Previous experiments have found that nitrate photolysis in LLR of ice behaves similarly to that of a supercooled solution, and the two channels have similar quantum yield. Conversely, the turnover for channel (2) becomes three times higher when nitrate is solvated at the air-ice interface than in water. While an increase in quantum yield is usually considered the primary factor for the enhanced reactivity, a higher molar absorption coefficient of nitrate at the air-ice interface could further enhance nitrate photochemistry. Former works suggest that the absorbance of nitrate in ice LLRs is similar to that in bulk solution. However, surprisingly a recent study reported a molar absorption coefficient at 308 nm at the air-ice interface that is nearly 50 times higher than in solution. Such a large variability in experimental results may be ascribed to the difficulties of measuring UV-visible absorption spectra at low concentrations, comparable to environmental abundances. Molecular modeling allows one to overcome these issues as it provides an atomistic insight into the solvation environment of ions and small molecules at water and ice surfaces and may be used to compute absorption spectra in the limit of infinite dilution. In this article, we use first-principles molecular dynamics (FPMD) simulations and a multimodel approach to investigate the solvation shell and compute the UV-visible absorption spectra of nitrate at the air-ice interface and in water. We also investigate the effect of pairing with ammonium, an environmentally abundant counter ion often used in experiments, on the molar absorption coefficient of NO - 3 . Our multimodel approach combines density functional theory (DFT) based FPMD to sample the configurations of the ions in the solvation environment at finite temperature, and time-dependent density functional theory (TDDFT) to compute the UV-visible absorption spectra. This method has been previously employed to assess the impact of the bathochromic shift in the UV-visible absorption spectra on the photolysis rates of organic pollutants at the air-ice interface. Here we investigate the effect of the solvation environment by comparing bulk solution to the air-ice interface while considering the effect of two common sources of nitrate on snowpack: nitric acid (HNO 3 ), and ammonium nitrate (NO - 3 /NH + 4 ). The main goal is to test the hypothesis that the molar absorption coefficient of nitrate may be enhanced at the air-ice interface due to either solvatochromic shift or the formation of aggregates. The choice of modeling nitric acid and ammonium nitrate in these two solvation environments is motivated by both their broad environmental relevance and the availability of experimental data.