Journal of Southern Hemisphere Earth Systems Science最新文献

{"title":"Atmospheric rivers associated with summer heavy rainfall over the Yangtze Plain","authors":"P. Liang, Guangtao Dong, Huqiang Zhang, Mei Zhao, Yuexiong Ma","doi":"10.1071/ES19028","DOIUrl":"https://doi.org/10.1071/ES19028","url":null,"abstract":"\u0000Atmospheric rivers (ARs) are long, narrow bands of enhanced water vapour transport in the low atmosphere, mainly from the tropics into the midlatitudes. However, it is still unclear how ARs act on different timescales during the boreal summer when frequent heavy precipitation events take place in East Asia, often resulting in severe flood that impacts property and human lives. In this study, we investigated climatological ARs, and their evolution on both synoptic and subseasonal timescales, associated with heavy rainfall events over the Yangtze Plain in China. Furthermore, their predictability was assessed by examining hindcast skills from an operational coupled seasonal forecast system of the Australian Bureau of Meteorology named ACCESS-S1. Results showed that ARs embedded within the South Asian monsoon and Somali cross-equatorial flow provide a favourable background for steady moisture supply of summer rainfall into East Asia. We call this favourable background a ‘climatological East Asian AR’, which has close connections with seasonal cycles and climatological intraseasonal oscillation of rainfall in the Yangtze Plain during its Meiyu season. The East Asian AR was also influenced by anomalous anticyclonic circulations over the tropical West Pacific when heavy rainfall events occurred over the Yangtze Plain. Different from orography-induced precipitation, ARs that led to heavy rainfall over the Yangtze Plain were linked with the intrusions of cold air from the north. The major source of ARs responsible for heavy precipitation events over the Yangtze Plain appeared to originate from the tropical West Pacific on both synoptic and subseasonal timescales. In 23-year hindcasts for May-June-July the current model, ACCESS-S1, had skillful rainfall forecasts at a lead time of 0 month, but the skill degraded significantly with longer lead times. Nevertheless, the model showed skills in predicting the variations of low-level moisture transport affecting the Yangtze River at longer lead time, suggesting that the ARs influencing summer monsoon rainfall in the East Asian region are likely to be more predictable than rainfall itself. There is potential in using AR predictions from the coupled forecast system to guide rainfall forecasts in the East Asian summer season at longer lead time, which can contribute to disaster prevention and reduction in East Asia.\u0000","PeriodicalId":55419,"journal":{"name":"Journal of Southern Hemisphere Earth Systems Science","volume":"87 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2020-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75242018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Potential connections between atmospheric rivers in China and Australia","authors":"Lin Xu, Huqiang Zhang, Weiwei He, Chengzhi Ye, A. Moise, José María Rodríguez","doi":"10.1071/ES19027","DOIUrl":"https://doi.org/10.1071/ES19027","url":null,"abstract":"\u0000Results from a collaborative project between the Australian Bureau of Meteorology and China Meteorological Administration found that atmospheric rivers (ARs) can occur simultaneously in East Asia and Australia. Furthermore, ARs and the Northwest Cloud Band in the Australia region tend to reach their peaks during austral cool season (May–August). At the same time that the Asian summer monsoon develops and its meridional moisture transport and AR activities intensify. This has prompted us to explore potential connections of ARs in the two regions. In this study, we firstly analysed two ARs and their mechanism that occurred in China and Australia in June 2016, which caused significant rainfall in both countries. We then explored the atmospheric circulation background for such AR connections. From this case study, we show that ARs originating from the tropical Indian and Pacific oceans can become bifurcated through Indo-Pacific inter-basin interactions. The position of the bifurcation appears to depend on the location and intensity of Western Pacific Subtropical High (WPSH), the subtropical high in the Australian region and the middle-latitude storm track migration in the southern hemisphere. Moreover, by analysing bifurcated AR events from the past two decades, we show that they are more likely to occur during boreal summer months. Most of the bifurcations occurred in the boreal summer following the decaying phase of an El Niño in its preceding winter, due to a delayed El Niño Southern Oscillation influence on the WPSH and a subtropical high in the Australian region. Our research further demonstrates the value of applying AR analysis in improving our understanding of the weather and climate in the Australia–Asian monsoon region.