Land Surface Temperature in the EUMETSAT LSA SAF: Current Service and Perspectives. Isabel Trigo

Transcription

1 Land Surface Temperature in the EUMETSAT LSA SAF: Current Service and Perspectives Isabel Trigo

2 Outline EUMETSAT Land-SAF: Land Surface Temperature Geostationary Service SEVIRI Polar-Orbiter AVHRR/Metop Validation On-going Developments Modelling LST Directional Effects Direct Retrieval of SEVIRI Emissivity All-Weather LST Meteosat Third Generation

3 EUMETSAT Satellites - GEO Meteosat Second Generation Geostationary orbit Nominal sub-satellite point at 0º long Spinning Enhanced Visible and Infrared Imager - SEVIRI 12 Channels (VIS TIR) 15 min (96 obs per day) 3 km sub-satellite point

4 SEVIRI/MSG - LST Generalised Split-Window 10.8m and 12.0m (Wan & Dozier, 1996) Trained using CLEAR SKY synthetic SEVIRI/MSG data T s ( A 1 A 2 1 A 3 ) 2 T T 12.0 ( B 1 B 2 1 B 3 ) 2 T T 12.0 C GSW parameters depend on: total column water vapour (ECMWF forecasts) viewing angle Channel Emissivity Fraction Vegetation Cover Operational LST Product

5 LST SEVIRI/MSG - LST LST uncertainty Operational since 2005 Ongoing: Reprocessing & validation of 15 min SEVIRI LST from 2004 onwards Review & Dataset Release in 2016 Temporal sampling: 15 min; poorer in cloudy areas (mid-lat; tropics) Spatial resolution: 3km at nadir (Europe ~4.5 km up to ~10 km) LST uncertainty highly influenced by emissivity over (semi-)arid regions Developer: LSA SAF / IPMA Trigo et al. (2008) in J. Geophys. Res., DOI: /2008JD Freitas et al. (2010) in IEEE Trans Geosc Remote Sens, DOI: /TGRS

6 SEVIRI/MSG - LST 10-day Composited Diurnal Cycles Maximum and Median per 15-minute time-slot Thermal Surface Parameters (5) which summarize the 10-daily Diurnal Cycle To be Release in 2016 Developer: LSA SAF / KIT Göttsche, F.-M., and Olesen, F.S. (2009). Modelling the effect of optical thickness on diurnal cycles of land surface temperature. Remote Sensing of Environment, 113,

7 AVHRR/Metop - LST Daily Composite Split-window applied to AVHRR TIR channels Daytime & night-time LST per day, sinusoidal grid (1-km resolution) LST Daytime Overpasses LST Night-time Overpasses Under Review To be Release in 2016

8 LSA SAF Product Validation Intercomparison of satellite derived similar products (MODIS, AATSR, VIIRS, ) Relevant to assess consistency among different product Validation against ground observations KIT Stations Portugal (Évora), Namibia (Gobabeb, Kalahari), Senegal (Dahra) As an Indenpendent Reference Göttsche, F.-M., F.-S. Olesen, I. F. Trigo, A. Bork-Unkelbach, and M. A. Martin, 2016: Long term validation of land surface temperature retrieved from MSG/SEVIRI with continuous in-situ measurements in Africa. Remote Sensing, 8, 410, doi: /rs

9 In Situ Observations LST - Evora High Variability in Space and Time: - Impact of view & illumination geometry on retrievals - Needs to be taken into account when comparing LST products and Ground obs

10 Directional Effects Directional Effects on LST Idealized single tree view at Évora: Nadir & SEVIRI view at different local times in July Geometric Model estimate shapes of objects seen by the sensor Boolean model derive overlap probabilities and the actual fraction of each end-member Different Viewing Angles Different LST

11 Intercomparison LEO - SEVIRI LST versus in situ T sfc Direction effects at Évora Without Geometric Correction MODSW (MOD11) MODTES (MOD21) Day Night -5.0/ / /1.4 SEVIRI -1.2/ /1.2 With Geometric Correction MODSW (MOD11) MODTES (MOD21) Day Night -2.7/ / /1.3 SEVIRI 0.5/ /1.2 (Bias/StDev) Ermida et al (2014) GlobTemp in Remote User Sens Consultation Environ, Meeting, DOI: /j.rse Lisbon 7 8 Jun 2016

12 LST - Directional Effects Assessing Directional Effects Use Kernel Model calibrated with colocated SEVIRI & MODIS observations to estimate LST (T) deviations from reference view (T o at nadir): T(θ v, θ i, φ T 0 = 1 + AΦ θ v + DΨ(θ v, θ i, φ Add the modelled deviation to nadir as an extra layer of information to LSA SAF SEVIRI 15-minute LST As done in GlobTemp As another source of LST uncertainty

13 Emissivty Kalman Filter (15-minute) 3-hourly observations; channels 8.7, 10.8 e 12.0 m state vector: 3 SEVIRI channel surface emissivities & LST But using: e = ln ε where e ]-, +[ and ε [0, 1 ] 1 ε Masiello, et al., (2015) in Atmos. Meas. Tech., 8, , doi: /amt Masiello, et al., (2013) in Atmos. Meas. Tech., 6, , doi: /amt

14 SEVIRI Split-Windows LST (OPS) Emissivty Evora (Southern Portugal) 1-31 Jul 2010 = 0.02 SEVIRI Kalman Filter LST Kalman Filter LST vs In situ Gobabeb (Namibia) Land-SAF LST vs In situ Kalman Filter Emissivity

15 All-Weather LST Land Surface Model (SVAT) solving the Surface Energy Budget Tiles within 1 SEVIRI pixel NET SW + L LW T 4 + H +LE v G = 0 Tiles: Bare soil, Forest, Crops, Grassland,... Land-SAF (SEVIRI) - Albedo - LAI - SW & LW Downwelling ECMWF - Screen Variables - Soil moisture Land-SAF (SEVIRI) - LE v (or E v ) - H and - T skin LST Pixel Fluxes weighted average over tiles

16 All-Weather LST Validation at Gobabeb All- Weather SVAT SVAT Land-SAF Operational Product

17 EUMETSAT Satellites - GEO Meteosat First Generation Geostationary orbit 0º images available since 1982 Meteosat-7 LST Climate Data Record 3 Channels: 5 km sampling distance at nadir 30 minutes Channel VIS m Channel WV Channel TIR ~ 11.0 m

18 EUMETSAT Satellites - GEO Meteosat First Generation Geostationary orbit 0º images available since 1982 Statistical Mono-Window 1991 Physical Mono-Window Climate and Land- SAF 30-Year LST CDR 1st Version to be released in 2016/2017 Duguay-Tetzlaff et. al 2015 in Remote Sens., 7, ; doi: /rs

19 Meteosat Third Generation EUMETSAT MTG-I (launch foreseen for 2018) Evolution of SEVIRI Flexible Combined Imager (FCI) 16 channels (1km / 2 km; high-resolution 0.5 km) 10 min A split-window is being used to process Himawari LST within Copernicus Global Land: To be used as a prototype for MTG Day-1 prodcut Next, further channels will be exploited Kalman Filter approach to improve surface emissivity.

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