How can I read variables （lat lon and chl-a）in nc files with groups？

Hi，

I download Aqua-MODIS nc file from Level-3 Binned/Aqua-MODIS/2019/064 (nasa.gov)，the file is too large to upload.

I already used the command "chla_a=ncread("H:\chla\A2019352.L3b_DAY_CHL.nc",'/level-3_binned_data/chlor_a');" to read data, however, it is wrong-"Incorrect use of netcdf.getVar (line 137)33 is an unrecognized netCDF data type."

I want to know how can I read the chl-a data and it lat and lon?

Below is the information:

ncdisp("H:\chla\A2019352.L3b_DAY_CHL.nc")

Source:
           H:\chla\A2019352.L3b_DAY_CHL.nc
Format:
           netcdf4
Global Attributes:
           product_name                     = 'A2019352.L3b_DAY_CHL.nc'
           title                            = 'MODIS Level-3 Binned Data'
           instrument                       = 'MODIS'
           platform                         = 'Aqua'
           temporal_range                   = 'day'
           start_orbit_number               = 93736
           end_orbit_number                 = 93751
           date_created                     = '2020-04-01T00:40:24.000Z'
           processing_version               = '2018.1'
           history                          = 'l2bin par=A2019352.L3b_DAY_CHL.param'
           time_coverage_start              = '2019-12-18T00:20:01.000Z'
           time_coverage_end                = '2019-12-19T02:34:59.000Z'
           northernmost_latitude            = 90
           southernmost_latitude            = -90
           easternmost_longitude            = 180
           westernmost_longitude            = -180
           geospatial_lat_max               = 90
           geospatial_lat_min               = -90
           geospatial_lon_max               = 180
           geospatial_lon_min               = -180
           geospatial_lat_units             = 'degrees_north'
           geospatial_lon_units             = 'degrees_east'
           geospatial_lon_resolution        = 0.041667
           geospatial_lat_resolution        = 0.041667
           spatialResolution                = '4.6 km'
           data_bins                        = 1468593
           percent_data_bins                = 6.1805
           units                            = 'chlor_a:mg m^-3,chl_ocx:mg m^-3'
           binning_scheme                   = 'Integerized Sinusoidal Grid'
           project                          = 'Ocean Biology Processing Group (NASA/GSFC/OBPG)'
           institution                      = 'NASA Goddard Space Flight Center, Ocean Ecology Laboratory, Ocean Biology Processing Group'
           standard_name_vocabulary         = 'CF Standard Name Table v36'
           Conventions                      = 'CF-1.6 ACDD-1.3'
           naming_authority                 = 'gov.nasa.gsfc.sci.oceandata'
           id                               = 'A2019352.L3b_DAY_CHL.nc/L3/A2019352.L3b_DAY_CHL.nc'
           license                          = 'https://science.nasa.gov/earth-science/earth-science-data/data-information-policy/'
           creator_name                     = 'NASA/GSFC/OBPG'
           publisher_name                   = 'NASA/GSFC/OBPG'
           creator_email                    = '[e-mail]'
           publisher_email                  = '[e-mail]'
           creator_url                      = 'https://oceandata.sci.gsfc.nasa.gov'
           publisher_url                    = 'https://oceandata.sci.gsfc.nasa.gov'
           processing_level                 = 'L3 Binned'
           cdm_data_type                    = 'point'
           identifier_product_doi_authority = 'https://dx.doi.org'
           identifier_product_doi           = '10.5067/AQUA/MODIS/L3B/CHL/2018'
           keywords_vocabulary              = 'NASA Global Change Master Directory (GCMD) Science Keywords'
           keywords                         = 'Earth Science > Oceans > Ocean Chemistry > Pigments > Chlorophyll; Earth Science > Oceans > Ocean Chemistry > Chlorophyllr'
Groups:
    /level-3_binned_data/
        Dimensions:
                   binListDim  = 1468593 (UNLIMITED)
                   binDataDim  = 1468593 (UNLIMITED)
                   binIndexDim = 4320  (UNLIMITED)
        Variables:
            BinList 
                   Size:       1468593x1
                   Dimensions: binListDim
                   Datatype:   UNSUPPORTED DATATYPE
            chlor_a 
                   Size:       1468593x1
                   Dimensions: binDataDim
                   Datatype:   UNSUPPORTED DATATYPE
            chl_ocx 
                   Size:       1468593x1
                   Dimensions: binDataDim
                   Datatype:   UNSUPPORTED DATATYPE
            BinIndex
                   Size:       4320x1
                   Dimensions: binIndexDim
                   Datatype:   UNSUPPORTED DATATYPE
    
