GCOS 2 nd Report on Adequacy … Perspectives from GCM / RCM modeling, climate downscaling, and developing nations From the view of practicing climate change and variability research in Africa Bruce Hewitson – University of Cape Town Climate change projection: Multi- model mean Δ precipitation 4 of 6 agreement on sign … but which models are correct …

Data needs: GCMs / RCMs / downscaling for impacts … the key issues … Baseline Climate Understanding (through analysis and modeling) Historical variability and change  what is the envelope and trend? Climate system processes  sensitivity to perturbations, feedback processes? GCM/RCM Models Development and tuning  What is real? Evaluation and validation  What is the systematic bias, process error? Application and Contextualization  Where in data space is the model “skillful”? Empirical downscaling Development and skill  Identifying the “true” scale translation function Stationarity assessment  How much do future projections transgress historical envelope? Related problems: Data representation  model / observation data on appropriate time/space scales Political access  inter-nation barriers - NWS limitations and poor links with researchers Formats (paper / electronic)  finding / rescuing “lost” archives, standard data structures Bandwidth access  (Meta-)data dissemination to broad community

AIACC Example: An end-to-end process with dependency on observations at all stages Acquire GCM Simulations Assess control simulations Quantify skill & uncertainty Develop GCM-based regional scenarios Acquire Observational Data Quality Control Collate to common format Include reanalysis fields Assess User Needs Review AIACC projects Integrate GCM and obs data Disseminate via web Common multi-GCM / Observational data sets for participants usage Availibility via internet and CD- ROM Regional Climate Model Simulations Control simulations with reanalysis forcing Quantify skill & uncertainty Simulations with GCM boundary forcing Long-term for large sub-continental domains Short-term high resolution on focus domains Process-based investigations Empirical downscaling Downscaling functions from reanalysis data Quantify skill & uncertainty Downscaling of GCM simulation data Initial downscaling to station scale ppt and T Additional downscaling to impacts variables Integration and Analysis Inter-GCM comparison -- Inter-RCM comparison -- Regional skill variability -- RCM versus Empirical downscaling Confidence levels and uncertainty of regional scenarios -- tailoring of results to user needs Journal papers -- workshops and training -- inter-institutional visits and internships * * * * ** * * * * *

Key issue: delivery of / access to products appropriate to user needs

Data needs: GCMs / RCMs / downscaling for impacts … Data specifics (ideals) … Application of models and climate change scenario for impacts assessments: Necessity to develop/validate for time/space scales of application Atmospheric dynamics: - On model grid, at sub-daily resolution - Model comparable area averages - 3D atmospheric u,v,q,T - 3D cloud fields - GCMs: 6-12 hourly on ~2.5º grid - RCMs: 6 hourly on 20-50km grid Surface variables - At time resolutions resolving extremes (eg: for rain rates etc). -(Long term) precipitation and temperature - Land use/cover and albedo - Radiative fluxes at surface and top of atmosphere - Sea Surface Temperatures - Soil moisture - Key vulnerability variables: Stream flow, extremes, etc.

Data needs: GCMs / RCMs / downscaling for impacts … Principal data sources used and problems … a) Radiosondes and upper air observations Network declining Access to archived data problematic b) Surface precipitation / air temp / stream gauge observations Network declining or absent Issues of quality and duration Access to archived data problematic c) Satellite derived albedo / radiation / skin temperature / surface winds Observations increasing – but short data record Access to archived data problematic d) Reanalysis data sets Uncertainty on quality (NCEP / ERA / Truth!) Regionally dependant problems pre-79 Access to archived data problematic

Data needs: GCMs / RCMs / downscaling for impacts … Long-term surface observations … 50-yr trend (robust regression) Number of raindays > 2mm in a month

Green: 1-day snapshot of station presence Black + Green: Station presence between

