Tropical cyclone contribution to extreme rainfall over southwest Pacific Island nations

Southwest Pacific nations are among some of the worst impacted and most vulnerable globally in terms of tropical cyclone (TC)-induced flooding and accompanying risks. This study objectively quantifies the fractional contribution of TCs to extreme rainfall (hereafter, TC contributions) in the context of climate variability and change. We show that TC contributions to extreme rainfall are substantially enhanced during active phases of the Madden–Julian Oscillation and by El Niño conditions (particularly over the eastern southwest Pacific region); this enhancement is primarily attributed to increased TC activity during these event periods. There are also indications of increasing intensities of TC-induced extreme rainfall events over the past few decades. A key part of this work involves development of sophisticated Bayesian regression models for individual island nations in order to better understand the synergistic relationships between TC-induced extreme rainfall and combinations of various climatic drivers that modulate the relationship. Such models are found to be very useful for not only assessing probabilities of TC- and non-TC induced extreme rainfall events but also evaluating probabilities of extreme rainfall for cases with different underlying climatic conditions. For example, TC-induced extreme rainfall probability over Samoa can vary from ~ 95 to ~ 75% during a La Niña period, if it coincides with an active or inactive phase of the MJO, and can be reduced to ~ 30% during a combination of El Niño period and inactive phase of the MJO. Several other such cases have been assessed for different island nations, providing information that have potentially important implications for planning and preparing for TC risks in vulnerable Pacific Island nations. © 2021, The Author(s). *Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliate “Anil Deo and Savin Chand” is provided in this record*

The varied impacts of El Nino-Southern Oscillation on Pacific Island climates

El Nino-Southern Oscillation (ENSO) drives interannual climate variability in many tropical Pacific island countries, but different El Nino events might be expected to produce varying rainfall impacts. To investigate these possible variations, El Nino events were divided into three categories based on where the largest September-February sea surface temperature (SST) anomalies occur: warm pool El Nino (WPE), cold tongue El Nino (CTE), and mixed El Nino (ME), between the other two. Large-scale SST and wind patterns for each type of El Niño show distinct and significant differences, as well as shifts in rainfall patterns in the main convergence zones. As a result, November to April rainfall in many Pacific island countries is significantly different among the El Nino types. In western equatorial Pacific islands, CTE events are associated with drier than normal conditions whereas ME and WPE events are associated with significantly wetter than normal conditions. This is due to the South Pacific convergence zone and intertropical convergence zone moving equatorward and merging in CTE events. Rainfall in the convergence zones is enhanced during ME and WPE and the displacement is smaller. La Nina events also show robust impacts that most closely mirror those of ME events. In the northwest and southwest Pacific strong CTE events have much larger impacts on rainfall than ME and WPE, as SST anomalies and correspondingly large-scale surface wind and rainfall changes are largest in CTE. While variations in rainfall exist between different types of El Nino and the significant impacts on Pacific countries of each event are different, the two extreme CTE events have produced the most atypical impacts

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

Observed global changes in sector-relevant climate extremes indices—an extension to HadEX3

DATA AVAILABILITY STATEMENT : The gridded dataset are available at www.metoffice.gov.uk/hadobs/hadex3 and at www.climdex.org. In addition, a version is available on the CEDA archive (https://dx.doi.org/10.5285/2bfbdba03d9b423f99cadf404ca2daab). The underlying station indices will be made available on www.climdex.org where we are allowed to do so. For some collections we are not allowed to make the underlying station data public under terms of their licence.Please read abstract in the article.PLAIN LANGUAGE SUMMARY : To be able to assess changes in extreme temperature and rainfall events across the globe, data sets which capture characteristics of these extreme events are required. The use of indices for these characteristics further enables both data sharing and the comparison of events across the world. Extreme events have impacts across human health, our infrastructure and the natural environment. So far there has not been a global product which presents indices which are relevant for different sectors of our society, including health, agriculture and water resources. In this work we present an extension to an existing data set of extremes indices, HadEX3, by including indices defined by the World Meteorological Organization which were developed with sector specific applications in mind. We have used the same approach and methodology, and where possible the same underlying daily temperature and rainfall observations. The temperature indices show changes consistent with global scale warming, with heat wave characteristics showing increases in the number, duration and intensity of these extreme events in most places. The data files are available for use by interested researchers in their work.The Met Office Hadley Centre Climate Programme funded by DSIT and by the UK-China Research & Innovation Partnership Fund through the Met Office Climate Science for Service Partnership (CSSP) China under the International Science Partnerships Fund (ISPF); Australian Research Council Grant; the Horizon 2020 LANDMARC project; the RED-CLIMA (Red Española e Iberoamericana sobre Variabilidad Climática y Servicios Climáticos en Ecosistemas Terrestres y Marinos: RED-CLIMA) Project from the Consejo Superior de Investigaciones Científicas LINCGLOBAL CSIC from Spain; National Institute of Science and Technology for Climate Change Phase 2; the National Coordination for Higher Education and Training (CAPES).https://agupubs.onlinelibrary.wiley.com/journal/23335084hj2024Geography, Geoinformatics and MeteorologySDG-13:Climate actio

Trends and Variability in Droughts in the Pacific Islands and Northeast Australia

