Tomoaki Mega

Improvement of High-Resolution Satellite Rainfall Product for Typhoon Morakot (2009) over Taiwan

The authors improve the high-resolution Global Satellite Mapping of Precipitation (GSMaP) product for Typhoon Morakot (2009) over Taiwan by using an orographic/nonorographic rainfall classification scheme. For the estimation of the orographically forced upward motion used in the orographic/nonorographic rainfall classification scheme, the optimal horizontal length scale for averaging the elevation data is examined and found to be about 50km. It is inferred that as the air ascends en masse on the horizontal scale, it becomes unstableandconvectiondevelops.Theorographic/nonorographic rainfallclassification schemeis extendedto the GSMaP algorithm for all passive microwave radiometers in orbit, including not just microwave imagers butalsomicrowavesounders. Theretrievedrainfallrates,togetherwithinfraredimages,areusedforthehighresolution rainfall products, which leads to much better agreement with rain gauge observations.

Development and Initial Observation of High-Resolution Volume-Scanning Radar for Meteorological Application

A new high-resolution Doppler radar, called Ku-band broadband radar (BBR), with fast scanning capability for meteorological application has been developed. Due to the new system design, the BBR can accurately measure the radar reflectivity factor with a range resolution of several meters and a time resolution of 55 s per volume scan from the nearest range of 50 m to 15 km for 10-W power using pulse compression. In this paper, the basic concepts, configuration, and signal processing of the BBR are described. In the initial observation, the observation accuracy of reflectivity is evaluated using Joss-Waldvogel disdrometer (JWD). As a result, the reflectivity of the BBR is in fairly good agreement with that of JWD. In addition, in the spiral observation, a fine structure of a thunderstorm obtained by the BBR is presented.

A Low-Power High-Resolution Broad-Band Radar Using a Pulse Compression Technique for Meteorological Application

A new high-resolution Ku-band Doppler radar for meteorological applications has been developed. With the new system design, the radar can accurately measure the radar reflectivity factor with 4-m resolution over a range from 40 m to several kilometers for 100-mW power using a pulse compression technique. Details of the system design, signal processing algorithm, and data acquisition procedures are described. To demonstrate the accuracy of the system, the radar reflectivity measurements are compared with the Joss-Waldvogel disdrometer measurements, and fairly good agreement is shown. The ability of the system to capture the backscattered signal and Doppler spectrum from rain volume at low altitude with high resolution is demonstrated for both convective- and stratiform-type rain events.

Gauge adjusted global satellite mapping of precipitation (GSMaP_Gauge)

Precipitation is one of the most important resources for human activity, and global distribution of precipitation amount and its change are essential data for modeling the water cycle and global energy cycle. Space-borne Passive Microwave Radiometers (PMRs) are working on many satellites. PMR observes emission and scattering from precipitation and provide uniform global data. The Global Satellite Mapping of Precipitation Moving Vector with Kalman-filter (GSMaP_MVK) estimates hourly and 0.1 degree gridded precipitation map from PMRs. Because land is radiometrically warm region, estimation of precipitation over land is difficult. Global precipitation over land, however, is most important for human activity, such as management of water and flood warning. We are developing a gauge adjusted algorithm for GSMaP (GSMaP_Gauge). In this paper, we show performance of the algorithm and some initial evaluation tests. We introduce the GSMaP_Gauge algorithm and show the validation of the algorithm.

Improvements of Rain/No-Rain Classification Methods for Microwave Radiometer over Coasts by Dynamic Surface-Type Classification

AbstractThe rain/no-rain classification for the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) fails to detect rain over coasts, where the microwave footprint encompasses a mixture of radiometrically cold ocean and radiometrically warm land. A static land–ocean–coast mask is used to determine the surface type of each satellite footprint. The coast mask is conservatively wide to account for the largest footprints, preventing use of the more appropriate ocean or land algorithm for coastal regions.The purpose of this paper is to develop a classification whereby the smallest region possible is defined as coast. In this endeavor, two major improvements are applied to the land–ocean–coast classification. First, the surface classification based on microwave footprints of the high frequency actually used in rain detection is employed. Second, the footprint area of the surface classification is established using an effective field-of-view size and scan geometry of the TMI. These improvements are...

