86 resultados para ISM: clouds


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The video FireMovie_2000-2011.avi shows an animation with all MODIS fire product maps of the area sequenced over time. Colors in the video describe MODIS classes as follows: MODIS classification and color scale: Class 0 - not processed - Dark blue (1 frame) Class 3 - water - Light Blue (rivers and some lakes) Class 4 - clouds - Green blue Class 5 - non fire land - Yellow green Class 8 - nominal confidence fire - Red Class 9 - high confidence fire - Dark red

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Remote sensing instruments are key players to map land surface temperature (LST) at large temporal and spatial scales. In this paper, we present how we combine passive microwave and thermal infrared data to estimate LST during summer snow-free periods over northern high latitudes. The methodology is based on the SSM/I-SSMIS 37 GHz measurements at both vertical and horizontal polarizations on a 25 km × 25 km grid size. LST is retrieved from brightness temperatures introducing an empirical linear relationship between emissivities at both polarizations as described in Royer and Poirier (2010). This relationship is calibrated at pixel scale, using cloud-free independent LST data from MODIS instruments. The SSM/I-SSMIS and MODIS data are synchronized by fitting a diurnal cycle model built on skin temperature reanalysis provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). The resulting temperature dataset is provided at 25 km scale and at an hourly time step during the ten-year analysis period (2000-2011). This new product was locally evaluated at five experimental sites of the EU-PAGE21 project against air temperature measurements and meteorological model reanalysis, and compared to the MODIS LST product at both local and circumpolar scale. The results giving a mean RMSE of the order of 2.2 K demonstrate the usefulness of the microwave product, which is unaffected by clouds as opposed to thermal infrared products and offers a better resolution compared to model reanalysis.

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The Indian Summer Monsoon (ISM) is an inter-hemispheric and highly variable ocean-atmosphere-land interaction that directly affects the densely populated Indian subcontinent. Here, we present new records of palaeoceanographic variability that span the last 500,000 years from the eastern equatorial Indian Ocean, a relatively under-sampled area of ISM influence. We have generated carbon and oxygen stable isotope records from three foraminiferal species from Ocean Drilling Program Site 758 (5°N, 90°E) to investigate the oceanographic history of this region. We interpret our resultant Dd18O (surface-thermocline) record of upper water-column stratification in the context of past ISM variability, and compare orbital phase relationships in our Site 758 data to other climate and monsoon proxies in the region. Results suggest that upper water-column stratification at Site 758, which is dominated by variance at precession and half-precession frequencies (23, 19 and 11 ka), is forced by both local (5°N) insolation and ISM winds. In the precession (23 ka) band, stratification minima at Site 758 lag northern hemisphere summer insolation maxima (precession minima) by 9 ka, which is consistent with Arabian Sea ISM phase estimates and suggests a common wind forcing in both regions. This phase implicates a strong sensitivity to both ice volume and southern hemisphere insolation forcing via latent heat export from the southern subtropical Indian Ocean. Additionally, we find evidence of possible overprinting of millennial-scale events during glacial terminations in our stratification record, which suggests an influence of remote abrupt climate events on ISM dynamics.