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TOWARDS IMPROVED CLIMATE DATA RECORDS FOR CLIMATE SYSTEM ANALYSIS AND CLIMATE SERVICES Jörg Schulz, Rob Roebeling, Roger Huckle, Tim Hewison, Viju John, Alessio Lattanzio EUMETSAT Abstract This paper gives an overview of EUMETSAT's activities to generate high-quality climate data records. It will demonstrate the chain of activities from the space-based observations, the generation of climate data records down to the mechanisms that facilitate the use of products for climate services. In the first part individual challenges such as the inter-satellite calibration of geostationary and polar orbiting data, the evaluation of climate data record quality and some application examples are discussed. The second part concentrates on methods we have developed to provide guidance on the suitability of data records for specific application areas. This includes an updated version of the original NOAA maturity matrix, a metric that measures how far the production follows best practises developed in science and engineering as well as the sustainability of the production process that includes user feedback and data record updates. It also discusses a newly developed metric called Application Performance Matrix that attempts to measure the suitability of a data record for a specific application by evaluating the technical specifications and validation results for a data set versus user requirements for an application. These metrics help to ensure transparency, traceability, and sound scientific judgment for climate data records and are planned to be used in the assessment of the European capacity to produce high quality Climate Data Records as conducted by the European CORE-CLIMAX project. INTRODUCTION Earth observations constitute a critical input for monitoring and advancing understanding of the Earth climate system including its variability and change. From observations taken by satellites or groundbased systems so-called climate data records can be created. In particular long records of satellite data have a high potential for being utilised for assimilation into Numerical Weather Prediction models to create a physically consistent model-based reanalysis, for the assessment of climate model performance and climate studies directly targeting an improved understanding of the mechanisms of climate change and variability. However, the requirements concerning long-term stability and uncertainty for climate data records are challenging. This is because many long-term satellite observations are provided by operational satellite systems build for the purpose of weather and not climate monitoring. Thus, a high demand for satellite radiance and geophysical data records with quality analysed and corrected observations as well as a homogenisation over time facilitating the use of multiple satellites carrying similar and different instruments exists. PART I EUMETSAT’S ROLE IN PROVIDING CLIMATE DATA RECORDS EUMETSAT plays a crucial role in the world wide network of space agencies that have the potential to provide climate data records. With the Meteosat First and Second Generation satellite series and the already committed Meteosat Third Generation (MTG) EUMETSAT maintains one of the longest satellite time series in the world. The coverage with useful data for climate monitoring starts in 1982 and with the commitment for MTG it is extended to approximately 2040. The EPS program Metop satellites carry the IASI instrument, providing benchmark quality measurements that have the potential to serve as reference for instruments from other space agencies in the infrared spectral range. The Global Space Based Inter-calibration System (GSICS) has already demonstrated by comparisons to similar instruments as AIRS and CrIS that the level of accuracy is high enough to serve as a reference until a real traceable reference mission such as teh planned CLARREO is in space. EUMETSAT has the capability to enhance the value of past observations by using reference observations in inter-satellite calibration and reprocessing activities. This enhances the value of the observations for the targeted users which are weather model-based reanalysis, the climate modelling community and data driven climate system analysis. In particular the contribution to global reanalysis at ECMWF is a major component of the EUMETSAT Secretariats activities. Within the EU FP7 project ERA-CLIM and its successor ERA-CLIM2 we are providing satellite data records with assessed and enhanced quality as input to reanalysis. We also support ECMWF to coordinate other space agencies input into European reanalysis, e.g., we support the reprocessing of Atmospheric Motion Vectors at other space agencies and research institutions to facilitate the production of consistent products and an easy use of them. There is also an increasing use of EUMETSAT climate data records in the climate modelling community. For instance the surface albedo record derived from Meteosat First Generation data has successfully been used by Loew (2013) to study the robustness of long term records of land surface properties before using them in the context of climate models. The Meteosat surface albedo has also been used in addition to sea surface temperature in a climate model to better understand precipitation anomalies in the Sahel region (Loew, 2012, pers. comm.). Table 1 shows the data records currently available, in production and planned at EUMETSAT Secretariat. It is evident that major activities are oriented towards the generation of Fundamental Climate Data Record (FCDRs), i.e., improved Level 1 data records that form the backbone