~50-100km observational network

Data needs: GCMs / RCMs / downscaling for impacts … Long-term surface observations … Serious problems with data coverage not appropriate to regional climate gradients Quality control poor (Sunday/Monday problem) Non-homogeneous data sets, widely differing (cryptic) data formats with variable user-skill in data management (eg: NCAR formats, GRIB, etc) “Lost” data – hardcopy in diverse (unknown?) institutional archives Almost insurmountable bureaucratic / political barriers to accessing data Network bandwidth in Developing nations extremely inadequate

Data needs: GCMs / RCMs / downscaling for impacts … Long-term surface observations … Serious problems with data coverage not appropriate to regional climate gradients Quality control poor (Sunday/Monday problem) Non-homogeneous data sets, widely differing (cryptic) data formats with variable user-skill in data management (eg: NCAR formats, GRIB, etc) “Lost” data – hardcopy in diverse (unknown?) institutional archives Almost insurmountable bureaucratic / political barriers to accessing data Network bandwidth in Developing nations extremely inadequate GCOS: addresses these in principal, but …. - Capacity: resources for developing nation to collate / process archives - Politics: How to break through inter-agency and inter-nation barriers - Communication: Facilitating access by the research community - Bandwidth: Internet in developing nations not adequate for data access!

Data needs: GCMs / RCMs / downscaling for impacts … Free atmosphere variables / boundary fields … Dependency on radiosondes, satellites, reanalysis data sets Declining radiosonde network – seriously absent in most developing nations Issues of comparing data of different character derived from different sources eg: satellite vs radiosonde vs model area averages Question of reanalysis skill in data sparse regions, esp. prior to 1979 in SH GCOS: addresses these in principal, but …. - Data access: problematic, especially for nationally held archives - Reanalysis data – quantification of error / skill in data spare regions - Reanalysis access – eg: ERA 40 not affordable by developing nations - Bandwidth: developing nation internet currently not adequate! Land cover / SST / and other spatially continuous boundary fields GCOS: addresses these in principal, but …. - Bandwidth a problem

Eg: Perturbation simulations: Experiment: 20% change in land surface albedo (within natural variability), can generate a temperature anomaly of 1°C Q: notable difference to reanalysis: is the baseline of model correct, or reanalysis due to absence of constraining observations? Dynamics driving perturbation response related to moisture flux – yet strong baseline moisture flux disagreement between NCEP/ERA

Eg: Perturbation simulations: Experiment: Desiccation of soil moisture – temperature increases up to 4°C Q: What should the “real” soil moisture be?

Summary issues and questions Process based investigations: A need for quantified error / skill of reanalysis data Eg: NCEP Reanalysis I and ERA15 have marked differences in moisture flux over central and southern Africa – what is the baseline for model evaluation? The historical envelope: Proactively addressing regionally-held data (in developing nations), quality controlled, integration with existing archives? Data access for researchers: Significant barriers exist between the research community and the operational network / data archiving centers: Meta data not available, access procedures problematic, even finding data! What more be done than simply “urging” (GCOS term) nations to cooperate. Infrastructural limitations on data dissemination: Beyond western developed nations, capacity to download or even store data is woefully inadequate Data massaging: Compiling data sets appropriate to end user needs

GCOS 2 nd Report on Adequacy … Shortcomings in observing network … … but secondary to issues of access Adequacy in principal, inadequacy in practice Fundamental constraints: Financial resources and political willingess Facilitate an appropriate resource base from governments

GCOS 2 nd Report on Adequacy … Shortcomings in observing network … … but secondary to issues of access Adequacy in principal, inadequacy in practice Fundamental constraints: Financial resources and political willingess Facilitate an appropriate resource base from governments Strengthen statements relating to barriers to accessing data: - Sharing of data / barriers between archives and researchers - Proactively communicating metadata (perhaps modeled on the DDC) - Facilitating dissemination / addressing bandwidth in developing nations - Reanalysis data – financial barriers! Data products appropriate to endusers in the research community - Adding conversion activities to existing archiving procedures Tropical regions, and 3D atmosphere data, especially moisture - Special focus need for understanding climate processes, model skill assessment