Geophysical Research Letters最新文献

The probability density function of drops is difficult to model. Current approaches make assumptions that are often problematic, as they allow negative values for the mean of the distribution. While the statistical goodness of fit of those models might be reasonable for precipitation radar estimation, the situation is unsatisfactory if a fully consistent physical modeling of precipitation across scales is desired. This is the case of weather and climate models. This paper discusses a model that satisfies mathematical and physical consistency. The model can be seamlessly integrated into the parameterizations of the microphysics of precipitation and is tested on an extensive disdrometer data set. Comparison with existing models shows that the new method has substantial practical and theoretical advantages. The research has implications in elucidating the role of clouds in the climate sensitivity of climate models.

The response of marine low-cloud mesoscale morphologies to climate change and emission reductions remains poorly understood. Here, we link long-term trends in six cloud morphologies to variations in large-scale meteorology and aerosols. The trends show strong spatial heterogeneity, with closed and disorganized mesoscale cellular convection decreasing in the Northeast Pacific and Southeast Atlantic. We develop a deep learning model (UMorNet) to predict instantaneous cloud morphologies from meteorology and cloud droplet number concentration (N_d), a proxy for aerosols. UMorNet achieves an average test accuracy of 0.55 and captures spatial patterns of climatology and long-term trends. Out-of-sample test with a marine heatwave event further demonstrates the model's performance. Sensitivity experiments identify N_d, marine cold-air outbreak index, sea surface temperature, and inversion strength as key drivers. Different responses of clustered Cu and suppressed Cu to N_d was identified. These findings highlight the potential role of aerosols in shaping cloud morphological changes.

Oxygen in the global oceans has declined since the 1960s, including in the Eastern Equatorial Pacific (EEP). Reconstructions of EEP glacial oxygenation help advance understanding of current and projected ocean deoxygenation. Previous estimates of the glacial oxygen deficient zones (ODZs) in the upper EEP are poorly constrained. Here we include sediment cores that extend shallower into the ODZ and quantitatively reconstruct the glacial oxygen depth profile. We find glacial oxygen levels were similar or slightly lower than modern in the upper-intermediate ocean and much lower in the deep EEP. We estimate ∼95% of the lower glacial oxygen occurred in the deep EEP. This contrasts with modern, where only 67% of oxygen loss is in the deep ocean, and could be due to a smaller role of temperature-dependent oxygen solubility in modulating oxygen on longer timescales and/or a longer ocean response time to record oxygen changes at depths during glacial times.

Northwest China is facing socio-environmental challenges linked to ongoing climatic warming. However, a scarcity of regional paleorecord syntheses limits our understanding of natural long-term climate variability in the region and hinders the contextualization of contemporary warming. Here, we present paleorecord syntheses for both summer and annual temperatures during the Holocene based on a range of lacustrine sediment records from northwest China, with consideration of chronological uncertainties within records. The syntheses show similar summer and annual temperature variations, including peak warmth at ∼9000 years BP, followed by a 2000-year cooling trend, and stable temperatures thereafter. These variations may reflect inter-seasonal impact of summer insolation forcing through climate feedbacks (e.g., Arctic sea-ice cover) that are still not well represented in climate models. The early-Holocene peak warmth was >1.0°C warmer than the 20th century mean warmth, but is expected to be exceeded during the 21st century even under a low emission scenario.

The downward influence of extreme stratospheric events is typically described by the evolution of the Northern Annular Mode (NAM) across atmospheric levels. However, the dynamics and uncertainty in vertical coupling are not fully resolved. By applying the linear inverse model (LIM) to daily, multi-level NAM indices from reanalysis and CMIP6 models, we show that the leading eigenmode of NAM displays a deep structure extending from the stratosphere to the surface, with an e-folding timescale of about 30 days in reanalysis data. This stratospheric mode captures the downward propagation of NAM anomalies during weak polar vortex events, further supported by the LIM simulations forced by white noise. Analysis of inter-model spread suggests that the LIM-based estimates can reduce the uncertainty in the surface response to stratospheric extreme events by more than 50%. These findings provide dynamic insights into stratosphere-troposphere coupling of NAM and its representations in climate models.

