Meteotsunamis are both a well-known and poorly understood phenomenon. In particular, the influence of and disturbance by meteotsunami on coastal wetlands is largely unknown. This paper documents a case illustrating how water levels in an isolated wetland, specifically an incipient foredune/swale complex, in northern Lake Michigan responded to a meteotsunami event. We identified potential meteotsunami influence on wetland water levels through slope-break analysis, verified the presence of meteotsunami waves at surrounding lake water level gauge stations with wavelet analysis, analyzed both regional and small-scale meteorological data to establish what source of atmospheric forcing resulted in meteotsunami formation, and used a hydrodynamic model to simulate lake surface response and meteotsunami generation. Here, we present what we hypothesize reflects an idealized response of wetland water levels to meteotsunami influence where an atmospheric bore propagating away from a convective system formed a meteotsunami event that was captured in subsurface water levels beneath the isolated wetland. While this event produced an obvious response, the potential for multiple sources of meteorological forcing and secondary wave refraction highlights several of the challenges with predicting generation of and hazard from meteotsunami events. These issues equally translate in how the current methodology can be applied to isolated wetland systems. The event presented in this study make a strong case for focused research on coastal wetland response to meteotsunamis (and meteotsunami-like events) to address this understudied impact given its implications for coastal processes and resiliency.

We investigate trends in the magnitude and frequency of extreme storm surge events at 320 tide gauges across the globe from 1930, 1950, and 1980 to present. We use two centennial and three satellite-era daily storm surge time series from the Global Storm Surge Reconstructions (GSSR) database. Before calculating trends, we perform change point analysis to identify and remove data where inhomogeneities in atmospheric reanalysis products could lead to spurious trends in the storm surge data. Even after removing unreliable data, the database still extends existing storm surge records by several decades for most of the tide gauges. Storm surges derived from the centennial 20CR and ERA-20C atmospheric reanalyses show consistently significant positive trends along the southern North Sea and the Kattegat Bay regions during the periods from 1930 and 1950 onwards and negative trends since 1980 period. When comparing all five storm surge reconstructions and observations for the overlapping 1980-2010 period we find overall good agreement, but distinct differences along some coastlines, such as the Bay of Biscay and Australia. We also assess changes in the frequency of extreme surges and find that the number of annual exceedances above the 95th percentile has increased since 1930 and 1950 in several regions such as Western Europe, Kattegat Bay, and the US East Coast.

Horizontal gravity wave (GW) refraction was observed around the Andes and Drake Pas- sage during the SouthTRAC campaign. GWs interact with the background wind through refraction and dissipation. This interaction helps to drive mid-atmospheric circulations and slows down the polar vortex by taking GW momentum flux from one location to an- other. The SouthTRAC campaign was composed to gain improved understanding of the propagation and dissipation of GWs. This study uses observational data from this cam- paign collected by the German research aircraft on 12 September 2019. During the cam- paign a minor sudden stratospheric warming in the Southern Hemisphere occurred, which heavily influenced GW propagation and refraction and thus also the location and amount of GW momentum flux deposition. Observations include, amongst others, measurements from below the aircraft by GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere), and above the aircraft by ALIMA (Airborne Lidar for the Middle Atmosphere). Refraction is identified in two different GW packets as low as ≈4 km and as high as 58 km. One GW packet of orographic origin and one of non-orographic ori- gin is used to investigate refraction. Observations are supplemented by the Gravity-wave Regional Or Global Ray Tracer (GROGRAT), a simplified mountain wave model, ERA5 data and high-resolution (3 km) WRF data. Contrary to some previous studies we find that refraction makes a noteworthy contribution in the amount and the location of GW momentum flux deposition. This case study highlights the importance of refraction and provides compelling arguments that models should account for this.

