A perspective on the fundamental quality of GPS radio occultation data

Abstract. Radio Occultation (RO) is a promising source of observation for weather and climate applications. However, the uncertainties in processing and retrieving RO data may weaken the overall confidence in the data and discourage their use. This study assesses the fundamental quality of RO data, by modeling the "raw" measurement, phase path, through a ray tracing method without the nuisance of retrieval errors. The comparison of phase measurements with the European Center for Medium-Range Weather Forecasts (ECMWF) data made in the observation space shows that the RO measurement is of sufficient accuracy to uncover regional-scale systematic errors in ECMWF's operational analysis and the 45 year reanalysis (ERA40), and to clearly depict the error growth of short-term ERA40 forecasts. In the southern hemispheric stratosphere, in particular, the RO measurement served as a robust reference against which both of the two analyses were significantly biased in opposite directions even though they were produced by the same center using virtually the same set of data. The measurement and ECMWF analyses showed a close agreement in the standard deviation. This confirms the high accuracy of the RO measurement and also indicates that the main problem of the ECMWF analyses lies in their systematic error.

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A perspective on the fundamental quality of GPS radio occultation data

Atmospheric Measurement Techniques ◽

10.5194/amt-8-4281-2015 ◽

2015 ◽

Vol 8 (10) ◽

pp. 4281-4294 ◽

Cited By ~ 3

Author(s):

T.-K. Wee ◽

Y.-H. Kuo

Keyword(s):

Radio Occultation ◽

Regional Scale ◽

Phase Measurements ◽

Weather Forecasts ◽

Alternative Approach ◽

Occultation Data ◽

Observation Space ◽

Ray Path ◽

Promising Source

Abstract. Radio occultation (RO) is a promising source of observation for weather and climate applications. However, the uncertainties arising from imperfect retrieval algorithms may weaken the overall confidence in the data and discourage their use. As an alternative approach of assessing the quality of RO data while avoiding the nuisance of retrieval errors, this study proposes to use minimally processed data (measurement) instead of derived RO data. This study compares measured phase paths with their model counterparts, simulated with an effective ray tracer for which the refractive indices along the complete ray path linking the transmitter and the receiver are realistically specified. The comparison of phase measurements with the European Centre for Medium-Range Weather Forecasts (ECMWF) data made in the observation space shows that the RO measurements are of sufficient accuracy to uncover regional-scale systematic errors in ECMWF's operational analysis and the 45-year reanalysis (ERA40), and to clearly depict the error growth of short-term ERA40 forecasts. In the southern hemispheric stratosphere, in particular, the RO measurements served as a robust reference against which both of the two analyses were significantly biased in opposite directions even though they were produced by the same center using virtually the same set of data. The measurement and ECMWF analyses showed a close agreement in the standard deviation except for the regions and heights that the quality of the ECMWF data is controversial. This confirms the high precision of RO measurements and also indicates that the main problem of the ECMWF analyses lies in their systematic error.

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GRACE-FO radio occultation data processing – First result

10.5194/gstm2020-76 ◽

2020 ◽

Author(s):

Torsten Schmidt ◽

Patrick Schreiner ◽

Byron Iijima ◽

Chi Ao

Keyword(s):

Data Processing ◽

Radio Occultation ◽

Temperature Data ◽

Gps Satellites ◽

Weather And Climate ◽

First Results ◽

Software Updates ◽

Occultation Data ◽

Radio Occultation Data

An objective of the GRACE-FO mission is the continuation of GRACE radio occultation measurements successfully performed between 2006 and 2017. GRACE and GRACE-FO radio occultations contribute to the overall radio occultation dataset used in weather and climate applications. Since mid-2019 rising occultations from GF1 are available while setting radio occultations from GF2 are still disabled. After several on-board software updates and raw data reader improvements about 280 daily GF1 radio occultations are available since March 2020. Currently GF1 radio occultation data are processed on the basis of different measured variables: For different GPS satellites a combination of L1CA/L2P, L1CA/L2C, or L1CA/L5 is available. In this study first results of GF1 processing are presented. Refractivity and temperature data up to an altitude of 60 km will be compared with ECMWF operational analyses and the quality of the different measured variables will be evaluated.

