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This study describes a calculation of the brightness temperature obtained from the spaceborne precipitation radar to utilize possible uses of precipitation estimates. Since the radar viewed from space measures emission and scattering signals from the earth, the brightness temperature at the radar's frequency is obtained from the noise power measured by the radar. The measurement accuracy of the radar's brightness temperature is also computed from the signal characteristics of the noise power. This study analyzes the noise power data of the Dual-frequency precipitation radar (DPR), whose frequency is at 13.6 and 35.5 GHz, onboard the Global Precipitation Measurement mission's (GPM's) core satellite. The calibrated brightness temperature data obtained from the DPR show the regional gradient between ocean and land surfaces and the emission signal from precipitation even if the measurement accuracy of the radar's brightness temperature is about 30 (50) K for the Ku-band (Ka-band) channel.

Algorithms to determine the thermodynamic phase state of precipitation observed from spaceborne radar are provided in this section. After briefly describing the classical methods to determine the thermodynamic phase of precipitation at the surface, some advanced methods to separate solid precipitation regions from liquid precipitation regions in the vertical profiles of radar measurements are described.

In this study, the spatial variability in precipitation at a 0.1° scale is investigated using long-term data from the Tropical Rainfall Measuring Mission Precipitation Radar. Marked regional heterogeneities emerged for orographic rainfall on characteristic scales of tens of kilometers, high concentrations of small-scale systems (100 km) result in more rainfall over the adjacent ocean. Finescale hourly data represented the abrupt asymmetric fluctuation in rainfall across the coastline in the tropics and subtropics (30°S–30°N). Significant diurnal modulations in the rainfall due to large-scale systems are found over tropical offshore regions of vast landmasses but not over small islands or in the midlatitudes between 30° and 36°. Rainfall enhancement over small tropical islands is generated by abundant afternoon rainfall, which results from medium-scale storms that are regulated by the island size and inactivity of rainfall over coastal waters.

Observations of the Tropical Rainfall Measuring Mission Precipitation Radar (TRMM PR) over 16 yr yielded hundreds of large precipitation systems (≥100 km) for each 0.1° grid over major rainy regions. More than 90% of the rainfall was attributed to large systems over certain midlatitude regions such as La Plata basin and the East China Sea. The accumulation of high-impact snapshots reduced the significant spatial fluctuation of the rain fraction arising from large systems and allowed the obtaining of sharp images of the geographic rainfall pattern. Widespread systems were undetected over low-rainfall areas such as regions off Peru. Conversely, infrequent large systems brought a significant percentage of rainfall over semiarid tropics such as the Sahel. This demonstrated an increased need for regional sampling of extreme phenomena. Differences in data collected over a period of 16 yr were used to examine sampling adequacy. The results indicated that more than 10% of the 0.1°-scale sampling error accounted for half of the TRMM domain even for a 10-yr data accumulation period. Rainfall at the 0.1° scale was negatively biased in the first few years for over more than half of the areas because of a lack of high-impact samples. The areal fraction of the 0.1°-scale climatology with a 50% accuracy exceeded 95% in the ninth year and in the fifth year for those areas with rainfall >2 mm day−1. A monotonic increase in the degree of similarity of finescale rainfall to the best estimate with an accuracy of 10% illustrated the need for further sampling.

This paper demonstrates the impact of the enhancement in detectability by the dual-frequency precipitation radar (DPR) on board the Global Precipitation Measurement (GPM) core observatory. By setting two minimum detectable reflectivities—12 and 18 dBZ—artificially to 6 months of GPM DPR measurements, the precipitation occurrence and volume increase by ~21.1% and ~1.9%, respectively, between 40°S and 40°N.GPM DPR is found to be able to detect light precipitation, which mainly consists of two distinct types. One type is shallow precipitation, which is most significant for convective precipitation over eastern parts of subtropical oceans, where deep convection is typically suppressed. The other type is probably associated with lower parts of anvil clouds associated with organized precipitation systems.While these echoes have lower reflectivities than the official value of the minimum detectable reflectivity, they are found to mostly consist of true precipitation signals, suggesting that the official value may be too conservative for some sort of meteorological analyses. These results are expected to further the understanding of both global energy and water budgets and the diabatic heating distribution.