Hydroclimate variability of the southwest United States (SWUS) is influenced by the tropical Pacific Ocean, particularly the phase of the El Niño/Southern Oscillation (ENSO), via teleconnections, which are expected to be altered by climate change. However, natural variability in this teleconnection has not been robustly quantified, complicating the detection of anthropogenic climate change. Here, we use a linear inverse model (LIM) to quantify natural variability in the ENSO-SWUS teleconnection. The LIM yields realistic teleconnection patterns with century-scale variability in teleconnection strength comparable to simulations from the Last Millennium Ensemble project and the Coupled Model Intercomparison Project Phases 5 and 6. The variability quantified by the LIM illuminates two aspects of our understanding of ENSO and its impacts: the inherent statistics of the observable system can produce century-long periods of nonsignificant correlation, and detecting changes in ENSO-related hydroclimate variability is challenging in a changing climate.

The eastern Tsugaru Strait is an important area because it is located at the southwestern boundary of the subarctic gyre in the North Pacific, and it connects the Pacific Ocean and the Sea of Japan. Combining continuous monitoring (including fixed-point temperature measurements, shipboard observations, and high-frequency radar system observations) with a data-assimilated numerical model (JCOPE2M), we investigated the processes associated with an event characterized by extremely cold surface water observed in winter of 2014 at the southeastern side of the Tsugaru Strait. JCOPE2M outputs reproduce the event closely and reveal a low-temperature, low-salinity region of water generated from around Cape Erimo (probably by wind associated with migrating lows passing across Japan) and propagating from east to west over multiple timescales. This pattern is interpreted as representing the spreading of Coastal Oyashio Water (COW; with a density of 26.2 σθ) along the Hokkaido coast. JCOPE2M outputs also show a subsequent increase in denser water (26.6–26.8 σθ) inflowing from the Sea of Japan into the bottom of the strait. The JCOPE2M results also indicate baroclinic instability in the eastern part of the strait following the inflow of dense water. The confluence of COW and denser water is presumed to lead to horizontal exchange, with cold COW riding up on the denser water, in turn generating the pronounced cold-surface-water event. Some past cold-water events correspond in timing to negative anomalies of the West Pacific pattern, which suggests the important influence of southward shifts in storm-track latitude of migrating atmospheric lows across Japan.

The structure of the bottom boundary layer (BBL) in aquatic flows influences a range of biophysical processes, including sediment transport, hyporheic exchange, and biofilm formation. While the structure of BBL above bare sediment beds has been well studied, little is known about the complex near-bed flow structure within canopies of aquatic vegetation. In this study, we used high-resolution laboratory measurements and numerical Large Eddy Simulations to investigate the near-bed mean and turbulent flow properties within staggered-ordered emergent canopies under a wide range of flow and canopy conditions. There is strong horizontal variability of key near-bed flow characteristics on the scale of the vegetation elements. Measurement locations that provide single-point flow characteristics closest to the spatially-averaged values were identified. The spatially-averaged BBL thickness is influenced strongly by canopy density. This impact of canopy density is engendered through its direct control of near-bed turbulent kinetic energy (TKE), which in turn is negatively correlated with BBL thickness, both locally in a given flow and across the range of flow conditions studied here. A model based on the near-bed TKE is developed to predict the BBL thickness and, ultimately, the bed shear stress. The strong agreement between model predictions and experimental data may explain why both TKE and bed shear stress may be seen as drivers of sediment transport processes in vegetated flows. These findings provide new insights into the physical links between near-bed flow variables and therefore contribute to the understanding of some of the complex biophysical processes present in vegetated flows

One of the key questions in fault mechanics is how do earthquakes begin ? This is central to our understanding of earthquakes, including the long controversial issue of their predictability. Earthquakes preceding large events are commonly referred to as foreshocks. They are often considered as precursory phenomena reflecting a nucleation process of the main rupture potentially driven by an underlying slow pre-slip. On the other hand, some studies suggest that foreshock sequences may only be explained by cascades of triggered events. In this work, we choose to test the cascading hypothesis against the foreshock seismicity observed during a previously reported slow slip event preceding the 2017 Mw=6.9 Valparaiso earthquake. We build a very complete 5 years long earthquake catalog of the sequence using refine detection and location algorithms. We test the detected seismicity against the Epidemic Type Aftershock Sequences model. We identify time windows with anomalously high seismic activity compared to what is expected by the typical earthquake interactions. We analyze statistically these anomalies over 5 years to understand if the Mw=6.9 foreshock sequence presents a specific anomalous activity. In addition, using a hierarchical clustering method, we identify earthquakes with similar waveforms to evidence any repeating ruptures. We analyze the time distribution of these clusters over 5 years to understand if unusual rates of repeating events emerge during foreshock time ranges. The conjoint analysis of seismicity rate anomalies and repeating events along with the results of previous pre-slip studies allows to accurately describe the nucleation process and evolution of the 2017 Valparaiso earthquake sequence.

