2025 Advancing Understanding of Land-Atmosphere Interactions and Processes on S2S Predictability Workshop What: 227 registered workshop participants gathered in person (43%) and online (57%) to discuss state-of-the-art scientific understanding and modeling of land-atmosphere interactions and related processes in the context of subseasonal-to-seasonal (S2S) predictability. Topics covered sources of S2S predictability, land model initialization methods, model diagnosis and evaluation metrics, AI/ML analysis and applications, and coordination of future community multimodel S2S forecast-focused experiments. To advance the science, this community workshop, organized by NSF NCAR, NOAA, NASA, and DOE, aimed to 1) identify process-and application-oriented metrics for assessing S2S prediction skill and 2) develop experimental protocols for coordinated experiments to isolate, quantify, and understand the role of land-atmosphere interactions in S2S predictability. When: 16-18 June 2025 Where: Boulder, Colorado and online
The capacity of terrestrial ecosystems to retain carbon or sequester more atmospheric carbon is frequently investigated as a potential natural climate solution. However, global carbon inventories, national carbon assessments, and atmospheric inversion studies suffer from key limitations: infrequent estimates, low spatial resolution, or a lack of partitioning into different carbon sinks and sources. In contrast, process-based ecosystem models can represent ecosystem biogeochemical fluxes on daily time scales, globally, constrained by near-real time observations from satellite sensors. The NASA Soil Moisture Active Passive mission Level 4 Carbon (L4_C) data set now provides over a decade of daily, global estimates of gross primary production (GPP), soil heterotrophic respiration, net ecosystem exchange, and soil organic carbon for terrestrial ecosystems. We present a validation of the latest L4_C product release, Version 8 (V8), and its updates compared to the previous version. Since 2015, L4_C has consistently met its performance target and provides carbon flux estimates similar to or better than global extrapolations such as FLUXCOM-X when compared to eddy-covariance tower measurements (ubRMSE of NEE , GPP = 1.13 g C ). We also compare L4_C V8 to the magnitude and direction of trends in global carbon uptake and net carbon balance predicted by the TRENDYv13 ensemble of dynamic global vegetation models. Based on regional case studies for recent extremes of fire weather, heat, and drought, L4_C demonstrates sensitivity to the impacts of short-term climate variability on the terrestrial carbon cycle and provides a basis for near-real time assessment of global carbon sinks and sources.
Turbulent cascades characterize the transfer of energy injected by a random force at large scales towards the small scales. In hydrodynamic turbulence, when the Reynolds number is large, the velocity field of the fluid becomes irregular and the rate of energy dissipation remains bounded from below even if the fluid viscosity tends to zero. A mathematical description of the turbulent cascade is a very active research topic since the pioneering work of Kolmogorov in hydrodynamic turbulence and that of Zakharov in wave turbulence. In both cases, these turbulent cascade mechanisms imply power-law behaviors of several statistical quantities such as power spectral densities. For a long time, these cascades were believed to be associated with nonlinear interactions, but recent works have shown that they can also take place in a dynamics governed by a linear equation with a differential operator of degree 0. In this spirit, we construct a linear equation that mimics the phenomenology of energy cascades when the external force is a statistically homogeneous and stationary stochastic process. In the Fourier variable, this equation can be seen as a linear transport equation, which corresponds to an operator of degree 0 in physical space. Our results give a complete characterization of the solution: it is smooth at any finite time, and, up to smaller order corrections, it converges to a fractional Gaussian field at infinite time.
O sistema de aterramento em instalações elétricas de baixa tensão é fundamental para a proteção contra descargas atmosféricas. O Brasil possui uma das maiores incidências de raios do mundo, o que torna essencial a adoção de medidas técnicas adequadas para garantir a integridade de edificações, equipamentos e, sobretudo, a segurança das pessoas. Muitos sistemas elétricos apresentam deficiências estruturais em seus aterramentos, seja por desconhecimento técnico, omissão em projetos ou tentativa de redução de custos. Tais falhas aumentam a vulnerabilidade das instalações a choques elétricos, surtos de tensão e danos causados por raios, comprometendo a segurança e o funcionamento adequado dos sistemas. O objetivo é analisar, por meio de revisão de literatura, os fundamentos técnicos, normativos e operacionais do aterramento em baixa tensão, com ênfase em sua função protetiva contra descargas atmosféricas. A metodologia adotada foi uma revisão bibliográfica com abordagem qualitativa. A análise dos materiais selecionados evidenciou a importância do cumprimento das normas ABNT NBR 5410, 5419 e 7117, além de lacunas na formação técnica e na fiscalização de projetos elétricos. A literatura consultada destaca que o sistema de aterramento deve ser parte central de qualquer instalação segura, sendo essencial não apenas para proteção contra falhas internas, mas também como mecanismo de dissipação de energia de descargas atmosféricas. Conclui-se que o tema permanece de grande relevância para a engenharia elétrica, exigindo constante atualização profissional, padronização de procedimentos e valorização das boas práticas técnicas.
In this paper we propose a systematic study of classical and multilevel variants of the Uzawa and Arrow–Hurwicz methods. The multilevel methods are obtained from the classical ones by the introduction of multilevel inner iterations to calculate the solution of the first equation instead of its exact calculation as in the classical Uzawa or Arrow–Hurwicz methods. In our study, an essential role is played by the LBB condition. For classical and multilevel variants of the Uzawa and Arrow–Hurwicz algorithms, we prove theorems which give the convergence conditions of the methods and explicit formulas of the convergence rates. On the basis of these results we compare the convergence conditions and the convergence rates of the classical methods with those of their corresponding ones in the multilevel methods. Concerning the Uzawa methods, we prove that, the limit of the convergence condition and the convergence rate of the multilevel method, when the number of the inner iterations tends to infinity, coincide with those of the classical one. Also, from the dependence of the convergence rate on the number of inner iterations of the multilevel method, we conclude that, the multilevel method with a small number of inner iterations converges better than the classical one. For the Arrow–Hurwicz methods we found that for a large number of inner iterations of the multilevel algorithm, the convergence condition of the multilevel method coincides with that of the classical method and the convergence rate of the multilevel method is equal to or smaller than that of the classical method. Finally, the behavior of the introduced methods is investigated by numerical experiments carried out for the driven-cavity Stokes problem and they confirm the theoretical results.
