Difference between revisions of "Sea salt aerosols"
From Geos-chem
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+ | == Updates to sea salt emissions algorithm == | ||
+ | |||
+ | === Updated hygroscopic == | ||
+ | |||
+ | Please see the dis GEOS-Chem_v8-02-04#Updated_hygroscopic_growth_factors_for_sea-salt | ||
+ | |||
+ | === Bug fixes in seasalt_mod.f === | ||
+ | |||
+ | Please see [[this discussion | ||
+ | |||
+ | === Modification of size bins for coarse mode aerosols === | ||
+ | |||
+ | '''''Lyatt Jaeglé (jaegle@atmos.washington.edu) wrote:''''' | ||
+ | |||
+ | :I think that we should change the dry size bins for the coarse mode aerosols in <tt>input.geos</tt>. Instead of using: | ||
+ | |||
+ | Online SEASALT AEROSOLS : T | ||
+ | => SALA radius bin [um]: 0.1 0.5 | ||
+ | => SALC radius bin [um]: 0.5 10.0 | ||
+ | |||
+ | :we should use a smaller upper cut for the dry radius of the coarse mode aerosols (up to 4 microns dry size ==> 8-10 microns radius for wet sea salt). | ||
+ | |||
+ | Online SEASALT AEROSOLS : T | ||
+ | => SALA radius bin [um]: 0.1 0.5 | ||
+ | => SALC radius bin [um]: 0.5 4.0 | ||
+ | |||
+ | :The first two changes lead to a factor of 2 decrease in total sea-salt emissions (from ~8000 Tg/yr to ~4300 Tg/yr using GEOS-4 winds for 2003 2x2.5). The last change leads to another reduction by 40% in emissions. However the total burden of sea-salt aerosols (~12.5 Tg) remains nearly unchanged compared to the old formulation (~13.7 Tg) because of the strong non-linearity of the dry deposition velocity at sizes > 2 microns. Indeed the lifetime of coarse mode sea-salt aerosols (0.5-4um vs 0.5-10um) increases by a factor of almost 3. | ||
+ | |||
+ | :Here is a summary of the changes: | ||
+ | |||
+ | Old formulation in GEOS-Chem (2x2.5 GEOS-4 winds 2003) | ||
+ | |||
+ | {| border=1 cellspacing=0 cellpadding=5 | ||
+ | |- bgcolor="#cccccc" | ||
+ | ! | ||
+ | !0.1-0.5 um | ||
+ | !0.5-10 um | ||
+ | !Total: 0.1-10 um | ||
+ | |- | ||
+ | |Emissions (Tg/yr) | ||
+ | |106 | ||
+ | |7865 | ||
+ | |7970 | ||
+ | |- | ||
+ | |Dry deposition (Tg/yr) | ||
+ | |4.7 | ||
+ | |5012 | ||
+ | |5016 | ||
+ | |- | ||
+ | |Wet deposition (Tg/yr) | ||
+ | |102 | ||
+ | |2859 | ||
+ | |2955 | ||
+ | |- | ||
+ | |Burden (Tg) | ||
+ | |0.73 | ||
+ | |13.01 | ||
+ | |13.74 | ||
+ | |- | ||
+ | |Lifetime (hours) | ||
+ | |60 | ||
+ | |14 | ||
+ | |15 | ||
+ | |} | ||
+ | |||
+ | {| border=1 cellspacing=0 cellpadding=5 | ||
+ | |- bgcolor="#cccccc" | ||
+ | ! | ||
+ | !0.1-0.5 um | ||
+ | !0.5-10 um | ||
+ | !Total: 0.1-10 um | ||
+ | |||
+ | |||
+ | New formulation (changes 1-3) | ||
+ | |||
+ | {| border=1 cellspacing=0 cellpadding=5 | ||
+ | |- bgcolor="#cccccc" | ||
+ | ! | ||
+ | !0.1-0.5 um | ||
+ | !0.5-4 um | ||
+ | !Total: 0.1-4 um | ||
+ | |- | ||
+ | |Emissions (Tg/yr) | ||
+ | |92 | ||
+ | |2633 | ||
+ | |2725 | ||
+ | |- | ||
+ | |Dry deposition (Tg/yr) | ||
+ | |4 | ||
+ | |689 | ||
+ | |693 | ||
+ | |- | ||
+ | |Wet deposition (Tg/yr) | ||
+ | |87 | ||
+ | |1944 | ||
+ | |2031 | ||
+ | |- | ||
+ | |Burden (Tg) | ||
+ | |0.63 | ||
+ | |11.92 | ||
+ | |12.55 | ||
