Abstract
In the moist lower troposphere, a limitation of the sliding spectral (SS) method is the restriction of the resolution of bending angle profiles because of the atmospheric multipath effect and noise. A modified sliding spectral (MSS) method is proposed in this paper to improve the inversion resolution of SS method in the moist lower troposphere. Simulation results show that the noise in the signal may cause inversion error in the classical SS method. The MSS method can decrease the influence of the noise to some extent. The SS and MSS methods were used to process COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) atmPhs profiles from DOY (day of year) 71–DOY 100 in 2007. The retrieved refractivity profiles were compared with those from the corresponding ECMWF (European Centre for Medium-Range Weather Forecasts) analysis. The results show that the SS method contains systematic positive biases in the 3–10 km height range and systematic negative biases below 3 km. The MSS method, in comparison to SS method, has decreased the maximum positive bias in the range of 3–10 km height from 0.37% to 0.23% in the northern hemisphere, from 1.3% to 0.25% in the tropics, and from 0.60% to 0.35% in the southern hemisphere. The biases of the MSS method are comparable to those announced for the COSMIC atmPrf profile; the latter is inverted by full spectrum inversion (FSI) method.
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Anthes R A, Bernhardt P A, Chen Y, Cucurull L, Dymond K F, Ector D, Healy S B, Ho S P, Hunt D C, Kuo Y H, Liu H, Manning K, McCormick C, Meehan T K, Randel W J, Rocken C, Schreiner W S, Sokolovskiy S V, Syndergaard S, Thompson D C, Trenberth K E, Wee T K, Yen N L, and Zeng Z 2008 The COSMIC/FORMOSAT-3 mission: Early results; Bull. Am. Meteor. Soc. 89 (3) 313–333, doi: 10.1175/BAMS-89-3-313.
Ao C O, Meehan T K, Hajj G A, and Mannucci A J 2003 Lower troposphere refractivity bias in GPS occultation retrievals; J. Geophys. Res. 108 (D18) 4577, doi: 10.1029/2002JD003216.
Ao C O, Hajj G A, Meehan T K, Dong D, Iijima B A, Mannucci A J, and Kursinski E R 2009 Rising and setting GPS occultations by use of open-loop tracking; J. Geophys. Res. 114 D04101, doi: 10.1029/2008JD010483.
Beyerle G, Hocke K, Wickert J, Schmidt T, Marquardt C, and Reigber C 2002 GPS radio occultations with CHAMP: A radio holographic analysis of GPS signal propagation in the troposphere and surface reflections; J. Geophys. Res. 107(D24) 4802, doi: 10.1029/2001JD001402.
Fjeldbo G, Kliore A J and Eshleman V R 1971 The neutral atomosphere of Venus as studied with the Mariner V radio occultation experiments; Astron. J. 76(2) 123–140.
Gorbunov M E, Gurvich A S and Kornblueh L 2000 Comparative analysis of radioholographic methods of processing radio occultation data; Radio Sci. 35 (4) 1025–1034.
Gorbunov M E and Kornblueh L 2001 Analysis and validation of GPS/MET radio occultation data; J. Geophys. Res. 106 (D15) 17,161–17,169.
Gorbunov M E 2002a Radio-holographic analysis of Microlab-1 radio occultation data in the lower troposphere; J. Geophys. Res. 107 (D12), doi: 10.1029/2001JD000889 10.1029/2001JD000889.
Gorbunov M E 2002b Canonical transform method for processing radio occultation data in the lower troposphere; Radio Sci 37 (5) 1076, doi: 10.1029/2000RS002592.
Gorbunov M E and Lauritsen K B 2004 Analysis of wave fields by Fourier integral operators and their application for radio occultations; Radio Sci. 39 RS4010, doi: 10.1029/2003RS002971.
Hocke K, Pavelyev A G, Yakovlev O I, Barthes L and Jakowski N 1999 Radio occultation data analysis by the radioholographic method; J. Atmos. Sol.-Terr. Phys. 61 1169–1177.
Jensen A S, Lohmann M S, Benzon H H and Nielsen A S 2003 Full spectrum inversion of radio occultation signals; Radio Sci. 38 (3) 1040, doi: 10.1029/2002RS002763 10.1029/2002RS002763.
Jensen A S, Lohmann M S, Nielsen A S and Benzon H H 2004 Geometrical optics phase matching of radio occultation signals; Radio Sci. 39 RS3009, doi: 10.1029/2003RS002899.
Kursinski E R, Hajj G A, Leroy S S and Herman B 2000 The GPS radio occultation technique; Terr. Atmos. Oceanic Sci. 11 (1) 53–114.
Liou Y A, Pavelyev A G, Liu S F, Pavelyev A A, Yen N, Huang C Y and Fong C J 2007 FORMOSAT-3 GPS radio occultation mission: Preliminary results; IEEE Trans. Geosci. Remote Sens. 45 (11) 3813–3826, doi: 10.1109/TGRS.2007.903365.
Lohmann M S, Jensen A S, Benzon H H and Nielsen A S 2003 Radio occultation retrieval of atmospheric absorption based on FSI; Scientific Report 03-20 Danish Meteorological Institute, Copenhagen.
Lohmann M S 2006 Dynamic error estimation for radio occultation bending angles retrieved by the full spectrum inversion technique; Radio Sci. 41 RS5005, doi: 10.1029/2005RS003396.
Sokolovskiy S 2001 Modeling and inverting radio occultation signals in the moist troposphere; Radio Sci. 36 (3) 441–458.
Sokolovskiy S, Kuo Y H, Rocken C, Schreiner W S, Hunt D and Anthes R A 2006 Monitoring the atmospheric boundary layer by GPS radio occultation signals recorded in the open-loop mode; Geophys. Res. Lett. 33 L12813, doi: 10.1029/2006GL025955.
Sokolovskiy S, Rocken C, Schreiner W, Hunt D and Johnson J 2009 Postprocessing of L1 GPS radio occultation signals recorded in open-loop mode; Radio Sci. 44 RS2002, doi: 10.1029/2008RS003907.
Sokolovskiy S, Rocken C, Schreiner W and Hunt D 2010 On the uncertainty of radio occultation inversions in the lower troposphere; J. Geophys. Res. 115 D22111, doi: 10.1029/2010JD014058.
Acknowledgements
The authors are grateful to University Corporation for Atmospheric Research (UCAR) for access to COSMIC RO data and ECMWF analysis data. Thanks are also due to Wegener Centre and University of Graz for providing the EGOPS software. This research is supported by the National Natural Science Foundation of China (11273047, 41305016), the Natural Science Foundation of Zhenjiang province (LQ13D050002) and the Natural Science Foundation of Ningbo (2014A610156, 2014A610022).
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Xu, XS., Guo, P. & Hong, ZJ. A modified sliding spectral method and its application to COSMIC radio occultation data. J Earth Syst Sci 123, 1749–1758 (2014). https://doi.org/10.1007/s12040-014-0507-z
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DOI: https://doi.org/10.1007/s12040-014-0507-z