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The value is nan for chlor_a from MODIS
Posted: Wed Jan 27, 2021 11:46 pm America/New_York
by megasaputra8
Dear all,
I have run l2gen for MODIS data. I want to extract chlor_a. But the result value is nan. Why ?
While for other date MODIS data, the data is not nan.
The MODIS data is in :
https://1drv.ms/u/s!AjXAWS5maHffhyu6DmUAGwxoJaJq?e=eUzkBfI put the result of chlor in that link.
Thank you.
The value is nan for chlor_a from MODIS
Posted: Thu Jan 28, 2021 11:27 am America/New_York
by OB SeaDAS - dshea
Looks like this is a night time file. All pixels PRODFAIL and HISOLZEN. L2gen flagged it as :day_night_flag = "Night"
can't get chl at night.
don
The value is nan for chlor_a from MODIS
Posted: Thu Jan 28, 2021 11:49 am America/New_York
by gnwiii
l2gen output includes a summary of flags:
[...]
Flag #13: HISOLZEN 5524320 86.4407
[...]
Flag #31: PRODFAIL 6390880 100.0000
The HISOLZEN flag indicates the sun is close to the horizon, so
you should not expect useful results.
You can also see the percentages in the NetCDF metadata:
$ ncdump -h chla
[...]
group: flag_percentages {
// group attributes:
:ATMFAIL = 0.f ;
:LAND = 26.62129f ;
:PRODWARN = 0.f ;
:HIGLINT = 0.f ;
:HILT = 0.f ;
:HISATZEN = 5.927666f ;
:COASTZ = 4.799761f ;
:SPARE = 0.f ;
:STRAYLIGHT = 0.f ;
:CLDICE = 0.f ;
:COCCOLITH = 0.f ;
:TURBIDW = 0.f ;
:HISOLZEN = 86.44067f ;
:LOWLW = 0.f ;
:CHLFAIL = 0.f ;
:NAVWARN = 13.34746f ;
:ABSAER = 0.f ;
:MAXAERITER = 0.f ;
:MODGLINT = 0.6738195f ;
:CHLWARN = 0.f ;
:ATMWARN = 0.f ;
:SEAICE = 0.f ;
:NAVFAIL = 13.55932f ;
:FILTER = 0.f ;
:BOWTIEDEL = 0.f ;
:HIPOL = 0.f ;
:PRODFAIL = 100.f ;
} // group flag_percentages
The value is nan for chlor_a from MODIS
Posted: Sun Jan 31, 2021 6:33 pm America/New_York
by megasaputra8
oh I see.
I did't see the time of acquisition.
Thank you for your information