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The retrieval of Snow Water Equivalent (SWE) from remote sensing satellites continues to be a very challenging problem. In this paper, we evaluate the accuracy of a new SWE product derived from the blending of a passive microwave SWE product based on the Advanced Microwave Sounding Unit (AMSU) with a multi‐sensor snow cover extent product based on the Interactive Multi‐sensor Snow and Ice Mapping System (IMS). The microwave measurements have the ability to penetrate the snow pack, and thus, the retrieval of SWE is best accomplished using the AMSU. On the other hand, the IMS maps snow cover more reliably due to the use of multiple satellite and ground observations. The evolution of global snow cover from the blended, the AMSU and the IMS products was examined during the 2006 snow season. Despite the overall good inter‐product agreement, it was shown that the retrievals of snow cover extent in the blended product are improved when using IMS, with implications for improved microwave retrievals of SWE. In a separate investigation, the skill of the microwave SWE product was also examined for its ability to correctly estimate SWE globally and regionally. Qualitative evaluation of global SWE retrievals suggested dependence on land surface temperature: the lower the temperature, the higher the SWE retrieved. This temperature bias was attributed in part to temperature effects on those snow properties that impact microwave response. Therefore, algorithm modifications are needed with more dynamical adjustments to account for changing snow cover. Quantitative evaluation over Slovakia in central Europe, for a limited period in 2006, showed reasonably good performance for SWE less than 100 mm. Sensitivity to deeper snow decreased significantly. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Julio Cezar Mendes Ciro Alexandre vila Ronaldo Mello Pereira Mnica P.L. Heilbron Candido A.V. Moura 《Gondwana Research》2006,9(3):326-336
In the central segment of the Ribeira belt, southeast Brazil, several foliated porphyritic granitic bodies intrude high-grade migmatitic gneisses of the Andrelândia and Juiz de Fora domains and Embú Complex. Results of geological, geochemical and geochronological investigations of the Maromba, Pedra Selada, Serra do Lagarto and Funil porphyritic I-type granites provide profound similarities, except for the distinct geochemical behavior of the Funil Granite, perhaps related to a different crustal source. These granitoids show similar structural, textural and mineralogical features. Pb-evaporation of single zircons provided ages of 586 ± 6, 579.6 ± 6.3, 586.3 ± 4.8 and 584 ± 5 Ma for the granites, respectively, coincident with the syn-collision I episode of the central Ribeira belt. The intrusion of I-type porphyritic granitoids coeval with the main collisional event has not often been reported in the geological literature. The most common syn-collisional granitic magmatism has normally an S-type signature or even a slightly peraluminous I-type character. However, the occurrence of coeval I- and S-type syn-tectonic granites along the central Ribeira belt, as observed in the investigated area and discussed in this paper is noteworthy. 相似文献
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The impact of taro (Colocasia esculenta) cultivation on the total evaporation of a Cyperus latifolius marsh 
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下载免费PDF全文 Total evaporation (ET) is one of the major components of the water budget of a wetland. Very little research has been conducted on the loss of water to the atmosphere from different wetland vegetation types occurring in southern Africa. This study on the ET of taro (locally known as madumbe) and sedge within the Mbongolwane wetland was conducted to assess the potential impact of madumbe cultivation on the hydrology of the wetland. Sugarcane planted on the contributing catchment outside the wetland was the other crop examined. Two field campaigns were conducted in November 2009 and January 2010 during the growing season of the madumbe crop to quantify ET rates in the Mbongolwane wetland and from sugar cane in the surrounding catchment. ET was measured over two vegetation types in the wetland, namely: madumbe (Colocasia esculenta); sedge (Cyperus latifolius) with some reeds (Phragmites australis); and sugarcane in adjacent terrestrial areas. ET from the madumbes ranged from 1.0 to 6.0 mm day?1. The daily average ET rates in November 2009 were 3.5 and 4.9 mm for the madumbe and sedge sites, respectively, and 4.0 mm for sugarcane grown in the catchment. The daily average ET rates in January 2010 were 3.3 and 3.7 mm for the madumbes and sedge sites, respectively, and 2.4 mm for the sugarcane site. The daily ET was therefore lower at the madumbe site in November 2009 and in January 2010 compared to the sedge site. An average crop factor of 0.6 was obtained from this study during the growth stage of the madumbes. