A Microwave Occultation Observing System Optimized to Characterize Atmospheric Water, Temperature, and Geopotential via Absorption

Abstract

A new remote sensing concept extrapolated from the GPS occultation concept is presented in which the signal frequencies are chosen to determine atmospheric water, temperature, and the geopotential of atmospheric pressure surfaces. Using frequencies near the 22-and 183-GHz water lines allows not only the speed of light to be derived as a GPS occultation but also derivation of profiles of absorption caused by atmospheric water. Given the additional water information, moisture and temperature as well as the geopotential of pressure surfaces can be separated and solved for. Error covariance results indicate that the accuracies of individual water profiles will be 0.5%-3% extending from roughly 1-75-km altitude. Temperature accuracies of individual profiles will be sub-Kelvin from ϳ1to 70-km altitude depending on latitude and season. Accuracies of geopotential heights of pressure will be 10-20 m from the surface to 60-km altitude. These errors are random such that climatological averages derived from this data will be significantly more accurate. Owing to the limb-viewing geometry, the along-track resolution is comparable to the 200-300 km of the GPS occultation observations, but the shorter 22-and 183-GHz wavelengths improve the diffraction-limited vertical resolution to 100-300 m. The technique can be also used to determine profiles of other atmospheric constituents such as upper-tropospheric and stratospheric ozone by using frequencies near strong lines of that constituent. The combined dynamic range, accuracy, vertical resolution, and ability to penetrate clouds far surpass that of any present or planned satellite sensors. A constellation of such sensors would provide an all-weather, global remote sensing capability including full sampling of the diurnal cycle for process studies related to water, climate research, and weather prediction in general.

Greenhouse gas profiling by infrared-laser and microwave occultation: retrieval algorithm and demonstration results from end-to-end simulations

“…This target species transmission is the pure transmission due to a single GHG (e.g., 12 CO 2 ), with effectively negligble influence of foreign species. The target species transmission is then used, together with the IR impact parameter and the IR refractivity, to retrieve the target species absorption coefficient on the IR altitude grid by use of the "absorptive" Abel transform (Kursinski et al, 2002;Schweitzer et al, 2011b). Finally, the GHG/isotope volume mixing ratio profile is derived from the target species absorption coefficient and a modeled absorption cross section of the target species for which we employ RFM based on the initial/background target species profile and the p and T profiles from LMO; likewise it could also be the mole fraction profile.…”

“…To isolate the absorption due to the target GHG from the absorption of foreign species and broadband atmospheric effect, an adjacent pair of signals, one "absorption signal" (at the center of an absorption line of a target species) and one "reference signal" (off-line of any trace species absorption) is employed using a differential absorption principle (Kursinski et al, 2002;Gorbunov and Kirchengast, 2007;Kirchengast et al, 2010a;Kirchengast and Schweitzer, 2011;Schweitzer et al, 2011a), which will be explained in detail in Sect. 3.…”

“…The LMO part of LMIO has substantial heritage from a range of studies over the recent decade (Kursinski et al, 2002Herman et al, 2004;Kirchengast and Hoeg, 2004;Kirchengast, 2005, 2007) and very recently a detailed LMO algorithm description and performance analysis was provided by Schweitzer et al (2011b). This heritage work established well the expected performance of LMO for accurate thermodynamic state profiling in the UTLS, which serves as the basis for the LIO-related GHG profiling introduced here.…”

Development and testing of the Active Temperature, Ozone and Moisture Microwave Spectrometer (ATOMMS) cm and mm wavelength occultation instrument

“…This ignores possible errors in the spectroscopic model. The ability to measure line shape is a key advantage of ATOMMS over GPS RO because it enables ATOMMS to determine the upper boundary of the hydrostatic integral directly from the ATOMMS observations (Kursinski et al, 2002) without relying on an NWP analysis or climatology to set the upper boundary as GPS RO must do. This GPS RO sensitivity to systematic biases in those analyses limits the utility of GPS RO for climate in the mid stratosphere and above (e.g., Ho et al, 2009).…”

“…When implemented as a constellation of small spacecraft analogous to the present COSMIC GPS RO mission, ATOMMS will yield an unprecedented combination of performance by delivering measured atmospheric profiles that are unbiased by a priori model assumptions with complete global and diurnal coverage, which are critical for monitoring and understanding climate. ATOMMS achieves its unique performance via differential absorption by measuring signal levels at two or more frequencies simultaneously in order to reduce or eliminate many types of common mode noise (Kursinski et al, 2002(Kursinski et al, , 2004). The ATOMMS prototype instrument that we are developing at the University of Arizona probes atmospheric absorption within two spectral intervals near the 22 GHz and 183 GHz absorption lines of water vapor.…”