Daytime Cirrus Cloud Top-of-the-Atmosphere Radiative Forcing Properties at a Midlatitude Site and Their Global Consequences

• DOI: 10.1175/jamc-d-15-0217.1
• Publication Date: 2016-05-03T18:11:30Z
• Authors: James R. Campbell; Simone Lolli; Jasper R. Lewis; Yu Gu; Ellsworth J. Welton
• Keywords: Cirrus; Cloud forcing; Cloud height; Solar zenith angle; Zenith; Forcing (mathematics); Cloud albedo; Cloud top; Middle latitudes

Abstract One year of continuous ground-based lidar observations (2012) is analyzed for single-layer cirrus clouds at the NASA Micro Pulse Lidar Network site Goddard Space Flight Center to investigate top-of-the-atmosphere (TOA) annual net daytime radiative forcing properties. A slight positive estimated (i.e., warming): 0.07–0.67 W m −2 in sample-relative terms, which reduces 0.03–0.27 absolute terms after normalizing unity based on a 40% midlatitude occurrence frequency rate from satellite data. Results are bookend solutions extinction-to-backscatter (20 and 30 sr) corresponding retrievals 532-nm cloud extinction coefficient. Uncertainties due undersampling, attenuation effects, sample selection, multiple scattering described. cooling effect found very thinnest (cloud optical depth ≤ 0.01), attributed relatively high solar zenith angles. relationship involving positive/negative demonstrated as function angle cloud-top temperature. These properties, combined with influence varying surface albedos, used conceptualize how likely varies latitude season, exerting less potentially TOA approaching summer poles (not ice snow covered) versus greater warming equator. The existence such gradient would lead induce annually seasonally, making it far challenge than presently believed constrain diurnal contributions global radiation budgets.