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1.
The estimate of the release of radioactive substances (133Xe, 131I, and 137Cs) into the atmosphere from the Fukushima Daiichi nuclear disaster is presented. It was obtained using the FLEXPART Lagrangian dispersion model and the data of local ground-based measurements of radiation dose rate. The computation period covers the active phase of the nuclear disaster that lasted 20 days after the tsunami. To get the quantitative characteristics of emissions of radioactive substances, the inverse modeling based on the Bayesian approach is used. The emissions were estimated for three altitudes. The total emissions are equal to 2.1 + 0.4 kg (14 000 + 2700 PBq) for 133Xe, (3.8 + 0.4) x 10-2 kg (174 + + 18 PBq) for 131I, and 5.7 + 1.2 kg (18 + 4 PBq) for 137Cs that is consistent with the results of other studies. Retrieved emissions were used to provide the forward modeling for mapping the areas of radionuclide deposition. The developed method of retrieving the emission of radioactive substances makes a useful instrument that operationally estimates and localizes the areas of potential pollution in case of nuclear accidents and could be used for making decisions on the population evacuation.  相似文献   

2.
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3.
The analysis of possible mechanisms of 137Cs concentration changes in surface waters was performed in the process of preparation of reliable long-range forecasts of radioactive river contamination after the Chernobyl accident. The following mechanisms were considered: (1) radioactive decay; (2) advective transport with river waters; (3) irreversible sorption; (4) vertical migration deep into bottom sediments due to diffusion; (5) burial in clean bottom sediments. The data published on 137Cs monitoring at Dobrush, on the Iput’ River in Belarus were used in the analysis. It is shown that the best agreement with the experimental results is achieved when the second, third, and fifth mechanisms are used in calculations. However, a dominating mechanism still cannot be chosen at the present stage of our study. Most probably, all of these mechanisms act simultaneously.  相似文献   

4.
Experimental field and laboratory studies on washout of radionuclides from the snow cover during snow melting were carried out in the winter of 2005/06. In the field studies, a specially equipped runoff site was used. In the laboratory conditions, the experiments were conducted using prepared soil monoliths. In the winter of 2006, 25 g/m2 of water-free cesium chloride (CsCl) and 25 g/m3 of strontium chloride (SrCl2) were put onto the snow cover surface of the runoff site. The snow surface of the soil monolith was coated with a 137Cs-bearing solution, then with SrCl2. Under experimental conditions, practically no surface runoff from the runoff site was recorded. The experiments with the soil monoliths demonstrated that the coefficient of the liquid washout of 137Cs normalized to the runoff layer was within 0.9 × 10?6–1.2 × 10?4 mm?1, and that of 90Sr normalized to the runoff layer was within 2 × 10?–1.6 × 10?4 mm?1.  相似文献   

5.
Abstract

A realistic kinematic model of cloud microphysical processes is presented. Heat and water substances in various phases are transported in the model by specific horizontal and vertical velocities using a semi‐Lagrangian numerical transport scheme. The model is applied to a CASP case study with horizontal and vertical velocities consistent with radiosondes and radar observations. The model is shown to capture the general observed features of the cloud and precipitation fields. In particular, it is shown that for the case studied stratiform clouds extend much higher than the top of detectable precipitation. This numerical model constitutes a useful tool for understanding the life cycle of hydrometeors as a function of their position within the storm system.  相似文献   

6.
The carbon kinetic isotope effects (KIEs) in the reactions of several unsaturated hydrocarbons with chlorine atoms were measured at room temperature and ambient pressure using gas chromatography combustion isotope ratio mass spectrometry (GCC-IRMS). All measured KIEs, defined as the ratio of the rate constants for the unlabeled and labeled hydrocarbon reaction k 12/k 13, are greater than unity or normal KIEs. The KIEs, reported in per mil according to Cl ɛ = (k 12/k 13−1) × 1000‰ with the number of experimental determinations in parenthesis, are as follows: ethene, 5.65 ± 0.34 (1); propene, 5.56 ± 0.18 (2); 1-butene, 5.93 ± 1.16 (1); 1-pentene, 4.86 ± 0.63 (1); cyclopentene, 3.75 ± 0.14 (1); toluene, 2.89 ± 0.31 (2); ethylbenzene, 2.17 ± 0.17 (2); o-xylene, 1.85 ± 0.54 (2). To our knowledge, these are the first reported KIE measurements for reactions of unsaturated NMHC with Cl atoms. Relative rate constants were determined concurrently to the KIE measurements. For the reactions of cyclopentene and ethylbenzene with Cl atoms, no rate constant has been reported in refereed literature. Our measured rate constants are: cyclopentene (7.32 ± 0.88) relative to propene (2.68 ± 0.32); ethylbenzene (1.15 ± 0.04) relative to o-xylene (1.35 ± 0.21), all × 10−10 cm3 molecule−1 s−1. The KIEs in reactions of aromatic hydrocarbons with Cl atoms are similar to previously reported KIEs in Cl-reactions of alkanes with the same numbers of carbon atoms. Unlike the KIEs for previously studied gas-phase hydrocarbon reactions, the KIEs for alkene–Cl reactions do not exhibit a simple inverse dependence on carbon number. This can be explained by competing contributions of normal and inverse isotope effects of individual steps in the reaction mechanism. Implications for the symmetries of the transition state structures in these reactions and the potential relevance of Cl-atom reactions on stable carbon isotope ratios of atmospheric NMHC are discussed.  相似文献   

