Questions regarding the development of folds and their interactions with the seismic faults within thrust systems remain unanswered. However, estimating fault slip and earthquake hazards using surface observations and kinematic models of folding requires an understanding of how the shortening is accommodated during the different phases of the earthquake cycle. Here, we construct 16-years of InSAR time series across the North Qaidam thrust system (NE Tibet), where three Mw 6.3 earthquakes occurred along basement faults underlying shortened folded sediments. The analysis reveals spatio-temporal changes of post-seismic surface displacement rates and patterns, which continue more than ten years after the seismic events. The decomposition of the Sentinel-1 ascending and descending LOS velocities into vertical and shortening post-seismic components indicates that long-term transient uplift and shortening coincide spatially with young anticlines observed in the geomorphology and cannot simply be explained by elastic slip along dislocations. These findings provide evidences for fold buckling during the post-earthquake phase and highlight the contribution of distributed aseismic deformation to the growth of topography.

The chorus whistler-mode emission, a major driver of radiation belt electron energization and precipitation, exhibits significant amplitude modulations on millisecond timescales. These subpacket modulations are accompanied by fast changes in the wave normal angle. Understanding the evolution of wave propagation properties inside chorus elements is essential for modeling nonlinear chorus-electron interactions, but the origin of these rapid changes is unclear. We propose that the variations come from propagation inside thin, field-aligned cold plasma enhancements (density ducts), which produce differing modulations in parallel and perpendicular wave magnetic field components. We show that a full-wave simulation on a filamented density background predicts wave vector and amplitude evolution similar to Van Allen Probes spacecraft observations. We further demonstrate that the commonly assumed wide density ducts, in which wave propagation can be studied with ray tracing methods, cannot explain the observed behavior. This indirectly proves the existence of wavelength-scale field-aligned density fluctuations.

The Greenland ice sheet (GrIS) has been losing mass in the last several decades, and is currently contributing around 0.7 mm sea level equivalent (SLE) yr-1 to global mean sea level rise (SLR). As ice sheets are integral parts of the Earth system, it is important to gain process-level understanding of GrIS mass loss. This paper presents an idealized high-forcing simulation of 350 years with the Community Earth System Model version 2.1 (CESM2.1) including interactively coupled, dynamic GrIS with the Community Ice Sheet Model v2.1 (CISM2.1). From pre-industrial levels (287 ppmv), the CO2 concentration is increased by 1% yr-1 till quadrupling (1140 ppmv) is reached in year 140. After this, the forcing is kept constant. Global mean temperature anomaly of 5.2 K and 8.5 K is simulated by years 131–150 and 331-150, respectively. The North Atlantic Meridional Overturning Circulation strongly declines, starting before GrIS runoff substantially increases. The projected GrIS contribution to global mean SLR is 107 mm SLE by year 150, and 1140 mm SLE by year 350. The accelerated mass loss is driven by the SMB. Increased long-wave radiation from the warmer atmosphere induces an initial slow SMB decline. An acceleration in SMB decline occurs after the ablation areas have expanded enough to trigger the ice-albedo feedback. Thereafter, short-wave radiation becomes an increasingly important contributor to the melt energy. The turbulent heat fluxes further enhance melt and the refreezing capacity becomes saturated. The global mean temperature anomaly at the start of the accelerated SMB decline is 4.2 K.

We present an empirical model of the seasonal variability of the internal tide using seasonal harmonics to modulate the amplitude of the fundamental tidal constituents. Internal tide data, from both long-term, in-situ moorings and a mesoscale- and internal tide-resolving ocean model, are used to demonstrate the performance of the seasonal harmonic model for the Indo-Australian Basin Region. The seasonal model describes up to 15 % more of the observed (baroclinic) sea surface height variance than a fixed-amplitude harmonic mode at the mooring sites. The ocean model results demonstrate that the study region, which includes the Australian North West Shelf (NWS), Timor Sea and southern Indonesian Islands, is dominated by standing wave interference patterns due to the presence of multiple generation sites. The seasonal harmonic model reveals that temporal shifts in the standing wave patterns coincide with seasonal variations in density stratification. This shift is particularly evident within distances of 2 - 3 internal wave lengths from strong generation sites. The fraction of the variance of the internal tide signal explained by seasonal modulations is largest in standing wave node regions, contributing to differences in predictive skill of the seasonal harmonic model at two moorings separated by only 38 km. Output of the harmonic model also demonstrated that the seasonally-evolving M2 internal tide propagating southward from Lombok Strait had a small amplitude in October when shear from the Indonesian Throughflow was strongest.

