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 tropicalcyclones with 1189 orbits passing within 750km of a tropical cyclone center (19% of 6227 total orbits).This sample represents over an order of magnitudemore 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 ofHurricane 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 slightlyinward toward the eye.Other radar cross sections show cloud materialextruding from the cloud into the eye and almost surely sinking. Theconvective 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 spatialintegrated 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 regioninterested.Users also can further reduce data amount by specifying the time period interested. (see disc.sci.gsfc.nasa.gov/uui/search/TRMM)
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 theorbit can be zoomed to reveal detail. Both horizontal and vertical slices ofthe 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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