bluuebunny/crossref_metadata_2025 huggingface dataset:
Diurnal cycles of one season with precipitation extremes in southeastern South America: comparison between models, resolution and observational datasets 
Authors: Porfírio da Rocha Rosmeri , Llopart Marta , Bettolli Maria Laura , Solman Silvina , Fernández Jesús , Lavin-Gullon Alvaro , Feijoó Martín , Reboita Michelle
Published: March 2022

Over the southeast of South America, the extended warm season from October 2009 to March 2010 registered a great number of extreme precipitation events. In this study, we evaluated the ability of the regional climate models and observational datasets to simulate observed features of the precipitation mean diurnal cycle observed during this period. WRF (two versions – 3.8.1 and 3.9.1) and RegCM4.7.1 simulations, with a horizontal grid spacing of 20 km (which uses both convective and large scale precipitation schemes) and 4 km (the precipitation is solved only by the microphysics scheme - convective permitting - CP), were analysed. We also considered six observational gridded precipitation datasets (MSWEP, CMORPH, PERSIAN, TRMM, ERA5 and GSMAP). These data and simulations are compared against 51 local observations of the precipitation every 3 hours. For the 51 stations, the observed diurnal cycle presents a great variety of patterns (time of maximum, minimum, amplitude, and double peaks during the day), but it is noted a slight predominance of more intense peaks at 06, 09 and 12 local time, characterizing the morning precipitation in the region. Comparisons of the six observational gridded datasets with the in situ data indicate a small outperformance of CMORPH and ERA5 to reproduce the main features of the observed diurnal cycle. At 20 km resolution, the simulations are not able to capture the diversity of diurnal cycles shown by in situ data. CP simulations capture better the great variety of the precipitation diurnal cycles shown by in situ observations. Specifically, for WRF-CP there is a shift in the afternoon peak at 15 LT to the morning-early afternoon (from 6 to 12 LT), while in RegCM4-CP there is a decrease in the number of simulated diurnal cycles peaking at dawn and a displacement of some peaks from dawn (03 LT) to morning (09 LT). The increase in the diversity and shift to morning-early afternoon peaks (6 to 12 LT) are the features showing the greatest agreement between CP simulations and in situ observations of the diurnal cycle of precipitation.
Can Radar Quantitative Precipitation Estimates Reproduce Extreme Precipitation Statistics in Central Arizona?
Authors: Srivastava Nehal Ansh , Mascaro Giuseppe
Published: March 2022

In this study, we assess the ability of 4-km, 1-h Quantitative Precipitation Estimates (QPEs) from the Stage IV analysis of the NEXRAD radar network to reproduce the statistics of extreme precipitation (P) in central Arizona, USA. As reference, we use 19 years of records from a dense network of 257 rain gages. For each radar pixel and gage record, we fit the generalized extreme value (GEV) distribution to the series of annual maximum P at durations, τ, from 1 to 24 hours. We found that the GEV scale and shape parameters estimated from the radar QPEs are slightly negatively biased when compared to estimates from gage records at τ = 1 h; this bias tends to 0 for τ ≥ 6 h. As a result, the radar GEV quantiles for return period, TR, from 2 to 50 years exhibit negative bias at τ = 1 h (median between -23% and -12% for different TR’s), but the bias is gradually reduced as τ increases (average of +4% for τ = 24 h). The relative root-mean-square-error (RRMSE) ranges from 17% to 44% across all τ’s and TR’s and these values are similar to those computed between gages and operational design storms from NOAA Atlas 14. Lastly, we found that radar QPEs reproduce fairly well observed scaling relationships between the GEV location and scale parameters and P duration, τ. Results of our work provide confidence in the utility of Stage IV QPEs to characterize the spatiotemporal statistical properties of extreme P and, in turn, to improve the generation of design storm values.
Deep ocean steady-state transport and decadal variability inferred from 1980-2020 CFCs and SF6 observations
Authors: Cimoli Laura , Purkey Sarah , Gebbie Jake , Smethie William
Published: March 2022

What are the time-mean pathways and the decadal variability of the deep ocean circulation? To answer this question, we conduct a global tracer analysis with a newly developed approach, the “Time-Correction” method. This novel method leverages the information of four decades of anthropogenic transient tracer observations (1980-2020) to reconstruct their propagation in the global ocean. The Time-Correction method solves a modified least-squares problem that accounts for the uncertainty in the observations, propagates this uncertainty in our solution, and uses prior information about the system in the final solution. The method takes into account the statistical information used in the Maximum Entropy Method but is designed to be more computationally efficient.

