Climate benchmark profiling of greenhouse gases and thermodynamic structure and wind from space

Abstract

Accurate, long‐term, consistent data are fundamental to climate science and satellite observations are the key to obtain such data globally in the Earth's atmosphere. Current methods are unable to jointly and consistently observe essential climate variables including thermodynamic ones (temperature, pressure, humidity), wind, and greenhouse gases. Here we introduce a method that profiles these variables over the upper troposphere and lower stratosphere and beyond as consistent benchmark dataset (e.g., monthly‐mean temperature accurate to 0.1 K, wind to 0.5 m s−1, carbon dioxide concentration to within 1 ppm). It combines microwave and infrared‐laser occultation between satellites in low Earth orbit for thermodynamic state, greenhouse gas and line‐of‐sight wind profiling. With adequate scaling it can also be applied beyond Earth's atmosphere such as in planetary atmospheres. The method may become an authoritative reference standard for global monitoring of greenhouse gases and climate change in Earth's free atmosphere over the 21st century.

Atmospheric influences on infrared-laser signals used for occultation measurements between Low Earth Orbit satellites

“…The reason is that except for thermal radiation these influences are more complex and therefore require separate papers. Moreover, since these influences exert, except for clouds, small to negligible effects in differential transmission (Schweitzer, 2010;Kirchengast et al, 2010;Kirchengast and Schweitzer, 2011), they are not that fundamental in the context of this paper. Clouds will typically block the whole signal, leading to effectively zero transmission and no received SWIR-laser pulse signal at cloud-contaminated height levels.…”

“…We show most of them for the set of 19 LIO channels (resulting in 13 channel pairs for the retrieval of 10 different species) proposed by Kirchengast et al (2010) and Kirchengast and Schweitzer (2011), which have been selected on the basis of studies by Schweitzer (2010). The frequencies belonging to these channel pairs and their spectral separation are summarised in Table 1.…”

“…on the ratio of received signal power to the noise-equivalent power (NEP) of the detection system. For the ACCURATE mission this is designed to be at least 34 dB at 1 Hz bandwidth Kirchengast and Schweitzer, 2011). The total atmospheric loss down to the UTLS bottom (5 km) should thus not exceed about 21 dB, leaving 13 dB SNR margin (5 % relative accuracy of signal).…”

“…This mission concept applies the occultation measurement principle (Phinney and Anderson, 1968; in a novel way, called LEO-LEO microwave and infrared-laser occultation (LMIO), recently introduced by Kirchengast and Schweitzer (2011). A graphical view of the concept is given in Fig.…”

“…The retrieved profiles are expected very accurate, have a high vertical resolution (about 1 km) and typically cover the whole UTLS region, which is an important region for climate and chemistry (Li et al, 2008;Steiner et al, 2009). For a detailed introduction of the LMIO method, and the proposed mission concept ACCURATE to implement it, see Kirchengast and Schweitzer (2011); Kirchengast et al (2010); Schweitzer (2010).…”