Thermodynamic phase profiles of optically thin midlatitude clouds and their relation to temperature

• Published in: Journal of Geophysical Research
• Main Authors: Naud, C. M., del Genio, A. D., Haeffelin, M., Morille, Y., Noel, V., Dupont, J. -C., Turner, D. D., Lo, C., Comstock, J.
• Other Authors: Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-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)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2010
• Subjects: Atmospheric Processes: Clouds and aerosols; Atmospheric Processes: Remote sensing; Atmospheric Processes: Instruments and techniques; Atmospheric Composition and Structure: Cloud physics and chemistry; mixed phase clouds; supercooled water; depolarization; optically thin clouds; ground-based lidar; Earth Science; [SDU]Sciences of the Universe [physics]; Arctic
• Online Access: https://hal.science/hal-04113839; https://hal.science/hal-04113839/document; https://hal.science/hal-04113839/file/Journal%20of%20Geophysical%20Research%20Atmospheres%20-%202010%20-%20Naud%20-%20Thermodynamic%20phase%20profiles%20of%20optically%20thin%20midlatitude.pdf; https://doi.org/10.1029/2009JD012889

International audience The relationship between cloud thermodynamic phase and temperature in some aircraft measurements conducted in midlatitude frontal clouds suggests that significant liquid does not exist at temperatures colder than 258 K. This data set is often used to verify parameterizations of cloud phase in general circulation models. However, other aircraft campaigns and different instruments suggest a different relationship. Here we examine the temperature-phase relationship for midlatitude optically thin winter clouds. Cloud phase and temperature profiles derived from 5 years of ground-based lidar depolarization and radiosonde measurements are analyzed for two midlatitude locations: the U. S. Atmospheric Radiation Measurement Program Southern Great Plains site and the Site Instrumental de Recherche par Télédétection Atmosphérique in France. Because lidars are attenuated in optically thick clouds, the data set only includes clouds with optical thickness of <3. Cloud phase is obtained by using the classical method based on a depolarization ratio threshold of 11% for differentiating liquid from ice. The frequency of occurrence of clouds either completely liquid or completely glaciated in the temperature range from 233 to 273 K is similar to previous observations in the midlatitudes but somewhat greater than in the Arctic. The relationship between ice phase occurrence and temperature only slightly changes between cloud base and top. At both sites, liquid is more prevalent at colder temperatures than has been found previously in some thicker frontal clouds, suggesting different processes for glaciation in nonfrontal optically thin clouds.