沈积岩石学     

克鲁比  比迪詹  李广源 《地质论评》1947,12(Z2):307-309

沈积学,在二十世纪初叶始渐起而为地质学中之新支,近数十年来随着石油工业之发达,而日趋蓬勃;一变昔日仅以岩石性质研究为沈积原因之解说,而侧重沈积作用及沈积环境之  相似文献   

Numerical simulations of optical properties of Saharan dust aerosols with emphasis on lidar applications     

By M. WIEGNER  J. GASTEIGER  K. KANDLER  B. WEINZIERL  K. RASP  M. ESSELBORN  V. FREUDENTHALER  B. HEESE  C. TOLEDANO  M. TESCHE  D. ALTHAUSEN 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):180-194

In the framework of the Saharan Mineral Dust Experiment (SAMUM) for the first time the spectral dependence of particle linear depolarization ratios was measured by combining four lidar systems. In this paper these measurements are compared with results from scattering theory based on the T-matrix method. For this purpose, in situ measurements—size distribution, shape distribution and refractive index—were used as input parameters; particle shape was approximated by spheroids. A sensitivity study showed that lidar-related parameters—lidar ratio   S _p   and linear depolarization ratio  δ _p   —are very sensitive to changes of all parameters. The simulated values of the  δ _p   are in the range of 20% and 31% and thus in the range of the measurements. The spectral dependence is weak, so that it could not be resolved by the measurements. Calculated lidar ratios based on the measured microphysics and considering equivalent radii up to 7.5 μm show a range of possible values between 29 and 50 sr at  λ= 532 nm  . Larger   S _p   might be possible if the real part of the refractive index is small and the imaginary part is large. A strict validation was however not possible as too many microphysical parameters influence   S _p   and  δ _p   that could not be measured with the required accuracy.  相似文献   

Fine structure of a Greenland reverse tip jet: a numerical simulation     

By TADAYASU OHIGASHI  G. W. KENT MOORE 《地球，A辑:动力气象学与海洋学》2009,61(4):512-526

Reverse tip jets are strong low-level winds with easterly component that form near the southern tip of Greenland. In the present study, a reverse tip jet case which occurred from 21 to 22 December 2000 was examined to clarify its fine structure using a numerical model with a horizontal resolution of 3 km. The reverse tip jet, showing the supergeostrophic wind speed with a maximum wind speed in excess of 45 m s⁻¹, extended from the east coast of Greenland to the west of Cape Farewell with anticyclonic curvature. A cloud free region coincided with the jet indicated that there was a mesoscale downdraft. Along the eastern edge of the jet, a banded cloud formed between the upstream easterly wind and the colder northerly wind that is a part of the jet and is located along the east coast. This cloud was associated with large gradients in surface wind speed, temperature, moisture, and heat flux. A maximum surface total heat flux of 300 W m⁻² coincided with the location of the jet. It is suggested that the orographic deflection by Greenland's large-scale topography as well as small-scale downslope winds behind mountains with fiords causes the reverse tip jet.  相似文献   

Reconciliation of excess ¹⁴C-constrained global CO₂ piston velocity estimates     

By TOBIAS NAEGLER 《Tellus. Series B, Chemical and physical meteorology》2009,61(2):372-384

Oceanic excess radiocarbon data is widely used as a constraint for air–sea gas exchange. However, recent estimates of the global mean piston velocity  〈 k 〉  from Naegler et al., Krakauer et al., Sweeney et al. and Müller et al. differ substantially despite the fact that they all are based on excess radiocarbon data from the GLODAP data base. Here I show that these estimates of  〈 k 〉  can be reconciled if first, the changing oceanic radiocarbon inventory due to net uptake of CO₂ is taken into account; second, if realistic reconstructions of sea surface  Δ¹⁴C  are used and third, if  〈 k 〉  is consistently reported with or without normalization to a Schmidt number of 660. These corrections applied, unnormalized estimates of  〈 k 〉  from these studies range between 15.1 and 18.2 cm h⁻¹. However, none of these estimates can be regarded as the only correct value for  〈 k 〉  . I thus propose to use the 'average' of the corrected values of  〈 k 〉  presented here (16.5 ± 3.2 cm h⁻¹) as the best available estimate of the global mean unnormalized piston velocity  〈 k 〉  , resulting in a gross ocean-to-atmosphere CO₂ flux of 76 ± 15 PgC yr⁻¹ for the mid-1990s.  相似文献   

