Retrieving vertical profiles of cloud droplet effective radius using multispectral measurements from MODIS: examples and limitations
Year: 2025
Type: article
Abstract: . With the coming launch of the Climate Absolute Radiance and Refractivity Earth Observatory (CLARREO) Pathfinder (CPF) comes an opportunity to develop a new cloud retrieval from spectral reflectance measurements. With continuous coverage across the shortwave spectrum and a factor of 5 to 10 lower radiometric uncertainty than the Moderate Resolution Imaging Spectroradiometer (MODIS), CPF facilitates the retrieval of a vertical profile of droplet size, providing insight into the internal structure of a cloud. Measurements from MODIS coincident with in situ observations provide the foundation for developing a constrained optimal estimation technique, ensuring a solution consistent with forward model assumptions. The limited unique information in the MODIS bands used in this analysis led to a non-unique solution, with many droplet profiles leading to convergence. Droplet size at cloud bottom is difficult to constrain because visible and near-infrared reflectances have an average penetration depth near cloud top. The region of convergence within the solution space decreased along the cloud bottom radius dimension by 2 μm when increasing the number of wavelengths used in the retrieval from seven to 35, and by 5 μm when reducing the measurement uncertainty from 2 % to 0.3 %. The enhanced accuracy and, to a lesser degree, the enhanced spectral sampling provided by CPF measurements are essential to extracting vertically resolved droplet size information from moderately thick, warm clouds.
Authors: Andrew J. Buggee, Peter Pilewskie
Language: English
Subfield: Global and Planetary Change
Field: Environmental Science
Domain: Physical Sciences
SDG: Climate action
Open Access status: gold
Estimated APC paid: $1,585
OpenAlex ID: W4415160940