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SEN4SCI (Sentinels for Science): Assessing Product Requirements for the Scientific Exploitation of the SENTINEL Missions
Preliminary scientific needs for Ocean Sentinel 1-2-3 products
Preparatory material up-dated after the SEN4SCI workshop (ESA-ESRIN, Frascati, March 2011)
Prepared by: Zbyn!k Malenovsk" (RSL) and Michael Schaepman (RSL)
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!"#$%&'(&)'*+%*+,!! Oceans!"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""!#! 1. Research projects and programmes with specified ocean observational requirements!""""""""""""""!#! 2. Ocean observational requirements!""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""!$! 3. Capabilities of present and future ESA satellite missions in ocean products!""""""""""""""""""""""""""""""""""!%&! 4. Preliminary priorities for satellite products of ocean variables!"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""!%'! 5. References!"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""!&&! !
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1 Oceans
2 This ‘working’ document provides results from a literature review on scientific needs of the ocean 3 Sentinel 1-2-3 products, consolidated during the SEN4SCI workshop (March 22-24, 2011, ESA- 4 ESRIN, Frascati, Italy). Threshold and goal user observational needs were extracted from publicly 5 available documents that might be partially incomplete or out-dated. The document content will be 6 publically revised within the open internet-based revision (therefore, it should be referred to as a 7 draft).
8 1. Research projects and programmes with specified ocean observational requirements
9 “The Changing Earth” (ESA, 2006), a report outlining the science objectives of ESA’s Living Planet 10 Programme, defined six specific scientific challenges of the Oceans: 11 1. Quantify the interaction between variability in ocean dynamics, thermohaline circulation, sea 12 level, and climate. 13 2. Understand physical and bio-chemical air/sea interaction processes. 14 3. Understand internal waves and the mesoscale in the ocean, its relevance for heat and energy 15 transport and its influence on primary productivity. 16 4. Quantify marine-ecosystem variability, and its natural and anthropogenic physical, biological 17 and geochemical forcing. 18 5. Understand land/ocean interactions in terms of natural and anthropogenic forcing. 19 6. Provide reliable model- and data-based assessment and predictions of the past, present and 20 future state of the ocean. 21 In total 70 research project and programmes were reviewed during the first task 1 of the SEN4SCI 22 project, out of which 43 are dealing with the oceans, and 11 science question-driven projects were 23 directly addressing the above-specified six ESA Living Planet challenges. Documentation of all 43 24 ocean addressing project was reviewed to search for the specific technical requirements of the ocean 25 satellite products. Only 8 reviewed projects were stating the ocean product requirements (AMMA, 26 BALTEX, CLIVAR, GCP, GCOS, GOOS, TACE, WCRP), out of which only 5 were proposing the 27 threshold and/or goal technical specifications (in some cases not for all variables): 28 AMMA (African Monsoon Multidisciplinary Analyses, https://www.amma-eu.org/) aim to 29 provide the African decision makers with improved assessments of similar rainfall changes 30 which are likely to occur during the 21st century due to natural fluctuations and as a result of 31 anticipated global climate change. Only names of 5 required ocean variables were found. 32 33 BALTEX (The Baltic Sea Experiment, http://www.baltex-research.eu/) encompasses direct 34 observations and primary data acquisition. Although, no overall satellite observation 35 requirements have been described, very sparse technical specifications of 19 ocean products 36 were found. 37 38 CLIVAR (Climate Variability and Predictability, http://www.clivar.org/) is an international 39 project of the World Climate Research Programme (WCRP) with a particular focus on the role 40 of ocean-atmosphere interactions in climate. Threshold requirements for spatial resolution,
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41 temporal sampling, and variable accuracy of 7 specific ocean products were found. 42 43 GCP (Global Carbon Project, http://www.globalcarbonproject.org/) aims to develop a 44 complete picture of the global carbon cycle, including both its biophysical and human 45 dimensions together with the interactions and feedbacks between them. Only names of 5 46 required ocean variables without any technical specifications were found. 47 48 GCOS (Global Climate Observing System, http://www.wmo.int/gcos/) addresses the total 49 climate system including physical, chemical and biological properties, and atmospheric, 50 oceanic, terrestrial, hydrologic, and cryospheric components. GCOS provides detailed 51 observational requirement specifications for 12 ocean products. 52 53 GOOS (Global Ocean Observing System, http://www.ioc-goos.org/) is a permanent global 54 system for observations, modelling and analysis of marine and ocean variables to support 55 operational ocean services worldwide. As ocean is the main objective of GOOS, detailed 56 requirements of 25 satellite observation products were provided. 57 58 TACE (http://www.clivar.org/organization/atlantic/TACE/tace.php, Tropical Atlantic Climate 59 Experiment) aims, as a part of the CLIVAR project, to advance the understanding of coupled 60 ocean-atmosphere processes and to improve climate prediction for the Tropical Atlantic 61 region. TACE documentation states need for 5 ocean observation products, however, no 62 technical requirements are mentioned. 63 64 WCRP (World Climate Research Programme, http://www.wcrp-climate.org/) has a major 65 objective to determine the predictability of climate and the effect of human activities on 66 climate. WCRP documents provided detailed technical specifications of 12 reviewed ocean 67 variables. 68 69 Additionally, the IGOS Themes (Integrated Global Observing Strategy, http://www.igospartners.org/) 70 were reviewed. The objectives and activities of the IGOS Themes are now being pursued within the 71 framework of the Group on Earth Observations (GEO, http://www.earthobservations.org/cop.shtml) 72 by the Communities of Practice (CoP). No requirements on ocean observations were, however, found 73 in documentation of the Biodiversity, Carbon Cycle, Geohazards, and Water Cycle CoP. Tracing back 74 the IGOS documentation, specifications of several ocean products required by the Carbon (IGOS- 75 Carbon, 2003), Coastal Zone (IGOS-Coastal Zone, 2006), and mostly Coral Reef (IGOS-Coral Reef, 76 2003) Observation Themes were revealed. No consistent scientific user requirements were found in 77 the Final Report from the Ocean Theme Team (IGOS-Ocean, 2001). 78 79 After SEN4SCI workshop, taking place on 22-25 March 2011 in ESA-ESRIN (Frascati, Italy), a draft 80 of User Requirements Document (URD, 2011) forming during phase one of the Ocean Colour Climate 81 Change Initiative (OC-CCI) was obtained. URD reports on user needs of several ocean-colour 82 variables in climate research coming out of the consultation meeting and the analysis of user survey. 83 Although it provides precisely specified requirements, it was still a document under revision, which 84 means that stated values were still subjects of possible change. 85 86 Finally, the Database of Observational Requirements of the World Meteorological Organization 87 (WMO) was included as an additional source specifying the ocean observational requirements
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88 independent of any particular measurement technique or instrument (WMO, 2011; 89 http://www.wmo.int/pages/prog/sat/Databases.html#User). This database is a component of the 90 Rolling Requirements Review process, which collects requirements of the several WMO application 91 areas and co-sponsored programmes (GCOS, GOOS, and World Climate Research Programme – 92 WCRP). Five out of nine WMO application areas have specified various number of the ocean 93 observation requirements: 6 for the Global Numerical Weather Prediction (GNWP), 6 for the High- 94 Resolution Numerical Weather Prediction (HR NWP), 4 for the Nowcasting and Very Short Range 95 Forecasting (NWC-VSRF), 5 for the Synoptic Meteorology (SynopMet), and 6 for the Seasonal and 96 Inter-annual Forecasting (S&IA).
