A coupled ocean-atmosphere climate model is used to depict changes in precipitation characteristics around Japan in the 21st century. A comparison between high (T106 atmosphere) and medium (T42) resolution versions for the present-day climate shows that the higher resolution version better represents not only the mean but also the frequency distribution of precipitation. The climate projection for the 21st century by the high resolution version shows that mean precipitation increases more than 10% in 100 years from the present, especially in warm seasons. Increases in frequencies of non-precipitating and heavy ( 30 mm day 1 ) rainfall days and decrease in relatively weak (1 20 mm day 1 ) rainfall days are significant.

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Three-dimensional rain characteristics of tropical cyclones (TCs) are statistically quantified, using Tropical Rainfall Measuring Mission (TRMM) data from December 1997 to December 2003. Tropical cyclones are classified into four maximum intensity classes (Ͻ34, 34-64, 64-128, and Ն128 kt) and three stages (developing, mature, and decaying). First, rain characteristics of TCs are compared with those of the equatorial (10°N-10°S) mean. A notable finding here is that the average stratiform rain ratio (SRR), which is the contribution from stratiform rain in the total rainfall, of TCs is 52%, while it is 44% for the equatorial oceanic mean and 46% for the Madden-Julian oscillation in its mature phase. Stronger rain is observed in TCs both for convective and stratiform rain. Second, radial rain characteristics of TCs suggest that the region 0-60 km can be classified as "the inner core," and 60-500 km as "the rainband." The inner core is characterized with small SRR, very high rain-top height, and a large flash rate, indicating the vigor of convective activity. In contrast, the rainband is characterized with large SRR and relatively large rain yield per flash, indicating a large rainfall amount with a moderate convective activity. An important implication of this study is that TCs are listed in the high end of tropical oceanic organized rain systems, in terms of the organization levels of rain. Last, we use the above composite results to calculate the rainfall contribution of TCs to total annual rainfall between 35°N and 35°S as 3.3% Ϯ 0.1%.

The spectral latent heating (SLH) algorithm was developed to estimate latent heating profiles for the Tropical Rainfall Measuring Mission Precipitation Radar (TRMM PR). The method uses TRMM PR information (precipitation-top height, precipitation rates at the surface and melting level, and rain type) to select heating profiles from lookup tables (LUTs). LUTs for the three rain types-convective, shallow stratiform, and anvil rain (deep stratiform with a melting level)-were derived from numerical simulations of tropical cloud systems from the Tropical Ocean and Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) using a cloud-resolving model (CRM).The two-dimensional (2D) CRM was used in previous studies. The availability of exponentially increasing computer capabilities has resulted in three-dimensional (3D) CRM simulations for multiday periods becoming increasingly prevalent. In this study, LUTs from the 2D and 3D simulations are compared. Using the LUTs from 3D simulations results in less agreement between the SLH-retrieved heating and sounding-based heating for the South China Sea Monsoon Experiment (SCSMEX). The level of SLH-estimated maximum heating is lower than that of the sounding-derived maximum heating. This is explained by the fact that using the 3D LUTs results in stronger convective heating and weaker stratiform heating above the melting level than is the case if using the 2D LUTs. More condensate is generated in and carried from the convective region in the 3D model than in the 2D model, and less condensate is produced by the stratiform region's own upward motion.

A quasi-stationary front, called the baiu front, often appears during the early-summer rainy season in East Asia (baiu in Japan). The present study examines how precipitation characteristics during the baiu season are determined by the large-scale environment, using satellite observation three-dimensional precipitation data. Emphasis is placed on the effect of subtropical jet (STJ) and lower-tropospheric convective instability (LCI). A rainband appears together with a deep moisture convergence to the south of the STJ. Two types of mesoscale rainfall events (REs; contiguous rainfall areas), which are grouped by the stratiform precipitation ratio (SPR; stratiform precipitation over total precipitation), are identified: moderately stratiform REs (SPR of 0%–80%) representing tropical organized precipitation systems and highly stratiform REs (SPR of 80%–100%) representing midlatitude precipitation systems associated with extratropical cyclones. As the STJ becomes strong, rainfall from both types of mesoscale precipitation systems increases, with a distinct eastward extension of a midtropospheric moist region. In contrast, small systems appear regardless of the STJ, with high dependency on the LCI. The results indicate that the STJ plays a role in moistening the midtroposphere owing to ascent associated with secondary circulation to the south of the STJ, producing environments favorable for organized precipitation systems in the southern part of the rainband. The horizontal moisture flux convergence may also contribute to precipitation just along the STJ. On the other hand, the LCI plays a role in generating shallow convection. In high-LCI conditions, deep convection can occur without the aid of mesoscale organization.