Characteristics of large-scale atmospheric circulation related to extreme monthly rainfall anomalies in the Pampa Region, Argentina, under non-ENSO conditions     

B. Scian  J. C. Labraga  W. Reimers  O. Frumento 《Theoretical and Applied Climatology》2006,85(1-2):89-106

Summary There is a widely held view that the Pampa region (PR) dry and wet periods are predominantly a consecuence of the El Ni?o-Southern oscillation (ENSO) phenomenom. The current paper focuses on non-ENSO rainfall anomalies for the period 1948–2000, the more recent of which have had catastrophic consequences throughout the region. We analyze horizontal water vapor transport, pressure and circulation anomalies occurring in Southern South America (SSA) during this type of event. Positive and negative (wet and dry) extreme events during the rainy and dry seasons in the region were registered. Based on NCEP reanalysis data it was established that under rainfall deficit, anomalies of similar intensity occurred simultaneously in the PR and in central Chile, whereas under excess rainfall the anomalies were mostly confined to the PR. The existence of a cyclone-anticyclone pair in the anomalous circulation pattern over mid latitudes of the Atlantic and Pacific oceans and straddling the southern portion of the continent maintains an intense and extense meridional circulation over the continental plains, which leads to the abnormal values in moisture transport and rainfall rate. The atmospheric water balance equation calculated for the PR indicates that anomalous water vapor is carried in from the continental equatorial region and from the subtropical Atlantic, its magnitude varying in accordance with the season and the sign of the anomaly. Furthermore, evidence of the important role of transient terms corroborates their contribution to the anomalous total moisture flux divergence under rainfall deficit during the dry season. The mean sea-level pressure anomaly fields of the extreme cases were further examined by principal component analysis to discern those circulation features directly linked to rainfall deviations.  相似文献   

Estimation of monthly average solar radiation in Libya     

F. K. Bannani  T. A. Sharif  A. O. R. Ben-Khalifa 《Theoretical and Applied Climatology》2006,83(1-4):211-215

Summary In order to estimate the monthly average global radiation, regression equations for eleven stations in Libya are fitted, using monthly average hours of sunshine duration as predictors. Since only eight years of monthly average global radiation are available for each station, a reliable model for estimating solar radiation for each single month could not be obtained. The monthly data were merged together to produce a single regression equation for each station rather than twelve monthly regression equations. The results indicate that the regression equations for ten stations out of eleven hold very well.  相似文献   

Past and future polar amplification of climate change: climate model intercomparisons and ice-core constraints   总被引：1，自引：0，他引：1  

V. Masson-Delmotte  M. Kageyama  P. Braconnot  S. Charbit  G. Krinner  C. Ritz  E. Guilyardi  J. Jouzel  A. Abe-Ouchi  M. Crucifix  R. M. Gladstone  C. D. Hewitt  A. Kitoh  A. N. LeGrande  O. Marti  U. Merkel  T. Motoi  R. Ohgaito  B. Otto-Bliesner  W. R. Peltier  I. Ross  P. J. Valdes  G. Vettoretti  S. L. Weber  F. Wolk  Y. Yu 《Climate Dynamics》2006,27(4):437-440

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Determining rainy season onset and retreat over Nigeria from precipitation amount and number of rainy days     

T. O. Odekunle 《Theoretical and Applied Climatology》2006,83(1-4):193-201

Summary This study assesses the relative efficiency of the use of rainfall amount and rainy days in the determination of rainfall onset and retreat dates in Nigeria based on rainfall data for the period 1961 to 2000. Daily rainfall data were sourced from the archives of the Nigerian Meteorological Services, Oshodi Lagos. The specific locations for which data were collected are: Ibadan, Ilorin, Kaduna and Kano. The method of percentage cumulative mean rainfall values was employed in the determination of the rainfall onset and retreat dates. The results obtained show that both rainfall amount and rainy days are equally effective in the determination of the mean rainfall onset and retreat dates in Nigeria. With regards to the rainfall onset and retreat dates of the individual years however, the method based on the rainy days is more effective than that based on rainfall amount, as the former yielded more realistic dates than the latter. It is thus recommended that studies investigating rainfall onset and retreat dates within a series of individual years in Nigeria, should be based on rainy days rather than rainfall amount.  相似文献   

Assessment of the atmospheric concentration of pollutants evaporated from the soil     

A. I. Burkov  O. I. Vozzhennikov 《Russian Meteorology and Hydrology》2007,32(6):366-372

A model for pollutant redistribution in the soil-atmosphere system is suggested for the case of the local pollution of the underlying surface. The vertical migration of soil pollution is described with a convection-diffusion equation in the sorbing medium, supposing an instantaneous equilibrium is established between the pollutant phases in the soil. The Monin-Obukhov similarity theory for the surface atmospheric layer, modified for the case of limited pollution of the underlying surface, is used to parametrize the pollutant transport and dispersion in the atmosphere. A characteristic feature of the model is its ability to calculate the air pollution concentrations over the polluted soil surface. The model was tested on the results of a field experiment with volatile pesticides.  相似文献   