Data assimilation in a system with two scales—combining two initialization techniques     

By JOAQUIM BALLABRERA-POY  EUGENIA KALNAY  SHU-CHIH YANG 《地球，A辑:动力气象学与海洋学》2009,61(4):539-549

An ensemble Kalman filter (EnKF) is used to assimilate data onto a non-linear chaotic model, coupling two kinds of variables. The first kind of variables of the system is characterized as large amplitude, slow, large scale, distributed in eight equally spaced locations around a circle. The second kind of variables are small amplitude, fast, and short scale, distributed in 256 equally spaced locations. Synthetic observations are obtained from the model and the observational error is proportional to their respective amplitudes. The performance of the EnKF is affected by differences in the spatial correlation scales of the variables being assimilated. This method allows the simultaneous assimilation of all the variables. The ensemble filter also allows assimilating only the large-scale variables, letting the small-scale variables to freely evolve. Assimilation of the large-scale variables together with a few small-scale variables significantly degrades the filter. These results are explained by the spurious correlations that arise from the sampled ensemble covariances. An alternative approach is to combine two different initialization techniques for the slow and fast variables. Here, the fast variables are initialized by restraining the evolution of the ensemble members, using a Newtonian relaxation toward the observed fast variables. Then, the usual ensemble analysis is used to assimilate the large-scale observations.  相似文献   

The maximum likelihood ensemble filter performances in chaotic systems     

By ALBERTO CARRASSI  STEPHANE VANNITSEM  DUSANKA ZUPANSKI  MILIJA ZUPANSKI 《地球，A辑:动力气象学与海洋学》2009,61(5):587-600

The performance of the maximum likelihood ensemble filter (MLEF), is investigated in the context of generic systems featuring the essential ingredients of unstable dynamics and on a spatially extended system displaying chaos. The main objective is to clarify the response of the filter to different regimes of motion and highlighting features which may help its optimization in more realistic applications. It is found that, in view of the minimization procedure involved in the filter analysis update, the algorithm provides accurate estimates even in the presence of prominent non-linearities. Most importantly, the filter ensemble size can be designed in connection to the properties of the system attractor (Kaplan–Yorke dimension), thus facilitating the filter setup and limiting the computational cost by using an optimal ensemble. As a corollary, this latter finding indicates that the ensemble perturbations in the MLEF reflect the intrinsic system error dynamics rather than a sampling of realizations of an unknown error covariance.  相似文献   

In situ measurements of optical properties at Tinfou (Morocco) during the Saharan Mineral Dust Experiment SAMUM 2006     

By A. SCHLADITZ  T. MÜLLER  N. KAADEN  A. MASSLING  K. KANDLER  M. EBERT  S. WEINBRUCH  C. DEUTSCHER  A. WIEDENSOHLER 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):64-78

In situ measurements of optical and physical properties of mineral dust were performed at the outskirts of the Saharan Desert in the framework of the Saharan Mineral Dust Experiment part 1 (SAMUM-1). Goals of the field study were to achieve information on the extent and composition of the dust particle size distribution and the optical properties of dust at the ground. For the particle number size distribution, measured with a DMPS/APS, a size dependent dynamic shape factor was considered. The mean refractive index of the particles in this field study is  1.53–4.1 × 10⁻³ i   at 537 nm wavelength and  1.53–3.1 × 10⁻³ i   at 637 nm wavelength derived from measurements of scattering and absorption coefficients, as well as the particle size distribution. Whereas the real part of the refractive index is rather constant, the imaginary part varies depending on the mineral dust concentrations. For high dust concentration the single scattering albedo is primarily influenced by iron oxide and is  0.96 ± 0.02  and  0.98 ± 0.01  at 537 nm and 637 nm wavelength, respectively. During low dust concentration the single scattering albedo is more influenced by a soot-type absorber and is  0.89 ± 0.02  and  0.93 ± 0.01  for the same wavelengths.  相似文献   

Spring initiation and autumn cessation of boreal coniferous forest CO₂ exchange assessed by meteorological and biological variables     

