Explanations for simultaneous laminae in water vapor and aerosol profiles found during the SESAME experiment

An instrumented balloon launched from Kiruna during the SESAME experiment displayed simultaneous local decreases of water vapor and aerosol at 2 different potential temperature levels 410 K and 364 K. Despite the similar characteristics present at both levels, 2 different explanations are given for these laminae. At the highest level, the air mass showing the water vapor and aerosol decrease is found when the balloon travels in the vortex edge region. A back trajectory shows that this air mass was trapped in the vortex edge region for several days and processed by a PSC causing the water vapor and aerosol decreases. On the other hand, the lowest level air mass was found to be in the sub‐vortex region. No local conditions can explain the observed decreases of water vapor and aerosol. Back trajectories show that this air mass originates from middle latitudes. Although the back trajectories calculated in these conditions are more subject to caution, comparison of several characteristics at the measurement point and at the middle latitude sites corroborates the explanation of the decrease of water vapor and aerosol by the origin of the air mass.     

Cloud condensation nuclei activity of the Aitken mode particles near St. Petersburg,Russia

Aitken mode atmospheric particles largely control the formation and transformation of cloud systems, which in turn have an effect on their radiative properties. In this paper, a measurement technique for the cloud condensation nuclei (CCN) activity of monodisperse particles is described and the measurement data (results) obtained for monodisperse aerosol fractions with diameters of 60, 80, and 100 nm are presented. The measurements were performed during March and April 2014 at the urban background station located in a suburban area of St. Petersburg. The CCN concentration in the water-vapor supersaturation range of 0.1–1.1% and the cloud particle activation parameters were determined. The fraction of active particles capable to serve as CCN is found to be less than 33%, which is characteristic of anthropogenic aerosols containing hydrophobic organic components. Based on the measurement data, the hygroscopicity parameter κ characterizing the chemical composition effect on condensational properties of particles has been determined. During the measurement campaign, the value of the hygroscopicity parameter varied between 0.1 and 0.8. The lower limit of κ corresponds to organic species and its higher values occurs due to presence of hygroscopically active inorganic species in particles. The average value of κ was estimated to be 0.34 ± 0.19, which is in good agreement with literature data obtained for megapolises and European continental aerosols.     

Modeling radiative forcing by background aerosol on the basis of measurement data

The solar radiation flux incident on the land surface and aerosol radiative forcing are calculated from measurements carried out under clear skies during the summers of 2004 and 2005 at the Zvenigorod Scientific Station (ZSS) of the A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences. In these calculations, the following five models of aerosol optical parameters are used: a standard model of continental aerosol, a semiempirical model based on measurement data, and three models obtained from calculations on the basis of the Mie scattering theory for the mean size distribution of aerosol particles (which is retrieved from aureole measurements). A study of the sensitivity of the flux and forcing to the choice of aerosol model has shown that the relative error related to the model choice is not large (<5%) for the incident radiation flux and reaches 120% for aerosol forcing at the atmospheric upper boundary. The aerosol radiative forcing at the atmospheric upper boundary is also estimated and, according to our calculations, varies from −15 to −2 W/m². The use (in calculations) of the values of the albedo of single-scattering and the factor of scattering-indicatrix asymmetry at a wavelength of 550 nm, which were obtained for each of the observation periods, has made it possible to significantly refine the value of aerosol radiative forcing (compared to that calculated for the means of these parameters over all the periods). An even more accurate determination of aerosol radiative forcing is possible only when data on the size-distribution of aerosol particles and their chemical composition for a certain situation under analysis are available. As a result of this study, two models of the optical parameters of background aerosol have been proposed for use in radiation calculations: a semiempirical model and a mean model obtained from the calculations based on the theory of scattering. Both models use the values of the albedo of single scattering and the factor of asymmetry (at a wavelength of 550 nm) retrieved from the measurements for each of the observation periods.     

