An improved algorithm based on the self-consistent principle for rain attenuation correction of reflectivity Z H and differential reflectivity Z DR are presented for X-band radar. The proposed algorithm calculates the optimum coefficients for the relation between the specific attenuation coefficient and the specific differential phase, every 1 km along a slant range. The attenuation-corrected Z DR is calculated from reflectivity at horizontal polarization and from reflectivity at vertical polarization after attenuation correction. The improved rain attenuation correction algorithm is applied to the range-height indicator (RHI) scans as well as the plan position indicator (PPI) volume scan data observed by X-band wavelength (MP-X) radar, as operated by the National Research Institute for Earth Science and Disaster Prevention (NIED) in Japan. The corrected Z H and Z DR values are in good agreement with those calculated from the drop size distribution (DSD) measured by disdrometers.The two governing parameters of a normalized gamma DSD, normalized number concentration N W , and drop median diameter D 0 are estimated from the corrected Z H and Z DR , and specific differential phase K DP values based on the ''constrained-gamma'' method. The method is applied to PPI and RHI data of a typhoon rainband to retrieve the three-dimensional distribution of DSD. The retrieved DSD parameters show reasonable agreement with disdrometer data. The present results demonstrate that high-quality correction and retrieval DSDs can be derived from X-band polarimetric radar data.

Decadal climatology of aerosol optical parameters derived from Moderate Resolution Imaging Spectroradiometer (MODIS) on board Terra satellite has been analysed during past decade (February 2000 to February 2010) over three different environments in South Korea. Seoul, a continental urban station showed a significant decadal decrease of around 22% in aerosol optical depth (AOD) at 550 nm during observational period. The corresponding decrease in AOD found to be 18.7% over Busan, a coastal station. However Jeju, a volcanically sedimented island station in Korea showed negligible changes in AOD (1.4%). Fine mode fraction (FMF) and Angstrom exponent (ANG) parameters also showed a significant decadal reduction, indicating the decrease in fine mode aerosols, which are majorly produced due to anthropogenic activities in land areas. On analysing the decadal trends in seasonal climatology, it is found that aerosol parameters in general were showing a decreasing trend in different seasons except during spring. The decadal trend in meteorological parameters did not show a perfect alignment with aerosol trends. This suggests that the decadal decrease in aerosols could be mainly attributed to reduction in anthropogenic aerosol emissions. The surface temperature over the stations showed a significant increase of 8% to 11%. This study suggests that, in spite of positive effects in pollution perspective, the reduced AOD may in part contribute the increasing trend of surface temperature.

Abstract.To understand the different environment and morphology for heavy rainfall during 9-10 July 2007, over the Korean Peninsula, mesoscale convective systems (MCSs) that accompanied the Changma front in two different regions were investigated. The sub-synoptic conditions were analysed using mesoscale analysis data (MANAL), reanalysis data, weather charts and Multi-functional Transport Satellite (MTSAT-IR) data. Dual-Doppler radar observations were used to analyse the wind fields within the precipitation systems. During both the case periods, the surface lowpressure field intensified and moved northeastward along the Changma front. A low-level warm front gradually formed with an east-west orientation, and the cold front near the low pressure was aligned from northeast to southwest.The northern convective systems (meso-α-scale) were embedded within an area of stratiform cloud north of the warm front. The development of low-level pressure resulted in horizontal and vertical wind shear due to cyclonic circulation. The wind direction was apparently different across the warm front. In addition, the southeasterly flow (below 4 km) played an important role in generating new convective cells behind the prevailing convective cell. Each isolated southern convective cell (meso-β-scale) moved along the line ahead of the cold front within the prefrontal warm sector. These convective cells developed when a strong southwesterly low-level jet (LLJ) intensified and moisture was deeply advected into the sloping frontal zone. A high equivalent potential temperature region transported warm moist air in a strong southwesterly flow, where the convectively unstable air led to updraft and downdraft with a strong reflectivity core.

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