Low Surface Pressure Research Articles

Interannual variability of the summer wind energy over China: A comparison of multiple datasets

AbstractBecause of the increase in the nation's need for wind energy, the impacts of climate change on wind energy have been investigated. In addition to long‐term changes, wind energy also shows robust interannual variations, but little effort has been devoted to understanding the underlying mechanisms. In this study, the impact of El Niño on the summer mean wind power density (WPD) over China is investigated. The abilities of five sets of reanalysis data in measuring the interannual variability of the WPD over China are assessed. Encouraging results are seen for all reanalysis datasets, with the MERRA and ERA‐Interim datasets showing the best performance. The relationship between El Niño and the following summer WPD is identified over China. During El Niño decaying year summers, the WPD over south of the Yangtze River valley increases, whereas the WPD over north of the Yangtze River valley decreases. The WPD changes are dominated by an anomalous anticyclone located in the northwestern Pacific. The anticyclone leads to strong southerly winds in southern China and thereby enhances the WPD. In regions north of the Yangtze River valley, the low surface pressure gradient causes a reduction in wind speed and thereby a weak WPD. Because the year‐by‐year variation in El Niño‐Southern Oscillation (ENSO) is highly predictable, our results shed light on the seasonal prediction of wind power over China.

Real-time monitoring of the effect of carbon nanoparticles on the surface behavior of DPPC/DPPG Langmuir monolayer

Air pollution has become increasingly serious. Fine particulate matter (PM2.5) is the most well-known air pollutant, which leads to some common respiratory diseases when inhaled into the lungs to certain concentration. However, there is a lack of research on the process of dynamically monitoring the real-time effect of nanoparticles on the pulmonary surfactant monolayer. In this study, the DPPC/DPPG monolayer is prepared by the Langmuir method to simulate the lung surfactant monolayer during respiration and the carbon nanoparticles are introduced to the monolayer under different surface pressures to simulate the real dynamic process of inhaling nanoparticles during breathing. The effect of carbon nanoparticles on the surface behavior of DPPC/DPPG monolayer in real-time was examined in details by a combination of surface pressure (π)-area (A) isotherms, compressibility modulus (Cs-1)-surface pressure (π) isotherms and the Brewster angle microscopy (BAM). The results have shown that the introduction of carbon nanoparticles under different surface pressures affects the properties of lipid monolayers. The added carbon nanoparticles under lower surface pressure are easy to penetrate the lipid molecules to inhibit monolayer phase transition. When the carbon nanoparticles are introduced to the monolayer under higher surface pressure, they tend to self-aggregate to reduce the monolayer stability rather than interact with lipid tail chains. This work not only confirms the exotic hydrophobic carbon nanoparticles retain in the DPPC/DPPG monolayer irreversibly and affect the surface behavior of monolayer during respiration, but also opens a new idea for real-time monitoring of the effects of PM2.5 on lung health.

Scaling of cylinder-generated shock-wave/turbulent boundary-layer interactions

Scaling parameters of shock-wave/turbulent boundary-layer interactions generated by a semi-infinite standing cylinder were explored in a combined numerical and experimental effort, consisting of Reynolds-averaged Navier–Stokes simulations and high-speed schlieren imaging. The primary interaction variable, the cylinder diameter (d), and a secondary interaction variable, the boundary-layer thickness ($$\delta $$), were varied to study the effects of the parameter $$d/\delta $$. This was found to be an appropriate scaling parameter for mean features. The characteristic interaction variables (the maximum separation distance, S, and the triple-point height, $$h_\mathrm{tp}$$) followed a linear trend when normalized as $$S/\delta $$ and $$h_\mathrm{tp}/\delta $$; however, when the boundary layer became larger than the cylinder diameter, a power law trend became more representative. The parameter $$d/\delta $$ also determined the role that viscous effects have on the strength of the interaction, where a lower $$d/\delta $$ was characterized by a greater interaction scale and lower surface pressure peaks. Moreover, the high surface pressure on the cylinder leading edge due to the Edney interaction was found to be reduced for $$d/\delta \le 0.45$$, as the boundary layer encompassed the lambda-shock structure. Trends in the shapes or peaks of the auto-spectral density function were not observed based on $$d/\delta $$, but appeared to be dominated by broadband low-frequency ($$f < 1~\hbox {kHz}$$) content. While the position and structure of the interaction may change as a result of varying $$d/\delta $$, the effects on the unsteady dynamics were minimal.