Influence of chemical composition and microstructure on the hygroscopic growth of pyrogenic aerosol

The hygroscopic properties of a model smoke aerosol series including ammonium sulfate, levoglucosan, and oxalic and humic acids were investigated. The condensation growth of particles and the relative humidity of direct and inverse particle-droplet phase transitions were measured with a tandem differential mobility analyzer. The data were obtained in the range of relative humidity from 4 to 95% at 298 K. Experimental growth factors were compared to the results of Koehler theory by using contemporary models of water activity in particles. It was shown that the hygroscopic properties of the aerosols were substantially different from the hygroscopic properties of the corresponding bulk phases. It was found that a complex microstructure of nanoparticles resulted in excess volume absorption of water, in some cases causing their full deliquescence at lower relative humidities than in macrosystems of identical composition. From the measurement data, a parametrization of hygroscopic particle growth was performed. The results of parametrization can be used to construct refined models of a smoke aerosol.     

Variations of the aerosol concentration and chemical composition over the arid steppe zone of Southern Russia in summer

Variations in the surface aerosol over the arid steppe zone of Southern Russia have been measured. The parameters of atmospheric aerosol (mass concentration, both dispersed and elemental compositions) and meteorological parameters were measured in Tsimlaynsk raion (Rostov oblast). The chemical composition of aerosol particles in the atmospheric surface layer has been determined, and the coefficients of enrichment of elements with respect to clarkes in the Earth’s crust have been calculated. It is shown that, in summer, arid aerosols are transported from both alkaline and sandy soils of Kalmykia to the air basin over the observation zone. Aerosol particles in the surface air layer over this region have been found to contain the products of combustion of oil, coal, and ethylized fuel. These combustion products make a small contribution to the total mass concentration of atmospheric aerosol; however, they are most hazardous to the health of people because of their sizes and heavy-metal contents. A high concentration of submicron sulfur-containing aerosol particles of chemocondensation nature has been recorded. Sources of aerosol of both natural and anthropogenic origins in southern Russia are discussed.     

Brown Carbon and Black Carbon in the Smoky Atmosphere during Boreal Forest Fires

We have investigated the variability of smoke aerosol absorbing ability with variations in the content of brown carbon (BrC) and black carbon (BC). Using monitoring data on radiative characteristics of smoke aerosol at AERONET stations and the spatial distribution of aerosol optical depth (AOD) obtained by the MODIS spectrometer (Terra satellite), we have detected large-scale smokes during boreal forest fires in Russia and Canada (1995–2012). The spatial distribution (50°–70° N, 95°–125° W) and temporal variability (at AERONET station Fort McMurray) of AOD during the smoking of a part of Canada in July 2012 have been analyzed. AOD probability distributions for July 14–18, 2012, and an estimate of aerosol radiative forcing of smoke aerosol at the upper boundary of the atmosphere have been obtained. We have proposed a technique for the diagnostics of BrC and BC in smoke aerosol particles from the spectral dependence of the imaginary part of the refractive index. At a wavelength of 440 nm, the contributions of BrC and BC to the smokeaerosol absorbing abitity can be comparable in magnitude. In many cases, the absorption spectra of smoke aerosol can be adequately approximated by either power or exponential functions. The presence of BrC in smoke-aerosol particles highly extends the variety of observed absorption spectra in a smoky atmosphere and spectral dependences of single scattering albedo. In the spectral range of 440–1020 nm, the radiative characteristics of smoke aerosol are largely contributed by its fine mode.     

Characterization of the proteinaceous matter in marine aerosols

Marine aerosols play a dominant role in the transfer of oceanic material to the atmosphere. Most marine aerosol originates when air bubbles burst at the sea surface ejecting material from the sea surface microlayer and bubble surface layers into the air. Concentrations of chemical compounds in these surface layers often differ from their concentrations in bulk water. We examined the enrichment of aerosols with proteinaceous matter and attempted to characterize the physical nature and sources of this matter. We measured concentrations of dissolved free (DFAA), dissolved combined (DCAA), and particulate (PAA) amino acids, transparent stainable particles (TSP), and bacteria and virus-like particles as carriers of protein, in natural and simulated aerosols. We also evaluated D/L ratios certain amino acids in all amino acid fractions.DFAA and DCAA enriched the aerosols we sampled by 1.2–20 times compared to bulk seawater; PAA enrichment was usually higher (up to 50-fold). Aerosols contained particles typical of seawater, e.g., microorganisms, organic debris, inorganic particles with adsorbed organic matter, but also a large number of semitransparent gel-like particles, which all contained amino acids. Some of these particles were probably scavenged from bulk water, but new particles produced as bubbles burst at the surface comprised at least 10% of total proteinaceous matter in the aerosol. D/L ratios of certain amino acid suggested that the particles were most likely made from dissolved polymers secreted by phytoplankton that were concentrated on bubble surfaces and in the microlayer. Examination with Alcian Blue (a dye that targets carbohydrates) and Coomassie Blue (a dye that targets proteins) showed that most TSP in the aerosols contained both proteins and polysaccharides. Microorganisms enriched the aerosols by up to two orders of magnitude, but contributed less than 4% to the total protein pool.     

