Abstract
Abstract. High-resolution Fourier transform infrared (FTIR) solar observations are particularly relevant for climate studies, as they allow atmospheric gaseous composition and multiple climate processes to be monitored in detail. In this context, the present paper provides an overview of 20 years of FTIR measurements taken in the framework of the NDACC (Network for the Detection of Atmospheric Composition Change) from 1999 to 2018 at the subtropical Izaña Observatory (IZO, Spain). Firstly, long-term instrumental performance is comprehensively assessed, corroborating the temporal stability and reliable instrumental characterization of the two FTIR spectrometers installed at IZO since 1999. Then, the time series of all trace gases contributing to NDACC at IZO are presented (i.e. C2H6, CH4, ClONO2, CO, HCl, HCN, H2CO, HF, HNO3, N2O, NO2, NO, O3, carbonyl sulfide (OCS), and water vapour isotopologues H216O, H218O, and HD16O), reviewing the major accomplishments drawn from these observations. In order to examine the quality and long-term consistency of the IZO FTIR observations, a comparison of those NDACC products for which other high-quality measurement techniques are available at IZO has been performed (i.e. CH4, CO, H2O, NO2, N2O, and O3). This quality assessment was carried out on different timescales to examine what temporal signals are captured by the FTIR records, and to what extent. After 20 years of operation, the IZO NDACC FTIR observations have been found to be very consistent and reliable over time, demonstrating great potential for climate research. Long-term NDACC FTIR data sets, such as IZO, are indispensable tools for the investigation of atmospheric composition trends, multi-year phenomena, and complex climate feedback processes, as well as for the validation of past and present space-based missions and chemistry climate models.
Highlights
The recognition that changes in the composition of the Earth’s atmosphere are occurring, on both long and short timescales and thereby modifying our environment and climate, has resulted in scientific debate, as well as public concern in the last decades (Gottwald et al, 2006)
The time series of all trace gases contributing to NDACC at Izaña Observatory (IZO) are presented (i.e. C2H6, CH4, ClONO2, carbon monoxide (CO), hydrogen chloride (HCl), hydrogen cyanide (HCN), H2CO, hydrogen fluoride (HF), HNO3, N2O, NO2, NO, O3, carbonyl sulfide (OCS), and water vapour isotopologues H126O, H128O, and HD16O), reviewing the major accomplishments drawn from these observations
By evaluating spectral signatures of vibrational–rotational transitions contained in the solar absorption spectra measured, the Fourier transform infrared (FTIR) technique allows total column amounts and low-resolution vertical profiles of different atmospheric trace gases to be retrieved with a high degree of precision
Summary
The recognition that changes in the composition of the Earth’s atmosphere are occurring, on both long and short timescales and thereby modifying our environment and climate, has resulted in scientific debate, as well as public concern in the last decades (Gottwald et al, 2006). While NDACC aims mainly to establish a long-term database to detect changes and trends in atmospheric composition and to understand their impact on the Earth’s atmosphere (De Mazière et al, 2018), TCCON focuses more on research on greenhouse gases, improving our understanding of the carbon cycle and providing reference validation data sets for climate models and space-based observations (Wunch et al, 2011). These high-resolution FTIR observations have been extended by COCCON Since 2018 NDACC and TCCON activities have been complemented by a portable, low-resolution FTIR spectrometer (a Bruker EM27/SUN), which operates within the COCCON research infrastructure
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