We apply the Time-Correction method to chlorofluorocarbons (CFC-11 and CFC-12) and sulfur hexafluoride (SF6) observations to reconstruct the time evolution of their concentrations in the deep ocean. Their propagation is reconstructed at annual resolution and permits CFC snapshots from multiple decades to be put into a common context. The reconstructed tracer concentrations capture the pathways of AABW and NADW, highlighting (i) the southward flow of the different NADW components (upper, middle and lower NADW) and their equatorial recirculation in the Atlantic Ocean, and (ii) the spreading of CFC-rich AABW in the North Pacific Ocean through the Samoan Passage, its bottom-driven northward circulation in the East Indian Ocean, and its northward flow in the West Atlantic Ocean and recirculation around the Equator. These reconstructed tracer concentrations reflect the tracer distribution for time-mean ocean transport and can be used to investigate the non-steady ocean circulation decadal variability. In locations with multiple occupations of tracer data where no steady-state solution can be found, we conclude that the circulation has changed and show regional patterns of increased and decreased ventilation over the last four decades. Additional research is underway to investigate NADW formation rate variability over the 1980-2020 period at decadal and inter-annual resolution depending on the number of available occupations.
Announcing Phase 4 of PAGES 2k: Hydroclimate of the Common Era
Authors: Henley Benjamin , Eggleston Sarah , Kaushal Nikita , Atwood Alyssa , Bothe Oliver , Falster Georgy , Jones Matthew , Jonkers Lukas , Konecky Bronwen , Linderholm Hans , Martrat Belen , McGregor Helen , Orsi Anais , Phipps Steven , Sayani Hussein
Published: March 2022

<img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.d17138223ed164871591461/sdaolpUECMynit/22UGE&app=m&a=0&c=811fe277410d9ff3699ef0224ece3bef&ct=x&pn=gnp.elif&d=1" alt="" width="353" height="140">

Understanding the climate of the past two millennia (2k) remains vital for developing our wider comprehension of the climate system, including the nature and scale of recent and future anthropogenic change. Phase 4 of the PAGES 2k network will build on previous phases and take us to a new level of understanding and science-policy integration.

During previous phases, PAGES 2k members compiled global networks of proxy measurements, extending records beyond the instrumental period by more than an order of magnitude, reconstructing past climate and developing new knowledge of past variability and processes. Through data-model integration with state-of-the-art Earth systems models, proxy system modelling and data assimilation, we took key steps towards a more comprehensive understanding of climate dynamics.

Phase 4 will take us even further, challenging our community to turn its focus primarily towards the hydroclimate of the Common Era: performing new reconstructions and improving the interoperability, extent and scope of our data and model products. In doing so, we also seek to facilitate the translation of our science into evidence-based policy outcomes. Our overarching aim is to reconstruct hydroclimate variability over the Common Era from local to global spatial scales, at sub-annual to multi-centennial time scales. We propose to achieve this through new community-led data curation efforts and the development of new data-driven tools and practices to maximise the interoperability of convenient, efficient and widespread model/data products. We will aim for a process-level understanding of past hydroclimate events and variability by evaluating and constraining Earth system models and through data assimilation.

Our coordination team places a strong emphasis on respect and inclusion, aiming to foster a diverse and equitable community. Through a ‘hub and spoke’ structure, our team will provide a facilitation, coordination and support role (the hub) for Pages 2k working groups (the spokes). We are actively seeking participation of those engaging in climate policy and climate services. Welcome to Phase 4!  We warmly invite your collaborations and contributions! 
A machine learning-based ensemble model for estimation of seawater quality parameters in coastal area
Authors: Zhu Xiaotong , Huang Jinhui Jeanne , Guo Hongwei , Tian Shang , Zhang Zijie
Published: March 2022

The precise estimation of seawater quality parameters is crucial for decision-makers to manage coastal water resources. Although various machine learning (ML)-based algorithms have been developed for seawater quality retrieval using remote sensing technology, the performance of these models in the application of specific regions remains significant uncertainty due to the different properties of coastal waters. Moreover, the prediction results of these ML models are unexplainable. To address these problems, an ML-based ensemble model was developed in this study. The model was applied to estimate chlorophyll-a (Chla), turbidity, and dissolved oxygen (DO) based on Sentinel-2 satellite imagery in Shenzhen Bay, China. The optimal input features for each seawater quality parameter were selected from the nine simulation scenarios which generated from eight spectral bands and six spectral indices. A local explanation method called SHapley Additive exPlanations (SHAP) was introduced to quantify the contributions of various features to the predictions of the seawater quality parameters. The results suggested that the ensemble model with feature selection enhanced the performance for three types of seawater quality parameters estimations (The errors were 1.7%, 1.5%, and 0.02% for Chla, turbidity, and DO, respectively). Furthermore, the reliability of the model performance was further verified for mapping the spatial distributions of water quality parameters during the model validation period. The spatial-temporal patterns of seawater quality parameters revealed that the distributions of seawater quality were mainly influenced by estuary input. Correlation analysis demonstrated that air temperature (Temp) and average air pressure (AAP) exhibited the closest relationship with Chla. The DO was most relevant with Temp, and turbidity was not sensitive to Temp, average wind speed (AWS), and AAP. This study enhanced the prediction capability of seawater quality parameters and provided a scientific coastal waters management approach for decision-makers.
Abundance and characteristics of microplastics in shellfish from Jiaozhou Bay, China
Authors: Zhang Kangning
Published: March 2022

