Miracle-dz/UniFAR-FTUs huggingface dataset:
On the importance of atmospheric loss of organic nitrates by aqueous-phase ●OH oxidation

Abstract. Organic nitrates are secondary species in the atmosphere. Their fate is related to the chemical transport of pollutants from polluted areas to more distant zones. While their gas-phase chemistry has been studied, their reactivity in condensed phases is far from being understood. However, these compounds represent an important fraction of organic matter in condensed phases. In particular, their partition to the aqueous phase may be especially important for oxidized organic nitrates for which water solubility increases with functionalization. This work has studied for the first time the aqueous-phase ⚫OH-oxidation kinetics of four alkyl nitrates (isopropyl nitrate, isobutyl nitrate, 1-pentyl nitrate, and isopentyl nitrate) and three functionalized organic nitrates (α-nitrooxyacetone, 1-nitrooxy-2-propanol, and isosorbide 5-mononitrate) by developing a novel and accurate competition kinetic method. Low reactivity was observed, with kOH ranging from 8×107 to 3.1×109 L mol−1 s−1 at 296±2 K. Using these results, a previously developed aqueous-phase structure–activity relationship (SAR) was extended, and the resulting parameters confirmed the extreme deactivating effect of the nitrate group, up to two adjacent carbon atoms. The achieved extended SAR was then used to determine the ⚫OH-oxidation rate constants of 49 organic nitrates, including hydroxy nitrates, ketonitrates, aldehyde nitrates, nitrooxy carboxylic acids, and more functionalized organic nitrates such as isoprene and terpene nitrates. Their multiphase atmospheric lifetimes towards ⚫OH oxidation were calculated using these rate constants, and they were compared to their gas-phase lifetimes. Large differences were observed, especially for polyfunctional organic nitrates: for 50 % of the proposed organic nitrates for which the ⚫OH reaction occurs mainly in the aqueous phase (more than 50 % of the overall removal), their ⚫OH-oxidation lifetimes increased by 20 % to 155 % under cloud/fog conditions (liquid water content LWC = 0.35 g m−3). In particular, for 83 % of the proposed terpene nitrates, the reactivity towards ⚫OH occurred mostly (>98 %) in the aqueous phase, while for 60 % of these terpene nitrates, their lifetimes increased by 25 % to 140 % compared to their gas-phase reactivity. We demonstrate that these effects are of importance under cloud/fog conditions but also under wet aerosol conditions, especially for the terpene nitrates. These results suggest that considering aqueous-phase ⚫OH-oxidation reactivity of biogenic nitrates is necessary to improve the predictions of their atmospheric fate.
Observed trends in clouds and precipitation (1983–2009): implications for their cause(s)

Abstract. Satellite observations (International Satellite Cloud Climatology Project (ISCCP), 1983–2009) of linear trends in cloud cover are compared to those in global precipitation (Global Precipitation Climatology Project (GPCP) pentad V2.2, 1983–2009), to investigate possible cause(s) of the linear trends in both cloud cover and precipitation. The spatial distributions of the linear trends in total cloud cover and precipitation are both characterized primarily by a broadening of the major ascending zone of Hadley circulation. Our correlation studies suggest that global warming, Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO) can explain 67 %, 49 % and 38 %, respectively, of the spatial variabilities in the linear trends in cloud cover, but causality is harder to establish. Further analysis of the broadening of the major ascending zone of Hadley circulation shows that the trend in global temperature, rather than those in AMO and PDO, is the primary contributor to the observed linear trends in total cloud cover and precipitation in 1983–2009. The underlying mechanism driving this broadening is proposed to be the moisture–convection–latent-heat feedback cycle under global warming conditions. The global analysis is extended by investigating connections between clouds and precipitation in China, based on a large number of long-running, high-quality surface weather stations in 1957–2005. This reveals a quantitative matching relationship between the reduction in light precipitation and the reduction in total cloud cover. Furthermore, our study suggests that the reduction in cloud cover in China is primarily driven by global temperature; PDO plays a secondary role, while the contribution from AMO and Niño3. 4 is insignificant, consistent with the global analysis.
Upscaling Sediment‐Flux‐Dependent Fluvial Bedrock Incision to Long Timescales

