Reading CLAVR-x Data


The CLAVR-x HDF4 files can be read in usig standard HDF calls in many languages (C,F90, IDL and MATLAB).

Currently, we only support the following IDL code as generic CLAVR-x data reader.

An IDL program, read_clavrx_hdf.pro,  has been written by Michael Pavolonis  to view the CLAVR-x/PATMOS-x HDF files.    This routine, documented in the top of the IDL source code, has optional arguments to return many attributes of each parameter.

 Here are some examples using a file named  clavrx_n17_des_05_1_2004_197.cell.hdf

• To read in the total cloud fraction (sds name = 'frac_total_cld') do this

          cloud_fraction = read_clavrx_hdf('clavrx_n17_des_05_0_2004_197.cell.hdf', 'frac_total_cld')

• To read in the mean channel 4 radiance for clear pixels (sds name = ch4_clr) to the following

            ch4_rad_clr = read_clavrx_hdf('clavrx_n17_des_05_0_2004_197.cell.hdf', 'ch4_clr')

• To read in the mean channel 4 radiance converted to a brightness temperature, do this

            ch4_bt_clr = read_clavrx_hdf('clavrx_n17_des_05_0_2004_197.cell.hdf', 'ch4_clr',/temperature)

            note, the /temperature keyword does not convert the radiance standard deviation to brightness temperature standard deviations.

• To read in the SST standard deviation (sds = sst_clr_std) and some of  its attributes, do this

        lst = read_clavrx_hdf('clavrx_n17_des_05_0_2004_197.cell.hdf', 'sst_clr_std',units=units, day=start_day)

        where units will have the value of unit of this parameter (K)  and day will have the value of the Julian day of this data (197).