A Composite Analysis of Snowfall Modes from Four Winter Seasons in Marquette, Michigan

AbstractPresented are four winter seasons of data from an enhanced precipitation instrument suite based at the National Weather Service (NWS) Office in Marquette (MQT), Michigan (250–500 cm of annual snow accumulation). In 2014 the site was augmented with a Micro Rain Radar (MRR) and a Precipitation Imaging Package (PIP). MRR observations are utilized to partition large-scale synoptically driven (deep) and surface-forced (shallow) snow events. Coincident PIP and NWS MQT meteorological surface observations illustrate different characteristics with respect to snow event category. Shallow snow events are often extremely shallow, with MRR-indicated precipitation heights of less than 1500 m above ground level. Large vertical reflectivity gradients indicate efficient particle growth, and increased boundary layer turbulence inferred from observations of spectral width implies increased aggregation in shallow snow events. Shallow snow events occur 2 times as often as deep events; however, both categories contribute approximately equally to estimated annual accumulation. PIP measurements reveal distinct regime-dependent snow microphysical differences, with shallow snow events having broader particle size distributions and comparatively fewer small particles and deep snow events having narrower particle size distributions and comparatively more small particles. In addition, coincident surface meteorological measurements indicate that most shallow snow events are associated with surface winds originating from the northwest (over Lake Superior), cold temperatures, and relatively high surface pressures, which are characteristics that are consistent with cold-air outbreaks. Deep snow events have meteorologically distinct conditions that are accordant with midlatitude cyclones and frontal structures, with mostly southwest surface winds, warmer temperatures approaching freezing, and lower surface pressures.

Influence of global sea‐surface temperature on ultra‐low‐frequency variability in Indian summer monsoon rainfall

AbstractA multidecadal or ultra‐low‐frequency mode of variability in Indian summer monsoon rainfall (ISMR) with a spectral peak at nearly 67 years is identified using a nonparametric approach, namely, singular spectrum analysis. Not only does this mode modulate the seasonal mean rainfall over India, but also frequent occurrences of excess or below normal rainfall over India are favored by the phases of this mode. We show that 80% of all droughts occur during the negative phase of this mode, compared with 60% of all floods during its positive phase. Although the existence of this mode was reported in many previous studies, proper understanding of its exact nature and driving mechanism, and how it relates to global sea‐surface temperature (SST), is still not clear. Here, we show that the 67‐year variability in ISMR is associated with a SST mode of similar periodicity, which primarily exhibits a hemispheric SST difference, with the strongest signals over the northern Pacific and Atlantic. The positive phase of this SST mode induces low surface pressure over the northern Arabian Sea. Changes in surface pressure over the northern Arabian Sea govern changes in ISMR. The bridge between the SST mode and central Asian circulation is possibly established through the North Pacific Oscillation. The positive phase of this mode enhances the meridional temperature gradient over India, which acts to strengthen the tropical easterly jet, and subsequently the low‐level westerly jet over India. These lead to a negative surface pressure anomaly over the Indian subcontinent and an associated anomalous cyclonic circulation. The environment thus created is conducive to increased seasonal mean monsoon rainfall over India. The phase of the SST mode is remarkably similar to, and leading by 2–3 years, that of the multidecadal mode in ISMR up to the 1990s. However, the relationship weakens after the early 1990s.

Tyrosinase enzyme Langmuir monolayer: Surface chemistry and spectroscopic study

This study investigates the surface chemistry properties of the tyrosinase enzyme Langmuir monolayer at air-aqueous interface using sodium chloride in the subphase to induce the surface activity of the enzyme. Investigation of surface packing and stability of the tyrosinase Langmuir monolayer were performed using surface chemistry experiments while spectroscopic analysis was done to study enzyme conformation. It was found that the tyrosinase enzyme forms a fluid film at air-aqueous interface with good stability as shown by compression-decompression cycles experiments and stability measurements at various surface pressures. UV-vis absorption and fluorescence measurements at different surface pressures revealed that the Langmuir monolayer has good homogeneity with no evidence of aggregates during compression. To gain insight on the conformation of tyrosinase Langmuir monolayer p-polarized infrared-reflection absorption spectroscopy was used. It was found that at high surface pressures the predominant secondary structures were β-sheets while at lower surface pressure both α -helices and β-sheets were present. The circular dichroism spectra were obtained by transferring the Langmuir monolayer at 10 mN.m−1 to a solid quartz support (Langmuir-Blodgett film, LB film), which showed that the major conformation present were α-helices. Images from the immobilized LB films were obtained using atomic force microscopy which showed homogenous and regular deposition with a mean thickness ranging from 3 to 4 nm.

