Geophysical Research Letters最新文献

There is a lack of consensus on how tropical cyclone outer winds may change, if at all, due to extratropical transition. Hence, this study examines changes in North Atlantic tropical cyclone outer size and structure using a large, multidecadal sample of cases from reanalysis data. These results suggest that tropical cyclone outer size and structure typically remain unchanged until after extratropical transition end. In those minority of cases with strong expansion during extratropical transition, increases in tropical cyclone outer winds begin first in the lower troposphere during extratropical transition and build upwards over time. This broadening of the azimuthal-mean outer winds is also associated with an increasingly asymmetric outer wind field with the strongest winds concentrated downstream of the tropical cyclone. These storms that expand most strongly during transition are typically smaller at transition start and eventually become embedded in more strongly baroclinic environments by extratropical transition end.

Lightning is the most important source of nitric oxide (NO) in the tropical upper troposphere and controls the formation of tropospheric ozone ($��O_3�$). It is associated with deep convection and occurs mostly over continents. The Chemistry of the Atmosphere Field Experiment in the Pacific (CAFE Pacific) was conducted in early 2024 from Cairns, Australia, taking airborne measurements across the Australian continent and the surrounding maritime regions. Based on cloud top properties, lightning data and in situ observations of NO, $��O_3�$ and carbon monoxide, we show that deep convection occurs over Northern Australia and the Indo-Pacific Warm Pool. While we identify strong lightning activity over Australia, we observe deep convection in the Warm Pool that is not electrified. Our observations of low $��O_3�$ in the Warm Pool can be attributed to $��O_3�$-poor air from the marine boundary layer, which is not replenished by photochemical production from NO at high altitudes.

Climate change and human activity are dramatically reshaping how water is distributed on Earth. High quality observations and products that bridge the gap between low-level data and actionable information are needed to support the understanding of current and future water availability. Two new developments are addressing these needs. The SWOT satellite is measuring water elevation with unprecedented detail, while the OPERA project is turning satellite observations into clear, interpretable maps of surface water extent. Together, these represent a major advance in our ability to measure and monitor water from space. We demonstrate their capability by tracking the transformation of Badwater Basin, Death Valley–one of the driest, hottest places on Earth–into an ephemeral lake following extreme precipitation events starting with Hurricane Hilary in August 2023. As a challenging area to understand water dynamics, Badwater Basin serves as a model for how these new observations enable more effective water management.

Time slice experiments for past interglacial climates of Marine Isotope Stage (MIS)1, MIS5e, and MIS11 are simulated using an atmosphere-ocean-vegetation coupled general circulation model with prescribed remnant ice sheet distributions. We examine Arctic climate responses to insolation intensity as well as remnant ice sheets through atmosphere-ocean-vegetation feedback quantitatively. During periods when Northern Hemisphere ice sheets remain, Arctic sea ice maintains a large extent in summer, and annual mean surface air temperatures are low enough to outweigh the warming expected from summer insolation intensity and greenhouse gases alone. This indicates that glacial ice sheets, due to their high albedo and their role as a heat sink, suppress the accumulation of heat in the Arctic Ocean in summer and the associated warming feedback. The results suggest a need to consider the history of remnant ice sheets and the duration of ice-free periods to explain different Arctic climate responses within and between interglacials.

The study investigates Power Dissipation Index (PDI) of tropical cyclones (TCs) over the North Indian Ocean (NIO) and their relationship with sea surface temperature (SST) over the global ocean from 1982 to 2021. PDI of TCs over the Arabian Sea (AS) has a significant positive correlation with SST over the East Central Pacific Ocean (ECPO). This relationship appears to develop in March and peaks during the monsoon and post-monsoon seasons. Conversely, PDI of TCs over the Bay of Bengal has a significant negative association with SST over the Niño region. Regression analysis and numerical simulations reveal that heating over ECPO produces anomalous walker circulation, leading to favorable conditions for TC genesis and intensification over AS. This study has implication for forecasting TC activity and understanding how SST variability affects TCs over NIO in a changing climate.

Previous statistical studies have described the distributions and properties of whistler-mode waves in Jupiter's magnetosphere, but explaining these wave distributions requires modeling wave propagation from their generation near the magnetic equator. In this letter, we conduct ray tracing of whistler-mode waves based on realistic Jovian magnetic field and density models. The ray tracing results generally agree with the statistical wave distributions based on Juno measurements. The modeled ray paths show that high-frequency waves generated near the equator are confined within 20° magnetic latitude due to Landau damping, low-frequency waves can propagate to higher latitudes and lower M-shells, with changing wave normal angles, and a portion of low-frequency waves could propagate to high M shells at high latitudes. Our modeling results provide a theoretical interpretation of whistler-mode wave distributions and properties, providing essential insights for future radiation belt models at Jupiter.

During a Juno spacecraft encounter with Jupiter's volcanic moon Io (30 December 2023), the Jupiter Energetic Particle Detector Instrument (JEDI) observed Energetic Neutral Atoms (ENAs) of >150 keV oxygen and sulfur (O + S) coming from Io's mostly nightside atmosphere. JEDI lines-of-sight approached closest to Io between 1.31 and 1.49 Io radii (R_Io), above the predominantly SO₂ core atmosphere but imbedded within the extended atmosphere and corona of SO₂, SO, O, and S. The ratio of O + S ENA intensities and O + S ion intensities estimated to be interacting with Io's atmosphere along JEDI lines-of-sight are 4%–7%. Those estimates are below expectations (∼11%–∼14%), but presently within uncertainties, based on integrations along the JEDI lines-of-sight through a prevailing but uncertain, local-time-symmetric model of Io's extended atmosphere. Expected ENA production rates will remain uncertain until detailed modeling of ion/atmosphere interactions are performed, and knowledge of charge exchange cross sections is verified.

Improving accuracy and reducing uncertainty in ground motion models (GMMs) are crucial for the safe design of infrastructure. Traditional GMMs often oversimplify source complexity, such as stress drop, due to high variability in estimation. This study aims to address this issue by extracting robust spatial variations in stress drop estimates and ground motion residuals. We introduce a non-ergodic modeling framework using Bayesian Gaussian Process regression to analyze data from over 5,000 earthquakes (M2-4.5) in the San Francisco Bay area. Our findings reveal consistent spatial patterns in non-ergodic stress drop and peak ground acceleration (PGA), providing a reliable approach to understanding the spatial distribution of stress drop and its link to regional tectonics. Furthermore, integrating source models derived from the non-ergodic stress drop into GMMs can effectively account for source effect in ground motions and reduce aleatory uncertainty. This study establishes a framework for utilizing stress drop data sets to enhance seismic hazard assessment.

Atmospheric rivers (ARs) have been linked with extreme rainfall and melt events across the Greenland ice sheet (GrIS), accelerating its mass loss. However, the impact of AR-fueled snowfall has received less attention, partly due to limited empirical evidence. Here, we relate new firn core stratigraphy and isotopic analyses with glacio-meteorological data sets from SE Greenland to examine an intense AR in mid-March 2022. We demonstrate that the associated snowfall—up to 11.6 gigatons d⁻¹—delayed summer melt onset by11-days and offset Greenland's 2022 net mass loss by 8%. Since 2010, our synoptic analysis reveals that snow accumulation across SE Greenland increased by 20 mm water equivalent a⁻¹, driven by enhanced Atlantic cyclonicity. We find that the impact of ARs on the GrIS is not exclusively negative and their capacity to contribute mass recharge may become increasingly significant under ongoing Arctic amplification and predicted poleward intrusion of mid-latitude moisture.