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141.
Jun A. Zhang Kristina B. Katsaros Peter G. Black Susanne Lehner Jeffrey R. French William M. Drennan 《Boundary-Layer Meteorology》2008,128(2):173-189
Boundary-layer secondary circulations or ‘roll vortices’ can have a significant influence on the turbulent exchange of momentum,
sensible heat and moisture throughout the hurricane boundary layer. In this study, analyses of data from a WP-3D aircraft
of the National Oceanic and Atmospheric Administration (NOAA) are presented. As part of the Coupled Boundary Layer Air-Sea
Transfer (CBLAST)-hurricane experiment sponsored through the Office of Naval Research and NOAA’s annual hurricane research
program, flights were conducted to investigate energy exchange across the air–sea interface. We present the first in-situ
aircraft-based observations of rolls in the hurricane boundary layer and investigate their influence on energy and momentum
exchange. The rolls detected in Hurricane Isidore (year 2002) have a characteristic wavelength of about 900 m, in good agreement
with analyses of data from a synthetic aperture radar image captured by the Canadian Space Agency’s RADARSAT satellite in
the same storm. Our analyses of the airborne data suggest that roll vortices may be a significant factor modulating the air–sea
momentum exchange. 相似文献
142.
A high-resolution 43-year atmospheric hindcast for South America generated with the MPI regional model 总被引:1,自引:1,他引:0
Gabriel Silvestri Carolina Vera Daniela Jacob Susanne Pfeifer Claas Teichmann 《Climate Dynamics》2009,32(5):693-709
An evaluation of the present-day climate in South America simulated by the MPI atmospheric limited area model, REMO, is made.
The model dataset was generated by dynamical downscaling from the ECMWF-ERA40 reanalysis and compared to in-situ observations.
The model is able to reproduce the low-level summer monsoon circulation but it has some deficiencies in representing the South
American Low-Level Jet structure. At upper levels, summer circulation features like the Bolivian High and the associated subtropical
jet are well simulated by the model. Sea-level pressure fields are in general well represented by REMO. The model exhibits
reasonable skill in representing the general features of the mean seasonal cycle of precipitation. Nevertheless, there is
a systematic overestimation of precipitation in both tropical and subtropical regions. Differences between observed and modeled
temperature are smaller than 1.5°C over most of the continent, excepting during spring when those differences are quite large.
Results also show that the dynamical downscaling performed using REMO introduces some enhancement of the global reanalysis
especially in temperature at the tropical regions during the warm season and in precipitation in both the subtropics and extratropics.
It is then concluded that REMO can be a useful tool for regional downscaling of global simulations of present and future climates. 相似文献
143.
Susanne C. Moser 《Climatic change》2012,111(2):165-175
The frequently heard call to harmonize adaptation and mitigation policies is well intended and many opportunities exist to
realize co-benefits by designing and implementing both in mutually supportive ways. But critical tradeoffs (inadequate conditions,
competition among means for implementation, and negative consequences of pursuing both simultaneously) also exist, along with
policy disconnects that are shaped by history, sequencing, scale, contextual variables, and controversial climate discourses
in the public. To ignore these issues can be expected to undermine a more comprehensive, better integrated climate risk management
portfolio. The paper discusses various implications of these tradeoffs between adaptation and mitigation for science and policy. 相似文献
144.
Anders Levermann Jonathan L. Bamber Sybren Drijfhout Andrey Ganopolski Winfried Haeberli Neil R. P. Harris Matthias Huss Kirstin Krüger Timothy M. Lenton Ronald W. Lindsay Dirk Notz Peter Wadhams Susanne Weber 《Climatic change》2012,110(3-4):845-878
We discuss potential transitions of six climatic subsystems with large-scale impact on Europe, sometimes denoted as tipping elements. These are the ice sheets on Greenland and West Antarctica, the Atlantic thermohaline circulation, Arctic sea ice, Alpine glaciers and northern hemisphere stratospheric ozone. Each system is represented by co-authors actively publishing in the corresponding field. For each subsystem we summarize the mechanism of a potential transition in a warmer climate along with its impact on Europe and assess the likelihood for such a transition based on published scientific literature. As a summary, the ‘tipping’ potential for each system is provided as a function of global mean temperature increase which required some subjective interpretation of scientific facts by the authors and should be considered as a snapshot of our current understanding. 相似文献
145.
