GPS radio occultation with CHAMP: First results and status of the experiment

Wickert, Jens; Schmidt, T.; Marquardt, Christian; Reigber, C.; Neumayer, Karl Hans; Beyerle, G.; Galas, R.; Grunwaldt, L.

doi:10.1007/978-3-662-04709-5_45

Cited by 10 publications

(3 citation statements)

References 19 publications

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“…Following the proof of concept mission GPS/MET, RO receivers are considered to be one of the key "must have" payloads for observing the atmosphere in the design of many LEO satellite systems. For example, the Challenging Minisatellite Payload (CHAMP) satellite was launched by the US and Germany in 2000 [21,22]. It carried a BlackJack RO receiver developed by Jet Propulsion Laboratory (JPL), which was more powerful than the receiver on the MicroLab-1 satellite and sounded the atmosphere well in the lower troposphere region [23].…”

Section: Introductionmentioning

confidence: 99%

An Evaluation of Fengyun-3C Radio Occultation Atmospheric Profiles Over 2015–2018

et al. 2020

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Fengyun-3C (FY-3C) is the first Chinese satellite that is capable of using the Radio Occultation (RO) technique to retrieve atmospheric profiles. This research evaluates the quality of FY-3C RO profiles including refractivity, temperature, and specific humidity by comparing with corresponding information from the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Reanalysis (ERA-Interim) data over the period of 2015–2018. The evaluation is carried out by calculating and analyzing mean systematic differences between FY-3C and ERA-Interim profiles and corresponding standard deviations over a selected spatial and temporal domain. Results show that the FY-3C RO profiles are overall with good agreements with the ERA-Interim data. Global mean refractivity systematic differences are within ±0.2% from 5 to 30 km altitude range with relative standard deviations of less than 2%. Global temperature mean systematic differences vary within ±0.2 K from a 10- to 20-km altitude range with standard deviations of less than 2 K. Global mean specific humidity differences are found to be within ±0.2 g/kg from 2 to 20 km with standard deviations of less than 1 g/kg. FY-3C profiles show visible latitudinal and altitudinal variations, while the seasonal variations are minor. Sampling errors of refractivity and temperature are also found to be larger at higher latitudinal regions due to RO events being less sampled in the polar region.

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Section: Introductionmentioning

confidence: 99%

An Evaluation of Fengyun-3C Radio Occultation Atmospheric Profiles Over 2015–2018

et al. 2020

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“…For example, Bell and Geller (2008) analyzed the twice daily standard radiosonde data from WMO stations and found that the thickness was ~1 km at low latitudes. Using data from the CHAllenging Mini satellite Payload (CHAMP) Global Navigation Satellite System Radio Occultation (GNSS-RO) mission (Wickert et al, 2001), Schmidt et al (2005) reported that the tropopause sharpness varies less throughout the year in the tropics than in polar regions. Ratnam et al (2005), also using the CHAMP dataset, reported an association between greater sharpness and a higher and colder tropopause.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of the tropical tropopause inversion layer using high-resolution temperature profiles retrieved from COSMIC GNSS Radio Occultation

