Forward Model Development

3D polarised simulations of space-borne passive mm/sub-mm midlatitude cirrus observations: A case study Date: 27 September 2006 Global observations of ice clouds are needed to improve our understanding of their impact on earth’s radiation balance and the water-cycle. Passive mm/sub-mm has some advantages compared to other space-borne cloud-ice remote sensing techniques. This paper presents detailed simulated observations for three such instruments, AMSU-B, CIWSIR, and EOS-MLS. The Monte-Carlo radiative transfer code, ARTS-MC, makes proper account of polarisation and uses 3D spherical geometry. The actual field of view characteristics for each instrument are also accounted for. A 3D midlatitude cirrus scenario is used, which is derived from Chilbolton cloud radar data and a stochastic method for generating 3D ice water content fields. Although the main purpose of the work was to demonstrate the capability of accurately simulating observations of this type, the results suggest that cloud inhomogeneity will affect CIWSIR, and EOSMLS low tangent height observations via the beamfilling effect. Also, the results confirm that preferentially oriented ice crystals will produce significant polarisation effects. +Read more

The Clear-Sky Unpolarized Forward Model for the EOS Aura Microwave Limb Sounder (MLS) Date: May 2006 This paper describes the Earth Observing System (EOS) Aura Microwave Limb Sounder (MLS) forward model for a clear-sky atmosphere emitting unpolarized radiation. This model is used for the majority of the EOS MLS radiance calculations. The orbital and viewing geometry of MLS on Aura is such that a two-dimensional (vertical and line-of-sight, horizontal) forward model provides the most accurate basis for the inversion performed in retrievals. The model consists of atmospheric radiative transfer convolved with the instrumental field of view and the spectral response. An additional model relating the pointing heights supplied by the Aura satellite operations and MLS scan pointing encoders to the limb tangent pressure and atmospheric temperature is described. The analytic computation of Jacobians needed for retrievals is given. +Read more

EOS MLS Forward Model Polarized Radiative Transfer for Zeeman-Split Oxygen Lines Date: May 2006 This work supplements the Earth Observing System (EOS) Microwave Limb Sounder (MLS) clear-sky unpolarized forward model with algorithms for modeling polarized emission from the Zeeman-split 118.75-GHzO2 spectral line. The model accounts for polarization-dependent emission and for correlation between polarizations with complex, 2x2 intensity and absorption matrices. The oxygen line is split into three Zeeman components by the interaction of oxygen’s electronic spin with an external magnetic field, and the splitting is of order +/-0.5 MHz in a typical geomagnetic field. Zeeman splitting is only significant at pressures low enough that collisional broadening (~1.6 MHz/hPa) is not very large by comparison. The polarized forward model becomes significant forMLStemperature retrievals at pressure below1.0 hPa and is crucial at pressures below ~0.03 hPa. Interaction of theO2 molecule with the radiation field depends upon the relative orientation of the radiation polarization mode and the geomagnetic field direction. The model provides both limb radiances and the derivatives of these radiances with respect to atmospheric temperature and composition, as required by MLS temperature retrievals. EOS MLS views the atmospheric limb at 118.75 GHz with a pair of linearcross- polarized, 100-kHz-resolution, 10-MHz-wide spectrometers. The antennas of the associated receivers are scanned to view rays with tangent heights from the Earth’s surface to 0.001 hPa. Comparisons of the modeled MLS radiances with measurements show generally good agreement in line positions and strengths, however residuals in the line centers at the highest tangent heights are larger than desired and still under investigation. +Read more

EOS MLS Cloud Ice Measurements and Cloudy-Sky Radiative Transfer Model Date: May 2006 A cloud ice retrieval technique is described here using measurements at frequencies near 118, 190, 240, and 640 GHz and 2.5 THz from the Earth Observing System Microwave Limb Sounder on the NASA Aura satellite. Measurement principles, methods for cloud detection, and radiative transfer models for retrieving cloud properties are discussed. The 240-GHz data from high-tangent heights are used to retrieve ice water content at pressures <215 hPa, and the 118-, 190-, 240-, and 640-GHz radiances from low-tangent heights are used to retrieve ice water paths with different penetration depths. Some early Microwave Limb Sounder (MLS) results are highlighted, and the observed cloud signatures are consistent with the expectation from model simulations, in general. The simultaneous measurements from MLS 240 and 640 GHz radiometers contain useful information on particle sizes. There are significant cloud-induced radiances at 2.5 THz, despite strong attenuation from the atmosphere. Cloud-scattering signatures are polarized at 122 GHz, but the polarization differences are typically less than 10% of the total cloud-induced radiance. +Read more