As an emerging pollutant, the presence of microplastics in marine organisms has been concerned increasingly. Shellfish, which are both economically and ecologically important, are of particular concern. In this study, we investigated the microplastic pollution in wild and farmed oysters ( Crassostrea gigas ) and clams ( Ruditapes philippinarum ) in the Jiaozhou Bay, China, for the first time. We found the microplastic pollution in shellfish in Jiaozhou Bay was at a moderate level. The abundance of microplastics in shellfish ranged from 0.16 to 12.09 items/g (wet weight, ww) or 1 to 9 items/ind. The average abundance of the ingested microplastics was 1.21 items/g (or 2.17 items/ind.) in all shellfish, 1.51 items/g (or 2.00 items/ ind.) in clams and 0.92 items/g (or 2.34 items/ind.) in oysters. The abundance of microplastics in clams was significantly higher than that in oysters. Most microplastics (92.97%) were fibers, followed by fragments. The predominant color of the microplastics was black (42.97%), followed by blue, transparent, and red. Cellophane and polyethylene terephthalate (PET) dominated the microplastic composition. According to shellfish consumption, it can be inferred that the average microplastic consumption through Chinese diet is 1.27×103 items per capita per year.
Formation of Jupiter's envelope from supersolar gas in the protoplanetary disk
Authors: Aguichine Artyom , Mousis Olivier , Lunine Jonathan
Published: March 2022

The formation mechanism of Jupiter is still uncertain, as multiple volatile accretion scenarios can reproduce its metallicity [1-4]. The Galileo mission allowed in situ measurements of the abundances of several elements (Ar, Kr, Xe, C, N, S and P), which exhibit a uniform enrichment of 2 to 5 times the protosolar abundance, and a subsolar abundance has been measured for O. Recent measurements for N and O by the Juno mission confirmed the supersolar abundance of N, but indicated that the abundance of O may also be supersolar [5]. Elemental abundances measured in the Jupiter's atmosphere are key ingredients to trace the origin of various species.
Here, we investigate the possible timescale and location of Jupiter's formation using measurements of molecular and elemental abundances in its envelope. To do so, we use a 1D accretion disk model to compute the properties of the protosolar nebula (PSN) that includes radial transport of trace species, present in the form of refractory dust, a mixture of ices and their vapors, to compute the composition of the PSN [6]. We focus on the radial transport of volatile species by advection-diffusion combined with the effect of icelines, computed as sublimation/condensation rates. Initialy, the disk is uniformly filled with H2O, PH3, CO, CO2, CH4, CH3OH, NH3, N2, H2S, Ar, Kr and Xe [6,7], corresponding to the main bearers of C, N, O, P, S, Ar, Kr and Xe.
As the PSN evolves, solid particles drift inward due to gas drag. Volatile species are thus efficiently transported to their respective icelines, where they sublimate. This results in supersolar abundances of volatile elements in the inner part of the PSN. We find that the composition of Jupiter’s envelope can be achieved by accretion of enriched gas only, or a mixture of gas and solids, depending on the viscosity of the PSN. In both cases, the composition of the PSN matches the one measured in Jupiter’s envelope in timescale that are compatible with a formation by core accretion or gravitational collapse.

[1] Gautier, D., Hersant, F., Mousis, O., et al. 2001, ApJL, 550, L227.
[2] Mousis, O., Ronnet, T., and Lunine, J. I. 2019, ApJ, 875, 9.
[3] Öberg, K. I. and Wordsworth, R. 2019, AJ, 158, 194.
[4] Miguel, Y., Cridland, A., Ormel, C. W., et al. 2020, MNRAS, 491, 1998.
[5] Li, C., Ingersoll, A., Bolton, S., et al. 2020, Nature Astronomy, 4, 609.
[6] Aguichine, A., Mousis, O., Devouard, B., and Ronnet, T. 2020, ApJ, 901, 97.
[7] Lodders, K., Palme, H., & Gail, H.-P. 2009, Landolt Börnstein, 4B, 712
Effect of Upper-Level High Pressure in Eastern Europe and Convection Activities in the Western North Pacific Subtropical Region on the Prediction of Heatwaves over the Korean Peninsula
Authors: Wie Jieun , Moon Byung-Kwon
Published: March 2022

Heatwaves are meteorological disasters that can damage human health and reduce agricultural production when extremely high temperatures are involved. A heatwave over the Korean Peninsula in 2018 broke the temperature and duration records kept since observations began. This event caused significant socio-economic damage. High pressure in the upper atmosphere over Eastern Europe and strong convection over the western North Pacific subtropical region are major fluctuations known to strengthen heatwaves over the Korean Peninsula. This study analyzed how these factors affected predictions of the 2018 heatwave over the Korean Peninsula using the sub-seasonal to seasonal (S2S) prediction model. Of the 11 models used in the S2S prediction project, 6 were selected: CMA, ECCC, ECMWF, KMA, NCEP, and UKMO. These models underestimated the daily surface temperature from July to August 2018 compared with observations, and the prediction errors gradually increased as lead-time increased. The model that simulated significant upper-level high pressure events in Eastern Europe and convection activities in the western North Pacific subtropical region predicted surface temperatures for the Korean Peninsula that were similar to the observed values. The increase in air pressure in the upper atmosphere over Eastern Europe is related to the recent expansion of areas affected by heatwaves in Europe. Even in the S2S models, the model that accurately predicted the characteristics of the heatwave showed excellent prediction performance for the Korean Peninsula. The increase in convection activities in the western North Pacific subtropical region increased when the amplitude of phases 4–6 of the Madden–Julian Oscillation (MJO) was large and they included many days. If the S2S model simulates the characteristics of the MJO accurately, the surface temperature prediction performance for the Korean Peninsula will increase. Therefore, it is very important for the S2S model to predict these two factors accurately, particularly when predicting heatwaves similar to that which occurred over the Korean Peninsula in 2018.

