Tropical Cyclone Research and Review最新文献

Over the past four years, significant research has advanced our understanding of how external factors influence tropical cyclone (TC) intensity changes. Research on air-sea interactions shows that increasing the moisture disequilibrium is a very effective way to increase surface heat fluxes and that ocean salinity-stratification plays a non-negligible part in TC intensity change. Vertical wind shear from the environment induces vortex misalignment, which controls the onset of significant TC intensification. Blocking due to upper-level outflow from TCs can reduce the magnitude of vertical wind shear, making for TC intensification. Enhanced TC-trough interactions are vital for rapid intensification in some TC cases because of strengthened warm air advection, but upper-level troughs are found to limit TC intensification in other cases due to dry midlevel air intrusions and increased shear. Aerosol effects on TCs can be divided into direct effects involving aerosol-radiation interactions and indirect effects involving aerosol-cloud interactions. The radiation absorption by the aerosols can change the temperature profile and affect outer rainbands through changes in stability and microphysics. Sea spray and sea salt aerosols are more important in the inner region, where the aerosols increase precipitation and latent heating, promoting more intensification. For landfalling TCs, the intensity decay is initially more sensitive to surface roughness than soil moisture, and the subsequent decay is mainly due to the rapid reduction in surface moisture fluxes. These new insights further sharpen our understanding of the mechanisms by which external factors influence TC intensity changes.

This review article summarizes the current understanding and recent updates to tropical cyclone outer size and structure forecasting and research primarily since 2018 as part of the World Meteorological Organization's 10th International Workshop on Tropical Cyclones. A more complete understanding of tropical cyclone outer wind and precipitation is key to anticipating storm intensification and the scale and magnitude of landfalling hazards. We first discuss the relevance of tropical cyclone outer size and structure, improvements in our understanding of its life cycle and inter-basin variability, and the processes that impact outer size changes. We next focus on current forecasting practices and differences among warning centers, recent advances in operational forecasting, and new observations of the storm outer wind field. We also summarize recent research on projected tropical cyclone outer size and structure changes by the late 21st century. Finally, we discuss recommendations for the future of tropical cyclone outer size forecasting and research.

Seasonal tropical cyclone (TC) forecasting has evolved substantially since its commencement in the early 1980s. However, present operational seasonal TC forecasting services still do not meet the requirements of society and stakeholders: current operational products are mainly basin-scale information, while more detailed sub-basin scale information such as potential risks of TC landfall is anticipated for decision making. To fill this gap and make the TC science and services move forward, this paper reviews recent research and development in seasonal tropical cyclone (TC) forecasting. In particular, this paper features new research topics on seasonal TC predictability in neutral conditions of El Niño–Southern Oscillation (ENSO), emerging forecasting techniques of seasonal TC activity including Machine Learning/Artificial Intelligence, and multi-annual TC predictions. We also review the skill of forecast systems at predicting landfalling statistics for certain regions of the North Atlantic, Western North Pacific and South Indian oceans and discuss the gap that remains between current products and potential user's expectations. New knowledge and advanced forecasting techniques are expected to further enhance the capability of seasonal TC forecasting and lead to more actionable and fit-for-purpose products.

A substantial number of studies have been published since the Ninth International Workshop on Tropical Cyclones (IWTC-9) in 2018, improving our understanding of the effect of climate change on tropical cyclones (TCs) and associated hazards and risks. These studies have reinforced the robustness of increases in TC intensity and associated TC hazards and risks due to anthropogenic climate change. New modeling and observational studies suggested the potential influence of anthropogenic climate forcings, including greenhouse gases and aerosols, on global and regional TC activity at the decadal and century time scales. However, there are still substantial uncertainties owing to model uncertainty in simulating historical TC decadal variability in the Atlantic, and the limitations of observed TC records. The projected future change in the global number of TCs has become more uncertain since IWTC-9 due to projected increases in TC frequency by a few climate models. A new paradigm, TC seeds, has been proposed, and there is currently a debate on whether seeds can help explain the physical mechanism behind the projected changes in global TC frequency. New studies also highlighted the importance of large-scale environmental fields on TC activity, such as snow cover and air-sea interactions. Future projections on TC translation speed and medicanes are new additional focus topics in our report. Recommendations and future research are proposed relevant to the remaining scientific questions and assisting policymakers.