MLS publications related to "forward model"

2008

1. Pickett, H.M., B.J. Drouin, T. Canty, R.J. Salawitch, R.A. Fuller, V.S. Perun, N.J. Livesey, J.W. Waters, R.A. Stachnik, S.P. Sander, W.A. Traub, K.W. Jucks, K. Minschwaner, "Validation of Aura Microwave Limb Sounder OH and HO₂ Measurements", vol 113, 2008. Preprint

2007

1. Davis, C.P., H.C. Pumphrey, K.F. Evans, S. Buehler, D.L. Wu, "3D polarised simulations of space-borne passive mm/sub-mm midlatitude cirrus observations: A case study", vol 7, pgs. 4149-4158, 2007. Reprint
2. Read, W.G., A. Lambert, J. Bacmeister, R.E. Cofield, L.E. Christensen, D.T. Cuddy, W.H. Daffer, B.J. Drouin, E. Fetzer, L. Froidevaux, R. Fuller, R. Herman, R.F. Jarnot, J.H. Jiang, Y.B. Jiang, K. Kelly, B.W. Knosp, H.C. Pumphrey, K.H. Rosenlof, X. Sabounchi, M.L. Santee, M.J. Schwartz, W.V. Snyder, P.C. Stek, H. Su, L.L. Takacs, R.P. Thurstans, H. Vomel, P.A. Wagner, J.W. Waters, C.R. Webster, E.M. Weinstock, D.L. Wu, "Aura Microwave Limb Sounder upper tropospheric and lower stratospheric H2O and relative humidity with respect to ice validation", vol 112, pgs. D24S35, 2007. Reprint Supplemental

2006

1. Wu, D.L., J.H. Jiang, C.P. Davis, "EOS MLS cloud ice measurements and cloudy-sky radiative transfer model", vol 44, num no. 5, pgs. 1156-1165, 2006. Reprint
2. Schwartz, M.J., W.G. Read, W.V. Snyder, "EOS MLS forward model polarized radiative transfer for Zeeman-split oxygen lines", vol 44, num no. 5, pgs. 1182-1191, 2006. Reprint
3. Read, W.G., Z. Shippony, M.J. Schwartz, N.J. Livesey, W.V. Snyder, "The clear-sky unpolarized forward model for the EOS Microwave Limb Sounder (MLS)", vol 44, num no. 5, pgs. 1367-1379, 2006. Reprint

2005

1. Davis, C., C. Emde, R. Harwood, "A 3D polarized reversed Monte Carlo radiative transfer model for mm and sub-mm passive remote sensing in cloudy atmospheres", vol 43, num no. 5, pgs. 1096-1101, 2005. Reprint Summary
2. Davis, C.P., D.L. Wu, C. Emde, J.H. Jiang, R.E. Cofield, R.S. Harwood, "Cirrus Induced Polarization in 122 GHz Aura Microwave Limb Sounder Radiances", vol 32, pgs. L14806, 2005. Reprint Summary

2004

1. Jiang, J.H., D.L. Wu, "Ice and Water Permittivities for Millimeter and Sub-millimeter Remote Sensing Applications", vol 5, pgs. 146-151, 2004. Reprint Summary
2. Jiang, Y., Y.L. Yung, S.P. Sander, L.D. Travis, "Modeling of atmospheric radiative transfer with polarization and its application to the remote sensing of tropospheric ozone", vol 88, pgs. 169-179, 2004. Reprint

2003

1. Shippony, Z., W.G. Read, "A Correction to a Highly Accurate Voigt Function Algorithm", vol 78, num Issue 2, pgs. 255, 2003. Reprint

1993

1. Shippony, Z., W.G. Read, "A very accurate algorithm for the Voigt profile", vol 50, pgs. 635-646, 1993.

1976

1. Waters, J.W., "Absorption and emission by atmospheric gases", vol 12B, 1976.