As part of the Whole Heliosphere and Planetary Interactions (WHPI) initiative, contrasting drivers of radiation belt electron response at solar minimum have been investigated with MHD-test particle simulations for the 13 – 14 May 2019 CME-shock event and the 30 August – 3 September 2019 high speed solar wind interval. Both solar wind drivers produced moderate geomagnetic storms characterized by a minimum Dst = - 65 nT and - 52 nT, respectively, with the August - September event accompanied by prolonged substorm activity. The latter, with characteristic features of a CIR-driven storm, produced the hardest relativistic electron spectrum observed by Van Allen Probes during the last two years of the mission, ending in October 2019. MHD simulations were performed using both the Lyon-Fedder-Mobarry global MHD code and recently developed GAMERA model coupled to the Rice Convection Model, run with measured L1 solar wind input for both events studied, and coupled with test particle simulations, including an initial trapped and injected population. Initial electron phase space density (PSD) profiles used measurements from the Relativistic Electron Proton Telescope (REPT) and MagEIS energetic particle instruments on Van Allen Probes for test particle weighting and updating of the injected population at apogee. Results were compared directly with measurements and found to reproduce magnetopause loss for the CME-shock event and increased PSD for the CIR event. The two classes of events are contrasted for their impact on outer zone relativistic electrons near the end of Solar Cycle 24.

Tropical cyclones bring health risks and can trigger outbreaks of diarrheal diseases in affected populations. There are several reviews that mention the relationship between tropical cyclones and diarrheal diseases. However, there is no dedicated review of the current evidence and extent of research on the association between tropical cyclones and diarrheal diseases. We performed a scoping review to thoroughly examine the available literature. We also thematically analyzed the transmission pathways explained in the literature. A total of 96 studies were included. Twenty-three studies quantitatively measured the tropical cyclone--diarrhea associations, with half reporting positive associations. We found that the studies defined and measured tropical cyclone exposure differently and mostly analyzed a single event. The study designs employed were mostly pre-post comparisons that had several limitations affecting internal validity. These differences also prevent the quantitative pooling of evidence. A standardized approach to measuring the association between tropical cyclones and diarrheal diseases can be devised by suggesting the most appropriate exposure definition and modeling.

In this study, we investigate the relationship between mid-Atlantic tropical cyclone (TC) landfalls and the Madden-Julian oscillation (MJO). This is done by using a high-atmoshperic-resolution ensemble prediction system based on the ECMWF operational model (Project Minerva) to compile the statistics of these rare events, and the velocity potential MJO (VPM) index to define the phase and amplitude of the MJO. We find that these TC landfalls are most likely to occur during VPM phases 1-3. At shorter lead times, phase 1 is strongly favored, with some contribution of phase 3. At longer lead times (between the 6- and 12-day leads), phases 1 and 2 consistently show significant TC landfall frequencies. This result suggests a potential for extended-range predictions of the mid-Atlantic TC landfall risk based on the phase of the MJO.

Magnetosheath jets are dynamic pressure enhancements observed in the terrestrial magnetosheath. Their generation mechanisms are currently debated but can be linked to foreshock processes. Recent results showed that jets are less numerous when coronal mass ejections (CME) cross the magnetosheath. Here, we show for the first time how CMEs and their magnetic ejecta (ME) region are related to jet production. Based on THEMIS and OMNI data covering 2008–2021, we show the probability distribution of jet production in 2D parameter histograms using the IMF cone angle and Alfvén Mach number. We compare this distribution with the values within CME-MEs. We find high cone angles and low Alfvén Mach numbers within CME-MEs, which both are unfavorable for jet production as they may inhibit a proper foreshock region. We predict that future missions, measuring the magnetosheath of Mercury, will find low numbers of jets due to low Alfvén Mach numbers.

