Search results for "Oceano"
showing 10 items of 1626 documents
Comparison of ERA40 cloud top phase with POLDER-1 observations
2008
[1] A detailed grid-point-based comparison of the cloud top phase derived from the 40-year reanalyses (ERA40) of the European Centre for Medium-Range Weather Forecasts (ECMWF) with satellite measurements is presented. For this purpose an algorithm is implemented to extract a two-dimensional “satellite-like” field of the cloud top phase from ERA40 data. This field is compared with cloud top phase data from the Polarization and Directionality of the Earth Reflectances (POLDER-1) instrument which was in orbit from November 1996 to June 1997. The thermodynamic cloud phase in ERA40 data is parameterized as a function of temperature with pure liquid clouds above 0°C, pure ice clouds below −23°C a…
Comparative study of three satellite image time-series decomposition methods for vegetation change detection
2018
International audience; Satellite image time-series (SITS) methods have contributed notably to detection of global change over the last decades, for instance by tracking vegetation changes. Compared with multi-temporal change detection methods, temporally highly resolved SITS methods provide more information in a single analysis, for instance on the type and consistency of change. In particular, SITS decomposition methods show a great potential in extracting various components from non-stationary time series, which allows for an improved interpretation of the temporal variability. Even though many case studies have applied SITS decomposition methods, a systematic comparison of common algori…
Dynamics of a local Alpine flooding event in October 2011: moisture source and large‐scale circulation
2014
Alpine heavy precipitation events often affect small catchments, although the circulation pattern leading to the event extends over the entire North Atlantic. The various scale interactions involved are particularly challenging for the numerical weather prediction of such events. Unlike previous studies focusing on the southern Alps, here a comprehensive study of a heavy precipitation event in the northern Alps in October 2011 is presented with particular focus on the role of the large-scale circulation in the North Atlantic/European region. During the event exceptionally high amounts of total precipitable water occurred in and north of the Alps. This moisture was initially transported alon…
Overview of the Spirit Mars Exploration Rover Mission to Gusev Crater: Landing site to Backstay Rock in the Columbia Hills
2006
Spirit landed on the floor of Gusev Crater and conducted initial operations on soil covered, rock-strewn cratered plains underlain by olivine-bearing basalts. Plains surface rocks are covered by wind-blown dust and show evidence for surface enrichment of soluble species as vein and void-filling materials and coatings. The surface enrichment is the result of a minor amount of transport and deposition by aqueous processes. Layered granular deposits were discovered in the Columbia Hills, with outcrops that tend to dip conformably with the topography. The granular rocks are interpreted to be volcanic ash and/or impact ejecta deposits that have been modified by aqueous fluids during and/or after…
Geochemical properties of rocks and soils in Gusev Crater, Mars: Results of the Alpha Particle X-Ray Spectrometer from Cumberland Ridge to Home Plate
2008
Geochemical diversity of rocks and soils has been discovered by the Alpha Particle X-Ray Spectrometer (APXS) during Spirit’s journey over Husband Hill and down into the Inner Basin from sol 470 to 1368. The APXS continues to operate nominally with no changes in calibration or spectral degradation over the course of the mission. Germanium has been added to the Spirit APXS data set with the confirmation that it occurs at elevated levels in many rocks and soils around Home Plate. Twelve new rock classes and two new soil classes have been identified at the Spirit landing site since sol 470 on the basis of the diversity in APXS geochemistry. The new rock classes are Irvine (alkaline basalt…
Some aspects of the seasonal variation of carbon dioxide and ozone
1968
An attempt is made to estimate the seasonal source function, Q , of CO 2 on the basis of data for the biosphere, provided by Lieth, and for other sources. The variation of soil respiration appears to be the most uncertain factor. The resulting CO 2 variations in the atmosphere are calculated for horizontal exchange coefficients, K , which vary with latitude. Comparison with observations given by Bolin & Keeling shows that the results are not very sensitive with respect to the assumed variations of Q and of K with latitude. Previous results on the 0 3 budget are used to calculate seasonal variations of tropospheric 0 3 for stratospheric injection rates, and K values which vary with latitude.…
Effects of dead time losses on terrestrial gamma ray flash measurements with the Burst and Transient Source Experiment
2010
[1] Measurements from the Burst and Transient Source Experiment (BATSE) instrument on the Compton Gamma Ray Observatory (CGRO) are the only ones where characteristics of single terrestrial gamma ray flashes (TGFs) have been obtained thus far. However, it has been reported that the measurements suffer from significant dead time losses which complicates the analysis and raises question about earlier BATSE studies. These losses are due to the high-intensity flux combined with limitations of the time resolution of the instrument. Since these losses will affect both the spectrum and the temporal distribution of the individual TGFs, results based on BATSE data need to be revisited, including our …
Soil sedimentology at Gusev Crater from Columbia Memorial Station to Winter Haven
2008
[1] A total of 3140 individual particles were examined in 31 soils along Spirit's traverse. Their size, shape, and texture were quantified and classified. They represent a unique record of 3 years of sedimentologic exploration from landing to sol 1085 covering the Plains Unit to Winter Haven where Spirit spent the Martian winter of 2006. Samples in the Plains Unit and Columbia Hills appear as reflecting contrasting textural domains. One is heterogeneous, with a continuum of angular-to-round particles of fine sand to pebble sizes that are generally dust covered and locally cemented in place. The second shows the effect of a dominant and ongoing dynamic aeolian process that redistributes a un…
Composition-resolved size distributions of volcanic aerosols in the Mt. Etna plumes
2008
Particle size distributions for soluble and insoluble species in Mt. Etna's summit plumes were measured across an extended size range (10 nm < d < 100 μm) using a combination of techniques. Automated scanning electron microscopy (QEMSCAN) was used to chemically analyze many thousands of insoluble particles (collected on pumped filters) allowing the relationships between particle size, shape, and composition to be investigated. The size distribution of fine silicate particles (d < 10 μm) was found to be lognormal, consistent with formation by bursting of gas bubbles at the surface of the magma. The compositions of fine silicate particles were found to vary between magmatic and nearl…
Column-integrated aerosol optical properties from ground-based spectroradiometer measurements at Barrax (Spain) during the Digital Airborne Spectrome…
2003
[1] The Digital Airborne Imaging Spectrometer Experiment (DAISEX) was carried out for the European Space Agency (ESA) in order to develop the potential of spaceborne imaging spectroscopy for a range of different scientific applications. DAISEX involved simultaneous data acquisitions using different airborne imaging spectrometers over test sites in southeast Spain (Barrax) and the Upper Rhine valley (Colmar, France, and Hartheim, Germany). This paper presents the results corresponding to the columnintegrated aerosol optical properties from ground-based spectroradiometer measurements over the Barrax area during the DAISEX campaign days in the years 1998, 1999, and 2000. The instruments used f…