Earthdata Forum

I have processed a L1A MODIS-Aqua file through to L2 using the default atmospheric correction options, and I came across a region where the aerosol radiances (La) return NaN, but values of water leaving radiance (Lw) are non-nan. I am struggling to understand how a value of Lw was calculated if the aerosol retrieval of La returned NaN.

For most of these pixels, La is NaN for every wavelength, but some have valid data in the red (i.e. 667, 678). These pixels are not lighting up any of the flags, but there are likely some absorbing aerosols in the scene. I would be very appreciative if someone could help me to understand what is going on here.

I have included info from an example pixel below.

Cheers,
Brian Collister



SeaDAS Version 8.1.0
L1A File: A2014211173500.L1A_LAC

Pixel Info:

Product: A2014211173500.L2_LAC_IOP_RRS

Image-X: 152 pixel
Image-Y: 1448 pixel
Longitude: 73°44'53" W degree
Latitude: 35°23'04" N degree

BandName Wavelength Unit Bandwidth Unit Value Unit Solar Flux Unit
Es_412: 412.0 nm 0.0 nm 1322.08984 W m^-2 um^-1
Es_443: 443.0 nm 0.0 nm 1486.02856 W m^-2 um^-1
Es_469: 469.0 nm 0.0 nm 1665.58020 W m^-2 um^-1
Es_488: 488.0 nm 0.0 nm 1597.79883 W m^-2 um^-1
Es_531: 531.0 nm 0.0 nm 1537.14709 W m^-2 um^-1
Es_547: 547.0 nm 0.0 nm 1546.28882 W m^-2 um^-1
Es_555: 555.0 nm 0.0 nm 1523.77930 W m^-2 um^-1
Es_645: 645.0 nm 0.0 nm 1349.96069 W m^-2 um^-1
Es_667: 667.0 nm 0.0 nm 1317.93774 W m^-2 um^-1
Es_678: 678.0 nm 0.0 nm 1288.35950 W m^-2 um^-1
La_412: 412.0 nm 0.0 nm NaN W m^-2 um^-1 sr^-1
La_443: 443.0 nm 0.0 nm NaN W m^-2 um^-1 sr^-1
La_469: 469.0 nm 0.0 nm NaN W m^-2 um^-1 sr^-1
La_488: 488.0 nm 0.0 nm NaN W m^-2 um^-1 sr^-1
La_531: 531.0 nm 0.0 nm NaN W m^-2 um^-1 sr^-1
La_547: 547.0 nm 0.0 nm NaN W m^-2 um^-1 sr^-1
La_555: 555.0 nm 0.0 nm NaN W m^-2 um^-1 sr^-1
La_645: 645.0 nm 0.0 nm 9.78091 W m^-2 um^-1 sr^-1
La_667: 667.0 nm 0.0 nm 9.14381 W m^-2 um^-1 sr^-1
La_678: 678.0 nm 0.0 nm 8.83707 W m^-2 um^-1 sr^-1
Lr_412: 412.0 nm 0.0 nm 62.72575 W m^-2 um^-1 sr^-1
Lr_443: 443.0 nm 0.0 nm 52.87354 W m^-2 um^-1 sr^-1
Lr_469: 469.0 nm 0.0 nm 47.29712 W m^-2 um^-1 sr^-1
Lr_488: 488.0 nm 0.0 nm 37.41549 W m^-2 um^-1 sr^-1
Lr_531: 531.0 nm 0.0 nm 25.28712 W m^-2 um^-1 sr^-1
Lr_547: 547.0 nm 0.0 nm 22.31934 W m^-2 um^-1 sr^-1
Lr_555: 555.0 nm 0.0 nm 20.94044 W m^-2 um^-1 sr^-1
Lr_645: 645.0 nm 0.0 nm 9.61009 W m^-2 um^-1 sr^-1
Lr_667: 667.0 nm 0.0 nm 8.08776 W m^-2 um^-1 sr^-1
Lr_678: 678.0 nm 0.0 nm 7.33139 W m^-2 um^-1 sr^-1
Lt_412: 412.0 nm 0.0 nm 87.77496 W m^-2 um^-1 sr^-1
Lt_443: 443.0 nm 0.0 nm 78.54639 W m^-2 um^-1 sr^-1
Lt_469: 469.0 nm 0.0 nm 73.01749 W m^-2 um^-1 sr^-1
Lt_488: 488.0 nm 0.0 nm 59.62201 W m^-2 um^-1 sr^-1
Lt_531: 531.0 nm 0.0 nm 39.50986 W m^-2 um^-1 sr^-1
Lt_547: 547.0 nm 0.0 nm 35.20090 W m^-2 um^-1 sr^-1
Lt_555: 555.0 nm 0.0 nm 32.97606 W m^-2 um^-1 sr^-1
Lt_645: 645.0 nm 0.0 nm 18.24416 W m^-2 um^-1 sr^-1
Lt_667: 667.0 nm 0.0 nm 16.66957 W m^-2 um^-1 sr^-1
Lt_678: 678.0 nm 0.0 nm 15.75823 W m^-2 um^-1 sr^-1
Lt_748: 748.0 nm 0.0 nm 11.04335 W m^-2 um^-1 sr^-1
Lt_859: 859.0 nm 0.0 nm 6.50305 W m^-2 um^-1 sr^-1
Lt_869: 869.0 nm 0.0 nm 6.24617 W m^-2 um^-1 sr^-1
Lt_1240: 1240.0 nm 0.0 nm 1.80549 W m^-2 um^-1 sr^-1
Lt_1640: 1640.0 nm 0.0 nm 0.77440 W m^-2 um^-1 sr^-1
Lt_2130: 2130.0 nm 0.0 nm 0.24659 W m^-2 um^-1 sr^-1
Lw_412: 412.0 nm 0.0 nm 15.06610 W m^-2 um^-1 sr^-1
Lw_443: 443.0 nm 0.0 nm 14.04992 W m^-2 um^-1 sr^-1
Lw_469: 469.0 nm 0.0 nm 13.04395 W m^-2 um^-1 sr^-1
