Dear all,
I recently conducted a simulation using CMAQ_ISAM V5.4 for a scenario encompassing the Erhai Lake area in Yunnan Province, China. The 22-day simulation period spanned from 2023-10-09 to 2023-10-30, with a 6-day spin-up period.
By analyzing the generated CCTM_SA_DRYDEP and CCTM_SA_WETDEP files, I calculated the deposition contributions from different tagged regions to Erhai Lake. The metrics used were total ammonium nitrogen deposition and total nitrate nitrogen deposition, calculated as follows:
NHx Dep: 0.7777 × (ANH4I + ANH4J + ANH4K + 1.059 × NH3)
TNO3 Dep: 0.22581 × (ANO3I + ANO3J + ANO3K + 0.984 × HNO3)
However, when I calculated the sources of deposition to Erhai Lake over the simulation period, I encountered an issue where the BCO contributions were excessively high for both metrics. Could anyone please provide insights into what might be causing this issue?
VVuhony
How large is your modeling domain? Specifically, how far away are the domain boundaries from Erhai Lake? Many of the regions shown in your pie charts appear to be relatively close to Erhai Lake and Dali City, suggesting that you may be using a fairly local domain in which case a large contribution from boundary inflow into the domain might not be unrealistic. You would also want to analyze the concentrations of oxidized and reduced N species at your domain boundary. How did you generate the boundary conditions? Do the N concentrations at the boundary look realistic?
As an aside, the TNO3 Dep and NHx Dep definitions in your first post appear to be flipped.
Hi Christian,
My definition for modeling is a 125 × 125 grids domain where each grid is 6km × 6km and no nested domains.
Erhai Lake is off to the upper left corner, near the center of domain. As you mentioned the tagged regions are counties adjacent to Erhai Lake, showing relatively high contributions.
I generated the boundary conditions using BCON with profile CSV file, avprofile_saprc07tc_ae6_aq_derived_from_cb6r3m_ae7_kmtbr_hemi2016_v53beta2_m3dry_col051_row068.csv. It supplies background boundary conditions for global use and looks lower than the realistic value.
The Dep definitions in my first post have been fixed. Thanks for your correction.
VVuhony
Hello VVuhony,
if the entire extent of the modeling domain is 750 km x 750 km, seeing a significant boundary condition contribution to both concentration and deposition fields as shown in the pie charts in your first post may not be unrealistic. However, I am not familiar with the circulation patterns in this region and local and regional emission sources to have a good conceptual picture of the relative importance of the processes governing pollutant transport, transformation, and deposition at multiple scales.
You are correct that the avprofile_saprc07tc_ae6_aq_derived_from_cb6r3m_ae7_kmtbr_hemi2016_v53beta2_m3dry_col051_row068.csv file distributed with the CMAQ source code represent annual mean conditions in a rather clean remote marine environment derived from an 2016 hemispheric CMAQ simulation. As such, these conditions likely are too low compared to actual conditions for most species for your region of interest.