97 Since the WMO requirements are related to nowcasting and short range forecasting, they differ 98 significantly from the scientific needs of the global change projects focusing on a long term 99 forecasting. Therefore, the global change ‘climate research’ needs, required specifications of ‘IGOS 100 Themes’, and WMO ‘operational meteorology’ requirements are presented in this document 101 separately.
102 2. Ocean observational requirements
103 Interest in many ocean-related Earth observational (EO) products was expressed in reviewed 104 documents, however, specific (numerical) requirements (i.e. spatial resolution, temporal sampling, and 105 accuracy) of only 20 ocean variables were retrieved from the P&P documentation. Following variables 106 with non-defined or sparsely technically defined observational requirements were noted (in 107 alphabetical order): 108 • Bathymetry, 109 • Chlorophyll fluorescence, 110 • Nutrient concentrations, 111 • Potential primary production, 112 • Pollutant concentrations, 113 • Occurrence of filamentous cyanobacteria, 114 • Ocean/Sea chemistry,
115 • O2 and pCO2, 116 • Phytoplankton concentration (biomass), 117 • Reef maps, 118 • Shoreline position, 119 • Slicks, spills, films (sun glint), 120 • Swell (sea state). 121 122 Ocean scientific experts invited to the SEN4SCI workshop identified several additional EO ocean 123 products of various development stages (in alphabetical order): 124 • Aerosol optical thickness (AOT), aerosol angstrom exponent, dust AOT 125 • Carbon-to-chlorophyll ratio, 126 • Current fronts, 127 • Divergence/convergence, 128 • Eddies, 129 • Euphotic depth, depth of heated layer,
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130 • Floating vegetation and surface bloom slicks 131 • Fluorescence line height (physiology), 132 • Internal waves, 133 • Langmuir circulation, 134 • Mean dynamic topography, 135 • Particulate backscattering, 136 • Particulate organic carbon, 137 • Particulate inorganic carbon, 138 • Phytoplankton (growth rate, loss rate, carbon, etc.), 139 • Precipitation rate, 140 • Rossby waves, 141 • Spring bloom (initiation, amplitude, duration, total production, etc.), 142 • Total suspended matter, 143 • Upwelling zones, 144 • Wave-current interaction, 145 • Waveforms. 146 147 The P&P observational variables with defined requirements were for purpose of easier comprehension 148 grouped into two thematic categories: 149 1. Physical oceanography, 150 2. Biological and biogeochemical oceanography. 151 The threshold and goal values of observational spatial resolution, temporal sampling, and accuracy for 152 variables of both categories as required by reviewed P&P are specified in Table 1. The ‘Threshold’ 153 value is the minimum requirement to be met to ensure that data are useful, while the ‘Goal’ value is an 154 ideal requirement above which further improvement is not necessary. To synthesize and present 155 properly the required goal and threshold values of all the P&P, Table 1 was divided into the ‘climate 156 research’, ‘operational meteorology‘, and ‘IGOS Theme’ requirements (obtained from IGOS Carbon, 157 2003; IGOS Costal Zone, 2006; and IGOS Corral Reef, 2003; the IGOS Ocean, 2001 final report does 158 not contain any specific requirements). The objective of Table 1 is not to provide one representative 159 value, but to illustrate the variability in Goal and Threshold requirement values as defined by the 160 reviewed P&Ps. Therefore, the most demanding (minimum: Min), the most frequent (modus: Mod) 161 and the most relaxed (maximum: Max) requirement values are stated whenever possible. In case of 162 only two available values both are stated as Min – Max and finally a single value is stated in case of 163 only one available requirement. Because many reviewed P&Ps do not make clear distinction between 164 the open ocean and the coastal water requirements, numbers in Table 1 represent mixture of both cases 165 (except the marine biodiversity and habitat properties that are related only to the coastal waters). The 166 next two columns present number and names of P&P stating the particular ocean variable. Finally, the 167 confidence level of the product is estimated in a scale of four grades: Firm (very high confidence), 168 Reasonable (acceptable confidence), Speculative (low confidence), and Unspecified (unknown 169 confidence). It is necessary to mention that the reviewed ocean surface variables do not include the 170 Sea-Ice parameters (ice thickness, ice coverage/concentration, ice type/form, ice movement, etc.) as 171 these are being analysed by the cryosphere part of the SEN4SCI project. 172 173 Specific observing requirements of following physical, biological and biogeochemical variables are 174 presented in Table 1: 175 1. Physical oceanography (alphabetically) ______
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176 Ocean circulation – Surface currents 177 Ocean circulation is large-scale horizontal flow of ocean water in [m/s] that is persistent and driven by 178 atmospheric circulation. Spatial changes in water mass density properties also trigger ocean motion 179 along the density front. Observations of the ocean currents are required to advance the understanding 180 of ocean dynamics, for marine services applications, and also for testing and validation of the ocean 181 models. 182 183 Ocean dynamic topography (Sea surface topography) 184 Ocean dynamic topography is deviation of the time-averaged sea level from the geoid, after 185 corrections for tides and atmospheric pressure effects, caused by the ocean currents. Physical unit 186 including accuracy unit is [cm]. In general, the maps of dynamic ocean topography change very little 187 over time since our major ocean currents are stable. 