Hiroshi Hanado

Diurnal change of Amazon rain forest /spl sigma//sup 0/ observed by Ku-band spaceborne radar

A Ku-band precipitation radar on the Tropical Rainfall Measuring Mission satellite provides backscattering coefficients (/spl sigma//sup 0/) of Earth surfaces. The data are used to investigate /spl sigma//sup 0/ characteristics of rain forest, and they show unique dependence on incidence angles and little dependence on seasons. A diurnal cycle is found in /spl sigma//sup 0/ of the Amazon rain forest, showing the maximum /spl sigma//sup 0/ in the morning and the minimum in the evening. It is inferred that the diurnal cycle is caused by dew drops on the leaves in the forests, and discussion on the dew effects with a simple model follows.

Evaluation of Precipitation Estimates by at-Launch Codes of GPM/DPR Algorithms Using Synthetic Data from TRMM/PR Observations

The Global Precipitation Measurement (GPM) Core Observatory will carry a Dual-frequency Precipitation Radar (DPR) consisting of a Ku-band precipitation radar (KuPR) and a Ka-band precipitation radar (KaPR). In this study, “at-launch” codes of DPR precipitation algorithms, which will be used in GPM ground systems at launch, were evaluated using synthetic data based upon the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) data. Results from the codes (Version 4.20131010) of the KuPR-only, KaPR-only, and DPR algorithms were compared with “true values” calculated based upon drop size distributions assumed in the synthetic data and standard results from the TRMM algorithms at an altitude of 2 km over the ocean. The results indicate that the total precipitation amounts during April 2011 from the KuPR and DPR algorithms are similar to the true values, whereas the estimates from the KaPR data are underestimated. Moreover, the DPR estimates yielded smaller precipitation rates for rates less than about 10 mm/h and greater precipitation rates above 10 mm/h. Underestimation of the KaPR estimates was analyzed in terms of measured radar reflectivity (Zm) of the KaPR at an altitude of 2 km. The underestimation of the KaPR data was most pronounced during strong precipitation events of Zm <; 18 dBZ (high attenuation cases) over heavy precipitation areas in the Tropics, whereas the underestimation was less pronounced when the Zm > 26 (moderate attenuation cases). The results suggest that the underestimation is caused by a problem in the attenuation correction method, which was verified by the improved codes.

Evaluation of surface clutter for the design of the TRMM spaceborne radar

Surface clutter interference through antenna sidelobes on rainfall measurements by spaceborne rain radar is quantitatively examined in order to clarify design criteria for the antenna. The received intensities of both rain echo and sea clutter are evaluated numerically, assuming appropriate precipitation and sea surface scattering models and a realistic antenna pattern for a phased array antenna, which is fed with the Taylor distribution. The results indicate that a region exists just above the sea surface where the sea surface clutter masks the backscattered power from the rain. The results also demonstrate the feasibility of quantitative measurements of rainfall in regions above this interference zone if a planar array antenna fed with the Taylor distribution of peak sidelobe level -30 dB is used. >

Estimation of Path-Integrated Attenuation and Its Nonuniformity From TRMM/PR Range Profile Data

Range profile data from the surface echo of the Precipitation Radar (PR) onboard the Tropical Rainfall Measuring Mission (TRMM) satellite enable the assessment of the nonuniformity of rainfall. The surface echo profile can be converted to a horizontal pattern of surface echo strength within the PRs footprint at off-nadir angles. Then, using the no-rain surface echo profile over ocean as a reference, the horizontal pattern of the path-integrated attenuation (PIA) can be estimated under moderate to heavy rainfall. Based on the horizontal pattern of the PIA, the nonuniform beam-filling parameter is estimated. However, this technique is applicable only to off-nadir angles and over ocean. Comparisons using ground-based radar data obtained simultaneously with TRMM data verify the effectiveness of this technique

Development of an active radar calibrator for the TRMM precipitation radar

An active radar calibrator (ARC) was developed for the calibration of the first spaceborne Precipitation Radar (PR) onboard the Tropical Rainfall Measuring Mission (TRMM) satellite. The ARC has three functions of the radar receiver, beacon-signal transmitter, and delayed-transponder. A ground-based measurement using a prototype ARC and a bread-board model of the TRMM-PR demonstrated the ARCs capability for the on-orbit TRMM-PR calibration.

