INDOEX: Satellite AVHRR Aerosol Optical Depth (Coakley) Author: > ----------------------------------------------------------------- > James A. Coakley, Jr., Professor Ph: (541) 737-5686 > College of Oceanic and Fax: (541) 737-2540 > Atmospheric Sciences E-mail: coakley@coas.oregonstate.edu > Oregon State University > Oceanography Admin 104 College Main Ph: > Corvallis, OR 97331-5503 USA (541) 737-3504 > ----------------------------------------------------------------- Daily NOAA-14 AVHRR 4-km Global Area Coverage (GAC) measurements were collected for January-March 1996-2000. Analyses were performed for ascending daytime passes in the INDOEX region: 30S to 30N and 50E to 110E. The data were analyzed on a 60 by 60 1 degree latitude-longitude grid to produce daily, weekly, and monthly composites of data for the INDOEX region. For each 1 degree by 1 degree latitude-longitude region, the aerosol properties and cloud-free radiative forcing were composited along with the numbers of cloud-free, partly cloudy, and overcast pixels, as well as other cloud related indices. Estimates of the diurnally averaged radiative forcing were derived assuming that the aerosol mixture, optical depth, and cloud conditions encountered at the time of the NOAA-14 overpass were constant for the daytime hours. See Coakley et al (2002) for details. The daily composites are unformatted files consisting of a 15-word header and a 60 by 60 by 67 word data array. The weekly, and monthly composites are unformatted files consisting of a 15-word header and a 60 by 60 by 86 word data array. All composites can be read using the sample fortran program supplied (read_indoex.f) or read into idl using the idl procedure provided (gfileopen.pro). The averaging period of the data contained in a composite is apparent from the file name. The information in the header and data array is arranged as follows: The 15-word header record is organized as follows: c c FOR WORD(I), c c I = 1, Number of words in header c 2, Number of 1-degree regions along a meridian from 50E to 110E c 3, Number of 1-degree regions along a parallel from 29.5S to 30.5N c 4, Number of parameters saved for each 1-degree region c 5, Satellite ID (NOAA-14) c 6, Instrument ID (AVHRR) c 7, Year c 8, Julian Day c 9, Hour c 10, Minute c 11, Second expressed as a fraction c TIME INDICATES TIME OF EARLIEST DATA USED IN THE COMPOSITE c c 12, Absolute start latitude of southernmost 1-degree region c 13, NODE: ASCENDING (NODE=1) DESCENDING (NODE=0) c 14, Absolute longitude of westernmost 1-degree region c 15, Longitude and latitude increment in degrees The daily composite data array (i=60,j=60,k=67) has for each longitude i and latitude j the following data: NOTE: FOR REFLECTANCES: Cosine of solar zenith angle NOT accounted for c k = 1, total number of pixels c 2, mean latitude c 3, std deviation of latitude c 4, mean longitude c 5, std deviation of longitude c 6, mean solar zenith angle c 7, std deviation of solar zenith angle c 8, mean satellite zenith angle c 9, std deviation of satellite zenith angle c 10, mean azimuth angle c 11, std deviation of azimuth angle c 12, average reflectance (in %) channel 1 c 13, 5th lowest percentile of channel 1 reflectance c 14, 5th highest percentile of channel 1 reflectance c 15, average reflectance (in %) channel 2 c 16, 5th lowest percentile of channel 2 reflectance c 17, 5th highest percentile of channel 2 reflectance c 18, average radiance (in mWm-2sr-1cm) channel 3 c 19, 5th lowest percentile of channel 3 radiance c 20, 5th highest percentile of channel 3 radiance c 21, average radiance (in mWm-2sr-1cm) channel 4 c 22, 5th lowest percentile of channel 4 radiance c 23, 5th highest percentile of channel 4 radiance c 24, average radiance (in mWm-2sr-1cm) channel 5 c 25, 5th lowest percentile of channel 5 radiance c 26, 5th highest percentile of channel 5 radiance c 27, number of cloud-free pixels c 28, mean of channel 1 reflectance (in %) for cloud-free pixels c 29, std