188 189 Ocean/Sea surface height (SSH; Sea level) 190 Sea surface height (SSH) is actual and local sea level in [cm] inclusive of sea level anomaly, mean sea 191 surface and known geophysical perturbations (tides, air pressure, etc.). Traditionally, permanent sea 192 level stations around the world have been primarily devoted to tide and mean sea level applications, 193 both non-requiring real or near-real time delivery. Importance of the SSH observations increases due 194 to the higher demand for tsunamis, storm surges and coastal flooding forecasting and warning 195 systems, but also for assimilation of sea level data into ocean circulation models. Therefore, lately the 196 requirements been extended on making the SSH data available in real and/or near-real time. 197 198 Ocean/Sea surface salinity (SSS) 199 Sea-surface salinity (SSS) measures content of anion chlorine in the upper surface layer (~ 1 m) of 200 sea/ocean water masses. Physical unit is Practical Salinity Unit [psu], which corresponds with 1 ‰, or 201 1 g of salt per 1 litre of solution. High-resolution and high quality SSS observations are required for 202 ocean forecasting systems (assimilation into and validation of the ocean models). SSS in the coastal 203 and inland regions have a larger variability due to coastal systems (upwelling/downwelling processes) 204 and river discharge, and also enhanced evaporation in regions shallower than the optical depth or weak 205 circulation. The coastal ocean research requires high spatial resolution resolving SSS data with a good 206 accuracy, while the open ocean research is dominated by the mesoscale resolution. 207 208 Ocean/Sea surface temperature (SST) 209 Sea-surface temperature (SST) is temperature of the seawater at the depth of 2 m (‘bulk’ temperature; 210 < 1 mm ~ ‘skin’ temperature). Physical unit including accuracy is [K]. The high-resolution SST 211 observations are required to address the global and regional numerical weather prediction, the seasonal 212 to inter-annual weather forecast, the ocean forecasting systems (assimilation in and validation of ocean 213 models), and the marine services. SST in the coastal and inland regions have a large variability due to 214 the diurnal cycle of solar radiation, which enhances differences in surface characteristics of the land 215 and sea, and forces land-air-sea interactions (i.e., land-sea breezes). 216 217 Sea state (Wind-Wave) parameters 218 An accurate analysis of the sea state is required on regular bases. The observational requirements for 219 global and regional wave modelling are depended on the applications for which the data are needed, 220 which includes: assimilation into wave forecast models, validation of wave forecast models, 221 calibration/validation of satellite wave sensors, and ocean wave climate and its variability on seasonal 222 to decadal time scales. Additionally, wave observations are also required for now casting and
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223 issuing/cancelling warnings, and very-short-range forecasting (up to 12 hours) of extreme waves 224 associated with extra-tropical and tropical storms. Whilst now casting is largely based on 225 observational data, very-short-range forecasting is being generated based on high-resolution regional 226 wave models. Long-term, stable time series of repeat observations are required for climate 227 applications. The key required sea state parameters are: significant wave height (average amplitude 228 of the highest 30 of 100 waves in [m]), dominant wave direction (direction of the most energetic 229 wave of the ocean wave spectrum in [°]), and dominant wave period (period of the most energetic 230 wave of the ocean wave spectrum in [s]). 231 232 Surface wind 233 The surface wind variables are the key parameters for driving ocean models and to now cast and 234 forecast marine meteorological and oceanographic conditions. Wind vector over sea surface 235 represents the motion of the air mass over the ground, described by wind speed and the inverse of 236 wind direction. Wind speed over sea surface is the horizontal vector component of the 3D wind 237 vector over the sea surface with physical unit [m/s]. Surface wind observations are, at the coast, 238 strongly influenced by the coastal topography and land-sea surface conditions. 239 240 241 2. Biological and biogeochemical oceanography (alphabetically) 242 Inherent optical properties (IOP) 243 Inherent optical properties (IOP) include light absorption, scattering, and backscattering. They are 244 defined as optical properties independent of variations in the angular distribution of the incident light. 245 246 Marine biodiversity and habitat properties 247 Marine biodiversity and habitat properties stand for various biological variables that can be derived 248 from the water leaving radiance observations to indicated actual status of costal waters and coral reefs. 249 250 Normalised water-leaving radiance 251 Water-leaving radiance is the upwelling radiance just below the sea surface, which is a function of the 252 view angle. Normalised water-leaving radiance approximates the radiance that would leave the sea 253 surface in the absence of an atmosphere, and with sun at the zenith. 254 Ocean colour 255 The ocean colour observations can detect several types of marine pollutions, harmful algae and 256 phytoplankton blooms. Colour dissolved organic matter (CDOM; formerly called ‘yellow 257 substance’) is indicative of biomass undergoing decomposition processes. Physical unit is [m-1] with 258 accuracy unit [%] at a specific concentration (e.g., 1 m-1). Suspended sediment concentration of 259 river outflow measures re-suspension or pollution of other-than-biological origin. Physical unit is 260 [g/m3] with accuracy unit [%] at a specific concentration (e.g., 1 g/m3). Finally, ocean chlorophyll 261 concentration is an indicator of the living phytoplankton biomass with physical unit [mg/m3] and 262 accuracy unit [%] at a specific concentration (e.g., 1 mg/m3). The algorithms to separate the ocean 263 colour signal among different phytoplankton functional types are currently under development. This 264 is a new scientific product of high importance that, in most cases, considers phytoplankton functional 265 types in oceanic waters, and it refers often to separation by size class. 266 267 Particle size distribution (PSD) 268 Particle size distribution, expressing the number or mass of common mineral particles as a function of 269 their size, is another experimental product from remote sensing. Although many users are aware of the ______