In this review, advances in the understanding of the controlling factors and physical mechanisms of tropical cyclogenesis (TCG) are summarized from recent (2018–2022) research on TCG, as presented in the Tenth International Workshop on Tropical Cyclones (IWTC-10). Observational, theoretical, and numerical modeling studies published in recent years have advanced our knowledge on the influence of large-scale environmental factors on TCG. Furthermore, studies have shown clearly that appropriate convective coupling with tropical equatorial waves enhances the development chances of TCG. More recently, illuminating research has been carried out on analyzing the mechanisms by which oscillations and teleconnections (El Niño Southern Oscillation (ENSO) in particular) modulate TCG globally, in association with changes in the sea surface temperature (SST). In addition to this, recent research has diligently addressed different aspects of TCG. Multiple studies have reported the applicability of unified theories and physical mechanisms of TCG in different ocean basins. Recently, research has been carried out on TCG under different flow pattern regimes, dry air intrusion, importance of marsupial pouch, genesis of Medicanes, wind shear, convection and vertical structure. Furthermore, studies have discussed the possibility of near equatorial TCG provided that there is enough supply of background vertical vorticity and relatively low vertical wind shear. Progress has been made to understand the role of climate change on global and regional TCG. However, there are still significant gaps which need to be addressed in order to better understand TCG prediction.

This review summarizes the rapporteur report on advances in monitoring and forecasting of rainfall associated with tropical cyclones (TCs) and its impact during 2014–18, as presented to the 10th International Workshop on TCs (IWTC-10) held in Bali, Indonesia during 5th – 9th December 2022. Major physical processes that can modulate TC rainfall distribution, including topography, storm motion, vertical wind shear, and intensity, along with the fundamental physics of rain bands and clouds as simulated by numerical models, diurnal variation of rainfall, and various synoptic and mesoscale features controlling the rainfall distribution are briefly discussed. Improvements to the dynamic core and physical processes in global models are providing useable forecasts nearly up to 7 days. This report also summarizes, some tools that have been developed to predict TC rainfall. Lately there is a tendency for operational forecasting centers to utilize multi-model ensemble systems for rainfall forecasting that demonstrate superior performance than individual models, ensemble members, or even single model ensembles. Major impacts include pluvial and fluvial floods, and landslides. The techniques developed by various forecasting centers to assist in predicting and communicating the impacts associated with these events are also presented in this report.

In this paper, we summarize findings from the Tenth International Workshop on Tropical Cyclones (IWTC-10) subgroup on forecasting wind hazards and impacts. We found that new approaches to TC wind hazard forecasts continue to be developed and are becoming an increasingly common product offered by operational centres. To add greater context to wind risk information for users, many operational and research centres are also working to develop impact-based forecasts that incorporate hazard, vulnerability, and exposure data. Efforts to develop tropical cyclone wind impact forecasts present resourcing challenges, and when compared to wind hazard forecasting, are generally still in their infancy. Overall, both operational and research centres are extending significant efforts to meet the strong public need for accurate predictions of TC wind hazards and impacts around the world.

This review describes advances in understanding and forecasting tropical cyclone (TC) subseasonal variability during the past four years. A large effort by the scientific community has been in understanding the sources of predictability at subseasonal timescales beyond the well-known modulation of TC activity by the Madden-Julian Oscillation (MJO). In particular, the strong modulation of TC activity over the western North Pacific by the Boreal Summer Intra-Seasonal Oscillation (BSISO) has been documented. Progress has also been realized in understanding the role of tropical-extratropical interactions in improving subseasonal forecasts. In addition, several recent publications have shown that extratropical wave breaking may have a role in the genesis and development of TCs. Analyses of multi-model ensemble data sets such as the Subseasonal to Seasonal (S2S) and Subseasonal Experiment (SubX) have shown that the skill of S2S models in predicting the genesis of TCs varies strongly among models and regions but is often tied to their ability to simulate the MJO and its impacts. The skill in select models has led to an increase over the past four years in the number of forecasting centers issuing subseasonal TC forecasts using various techniques (statistical, statistical-dynamical and dynamical). More extensive verification studies have been published over the last four years, but often only for the North Atlantic and eastern North Pacific.

Observations of tropical cyclones (TC) from aircraft and in situ platforms provide critical and unique information for analyzing and forecasting TC intensity, structure, track, and their associated hazards. This report, prepared for the tenth International Workshop on Tropical Cyclones (IWTC-10), discusses the data collected around the world in TCs over the past four years since the IWTC-9, improvements to observing techniques, new instruments designed to achieve sustained and targeted atmospheric and oceanic observations, and select research results related to these observations.

In the Atlantic and Eastern and Central Pacific basins, changes to operational aircraft reconnaissance are discussed along with several of the research field campaigns that have taken place recently. The changes in the use and impact of these aircraft observations in numerical weather prediction models are also provided along with updates on some of the experimental aircraft instrumentation. Highlights from three field campaigns in the Western Pacific basin are also discussed. Examples of in-situ data collected within recent TCs such as Hurricane Ian (2022), also demonstrate that new, emerging technologies and observation strategies reviewed in this report, definitely have the potential to further improve ocean-atmosphere coupled intensity forecasts.