MODIS satellite data
See the NASA Ocean Color website for more information on the MODIS Aqua and Terra instruments. So far, only a small subset of the available data products can be accessed using dreamcoat, but this will be improved in future versions.
Set up credentials
You need to create a NASA Earthdata account in order to download MODIS data.
Create a .netrc file and generate an AppKey as described here (check the Download Methods tab on that page). Put the appkey in ~/.dreamcoat/nasa_appkey.dat
.
The download functions use wget
, so they won't work natively on Windows.
Download dataset
Dreamcoat downloads the daily L3-mapped observations from MODIS Aqua and Terra and combines them into a single dataset for each day, taking the mean of the two instruments. To get a day or some consecutive days of data, use get_days()
:
import dreamcoat as dc
modis = dc.modis.get_days(
date_min=None,
date_max=None,
latitude_min=-90,
latitude_max=90,
longitude_min=-180,
longitude_max=180,
appkey=None,
delete_nc=False,
filepath=".",
resolution="9km",
)
- Dates should be given in
%Y-%m-%d
format. If left blank, yesterday is used for both. - Resolution can be
"4km"
or"9km"
. - Files are downloaded as netCDFs into the
filepath
.
Only particulate inorganic carbon (PIC) data are downloaded. These data are in mol/m3.
Open daily datasets
To open a sequence of already-downloaded daily datasets and combine them into a single xarray Dataset, use open_days()
:
Note that this converts the PIC data into units of mmol/m3.
Plotting
MODIS PIC data opened with dc.modis.open_days()
can be mapped with dc.plot.surface_map()
.