deviation of channel 1 reflectance for cloud-free pixels c 30, mean of channel 2 reflectance (in %) for cloud-free pixels c 31, std deviation of channel 2 reflectance for cloud-free pixels c 32, mean of channel 3 radiance (in mWm-2sr-1cm) for cloud-free pixels c 33, std deviation of channel 3 radiance for cloud-free pixels c 34, mean of channel 4 radiance (in mWm-2sr-1cm) for cloud-free pixels c 35, std deviation of channel 4 radiance for cloud-free pixels c 36, mean of channel 5 radiance (in mWm-2sr-1cm) for cloud-free pixels c 37, std deviation of channel 5 radiance for cloud-free pixels c 38, mean size index c 39, std deviation of size index c 40, mean optical depth at 0.55 microns c 41, std deviation of optical depth at 0.55 microns c 42, mean optical depth at 0.65 microns c 43, std deviation of optical depth at 0.65 microns c 44, mean optical depth at 0.80 microns c 45, std deviation of optical depth at 0.80 microns c 46, mean optical depth at 0.90 microns c 47, std deviation of optical depth at 0.90 microns c 48, mean toa aerosol direct radiative forcing c 49, std deviation of toa aerosol direct radiative forcing c 50, mean surface aerosol direct radiative forcing c 51, std deviation surface aerosol direct radiative forcing c 52, not used c 53, not used c 54, number of pixels overcast by layered cloud systems c 55, mean ch1 reflectance (in %) for overcast pixels c 56, std deviation ch1 reflectance for overcast pixels c 57, mean ch2 reflectance (in %) for overcast pixels c 58, std deviation ch2 reflectance for overcast pixels c 59, mean ch3 radiance (in mWm-2sr-1cm) for overcast pixels c 60, std deviation ch3 radiance for overcast pixels c 61, mean ch4 radiance (in mWm-2sr-1cm) for overcast pixels c 62, std deviation ch4 radiance for overcast pixels c 63, mean ch5 radiance (in mWm-2sr-1cm) for overcast pixels c 64, std deviation ch5 radiance for overcast pixels c 65, number of times size index is <= 0 c 66, number of times size index is between 0 and 1 c 67, number of times size index is >= 1 The weekly and monthly composite data array (i=60,j=60,k=86) has for each longitude i and latitude j the following data: Note: Reflectances are given as AVHRR REFLECTANCE/COSINE(SOLAR ZENITH ANGLE) c CATEGORY: FOR EACH REGION c k = 1, central latitude c 2, central longitude c 3, total number of days observed (number of pixels in region >= 200) c 4, mean reflectance (in %) for channel 1 c 5, period minimum 5th lowest percentile of channel 1 reflectance c 6, period maximum 5th highest percentile of channel 1 reflectance c 7, mean reflectance (in %) for channel 2 c 8, period minimum 5th lowest percentile of channel 2 reflectance c 9, period maximum 5th highest percentile of channel 2 reflectance c 10, mean radiance (in mWm-2sr-1cm) for channel 3 c 11, period minimum 5th lowest percentile of channel 3 radiance c 12, period maximum 5th highest percentile of channel 3 radiance c 13, mean radiance (in mWm-2sr-1cm) for channel 4 c 14, period minimum 5th lowest percentile of channel 4 radiance c 15, period maximum 5th highest percentile of channel 4 radiance c 16, mean radiance (in mWm-2sr-1cm) for channel 5 c 17, period minimum 5th lowest percentile of channel 5 radiance c 18, period maximum 5th highest percentile of channel 5 radiance c 19, mean frequency of occurrence of cloud-free pixels c 20, daily stdev of frequency of occurrence of cloud-free pixels c 21, mean frequency of occurrence of partly cloudy pixels c 22, daily stdev of frequency of occurrence of partly cloudy pixels c 23, total number of days with upper level clouds, but not overcast c 24, mean frequency of occurrence of upper level clouds, but not overcast c 25, total number of days overcast by upper level clouds c (number of overcast pixels in region >= 12) c 26, mean frequency of occurrence of overcast by upper level clouds c 27, mean fractional cloud cover for partly cloudy pixels c (number of partly cloudy pixels in region >= 12) c 28, daily stdev of fractional