Abstract
Abstract. The Community Long-term Infrared Microwave Combined Atmospheric Product System (CLIMCAPS) retrieves vertical profiles of temperature, water vapor, greenhouse and pollutant gases, and cloud properties from measurements made by infrared and microwave instruments on polar-orbiting satellites. These are AIRS/AMSU on Aqua and CrIS/ATMS on Suomi NPP and NOAA20; together they span nearly 2 decades of daily observations (2002 to present) that can help characterize diurnal and seasonal atmospheric processes from different time periods or regions across the globe. While the measurements are consistent, their information content varies due to uncertainty stemming from (i) the observing system (e.g., instrument type and noise, choice of inversion method, algorithmic implementation, and assumptions) and (ii) localized conditions (e.g., presence of clouds, rate of temperature change with pressure, amount of water vapor, and surface type). CLIMCAPS quantifies, propagates, and reports all known sources of uncertainty as thoroughly as possible so that its retrieval products have value in climate science and applications. In this paper we characterize the CLIMCAPS version 2.0 system and diagnose its observing capability (ability to retrieve information accurately and consistently over time and space) for seven atmospheric variables – temperature, H2O, CO, O3, CO2, HNO3, and CH4 – from two satellite platforms, Aqua and NOAA20. We illustrate how CLIMCAPS observing capability varies spatially, from scene to scene, and latitudinally across the globe. We conclude with a discussion of how CLIMCAPS uncertainty metrics can be used in diagnosing its retrievals to promote understanding of the observing system and the atmosphere it measures.
Highlights
Instruments onboard satellites observe the global Earth atmosphere with unprecedented regularity in space and time
In this paper we focus on satellite sounding systems that retrieve atmospheric variables as vertical profiles from topof-atmosphere radiance measurements, on the Community Long-term Infrared Microwave Combined Atmospheric Product System (CLIMCAPS; Smith and Barnet, 2019)
We see this in CLIMCAPS-NOAA20 observing capability that is lower for both H2O and CH4, while in CLIMCAPS-Aqua it is higher for both variables
Summary
Instruments onboard satellites observe the global Earth atmosphere with unprecedented regularity in space and time. Smith and Barnet (2019) described how CLIMCAPS quantifies and propagates scene-dependent uncertainty using error covariance matrices (ECMs) in a sequential retrieval approach that starts with retrieving clouds, followed by temperature, water vapor, and the trace gas species O3, CO, CH4, CO2, N2O, SO2, and HNO3. We present CLIMCAPS version 2.0 AKMs for a range of different retrieval variables, different scenes across time and space, and multiple satellite platforms and instrument types with the goal of characterizing CLIMCAPS observing capability and promoting a better understanding of its retrieved soundings and their value in applications. We define a CLIMCAPS retrieval scene (or “field of regard”) as the spatial and spectral aggregate of radiance measurements that results from performing cloud clearing (Chahine, 1982; Susskind et al, 1998; Smith and Barnet, 2019).
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