Climate Analysis and Reanalysis Program Development Phil Arkin, ESSIC, University of Maryland

1. Climate Analysis and Reanalysis Program DevelopmentPhil Arkin, ESSIC, University of Maryland • Programmatic Background • Atmospheric Activities • Ocean Activities • Conclusions and Issues

2. We need more comprehensive climate observations and we must make more efficient use of those that are and will be available. THE NEED FOR A SYSTEMS APPROACH TO CLIMATE OBSERVATIONS BY KEVIN E. TRENBERTH, THOMAS R. KARL, AND THOMAS W. SPENCE Because climate is changing, we need to determine how and why. How do we best track and provide useful information of sufficient quality on climate? Bulletin of the American Meteorological Society: November 2002, 83, 1593-1602

3. Observing systemmeans a comprehensive approach, including • Climate observations from both space-based and in situ platforms taken in ways that address climate needs and adhere to the ten principles outlined by the NRC (1999). • A global telecommunications network and satellite data telemetry capacity to enable data and products to be disseminated. • A climate observations analysis capability that produces global and regional analyses of products for the atmosphere, oceans, land surface and hydrology, and the cryosphere, based on four dimensional data assimilation capabilities that process the multivariate data in a physically consistent framework to enable production of the analyses: for the atmosphere and oceans, land surface and so on. • Global climate models that encompass all parts of the climate system and which are utilized in data assimilation and in making ensemble predictions.

4. GEOSS--- Creating a “System of Systems” Global Observing Systems GCOS GOOS GTOS WHYCOS World Weather Watch IGBP IOOS CEOS IGOS National/Multinational Observing Systems Satellites Surface Observations Radar Aircraft Ocean Observations Paleo-data Private Sector Observing Systems Satellites Mesonets Lightning Commercial Aircraft Climate Variability and Change Disasters Agriculture Ocean Resources Water Resources Health Energy Ecosystem Societal Benefits 4

5. GEOSS--- Creating a “System of Systems” Global Observing Systems GCOS GOOS GTOS WHYCOS World Weather Watch IGBP IOOS CEOS IGOS National/Multinational Observing Systems Satellites Surface Observations Radar Aircraft Ocean Observations Paleo-data Private Sector Observing Systems Satellites Mesonets Lightning Commercial Aircraft Integration / Synthesis / Analysis (of the physical climate system) Climate Variability and Change Disasters Agriculture Ocean Resources Water Resources Health Energy Ecosystem Societal Benefits 5

6. Reprocessing and Reanalysis are essential Given the continuing improvement in climate observations and the need for long time series, reprocessing is an essential element of every climate observing system. Workshop on Ongoing Analysis of the Climate System18-20 August 2003, Boulder, Colorado • Workshop report distributed • See workshop web site (http://www.joss.ucar.edu/joss_psg/meetings/climatesystem/) for pdf version of report and background information from the workshop.

7. The Workshop concluded that the U.S. must establish a National Program for Ongoing Analysis of the Climate System to provide a retrospective and ongoing physically consistent synthesis of earth observations in order to: • Guide the design and operation of observing systems • Produce and sustain the growing climate record • Reconcile disparate climate observations and characterize analysis uncertainty • Establish initial conditions for climate prediction • Validate prediction and projection models on all time scales • Provide long time series of global and regional climatic analyses for all types of prediction and projection verification

8. Elements of a Comprehensive Ongoing Analysis of the Atmosphere • Enhancing and managing the observational database • Archeology, new sensors, continuity and feedback • Ongoing analysis: • Continually update most recent reanalyses (CDAS) • Use OSEs and OSSEs to document impact of continuing observing system changes • Provide feedback to observing system developers/operators • Periodic reanalyses • Post 1979 reanalysis with goal of continuous climate record • Post 1950 reanalysis with same goal • Post 1850 surface NH oriented • Continental-scale regional reanalysis at very high spatial resolution • Stewardship and dissemination • Ensure that the products are useable • Applied research • Develop improved methods and products • Intended to solve problems identified within program

9. Current/Planned U.S. Atmospheric Activities • Climate Data Assimilation System (CDAS) – operational extension of NCEP/NCAR reanalysis run by CPC • Regional CDAS – operational extension of Regional Reanalysis, also run by CPC • MERRA (Modern Era Reanalysis for Research and Applications) – NASA/GSFC research project focused on satellite era hydrological cycle • Surface-based reanalysis of Northern Hemisphere – NOAA/CDC research project • Extension of MERRA to include climate transition during 1970s • Community Reanalysis System • Consolidated reanalysis database suitable for distributed experiments • Facility for a variety of experiments (OSE/OSSEs, system test, etc.) – could be either a portable code or a “testbed” • CCSP reanalysis support

10. CLIVAR Ocean Reanalysis WorkshopNov 8-10, 2004 - Boulder, COAn activity of the CLIVAR Global Synthesis and Observations Panel (GSOP) Workshop Objectives: • Establish the requirements for ocean reanalysis. • Review the usage of ongoing and planned ocean reanalysis efforts. • Stimulate new applications of existing ocean reanalyses. • Review the synergy between ocean and atmospheric reanalysis activities. • Review long-term observing system strategies and designs. • Identify model improvements required for ocean and coupled reanalyses.

11. CLIVAR Ocean Reanalysis Workshop • Climate relevant applications of ocean reanalysis include: • 1) Understanding climate dynamics from reanalyses. • 2) Reanalysis, sea level rise and 5th IPCC assessment. • 3) CO2 sequestering. • 4) Regional impacts. • 5) Initializing coupled models from ocean reanalyses. • 6) Observing System Experiments (OSE): need to be carefully prepared and evaluated. • CLIVAR GSOP should promote a wider use of reanalysis result for science and societal needs. • CLIVAR will aim to make reanalysis products available in 2009 in time to contribute to the 5th IPCC Assessment Report.

12. CLIVAR Ocean Reanalysis Workshop: Issues • There is not yet a sustained activity to address climate-quality hindcasts/reanalyses as well as Dec-Cen initialization and anthropogenic time-scale projection problems. • There seems to be a well organized data stream for SI efforts that is partially used by other ocean reanalyses efforts. • Testing the existing reanalyses in terms of their quality for each of the above requirements is urgent. This includes determining uncertainties and ensembles. This needs to be done in close collaboration with WGOMD, GODAE and the basin panels. (model-model; model-data; prediction, residuals) • Data stream and data QC became large issues for decadal reanalysis efforts. • Surface flux (plus run off and ice volume advection) uncertainties remain a large issue. Reanalyses efforts need to work with WGOMD on identifying useful surface flux products and standards in support of ocean reanalysis.

13. CLIVAR Ocean Reanalysis Workshop: Actions Underway • Working group on data quality requirements for reanalyses and ocean data systems • Working group on intercomparison of reanalyses (in partnership with GODAE, WGOMD and CLIVAR panels). This would initially be done in a pilot intercomparison process to be developed in the coming year. • Preparation of recommendations for model standards and surface fluxes that should be used by reanalysis efforts. To be done in close link to CLIVAR-WGOMD and Flux WG.

14. Conclusions/Issues • The goal is an accurate description of the current and past state of the complete coupled climate system – ocean, land, atmosphere, … • Such a description is the product of an analysis system • Ocean Climate Observing System(s) must be accompanied by appropriate Climate Analysis System(s) • For NOAA’s OCO, the partnership with EMC/CPC is an initial step in this direction • Utilize the analysis system to inform decisions on observing system design • The analysis community has to strive toward a coupled system • Analysis provides the essential link between observations and modeling – for climate, it’s NOAA’s responsibility to figure out how to get it done!