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1.
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.  相似文献   

2.
The aerosol longwave radiative forcing of the atmosphere and heating rate of the near-surface aerosol layer are estimated for the extreme smoke conditions in the Moscow region in summer 2010. Thermal radiation fluxes in the atmosphere are determined using the integral transmission function and semiempirical aerosol model developed on the basis of standard aerosol models and measurements at the Zvenigorod Scientific Station, Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences. The aerosol radiative forcing reached 33 W/m2 at the lower atmospheric boundary and ranged between–1.0 and 1.0 W/m2 at the upper atmospheric boundary. The heating rate of the 10-m atmospheric layer near surface was up to 0.2 K/h during the maximum smoke conditions on August 7–9. The sensitivity of the aerosol longwave radiative forcing to the changes in the aerosol absorption coefficient and aerosol optical thickness are estimated.  相似文献   

3.
Temperature and radiation effects of the 2010 summer fires are estimated on the basis of measurements at the Zvenigorod Scientific Station (ZSS) of the Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (RAS), in the Moscow region. The surface air temperature during the 2010 summer smoke varied in antiphase with the aerosol mass concentration, and the thermal radiation balance in the surface layer of the atmosphere varied in phase. Under extreme smoke of the surface layer in August 2010, the reduction in surface air temperature at ZSS has been found to reach 4 K with an increase in the downward flux of thermal radiation by an average of 20 W/m2 and a decrease in the difference between upward and downward fluxes of thermal radiation by an average of 24 W/m2.  相似文献   

4.
The evolution of smoke plume over European Russia (ER) during the massive forest and peatbog fires of summer 2010 has been studied using observations of aerosol optical depth (AOD) from MODIS instruments (both Aqua and Terra platforms), objective analysis of meteorological fields performed at the Russian Hydrometeorological Research Center, NCEP/NCAR reanalysis, as well as upper air data. A relation between the structure inhomogeneities of the AOD field and regional atmospheric circulation has been found. It is shown that, on August 5–9, 2010, the maximum of smoke pollution did complete turn around Moscow, while remaining at a distance of 200 to 650 km from the megacity. Both regionally averaged shortwave aerosol radiative forcings (ARFs) at the top and the bottom of the atmosphere are estimated for the period of extreme smoke pollution over ER. The spatial distributions of ARF values over the territory of the region and the estimates of the local and spatially distributed thermal effects of smoke aerosol are given. It is shown that, on August 5–9, 2010, the spatial distribution of AOD and the calculated thermal effects of smoke aerosol were in agreement with the spatial distributions of air-temperature anomalies observed in the lower 1.5-km layer of the atmosphere. MODIS’s AOD data obtained during the wildfires were validated by AOD observations from the CIMEL sun photometer operated at the AERONET station Zvenigorod.  相似文献   

5.
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.  相似文献   

6.
Estimates of some aerosol and radiation characteristics of the atmosphere in the summer of 2010 are obtained according to the results of the measurements made at the Meteorological Observatory (MO) at Moscow State University and are compared with the results of the measurements performed in 2002 and 1972 during the forest and peat fires. In contrast to 1972 and 2002, the period under study in 2010 is characterized by a greater frequency of the highest class of fire danger according to Nesterov, higher aerosol optical depths of the atmosphere up to 4.6, and a more significant weakening of solar radiation in different spectrum regions. In 2010 the smoke aerosol caused losses of the total shortwave radiation of 33%, visible radiation of 39%, ultraviolet radiation of 300–380 nm of 51%, and erythemal radiation of 63%. At the same time, an increase in the downward long-wave radiation to 40–50 W/m2 under extreme aerosol optical depths is recorded.  相似文献   

