Earthdata Forum

Dear all,
I have a station that it has latitude and longitude (-64N , -56W). I want to extract ‘cholorophyll a concentration’ for 1000km around of this area from January 2018 to end of February 2018.
Actually I do not know what is the best way for doing it but I found below link that I think we can extract the data that I want for Modis:

https://oceancolor.gsfc.nasa.gov/cgi/browse.pl?per=MO&day=17532&sub=level3&prm=CHL&set=10&ndx=0&mon=17683&sen=am&rad=0&frc=0&dnm=D@M

As it does not have 1000 km, so I chose 1200 km around of my station and also I chose only January and then as you can see in picture, I chose other options BUT when I pressed ‘search’, it did not show me anything!!!!
Would you please let me know why? Do we have any data at that time around of my station or not? Or maybe I did something wrong?

Cheers,
Marjan

Hi Marjan,

Because of the MODIS swath width and the division of the data into
5-minute chunks,  there is no way that a single MODIS scene can contain
the entire region within 1200 kilometers of your station.  To get any
results, you need to either reduce the percentage of your area of
interest that each swath must contain like this, for example,
https://oceancolor.gsfc.nasa.gov/cgi/browse.pl?sub=level1or2list&per=MO&day=17532&sen=am&hlt=1&rad=1200&frc=0.25&s=-64.2&w=-56.6&dnm=D
or reduce the radius of your search like this, for example,
https://oceancolor.gsfc.nasa.gov/cgi/browse.pl?sub=level1or2list&per=MO&day=17532&sen=am&hlt=1&rad=800&frc=1&s=-64.2&w=-56.6&dnm=D
or some combination of both.  The less restrictive your search, the
more scenes you will find, but your edge cases will also increase.

Note also that the radii indicated on the browser page are just
rough guidelines since the granularity of geographical searches
in our database is based on quadsphere level-6 bins.  See
https://oceancolor.gsfc.nasa.gov/browse_help/top_level/quadsphere/
and
https://oceancolor.gsfc.nasa.gov/browse_help/development/  (scroll down).

Unfortunately, your area of interest happens to lie in a very
cloudy (and often icy) part of our planet, so finding good coverage
will be harder for you.  Welcome to the joys of ocean-color
remote sensing.  :-)

Regards,
Norman