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Retrieving Cloud Ice Water, Cloud Liquid Water, and other Cloud Parameters from GPS Radio Occultation and Satellite Microwave Imager/Sounder in Heavy Precipitation


OBJECTIVE: Develop techniques to improve the diagnosis and forecast of cloud parameters associated with the transmission and emission of polarized radiances through all weather conditions, including heavy precipitation. DESCRIPTION: Remarkable advances in remote sensing technology have occurred since the first applications of the formal solutions of radiative transfer to cloudy atmospheres (for example, Liou, 1973). The capability of current and future remote space-based sensors to measure polarized radiative information correlates well with the theoretical development of polarized radiative transfer in the vertically-layered atmosphere (Weng, 1992). Microwave emissions from precipitating clouds associated with moderate precipitation rates penetrate non-precipitating clouds. These emissions can be detected and measured by satellite microwave sounding instruments. Such passive measurements at mm-wave frequencies can be used to derive vertical profiles of cloud liquid water content (CLW) and cloud ice water content (IWC) (Weng and Grody, 1994); (Weng and Grody, 2000). Recent studies have shown that GPS radio signals are sensitive to clouds, as well as refractive bending, in heavy-precipitation conditions (Lin et al, 2010). Extracting IWC and CLW from GPS Radio Occultation (GPS RO) (in addition to temperature and humidity) in heavy precipitation conditions is a unique and un-explored area. GPS RO can complement satellite passive microwave observations as well as other types of sensor measurements (Lin et al, 2010). The new capability of COSMIC-2 (Cook et al, 2011), where a phased array receiver is employed to increase the gain in the lower troposphere and improve GPS RO measurement accuracy down to the surface, will also allow low-level cloud parameters to be diagnosed. While this may be a good approximation in most cases, it could fail in heavy precipitation due to attenuation over long slant paths at frequencies near 1.1 GHz. To produce the CLW, IWC, and other cloud parameters, a numerically-based data assimilation system capable of using various measurements from satellite remote sensors to produce gridded spatial distributions of cloud variables using forward integration may also be desirable. Such a system should be adaptive and capable of handling satellite radiances sensed with various orientation angles. A variety of theoretical and technological considerations can also be applied relating to scattering effects of clouds on the remote measurements. An advantage to using a data assimilation system is the ability to produce gridded fields of the cloud parameters. While the data assimilation system is not required, proposers might also wish to consider this. AFRL Relevance: AFRL (Space Vehicles Directorate) maintains the MODerate Resolution Atmospheric TRANsmission Model (MODTRAN). MODTRAN is used in a myriad of critical DOD remote sensing applications (Anderson et al, 2012). MODTRAN is also used by the armed services of major U.S. allies. Retrievals developed through this SBIR topic can be used to improve MODTRAN"s diagnosis of scattering, absorption, and emission associated with clouds and precipitation. PHASE I: Develop a retrieval system design which can retrieve the cloud parameters needed for polarized radiative transfer models. Deliverable: Demonstrate the physical applicability and accuracy needed to meet radiative transfer model requirements. PHASE II: Complete, implement, and assess the system used for cloud parameter retrievals. Validate and verify cloud properties retrieval according to microphysical criteria and usability in radiative transfer models. Deliverable: Cloud parameter retrievals which also demonstrate the suitability for using microwave satellite and GPS RO observations to monitor the global cloud distributions. PHASE III: Improved numerical weather prediction model initialization and parameterization. (2) Performance assessment of RF communications networks. (3) Improved characterization of polarized rad transfer through cloudy atmospheres.Similar applications for Commercial satellite industry is envisioned. REFERENCES: 1. Anderson, G., T. Cooley, J. van den Bosch, A. Berk, M. Fox, and D. Dion, 2012: 34th Review of Atmospheric Transmission Models Meeting, Final Program. Albuquerque, NM, 21 pp. 2. Cook, K.L.B., P. Wilczynski, C.J. Fong, N.L. Yen, and G.S. Chang, 2011: The Constellation Observing System for Meteorology Ionosphere and Climate Follow-On Mission. Aerospace Conf. 2011, IEEE, pp. 1-7. 3. Lin, L, X. Zou, R. Anthes, and Y.-H. Kuo, 2010: COSMIC GPS radio occultation temperature profiles in clouds. Mon. Wea. Rev., 138, 1104-1118. 4. Liou, K.N., 1973: A numerical experiment on Chandrasekhar"s discrete-ordinate method for radiative transfer: Application to cloudy and hazy atmospheres. J. Atmos. Sci., 30, 1303-1326. 5. Weng, F., 1992: A multi-layered discrete-ordinate method for vector radiative transfer in a vertically-inhomogeneous emitting and scattering atmosphere -1. Theory. J. Quant. Spectrosc. Radiat. Transfer. 47, 19-33. 6. Weng, F., and N.C. Grody, 1994: Retrieval of cloud liquid water using the special sensor microwave imager (SSM/I)..J. Geophys. Res., 99, 25535-25551. 7. Weng, F., and N.C. Grody, 2000: Retrieval of ice cloud parameters using a microwave imaging radiometer. J. Atmos. Sci., 57, 1069-1081.
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