Compositions,sources and depositional environments of organic matter from the Middle Jurassic clays of Poland     

Leszek Marynowski  Michał Zatoń  Bernd R.T. Simoneit  Angelika Otto  Mariusz O. Jędrysek  Cezary Grelowski  Slawomir Kurkiewicz 《Applied Geochemistry》2007

The comprehensive biomarker characteristics from previously undescribed Middle Jurassic clays of Poland are presented. The molecular composition of the organic matter (OM) derived from clays of Aalenian to Callovian age has not changed significantly through time. High relative concentrations of many biomarkers typical for terrestrial material suggest a distinct dominance of OM derived from land plants. Increasing concentrations of C₂₉-diaster-13(17)-enes towards the northern part of the basin indicate an increase in terrestrial input. This terrestrial material would have originated from the enhanced transport of organic matter from land situated at the northern bank of the basin, i.e., the Fennoscandian Shield. The organic matter was deposited in an oxic to suboxic environment, as indicated by relatively low concentrations of C₃₃–C₃₅ homohopanes, moderate to high Pr/Ph ratio values, an absence of compounds characteristic for anoxia and water column stratification, such as isorenieratane, aryl isoprenoids and gammacerane, as well as common benthic fauna and burrows. δ¹⁸O measurements from calcitic rostra of belemnites suggest that the mean value of the Middle Jurassic sea-water temperature of the Polish Basin was 13.1 °C. It is suggested that this mirrored the temperature of the lower water column because belemnites are considered here to be necto-benthic. The organic matter from the Middle Jurassic basin of Poland is immature. This is clearly indicated by a large concentration of biomarkers with the biogenic configurations, such as ββ-hopanes, hop-13(18)-enes, hop-17(21)-enes, diasterenes and sterenes. The identification of preserved, unaltered biomolecules like ferruginol, 6,7-dehydroferruginol and sugiol in Protopodocarpoxylon wood samples from these sediments present particularly strong evidence for the presence of immature OM in the Middle Jurassic sediments. Moreover, the occurrence of these polar diterpenoids is important due to the fact that they are definitely the oldest known natural products detected in geological samples.  相似文献   

Aqueous uptake of uranium onto pyrite surfaces; reactivity of fresh versus weathered material     

T.B. Scott  O. Riba Tort  G.C. Allen 《Geochimica et cosmochimica acta》2007,71(21):5044-5053

In order to better understand the interaction between aqueous uranium and pyrite (FeS₂) the uptake of uranium onto the surfaces of both weathered and freshly generated pyrite surfaces was examined using batch sorption experiments. Analysis was performed using X-ray photoelectron spectroscopy (XPS). The results clearly indicate that freshly polished pyrite surfaces are efficient scavengers of uranium from solution, while weathered surfaces exhibit only limited uptake. Results also indicate partial reduction of uranium at the pyrite surfaces, with a heterogeneous distribution of U(IV) and U(VI) species.  相似文献   

Cl,N, C isotopic analysis of common agro-chemicals for identifying non-point source agricultural contaminants     

W.K. Annable  S.K. Frape  O. Shouakar-Stash  T. Shanoff  R.J. Drimmie  F.E. Harvey 《Applied Geochemistry》2007

The isotopic compositions of commercially available herbicides were analyzed to determine their respective ¹⁵N, ¹³C and ³⁷Cl signatures for the purposes of developing a discrete tool for tracing and identifying non-point source contaminants in agricultural watersheds. Findings demonstrate that of the agrochemicals evaluated, chlorine stable isotopes signatures range between δ³⁷Cl = −4.55‰ and +3.40‰, whereas most naturally occurring chlorine stable isotopes signatures, including those of road salt, sewage sludge and fertilizers, vary in a narrow range about the Standard Mean Ocean Chloride (SMOC) between −2.00‰ and +1.00‰. Nitrogen stable isotope values varied widely from δ¹⁵N = −10.86‰ to +1.44‰ and carbon stable isotope analysis gave an observed range between δ¹³C = −37.13‰ and −21.35‰ for the entire suite of agro-chemicals analyzed. When nitrogen, carbon and chlorine stable isotope analyses were compared in a cross-correlation analysis, statistically independent isotopic signatures exist suggesting a new potential tracer tool for identifying herbicides in the environment.  相似文献   

Functioning of the ecosystem in the Sea of Azov during winter     

G. G. Matishov  O. V. Stepan’yan  V. V. Povazhnyi  G. V. Kovaleva  K. V. Kreneva 《Doklady Earth Sciences》2007,413(1):297-299

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Effective coefficients of quasi-stationary Maxwell equations with multiscale random inhomogeneous electroconductivity     

E. P. Kurochkina  O. N. Soboleva  M. I. Epov 《Doklady Earth Sciences》2007,413(2):491-496

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