# Evaluating Uncertainties in Marine Biogeochemical Models: Benchmarking Aerosol Precursors
## 1 Introduction  
The global natural aerosol system is dominated on an areal basis by remote oceanic processes driven by phytoplankton that lead to the formation of an array of chemical cloud condensation nucleus types [1; 2; 3; 4; 5; 6]. Reduced compounds of biological origin also help set the bioavailability of certain nutrient elements transported from atmosphere to ocean [7; 8]. However, marine biogenic emissions are highly heterogeneous in their ecological geography, and the substances themselves are formed by (and participate in) highly nonlinear chemical processing both below and above the sea surface. The materials serve as cloud condensation nuclei (CCN), which contribute to radiative forcing andlimit our ability to predict climate sensitivity. The attendant influence on climate has traditionally been very difficult to quantity. Uncertainties abound, and they can be reduced only through validation based on comparisons of model output with a multitude of independent measurements. The cloud seeding activity of dimethylsulfide (DMS) that was hypothesized decades ago is one of the mechanisms with significant uncertainty in sea-air coupling. In the present work, we will use the well-known CLAW hypothesis (originally proposed by [PERSON], [PERSON], [PERSON] and [PERSON], and the acronym comes from the first letter of their surnames) [9] exhibited with DMS as a primary example of how benchmarking can be accomplished. We will show that the methodology developed for the International Land Model Benchmarking (ILAMB) project [10], some of which are currently incorporated into the International Ocean Model Benchmarking (IOMB) package, can be adapted to validate not only traditional carbon cycling from the surface ocean to deep sea, but also aerosol precursor generation, along with their distributions and effects.  
DMS is the focus of our discussion, but we also comment on the potential and requirements for extension to a variety of other organic compounds [2; 11]. Reduced carbon enters the marine boundary layer in a variety of volatile and primary forms, and we briefly discuss the validation of models that will be inclusive of all natural organics, even though measurements tend to be scarce relative to those of the often-studied sulfide [12; 13; 14]. It will also be sensible to post-validate the oceanic production processes against ship and aircraft-based datasets, which reflect the resulting chemical complexity [15].  
Our text is structured as follows. The background section overviews and motivates the general challenges associated with marine aerosol. We then briefly describe a geophysical context for the study of ocean-derived aerosol, which is the chemical environment of the surface sea plus boundary layer. This section is followed by a description of the open source automated software system that is now under development for the benchmarking of marine biogeochemical processes and feedbacks. A section on methods demonstrates the application of our new IOMB-derived suite to validate outputs from contemporary Earth System Models (ESMs), given the available observational datasets. In our results section, detailed analyses are performed as proof of principle, and we end with some discussion of ways to further advance the current autonomous system. We also outline some of the research areas that we have been able to identify, within which uncertainties might be reduced through the evaluation of marine and general natural aerosols.