Characteristics of In-Situ Soil Water Hysteresis Observed through Multiple-Years Monitoring

A soil water retention curve (SWRC) is an essential soil physical property for analyzing transport and retention of water in a soil layer. A SWRC is often described as a single-valued function that relates the soil water potential ψ to volumetric water content θ of the soil. However, an in-situ ψ − θ relation should show soil water hysteresis, though this fact is often neglected in analyses of field soil water regimes while long-term in-situ soil water hysteresis is not well characterized. This study aimed at probing and characterizing in-situ ψ − θ relations. The developments of large hysteresis in the in-situ ψ − θ relations were observed only a few times during the study period of 82 months. Any of the large hysteretic behaviors in the ψ − θ relations began with an unusually strong continual reduction in ψ. The completion of a hysteresis loop required a recorded maximum rainfall. Because the study field had very small chances to meet such strong rainfall events, it took multiple years to restore the fraction of soil water depleted by the unusually strong continual reduction in ψ. While wetting-drying cycles had occurred within a certain domain of ψ, hysteretic behaviors tended to be so small that the in-situ ψ − θ relation can be approximated as a single-valued function of θ(ψ). These observed patterns of the in-situ ψ − θ relations were characterized by kinds of difference in dθ/dψ between a drying process and a wetting process at a given ψ. Thus, more amounts of experimental facts about wetting SWRCs in parallel with drying SWRCs should be needed for correct modelling, analyzing, and predicting soil water regimes in fields. It is also necessary to increase our understandings about the long-term trends of occurrences of extreme weather conditions associated with possible change in climate.

Vertical distribution of sand-dust aerosols and the relationships with atmospheric environment

The vertical distribution of aerosols in the troposphere is important for determining their effects on cli- mate. The vertical distribution of aerosols under different atmospheric conditions in the free troposphere was di- rectly observed using a surface micro-pulse LIDAR （MPL） and a TP/WVP-3000 microwave radiometer at the Semi-Arid Climate ＆ Environment Observatory of Lanzhou University （SACOL, 35.95~N, 104.10~E） in the western Loess Plateau, China, in the spring of 2008. The results showed two possible transportation paths of a sandstorm from May 1 to May 4 in 2008. In one path, sand-dust aerosols were transported toward the east from the Taklimakan Desert to the Badain Jaran Desert and the Tengger Desert by a westerly wind and then toward the southeast to Jingtai and Lanzhou. A weak aerosol index （AI） indicated another possible transport path toward the east from the Taklimakan Desert to the Qaidam Basin and through the Tibetan Plateau eastward to SACOL. The aerosol profile of sandstorm processes over the SACOL area displayed three patterns： a single peak distribution under stable at- mospheric conditions, indicating urban aerosol distribution; an exponential decrease under unstable atmospheric conditions in the presence of a sandstorm; and a slight change in the mixed layer during the first and last stages of the sandstorm, indicative of thorough mixing during lifting and deposition stages. Analyses of the aerosol layer height （ALH） showed that there are two types of ALH diurnal variation. The ALH during the first sandstorm stage was complex and disordered, and affected by atmospheric circulation. While the ALH had obvious diurnal variation in the other stage, the ALH and aerosol extinction coefficient （AEC） had a single peak, and was higher in the af- ternoon and lower in the morning. In the second case the ALH was in agreement with the atmospheric boundary layer height （BLH） variation. As a result of the development of the atmospheric boundary layer （ABL） during day and maintenance at night, ALH during sandstorm-free days showed obvious diurnal variations. Multiple vertical distribu- tion patterns of sand-dust aerosols will result in different climate effects; therefore, the vertical distribution patterns can be used to parameterize climate and aerosol models.

Laboratory studies on the infectivity of human respiratory viruses:Experimental conditions,detections,and resistance to the atmospheric environment

The environmental stability of infectious viruses in the laboratory setting is crucial to the transmission potential of human respiratory viruses.Different experimental techniques or conditions used in studies over the past decades have led to diverse understandings and predictions for the stability of viral infectivity in the atmospheric environment.In this paper,we review the current knowledge on the effect of simulated atmospheric conditions on the infectivity of respiratory viruses,mainly focusing on influenza viruses and coronaviruses,including severe acute respiratory syndrome coronavirus 2 and Middle East respiratory syndrome coronavirus.First,we summarize the impact of the experimental conditions on viral stability;these involve the methods of viral aerosol generation,storage during aging and collection,the virus types and strains,the suspension matrixes,the initial inoculum volumes and concentrations,and the drying process.Second,we summarize and discuss the detection methods of viral infectivity and their disadvantages.Finally,we integrate the results from the reviewed studies to obtain an overall understanding of the effects of atmospheric environmental conditions on the decay of infectious viruses,especially aerosolized viruses.Overall,this review highlights the knowledge gaps in predicting the ability of viruses to maintain infectivity during airborne transmission.

