# Evaluating Uncertainties in Marine Biogeochemical Models: Benchmarking Aerosol Precursors
## 1 Introduction
### Automated Validation: Ocean biogeochemical Regime  
We have recently developed a set of ESM analysis methods and metrics specific to the marine biogeochemistry realm, as part of the ongoing International Ocean Model Benchmarking (IOMB)effort. This is with the intent to meet intensifying validation needs for biogeochemical modelers and measurement scientists within the ocean community. The tool is derived from the International Land Model Benchmarking (ILAMB), which is a closely related model validation project that is focused on terrestrial ecosystem dynamics [10]. Our fundamental strategy is to automate the confrontation of ocean physics, biology, and chemistry simulations with a wealth of observational datasets. We refer to the full variety of analyses, from shipboard studies to remote sensing measurements. The IOMB package is already capable of assessing global light-driven nutrient uptake by phytoplankton (photosynthesis as represented by primary production). Furthermore, it has been extensively tested relative to global carbon budgets. Here, we explore the methods in a general manner, with extension to aerosol cycling.  
We incorporate long-standing and newer observational datasets to evaluate simulation performance and guide future model development. The hope is to assist the international community in reducing marine biogeochemical uncertainty, and discovering the crucial links to indirect radiation effects [2; 18; 21]. There is currently a handful of custom packages used by different modeling communities to benchmark model results, but IOMB presents the first objectively open access platform to the ocean community with complete freedom to benchmark any model with a chosen observational dataset. The emphasis here is placed upon tests for volatile sulfur as a subset of BVOCs, which still tend to be rare in ESM output. Strategies are discussed for enhancing sparse aerosol and precursor data sets through ecogeographic comparisons, and for making them more convenient to use and more readily available.  
To date, only a handful of research groups have explored the concept of developing reasonable metrics to objectively validate ESM skill sets [48; 49; 50; 51; 52]. There is still a need to sensitize the biogeochemistry and natural aerosol communities to the timeliness and importance of benchmarking, and thus constraining model outputs. Uncertainties must be reduced in support of future model development efforts; this is the major channel through which improvements can be achieved. A recent review showed that more than 60% of the marine biogeochemistry literature provides only a visual comparison between model results and field data. The result is especially striking when viewed in the following light: a mere 10% accepted the challenge of validating with effective statistical methods [51]. Quantitative techniques are thus essential and timely at this point in the history of climate systems simulation. The statement remains true even if the strategies are taxing to implement; multiple spatial and temporal scales must be considered when comparing model output with the available field data or remotely-sensed distributions. Detailed benchmarks for the aerosol precursors and their marine sources are now required, and should be adapted systematically to constrain modeling activities.