Development and Observation of the Ku-band Broad-Band Radar for Meteorological Application

Hazardous weather such as severe storms, tornadoes and hurricanes are small scale weather phenomena whose detailed profiles are important practically and scientifically. Despite this, conventional radars cannot resolve them, because of their low resolution capability. In this study, we developed a new high resolution Ku-band Doppler radar with scanning capability for meteorological applications. With the new radar system design, the radar can accurately measure the radar reflectivity factor with the range resolution of 4 m and the time resolution of 1 min per 1 volume scan from the nearest range of 50 m to about 15 km for 10 W power using pulse compression technique. In this paper, the details of the system design and the signal processing algorithm are described. To demonstrate the accuracy of this system, the radar reflectivity measurements are compared with 2D-video disdrometer measurements. The initial observation results of spiral mode are also shown.

Recent improvements in the global satellite mapping of precipitation (GSMaP)

The Global Satellite Mapping of Precipitation (GSMaP) product, which was developed toward the Global Precipitation Measurement (GPM), is operating and distributed in near-real-time basis at the Japan Aerospace Exploration Agency (JAXA). In this paper, we will introduce development status of the latest GSMaP algorithm, which will be distributed as one of JAXA GPM product.

Near real time product of the gauge adjusted GSMaP (GSMaP_Gauge_NRT)

This paper describes the rain gauge adjusted algorithm for the Global Satellite Mapping of Precipitation (GSMaP_Gauge_NRT) that estimates the surface rainfall rate with the resolution of 0.1 degree and 1 hour resolution over the globe in near realtime. Precipitation is one of the most important parameters on the earth system, and the global distribution of precipitation and its change are essential data for modeling the water cycle, maintaining the ecosystem environment, agricultural production, improvements of the weather forecast precision, flood warning and so on. In the GPM (Global Precipitation Measurement) project, the integrated products of high resolution mapping of precipitation from microwave measurements from constellation satellite and infrared radiometers from geo-stationary orbit are developed and supplied to the public. However, sometimes such high resolution product such as GSMaP_NRT underestimates the surface precipitateon and causes large error for hydrological modeling. In this paper, global gauge data set are combined with GSMaP_NRT. After describing and evaluating the GSMaP_Gauge which is a gauge adjusted product of the GSMaP_MVK, the methodology of a new combined algorithm (GSMaP_Gauge_NRT) is described.

Initial observation results for precipitation on the Ku-band broadband radar network

A radar network with several Ku-band broadband radars (BBR), which are short-range (15 km) and ground-based Doppler radar with remarkably high range and temporal resolution of about several meters and 1 min per volume scan, respectively, observes multi-directionally and simultaneously hazardous small-scale phenomena such as tornadoes and microbursts with high resolution and accuracy. In this paper, initial observation results of the BBR network are presented. Two BBRs observes significantly similar patterns of precipitation due to the high temporal resolution, and integrated reflectivity between the two BBRs showed impressively high quality images of precipitation.

Rainfall observation with high resolution using Ku-band broad band radar

A new high resolution Doppler radar, the Ku-band broad band radar, with scanning capability for meteorological application has been developed. Due to the new system design, the BBR can accurately measure the radar reflectivity factor with the range resolution of 5 m and the time resolution of 1 min per 1 volume scan from the nearest range of 50 m to 15 km for 10 W power using pulse compression. In this paper, the brief description of the BBR and the initial observation results are shown. In the calibration, reflectivity factor of the BBR is fairly good agreement with the Joss-Waldvogel disdrometer. In the volume scanning observation, we succeeded to detect fine 3 dimensional structures of precipitation.