Dual-frequency precipitation radar (DPR) development on theglobal precipitation measurement (GPM) core observatory

The Dual-frequency Precipitation Radar (DPR) on the Global Precipitation Measurement (GPM) core observatory is developed by Japan Aerospace Exploration Agency (JAXA) and National Institute of Information and Communications Technology (NICT). GPM objective is to observe global precipitation more frequently and accurately. GPM contributes to climate and water cycle change studies, flood prediction and numerical weather forecast. GPM consists of GPM core observatory and constellation satellites carrying microwave radiometers (MWRs) and/or sounders (MWSs). The frequent measurement will be achieved by constellation satellites, and the accurate measurement will be achieved by DPR with high sensitivity and dual frequency capability. GPM core observatory is jointly developed by National Aeronautics and Space Administration (NASA) and JAXA. NASA is developing the satellite bus and GPM microwave radiometer (GMI), and JAXA is developing DPR. GPM algorithms for data processing are developed jointly. The DPR consists of Ku-band (13.6 GHz) radar suitable for heavy rainfall in the tropical region, and Ka-band (35.55 GHz) radar suitable for light rainfall in higher latitude region. Drop size distribution information will be derived which contributes to the improvement of rainfall estimate accuracy. DPR will also play a key role to improve rainfall estimation accuracy of constellation satellites. DPR proto-flight test at JAXA Tsukuba space center is finished and it is delivered to NASA for integration to the GPM observatory. In this paper, DPR PFT test result at Tsukuba space center, DPR status in the GPM observatory environmental test, and DPR on-orbit calibration plan will be presented.

A Statistical Method for Reducing Sidelobe Clutter for the Ku-Band Precipitation Radar on board the GPM Core Observatory

AbstractA statistical method to reduce the sidelobe clutter of the Ku-band precipitation radar (KuPR) of the Dual-Frequency Precipitation Radar (DPR) on board the Global Precipitation Measurement (GPM) Core Observatory is described and evaluated using DPR observations. The KuPR sidelobe clutter was much more severe than that of the Precipitation Radar on board the Tropical Rainfall Measuring Mission (TRMM), and it has caused the misidentification of precipitation. The statistical method to reduce sidelobe clutter was constructed by subtracting the estimated sidelobe power, based upon a multiple regression model with explanatory variables of the normalized radar cross section (NRCS) of surface, from the received power of the echo. The saturation of the NRCS at near-nadir angles, resulting from strong surface scattering, was considered in the calculation of the regression coefficients.The method was implemented in the KuPR algorithm and applied to KuPR-observed data. It was found that the received power fro...

Satellite system test status of The Dual-Frequency Precipitation Radar on the global precipitation measurement core spacecraft

The Dual-frequency Precipitation Radar (DPR) installed on the Global Precipitation Measurement (GPM) core satellite is being developed by JAXA and NICT. This paper describes mission objectives, technical performance, resource allocation, critical design, proto-flight test (PFT) of the DPR instrument and satellite system test status. The DPR system PFT has completed in February 2012. DPR has handed over to NASA and integration of the DPR to the GPM core spacecraft have completed in May 2012. GPM core spacecraft satellite system test has started at NASA Goddard Space Flight Center. After completion of all satellite system tests, the GPM core spacecraft will be sent to JAXA Tanegashima Space Center and launched by H-IIA launch vehicle.

Dual-frequency rain profiling method without the use of surface reference technique

A method to estimate the drop size distribution (DSD) parameters for dual-frequency radar observations that does not rely on the surface echoes is proposed. The method adjusts the esti- mates of attenuation factor at the surface iteratively until these esti- mates retrieve the reflectivity factors that are equal to the original measured reflectivity factors. In this iteration method, the back- ward-recursion equations are used as a main routine to calculate the DSD parameters for each range bin. The estimates of attenua- tion factor at the surface are obtained from these DSD parameters. The method is applied to the airborne radar data from the CaPE experiment in 1991. The comparison between the results derived from the surface reference technique and those derived from the proposed method is presented and discussed.

Estimation of PWC gradients over the Kanto Plain using GPS data: Validation and possible meteorological implications

Simultaneous GPS and water vapor radiometer (WVR) observations were carried out in Tsukuba during May–June 1998, for the validation of precipitable water content (PWC) gradients estimated from single-site GPS data. Slant path PWC observed by WVR were fitted into hourly PWC gradients (WVR gradients) using the least-square method. GPS PWC gradients were retrieved from tropospheric delay gradients that were estimated with GIPSY OASYS 2 package (GIPSY gradients). The results indicate that GIPSY gradients had good, linear correlation with WVR gradients, especially for a large gradient range. Both gradients had spike-shaped, short time-scale (∼ hours) peaks which were mostly associated with synoptic fronts. The GIPSY gradients were also compared with meso-scale PWC gradients calculated from zenith wet delay data of GPS network (NET gradients). The results show that GIPSY gradients did not have very good correlation with NET gradients, and that significant meso-scale discrepancy existed between the two gradients for a cold frontal case on 19 June 1998. One possible reason for this discrepancy is vertical differences in RH gradients, because GIPSY gradients are sensitive to RH gradients around the scale height of humidity (∼2500 m) while RH gradients in lowermost level have largest weights for NET gradients. To study PWC gradients associated with the fronts, GPS gradients were compared with other meteorological data over the Kanto Plain for two frontal cases. The results indicate that large PWC gradient zones with horizontal scale of about several tens kilometers in cross-frontal directions were collocated with the surface wind shear zones of the fronts. This suggests that the large PWC gradients were due to humidity discontinuity around the fronts.