+ | |- | ||
+ | |Lifetime (hours) | ||
+ | |60 | ||
+ | |40 | ||
+ | |40 | ||
+ | |} | ||
+ | |||
+ | :I am also including calculations for a 3rd bin size 4-10 microns | ||
+ | |||
+ | {| border=1 cellspacing=0 cellpadding=5 | ||
+ | |- bgcolor="#cccccc" | ||
+ | ! | ||
+ | !4-10 um | ||
+ | |- | ||
+ | |Emissions (Tg/yr) | ||
+ | 1544 | ||
+ | |- | ||
+ | |Dry deposition (Tg/yr) | ||
+ | |1156 | ||
+ | |- | ||
+ | |Wet deposition (Tg/yr) | ||
+ | |387 | ||
+ | |- | ||
+ | |Burden (Tg) | ||
+ | |1.6 | ||
+ | |- | ||
+ | |Lifetime (hours) | ||
+ | |9 | ||
+ | |} | ||
+ | |||
+ | :While these larger aerosols (4-10 microns dry size) add another 50% to the emissions, they only contribute to 12% of the burden because of their short lifetime. So if we want to stick to 2 size bins, I think that it's fine to neglect these larger aerosols and limit the upper cut of the coarse mode sea-salt aerosols to 4 microns. | ||
+ | |||
+ | :The overall sea-salt emissions ~3000 Tg/year is now similar to what other studies found when applying the Monahan formula: Monahan (1986), Spillane et al. (1986), Gong et al. (1998), Penner et al. (2001), etc... This is also within the range recommended by Lewis & Schwartz. | ||
+ | |||
+ | :I also tried the Gong (2003) formulation which leads to a factor of ~2 decrease in emissions of accumulation mode aerosols but little change to the coarse mode aerosols. I am in the process of evaluating the sea-salt formulation against comparisons to cruise sea-salt observations from PMEL and find that both Gong (2003) and Monahan tend to overestimate sea-salt emissions at the high wind speeds in mid-latitudes and underestimate emissions in subtropical warmer waters. I am working on updating the Gong formulation based on SST. | ||
+ | |||
+ | :Note that the optical properties currently used in the GEOS-Chem (jv_spec.dat) assume log-normal size distributions that lead to effective radii that are too large for coarse mode aerosols: ~9 microns at 50% RH! Based on observed sea-salt size distributions, this should be much smaller ~ 1-2 microns. This correction leads to larger AODs due to sea-salt. I think that Colette and Randall are working on updating jv_spec.dat and I will send them my recommendations. | ||
+ | |||
+ | --[[User:Bmy|Bob Y.]] 10:49, 23 November 2009 (EST) | ||
+ | |||
== Double-substitution bug in routine GET_ALK == | == Double-substitution bug in routine GET_ALK == | ||
Revision as of 15:49, 23 November 2009
Contents
Updates to sea salt emissions algorithm
= Updated hygroscopic
Please see the dis GEOS-Chem_v8-02-04#Updated_hygroscopic_growth_factors_for_sea-salt
Bug fixes in seasalt_mod.f
Please see [[this discussion
Modification of size bins for coarse mode aerosols
Lyatt Jaeglé (jaegle@atmos.washington.edu) wrote:
- I think that we should change the dry size bins for the coarse mode aerosols in input.geos. Instead of using:
Online SEASALT AEROSOLS : T => SALA radius bin [um]: 0.1 0.5 => SALC radius bin [um]: 0.5 10.0
- we should use a smaller upper cut for the dry radius of the coarse mode aerosols (up to 4 microns dry size ==> 8-10 microns radius for wet sea salt).
