POSTER SESSION 2
10:30–12:30, Tuesday, September 15
Poster Session | 1 | 2 | 3 | 4 | Schedule at a Glance
ABSTRACT 1090 | POSTER 158
EVALUATION OF A THREE-COMPONENT, SEMI-ANALYTIC IRRADIANCE MODEL FOR USE IN OCEAN ECOSYSTEM MODELS
In 1994 Ackleson et al. (J. Geophys. Res. 99 (C4), 7483-7499) developed a three-component model (3CM) for estimation of direct and diffuse downwelling, and upwelling, irradiances within a water column. The 3CM contains six parameters, which are given constant values independent of depth and wavelength and are taken to be the same for all water bodies. In reality these parameters depend on the water IOPs and thus depend on depth and wavelength, as well as on solar zenith angle and sky conditions.
Even though the 3CM is over 30 years old and is now used in several ocean ecosystem models, no study has evaluated the accuracy of the 3CM. We compared the irradiances computed by the 3CM with those computed by HydroLight for a range of water IOPs and solar zenith angles, and for several algorithms used to solve the 3CM equations. We found two sources of error: errors due to the approximations made in developing the 3CM equations, and errors due to the numerical algorithms used to solve the equations.
When solved accurately as ODEs with depth-continuous IOPs, the 3CM equations usually give PAR values that are accurate to within 10% in near-surface waters. The errors in PAR increase with depth and can be hundreds of percent at the bottom of the euphotic zone. For layered IOPs, we compared results from several solution algorithms and found that the algorithm described in Dutkiewicz et al. (Biogeosci., 12, 4447-4481, 2015) is extremely fast and sufficiently accurate for use in many ecosystem models.
Curtis Mobley, Retired from Sequoia Scientific, Inc., [email protected], https://orcid.org/0000-0003-0556-3657
Elena Terzic, Ruder Boskovic Institute, Division for Marine and Environmental Research, Zagreb, Croatia, [email protected], https://orcid.org/0000-0002-9335-6174
Poster Session | 1 | 2 | 3 | 4 | Schedule at a Glance