Pristine atmospheric condition over the Third Pole:An insight from levoglucosan records

Expanding urbanization and agricultural intensification across neighboring South Asia and East Asia have substantially threatened atmospheric condition over the Third Pole(TP)during the past few decades.Whether the atmospheric condition over the TP is still as clean as a representative of the regional background draws great concern.In this work,great differences in levoglucosan concentration within/above the atmospheric boundary layer height are revealed.Levoglucosan results support the hypothesis that atmospheric pollutants in the mid-troposphere over the TP are mainly affected by long-range transport,although there are some local biomass burning emissions in residential areas.In addition,levoglucosan concentration in the midtroposphere over the TP is at the same magnitude as marine and polar regions,but about 2–3 magnitudes lower than neighboring densely-populated Asian regions.With insights of levoglucosan records,this work therefore proves that the high-altitude TP still has largely pristine atmospheric conditions,and is one of the cleanest remote regions on the Earth.

The Nature and Predictability of the East Asian Extreme Cold Events of 2020/21

Three extreme cold events invaded China during the early winter period between December 2020 to mid-January 2021 and caused drastic temperature drops,setting new low-temperature records at many stations during 6−8 January 2021.These cold events occurred under background conditions of low Arctic sea ice extent and a La Niña event.This is somewhat expected since the coupled effect of large Arctic sea ice loss in autumn and sea surface temperature cooling in the tropical Pacific usually favors cold event occurrences in Eurasia.Further diagnosis reveals that the first cold event is related to the southward movement of the polar vortex and the second one is related to a continent-wide ridge,while both the southward polar vortex and the Asian blocking are crucial for the third event.Here,we evaluate the forecast skill for these three events utilizing the operational forecasts from the ECMWF model.We find that the third event had the highest predictability since it achieves the best skill in forecasting the East Asian cooling among the three events.Therefore,the predictability of these cold events,as well as their relationships with the atmospheric initial conditions,Arctic sea ice,and La Niña deserve further investigation.

THE EFFECT OF THE NEGATIVE ENTROPY FLOW ON THE ORGANIZATION OF ATMOSPHERIC DISSIPATIVE STRUCTURES IN NON-EQUILIBRIUM CONDITIONS

The entropy balance equation that describes the entropy budget of atmospheric systems is derived from the Gibbs relation.The distribution of the entropy flows of a west-Pacific typhoon and a Bengal-Bay cyclone is calculated and thus the dissipativity of the atmospheric systems is revealed.

Diagnosis of the Causes of the Rain Flooding in June in the West Africa Coastal Area

Rain flooding during June on the West Africa coastal area is analyzed by using the 95th and 75th percentiles, which represent extreme and intense rainfall events respectively. Thus, the contribution of these events that reaches around 50% shows their impact on the rainfall in June. Atmospheric and oceanic factors influence the rain flooding. Indeed, the extreme events are associated with easterly waves propagating from 20°E, while those of intense events are initiated around 5°E. The impact of oceanic conditions exhibits the warming of the equatorial rail and the Atlantic cold tongue, the warming of the whole ocean basin and a north-south dipole of SST anomalies. The West African monsoon that reaches Abidjan corresponds to a low-level atmospheric flow, whose upward motion extends in latitude from the ocean to the continent. An increase of disturbance contributes to enhancing these events. This is confirmed by the inflow on to the continent of oceanic moisture coming from the ventilation by evaporation of warm water. In addition, the coupled ocean-atmosphere simulations are one of the best candidates that could help to better explain these dramatic events. This study is useful because of showing solutions that could help in adoption of policies for the risks management related to these events.

