The Experts below are selected from a list of 6792 Experts worldwide ranked by ideXlab platform
David B Wolff - One of the best experts on this subject based on the ideXlab platform.
-
Evaluation of TRMM Rain Estimates Using Ground Measurements over Central Florida
Journal of Applied Meteorology and Climatology, 2012Co-Authors: Jianxin Wang, David B WolffAbstract:AbstractThis study evaluates space-based rain estimates from the Tropical Rainfall Measuring Mission (TRMM) Satellite using ground-based measurements from the radar (GR) and tipping-bucket rain gauges (TG) over the TRMM Ground Validation (GV) site at Melbourne, Florida. The Satellite rain products are derived from the TRMM Microwave Imager (TMI), precipitation radar (PR), and combined (COM) rain algorithms using observations from both instruments. The TRMM Satellite and GV rain products are spatiotemporally matched and are intercompared at multiple time scales over the 12-yr period from 1998 to 2009. On monthly and yearly scales, the TG agree excellently with the GR because the GR rain rates are generated using the TG data as a constraint on a monthly basis. However, large disagreements exist between the GR and TG at shorter time scales because of their significantly different spatial and temporal sampling modes. The yearly biases relative to the GR for the PR and TMI are generally negative, with a few exceptions. The COM bias fluctuates from year to year over the 12-yr period. The PR, TMI, and COM are in good overall agreement with the GR in the lower range of rain rates, but the agreement is notably worse at higher rain rates. The diurnal cycle of rainfall is captured well by all products, but the peak Satellite-derived rainfall (PR, TMI, and COM) lags the peak from the ground measurements (GR and TG) by ~1 h.
-
Availability of High-Quality TRMM Ground Validation Data from Kwajalein, RMI: A Practical Application of the Relative Calibration Adjustment Technique
Journal of Atmospheric and Oceanic Technology, 2009Co-Authors: David A Marks, David B Wolff, David S. Silberstein, Ali Tokay, Jason L. Pippitt, Jianxin WangAbstract:Abstract Since the Tropical Rainfall Measuring Mission (TRMM) Satellite launch in November 1997, the TRMM Satellite Validation Office (TSVO) at NASA Goddard Space Flight Center (GSFC) has been performing quality control and estimating rainfall from the KPOL S-band radar at Kwajalein, Republic of the Marshall Islands. Over this period, KPOL has incurred many episodes of calibration and antenna pointing angle uncertainty. To address these issues, the TSVO has applied the relative calibration adjustment (RCA) technique to eight years of KPOL radar data to produce Ground Validation (GV) version 7 products. This application has significantly improved stability in KPOL reflectivity distributions needed for probability matching method (PMM) rain-rate estimation and for comparisons to the TRMM precipitation radar (PR). In years with significant calibration and angle corrections, the statistical improvement in PMM distributions is dramatic. The intent of this paper is to show improved stability in corrected KPOL r...
-
Comparisons of Instantaneous TRMM Ground Validation and Satellite Rain-Rate Estimates at Different Spatial Scales
Journal of Applied Meteorology and Climatology, 2008Co-Authors: David B Wolff, Brad L FisherAbstract:Abstract This study provides a comprehensive intercomparison of instantaneous rain rates observed by the two rain sensors aboard the Tropical Rainfall Measuring Mission (TRMM) Satellite with ground data from two regional sites established for long-term ground validation: Kwajalein Atoll and Melbourne, Florida. The Satellite rain algorithms utilize remote observations of precipitation collected by the TRMM Microwave Imager (TMI) and the Precipitation Radar (PR) aboard the TRMM Satellite. Three standard level II rain products are generated from operational applications of the TMI, PR, and combined (COM) rain algorithms using rain information collected from the TMI and the PR along the orbital track of the TRMM Satellite. In the first part of the study, 0.5° × 0.5° instantaneous rain rates obtained from the TRMM 3G68 product were analyzed and compared to instantaneous Ground Validation (GV) program rain rates gridded at a scale of 0.5° × 0.5°. In the second part of the study, TMI, PR, COM, and GV rain rates were spatiotemporally matched and averaged at the scale of the TMI footprint (∼150 km2). This study covered a 6-yr period (1999–2004) and consisted of over 50 000 footprints for each GV site. In the first analysis, the results showed that all of the respective rain-rate estimates agree well, with some exceptions. The more salient differences were associated with heavy rain events in which one or more of the algorithms failed to properly retrieve these extreme events. Also, it appears that there is a preferred mode of precipitation for TMI rain rates at or near 2 mm h−1 over the ocean. This mode was noted over ocean areas of Kwajalein and Melbourne and has been observed in TRMM tropical–global ocean areas as well.