Online SEASALT AEROSOLS : T => SALA radius bin [um]: 0.1 0.5 => SALC radius bin [um]: 0.5 4.0
- The first two changes lead to a factor of 2 decrease in total sea-salt emissions (from ~8000 Tg/yr to ~4300 Tg/yr using GEOS-4 winds for 2003 2x2.5). The last change leads to another reduction by 40% in emissions. However the total burden of sea-salt aerosols (~12.5 Tg) remains nearly unchanged compared to the old formulation (~13.7 Tg) because of the strong non-linearity of the dry deposition velocity at sizes > 2 microns. Indeed the lifetime of coarse mode sea-salt aerosols (0.5-4um vs 0.5-10um) increases by a factor of almost 3.
- Here is a summary of the changes:
Old formulation in GEOS-Chem (2x2.5 GEOS-4 winds 2003)
0.1-0.5 um | 0.5-10 um | Total: 0.1-10 um | |
---|---|---|---|
Emissions (Tg/yr) | 106 | 7865 | 7970 |
Dry deposition (Tg/yr) | 4.7 | 5012 | 5016 |
Wet deposition (Tg/yr) | 102 | 2859 | 2955 |
Burden (Tg) | 0.73 | 13.01 | 13.74 |
Lifetime (hours) | 60 | 14 | 15 |
0.1-0.5 um | 0.5-10 um | Total: 0.1-10 um
--Bob Y. 10:49, 23 November 2009 (EST) Double-substitution bug in routine GET_ALKBecky Alexander (beckya@u.washington.edu) wrote:
|
---------------------------------- | SO2 uptake onto fine particles | ---------------------------------- | calculate gas-to-particle rate constant for uptake of | SO2 onto fine sea-salt aerosols [Jacob, 2000] analytical solution
CONST1 = 4.D0/(V*GAMMA_SO2) A1 = (RAD1/DG)+CONST1 B1 = (RAD2/DG)+CONST1 |
----------------------------------------------------------------------------- | Prior to 7/18/08: | Becky Alexander's fix to remove double-substitution (bec, bmy, 7/18/08) | Remove these lines: | TERM1A = (((B1/DG)**2)+(2.0D0*CONST1*B1/DG)+(CONST1**2)) - | & (((A1/DG)**2)+(2.0D0*CONST1*A1/DG)+(CONST1**2)) | TERM2A = 2.D0*CONST1*(((B1/DG)+CONST1)-((A1/DG)+CONST1)) | TERM3A = (CONST1**2)*(LOG((B1/DG)+CONST1) - | & LOG((A1/DG)+CONST1)) | KT1 = 4.D0*PI*N1*(DG**2)*(TERM1A - TERM2A + TERM3A) | -----------------------------------------------------------------------------
TERM1A = ((B1**2)/2.0d0) - (((A1**2)/2.0d0) TERM2A = 2.D0*CONST1*(B1-A1) TERM3A = (CONST1**2)*LOG(B1/A1) KT1 = 4.D0*PI*N1*(DG**3)*(TERM1A - TERM2A + TERM3A) |
---------------------------------- | SO2 uptake onto coarse particles | ---------------------------------- | calculate gas-to-particle rate constant for uptake of | SO2 onto coarse sea-salt aerosols [Jacob, 2000] analytical solution
CONST2 = 4.D0/(V*GAMMA_SO2) A2 = (RAD2/DG)+CONST2 B2 = (RAD3/DG)+CONST2 |
------------------------------------------------------------------------------ | Prior to 7/18/08: | Becky Alexander's fix to remove double-substitution (bec, bmy, 7/18/08) | Remove these lines: | TERM1B = (((B2/DG)**2)+(2.0D0*CONST2*B2/DG)+(CONST2**2)) - | & (((A2/DG)**2)+(2.0D0*CONST2*A2/DG)+(CONST2**2)) | TERM2B = 2.D0*CONST2*(((B2/DG)+CONST2)-((A2/DG)+CONST2)) | TERM3B = (CONST2**2)*(LOG((B2/DG)+CONST2) - | & LOG((A2/DG)+CONST2)) | KT2 = 4.D0*PI*N2*(DG**2)*(TERM1B - TERM2B + TERM3B) | ------------------------------------------------------------------------------
