Ground-based atmospheric measurements from CHRIS for satellite validation.
Authors: Marie-Thérèse El Kattar , Frédérique Auriol , Hervé Herbin 
Published: March 2020

&lt;p&gt;Ground-based high spectral resolution infrared measurements are considered to be the most efficient way to obtain accurate tropospheric abundances of different gaseous species and in particular greenhouse gases, such as CO&lt;sub&gt;2&lt;/sub&gt; and CH&lt;sub&gt;4&lt;/sub&gt;. Furthermore, this type of measurement is also commonly used to validate the satellite retrievals. Despite the outstanding capabilities of the spectrometers used by the TCCON and NDACC networks, they are inadequate for field campaigns; therefore, more compact and stable spectrometers have been developed. &lt;strong&gt;CHRIS&lt;/strong&gt; (&lt;strong&gt;C&lt;/strong&gt;ompact &lt;strong&gt;H&lt;/strong&gt;igh &lt;strong&gt;S&lt;/strong&gt;pectral &lt;strong&gt;R&lt;/strong&gt;esolution &lt;strong&gt;I&lt;/strong&gt;nfrared &lt;strong&gt;S&lt;/strong&gt;pectrometer) is a new prototype based on the EM27-SUN from Bruker, with unique characteristics such as its high spectral resolution (0.135 cm&lt;sup&gt;-1&lt;/sup&gt; non-apodized) with a spectral sampling every 0.065 cm&lt;sup&gt;-1&lt;/sup&gt; to satisfy the Nyquist criterion. This optically stable instrument allows recording solar transmission light spectra in a wide spectral range (680 to 5200 cm&lt;sup&gt;-1&lt;/sup&gt;) with a relatively high SNR (~780 in average).&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; This instrumental prototype is designed to perform measurements of greenhouse gases (CO&lt;sub&gt;2&lt;/sub&gt;, CH&lt;sub&gt;4&lt;/sub&gt; and H&lt;sub&gt;2&lt;/sub&gt;O), trace gases (SO&lt;sub&gt;2&lt;/sub&gt;, CO, HCl, NO&lt;sub&gt;x&lt;/sub&gt;&amp;#8230;) but also aerosols and clouds that have very typical spectral features in particular in the thermal infrared region. The main objective of this study is the accurate retrieval of tropospheric abundances of the greenhouse gases, CO&lt;sub&gt;2&lt;/sub&gt; and CH&lt;sub&gt;4&lt;/sub&gt;, in the TIR/SWIR regions, and study the synergy between them especially for the MAGIC campaign. CHRIS is a part of this ongoing campaign in an attempt to monitor the GHG and validate the actual space missions like IASI, OCO-2, GOSAT-2 and future space missions like Merlin, MicroCarb and IASI-NG.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; Here, the spectral and radiometric characterization of this instrument is briefly explained. Furthermore, we present CHRIS&amp;#8217;s capabilities to measure CO&lt;sub&gt;2&lt;/sub&gt; and CH&lt;sub&gt;4&lt;/sub&gt; vertical profiles through a complete information content analysis, a channel selection and an error budget estimation. The preliminary results of the retrieval of these gases using the radiative transfer model ARAHMIS developed at the LOA is also presented. CHRIS is also part of other campaigns such as ImagEtna and Shadow-2 to study the trace gases and aerosols respectively.&lt;/p&gt;