Abstract
Abstract. Aerosol heating due to shortwave absorption has implications for local atmospheric stability and regional dynamics. The derivation of heating rate profiles from space-based observations is challenging because it requires the vertical profile of relevant properties such as the aerosol extinction coefficient and single-scattering albedo (SSA). In the southeastern Atlantic, this challenge is amplified by the presence of stratocumulus clouds below the biomass burning plume advected from Africa, since the cloud properties affect the magnitude of the aerosol heating aloft, which may in turn lead to changes in the cloud properties and life cycle. The combination of spaceborne lidar data with passive imagers shows promise for future derivations of heating rate profiles and curtains, but new algorithms require careful testing with data from aircraft experiments where measurements of radiation, aerosol, and cloud parameters are better colocated and readily available. In this study, we derive heating rate profiles and vertical cross sections (curtains) from aircraft measurements during the NASA ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) project in the southeastern Atlantic. Spectrally resolved irradiance measurements and the derived column absorption allow for the separation of total heating rates into aerosol and gas (primarily water vapor) absorption. The nine cases we analyzed capture some of the co-variability of heating rate profiles and their primary drivers, leading to the development of a new concept: the heating rate efficiency (HRE; the heating rate per unit aerosol extinction). HRE, which accounts for the overall aerosol loading as well as vertical distribution of the aerosol layer, varies little with altitude as opposed to the standard heating rate. The large case-to-case variability for ORACLES is significantly reduced after converting from heating rate to HRE, allowing us to quantify its dependence on SSA, cloud albedo, and solar zenith angle.
Highlights
Off the western coast of southern Africa, a semi-permanent, seasonal stratocumulus cloud deck occurs in a broad region of subsidence in the southeastern Atlantic Ocean (Zuidema et al, 2016; Gordon et al, 2018)
(both obtained from a spiral retrieval and held constant); (b) the Solar Spectral Flux Radiometer (SSFR)-measured albedo spectra, the aerosol optical depth (AOD) spectra, and column ozone retrievals from 4STAR, all of which are measured from the bottom of the layer (BOL) leg of the radiation wall; and (c) aerosol extinction profiles at 532 nm of the full aerosol layer measured by High Spectral Resolution Lidar 2 (HSRL-2) from the the aerosol layer (TOL) leg (Table 2)
Observations from the ORACLES 2016 and 2017 experiments allow us to introduce a method of determining heating rate profiles as directly as possible by linking the heating rates to SSFR-measured irradiance profiles
Summary
Off the western coast of southern Africa, a semi-permanent, seasonal stratocumulus cloud deck occurs in a broad region of subsidence in the southeastern Atlantic Ocean (Zuidema et al, 2016; Gordon et al, 2018). Lidar instruments can provide aerosol extinction profiles for large spatial regions, which can be combined with additional observations that provide aerosol optical properties (e.g., Deaconu et al, 2019) or incorporated into climate models (Mallet et al, 2019; Tummon et al, 2010; Gordon et al, 2018; Adebiyi et al, 2015; Wilcox, 2010). High-spectral-resolution lidars (HSRLs) are likely to be included in future space architectures Among other advantages, they will provide extinction profiles directly (Hu et al, 2007; Hair et al, 2008). They will provide extinction profiles directly (Hu et al, 2007; Hair et al, 2008) This would be useful with the new concept of heating rate efficiency (HRE) first introduced in this paper
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