of input to reanalysis systems but also to retrieval systems as applied by the EUMETSAT SAF network and the ESA Climate Change Initiative (CCI). The work on FCDRs is also supported by the CM SAF which issued a Special Sensor Microwave/Imager FCDR in 2013. Table 1: Status of Climate Data Records produced at the EUMETSAT Secretariat. The colours indicate which EU FP7 project contributes to the data record (blue: ERA-CLIM 1 and 2, orange: QA4ECV, green: basic EUMETSAT activity). The following sysmbols are sued to indicate the current status of the data records: = finished, = ongoing, = planned. In terms of GCOS ECVs EUMETSAT with its Satellite Application Facility network contributes to the production of 18 GCOS ECVs (12 Atmospheric, 2 Oceanic and 4 Terrestrial) and the important variable Land Surface Temperature which is not a GCOS ECV. Table 2 shows the EUMETSAT contributions underplayed in green colour. In addition, Table 2 shows also GCOS ECVs that are currently worked on in the framework of the ESA CCI or that fall into the CCI scope. Some of the CCI ECVs, e.g., ozone, soil moisture, sea ice and also sea surface temperature benefit from the activities on FCDRs at EUMETSAT Secretariat and the CM SAF. All EUMETSAT contributions shown here will add value to the European Copernicus Climate Change Service and the WMO led Global Framework of Climate Services (GFCS). The current overall coverage of GCOS ECVs by European activities is impressive and represents an overall strength of Europe in the generation of climate data records. Table 2: European potential to provide GCOS ECV data records for Climate Services and research. Colour code: green: EUMETSAT (Secretariat and SAF network), cyan: started by ESA CCI, and yellow: within ESA CCI scope. Improvements of the Meteosat Data Record As shown in Table 1 EUMETSAT tries to improve the Meteosat L1.5 data record for the first and second generation satellites by inter-calibration to a reference instruments in space. The IASI instrument on Metop-A is presumably the best reference in space to date that can be used as reference for a full time series by establishing an uninterrupted chain of comparisons down to the Meteosat-2 satellite by propagating the reference information with transfer instruments. Candidate transfer instruments can be the series of HIRS observations that cover time back to 1979 and the AIRS instrument with data from 2002 onwards. GSICS provides methods to derive calibration corrections for the Meteosat SEVIRI instrument with respect to IASI that needed to be extended to the MVIRI, HIRS and AIRS instruments. The corrections are derived from direct collocations of the reference with the monitored instrument. For instance, by matching the reference instrument with two monitored instruments the difference between the monitored instruments can be derived by double differencing. Because the length of the Meteosat time series is a little more than 30 years an effective tool for the collocation was developed. Instead of expensive distance calculations between pixels of different satellites it is mapping all instruments to a common grid with appropriate mesh width. The collocation of one Meteosat image with HIRS takes only about 5 seconds instead of one minute as with standard existing GSICS tools at EUMETSAT. The current tool is applicable to all Meteosat, IASI, and HIRS, will be extended with AIRS and is generally applicable to other geostationary sensors such as GOES, GMS, MTSAT. The inter-calibration of the Meteosat series using another instrument series as reference involves a couple of uncertainties that need to be quantified to provide an uncertainty estimate. Table 3 lists potential uncertainties that have already been analysed. The publications listed in Table 3 analyse uncertainties that are introduced by the different filter functions of MVIRI/SEVIRI and HIRS, different filter functions within both the MVIRI/SEVIRI and HIRS instrument series, noise in the collocation of instrument pixels due to spatial and temporal variability in imperfectly matched scenes, radiometric noise as well as potential orbital and instrumental drift. These analyses need to be done for all involved instruments to find the best so called inter-calibration path through both instrument series. Table 3: Uncertainty analysis for the inter-calibration of Meteosat IR data using HIRS. SBAF stands for Spectral Band Adjustment Factor. Part II: Towards utilisation of Climate Data Records in Climate Services for Decision and Policy Making Developing ECV climate data records poses many challenges because of the varied use of climate data, the complexities of data generation, and the difficulties in sustaining the program over extended periods of time. Therefore it is essential to assess the capability of the existing climate data development activities/programs to ensure the prolonged generation of high quality ECV climate data records so that they can help to produce the underpinning science that supports decisions on mitigation and adaptation for a warming Earth and its changing climate. In preparation of the Copernicus Climate Change Service an assessment of the needs for full access to standardised climate change data is mandatory. The European Joint Research Centre conducted a workshop 2009 that did an ad hoc analysis of the European capacity on the means to provide these data and how Copernicus Services can effectively contribute to providing these data. The report by Wilson et al. (2010) is summarising the results of this workshop that identified 44 GCOS ECVs as the minimum set of standardised climate data that EC should be considering. This workshop