Assessing 1D Atmospheric Solar Radiative Transfer Models: Interpretation and Handling of Unresolved Clouds

• DOI: 10.1175/1520-0442(2003)016<2676:adasrt>2.0.co;2
• Publication Date: 2003-08-06T16:45:15Z
• Authors: H. W. Barker; G. L. Stephens; P. T. Partain; J. W. Bergman; B. Bonnel; K. Campana; E. E. Clothiaux; S. Clough; S. Cusack; J. Delamere; J. Edwards; K. F. Evans; Y. Fouquart; S. Freidenreich; V. Galin; Y. Hou; S. Kato; J. Li; E. Mlawer; J.-J. Morcrette; W. O'Hirok; P. Räisänen; V. Ramaswamy; B. Ritter; E. Rozanov; M. Schlesinger; K. Shibata; P. Sporyshev; Z. Sun; M. Wendisch; N. Wood; F. Yang
• Keywords: Overcast; Albedo (alchemy); Longwave; Shortwave; Atmospheric models; Downwelling

The primary purpose of this study is to assess the performance 1D solar radiative transfer codes that are used currently both for research and in weather climate models. Emphasis on interpretation handling unresolved clouds. Answers sought following questions: (i) How well do interpret handle columns information pertaining partly cloudy atmospheres? (ii) Regardless adequacy their assumptions about clouds, perform as intended? One clear-sky two plane-parallel, homogeneous (PPH) overcast cloud cases serve elucidate model differences due varying treatments gaseous transmittances, optical properties, basic transfer. remaining four involve 3D distributions water vapor simulated by cloud-resolving Results 25 codes, which included line-by-line (LBL) models (clear only) Monte Carlo (MC) photon transport algorithms, were submitted 22 groups. Benchmark, domain-averaged irradiance profiles computed MC codes. For clear cases, all estimates top-of-atmosphere albedo, atmospheric absorptance, surface absorptance agree with one LBL within ±2%. Most underestimate typically 15–25 W m–2 at overhead sun standard tropical atmosphere regardless Depending partitioned into genres: horizontal variability, exact overlap PPH (iii) maximum/random (iv) random A single code was establish conditional benchmarks applicable each genre, full benchmarks. There a tendency cluster near respective benchmarks, though intragenre variances exceed those cases. majority fall extreme category clouds thus generally disagree benchmark values. Given fairly limited scope these tests inability any extremely begs question paradigm shift modeling fluxes atmospheres.