951 resultados para Air-sea interactions


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The extent of snow cover at the end of the ablation season on glaciers in the Tyrolean Alps in 1972 and 1973 was determined from Landsat-1 Multispectral Scanner (MSS) images. For snovv mapping the MSS-images with a ground resolution of 80 meters were enlarged to a scale of 1: 100.000 by photographic methods. Different appearance of snow cover in the 4 MSS-channels is discussed in connection with ground truth control. The accuracy of snow and ice mapping from Landsat images was checked on 15 glaciers with an area from 1 to 10 km2 by aerial photography and/or ground truth control. These comparisons imply the usefulness of Landsat images for snow mapping on glaciers of a few square kilometers. The altitude of the equilibrium line was determined from Landsat images for 53 glaciers in the Tyrolean Alps. The regional differences in the equilibrium line altitude correspond to the regional precipitation patterns. The equilibrium line was identical with the snow line at the end of the budget year 1971/1972; therefore it was possible to determine the equilibrium line from satellite images. For 1968/69 the equilibrium line was mapped from aerial photographs for several glaciers. In 1972/73 mass balance was strongly negative and the equilibrimn line was within the firn area of the glaciers. Therefore it was not possible to distinguish between accumulation and ablation areas from the Landsat images of September 1973; however, snow and ice areas could be olearly differentiated. The ratios of accumulation area 01' snow area to the total area of the glaciers were determineel from satellite images and aerial photography separately for aelvancing anel for retreating glaciers and were relateel to the mass balance. In the budget years 1968/69 and 1972/73 with negative mass balance the accumulation area ratios of the advancing glacien; were olearly different from the ratios of the retreating glaciers, in 1971/72 with positive 01' balanced mass budget the differences between advancing and retreating glaciers were not significant.

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As part of the JGOFS field program, extensive CO2 partial-pressure measurements were made in the atmosphere and in the surface waters of the equatorial Pacific from 1992 to 1999. For the first time, we are able to determine how processes occurring in the western portion of the equatorial Pacific impact the sea-air fluxes of CO2 in the central and eastern regions. These 8 years of data are compared with the decade of the 1980s. Over this period, surface-water pCO2 data indicate significant seasonal and interannual variations. The largest decreases in fluxes were associated with the 1991-94 and 1997-98 El Niño events. The lower sea-air CO2 fluxes during these two El Niño periods were the result of the combined effects of interconnected large-scale and locally forced physical processes: (1) development of a low-salinity surface cap as part of the formation of the warm pool in the western and central equatorial Pacific, (2) deepening of the thermocline by propagating Kelvin waves in the eastern Pacific, and (3) the weakening of the winds in the eastern half of the basin. These processes serve to reduce pCO2 values in the central and eastern equatorial Pacific towards near-equilibrium values at the height of the warm phase of ENSO. In the western equatorial Pacific there is a small but significant increase in seawater pCO2 during strong El Niño events (i.e., 1982-83 and 1997-98) and little or no change during weak El Niño events (1991-94). The net effect of these interannual variations is a lower-than-normal CO2 flux to the atmosphere from the equatorial Pacific during El Niño. The annual average fluxes indicate that during strong El Niños the release to the atmosphere is 0.2-0.4 Pg C/yr compared to 0.8-1.0 Pg C/yr during non-El Niño years.

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The dataset is based on samples collected in the summer of 2002 in the Western Black Sea in front of Bulgaria coast. The whole dataset is composed of 47 samples (from 19 stations of National Monitoring Grid) with data of mesozooplankton species composition abundance and biomass. Sampling for zooplankton was performed from bottom up to the surface at depths depending on water column stratification and the thermocline depth. Zooplankton samples were collected with vertical closing Juday net,diameter - 36cm, mesh size 150 µm. Tows were performed from surface down to bottom meters depths in discrete layers. Samples were preserved by a 4% formaldehyde sea water buffered solution. Sampling volume was estimated by multiplying the mouth area with the wire length. Mesozooplankton abundance: The collected material was analysed using the method of Domov (1959). Samples were brought to volume of 25-30 ml depending upon zooplankton density and mixed intensively until all organisms were distributed randomly in the sample volume. After that 5 ml of sample was taken and poured in the counting chamber which is a rectangle form for taxomomic identification and count. Large (> 1 mm body length) and not abundant species were calculated in whole sample. Counting and measuring of organisms were made in the Dimov chamber under the stereomicroscope to the lowest taxon possible. Taxonomic identification was done at the Institute of Oceanology by Lyudmila Kamburska using the relevant taxonomic literature (Mordukhay-Boltovskoy, F.D. (Ed.). 1968, 1969,1972). Taxon-specific abundance: The collected material was analysed using the method of Domov (1959). Samples were brought to volume of 25-30 ml depending upon zooplankton density and mixed intensively until all organisms were distributed randomly in the sample volume. After that 5 ml of sample was taken and poured in the counting chamber which is a rectangle form for taxomomic identification and count. Copepods and Cladoceras were identified and enumerated; the other mesozooplankters were identified and enumerated at higher taxonomic level (commonly named as mesozooplankton groups). Large (> 1 mm body length) and not abundant species were calculated in whole sample. Counting and measuring of organisms were made in the Dimov chamber under the stereomicroscope to the lowest taxon possible. Taxonomic identification was done at the Institute of Oceanology by Lyudmila Kamburska using the relevant taxonomic literature (Mordukhay-Boltovskoy, F.D. (Ed.). 1968, 1969,1972).