NCDC: OPTICAL RAIN GAUGE DATA

RESEARCH VESSELS - OPTICAL RAIN GAUGE DATA
KAPINGAMARANGI - DISDROMETER AND TIPPING BUCKET DATA

B. Fisher (NASA/GSFC, USA)

Announced availability: 1 January 1994

Data Access

Optical Rain Gauge (ORG) data for COARE research vessels, Atlas moorings and IMET buoy, Kapingamarangi and Manus are available via anonymous FTP from ftp://radar.gsfc.nasa.gov/pub/TOGA_COARE/gauge or via the World Wide Web from http://trmm-fc.gsfc.nasa.gov/trmm_gv/field_campaigns/toga_coare/gauge/gauge.html.

Background

The optical precipitation sensors measure rainfall by detecting the optical irregularities induced within the sample volume by hydrometeors passing through a beam of partially coherent infrared radiation. These irregularities are known as scintillation and produce an electromagnetic disturbance that is detected by the instrument. By measuring the intensity of the scintillations characteristic of rainfall, the actual rainfall rate is determined.

The ORG sensor consists of:

IRED modulator and IR light Emitting Diode
receiver optical assembly
PIN photodetector and preamplifier
automatic Gain Controlled (AGC) normalizer
signal processing subsystem

ORG Specifications:

Dynamic Range:

0.5 mm/h to 1600 mm/h

Accuracy
1% over the range 10 to 100 mm/hr

5% over the range 1 to 500 mm/hr

10% over the range .5 to 1600 mm/hr

Fog, Haze, Wind
Negligible effect on sensor accuracy

Data File Information

The data products consist primarily of 1-minute rainrate averages. Le Noroit data consist of 5-minute averaged rainfall data. Each site contains README files describing the data format. In addition the navigation data for each moving site is included as a separate file which provides the recorded ship coordinates as obtained from GPS updates. In some cases, surface met data are also included.

Data are available for the R/Vs Alis, Franklin, Hakuho-maru, Keifu-maru, Kexue, Le Noroit, Moana Wave, Natsushima, Shiyan #3, Vickers, Wecoma, and Xiangyanghong #5. Data are also available for some of the Atlas and the IMET mooring and for Kapingamarangi and Manus. A hard copy of a Optical Rain Gauge Workshop Report held at NOAA/PMEL in March/April 1993 is available through the TOGA COARE International Project Office (TCIPO).

For more information, please contact:

Brad Fisher
NASA Goddard Space Flight Center
Greenbelt, MD 20910
USA

email: fisher@echo.gsfc.nasa.gov
Phone: (301) 286-8912

References

McPhaden, M. J., H. B. Milburn, P. A. Arkin, O. W. Thiele, J. Wilkerson, and W. Krajewski, 1993: Moored optical rain gage measurements from the equatorial Pacific ocean. Proceedings from the Fourth Int'l Conf. on Precipitation: Hydrological and Meteorological Aspects of Rainfall Measurements and Predictability. University of Iowa, Iowa City, Iowa.

Short, D. A., and O. W. Thiele, 1993: TRMM validation program. Proceedings, 1993 International Geoscience and Remote Sensing Symposium (IGARSS'93), Tokyo, Japan, page 614.

Short, D. A., O. W. Thiele, and M. J. McPhaden, editors, 1994: Optical Rain Gauge Performance (Second Workshop on Optical Rain Gauge Measurements). NASA Conference Publication 3288, Proceedings of a workshop held at NASA/GSFC, April 21-22, 76 pp.

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