In this study, we carried out a backprojection (BP) analysis to image the rupture process of the newly happened September 8, 2017 Mww8.1 Mexico earthquake based on a global 3D P-wave tomography model, the LLNL-G3Dv3 model. Limited to epicenter distance and data quality, only waveform observation data from Alaska (AL), USA was utilized finally, with some data from South America (SA) as supplement. First, we compared the HF BP results of 1D and 3D model to illustrate the higher resolution and reliability of the 3D one. Then we discussed the consistency among the overall rupture pattern, the main event focal mechanism and aftershocks distribution, and further inferred the possible fault geometry. After that, we explained the rationality of the setting for rupture duration based on beamforming energy pattern, normalized power variation and other previous works. We then seriously examined the creditability of stage 2 and explained why speed in stage 2 is much bigger than in 1. Finally, we obtained the coulomb stress change imparted on the faults of the subsequent September 19 Mww7.1 event and September 23 Mww6.1 event to find out if they are positively triggered by this main event. From our current research, the complete ~53s rupture process of this earthquake can be divided into two stages. In stage 1, which lasted for ~37s, the rupture propagated from the epicenter towards the NW direction (~330°measured from north clockwise) with a speed of ~2.8 km/s, and extended to a length of ~89 km. Then it made a right turn and shortly after, it continued to propagate to near N (~3°) with a higher speed of ~5.3 km/s and a scale of ~75 km. Our study intended to believe that the Mww8.1 event has almost nothing to do with the Mww7.1 event while it strongly triggered the occurrence of the latter Mww6.1 event.

Mega-fires have occurred in Australia during the 2019/2020 bushfire season, leading to enhanced concentrations of many tropospheric pollutants. Here we report on a fire plume with unusually high and persistent HONO levels that we could tracked during one day at free tropospheric levels over the Tasman Sea on 4 January 2020 using IASI and CrIS satellite observations. HONO concentrations up to about 8 ppb were retrieved during nighttime. Persistent HONO concentrations (>1ppb) were still observed at sunrise. Model simulations suggest a significant contribution of primary fire emissions and heterogeneous photo-induced reactions to explain the observed concentrations. However, many uncertainties and unknowns remain in the plume aerosol load and in the chemical processes which may explain the model inability to reproduce HONO concentrations at sunrise.

This study applies new satellite datasets and methodologies to build on previous research exploring the physical relationship between lightning and precipitation in mid-/high latitudes. Specifically, three years of Geostationary Lightning Mapper (GLM) and Global Precipitation Measurement (GPM) Mission core satellite coincident observations are examined to investigate relationships between lightning flash rate and microwave characteristics of convective precipitation features (cPFs) over the Americas and surrounding oceans between ± 50° latitude. Mid-/high latitude cPFs with lightning are characterized by colder temperatures of maximum 30 dBz echo top height and a smaller range of microwave brightness temperatures when compared to the tropics. Brightness temperature characteristics of electrically active cPFs are highly correlated to radar-diagnosed ice mass and largely insensitive to synoptic-scale proxies for convective strength and organization. Low flash density cPFs tend to be more sensitive to synoptic-scale instability and shear than high flash density cPFs. Regional differences in the environmental forcing and characteristics of electrically active cPFs are shown. For example, the elevated terrain surrounding the Amazon River Basin is characterized by stronger vertical updrafts indicated by higher values of normalized CAPE (NCAPE) while the La Plata River Basin is characterized by both stronger updrafts and higher values of radar-diagnosed ice water mass.