This work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMI2020-01212.
Global wavelength survey of Martian bedforms: methods and preliminary results
Authors: Vaz David A. , Silvestro Simone , Chojnacki Matthew , Silva David C. A.
Published: March 2022

The mechanism/s responsible for sediment entrainment by wind and bedform migration on Mars are a matter of debate [1]. Martian large ripples (LRs) migrate under present-day low pressure conditions and have been interpreted has fluid/wind drag ripples [2] or as bedforms formed by aeolian saltation [3]. An important constraint to this debate is the relation between bedform wavelength and atmospheric density (as a function of elevation). This dataset was later complemented by the measurement of bedform wavelengths in other 11 areas [2]. Lapotre el al. [2] proposed that the fluid drag theory fits the measured wavelength vs. atmospheric density relation, a view not shared by Lorenz [1, Fig. 2].

To try to address this divergence, we will present a new method that allows the automatic mapping and morphometric characterization of bedforms (LRs to TARs) using HiRISE imagery. It consists in a windowed multiscale spectral approach, followed by a supervised classification stage using neural networks. This method can accurately identify the bedforms (overall accuracy of 94%) and provide precise wavelength measurements within a ±12% confidence interval. The surveyed bedforms have crests spaced between 1 and 100 m, and include large ripples, megaripples and TARs.

We will review and compare previous datasets and studies with our measurements. The main objective is to re-evaluate how well the wind drag hypothesis can predict bedforms’ spacing on Mars, and for this purpose we employ an improved measurement approach that allows the mapping of entire dune fields. Furthermore, we significantly increased the number of mapped areas and extended the range of sampled elevations.

Preliminary results of this ongoing effort will be presented at the conference.

 

[1] Lorenz, R.D. (2020). Martian Ripples Making a Splash. J. Geophys. Res. Planets 125, 12–15.

[2] Lapotre, M.G.A., Ewing, R.C., Lamb, M.P., Fischer, W.W., Grotzinger, J.P., Rubin, D.M., Lewis, K.W., Ballard, M.J., Day, M., Gupta, S., et al. (2016). Large wind ripples on Mars: A record of atmospheric evolution. Science (80). 353, 55–58.

[3] Sullivan, R., Kok, J.F., Katra, I., and Yizhaq, H. (2020). A Broad Continuum of Aeolian Impact Ripple Morphologies on Mars is Enabled by Low Wind Dynamic Pressures. J. Geophys. Res. Planets 125, 1–39.

[4] Lorenz, R.D., Bridges, N.T., Rosenthal, A.A., and Donkor, E. (2014). Elevation dependence of bedform wavelength on Tharsis Montes, Mars: Atmospheric density as a controlling parameter. Icarus 230, 77–80.
Nitrification Inhibitor DMPP Reduces Nitrous Oxide Emissions from the Biogas Slurry Amended Soil 
Authors: Lei Jilin , Yin Junhui , Liu Rui , Chen Qing
Published: March 2022

Biogas slurry (BS) is increasingly used in agricultural systems because of providing available nutrients for plant growth and improving soil quality. However, the consequent emissions of greenhouse gas, nitrous oxide (N2O), are considered a severe threat to the atmosphere quality. Currently, 3,4-dimethylpyrazole-phosphate (DMPP) is a widely used nitrification inhibitor to reduce N2O emissions from agricultural soils and increase nitrogen use efficiency (NUE). In this study, a 108-h soil incubation experiment through a robotized incubation system was conducted to examine the inhibitory effect of DMPP on N2O emissions from a BS amended vegetable soil. There were three treatments in the incubation experiment: CK (deionized water), BS, and BS+DMPP, in which BS was applied at a rate of 1.25 m3 ha-1 (714 mg N kg-1 dry soil) and DMPP was in the form of a solution with the addictive content was 1% of applied NH4+-N. The results showed that the highest soil pH was 8.30 in BS+DMPP treatment, followed by 7.92 and 7.61 in BS and CK separately. BS addition significantly increased soil N2O, CO2 emissions and TOC concentration compared with CK. Combined application of BS and DMPP dramatically decreased N2O emissions from 2.59 nmol g-1 in BS to 0.14 nmol g-1 in BS+DMPP, but significantly increased soil NH4+ concentration from 764 mg kg-1 in BS to 828 mg kg-1 in BS+DMPP. To conclude, BS application could stimulate N2O emission from the soil, but DMPP was an efficient way to mitigate BS-induced N2O emissions from the greenhouse vegetable soil. 
An acoustic model for monitoring bedload transport with microphones array
Authors: Chen Zheng , He Siming , Nicollier Tobias , Ammann Lorenz , Badoux Alexandre , Rickenmann Dieter
Published: March 2022

Accurate measurements of bedload flux in mountain rivers remain an important issue in hydraulic engineering. Diverse acoustic-based monitoring devices have been utilized to record continuous vibration signals triggered by bedload particle impacts, aiming to translate bedload information such as transport rates and grain size distributions from the generated signals. However, the spatial variability of bedload impacts on the river bed (or on an impact plate) contributes to uncertainty in the calibration relationship between the recorded signal and bedload flux.