Tuning band structure of graphitic carbon nitride for efficient degradation of sulfamethazine: Atmospheric condition and theoretical calculation

Numerous approaches have been used to modify graphitic carbon nitride (g-C_(3)N_(4)) for improving its photocatalytic activity. In this study, we demonstrated a facial post-calcination method for modified graphitic carbon nitride (g-C_(3)N_(4)-Ar/Air) to direct tuning band structure, i.e., bandgap and positions of conduction band (CB)/valence band (VB), through the control of atmospheric condition without involving any additional elements or metals or semiconductors. The synthesized g-C_(3)N_(4)-Ar/Air could efficiently degrade sulfamethazine (SMT) under simulated solar light, i.e., 99.0% removal of SMT with rate constant k1 = 2.696 h-1 within 1.5 h (4.9 times than pristine g-C_(3)N_(4)). Material characterizations indicated that the damaged/partial-collapsed structure and decreased nanosheet-interlayer distance for g-C_(3)N_(4)-Ar/Air resulted in the shift of band structure due to the denser stacking of pristine g-C_(3)N_(4) through oxidative exfoliation and planarization by air calcination. In addition, the bandgap of g-C_(3)N_(4)-Ar/Air was slightly shrunk from 2.82 eV (pristine g-C_(3)N_(4)) to 2.79 eV, and the CB was significantly upshifted from -0.44 eV (pristine g-C_(3)N_(4)) to -0.81 eV, suggesting the powerful ability for donating the electrons for O_(2) to form ^(·)O_(2)^(-). Fukui index (f -) based on theoretical calculation indicated that the sites of SMT molecule with high values, i.e., N9, C4 and C6, preferred to be attacked by ^(·)O_(2)^(-) and ^(·)OH, which is confirmed by the intermediates’ analysis. The tuning method for graphitic carbon nitride provides a simple approach to regulate the charge carrier lifetime then facilitate the utilization efficiency of solar light, which exhibits great potential in efficient removal of emerging organic contaminants from wastewater.

Physicochemical nature of iron oxidation in a damp atmospheric condition

The surface oxidation patterns of iron or low-carbon steels are critical to their life when serving in typical damp environments. An accurate determination of the oxidation pattern entails tracking the iron atoms oxidized at the iron/steel-moisture interface. Using a quantum chemistry-based force field that is capable of simulating chemical reactions, this paper studies the process of iron oxidation under a typical moist condition. The oxidation of iron surface was found to be highly thermodynamic and dependent on the availability of reactants. A triplex structure was formed at the end of a three-stage oxidation process to reduce the overall oxidation speed. The results from this study shed light on the atomistic mechanism of iron oxidation; therefore can be used to guide the protection of general ferrous-based iron/steel structures.

Analysis of the Haze Weather Process in the East of China from January 21 to 28, 2021

Haze is a pollution weather phenomenon that has been widely concerned by people in recent years. It has a significant impact on people’s production, life, and health. This study focuses on large-scale haze weather that happened in eastern China in late January 2021. The research uses multi-party data and synoptic analysis methods to analyze the occurrence, evolution, and end of the haze weather. The polar vortex, the change of the atmospheric circulation, the change of the cold air force, the temperature and humidity, and the rain and snow weather are the important reasons for this weathering process. It can be used for reference in future research on haze weather.

Evaluating the influence of air pollution on solar radiation observations over the coastal region of Alicante(Southeastern Spain)

The present study evaluates ground-based downward surface shortwave radiation (Rs) over the coastal region of Alicante (Southeastern Spain).Hourly measurements collected over the eleven-year period 2010-2020 are used.Two weather stations located over the region capital,Alicante,have been selected as representative of urban and suburban typologies.Two additional weather stations far from the city have been selected representing rural typologies.Rs is significantly reduced over the urban station during the morning hours within the winter season compared to the observations recorded over the suburban and rural stations,with a global mean difference of-81 and-120 W/m^(2)at 10 LT,respectively.However,no significant differences are obtained during the midday sun,with a global mean difference of-20 W/m^(2)between the urban and rural stations.With the aim of explaining these differences,the current paper investigates the relationship between Rsand different air pollutants:NOx,SO_(2),and fine particulate matter (PM_(2.5)and PM_(10)) as well as the wind field measured at the urban and suburban stations.The results found in this work point towards a close relationship between Rsand NOxconcentrations annual cycles,which are also influenced by the prevailing wind circulations observed over the study area.A global mean NOxconcentration of 107μg/m^(3)is observed over the urban station at 10 LT during the winter season.In contrast,these high concentrations are significantly reduced over the suburban station,with global mean value of 40μg/m^(3)at 10 LT,for this period of the year.