    /processing_control/
        Attributes:
                   software_name    = 'l2bin'
                   software_version = '6.2.0'
                   source           = 'A2019352000000.L2_LAC_OC.nc,A2019352000500.L2_LAC_OC.nc,A2019352001000.L2_LAC_OC.nc,A2019352001500.L2_LAC_OC.nc,A2019352002000.L2_LAC_OC.nc,A2019352002500.L2_LAC_OC.nc,A2019352003000.L2_LAC_OC.nc,A2019352012000.L2_LAC_OC.nc,A2019352012500.L2_LAC_OC.nc,A2019352013000.L2_LAC_OC.nc,A2019352013500.L2_LAC_OC.nc,A2019352014000.L2_LAC_OC.nc,A2019352014500.L2_LAC_OC.nc,A2019352015000.L2_LAC_OC.nc,A2019352015500.L2_LAC_OC.nc,A2019352020000.L2_LAC_OC.nc,A2019352020500.L2_LAC_OC.nc,A2019352021000.L2_LAC_OC.nc,A2019352025500.L2_LAC_OC.nc,A2019352030000.L2_LAC_OC.nc,A2019352030500.L2_LAC_OC.nc,A2019352031000.L2_LAC_OC.nc,A2019352031500.L2_LAC_OC.nc,A2019352032000.L2_LAC_OC.nc,A2019352032500.L2_LAC_OC.nc,A2019352033000.L2_LAC_OC.nc,A2019352033500.L2_LAC_OC.nc,A2019352034000.L2_LAC_OC.nc,A2019352034500.L2_LAC_OC.nc,A2019352035000.L2_LAC_OC.nc,A2019352043500.L2_LAC_OC.nc,A2019352044000.L2_LAC_OC.nc,A2019352044500.L2_LAC_OC.nc,A2019352045000.L2_LAC_OC.nc,A2019352045500.L2_LAC_OC.nc,A2019352050000.L2_LAC_OC.nc,A2019352050500.L2_LAC_OC.nc,A2019352051000.L2_LAC_OC.nc,A2019352051500.L2_LAC_OC.nc,A2019352052000.L2_LAC_OC.nc,A2019352052500.L2_LAC_OC.nc,A2019352053000.L2_LAC_OC.nc,A2019352061500.L2_LAC_OC.nc,A2019352062000.L2_LAC_OC.nc,A2019352062500.L2_LAC_OC.nc,A2019352063000.L2_LAC_OC.nc,A2019352063500.L2_LAC_OC.nc,A2019352064000.L2_LAC_OC.nc,A2019352064500.L2_LAC_OC.nc,A2019352065000.L2_LAC_OC.nc,A2019352065500.L2_LAC_OC.nc,A2019352070000.L2_LAC_OC.nc,A2019352070500.L2_LAC_OC.nc,A2019352075500.L2_LAC_OC.nc,A2019352080000.L2_LAC_OC.nc,A2019352080500.L2_LAC_OC.nc,A2019352081000.L2_LAC_OC.nc,A2019352081500.L2_LAC_OC.nc,A2019352082000.L2_LAC_OC.nc,A2019352082500.L2_LAC_OC.nc,A2019352083000.L2_LAC_OC.nc,A2019352083500.L2_LAC_OC.nc,A2019352084000.L2_LAC_OC.nc,A2019352084500.L2_LAC_OC.nc,A2019352093000.L2_LAC_OC.nc,A2019352093500.L2_LAC_OC.nc,A2019352094000.L2_LAC_OC.nc,A2019352094500.L2_LAC_OC.nc,A2019352095000.L2_LAC_OC.nc,A2019352095500.L2_LAC_OC.nc,A2019352100000.L2_LAC_OC.nc,A2019352100500.L2_LAC_OC.nc,A2019352101000.L2_LAC_OC.nc,A2019352101500.L2_LAC_OC.nc,A2019352102000.L2_LAC_OC.nc,A2019352102500.L2_LAC_OC.nc,A2019352111000.L2_LAC_OC.nc,A2019352111500.L2_LAC_OC.nc,A2019352112000.L2_LAC_OC.nc,A2019352112500.L2_LAC_OC.nc,A2019352113000.L2_LAC_OC.nc,A2019352113500.L2_LAC_OC.nc,A2019352114000.L2_LAC_OC.nc,A2019352114500.L2_LAC_OC.nc,A2019352115000.L2_LAC_OC.nc,A2019352115500.L2_LAC_OC.nc,A2019352120000.L2_LAC_OC.nc,A2019352120500.L2_LAC_OC.nc,A2019352125000.L2_LAC_OC.nc,A2019352125500.L2_LAC_OC.nc,A2019352130000