\u0000","PeriodicalId":55419,"journal":{"name":"Journal of Southern Hemisphere Earth Systems Science","volume":"62 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2020-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77924495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Climate sensitivity revisited","authors":"G. Ayers","doi":"10.1071/ES19031","DOIUrl":"https://doi.org/10.1071/ES19031","url":null,"abstract":"\u0000The commonly used energy balance model from Gregory et al. (2002) that underlies many published estimates of Equilibrium Climate Sensitivity (ECS) and Transient Climate Response (TCR) to anthropogenic forcing requires only four parameters for calculation of ECS and three for TCR. Both estimates require a value for the increase in global mean surface air temperature (ΔT) over a period of time, the increment in forcing driving the temperature change over that period (ΔF), and knowledge of the radiative forcing resulting from a doubling in CO2 concentration (F2×CO2). For ECS a value for the associated global heating rate (ΔQ) is also required. Each of these parameters has a best estimate available from the IPCC’s Fifth Assessment Report, but the authors did not provide best estimates for ECS and TCR within the broad uncertainty ranges quoted, 1.5–4.5K for ECS and 1.0–2.5K for TCR. Best estimates for ECS and TCR consistent with AR5 best estimates for ΔF and F2×CO2 are provided here. A well-known heuristic model was modified and applied to seven observation-based global temperature datasets to isolate temperature trend due to anthropogenic forcing from confounding effects of variability due to volcanism, cycles in solar irradiance and internal climate variability. The seven estimates of ECS and TCR were remarkably similar despite very large differences in time-base of the datasets analysed, yielding best estimates of 2.36±0.13K and 1.58±0.09K respectively at 95% confidence based on the AR5 best estimates for ΔF, F2×CO2 and ΔQ from Wijffels et al. (2016). The ECS and TCR best estimates here are tied to those AR5 and ΔQ best estimates, but can be simply scaled were those best estimate values to be refined in the future.\u0000","PeriodicalId":55419,"journal":{"name":"Journal of Southern Hemisphere Earth Systems Science","volume":"16 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2020-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78993014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Atmospheric rivers impacting mainland China and Australia: climatology and interannual variations","authors":"Xianghong Wu, Chengzhi Ye, Weiwei He, Jingjing Chen, Lin Xu, Huqiang Zhang","doi":"10.1071/ES19029","DOIUrl":"https://doi.org/10.1071/ES19029","url":null,"abstract":"\u0000In this study we have built two atmospheric river (AR) databases for mainland China and Australia using Japanese 55-year Reanalysis data with manual detections. By manually checking the magnitude, shape and orientation of vertically integrated vapour transport fields calculated from the reanalysis data and analysing its embedded synoptic patterns and other meteorological information, we detected 625 AR events over mainland China during 1986–2016 and 576 AR events over the Australian continent during 1977–2016. This manuscript documents the mean climatology, spatial distributions, seasonality and interannual variations of ARs occurring in these two regions. We also assessed possible underlying drivers influencing AR activities. Our results showed that: (i) most ARs over mainland China occured in its lower latitudes, including southern, eastern and central China, but ARs also reached its far north and northeast regions. In Australia, most ARs occurred in the states of Western Australia, South Australia and part of New South Wales and Victoria. These regions of high AR frequencies also frequently experienced Northwest Cloud Bands during the cool season; (ii) ARs in China reached their peak during the East Asian summer monsoon season (May–September). This was also the period when AR frequency in the Australian region tended to be higher, but its seasonal variation was weaker than in China; (iii) ARs exhibited large interannual variations in both regions and a declining trend in central and eastern China; (iv) there was a notable influence of tropical sea surface temperatures (SSTs) on the AR activities in the region, with the ARs in Australia being particularly affected by Indian Ocean SSTs and El-Niño Southern Oscillation (ENSO) in the tropical Pacific. ARs in China appear to be affected by ENSO in its decaying phase, with more ARs likely occurring in boreal summer following a peak El Nino during its preceding winter; (v) the Western Pacific Subtropical High plays a dominant role in forming major moisture transport channels for ARs in China, and South China Sea appears to be a key moisture source. In the Australian region, warm and moist air from the eastern part of the tropical Indian Ocean plays a significant role for ARs in the western part of the continent. In addition, moisture transport from the Coral Sea region was an important moisture source for ARs in its east. Results from this study have demonstrated the value of using AR diagnosis to better understand processes governing climate variations in the A–A region.\u0000","PeriodicalId":55419,"journal":{"name":"Journal of Southern Hemisphere Earth Systems Science","volume":"25 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2020-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84597940","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seasonal climate summary for the southern hemisphere (winter 2018): fifteenth-warmest and fourteenth-driest","authors":"Zhi-Weng Chua","doi":"10.1071/ES19038","DOIUrl":"https://doi.org/10.1071/ES19038","url":null,"abstract":"\u0000This is a summary of the southern hemisphere atmospheric circulation patterns and meteorological indices for winter 2018; an account of seasonal rainfall and temperature for the Australian region and the broader southern hemisphere is also provided. The climate influences from the El Niño–Southern Oscillation and the Indian Ocean Dipole were weak, with both demonstrating neutral conditions over the season. It was a dry and warm winter for Australia, being the fourteenth-driest and fifteenth-warmest (in terms of mean temperature) in a record of 119 and 109 years respectively. The warm and dry conditions were particularly pronounced over eastern Australia during July. Maximum temperatures were above average while minimum temperatures were below average.