Both proxy and model studies seeking to understand anthropogenic warming have revealed historical variations of sea surface temperature (SST) since the Industrial Revolution. However, because of discrepancies between observations and models for the late nineteenth century, the timing and degree of anthropogenic warming is still unclear. Here we reconstructed a 228-year record of SST and salinity using a coral core collected at Bicol, southern Luzon, Philippines, which is at the northern edge of the western Pacific warm pool. The SST record showed clear volcanic cooling after the eruptions of Tambora and Krakatau in 1815 and 1883, respectively, but the pattern of change differed between them. Although there were discrepancies in SST variations among modeled, observed, and proxy SST data for the late nineteenth to early twentieth century, SST data from the late twentieth century show globally coherent anthropogenic warming, especially after 1975.

Heatwaves cause excess mortality and physiological impacts on humans throughout the world, and climate change will intensify and increase the frequency of heat events. Many adaptation and mitigation studies use spatial distribution of highly vulnerable local populations to inform heat reduction and response plans. However, most available heat vulnerability studies focus on urban areas with high heat intensification by Urban Heat Islands (UHIs). Rural areas encompass different environmental and socioeconomic issues that require alternative analyses of vulnerability. We categorized Nebraska census tracts into four urbanization levels, then conducted factor analyses on each group and captured different patterns of socioeconomic vulnerabilities among resulted Heat Vulnerability Indices (HVIs). While disability is the major component of HVI in two urbanized classes, lower education and races other than white have higher contributions in HVI for the two rural classes. To account for environmental vulnerability of HVI, we considered different land type combinations for each urban class based on their percentage areas and their differences in heat intensifications. Our results demonstrate different combination of initial variables in heat vulnerability among urban classes of Nebraska and clustering of high and low heat vulnerable areas within the highest urbanized section. Less urbanized areas show no spatial clustering of HVI. More studies with separation on urbanization level of residence can give insights into different socioeconomic vulnerability patterns in rural and urban areas, while also identifying changes in environmental variables that better capture heat intensification in rural settings.

Plant and microbial nitrogen (N) dynamics and nitrogen availability regulate the photosynthetic capacity and capture, allocation, turnover of carbon (C) in terrestrial ecosystem. It is important to adequately represent plant N processes in land surface models. In this study, a plant C-N framework was developed by coupling a biophysical and dynamic land surface processes model, SSiB4/TRIFFID, with a soil organic matter cycling model, DayCent-SOM, to fully incorporate N regulations to investigate the impact of N on plant growth and C cycling. To incorporate the N limitation in the coupled system, the parameterization for dynamic C/N ratios for each plant functional type (PFT) was developed first. Then, after accounting for plant/soil N-cycling, when available N is less than demand, N would restrict the plant growth, reducing the net primary productivity (NPP), but also impact plant respiration rates and phenology. The improvements of the newly-developed model, the SSiB5/TRIFFID/DayCent-SOM, was preliminary verified at three flux tower sites with different PFTs. Furthermore, several offline global simulations were conducted from 1948 to 2007 to predict the long-term mean vegetation distribution and terrestrial C cycling, and the results are evaluated with satellite-derived observational data. The sensitivity of the terrestrial C cycle to N processes is also assessed. In general, new model can better reproduce observed emergent properties, including gross primary productivity (GPP), leaf area index (LAI), and respiration. The main improvements occur in tropical Africa and boreal regions, accompanied by a decrease of the bias in global GPP and LAI by 16.3% and 27.1%, respectively.

