Description: Understanding and predicting the interannual variations of the whole monsoon climate system has been, and will continue to be, one of the major reasons for studying the oceanography of the Indian Ocean; but there are other reasons. Knowledge about Indian Ocean current systems may have diverse practical applications, from fisheries through search and rescue to management of Exclusive Economic Zones. Our discussion mainly concerns the open ocean and the climate applications, but the results are important for most continental shelves of the Indian Ocean region on all but the shortest timescales. We start by discussing what we know now of the Indian Ocean’s mean annual cycle, painfully gleaned from sparse observations over the last four decades. This data base for understanding the interannual variability of the Indian Ocean climate has not been adequate until very recently; however, this data base is in the process of expanding radically, due to the availability of four new tools. These are: satellite data (altimeter, wind stress); surface flux products, from weather forecast reanalyses; output of fine-scale numerical models, driven with those fluxes; and data from profiling floats. As we will see in various talks, this is revolutionising our understanding of variability in the Indian Ocean. CLIVAR’s Asian-Australian Monsoon Panel is starting to plan a programme of further observations, to coincide with a useful conjunction of observation satellites in 2003. This will be aimed at filling the larger remaining gaps in our understanding of Indian Ocean dynamics, (with emphasis on understanding its role in the monsoon cycle).

Description: Published

Description: We explore the path between Indian Ocean observations and monsoon dynamics, the societal impacts of interannual climate variations and applications of resource predictions in southeastern Africa, the Mascarene Islands, India, southeast Asia and Australia. Recent progress in understanding ocean dynamics associated with SST variation is reviewed. The global El Niño-Southern Oscillation (ENSO) affects monsoon winds and ocean temperatures in a manner consistent with, but lagging, the Pacific. The ENSO influence often propagates across the tropical Indian Ocean from Africa to Indonesia, modulating the tropospheric moisture flux over the Indian Ocean and rainfall in surrounding continents. An east-west dipole in SST anomalies and monsoon rainfall is identified and related to the atmospheric Walker Cell. It appears partially in response to global ENSO conditions during build-up phase (July-Nov.). The eastern ‘node’ is confined near Sumatra, whilst the western centre of action extends from the Maldives to the Seychelles Islands. Correlations indicate that the strength of ENSO in the Indian Ocean region has decreased in recent decades, while large scale, spatial and temporal patterns suggest independent variations of the Indian Ocean. Apart from annual variations of the monsoon and year-to-year fluctuations of climate, short-term weather events have a dramatic impact on countries around the Indian Ocean. Recent floods in southern (2000) and eastern (1997- 98) Africa and southeast Asia (1998) are related to SST patterns and localised atmospheric responses. Predictions of the future availability of food and water resources, and short-term forecasts of storm events are some of the decision tools that can be offered through information from ocean data. The close relationship between regional SST anomalies and impacts on the food and water resources of surrounding countries provides a strong motivation for sustained observations in the Indian Ocean. A specific design plan for the observational network is proposed, linking eastern and western efforts in an efficient manner.

Description: Author Posting. © American Meteorological Society, 2009. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 90 (2009):459-480, doi:10.1175/2008BAMS2608.1.

Description: The Indian Ocean is unique among the three tropical ocean basins in that it is blocked at 25°N by the Asian landmass. Seasonal heating and cooling of the land sets the stage for dramatic monsoon wind reversals, strong ocean–atmosphere interactions, and intense seasonal rains over the Indian subcontinent, Southeast Asia, East Africa, and Australia. Recurrence of these monsoon rains is critical to agricultural production that supports a third of the world's population. The Indian Ocean also remotely influences the evolution of El Niño–Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), North American weather, and hurricane activity. Despite its importance in the regional and global climate system though, the Indian Ocean is the most poorly observed and least well understood of the three tropical oceans. This article describes the Research Moored Array for African–Asian–Australian Monsoon Analysis and Prediction (RAMA), a new observational network designed to address outstanding scientific questions related to Indian Ocean variability and the monsoons. RAMA is a multinationally supported element of the Indian Ocean Observing System (IndOOS), a combination of complementary satellite and in situ measurement platforms for climate research and forecasting. The article discusses the scientific rationale, design criteria, and implementation of the array. Initial RAMA data are presented to illustrate how they contribute to improved documentation and understanding of phenomena in the region. Applications of the data for societal benefit are also described.

Description: Author Posting. © American Meteorological Society, 2009. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 90 (2009): ES5-ES8, doi:10.1175/2008BAMS2608.2.

Description: The calicivirus minor capsid protein VP2 is expressed via termination/reinitiation. This process depends on an upstream sequence element denoted termination upstream ribosomal binding site (TURBS). We have shown for feline calicivirus and rabbit hemorrhagic disease virus that the TURBS contains three sequence motifs essential for reinitiation. Motif 1 is conserved among caliciviruses and is complementary to a sequence in the 18 S rRNA leading to the model that hybridization between motif 1 and 18 S rRNA tethers the post-termination ribosome to the mRNA. Motif 2 and motif 2* are proposed to establish a secondary structure positioning the ribosome relative to the start site of the terminal ORF. Here, we analyzed human norovirus (huNV) sequences for the presence and importance of these motifs. The three motifs were identified by sequence analyses in the region upstream of the VP2 start site, and we showed that these motifs are essential for reinitiation of huNV VP2 translation. More detailed analyses revealed that the site of reinitiation is not fixed to a single codon and does not need to be an AUG, even though this codon is clearly preferred. Interestingly, we were able to show that reinitiation can occur at AUG codons downstream of the canonical start/stop site in huNV and feline calicivirus but not in rabbit hemorrhagic disease virus. Although reinitiation at the original start site is independent of the Kozak context, downstream initiation exhibits requirements for start site sequence context known for linear scanning. These analyses on start codon recognition give a more detailed insight into this fascinating mechanism of gene expression.