Lw_488: 488.0 nm 0.0 nm 9.78760 W m^-2 um^-1 sr^-1
Lw_531: 531.0 nm 0.0 nm 3.23027 W m^-2 um^-1 sr^-1
Lw_547: 547.0 nm 0.0 nm 2.24980 W m^-2 um^-1 sr^-1
Lw_555: 555.0 nm 0.0 nm 1.69390 W m^-2 um^-1 sr^-1
Lw_645: 645.0 nm 0.0 nm -0.02863 W m^-2 um^-1 sr^-1
Lw_667: 667.0 nm 0.0 nm 0.09250 W m^-2 um^-1 sr^-1
Lw_678: 678.0 nm 0.0 nm 0.05935 W m^-2 um^-1 sr^-1
Rrs_412: 412.0 nm 0.0 nm 0.01184 sr^-1
Rrs_443: 443.0 nm 0.0 nm 0.00969 sr^-1
Rrs_469: 469.0 nm 0.0 nm 0.00819 sr^-1
Rrs_488: 488.0 nm 0.0 nm 0.00636 sr^-1
Rrs_531: 531.0 nm 0.0 nm 0.00221 sr^-1
Rrs_547: 547.0 nm 0.0 nm 0.00154 sr^-1
Rrs_555: 555.0 nm 0.0 nm 0.00118 sr^-1
Rrs_645: 645.0 nm 0.0 nm -0.00002 sr^-1
Rrs_667: 667.0 nm 0.0 nm 0.00007 sr^-1
Rrs_678: 678.0 nm 0.0 nm 0.00005 sr^-1
TLg_412: 412.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
TLg_443: 443.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
TLg_469: 469.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
TLg_488: 488.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
TLg_531: 531.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
TLg_547: 547.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
TLg_555: 555.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
TLg_645: 645.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
TLg_667: 667.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
TLg_678: 678.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
a_412_giop: 0.01870 m^-1
a_443_giop: 0.01780 m^-1
a_469_giop: 0.01890 m^-1
a_488_giop: 0.02050 m^-1
a_531_giop: 0.04490 m^-1
a_547_giop: 0.05200 m^-1
a_555_giop: 0.05890 m^-1
a_645_giop: 0.31930 m^-1
a_667_giop: 0.42640 m^-1
a_678_giop: 0.45380 m^-1
adg_443_giop: 0.00570 m^-1
adg_s_giop: 0.01800 m^-1 nm^-1
adg_unc_443_giop: 0.00030 m^-1
aph_443_giop: 0.00570 m^-1
aph_unc_443_giop: 0.00070 m^-1
bb_412_giop: 0.00462 m^-1
bb_443_giop: 0.00360 m^-1
bb_469_giop: 0.00298 m^-1
bb_488_giop: 0.00261 m^-1
bb_531_giop: 0.00200 m^-1
bb_547_giop: 0.00182 m^-1
bb_555_giop: 0.00175 m^-1
bb_645_giop: 0.00112 m^-1
bb_667_giop: 0.00102 m^-1
bb_678_giop: 0.00097 m^-1
bbp_443_giop: 0.00142 m^-1
bbp_s_giop: 1.99037 m^-1 nm^-1
bbp_unc_443_giop: 0.00011 m^-1
nLw_412: 412.0 nm 0.0 nm 20.27192 W m^-2 um^-1 sr^-1
nLw_443: 443.0 nm 0.0 nm 18.29313 W m^-2 um^-1 sr^-1
nLw_469: 469.0 nm 0.0 nm 16.66367 W m^-2 um^-1 sr^-1
nLw_488: 488.0 nm 0.0 nm 12.34142 W m^-2 um^-1 sr^-1
nLw_531: 531.0 nm 0.0 nm 4.10747 W m^-2 um^-1 sr^-1
nLw_547: 547.0 nm 0.0 nm 2.87965 W m^-2 um^-1 sr^-1
nLw_555: 555.0 nm 0.0 nm 2.16820 W m^-2 um^-1 sr^-1
nLw_645: 645.0 nm 0.0 nm -0.03500 W m^-2 um^-1 sr^-1
nLw_667: 667.0 nm 0.0 nm 0.11417 W m^-2 um^-1 sr^-1
nLw_678: 678.0 nm 0.0 nm 0.07337 W m^-2 um^-1 sr^-1
rrsdiff_giop: 0.02591
tLf_412: 412.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
tLf_443: 443.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
tLf_469: 469.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
tLf_488: 488.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
tLf_531: 531.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
tLf_547: 547.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
tLf_555: 555.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
tLf_645: 645.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
tLf_667: 667.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
tLf_678: 678.0 nm 0.0 nm 0.00000 W m^-2 um^-1 sr^-1
l2_flags: 0
longitude: -73.748146 degrees_east
latitude: 35.38446 degrees_north


