Atmospheric Climate Change Detection by Radio Occultation Data Using a Fingerprinting Method

Abstract

The detection of climate change signals in rather short satellite datasets is a challenging task in climate research and requires high-quality data with good error characterization. Global Navigation Satellite System (GNSS) radio occultation (RO) provides a novel record of high-quality measurements of atmospheric parameters of the upper-troposphere-lower-stratosphere (UTLS) region. Because of characteristics such as long-term stability, self calibration, and a very good height resolution, RO data are well suited to investigate atmospheric climate change. This study describes the signals of ENSO and the quasi-biennial oscillation (QBO) in the data and investigates whether the data already show evidence of a forced climate change signal, using an optimal-fingerprint technique. RO refractivity, geopotential height, and temperature within two trend periods (1995-2010 intermittently and 2001-10 continuously) are investigated. The data show that an emerging climate change signal consistent with the projections of three global climate models from the Coupled Model Intercomparison Project cycle 3 (CMIP3) archive is detected for geopotential height of pressure levels at a 90% confidence level both for the intermittent and continuous period, for the latter so far in a broad 508S-508N band only. Such UTLS geopotential height changes reflect an overall tropospheric warming. 90% confidence is not achieved for the temperature record when only large-scale aspects of the pattern are resolved. When resolving smaller-scale aspects, RO temperature trends appear stronger than GCM-projected trends, the difference stemming mainly from the tropical lower stratosphere, allowing for climate change detection at a 95% confidence level. Overall, an emerging trend signal is thus detected in the RO climate record, which is expected to increase further in significance as the record grows over the coming years. Small natural changes during the period suggest that the detected change is mainly caused by anthropogenic influence on climate.

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

“…Furthermore, geopotential height change (m decade −1 ) relates to relative pressure change (% decade −1 ) via the atmospheric scale height by a factor of about 70 m % −1 (e.g. Leroy et al, 2006b;Scherllin-Pirscher et al, 2011b) so that expected climate change signals in geopotential height of roughly 10 m decade −1 at low to mid latitudes (Leroy et al, 2006b;Lackner et al, 2011) suggest a stability requirement like 4 m decade −1 , and correspondingly of 0.06 % decade −1 for pressure, to be reasonable values.…”

“…For context, Lackner et al (2011) showed in a dedicated climate change signal detection study for RO a geopotential height increase of ∼15 m decade −1 , a warming of ∼0.3 K decade −1 in the UT and a cooling of a ∼0.6 K decade −1 in the LS tropics for the period 2001 to 2010. The corresponding structural uncertainty in the tropics as found from this uncertainty study is for geopotential height <3 m decade −1 in the UTLS.…”

Quantifying residual ionospheric errors in GNSS radio occultation bending angles based on ensembles of profiles from end-to-end simulations

“…Global Navigation Satellite System (GNSS) radio occultation (RO) (Melbourne et al, 1994;Kursinski et al, 1997;Hajj et al, 2002) is a relatively new atmospheric remote sensing technique. It can deliver data traceable to the international standard of time (the SI second) and has the potential for monitoring decadal-scale climate change (Steiner et al, 2009;Scherllin-Pirscher et al, 2011b;Lackner et al, 2011) due to its unique characteristics such as high vertical resolution, high accuracy and long-term stability of its observations, as well as self-calibration capability and global coverage (Gobiet and Kirchengast, 2004;Steiner et al, 2011). Figure 1 illustrates the GPS-to-LEO occultation geometry.…”

The FengYun-3C radio occultation sounder GNOS: a review of the mission and its early results and science applications

“…These missions have demonstrated the unique properties of the GNSS RO technique, such as high vertical resolution, high accuracy, all-weather capability and global coverage (Ware et al, 1996;Gorbunov et al, 1996;Rocken et al, 1997;Leroy, 1997;Steiner et al, 1999), and long-term stability and consistency of different RO mission observations (Foelsche et al, , 2011. Therefore, GNSS RO data products (i.e., bending angle, refractivity, temperature, 10 pressure, water vapor, and ionospheric electron density profiles) have been widely used for numerical weather prediction (NWP) (e.g., Healy and Eyre, 2000;Healy and Thepaut, 2006;Aparicio and Deblonde, 2008;Cucurull and Derber, 2008;Poli et al, 2008;Huang et al, 2010;Le Marshall et al, 2010;Harnisch et al, 2013), global climate monitoring (GCM) (e.g., Steiner et al, 2001Steiner et al, , 2009Steiner et al, , 2013Schmidt et al, 2005Schmidt et al, , 2008Schmidt et al, , 2010Loescher 15 and Kirchengast, 2008;Ho et al, 2009Ho et al, , 2012Foelsche et al, 2011a;Lackner et al, 2011) and space weather research (SWR) (Anthes, 2011;Anthes et al, 2008;Arras et al, 2008;Brahmanandam et al, 2012;Pi et al, 1997;Wickert, 2004;Yue et al, 2015).…”