did also a first attempt to analyse the capacity according to maturity, differentiating between sustained operational capacity and non-operational funded repetitive capacity and additional infrastructure needs in order to fill gaps identified. The report by Dowell et al. (2012) lines out a high level strategy for an architecture for climate monitoring from space that considers the whole value adding chain from making measurements to the development of policy and decision making. This report details two usage scenarios for such architecture: - The promotion of a common understanding of the implementation implications of meeting the various climate monitoring requirements, and - To support an assessment of the degree to which the current and planned systems that provide measurements from which climate data records are generated meet the requirements, and the generation of an action plan to address any identified shortfalls/gaps. Essential for the second usage scenario is to assess what exists, what the degree of completeness and sustainability of the existing is, what quality the existing has and what is planned/committed for the future. The group of authors of the Dowell et al. (2012) report and the CEOS Working Group Climate together with WMO established the so called GCOS ECV inventory (ecv-inventory.com) for climate data records derived from satellite measurements. Currently, the inventory consists of approximately 220 entries provided by space agencies around the world and provides a first basis for an analysis of the existing data records. Because the first call to populate the inventory was only directed to space agencies the current inventory holding is not complete and further work is needed to cover all relevant data records. In addition an analysis of the ‘fit for purpose’ of the data records needs to be done. To support the international activities described above and the establishment of the Copernicus Climate Change Services one major objective of the CORE-CLIMAX project is to systematically assess the capacity of ongoing European activities in the area of generation and provision of climate data records. With respect to a Copernicus Climate Change Service also the role of in situ data and model-based reanalysis needs to be considered. For an assessment of the European capacity in the most objective way possible we need tools that provide a basis for information preservation, expectations, and a metric for progress to completeness. The maturity matrix approach proposed by Bates and Privette (2012) offers a systematic mean to assess if the data record generation follows best practises in the areas science, information preservation and usage of the data. Some examples uses of MM are the assessments of data records developed in the NOAA Climate Data Record program and in the 2nd phase of SCOPE-CM to select candidate projects. For both these cases, maturity assessments were first done as self assessments which are then followed by external assessments in a form of audit. The CORE-CLIMAX project’s proposition is based on Bates and Privette (2012), but extending the model to more general so that it can be applied not only for satellite data sets, but for all climate data records (in situ, combined satellite and in situ, reanalyses). The project discussed its adapted approach with many leading initiatives in Europe such as the EUMETSAT network of Satellite Application Facilities (SAF) and the ESA Climate Change Initiative but also internationally with WMO, the CEOS WG Climate, NOAA and USGS. Basically, three different aspects of our capacity to generate data records need to be considered: - Scientific, engineering and information preservation practises; - Usage of products including feedback and update mechanisms ; - Quality of products with respect to applications. Assessing if data record generation follows best practises provides an internal view on strengths and weaknesses of the processes to generate, preserve and improve climate data records for agencies and each individual data record provider. It also provides a general information to the community concerning the status of individual data records as well as collective information on the state of all existing records, highlighting areas for development and improvement. The assessment of quality of products is facilitating an external view on data records trying to answer the most important user question: Is the quality good enough for my application? The CORE-CLIMAX project defined three major elements for its capacity assessment: - Data record descriptions that contain technical specifications and also information on quality, e.g., links to further documentation and/or inventories such as the CGMS-CEOS-WMO inventory; - A System Maturity Matrix (SMM) that evaluates if the production of a data record follows best practices for science, engineering, information preservation and facilitation of usage, and; - A new so called Application Performance Matrix (APM) that attempts to evaluate the performance of an ECV CDR with respect to a specific application. To be able to apply the APM, user requirements for each application are needed to compare the actual technical specifications and validation results to them. Creation of a climate data record is anchored on a bunch of assumptions and approximations, and thus is associated with significantly large uncertainties. This is mainly because the observing systems were designed to measure weather, but not for monitoring climate. Unless these assumptions and approximations are well understood and associated uncertainties are well characterized it is quite possible to misinterpret