A STUDY OF MOISTURE BUDGET OF A TYPHOON

This paper deals with the study of moisture budget of the typhoon No. 7507. The results show that the mass convergence produced by divergent wind has made the maximum contribution to precipitation, especially at the lower level, accounting for about 70% of the total precipitation, and that the advection term of water vapor is very small. The vertical flux term is to transport water vapor from the lower level to the middle and upper levels, resulting in the increase of water vapor accumulation at these levels. Evaporation term also plays an important role in precipitation, accounting for about 13% of the total precipitation and 23% of the horizontal moisture convergence. The moisture of the typhoon comes mainly from its southern boundary and the secondary inflow of moisture is from its western or eastern boundary. All the inflow layers of these three boundaries are very deep, reaching up to 300 hPa, while the strongest inflow occurs below 700 hPa. In the northern boundary of the typhoon, we obtained that     

Determination of stratospheric aerosol parameters from two-wavelength lidar sensing data

We calculate the microphysical characteristics of stratospheric aerosol from lidar-sensing data at wavelengths of 355 and 532 nm using a priori information about the aerosol spectra obtained from balloon and aircraft measurement data. We analyze the mode structure of the spectra and its coupling with the integral microphysical characteristics of aerosol. For most implementations, it was shown that two aerosol modes (of background and volcanic natures) make commensurate contributions to integral aerosol characteristics, which makes it difficult to use the traditional method of model estimates. It is more efficient to use an optical model of a statistical character that is based on approximation dependences between the required integral aerosol characteristics and lidar-measured optical characteristics. We found that the area, volume, and effective size of particles and the lidar ratio at a wavelength of 355 nm correlated with the absolute values of backscattering coefficients at wavelengths of 355 or 532 nm and the lidar ratio at the wavelength of 532 nm correlated with the ratio of backscattering coefficients at these wavelengths. We estimate the error in the determination of integral characteristics of aerosol using the model developed. The model efficiency is demonstrated on real data of stratospheric aerosol lidar sensing.     

The Increase of Biogenic Sulfate Aerosol and Particle Number in Marine Atmosphere over the Northwestern North Pacific

During a cruise aboard the R/V Hakuho-maru in the northwestern North Pacific in the summer of 1998 the particle number concentrations and the major ionic components of size fractionated aerosols were measured to investigate the aerosol produced by marine biological activity. Continuous low concentrations of nitrate (<1.8 nmol m⁻³), similar to the marine air background level, were found over the northwestern North Pacific (40–45°N) and the Sea of Okhotsk (44–45°N). Over the Sea of Okhotsk, a high concentration of chlorophyll-a (5.4 mg m⁻³) in seawater was observed, and atmospheric concentrations of non sea-salt (nss-) sulfate (44 nmol m⁻³), methane sulfonic acid (MSA) (1.8 nmol m⁻³) and particle number in the size range of 0.1 < D < 0.5 μm (199 cm⁻³) were found to be 9, 7, and 2 times, respectively, higher than those in the background marine air. The increase in particle number concentrations mainly in the size range of 0.2 < D < 0.3 μm was likely caused by the increase of biogenic sulfate over the high productive region of the Sea of Okhotsk. In humid air conditions (R.H. > 96%), the increased biogenic sulfate that condensed the large amount of water vapor would not have sufficient solute mass to activate as cloud condensation nuclei (CNN) and would remain as aerosol particles in the marine air with frequent sea-fogs over the high productive region. Biogenic sulfate originating from dimethyl sulfide (DMS) would gradually grow into the CCN size and continuously supply a great number of CCN to the marine air in the northwestern North Pacific. This revised version was published online in July 2006 with corrections to the Cover Date.     