7.
90Sr runoff amounted to 0.22–0.67% of its budget in the catchment; the value is lower for high-latitude rivers running in the zone of frozen and seasonally frozen grounds. The ecological half-period of a decrease in the 90Sr concentration in the river water of Eastern Fennoscandia amounted to 5.9–11.5 years in 1979–1985. The lake waters (Lake Ladoga and Lake Päijänne) were renewed approximately 4–5 times faster than the 90Sr content decreased in these lakes.  相似文献   

8.
Summary. ?Cyclone track predictions in the Indian seas (Bay of Bengal and Arabian Sea) with a quasi-Lagrangian model (QLM) have been attempted. QLM has a horizontal resolution of 40 km and 16 sigma levels in the vertical. It is integrated in a domain of about 4400 × 4400 km2. A new initialization procedure to provide initial fields for running the model has been designed. The initialization procedure consists of updating the global model forecasts, used as first guess, provided by the National Center for Medium Range Weather Forecasting (NCMRWF), New Delhi. A new version of IMD’s operational optimum interpolation scheme has been created to suit the QLM grid structure. Lateral boundary conditions are computed from the extended forecasts of NCMRWF. The track forecasts in each case show a reasonable skill of the forecast model in predicting the direction of movement within acceptable limits of forecast errors, which are comparable to some of the best models operated by advanced NWP centers of the world. Even the recurving storms are well predicted. Evolution of the vertical motion fields are also studied which reveal some interesting features, which are described in detail in the text. The composited vertical motion fields are projected against observed rainfall distribution, which show a good spatial correspondence. Received August 9, 2001; revised March 12, 2002; accepted June 17, 2002 Published online: May 8, 2003  相似文献   

9.
A global ocean general circulation model (L30T63) is employed to study the uptake and distribution of anthropogenic CO2 in the ocean. A subgrid-scale mixing scheme called GM90 is used in the model. There are two main GM90 parameters including isopycnal diffusivity and skew (thickness) diffusivity. Sensitivities of the ocean circulation and the redistribution of dissolved anthropogenic CO2 to these two parameters are examined. Two runs estimate the global oceanic anthropogenic CO2 uptake to be 1.64 and 1.73 Pg C yr-1 for the 1990s, and that the global ocean contained 86.8 and 92.7 Pg C of anthropogenic CO2 at the end of 1994, respectively. Both the total inventory and uptake from our model are smaller than the data-based estimates. In this presentation, the vertical distributions of anthropogenic CO2 at three meridional sections are discussed and compared with the available data-based estimates. The inventory in the individual basins is also calculated. Use of large isopycnal diffusivity can generally improve the simulated results, including the exchange flux, the vertical distribution patterns, inventory, storage, etc. In terms of comparison of the vertical distributions and column inventory, we find that the total inventory in the Pacific Ocean obtained from our model is in good agreement with the data-based estimate, but a large difference exists in the Atlantic Ocean, particularly in the South Atlantic. The main reasons are weak vertical mixing and that our model generates small exchange fluxes of anthropogenic CO2 in the Southern Ocean. Improvement in the simulation of the vertical transport and sea ice in the Southern Ocean is important in future work.  相似文献   

10.
Summary Satellite-derived datasets are used to verify the cloud cover and radiation field generated by a T62 (horizontal resolution) version of the operational global model at the National Meteorological Centre (NMC). An ensemble of five day forecasts for July 1985 is used, as well as 30 day climatological forecasts for July 1985, October 1985, January 1986, and April 1986.Monthly averages of radiation fields are compared with Earth Radiation Budget Experiment (ERBE) data. For the four months examined, clear-sky outgoing longwave radiation (clear-sky OLR) and absorbed shortwave radiation (clear-sky SW) tend to agree roughly with ERBE. Model global mean OLR, however, exceeds that of ERBE by 10 W m–2.Comparison of effective cloud cover to corresponding fields cataloged by the International Satellite Cloud Climatology Project (ISCCP C1) reveals deficiencies in the amount of supersaturation cloudiness and the vertical distribution of convective clouds. Large inaccuracies in model radiation fields are closely related to deficiencies in the cloud parameterization. An inventory of model cloudiness, in comparison to satellite data, is conducted.With 18 Figures  相似文献   