-
comparisons of instantaneous TRMM ground validation and Satellite rain rate estimates at different spatial scales
Journal of Applied Meteorology and Climatology, 2007Co-Authors: David B Wolff, Brad L FisherAbstract:Abstract This study provides a comprehensive intercomparison of instantaneous rain rates observed by the two rain sensors aboard the Tropical Rainfall Measuring Mission (TRMM) Satellite with ground data from two regional sites established for long-term ground validation: Kwajalein Atoll and Melbourne, Florida. The Satellite rain algorithms utilize remote observations of precipitation collected by the TRMM Microwave Imager (TMI) and the Precipitation Radar (PR) aboard the TRMM Satellite. Three standard level II rain products are generated from operational applications of the TMI, PR, and combined (COM) rain algorithms using rain information collected from the TMI and the PR along the orbital track of the TRMM Satellite. In the first part of the study, 0.5° × 0.5° instantaneous rain rates obtained from the TRMM 3G68 product were analyzed and compared to instantaneous Ground Validation (GV) program rain rates gridded at a scale of 0.5° × 0.5°. In the second part of the study, TMI, PR, COM, and GV rain rates ...
-
Climatological Processing of Radar Data for the TRMM Ground Validation Program
2000Co-Authors: Mark S Kulie, Michael Robinson, David A Marks, Brad S Ferrier, David B Wolff, Brad L Fisher, David S. Silberstein, Jianxin Wang, Eyal Amitai, David AugustineAbstract:The Tropical Rainfall Measuring Mission (TRMM) Satellite was successfully launched in November, 1997. The main purpose of TRMM is to sample tropical rainfall using the first active spaceborne precipitation radar. To validate TRMM Satellite observations, a comprehensive Ground Validation (GV) Program has been implemented. The primary goal of TRMM GV is to provide basic validation of Satellite-derived precipitation measurements over monthly climatologies for the following primary sites: Melbourne, FL; Houston, TX; Darwin, Australia; and Kwajalein Atoll, RMI. As part of the TRMM GV effort, research analysts at NASA Goddard Space Flight Center (GSFC) generate standardized TRMM GV products using quality-controlled ground-based radar data from the four primary GV sites as input. This presentation will provide an overview of the TRMM GV climatological processing system. A description of the data flow between the primary GV sites, NASA GSFC, and the TRMM Science and Data Information System (TSDIS) will be presented. The radar quality control algorithm, which features eight adjustable height and reflectivity parameters, and its effect on monthly rainfall maps will be described. The methodology used to create monthly, gauge-adjusted rainfall products for each primary site will also be summarized. The standardized monthly rainfall products are developed in discrete, modular steps with distinct intermediate products. These developmental steps include: (1) extracting radar data over the locations of rain gauges, (2) merging rain gauge and radar data in time and space with user-defined options, (3) automated quality control of radar and gauge merged data by tracking accumulations from each instrument, and (4) deriving Z-R relationships from the quality-controlled merged data over monthly time scales. A summary of recently reprocessed official GV rainfall products available for TRMM science users will be presented. Updated basic standardized product results and trends involving monthly accumulation, Z-R relationship, and gauge statistics for each primary GV site will be also displayed.
Nobuhiro Takahashi - One of the best experts on this subject based on the ideXlab platform.
-
Surface Echo Characteristics Derived From the Wide Swath Experiment of the Precipitation Radar Onboard TRMM Satellite During Its End-of-Mission Operation
IEEE Transactions on Geoscience and Remote Sensing, 2017Co-Authors: Nobuhiro TakahashiAbstract:The purpose of this paper is to assess the height and strength of the surface echo clutter from the wide swath operation of a future spaceborne precipitation radar (PR) using the wide swath observation data during the end-of-mission experiment of the PR onboard the Tropical Rainfall Measuring Mission (TRMM) Satellite. In this experiment, the maximum incident angle was expanded up to 32.5° from nadir, while the maximum incident angle is 18° for normal observation of the TRMM/PR. Although the results show that the clutter height monotonically increases with the incident angle as expected, the clutter height is suppressed for wide angles because of the weakening of the surface echo strength. As a result, the clutter height is less than 2 km if the rain echo is 15 dB higher than the noise level (i.e., about 34 dBZ echo for the TRMM/PR). The clutter height and the normalized backscattering cross section (0r0) are compared between ocean and land. Suppression of the clutter height is significant over ocean because of the relatively smaller 0r0 (smoother surface) and flat surface (no topography). The impact of the 0r0 for wide swath observation on the rain retrieval algorithm, especially on the surface reference technique, is also examined. The operation with a swath width almost twice the current TRMM/PR is achievable if relatively intense echoes are targeted; however, relatively weak and shallow precipitation will be masked by the clutter.