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Abstract A two-level quasi-geostrophic general circulation model is developed to test various theories relating to surface albedo changes in the Sahara/Sahel regions of Africa. The heating function in the model is varied so as to examine the effects of both increases and decreases in surface albedo. Loss of vegetation cover is linked to increased surface albedo, and from the experiments, the delicate balance between the Sahara/Sahel is noted. Revegetating the Sahara would tend to decrease the surface albedo and the model shows that this experiment would be successful in reclaiming some of the desert. 相似文献
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Julio Cezar Mendes Silvia Regina de Medeiros Ian McReath Cristina Maria Pinheiro de Campos 《Gondwana Research》2005,8(3):337-345
In the central-southern region of Espírito Santo State, southeastern Brazil, several granitoids with a variable composition intruded high-grade metamorphic rocks, in the northern segment of the Ribeira fold belt. A close relationship between hydrous and anhydrous facies is present in some of the plutons, including the Varzea Alegre Igneous Complex, which has an inner domain formed by gabbro, diorite and granite, and an irregular outer ring of charnockitic rocks. These green megaporphyritic charnockites have primary anhydrous mineral assemblage, I-type and metaluminous character, and high-K calc-alkaline signature. U-Pb zircon single crystal ages obtained by TIMS indicate crystallization at about 500 Ma, similar to other late tectonic plutons of this part of the Ribeira belt. Sr and Nd isotopic ratios ranging from 0.7078 to 0.7096 and 0.5114 to 0.5116 respectively, are interpreted to be indicative of a hybrid origin from crustal and mantle-derived magmas. A binary diagram using Sr isotope ratios also demonstrates that the genesis of the charnockites probably included both magma mixing and fractional crystallization processes. 相似文献
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The Venda Nova Pluton(VNP) is a zoned ring structure emplaced in the southern portion of the Neoproterozoic Aracuai Belt,in Espirito Santo.Brazil.It is a slightly westward tilted cylinder-like intrusion,with an almost circular horizontal section.In the center of this structure,an off-centered gabbro-noritic core,surrounded by syeno-monzonitic rocks,intrudes an outer ring of charnockites and norite.These envelop the syeno-monzonitic and gabbro-noritic center,as a narrow discontinuous belt. While,in the core intrusion,mingling and mixing processes are widespread and well documented in the literature,in the outer ring,the norite and charnockite layers show predominantly homogeneous and isotropic internal structures.Nevertheless,smaller interaction zones between charnockites and norite denote a comparatively more restricted mingling process.The norite is a fine-grained rock with hypidiomorphic granular to intergranular texture.The charnockites are medium-grained and made up of: (a) orthopyroxene-tonalite.(b) orthopyroxene-quartz-diorite,and(c) orthopyroxene-granodiorite with hypidiomorphic granular to porphyritic textures.In all lithotypes both ortho- and clinopyroxene are replaced by hornblende and biotite.Two contrasting compositional sequences have been recognized,based on whole rock geochemistry:(1) a basic,with tholeiitic affinities(norite) and,(2) an intermediate. medium-K calc-alkaline,comprising the charnockites.Estimated crystallization temperatures,which have been calculated from micro-probe analysis of pyroxenes,range from 915±25℃to 960±50℃.Re-equilibration temperature(ilmenite-magnetite calibration) is around 600±50℃.This indicates oxygen fugacities four order of magnitude below the FMQ-buffer and a reduced environment. Coeval pressure conditions estimated from the Al-content in hornblende range from 5.5±0.6 kbar.Data obtained for the norite point toward an evolution from the partial melting of an anhydrous tholeiitic mantle magma.The charnockites may correspond to the differentiation of a calc-alkaline parental magma.The later could be the hybrid product from the contamination and mixing between the anhydrous tholeiitic magma with other deeper crustal sources.Further the magmatic system evolved through fractionation of orthopyroxene.clinopyroxene.plagioclase and ilmenite.Our results support the hypothesis for the evolution of the Venda Nova Pluton through a mantle-crust delamination process probably related to the collapse of the Aracuai orogeny. 相似文献
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