Abstract
Abstract. Thermodynamic profiles in the planetary boundary layer (PBL) are important observations for a range of atmospheric research and operational needs. These profiles can be retrieved from passively sensed spectral infrared (IR) or microwave (MW) radiance observations or can be more directly measured by active remote sensors such as water vapor differential absorption lidars (DIALs). This paper explores the synergy of combining ground-based IR, MW, and DIAL observations using an optimal-estimation retrieval framework, quantifying the reduction in the uncertainty in the retrieved profiles and the increase in information content as additional observations are added to IR-only and MW-only retrievals. This study uses ground-based observations collected during the Perdigão field campaign in central Portugal in 2017 and during the DIAL demonstration campaign at the Atmospheric Radiation Measurement Southern Great Plains site in 2017. The results show that the information content in both temperature and water vapor is higher for the IR instrument relative to the MW instrument (thereby resulting in smaller uncertainties) and that the combined IR + MW retrieval is very similar to the IR-only retrieval below 1.5 km. However, including the partial profile of water vapor observed by the DIAL increases the information content in the combined IR + DIAL and MW + DIAL water vapor retrievals substantially, with the exact impact vertically depending on the characteristics of the DIAL instrument itself. Furthermore, there is a slight increase in the information content in the retrieved temperature profile using the IR + DIAL relative to the IR-only; this was not observed in the MW + DIAL retrieval.
Highlights
High-temporal-resolution thermodynamic profiles in the planetary boundary layer (PBL) are needed for a wide range of research and operational weather forecasting needs (Wulfmeyer et al, 2015)
As we can see, the degrees of freedom for signal (DFS) are typically much smaller than unity, so we look at the profile of the cumulative DFS as this allows us to quickly determine how many independent levels are below some specified height, which is advantageous when talking about where in the vertical the different instruments provide sensitivity to changes in temperature and water vapor
What is not known is how the information content changes when partial profiles of water vapor from a differential absorption lidar are included in a retrieval considering the synergy of Atmospheric Emitted Radiance Interferometer (AERI), microwave radiometer (MWR), and nDIAL or vDIAL
Summary
High-temporal-resolution thermodynamic profiles in the planetary boundary layer (PBL) are needed for a wide range of research and operational weather forecasting needs (Wulfmeyer et al, 2015). The PECAN observations are being used to study a range of atmospheric phenomena both observationally (e.g., Gasmick et al, 2018; Loveless et al, 2019) and via use in numerical weather prediction models (Johnson et al, 2018; Degelia et al, 2019). These different ground-based remote sensors have generally not been collocated, which makes evaluating the relative differences in the information content of the observations difficult.
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