Fluvial bedrock incision is driven by the impact of moving bedload particles. Mechanistic, sediment‐flux‐dependent incision models have been proposed, but the stream power incision model (SPIM) is frequently used to model landscape evolution over large spatial and temporal scales. This disconnect between the mechanistic understanding of fluvial bedrock incision on the process scale, and the way it is modeled on long time scales presents one of the current challenges in quantitative geomorphology. Here, a mechanistic model of fluvial bedrock incision that is rooted in current process understanding is explicitly upscaled to long time scales by integrating over the distribution of discharge. The model predicts a channel long profile form equivalent to the one yielded by the SPIM, but explicitly resolves the effects of channel width, cross‐sectional shape, bedrock erodibility, and discharge variability. The channel long profile chiefly depends on the mechanics of bedload transport, rather than bedrock incision. In addition to the imposed boundary conditions specifying the upstream supply of water and sediment, and the incision rate, the model includes four free parameters, describing the at‐a‐station hydraulic geometry of channel width, the dependence of bedload transport capacity on channel width, the threshold discharge of bedload motion, and reach‐scale cover dynamics. For certain parameter combinations, no solutions exist. However, by adjusting the free parameters, one or several solutions can usually be found. The controls on and the feedbacks between the free parameters have so far been little studied, but may exert important controls on bedrock channel morphology and dynamics.
Stirring of Sea‐Ice Meltwater Enhances Submesoscale Fronts in the Southern Ocean

In the sea ice-impacted Southern Ocean, the spring melt of sea ice modifies the upper ocean. These modified waters subduct and enter the global overturning circulation. Submesoscale processes act to modulate the stratification of the mixed layer and therefore mixed layer properties. Sparse observations mean that the role of submesoscales in exchange across the base of the mixed layer in this region is not well constrained. The goal of this study is to determine the interplay between sea ice melt, surface boundary layer forcing, and submesoscale flows in regulating the mixed layer structure in the Antarctic Marginal Ice Zone. High-resolution observations suggest that fine-scale lateral fronts, representative of submesoscale mixed layer eddies (MLEs), arise from mesoscale gradients produced by northwards advecting sea ice meltwater. The strong salinity-driven stratification at the base of the mixed layer confined the MLEs to the upper ocean, limiting submesoscale vertical fluxes across the mixed layer base. This strong stratification prevents the local subduction by submesoscale flow of these modified waters, suggesting that the subduction site that links to the global overturning circulation does not correspond with the location of sea ice melt. However, the presence of MLEs enhanced the magnitude of lateral gradients through stirring and increased the potential for Ekman-driven cross-frontal flow to modulate the stability of the mixed layer and mixed layer properties. The inclusion, particularly of submesoscale Ekman Buoyancy Flux parameterizations, in coupled-climate models, may improve the representation of mixed layer heat and freshwater transport in the ice-impacted Southern Ocean during summer.
Characteristics of the summer atmospheric boundary layer height over the Tibetan Plateau and influential factors

