Assimilation of Global Positioning System radio occultation data in the ECMWF ERA–Interim reanalysis

Poli, Paul; Healy, S. B.; Dee, Dick

doi:10.1002/qj.722

Cited by 200 publications

(167 citation statements)

References 36 publications

(45 reference statements)

Supporting

Mentioning

154

Contrasting

Order By: Relevance

“…The pressure altitude is defined as z p We account for sampling error which stems from discrete sampling in space and time, since the centers provide slightly different numbers of high quality profiles. We use the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis ERA-Interim (Poli et al, 2010;Dee et al, 2011) as a reference field for sampling error estimation . We compute the sampling error for each atmospheric parameter except bending angle and subtract it from the RO climatologies (Scherllin-Pirscher et al, 2011a).…”

Section: Study Setup and Methodsmentioning

confidence: 99%

Quantification of structural uncertainty in climate data records from GPS radio occultation

et al. 2013

View full text Add to dashboard Cite

Global Positioning System (GPS) radio occultation (RO) has provided continuous observations of the Earth's atmosphere since 2001 with global coverage, all-weather capability, and high accuracy and vertical resolution in the upper troposphere and lower stratosphere (UTLS). Precise time measurements enable long-term stability but careful processing is needed. Here we provide climate-oriented atmospheric scientists with multicenter-based results on the long-term stability of RO climatological fields for trend studies. We quantify the structural uncertainty of atmospheric trends estimated from the RO record, which arises from current processing schemes of six international RO processing centers, DMI Copenhagen, EUM Darmstadt, GFZ Potsdam, JPL Pasadena, UCAR Boulder, and WEGC Graz. Monthly-mean zonal-mean fields of bending angle, refractivity, dry pressure, dry geopotential height, and dry temperature from the CHAMP mission are compared for September 2001 to September 2008. We find that structural uncertainty is lowest in the tropics and mid-latitudes (50° S to 50° N) from 8 km to 25 km for all inspected RO variables. In this region, the structural uncertainty in trends over 7 yr is <0.03% for bending angle, refractivity, and pressure, <3 m for geopotential height of pressure levels, and <0.06 K for temperature; low enough for detecting a climate change signal within about a decade. Larger structural uncertainty above about 25 km and at high latitudes is attributable to differences in the processing schemes, which undergo continuous improvements. Though current use of RO for reliable climate trend assessment is bound to 50° S to 50° N, our results show that quality, consistency, and reproducibility are favorable in the UTLS for the establishment of a climate benchmark record

show abstract

Section: Study Setup and Methodsmentioning

confidence: 99%

Quantification of structural uncertainty in climate data records from GPS radio occultation

et al. 2013

View full text Add to dashboard Cite

show abstract

“…We choose the 100 hPa level because it is the standard pressure level from ERA-Interim that is closest to the climatological tropopause in the tropics (96-100 hPa in summer, 86-88 hPa in winter; Kim and Son, 2012). Tropical winds near the tropopause in ERA-Interim differ from observations slightly more than in the extratropics, but still are of good quality (Poli et al, 2010;Dee et al, 2011), and the variability of horizontal divergence is in balance with temperatures, which are constrained by GPS-RO in the upper troposphere -lower stratosphere (UTLS).…”

Section: Data Setsmentioning

confidence: 99%

The tropical tropopause inversion layer: variability and modulation by equatorial waves