\u0000","PeriodicalId":55419,"journal":{"name":"Journal of Southern Hemisphere Earth Systems Science","volume":"64 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2020-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89366005","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Atmospheric rivers in the Australia-Asian region: a BoM–CMA collaborative study","authors":"Chengzhi Ye, Huqiang Zhang, A. Moise, R. Mo","doi":"10.1071/es19025","DOIUrl":"https://doi.org/10.1071/es19025","url":null,"abstract":"\u0000The name ‘atmospheric river’ (AR) could easily be misinterpreted to mean rivers flowing in the sky. But, ARs actually refer to narrow bands of strong horizontal water vapour transport that are concentrated in the lower troposphere. These bands are called ‘atmospheric rivers’ because the water vapour flux they carry is close to the volume of water carried by big river systems on the ground. ARs can cause heavy rainfall events if some physical mechanisms, such as orographic enhancement, exist to set up the moisture convergence and vertical motions necessary to produce condensation. In recent decades, these significant moisture plumes have attracted increasing attention from scientific communities, especially in North America and western Europe, to further understand the connections between ARs and extreme precipitation events which can trigger severe natural disasters such as floods, mudslides and avalanches. Yet very limited research has been conducted in the Australia-Asian (A-A) region, where the important role of atmospheric moisture transport has long been recognised for its rainfall generation and variations. In this paper, we introduce a collaborative project between the Australian Bureau of Meteorology and China Meteorological Administration, which was set up to explore the detailed AR characteristics of atmospheric moisture transport embedded in the A-A monsoon system. The project in China focused on using AR analysis to explore connections between moisture transport and extreme rainfall mainly during the boreal summer monsoon season. In Australia, AR analysis was used to understand the connections between the river-like Northwest Cloud Band and rainfall in the region. Results from this project demonstrate the potential benefits of applying AR analysis to better understand the role of tropical moisture transport in rainfall generation in the extratropics, thus achieve better rainfall forecast skills at NWP (Numerical Weather Prediction), sub-seasonal and seasonal time scales. We also discuss future directions of this collaborative research, including further assessing potential changes in ARs under global warming.\u0000","PeriodicalId":55419,"journal":{"name":"Journal of Southern Hemisphere Earth Systems Science","volume":"2 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2020-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79566257","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Atmospheric rivers in the Australia-Asian region","authors":"C. Frederiksen","doi":"10.1071/ESV70N1_FO1","DOIUrl":"https://doi.org/10.1071/ESV70N1_FO1","url":null,"abstract":"In recent years,more andmore attention has been focused on the atmospheric river (AR) diagnosis and its application in characterising atmospheric moisture transport between the tropics and the extratropics. Significant research (see, for example, references in Ye et al. 2020) has been conducted over North America due to a close association between ARs and extreme rainfall events over thewest coast.More studies are beginning to emerge over other parts of the globe such as, for example, along the South American coasts and parts of Europe. There are hundredsofARstudiesbeingpublishedeachyear frommeteorologicalandhydrometeorologicalcommunitiesworldwide.However, there are only very limited AR studies in our region even though we have a significant number of synoptic events, such as Northwest Cloud Bands (NWCBs), which share some common features as described by the AR concept. Therefore, it is very pleasing to see this collaboration between scientists in the AustralianBureauofMeteorologyandtheChinaMeteorological Administration focused on this series of AR diagnostic studies over the Australia-Asian (A-A) region. I commend the strong scientific leadership and significant efforts of Dr. Huqiang Zhang and his collaborators in conducting this important researchandfurtherdeveloping their studies intosixmanuscripts in this Research Front of the Journal of Southern Hemisphere Earth Systems Science. I believe they will attract more interest from our research community and lead to further investigations of this important topic. I agree with the authors that the term ‘atmospheric river’ may create the wrong impression that the research is about ‘rivers’ in the sky,when in fact it refers to anarrowbandof stronghorizontal water vapour transport concentrated in the lower troposphere.As the authors point out, the use of the word ‘river’ comes from the fact that the amount of atmospheric vapour flux associated with such a structure is about the samevolume as for river flows on the ground. In this Research Front, the researchers have comprehensively documented their analysis ofARs inour region.Theyhave conducted detailed observational case studies of AR characteristics operating in the A-A region and their differences to ARs reported for the North American middle and high latitudes (Ye et al. 2020). They have applied backward trajectory analysis to explore the atmospheric moisture source for such ARs and highlighted tropical moisture as the primary contributor to the corresponding rainfall generated in the extratropics. They have investigatedthepotential linksbetweenARsinEastAsiaandover theAustralian continent andused suchconnections to explain the seasonality of NWCBs and ARs in our region (Xu et al. 2020a). They have further proposed a mechanism associated with teleconnections in the subtropical highs of both hemispheres to