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270 importance to retrieve this variable from space, the application into climate models has not been yet 271 explored. 272 273 Photosynthetically Active Radiation (PAR) 274 Photosynthetically Active Radiation (PAR) is amount of the photosynthetically active photons of the 275 wavelengths between 400-700 nm that diffuses through the water compared to the downwelling at- 276 surface flux. PAR is important for the dynamics of the photic zone, typically 1-5 meters below the 277 surface, and leads to an understanding of photosynthesis, toxic algae blooms, and eutrophication. PAR 278 measurements can be used to calculate the euphotic depth in the ocean. 279 280 Spectral attenuation coefficient for downwelling irradiance 281 Spectral attenuation coefficient for downwelling irradiance provides the underwater rate of decrease of 282 the irradiance with unit distance, and per unit incident flux. 283 284 285 Table 1. Minimal/most demanding (Min), the most frequent (Mod), and maximal/most relaxed (Max) 286 Goal and Threshold observational requirements for ocean research of the projects and programmes 287 reviewed in the SEN4SCI project (for more detailed explanation and definitions see text above). Nr Variable Goal Thresh. Goal Threshold Goal Thresh. No. of Projects Esti- Spatial Spatial Temporal Temporal Acuracy Acuracy Pro- with mated Reso- Reso- Sampling Sampling (Min- (Min- jects require- Confi- lution lution (Min-Mod- (Min-Mod- Mod- Mod- ments dence * (Min- (Min- Max) Max) Max) Max) Mod-Max Mod-Max in km) in km) Physical oceanography 1 Dominant GOOS Firm wave direction (Sea 10 30 1 h 6 h 10° 20° 1 state) /climate research/ /IGOS IGOS Themes/ 1 10 3 h-1 d 1-3 d 5-10° 10-30° 2 Coastal, IGOS Coral /operational HR NWP, meteorology/ 5-50 40-250 0.5-3 h 6-12 h 10-20° 20-30° 3 SynopMet, GNPW 2 Dominant GOOS Firm wave period (Sea state) 10 30 1 h 6 h 0.5 s 1 s 1 /climate research/ /operational HR NWP, 0.25-0.5 meteorology/ 5-50 40-250 1-3 h 6-12 h 1 s 3 SynopMet, s GNPW 3 Ocean BALTEX, Firm circulation CLIVAR (Surface - - - - - 2 cm/s 2 currents) /climate research/ /IGOS IGOS 0.3 1 1 h 1 d 3 cm/s 10 cm/s 1 Themes/ Coastal /operational NWC- 10 50 6 h 6 d 0.5 cm/s 1 cm/s 1 meteorology/ VSRF 4 Ocean GCOS, Firm dynamic GOOS, topography 25-100 100-300 1-7-10 d 10-30 d 1-2 cm 5-10 cm 3 WCRP - (Sea surface CLIVAR topography)
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/climate research/
/operational S&IA 25 100 7 d 30 d 1 cm 4 cm 1 meteorology/ 5 Ocean/Sea WRCP- Reason. surface CLIVAR, height (Sea 2-10 WMO 0.1 5-10 1 d 2-7 d 2 cm 2 level) cm+ /climate research/ IGOS 4-10 6-30 Coastal, 1 5-15 1-10 d 10-30 d 2 /IGOS cm+ cm+ IGOS Themes/ Coral, 6 Ocean/Sea WCRP- Firm surface CLIVAR, 0.05-0.1 0.3-1 salinity 100-200 250-500 7-10-30 d 30-60 d 3 GCOS, psu psu /climate GOOS, research/ IGOS 0.3-1 Coral, 1 25-100 1-8 d 7-30 d 0.1 psu 2 /IGOS psu IGOS Themes/ Coastal /operational GNWP, 5-100 250 1-30 d 60 d 0.1 psu 0.3 psu 2 meteorology/ S&IA 7 Ocean/Sea CLIVAR, Firm surface GCOS, 0.2-1-2 temperature 1-10-50 5-50-500 1-6-24 h 6h-1d-30d 0.1-0.5 K 4 GOOS, K /climate WCRP research/ IGOS Coral, 0.1-0.2 1 3 h-1 d 6 h-2 d 0.1-0.2 K 0.5 K 2 /IGOS IGOS Themes/ Coastal GNWP, HR NWP, 40-50- 0.5-1-2 SynopMet, 1-5-50 1-3 h 6h-1d-5d 0.1-0.5 K 5 250 K S&IA, /operational NWC- meteorology/ VSRF 8 Significant GCOS, Reason. wave height WCRP /Firm (Sea state) 25-100 250 3-12 h 6 h-1 d 0.1-0.5 m 1-2 m 2 /climate research/ /IGOS IGOS 1 10 3 h 1 d 0.2 m 0.2 m 1 Themes/ Coastal /operational 0.2-0.5 HR NWP, 5-15 40-250 0.5-1 h 6-12 h 0.1 m 2 meteorology/ m GNWP 9 Wind speed GOOS, Firm over sea GCOS surface 10-25 100-500 1 h -1 d 1-7 d 0.5-1 m/s 1-2 m/s 2 /climate research/ IGOS /IGOS 0.3-2 5-10 1 h-1 d 6 h-2 d 0.5-1 m/s 2 m/s 2 Coastal, Themes/ IGOS Coral GNWP, HR NWP, 0.5-20 20-250 0.25-1 h 3-12 h 0.5-2 m/s 2-5 m/s 4 SynopMet, /operational NWC- meteorology/ VSRF 10 Wind vector WCRP- Firm over sea CLIVAR, 50-100- 0.5-1-2 surface 4-25-50 1-12-24 h 6 h-1d-7 d 2-5 m/s 1 GOOS, 500 m/s /climate GCOS research/
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GNWP, HR NWP, 0.25-0.5-1 0.5-1-2 2-20 40-250 3-12 h 3-5 m/s 4 SynopMet, h m/s /operational NWC- meteorology/ VSRF Biological and biogeochemical oceanography 11 Colour GOOS, Firm dissolved WCRP- organic CLIVAR, matter/yellow TACE, 0.1-1- 10-20- substance 5-10-500 1 d 2-7 d 5% 4 OC-CCI # 100 25% (Ocean colour) /climate research/ /IGOS IGOS Themes/ Coastal, 0.1 0.5-1 1 h 2 h-1 d 30% 40% 2 IGOS Carbon /operational S&IA 100 500 1 d 6 d 5% 20% 1 meteorology/ 12 Inherent OC-CCI # Unspec. optical properties - 0.1-1-10 - 1-7 d - 10-25% 1 /climate research/ 13 Marine IGOS Unspec. biodiversity Coastal, and habitat IGOS Coral 0.001 0.01 3 d 12 d - - 2 properties /IGOS Themes/ 14 Normalised OC-CCI # Unspec. water-leaving radiance - 0.1-100 - 1-30 d - 10-25% 1 /climate research/ 15 Ocean GCOS, Firm chlorophyll GOOS, (Ocean 0.1-1- 5-100- 0.5-20- WCRP – 1 d 3-7 d 0.1-5% 4 colour) 100 500 25% CLIVAR, /climate OC-CCI # research/ IGOS /IGOS 0.1-0.2 0.5-1 1 h-1 d 2 h-3 d 10-20% 30% 2 Coastal, Themes/ IGOS Coral /operational S&IA 25 100 1 d 3 d 5% 20% 1 meteorology/ 16 Particle size OC-CCI # Unspec. distribution - 0.1-1-10 - 7 d - 10-25% 1 /climate research/ 17 Photosynthe- GOOS Firm tically Active Radiation 1-10 5-50 1 h 1 d 5% 20% 1 /climate research/ IGOS /IGOS 0.1-1 0.5-5 1 h 2 h-1 d 5-10% 20% 2 Coastal, Themes/ IGOS Coral 18 Phyto- OC-CCI # Unspec. plankton functional types (Ocean - 1-10 - 7 d - 10-25% 1 colour) /climate research/
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19 Spectral OC-CCI # Unspec. attenuation coeff. for downwelling - 0.1-1-10 - 1-7 d - 10-25% 1 irradiance /climate research/ 20 Suspended WCRP - Specu- sediment CLIVAR lative concentration (Ocean 100 500 1 d 6 d 5% 20% 1 colour) /climate research/ /IGOS IGOS 0.1 0.5 1 h 2 h 30% 40% 1 Themes/ Coastal /operational S&IA 100 500 1 d 6 d 5% 20% 1 meteorology/ * Estimated Confidence is adopted from WMO documentation and should be revised during the public SEN4SCI internet revision. + More accurate estimates are actually achievable. # Requirements of OC-CCI are not of final nature as they were obtained from draft the OC-CCI user requirement document (URD, 2011).