-
Estimation of Path-Integrated Attenuation and Its Nonuniformity From TRMM/PR Range Profile Data
IEEE Transactions on Geoscience and Remote Sensing, 2006Co-Authors: Nobuhiro Takahashi, H. Hanado, T. IguchiAbstract: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 PR's 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
-
Four-year result of external calibration for Precipitation Radar (PR) of the Tropical Rainfall Measuring Mission (TRMM) Satellite
IEEE Transactions on Geoscience and Remote Sensing, 2003Co-Authors: Nobuhiro Takahashi, Hiroshi Kuroiwa, Toneo KawanishiAbstract:External calibration experiments using active radar calibrator (ARC) were conducted for the calibration of the Precipitation Radar (PR) of the Tropical Rainfall Measuring Mission (TRMM) Satellite from 1998 to 2001. Three modes of ARC operation are used for the experiment: the ARC transmitter mode for the receiver system of PR, the ARC receiver mode for the transmitter of PR, and the transponder mode for the overall system of PR. The experiments were conducted several times a year. The results of the experiments show that the performance of the PR is close to the prelaunch performance and that PR has been working stably for four years.
-
Two year operation of the Precipitation Radar (PR) onboard TRMM Satellite
IGARSS 2000. IEEE 2000 International Geoscience and Remote Sensing Symposium. Taking the Pulse of the Planet: The Role of Remote Sensing in Managing t, 1Co-Authors: Nobuhiro Takahashi, Toneo Kawanishi, Masahiro Kojima, K. Oikawa, Hiroshi Kuroiwa, Ken'ichi Okamoto, Toshiaki Kozu, Minoru Okumura, H. Nakatsuka, K. NishikawaAbstract:The Tropical Rainfall Measuring Mission (TRMM) Satellite was successfully launched in November 1997. Since then, Precipitation Radar (PR) onboard TRMM has been producing unique and useful global data sets of the rainfall. After two year operation of its nominal 3 years' mission life, the PR is showing very stable performance. For example, power monitor shows that SSPA has been working stable and temperature monitor shows short term cycle (depending on Satellite orbital period) and long term cycle (depending on beta angle) within designed temperature range. Internal calibration has been performed everyday and its results show that receiver system is working stable and is not needed to change calibration table after setting internal attenuator as 9 dB in February 1998. Overall performance of the PR is examined by external calibration experiments with active radar calibrator (ARC) which has been performed every other month. The results of the external calibration experiment confirmed the stability of the PR.
-
Utilization of range profile data of surface echo from TRMM/PR
IGARSS 2003. 2003 IEEE International Geoscience and Remote Sensing Symposium. Proceedings (IEEE Cat. No.03CH37477), 1Co-Authors: Nobuhiro Takahashi, H. Hanado, T. IguchiAbstract:The use of range profile data of surface echo in order to improve the current standard algorithm for the Precipitation Radar (PR) of the Tropical Rainfall Measuring Mission (TRMM) Satellite is shown in this study. For example, the surface range bin is determined more precisely using profile data over ocean. The surface echo profile is also used to estimate the path integrated attenuation (PIA) and its variation within a footprint of PR and to estimate the geographical information.
Toneo Kawanishi - One of the best experts on this subject based on the ideXlab platform.
-
Four-year result of external calibration for Precipitation Radar (PR) of the Tropical Rainfall Measuring Mission (TRMM) Satellite
IEEE Transactions on Geoscience and Remote Sensing, 2003Co-Authors: Nobuhiro Takahashi, Hiroshi Kuroiwa, Toneo KawanishiAbstract:External calibration experiments using active radar calibrator (ARC) were conducted for the calibration of the Precipitation Radar (PR) of the Tropical Rainfall Measuring Mission (TRMM) Satellite from 1998 to 2001. Three modes of ARC operation are used for the experiment: the ARC transmitter mode for the receiver system of PR, the ARC receiver mode for the transmitter of PR, and the transponder mode for the overall system of PR. The experiments were conducted several times a year. The results of the experiments show that the performance of the PR is close to the prelaunch performance and that PR has been working stably for four years.