7.
Time-series measurements of dissolved inorganic carbon (DIC) and nutrient concentrations were conducted in the northwestern North Pacific from October 2002 to August 2004. Assuming that data obtained in different years represented time-series seasonal data for a single year, vertical distributions of DIC and nutrients showed large seasonal variabilities in the surface layer (∼100 m). Seasonal variabilities in normalized DIC (nDIC) and nitrate concentrations at the sea surface were estimated to be 81–113 μmol kg−1 and 12.7–15.7 μmol kg−1, respectively, in the Western Subarctic Gyre. The variability in nutrients between May and July was generally at least double that in other seasons. In the Western Subarctic Gyre, estimations based on statistical analyses revealed that seasonal new production was 39–61 gC m−2 and tended to be higher in the southwestern regions or coastal regions. The seasonal new productions in the northwestern North Pacific were two or more times higher than in the North Pacific subtropical gyre and the northeastern North Pacific. It is likely that this difference is due to spatial variations in the concentrations of trace metals and the species of phytoplankton present. In addition, from estimations of surface pCO2 it was verified that the Western Subarctic Gyre is a source of atmospheric CO2 between February and May and a sink for CO2 between July and October.  相似文献   

8.
利用第六次国际耦合模式比较计划（Coupled Model Intercomparison Project Phase 6, CMIP6）中的两组子试验,结合线性斜压模式模拟的结果,研究了近年来亚洲内部出现的东亚减少、南亚增加的偶极子型人为气溶胶排放变化调控亚洲夏季风响应的特征及物理机制。对东亚夏季风而言,在考虑海洋-大气耦合作用的气候系统总响应中,东亚夏季风环流和降水显著地加强;在不考虑海洋调控作用的大气直接响应过程中,东亚人为气溶胶排放减少导致的陆地升温使得海陆温差增大,进而通过引起东亚陆地上的气旋式环流异常加强东亚夏季风环流和降水。对南亚夏季风而言,其在偶极子型人为气溶胶强迫下呈现出更为复杂的变化特征。在大气直接响应过程中,人为气溶胶强迫引起的海陆热力差异变化导致南亚夏季风环流减弱、降水减少。在考虑海洋-大气耦合过程的总响应中,南亚夏季风环流表现出微弱增强,同时印度次大陆的南亚夏季风降水也出现增多的异常变化。这表明,局地和海洋-大气动力耦合过程在区域气候对人为气溶胶强迫的响应中扮演着非常重要的角色。此外,通过线性斜压模式发现,东亚和南亚局地的人为气溶胶强迫导致的大气加热场异常不仅能影响局地的夏季风环流,还可以通过引起大范围的表面气压异常进而调控整个亚洲夏季风环流的变化。  相似文献   

9.
Based on the surface drifters that moved out from the Sea of Okhotsk to the Pacific, the surface velocity fields of mean, eddy, and tidal components in the Oyashio region are examined for the period September 1999 to August 2000. Along the southern Kuril Island Chain, the Oyashio Current, having a width of ∼100 km, exists with velocities of 0.2–0.4 m s−1. From 40°N to 43°N, the Subarctic Current flows east- or northeastward with velocities of 0.1–0.3 m s−1, accompanied by a meandering Oyashio or Subarctic front. Between the Oyashio and Subarctic current regions, an eddy-dominant region exists with both cyclonic and anticyclonic eddies. The existence of an eastward flow just south of Bussol' Strait is suggested. The 2000 anticyclonic warmcore ring located south of Hokkaido was found to have a nearly symmetric velocity structure with a maximum velocity of ∼0.7 m s−1 at 70 km from the eddy center. Diurnal tidal currents with a clockwise tidal ellipse are amplified over the shelf and slope off Urup and Iturup Islands, suggesting the presence of diurnal shelf waves. From Lagrangian statistics, the single-particle diffusivity is estimated to be ∼10 × 107 cm2s−1.  相似文献   