Fluidity of binary monolayers of semi-fluorinated and non-fluorinated fatty alcohols at the air−water interface

The focus of this study is to elucidate lateral interactions between pentadecanol (H15OH) and (perfluorohexyl)nonanol (F6H9OH) at the air–water interface. The surface pressure (π)−molecular area (A) and surface potential (ΔV)−A isotherms of the binary monolayer were measured as a function of mole fraction. The excess Gibbs free energy of mixing was calculated from the π−A isotherms. In addition, a two-dimensional phase diagram of the system was constructed by analyzing the isotherm data. These results suggested miscibility between the two components. Furthermore, the addition of F6H9OH induced the fluidization and stabilization of H15OH monolayers at the low and high surface pressures, respectively. The phase behavior upon monolayer compression was visualized with in situ fluorescence microscopy and ex situ atomic force microscopy. A combination of both the microscopic images was successful in capturing the evidence of the two-component miscibility and phase transition at large F6H9OH mole fractions.

Structure and dilatational rheological behavior of heat-treated lotus (Nelumbo nucifera Gaertn.) seed protein

The influences of heat treatment (60, 80 and 100 °C, 30min) on the structure and interfacial properties (adsorption at the oil−water interface and dilatational rheology of interfacial layers) of lotus seed protein (LSP) were evaluated. Heat treatment induced an increase in average diameter and surface hydrophobicity due to partial unfolding and aggregation of LSP. Specifically, the moderate heat treatment (60 and 80 °C) could significantly increase the net surface potential of LSP, while heating at 100 °C had no effect. Additionally, the lower surface pressure at long-term adsorption and similar dynamic interfacial rheology were observed as compared to native LSP. In contrast, heat treatment led to a higher diffusion and penetration rate of protein, as observed by a faster increase of surface pressure. Nevertheless, the viscoelastic properties of the adsorbed layer of LSP after heat treatment decreased and when the interfacial pressure was greater than 18 mN/m, the interfacial modulus showed a downward trend. These findings increase our understanding of the structural dependence of protein interface behavior and the application of heat-treated proteins in emulsion preparation.

The bidesmosidic triterpene saponins hederacoside C and ginsenoside Rb1 exhibit low affinity to cholesterol in liposomal membranes

The formation of nanoparticulate structures in the presence of liposomal components has recently been demonstrated for a few saponins, with cholesterol being the essential component.As a follow-up from previous studies, we have studied the interaction of two bidesmosidic triterpene saponins (ginsenoside Rb1, hederacoside C) with liposomal components (cholesterol, DPPC (dipalmitoylphosphatidylcholine)) using the Langmuir film balance technique. In addition, we examined the influence of saponins in aqueous pseudo-binary (saponin:cholesterol/DPPC) and pseudo-ternary systems (saponin:cholesterol:DPPC) regarding particle formation utilizing transmission electron microscopy (TEM). Saponin formulations with liposomal components were prepared by the lipid film method.Langmuir monolayer studies showed a weak affinity of both saponins to cholesterol. Saponin molecules from the subphase migrated into the cholesterol monolayer only at low surface pressure. Further compression of the monolayer led to an exclusion of the saponin molecules back into the subphase. In mixed monolayers (cholesterol, DPPC) as well as in a pure DPPC monolayer, the saponins remained completely in the subphase independent of the pressure applied. TEM images of aqueous pseudo-ternary systems showed no colloidal associations along with the weak affinity for cholesterol. These results emphasize the correlation between the affinity for cholesterol and the formation of nanoparticular structures with liposomal components.

Surfactant Charge Modulates Structure and Stability of Lipase-Embedded Monolayers at Marine-Relevant Aerosol Surfaces.