Internal mechanism of metastable liquid water crystallization and its effects on intracloud processes

Specific features of an internal freezing (crystallization) mechanism for both ordinary supercooled water and amorphous water (A-water) are considered. Amorphous water plays the role of an intermediate phase in condensation ice formation and is capable of metastable existence in the form of cloud drops. It is demonstrated that, after passing the crystallization front, the ice phase takes the liquid-phase volume and the excessive water mass is detached from the front in the form of free molecules, which escape through the liquid into the gaseous medium. The released energy of the phase transition is removed with these molecules, so that the formed ice retains the initial temperature of the liquid. A high-rate vapor outflow from the freezing drop generates (around the drop) a zone of microscale turbulence, which accelerates the mass exchange between cloud particle and vapor. Since the freezing frequency of drops in a cloud increases with their size, the effects of their freezing develop initially in time. At the same time, these effects initiate such processes that end in a complete evaporation of supercooled water drops and in a sharp enlargement of A-water and ice particles, i.e., in cloud transition to such a phase-mixed state where the liquid disperse phase consists of A-water drops. A reduction in the duration of the initial (fine-dispersed) stage of the evolution of clouds with their temperature lowering can be explained only by the development of microscale disturbances as a result of the freezing of drops.     

Estimation of the PAR irradiance ratio and its variability under clear-sky conditions at ieodo in the east china sea

Determining ‘photosynthetically active radiation’ (PAR) is a key part of calculating phytoplankton productivity in a biogeochemical model. We explore the daily and seasonal variability in the ratio of PAR irradiance to total irradiance that occurred at Ieodo Ocean Research Station (IORS) in the East China Sea under clear-sky conditions in 2004 using a simple radiative transfer model (RTM). Meteorological data observed at IORS and aerosol optical properties derived from Aerosol Robotic Network observations at Gosan are used for the RTM. Preliminary results suggest that the use of simple PA R irradianceratio values is appropriate in calculating phytoplankton productivity as follows: an average of 0.44 (±0.01) in January to an average of 0.48 (±0.01) in July, with average daily variabilities over these periods of about 0.016 (±0.008) and 0.025 (±0.008), respectively. The model experiments demonstrate that variations in the major controlling input parameters (i.e. solar zenith angle, precipitable water vapor and aerosol optical thickness) cause PAR irradiance ratio variation at daily and seasonal timescales. Further, increases (>0.012) in the PAR irradiance ratio just below the sea-surface are positively correlated with high solar zenith angles and strong wind stresses relative to those just above the sea-surface.     

Estimation of annual variation of water vapor in the Arctic Ocean between 80°–87°N using shipborne GPS data based on kinematic precise point positioning

The measurement of atmospheric water vapor(WV) content and variability is important for meteorological and climatological research. A technique for the remote sensing of atmospheric WV content using ground-based Global Positioning System(GPS) has become available, which can routinely achieve accuracies for integrated WV content of 1–2 kg/m2. Some experimental work has shown that the accuracy of WV measurements from a moving platform is comparable to that of(static) land-based receivers. Extending this technique into the marine environment on a moving platform would be greatly beneficial for many aspects of meteorological research, such as the calibration of satellite data, investigation of the air-sea interface, as well as forecasting and climatological studies. In this study, kinematic precise point positioning has been developed to investigate WV in the Arctic Ocean(80°–87°N) and annual variations are obtained for 2008 and 2012 that are identical to those related to the enhanced greenhouse effect.     

