I am new to using netcdf files. I have downloaded netcdf files related to SST (sea surface temperature) from the Copernicus interface (https://cds.climate.copernicus.eu/cdsapp#!/dataset/satellite-sea-surface-temperature?tab=overview)
Basically, the data is provided in a zipped folder that contains one .nc file for each day that I am interested in (I have asked for a range of dates).
The data is in .5 degree resolution, from what I can see this means 7200,3600 (lon,lat). Given that I'm not interested in worldwide data the first thing I need to do is to subset the data for each day for a specific region of the world. I have the bounding box coordinates for the region (6.6173,42.8348, 11.1534,44.931) lon/lat, lon/lat).
How do I go about doing this for one file?
So far I have gotten to:
library(netcdf4)
#(ncin is the file name for one netcdf file for one day- using one day as an example, there's a long process of setting paths etc before you get to this stage)
# extracting longitude
lon <- ncvar_get(ncin,"lon")
# finding out how many points of longitude there are
nlon <- dim(lon)
# extracting latitude
lat <- ncvar_get(ncin,"lat")
# finding out how many points of latitude there are
nlat <- dim(lat)
# time is just 1 figure because it's just one day
time <- ncvar_get(ncin,"time")
# temparray dim are 7200 (longitude) and 3600 (latitude)
temp_array <- ncvar_get(ncin,"analysed_sst")
# closing the file as it saves a lot of resources
nc_close(ncin)
I have tried which(lon > 6.6173 & lon < 11.1534) which gives me the indices of all the lon for example that fall within the bounding box but then I'm struggling as I'm getting more latitude observations than longitude and then I need to related this to the SST which I don't really know how to do.
In summary, is there an easy way for me to provide coordinates for a bounding box that I'm interested in and extract all data related to this from the netcdf file? Also, once I have established how to do this do I need to loop through each day extracting and thus each file within the zipped folder or can I combine all the files (perhaps they're too big?)
Thank you.