Abstract Drought is a recurrent climate feature of the Pacific Islands and northeast Australia with meteorological and socioeconomic impacts documented from early European settlement. In this study, precipitation records for 21 countries and territories in the Pacific for the period 1951 to 2010 have been examined to identify trends in drought occurrence, duration, and magnitude. The strength of the relationships between the main climate drivers in the Pacific—El Niño–Southern Oscillation (ENSO), the interdecadal Pacific oscillation (IPO), and the Pacific decadal oscillation (PDO)—and precipitation has been also examined. Station-scale drought trends are largely positive, but the majority are statistically nonsignificant with the significant trends mainly in the subtropics. Spatially, trend patterns are largely heterogeneous. A significant relationship between the oceanic component of ENSO and precipitation is confirmed for a large part of the Pacific Islands and eastern Australia with a strong lagged relationship in the year after the El Niño onset at locations southwest of the South Pacific convergence zone (SPCZ) and north of the intertropical convergence zone (ITCZ). Similarly, a strong relationship was found with the IPO and PDO at most locations. Drought was found to be longer and more severe southwest of the SPCZ and north of the ITCZ during the positive phases of the IPO and PDO.</jats:p

Unambiguous warming in the western tropical Pacific primarily caused by anthropogenic forcing

Small Island Developing States in the tropical western Pacific are among the most vulnerable to climate change. While a great deal of information on the observed climate change trends and their cause is available for many other regions and for the globe as a whole, much less information has been available specifically for the Pacific. Here, we show that warming over the past 50years in the western Pacific is evident in recently homogenized tropical station data, and in gridded surface temperature data sets for the region. The warming has already emerged from the background climate variability. The observational data and Coupled Model Intercomparison Project Phase 5 climate model output are used to show that the observed warming was primarily caused by human-forced changes to the earth's radiative balance. Further warming is projected to occur in the same models under all three Representative Concentration Pathways (RCPs) considered (RCP2.6, RCP4.5 and RCP8.5), with the magnitude far exceeding the warming to date under the two scenarios with higher emissions (RCP4.5 and RCP8.5)

On the use of mean and extreme climate indices to predict sugar yield in western Fiji

Sugarcane is one of Fiji's largest commercial agricultural crops and greater than 80% of the raw sugar produced is exported. Few sugar-producing countries are as dependant on the contribution of sugar to the export market as Fiji. There has been a statistically significant decline in sugar yield since 1975. The proportion of sugar extracted from sugarcane has also declined as shown by the positive trend in the tonnes cane to tonnes sugar ratio (+0.07/year, p < 0.001). The role of climate in these changes was investigated by first using principal component analysis then stepwise regression to predict sugarcane and sugar yield. ‘Mild drought conditions’, an increase in the diurnal temperature range and cool conditions during the ripening and maturation period are favourable for sugar yield. The impact of future warmer, wetter and drier conditions on sugar yield was also examined, in the absence of adaptive measures. Results show declines in sugar yield with an increase in mean and extreme temperature. Results also show an increase in the number of rain days in March offsets the increase in temperature suggesting that an increase the number of rain days in the late growing season in a future climate may counter the influence of higher temperatures. As for Australia and other developed sugar producing countries, irrigation in the late growing season may be an option to increase yields and/or adapt to a warmer climate

Trends and Variability in Droughts in the Pacific Islands and Northeast Australia

Drought is a recurrent climate feature of the Pacific Islands and northeast Australia with meteorological and socioeconomic impacts documented from early European settlement. In this study, precipitation records for 21 countries and territories in the Pacific for the period 1951 to 2010 have been examined to identify trends in drought occurrence, duration, and magnitude. The strength of the relationships between the main climate drivers in the Pacific-El Niño-Southern Oscillation (ENSO), the interdecadal Pacific oscillation (IPO), and the Pacific decadal oscillation (PDO)-and precipitation has been also examined. Station-scale drought trends are largely positive, but the majority are statistically nonsignificant with the significant trends mainly in the subtropics. Spatially, trend patterns are largely heterogeneous. A significant relationship between the oceanic component of ENSO and precipitation is confirmed for a large part of the Pacific Islands and eastern Australia with a strong lagged relationship in the year after the El Niño onset at locations southwest of the South Pacific convergence zone (SPCZ) and north of the intertropical convergence zone (ITCZ). Similarly, a strong relationship was found with the IPO and PDO at most locations. Drought was found to be longer and more severe southwest of the SPCZ and north of the ITCZ during the positive phases of the IPO and PDO

A new index for variations in the position of the South Pacific convergence zone 1910/11-2011/2012

Quality controlled and recently homogenised mean sea level pressure records for the South Pacific are used to specify the location and variability of the South Pacific convergence zone (SPCZ) during the austral warm season (November-April). The SPCZ is the world's largest rainfall band during the austral summer, when it dominates the climate of the South Pacific. A new index called the South Pacific convergence zone index (SPCZI) is derived, and is shown to be coherent with changes in low level wind convergence associated with the SPCZ. This index replaces the earlier SPCZ position index because it uses higher quality mean sea level pressure data than the superseded index and extends the time series further forward in time. The SPCZI allows interannual to decadal variability in the climate of the South Pacific to be tracked for more than a century from 1910/1911 to 2011/2012. During El Niño episodes the SPCZ is displaced by about 1°-3° east, and La Niña events 1°-3° west of the mean position on average. The index indicates a striking movement eastward for the period 1977/78-1998/99, compared with 1944/45-1976/77 in association with the Interdecadal Pacific oscillation (IPO). The eastward movement of the SPCZ in the late twentieth century is related to significant precipitation trends in the South Pacific region. Since 1998/99 the SPCZ has regressed westward with the negative phase change of the IPO. The long-term trend in the SPCZI is very small relative to the interannual to decadal variability and is not statistically significant, suggesting that there has been little overall change in the mean position of the SPCZ over the past century. © 2014 Springer-Verlag Berlin Heidelberg