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321.
322.
A glacier parameterization scheme has been developed and implemented into the regional climate model REMO. The new scheme
interactively simulates the mass balance as well as changes of the areal extent of glaciers on a subgrid scale. The temporal
evolution and the general magnitude of the simulated glacier mass balance in the European Alps are in good accordance with
observations for the period 1958–1980, but the strong mass loss towards the end of the twentieth century is systematically
underestimated. The simulated decrease of glacier area in the Alps between 1958 and 2003 ranges from −17.1 to −23.6%. The
results indicate that observed glacier mass balances can be approximately reproduced within a regional climate model based
on simplified concepts of glacier-climate interaction. However, realistic results can only be achieved by explicitly accounting
for the subgrid variability of atmospheric parameters within a climate model grid box. 相似文献
323.
K. Wyser C. G. Jones P. Du E. Girard U. Willén J. Cassano J. H. Christensen J. A. Curry K. Dethloff J.-E. Haugen D. Jacob M. Køltzow R. Laprise A. Lynch S. Pfeifer A. Rinke M. Serreze M. J. Shaw M. Tjernström M. Zagar 《Climate Dynamics》2008,30(2-3):203-223
Eight atmospheric regional climate models (RCMs) were run for the period September 1997 to October 1998 over the western Arctic
Ocean. This period was coincident with the observational campaign of the Surface Heat Budget of the Arctic Ocean (SHEBA) project.
The RCMs shared common domains, centred on the SHEBA observation camp, along with a common model horizontal resolution, but
differed in their vertical structure and physical parameterizations. All RCMs used the same lateral and surface boundary conditions.
Surface downwelling solar and terrestrial radiation, surface albedo, vertically integrated water vapour, liquid water path
and cloud cover from each model are evaluated against the SHEBA observation data. Downwelling surface radiation, vertically
integrated water vapour and liquid water path are reasonably well simulated at monthly and daily timescales in the model ensemble
mean, but with considerable differences among individual models. Simulated surface albedos are relatively accurate in the
winter season, but become increasingly inaccurate and variable in the melt season, thereby compromising the net surface radiation
budget. Simulated cloud cover is more or less uncorrelated with observed values at the daily timescale. Even for monthly averages,
many models do not reproduce the annual cycle correctly. The inter-model spread of simulated cloud-cover is very large, with
no model appearing systematically superior. Analysis of the co-variability of terms controlling the surface radiation budget
reveal some of the key processes requiring improved treatment in Arctic RCMs. Improvements in the parameterization of cloud
amounts and surface albedo are most urgently needed to improve the overall performance of RCMs in the Arctic. 相似文献
324.
Holger Göttel Jörn Alexander Elke Keup-Thiel Diana Rechid Stefan Hagemann Tanja Blome Annett Wolf Daniela Jacob 《Climatic change》2008,87(1-2):35-50
In the context of the EU-Project BALANCE () the regional climate model REMO was used for extensive calculations of the Barents Sea climate to investigate the vulnerability
of this region to climate change. The regional climate model REMO simulated the climate change of the Barents Sea Region between
1961 and 2100 (Control and Climate Change run, CCC-Run). REMO on ~50 km horizontal resolution was driven by the transient
ECHAM4/OPYC3 IPCC SRES B2 scenario. The output of the CCC-Run was applied to drive the dynamic vegetation model LPJ-GUESS.
The results of the vegetation model were used to repeat the CCC-Run with dynamic vegetation fields. The feedback effect of
the modified vegetation on the climate change signal is investigated and discussed with focus on precipitation, temperature
and snow cover. The effect of the offline coupled vegetation feedback run is much lower than the greenhouse gas effect. 相似文献
325.
Jacob B. Forshaw David J. Waters David R. M. Pattison Richard M. Palin Phillip Gopon 《Journal of Metamorphic Geology》2019,37(2):153-179
Recently published activity–composition (a–x) relations for minerals in upper amphibolite‐ and granulite facies intermediate and basic rocks have expanded our ability to interpret the petrological evolution of these important components of the lower continental crust. If such petrological modelling is to be reliable, the abundances and compositions of phases calculated at the interpreted conditions of metamorphic equilibration should resemble those in the sample under study. Here, petrological modelling was applied to six granulite facies rocks that formed in different tectonic environments and reached different peak metamorphic pressure–temperature (P–T) conditions. While phase assemblages matching those observed in each sample can generally be calculated at P–T conditions that approximate those of peak metamorphism, a consistent discrepancy was found between the calculated and observed compositions of amphibole and clinopyroxene. In amphibole, Si, Ca and A‐site K are underestimated by the model, while Al and A‐site Na are overestimated; comparatively, in clinopyroxene, Mg and Si are generally underestimated, while Fe2+ and Al are typically overestimated, compared to observed values. One consequence is a reversal in the Fe–Mg distribution coefficient (KD) between amphibole and clinopyroxene compared to observations. Some of these mismatches are attributed to the incorrect partitioning of elements between the predicted amphibole and clinopyroxene compositions; however, other discrepancies are the result of the incorrect prediction of major substitution vectors in amphibole and clinopyroxene. These compositional irregularities affect mineral modal abundance estimates and in turn the position and size (in P–T space) of mineral assemblage fields, the effect becoming progressively more marked as the modal abundance of hornblende increases; hence, this study carries implications for estimating P–T conditions of high‐temperature metabasites using these new a–x relations. 相似文献
326.