10.
Seasonal evolution of surface mixed layer in the Northern Arabian Sea (NAS) between 17° N–20.5° N and 59° E-69° E was observed by using Argo float daily data for about 9 months, from April 2002 through December 2002. Results showed that during April - May mixed layer shoaled due to light winds, clear sky and intense solar insolation. Sea surface temperature (SST) rose by 2.3 °C and ocean gained an average of 99.8 Wm−2. Mixed layer reached maximum depth of about 71 m during June - September owing to strong winds and cloudy skies. Ocean gained abnormally low ∼18 Wm−2 and SST dropped by 3.4 °C. During the inter monsoon period, October, mixed layer shoaled and maintained a depth of 20 to 30 m. November - December was accompanied by moderate winds, dropping of SST by 1.5 °C and ocean lost an average of 52.5 Wm−2. Mixed layer deepened gradually reaching a maximum of 62 m in December. Analysis of surface fluxes and winds suggested that winds and fluxes are the dominating factors causing deepening of mixed layer during summer and winter monsoon periods respectively. Relatively high correlation between MLD, net heat flux and wind speed revealed that short term variability of MLD coincided well with short term variability of surface forcing.  相似文献   

11.
Using time series of hydrographic data in the wintertime and summertime obtained along 137°E from 1971 to 2000, we found that the average contents of nutrients in the surface mixed layer showed linear decreasing trends of 0.001∼0.004 μmol-PO4 l−1 yr−1 and 0.01∼0.04 μmol-NO3 l−1 yr−1 with the decrease of density. The water column Chl-a (CHL) and the net community production (NCP) had also declined by 0.27∼0.48 mg-Chl m−2 yr−1 and 0.08∼0.47 g-C-NCP m−2 yr−1 with a clear oscillation of 20.8±0.8 years. These changes showed a strong negative correlation with the Pacific Decadal Oscillation Index (PDO) with a time lag of 2 years (R = 0.89 ± 0.02). Considering the recent significant decrease of O2 over the North Pacific subsurface water, these findings suggest that the long-term decreasing trend of surface-deep water mixing has caused the decrease of marine biological activity in the surface mixed layer with a bidecadal oscillation over the western North Pacific.  相似文献   

12.
Air-sea interaction, coastal circulation and primary production exhibit an annual cycle in the eastern Arabian Sea (AS). During June to September, strong southwesterly winds (4∼9 m s−1) promote sea surface cooling through surface heat loss and vertical mixing in the central AS and force the West India Coastal Current equatorward. Positive wind stress curl induced by the Findlater jet facilitates Ekman pumping in the northern AS, and equatorward-directed alongshore wind stress induces upwelling which lowers sea surface temperature by about 2.5°C (compared to the offshore value) along the southwestern shelf of India and enhances phytoplankton concentration by more than 70% as compared to that in the central AS. During winter monsoon, from November to March, dry and weak northeasterly winds (2–6 m s−1) from the Indo-China continent enhance convective cooling of the upper ocean and deepen the mixed layer by more than 80 m, thereby increasing the vertical flux of nutrients in the photic layer which promotes wintertime phytoplankton blooms in the northern AS. The primary production rate integrated for photic layer and surface chlorophyll-a estimated from the Coastal Zone Color Scanner, both averaged for the entire western India shelf, increases from winter to summer monsoon from 24 to 70 g C m−2month and from 9 to 24 mg m−2, respectively. Remotely-forced coastal Kelvin waves from the Bay of Bengal propagate into the coastal AS, which modulate circulation pattern along the western India shelf; these Kelvin waves in turn radiate Rossby waves which reverse the circulation in the Lakshadweep Sea semiannually. This review leads us to the conclusion that seasonal monsoon forcing and remotely forced waves modulate the circulation and primary production in the eastern AS. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

13.
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.  相似文献   

14.
The temporal variability of the chemical composition of surface aerosol with particle diameters of 0.7–2 μm is analyzed. This analysis is based on the results of measurements of infrared transmission spectra of aerosol samples collected with the use of a cascade impactor at the Zvenigorod Scientific Station of the Institute of Atmospheric Physics (IAP) in 1999–2005. Seasonal features of the aerosol chemical composition and its dependence on the particle size are revealed. The interdiurnal variability of the aerosol composition depends on the season, and it manifests itself more strongly in winter and spring. Air-mass changes lead to changes in the relation of sulfates and nitrates in the micron fraction of aerosol. The enrichment of samples in nitrates is especially characteristic of the winter and spring seasons. Compounds containing the NO2 group are often met in the samples of aerosol with particle sizes of 0.7–1.3 μm during the cold time of the year. The estimates of the optical thickness of micron aerosol in the sulfate absorption band are obtained, and optical-thickness variations of some scales are detected. The quantitative characteristics of statistical relations between different chemical components of aerosol inside individual fractions and between chemical components of the micron and submicron fractions are obtained and analyzed.  相似文献   