-
development of precipitation radar onboard the tropical rainfall measuring mission TRMM Satellite
IEEE Transactions on Geoscience and Remote Sensing, 2001Co-Authors: Toshiaki Kozu, Toneo Kawanishi, Masahiro Kojima, K. Oikawa, Hiroshi Kuroiwa, Ken'ichi Okamoto, Minoru Okumura, H. Nakatsuka, Hiroshi Kumagai, K. NishikawaAbstract:The precipitation radar (PR) onboard the Tropical Rainfall Measuring Mission (TRMM) Satellite is the first spaceborne radar to measure precipitation from space. The PR, operating at 13.8 GHz, is a 128-element active phased array that allows a fast and sophisticated cross-track scanning over a swath width of 215 km with a cross-range spatial resolution of about 4.3 km. The PR has a minimum detectable rain rate of 0.5 mm/h with range resolution of 250 m. In order to achieve a reliable and accurate rain echo data for three years mission life, functions for internal and external calibrations are implemented. Through a series of PR flight-model tests on the ground and an initial checkout just after the TRMM launch, it is confirmed that the PR functions properly and meets the performance requirements to quantitatively measure three-dimensional (3D) precipitation distribution from space.
-
On-orbit test and calibration results of TRMM precipitation radar
Microwave Remote Sensing of the Atmosphere and Environment, 1998Co-Authors: Toneo Kawanishi, Hiroshi Kuroiwa, Toshiaki Kozu, Yoshio Ishido, Toshihiko Umehara, Ken'ichi OkamotoAbstract:Precipitation radar (PR) on-board the Tropical Rainfall measuring Mission (TRMM) Satellite is the first rain radar to measure precipitation from space. After the successful launch of the TRMM Satellite in last November, initial on- orbit test and calibration of the PR were conducted for about two months. From these tests, it was confirmed that on-orbit performances of the PR are fundamentally coincident with those verified at ground test and satisfy the specifications.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
-
Precipitation radar onboard the Tropical Rainfall Measuring Mission (TRRM) Satellite
IGARSS '98. Sensing and Managing the Environment. 1998 IEEE International Geoscience and Remote Sensing. Symposium Proceedings. (Cat. No.98CH36174), 1998Co-Authors: Toneo Kawanishi, Masahiro Kojima, K. Oikawa, Hiroshi Kuroiwa, Ken'ichi Okamoto, Toshiaki Kozu, Minoru Okumura, H. Nakatsuka, Hiroshi Kumagai, K. NishikawaAbstract:The precipitation radar (PR) onboard the Tropical Rainfall Measuring Mission (TRMM) Satellite is the first rain radar to measure precipitation from space. After the successful launch of the TRMM Satellite in last November, initial checkout of the PR was conducted for about two months. From this checkout, it was confirmed that in-orbit performances of the PR satisfy the specifications.
-
Title: Development Results of TRMM Precipitation Radar
1997Co-Authors: K. Oikawa, Toneo Kawanishi, Masahiro Kojima, Hiroshi Kuroiwa, Toshiaki Kozu, Hamamatsu-cho Minato-ku, Nukui-kitamachi KoganeiAbstract:Precipitation radar (PR) has been developed by National Space Development Agency of Japan (NASDA) in cooperation with Communication Research Laboratory (CRL). PR was integrated onto Tropical Rainfall Measuring Mission (TRMM) Satellite and TRMM Satellite system test is ongoing by NASA. Throughout the various tests of PR, it was confirmed that PR satisfies its requirements.
James W Hardin - One of the best experts on this subject based on the ideXlab platform.
-
diurnal cycle of tropical precipitation in tropical rainfall measuring mission TRMM Satellite and ocean buoy rain gauge data
Journal of Geophysical Research, 2005Co-Authors: Kenneth P Bowman, Gerald R North, Craig J Collier, James W HardinAbstract:[1] The climatological diurnal cycle of precipitation in the tropics is analyzed using data from rain gauges on ocean buoys and Satellite measurements by the Tropical Rainfall Measuring Mission (TRMM) Satellite. The ocean buoy data are from the NOAA/Pacific Marine Environmental Laboratory Tropical Atmosphere-Ocean/Triangle Trans-Ocean buoy Network in the tropical Pacific Ocean. TRMM data are from the precipitation radar (PR) and the TRMM microwave imager (TMI). Climatological hourly mean precipitation rates are analyzed in terms of the diurnal and semidiurnal harmonics. Both data sets confirm an early morning peak in precipitation over ocean regions. The amplitude of the diurnal harmonic over the oceans is typically less than 25% of the mean precipitation rate. Over tropical land masses the rainfall peaks in the afternoon and evening hours. The relative amplitude of the diurnal harmonic over land is larger than over the ocean, often exceeding 50% of the mean rain rate. Previously noted differences between the TMI and PR rainfall retrievals persist in the diurnal cycle. On average the TMI measures more rainfall than the PR and has a larger diurnal variation. Phase differences between the two instruments do not show a consistent bias.
