Recent Submissions

  • Warm conveyor belt activity over the Pacific: modulation by the Madden–Julian Oscillation and impact on tropical–extratropical teleconnections

    Quinting, Julian F.; Grams, Christian M.; Kar-Man Chang, Edmund; Pfahl, Stephan; Wernli, Heini (2024)
    Weather and Climate Dynamics
    Research in the last few decades has revealed that rapidly ascending airstreams in extratropical cyclones – socalled warm conveyor belts (WCBs) – play an important role in extratropical atmospheric dynamics. However on the subseasonal timescale, the modulation of their occurrence frequency, henceforth referred to as WCB activity, has so far received little attention. Also, it is not yet clear whether WCB activity may affect tropospheric teleconnection patterns, which constitute a source of predictability on this subseasonal timescale. Using reanalysis data, this study analyzes the modulation of WCB activity by the Madden–Julian Oscillation (MJO). A key finding is that WCB activity increases significantly over the western North Pacific when the convection of the MJO is located over the Indian Ocean. This increased WCB activity, which is stronger during La Niña conditions, is related to enhanced poleward moisture fluxes driven by the circulation of subtropical Rossby gyres associated with the MJO. In contrast, when the convection of the MJO is located over the western North Pacific, WCB activity increases significantly over the eastern North Pacific. This increase stems from a southward shift and eastward extension of the North Pacific jet stream. However, while these mean increases are significant, individual MJO events exhibit substantial variability, with some events even exhibiting anomalously low WCB activity. Individual events of the same MJO phase with anomalously low WCB activity over the North Pacific tend to be followed by the known canonical teleconnection patterns in the Atlantic–European region; i.e., the occurrence frequency of the positive phase of the North Atlantic Oscillation (NAO) is enhanced when convection of the MJO is located over the Indian Ocean and similarly for the negative phase of the NAO when MJO convection is over the western North Pacific. However, the canonical teleconnection patterns are modified when individual events of the same MJO phase are accompanied by anomalously high WCB activity over the North Pacific. In particular, the link between MJO and the negative phase of the NAO weakens considerably. Reanalysis data and experiments with an idealized general circulation model reveal that this is related to anomalous ridge building over western North America favored by enhanced WCB activity. Overall, our study highlights the potential role of WCBs in shaping tropical–extratropical teleconnection patterns and underlines the importance of representing them adequately in numerical weather prediction models in order to fully exploit the sources of predictability emerging from the tropics.
  • Atmospheric Flash Drought in the Caribbean

    Ramseyer, Craig A.; Miller, Paul W. (2023)
    Journal of Hydrometeorology
    Despite the intensifying interest in flash drought both within the United States and globally, moist tropical landscapes have largely escaped the attention of the flash drought community. Because these ecozones are acclimatized to receiving regular, near-daily precipitation, they are especially vulnerable to rapid-drying events. This is particularly true within the Caribbean Sea basin where numerous small islands lack the surface and groundwater resources to cope with swiftly developing drought conditions. This study fills the tropical flash drought gap by examining the pervasiveness of flash drought across the pan-Caribbean region using a recently proposed criterion based on the evaporative demand drought index (EDDI). The EDDI identifies 46 instances of widespread flash drought “outbreaks” in which significant fractions of the pan-Caribbean encounter rapid drying over 15 days and then maintain this condition for another 15 days. Moreover, a self-organizing maps (SOM) classification reveals a tendency for flash drought to assume recurring typologies concentrated in one of the Central American, South American, or Greater Antilles coastlines, although a simultaneous, Caribbean-wide drought is never observed within the 40-yr (1981–2020) period examined. Furthermore, three of the six flash drought typol- ogies identified by the SOM initiate most often during Phase 2 of the Madden–Julian oscillation. Collectively, these find- ings motivate the need to more critically examine the transferability of flash drought definitions into the global tropics, particularly for small water-vulnerable islands where even island-wide flash droughts may only occupy a few pixels in most reanalysis datasets.
  • The Ocean Impact Navigator. A new impact measurement framework for the ocean innovation ecosystem. Technical Appendix. Work in Progress.

    Systemiq; 1000 Ocean Startups Impact Working Group (IOOO Ocean Startups, 2022)
    This Technical Appendix has been written as a companion to the Ocean Impact Navigator: A New Impact Measurement Framework for the Ocean Innovation Ecosystem. It provides further details on the KPIs proposed within the Navigator framework. At the time of publication in June 2022, the Navigator has not yet been finalised, but is embarking on a period of testing, feedback and refinement that is expected to culminate in the launch of an online tool at the end of the year. It is in this spirit of soliciting feedback from the ocean impact and innovation community that this Appendix is published, as we hope that it will enable interested members of the community to review and provide more nuanced and detailed comments on the proposed framework. It is expected both that the set of KPIs elaborated in this Appendix will be revised in the coming months, and that the detailed guidance outlined in this Appendix will also be refined, based on the feedback that is received. It is also hoped that Navigator users – both now and in the future, will find this a practical tool to support implementation of the framework for their own impact measurement.
  • The Ocean Impact Navigator. A new impact measurement framework for the ocean innovation ecosystem.

    Vincent, Adrien; Ring, Jennifer; Stodulka, Katherine; Juenet, Jacques; 1000 Ocean Startups Impact Working Group: (1000 Ocean Startups Coalition, 2022)
    Creating positive impact for the ocean has never been more urgent. Measuring this impact, however, remains a critical challenge. To support innovators, their investors, and backers in charting these turbulent waters, this report presents the Ocean Impact Navigator, a new KPI impact framework for the Ocean Innovation Ecosystem. Ocean health is in peril. Multiple compounding stressors, including habitat destruction, overfishing, invasive species, pollution, and climate change, pose an existential threat to marine ecosystems and the crucial services they provide. These stressors and their cascading systemic impacts, combined with historic underinvestment in regenerative and nature-positive ocean sectors, are ushering in grave consequences for the 3 billion people worldwide who consume nutritious blue food, for coastal communities at risk of flooding, and for all those whose livelihoods and well-being relies on the ocean. Despite this bleak outlook, hope remains. The ocean holds astonishing potential for regeneration and, crucially, offers solutions that can address not only the threats it faces, but also the world’s broader climatic, biodiversity and social challenges. Capitalising on this potential, new start-ups and innovators are emerging, offering solutions to regenerate ocean health and catalyse the transition to a Sustainable Ocean Economy that unites effective ocean protection, sustainable production, and equitable prosperity. These innovations span a range of interrelated sectors – across food production, energy, biotech, data, transport, tourism, and solutions to pollution – that can drive systemic transformation in the blue economy. In parallel, new private and public capital is being mobilised for investment in the ocean, and incubators, accelerators, competitions, and matching platforms provide innovators with crucial backing and support. Together, these players make up the Ocean Impact Innovation (OII) ecosystem, largely encompassed by the 1000 Ocean Startups coalition