Geophysical Research Letters最新文献

Sea-land breeze (SLB) is particularly important in coastal regions and can affect weather conditions and air quality. However, previous research on SLB has predominantly focused on specific locations, with varying methodologies used to identify SLB days (SLBDs), leading to a limited understanding of long-term SLB trends across extensive coastal areas. Here, a unified method for gridded reanalysis dataset to identify SLBDs is proposed for the first time, and the trend, influencing factors, and effects on air pollutant recirculation over coastal China are explored. The results demonstrate that SLBDs have increased in 70% of China's coastal areas in the past five decades. Key driving factors include the growing temperature contrast between land and sea, increasing solar radiation, and the weakening background winds. The study suggests that the increasing SLB frequency will enhance air pollutant accumulations, making it challenging to manage air quality effectively in these coastal areas.

Extreme precipitation is becoming more intense and frequent. The increasing trends in extreme precipitation in China in warm season related to changes in aerosols and greenhouse gases (GHGs) are investigated using observations, reanalysis data and model simulations. A significant accelerating increase in extreme precipitation occurred around 2010, with the trend in accumulated extreme rainfall amount (R95pTOT) increasing from 2.88 mm per decade during 2000–2010 to 22.88 mm per decade during 2010–2023. The sudden acceleration of the increasing extreme precipitation is largely attributed to the reverse in aerosol trends associated with China’s clean air actions, which affects extreme precipitation through perturbing cloud microphysics and atmospheric dynamics, accounting for half of the change in R95pTOT trends. Future aerosol reduction to achieve carbon neutrality is shown to continue to intensify the extreme precipitation, which overweighs the effect induced by GHGs, highlighting the importance of aerosol changes in modulating future climate and weather extremes.

Differentiable geoscientific modeling has shown promise for leveraging machine learning (ML) to unify physically based and data-based modeling. Here, we critically analyze this promise in the context of large-scale parameter optimization with the Noah-MP land model as an example. The differentiable parameter learning framework is used to calibrate Noah-MP soil and vegetation parameters such that the simulated surface soil moisture better matches satellite observations over the contiguous US. We found that the optimized parameters only marginally improved soil moisture (average RMSE = 0.092 m³ m⁻³) upon uncalibrated Noah-MP (RMSE = 0.10 m³ m⁻³). Scaling and bias correction factors, often used in ML approaches for enhancing generalizability, were found to limit the transferability of the optimized physical parameters to the land model. The global objective function further compromises the algorithm's ability to simultaneously capture contrasting moisture regimes. Addressing these challenges is necessary to advance ML-based calibration frameworks to better learn and represent the constraints of the physical model.

Nearshore erosion is well-documented in sediment-deficit river deltas but remains less understood beyond their delta front (DF), particularly its extension to the deeper prodelta (PD) and distal mud (DM). This study investigates the response of Changjiang subaqueous delta and its DM to sediment decline following the 2003 closure of the Three Gorges Dam. By analyzing temporal and spatial variations in ²¹⁰Pb_ex profile styles, discrepancies between ²¹⁰Pb and ¹³⁷Cs sediment accumulation rates, and surface sediment grain sizes, we identified the onset of erosion at the DF shortly after 2003, which spread to the PD by 2009 and reached the northern DM by 2015. By tracking the burial depths of the 1963 ¹³⁷Cs peak, we found progressively lower erosion rates in newly eroded subzones primarily due to sediment redistribution. This study, leveraging historical radionuclides data, offers a valuable approach for monitoring erosion in areas lacking remote sensing detection and historical bathymetric data.

Quantitative understanding is lacking on how the depth of active groundwater circulation in bedrock affects mountain streamflow response to a multi-year drought. We use an integrated hydrological model to explore the sensitivity of a variety of streamflow metrics to bedrock circulation depth and porosity under a plausible extreme drought scenario lasting up to 5 years. Endmember depth versus hydraulic conductivity relationships and porosity values for fractured crystalline rock are simulated. With drought, a deeper circulation system with higher drainable porosity more effectively buffers minimum flow and significantly limits perennial stream loss in comparison to a shallow circulation system. Streamflow buffering is accomplished through extensive groundwater storage loss. However, deeper circulation systems experience prolonged recovery from drought in comparison to storage-limited shallow systems. Research highlights the importance of characterizing the deeper bedrock hydrogeology in mountainous watersheds to better understand and predict drought impacts on stream ecosystem health and water resource sustainability.