Many solar wind parameters correlate with one another, which complicates the causal-effect studies of solar wind driving of the magnetosphere. Conditional mutual information (CMI) is used to untangle and isolate the effect of individual solar wind and magnetospheric drivers of the radiation belt electrons. The solar wind density (nsw) negatively correlates with electron phase space density (PSD) (average energy ~ 1.6 MeV) with time lag (t) = 15 hr. This effect of nsw on PSD has been attributed to magnetopause shadowing losses, but when the effect of solar wind velocity (Vsw) is removed, t shifts to 7–11 hr, which is a more accurate time scale for this process. The peak correlation between Vsw and PSD shifts from t = 38 to 46 hr, when the effect of nsw is removed. This suggests that the time scale for electron acceleration to 1–2 MeV is about 46 hr following Vsw enhancements. The effect of nsw is significant only at L* = 4.5–6 (L* > 6 is highly variable) whereas the effect of Vsw is significant only at L* = 3.5–6.5. The peak response of PSD to Vsw is the shortest and most significant at L* = 4.5–5.5. As time progresses, the peak response broadens and shifts to higher t at higher and lower L*, consistent with local acceleration at L* = 4.5–5.5 followed by outward and inward diffusion. The outward radial diffusion time scale at L* = 5–6 is ~40 hr per RE.

A document by Ekaterina Bogdanovich. Click on the document to view its contents.

Global-scale changes in water vapor and responses to surface temperature variability since 1979 are evaluated across a range of satellite and ground-based observations, a reanalysis (ERA5) and coupled and atmosphere-only CMIP6 climate model simulations. Global-mean column integrated water vapor increased by 1\%/decade during 1988-2014 in observations and atmosphere-only simulations but coupled simulations overestimate trends because internal climate variability suppressed observed warming in this period. Decreases in low-altitude tropical water vapor in ERA5 and ground-based observations before around 1993 are inconsistent with simulations and increased column integrated water vapor in a satellite dataset since 1987. AIRS satellite data does not capture the increased tropospheric water vapor since 2002 in other satellite, reanalysis and model products. However, global water vapor responses to interannual temperature variability is consistent across datasets with increases of $\sim$4-5\% per K near the surface and 10-15\%/K at 300 hPa. Global water vapor responses are explained by thermodynamic amplification of upper tropospheric temperature changes and the Clausius Clapeyron temperature dependence of saturation vapor pressure that are dominated by the tropical ocean responses. Upper tropospheric moistening is larger in climate model simulations with greater upper tropospheric warming.

A document by Wenxian Guo. Click on the document to view its contents.

Anthropogenic activity drives extensive tropical deforestation, particularly in Southeast Asia where 16% of total forest cover was lost between 2000 and 2020. While land surface changes significantly affect the atmosphere, their net impact on convective clouds is not well-constrained. Here, we use satellite data to provide the first observational evidence that long-term deforestation in Southeast Asia robustly alters cloud properties, and that the magnitude of this response depends on the atmospheric environment. Deforestation drives a shift towards more widespread, shallower clouds during the daytime, with amplified effects in dry inland areas compared with moist coastal regions. Aerosols only weakly modulate the cloud fraction response, but offset the cloud top height response to deforestation, suggesting the influence of aerosol indirect effects. We conclude that the local signature of forest loss is not uniform, and regional differences in climatology must be considered when assessing deforestation impacts on clouds and the climate system.

Brief bursts of high frequency (HF) and very high frequency (VHF) radio emissions unaccompanied by strong low frequency radiation have been observed during initiation and propagation of lightning or thunderstorm electrical breakdown without leading to fully-fledged lightning. This paper investigates a physical mechanism to generate such radio bursts by electrical discharge activity inside a thundercloud. When a discharge consists of many high frequency emission sources, such as streamers, that generate currents in random directions, its radiation spectrum peaks in the HF and VHF bands, and the spectral magnitudes in low frequencies are much smaller or even negligible. Combined with recent observational findings, the present study suggests that lightning initiation may begin with a short burst of many randomly occurring small-scale discharges in a localized thundercloud region.

Underwater disturbances are the largest error source in GNSS-A seafloor geodetic observation. In particular, the gradient of sound speed structure directly affects the horizontal accuracy and needs to be examined. Previous studies have not investigated its temporal change component. In this paper, we verified the assumption that the underwater gradient structure does not change significantly during GNSS-A observation for several hours through applying a modified version of an analysis software called GARPOS to actual data of SGO-A (provided by Japan Coast Guard). Obtained results suggested that this assumption holds at many observation data, and the positioning accuracy becomes better. Some non-improved observation epochs were speculated to be accompanied by structure changes for which this assumption was not valid. It is suggested that the sound speed structure change during observation will be an important research topic in GNSS-A.