This study investigated the drop size distribution (DSD) observed by the Dual-frequency Precipitation Radar (DPR) onboard the Global Precipitation Measurement (GPM) core satellite, which makes the world’s first dual-frequency preciptation observations by space-borne radar. Four years have passed since the launch of the GPM core satellite, and data have been accumulated. This study focuses on the characteristics of DSD derived from the GPM/DPR measurements. In this study, DSD parameters (especially for a mass-weighted mean diameter, Dm) which are estimated based on dual-frequency information derived from GPM/DPR are analyzed with seasonal variations and precipitation characteristics. Values of Dm are generally larger over land than over the oceans. DSD shows seasonal variation, especially over the mid-latitude ocean; Dm in the winter season over the mid-latitude ocean is larger than that in the summer season in both the Northern and Southern hemispheres. Focusing on the mid-latitude North Pacific Ocean close to Japan in winter, precipitation top height is lower and stratiform ratio is higher than those in summer. It suggests that differences of Dm are associated with those of precipitation regimes, such as organized precipitation system in summer season and extratropical frontal systems in winter season.

Characteristics and global distribution of regional extreme rainfall are presented using 12 yr of the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) measurements. By considering each rainfall event as a set of contiguous PR rainy pixels, characteristic values for each event are obtained. Regional extreme rainfall events are defined as those in which maximum near-surface rainfall rates are higher than the corresponding 99.9th percentile on a 2.5° × 2.5° horizontal-resolution grid. The geographical distribution of extreme rainfall rates shows clear regional differences. The size and volumetric rainfall of extreme events also show clear regional differences. Extreme rainfall rates show good correlations with the corresponding rain-top heights and event sizes over oceans but marginal or no correlation over land. The time of maximum occurrence of extreme rainfall events tends to be during 0000–1200 LT over oceans, whereas it has a distinct afternoon peak over land. There are also clear seasonal differences in which the occurrence over land is largely coincident with insolation. Regional extreme rainfall is classified by extreme rainfall rate (intensity) and the corresponding event size (extensity). Regions of “intense and extensive” extreme rainfall are found mainly over oceans near coastal areas and are likely associated with tropical cyclones and convective systems associated with the establishment of monsoons. Regions of “intense but less extensive” extreme rainfall are distributed widely over land and maritime continents, probably related to afternoon showers and mesoscale convective systems. Regions of “extensive but less intense” extreme rainfall are found almost exclusively over oceans, likely associated with well-organized mesoscale convective systems and extratropical cyclones.

This study reports on the presence of suspicious “extreme rainfall” data in the 2A25 version-7 (V7) product of the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) dataset and introduces a simple method for detecting and filtering out the suspicious data. These suspicious data in V7 are found by comparing the extreme rainfall characteristics in the V7 and version-6 products. Most of the suspicious extremes are located over land, especially in mountainous regions. Radar reflectivities in the suspicious extremes show significant monotonic increases toward the echo bottom. These facts indicate that the suspicious extremes are mainly caused by contamination from ground or sea clutter. A simple thresholding filter for eliminating the suspicious extreme data is developed using common characteristics in the horizontal and vertical rainfall structures and reflectivities in the suspicious extremes. The proposed filter mitigates deformations in the frequency distribution of the surface rainfall rate in the 2A25 V7 product.

Lookup tables for estimating the cloud-top height and visible optical thickness of upper-tropospheric clouds by the infrared brightness temperature TB at 10.8 μm (T11) and its difference from TB at 12 μm (ΔT11–12) measured by a geostationary satellite are presented. These lookup tables were constructed by regressing the cloud radar measurements by the CloudSat satellite over the infrared measurements by the Japanese geostationary multifunctional transport satellite MTSAT-1R. Standard deviations of measurements around the estimates were also displayed as an indicator of the ambiguity in the estimates. For the upper-tropospheric clouds with T11 < 240 K, the standard deviations of the height estimations were less than 1 km. The dependences of the estimates of cloud-top height at each point in T11−ΔT11–12 space on latitude, season, satellite zenith angle, day–night, and land–sea differences were examined. It was shown that these dependences were considered uniform in the tropics except for the region with large satellite zenith angle. The presented lookup tables can provide hourly estimates of cloud-top height and optical thickness at a specified location and are fairly useful in comparing them with ground-based observations such as vertical profiles of humidity and/or wind.

