Predictability of weather and climate

Abstract:

Negating the Measurement Independence assumption (MI) is often referred to as the ‘third way’ to account for the experimental violation of Bell’s inequality. However, this route is generally viewed as ludicrously contrived, implying some implausible conspiracy where experimenters are denied the freedom to choose measurement settings as they like. Here, a locally realistic model of quantum physics is developed (Rational Mechanics - RaQM - based on a gravitational discretisation of Hilbert Space) which violates MI without denying free will. Crucially, RaQM distinguishes experimenters’ ability to freely choose measurement settings to some nominal accuracy, from an inability to choose exact settings which were never under their control anyway. In RaQM, Hilbert states are necessarily undefined in bases where squared amplitudes and/or complex phases are irrational numbers. Such ‘irrational’ bases correspond to conceivable but necessarily impossible counterfactual measurements and are shown to play a ubiquitous role in the analysis of both single- and entangled-particle quantum physics. It is concluded that violation of Bell inequalities can be understood with none of the strange processes historically associated with it. Instead, using concepts from (non-classical) p-adic number theory, we relate RaQM to Bohm and Hiley’s concept of a holistic Machian-like Undivided Universe. If this interpretation of Bell’s Theorem is correct, building more and more energetic particle accelerators to probe smaller and smaller scales, in the search for a theory which synthesises quantum and gravitational physics and hence a Theory of Everything, may be a fruitless exercise.

Abstract:

The Quasi-Biennial Oscillation (QBO) is the dominant mode of tropical stratospheric variability that modulates global circulation and climate. Although a long-term weakening of QBO amplitude has been observed under global warming, the relative roles of different tropical oceans remain unclear. We perform sensitivity experiments forced by sea surface temperature perturbations over the tropical Pacific, Atlantic, and Indian Oceans, as well as their combined warming, to separate individual and joint effects. Pacific warming produces the strongest weakening and slowest descent of the QBO, whereas Atlantic warming slightly strengthens the amplitude and extends the vertical structure. Indian Ocean warming slightly weakens the amplitude and accelerates the descent. When all three oceans warm simultaneously, the QBO exhibits a weaker amplitude and faster descent, consistent in sign with the combined single-basin responses but with a reduced magnitude owing to diminished zonal and inter-basin SST gradients. Momentum budget analyses further show that basin-dependent competition between equatorial wave forcing and tropical upwelling underlies these contrasting responses.

Abstract:

ABSTRACT Dengue fever outbreaks impose a severe healthcare burden in Vietnam; therefore, the development of a Dengue early warning system is key to improve public health planning and mitigate this burden. This study assesses the ECMWF medium‐range (up to 10 days) forecast skill for relative humidity in Vietnam—a key factor for vector‐borne disease transmission—in re‐forecasts between 2001 and 2020. Analysis focused on the rainy season (May–October) with ERA5 reanalysis as a reference dataset. Re‐forecast data were pre‐processed using a lead‐time dependent quantile mapping technique to reduce the bias between forecasted and observational data, and skill was assessed using climatology and persistence as a reference. Rank histograms showed that the humidity forecast is reliable up to 10 days, and continuous ranked probability skill score (CRPSS) values show that the forecast is more skilful than the climatology up to 10 days. Nonetheless, when using persistence as a reference, CRPSS values are lower in South Vietnam, which was associated with the inaccurate representation of 2 m dew point temperature in the tropical regions, and the fact that persistence is a hard reference to beat in the tropics, hindering model forecast skill. Results from this study demonstrate that ECMWF ensemble forecasts of relative humidity are suitable to use as inputs for a Dengue early warning system up to 10 days in advance.

Abstract:

Abstract. This study uses an ensemble of climate model experiments coordinated by the Quasi-Biennial Oscillation initiative (QBOi) to analyze the Madden-Julian Oscillation (MJO) in the presence of either perpetual El Niño or La Niña sea surface temperatures during boreal winter. In addition to the prescribed El Niño Southern Oscillation (ENSO) conditions, the nine models internally generate QBOs, meaning each may influence the MJO. Objectives of our analyses are to assess the response of the MJO to strong idealized ENSO forcing and look for evidence of a QBO influence on the MJO in a multi-model context. The diagnostics used include wavenumber-frequency spectra of tropical convective and dynamical fields, measures of MJO lifetime, an evaluation of MJO diversity and visualization of MJO vertical structure, as well as an assessment of QBO morphology and the QBO's impact on tropical convection. Kelvin wave spectral power increases in the El Niño simulations whereas equatorial Rossby waves power is stronger in the La Niña simulations. All models simulate faster MJO propagation under El Niño conditions. This change in speed is corroborated by the MJO diversity analysis, which reveals that models better reproduce the observed “fast propagating” and “standing” MJO archetypes given perpetual El Niño and La Niña, respectively. Regardless of ENSO, QBO descent into the lower stratosphere is underestimated and we detect little QBO influence on tropical tropopause stability and MJO activity. With little influence from the QBO on the MJO activity in these runs, we can be confident that the aforementioned changes in the MJO indeed arise from the different ENSO boundary conditions.

Abstract:

Cities worldwide are increasingly facing the challenges of heat stress, a problem expected to worsen with ongoing climate change. The lack of detailed, city-specific data hinders effective response measures and limits the adaptive capacity of urban populations. In this data descriptor, we introduce a comprehensive database providing climate and heat stress information for 142 cities globally, covering the present and extending projections up to 2100 across three distinct climate scenarios, including two overshoot scenarios. This dataset includes 34 heat stress indicators at a spatial resolution of 100 meters, offering a unique database to identify vulnerable areas and deepen the understanding of urban heat risks. The data is presented through an accessible, user-friendly dashboard, enabling policymakers, researchers, and city planners, as well as non-experts, to easily visualise and interpret the findings, supporting more informed decision-making and urban adaptation strategies.