Multi-model mean nitrogen and sulfur deposition from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP): evaluation of historical and projected future changes

Abstract

We present multi-model global datasets of nitrogen and sulfate deposition covering time periods from 1850 to 2100, calculated within the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP). The computed deposition fluxes are compared to surface wet deposition and ice core measurements. We use a new dataset of wet deposition for 2000–2002 based on critical assessment of the quality of existing regional network data. We show that for present day (year 2000 ACCMIP time slice), the ACCMIP results perform similarly to previously published multi-model assessments. For this time slice, we find a multi-model mean deposition of approximately 50 Tg(N) yr⁻¹ from nitrogen oxide emissions, 60 Tg(N) yr⁻¹ from ammonia emissions, and 83 Tg(S) yr⁻¹ from sulfur emissions. The analysis of changes between 1980 and 2000 indicates significant differences between model and measurements over the United States but less so over Europe. This difference points towards a potential misrepresentation of 1980 NH₃ emissions over North America. Based on ice core records, the 1850 deposition fluxes agree well with Greenland ice cores, but the change between 1850 and 2000 seems to be overestimated in the Northern Hemisphere for both nitrogen and sulfur species. Using the Representative Concentration Pathways (RCPs) to define the projected climate and atmospheric chemistry related emissions and concentrations, we find large regional nitrogen deposition increases in 2100 in Latin America, Africa and parts of Asia under some of the scenarios considered. Increases in South Asia are especially large, and are seen in all scenarios, with 2100 values more than double their 2000 counterpart in some scenarios and reaching > 1300 mg(N) m⁻² yr⁻¹ averaged over regional to continental-scale regions in RCP 2.6 and 8.5, ~ 30–50% larger than the values in any region currently (circa 2000). However, sulfur deposition rates in 2100 are in all regions lower than in 2000 in all the RCPs. The new ACCMIP multi-model deposition dataset provides state-of-the-science, consistent and evaluated time slice (spanning 1850–2100) global gridded deposition fields for use in a wide range of climate and ecological studies

Earth System Chemistry integrated Modelling (ESCiMo) with the Modular Earth Submodel System (MESSy) version 2.51

“…Compared to the ACCMIP evaluation for the year 2000 sulfur emissions (especially DMS) are slightly enhanced, whereas NO x and NH 3 emissions are a bit lower. The ratio of dry deposition to wet deposition is slightly lower in the present simulations compared to the model mean determined by Lamarque et al (2013), with, e.g., 0.64 for oxidized sulfur compared to 0.72. Similar differences are found for NH x and NO x,y , with ratios of 0.5 compared to 0.66 and 0.63 to 0.72, respectively.…”

Increased vegetation growth and carbon stock in China karst via ecological engineering

“…LAI and ABC were simulated at 0.5° spatial resolution with a Farquhar-type photosynthesis model 47 at a daily time step 48 . Simulations with LPJ-GUESS were performed for 1901-2015 applying gridded monthly climate data (temperature, precipitation and cloud cover) from CRU TS 3.24.01 46 , monthly nitrogen deposition 49 , and annual mean atmospheric CO 2 concentration 50,51 as forcing. The simulation was preceded by a 500-year-long spinup in which the climate forcing was used for 1901-1930, applying the interannual variability for this period to capture realistic climatic variations, and 1901 values for atmospheric CO 2 concentration and N deposition were applied.…”

Multi-model study of HTAP II on sulphur and nitrogen deposition

“…The modelled dry deposition is compared with the inferential data in North America (see detail in Section 3.1). We 115 also compare the model performance of this study with previous studies in 2001 of PhotoComp (Dentener et al, 2006), HTAP I (Vet et al, 2014), and ACCMIP (Lamarque et al, 2013 inventory is described in Janssens-Maenhout et al (2015).…”

“…The NH 4 + wet 265 deposition is somewhat underestimated in all 3 regions, especially in East Asia. Table 1 compares the model performance of this study (HTAP II) with previous projects of PhotoComp (Dentener et al, 2006), HTAP I (Vet et al, 2014) and ACCMIP (Lamarque et al, 2013). It should be noted that the emission inputs, simulation periods and participating groups of …”

“…To compare the model performance with previous projects consistently, we adopt the following metrics in Lamarque et al, (2013): Linear fit slope, mean bias, mean observation, mean model, correlation coefficient (R) and fraction (of model results) within ± 50% (of observations).…”