Abstract. The important roles of the Tibetan Plateau (TP) atmospheric boundary layer (ABL) in climate, weather, and air quality have long been recognized, but little is known about the TP ABL climatological features and their west–east discrepancies due to the scarce data in the western TP. Based on observational datasets of intensive sounding, surface sensible heat flux, solar radiation, and soil moisture from the Third Tibetan Plateau Atmospheric Scientific Experiment (TIPEX-III) and the routine meteorological-operational-sounding and ground-based cloud cover datasets in the Tibetan Plateau for the period 2013–2015, we investigate the west–east differences in summer ABL features over the TP and the associated influential factors for the first time. It is found that the heights of both the convective boundary layer (CBL) and the neutral boundary layer (NBL) exhibit a diurnal variation and a west–east difference in the TP, while these features are not remarkable for the stable boundary layer (SBL). Moreover, the ABL shows significant discrepancies in the amplitude of the diurnal variation and the persistent time of the development between the eastern and western TP. In the early morning (08:00 BJT, Beijing time), the ABL height distribution is narrow, with a mean height below 450 m a.g. l. (above ground level) and a small west–east difference. The SBL observed at this moment accounts for 85 % of the total TP ABL. There is a wide distribution in the ABL height up to 4000 m a.g. l. and a large west–east difference for the total ABL height at noon (14:00 BJT), with a mean height above 2000 m a.g. l. in the western TP and around 1500 m a.g. l. in the eastern TP. The CBL accounts for 77 % of the total TP ABL at this moment, with more than 50 % of the CBL above 1900 m a.g. l. In the late afternoon (20:00 BJT), the CBL and SBL dominate the western and eastern TP, respectively, which results in a larger west–east difference of 1054.2 m between the western and eastern TP. The high ABL height in a cold environment over the western TP (relative to the plain areas) is similar to that in some extreme hot and arid areas such as Dunhuang and Taklimakan deserts. In general, for the western (eastern) TP, there is low (high) total cloud coverage, with large (small) solar radiation at the surface and dry (wet) soil. These features lead to high (low) sensible heat flux and thus promote (inhibit) the local ABL development. This study provides new insights for west–east structures of the summer ABL height, occurrence frequency, and diurnal amplitude over the TP region and the associated reasons.
Mathematical Modeling on Transient Multiphase Flow and Slag Entrainment in Continuously Casting Mold with Double-ruler EMBr through LES+VOF+DPM Method

To investigate the transient multiphase flow, slag entrainment and exposed slag eye in the mold with EMBr and argon injection, a transient multiphase LES model was constructed. In the model, the multiphase (steel-slag-air) flow was simulated through VOF method, argon bubbles were tracked using DPM method. The model was validated by previous experimental measurements through the particle image velocimetry. The results indicated that argon injection weakened the upper recirculation flow, and reduced the molten steel jet downward angle. Moreover, the turbulent flow in the mold was suppressed by EMBr. The slag entrainment mechanisms are different under different conditions. In the case without argon injection and EMBr, three slag entrainment mechanisms were found: shear flow, Von Kármán vortex, and level fluctuation. Nevertheless, when argon was injected, in addition to the above mechanisms, one extra mechanism was predicted that was bubble interaction. Additionally, bubble interaction was the unique slag entrainment mechanism in the case with argon injection and EMBr. The impact of argon bubbles on the steel-slag interface resulted in exposed slag eye. In the case without EMBr, the exposed slag eye phenomenon was intermittent. However, the phenomenon was persistent when EMBr was applied.
The response of terrestrial ecosystem carbon cycling under different aerosol-based radiation management geoengineering

Abstract. Geoengineering has been discussed as a potential option to offset the global impacts of anthropogenic climate change and at the same time reach the global temperature targets of the Paris Agreement. Before any implementation of geoengineering, however, the complex natural responses and consequences of such methods should be fully understood to avoid any unexpected and potentially degrading impacts. Here we assess the changes in ecosystem carbon exchange and storage among different terrestrial biomes under three aerosol-based radiation management methods with the baseline of RCP8.5 using an Earth system model (NorESM1-ME). All three methods used in this study (stratospheric aerosol injection, marine sky brightening, cirrus cloud thinning) target the global mean radiation balance at the top of the atmosphere to reach that of the RCP4.5 scenario. The three radiation management (RM) methods investigated in this study show vastly different precipitation patterns, especially in the tropical forest biome. Precipitation differences from the three RM methods result in large variability in global vegetation carbon uptake and storage. Our findings show that there are unforeseen regional consequences under geoengineering, and these consequences should be taken into account in future climate policies as they have a substantial impact on terrestrial ecosystems. Although changes in temperature and precipitation play a large role in vegetation carbon uptake and storage, our results show that CO 2 fertilization also plays a considerable role. We find that the effects of geoengineering on vegetation carbon storage are much smaller than the effects of mitigation under the RCP4.5 scenario (e.g., afforestation in the tropics). Our results emphasize the importance of considering multiple combined effects and responses of land biomes while achieving the global temperature targets of the Paris Agreement.
Antarctic atmospheric boundary layer observations with the Small Unmanned Meteorological Observer (SUMO)

