opportunities needs to be accompanied by supporting advances in infrastructure, including computers, communication technologies, and data-assimilation methods.

This chapter is not meant to be a comprehensive description of all important technologies or missions. It concentrates on technologies and missions that are currently scheduled to be transitioned into operations or tested in real time in order to determine their impact on operations.

ADVANCES IN SPACE-BASED MEASUREMENT TECHNOLOGIES

New space-based remote sensing, communication, and processing technologies are being demonstrated through a number of research and development programs. The next-generation National Polar-orbiting Operational Environmental Satellite System (NPOESS), a joint program of the DOD, NOAA, and NASA, represents a giant step forward in global weather sensing capability. Imaging Fourier transform spectrometers, providing hyperspectral imagery of the atmosphere with unprecedented resolution, are being developed to observe the dynamics of the three-dimensional thermodynamic structure of the troposphere with high spatial and temporal resolution from geostationary satellites. Complementing these thermodynamic observations, a constellation of small, polar-orbiting satellites will retrieve thermodynamic profiles from the tracked GPS radio signals as they are occulted behind Earth’s limb. Doppler light detection and ranging systems, or lidars, which observe aerosol motion from the spectral frequency change of the backscattered light generated by a laser, are under development for polar-orbiting satellites in order to observe the global tropospheric wind structure.

Scatterometers will provide surface wind data over the oceans. Lidars and radars will fly on low-altitude satellites for cloud, aerosol, and precipitation measurements, with the future possibility for high-vertical-resolution water vapor profiling. NPOESS will carry advanced instruments that detect the natural microwave radiation emitted by Earth’s surface and atmosphere. These instruments will enable atmospheric profiling through clouds and will provide surface wind and precipitation observations. Large, lightweight antenna systems are also under development, to enable similar microwave measurements from geostationary orbit for the monitoring of precipitation. These would also provide thermodynamic information below clouds in support of the infrared imaging spectrometer sounding systems. Dual-frequency radars will measure precipitation and associated latent heating rates. A visible-wavelength digital camera, which will sense lightning strokes, is also being developed to monitor convective storm dynamics from geostationary satellites. These new technologies (Kramer, 2001) are being developed during this decade through the U.S. New Millennium Program (NMP) and Earth System Science



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