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Update convert_airs_L2 docs.
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Condensed the description of the vertical levels and layers.
Added field names in the AIRS files which define them.
Changed 'mb' to 'hPa'.
Removed warnings in the namelist table about directory names in l2_files names.
  Example contents have ../data/file_name.
  Utilities_mod.f90 says "!> We agreed to support filenames/pathnames up to 256."
  I found no checks into whether there's a directory in the pathname,
  and no directory name is supplied to add to l2_files elements.
Updated namelist to specify default version to be 7.
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@kdraeder
kdraeder committed Mar 27, 2024
1 parent 4fada42 commit b3e0033
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2 changes: 1 addition & 1 deletion observations/obs_converters/AIRS/convert_airs_L2.nml
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Expand Up @@ -11,6 +11,6 @@
cross_track_thin = 0
along_track_thin = 0
use_NCEP_errs = .false.
version = 6
version = 7
/

60 changes: 30 additions & 30 deletions observations/obs_converters/AIRS/convert_airs_L2.rst
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Expand Up @@ -16,8 +16,8 @@ The AIRS Standard Retrieval Product consists of retrieved estimates of cloud
and surface properties, plus profiles of retrieved temperature, water vapor,
ozone, carbon monoxide and methane. Estimates of the errors associated with these
quantities will also be part of the Standard Product. The temperature profile
vertical resolution is 28 levels total between 1100 mb and 0.1 mb, while moisture
profile is reported at 14 atmospheric layers between 1100 mb and 50 mb. The
vertical resolution is 28 levels total between 1100 and 0.1 hPa, while moisture
profile is reported at 14 atmospheric layers between 1100 hPa and 50 hPa. The
horizontal resolution is 50 km. An AIRS granule has been set as 6 minutes of data,
There are 240 granules per day, with orbit repeat cycle of approximately 16 days.

Expand Down Expand Up @@ -89,21 +89,22 @@ convert_airs_L2.f90
-------------------

The ``convert_airs_L2`` converter is for **temperature and moisture retrievals** from
the L2 data. The temperature observations are at the
corresponding vertical pressure levels. However, the moisture obs are the mean for
the layer, so the location in the vertical is the midpoint, in log space, of the
current layer and the layer above it. There is an alternative computation for the
moisture across the layer which may be more accurate, but requires a forward
operator subroutine to be written and for the observation converter to include
additional metadata to support this forward operator. For more information see
the `Future Plans` section below.

The temperature observations are located on standard levels; there is a single array
of heights in each file and all temperature data is located on one of these levels.
The moisture observations, however, are an integrated quantity for the space between
the levels; in their terminology the fixed heights are 'levels' and the space between
them are 'layers'. The current converter locates the moisture obs at the midpoint,
in log space, between the levels.
the L2 data.
The vertical coordinate is pressure.
The temperature observations are defined at standard pressure levels (see Overview).
Those are defined in each file by the array
'StdPressureLev:L2_Standard_atmospheric&surface_product'.
Between 2 levels is a "layer".
A moisture observation is an average across the layer
and is defined at the midpoint (in log(pressure)) of the layer.
This choice makes half of the mass of the layer above the midpoint and half below.
The midpoints are defined in 'H2OPressureLay:L2_Standard_atmospheric&surface_product'.

There is an alternative computation for the moisture across the layer
which may be more accurate, but requires a forward operator subroutine
to be written and for the observation converter to include additional metadata
to support this forward operator.
For more information see the Future Plans section below.

The converter program reads each AIRS hdf file granule and outputs a DART obs_seq file
containing up to 56700 observations. Only those with a quality control of 0 (Best)
Expand Down Expand Up @@ -154,18 +155,17 @@ The default values are shown below. More realistic values are provided in
+--------------------+------------------------+--------------------------------------------------------------+
| Contents | Type | Description |
+====================+========================+==============================================================+
| l2_files | character(len=256), | A list of one or more names of the HDF file(s) to read, |
| | dimension(512) | NOT including the directory. If multiple files are listed, |
| | | each will be read and the results will be placed in a |
| | | separate file with an output filename constructed based on |
| | | the input filename. |
| l2_files | character(len=256), | A list of one or more names of the HDF file(s) to read. |
| | dimension(512) | If multiple files are listed, each will be read and |
| | | the results will be placed in a separate file with |
| | | an output filename constructed based on the input filename. |
+--------------------+------------------------+--------------------------------------------------------------+
| l2_file_list | character(len=256) | The name of an ascii text file which contains one filename |
| | | per line, NOT including the directory. Each file will be |
| | | read and the observations converted into an output file |
| | | where the output filename is based on the input filename. |
| | | Only one of 'l2_files' and 'l2_file_list' can be |
| | | specified. The other must be ' ' (empty). |
| | | per line. Each file will be read and the observations |
| | | converted into an output file where the output filename |
| | | is based on the input filename. |
| | | Only one of 'l2_files' and 'l2_file_list' can be specified. |
| | | The other must be ' ' (empty). |
+--------------------+------------------------+--------------------------------------------------------------+
| outputfile | character(len=256) | The name of the output observation sequence file. |
+--------------------+------------------------+--------------------------------------------------------------+
Expand All @@ -177,11 +177,11 @@ The default values are shown below. More realistic values are provided in
+--------------------+------------------------+--------------------------------------------------------------+
| lat2 | real(r8) | The North-most latitude of interest in degrees. [-90.0,90.0] |
+--------------------+------------------------+--------------------------------------------------------------+
| min_MMR_threshold | real(r8) | The data files contains 'Retrieved Water Vapor Mass Mixing |
| | | Ratio'. This is the minimum threshold (gm/kg) that will |
| min_MMR_threshold | real(r8) | The data files contain 'Retrieved Water Vapor Mass Mixing |
| | | Ratio'. This is the minimum threshold (g/kg) that will |
| | | be converted into a specific humidity observation (kg/kg). |
+--------------------+------------------------+--------------------------------------------------------------+
| top_pressure_level | real(r8) | The highest pressure level of interest (in mb). |
| top_pressure_level | real(r8) | The highest pressure level of interest (in hPa). |
+--------------------+------------------------+--------------------------------------------------------------+
| cross_track_thin | integer | Provides ability to thin the data by keeping every Nth data |
| | | value in the cross-track scan. [0,30] |
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