Lipases, as well as other enzymes, are present and active within the sea surface microlayer (SSML). Upon bubble bursting, lipases partition into sea spray aerosol (SSA) along with surface-active molecules such as lipids. Lipases are likely to be embedded in the lipid monolayer at the SSA surface and thus have the potential to influence SSA interfacial structure and chemistry. Elucidating the structure of the lipid monolayer at SSA interfaces and how this structure is altered upon interaction with a protein system like lipase is of interest, given the importance of how aerosols interact with sunlight, influence cloud formation, and provide surfaces for chemical reactions. Herein, we report an integrated experimental and computational study of Burkholderia cepacia lipase (BCL) embedded in a lipid monolayer and highlight the important role of electrostatic, rather than hydrophobic, interactions as a driver for monolayer stability. Specifically, we combine Langmuir film experiments and molecular dynamics (MD) simulations to examine the detailed interactions between the zwitterionic dipalmitoylphosphatidylcholine (DPPC) monolayer and BCL. Upon insertion of BCL from the underlying subphase into the lipid monolayer, it is shown that BCL permeates and largely disorders the monolayer while strongly interacting with zwitterionic DPPC molecules, as experimentally observed by Langmuir adsorption curves and infrared reflectance absorbance spectroscopy. Explicitly solvated, all-atom MD is then used to provide insights into inter- and intramolecular interactions that drive these observations, with specific attention to the formation of salt bridges or ionic-bonding interactions. We show that after insertion into the DPPC monolayer, lipase is maintained at high surface pressures and in large BCL concentrations by forming a salt-bridge-stabilized lipase-DPPC complex. In comparison, when embedded in an anionic monolayer at low surface pressures, BCL preferentially forms intramolecular salt bridges, reducing its total favorable interactions with the surfactant and partitioning out of the monolayer shortly after injection. Overall, this study shows that the structure and dynamics of lipase-embedded SSA surfaces vary based on surface charge and pressure and that these variations have the potential to differentially modulate the properties of marine aerosols.

Vertical observations of the atmospheric boundary layer structure over Beijing urban area during air pollution episodes

Abstract. We investigated the interactions between the air pollutants and the structure of the urban boundary layer (UBL) over Beijing by using the data mainly obtained from the 325 m meteorological tower and a Doppler wind lidar during 1–4 December 2016. Results showed that the pollution episodes in this period could be characterized by low surface pressure, high relative humidity, weak wind, and temperature inversion. Compared with a clean daytime episode that took place on 1 December, results also showed that the attenuation ratio of downward shortwave radiation was about 5 %, 24 % and 63 % in afternoon hours (from 12:00 to 14:00 local standard time, LST) on 2–4 December, respectively, while for the net radiation (Rn) attenuation ratio at the 140 m level of the 325 m tower was 3 %, 27 % and 68 %. The large reduction in Rn on 4 December was not only the result of the aerosols, but also clouds. Based on analysis of the surface energy balance at the 140 m level, we found that the sensible heat flux was remarkably diminished during daytime on polluted days and even negative after sunrise (about 07:20 LST) till 14:00 LST on 4 December. We also found that heat storage in the urban surface layer played an important role in the exchange of the sensible heat flux. Owing to the advantages of the wind lidar having superior spatial and temporal resolution, the vertical velocity variance could capture the evolution of the UBL well. It clearly showed that vertical mixing was negatively related to the concentrating of pollutants, and that vertical mixing would also be weakened by a certain quantity of pollutants, and then in turn worsened the pollution further. Compared to the clean daytime on 1 December, the maximums of the boundary layer height (BLH) decreased about 44 % and 56 % on 2–3 December, when the average PM2.5 (PM1) concentrations in afternoon hours (from 12:00 to 14:00 LST) were 44 (48) µg m−3 and 150 (120) µg m−3. Part of these reductions of the BLH was also contributed by the effect of the heat storage in the urban canopy.