2016

View full text Add to dashboard Cite

Abstract. The tropical tropopause layer (TTL) acts as a transition layer between the troposphere and the stratosphere over several kilometers, where air has both tropospheric and stratospheric properties. Within this region, a fine-scale feature is located: the tropopause inversion layer (TIL), which consists of a sharp temperature inversion at the tropopause and the corresponding high static stability values right above, which theoretically affect the dispersion relations of atmospheric waves like Rossby or inertia-gravity waves and hamper stratosphere-troposphere exchange (STE). Therefore, the TIL receives increasing attention from the scientific community, mainly in the extratropics so far. Our goal is to give a detailed picture of the properties, variability and forcings of the tropical TIL, with special emphasis on small-scale equatorial waves and the quasi-biennial oscillation (QBO).We use high-resolution temperature profiles from the COSMIC satellite mission, i.e., ∼ 2000 measurements per day globally, between 2007 and 2013, to derive TIL properties and to study the fine-scale structures of static stability in the tropics. The situation at near tropopause level is described by the 100 hPa horizontal wind divergence fields, and the vertical structure of the QBO is provided by the equatorial winds at all levels, both from the ERA-Interim reanalysis.We describe a new feature of the equatorial static stability profile: a secondary stability maximum below the zero wind line within the easterly QBO wind regime at about 20-25 km altitude, which is forced by the descending westerly QBO phase and gives a double-TIL-like structure. In the lowermost stratosphere, the TIL is stronger with westerly winds. We provide the first evidence of a relationship between the tropical TIL strength and near-tropopause divergence, with stronger (weaker) TIL with near-tropopause divergent (convergent) flow, a relationship analogous to that of TIL strength with relative vorticity in the extratropics.To elucidate possible enhancing mechanisms of the tropical TIL, we quantify the signature of the different equatorial waves on the vertical structure of static stability in the tropics. All waves show, on average, maximum cold anomalies at the thermal tropopause, warm anomalies above and a net TIL enhancement close to the tropopause. The main drivers are Kelvin, inertia-gravity and Rossby waves. We suggest that a similar wave modulation will exist at mid-and polar latitudes from the extratropical wave modes.

show abstract

“…The ECMWF assimilation has incorporated the COS-MIC RO soundings in its analysis . However, ECMWF does not assimilate the RO profiles below the ducting layer at the ABL top (Poli et al, 2010), which is frequently seen in the analysis over subtropical eastern oceans, especially over SE Pacific (e.g., von Engeln and Teixeira, 2004;Lopez, 2009). Also the VOCALS radiosondes are not assimilated into the analysis.…”

Section: Data Descriptionmentioning

confidence: 99%

Advances and limitations of atmospheric boundary layer observations with GPS occultation over southeast Pacific Ocean

Xie

et al. 2012

Atmos. Chem. Phys.

View full text Add to dashboard Cite

Abstract. The typical atmospheric boundary layer (ABL) over the southeast (SE) Pacific Ocean is featured with a strong temperature inversion and a sharp moisture gradient across the ABL top. The strong moisture and temperature gradients result in a sharp refractivity gradient that can be precisely detected by the Global Positioning System (GPS) radio occultation (RO) measurements. In this paper, the Constellation Observing System for Meteorology, Ionosphere & Climate (COSMIC) GPS RO soundings, radiosondes and the high-resolution ECMWF analysis over the SE Pacific are analyzed. COSMIC RO is able to detect a wide range of ABL height variations (1-2 km) as observed from the radiosondes. However, the ECMWF analysis systematically underestimates the ABL heights. The sharp refractivity gradient at the ABL top frequently exceeds the critical refraction (e.g., −157 N-unit km −1 ) and becomes the so-called ducting condition, which results in a systematic RO refractivity bias (or called N -bias) inside the ABL. Simulation study based on radiosonde profiles reveals the magnitudes of the N-biases are vertical resolution dependent. The N -bias is also the primary cause of the systematically smaller refractivity gradient (rarely exceeding −110 N-unit km −1 ) at the ABL top from RO measurement. However, the N-bias seems not affect the ABL height detection. Instead, the very large RO bending angle and the sharp refractivity gradient due to ducting allow reliable detection of the ABL height from GPS RO. The seasonal mean climatology of ABL heights derived from a nine-month composite of COSMIC RO soundings over the SE Pacific reveals significant differences from the ECMWF analysis. Both show an increase of ABL height from the shallow stratocumulus near the coast to a much higher trade wind inversion further off the coast. However, COSMIC RO shows an overall deeper ABL and reveals different locations of the minimum and maximum ABL heights as compared to the ECMWF analysis. At low latitudes, despite the decreasing number of COSMIC RO soundings and the lower percentage of soundings that penetrate into the lowest 500-m above the mean-sea-level, there are small sampling errors in the mean ABL height climatology. The difference of ABL height climatology between COSMIC RO and ECMWF analysis over SE Pacific is significant and requires further studies.

show abstract

Assimilation of Global Positioning System radio occultation data in the ECMWF ERA–Interim reanalysis

Cited by 200 publications

References 36 publications

Quantification of structural uncertainty in climate data records from GPS radio occultation

Quantification of structural uncertainty in climate data records from GPS radio occultation

The tropical tropopause inversion layer: variability and modulation by equatorial waves

Advances and limitations of atmospheric boundary layer observations with GPS occultation over southeast Pacific Ocean

Contact Info

Product

Resources

About