Abstract
Abstract. Land-use activities affect Earth's energy balance not only via biogeochemical emissions, but also through perturbations in surface albedo, the latter of which is often excluded in impact assessment studies. In this short technical note, we present and compare a simple model for estimating shortwave radiative forcings at the top of Earth's atmosphere to a more sophisticated 8-stream radiative transfer model based on a discrete ordinate method. Outcomes from monthly albedo change simulations for ten globally distributed regions and a single year revealed that the simple model – based on a single exogenously supplied meteorological variable – performed quite well, having a sample correlation coefficient of 0.93 and a normalized root mean square error of 7.2%. Simple models like the one presented here can offer an attractive and efficient means for non-experts to begin including albedo change considerations in climate impact assessment studies enveloping land use activities.
Highlights
Perturbations in the global energy balance due to changes in land surface albedo are important to consider when attributing climate impacts to policies and product systems originating in the Agriculture, Forestry, and Other Land Use (AFOLU) sectors
The most common method in global climate modeling is to solve the radiative transfer equation numerically when shortwave radiation is propagating in discrete directions, called the discrete ordinate method (DOM) (Chandrasekhar, 1960) and the electromagnetic spectrum is divided into spectral broad bands
A site-by-site comparison of monthly Rs presented in Table 2 reveals that these fluxes are generally higher overall for the Simple relative to the DIScrete Ordinates Radiative Transfer program (DISORT) model, with increasing deviation linked to months with lower incoming extraterrestrial solar radiation – such as in winter for northern latitudes
Summary
Perturbations in the global energy balance due to changes in land surface albedo are important to consider when attributing climate impacts to policies and product systems originating in the Agriculture, Forestry, and Other Land Use (AFOLU) sectors. Surface albedo change considerations are typically neglected due to perceived challenges associated with data requirement and radiative transfer model complexity. This is evidenced by the lack of attention given by Working Group III in the previous (Nabuurs et al, 2007; Smith et al, 2007) and upcoming (Mahmood et al, 2013) IPCC Assessment Reports, where reviews of the literature span analyses restricted to application of emission metrics or to biogeochemical concerns following land cover changes in regions where surface albedo is known to be an important contributor to the global energy balance. Kvalevåg: Evaluating a simple parameterization of radiative shortwave from several albedo change simulations to those generated by a more advanced 8-stream radiative transfer model based on DISORT
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