1 / 16

The GCOS Reference Upper Air Network

The GCOS Reference Upper Air Network. What is GRUAN?. GCOS Reference Upper Air Network Network for ground-based reference observations for climate in the free atmosphere in the frame of GCOS Initially 15 stations, envisaged to be a network of 30-40 sites across the globe

mira-vang
Download Presentation

The GCOS Reference Upper Air Network

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. The • GCOS Reference • Upper Air Network

  2. What is GRUAN? • GCOS Reference Upper Air Network • Network for ground-based reference observations for climate in the free atmosphere in the frame of GCOS • Initially 15 stations, envisaged to be a network of 30-40 sites across the globe • See www.gruan.org for more detail

  3. GRUAN tasks • Provide long-term high-quality upper-air climate records • Constrain and calibrate data from more spatially-comprehensive global observing systems (including satellites and current radiosonde networks) • Fully characterize the properties of the atmospheric column

  4. GRUAN goals • Maintain observations over several decades for accurately estimating climate variability and change • Focus on characterizing observational biases, including complete estimates of measurement uncertainty • Ensure traceability of measurements by comprehensive metadata collection and documentation • Ensure long-term stability by managing instrumental changes • Tie measurements to SI units or internationally accepted standards • Measure a large suite of co-related climate variables with deliberate measurement redundancy Priority 1: Water vapor, temperature, (pressure and wind) Priority 2: Ozone, clouds, …

  5. GRUAN structure • GCOS/WCRP AOPC Working Group on Atmospheric Reference Observations (WG-ARO) • GRUAN Lead Centre at the Lindenberg Meteorological Observatory (DWD) • GRUAN sites world wide (currently 15 to be expanded to 30-40) • GRUAN task teams for • Radiosondes • GNSS-Precipitable Water • Measurement schedules and associated site requirements • Ancillary measurements • Site representation • GRUAN Analysis Team for Network Design and Operations Research (GATNDOR) • See www.gruan.org for more detail

  6. Focus on referenceobservations • A GRUAN reference observation: • Is traceable to an SI unit or an accepted standard • Provides a comprehensive uncertainty analysis • Is documented in accessible literature • Is validated (e.g. by intercomparison or redundant observations) • Includes complete meta data description

  7. Establishing reference quality

  8. Establishing Uncertainty • Error is replaced by uncertainty • Important to distinguish contributions from systematic error and random error • A measurement is described by a range of values • generally expressed by m ± u • m is corrected for systematic errors • u is random uncertainty Literature: • Guide to the expression of uncertainty in measurement (GUM, 1980) • Guide to Meteorological Instruments and Methods of Observation, WMO 2006, (CIMO Guide) • Reference Quality Upper-Air Measurements: Guidance for developing GRUAN data products, Immler et al. (2010), Atmos. Meas. Techn.

  9. Uncertainty, Redundancy and Consistency • GRUAN stations should provide redundant measurements • Redundant measurements should be consistent: • No meaningful consistency analysis possible without uncertainties • if m2 has no uncertainties use u2 = 0 (“agreement within errorbars”)

  10. Uncertainty, Redundancy and Consistency • Understand the uncertainties: • Analyze sources: Identify, which sources of measurement uncertainty are systematic (calibration, radiation errors, …), and which are random (noise, production variability …). Document this. • Synthesize best uncertainty estimate: • Uncertainties for every data point, i.e. vertically resolved • Use redundant observations: • to manage change • to maintain homogeneity of observations across network • to continuously identify deficiencies

  11. Consistency in a finite atmospheric region • Co-location / co-incidence: • Determine the variability () of a variable (m) in time and space from measurement or model • Two observations on different platforms are consistent if • This test is only meaningful, i.e. observations are co-located or co-incident if:

  12. Uncertainty example: Daytime temperature Vaisala RS92 Sources of measurement uncertainty (in order of importance): • Sensor orientation • Radiative heating of sensor • Unknown radiation field • Ventilation • Ground check • Calibration • Time lag

  13. Uncertainty example: Comparison Vaisala RS92 with Multithermistor • Minor systematic difference at night • Significant systematic difference during the day • But observations are consistent with the understanding of the uncertainties in the Vaisala temperature measurements • Lack of uncertainties in Multithermistor measurements precludes further conclusions

  14. Principles of GRUAN data management • Archiving of raw data is mandatory • All relevant meta-data is collected and stored in a meta-data base (at the lead centre) • For each measuring system just one data processing center • Version control of data products. Algorithms need to be traceable and well documented. • Data levels for archiving: • level 0: raw data • level 1: raw data in unified data format (pref. NetCDF) • level 2: processed data product → dissemination (NCDC)

  15. Distributed data processing

  16. Summary • GRUAN is a new approach to long term observations of upper air essential climate variables • Focus on priority 1 variables to start: Water vapor and temperature • Focus on reference observation: • quantified uncertainties • traceable • well documented • Understand the uncertainties: • analyze sources • synthesize best estimate • verify in redundant observations • GRUAN requires a new data processing and data storage approach

More Related