From brightening to dimming in sunshine duration over the eastern and central Tibetan Plateau (1961–2005)     

Qinglong You  Shichang Kang  Wolfgang-Albert Flügel  Arturo Sanchez-Lorenzo  Yuping Yan  Jie Huang  Javier Martin-Vide 《Theoretical and Applied Climatology》2010,101(3-4):445-457

The Tibetan Plateau (TP) with an average elevation of over 4,000 m asl is the highest and most extensive highland in the world. We used monthly mean sunshine duration from the Chinese Meteorological Administration to examine the spatial and temporal variability of sunshine duration at 71 stations with elevations above 2,000 m asl in the eastern and central TP during the 1961–2005 period. The temporal evolution of the mean annual sunshine duration series shows a significant increase from 1961 to 1982 at a rate of 49.8 h/decade, followed by a decrease from 1983 to 2005 at a rate of ?65.1 h/decade, with an overall significant decrease at a rate of ?20.6 h/decade during the whole 1961–2005 period, which is mainly due to the summer and spring seasons. This confirms the evidence that sunshine duration in the TP ranges from brightening to dimming in accordance with sunshine duration trends in the rest of China. The surface solar radiation downwards from ERA-40 reanalysis data in the same region confirms the brightening/dimming phenomenon shown by the sunshine duration before/after the 1980s. Otherwise, additional climatic variables such as low cloud amount, total cloud amount, precipitation, relative humidity and water vapor pressure, in most cases, exhibit significant negative correlation with sunshine duration in the TP on an annual and seasonal basis before and after 1982, respectively. The trends of these variables suggest that changes in some of them might be related to the brightening and dimming detected with the use of sunshine duration measurements over the TP. We also hypothesize that the impact of anthropogenic aerosols upon the climatic variables analyzed cannot be rejected, especially in the significant increase in low cloud cover since approximately 1980.  相似文献   

Impacts of warm and cold situations in the Mediterranean basins on the West African monsoon: observed connection patterns (1979–2006) and climate simulations     

Bernard Fontaine  Javier Garcia-Serrano  Pascal Roucou  Belen Rodriguez-Fonseca  Teresa Losada  Fabrice Chauvin  Sébastien Gervois  Sivarajan Sijikumar  Paolo Ruti  Serge Janicot 《Climate Dynamics》2010,35(1):95-114

Using both empirical and numerical ensemble approaches this study focuses on the Mediterranean/West African relationship in northern summer. Statistical analyses utilize skin temperature, sea surface temperature, in situ and satellite rainfall, outgoing longwave radiation (OLR) observations and reanalyzed data winds and specific humidity on isobaric surfaces. Numerical investigations are based on a large set of sensitivity experiments performed on four atmospheric general circulation models (AGCM): ARPEGE-Climat3, ECHAM4, LMDZ4 and UCLA7.3. Model outputs are compared to observations, discussed model by model and with an ensemble (multi-model) approach. As in previous studies the anomalous Mediterranean warm events are associated with specific impacts over the African monsoon region, i.e., a more intense monsoon, enhanced flux convergence and ascendances around the ITCZ, a strengthening of low level moisture advection and a more northward location of ascending motion in West Africa. The results show also new features (1) thermal variability observed in the two Mediterranean basins has unalike impacts, i.e. the western Mediterranean covaries with convection in Gulf of Guinea, while the eastern Mediterranean can be interpreted as Sahelian thermal-forcing; (2) although observations show symmetry between warming and cooling, modelling evidences only support the eastern warming influence; (3) anomalous East warm situations are associated with a more northward migration of the monsoon system accompanied by enhanced southwertely flow and weakened northeasterly climatological wind; (4) the multi-model response shows that anomalous East warm surface temperatures generate an enhancement of the overturning circulation in low and high levels, an increase in TEJ (Tropical Eeasterly Jet) and a decrease in AEJ (African Eeasterly Jet).  相似文献   

Objective probabilities about future climate are a matter of opinion     

Carlos Gay  Francisco Estrada 《Climatic change》2010,99(1-2):27-46

In this paper, the unfeasibility of producing “objective” probabilistic climate change scenarios is discussed. Realizing that the knowledge of “true” probabilities of the different scenarios and temperature changes is unachievable, the objective must be to find the probabilities that are the most consistent with what our state of knowledge and expert judgment are. Therefore, subjective information plays, and should play, a crucial role. A new methodology, based on the Principle of Maximum Entropy, is proposed for constructing probabilistic climate change scenarios when only partial information is available. The objective is to produce relevant information for decision-making according to different agents’ judgment and subjective beliefs. These estimates have desirable properties such as: they are the least biased estimate possible on the available information; maximize the uncertainty (entropy) subject to the partial information that is given; The maximum entropy distribution assigns a positive probability to every event that is not excluded by the given information; no possibility is ignored. The probabilities obtained in this manner are the best predictions possible with the state of knowledge and subjective information that is available. This methodology allows distinguishing between reckless and cautious positions regarding the climate change threat.  相似文献   

Dynamic adaptation of maize and wheat production to climate change   总被引：2，自引：0，他引：2  

Francisco J. Meza  Daniel Silva 《Climatic change》2009,94(1-2):143-156

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Gas kinematics in the halo of the warm ULIRG PKS1345+12     

Javier Rodríguez Zaurín  Joanna Holt  Clive N. Tadhunter  Rosa M. González Delgado 《Astrophysics and Space Science》2009,324(2-4):225-229