.L2_LAC_OC.nc,A2019352130500.L2_LAC_OC.nc,A2019352131000.L2_LAC_OC.nc,A2019352131500.L2_LAC_OC.nc,A2019352132000.L2_LAC_OC.nc,A2019352132500.L2_LAC_OC.nc,A2019352133000.L2_LAC_OC.nc,A2019352133500.L2_LAC_OC.nc,A2019352134000.L2_LAC_OC.nc,A2019352143000.L2_LAC_OC.nc,A2019352143500.L2_LAC_OC.nc,A2019352144000.L2_LAC_OC.nc,A2019352144500.L2_LAC_OC.nc,A2019352145000.L2_LAC_OC.nc,A2019352145500.L2_LAC_OC.nc,A2019352150000.L2_LAC_OC.nc,A2019352150500.L2_LAC_OC.nc,A2019352151000.L2_LAC_OC.nc,A2019352151500.L2_LAC_OC.nc,A2019352152000.L2_LAC_OC.nc,A2019352161000.L2_LAC_OC.nc,A2019352161500.L2_LAC_OC.nc,A2019352162000.L2_LAC_OC.nc,A2019352162500.L2_LAC_OC.nc,A2019352163000.L2_LAC_OC.nc,A2019352163500.L2_LAC_OC.nc,A2019352164000.L2_LAC_OC.nc,A2019352164500.L2_LAC_OC.nc,A2019352165000.L2_LAC_OC.nc,A2019352165500.L2_LAC_OC.nc,A2019352170000.L2_LAC_OC.nc,A2019352174500.L2_LAC_OC.nc,A2019352175000.L2_LAC_OC.nc,A2019352175500.L2_LAC_OC.nc,A2019352180000.L2_LAC_OC.nc,A2019352180500.L2_LAC_OC.nc,A2019352181000.L2_LAC_OC.nc,A2019352181500.L2_LAC_OC.nc,A2019352182000.L2_LAC_OC.nc,A2019352182500.L2_LAC_OC.nc,A2019352183000.L2_LAC_OC.nc,A2019352183500.L2_LAC_OC.nc,A2019352184000.L2_LAC_OC.nc,A2019352192500.L2_LAC_OC.nc,A2019352193000.L2_LAC_OC.nc,A2019352193500.L2_LAC_OC.nc,A2019352194000.L2_LAC_OC.nc,A2019352194500.L2_LAC_OC.nc,A2019352195000.L2_LAC_OC.nc,A2019352195500.L2_LAC_OC.nc,A2019352200000.L2_LAC_OC.nc,A2019352200500.L2_LAC_OC.nc,A2019352201000.L2_LAC_OC.nc,A2019352201500.L2_LAC_OC.nc,A2019352202000.L2_LAC_OC.nc,A2019352210500.L2_LAC_OC.nc,A2019352211000.L2_LAC_OC.nc,A2019352211500.L2_LAC_OC.nc,A2019352212000.L2_LAC_OC.nc,A2019352212500.L2_LAC_OC.nc,A2019352213000.L2_LAC_OC.nc,A2019352213500.L2_LAC_OC.nc,A2019352214000.L2_LAC_OC.nc,A2019352214500.L2_LAC_OC.nc,A2019352215000.L2_LAC_OC.nc,A2019352215500.L2_LAC_OC.nc,A2019352224500.L2_LAC_OC.nc,A2019352225000.L2_LAC_OC.nc,A2019352225500.L2_LAC_OC.nc,A2019352230000.L2_LAC_OC.nc,A2019352230500.L2_LAC_OC.nc,A2019352231000.L2_LAC_OC.nc,A2019352231500.L2_LAC_OC.nc,A2019352232000.L2_LAC_OC.nc,A2019352232500.L2_LAC_OC.nc,A2019352233000.L2_LAC_OC.nc,A2019352233500.L2_LAC_OC.nc,A2019353002000.L2_LAC_OC.nc,A2019353002500.L2_LAC_OC.nc,A2019353003000.L2_LAC_OC.nc,A2019353003500.L2_LAC_OC.nc,A2019353004000.L2_LAC_OC.nc,A2019353004500.L2_LAC_OC.nc,A2019353005000.L2_LAC_OC.nc,A2019353005500.L2_LAC_OC.nc,A2019353010000.L2_LAC_OC.nc,A2019353010500.L2_LAC_OC.nc,A2019353011000.L2_LAC_OC.nc,A2019353011500.L2_LAC_OC.nc,A2019353020000.L2_LAC_OC.nc,A2019353020500.L2_LAC_OC.nc,A2019353021000.L2_LAC_OC.nc,A2019353021500.L2_LAC_OC.nc,A2019353022000.L2_LAC_OC.nc,A2019353022500.L2_LAC_OC.nc,A2019353023000.L2_LAC_OC.nc,A2019353023500.L2_LAC_OC.nc,A2019353024000.L2_LAC_OC.nc,A2019353024500.L2_LAC_OC.nc,A2019353025000.L2_LAC_OC.nc,A2019353025500.L2_LAC_OC.nc'