大气气溶胶干沉降对海域微量金属输入的研究现状

对国内外学者近年来在大气干沉降对海域微量金属输入方面的研究工作做了较为系统的综述 :包括样品采集、分析、干沉降通量估算和污染物来源识别。重点讨论了常用分析方法的优缺点以及它们在气溶胶物理、化学性质研究中的应用和已取得的成果 ,旨在为气溶胶分析方法的选择提供参考。     

Sinking Particle Flux in the Subtropical Oligotrophic Northwestern Pacific from a Short-term Sediment Trap Experiment

Time-series sediment traps were deployed in the subtropical oligotrophic northwestern Pacific (SONP) at three depths from August to September 2015 to better understand vertical flux of sinking particles. Sinking particles were collected at 5-day intervals over the sediment trap deployment period. The average total mass flux at water depths of 400 m, 690 m, and 1,710 m was 9.1, 4.4, and 4.1 mg m^-2day^-1, respectively. CaCO₃ materials constituted 50 to 70% of sinking particles while in comparison particulate organic carbon (POC) constituted up to 20%. A synchronous variation of total mass flux was observed at the three depths, indicating that calcite-dominated particles sank from 400 to 1,710 m within a 5-day period. POC flux at these water depths was 2.4, 0.38, and 0.31 mg m^-2day^-1, respectively. Our results indicate low transfer efficiencies of 16% from 400 to 690 m and 13% for the 400 to 1,710 m depth range. The estimated transfer efficiencies were significantly lower than those observed at the K2 station in the northwest Pacific subarctic gyre, presumably because of a prevalence of pico-cyanobacteria in the SONP. Because cyanobacteria have a semi-permeable proteinaceous shell, they are more readily remineralized by bacteria than are siliceous phytoplankton in the northwest Pacific subarctic gyre. Continued surface water warming and expansion of the SONP will likely have a profound impact on ocean acidification in the northwest Pacific, possibly affecting the transfer efficiency of sinking POC to the deep-sea.     

袁河流域极端降水事件成因分析

利用欧洲中期天气预报中心格点再分析资料和HYSPLIT模式对袁河流域5次极端降水天气过程的平均环流背景、主要影响系统、物理量场以及降水发生过程中的120 h气块后向轨迹特征进行分析。结果发现:(1)极端降水发生时,高层袁河流域处于南亚高压东侧辐散气流中,中层副热带高压位置适中,受584 dagpm线附近的西南气流控制,低层正好处于切变线上,且有强盛的西南气流向降水区输送能量和水汽。(2)物理量场上,袁河流域附近低层辐合、高层辐散,垂直速度场、水汽分布、水汽通量散度场都有利于该区域出现暴雨天气。(3)与袁河流域一般性暴雨的平均t-lnp图对比分析可见,极端暴雨的能量条件更好,降水对流性更强,水汽条件也更为充沛。(4)袁河流域极端降水上空的水汽路径总体上可以归纳为5条。来源于孟加拉湾附近、中南半岛南部和云南南部的西南水汽路径最多,占轨迹总数的59.5%;其次是来源于我国南海的南方路径,主要位于1 500 m以下,占轨迹总数的15.0%。     

Aerosol optical thickness and the total carbon monoxide content over the European Russia territory in the 2010 summer period of mass fires: Interrelation between the variation in pollutants and meteorological parameters

The spatial and temporal variabilities of the aerosol optical thickness (AOT) and the total carbon monoxide content (CO) in the period of development and weakening of mass forest and peatbog fires in the European Russia territory (ERT) in the summer of 2010 are investigated from data of the AOT and CO satellite observations. The intensities of aerosol and CO emissions in the period of mass fires and the ratio of the emission factors of aerosol particles and CO are estimated on the basis of calculations of the smoke and CO masses over the ERT. The interrelation between variations in the levels of the regional pollution by combustion products and the variability of meteorological parameters is investigated. Various aspects of the manifestation of radiation effects of aerosols are discussed. The synchronization of weekly signals of the AOT, CO, and meteorological parameters in the period of mass fires is noted.     

