Tropical Cyclones: New views
Tropical cyclones bring strong wind and heavy rainfall on their path. The
strong tropical cyclones, such as hurricanes or typhoons, cause economic loss
and damage to human life when they cross the land. For tropical cyclones
initiated over the oceans, it was difficult to monitor them and to forecast
their intensity change, since there were no sufficient observations over the
oceans. But TRMM, for the first time, offers unique oppotunities to examine
tropical cyclones. With TRMM, scientists are able to make extremely precise
radar measurements of tropical storms over the oceans, and identify both
accelerators and brakes upon their intensity. The resulting data has provided
invaluable insights into the dynamics of tropical storms and rainfall.
TRMM marks the first time that tropical cyclones in all ocean basins are
able to be viewed from above by high resolution down-looking rain radar. In
the first 13 months of operation TRMM samples 84 tropical cyclones with 1189
orbits passing within 750km of a tropical cyclone center (19% of 6227 total
orbits). This sample represents over an order of magnitude more data than can
be obtained from any other platform. Image Archive
for TRMM is available at TRMM
Project Web Site . It collects the tropical hurricanes and typhoons
observed by TRMM. Below is an image of Hurricane Bonnie (August 22, 1998) and
chimney cloud, observed by TRMM instruments.
As pointed out in the reference below, the ability to forecast intensity
changes in tropical cyclones has shown little progress in the past two
decades. Now, with TRMM's intensive observations, scientists are able to
examine the intensity changes of tropical cyclones. The study on super typhoon
KAPA is an example. PAKA formed in the Northern Hemisphere and PAM in the
Southern. At first PAKA remained weak, until on December 10 when a huge
convective burst occurred:
(PAKA observed by TRMM, courtesy of Dr. Simpson at
GSFC/NASA) |
In the figure the upper left panel shows the geosychronous view from GMS
satellite. The large round white area is the top of one of the early "hot
towers". The upper right panel shows the TRMM radar superimposed on the
geosynchronous image, while the lower left panel is the 85 GHz image from the
TMI. Both the radar and the passive microwave show a clear eye, which was
hidden on the geosynchronous image. The lower right shows a radar
cross-section from A to B on the radar image above. The very hight tower leans
slightly inward toward the eye. Other radar cross sections show cloud
material extruding from the cloud into the eye and almost surely sinking.
The convective burst is associated with PAKA's first rapid intensity increase
from about 27 m s-1 to above 50m s-1 on December 11,
1997. This first rapid deepening has been studied and related to a combination
of the convective burst's carrying up high energy air and the storm core moving
over warmer.
Reference: Simpson, J., Kummerow, C.D., Meneghini, R., Hou, A.,
Adler, R.F., Huffman, G., Barkstrom, B., Wielicki, B., Goodman, S.J.,
Christian, H., Kozu, T., Krishnamurti, T.N., Yang, S., Ferrier, B., 2000: The
tropical rainfall measuring Mission (TRMM) progress Report, Earth
Observation and Remote Sensing, Vol. 18, August Issue.
TRMM standard products include orbital data derived from TMI and PR. Each
file consists of the whole scans of one orbit. TSDIS also provides browse
images for selective parameters, which give the geographical tracks of all
orbits and a specific unique orbit number for a given day. To see and track
tropical cyclones, orbital data are suitable, because they are in higher
temporal and spatial resolution than temporal or spatial integrated data.
TRMM web-based on-line data search and order system provides a handy way for
orbital data. Users can first screen data files by choosing only the data
files over the region interested. Users also can further reduce data amount
by specifying the time period interested. (see TRMM DATA Spatial Search )
A
Readme file for TRMM data is available
at DAAC. Sample Fortran and C programs to read HDF data are available
(see Relevant Links).
TSDIS provides a specific software, Orbit
Viewer , to plot and analyze TRMM satellite products, levels 1B
through 3. For level 1 and 2 products, the entire orbit can be viewed at once,
and a portion of the orbit can be zoomed to reveal detail. Both horizontal and
vertical slices of the zoomed region can be viewed. For level 3 products, the
entire tropics can be viewed at once, and a portion of the tropics can be
zoomed to reveal details.
PAKA images observed by TRMM TMI for Dec. 16 and 17, 1997 are archived at
TRMM project on-line site. See the images
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Atmos Composition
![[Hurricane Bon nie 3D image]](images/big_bonnie2_sm_000.jpg)
