Surface longwave cloud radiative effect derived from space lidar observations : application in the Arctic

• Main Author: Arouf, Assia
• Other Authors: Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL), Sorbonne Université, Hélène Chepfer
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2023
• Subjects: Space-Lidar; Surface cloud radiative effect; Radiative transfer; Longwave; Arctic; Lidar spatial; Effet radiatif des nuages; Transfert radiatif; Infrarouge; Surface de la Terre; Arctique; [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]; Arctique*; Sea ice
• Online Access: https://theses.hal.science/tel-04193782; https://theses.hal.science/tel-04193782/document; https://theses.hal.science/tel-04193782/file/AROUF_Assia_these_2023.pdf

Clouds play an important role in regulating Earth’s energy budget at the surface. For example, clouds absorb thermal radiation emitted by Earth’s surface and reemit it toward the surface and warming the surface. This can be quantified through surface LongWave (LW) Cloud Radiative Effect (CRE). However, surface LW CRE on a global scale is not well retrieved and its instantaneous and interdecadal variability is poorly known. Indeed, it depends highly on vertical cloud distribution, which is poorly documented globally. In this thesis, we propose to retrieve the surface LW CRE over 13 years (2008 − 2020) at a global scale using Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) spaceborne lidar observations. From 1D radiative transfer computations, we establish linear parametrizations between surface LW CRE and cloud properties including cloud altitude. Combining the parametrizations with the cloud observations, we derive two datasets of surface LW CRE, at monthly–2° × 2° gridded scale and instantaneously at full CALIPSO horizontal resolution (90 m cross-track; 330 m along orbit-track). We found that clouds warm the surface by 27.0 W/m2 over the 2008 − 2020 time period at a global scale. Surface LW CRE is particularly important in polar regions such that clouds may have an effect on ice melting. By instantaneously co-locating surface cloud warming and sea ice observations in regions where sea ice varies, we showed that large surface cloud warming values (> 80 W/m2 ) are much more frequent over open water than over sea ice during late Fall. Our results suggest that clouds may delay sea ice freeze-up later into the Fall. Les nuages jouent un rôle important dans la régulation du bilan énergétique à la surface de la Terre. Par exemple, ils absorbent le rayonnement tellurique émis par la surface de la Terre et le réémettent vers la surface, réchauffant ainsi cette dernière. Ce réchauffement peut être quantifié au travers de l’effet radiatif des nuages (Cloud Radiative Effect (CRE)) ...