Aqueous-phase uptake and processing of water-soluble organic compounds can promote secondary organic aerosol (SOA) production. We evaluated the contributions of aqueous-phase chemistry to summertime urban SOA at two sites in New York City. The relative role of aqueous-phase processing varied with chemical and environmental conditions, with evident daytime SOA enhancements (e.g., >1 μg/m³) during periods with relative humidities (RH) exceeding 65% and often higher temperatures. Oxygenated organic aerosol (OOA) production was also sensitive to secondary inorganic aerosols, in part through their influence on aerosol liquid water. On average, high-RH periods exhibited a 69% increase in less-oxidized OOA production in Queens, NY. These enhancements coincided with southerly backward trajectories and greater inorganic aerosol concentrations, yet showed substantial intra-city variability between Queens and Manhattan. The observed aqueous-phase SOA production, even with historically low sulfate and nitrate aerosol loadings, highlights both opportunities and challenges for continued reductions in summertime PM_2.5 in urban communities.

This study identifies a significant positive relationship between Indian Ocean dipole mode (IODM) and Greenland Sea sea ice concentration (GSSIC) in autumn during 1980–2023. The increasing GSSIC can lead to a vertical circulation cell anomaly between the polar region and middle latitude over the North Atlantic due to the thermal condition anomalies. The associated anomalous ascending flow over the coast of western Europe generates wave train propagating southeastward from mid-high latitude Atlantic to the North Indian Ocean (IO), causing anomalous anticyclone over the Indian Ocean. The related anomalous easterlies over tropical IO contribute to the positive IODM (warmer SSTA over west tropical IO but cooler SSTA off Sumatra–Java) through weakening the wind-evaporation-SST feedback over tropical IO and shallowing (deepening) thermocline along the coastal of Sumatra-Java (west tropical IO). Moreover, the numerical experiments can basically reproduce the observed mechanisms.

Percolation of dioritic melts through ultramafic cumulate mushes and their reaction and hybridization have been documented in some arcs, but the impact of the processes on the compositions of arc igneous rocks is not yet fully understood. Here, we investigate the petrogenesis of meladiorites from the ca. 200 Ma Cuijiu Igneous Complex in the eastern Gangdese Arc, southern Tibet. The meladiorites are pervasively intruded by normal diorite dykes and show geochemical affinities with high-Mg intermediate igneous rocks, and their amphibole is characterized by low-Mg core and high-Mg rim. Our new data, together with published data, demonstrate that the meladiorites resulted from hybridization of an ultramafic cumulate mush (∼30%–∼50%) with percolating normal dioritic melts (∼50%–∼70%), and that dissolution-crystallization and chemical diffusion dominated the hybridization. We propose that percolation of dioritic melts through ultramafic cumulate mushes is a viable way to form hybrid high-Mg intermediate igneous rocks.

Turbulence is of great importance for aviation safety, but its long-term trend in China remains unclear due to the scarcity of in-situ measurements. Here the national-scale assessment of turbulence dissipation rate (ε) at flight cruising altitude (200 hPa) in China is conducted for the period from 2010 to 2022 using high-resolution radiosonde measurements. Results show that both the intensity and frequency of turbulence exhibit a significant upward trend, particularly in the mid-latitude regions. Furthermore, 12 other turbulence diagnostic parameters from ERA5 reanalysis show a similar increasing trend, corroborating the intensified trend in radiosonde-derived turbulence. This more intensified and frequent turbulence is found to be closely associated with the increasing occurrence of jet streams, which could be attributed to the dynamic instability induced by the wind shear around jet streams. The findings help advance our understanding of turbulence trend and its underlying mechanism in the mid-latitude regions under global warming.

On behalf of the journal, AGU, and the scientific community, the editors of Geophysical Research Letters would like to sincerely thank those who reviewed manuscripts in 2024. The hours reading and commenting on manuscripts not only improve the manuscripts but also increase the scientific rigor of future research in the field. With the advent of AGU's data policy, many reviewers have also helped immensely to evaluate the accessibility and availability of data, and many have provided insightful comments that helped to improve the data presentation and quality. We greatly appreciate the assistance of the reviewers in advancing open science, which is a key objective of AGU's data policy. We particularly appreciate the timely reviews in light of the demands imposed by the rapid review process at Geophysical Research Letters. We received 5,225 submissions in 2024, and 5,597 reviewers contributed to their evaluation by providing 9,697 reviews in total. We deeply appreciate their contributions. We would also like to acknowledge the passing of our beloved colleague, Harihar Rajaram. An AGU Fellow and longtime affiliate of AGU's Hydrology Section, Hari was the Editor-in-Chief of Geophysical Research Letters since 2019, a former editor on Water Resources Research, and served on the AGU Publications Committee.