Abstract. Between January 2012 and June 2017 a small unmanned aerial system (sUAS), known as the Small Unmanned Meteorological Observer (SUMO), was used to observe the state of the atmospheric boundary layer in the Antarctic. During six Antarctic field campaigns, 116 SUMO flights were completed. These flights took place during all seasons over both permanent ice and ice-free locations on the Antarctic continent and over sea ice in the western Ross Sea. Sampling was completed during spiral ascent and descent flight paths that observed the temperature, humidity, pressure and wind up to 1000 m above ground level and sampled the entire depth of the atmospheric boundary layer, as well as portions of the free atmosphere above the boundary layer. A wide variety of boundary layer states were observed, including very shallow, strongly stable conditions during the Antarctic winter and deep, convective conditions over ice-free locations in the summer. The Antarctic atmospheric boundary layer data collected by the SUMO sUAS, described in this paper, can be retrieved from the United States Antarctic Program Data Center (https://www.usap-dc.org, last access: 8 March 2021). The data for all flights conducted on the continent are available at https://doi.org/10.15784/601054 (Cassano, 2017), and data from the Ross Sea flights are available at https://doi.org/10.15784/601191 (Cassano, 2019).
Effects of coupling a stochastic convective parameterization with the Zhang–McFarlane scheme on precipitation simulation in the DOE E3SMv1.0 atmosphere model

Abstract. A stochastic deep convection parameterization is implemented into the US Department of Energy (DOE) Energy Exascale Earth System Model (E3SM) Atmosphere Model version 1.0 (EAMv1). This study evaluates its performance in simulating precipitation. Compared to the default model, the probability distribution function (PDF) of rainfall intensity in the new simulation is greatly improved. The well-known problem of “too much light rain and too little heavy rain” is alleviated, especially over the tropics. As a result, the contribution from different rain rates to the total precipitation amount is shifted toward heavier rain. The less frequent occurrence of convection contributes to suppressed light rain, while more intense large-scale and convective precipitation contributes to enhanced heavy total rain. The synoptic and intraseasonal variabilities of precipitation are enhanced as well to be closer to observations. The sensitivity of the rainfall intensity PDF to the model vertical resolution is examined. The relationship between precipitation and dilute convective available potential energy in the stochastic simulation agrees better with that in the Atmospheric Radiation Measurement (ARM) observations compared with the standard model simulation. The annual mean precipitation is largely unchanged with the use of the stochastic scheme except over the tropical western Pacific, where a moderate increase in precipitation represents a slight improvement. The responses of precipitation and its extremes to climate warming are similar with or without the stochastic deep convection scheme.
Stress Drop Variations in the Region of the 2014 MW8.1 Iquique Earthquake, Northern Chile

We compute stress drops from P and S phase spectra for 534 earthquakes in the source region of the 2014 MW8.1 Iquique megathrust earthquake in the northern Chilean subduction zone. An empirical Green's function based method is applied to suitable event pairs selected by template matching of eight years of continuous waveform data. We evaluate the parameters involved in the stress drop estimation, consider the effect of the local velocity structure and apply an empirical linear relation between P and S phase related geometry factors (k values). Data redundancy produced by multiple empirical Green's function and the combination of P and S phase spectra leads to a substantial reduction of uncertainty and robust stress drop estimates. The resulting stress drop values show a well‐defined log‐normal distribution with a median value of 4.36 MPa; most values range between 0.1 and 100 MPa. There is no evidence for systematic large scale lateral variations of stress drop. A detailed analysis reveals several regions of increased median stress drop, an increase with distance to the interface, but no consistent increase with depth. This suggests that fault regime and fault strength have a stronger impact on the stress drop behavior than absolute stresses. Interestingly, we find a weak time‐dependence of the median stress drop, with an increase immediately before the April 1, 2014 MW8.1 Iquique mainshock, a continuous reduction thereafter and a subsequent recovery to average values. Additionally, the data set indicates a relatively strong dependence of stress drop on magnitude which extends over the entire analyzed magnitude range.
Performance, intestinal microbial population, immune and physiological responses of broiler chickens to diet with different levels of silver nanoparticles coated on zeolite