Tom Akkermans Tim B?hme Matthias Demuzere Susanne Crewell Christoph Selbach Thorsten Reinhardt Axel Seifert Felix Ament Nicole P. M. van Lipzig 《Theoretical and Applied Climatology》2012,108(1-2):39-52
Regime-dependent evaluation is a relatively new approach to assess model performance. It consists of classifying the model biases according to a discrete number of regimes and evaluating model output within each regime. In this paper, the regimes are firstly defined by the large-scale atmospheric circulation, based on the objective Jenkinson-Collison classification technique which distinguishes synoptic patterns by strength, direction and vorticity of the geostrophic flow. Eight directional and two vorticity circulation regimes (circulation types) are specified. In this way, it is possible to quantify the model performance for cases with for example westerly winds only, or with cyclonic circulation only. A second regime classification is based on temperature, which allows for detection of temperature-dependent model performance. Modelled accumulated precipitation (mm/6?h) is evaluated with rain gauges for the years 2007 and 2008. Two variants of the COSMO model are evaluated: a fine-resolution version (2.8?km, COSMO-DE) and a coarse-resolution version (7?km, COSMO-EU). In COSMO-EU, a windward/leeward effect becomes visible since circulation is related to dominant wind direction, hence to windward and lee side of orography. In COSMO-DE, no circulation dependent but a height-related bias is identified and further explored, making use of temperature-dependent evaluation which unveils a positive model bias related to solid precipitation. 相似文献
146.
Jean Vallance Lluís Fontboté Massimo Chiaradia Agnès Markowski Susanne Schmidt Torsten Vennemann 《Mineralium Deposita》2009,44(4):389-413
The Jurassic (approximately 145 Ma) Nambija oxidized gold skarns are hosted by the Triassic volcanosedimentary Piuntza unit
in the sub-Andean zone of southeastern Ecuador. The skarns consist dominantly of granditic garnet (Ad20–98) with subordinate pyroxene (Di46–92Hd17–42Jo0–19) and epidote and are spatially associated with porphyritic quartz-diorite to granodiorite intrusions. Endoskarn is developed
at the intrusion margins and grades inwards into a potassic alteration zone. Exoskarn has an outer K- and Na-enriched zone
in the volcanosedimentary unit. Gold mineralization is associated with the weakly developed retrograde alteration of the exoskarn
and occurs mainly in sulfide-poor vugs and milky quartz veins and veinlets in association with hematite. Fluid inclusion data
for the main part of the prograde stage indicate the coexistence of high-temperature (500°C to >600°C), high-salinity (up
to 65 wt.% eq. NaCl), and moderate- to low-salinity aqueous-carbonic fluids interpreted to have been trapped at pressures
around 100–120 MPa, corresponding to about 4-km depth. Lower-temperature (510–300°C) and moderate- to low-salinity (23–2 wt.%
eq. NaCl) aqueous fluids are recorded in garnet and epidote of the end of the prograde stage. The microthermometric data (Th
from 513°C to 318°C and salinity from 1.0 to 23 wt.% eq. NaCl) and δ18O values between 6.2‰ and 11.5‰ for gold-bearing milky quartz from the retrograde stage suggest that the ore-forming fluid
was dominantly magmatic. Pressures during the early retrograde stage were in the range of 50–100 MPa, in line with the evidence
for CO2 effervescence and probable local boiling. The dominance of magmatic low-saline to moderately saline oxidizing fluids during
the retrograde stage is consistent with the depth of the skarn system, which could have delayed the ingression of external
fluids until relatively low temperatures were reached. The resulting low water-to-rock ratios explain the weak retrograde
alteration and the compositional variability of chlorite, essentially controlled by host rock compositions. Gold was precipitated
at this stage as a result of cooling and pH increase related to CO2 effervescence, which both result in destabilization of gold-bearing chloride complexes. Significant ingression of external
fluids took place after gold deposition only, as recorded by δ18O values of 0.4‰ to 6.2‰ for fluids depositing quartz (below 350°C) in sulfide-rich barren veins. Low-temperature (<300°C)
meteoric fluids (δ18Owater between −10.0‰ and −2.0‰) are responsible for the precipitation of late comb quartz and calcite in cavities and veins and
indicate mixing with cooler fluids of higher salinities (about 100°C and 25 wt.% eq. NaCl). The latter are similar to low-temperature
fluids (202–74.5°C) with δ18O values of −0.5‰ to 3.1‰ and salinities in the range of 21.1 to 17.3 wt.% eq. CaCl2, trapped in calcite of late veins and interpreted as basinal brines. Nambija represents a deep equivalent of the oxidized
gold skarn class, the presence of CO2 in the fluids being partly a consequence of the relatively deep setting at about 4-km depth. As in other Au-bearing skarn
deposits, not only the prograde stage but also the gold-precipitating retrograde stage is dominated by fluids of magmatic
origin. 相似文献
147.