Palaeoclimate variability must be constrained to predict the nature and impacts of future climate change in the Eastern Mediterranean. Here, we present a high-resolution multiproxy dataset from Kocain Cave, the first of its kind from SW Turkey. Regional fluctuations in effective-moisture are recorded by variations in magnesium, strontium, phosphorous and carbon isotopes, with oxygen isotopes reacting to changes in precipitation amount and temperature. Important are: a double-peak of arid conditions at 1150 and 800 BCE, a wet period 330-460 CE followed by a rapid shift to dry conditions 460-830 CE, and a distinct dry/wet Medieval Climate Anomaly/Little Ice Age pattern. There are large discrepancies between Turkish records and the Kocain record, which shares more similarities with other Eastern Mediterranean coastal records. Heterogeneity of regional climate and palaeoclimate proxy records are emphasised.

Two cloud-resolving models (SCALE and VVM) take different pathways toward convective self-aggregation under a radiative-convective equilibrium condition, although the model setups are the same. The physical processes driving the development of self-aggregation in SCALE and VVM, respectively, correspond to the mechanisms for self-aggregation in cold and warm climate states discussed in a previous study. Analyses in the moisture space show that radiative cooling in the dry area mainly drives the aggregation in SCALE, while subsidence induced by the convection in the moist region dominates in VVM. The transition of the convective circulation from convective scale to mesoscale is found on the isentropic diagram in VVM, but this transition is unclear in SCALE. The convective clouds with larger sizes are rare in SCALE. The frequent occurrence of larger convective clouds efficiently drives self-aggregation from the moist area in VVM. These results provide a new insight to understand convective self-aggregation among models.

Lots of works aim to reveal the driving factors of COVID-19 pandemic trajectory yet ignore the confidence of utilized trajectory data, making consequent results suspicious. Hereby, we proposed a pandemic metric with confidence (PMC) model in the hypothesis of Bernoulli Distribution of nine trajectories reported from 113 countries. Results exhibit the average confidence of trajectories across the global not in excess of 12.1% with the error threshold configuration of 1E-5. In contrast, the 95% high confidence setting also failed to predict the trajectory containing the acceptable error not beyond 1E-3. Thus, a proposed trade-off strategy between two contradictory expections (>50% confidence, <1E-3 error) supports 61% of investigated countries to predict the varying trajectory with confidence beyond 50%. Moreover, PMC model recommend the remanent 39% countries to extend the proportion of populaces in COVID-19 detecting-pool to a suggested-value (>1% of populations), ensuing the average confidence up to 70%.

Thermal and dynamic perturbations at MLT heights during the strong stratospheric polar vortex as measured by the meteor radar at 67°N and the Aura satellite are presented. Mesospheric winds are dominated by vertical shears in the zonal component and the intense alternating north- and southward flows with a period of half a month. A temperature reduction at 90 km height is observed in the mid-winter and likely associated with a localized temperature increase in the upper stratosphere. Throughout January, a long-lived ~20K inversion layer persists just below the mesopause. These features are likely indicative of considerable stratification in the MLT as well as a decoupling of the middle and upper atmosphere.

A one-year’s worth of global (except poleward of 65 º N/S) marine shallow single-layer cloud-top radiative cooling (CTRC) is derived from a radiative transfer model with inputs from the satellite cloud retrievals and reanalysis sounding. The mean cloud-top radiative flux divergence is 61 Wm-2, decomposed into the longwave and shortwave components of 73 and -11 W m-2, respectively. The CTRC is largely a reflection of free-atmospheric specific humidity distribution: a dry atmosphere enhances CTRC by reducing downward thermal radiation. Consequently, the cooling minimizes in the “wet” tropics and maximizes in the “dry” eastern subtropics. Poleward of 30 º N/S, the CTRC decreases slightly due to the colder clouds that emit less effectively. The CTRC exhibits distinctive seasonal cycles with stronger cooling in the winter and has amplitudes of order 10~20 Wm-2 in stratocumulus-rich regions. The datasets were used to train a machine-learning model that substantially speeds up the retrieval.

