Evaluation of atmospheric profiles derived from single- and zero-difference excess phase processing of BeiDou radio occultation data from the FY-3C GNOS mission
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Published:2018-02-13
Issue:2
Volume:11
Page:819-833
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ISSN:1867-8548
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Container-title:Atmospheric Measurement Techniques
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language:en
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Short-container-title:Atmos. Meas. Tech.
Author:
Bai Weihua, Liu Congliang, Meng Xiangguang, Sun Yueqiang, Kirchengast GottfriedORCID, Du Qifei, Wang Xianyi, Yang Guanglin, Liao Mi, Yang Zhongdong, Zhao Danyang, Xia Junming, Cai Yuerong, Liu Lijun, Wang Dongwei
Abstract
Abstract. The Global Navigation Satellite System (GNSS) Occultation Sounder (GNOS) is one of the new-generation payloads onboard the
Chinese FengYun 3 (FY-3) series of operational meteorological satellites for sounding the Earth's neutral atmosphere and
ionosphere. The GNOS was designed for acquiring setting and rising radio occultation (RO) data by using GNSS signals from
both the Chinese BeiDou System (BDS) and the US Global Positioning System (GPS). An ultra-stable oscillator with 1 s
stability (Allan deviation) at the level of 10−12 was installed on the FY-3C GNOS, and thus both zero-difference and
single-difference excess phase processing methods should be feasible for FY-3C GNOS observations. In this study we focus
on evaluating zero-difference processing of BDS RO data vs. single-difference processing, in order to investigate the
zero-difference feasibility for this new instrument, which after its launch in September 2013 started to use BDS signals
from five geostationary orbit (GEO) satellites, five inclined geosynchronous orbit (IGSO) satellites and four medium Earth orbit
(MEO) satellites. We used a 3-month set of GNOS BDS RO data (October to December 2013) for the evaluation and compared
atmospheric bending angle and refractivity profiles, derived from single- and zero-difference excess phase data, against
co-located profiles from European Centre for Medium-Range Weather Forecasts (ECMWF) analyses. We also compared against
co-located refractivity profiles from radiosondes. The statistical evaluation against these reference data shows that the
results from single- and zero-difference processing are reasonably consistent in both bias and standard deviation, clearly demonstrating
the feasibility of zero differencing for GNOS BDS RO observations. The average bias (and standard deviation) of the bending angle and
refractivity profiles were found to be about 0.05 to 0.2 % (and 0.7 to 1.6 %) over the upper troposphere and lower
stratosphere. Zero differencing was found to perform slightly better, as may be expected from its lower vulnerability to
noise. The validation results indicate that GNOS can provide, on top of GPS RO profiles, accurate and precise BDS RO
profiles both from single- and zero-difference processing. The GNOS observations by the series of FY-3 satellites are thus
expected to provide important contributions to numerical weather prediction and global climate change analysis.
Publisher
Copernicus GmbH
Subject
Atmospheric Science
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