Acronyms: BALTEX Baltic Sea Experiment CLIVAR Climate Variability and Predictability GCP Global Carbon Project Thresh. = Threshold GCOS Global Climate Observing System Reason. = Reasonable GNWP Global Numerical Weather Prediction Unspec. = Unspecified GOOS Global Ocean Observing System HR NWP High-Resolution Numerical Weather Prediction IGOS Integrated Global Observing Strategy NWC-VSRF Nowcasting and Very Short Range Forecasting OC-CCI Ocean Colour Climate Change Initiative SynopMet Synoptic Meteorology S&IA Seasonal and Inter-annual Forecasting TACE Tropical Atlantic Climate Experiment WCRP World Climate Research Programme 288 289 Global Climate Observing System (GCOS, 2010) defined eleven Ocean surface Essential Climate 290 Variables (ECVs) that are required to support research of the United Nations Framework Convention 291 on Climate Change (UNFCCC) and the Intergovernmental Panel on Climate Change (IPCC) related to 292 the global climate change: 293 Sea-surface temperature, Sea-surface salinity, Sea level, Sea state, Sea ice, Surface currents, 294 Ocean colour, Carbon dioxide partial pressure, Ocean acidity, Phytoplankton. 295 Besides Carbon dioxide partial pressure and Ocean acidity our analysis covers the majority of the 296 ocean surface ECVs. A tentative list of the future potential ECV candidates was proposed by the 297 ocean experts at the SEN4SCI workshop based on continuity of the related satellite missions, maturity 298 of the generating algorithms, and possibility of the in-situ validation and the per-pixel uncertainty 299 estimation. Following variables were found to have high score for becoming the next ECV candidate: 300 Normalized water leaving reflectance, Chlorophyll concentration (for Case 1 – open ocean 301 waters), Diffused spectral attenuation coefficient, Aerosol optical thickness (AOT), Euphotic 302 depth and depth of the heated layer, and Fluorescence line height. 303 First four mentioned products could be operationally derived from the Sentinel 3 imaging 304 spectroradiometrs. 305
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306 3. Capabilities of present and future ESA satellite missions in ocean products
307 The GMES Sentinel 1-2-3 missions will allow development of new scientific applications based on: 308 • Better performance of instruments, 309 • Improved sensor modes and extensions, 310 • Possible synergy of instruments allowing to study complex interaction on different spatial and 311 temporal scales, 312 • Long time series perspective, 313 • Characterisation and reduction of uncertainties. 314 Capabilities of the current and future European satellite mission, i.e. GMES Sentinels (1-2-3), Earth 315 Explorers, other ESA mission, and MetOp satellites, to provide 20 defined ocean surface variables are 316 given in Table 2. Data in Table 2 is indicating not only the type of sensor and the mission with sensor 317 name, but also the spatial resolutions of the sensor and the product accuracy achieved (if known), as 318 stated in the CEOS EO Handbook (2010) and the CEOS Systems Database (2011). 319 320 Table 2. Observational capabilities of Sentinel 1-2-3, approved Earth Explorers, other ESA and 321 MetOp missions for ocean surface physical, biological, and biogeochemical variables. Nr Variable Sensor type* Sentinel mission Earth Explorer / Other ESA MetOp (SG) / sensor (spatial sensor (spatial mission / sensor (spatial resolution resolution / resolution) (spatial resolution/ / accuracy) accuracy) accuracy) Physical oceanography 1 Dominant wave SAR S-1/C-BandSAR Envisat/ASAR direction (Sea (5x5, 5x20, (10, 30, 150 m & state) 20x40 m / -) 1 km / -), ERS- 2/AMI &SAR (30 m / -) 2 Dominant wave SAR S-1/C-BandSAR Envisat/ASAR period (Sea (5x5, 5x20, (10, 30, 150 m & state) 20x40 m / -) 1 km / -), ERS- 2/AMI (30 m / -) 3 Ocean RA S-1/C-BandSAR GOCE/EGG (-) Envisat/ASAR circulation (5x5, 5x20, (10, 30, 150 m & (Surface 20x40 m / -) 1 km / -) currents) 4 Ocean dynamic RA, SAR S-3/SRAL GOCE/EGG (-) Envisat/RA-2 (- / topography (Sea (- / -) <4.5 cm) surface topography) 5 Ocean/Sea RA, POD S-3/SRAL CryoSat2/ Envisat/RA-2 & surface height (- / -) & POD DORIS-NG DORIS-NG (- / (Sea level) (-) <4.5 cm), ERS- 2/RA (footprint 16- 20 km / <10 cm) 6 Ocean/Sea MWR SMOS/ MIRAS surface salinity (L-band) (33 - 50 km) 7 Ocean/Sea MROI (IR), S-3/SLSTR Envisat/AATSR (1 IASI (1-30 km / surface MWI, IS (1 km / 0.2 K) km / <0.5 K) 0.5-2 K), temperature ERS-2/ATSR-2 AVHRR/3 (1.1 km (20 km / <0.5K ) / -), HIRS/4 (20.3 km / -)
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8 Significant wave RA, SAR S-1/C-BandSAR Envisat/ASAR height (Sea (5x5, 5x20, (10, 30, 150 m & state) 20x40 m / -), 1 km / -) & RA-2 (- S-3/SRAL (- / -) / <0.25 m), ERS- 2/RA (footprint 16- 20 km / 0.5 m) & AMI (30 m / 0.2 m) 9 Wind speed over RA, SCAT, S-1/C-BandSAR Envisat/RA-2 (- / ASCAT (25-37 sea surface SAR (5x5, 5x20, 35 d / -) & ASAR km, 50 km / 2 20x40 m / -), (10, 30, 150 m & m/s), AMSU-A (48 S-3/SRAL (- / -) 1 km / -), ERS- km / -) 2/RA (footprint 16- 20 km / -) & AMI (50 km / 3 m/s) 10 Wind vector SAR, SCAT S-1/C-BandSAR Envisat/ASAR ASCAT (25-37 over sea surface (5x5, 5x20, (10, 30, 150 m & km, 50 km / -) 20x40 m / -), 1 km / -), ERS- 2/AMI (50 km / -) & SAR (30 m / -) Biological and biochemical oceanography 11 Colour MROI S-3/OLCI Envisat/MERIS dissolved (ocean colour (0.3, 1.2 km / -) (0.3, 1.2 km / -) organic instruments) matter/yellow substance (Ocean colour) 12 Inherent optical MROI S-3/OLCI (0.3, Envisat/MERIS properties 1.2 km / -) & (0.3, 1.2 km / -) SLSTR (0.5, 1 km / -) 13 Marine HROI S-2/MSI (10, 20, Proba/CHRIS biodiversity and 60 m / -) (18, 36 m / -) habitat properties 14 Normalized MROI, HROI S-3/OLCI (0.3, Envisat/MERIS water-leaving 1.2 km / -) & (0.3, 1.2 km / -) radiance SLSTR (0.5, 1 km / -), S-2/MSI (20, 60 m / -), 15 Ocean MROI S-3/OLCI Envisat/MERIS chlorophyll (ocean colour (0.3, 1.2 km / -) (0.3, 1.2 km / -) (Ocean colour) instruments)
16 Particle size MROI S-3/OLCI (0.3, Envisat/MERIS distribution 1.2 km / -) (0.3, 1.2 km / -)
17 Photosyntheti- MROI, HROI S-3/OLCI (0.3, Envisat/MERIS cally Active 1.2 km / -), (0.3, 1.2 km / -) Radiation S-2/MSI (20, 60 m / -), 18 Phytoplankton MROI S-3/OLCI Envisat/MERIS functional types (ocean colour (0.3, 1.2 km / -) (0.3, 1.2 km / -) (Ocean colour) instruments)
19 Spectral MROI, HROI S-3/OLCI (0.3, Envisat/MERIS attenuation 1.2 km / -) & (0.3, 1.2 km / -) coeff. for SLSTR downwelling (0.5, 1 km / -), ______
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irradiance S-2/MSI (20, 60 m / -),
20 Suspended MROI S-3/OLCI Envisat/MERIS sediment (ocean colour (0.3, 1.2 km / -) (0.3, 1.2 km / -) concentration instruments) (Ocean colour)
