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MIMIC-IR
(Morphed Integrated Microwave Imagery at CIMSS, with Infrared)
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Product Description
MIMIC-IR is an enhancement of the original MIMIC product, incorporating
the morphed microwave data with complementary geostationary infrared
imagery. This combination of microwave and infrared imagery creates a
simultaneous view of convection and cloud distribution, similar to an
overlay of radar with geostationary imagery with radar. MIMIC-IR
further enhances the morphed microwave product, because the
geostationary infrared imagery provides a good instantaneous
verification of the position of microwave-retrieved convection.
The microwave imagery used in MIMIC-IR is the polarization corrected
temperature (PCT), which is a bit different from the brightness
temperature used in MIMIC. The PCT is computed from a weighted
difference between the vertical and horizontal polarizations of the 85
to 89 GHz channel, which isolates the effect of signal attenuation from
hydrometeors, and removes the effect of surface temperatures. (In the
MIMIC product, the horizontal polarization brightness temperature is
preferred over the PCT because the horizontal polarization shows
important textures that indicate the storm's circulation). PCT values
have been shown to vary inversely with precipitation, as described in
this tutorial
from the Naval Research Laboratory Marine Meteorology Division.
Infrared imagery is taken from the "closest" of five possible
geostationary satellites: GOES-East (covering most of the Atlantic
basin), Meteosat-7 (covering the far east of the Atlantic Basin),
Meteosat-5, a.k.a. "Indoex" (covering the Indian Ocean), MTSAT
(covering the West Pacific basin and the South Pacific basin) and
GOES-West (covering the East Pacific basin). The temporal frequency of
these satellites' images is normally between 15 and 60 minutes,
although each experiences an occasional "blackout" (either because of
an eclipse period or because of technical problems), which causes
longer gaps in the data availability. The infrared image shown in the
MIMIC-IR product is the one closest in time to the display time (either
before or after). In contrast to the morphed microwave product, the
infrared imagery is always displayed in its original position in order
to serve as a spatial reality-check for the morphed microwave product.
In MIMIC-IR, PCT and infrared are two unique "layers" of imagery. The
PCT layer is semitransparent to permit a direct comparison with the
underlying infrared image. For example, if an eye or a "mote" is
directly underneath a PCT pattern, the PCT pattern will assume a darker
tint proportional to the darkness of the infrared feature. This is
important to note when viewing the imagery, because these darker tints
should not be mistaken for changes in PCT value.
The comparison between infrared and the semitransparent PCT is
especially useful for tracking the motion of outer spiral bands. Often
an outer spiral band will move rapidly away from the storm center, but
the morphed PCT pattern will not follow the motion apparent in the
clouds. In this case the end-user must mentally picture the
PCT-resolved convection moving in tandem with the infrared-resolved
cloud advection. A similar case exists when the PCT-resolved eye is
offset from the IR-resolved eye. Specifically, if the eye in the PCT
layer is fixed in the center while the eye in the IR revolves within a
small space around the center, the end-user should picture the PCT
eyewall revolving along with the IR eye.
For more information, please refer to the MIMIC-IR
FAQ and the MIMIC
FAQ. For topics not covered there, questions and comments are
always welcome.
Acknowledgment:
This project is supported financially by
the Naval Research Laboratory's Marine Meteorology Division in
Monterey, CA, and by the office of Naval Research, Program Element
(PE-0602435N). The NRL Satellite Meteorological Applications Section
has worked with CIMSS to create, validate and transition products and
algorithms that enable the tropical cyclone community to extract
reliable TC position, intensity and storm structure information via
automated processing software.
Updated 10/21/2004
Tony Wimmers and Chris Velden
Tropical Cyclone Research Team
Cooperative Institute for Meteorological
Satellite Studies (CIMSS)
University of Wisconsin - Madison
Comments welcome: wimmers@ssec.wisc.edu,
chrisv@ssec.wisc.edu