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Empirical model of the ionosphere based on COSMIC/FORMOSAT-3 for neutral atmosphere radio occultation processing

10.5194/amt-2017-217 ◽

2017 ◽

Cited By ~ 1

Author(s):

Miquel Garcia-Fernandez ◽

Manuel Hernandez-Pajares ◽

Antonio Rius ◽

Riccardo Notarpietro ◽

Axel von Engeln ◽

...

Keyword(s):

Electron Density ◽

Empirical Model ◽

Radio Occultation ◽

Scintillation Index ◽

Neutral Atmosphere ◽

Vertical Profiles ◽

New Feature ◽

Occultation Data ◽

Relevant Level ◽

Made In

Abstract. The Radio Occultation instrument at the upcoming EUMETSAT Polar System – Second Generation (EPS-SG) mission will be devoted primarily to monitor the neutral atmosphere through this payload, consisting of a GNSS receiver and occultation antennae pointing slightly below the Earth's limb. The resulting data will be processed by EUMETSAT (primarily for L1B data) and by the ROMSAF's Radio Occultation Processing Package (ROPP) software to obtain the vertical profiles of temperature, pressure and other relevant level 2 parameters of the neutral atmosphere. Newer versions of this software might include a feature by which empirical models of the ionosphere (i.e. vertical profiles of electron density) can be included in the processing in order to increase the accuracy of the inverted bending angle profiles. In order to test this new feature, this work includes the efforts that have been made in order to provide an empirical model of the ionosphere purely based on vertical profiles of electron density inverted from data of previous radio occultation (RO) missions (i.e. COSMIC/FORMOSAT-3). The methodology used in this work is based on using the separability hypothesis, to overcome the spherical symmetry assumption of the Abel inversion as well as a new mechanization of the inversion process, based on a joint processing of all the occultation data via a linear mean square filter, rather than adopting the classical peel onion approach. Additionally, with the development of this empirical model, efforts have been made to construct a proxy index for scintillation monitoring based on the inverted profiles (Occultation Scintillation Proxy Index or OSPI), which shows reasonable correlation with the amplitude scintillation index S4.

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The ROCSAT-3/COSMIC mission and applications of GPS radio occultation data to weather and climate

10.1117/12.566544 ◽

2004 ◽

Cited By ~ 2

Author(s):

Christian Rocken ◽

Ying-Hwa Kuo ◽

Sergey V. Sokolovskiy ◽

Richard A. Anthes

Keyword(s):

Radio Occultation ◽

Gps Radio Occultation ◽

Weather And Climate ◽

Occultation Data ◽

Radio Occultation Data

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Generation of a Bending Angle Radio Occultation Climatology (BAROCLIM) and its use in radio occultation retrievals

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-7-8193-2014 ◽

2014 ◽

Vol 7 (8) ◽

pp. 8193-8231 ◽

Cited By ~ 2

Author(s):

B. Scherllin-Pirscher ◽

S. Syndergaard ◽

U. Foelsche ◽

K. B. Lauritsen

Keyword(s):