Trajectory modeling revealed a southwest-northeast migration corridor for fall armyworm Spodoptera frugiperda(Lepidoptera:Noctuidae)emerging from the North China Plain

The fall armyworm Spodoptera frugiperda,an invasive insect pest native to the Americas,has established populations throughout eastern China.The North China Plain一a key corn-producing area in East China with a unique topography一was invaded by fall armyworm in 2019 and is seriously threatened by this migratory pest.However,the spatiotemporal extent of the migratory movements of fall armyworm from the North China Plain remains poorly understood.Using an air transport-based trajectory modeling approach that incorporates flight behavior,we simulated the potential nocturnal migration trajectories of fall armyworm from the North China Plain based on historical meteorological data from June to October of 2015-2019,and examined the night-time atmospheric conditions associated with their possible flights.The emigration patterns showed monthly variation in the main landing area and common migration direction.The displacement of newly emerged moths from the North China Plain was concentrated in the Northeast China Plain(including Liaoning,Jilin and Heilongjiang provinces)before late summer,after which they were most likely to undertake return flights to the south(especially into Hubei,Anhui and Hunan provinces).This southwest-northeast aerial migration corridor follows the topography of East China and is affected by the East Asian monsoon.These topographic-atmospheric conditions have resulted in the North China Plain becoming a key stopover for fall armyworm populations engaging in multigenerational long-distance migration across East China.These findings contribute to our knowledge of fall army-worm migration and will aid in the implementation of management and control strategies against this highly migratory agricultural pest.

Greenhouse gas emissions from oilfield-produced water in Shengli Oilfield,Eastern China

Greenhouse gas（GHG） emissions from oil and gas systems are an important component of the GHG emission inventory. To assess the carbon emissions from oilfield-produced water under atmospheric conditions correctly, in situ detection and simulation experiments were developed to study the natural release of GHG into the atmosphere in the Shengli Oilfield,the second largest oilfield in China. The results showed that methane（CH4） and carbon dioxide（CO2） were the primary gases released naturally from the oilfield-produced water.The atmospheric temperature and release time played important roles in determining the CH4 and CO2emissions under atmospheric conditions. Higher temperatures enhanced the carbon emissions. The emissions of both CH4 and CO2from oilfield-produced water were highest at 27°C and lowest at 3°C. The bulk of CH4 and CO2was released from the oilfield-produced water during the first release period, 0–2 hr, for each temperature, with a maximum average emission rate of 0.415 g CH4/（m3·hr） and 3.934 g CO2/（m3·hr）, respectively. Then the carbon emissions at other time periods gradually decreased with the extension of time. The higher solubility of CO2 in water than CH4 results in a higher emission rate of CH4 than CO2over the same release duration. The simulation proved that oilfield-produced water is one of the potential emission sources that should be given great attention in oil and gas systems.

Analysis on the impact of two winter precipitation episodes on PM_(2.5) in Beijing

In this paper,the circulation background,the characteristics of meteorological elements configuration in the boundary layer and the stable meteorological conditions in two precipitation episodes(during February 19-21,2015 and February 10-13,2016,respectively)within the Beijing-Tianjin-Hebei region are compared and analyzed.Data from conventional meteorological observations,air quality monitoring,reanalysis and numerical models are used.The results show that before the two precipitation processes in 2015 and 2016,the circulations in the middle and high latitudes of Asia and Europe demonstrate“two troughs and one ridge”.Besides,the weather is stable and the pollutant concentration is relatively high.During the precipitation,the circulation is relatively stable for the episode in 2015,and no obvious change in the synoptic system is observed.However,during the episode in 2016,the formation of blocking high and the enhancement of the average ridge in western Asia cause obvious change in the circulation.The simulation results show that significant removal can be detected in both cases,and the PM_(2.5) wet deposition fluxes are 647 g/ha and 486 g/ha,respectively,with the removal in 2015 slightly stronger than that in 2016.The removal and dissipation of pollutants is determined by the atmospheric diffusion conditions and the precipitation,especially in the former episode.In the case of February 2016,good diffusion conditions and the precipitation demonstrate obvious PM_(2.5) removal effect.In the case of February 2015,the longstanding calm wind with high humidity and the physical quantity configuration in the lower mixed layer lead to the poor pollutant removal.