An investigation on the multiorder Fabry-Perot interferometer as a satellite-borne high-resolution atmospheric temperature sounder.

Abstract

With the development of high resolution atmospheric modeling and mesoscale numerical prediction models for weather forecasting,there is an increasing demand to improve the vertical resolution and retrieval accuracy of the present atmospheric temperature sounder. The most effective way to improve the vertical resolution and retrieval accuracy of atmospheric temperature sounding is to use high spectral resolution instruments. It is well known that carbon dioxide (CO$\sb2$) has a periodic spectrum in its P and R branches of the 15-$\mu$m and 4.3-$\mu$m bands. The Fabry-Perot interferometer (FPI) is a periodic, high resolution, and high throughput instrument. The use of FPI, denoted as the Multiorder Etalon Sounder (MOES), to observe the periodic CO$\sb2$ spectrum presents a novel approach to atmospheric temperature sounding. In this thesis project, the concept of vertical temperature profiling with the multiorder Fabry-Perot interferometer has been established. Suitable spectral regions and optimum FPI free spectral ranges have been calculated. A conceptual instrument design for a Low-Earth-Orbit (LEO) satellite has been carried out, critical instrumentation issues have been identified and discussed. Instrument performance has been simulated and compared with the current operational High Resolution Infrared Radiation Sounder (HIRS/2). The characteristics of 44 temperature sounding channels and 12 water vapor sounding channels have been studied, results indicate that MOES is capable of achieving some narrow and sharp weighting functions. Instrument sensitivity analysis indicates that to achieve a NE$\Delta$T of 0.2 K at T = 260 K, a 10 km nadir footprint, and synchronization with AMSU, at least a 12 inch (diameter) telescope is needed. The retrieval simulation studies show that MOES can provide much better temperature and water vapor profiles than HIRS/2. Because of the uniform vibrational-rotational band structures of carbon monoxide (CO) and nitrous oxide (N$\sb2$O), MOES is also a potentially feasible technique to measure the global tropospheric CO and N$\sb2$O concentrations. The characteristics of possible CO and N$\sb2$O sounding channels and instrument sensitivities have also been briefly discussed.