Radio Occultation ◽

Weather Prediction ◽

A Priori ◽

A Priori Information ◽

Bending Angle ◽

Weather Forecasts ◽

Global Statistics ◽

Priori Information ◽

Bending Angles

Abstract. In this paper, we introduce a bending angle radio occultation climatology (BAROCLIM) based on Formosat-3/COSMIC (F3C) data. This climatology represents the monthly-mean atmospheric state from 2006 to 2012. Bending angles from radio occultation (RO) measurements are obtained from the accumulation of the change in the raypath direction of Global Positioning System (GPS) signals. Best quality of these near-vertical profiles is found from the middle troposphere up to the mesosphere. Beside RO bending angles we also use data from the Mass Spectrometer and Incoherent Scatter Radar (MSIS) model to expand BAROCLIM in a spectral model, which (theoretically) reaches from the surface up to infinity. Due to the very high quality of BAROCLIM up to the mesosphere, it can be used to detect deficiencies in current state-of-the-art analysis and reanalysis products from numerical weather prediction (NWP) centers. For bending angles derived from European Centre for Medium-Range Weather Forecasts (ECMWF) analysis fields from 2006 to 2012, e.g., we find a positive bias of 0.5% to % at 40 km, which increases to more than 2% at 50 km. BAROCLIM can also be used as a priori information in RO profile retrievals. In contrast to other a priori information (i.e., MSIS) we find that the use of BAROCLIM better preserves the mean of raw RO measurements. Global statistics of statistically optimized bending angle and refractivity profiles also confirm that BAROCLIM outperforms MSIS. These results clearly demonstrate the utility of BAROCLIM.

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Use of automatic radiosonde launchers to measure temperature and humidity profiles from the GRUAN perspective

Atmospheric Measurement Techniques ◽

10.5194/amt-13-3621-2020 ◽

2020 ◽

Vol 13 (7) ◽

pp. 3621-3649

Author(s):

Fabio Madonna ◽

Rigel Kivi ◽

Jean-Charles Dupont ◽

Bruce Ingleby ◽

Masatomo Fujiwara ◽

...

Keyword(s):

Relative Humidity ◽

Urban Areas ◽

Global Climate ◽

Forecast Model ◽

Primary Data ◽

Weather Forecasts ◽

Technical Performance ◽

Weather And Climate ◽

Mean Differences

Abstract. In the last two decades, technological progress has not only seen improvements to the quality of atmospheric upper-air observations but also provided the opportunity to design and implement automated systems able to replace measurement procedures typically performed manually. Radiosoundings, which remain one of the primary data sources for weather and climate applications, are still largely performed around the world manually, although increasingly fully automated upper-air observations are used, from urban areas to the remotest locations, which minimize operating costs and challenges in performing radiosounding launches. This analysis presents a first step to demonstrating the reliability of the automatic radiosonde launchers (ARLs) provided by Vaisala, Meteomodem and Meisei. The metadata and datasets collected by a few existing ARLs operated by the Global Climate Observing System (GCOS) Reference Upper-Air Network (GRUAN) certified or candidate sites (Sodankylä, Payerne, Trappes, Potenza) have been investigated and a comparative analysis of the technical performance (i.e. manual versus ARL) is reported. The performance of ARLs is evaluated as being similar or superior to those achieved with the traditional manual launches in terms of percentage of successful launches, balloon burst and ascent speed. For both temperature and relative humidity, the ground-check comparisons showed a negative bias of a few tenths of a degree and % RH, respectively. Two datasets of parallel soundings between manual and ARL-based measurements, using identical sonde models, provided by Sodankylä and Faa'a stations, showed mean differences between the ARL and manual launches smaller than ±0.2 K up to 10 hPa for the temperature profiles. For relative humidity, differences were smaller than 1 % RH for the Sodankylä dataset up to 300 hPa, while they were smaller than 0.7 % RH for Faa'a station. Finally, the observation-minus-background (O–B) mean and root mean square (rms) statistics for German RS92 and RS41 stations, which operate a mix of manual and ARL launch protocols, calculated using the European Centre for Medium-Range Weather Forecasts (ECMWF) forecast model, are very similar, although RS41 shows larger rms(O–B) differences for ARL stations, in particular for temperature and wind. A discussion of the potential next steps proposed by GRUAN community and other parties is provided, with the aim to lay the basis for the elaboration of a strategy to fully demonstrate the value of ARLs and guarantee that the provided products are traceable and suitable for the creation of GRUAN data products.

