1. Looking at Ammonia in ACE-1 Data Sara Lance

2. Aerosol Characterization Experiments (ACE) Goal of ACE is “to provide the necessary data to incorporate aerosol particles into global climate models and to reduce the overall uncertainty in calculating the climatic effect of aerosols” ACE-1 –Remote Marine Environment, Nov/Dec 1995 ACE –2 –Northeastern Atlantic, June/July 1997 ACE-ASIA –March-May 2001

3. So – what did we see at ACE-1 that’s worth talking about? Persistent peak in NH 3 concentration How many of the flights showed this phenomena? –Flights 16-23, 25, 27-32 (out of 33 Flights) –All flights with NH 3 /NH 4 + measurements show a peak in NH 3 concentration between ~100-600m My Focus: Flight-18 (December 1 st, 1995) –NH 3 peak at ~600m

4. Flight 18: NH 3 and NH 4 +

5. Liquid Water Content and NH 3 /NH 4 +

6. H 2 SO 4 /OH and NH 3 /NH 4 +

7. Ambient Conditions

8. Possible Remote Marine Sources of NH 3 (g)/NH 4 + Sea salt spray – NH 4 + Marine biogenic emissions – NH 3 (g) Advection of continental sources – NH 3 (g)/NH 4 +

9. Thermodynamic Modeling The higher aerosol SO 4 = concentration, the more NH 3 (g) is absorbed by a cloud droplet (in order to regulate the pH), thereby causing a sink of gas phase ammonia. NH 4 + SO 4 = NH 3 (g) NH 3 (aq) + H 2 O(aq)  NH 4 + (aq) + OH - (aq) NH 3 (g)  NH 3 (aq) HSO 4 - (aq)  H+(aq) + SO 4 2=

10. ISORROPIA Thermodynamic equilibrium model for multiphase multi-component inorganic aerosols Assumption: Chemical Equilibrium Valid when ambient conditions change slowly compared to chemical changes within the aerosol droplet. SOLID LIQUID GAS PHASE

11. ISORROPIA - speciation Gas: HNO 3, HCl, NH 3, H 2 O Liquid: Na +, NH4 +, H +, OH -, HSO 4 -, SO 4 2-, NO 3 -, Cl -, H 2 O Solid: NaHSO 4, NH 4 HSO 4, Na 2 SO 4, (NH 4 ) 2 SO 4, (NH 4 ) 3 H(SO 4 ) 2, NH 4 NO 3, NH 4 Cl, NaNO 3, NaCl

12. ISORROPIA - inputs If the system is in thermodynamic equilibrium, then the model should give a good estimate of the gas phase ammonia concentration given the total concentrations (gas+aerosol) of: –Na + –HCl/Cl - –NH 3 /NH 4 + –H 2 SO 4 /SO 4 = –HNO 3 /NO 3 - The model also needs the corresponding relative humidity and temperatures

13. ISORROPIA - results

14. Conclusion The NH 3 (g) concentration measured during ACE-1 is consistent with a thermodynamic equilibrium model (ISORROPIA) for points above, within and below a cloud. Because the concentration of SO 4 2= in the ACE-1 measurements was so low, nearly all of the NH 3 was partitioned to the gas phase.