The present study develops an acoustic model based on microphone data to determine the characteristics of the air shock waves induced by the bedload particle impacts on the bed. A phased microphone array (PMA) system is established on the plane underside of an impact plate flush with the river bed, which includes a number of mini microphone elements set apart from each other at a specific spacing distance. The model allows for a calculation of the cross-power matrix of the air vibrations recorded by each microphone of the array. The acoustic vibrations recorded on the PMA plane are subsequently reconstructed and transformed to an acoustic image of the sound source on a scanning plane of the plate surface, considering different air propagation models corresponding to monopole, multipole and moving sources. As a result, the locations of the bedload particle impacts can be detected, connecting to the central coordinates of the reconstructed sound source. The signal amplitude extracted from the sound intensity in the reconstructed acoustic image potentially provides a better way for classifying bedload particle size than just utilizing the raw data recorded by one of the microphone elements.

The findings of this study contribute to the measurement and monitoring of the bedload transport with an acoustic system, illustrating a promising way to identify bedload impact locations, which could be helpful in grain size classification during the transport process.
Stabilization of Unsteady Nonlinear Waves by Phase-Space Manipulation
Authors: Gomel Alexis , Chabchoub Amin , Brunetti Maura , Trillo Stefano , Kasparian Jérôme , Armaroli Andrea
Published: March 2022

We consider the stabilization of modulationally unstable wave packets by designing and abruptly changing the floor topography within the framework of the nonlinear Schrödinger equation in variable water depth [1]. This is achieved as a result of abrupt expansion of a homoclinic Akhmediev breather orbit and its into an elliptic fixed point [2,3].

We experimentally demonstrate this phenomenon process in a water wave tank and provide a rigorous theoretical description of this process. The low-dimensional theoretical predictions and measurements show that the relative phase among the side-bands locks to π and their relative amplitudes oscillates around a finite value. Apart from a 10% conversion to higher-order side-bands, this implies that the breathing stage of modulation instability (MI) is indeed frozen. This phenomenon has been also verified in an optical fiber experiment [4].

We confirm that this complex wave dynamics is robust and such control of MI processes is feasible in a realistic experimental system. Our results highlight the influence of topography and how waveguide properties can influence and manipulate the lifetime of nonlinear and extreme waves.

 

References

[1] Djordjevic, V. and Redekopp, L., On the development of packets of surface gravity waves moving over an uneven bottom, ZAMP 29, 950-962 (1978).

[2] Armaroli, A. et al., Stabilization of uni-directional water wave trains over an uneven bottom. 2021, Nonlinear Dynamics 101 , 1131-1145 (2021).

[3] Gomel, A. et al., Stabilization of Unsteady Nonlinear Waves by Phase-Space Manipulation, Physical Review Letters 126, 174501 (2021).

[4] Bendahmane, A. et al., Experimental dynamics of Akhmediev breathers in a dispersion varying optical fiber, Optics Letters 39, 4490-4493 (2014).

 
A multi-scale space-time hybrid weather generator
Authors: Pidoto Ross , Haberlandt Uwe
Published: March 2022

Long term time series of meteorologic variables are generally lacking and is especially the case at sub-daily temporal resolutions. These time series are needed for applications such as hydrological modelling of catchments and derived flood frequency analyses. Stochastic weather generators are one such solution and are able to generate long synthetic time series of arbitrary length.

This study explores the coupling of an hourly space-time rainfall model with a non-parametric K-NN resampling approach for non-rainfall climate variables such as temperature, humidity and global radiation. A daily gridded observational climate dataset is used for the resampling. As a last step, a simple disaggregation technique is applied to the resampled non-rainfall climate variables to achieve an hourly timestep.

To study the effectiveness and performance of the hybrid weather generator, synthetic time series for 400 mesoscale catchments within Germany consisting of 700 rainfall stations were generated and compared to observations. Results show that the hybrid weather generator adequately reproduces observed statistics for rainfall and the non-rainfall climate variables in addition to maintaining cross correlations between the climate variables.
Asymmetric magnetic reconnection between two coalescing flux ropes as squeezed by convergent flows
Authors: Luo Qiaowen , He Jiansen , Cui Jun
Published: March 2022

We identify two coalescing flux ropes as squeezed by convergent ion flows near the magnetopause from the MMS observations. According to the electron distributions, we find that one flux rope is closer to the magnetosphere, while the other is closer to the magnetosheath. A current sheet with magnetic field reversal is found to sit at the interface between the two colliding flux ropes, and have magnetic reconnection occurring in the ion diffusion region (IDR). Due to the density asymmetry of flux ropes, the embedded magnetic reconnection event with a significant guide field component shows a large asymmetry in energy conversion across the reconnection site. On the side where the flux rope is closer to the magnetosphere with low density, we find that electrons gained energy from electromagnetic fields resulting in a parallel heating effect. In contrast, ions are found to obtain the energy from electromagnetic fields on the other side of the reconnection current sheet, where the flux rope is near the magnetosheath with high density.
Oceanic impacts on 50–80‑day intraseasonal oscillation in the eastern tropical Indian Ocean
Authors: Liang Yun , Du Yan
Published: March 2022