Modeling the Transient Response of Tropical Convection to Mesoscale SST Variations

Abstract A cloud-resolving model coupled to a mixed layer ocean with an initial 500-km-wide, +3-K sea surface temperature (SST) patch is used to demonstrate the relationship between tropical mesoscale SST gradients and convection under different wind speeds. On these scales, boundary layer convergence toward hydrostatic low surface pressure is partially responsible for triggering convection, but convection subsequently organizes into cells and squall lines that propagate away from the patch. For strong wind (12 m s−1), enhanced convection is shifted downstream from the patch and consists of relatively small cells that are enhanced from increased moist static energy (MSE) flux over the patch. Convection for weak wind (6 m s−1) develops directly over the patch, merging in larger-scale coherent squall-line systems that propagate away from the patch. Squall lines decay after approximately 1 day, and convection redevelops over the patch region after 2 days. Decreasing patch SST from ocean mixing in the coupled simulations affects the overall strength of the convection, but does not qualitatively alter the convective behavior in comparison with cases with a fixed 3-K SST anomaly. In all cases, increased fluxes of heat and moisture, along with latent heating from shallow convection, initially generate lower pressure over the patch and convergence of the boundary layer winds. Within about 1 day, secondary convective circulations, such as surface cold pools, act to spread the effects of the convection over the model domain and overwhelm the effect of low pressure. SST anomalies (1 and 0.5 K) generate enhanced convection only for winds below 6 m s−1.

Linking quasi-biweekly variability of the South Asian high to atmospheric heating over Tibetan Plateau in summer

This study investigates the summertime day-to-day variability of the South Asian high (SAH) driven by atmospheric heating over Tibetan Plateau (TP) using the NCEP/NCAR reanalysis dataset. We first isolate the day-to-day variability of SAH in summertime based on the intensity of the summertime Tibetan Plateau upper-atmospheric heat source (TPUHS). It shows that anomalously stronger TPUHS days are accompanied with SAH center over Iranian Plateau (IP or the IP phase of the SAH) and the SAH center moves to TP (or the TP phase) during weaker TPUHS days, which contrasts with the corresponding relationship between SAH IP/TP phase and weaker/stronger TP heating in monthly and longer timescale. We further demonstrate that the SAH IP/TP phase coincides with stronger/weaker low surface pressure anomalies over TP. The stronger ascending and upper-tropospheric divergence anomalies above TP during stronger TPUHS days connect to compensatory stronger descending and upper-tropospheric convergence anomalies over IP. Such day-to-day SAH variability associated with TPUHS exhibits a quasi-biweekly time scale with a pronounced westward propagating signal.

Langmuir monolayer study of phospholipid DPPC on the titanium dioxide\u2013chitosan\u2013hyaluronic acid subphases

The studies of model biological membranes consisted of phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) were carried out by means of the Langmuir monolayer technique using subphases containing chitosan (Ch), titanium (IV) oxide (TiO2), hyaluronic acid (HA) or mixture of them. The aim was to determine the effect of individual components of subphase and their respective combinations on behavior of the DPPC membrane. The systems were tested at room temperature (20 °C) and at a natural pH of about 4.8, which was close to the pH of the human skin (4.7–5.6). The surface pressure–area per molecule (π–A) isotherms were obtained. Their analysis showed that all substances studied affected the phospholipid membrane which was revealed in the changes of mean molecular area, compression modulus and pressure of the liquid-expanded/liquid-condensed (LE/LC) phase transition. The results were discussed in terms of the nature and strength of mutual interactions. The more profound effect was found at low surface pressures at which the monolayers occurred in more expanded state. However, at the surface pressure corresponding to that of biological membranes, systems had very similar parameters compared to model DPPC isotherm.