Noersomadi

Tsuda

Fujiwara

2018

Preprint

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Abstract. Using COSMIC GNSS Radio Occultation (RO) observations from January 2007 to December 2016, we retrieved temperature profiles with 0.1&#8201;km vertical resolution in the upper troposphere and lower stratosphere (UTLS). We investigated the global distribution of static stability (N2) and the characteristics of the tropopause inversion layer (TIL) in the tropics, where a large change in temperature gradient occurs associated with sharp variations of N2. We show the variations of the mean N2 profiles in conventional height coordinates as well as in coordinates relative to both the Lapse Rate Tropopause (LRT) and the Cold Point Tropopause (CPT). When the N2 profiles are averaged relative to CPT height, there is a very thin (<&#8201;1&#8201;km) layer with average maximum N2 in the range 11.0&#8211;12.0 &#215; 10&#8722;4&#8201;s&#8722;2. The mean and standard deviation of the tropopause sharpness (S-ab), defined as the difference between the maximum N2 (maxN2) and minimum N2 (minN2) within &#177;1&#8201;km of the CPT, is (10.5 &#177; 3.7) &#215; 10&#8722;4&#8201;s&#8722;2. About 70&#8201;% of the values of TIL thickness (dH), which is the thickness of the layer over which N2 &#8805; 0.8maxN2, were in the range 0.4 &#177; 0.04&#8201;km. We focused on the variation of S-ab in two longitude regions, 90&#176;&#8211;150&#176;&#8201;E (Maritime Continent; MC) and 170&#176;&#8211;230&#176;&#8201;E (Pacific Ocean; PO), with different land&#8211;sea distribution. Seasonal variations of S-ab and dH were related to the deep convective activity represented by low Outgoing Longwave Radiation (OLR) during the Australian and Asian monsoons. The S-ab anomaly (S-ab*) was out-of-phase with the OLR anomaly in both the MC and PO. The correlation between S-ab* over the MC and PO and the sea surface temperature (SST) Ni&#241;o 3.4 index was &#8722;0.66 and +0.88, respectively. This means that during La Ni&#241;a (SST Nino 3.4 < &#8722;0.5 K) in the MC, and El Ni&#241;o (SST Nino 3.4 > +0.5&#8201;K) in the PO, warmer SSTs in the MC and PO produce more active deep convection that tends to force the air upward to the tropopause layer and increase the temperature gradient there. The intra-seasonal variation in S-ab* during slow and fast episodes of the Madden&#8211;Julian Oscillation (MJO) demonstrates that eastward propagation of positive S-ab* is associated with organized deep convection. This suggests that convective activity in the tropics is a major control on variations in tropopause sharpness at intra-seasonal to interannual time-scales.

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“…On 11 February 2001 the occultation experiment aboard the CHAMP (Challenging Minisatellite Payload) satellite [ Reigber et al , 2000] was activated. Between 11 February 2001 and 31 December 2001 more than 25,000 occultation events with about 120 temperature soundings per day have been recorded [ Wickert et al , 2002].…”

Section: Introductionmentioning

confidence: 99%

GPS radio occultations with CHAMP: A radio holographic analysis of GPS signal propagation in the troposphere and surface reflections

Beyerle

Hocke²,

Wickert

et al. 2002

J.‐Geophys.‐Res.

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[1] Within the first nine months following the activation of the GPS radio occultation experiment aboard the low Earth orbiting satellite CHAMP, more than 25,000 occultation events have been observed. A radio holographic analysis of 3783 occultation events, recorded between 14 May 2001 and 10 June 2001, reveals that in about 20-30% of these events the received signal contains contributions from components reflected at Earth's surface. On the basis of geometrical ray tracing and multiple phase screen calculations, characteristic frequency shifts in the radio holograms' power spectral densities are analyzed quantitatively. These frequency shifts are found to be dominated by surface elevation at the reflection point location and ground-level refractivity. Using temperature and pressure profiles from European Centre for Medium-Range Weather Forecasting (ECMWF) analyses, ground-level specific humidities are derived in good agreement with ECMWF values. Complex patterns found in radio hologram spectra within a subset of observations at low latitudes are interpreted in terms of multipath propagation caused by layered structures in the refractivity field.INDEX TERMS: 1640 Global Change: Remote sensing; 0669 Electromagnetics: Scattering and diffraction; 6994 Radio Science: Instruments and techniques; 6964 Radio Science: Radio wave propagation; KEYWORDS: GPS radio occultation, GPS reflectometry, GPS scatterometry, radio holography, global positioning system, CHAMP Citation: Beyerle, G., K. Hocke, J. Wickert, T. Schmidt, C. Marquardt, and C. Reigber, GPS radio occultations with CHAMP: A radio holographic analysis of GPS signal propagation in the troposphere and surface reflections,

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GPS radio occultation with CHAMP: First results and status of the experiment

Cited by 10 publications

References 19 publications

An Evaluation of Fengyun-3C Radio Occultation Atmospheric Profiles Over 2015–2018

An Evaluation of Fengyun-3C Radio Occultation Atmospheric Profiles Over 2015–2018

Characteristics of the tropical tropopause inversion layer using high-resolution temperature profiles retrieved from COSMIC GNSS Radio Occultation

GPS radio occultations with CHAMP: A radio holographic analysis of GPS signal propagation in the troposphere and surface reflections

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