modis_L1B output depends on MODIS granule date ?

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jstum
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modis_L1B output depends on MODIS granule date ?

by jstum » Thu Oct 20, 2022 6:31 am America/New_York

Good morning,

I used modis_L1B on two MODIS granules, respectively from 2020 and 2022, but the output is not the same :
modis_L1B A2020168174500.L1A_LAC A2020168174500.GEO outputs only one file : AQUA_MODIS.20200616T174500.L1B.hdf

whereas modis_L1B A2022285162000.L1A_LAC A2022285162000.GEO outputs 3 files :
AQUA_MODIS.20221012T162000.L1B.hdf
AQUA_MODIS_HKM.20221012T162000.L1B.hdf
AQUA_MODIS_QKM.20221012T162000.L1B.hdf

I'm using SeaDAS 8.2.0, tag T2022.15

Info returned by modis_GEO is :
MODIS Aqua L1B version 6.2.1_obpg, built Jun 27 2022 12:15:36
scan: 0 out of 203 Thu Oct 20 10:08:33 2022
...

As I'm using l2gen with resolution=250, the QKM file is needed in input :
-W- /home/dshea/focs/oel_hdf4/libl1/l1_hmodis_hdf.c:239: Cannot open file: ./AQUA_MODIS_QKM.20200616T174500.L1B.hdf
File not found: ./AQUA_MODIS_QKM.20200616T174500.L1B.hdf
Processing at 250m resolution requires a QKM file to be present in the same directory as the 1KM L1B file.

This result seems weird, could the modis_L1B script for SeaDAS 8.2.0, tag T2022.15 have such behaviour ?

Thank you for your help,
Jacques

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jstum
Posts: 74
Joined: Mon Jul 04, 2005 4:54 am America/New_York
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Re: modis_L1B output depends on MODIS granule date ?

by jstum » Thu Oct 20, 2022 7:58 am America/New_York

I just tried with one 2021 granule and one 2019 granule, and modis_L1B outputs 3 files

OB.DAAC - SeanBailey
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Re: modis_L1B output depends on MODIS granule date ?

by OB.DAAC - SeanBailey » Thu Oct 20, 2022 9:13 am America/New_York

Jacques,

The A2020168174500.L1A_LAC scene is a nighttime scene:

https://oceancolor.gsfc.nasa.gov/cgi/browse.pl?file=AQUA_MODIS.20200616T174501.L2.SST.nc_SST_BRS

By default, the modis_L1B script disables the HKM and QKM output for nighttime granules as the 250 and 500m bands are only reflective solar bands, so no valid data at night. You can reenable it, but it requires editing the PCF template, which is found under:

$OCDATAROOT/modis/pcf/L1B_template.pcf

Change the line:

Code: Select all

800615|Write_Night_Mode_HiRes_Data|0
to be:

Code: Select all

800615|Write_Night_Mode_HiRes_Data|1
BTW, this is not new behavior, it has been that way for quite a long time...

Sean

jstum
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Joined: Mon Jul 04, 2005 4:54 am America/New_York
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Re: modis_L1B output depends on MODIS granule date ?

by jstum » Thu Oct 20, 2022 11:42 am America/New_York

Sorry for my error, Sean, I selected A2020168170500.L1A_LAC from the Browser, but I wget 1745, bad paste
Thank you
Jacques

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