TERM1B = ((B2**2)/2.0d0) - (((A2**2)/2.0d0) TERM2B = 2.D0*CONST2*(B2-A2) TERM3B = (CONST2**2)*LOG(B2/A2) KT2 = 4.D0*PI*N2*(DG**3)*(TERM1B - TERM2B + TERM3B) KT = KT1 + KT2 |
---------------------------------- | HNO3 uptake onto fine particles | ---------------------------------- | calculate gas-to-particle rate constant for uptake of | HNO3 onto fine sea-salt aerosols [Jacob, 2000] analytical solution
CONST1N = 4.D0/(V*GAMMA_HNO3) A1N = (RAD1/DG)+CONST1N B1N = (RAD2/DG)+CONST1N |
----------------------------------------------------------------------------- | Prior to 7/18/08: | Becky Alexander's fix to remove double-substitution (bec, bmy, 7/18/08) | Remove these lines: | TERM1AN = (((B1N/DG)**2)+(2.0D0*CONST1N*B1N/DG)+(CONST1N**2)) - | & (((A1N/DG)**2)+(2.0D0*CONST1N*A1N/DG)+(CONST1N**2)) | TERM2AN = 2.D0*CONST1N*(((B1N/DG)+CONST1N)-((A1N/DG)+CONST1N)) | TERM3AN = (CONST1N**2)*(LOG((B1N/DG)+CONST1N) - | & LOG((A1N/DG)+CONST1N)) | KT1N = 4.D0*PI*N1*(DG**2)*(TERM1AN - TERM2AN + TERM3AN) | -----------------------------------------------------------------------------
TERM1AN = ((B1N**2)/2.0d0) - (((A1N**2)/2.0d0) TERM2AN = 2.D0*CONST1N*(B1N-A1N) TERM3AN = (CONST1N**2)*LOG(B1N/A1N) KT1N = 4.D0*PI*N1*(DG**3)*(TERM1AN - TERM2AN + TERM3AN) |
---------------------------------- | HNO3 uptake onto coarse particles | ---------------------------------- | calculate gas-to-particle rate constant for uptake of | HNO3 onto coarse sea-salt aerosols [Jacob, 2000] analytical solution
CONST2N = 4.D0/(V*GAMMA_HNO3) A2N = (RAD2/DG)+CONST2N B2N = (RAD3/DG)+CONST2N |
----------------------------------------------------------------------------- | Prior to 7/18/08: | Becky Alexander's fix to remove double-substitution (bec, bmy, 7/18/08) | Remove these lines: | TERM1BN = (((B2N/DG)**2)+(2.0D0*CONST2N*B2N/DG)+(CONST2N**2)) - | & (((A2N/DG)**2)+(2.0D0*CONST2N*A2N/DG)+(CONST2N**2)) | TERM2BN = 2.D0*CONST2N*(((B2N/DG)+CONST2N)-((A2N/DG)+CONST2N)) | TERM3BN = (CONST2N**2)*(LOG((B2N/DG)+CONST2N) - | & LOG((A2N/DG)+CONST2N)) | KT2N = 4.D0*PI*N2*(DG**2)*(TERM1BN - TERM2BN + TERM3BN) | -----------------------------------------------------------------------------
TERM1BN = ((B2N**2)/2.0d0) - (((A2N**2)/2.0d0) TERM2BN = 2.D0*CONST2N*(B2N-A2N) TERM3BN = (CONST2N**2)*LOG(B2N/A2N) KT2N = 4.D0*PI*N2*(DG**3)*(TERM1BN - TERM2BN + TERM3BN) Please make the fix in your version, or you may download it from ftp://ftp.as.harvard.edu/pub/geos-chem/patches/v8-01-01/seasalt_mod.f_w_getalk_fix. Also see this document by Becky Alexander which describes the analytical solution in more detail. Duncan Fairlie (t.d.fairlie@nasa.gov) replied:
Kt = 4.pi.N.D(cubed)[ ] ,
dr = D.dx,
( r=[a,b] )
X = [a/D+c, b/D+c]
NOTE: This fix has been incorporated into GEOS-Chem v8-01-02. --Bob Y. 16:15, 7 August 2008 (EDT) |
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