results of scientific analyses using these data sets. Therefore uncertainty characterisation is a key area where CDRs need to achieve high levels of maturity. Stable and easily maintainable software is one of the essential components of successful CDRs. It should be easy to diagnose deficiencies, to make changes to the software, and to test the software after modification. Non-maintainable software can result in unexpected increase in the production cost of data sets in the long-term. The metadata, especially describing the input raw data are essential because development of a CDR is often an evolutionary process and repeated reprocessing of the input dataset is necessary. This also demands the archival of the raw data for reprocessing. CDRs shall be archived in a way that allows easy access to the users with varying requirements and skills. Therefore it demands less complicated file structures and provisions for read and analyses (e.g., subsetting, plotting) software. Availability of comprehensive descriptions of technical and scientific aspects of the production chain is another essential characteristic of a mature CDR. Above all the most important maturity characteristic of a successful CDR is the acceptance and usage by the user community and whether there are mechanisms to receive and incorporate feedbacks from the user community. Figure 1: Concept of the new Application Performance Matrix that tries to answer the user question if a data record is suitable for the application in mind. The APM (shown in Figure 1) is used to evaluate the suitability of a data record for a particular application. The APM poses typical questions that a user asks when a data record is being searched for. Whereas questions towards the spatiotemporal coverage may be easy to answer from the technical specifications of a data record, questions towards results of uncertainty analysis are more difficult and a suggestion on the suitability of a data record for an application needs most likely interaction between the application and data record experts. Key for any suggestion for usage based on this is an understanding of the user requirements for an application. For instance GCOS provides useful requirements for its ECVs which can be used as guidelines for suggestions of data records for applications in climate system analysis. However, a detailed analysis of user requirements per application would be useful to enhance the usability of the APM in the future. It should be kept in mind that the APM is a new tool that has never been used before and is considered to be experimental. The usage of the APM in this workshop shall help to analyse its usefulness and a potential way for further development. Many items, e.g., all technical specification, of the APM could be automatically evaluated from an ECV inventory assuming the inventory contains this information. Another useful element of the APM could also be the addition of experiences of other users of a data record for the same or a similar application. This might be facilitated by so called commentary meta data as being explored in the EU FP7 project CHARMe (http://www.charme.org.uk/). CONCLUSIONS The major conclusions from this study are: • EUMETSAT provides key measurements, methodology and data records to Earth system science and climate services; • The Meteosat radiance record can be further improved by the process of inter-calibration which is Internationally coordinated in activities such as GSICS and SCOPE-CM that help to enable global consistent data records and foster collaboration; • The European capacity producing GCOS ECV CDRs is fairly well developed but work is needed to sustain it into the future; • A European capacity assessment performed by the EU FP7 CORE-CLIMAX project will further help to establish advice on how CDR development shall be continued and how we better support downstream application. REFERENCES Bates, J. J. and J. L. Privette, 2012: A maturity model for assessing the completeness of climate data records. Eos Trans. AGU, 93(44): 441.DOI: 10.1029/2012EO440006. Dowell, M., P. Lecomte, R. Husband, J. Schulz, T. Mohr, Y. Tahara, R. Eckman, E. Lindstrom, C. Wooldridge, S. Hilding, J. J. Bates, B. Ryan, J. Lafeuille, and S. Bojinski (2013): Strategy towards and architecture for climate monitoring from space. 39 pp., [available from: www.ceos.org, www.wmo.int/sat, www.cgms-info.org]. Hewison, T. J., 2013: “An Evaluation of the Uncertainty of the GSICS SEVIRI-IASI Inter-Calibration Products", IEEE Trans. Geosci. Remote Sens., vol. 51, no. 3, Mar. 2013. Hewison, T. J, 2013: Long-term drift in the error budget of Meteosat-HIRS inter-calibration, Poster 157 at the 2013 EUMETSAT Meteorological Satellite Conference and 19th AMERICAN Meteorological Society Satellite Meteorology, Oceanography, and Climatology Conference, Vienna, Austria, 16-20 September 2013 [available from www.eumetsat.int]. Lindfors et al, 2011, “Climatological Diurnal Cycles in Clear-Sky Brightness Temperatures from the HIRS”, J. Atmos. Oceanic Technol., 28, 1199–1205. Loew, A., 2013: Terrestrial satellite records for climate studies: how long is long enough? A test case for the Sahel. Theor. Appl. Climatol., DOI: 10.1007/s00704-013-0880-6. Roebeling, R., J. Schulz, T. Hewison, B. Theodore, 2012: “Inter-calibration of METEOSAT IR and WV channels using HIRS”, Proceedings of International Radiation Symposium 2012, 6-10 Aug 2012, Berlin, Germany. Wilson, J., M. Dowell and A. Belward (2010): European capacity for monitoring and assimilating space based climate observations – Status and prospects. JRC Scientific and Technical Report, EUR 24273 EN, 46 pp., DOI: 10.2788/70393.