Summer Arctic Cold Anomaly Dynamically Linked to East Asian Heat Waves

During recent years, the rapidly warming Arctic and its impact on winter weather and climate variability in the mid- and low latitudes have been the focus of many research efforts. In contrast, anomalous cool Arctic summers and their impacts on the large-scale circulation have received little attention. In this study, we use atmospheric reanalysis data to reveal a dominant pattern of summer 1000–500-hPa thickness variability north of 30°N and its association with East Asian heat waves. It is found that the second thickness pattern exhibits strong interannual variability but does not exhibit any trend. Spatially, the positive phase of the second thickness pattern corresponds with significant Arctic cold anomalies in the mid- and low troposphere, which are surrounded by warm anomalies outside the Arctic. This pattern is the thermodynamic expression of the leading pattern of upper-tropospheric westerly variability and significantly correlated with the frequency of East Asian heat waves. The Arctic has experienced frequent summer cold anomalies since 2005, accompanied by strengthened tropospheric westerly winds over most of the Arctic and weakened westerlies over the mid- and low latitudes of Asia. The former significantly enhances baroclinicity over the Arctic, which dynamically contributes to increased frequency of anomalous low surface pressure during summer along with decreased frequency over high latitudes of Eurasia and North America. The latter is exhibited by sustained high pressure anomalies in the mid- and low troposphere that dynamically facilitate the occurrence of East Asian heat waves. A systematic northward shift of Asian zonal winds dynamically links Arctic cold anomalies with East Asian heat waves and produces a seesaw structure in zonal wind anomalies over the Arctic and the Tibetan Plateau (the third pole). Evidence suggests that enhanced Arctic westerlies may provide a precursor to improve predictions of the East Asian winter monsoon, though the mechanism for this lag association is unclear.

Fabricating and Examining of Langmuir Films of Reduced Graphene Oxide

The effect the transfer pressure has on structural, optical, and electrophysical properties of Langmuir-Blodgett (LB) films of reduced graphene oxide (rGO) is studied. Investigation of physicochemical properties of rGO monolayers on the subphase surface shows that the rGO monolayer on the subphase surface predominantly exists in the liquid state. Increased surface pressure in the film makes rGO particles lie closer to and contact one another, followed by the overlapping and crumpling of some film sheets. Electron microscope studies show that as monolayers are transferred onto solid substrates, rGO forms uniform island-type films with clearly discernible clusters whose density grows along with surface pressure. The synthesized rGO films are highly transparent (87–96%) in the visible spectral region. The LB films transferred onto solid substrates at a lower surface pressure exhibit the best electrophysical and electroconductive properties. The reported findings can be used in developing technology for synthesizing transparent nanosized films from reduced graphene oxide and its derivatives for use in molecular electronics and photovoltaics.

Aerosol Impacts on Meteorological Elements and Surface Energy Budget over an Urban Cluster Region in the Yangtze River Delta

ABSTRACT The Yangtze River Delta (YRD) is a typical example of regions that are dramatically influenced by both human activity and a monsoonal climate. Data on the near-surface micro-meteorology, radiation, and energy fluxes were collected and analyzed at the Lishui field observation site in the suburb of Nanjing to investigate aerosol impacts on the radiation budget and land surface-atmosphere heat, water, and mass exchanges. Cluster analysis, composite analysis, and case study were applied to selected typical polluted/non-polluted days. The results indicate that the mean daily surface pressure is 6.6 hPa lower on polluted than non-polluted days in Nanjing. Northeasterly winds often prevail on the polluted days, with wind speeds being 60% lower than on non-polluted days. Aerosols directly reduce the net radiation flux at the surface, with a maximum reduction of 180 W m–2. During the early stage of air pollution events, the surface pressure is lower, and wind speeds rapidly decrease, whereas during the peak of pollution, low surface pressure and wind speeds linger, effectively preventing the dispersion of air pollutants. Meanwhile, the temperature often decreases, and the relative humidity subsequently increases. As the wind speed and surface pressure increase, the AQI gradually decreases, and the air pollution event ends.

Assessing geochemical reactions during CO2 injection into an oil-bearing reef in the Northern Michigan basin