* Sensor types: Source: HROI High resolution multispectral optical imager http://database.eohandbook.com/ IS Infrared sounder http://ceos-sysdb.com/ MROI Medium resolution multispectral optical imager MWR Microwave radiometer MWI Multispectral imaging microwave radiometer POD Precise orbit determination RA Radar altimeter SAR Synthetic aperture radar SCAT Scatterometer 322 323 As stated in Table 2, the future GMES Sentinel 1-2-3 missions will be able to directly address 19 of 20 324 reviewed ocean surface variables. The Sentinel-1 (S-1) C-band Synthetic Aperture Radar (SAR) will 325 contribute mainly to the physical oceanography research of sea state, ocean circulation (currents), and 326 wind sea surface measurements. The Sentinel-2 (S-2) Multi Spectral Instrument (MSI) will provide 327 input images for the high-resolution marine biodiversity and habitat mapping and estimation of ocean 328 PAR, but also support products primarily derived from the Sentinel-3 (S-3) data (normalized water- 329 leaving radiance, spectral attenuation of downwelling irradiance). Sensors aboard of S-3 will be 330 strongly contributing to the ocean research. The optimized viewing ability of the Ocean Land Colour 331 Instrument (OLCI), a spectroradiometer operating in 21 bands from ultraviolet to near-infrared 332 wavelengths, will provide high quality optical ocean observations (normalized water-leaving radiance, 333 inherent optical properties, spectral attenuation of downwelling irradiance, PAR, particle size 334 distribution), from which some can be used for retrieval of the ocean colour variables (colour 335 dissolved organic matter - CDOM, suspended sediment and chlorophyll concentrations, phytoplankton 336 functional types). The S-3 Synthetic Aperture Radar Altimeter (SRAL) will contribute to the 337 measurements of sea surface height (SSH), ocean dynamic topography, and significant wave height. 338 Finally, the S-3 Sea Land Surface Temperature Radiometer (SLSTR) is designed for sea surface 339 temperature measurements, but it can also support retrieval of products related to the irradiance-water 340 interactions. The only ocean measurement not being directly addressed by the first three Sentinels is 341 Sea Surface Salinity. 342 343 Three currently operational ESA Earth Explorer missions are contributing to the ocean observations. 344 The Soil Moisture and Ocean Salinity (SMOS) is an opportunity mission observing the ocean surface 345 salinity by capturing images of emitted microwave radiation around the frequency of 1.4 GHz (L- 346 band) by the Microwave Imaging Radiometer using Aperture Synthesis (MIRAS) instrument. 347 Cryosat2 is a dedicated ‘ice’ mission, however, it carries onboard the Doppler Orbitography and 348 Radio-positioning Integrated by Satellite (DORIS-NG) sounding system contributing to the Sea level 349 and Ocean currents monitoring. Finally, combining the Gravity Field and Steady-State Ocean 350 Circulation Explorer (GOCE) data with the satellite altimetry measurements gives the difference 351 between the geoid height and the sea-surface height, which provide insight into the Sea surface
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352 topography. 353 354 Three other ESA satellite missions are currently delivering data for ocean products. The radar 355 altimeters (RA) aboard Envisat and ERS-2, and also the Envisat’s DORIS-NG, are providing data for 356 the Sea level measurements. The TIR bands of the Envisat’s Advanced Along-Track Scanning 357 Radiometer (AATSR) and the European Remote Sensing (ERS-2) satellite Along Track Scanning 358 Radiometer (ATSR-2) measure the Sea surface temperature, Advanced Synthetic-Aperture Radar 359 (ASAR) measures the Ocean circulation, and the Envisat’s Medium Resolution Imaging Spectrometer 360 (MERIS) is able to address most of the biochemical ocean products (i.e., the Ocean colour parameters, 361 PAR, and products describing the interactions of solar irradiation with the ocean/sea water bodies). 362 Sea surface topography is observed by the RA-2 carried by the Envisat platform. Similarly, the Sea 363 state and the Wind sea surface variables are obtained from the radar altimeters, synthetic aperture 364 radars, and the Active Microwave Instrumentation (AMI) of Envisat and ERS-2. Finally, the Marine 365 biodiversity and habitat properties can be derived from the Compact High Resolution Imaging 366 Spectrometer (CHRIS) aboard the PROBA satellite. 367 368 The MetOp missions contribute to the observation of three ocean surface parameters. Data of Infrared 369 Atmospheric Sounding Interferometer (IASI), Advanced Very High Resolution Radiometer/3 370 (AVHRR/3), and High Resolution Infra-red Sounder/4 (HRIS/4) are used to monitor the Sea surface 371 temperature, while the Advanced Scatterometer (ASCAT) and Advanced Microwave Sounding Unit - 372 A (AMSU-A) observations are used to measure the Wind speed and Wind vector over sea surface.
373 4. Preliminary priorities for satellite products of ocean variables
374 A preliminary priority assessment for ocean surface products required by the research P&P and 375 provided by current and future ESA missions was carried out using information in Tables 1 and 2. 376 Table 3 shows which of 20 reviewed ocean variables can be addressed by the Sentinel 1-2-3, Earth 377 Explorer, and MetOp sensors, minimum-maximum intervals of the threshold spatial and temporal 378 resolutions (as required by the reviewed P&Ps), and the relevant product auxiliary data (i.e., other data 379 inputs needed to generate the required product) together with the space mission/sensor providing 380 auxiliary data. 381 382 In the frame of its own programmes, ESA initialized several scientific projects demonstrating 383 feasibility and supporting the development of processing chains for several ocean products. The ESA 384 programmes contributing to the pool of ocean space-borne scientific products are: 385 • ESA Data User Element (DUE, 2011; http://due.esrin.esa.int/), 386 • ESA Support to Science Element (STSE, 2011; http://wfaa-dat.esrin.esa.int/stse/), 387 • ESA Climate Change Initiative (CCI). 388 For defining priorities of the future Sentinel Scientific Products the liaison with these programmes is 389 important. Therefore, ESA DUE, STSE, and CCI projects dealing with the required ocean variables 390 are stated in the Table 3 as ‘Heritage activity’. 391 392 Priority estimation took into the account the following: 393 • Scientific importance, matching the requirements for ECVs (GCOS, 2010) and meeting the 394 scientific challenges of the ESA Living Planet Programme (ESA, 2006).
