Fixes to the Ryden & McNeil Ammonia Flux Model

TL;DR

This paper introduces two simple modifications to the Ryden & McNeil ammonia flux model to ensure physically realistic estimates, addressing issues of unphysical outputs and background ammonia contributions.

Contribution

The paper presents novel parameter constraints and background level estimation methods to improve the physical validity of the ammonia flux model.

Findings

Model estimates become physically consistent with the proposed fixes.

The fixes prevent absurd parameter values and better account for natural background ammonia.

Some experimental setups still lead to over-estimates with the modified model.

Abstract

We propose two simple fixes to the Ryden and McNeil ammonia flux model. These are necessary to prevent estimates from becoming unphysical, which very often happens and which has not yet been noted in the literature. The first fix is to constrain the limits of certain of the model's parameters; without this limit, estimates from the model are seen to produce absurd values. The second is to estimate a point at which additional contributions of atmospheric ammonia are not part of a planned expert but are the result of natural background levels. These two fixes produce results that are everywhere physical. Some experiment types, such as surface broadcast, are not well cast in the Ryden and McNeil scheme, and lead to over-estimates of atmospheric ammonia.