11.
The series of δ18O values is presented for all precipitation events in Moscow in 2014. Precipitation samples were taken at the observation site of the Meteorological Observatory of Lomonosov Moscow State University (MSU MO), and the isotopic analysis was carried out in the isotopic laboratory of the Department of Geography of MSU. The concentration of stable 18O in precipitation over Moscow in 2014 varied from -0.09 to -26.29‰. The maximum amplitudes of δ18O were registered in March-April and October. The pronounced interrelation was revealed between the oxygen isotopic composition of precipitation and surface air temperature (the correlation coefficient is 0.85). The computation of back trajectories of air masses and the analysis of weather charts demonstrated that the most isotopically light precipitation is typical of relatively cold air masses slowly moving over the continent during the last five days before precipitation. In this case, the ongoing condensation leads to the progressive isotopic depletion of precipitation (more and more isotope-depleted precipitation is registered). On the contrary, fast air transport from the middle and even from high latitudes of the Atlantic Ocean leads to the relatively constant of δ18O values of precipitation.  相似文献   

12.
The IPSL-CM5A climate model was used to perform a large number of control, historical and climate change simulations in the frame of CMIP5. The refined horizontal and vertical grid of the atmospheric component, LMDZ, constitutes a major difference compared to the previous IPSL-CM4 version used for CMIP3. From imposed-SST (Sea Surface Temperature) and coupled numerical experiments, we systematically analyze the impact of the horizontal and vertical grid resolution on the simulated climate. The refinement of the horizontal grid results in a systematic reduction of major biases in the mean tropospheric structures and SST. The mid-latitude jets, located too close to the equator with the coarsest grids, move poleward. This robust feature, is accompanied by a drying at mid-latitudes and a reduction of cold biases in mid-latitudes relative to the equator. The model was also extended to the stratosphere by increasing the number of layers on the vertical from 19 to 39 (15 in the stratosphere) and adding relevant parameterizations. The 39-layer version captures the dominant modes of the stratospheric variability and exhibits stratospheric sudden warmings. Changing either the vertical or horizontal resolution modifies the global energy balance in imposed-SST simulations by typically several W/m2 which translates in the coupled atmosphere-ocean simulations into a different global-mean SST. The sensitivity is of about 1.2 K per 1 W/m2 when varying the horizontal grid. A re-tuning of model parameters was thus required to restore this energy balance in the imposed-SST simulations and reduce the biases in the simulated mean surface temperature and, to some extent, latitudinal SST variations in the coupled experiments for the modern climate. The tuning hardly compensates, however, for robust biases of the coupled model. Despite the wide range of grid configurations explored and their significant impact on the present-day climate, the climate sensitivity remains essentially unchanged.  相似文献   

13.
The first-order (linear) response of the planetary boundary layer is calculated for flow over periodic terrain, for variations in both surface roughness and terrain elevation. Calculations are made for horizontal wavenumbers varying from 10–4m–1 to 3 × 10–3m–1. A simple second-order closure model of the turbulence is used, and Coriolis and buoyancy forces are neglected. As expected, flow over a periodic terrain produces corresponding periodic structure in all meteorological fields above the surface. The periodic structure consists of two components. The first is very nearly evanescent with height, showing little vertical structure. It corresponds to the motion that would be observed were the atmosphere inviscid. The second component, introduced by turbulent viscosity, exhibits considerable vertical structure, with vertical wavelengths the order of 100 m, and thus could be responsible for the layering often seen on acoustic sounder observations of the atmospheric boundary layer.Wave Propagation Laboratory.Environmental Science Group.  相似文献   

14.
An algorithm for retrieving polarimetric variables from numerical model fields is developed. By using this technique, radar reflectivity at horizontal polarization~ differential reflectivity, specific differential phase shift and correlation coefficients between the horizontal and vertical polarization signals at zero lag can be derived from rain, snow and hail contents of numerical model outputs. Effects of environmental temperature and the melting process on polarimetric variables are considered in the algorithm. The algorithm is applied to the Advanced Regional Prediction System （ARPS） model simulation results for a hail storm. The spatial distributions of the derived parameters are reasonable when compared with observational knowledge. This work provides a forward model for assimilation of dual linear polarization radar data into a mesoscale model.  相似文献   

