Retrieval and validation of carbon dioxide, methane and water vapor for the Canary Islands IR-laser occultation experiment

Abstract

Abstract. The first ground-based experiment to prove the concept of a novel space-based observation technique for microwave and infrared-laser occultation between low-Earthorbit satellites was performed in the Canary Islands between La Palma and Tenerife. For two nights from 21 to 22 July 2011 the experiment delivered the infrared-laser differential transmission principle for the measurement of greenhouse gases (GHGs) in the free atmosphere. Such global and long-term stable measurements of GHGs, accompanied also by measurements of thermodynamic parameters and line-of-sight wind in a self-calibrating way, have become very important for climate change monitoring. The experiment delivered promising initial data for demonstrating the new observation concept by retrieving volume mixing ratios of GHGs along a ∼ 144 km signal path at altitudes of ∼ 2.4 km. Here, we present a detailed analysis of the measurements, following a recent publication that introduced the experiment's technical setup and first results for an example retrieval of CO 2 . We present the observational and validation data sets, the latter simultaneously measured at the transmitter and receiver sites; the measurement data handling; and the differential transmission retrieval procedure. We also determine the individual and combined uncertainties influencing the results and present the retrieval results for 12 CO 2 , 13 CO 2 , C 18 OO, H 2 O and CH 4 . The new method is found to have a reliable basis for monitoring of greenhouse gases such as CO 2 , CH 4 , and H 2 O in the free atmosphere.

Impacts of Orbital and Constellation Parameters on the Number and Spatiotemporal Coverage of LEO-LEO Occultation Events

“…LIO measures the absorption of the signals to retrieve volume mixing ratio (VMR) profiles of the greenhouse gases, in which the differential transmission principle between carefully selected pairs of absorption signals and reference signals is commonly used. The feasibility of the LMO and LIO techniques has been proven by ground-based demonstration experiments [10,11,17,18,22,23].…”

An Abel transform for deriving line‐of‐sight wind profiles from LEO‐LEO infrared laser occultation measurements

“…wind speed (from LIO), jointly forming the LEO-LEO microwave and infrared laser occultation (LMIO) method .The retrieval of thermodynamic variables and greenhouse gases is well understood from a range of studies employing end-to-end simulations of the LMIO method. After the introduction of LMIO by Kirchengast and Schweitzer [2011] (linking for further details to the scientific reports by Kirchengast et al [2010] and Schweitzer [2010]), an up-to-date assessment of the LMO retrieval performance for thermodynamic profiles was provided by Schweitzer et al [2011a], a full LMIO clear-air retrieval performance assessment with focus on greenhouse gases was provided by Proschek et al [2011], an analysis of LIO signal propagation and signal-to-noise ratio aspects was provided by Schweitzer et al [2011b], and a study on LMIO greenhouse gas retrieval performance in cloudy air, accounting for scintillations from turbulence, was provided by Proschek et al [2014].An initial LIO ground demonstration experiment for greenhouse gas measurements over a 144 km cross-link at the Canary Islands was conducted as well [Brooke et al, 2012;Proschek et al, 2015] and needs for improved spectroscopic knowledge of target absorption lines for LIO laser signals were investigated [Harrison et al, 2011;Proschek et al, 2015].…”

“…An initial LIO ground demonstration experiment for greenhouse gas measurements over a 144 km cross-link at the Canary Islands was conducted as well [Brooke et al, 2012;Proschek et al, 2015] and needs for improved spectroscopic knowledge of target absorption lines for LIO laser signals were investigated [Harrison et al, 2011;Proschek et al, 2015].…”