Sofia Ermida

Dr. Sofia Ermida

Instituto Dom Luiz, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisbon, Portugal
orcid

Research Focus & Metrics

Academic Career Length

13Years (2014-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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6 May 2020 in Remote Sensing
Verified
Journal Article
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SESofia Ermida
Sofia Ermida
PSPatrícia Soares
Patrícia Soares
VMVasco Mantas
Vasco Mantas
Frank-Michael GöttscheFrank-Michael Göttsche
Frank-Michael Göttsche
Isabel TrigoIsabel Trigo
Isabel Trigo
Land Surface Temperature (LST) is increasingly important for various studies assessing land surface conditions, e.g., studies of urban climate, evapotranspiration, and vegetation stress. The Landsat series of satellites have the potential to provide LST estimates at a high spatial resolution, which is particularly appropriate for local or small-scale studies. Numerous studies have proposed LST retrieval algorithms for the Landsat series, and some datasets are available online. However, those datasets generally require the users to be able to handle large volumes of data. Google Earth Engine (GEE) is an online platform created to allow remote sensing users to easily perform big data analyses without increasing the demand for local computing resources. However, high spatial resolution LST datasets are currently not available in GEE. Here we provide a code repository that allows computing LSTs from Landsat 4, 5, 7, and 8 within GEE. The code may be used freely by users for computing Landsat LST as part of any analysis within GEE.

1 May 2014 in Remote Sensing of Environment
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Journal Article
Closed access
SESofia Ermida
Sofia Ermida
Isabel TrigoIsabel Trigo
Isabel Trigo
CDCarlos DaCamara
Carlos DaCamara
Frank-Michael GöttscheFrank-Michael Göttsche
Frank-Michael Göttsche
FOFolke S. Olesen
Folke S. Olesen
GHGlynn Hulley
Glynn Hulley

17 December 2019 in Remote Sensing
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Journal Article
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Joao Paulo Afonso MartinsJoao Paulo Afonso Martins
Joao Paulo Afonso Martins
Isabel TrigoIsabel Trigo
Isabel Trigo
NGNicolas Ghilain
Nicolas Ghilain
CJCarlos Jimenez
Carlos Jimenez
Frank-Michael GöttscheFrank-Michael Göttsche
Frank-Michael Göttsche
AAAlirio Arboleda
Alirio Arboleda
A new all-weather land surface temperature (LST) product derived at the Satellite Application Facility on Land Surface Analysis (LSA-SAF) is presented. It is the first all-weather LST product based on visible and infrared observations combining clear-sky LST retrieved from the Spinning Enhanced Visible and Infrared Imager on Meteosat Second Generation (MSG/SEVIRI) infrared (IR) measurements with LST estimated with a land surface energy balance (EB) model to fill gaps caused by clouds. The EB model solves the surface energy balance mostly using products derived at LSA-SAF. The new product is compared with in situ observations made at 3 dedicated validation stations, and with a microwave (MW)-based LST product derived from Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) measurements. The validation against in-situ LST indicates an accuracy of the new product between -0.8 K and 1.1 K and a precision between 1.0 K and 1.4 K, generally showing a better performance than the MW product. The EB model shows some limitations concerning the representation of the LST diurnal cycle. Comparisons with MW LST generally show higher LST of the new product over desert areas, and lower LST over tropical regions. Several other imagers provide suitable measurements for implementing the proposed methodology, which offers the potential to obtain a global, nearly gap-free LST product.