Ratan K. Mohapatra Susanne P. Schwenzer Siegfried Herrmann Ulrich Ott Jamie D. Gilmour 《Geochimica et cosmochimica acta》2009,73(5):1505-1522
Meteorite “finds” from the terrestrial hot deserts have become a major contributor to the inventory of Martian meteorites. In order to understand their nitrogen and noble gas components, we have carried out stepped heating experiments on samples from two Martian meteorites collected from hot deserts. We measured interior and surface bulk samples, glassy and non-glassy portions of Dar al Gani 476 and Sayh al Uhaymir 005. We have also analyzed noble gases released from the Antarctic shergottite Lewis Cliff 88516 by crushing and stepped heating. For the hot desert meteorites significant terrestrial Ar, Kr, Xe contamination is observed, with an elementally fractionated air (EFA) component dominating the low temperature releases. The extremely low Ar/Kr/Xe ratios of EFA may be the result of multiple episodes of trapping/loss during terrestrial alteration involving aqueous fluids. We suggest fractionation processes similar to those in hot deserts to have acted on Mars, with acidic weathering on the latter possibly even more effective in producing elementally fractionated components. Addition from fission xenon is apparent in DaG 476 and SaU 005. The Ar-Kr-Xe patterns for LEW 88516 show trends as typically observed in shergottites - including evidence for a crush-released component similar to that observed in EETA 79001. A trapped Ne component most prominent in the surface sample of DaG 476 may represent air contamination. It is accompanied by little trapped Ar (20Ne/36Ar > 50) and literature data suggest its presence also in some Antarctic finds. Data for LEW 88516 and literature data, on the other hand, suggest the presence of two trapped Ne components of Martian origin characterized by different 20Ne/22Ne, possibly related to the atmosphere and the interior. Caution is recommended in interpreting nitrogen and noble gas isotopic signatures of Martian meteorites from hot deserts in terms of extraterrestrial sources and processes. Nevertheless our results provide hope that vice-versa, via noble gases and nitrogen in meteorites and other relevant samples from terrestrial deserts, Martian secondary processes can be studied. 相似文献
148.
Justin Filiberto David Baratoux David Beaty Doris Breuer Benjamin J. Farcy Matthias Grott John H. Jones Walter S. Kiefer Prajkta Mane Francis M. McCubbin Susanne P. Schwenzer 《Meteoritics & planetary science》2016,51(11):1935-1958
Multiple observations from missions to Mars have revealed compelling evidence for a volatile‐rich Martian crust. A leading theory contends that eruption of basaltic magmas was the ultimate mechanism of transfer of volatiles from the mantle toward the surface after an initial outgassing related to the crystallization of a magma ocean. However, the concentrations of volatile species in ascending magmas and in their mantle source regions are highly uncertain. This work and this special issue of Meteoritics & Planetary Science summarize the key findings of the workshop on Volatiles in the Martian Interior (Nov. 3–4, 2014), the primary open questions related to volatiles in Martian magmas and their source regions, and the suggestions of the community at the workshop to address these open questions. 相似文献
149.
Benedikt Soja Richard S. Gross Claudio Abbondanza Toshio M. Chin Michael B. Heflin Jay W. Parker Xiaoping Wu Tobias Nilsson Susanne Glaser Kyriakos Balidakis Robert Heinkelmann Harald Schuh 《Journal of Geodesy》2018,92(9):1063-1077
The Global Geodetic Observing System requirement for the long-term stability of the International Terrestrial Reference Frame is 0.1 mm/year, motivated by rigorous sea level studies. Furthermore, high-quality station velocities are of great importance for the prediction of future station coordinates, which are fundamental for several geodetic applications. In this study, we investigate the performance of predictions from very long baseline interferometry (VLBI) terrestrial reference frames (TRFs) based on Kalman filtering. The predictions are computed by extrapolating the deterministic part of the coordinate model. As observational data, we used over 4000 VLBI sessions between 1980 and the middle of 2016. In order to study the predictions, we computed VLBI TRF solutions only from the data until the end of 2013. The period of 2014 until 2016.5 was used to validate the predictions of the TRF solutions against the measured VLBI station coordinates. To assess the quality, we computed average WRMS values from the coordinate differences as well as from estimated Helmert transformation parameters, in particular, the scale. We found that the results significantly depend on the level of process noise used in the filter. While larger values of process noise allow the TRF station coordinates to more closely follow the input data (decrease in WRMS of about 45%), the TRF predictions exhibit larger deviations from the VLBI station coordinates after 2014 (WRMS increase of about 15%). On the other hand, lower levels of process noise improve the predictions, making them more similar to those of solutions without process noise. Furthermore, our investigations show that additionally estimating annual signals in the coordinates does not significantly impact the results. Finally, we computed TRF solutions mimicking a potential real-time TRF and found significant improvements over the other investigated solutions, all of which rely on extrapolating the coordinate model for their predictions, with WRMS reductions of almost 50%. 相似文献
150.