                   l2_flag_names    = 'ATMFAIL,LAND,HILT,HISATZEN,STRAYLIGHT,CLDICE,COCCOLITH,LOWLW,CHLWARN,CHLFAIL,NAVWARN,MAXAERITER,ATMWARN,HISOLZEN,NAVFAIL,FILTER,HIGLINT'
        Groups:
            /processing_control/input_parameters/
                Attributes:
                           infile           = '/data7/sdpsoper/vdc/vpu20/workbuf/l2inlist.dat'
                           ofile            = 'A2019352.L3b_DAY_CHL.nc'
                           fileuse          = 'A2019352.L3b_DAY_CHL.contrib'
                           sday             = '2019352'
                           eday             = '2019352'
                           latnorth         = '90.000000'
                           latsouth         = '-90.000000'
                           loneast          = '0.000000'
                           lonwest          = '0.000000'
                           resolve          = '4'
                           rowgroup         = '270'
                           flaguse          = 'ATMFAIL,LAND,HILT,HISATZEN,STRAYLIGHT,CLDICE,COCCOLITH,LOWLW,CHLWARN,CHLFAIL,NAVWARN,MAXAERITER,ATMWARN,HISOLZEN,NAVFAIL,FILTER,HIGLINT'
                           l3bprod          = 'chlor_a,chl_ocx'
                           prodtype         = 'O'
                           pversion         = '2018.1'
                           suite            = 'CHL'
                           night            = '0'
                           verbose          = '0'
                           minobs           = '0'
                           deflate          = '4'
                           qual_prod        = ''
                           composite_prod   = ''
                           composite_scheme = ''
                           qual_max         = '2'
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 chla_a=ncread("H:\chla\A2019352.L3b_DAY_CHL.nc",'/level-3_binned_data/chlor_a');
 
Incorrect use of netcdf.getVar (line 137)
33 is an unrecognized netCDF data type.

Error in internal.matlab.imagesci.nc/read (line 607)
                 data = netcdf.getVar(gid, varid);

Error ncread (line 66)
vardata = ncObj.read(varName, varargin{:});

Thank you very much! I need your help.

Answer 1

[MJFcoNaN]

Hello,

If possible, I will suggest you choose the "level 3 mapped data" which is much more convenient to deal with in matlab, because of its traditional lon-lat grid.

Or you need to use h5read instead of ncread:

chla_a=h5read("H:\chla\A2019352.L3b_DAY_CHL.nc","/level-3_binned_data/chlor_a");

[Bei JIANG]

Thank you very much! When I download the level 3 mapped data，I solve my problem.