The early to middle Holocene Humid Period (HHP) was the last time when precession-forced intensification of summer monsoons and northward migration of associated rainfalls led to a greening of today’s arid Saharo-Arabian desert belt. While this wet phase is well confined in N Africa and the S Arabian Peninsula, robust evidence from N Arabia is lacking. Here, we fill this gap with unprecedented annually to sub-decadally resolved proxy data from Tayma, the only known varved lake sediments in N Arabia. Based on stable isotopes, micro-facies analyses and precise varve and radiocarbon dating we distinguish five phases of lake development and prove that the wet phase in N Arabia from 8,800–7,900 years BP is considerably shorter than the commonly defined HHP (11,000–5,500 years BP). Moreover, we find a two century-long peak humidity at Tayma at times when a centennial-scale dry anomaly around 8,200 years BP interrupted the HHP in adjacent regions. This regional disparity is explained by an increased frequency of tropical plumes reaching N Arabia and compensating for the weakened monsoons and/or winter rains. This peak humidity possibly favoured Neolithic migrations into N Arabia indicating very dynamic human response to environmental changes.

During the Arctic summer season, snow atop the sea ice melts and pools into low-lying areas on the surface. These melt ponds reduce surface albedo and increase solar absorption in the Arctic Ocean. Throughout the summer, melt ponds grow, drain, and connect, through a complex drainage system. Current melt pond schemes in sea ice models, such as the level-ice scheme in the Los Alamos Sea Ice Model (CICE), rely on a linear relationship between pond depth and fraction to predict the evolution of pond growth as the snow and sea ice melt. Although the inclusion of melt ponds in models has been shown to improve forecasts of end-of-summer sea ice extent, observations of melt pond depth and fraction guiding these models are from SHEBA, a spatially-limited field campaign which occurred over 20 years ago. Until recently, melt ponds characteristics have been difficult to resolve from spaceborne platforms due to their small size (10s - 100s m in diameter), and indistinguishable radiometric similarity to open water. Here we show that new, high-resolution laser altimetry measurements from ICESat-2 (IS2), combined with coincident high-resolution satellite imagery, provides a three-dimensional view of the melting sea ice cover. IS2, launched in September 2018, has now observed two summer melt seasons in the Arctic. IS2 operates at 532 nm, a wavelength that penetrates low turbidity water, and can therefore be used to capture the bathymetry of shallow water features. Building on previous work, we demonstrate IS2’s ability to detect and measure melt ponds on multiyear sea ice. We validate the existence of melt ponds with high resolution (10 m) visible imagery from the Sentinel-2 (S2) MultiSpectral Instrument. We apply the “density dimension algorithm – bifurcate” (DDA-bifurcate), an auto-adaptive algorithm utilizing data aggregation with the ability to track two surfaces, as well as a second algorithm that tracks melt pond surface and bottom, to derive melt pond depth for dozens of melt ponds in 2019 and 2020. Applying a sea ice surface classification algorithm to S2 imagery, we are able to determine melt pond fraction. We compare our findings of coincident melt pond fraction and depth with the melt pond parameterization used in the level-ice scheme in CICE. We discuss our results in the context of the existing literature on pond depth and volume.

A detailed 3-D tomographic model of the whole mantle beneath the circum-Arctic region is obtained by applying an updated global tomography method to a large amount of P-wave arrival time data. Our model clearly shows the subducted Izanagi and Farallon slabs penetrating into the lower mantle beneath Eurasia and North America, respectively. In the region from Canada to Greenland, a giant stagnant slab lying below the 660-km discontinuity is revealed. Because this slab has a texture that seems to be due to subducted oceanic ridges, the slab might be composed of the Izanagi, Farallon, Kula and Vancouver slabs that had subducted during ~80−20 Ma. During that period, a complex rift system represented by division between Canada and Greenland was developed. The oceanic ridge subduction and hot upwelling in the big mantle wedge above the stagnant slab caused a tensional stress field, which might have induced these complex tectonic events.