Abstract The aim of this study was to evaluate the effects of different levels of silver nanoparticles (Ag-NPs) coated on zeolite on performance, gastrointestinal microflora, heterophile to lymphocyte ratio and humoral immune system responses of broiler chickens. Three hundred seventy-five chicks (Cobb 500) in a completely randomised design were distributed to five diets: 1) basal diet, 2) basal diet containing 1% zeolite and 3, 4 and 5) basal diet containing 1% zeolite coated with 25, 50 and 75 ppm Ag-NPs. Performance traits were recorded and blood samples were taken to determine antibody response against Newcastle on day 14, infectious bursal disease on day 21 and serum immunoglobulins (Igs) were determined on day 42. Heterophile to lymphocyte ratio was evaluated on days 28, 35 and 42. The result showed that feed conversion ratio (FCR) was significantly decreased in Ag-NP treatments compared with control group (p < .05). Total anaerobic bacteria and the population of Escherichia coli in ileum and caecum were decreased (p < .05). The highest number of lactobacillus was observed in NS50 (p < .05). Antibody response against Gumboro was decreased as well as the amount of IgY antibody in Ag-NPs treatments. Significant differences were observed in heterophile to lymphocyte ratio on day 28 and 35 and the highest amount was observed in NS50 group (p < .05). In conclusion, although this study showed that using Ag-NP dietary coated on zeolite could improve gut microflora, but Ag-NPs could also have side effects on the immune mechanism of broiler chickens. Highlights Silver nanoparticles (Ag-NPs) coated on zeolite improved feed efficiency at different levels. Ag-NPs (50 ppm) coated on zeolite reduced Escherichia coli number and decreased lactobacillus number. Ag-NPs (50 ppm) coated on zeolite decreased antibody response against Gumboro and amount of IgY antibodies.
The role of edge-driven convection in the generation of volcanism – Part 1: A 2D systematic study

Abstract. The origin of intraplate volcanism is not explained by plate tectonic theory, and several models have been put forward for explanation. One of these models involves edge-driven convection (EDC), in which cold and thick continental lithosphere is juxtaposed with warm and thin oceanic lithosphere to trigger convective instability. To test whether EDC can produce long-lived high-volume magmatism, we run numerical models of EDC for a wide range of mantle properties and edge (i.e., the oceanic–continental transition) geometries. We find that the most important parameters that govern EDC are the rheological parameters mantle viscosity η0 and activation energy Ea . However, even the maximum melting volumes predicted by our most extreme cases are insufficient to account for island-building volcanism on old seafloor, such as at the Canary Islands and Cabo Verde. Also, beneath old seafloor, localized EDC-related melting commonly transitions into widespread melting due to small-scale sublithospheric convection, inconsistent with the distribution of volcanism at these volcano chains. In turn, EDC is a good candidate to sustain the formation of small seamounts on young seafloor, as it is a highly transient phenomenon that occurs in all our models soon after initiation. In a companion paper, we investigate the implications of interaction of EDC with mantle plume activity ( Manjon-Cabeza Cordoba and Ballmer , 2021 ) .
Water Depth Dependence of Long‐Range Correlation in Nontidal Variations in Seafloor Pressure

Isolating the source of nontidal oceanographic noise in seafloor pressure data is critical for improving the use of these data for seafloor geodetic applications. Residuals between nearby bottom pressure records have typically been used to remove the nontidal components, as these are largely common‐mode. To evaluate the similarities between pairs of observed bottom pressure records at a range of water depths, we calculate the standard deviations of the time series of residuals between data from all site pairs, installed in the Hikurangi subduction zone offshore New Zealand. We find that the magnitude of the standard deviation depends more on relative water depth than the distance between sites. This confirms the result of previous studies from Cascadia that nontidal components are more similar along isobaths even if the distance between sites is large. Furthermore, in order to reduce noises, the required depth difference between site pairs also varies with site depths.