Description: The pestivirus noncytopathic bovine viral diarrhea virus (BVDV) can suppress IFN production in the majority of cell types in vitro. However, IFN is detectable in serum during acute infection in vivo for ~5–7 d, which correlates with a period of leucopoenia and immunosuppression. In this study, we demonstrate that a highly enriched population of bovine plasmacytoid dendritic cells (DCs) produced IFN in response to BVDV in vitro. We further show that the majority of the IFN produced in response to infection both in vitro and in vivo is type III IFN and acid labile. Further, we show IL-28B (IFN-3) mRNA is induced in this cell population in vitro. Supernatant from plasmacytoid DCs harvested postinfection with BVDV or recombinant bovine IFN-α or human IL-28B significantly reduced CD4 + T cell proliferation induced by tubercle bacillus Ag 85–stimulated monocyte-derived DCs. Furthermore, these IFNs induced IFN-stimulated gene expression predominantly in monocyte-derived DCs. IFN-treated immature DCs derived from murine bone marrow also had a reduced capacity to stimulate T cell proliferative responses to tubercle bacillus Ag 85. Immature DCs derived from either source had a reduced capacity for Ag uptake following IFN treatment that is dose dependent. Immunosuppression is a feature of a number of pestivirus infections; our studies suggest type III IFN production plays a key role in the pathogenesis of this family of viruses. Overall, in a natural host, we have demonstrated a link between the induction of type I and III IFN after acute viral infection and transient immunosuppression.

Description: The Leeuwin Current, a warm, poleward flowing eastern boundary current, dominates the surface circulation off the west coast of Australia and has profound influence on regional marine ecosystem and fisheries recruitment. In this study, the seasonal and interannual variations of upper ocean heat balance in the Leeuwin Current region are analyzed by using an eddy-resolving numerical model simulation, as a first step to quantify the climate impacts on regional ocean thermodynamics and marine ecosystem. The volume transport and heat advection of the Leeuwin Current are stronger during the austral winter on the seasonal cycle and are stronger during a La Nina event on the interannual scale. On both seasonal and interannual timescales, the mixed layer heat budget off the west coast of Australia is predominantly balanced between the variations of the Leeuwin Current heat advection and heat flux across the air-sea interface. On the interannual timescale, the variation of the Leeuwin Current heat advection tends to lead that of the air-sea (latent) heat flux by two months, which is likely a reflection of advection timescales of the Leeuwin Current and its eddy field. The interannual variation of the average February–April sea surface temperature off the west coast of Australia, which is crucial for the larval settlement of western rock lobster, is mostly influenced by the Leeuwin Current heat advection as well as the ocean memory from the previous austral winter, with the air-sea heat exchange playing a buffering role.

Description: The tropical oceans have long been recognized as the most important region for large-scale ocean–atmosphere interactions, giving rise to coupled climate variations on several time scales. During the Tropical Ocean Global Atmosphere (TOGA) decade, the focus of much tropical ocean research was on understanding El Niño–related processes and on development of tropical ocean models capable of simulating and predicting El Niño. These studies led to an appreciation of the vital role the ocean plays in providing the memory for predicting El Niño and thus making seasonal climate prediction feasible. With the end of TOGA and the beginning of Climate Variability and Prediction (CLIVAR), the scope of climate variability and predictability studies has expanded from the tropical Pacific and ENSO-centric basis to the global domain. In this paper the progress that has been made in tropical ocean climate studies during the early years of CLIVAR is discussed. The discussion is divided geographically into three tropical ocean basins with an emphasis on the dynamical processes that are most relevant to the coupling between the atmosphere and oceans. For the tropical Pacific, the continuing effort to improve understanding of large- and small-scale dynamics for the purpose of extending the skill of ENSO prediction is assessed. This paper then goes beyond the time and space scales of El Niño and discusses recent research activities on the fundamental issue of the processes maintaining the tropical thermocline. This includes the study of subtropical cells (STCs) and ventilated thermocline processes, which are potentially important to the understanding of the low-frequency modulation of El Niño. For the tropical Atlantic, the dominant oceanic processes that interact with regional atmospheric feedbacks are examined as well as the remote influence from both the Pacific El Niño and extratropical climate fluctuations giving rise to multiple patterns of variability distinguished by season and location. The potential impact of Atlantic thermohaline circulation on tropical Atlantic variability (TAV) is also discussed. For the tropical Indian Ocean, local and remote mechanisms governing low-frequency sea surface temperature variations are examined. After reviewing the recent rapid progress in the understanding of coupled dynamics in the region, this study focuses on the active role of ocean dynamics in a seasonally locked east–west internal mode of variability, known as the Indian Ocean dipole (IOD). Influences of the IOD on climatic conditions in Asia, Australia, East Africa, and Europe are discussed. While the attempt throughout is to give a comprehensive overview of what is known about the role of the tropical oceans in climate, the fact of the matter is that much remains to be understood and explained. The complex nature of the tropical coupled phenomena and the interaction among them argue strongly for coordinated and sustained observations, as well as additional careful modeling investigations in order to further advance the current understanding of the role of tropical oceans in climate.