15.
The results of measurements of the concentration of carbon oxide (CO) in the atmospheric surface layer over the town of Obninsk (in European Russia, 105 km to the southwest of Moscow) are presented. Air samples were analyzed with the aid of a measuring system consisting of a Fourier-spectrometer and an optic multipass cell. The CO concentration was measured simultaneously with the measurements of air temperature up to a height of 300 m. The measurement data obtained from February 1998 to January 2009 suggest the presence of variations within the range 100–450 ppb (∼80% of all the data) and nonperiodic relatively short-term and anomalously high CO concentrations that reach several ppm. The highest concentrations are due to CO accumulated in the surface air in the presence of temperature inversion and during forest fires. The measurements of the concentration of CO throughout a day revealed its morning and evening maxima, which coincide in time with the increased traffic current. The maxima and minima of seasonal variations in the monthly mean concentrations of CO, which are due to variations in the sources and sinks of CO that happen within a year, are observed in January and June, respectively. The amplitudes of seasonal variations amounted to (53 ± 10)% of the annual mean. The annual mean concentration of CO decreased by ∼12% over the measurement period. A comparison was made with observational data obtained at five monitoring stations located in the latitudes that are close to the latitude of Obninsk. Over the European continent, the concentration of CO tends to decrease with a longitude decrease as it goes from east to west.  相似文献   

16.
The egg production rate (EPR) of Calanus sinicus was measured from March 2007 to April 2010 at three stations along the Korean coast of the Yellow Sea (in coastal waters off Saemangum, Yeongheungdo, and Asan Bay) to estimate in situ maximum egg production rate (MEPR) and to understand whether the females were limited in their growth or fecundity in the field. The mean EPR of C. sinicus at each sampling date ranged from 10.3–34.9 eggs female−1 d−1 (mean 23.4 eggs female−1 d−1), and the EPR of individual copepods ranged from 0–81 eggs female−1 d−1. The mean EPR was positively correlated with the body weight of female copepods. The MEPR at each sampling date ranged from 40–81 eggs female−1 d−1 (mean 50.4 eggs female−1 d−1). Over 84% of eggs spawned hatched successfully. The weight-specific growth rate (WSGR) ranged from 0.038–0.111 d−1 (mean 0.082 d−1), indicating that 3.8–11.1% of the carbon in an adult female was produced daily as female growth. The WSGR was negatively correlated with water temperature. The ratio of mean EPR to observed mean MEPR ranged from 20–70% (mean 46%), indicating that ∼54% of a female’s growth might be limited in the field. We suggest that the ratio of observed EPR to mean MEPR of copepod can be applied to understand how the copepod responds to environmental changes, as well as EPR and hatching success.  相似文献   

17.
The influence of the winter atmospheric forcing on the interannual variability of the Black Sea’s active layer’s thermohaline structure during 1982–2008 is investigated. The results are based on the combined analysis of the hydrological measurements from a ship, satellite measurements of the sea’s surface temperature (SST), and the NCEP/NCAR reanalysis data for the surface air temperature (SAT). A high correlation between the variability of the winter mean SST/SAT and the thermohaline characteristics of the active layer during the following warm season was found. It is shown that the winter atmospheric forcing significantly affects the variability of the temperature, salinity, and density down to the 150–200 m depth, and this has to be considered in the analysis of the interannual and long-term variability of the Black Sea’s active layer.  相似文献   