The stratigraphical occurrence of 35 known species from the Upper Cretaceous and Danian of Southern Limburg is presented based on existing collections and newly collected material. Corals are relatively rare, except in the Meerssen Member of the Maastricht Formation. Two faunas were recognised in the Meerssen Member: a fauna dominated by Cyclolites cancellata at the base of this member – which coincides with the sequence boundary of the third-order sequence cycle TA1.1 of Haq et al. (1988) – and a fauna dominated by mushroom-shaped and encrusting colonies at the top of the transgressive systems tract of the same sequence cycle. 相似文献
327.
328.
Coronal mass ejections (CMEs) are large-scale eruptions of plasma from the Sun, which play an important role in space weather. Faraday rotation is the rotation of the plane of polarization that results when a linearly polarized signal passes through a magnetized plasma such as a CME. Faraday rotation is proportional to the path integral through the plasma of the electron density and the line-of-sight component of the magnetic field. Faraday-rotation observations of a source near the Sun can provide information on the plasma structure of a CME shortly after launch. We report on simultaneous white-light and radio observations made of three CMEs in August 2012. We made sensitive Very Large Array (VLA) full-polarization observations using 1?–?2 GHz frequencies of a constellation of radio sources through the solar corona at heliocentric distances that ranged from 6?–?\(15~\mathrm{R}_{\odot}\). Two sources (0842+1835 and 0900+1832) were occulted by a single CME, and one source (0843+1547) was occulted by two CMEs. In addition to our radioastronomical observations, which represent one of the first active hunts for CME Faraday rotation since Bird et al. (Solar Phys., 98, 341, 1985) and the first active hunt using the VLA, we obtained white-light coronagraph images from the Large Angle and Spectrometric Coronagraph (LASCO) C3 instrument to determine the Thomson-scattering brightness [\(\mathrm{B}_{\mathrm{T}}\)], providing a means to independently estimate the plasma density and determine its contribution to the observed Faraday rotation. A constant-density force-free flux rope embedded in the background corona was used to model the effects of the CMEs on \(\mathrm{B}_{\mathrm{T}}\) and Faraday rotation. The plasma densities (\(6\,\mbox{--}\,22\times10^{3}~\mbox{cm}^{-3}\)) and axial magnetic-field strengths (2?–?12 mG) inferred from our models are consistent with the modeling work of Liu et al. (Astrophys. J., 665, 1439, 2007) and Jensen and Russell (Geophys. Res. Lett., 35, L02103, 2008), as well as previous CME Faraday-rotation observations by Bird et al. (1985). 相似文献
329.
Recent studies have promoted using soil phosphate analysis to detect ancient Maya sites by delimiting areas of occupation based on decomposed organic matter. Refuse associated with human activity increases organic matter around areas of ancient human habitation. Theoretically, the highest concentration of organic matter—detectable by phosphate analysis—should be directly associated with areas of refuse disposal. Thus, the objective of this study is to investigate the potential of phosphate analysis to detect residential middens in Piedras Negras, Guatemala. This paper presents the results of a sensitive, in‐field phosphate analysis method applied as a midden prospection tool in residential areas. Phosphate concentration is correlated with artifact data obtained from a total of 37 test pits excavated in areas of varying phosphate concentration in three residential sites. A positive correlation between phosphate concentration and ceramic density indicates the potential of this method in defining and orienting excavations of residential areas. © 2001 John Wiley & Sons, Inc. 相似文献
330.
Metop-GRAS in-orbit instrument performance 总被引:2,自引:1,他引:1
The GRAS instrument on the Metop-A satellite provides more than 600 radio occultation measurement profiles per day. The instrument
is characterized by its wide antenna coverage, high signal-to-noise ratio and an ultra-stable clock reference. The conventional
dual-frequency tracking of GPS signals is under dynamic atmosphere conditions complemented by open loop tracking with sampling
of the signal at a 1 kHz rate, providing an unprecedented view of the signal spectral environment. This paper presents the
instrument performance as derived from analysis of in-orbit measurement data. We show that the noise figure is low enough
to enable mapping of external radio noise variations over the earth’s surface. An error propagation model is presented to
relate instrument characteristics to bending angle performance. This model is also used to illustrate the relation between
filter bandwidth, resolution and measurement noise. The Doppler model, guiding open loop measurements, is found to be accurate
to better than 20 Hz with a possibility for improvement to 10 Hz. The high performance at low altitudes enables the presence
of surface reflections at the −20-dB level to be identified in more than 50% of the occultations. The potential performance
improvements for next generation receivers are discussed. 相似文献