260
11.5
C. Simmer
Satellite radiometers with precipitation-sensing
capabilities
The VIS/IR techniques are applicable to dual-channel data of the common geostationary and
polar-orbiting satellites, which are in orbit since the early days of satellite remote sensing beginning in the sixties of this century. Today five operational geostationary satellites (METEOSAT,
GOES-E, GOES-W, GMS, and INDSAT) are almost currently in orbit and provide visible and
infrared window measurements at least once an hour up to about 50° latitude. The data gaps
in the high latitudes are filled by at least two operational NOAA (National Oceanographic and
Atmospheric Administration) polar orbiting satellites. Additional measurements are available
by similar russian polar orbiters of the METEOR-type and a range of experimental satellites.
Longer term microwave observations of precipitation began 1972 with the single channel (19.35
GHz, horizontally polarized) cross-track scanning ESMR (Electronically Scanned Micowave
Radiometer) on Nimbus-5 (Wilheit et al., 1976). Three years later another ESMR with 37 GHz,
dual-polarization, was launched on Nimbus-7. For the first time a conical scan geometry was
used to accomplish a constant nadir view angle of 50°. Application for rainrate retrieval were
shown e.g. by Weinman and Guetter (1977) and Rodgers et al. (1979). Preceeded by the SMMR
(Scanning Multichannel Microwave Radiometer) instrument on Seasat, which functioned only
for three months (see Gloersen and Barath (1977) for applications to rainrate retrieval), SMMR
on Nimbus-7 provided five years of dual-polarized microwave measurements at 6.6, 10, 18, 21,
and 37 GHz, which have been extensively used and is still used for rainrate retrieval over ocean
(e.g. Spencer et al., 1983a; Petty and Katsaros,1990) and land surfaces (e.g. Spencer et al.,
1983b ).
Without any gap SMMR was followed by the SSM/I (Special Sensor Microwave/Imager) on the
operational DMSP (Defense Meteorological Satellite Program) series of the U.S. DoD (Departement of Defense). SSM/I comprises 7 channels (19 GHz, 37 GHz, and 85 GHz dual-polarized,
22 GHz only vertically polarized) and measures at a constant view angle of 53° over a swath
width of 1400 km. Since the beginning of the nineties always at least two DMSP satellites are
in operational orbit (currently DMSP-F10, DMSP-F12, DMSP-F13). Most of the algorithms
discussed in the following sections have been derived for SSM/I. In addition to the SSM/I
instrument the DMSP satellites carry also the microwave sounders SSM/T (for temperature
profiling) and SSM/T2 (for water vapour profiling), and the VIS/IR OLS (Operational Line
Scanner) radiometer. Attempts to use these radiometers together with the SSM/I for precipitation retrieval are currently studied.
It should be mentioned that other microwave radiometers suitable for precipitation retrieval
(e.g. MSR (Microwave Scanning Radiometer) on the Japanese MOS (Marine Observing Satellite) satellites, SAMIR (Satellite Microwave Radiometer) on the Indian Bhashkara satellites,
ATSR (Along-Track Scanning Radiometer) on the European ERS (European Research Satellite) satellites) have been or still are in orbit, but due to the restricted availability of the data
these instruments have not been much studied.
In the near future additional suitable measurements will be available from the AMSU (Advanced Microwave Sounding Unit) radiometer on the NOAA operational satellites, TMI (TRMM
Microwave Imager) on the TRMM satellite, and MIMR (Multichannel Imaging Microwave Radiometer) on the planned European polar orbiting METOP satellite series.
11.5
C. Simmer
Satellite radiometers with precipitation-sensing
capabilities
The VIS/IR techniques are applicable to dual-channel data of the common geostationary and
polar-orbiting satellites, which are in orbit since the early days of satellite remote sensing beginning in the sixties of this century. Today five operational geostationary satellites (METEOSAT,
GOES-E, GOES-W, GMS, and INDSAT) are almost currently in orbit and provide visible and
infrared window measurements at least once an hour up to about 50° latitude. The data gaps
in the high latitudes are filled by at least two operational NOAA (National Oceanographic and
Atmospheric Administration) polar orbiting satellites. Additional measurements are available
by similar russian polar orbiters of the METEOR-type and a range of experimental satellites.
Longer term microwave observations of precipitation began 1972 with the single channel (19.35
GHz, horizontally polarized) cross-track scanning ESMR (Electronically Scanned Micowave
Radiometer) on Nimbus-5 (Wilheit et al., 1976). Three years later another ESMR with 37 GHz,
dual-polarization, was launched on Nimbus-7. For the first time a conical scan geometry was
used to accomplish a constant nadir view angle of 50°. Application for rainrate retrieval were
shown e.g. by Weinman and Guetter (1977) and Rodgers et al. (1979). Preceeded by the SMMR
(Scanning Multichannel Microwave Radiometer) instrument on Seasat, which functioned only
for three months (see Gloersen and Barath (1977) for applications to rainrate retrieval), SMMR
on Nimbus-7 provided five years of dual-polarized microwave measurements at 6.6, 10, 18, 21,
and 37 GHz, which have been extensively used and is still used for rainrate retrieval over ocean
(e.g. Spencer et al., 1983a; Petty and Katsaros,1990) and land surfaces (e.g. Spencer et al.,
1983b ).
Without any gap SMMR was followed by the SSM/I (Special Sensor Microwave/Imager) on the
operational DMSP (Defense Meteorological Satellite Program) series of the U.S. DoD (Departement of Defense). SSM/I comprises 7 channels (19 GHz, 37 GHz, and 85 GHz dual-polarized,
22 GHz only vertically polarized) and measures at a constant view angle of 53° over a swath
width of 1400 km. Since the beginning of the nineties always at least two DMSP satellites are
in operational orbit (currently DMSP-F10, DMSP-F12, DMSP-F13). Most of the algorithms
discussed in the following sections have been derived for SSM/I. In addition to the SSM/I
instrument the DMSP satellites carry also the microwave sounders SSM/T (for temperature
profiling) and SSM/T2 (for water vapour profiling), and the VIS/IR OLS (Operational Line
Scanner) radiometer. Attempts to use these radiometers together with the SSM/I for precipitation retrieval are currently studied.
It should be mentioned that other microwave radiometers suitable for precipitation retrieval
(e.g. MSR (Microwave Scanning Radiometer) on the Japanese MOS (Marine Observing Satellite) satellites, SAMIR (Satellite Microwave Radiometer) on the Indian Bhashkara satellites,
ATSR (Along-Track Scanning Radiometer) on the European ERS (European Research Satellite) satellites) have been or still are in orbit, but due to the restricted availability of the data
these instruments have not been much studied.
In the near future additional suitable measurements will be available from the AMSU (Advanced Microwave Sounding Unit) radiometer on the NOAA operational satellites, TMI (TRMM
Microwave Imager) on the TRMM satellite, and MIMR (Multichannel Imaging Microwave Radiometer) on the planned European polar orbiting METOP satellite series.