18.
We selected surface flux datasets to investigate the heat fluxes during “hot events”; (HEs), defined as short-term, large-scale phenomena involving very high sea surface temperature (SST). Validation of the heat fluxes against in-situ ones, which are estimated from in-situ observation in HE sampling conditions, shows the accuracies (bias ± RMS error) of net shortwave radiation, net long wave radiation, latent heat and sensible heat fluxes are 20 ± 45.0 W m−2, −9 ± 12.3 W m−2, −2.3 ± 31.5 W m−2 and 1.5 ± 5.0 W m−2, respectively. Statistical analyses of HEs show that, during these events, net solar radiation remains high and then decreases from 246 to 220 W m−2, while latent heat is low and then increases from 100 W m−2 to 124 W m−2. Histogram peaks indicate net solar radiation of 270 W m−2 and latent heat flux of 90 W m−2 during HEs. Further, HEs are shown to evolve in three phases: formation, mature, and ending phases. Mean heat gain (HG) in the HE formation phase of 60 W m−2 is larger than the reasonably estimated annual mean HG range of 0–25 W m−2 in the Indo-Pacific Warm Pool. Such large daily HG in the HE formation phase can be expected to increase SSTs and produce large amplitudes of diurnal SST variations during HEs, which have been observed by both satellite and in-situ measurements in our previous studies.  相似文献   

19.
The petrophysical properties of sediment drill core samples recovered from the Sardinian margin and the abyssal plain of the Southern Tyrrhenian Basin were used to estimate the downhole change in porosity and rates of deposition and mass accumulation. We calculated how the deposited material has changed its thickness as a function of depth, and corrected the thickness for the compaction. The corresponding porosity variation with depth for terrigenous and pelagic sediments and evaporites was modelled according to an exponential law. The mass accumulation rate for the Plio-Quaternary is on average 4.8×104 kg m−2 my−1 on the Sardinian margin and for the Pliocene in the abyssal plain. In the latter area, the Quaternary attains its greatest thickness and a mass accumulation rate of 11–40×104 kg m−2 my−1. The basement response to sediment loading was calculated with Airy-type backstripping. On the lower part of the Sardinian margin, the basement subsidence rate due to sediment loading has decreased from a value of 300 m my−1 in the Tortonian and during the Messinian salinity crisis (7.0–5.33 Ma) to about 5 m my−1 in the Plio-Quaternary. In contrast, on the abyssal plain this rate has changed from 8–50 m my−1 during the period 3.6–0.46 Ma, to 95–130 m my−1 since 0.46 Ma, with the largest values in the Marsili Basin. The correlation between age and the depth to the basement corrected for the loading of the sediment in the ocean domain of the Tyrrhenian Basin argues for a young age of basin formation.  相似文献   

20.
In order to examine temporal variations of the surface oceanic and atmospheric fCO2 and the DIC concentration, we analyzed air and seawater samples collected during the period May 1992–June 1996 in the northwestern North Pacific, about 30 km off the coast of the main island of Japan. The atmospheric CO2 concentration has increased secularly at a rate of 1.9 ppmv yr−1, and it showed a clear seasonal cycle with a maximum in spring and a minimum late in summer, produced mainly by seasonally-dependent terrestrial biospheric activities. DIC also showed a prominent seasonal cycle in the surface ocean; the minimum and maximum values of the cycle appeared in early fall and in early spring, respectively, due primarily to the seasonally-dependent activities of marine biota and partly to the vertical mixing of seawater and the coastal upwelling. The oceanic fCO2 values were almost always lower than those of the atmospheric fCO2, suggesting that this area of the ocean acts as a sink for atmospheric CO2. Values varied seasonally, mainly reflecting seasonal changes of SST and DIC, with a secular increase at a rate of 3.7 μatm yr−1. The average values of the annual net CO2 flux between the ocean and the atmosphere calculated by using the different bulk equations ranged between −0.8 and −1.7 mol m−2yr−1, and its magnitude was enhanced and reduced late in spring and mid-summer, respectively, due mainly to the seasonally varying oceanic fCO2.  相似文献   

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