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395 • Exploitation of the potentials of the Sentinel missions complemented by other ESA missions and 396 third party missions (TPM). 397 • Feasibility to generate thoroughly validated geophysical products (Level-2, Level-3), matching 398 the requirements of the scientific community in terms of accuracy and data continuity. 399 Applying these criteria, Table 3 presents a priority grade per listed product. High priority (H) is 400 assigned to the scientifically highly important products generated by a solid and validated retrieval 401 algorithm. Medium priority (M) is attached to scientifically important products with an immature 402 (developing or experimental) retrieval algorithm that still needs a further validation. Ocean experts 403 reviewed the priority ranking during the SEN4SCI scientific workshop, but this can still be adjusted 404 according the input from internet-based revision of the broader ocean scientific community. 405 406 Table 3. List and priority rating of the ocean product deliverable by Sentinel 1-2-3, or Earth Explorers 407 (EE) and MetOp missions after the first revision at the SEN4SCI scientific workshop. Nr Variable Required Min.- Sentinel mission Auxiliary Synergy Heritage activity Priority* Max. Threshold (EE, MetOp) data mission spatial and /sensor /sensor temporal resolution Physical oceanography 1 Dominant wave 10-250 km, S-1/C-BandSAR Radarsat DUE GlobWave H direction (Sea 6 h-3 d SOWWC (R&D) (ECV) state) 2 Dominant wave 30-250 km, S-1/C-BandSAR Radarsat DUE GlobWave H period (Sea 6-12 h SOWWC (R&D) (ECV) state) 3 Ocean 1-50 km, S-1/C-BandSAR Geoid, Mean GOCE/ INCUSAR H circulation 1-6 d Sea Surface, EGG , SOWWC (R&D) (ECV) (Surface Geostrophic Alti- currents) current meters 4 Ocean dynamic 100-300 km, S-3/SRAL Geoid, Mean GOCE/ GOCE User H topography (Sea 10-30 d Sea Surface, EGG , Toolbox surface Geostrophic Alti- COASTALT topography) current meters 5 Ocean/Sea 5-15 km, S-3/SRAL, POD CCI Sea Level H surface height 2-30 d (CryoSat2/DORI CRYOSAT- (ECV) (SSH) S-NG) SAMOSA (Sea level) COASTALT 6 Ocean/Sea 25-500 km, (SMOS/MIRAS) Aquarius STSE SMOS+ H surface salinity 7-60 d (ECV) (SSS) 7 Ocean/Sea 1-500 km, S-3/SLSTR CCI SST H surface 6 h-30 d (Metop/ IASI, DUE GHRSST (ECV) temperature AVHRR/3, DUE GlobWave (SST) HIRS/4) MEDSPIRATION MICROWAT STARS 8 Significant wave 10-250 km, S-1/C-BandSAR Radarsat DUE GlobWave H height (Sea 6 h-1 d S-3/SRAL and alti- CRYOSAT- (ECV) state) meters SAMOSA COASTALT SOWWC (R&D) 9 Wind speed over 5-500 km, S-1/C-BandSAR Wind vectors Radarsat DUE GlobWave M sea surface 3 h-7 d S-3/SRAL (from and alti- INCUSAR (Metop/ASCAT, ECMWF) meters SOWWC (R&D) AMSU-A)
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10 Wind vector over 40-500 km, S-1/C-BandSAR Wind vectors MICROWAT M sea surface 3 h-7 d (in special (from INCUSAR cases) ECMWF) SOWWC (R&D) Comments from SEN4SCI scientific workshop: • Sentinel sensors have a high potential to reduce the uncertainty in the sea level products. • Ocean motions at sub-mesoscale to mesoscales are key players of the upper ocean dynamic. • Validated estimation of uncertainties will improve product analysis and assimilation into the models. • Few, if any, studies on altimetry, radiometry, spectrometry, scatterometry, and SAR synergies are limiting our ability to connect 2D surface expressions with upper layer 3D ocean dynamics.
Biological and biochemical oceanography 11 Colour dissolved 0.5-500 km, S-3/OLCI Cloud S-3/ DUE GlobColour H organic 2 h-7 d screening, SLSTR DUE (ECV) matter/yellow Atmospheric CoastColour substance correction CCI Ocean (CDOM) (Ocean Colour colour) 12 Inherent optical 0.1-10 km S-3/OLCI Cloud S-3/ DUE GlobColour H properties 1-7 d screening, SLSTR CCI Ocean Atmospheric Colour correction 13 Marine 0.01 km S-2/MSI M biodiversity and 12 d habitat properties 14 Normalized 0.1-100 km S-3/OLCI Cloud S-3/ DUE GlobColour H water-leaving 1-30 d S-2/MSI screening, SLSTR CCI Ocean radiance Atmospheric Colour correction 15 Ocean 0.5-500 km S-3/OLCI Cloud S-3/ DUE GlobColour H chlorophyll 2 h-7 d screening, SLSTR DUE (ECV) (Ocean colour) Atmospheric CoastColour correction CCI Ocean Colour 16 Particle size 0.1-10 km S-3/OLCI Cloud S-3/ DUE GlobColour M distribution 7 d screening, SLSTR CCI Ocean Atmospheric Colour correction 17 Photosynthe- 0.5-50 km S-3/OLCI Cloud S-3/ M tically Active 2 h-1 d S-2/MSI screening, SLSTR Radiation Atmospheric correction 18 Phytoplankton 1-10 km S-3/OLCI Cloud S-3/ DUE GlobColour H functional types 7 d screening, SLSTR CCI Ocean (Ocean colour) Atmospheric Colour correction, Temperature for parameter. 19 Spectral 0.1-10 km S-3/OLCI Cloud S-3/ DUE GlobColour H attenuation 1-7 d S-2/MSI screening, SLSTR CCI Ocean coeff. for Atmospheric Colour downwelling correction irradiance 20 Suspended 0.5-500 km S-3/OLCI Cloud S-3/ DUE GlobColour H sediment 2 h-6 d screening, SLSTR DUE (ECV) concentration Atmospheric CoastColour (Ocean colour) correction MOCCASSIN POWERS CCI Ocean ______
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Colour Comments from SEN4SCI scientific workshop: • Concurrent mapping of chlorophyll and temperature (S-3) helps to explore coupled dynamics of the ocean system. • Improved spectral attenuation coefficient has potential to represent better the contributions to light penetration from substances better other than phytoplankton. • Full-resolution image data (S-3, S-2) are needed to explore variability at scales hitherto inaccessible. • A concerted effort in collecting the relevant in-situ data (incl. permanent long-term super-sites) is necessary for obligatory product validation.
408 * H ~ High priority, M ~ Medium priority; ECV ~ Essential Climate Variable.
409 The physical oceanography Sentinel observations are primarily focused on global mapping (S-1, S-3), 410 but are able to bring new assets also for coastal monitoring. For instance, satellite-derived SST is a 411 mature and robust measurement, but it would still benefit from improved resolution in both space and 412 time. The wider dual-swath of SLSTR operated simultaneously aboard two Sentinel-3 units has the 413 potential to provide daily SST product with per-pixel uncertainty estimates. More than 1-year 414 overlapping operational periods of two SLSTR sensors will support independent measurement 415 stability (0.05 K / decade). New features of the Sentinel instrument and synergies of Sentinel products 416 will allow development and retrieval of new higher level (Level 3) ocean products, as for instance:
417 wave period (SAR), precipitation rate (combination of C-band with Ku-band), detection of vertical 418 motion (negative correlation between SST and chlorophyll concentration), etc. Continuity of the 419 measurements is also a concern. Plans for Sentinel fleet operability include a long-term commitment. 420 Launch of Sentinel-1A and 3A units is planned for 2013, both satellites being operational until 2020. 421 The second 1B unit in will accompany 1A in mid-2015, with foreseen operational time until 2022. The 422 3B unit will follow in 2017, delivering data until 2024. The planned third unit 1C and 3C should be 423 providing data from 2019 until 2026, and from 2021 until 2028, respectively. Finally, synergy of 424 space-borne physical oceanography with measurements from ground mobile and in-situ platforms (i.e. 425 sea level, surface currents, stream/tide gauges, precipitation, wind, river discharge, etc.) must be 426 properly established to ensure calibration and quality validation of the ocean Sentinel products.
