AVHRR Visible Band Calibration / Intercalibration (for Climate Studies). Andrew Heidinger and Michael Pavolonis * Changyong Cao, Aleksandar Jelenak, Jerry Sullivan, Fred Wu NOAA/NESDIS Office of Research and Applications *Cooperative Institute for Meteorological Satellite Studies (CIMSS)
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AVHRR Visible Band Calibration / Intercalibration (for Climate Studies)
Andrew Heidinger and Michael Pavolonis*
Changyong Cao, Aleksandar Jelenak, Jerry Sullivan, Fred Wu
NOAA/NESDIS Office of Research and Applications
*Cooperative Institute for Meteorological Satellite Studies (CIMSS)
2nd CORP Science Symposium – Madison Wisconsin, July 13, 2005
Why use the The AVHRR for Climate Studies
The Advanced Very High Resolution Radiometer (AVHRR) was launched in the 1979 for non-quantitative cloud imagery and SST. It flies on the NOAA Polar Orbiting Satellites (POES)
2. AVHRR provides enough spatial resolution (1 or 4 km) to resolve many atmospheric and surface features
1. AVHRR Provides enough spectral information for several applications
3. Combined with its long data record (1981-2012) make the 5-channel AVHRR data-set the best we have for decadal studies for many key climate parameters.
Why Improve the AVHRR Reflectance Calibration?
D.R. Doelling, 2001: Proceedings AMS 11th Conference on Satellite Meteorology and Oceanography, Madison, Wisconsin, October 15 – 18, pp. 614-617
Goals of this Work
Proposed Methodology – Simultaneous Nadir Observations (SNO)
Taken from Changyong Cao: http://www.orbit.nesdis.noaa.gov/smcd/spb/calibration/intercal/
Example Imagery from a SNO
Sensor #1 data projected on to Sensor #2 strip. These points comprise the SNO
± 5° Nadir Strip from Sensor #1
± 5° Nadir strip from Sensor #2
Example of one July’s SNO’s for ch1 and ch2 of TERRA and NOAA-16
(note y-axis should be ch1 not ch2 on left-hand plot)
SNO’s from MODIS and AVHRR allow us to transfer MODIS’s calibration to the AVHRR directly.
Example of SNO’s for one month of PATMOS-x data (July 1992)
For July 1992, NOAA-11 and NOAA-12 gave 78 grid-cells that met SNO criteria. Note dark counts are removed so line should pass through origin.
This data provides a constraint on the ratio of NOAA-11 to NOAA-12 calibration slopes. Does not provide any information on absolute calibration by itself.
ORA (C. Cao and others) has automated SNO’s from AVHRR, AMSU and HIRS and offers a real-time monitoring capability.
A New Libyan Desert Reference for pre-MODIS Calibration
In addition to SNO data (AVHRR/MODIS and AVHRR/AVHRR), we also employ a New Libyan Desert Reflectance Reference value to provide an estimate of the absolute calibration for the afternoon satellites.
This method gives us the absolute calibration
for the pre-MODIS AVHRR data.
MODIS TRUE COLOR
Ch1 Calibration Slopes from All Satellites and All Methods
Comparison of Ch 1 Equations for NOAA-7,9,11,14,16
RCS = Rao, Chen and SullivanVS = Vermote and El Saleous
TC = Tahnk and CoakleyWU = Fred Wu (Operational NOAA)
Testing the New Reflectance Calibrations
Testing Long Term Consistency
Testing Absolute Accuracy
AOT Tables from A. Ignatov
Testing the Consistency for bright scenes