American Meteorological Society Demo

decade [see Ruprecht and Müller (1995) and Wolberg (1998) for good overviews on morphing]. It has been applied more recently to meteorological imagery by the National Oceanic and Atmospheric Administration/ National Weather Service (NOAA/NWS) using the Climate Prediction Center (CPC) Morphing Technique (CMORPH) software (Joyce et al. 2004), wherein microwave rainfall retrievals are blended together by advection with satellite-derived midtropospheric cloud-drift winds. A related approach is the linear extrapolation of moving precipitation fields, such as with sequential radar imagery (Hohti et al. 2000; Germann and Zawadzki 2002) or satellite microwave-derived precipitation using geostationary cloud-drift winds (Grose et al. 2002). In this paper we introduce a novel morphing algorithm called the Morphed Integrated Microwave Imagery at the Cooperative Institute for Meteorological Satellite Studies (CIMSS) (MIMIC) that can be used to improve the visualization of tropical cyclones, which in turn should enhance the ability to analyze and forecast these events. This algorithm is used to create the following two products described herein: MIMIC-TC presents a tropical cyclone–centered LEO microwave imagery animation, and MIMIC-IR animates a tropical cyclone–retrieved precipitation field layered over geostationary infrared imagery. Several examples in this paper have supplemental movies, which can be found online at http://dx.doi. org/10.1175/BAMS-88-8-Wimmers). In addition, we maintain an experimental real-time Web site for the MIMIC-TC and MIMIC-IR products online at http://cimss.ssec.wisc.edu/mimic. THE MIMIC-TC MORPHING TECHNIQUE. The ultimate goal of MIMIC-TC is to create a smooth animation from sequential but irregularly spaced microwave imagery produced from multiple LEO satellites overflying a target tropical cyclone. MIMIC-TC incorporates 85–92-GHz microwave data from six LEO satellites (Table 1) in near–real time as the data become available. [The Advanced Microwave Sounding Unit-B (AMSU-B) instrument is not currently used because of the difficulty in incorporating imagery with its low resolution and changing polarization with zenith angle; however, it may be included in the future.] The signal from these channels is strongly attenuated by large hydrometeors (~2-mm diameter and greater) generated by deep convection (Spencer et al. 1989; Grody 1993), and therefore the imagery is often used as a proxy for the distribution of precipitation in tropical cyclones. The microwave signal can penetrate through obstructing ice clouds that are common in tropical cyclones and uniquely reveal the structure of the eyewall and organization of the spiral bands (Hawkins et al. 2001; Lee et al. 2002; Houze et al. 2006). Because the various LEO satellite instruments employed by MIMIC-TC have slightly different response functions and calibrations, it is necessary to perform an empirical adjustment to the brightness temperatures to minimize any differences and improve the visualization. This normalization process is described in the appendix. In order to ensure proper navigation, the algorithm uses only swaths that contain the center of the TC rotation. The final product is interpolated to a polar coordinate grid around the center of rotation (2.78-km radial resolution and 1° angular resolution), which facilitates the computation of angular motion. When blending sequential microwave images of a tropical cyclone, the morphing algorithm must balance two contending trends. The first trend is the cyclonic advection of convective signals within the circulation of the storm, which can be roughly approximated TABLE 1. Satellite microwave instruments that contribute to the MIMIC-TC product. Satellite DMSP*-13 DMSP-14 DMSP-15 DMSP-16 TRMM Aqua Instrument SSM/I SSM/I SSM/I SSMIS TMI AMSR-E Frequency (GHz) 85.5 H** 85.5, H 85.5, H 91.7, H 85.5, H 89.0, H Orbit Polar, sun synchronous Polar, sun synchronous Polar, sun synchronous Polar, sun synchronous Equatorial, between 38°S and 38°N Polar, sun synchronous Footprint (km) 16 × 14 16 × 14 16 × 14 14 × 13 7×5 6×4 References Raytheon (2000) " " NOAA OSDPD (2002) Kummerow et al. (1998) NASA MSFC (2001) *DMSP: Defense Meteorological Satellite Program **H: Horizontal polarization 1190 | AUGUST 2007 http://dx.doi.org/10.1175/BAMS-88-8-Wimmers http://dx.doi.org/10.1175/BAMS-88-8-Wimmers http://cimss.ssec.wisc.edu/mimic

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