By T. THUM  T. AALTO  T. LAURILA  M. AURELA  J. HATAKKA  A. LINDROTH  T. VESALA 《Tellus. Series B, Chemical and physical meteorology》2009,61(5):701-717

We studied the commencement and finishing of the growing season using different air temperature indices, the surface albedo, the chlorophyll fluorescence (Fv/Fm) and the carbon dioxide (CO₂) tropospheric concentration, together with eddy covariance measurements of CO₂ flux. We used CO₂ flux data from four boreal coniferous forest sites covering a wide latitudinal range, and CO₂ concentration measurements from Sammaltunturi in Pallas. The CO₂ gas exchange was taken as the primary determinant for the growing season to which other methods were compared.
Indices based on the cumulative temperature sum and the variation in daily mean temperature were successfully used for approximating the start and cessation of the growing season. The beginning of snow melt was a successful predictor of the onset of the growing season. The chlorophyll fluorescence parameter Fv/Fm and the CO₂ concentration were good indicators of both the commencement and cessation of the growing season. By a derivative estimation method for the CO₂ concentration, we were also able to capture the larger-scale spring recovery. The trends of the CO₂ concentration and temperature indices at Pallas/Sammaltunturi were studied over an 11-yr time period, and a significant tendency towards an earlier spring was observed. This tendency was not observed at the other sites.  相似文献   

Estimating the Asian radon flux density and its latitudinal gradient in winter using ground-based radon observations at Sado Island     

By ALASTAIR G. WILLIAMS  SCOTT CHAMBERS  WLODEK ZAHOROWSKI  JAGODA CRAWFORD  KIYOSHI MATSUMOTO  MITSUO UEMATSU 《Tellus. Series B, Chemical and physical meteorology》2009,61(5):732-746

Terrestrial radon-222 flux density for the Asian continent, integrated over distances of 4500 km, is estimated in two 20° latitudinal bands centred on 48.8°N and 63.2°N. The evaluation is based on three years of wintertime radon measurements at Sado Island, Japan, together with meteorological and trajectory information. A selection of 18% of observations are suitable for evaluation of an analytical expression for the continental surface flux. Various meteorological assumptions are discussed; it is found that there is a substantial effect of increased complexity of the formulation on the flux estimates obtained. The distribution of spatially integrated radon flux over the Asian landmass is reported for the first time. Expressed as geometric means and 1σ-ranges, estimated fluxes are 14.1 mBq m⁻² s⁻¹ (1σ-range: 18 mBq m⁻² s⁻¹) and 8.4 mBq m⁻² s⁻¹ (1σ-range: 10 mBq m⁻² s⁻¹) for the lower and higher latitude bands. These results constitute an annual minimum in flux densities for these regions, and are higher than previously reported. The existence of a latitudinal gradient in the continental radon source function is confirmed; the present estimate for Asia (−0.39 mBq m⁻² s⁻¹ per degree of latitude) is in agreement with the northern hemisphere terrestrial radon flux gradient proposed previously.  相似文献   

A national landfill methane budget for Sweden based on field measurements, and an evaluation of IPCC models     

By GUNNAR BÖRJESSON  JERKER SAMUELSSON  JEFFREY CHANTON  ROLF ADOLFSSON  BO GALLE  BO H. SVENSSON 《Tellus. Series B, Chemical and physical meteorology》2009,61(2):424-435

Seven Swedish landfills were investigated from 2001 to 2003. On each landfill, a measure of the total methane production was calculated from data on: (1) methane emissions (leakage); (2) methane oxidation and (3) from gas recovery.
Methane emissions were determined via a tracer gas (N₂O) release-based remote sensing method. N₂O and CH₄ were measured with an Fourier Transform infrared detector at a distance of more than 1 km downwind from the landfills. Methane oxidation in the landfill covers was measured with the stable carbon isotope method. The efficiency in gas recovery systems proved to be highly variable, but on an average, 51% of the produced landfill gas was captured.
A first-order decay model, based on four fractions (waste from households and parks, sludges and industrial waste), showed that the use of a degradable organic carbon fraction (DOCf) value of 0.54, in accordance with the default value for DOCf of 0.50 in the latest IPCC model, gave an emission estimate similar to the official national reports.  相似文献