1 Global Space-based Inter- Calibration System (GSICS) Mitchell D. Goldberg, Chief NOAA/NESDIS Center for SaTellite Applications and Research (STAR) Satellite Meteorology and Climate Division

2 Outline What is GSICS Why GSICS? How to implement GSICS

3 What is GSICS? Global Space-based Inter-Calibration System (GSICS) WMO sponsored Goal - Enhance calibration and validation of satellite observations and to intercalibrate critical components global observing system

4 Motivation Applications are becoming more demanding Demanding applications require accurate, well calibrated & characterized measurements Intercalibration of instruments achieves comparability of measurements from different instruments.

5 Climate & Weather Requirements Need excellent accuracy and long-term stability Instruments must be inter-calibrated Need high precision (low noise) Measurements must be well characterized

6 Error Characteristics Accuracy (bias) Precision (standard deviation) Stability

7 GSICS formulation The GCOS Climate Monitoring Principles (GCMPs) were extended to address the problems associated with developing long-term climate data records from satellite observations –Stable orbits –Continuity and adequate overlap of satellite observations –Improved calibration and validation CGMS tasked the WMO Space Programme to build an international consensus and consortium for a global space-based inter- calibration system for the World Weather Watch (WWW)/Global Observing System (GOS).

8 The Space Programme of WMO initiated a discussion and held two meetings (June and July 2005) to develop the concept of a Global Space-based Inter-Calibration System (GSICS). The following experts participated: – Mitch Goldberg – NOAA/NESDIS (Chair) – Gerald Frazer – NIST – Donald Hinsman – WMO (Space Program Director) – John LeMarshall - JC Sat. Data Assimilation – Paul Menzel –NOAA/NESDIS – Tillmann Mohr – WMO – Hank Revercomb – Univ. of Wisconsin – Johannes Schmetz – Eumetsat – Jörg Schulz – DWD, CM SAF – William Smith – Hampton University – Steve Ungar – CEOS, Chairman WG Cal/Val

9 WMO has approved the development of an Implementation Plan Co-ordination Group of Meteorological Satellites (CGMS) XXXIII WMO- WP-21 presented a draft concept and strategy for a Global Space-based Inter-calibration System (GSICS) Action 33.15: CGMS Members to establish a Task Force lead by NESDIS (Mitch Goldberg) with participation by EUMETSAT (Johannes Schmetz), JMA (Toshiyuki Kurino), CMA (Xu Jianmin) and assisted by the WMO Space Programme to prepare a draft Implementation Plan for GSICS by 1 July 2006 for review by CGMS Members by 1 August 2006 and approval at CGMS XXXIV.

10 GSICS Objectives To improve the use of space-based global observations for weather, climate and environmental applications through operational inter-calibration of satellite sensors. To provide for the ability to re-calibrate archived satellite data using the GSICS intercalibration system to enable the creation of stable long-term climate data sets To ensure that instruments meet specification, pre- launch tests are traceable to SI standards, and the on- orbit satellite instrument observations are well calibrated by means of careful analysis of instrument performance, satellite intercalibration, and validation with reference sites

11 Benefits - High Level Improved satellite products to observe climate variability and trends, and to support reanalysis projects. Improved utility (ease of use) of satellite radiances in NWP Reduced cost-benefit ratio from an optimized global system of satellites

12 Benefits - Technical Consistent calibration of space-based radiometers Significantly improved characterization of space-based radiometers Improved overall performance by moving towards absolute calibration Improved understanding of physical processes in atmospheric models Improved detection of climate trends, by tying entire intercalibrated system to absolute SI standards and ensuring that any drift of the entire intercalibrated system truly reflects changes of the Earth System. Improved assessment of sensor performance to validate that contractors meet the performance standards in their SOW.

13 Prerequisites  Extensive pre-launch characterization of all instruments traceable to SI standards  Benchmark instruments in space with appropriate accuracy, spectral coverage and resolution to act as a standard for inter- calibration  Independent observations (calibration/validation sites – ground based, aircraft)

14 Building Blocks for Satellite Intercalibration Collocation –Determination and distribution of locations for simultaneous observations by different sensors (space-based and in-situ) –Collocation with benchmark measurements Data collection –Archive, metadata - easily accessible Coordinated operational data analyses –Processing centers for assembling collocated data –Expert teams Assessments – communication including recommendations – Vicarious coefficient updates for “drifting” sensors

15 Global Space-based Inter-Calibration System (GSICS)

16 GSICS Organizational Chart

17 GSICS Executive Panel Monitor and evaluate the evolution and operations of the GSICS. Provide guidance and advice on the development and enhancement of the GSICS. Consist of representatives from the WMO and each satellite agency. Establish the GSICS Research Working Group (GRWG) and a Data Working Group (GDWG) to assist in the coordination, planning and implementation of GSICS research and data management activities The GRWG will consist of scientists and the GDWG of data management experts representing the participating agencies.

18 The GSICS Coordination Centre (GCC)

19 The GSICS Coordination Centre (GCC)

20 GSICS Processing and Research Centers (GPRC)

21 Toward an Integrated System for Intersatellite Calibration of POES and GOES using the SNO Method GOES vs. POES POES SNO: Simultaneous Nadir Overpass

22 GSICS Processing and Research Centers (GPRC)

23 Satellite Intercalibration improves MSU time series Simultaneous Nadir Overpass (SNO) NESDIS Operational Calibration Improved calibrated radiances using SNO- improved differences between sensors by order of magnitude. Trends for nonlinear calibration algorithm using SNO cross calibration 0.17 K Decade -1 Improved Calibration

24 Global ozone time series from 5 overlapping satellites Each satellite’s measurements have been subtracted from ground based Dobson instrument observations All satellite observations are adjusted to those of (NOAA – 9 minus Dobson) by taking advantage of overlapping satellite data records These adjustments minimize inter-satellite instrument biases and produce a more stable and reliable ozone time series Ozone time series courtesy of A.J. Miller Intersatellite Calibration using Overlapping Records

25 Calibration Support Segments (CSS) Pre-launch Instrument Characterization Earth-based Reference Sites Extraterrestrial Calibration Sources Model Simulations Benchmark Measurements

26 AVHRR VIS/NIR Vicarious Calibration using the Libyan Desert Target Courtesy of X. Wu –NOAA 16 AVHRR Albedo–NOAA 17 AVHRR Albedo CH1 CH2 CH3

27 N-17 coeff. update N-16 coeff. update AVHRR 0.86um channel (with vicarious calibration)

28 Understanding Global Biases and Developing Calibration Algorithms for Bias Correction SSMIS is the first conical microwave sounding instrument, precursor of NPOESS CMIS. Shown are the differences between observed and simulated measurements. Biases are caused by 1) antenna emission, 2) direct solar heating to warm load and 3) stray light contamination to its calibration targets. SSMIS (54.4 GHz)

29 National Roadmap Produce high-quality and well characterized measurements from domestic and foreign satellites for weather and climate applications through the state-of- the art calibration, intercalibration and validation procedures National contribution to GSICS Prelaunch Instrument Characterization On-orbit Calibration, Intercalibration and Validation Reference Sites Data Management