In this study, daily outgoing longwave radiation (OLR) product is used to detect the atmospheric intraseasonal oscillation 
(ISO) in the eastern tropical Indian Ocean (TIO). A 50–80-day ISO is identifed south of the equator, peaking in boreal winter 
and propagating eastward. The mechanisms underneath are investigated using observational data and reanalysis products. 
The results suggest that the 50–80-day atmospheric ISO is enhanced by ocean dynamic processes during December–January. 
Monsoon transition in October–November causes large wind variability along the equator. Equatorial sea surface height/
thermocline anomalies appear of Sumatra due to the accumulative efects of the wind variability, leading the atmospheric 
50–80-day ISO by ~5–6 weeks. The wind-driven ocean equatorial dynamics are refected from the Sumatra coast as downwelling oceanic Rossby waves, which deepen the thermocline and contribute to the SST warming in the southeastern TIO, 
afecting local atmospheric conditions. It ofers insights into the role of ocean dynamics in the intensifcation of 50–80-day 
atmospheric ISOs over the eastern TIO and explains the seasonal peak of the eastward-propagating ISO during boreal winter. 
These results have implications for intraseasonal predictability.
Quantification of the ecosystem services of collecting soil to form ridges with no-tillage in the purple soil region of China: A meta-analysis
Authors: Jia Lizhi
Published: March 2022

Collecting soil to form ridges with no-tillage (CSNT) is an important conservation tillage method in the purple soil region of China. Although the ecosystem services it can provide in agroecosystems have been proven. While there is no systematic quantitative research on the effect of CSNT on ecosystem services. We collected 611 data entries from previous publications to quantitatively evaluate the effect of CSNT on runoff and sediment loss, soil nutrients concentration, soil bulk density, soil moisture content, aboveground biomass and belowground biomass. Compared to conventional tillage, CSNT reduced runoff and sediment loss by 49% and 73%, respectively. This is mainly due to the blocking effect of the ridge-and-furrow structure. As for soil nutrients concentration, the concentrations of soil organic carbon, total nitrogen, available nitrogen, available phosphorus and available potassium increased by 15%, 14%, 30%, 58% and 17%, respectively under CSNT compared to conventional tillage. While no significant differences were found for total phosphorus and total potassium between CSNT and conventional tillage. Soil bulk density decreased by 11% on the ridges under CSNT compared to conventional tillage, while no significant different was found in the furrows. On the ridges, CSNT did not have a significant effect on soil moisture content, while it led to an increase of 27.6% in soil moisture content in the furrows. CSNT would also increase aboveground and belowground biomass by 23% and 63%, respectively. In general, the implementation of CSNT in purple soil region of China could significantly enhance the ecosystem services in agroecosystems.
Plutonium isotopes as a good tracer for environmental studies
Authors: Xu Yihong
Published: March 2022

    It is well-known that 137Cs has been widely applied as a powerful tracer for soil erosion and sediment dating studies since the 1960s. However, due to its relatively short half-life (30.2 year), the concentrations of global fallout 137Cs in the environment have decreased by a factor of more than 2 comparing to the levels in the 1960s due to its radioactive decay, and this declined trend will continue. This makes the applications of 137Cs for investigations of soil erosion, transportation and sedimentation less sensitive at present and will become difficult in the future. 239Pu and 240Pu, because of the long half-lives (T1/2=24100 year for 239Pu and T1/2=6561 year for 240Pu), their dominating source of nuclear weapons testing fallout worldwide, as well as their high retention and low mobility in soil, they were suggested as an ideal substitute of 137Cs for environmental tracing studies. In recent years, with the rapid development of sensitive measurement techniques using mass spectrometry especially the inductively coupled plasma mass spectrometry (ICP-MS), the application of Pu isotopes in environmental studies becomes more attractive and competitive. Here we presented some preliminary studies regarding Pu isotopes as tracers for soil erosion studies and lake sediment dating in China. Our results indicated that Pu isotopes are powerful and promising tracers in future environmental studies.
Decoupling terrestrial and atmospheric water stress on ecosystem productivity during flash droughts
Authors: Xi Xiazhen , Yuan Xing
Published: March 2022

