The ability of C-band polarimetric radar to account for strong attenuation/differential attenuation is demonstrated in two cases of heavy rain that occurred in the Chicago, Illinois, metropolitan area on 5 August 2008 and in central Oklahoma on 10 March 2009. The performance of the polarimetric attenuation correction scheme that separates relative contributions of ''hot spots'' (i.e., strong convective cells) and the rest of the storm to the path-integrated total and differential attenuation has been explored. It is shown that reliable attenuation correction is possible if the radar signal is attenuated by as much as 40 dB. Examination of the experimentally derived statistics of the ratios of specific attenuation A h and differential attenuation A DP to specific differential phase K DP in hot spots is included in this study. It is shown that these ratios at C band are highly variable within the hot spots. Validation of the attenuation correction algorithm at C band has been performed through cross-checking with S-band radar measurements that were much less affected by attenuation. In the case of the Oklahoma storm, a comparison was made between the data collected by closely located C-band and S-band polarimetric radars.

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The physical characteristics of rain are reflected by the shape of the raindrop size distribution (RDSD). Specifically, the RDSD is the result of different precipitation formation processes. We measured the RDSD at the surface in heavy rainfall during SoWMEX/TiMREX (2008) in Taiwan. The heavy rainfall was characterized by a squall line accompanied by trailing stratiform precipitation, and it was partitioned into three regions based on radar reflectivity patterns: convective line, stratiform, and reflectivity trough. The convective line was further partitioned into the convective center, leading edge, and trailing edge using a threshold rainfall intensity of 20 mm h -1 .The leading edge, which belongs to the convective line, had upward motion from the surface and contained many small drops. The leading edge was characterized by a small median volume diameter (D 0 ) and a linear shape of gamma RDSD. In the convective center, a strong updraught rose to the top of the cell with time, and many large drops over 4 mm were observed. The convective center, which had large D 0 and normalized intercept parameter (N W ), was characterized by an upward convex shape of gamma RDSD. The range of raindrop diameter decreased toward the trailing edge, with no updraught or only weak updraughts at high altitudes. The trailing edge had large shape and slope parameters, along with a more upward convex shape of gamma RDSD. A bright band was observed in the stratiform region with continual downward motion from the bright band to the surface, even though the intensity became weak. In the stratiform region, D 0 and N W were small and the gamma RDSD had an upward convex shape.The different RDSDs in each region of a maritime squall line suggest the existence of different cloud microphysical processes described by the change of RDSD parameters: the coalescence process induces an increase of D 0 and shape parameter and a decrease of N W , while the break-up process induces a decrease of D 0 and an increase of N W .In comparison with other maritime storms, the convective center has small log 10 N W and large D m value. And the convective edge region is positioned between convective center and stratiform region in the D m -log 10 N W scatter plot.

An elongated intense precipitation system associated with a stationary front delivered enhanced rainfall to the northern lateral and lee sides of an isolated mountain on Jeju Island on 6 July 2007. The convective region of the system passed around the mountain (Mt. Halla; height 1950 m, width 35 km, length 78 km) under moist synoptic conditions (relative humiditỹ 95% below 3 km) during the rainy season. In this study, the detailed 3-dimensional structure and enhancement mechanisms of this precipitation system are examined using dual-Doppler radar observations. Analysis of the Doppler radar indicates that the precipitation system was organized in an elongated shape that extended southwest-northeast about 20 km off the northwestern shore of Jeju Island. The development of this precipitation system with respect to Mt. Halla can be divided into three stages: approaching stage, lateral-side stage, and lee-side stage. During the approaching stage, variational wind analysis indicates that the updraft region was aligned with the convergence zone of relatively strong westerlies and weak southwesterlies on the western side of the system. The southwesterlies accelerated gradually, generating local updrafts between the system and the northwestern slope of the mountain that were crucial to the enhancement of the southern part of the system. The enhanced convective region intensified further as it reached the northwestern shore of the island. The elliptical shape and isolated terrain of Jeju Island played an important role in this intensification by modifying the low-level winds, with a relatively low Froude number of 0.2. This modification of the low-level wind by the terrain provided a plentiful supply of moist air to the convective region of the system, maintaining the enhanced convection. During the lee-side stage, the system was characterized by relatively weak westerlies at low altitude as it approached the eastern slope of the mountain. The convergence of these weak westerlies and relatively strong southwesterlies over the southeastern slope of the mountain induced a stationary updraft region and re-enhancement of convection on the lee-side of the mountain. The regional enhancement of this precipitation system on the lateral and lee sides of Mt. Halla resulted from localized terrain-induced low-level convergence under moist environmental conditions with predominant west-southwesterly winds. These environmental conditions are well organized when a stationary front is located off the northern shore of Jeju Island.

Three-year semi-operational observations of rainfall distributions with NIED X-band multiparameter (or polarimetric) radar started in the Kanto area of Japan from July 2003. The purposes and outlines of the radar observations with networks of rain gauges and disdrometers for ground validations are described. Preliminary results of validation analysis of polarimetric rain rate estimators show the usefulness of X-band multi-parameter radar for hydrological and meteorological applications in a small area.