We use long-slit spectra taken with the William Herschel Telescope on La Palma and high-resolution Hubble Space Telescope imaging to study the gas kinematic in the halo of the ultraluminous infrared/radio galaxy PKS1345+12 (z=0.122). Our long-slit spectra show line splitting at the locations of massive star clusters ( $10^{6}<M_{\mathrm{SSC}}^{\mathrm{YSP}}<10^{7}$ M_⊙), indicating that they are moving at up to 450 km?s^?1 with respect to the local ambient gas. Given their kinematics, it is plausible that these super star clusters have been formed either in fast-moving gas streams or tidal tails that are falling back into the nuclear regions as part of the merger process, or as a consequence of jet-induced star formation linked to the extended, diffuse radio emission detected in the halo of the galaxy.  相似文献   

The SDSS DR6 luminosity functions of galaxies     

Antonio D. Montero-Dorta  Francisco Prada 《Monthly notices of the Royal Astronomical Society》2009,399(3):1106-1118

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A new insight on the decreasing sea level trend over the Ionian basin in the last decades     

Jorge Del Río Vera  Francisco Criado-Aldeanueva  Jesús García-Lafuente  F. Javier Soto-Navarro 《Global and Planetary Change》2009,68(3):232-235

Altimetry measurements over the Ionian region and tide gauge records along the southern Italian coasts have been combined to analyse the negative sea level trend over the Ionian basin in the last decades. The apparent decreasing trend should be better understood as an abrupt sea level drop in 1998 probably linked to changes in the surface circulation in the Ionian basin induced by the Eastern Mediterranean Transient, which changed from anticyclonic to cyclonic about March 1998. From then onwards, a rising rate of 7.9 ± 0.9 mm/year is observed over the basin.  相似文献   

Regional stratigraphy and distribution of epigenetic stratabound celestine, fluorite, barite and Pb–Zn deposits in the MVT province of northeastern Mexico     

Francisco González-Sánchez  Antoni Camprubí  Eduardo González-Partida  Rafael Puente-Solís  Carles Canet  Elena Centeno-García  Viorel Atudorei 《Mineralium Deposita》2009,44(3):343-361

Northeastern Mexico hosts numerous epigenetic stratabound carbonate-hosted low-temperature hydrothermal deposits of celestine, fluorite, barite and zinc-lead, which formed by replacement of Mesozoic evaporites or carbonate rocks. Such deposits can be permissively catalogued as Mississippi Valley-type (MVT) deposits. The deposits studied in the state of Coahuila are associated with granitic and metasedimentary basement highs (horsts) marginal or central to the Mesozoic Sabinas Basin. These horsts controlled the stratigraphy of the Mesozoic basins and subsequently influenced the Laramide structural pattern. The Sabinas Basin consists of ~6,000-m-thick Jurassic to Cretaceous siliciclastic, carbonate and evaporitic series. The MVT deposits are mostly in Barremian and in Aptian-Albian to Cenomanian formations and likely formed from basinal brines that were mobilized during the Laramide orogeny, although earlier diagenetic replacement of evaporite layers (barite and celestine deposits) and lining of paleokarstic cavities in reef carbonates (Zn–Pb deposits) is observed. Fluid inclusion microthermometry and isotopic studies suggest ore formation due to mixing of basinal brines and meteoric water. Homogenization temperatures of fluid inclusions range from 45°C to 210°C; salinities range from 0 to 26 wt.% NaCl equiv., and some inclusions contain hydrocarbons or bitumen. Sulfur isotope data suggest that most of the sulfur in barite and celestine is derived from Barremian to Cenomanian evaporites. Regional geology and a compilation of metallogenic features define the new MVT province of northeastern Mexico, which comprises most of the state of Coahuila and portions of the neighboring states of Nuevo León, Durango and, perhaps extends into Zacatecas and southern Texas. This province exhibits a regional metal zonation, with celestine deposits to the south, fluorite deposits to the north and barite and Zn–Pb deposits mostly in the central part.  相似文献   

Structure and stratigraphy of the Sabinas Basin and the role of sedimentary brines in the formation of MVT deposits in Northeastern Mexico     

Francisco González-Sánchez  Antoni Camprubí  Eduardo González-Partida  Carles Canet  Antonin Richard  Viorel Atudorei  Marie-Christine Boiron 《Journal of Geochemical Exploration》2009

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Model prediction capacity of ephemeral gully evolution in conservation tillage systems     

Eduardo Luquin  Miguel A. Campo-Bescós  Rafael Muñoz-Carpena  Ronald L. Bingner  Richard M. Cruse  Henrique G. Momm  Robert R. Wells  Javier Casalí 《地球表面变化过程与地形》2021,46(10):1909-1925

Ephemeral gully (EG) erosion has an important impact on agricultural soil losses and increases field surface hydrology connectivity and transport of pollutants to nearby water bodies. Watershed models including an EG component are scarce and not yet properly evaluated. The objective of this study is to evaluate the capacity of one such tool, AnnAGNPS, to simulate the evolution of two EG formed in a conservation tillage system. The dataset for model testing included runoff measurements and EG morphological characteristics during 3 years. Model evaluation focused on EG evolution of volume, width, and length model outputs, and included calibration and testing phases and a global sensitivity analysis (GSA). While the model did not fully reproduce width and length, the model efficiency to simulate EG volume was satisfactory for both calibration and testing phases, supporting the watershed management objectives of the model. GSA revealed that the most sensitive factors were EG depth, critical shear stress, headcut detachment exponent coefficient b, and headcut detachment leading coefficient a. For EG outputs the model was additive, showing low sensitivity to interactions between the inputs. Prediction of EG spatial evolution on conservation tillage systems requires improved development of gully erosion components, since many of the processes were developed originally for traditional tillage practices or larger channel systems. Our results identify the need for future research when EG form within conservation tillage systems, in particular to study gully headcut, soil erodibility, and width functions specific to these practices.  相似文献