427 Traditionally, multi-spectral satellite sensors (e.g., MERIS, MODIS and also the Sentinel-3 OLCI) are 428 primarily designed for global biological and biochemical oceanography. The asymmetric view of 429 OLCI operated simultaneously from two S-3 units, will offer sun-glint free images with improved 430 spatial coverage and frequency. Synergy of OLCI with SLSTR will be able to fill gaps in cloud- 431 contaminated observations, improve image atmospheric corrections, and advance the retrieval of in- 432 water biochemical properties (e.g., primary production, mapping of slicks). The additional OLCI 433 spectral wavebands hold promise of potentially improved products, as for instance in the case of 434 phytoplankton functional types. Coastal (case-2) waters are optically more complex than open ocean 435 (case-1) waters, therefore, they require a multi-spectral satellite sensor with adequate spatial resolution 436 to fully resolve and discriminate their optical constituents. The Sentinel-2 MSI instrument could 437 answer this challenge, under the condition that the acquisitions would cover the sea surface from the 438 coastline to the limits of the continental shelf (i.e., in some cases more than 100 km from the sea 439 shoreline). Main role of MSI will be to support mapping of marine biodiversity indicators (especially 440 in case of coral reefs) and monitoring of coastal habitat changes. It will play also a high socio- 441 economic role in timely assessment of the natural hazard impacts (e.g., coastal flooding after tsunami 442 events). As these coastal applications are in need of frequent long-time observational time-series, 443 mission of two simultaneous Sentinel-2 satellites will provide global revisit time of 5 days (2-3 days in
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444 extended mode). The end of 2013 should bring launch of the first Sentinel-2A unit, which should stay 445 operational until 2020. The second 2B satellite will accompany the first unit in 2016, staying 446 operational until 2023. Finally, the third 2C satellite is planned for the time span between 2020-2027. 447 Similarly to the geophysical variables, in-situ observations are required to support the Sentinel product 448 calibration and validation for monitoring of the open ocean and costal waters.
449 In addition to identifying scientific user requirements and ocean product priorities, the ocean splinter 450 group at the SEN4SCI workshop made the following science-related recommendations:
451 • Understanding the ocean processes 452 Physical and biological remote sensing oceanography should join their forces together with in-situ 453 monitoring and 3D modelling to understand the complex interaction between physical and bio- 454 geochemical ocean processes. Further investigation of ocean-atmosphere interactions is crucial to 455 fully comprehend the ocean system. 456 457 • Recommended attributes and access to the global datasets 458 Understanding the climate-driven changes and their relation to global changes in the physical 459 environment requires data records (time-series) that are global, long-term (multi-decadal), and 460 highly accurate (undergoing the proper calibration and stability monitoring during the entire life of 461 Sentinel missions). The data archives should be ready for regular and timely reprocessing. Easy 462 access to the data archives and an availability of the common standardized processing tools (e.g., 463 open-source toolboxes) should be provided to foster the advance in the global ocean science. 464 465 • Cooperation between science and operational services 466 Challenging operational issues spawn good science, and new scientific discoveries open the door 467 to novel operational applications. Therefore, there is a need for an avenue to channel new 468 scientific achievements rapidly into Sentinel operational services. A direct and effective link 469 between operational engineers and scientists would help to explore efficiently new capabilities of 470 the Sentinel instruments. These capabilities need to be scientifically investigated first, and then 471 implemented into the processing chains of operational products. 472 473 • Synergies across the Sentinel missions 474 The Sentinel observations should be exploited in the synergistic manner to better understand the 475 mesoscale-to-submesoscale upper ocean dynamics and coupling between the physical and bio- 476 geochemical parts of ocean and the atmosphere. This synergistic exploitation should be supported 477 by a new generation of processing toolboxes (including shared libraries in C, Matlab, Python, 478 etc.). Still, before establishing the ocean product synergies the proper and stable cross-calibration 479 among the Sentinel instruments is required. 480 481 • Calibration/Validation and uncertainty estimation activities 482 The scientific community should be actively involved in development of the sensor long-life 483 calibration/validation procedures. These should be published in the peer-reviewed publications to 484 ensure a wide acceptance of products. This can, however, only be done if the access to the 485 instrument calibration and other technical specifications is granted. The permanent long-term 486 supported ground monitoring super-sites or ocean hot spots should be established for algorithm 487 calibration and error validation. Finally, methodologies for consistent per-pixel uncertainty 488 estimations of Sentinel products should be established to ensure the long-term data consistency for 489 the climate ocean research. ______
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490 491 • Support actions for Sentinel science 492 Clear interface between ESA and the science community would strengthen links between the 493 international science teams. The coordinated scientific studies, in frame of the ESA and European 494 Commission projects and programmes (offering user workshops, toolboxes, symposia, and expert 495 working groups), should be supported to develop processing algorithms and Sentinel product 496 prototypes. 497
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498 5. References 499 500 CEOS EO Handbook, 2010. http://database.eohandbook.com/, last access: Feb. 20, 2011. 501 502 CEOS Systems Database, 2011. http://ceos-sysdb.com/CEOS/, last access: Feb. 20, 2011. 503 504 DUE, 2011. “ESA Data User Element”, http://due.esrin.esa.int/, last access: Feb. 21, 2011. 505 506 ESA, 2006. “The Changing Earth – New Scientific Challenges for ESA’s Living Planet Programme”, 507 European Space Agency, SP-1304, pp. 1-83. 508 509 GCOS, 2010. “GCOS Essential Climate Variables”, http://www.wmo.int/pages/prog/gcos/index.php 510 ?name=EssentialClimateVariables, last access: Feb. 21, 2011. 511 512 IGBP, 2006. “Science Plan and Implementation Strategy”, IGBP Report No. 55, IGBP Secretariat, 513 Stockholm, pp. 76. 514 515 IGOS-Coastal Zone, 2006. “Report of the Coastal Theme Team”, A Coastal Theme for the IGOS 516 Partnership — For the Monitoring of our Environment from Space and from Earth. Paris, UNESCO, 517 pp. 60. 518 519 IGOS-Coral Reef, 2003. “IGOS Coral Reef Sub-theme Report”, A Coral Reef Sub-theme for the 520 IGOS Partnership, pp. 36. 521 522 IGOS-Carbon, 2003. “A Strategy to Realize a Coordinated System of Integrated Global Carbon Cycle 523 Observations”, pp 61. 524 525 IGOS-Ocean, 2001. “Final Report from the Ocean Theme Team”, NASA on behalf of the IGOS 526 Partnership, pp. 36. 527 528 STSE, 2011.”ESA Support To Science Element”, http://wfaa-dat.esrin.esa.int/stse/, last access: Feb. 529 21, 2011. 530 531 URD, 2011. “Draft of the User Requirement Document”, Ocean Colour Climate Change Initiative, 532 Plymouth Marine Laboratory, United Kingdom, pp. 70. 533 534 WMO, 2011. “Database of Observational Requirements”, http://www.wmo.int/pages/prog/sat/ 535 Databases.html#User Requirements, last access: April 28, 2011.
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