15.
A global three-dimensional model of the tropospheric sulfur cycle   总被引：9，自引：0，他引：9  
The tropospheric part of the atmospheric sulfur cycle has been simulated in a global three-dimensional model. The model treats the emission, transport, chemistry, and removal processes for three sulfur components; DMS (dimethyl sulfide), SO2 and SO4 2– (sulfate). These processes are resolved using an Eulerian transport model, the MOGUNTIA model, with a horizontal resolution of 10° longitude by 10° latitude and with 10 layers in the vertical between the surface and 100 hPa. Advection takes place by climatological monthly mean winds. Transport processes occurring on smaller space and time scales are parameterized as eddy diffusion except for transport in deep convective clouds which is treated separately. The simulations are broadly consistent with observations of concentrations in air and precipitation in and over polluted regions in Europe and North America. Oxidation of DMS by OH radicals together with a global emission of 16 Tg DMS-S yr–1 from the oceans result in DMS concentrations consistent with observations in the marine boundary layer. The average turn-over times were estimated to be 3, 1.2–1.8, and 3.2–6.1 days for DMS, SO2, and SO4 2– respectively.  相似文献   

16.
周玉奇  张宁 《气象科学》2018,38(1):85-94
为了解城市建筑群对周围风场结构的影响,本文利用大涡模拟方法对不同建筑群分布类型下的风场状况进行了模拟,并利用通风指数对风场进行定量评估。模拟结果表明:PALM(Parallelized LES model)能够反映出建筑物影响下风场的结构特征。建筑群风场受到建筑高度、高度方差、分布、初始入流的影响。风场衰减主要体现在水平分量上,尤其是平均高度较高、高度方差大、交错不规整分布使得水平方向风场衰减、通风效果变差,而同时又会使得垂直风速分量w增大,增大垂直方向的空气交换速率。初始入流不会影响风场风廓线形态,在低层风场中平均风速大小以及总体空气交换速率基本与入流成正比关系。  相似文献   

17.
Constructing β-mesoscale weather systems in initial fields remains a challenging problem in a mesoscale numerical weather prediction (NWP) model. Without vertical velocity matching the β-mesoscale weather system, convection activities would be suppressed by downdraft and cooling caused by precipitating hydrometeors. In this study, a method, basing on the three-dimensional variational (3DVAR) assimilation technique, was developed to obtain reasonable structures of β-mesoscale weather systems by assimilating radar data in a next-generation NWP system named GRAPES (the Global and Regional Assimilation and Prediction System) of China. Single-point testing indicated that assimilating radial wind significantly improved the horizontal wind but had little effect on the vertical velocity, while assimilating the retrieved vertical velocity (taking Richardson's equation as the observational operator) can greatly improve the vertical motion. Experiments on a typhoon show that assimilation of the radial wind data can greatly improve the prediction of the typhoon track, and can ameliorate precipitation to some extent. Assimilating the retrieved vertical velocity and rainwater mixing ratio, and adjusting water vapor and cloud water mixing ratio in the initial fields simultaneously, can significantly improve the tropical cyclone rainfall forecast but has little effect on typhoon path. Joint assimilating these three kinds of radar data gets the best results. Taking into account the scale of different weather systems and representation of observational data, data quality control, error setting of background field and observation data are still requiring further in-depth study.  相似文献   

18.
Experimental investigations under field and laboratory conditions of 137Cs washout from the periodically frozen and thawed soils were carried out. The experiments demonstrated that the amount of cesium washed out from the soil after freezing was much larger than from the non-frozen soils and by its intensity it corresponds to the washout under the influence of intensifiers. This fact allows recommending cheap and technologically simple measures for the in-snow runoff control to rehabilitate the contaminated lands.  相似文献   

19.
The vertically integrated horizontal energy transports and the vertically integrated vertical energy flux divergence from ERA-40 and ISCCP are not in balance assuming a stationary climate as a time mean over several years. The reasons are the inherent uncertainties in each of the respective data sets. We therefore modify them using a variational approach with a discretization in spherical harmonics to obtain consistent values. The variational approach only modifies the smaller yet more uncertain divergent part of the flow, leaving the large rotational part untouched. From these consistent fields we can calculate posterior covariance matrices of the vertically integrated horizontal energy transport and the vertically integrated vertical energy flux divergence, providing a measure of the uncertainty of the previous calculation. We are able to use these posterior covariance matrices to give an estimate of the uncertainty of the zonally and vertically integrated meridional energy transport, which is about 0.25 PW in the tropics and 0.04 PW in high latitudes, as well as for the vertical energy flux divergence of the atmosphere, which ranges from 2.5 to 5 W/m2 in the tropics to 15–17 W/m2 in high latitudes.  相似文献   

20.
The issues of assessing variability of 137Cs fallout of global and Chernobyl origin at reference sites are discussed with a purpose to use this isotope as a tracer for estimating the rates of erosion-accumulative processes. It is shown that local variability of soil contamination by 137Cs at reference sites is within 7–20%, which makes it possible to use the isotope as a tracer. When studies are conducted within drainage basins, the available trend of the atmospheric 137Cs fallout should be taken into account in assessing the soil and sedimentation redistribution.  相似文献   

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