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Applications of GPS Radio Occultation Data to Weather and Climate and the COSMIC Mission

Space 2004 Conference and Exhibit ◽

10.2514/6.2004-6067 ◽

2004 ◽

Author(s):

Ying-Hwa Kuo ◽

Christian Rocken ◽

Richard Anthes

Keyword(s):

Radio Occultation ◽

Gps Radio Occultation ◽

Weather And Climate ◽

Occultation Data ◽

Radio Occultation Data

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Studying the Weather and Climate of Alaska Across a Network of Observers

Bulletin of the American Meteorological Society ◽

10.1175/bams-d-15-00202.1 ◽

2016 ◽

Vol 97 (12) ◽

pp. 2275-2286

Author(s):

Richard L. Collins ◽

Susan P. Warner ◽

Cameron M. Martus ◽

Jennifer L. Moss ◽

Ketsiri Leelasaskultum ◽

...

Keyword(s):

Course Completion ◽

Completion Rates ◽

Weather Forecasts ◽

Climate Record ◽

Nonscience Majors ◽

Weather And Climate ◽

Science Classes ◽

Term Data

Abstract Weather and Climate of Alaska is an undergraduate course for nonscience majors where students study meteorology from their home as part of a statewide network of classmates. The students draw on their experience of the weather and climate by observing weather locally and sharing their work with classmates across the state. The goal of the class is to have this cohort of students understand weather and climate through exploring the relationships between processes at the local, regional, and global scales. The class is organized around weekly investigations where the students use an equipment kit to make observations, report their work with videos, and discuss the work with the instructor and their peers. The students use NWS resources extensively, including station data to check the quality of their observations, weather maps and satellite images to understand the weather they have observed, weather forecasts to evaluate different forecasting techniques, and long-term data to compare their observations with the climate record. The course also includes traditional quizzes and exams. The instructor has regular teleconferences with students and discusses their work firsthand. A teaching assistant also supports the students. Students take pre- and postcourse tests and show gains typical of interactive science classes. The level of student support results in high student course completion rates.

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Generation of a bending angle radio occultation climatology (BAROCLIM) and its use in radio occultation retrievals

Atmospheric Measurement Techniques ◽

10.5194/amt-8-109-2015 ◽

2015 ◽

Vol 8 (1) ◽

pp. 109-124 ◽

Cited By ~ 4

Author(s):

B. Scherllin-Pirscher ◽

S. Syndergaard ◽

U. Foelsche ◽

K. B. Lauritsen

Keyword(s):

Radio Occultation ◽

Weather Prediction ◽

A Priori ◽

A Priori Information ◽

Bending Angle ◽

Weather Forecasts ◽

Global Statistics ◽

Priori Information ◽

Bending Angles

Abstract. In this paper, we introduce a bending angle radio occultation climatology (BAROCLIM) based on Formosat-3/COSMIC (F3C) data. This climatology represents the monthly-mean atmospheric state from 2006 to 2012. Bending angles from radio occultation (RO) measurements are obtained from the accumulation of the change in the raypath direction of Global Positioning System (GPS) signals. Best quality of these near-vertical profiles is found from the middle troposphere up to the mesosphere. Beside RO bending angles we also use data from the Mass Spectrometer and Incoherent Scatter Radar (MSIS) model (modified for RO purposes) to expand BAROCLIM in a spectral model, which (theoretically) reaches from the surface up to infinity. Due to the very high quality of BAROCLIM up to the mesosphere, it can be used to detect deficiencies in current state-of-the-art analysis and reanalysis products from numerical weather prediction (NWP) centers. For bending angles derived from European Centre for Medium-Range Weather Forecasts (ECMWF) analysis fields from 2006 to 2012, e.g., we find a positive bias of 0.5 to 1% at 40 km, which increases to more than 2% at 50 km. BAROCLIM can also be used as a priori information in RO profile retrievals. In contrast to other a priori information (i.e., MSIS) we find that the use of BAROCLIM better preserves the mean of raw RO measurements. Global statistics of statistically optimized bending angle and refractivity profiles also confirm that BAROCLIM outperforms MSIS. These results clearly demonstrate the utility of BAROCLIM.

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