Search results for "surface temperature"
showing 10 items of 218 documents
Recent warming in the Balearic Sea and Spanish Mediterranean coast. Towards an earlier and longer summer
2015
This paper analyses recent changes in the temperature of the Balearic Sea and surrounding coastal areas. Monthly temperature data from several weather stations located around the Balearic basin have been used to obtain land temperatures during the period 1960-2010, and monthly thermal satellite images from the Physical Oceanography Distributed Active Archive Center (PO.DAAC) covering the period 1985-2009 have been processed to obtain sea surface temperatures (SSTs) in the Balearic Sea. A rise in temperature has been observed since 1980 and increasingly in the last 25 years, with an average warming trend of 0.039 ºC/year on land for the period 1960-2010 and 0.026 ºC/year in SSTs for 1985-200…
Surface Temperature trends in the Mediterranean Sea from MODIS data during years 2003–2019
2022
Abstract Sea Surface Temperature is a variable recognized as an Essential Climate Variable (ECV) by the Global Climate Observation System (GCOS), due to its determinant influence on climate dynamics, from micro scale to global levels The aim of this paper is to estimate Sea Surface Temperature trends in the Mediterranean Sea during years 2003–2019 by using the MODIS Level 3 SST Thermal IR 8 Day 4km V2019.0. Results show an SST increase of 0.040 ± 0.001 °C/yr. The seasonal maximum trend is associated to summer 0.070 ± 0.001 °C/yr, followed by winter, (0.040 ± 0.001) °C/yr, autumn 0.030 ± 0.001 °C/yr and spring, 0.020 ± 0.001 °C/yr. The total period analyzed has been divided into ten-year tim…
Recent trends of SST in the Western Mediterranean basins from AVHRR Pathfinder data (1985-2007)
2011
Climate change in the Mediterranean region cannot be understood without taking into account changes in the Mediterranean Sea, which is an important source of moisture and heat for the Mediterranean climate system. Many research papers have been published in the last two decades increasing our knowledge about long-term trends and inter-annual variability of temperature and salinity in the Western Mediterranean. Although recent changes have been better documented, there remain uncertainties because different results are obtained depending on the period of time analyzed or the geographic region selected. This paper analyses the regional, seasonal and decadal variability of sea surface temperat…
Characterization of the interannual and intraseasonal variability of West African vegetation between 1982 and 2002 by means of NOAA AVHRR NDVI data
2007
AbstractThe interannual and intraseasonal variability of West African vegetation over the period 1982–2002 is studied using the normalized difference vegetation index (NDVI) from the Advanced Very High Resolution Radiometer (AVHRR).The novel independent component analysis (ICA) technique is applied to extract the main modes of the interannual variability of the vegetation, among which two modes are worth describing. The first component (IC1) describes NDVI variability over the Sahel from August to October. A strong photosynthetic activity over the Sahel is related to above-normal convection and rainfall within the intertropical convergence zone (ITCZ) in summertime and is partly associated …
Sea surface temperature and torrential rains in the Valencia region: modelling the role of recharge areas
2015
Abstract. Heavy rain events are frequently recorded in the Western Mediterranean causing economic losses and even human casualties. The Western Mediterranean is a deep and almost closed sea surrounded by high mountain ranges and with little exchange of water with the Atlantic ocean. A main factor in the development of torrential rains is ocean-atmosphere exchanges of heat and moisture that can potentially destabilize air masses travelling over the sea. The study of air mass trajectories previous to the rain event permits the identification of sea areas that could probably contribute to the development or intensification of rainfall. From a previous Mediterranean sea surface temperature clim…
Proposal and Validation of an Emissivity-Dependent Algorithm to Retrieve Sea-Surface Temperature From MSG-SEVIRI Data
2010
A frequent and accurate determination of sea-surface temperature (SST) would permit an improvement in both the forecasting of natural hazards and the monitoring of the effects of climate change. The Meteosat Second Generation (MSG) spinning enhanced visible and infrared imager (SEVIRI) (MSG-SEVIRI) offers this possibility, since it has a temporal resolution of 15 min. Current algorithms for SST retrieval from MSG-SEVIRI data use angular-dependent coefficients, but they do not use sea-surface emissivity (SSE) as an explicit input. This letter proposes a both angular- and emissivity-dependent split-window equation, together with simple equations to estimate SSE and atmospheric water-vapor con…
NOAA-AVHRR Orbital Drift Correction From Solar Zenithal Angle Data
2008
This paper presents a new method for NOAA's (National Ocean and Atmospheric Administration) orbital drift correction. This method is pixel-based, and in opposition with most methods previously developed, does not need explicit knowledge of land cover. This method is applied to AVHRR (Advanced Very High Resolution Radiometer) channel information, and relies only on the additional knowledge of solar zenithal angle (SZA) and acquisition date information. In a first step, anomalies in SZA and channel time series are retrieved, and screened out for anomalous values. Then, the part of the parameter anomaly which is explained by SZA anomaly is removed from the data, to estimate new parameter anoma…
Automatic classification-based generation of thermal infrared land surface emissivity maps using AATSR data over Europe
2012
The remote sensing measurement of land surface temperature from satellites provides a monitoring of this magnitude on a continuous and regular basis, which is a critical factor in many research fields such as weather forecasting, detection of forest fires or climate change studies, for instance. The main problem of measuring temperature from space is the need to correct for the effects of the atmosphere and the surface emissivity. In this work an automatic procedure based on the Vegetation Cover Method, combined with the GLOBCOVER land surface type classification, is proposed. The algorithm combines this land cover classification with remote sensing information on the vegetation cover fract…
Forecasting the vegetation photosynthetic activity over the Sahel: a Model Output Statistics approach
2009
The predictability of the mean August–September photosynthetic activity of vegetation over the Sahel for the period 1982–2002 is explored through a Model Output Statistics approach using ECHAM4.5 retrospective forecasts. Given the poor ability of Atmospheric General Circulation Models (AGCMs) to correctly simulate rainfall over the Sahel, the stress is put on using atmospheric dynamics alone. The mean July–September predicted fields of zonal wind at 600 hPa, and humidity flux at 850 hPa, are selected because of their key role in the West African Monsoon system and their consistency in AGCMs. Coupled modes of NDVI/atmospheric dynamics are extracted using Canonical Correlation Analyses perfor…
Nile Basin Climates
2009
The climate of the Nile Basin is characterised by a strong latitudinal wetness gradient. Whereas the areas north of 18°N remain dry most of the year, to the south there is a gradual increase of monsoon precipitation amounts. Rainfall regimes can be divided into 9 types, among which summer peak regimes dominate. In the southern half of the basin, mesoscale circulation features and associated contrasts in local precipitation patterns develop as a result of a complex interplay involving topography, lakes and swamps. Precipitation changes and variability show up as 3 distinct modes of variability. Drying trends since the 1950s are found in central Sudan and to some extent the Ethiopian Highland…