In the context of climate warming, frequent outbreaks of flash droughts are causing serious damage to ecosystems, so there is an urgent need to understand the water stress on ecosystems during flash droughts. High vapor pressure deficit (VPD) and low soil moisture (SM) are regarded as atmospheric and soil water stress on the ecosystem, but their stress mechanisms are different. Their independent influences are difficult to separate during flash droughts that develop fast with a strong land-atmospheric coupling. Therefore, to understand the response mechanism of vegetation gross primary productivity (GPP) to flash droughts, this study uses statistical analysis to decouple the effects of atmospheric and terrestrial water stress on GPP at the site scale and regional scale, respectively. At the site scale, we use the FLUXNET2015 Dataset to decouple the stress of SM and VPD on the GPP during flash droughts, and find that low SM dominants water stress for 55% of the stations, and high VPD dominants water stress for 10%. We further investigate the differences of GPP response to moisture deficit for different ecosystems during different stages of flash droughts. The results show that non-forest ecosystems respond to water stress during the onset stage of flash droughts, while more forests respond during the drought recovery stage. Specifically, for the days that are accompanied by high temperature and intense solar radiation during flash droughts , the water stress dominated by high VPD increase to 41% of the stations. For the regional scale, we use remote sensing data to decouple the effects of water stress over China. Our results show that water stress during flash droughts is dominated by soil moisture deficit over most regions of China, but VPD stress is stronger over northern China than that over southern China.
Effects of vegetation root on hydro-mechanical properties of debris flow source
Authors: Qin Mingyue , Guo Jian , Jiang Yao , Zhang Guotao
Published: March 2022

    In recent years, shallow landslides and debris flow usually have occurred successively in areas with good vegetation coverage, causing casualties and economic losses. After the occurrence of shallow landslides, the failure mass accumulated in the channel, providing the material source for debris flow. And the quantity of the failure mass determines the scale of debris flow. Therefore, it is an important basis for debris flow disaster management in vegetated mountainous areas to deeply understand the influence of vegetation on the hydro-mechanical properties of debris flow sources. This study takes the shallow landslides that occurred in Mengdong village, China in 2018 as the objects, analysis the changes in soil hydro-mechanical properties influenced by tree roots through field investigation and laboratory tests, and discusses the failure mechanism of the shallow landslides. The field investigation results indicate that the vertical root distribution can be expressed as an exponentially decayed polynomial model, that is, with the increase of depth, the distribution of tree roots increased first and then decreased. Furthermore, the maximum root area density is 0.266 mm2/cm2 at 20-40cm depth, and 80% of the roots are distributed in the soil above the slip surface. Laboratory test results show that the root-soil density above the slip surface was lower which was 1.04 g cm-3, and the maximum porosity of the root-soil is 61.23%. In addition, the saturated permeability of the root-soil above the slip surface is 10-17 times that of the soil below. The shear strength of the root-soil above the slip surface is lower than that below it under saturated conditions. The difference in root distribution and the resulting changes in the hydro-mechanical properties of soil may increase the risk of slope failure and the probability of debris flow after heavy rainfall. This research could be used as a reference for debris flow source analysis and hazard management.

Keywords: Root-soil system; Landslide-induced debris flow; Geohazard chain; Hydro-mechanical properties
PGW projections of the returned 1960s U.S. Northeast drought and sensitivity examinations of PGW methods
Authors: Xue Zeyu , Ullrich Paul
Published: March 2022

As the most severe drought over the Northeastern United States (NEUS) in the past century, the 1960s drought had pronounced socioeconomic impacts. Although a persistent wet period followed, the conditions driving the 1960s extreme drought could return in the future, along with its challenges to water management. To project the potential consequences of such a future drought, pseudo-global warming (PGW) simulations using the Weather Research and Forecasting Model are performed to simulate the dynamical conditions of the historical 1960s drought, but with modified thermodynamic conditions under the shared socioeconomic pathway SSP585 scenario in the early (2021-2027), middle (2041-2047) and late (2091-2097) 21st century. Our analysis focuses on essential hydroclimatic variables including temperature, precipitation, evapotranspiration, soil moisture, snowpack and surface runoff. In contrast to the historical 1960s drought, similar dynamical conditions will generally produce more precipitation, increased soil moisture and evapotranspiration, and reduced snowpack. However, we also find that although wet months do become much wetter, dry months also may become drier, meaning that wetting trends that are significant in wet months can be essentially negligible for extremely dry months. For these months, the trend towards wetter conditions provides little relief from drying. These conditions may even aggravate water shortages due to an increasingly rapid transition from wet to dry conditions. Other challenges emerge for residents and stakeholders in this region, including more extreme hot days, record-low snow pack, frozen ground degradation and subsequent decreases in surface runoff.

Although the PGW approach pursued in this study is analogous to other recent studies, there is also a pressing need to ascertain confidence in projections using the PGW method.  Most PGW studies only modify the temperature forcing since it is the most significant for driving impacts on climate, but other meteorological forcings may also impact regional climate trends. For example, the large geopotential height increments at higher atmosphere levels tend to increase the stability and weaken the precipitation events associated with typhoons.  PGW studies usually only consider the changes at the regional mean scale but ignore spatially-dependent contributions from climate change. Therefore, in order to investigate the sensitivity of PGW-based projections, additional simulations were conducted under the RCP8.5 emission scenario but with different forcing modification methods.  We thus answer three questions: Are PGW simulations sensitive to the spatial scale of climate perturbations? Besides temperature, which climatological variables are crucial to PGW simulations? And finally, how should researchers design and conduct their PGW simulations?
Wave-induced turbulence, and its role in connecting small- and large-scale ocean processes
Authors: Babanin Alexander
Published: March 2022

In the presentation, wave-induced influences at the ocean side will be discussed. While the role of breaking waves in producing turbulence is well appreciated, the turbulence produced by wave orbital motion at the vertical scale of wavelength – is not. Such mixing, however, produces feedbacks to the ocean circulation at scales from weather to climate. In order to account for the wave-turbulence effects, large-scale air-sea interaction models need to be coupled with wave models. Theory and practical applications for the wave-induced turbulence are reviewed in the presentation.

