MIMIC-IR (Morphed Integrated Microwave Imagery at CIMSS, with Infrared)

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.


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