Interannual variation of atmospheric mass and the southern oscillation

Two reanalysis datasets, one generated by the Goddard Laboratory for Atmospheres for 1982–1993 and the other generated by the National Centers for Environmental Prediction for 1982–1995, are used to examine the relationship between the Southern Oscillation (SO) and the interannual variation of atmospheric mass. Both reanalyses show that atmospheric mass increases (decreases) during the positive (negative) SO phase. Atmospheric mass consists of dry air and moisture. Since dry mass is conserved, the interannual variation of atmospheric mass results from the variation of water vapor pressure. Thus, global atmospheric hydrological processes are analyzed to illustrate how the SO affects the interannual variation of atmospheric mass. During the positive (negative) SO phase, water vapor is converged (diverged) toward (out of) the central-eastern tropical Pacific [where sea surface temperatures (SSTs) are higher (lower) than normal] to maintain (suppress) cumulus convection in that area. An anomalous east-west Walker circulation straddling the Dateline is driven by the anomalous cumulus convection in this region to create positive (negative) surface pressure anomalies over the western tropical Pacific-Indian Ocean, which result in an increase (decrease) in atmospheric mass.     

Chemical composition and microphysical characteristics of atmospheric aerosol over moscow and its vicinity in June 2009 and during the fire peak of 2010

The microphysical characteristics of aerosol were measured in the atmospheric surface layer simultaneously over the center of Moscow and its vicinity (Zvenigorod Scientific Station, Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences) from June 15 to June 30, 2009, in order to compare the mass concentrations, particle-size distribution functions, and elemental compositions of aerosol over the megapolis and the background zone. During the fire peak of 2010, on August 8, aerosol samples were taken in the center of Moscow and their chemical composition was determined. Comparing results obtained from the simultaneous measurements of the concentrations of aerosol and its elemental composition made it possible to determine their interdiurnal variability, which suggests that the features of time variations are of a regional character and they are determined mainly by the dynamics of the synoptical processes of air-mass exchange. The chemical composition of obtained samples was determined using the method of atomic absorption spectrometry. The measurement results obtained in June 2009 revealed an increase in the content of anthropogenic elements in the atmosphere over Moscow when compared to their content in the atmosphere over the background zone. In Moscow, during the summer fires of 2010, the concentration of sulfur exceeded its concentration in June 2009 by an order of magnitude, and the concentrations of Na, Mg, Al, Si, K, Ca, and Fe increased several times. The mean mass concentration of aerosol amounted to 917 μg/m³ in August 2010 and 50–70 μg/m³ in June 2009.     

Assessment of the Jason Microwave Radiometer's Measurement of Wet Tropospheric Path Delay Using Comparisons to SSM/I and TMI

The Jason microwave radiometer (JMR) provides a crucial correction due to water vapor in the troposphere, and a much smaller correction due to liquid water, to the travel time of the Jason-1 altimeter radar pulse. An error of any size in the radiometer's measurement of wet path delay translates as an error of equal size in the measurement of sea surface height, the ultimate quantity that the altimetric system should yield. The estimate of globally-averaged sea surface height change associated with climate change, requires that uncertainties in the trends in such a global average be accurate to much better than the signal of 1–2 mm/yr. We first compare the JMR observations to those from the TOPEX/Poseidon radiometer (TMR) over approximately six months, since the intent of Jason is to continue the 10-year time series of precision ocean surface topography initiated by T/P. We then assess the stability of the JMR measurement by comparing its wet path delay to those of other orbiting radiometers over 22 months, specifically the Special Sensor Microwave Imager aboard the Defense Meteorological Satellite Program (DMSP-SSM/I) series of satellites, and the Tropical Rainfall Mapping Mission's Microwave Imager (TMI), as well as the European Center for Medium Range Weather Forecasting's (ECMWF) atmospheric numerical model estimate of water vapor. From the combined set, we obtain a robust assessment of the stability of JMR measurements. We find, that JMR is in remarkable agreement with TMR, only 2.5 mm longer, and 6–7 mm standard deviation on their difference in 0.5 degree averages; that JMR has experienced a globally-averaged step-function change, yielding an apparent shortening in wet path delay estimates of 4–5 mm around October 2002 (Jason cycles 28–32); that this step-function is visible only in the 23.8 GHz channel; and that the 34 GHz channel appears to drift at a rate of ?0.4K/year. In addition, we find that, while in 2002 there was no evidence of sensitivity to the Jason satellite's attitude (a correlation of the wet path delay with yaw state), in 2003 there are strong (2–3 mm, up to 7 mm globally averaged) changes associated with such yaw state. These JMR issues were all found in the first 22 months of Jason's geophysical data records (GDR) data, and thus they apply to any investigations that use such data without further corrections.