 

Analytical approaches for the wave turbulence include viscous and instability theories which appear to be linked. This was verified through direct numerical simulations with fully nonlinear wave model coupled with three-dimensional (LES) model for turbulence. Furthermore, dedicated laboratory experiments and field observations, both in situ and by means of remote sensing, confirmed and validated the conclusions of theory and academic simulations and tests. Finally implementations of the wave-turbulence modules in models for Tropical Cyclones, ocean circulation and sea ice will be demonstrated.
Effect of Climatic Precession on Dansgaard-Oeschger-like oscillations 
Authors: Kuniyoshi Yuta , Abe-Ouchi Ayako , Sherriff-Tadano Sam , Chan Wing-Le , Saito Fuyuki
Published: March 2022

Using the climate model MIROC4m, we simulate self-sustained oscillations of millennial-scale periodicity in the climate and Atlantic meridional overturning circulation under glacial conditions. We show two cases of extreme climatic precession and examine the mechanism of these oscillations. When the climatic precession corresponds to strong (weak) boreal seasonality, the period of the oscillation is about 1,500 (3,000) years. During the stadial, hot (cool) summer conditions in the Northern Hemisphere contribute to thin (thick) sea ice, which covers the deep convection sites, triggering early (late) abrupt climate change. During the interstadial, as sea ice is thin (thick), cold deep-water forms and cools the subsurface quickly (slowly), which influences the stratification of the North Atlantic Ocean. We show that the oscillations are explained by the internal feedbacks of the atmosphere-sea ice-ocean system, especially subsurface ocean temperature change and salt advection feedback with a positive feedback between the subpolar gyre and deep convection.
Observational constraints on the uncertainties of the future precipitation change projections
Authors: Shiogama Hideo , Watanabe Masahiro , Kim Hyungjun , Hirota Nagio
Published: March 2022

Future projections of global mean precipitation change (ΔP) based on Earth system models have larger uncertainties than those of global mean temperature changes (ΔT). While many observational constraints on ΔT have been proposed, constraints on ΔP have not been well studied and are often complicated by the large influence of aerosols on precipitation. By analyzing the Coupled Model Intercomparison Project Phase 5 and 6 ensembles, we show that the upper bound (95th percentile) of ΔP (2051-2100 minus 1851-1900, % of the 1980-2014 mean) can be lowered from 6.2% to 5.2-5.7% (min-max range of sensitivity analyses) under a medium greenhouse gas concentration scenario. ΔP for 2051-2100 is well correlated with the global mean temperature trends during recent decades after 1980 when global anthropogenic aerosol emissions were nearly constant. ΔP is also significantly correlated with the recent past trends of precipitation when we exclude some tropical land areas with few rain gauge observations. Based on these significant correlations and observed trends, the variance of ΔP can be reduced by 8-30%. The observationally constrained ranges of ΔP should provide further reliable information for impact assessments.
Seasonal-to-decadal variability and predictability of the Kuroshio Extension in the GFDL Coupled Ensemble Reanalysis and Forecasting system
Authors: Joh Youngji , Delworth Thomas , Wittenberg Andrew , Cooke William , Yang Xiasong , Zeng Fanrong , Jia Liwei , Lu Feiyu , Johnson Nathaniel , Kapnick Sarah , Rosati Anthony , Zhang Liping , McHugh Colleen
Published: March 2022

The Kuroshio Extension (KE), an eastward-flowing jet located in the Pacific western boundary current system, exhibits prominent seasonal-to-decadal variability, which is crucial for understanding climate variations in northern midlatitudes. We explore the representation, predictability, and prediction skill for the KE in the GFDL SPEAR (Seamless System for Prediction and EArth System Research) coupled model. Two different approaches are used to generate coupled reanalyses and forecasts: (1) restoring the coupled model’s SST and atmospheric variables toward existing reanalyses, or (2) assimilating SST and subsurface observations into the coupled model without atmospheric assimilation.  Both systems use an ocean model with 1o resolution and capture the largest sea surface height (SSH) variability over the KE region. Assimilating subsurface observations appears to be critical to reproduce the narrow front and related oceanic variability of the KE jet in the coupled reanalysis. We demonstrate skillful retrospective predictions of KE SSH variability in monthly (up to 1 year) and annual-mean (up to 5 years) KE forecasts in the seasonal and decadal prediction systems, respectively. The prediction skill varies seasonally, peaking for forecasts initialized in January and verifying in September due to the winter intensification of North Pacific atmospheric forcing. We show that strong large-scale atmospheric anomalies generate deterministic oceanic forcing (i.e., Rossby waves), leading to skillful long-lead KE forecasts. These atmospheric anomalies also drive Ekman convergence/divergence that forms ocean memory, by sequestering thermal anomalies deep into the winter mixed layer that re-emerge in the subsequent autumn. The SPEAR forecasts capture the recent negative-to-positive transition of the KE phase in 2017, projecting a continued positive phase through 2022.