Geoscience Reference
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IAPP using NOAA15 and 16 measurements. The root mean square (RMS)
errors of the ANN and International ATOVS Processing Package (IAPP)
retrievals are compared to the months of April 2008 to July 2008. These errors
have been computed against collocated data sets of NCEP GFS (Global Forecast
System) analysis at 0000, 1200 and 1800 UTC. The collocated data sets are
constructed based on the temperature profiles retrieved using ANN and IAPP
that are within 1.5 hours of time difference and within 2° × 2° lat/lon of NCEP
analysis. To test the quality of the neural network temperature retrievals, two
stations, namely Port Blair (Lat = 11.66° N, Lon = 92.71° E ) and Chennai (Lat
= 13° N, Lon = 80.18° E), where radiosonde flights are taken daily two times
at 00 and 12 UTC by the IMD were selected for the present study. The
radiosonde profiles over stations were collected for one month, June 2008. To
further enhance the quality control, only collocated radiosonde data (within
~2°) with five or more levels of good record have been accumulated for
validation. The total number of quality-controlled collocated radiosonde profiles
was found to be 97.
Further, to study upper tropospheric warm core anomaly of cyclone, the
network-based retrieval algorithm was applied for computing the anomaly near
the centre of the cyclones i.e., '
Gonu
'
and
'Nargis'
. Thereafter, the anomalies
are related to the intensification of the cyclone. The ANN model is trained and
tested using approximately 1700 real atmospheric conditions which includes
rare situations such as very complex temperature profiles that are often much
more irregular so that the dataset represents, as much as possible, all kinds of
possible atmospheric situations (initially for a pattern-recognition purpose).The
derived atmospheric temperature profiles are combined for land and ocean.
2. Temperature Profiles Retrievals Approaches
2.1 IAPP
In this study, NOAA-15 and -16, -17 and -18 satellite data over the Indian
region were used for reconstructing temperature profiles. The data were obtained
in the near-real time in the form of level 1b (instrument counts, navigation and
calibration information appended) format of NOAA satellite measurements
over the Indian region. Before the retrieval process, it is necessary to process
the raw format. To accomplish this work NOAA satellite data pre-processed
with the ATOVS and AVHRR Processing Package (AAPP) model (Klaes et al.
1999). The AAPP model was used to perform the ingestion and pre-processing
of the level 1b data and the radiances are corrected from the AMSU antenna
correction procedure (Mo et al.
,
1999). The AAPP tasks perform the computation
of the calibration coefficients, the satellite navigation (satellite position
calculation of its orbit) and image navigation (longitude and latitude position
of the pixels, taking into account the sensor geometry, solar angles, etc.). The
pre-processing tasks achieve the conversion of the raw data [Earth and
atmosphere visible (VIS) and infrared (IR) radiances] into physical parameters
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