Geoscience Reference
In-Depth Information
by Navy NRL was noted down from the website. Cyclone centre determined
by SSD NOAA also noted from their archive. Microwave channels from Polar
orbiting satellites of Aqua-1, DMSP (F-13, F-15, F-16, F-17 and F-18), NOAA
series (N-15, N-16, N-17, N-18, N-19), Metop-A and TRMM are used in this
study. The number of observations used from these satellites are given in Table 1.
Comparison is done only for those observations whose timings coincide
with each other or differ within three hours. The other observations of Kalpana
1 and polar orbiting satellites are not considered in the present analysis.
Comparison of centre and intensity given by Satellite Division operationally
is also done with SSD NOAA centre and intensity for microwave imageries.
Total number of observations which are compared is 60. Satellite-wise number
of observations are depicted in Table 2.
SSD, NOAA provides centre and intensity of CDs every six hourly while
the Satellite Meteorology Division of IMD gives three hourly centre and
intensity of CDs for T1.0 and T1.5 and hourly centre and intensity of CDs as
soon as it reaches the intensity T2.0 and more. So only observations of Satellite
Meteorology Division of IMD which coincides or nearer (within 3 hrs) with
the timings of SSD NOAA are compared and analysed.
Similarly, inter-comparison is done between 79 observations of SSD,
NOAA and Navy NRL. Satellite-wise and TC-wise observations considered
in the study are shown in Table 3.
3. Results and Discussion
3.1 Comparison of Intensity of CDs
The difference between the intensity (
T
number) given by Satellite Division of
IMD by using visible and infrared images and the intensity estimate by
microwave channel (85 GHz) of different satellites as given by NRL is shown
in Fig. 2. The average difference is found to be T0.5. The difference varies
from 0 to 1 T number. The intensity difference is higher in case of lower intensity
of the system such as depressions and cyclonic storms. It then decreases in
case of severe cyclonic storms and very severe cyclonic storms. However, the
difference is more when the intensity is 5.5 or more. Considering the cases
such as
T
2.5; 3
T
4.5;
T
5 assigned by satellite division of IMD, the
average absolute difference in intensity (
T
number) estimated by IMD and
NRL is about 0.5, 0.4 and 0.7 respectively.
The difference is negative i.e. intensity estimated by Microwave imagery
is higher in 55% cases than that estimated by infrared/visible imagery (Fig. 3).
The difference is positive in only 13% cases and equal in 32% cases. Considering
the cases such as
T
2.5; 3 <
T
4.5;
T
5 assigned by satellite division of
IMD, the average intensity (
T
number) estimated by NRL is higher in 58%,
44% and 71% cases and less in 10%, 18% and 29% cases and equal in 32%,
38% and 0% respectively.
Search WWH ::
Custom Search