterizes rainfall and temperature variability for the whole of Vietnam and for climate sub-regions over 40 years from 1971 to 2010. Vietnam's average temperature has increased at a rate of 0.26 ± 0.10 °C per decade since the 1970s, approximately twice the rate of global warming over the same period. The rate of increase is greater in winter than in summer. Except for the Central Highland, annual average temperatures in southern regions are increasing more rapidly than in the North. The increases in temperatures are statistically significant in most sub-regions; however this is not the case for rainfall. The locations of climate boundaries between sub-regions are also discussed and suggestions for repositioning of these are made. Temperature and rainfall variability are shown to be linked to El Niño-Southern Oscillation on both national and sub-regional scale. This relationship is stronger in lower latitudes and in winter.

Atmospheric blocking events over the South Pacific are investigated using a 39-yr record of 500-hPa height fields from the NCEP–NCAR reanalysis dataset. The analysis extends earlier work using a 16-yr record and confirms that the occurrence of blocking over the southeast Pacific is strongly modulated by the ENSO cycle during austral spring and summer. Comparison of results at 500 hPa with the 300-hPa meridional wind component showed that blocking events are associated with large-scale wave trains lying across the South Pacific from the region of Australia to southern South America. Similar wave trains are evident in both hemispheres in singular value decomposition analyses between 300-hPa meridional wind components and tropical Pacific outgoing longwave radiation (OLR) anomalies. The hypothesis that the divergence associated with tropical OLR anomalies forces an extratropical wave response that results in enhanced blocking over the southeast Pacific was tested using a linearized, barotropic vorti... Abstract Atmospheric blocking events over the South Pacific are investigated using a 39-yr record of 500-hPa height fields from the NCEP–NCAR reanalysis dataset. The analysis extends earlier work using a 16-yr record and confirms that the occurrence of blocking over the southeast Pacific is strongly modulated by the ENSO cycle during austral spring and summer. Comparison of results at 500 hPa with the 300-hPa meridional wind component showed that blocking events are associated with large-scale wave trains lying across the South Pacific from the region of Australia to southern South America. Similar wave trains are evident in both hemispheres in singular value decomposition analyses between 300-hPa meridional wind components and tropical Pacific outgoing longwave radiation (OLR) anomalies. The hypothesis that the divergence associated with tropical OLR anomalies forces an extratropical wave response that results in enhanced blocking over the southeast Pacific was tested using a linearized, barotropic vorti...