Dear MGET Team,

my name is Jan-Christopher Fischer. I am studying Global Change Ecology at the University Bayreuth in Germany. In my master thesis I am currently working on the coastal turbidity around La Réunion, France. I am using level 2 MODIS Aqua daily 1km resolution Kd_490 data which I downloaded for the full duration from 2002 until 2017 from the Ocean Color Website (https://oceancolor.gsfc.nasa.gov/cgi/browse.pl?sen=am). I would like to use the “Cayula-Cornillon Fronts in ArcGIS Raster” function from your Marine Geospatial Ecology Tool Kit in ArcMap in order to detect and visualize turbidity fronts in the satellite data.

Unfortunately, I have some problems with that and therefore would be very happy about your help:

• First if I open the tool in ArcGIS, the warning/error symbol (red circle with white x) is there right away next to the “Input raster” field. This does not disappear at all. Is there a general wrong setting?
• My downloaded and processed level 2 and level 3 files of Kd_490 are in nc (netCDF) format with floating points as pixel types (32 Bit). The scale factor of the Diffuse attenuation coefficient at 490 nm is 0.000199999994947575. So would the respective mapAlgebraExpression “int(inputRaster * 0.000199999994947575)” be? By typing this in and clicking on “Usage…” the “Grid Map Algebra Usages” interface opens. What do I have to select here? And how to apply whatever I might select? The only given option is “cancel”.
• Is there a way to use the nc files as input raster? I attached an example file to this mail…
• I thought a conversion of the nc files to tif format might solve this problem. In this case the pixel type is signed integer with a pixel depth of 16 bit. The values for this file displayed in ArcMap reach from high: 3514 to low: -32767. Which front detection threshold shall is set for this file? I have (and can not remove) the warning/error symbol here again next to the “Input raster” field. What is the reason for this?

I am sending lots of diffuse questions but I don´t know how to solve this. Can you help me to detect the fronts in the files downloaded from the Ocean Color Website?

Your help is highly appreciated. Thanks in advance! Looking forward to hear from you.

Kindest regards, Jan-Christopher

___

Mit freundlichen Grüßen / Kindest regards,

Jan-Christopher Fischer

Student of Global Change Ecology (M.Sc.)

University of Bayreuth

Ecopotential Project