cloud cover for partly cloudy pixels c c AVERAGE FORCING, ALL CLOUDS = 0 c 29, mean toa aerosol direct radiative forcing c 30, daily stdev toa aerosol direct radiative forcing c 31, mean surface aerosol direct radiative forcing c 32, daily stdev surface aerosol direct radiative forcing c AVERAGE FORCING-LOW, FORCING FOR LOW CLOUDS PRESENT, FOR UPPER-LEVEL CLOUDS = 0 c 33, mean toa aerosol direct radiative forcing c 34, daily stdev toa aerosol direct radiative forcing c 35, mean surface aerosol direct radiative forcing c 36, daily stdev surface aerosol direct radiative forcing c AVERAGE FORCING-HI, FORCING FOR LOW CLOUDS PRESENT, UPPER-LEVEL CLOUDS IGNORED c 37, mean toa aerosol direct radiative forcing c 38, daily stdev toa aerosol direct radiative forcing c 39, mean surface aerosol direct radiative forcing c 40, daily stdev surface aerosol direct radiative forcing c c CATEGORY: CLOUD-FREE PIXELS c 41, total number of days with cloud-free pixels and aerosol retrievals c (number of cloud-free pixels in region >= 12) c (5th lowest percentile 11-micron radiance >= 75.) c (glint angle >= 40.) c (relative azimuth angle >= 90.) c 42, mean channel 1 reflectance (in %) for cloud-free pixels c 43, daily stdev channel 1 reflectance for cloud-free pixels c 44, mean channel 2 reflectance (in %) for cloud-free pixels c 45, daily stdev channel 2 reflectance for cloud-free pixels c 46, mean channel 3 radiance (in mWm-2sr-1cm) for cloud-free pixels c 47, daily stdev channel 3 radiance for cloud-free pixels c 48, mean channel 4 radiance (in mWm-2sr-1cm) for cloud-free pixels c 49, daily stdev channel 4 radiance for cloud-free pixels c 50, mean channel 5 radiance (in mWm-2sr-1cm) for cloud-free pixels c 51, daily stdev channel 5 radiance for cloud-free pixels c 52, mean optical depth at 0.55 microns c 53, daily stdev optical depth at 0.55 microns c 54, mean optical depth at 0.65 microns c 55, daily stdev optical depth at 0.65 microns c 56, mean optical depth at 0.80 microns c 57, daily stdev optical depth at 0.80 microns c 58, mean optical depth at 0.90 microns c 59, daily stdev optical depth at 0.90 microns c 60, mean size index c 61, daily stdev size index c 62, mean fraction size index <= 0 c 63, daily stdev fraction size index <= 0 c 64, mean fraction size index between 0 and 1 c 65, daily stdev fraction size index between 0 and 1 c 66, mean fraction size index >= 1 c 67, daily stdev fraction size index >= 1 c 68, not used c 69, not used c c CLOUD-FREE RADIATIVE FORCING: c 70, mean toa aerosol direct radiative forcing c 71, daily stdev toa aerosol direct radiative forcing c 72, mean surface aerosol direct radiative forcing c 73, daily stdev surface aerosol direct radiative forcing c c CATRGORY: OVERCAST PIXELS c 74, total number of days overcast by low-level clouds c (number of overcast pixels in region >= 12) c 75, mean freq pixels overcast by low-level clouds c 76, daily stdev freq pixels overcast by low-level clouds c 77, mean ch1 reflectance (in %) for low-level overcast pixels c 78, daily stdev ch1 reflectance for low-level overcast pixels c 79, mean ch2 reflectance (in %) for low-level overcast pixels c 80, daily stdev ch2 reflectance for low-level overcast pixels c 81, mean ch3 radiance (in mWm-2sr-1cm) for low-level overcast pixels c 82, daily stdev ch3 radiance for low-level overcast pixels c 83, mean ch4 radiance (in mWm-2sr-1cm) for low-level overcast pixels c 84, daily stdev ch4 radiance for low-level overcast pixels c 85, mean ch5 radiance (in mWm-2sr-1cm) for low-level overcast pixels c 86, daily stdev ch5 radiance for low-level overcast pixels Fortran program: read_indoex.f Usage : read_indoex file_name IDL Procedure: gfileopen Usage: gfileopen,'file_name',header,data_array Coakley, J. A., Jr., W. R. Tahnk, A. Jayaraman, P. K. Quinn, C. Devaux, and D. Tanre, 2002: Aerosol optical depths and direct radiative forcing for INDOEX derived from AVHRR: Theory. Journal of Geophysical Research (submitted for publication).