l2_flags.ATMFAIL: false
l2_flags.LAND: false
l2_flags.PRODWARN: false
l2_flags.HIGLINT: false
l2_flags.HILT: false
l2_flags.HISATZEN: false
l2_flags.COASTZ: false
l2_flags.SPARE8: false
l2_flags.STRAYLIGHT: false
l2_flags.CLDICE: false
l2_flags.COCCOLITH: false
l2_flags.TURBIDW: false
l2_flags.HISOLZEN: false
l2_flags.SPARE14: false
l2_flags.LOWLW: false
l2_flags.CHLFAIL: false
l2_flags.NAVWARN: false
l2_flags.ABSAER: false
l2_flags.SPARE19: false
l2_flags.MAXAERITER: false
l2_flags.MODGLINT: false
l2_flags.CHLWARN: false
l2_flags.ATMWARN: false
l2_flags.SPARE24: false
l2_flags.SEAICE: false
l2_flags.NAVFAIL: false
l2_flags.FILTER: false
l2_flags.SPARE28: false
l2_flags.BOWTIEDEL: false
l2_flags.HIPOL: false
l2_flags.PRODFAIL: false
l2_flags.SPARE32: false

UPDATE:

I identified the cause of the behavior that I described in my original question, and I am posting the solution here in case anyone has this same question.

For the purpose of plotting within the SeaDAS GUI, values of La >10 W m^-2 um^-1 sr^-1 were converted to NaN by the "valid pixel expression" (under the "properties" option when you right-click on a variable in the file manager). For the purpose of atmospheric correction, pixels that violated the "valid pixel expression" remained unflagged, and the original value of La was used to calculate water leaving radiance (Lw).

Brian