Ken'ichi Okamoto - One of the best experts on this subject based on the ideXlab platform.
-
development of precipitation radar onboard the tropical rainfall measuring mission TRMM Satellite
IEEE Transactions on Geoscience and Remote Sensing, 2001Co-Authors: Toshiaki Kozu, Toneo Kawanishi, Masahiro Kojima, K. Oikawa, Hiroshi Kuroiwa, Ken'ichi Okamoto, Minoru Okumura, H. Nakatsuka, Hiroshi Kumagai, K. NishikawaAbstract:The precipitation radar (PR) onboard the Tropical Rainfall Measuring Mission (TRMM) Satellite is the first spaceborne radar to measure precipitation from space. The PR, operating at 13.8 GHz, is a 128-element active phased array that allows a fast and sophisticated cross-track scanning over a swath width of 215 km with a cross-range spatial resolution of about 4.3 km. The PR has a minimum detectable rain rate of 0.5 mm/h with range resolution of 250 m. In order to achieve a reliable and accurate rain echo data for three years mission life, functions for internal and external calibrations are implemented. Through a series of PR flight-model tests on the ground and an initial checkout just after the TRMM launch, it is confirmed that the PR functions properly and meets the performance requirements to quantitatively measure three-dimensional (3D) precipitation distribution from space.
-
On-orbit test and calibration results of TRMM precipitation radar
Microwave Remote Sensing of the Atmosphere and Environment, 1998Co-Authors: Toneo Kawanishi, Hiroshi Kuroiwa, Toshiaki Kozu, Yoshio Ishido, Toshihiko Umehara, Ken'ichi OkamotoAbstract:Precipitation radar (PR) on-board the Tropical Rainfall measuring Mission (TRMM) Satellite is the first rain radar to measure precipitation from space. After the successful launch of the TRMM Satellite in last November, initial on- orbit test and calibration of the PR were conducted for about two months. From these tests, it was confirmed that on-orbit performances of the PR are fundamentally coincident with those verified at ground test and satisfy the specifications.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
-
Precipitation radar onboard the Tropical Rainfall Measuring Mission (TRRM) Satellite
IGARSS '98. Sensing and Managing the Environment. 1998 IEEE International Geoscience and Remote Sensing. Symposium Proceedings. (Cat. No.98CH36174), 1998Co-Authors: Toneo Kawanishi, Masahiro Kojima, K. Oikawa, Hiroshi Kuroiwa, Ken'ichi Okamoto, Toshiaki Kozu, Minoru Okumura, H. Nakatsuka, Hiroshi Kumagai, K. NishikawaAbstract:The precipitation radar (PR) onboard the Tropical Rainfall Measuring Mission (TRMM) Satellite is the first rain radar to measure precipitation from space. After the successful launch of the TRMM Satellite in last November, initial checkout of the PR was conducted for about two months. From this checkout, it was confirmed that in-orbit performances of the PR satisfy the specifications.
-
Development of an active radar calibrator for the TRMM precipitation radar
IEEE Transactions on Geoscience and Remote Sensing, 1995Co-Authors: Hiroshi Kumagai, Toshiaki Kozu, M. Satake, Hiroshi Hanado, Ken'ichi OkamotoAbstract: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 ARC's capability for the on-orbit TRMM-PR calibration.
-
Two year operation of the Precipitation Radar (PR) onboard TRMM Satellite
IGARSS 2000. IEEE 2000 International Geoscience and Remote Sensing Symposium. Taking the Pulse of the Planet: The Role of Remote Sensing in Managing t, 1Co-Authors: Nobuhiro Takahashi, Toneo Kawanishi, Masahiro Kojima, K. Oikawa, Hiroshi Kuroiwa, Ken'ichi Okamoto, Toshiaki Kozu, Minoru Okumura, H. Nakatsuka, K. NishikawaAbstract:The Tropical Rainfall Measuring Mission (TRMM) Satellite was successfully launched in November 1997. Since then, Precipitation Radar (PR) onboard TRMM has been producing unique and useful global data sets of the rainfall. After two year operation of its nominal 3 years' mission life, the PR is showing very stable performance. For example, power monitor shows that SSPA has been working stable and temperature monitor shows short term cycle (depending on Satellite orbital period) and long term cycle (depending on beta angle) within designed temperature range. Internal calibration has been performed everyday and its results show that receiver system is working stable and is not needed to change calibration table after setting internal attenuator as 9 dB in February 1998. Overall performance of the PR is examined by external calibration experiments with active radar calibrator (ARC) which has been performed every other month. The results of the external calibration experiment confirmed the stability of the PR.
