- 1Institute of Climate and Atmospheric Sciences, University of Leeds, Leeds, United Kingdom of Great Britain – England, Scotland, Wales (eepvrj@leeds.ac.uk)
- 2School of Earth and Environmental Sciences, University of Saint Andrews, Saint Andrews, United Kingdom of Great Britain – England, Scotland, Wales
- 3Department of Mathematics and Statistics, University of Exeter, Exeter, United Kingdom of Great Britain – England, Scotland, Wales
Tropical high cloud feedback remains a key uncertainty in estimating Equilibrium Climate Sensitivity, particularly the optical depth feedback. The Pacific Intertropical Convergence Zone is a major contributor to tropical cloud radiative effect (CRE). The Tropical Pacific is also projected to see shifts in convection from West to East. In this study, we analyse the key differences in the observed high cloud radiative effect, optical depth and feedback between the East and West Pacific. Notably, we find that the strongest climatological high cloud optical depths and net radiative effects in the tropical region are found in the East Pacific, despite greater high cloud amounts in the West Pacific.
We further estimate the high cloud feedback from the observed variability, using 20 years of CERES Flux By Cloud Type data from MODIS satellite (Sun et al. 2022), following Raghuraman et al [2024] for the regions. We find significant, opposite total high cloud feedbacks between the East and West Pacific, driven primarily by the high cloud amount feedback, with smaller contributions from the optical depth and altitude feedbacks. The shortwave and longwave cloud amount feedbacks are significant in both regions, greater in the West and opposite in sign to the East Pacific. However, the net amount feedback is negative in both regions and twice as strong in the East Pacific than in the West. As expected, the cloud altitude feedback is positive in every region analysed, primarily driven by the longwave component. Only the West Pacific shows a significant optical depth feedback, driven by a positive shortwave feedback. The distinct high cloud amount and optical depth feedbacks estimated in the regions are not apparent when analysing the entire tropics.
We find that the estimated cloud feedbacks in the tropical Pacific strongly depend on the inclusion of ENSO events in the record. Since climate projections suggest an El Nino-like warming in response to CO2 forcing, understanding the potential for changes in high cloud properties in the Pacific, as suggested by our observational evidence, is vital.
References:
Raghuraman, S.P. et al. (2024) ‘Observational Quantification of Tropical High Cloud Changes and Feedbacks’, Journal of Geophysical Research: Atmospheres, 129(7), p. e2023JD039364. Available at: https://doi.org/10.1029/2023JD039364.
Sun, M. et al. (2022) ‘Clouds and the Earth’s Radiant Energy System(CERES) FluxByCldTyp Edition 4 Data Product’, Journal of Atmospheric and Oceanic Technology, 39(3), pp. 303–318. Available at: https://doi.org/10.1175/JTECH-D-21-0029.1.
How to cite: Romero Jure, P. V., Finney, D., Maycock, A., Blyth, A., Mackie, A., and Lambert, H.: Observational quantification of high cloud radiative effect and feedback: An Analysis of differences across the tropical Pacific, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4227, https://doi.org/10.5194/egusphere-egu25-4227, 2025.
