Fig. 4: Scatter plot of observed ammonium balance and pH for all campaigns. | Communications Earth & Environment

Fig. 4: Scatter plot of observed ammonium balance and pH for all campaigns.

From: Chemical transport models often underestimate inorganic aerosol acidity in remote regions of the atmosphere

Fig. 4: Scatter plot of observed ammonium balance and pH for all campaigns.

Scatter plot of the average NH4_Bal (top row) and aerosol pH (calculated from E-AIM) (bottom row) versus inorganic PM1 (NH4 + SO4 + NO3) for boundary layer (a, d, defined as surface to 800 hPa), free troposphere (b, e, defined as 800–400 hPa), and upper troposphere (c, f, defined as 400–250 hPa). Each point represents the average observed value for each campaign at the specified pressure level and latitude zone (see Supplementary Data 1). These include ARCTAS-A (orange triangle), ARCATS-B impacted by BB (biomass burning; green open triangle), ARCTAS-B not impacted by BB (green solid triangle), CalNex (gray triangle), DC3 (light blue triangle), INTEX-B (light purple triangle), KORUS-AQ (dark green triangle), MILAGRO (black triangle), SEAC4RS impacted by BB (purple open triangle), SEAC4RS not impacted by BB (purple solid triangle), WINTER (pink triangle), and ATom-1 (blue) and -2 (red) >50°N (circle), 25°N to 50°N Pacific Ocean (square), 25°S to 25°N Pacific Ocean (upside-down triangle), 50°S to 25°S Pacific Ocean (left sideways triangle), >50°S (right sideways triangle), 50°S to 25°S Atlantic Ocean (sideways thin diamond), 25°S to 25°N Atlantic Ocean (thin diamond), and 25°N to 50°N Atlantic Ocean (normal diamond). a,bData filtered by BB markers (HCN < 350 pptv and CH3CN < 225 pptv = Not Biomass Burning and HCN > 350 pptv and CH3CN > 225 pptv = Biomass Burning)116.

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