Cloud-top height (CTH) variability in the tropical tropopause layer (TTL) in association with equatorial Kelvin waves is investigated using a new CTH dataset based on MTSAT-1R geostationary satellite measurements with a statistical look-up table constructed based on CloudSat measurements. We focus on a case in the tropical Indian Ocean during October-December 2006, when shipboard radiosonde, TTL water vapor, and 95-GHz cloud radar measurements were taken during the Mirai Indian Ocean cruise for the Study of the MJO-convection Onset (MISMO) field campaign. At 10-15 km, the satellite-based CTH data agree well with the radar echo top heights from shipboard radar reflectivity data. During the MISMO campaign, cloud frequency was suppressed in the warm phase of equatorial Kelvin waves propagating in the TTL. The suppressed-cloud region moves eastward to the western Pacific together with Kelvin waves. We found that changes in CTH occurrence frequency over the vessel in association with Kelvin waves are much greater than those associated with the diurnal cycle. It is expected that the phase of equatorial Kelvin waves is important for the intraseasonal variabilities of both the radiative budget of the tropical atmosphere and water vapor transport in the TTL.

Poly(lactic acid) (PLA) was blended with baked shell powder increasing the content up to 10wt%, and the influence of mixing the powder on the physical properties of the obtained PLA compounds were investigated. The measurements for storage modulus E' revealed that the settled powder will promote the crystallization of PLA. Moreover not only the thermal decomposition but also the biodegradation in compost system for PLA were enhanced by the mixing the powder.

The life cycle of deep convective systems over the eastern tropical Pacific (30°N to 30°S, 180 to 90°W) was studied in terms of cloud types, as classified by a split window (11 μm and 12 μm). Hourly split window image data of Geostationary Operational Environmental Satellite (GOES-W) from January 2001 to December 2002 was used in this study. Deep convective systems consist mostly of optically thick cumulus type clouds in the earlier stage and a cirrus type cloud area that increases with time in the later stage. During this analysis period and over the analysis area, the life stage of deep convective system, to a large extent, can be identified by computing the percentage of cirrus type clouds within the deep convective system from a single snap shot of the split window image. Coincident Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) observations were used to study the relationship between the percentage of cirrus type clouds within a deep convective system (i.e., its life stage) and the rainfall rate. It was found that the rainfall rate tends to be larger in the earlier stage of the life cycle when a smaller percentage of cirrus type cloud is present within the deep convection.

Vertical motion W profiles in the stratiform precipitation region of mesoscale cloud clusters were investigated using wind data observed by VHF Doppler radar installed in western Sumatra Island (0.2°S, 100.32°E). A special mode for W observations was introduced in November 2003, and W data with high accuracy were obtained during most of the period, with fine resolutions of 3 min in time and 150 m in vertical direction. The typical fine structure of W within the nimbostratus in the stratiform precipitation region was investigated by the case study of 6, 8, and 20 November 2003. In the later 2 or 3 h of the stratiform precipitation period, gentle upward motions with small time and height fluctuations were observed over a several-kilometer height range from the middle to upper troposphere. Values of W were weakly positive (0–40 cm s−1) continuously, with little strong upward motion greater than 40 cm s−1 and downward motion.

Conventionally, the heaviest rainfall has been linked to the tallest, most intense convective storms. However, the global picture of the linkage between extreme rainfall and convection remains unclear. Here we analyse an 11-year record of spaceborne precipitation radar observations and establish that a relatively small fraction of extreme convective events produces extreme rainfall rates in any region of the tropics and subtropics. Robust differences between extreme rainfall and convective events are found in the rainfall characteristics and environmental conditions, irrespective of region; most extreme rainfall events are characterized by less intense convection with intense radar echoes not extending to extremely high altitudes. Rainfall characteristics and environmental conditions both indicate the importance of warm-rain processes in producing extreme rainfall rates. Our results demonstrate that, even in regions where severe convective storms are representative extreme weather events, the heaviest rainfall events are mostly associated with less intense convection., Conventionally, the heaviest rainfall is associated with the most intense storms, yet this relationship remains untested. Here, Hamada et al. analyse 11 years of radar observations from the topics and subtropics, and conclude that the heaviest rainfall is most commonly associated with less intense convection.