Increasing basal meltwater from Antarctic ice shelves may impact the Southern Ocean properties that feed back on the rate of melting. We investigate this feedback in a high-emissions scenario using an Earth-system model with interactive ice-shelf basal melting, an improvement on previous studies that did not have the capability to evolve melt rates and the ocean state self-consistently. We find that when interactive melt increases, it primarily accelerates the evolution of a spatial pattern of continental shelf warming and cooling that is initiated by freshening and sea-ice formation decline due to projected atmospheric warming. The competition between enhanced warming at depth from reduced ventilation and enhanced continental shelf cooling from reduced dense water export leads to net $��\sim �$35% reduction in ice-shelf meltwater input into the Southern Ocean over the 21st century. Omitting this feedback introduces a bias in the timing of projected ocean-melt-driven ice loss from Antarctica.

We deployed 30 temporary seismic stations around the source region of the 2024 M_w 7.5 Noto Peninsula earthquake to investigate the relationship between mainshock rupture and fault geometry. Using machine learning techniques, we detected and precisely located 46,252 aftershocks, revealing several fault planes corresponding to active faults ruptured during the mainshock. Two subparallel landward-dipping planar structures were identified near the mainshock hypocenter, converging westward to the Wajima-Oki segment. This geometry suggests that complex rupture episodes near the hypocenter resulted from successive ruptures on adjacent fault planes rather than slip on a single plane. At the western edge of the 2024 rupture area, aftershocks extend close to but rarely occur on the fault that ruptured during the 2007 M_w 6.7 earthquake, suggesting that the 2024 earthquake did not re-rupture the same faults of the 2007 earthquake.

Springtime warming over Northern Mid-High-latitude Land profoundly affects plant life cycles and water resources, yet large model uncertainty limits climate risk assessment. Here, we develop a novel emergent constraint that targets the key uncertainty source—model divergence in surface-albedo feedback linked to historical snowmelt sensitivity. This approach halves the spread of projected warming and reveals a pronounced geographical asymmetry. Under the high-emission scenario (SSP5-8.5), current climate models underestimate end-of-century warming over Eurasia by 0.80°C but overestimate it over North America by 0.44°C. These refined projections substantially alter ecological outcomes: the start of the growing season is predicted to advance by about 18 days in Eurasia and 8 days in North America, representing a 3-day greater advance and 1-day delay compared with original estimates. Our findings offer a more reliable basis for assessing climate change impacts on ecosystems and water resources and highlight the urgency of region-specific adaptation strategies.

While the isolated effects of solar flares on low-latitude ionospheric electrodynamics have been well documented, the coupled system response of the equatorial electrojet (EEJ), auroral electrojet (AEJ), field-aligned currents (FACs), and asymmetric ring current (ASY-H) remains poorly understood. This study statistically analyzes 1,657 X/M-class flares (2001–2017) to quantify rapid electrodynamic changes across current systems. Our results indicate (a) flare intensity-dependent enhancements in eastward EEJ, suppressed equatorial ionospheric vertical drift (V_z), and increased ASY-H; (b) negligible flare influence on AEJ; and (c) R2 FACs intensification in the dusk sector, linking ionospheric dynamics to asymmetric ring current perturbations. These observations reveal transient electrodynamic coupling within the geospace associated with flares, independent of solar wind forcing, advancing understanding of flare-driven ionosphere-magnetosphere interactions.

Quantifying how incident ocean waves transfer energy into seismic surface waves along the nearshore is essential for understanding coastal hazards and Earth–ocean coupling, yet time-resolved in situ estimates have been scarce. Here we use a beach-deployed distributed acoustic sensing array co-located with an ocean-bottom node to directly measure the conversion efficiency from wave impacts to Rayleigh-type ground motion at 4–12 Hz. Frequency–wavenumber analysis, beamforming, and local back-projection consistently locate sources along a fixed, wave-breaking coastal segment, while particle-motion ellipticity confirms the Rayleigh character. Calibrating distributed acoustic sensing strain to ground velocity and combining nearshore wave energetics yields an energy-conversion efficiency on the order of 10⁻⁶. The efficiency is strongly modulated by tide, with high-tide conditions enhancing coupling even though the source region remains stationary. Our results establish a quantitative benchmark for dynamic ocean-to-Earth energy transfer at the land–sea interface and provide a generalizable framework for coastal monitoring using existing fiber infrastructure.