# OMDOAO3 Release Specific Information

Pepijn Veefkind\
9 October 2007

## Software Version

This information applies to the software version 1.0.5 and higher.

## ECS Collection Number

The OMDOAO3 v1.0.5 is released for Collection 3.

## Known Issues List

### Noisy Behavior of Pixel 30

The following contains a list of known issues in the OMCLDO2 data
product:\
Across track 30 (0-based) is noisy for inhomogeneous scenes. The reason
for this behavior is that the wavelength assignement in the Level 1B is
not corrected for inhomogeneos scenes for this pixel. For pixel 30 the
ProcessingQualityFlag Earth Radiance Warning (bit 3) is always set. The
figure below shows the precision for pixel 30 and its neighbouring
pixels.\
In the next version of the 0-1B processor this behavior for pixel 30
will be resolved.\
![](media/image1.png){width="7.138888888888889in"
height="5.391666666666667in"}\
*Figure showing the the precision in the ozone column for orbit 17078
for the noisy pixel 30 and its neighbouring pixels 29 and 31.*

### Row Anomaly of Pixels 53 and 54 

Since the end of June 2007, across track pixels 53 and 54 (0-based) show
anomalous behavior. These pixels show a high fitting residuals, too high
ozone columns, and too low cloud fractions. This feature is probably
caused by blocking of part of the incoming Earth radiance. Since the
feature has been stable since the end of June it is expected that it can
be corrected for in a future version of the Level 0-1B data processor.
It is recommended not to use across track pixels 53 and 54 from June
2007 onwards, until the anomaly has been corrected for. The figure below
shows the ozone column amount precision for pixels 53 and 54 and the
neighbouring pixels 52 and 55, showing a lower precision for these
anomalous pixels 53 and 54. The bottom plot shows the median of the
column amount ozone for 100 measurements, showing too large values for
pixels 53 and 54.\
\
![](media/image2.png){width="6.397916666666666in"
height="4.831944444444445in"}\
*Figure showing the row anomaly for pixels 53 and 54. Top plot shows the
precision of the column amount ozone for pixels 53 and 54 and their
neighbours. Bottom plot show the median of the ozone column for 100
measurements in the flight direction. Pixels 53 and 54 have anomalous
high ozone columns.*

## Release History

### OMDOAO3 v1.0.5:

1.  Release for OMI Collection 3 data.

2.  The treatment of high reflective surfaces (snow/ice) has been
    changed. If a highly reflective surface is detected, the effective
    cloud fraction is set to zero, and the surface albedo is fitted
    instead of the cloud fraction. The reason for setting the cloud
    fraction to zero is that it is not possible to derive an accurate
    effective cloud fraction over snow/ice surfaces. Validation data
    from the Polar Ave campaign have shown that setting the cloud
    fraction to zero results in the most accurate results. It is noted
    that this approach is similar to what is used in the OMTO3 data
    product.

3.  The airmass factor tables ave been updated. The previous air mass
    factor tables were the primary cause for the Solar zenith angle
    dependent bias. The new air mass factor tables are based on a new
    set of radiative transfer calculations.

4.  The look-up table for the cloud radiance fraction has been updated.
    The radiative transfer calculations of the previous version were
    based on a plane-parallel atmopshere. In the new version,
    corrections are done for the sphericity of the atmosphere.

5.  A new static irradiance file has been produced by combining all the
    Solar irradiance data of Collection 3 for the year 2005.

### OMDOAO3 v1.0.1:

The median solar irradiance file has been updated such that the
Sun-normalized radiance is correct. The most important correction was
done for accross track pixel 0.

### OMDOAO3 v1.0.0: 

1.  Updated the reference cross sections for O3, Sun and ring reference
    spectra. The main differences are a new Sun reference spectrum and
    updated OMI slit functions.

2.  Updated OMDOAO3_OPF.txt file. This file contains settings for the
    algorithm. The following changes were made to this file: the file
    version was set to 1.0, the albedo for snow surfaces was set to 0.6,
    and several limit values were updated.

3.  Changed the flagging strategy: Now level 1b pixel qflag bits 0-5 are
    errors, bits 6-13 are warnings and the rest are ignored. This
    reduces the stripes in the ozone column.

4.  Corrected the radiances and irradiance for Sun-Earth distance. This
    allows radiance and irradiance product to be more distant in time.

5.  The current baseline is to use a static median solar irradiance
    file. This reduces the stripes.

6.  Corrected bug in High-Sampling interpolation that appeared when
    flagged spectral pixels are removed from spectra.

### OMDOAO3 v0.9.42

OMDOAO3 v0.9.42 is the first version to be released provisionally.