The Dover 33 Reef, part of the Niagaran Reef Complex in Northern Michigan (USA), has been the focus of an enhanced oil recovery/carbon capture utilization and storage (EOR/CCUS) project as part of the Phase III-Midwest Regional Carbon Sequestration Partnership (Gupta et al., 2013a,b). The Dover 33 structure has experienced significant CO2 flooding in the past two decades, and over the course of the current injection study (between February 2013 and July 2016) has received approximately 100 to 1000 tonnes/day into the central injection well (L-M) 1–33). As part of the geochemical monitoring effort of the study, gas and fluid samples were collected from Dover 33 reef, and several other nearby reef structures, to assess the impact of CO2 injection on the geochemical processes occurring within in the reef.The injected gas is composed of approximately 95% CO2, with a δ13CCO2 of ∼20.5‰, which is consistent with previously published compositions of Antrim shale gas, the source of the CO2. The concentrations and isotopic compositions of higher pressure gas collected from the L-M 5–33 monitoring well were similar to those measured in the injection well, but did exhibit a small but systematic shift in isotopic composition towards lower values over the course of the study, suggesting mixing and dilution between the gas in the reservoir and the injected gas. In contrast the δ13CCO2 of gas samples from the monitoring well with the lower surface pressure, L-M 2–33, are consistently lower throughout the study, ∼18.5‰, indicating that reactions with the injected CO2 are occurring within the reef or with the well casing.Fluid samples were collected to assess the extent of interaction among the injected gas, the reservoir rock, and the brine. The brine samples are acidic (pH ∼ 4.1 to 4.9) with a total salt content of nearly 400 g/L. Analysis of the isotopic composition of dissolved inorganic carbon (DIC) in the Dover 33 brine shows that δ13C is higher than the injected gas (27–33‰) suggesting that the gas is not in equilibrium with DIC in the brine, and that there has been little isotopic exchange with carbonate minerals in the reef. The water isotope composition of the brine, δ18O and δD, plot below the meteoric water line, indicating that the water is not of recent meteoric origin and has undergone isotopic exchange with both gas and minerals within the reef structure. The 87Sr/86Sr ratios of the brine samples range from 0.70865 to 0.70869, consistent with Silurian seawater composition.Geochemical modelling of the brine composition shows that the predicted CO2 solubility as DIC is much greater than the measured DIC, and that the brines are supersaturated with respect to carbonate minerals, suggesting the potential for significant trapping of CO2 in both dissolved and mineral form.

Surface Energy Budget Observed for Winter Wheat in the North China Plain During a Fog–Haze Event

In recent winters, fog–haze events have occurred frequently over the North China Plain. To understand the characteristics of conventional meteorological conditions, the near-surface radiation balance, and the surface energy budget under different pollution levels, we analyzed data collected at an observation site in Gucheng, which is located in the Hebei province in North China, based on a campaign that ran from December 1 2016 to January 31 2017. We found that meteorological conditions with a lower wind speed, weakly unstable (stable) stratification, higher relative humidity, and lower surface pressure during the daytime (night-time) are associated with fog–haze events. On heavy pollution days (defined as days with a daily mean PM2.5 concentration > 150 μg m−3), the decrease in downward shortwave radiation (S↓) and the increase in downward longwave radiation (L↓) are significant. The mean S↓ (L↓) values on clean-air days (daily mean PM2.5 concentration < 75 μg m−3) and heavily polluted days was 222 (222) W m−2 and 124 (265) W m−2, respectively. Due to the negative (positive) radiative forcing of aerosols during the daytime (night-time), the daily maximum (night-time mean) net radiation (Rn) is negatively (positively) related to the daily mean PM2.5 concentration, the correlation coefficient between the daily maximum (night-time mean) Rn and daily mean PM2.5 concentration being − 0.47 (0.51). Diurnal variations in sensible heat flux (H) and latent heat flux (λE) are insignificant on heavily polluted days, the mean daily maximum H (λE) is only 40 (28) W m−2 on heavily polluted days, but reaches 90 (42) W m−2 on clean-air days. Additionally, the friction velocity, standard deviation of vertical velocity, and turbulent kinetic energy on heavily polluted days are also quantified.

Effect of Geologically Constrained Environmental Parameters on the Atmosphere and Biosphere of Early Earth

The Great Oxidation Event (GOE) about 2.3 gigayears ago denotes the first major rise of atmospheric molecular oxygen (O2) in Earth’s history. As a consequence, the planet experienced the emergence of widespread habitability and complex life. Recently, there has been a revolution in improved methods for constraining geological data for atmospheric pressure, composition, and ocean temperature of the early Earth. We investigate the effect of this revised data upon processes which drove the GOE. Results suggest that increasing Archean carbon dioxide (CO2) produces increased O2 with height due to enhanced CO2 photolysis. This is counterbalanced by stronger O2 destruction as a result of enhanced carbon monoxide (CO) (from increased CO2) and nitrogen oxides (NOx) (from decreased hydroxyl via increased CO). Pre-GOE atmospheres with low O2 yet high CO2 could counteract O2 accumulation. For low surface pressures of 0.5 bar, O2 decreases between 0.5 to 0.005 bar. This arose mainly from O2 destruction via hydrogen ox...