explain these connections. They have also assessed the potential ofusingARsto linkmodelskill (bothNWPandseasonal forecast) inforecastingthesestro","PeriodicalId":55419,"journal":{"name":"Journal of Southern Hemisphere Earth Systems Science","volume":"1 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90799773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bureau of Meteorology Annual R&D Workshop 2019","authors":"D. Greenslade, L. Majewski","doi":"10.1071/ESV70N1_FO2","DOIUrl":"https://doi.org/10.1071/ESV70N1_FO2","url":null,"abstract":"The Bureau of Meteorology’s 31st Annual Research and Development workshop was held in Melbourne, in November 2019 and had the theme ‘Forecasting for the Future: New science for improved weather, water, ocean and climate services’. Environmental forecast services range from routine daily weather forecasts for the public, to seasonal outlooks and climate projections aimed at informing decisions by agriculture and water managers. Emergency managers rely on highly customised services during times of extreme weather such as fires, floods, heatwaves and tropical cyclones. Industry specific advice on the influences of climate variability and change enables society to deal with the challenges posed by our unique climate, both today and in the future. In order to meet the increasing demands of customers and deliver greater impact and value, service providers are transforming the way in which they work. This transformation process requires significantly enhanced capability in science and technology. Key advances that enhance our abilities to forecast from hourly to decadal scales include:","PeriodicalId":55419,"journal":{"name":"Journal of Southern Hemisphere Earth Systems Science","volume":"1 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88337034","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-impact thunderstorms of the Brisbane metropolitan area","authors":"J. Soderholm, Kathryn I. Turner, Jordan Brook, Tony Wedd, Jeffery Callaghan","doi":"10.1071/es19017","DOIUrl":"https://doi.org/10.1071/es19017","url":null,"abstract":"Accurate thunderstorm warnings in the hours-to-minutes preceding impact are often limited by the complex evolution of the mesoscale atmospheric environment. To accurately capture these complexities, analysis of observations remained central to operational short-term nowcasting predictions of thunderstorms. Over the past 40 years, multiple highimpact thunderstorm events have impacted the Brisbane Metropolitan Area (BMA) of South East Queensland resulting in significant insured losses. Four of these high-impact events were the focus of the following work. These cases included three events that resulted in the greatest insured losses for the BMA, exceeding AU$4 billion (2017) (18 January 1985, 16 November 2008 and 27 November 2014) and a fourth significant event (24 December 1989). Synthesis of previous work indicates that the four high-impact cases occurred during a south-easterly change with strengthening winds ahead of the change, suggesting commonalities may exist that can be exploited for forecasting. This paper provides a detailed observational analysis of the environment and convective storms from the four BMA events to explore discriminating characteristics that may improve the skill of nowcasting. For the four BMA events, significant deep convection was observed along the change for the hours prior to the change’s arrival at the Brisbane Airport, potentially acting as an early indicator of favourable conditions for high-impact thunderstorms. It was found that the timing of the south-easterly change through Brisbane was also highly correlated for all events, occurring within a 90-min window during the mid-afternoon convective heating maximum. Despite the destructive severe weather, upper air conditions were marginal for supporting organised thunderstorms, highlighting the importance of capturing mesoscale processes, such as the south-easterly change. To further understand possible discriminators of the four high-impact BMA cases, a 10-year climatology of the mesoscale and synoptic environment associated with south-easterly change events was developed for the warm season months of November to January. It is shown that although only a small number of events are associated with high-impact BMA thunderstorms, these events share a set of conditions relating to the prechange wind shift, timing of the south-easterly change and radar signatures.","PeriodicalId":55419,"journal":{"name":"Journal of Southern Hemisphere Earth Systems Science","volume":"24 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80203137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seasonal climate summary for the southern hemisphere (spring 2016): strong negative Indian Ocean Dipole ends, bringing second wettest September to Australia","authors":"B. Trewin, C. Ganter","doi":"10.1071/es19013","DOIUrl":"https://doi.org/10.1071/es19013","url":null,"abstract":"This summary looks at the southern hemisphere and equatorial climate patterns for spring 2016, with particular attention given to the Australasian and equatorial regions of the Pacific and Indian Ocean basins. Spring 2016 was marked by the later part of a strong negative phase of the Indian Ocean Dipole, alongside cool neutral El Niño–Southern Oscillation conditions. September was exceptionally wet over much of Australia, contributing to a wet spring with near-average temperatures. The spring was one of the warmest on record over the southern hemisphere as a whole, with Antarctic Sea ice extent dropping to record low levels for the season.","PeriodicalId":55419,"journal":{"name":"Journal of Southern Hemisphere Earth Systems Science","volume":"1 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83398712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}