Sea Salt extinction in FWmaCARMAHIST

[ilaria-quaglia]

We want to increase sea salt burden and extinction by modifying sea salt removal through hygroscopicity (Kappa_SALT from 1.0 to 0.4).

Cases in /glade/work/iquaglia/cases/

• 'CARMA14' : "FWmaCARMAHIST.f19_f19_mg17.carma_trop_strat14.1990_2000"
• 'CARMA16_Ks0.4' : "FWmaCARMAHIST.f19_f19_mg17.carma_trop_strat16_ksalt04.1990_2000"
• 'MAM4' : "FWmaHIST_MAM4_nudged_f19.carma_trop_strat.may11_2023.1990_1995.region.5TgS"

[ilaria-quaglia]

Sea salt burden increases of about 0.5 Tg in CARMA16_Ks0.4 compared with CARMA14, but is still 3.0 Tg lower than in MAM4 (average over 1990). This change also affected other species, particularly DUST.

[ilaria-quaglia]

However, the optical depth of sea salt decreases globally by 0.005, with positive changes only in some regions of the land.

[tilmes]

@ilaria-quaglia, thanks so much! Very interesting. I checked the kappa for sea-salt, and it is actually above 1, so I guess this is not what we want anyways. We could run a test where we increase it to 1.5 or even 2. still in the range of observations. However, I think that as Brian Toon has noted without more bins, to that extent, we may not have much success. Let's continue working on the 22-bin model (larger bins for dust and sea-salt and see how that changes things). I will start some new MAM runs for 1980-2000 soon.

[ilaria-quaglia]

We discarded the idea of changing Kappa_SALT and we consider a new simulation without SOA photolysis. The first figure show the volume mixing ratio averaged over 1990 in CARMA and over 2016-2018 in MAM.

The second figure shows the differences between CARMA and MAM.

[tilmes]

@ilaria-quaglia Thanks! Could you add the AOD comparisons for the different species? I am hoping that we are now higher than we were before....

[ilaria-quaglia]

Figure 1 shows the total AOD at 550 nm compared to MERRA, and the maps are averaged over the available volcanic quiescence period. The higher values in FWmaHIST_CARMA_nudged_16_no_soa_phot are due to the SOA (see Figure 2).

Figure 2 shows the global AOD at 550 nm for each species and average values over the available volcanic quiescence period are summarised in the following table.