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The purpose of this code is to add NH3 emissions from fertilizer and livestock waste under different environmental conditions. Volatilization of ammonia is a major pathway of nutrient loss in ecosystems and is the largest emission source of atmospheric NH3. Atmospheric emission, transport, and deposition of NH3 is an important component of the nitrogen cycle, and is sensitive to environmental conditions which are not captured with static emission inventories. This code includes volatilization of NH3 from both livestock manure and synthetic fertilizer as documented in Riddick et al. (2016) and Vira et al. (2020). I will include some of the major requirements in the following design documentation, but full details can be found in the published manuscripts linked. There are several modes that FAN can operate with: fan_on (emission calculation only), fan_soil (fan coupled to the soil biogeochemistry), fan_atm (fan coupled to the atmosphere only) and fan_full (coupled to both atmosphere and soil). Of these modes, only fan_on and fan_atm will be scientifically validated as fan_soil and fan_full do not have nitrogen balance checks between ELM and FAN (the N is balanced within FAN and ELM independently). FAN includes manure applications to grasslands; NH3 emissions are calculated at the sub-grid level separately for grasslands and managed crop.
This code also includes updates to the cropland fertilizer subroutines. Modifications include a gridded synthetic fertilizer dataset of both nitrogen and phosphorous for each crop type, as opposed to the current fixed rates of nitrogen only. These changes are incorporated into the surface dataset and include modifications to the mksurfdat tool for generating surface input data. The fixed fertilizer rate that was used previously will be converted to a manure input, which will be replaced by the FAN stream data when FAN is on. FAN will always use the ELM synthetic fertilizer data inputs and timing of fertilizer application.
Requirements
Requirement: name-of-requirement-here
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