Detailed information on
AAPP is the response to the demand of a large User Community for a standardized
software for the processing of direct readout HRPT data of TIROS-N/NOAA,
satellites. For a long time many different types of code have been
available to perform the processing steps from the received raw data
('from the antenna') to the pre-processed, calibrated and navigated
data ('to the product'). These processing steps can be standardized,
so that the retrieval step(s), in which the essential different scientific
approaches are embedded, can be based on the same input data and
thus a manifold of Users can apply satellite data in an efficient
Another advantage of AAPP is that it will be maintained
centrally (by the NWP
SAF), e.g. in case of necessary updates for new
space craft instruments the calibration coefficients will
be made available through updated versions of AAPP.
The AAPP web pages provide a forum to exchange experiences
in the use of AAPP, to make bugs known, and to get the
information dispatched to specialists in the respective
AAPP uses a processed TBUS message for the processing
of orbital information. With the aid of the BROLYD (Brower/Lyddane)
algorithm orbital parameters are predicted for the over
pass in question, and with the instrument information
available, the correct position of an instrument scan
pixel on the Earth's surface, together with the correct
time annotation, can be estimated.
TBUS messages can be received from e.g. following sites:
i) The most recent TBUS message via the internet from NOAASIS.
ii) TBUS messages for the past year, plus access to historical
tbus messages, from NOAASIS.
iii) Historical TBUS messages via ftp from
the University of Tokyo (ftp://ftp.tkl.iis.u-tokyo.ac.jp/pub/TBUS).
AAPP version 5 onwards can accept Two-line element(TLE) data
as an alternative to TBUS. TLE bulletins are available
and AAPP includes a script to retrieve and process the
For METOP, AAPP can process the SPOT bulletins that are available in the METOP Admin message.
- The decommutation step for NOAA satellites separates the instrument data
contained in an HRPT frame. The AAPP standard distribution
uses the data exactly in the format described in the
NESS/NOAA TM 107 - Rev. 1 (Planet, W. G. (Editor), 1988)
and also in the NOAA-KLM
User's Guide, but expects the original downlinked
10 bit words unpacked by being stored right justified
in 16 bit words. The data of the TIROS Information Processor
(TIP) and the AMSU Information Processor (AIP) as well
as the multiplexed AVHRR data from five channels will
be decommutated and stored in the respective instrument
specific HRPT level 1a files.
- For METOP the input to AAPP is the EPS Level 0 format defined by EUMETSAT. The
instruments are supplied in separate files and therefore there is no decommutation step. If your
reception system does not deliver EPS Level 0 format, you may wish to make use of the
METOPIzer tool supplied by EUMETSAT.
- Calibration means the extraction of the onboard calibration
parameters (e.g. Black Body Counts, Space counts etc.)
from the data stream, the transformation of these counts
into calibration coefficients, and finally the application
of these calibration coefficients to the Earth Observation
data, to transform them from binary units (counts) into
physical parameters (Brightness Temperatures or Reflectance
- Pre-Processing means the detection and flagging of
all information in the data which are deemed non suitable
for use in the subsequent retrieval step. These contamination
effects include effects by large rain drops, ice particles
in clouds, surface effects etc. The current baseline
does not include correction of these effects. Furthermore
a cloud clearing step is performed and corresponding
information is passed on. A second task of the pre-processor
is the mapping of all sounder instrument data to a common
grid to be used in the retrieval step. This may be the HIRS,
AMSU-A, AMSU-B or IASI grid.
- As stated above mapping means the transfer of the
information from the FOV-grid of one given instrument
to the FOV-grid of another.
For ATOVS, the AMSU-B/MHS data are mapped first to AMSU-A
FOV and these data and the AMSU-A data are mapped then
to the HIRS FOV. Optionally AMSU-A may also be mapped to the
AMSU-B (or MHS) grid. For TOVS, the MSU data are mapped
to the HIRS FOV. AVHRR data are mapped to the HIRS
FOV in form of statistical parameters. For METOP, AMSU-A and MHS
may in addition be mapped to the IASI grid.
- Tracking means the creation of information concerning
the visibility of overpasses for a given reception station.
The station coordinates and a recent set of orbital information
must be known.
- NOAA Level 1B File Formats
- The AAPP internal level 1b file format is similar
to the level 1b file format for the NOAA-KLM satellites
defined by NOAA/NESDIS (NESDIS
NOAA-KLM Level 1b data specification). This applies
to the AAPP processing of ATOVS data as well as TOVS
data. Nevertheless, there are slight differences in the
AVHRR and HIRS l1b file formats between AAPP and NOAA/NESDIS.
AAPP has been prepared to cope with the differences.
Therefore, unpacked NOAA/NESDIS level 1b data from NOAA-KLM
satellites can be ingested into AAPP but no NOAA/NESDIS
level 1b data from TIROS-N satellites since the NOAA-KLM
level 1b file specification differs from the specification
for the TIROS-N satellites. Furthermore note that GAC
AVHRR l1b files from NOAA's archive
cannot be processed by AAPP since
GAC AVHRR data has a reduced resolution compared to the
HRPT AVHRR full resolution data.
- IASI level 1 processing
- Processing of IASI data from level 0 to level 1c is performed by the IASI OPS-LRS, available
as an optional component of AAPP. Note that this software uses multithreaded techniques and
is more difficult to run than the ATOVS
processing modules. Furthermore not all platforms are supported (e.g. HPUX is not). For more
details on OPS-LRS, please consult the OPS-LRS User Manual.
- BUFR encoding and decoding
- AAPP version 6 onwards has tools to encode and decode BUFR level 1c data. This format is
widely used for international data exchange. The AAPP tools make use of the ECMWF BUFR library,
which must be downloaded from
ECMWF if the
tools are required.
AAPP is designed for UNIX or Linux systems. The software has been
tested on a range of systems, including Linux PC, HPUX, Sun Solaris, IBM AIX and SGI IRIX systems.
It may also be run on Windows PC using a Unix emulator.
The following components are needed:
- UNIX or Linux operating system
- FORTRAN 77 or Fortran 90 compiler
- make utilities
- tar, gzip and gunzip
- about 400 MB of free disk space
- KORN shell (adaptations required to BASH and C-shell)
- potentially X-Window.
|What you need to know about ATOVS
and AAPP to install and run it
Basically nothing on ATOVS except the HRPT format your
reception station delivers out of the frame synchronizer (in the case of NOAA satellites).
This determines the amount of changes you have to implement
in the routine decommutation.F. Note that AAPP expects
the HRPT data unpacked right justified in 16 bit words.
You will also have to arrange for the appropriate input files to be presented to AAPP -
especially in the case of METOP where there is a separate Level 0 file for each instrument.