1 November 2019 in Remote Sensing
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Journal Article
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FJFrederico Johannsen
Frederico Johannsen
SESofia Ermida
Sofia Ermida
Joao Paulo Afonso MartinsJoao Paulo Afonso Martins
Joao Paulo Afonso Martins
Isabel TrigoIsabel Trigo
Isabel Trigo
Miguel NogueiraMiguel Nogueira
Miguel Nogueira
Emanuel DutraEmanuel Dutra
Emanuel Dutra
Land surface temperature (LST) is a key variable in surface-atmosphere energy and water exchanges. The main goals of this study are to (i) evaluate the LST of the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim and ERA5 reanalyses over Iberian Peninsula using the Satellite Application Facility on Land Surface Analysis (LSA-SAF) product and to (ii) understand the main drivers of the LST errors in the reanalysis. Simulations with the ECMWF land-surface model in offline mode (uncoupled) were carried out over the Iberian Peninsula and compared with the reanalysis data. Several sensitivity simulations were performed in a confined domain centered in Southern Portugal to investigate potential sources of the LST errors. The Copernicus Global Land Service (CGLS) fraction of green vegetation cover (FCover) and the European Space Agency’s Climate Change Initiative (ESA-CCI) Land Cover dataset were explored. We found a general underestimation of daytime LST and slightly overestimation at night-time. The results indicate that there is still room for improvement in the simulation of LST in ECMWF products. Still, ERA5 presents an overall higher quality product in relation to ERA-Interim. Our analysis suggested a relation between the large daytime cold bias and vegetation cover differences between (ERA5 and CGLS FCocver) with a correlation of −0.45. The replacement of the low and high vegetation cover by those of ESA-CCI provided an overall reduction of the large Tmax biases during summer. The increased vertical resolution of the soil at the surface, has a positive impact, but much smaller when compared with the vegetation changes. The sensitivity of the vegetation density parameter, that currently depends on the vegetation type, provided further proof for a needed revision of the vegetation in the model, as there is a reasonable correlation between this parameter and the Tmax mean errors when using the ESA-CCI vegetation cover (while the same correlation cannot be reproduced with the original model vegetation). Our results support the hypothesis that vegetation cover is one of the main drivers of the LST summertime cold bias in ERA5 over Iberian Peninsula.

1 March 2017 in Remote Sensing of Environment
Verified
Journal Article
Closed access
SESofia Ermida
Sofia Ermida
CDCarlos C. DaCamara
Carlos C. DaCamara
ITIsabel F. Trigo
Isabel F. Trigo
APAna C. Pires
Ana C. Pires
DGDarren Ghent
Darren Ghent
JRJohn Remedios
John Remedios

8 June 2022 in Biogeosciences
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Journal Article
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SWSophia Walther
Sophia Walther
SBSimon Besnard
Simon Besnard
JNJacob Allen Nelson
Jacob Allen Nelson
TETarek El-Madany
Tarek El-Madany
MMMirco Migliavacca
Mirco Migliavacca
MJMartin Jung
Martin Jung
The eddy-covariance technique measures carbon, water, and energy fluxes between the land surface and the atmosphere at hundreds of sites globally. Collections of standardised and homogenised flux estimates such as the LaThuile, Fluxnet2015, National Ecological Observatory Network (NEON), Integrated Carbon Observation System (ICOS), AsiaFlux, AmeriFlux, and Terrestrial Ecosystem Research Network (TERN)/OzFlux data sets are invaluable to study land surface processes and vegetation functioning at the ecosystem scale. Space-borne measurements give complementary information on the state of the land surface in the surroundings of the towers. They aid the interpretation of the fluxes and support the benchmarking of terrestrial biosphere models. However, insufficient quality and frequent and/or long gaps are recurrent problems in applying the remotely sensed data and may considerably affect the scientific conclusions. Here, we describe a standardised procedure to extract, quality filter, and gap-fill Earth observation data from the MODIS instruments and the Landsat satellites. The methods consistently process surface reflectance in individual spectral bands, derived vegetation indices, and land surface temperature. A geometrical correction estimates the magnitude of land surface temperature as if seen from nadir or 40∘ off-nadir. Finally, we offer the community living data sets of pre-processed Earth observation data, where version 1.0 features the MCD43A4/A2 and MxD11A1 MODIS products and Landsat Collection 1 Tier 1 and Tier 2 products in a radius of 2 km around 338 flux sites. The data sets we provide can widely facilitate the integration of activities in the eddy-covariance, remote sensing, and modelling fields.