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•  > Xianqian (Fred) Wu

Physical Scientist

What do I do?

Instrument Calibration for NOAA's Geostationary Operational Environmental Satellite (GOES) and for the solar reflectance channels of the Advanced Very High Resolution Radiometer (AVHRR).

What is Calibration and How?

Satellite instrument responds to signal and its working environment. These "measurements" are recorded as electrical pulses in terms of "count". Users need the spectral radiation in terms of "radiance" that is purely from the signal and not affected by the instrument status. This process of conversion is instrument calibration. Though rightly transparent to most users, this is a critical step before any satellite product (picture of cloud or temperature or vegetation) can be generated.

Calibration typically involves characterizing instrument responses to known signals in such details that instrument responses to unknown signals can then be interpreted in terms of the known signals. The Sensor Physics Branch of STAR is responsible for the calibration of all NOAA satellite instruments.

Why Is Calibration An Integral Part of the NOAA Satellite Program?

• Calibration affects all products and users of satellite data because it is near the source of data stream.
• Calibration must be performed and monitored frequently and throughout the mission life because the working environment of the instrument may change rapidly and the instrument itself may degrade gradually.
• Calibration is imperative as scientific community sifts through historical data for implications of climate changes.
• And finally, calibration plays an important role in designing future satellite instrument and mission.

Current Projects:

• Calibration support for current satellite operations:
  • Operational calibration of the AVHRR solar reflectance channels
  • Operational calibration of the GOES Imager visible channels
  • Calibration support for GOES Imager and Sounder operations
  • Member, Calibration Product Oversight Panel
• Calibration support for re-processing of historical data:
  • Re-calibrate the AVHRR solar reflectance channels for the past quarter of century
• Calibration support for the development and deployment of future satellite systems:
  • Instrument Scientist, GOES-N series
  • Instrument Scientist, Visible/Infrared Imager/Radiometer Suite (VIIRS)
  • Member, VIIRS Operational Algorithm Team
  • Leader, Instrument Characterization Team of the NPOESS Data Exploitation (NDE) Project
  • Member, GOES-R Atmosphere, Ocean, and Land Products Technical Advisory Panel
  • Member and NOAA Climate Goal Representative, GOES-R Calibration and Validation Steering Committee
  • Member, GOES-R Calibration Working Group

Publications

Wu, X. and C. Cao (2006), Sensor calibration in support for NOAA's satellite mission, Adv. Atm. Sci., 23, 80-90.

Tian, B., B. J. Soden, and X. Wu (2004), Diurnal cycle of convection, clouds, and water vapor in the tropical upper troposphere: Satellites versus a general circulation model, J. Geophys. Res., 109, D10101, doi:10.1029/2003JD004117.

Huang, H.-L., W. L. Smith, J. Li, P. Antonelli, X. Wu, R. O. Knuteson, B. Huang, and B. J. Osborne (2004), Minimum local emissivity variance retrieval of cloud altitude and effective spectral emissivity -- Simulation and Initial verification, J. Appl. Meteor., 43, 795-809.

Jiang, S., Q. Ye, X. Yang, G. An, and X. Wu (2000), Climatological features of the global tropical subsidence region based on satellite observations, Adv. Atm. Sci., 17, 391-402.

Wu, X., W. P. Menzel, and G. S. Wade (1999), Estimation of sea surface temperatures using GOES-8/9 radiance measurements, Bull. Amer. Meteor. Soc., 80, 1127-1138.

Recent Presentations:

Operational Calibration of AVHRR/3 Solar Reflectance Channels, at the 2004 Conference on Characterization and Radiometric Calibration for Remote Sensing, Logan, Utah, 24 August 2004.

Calibration Support for NOAA's Satellite Operation, with C. Cao, at the 3rd International Ocean-Atmosphere Conference, Beijing, China, 24 June 2004.

Post-Launch Calibration of GOES Imager Visible Channel Using MODIS Data, at the 2003 International Symposium on Spectral Sensing Research, Santa Barbara, California, 2 June 2003.

Past Employment and Work:

1990 - 1993: Post-Doctoral Fellow at the Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado-Boulder.

• Constructed a climatology of the upper tropospheric humidity (UTH) from the High-resolution Infrared Radiation Sounder (HIRS) archive.

1993 - 2002: Associate Researcher, Assistant Scientist, and Associate Scientist from 1993-2002 at the Cooperative Institute for Meteorological Satellite Studies (CIMSS), University of Wisconsin-Madison.

• Derived UTH from geostationary satellites to study upper tropospheric dynamics (in conjunction with satellite-derived wind).
• Verified and improved an emissivity model for wind-roughened sea surface between 8-13 micron.
• Developed and implemented the algorithm to produce sea surface temperature (SST) from GOES.
• Assimilated Advanced Microwave Sounding Unit (AMSU) data into NWP model to infer water vapor and cloud water profiles.
• Participated in the post-launch science tests for GOES-10/11/12.

2002 - Present: Physical Scientist at NOAA/NESDIS/STAR.

Education:

B.S. (Geography), Beijing Normal University.

M. S. (Meteorology), University of Wisconsin-Madison.

• Intercomparison of Earth Radiation Budget Experiment (ERBE) Scanner and Nonscanner measurements

Ph.D. (Meteorology), University of Wisconsin-Madison.

• "Assimilation of ERBE data with nonlinear programming technique to improve cloud cover diagnosis in numerical weather prediction models".

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E-mail: Xiangqian.Wu@noaa.gov