Objective: Provide evidence for hypothesized mechanisms for Nuclear Nino during nuclear winter in CESM-WACCM4. Python code.

CLAIM: Westerly wind anomalies begin in the Indian Ocean and propagate eastward like an equatorially trapped Kelvin wave (as suggested by Kodri et al., 2017).

Evidence: Evidence of an eastward propagating wave of westerly wind anomalies is present in monthly zonal wind anomalies: 0005-06




CLAIM: Walker Circulation is reduced following soot injection

Evidence: Height / Longitude plot of the OMEGA (hPa / s) over the equatorial Pacific with wind vectors will show that increased convection occurs over the east Pacific.
View anomalies instead. These make a far stronger argument, clearly showing extreme subsidence over the Maritime Continent and extreme anomalous upward vertical motion over the Central and Eastern Pacific by 0005-07 (2 months following the injection of soot). This means that something is forcing the Walker Circulation to slow down.
Control Run / 150 Tg US-Russia


























Comparison of upward vertical motion across the Pacific during all El Nino and La Nina months during the control run:












CLAIM: Western Pacific cools off more quickly than the Eastern Pacific due to Ocean Thermodynamic Mechanism.

Evidence: Look at change in insolation at the surface across the Pacific and compare this to the rate of change of temperature from 0005-05-15 to 0005-05-31 (using daily data) Show that changes in SST gradient occur BEFORE westerly winds. Use Predybaylo et al (2017) to determine heat budget.

Plot of monthly change in SST gradient for all cases.

Plot of change in SST gradient from Western Pacific Ocean (150 to 200) to Eastern Pacific Ocean (230 to 280) between 5S and 5N during the first 2 weeks.





In summary: The month following the soot injection, the SST gradient (WP – EP) actually increases. Immediately following the soot injection, zonal winds across the West Pacific increase, but the SST gradient remains relatively constant through the end of May. The zonal winds increase through the end of May (El Nino forcing), but the SST gradient does not decrease. This indicates that during the first 2 weeks, the Ocean Dynamical Thermostat mechanism is NOT contributing to positive El Nino conditions. In fact, the increase in SST gradient starting on June 1st appears to have a negative effect on westerly zonal wind anomalies for the next week. Another increase in westerly zonal wind anomalies begins near June 10th, while the SST gradient is INCREASING (consistent with STRONGER TRADE WIND FORCING- which is NOT happening). This leads me to believe that the westerly zonal wind anomalies are acting first and forcing the El Nino. Worth noting, there are higher cloud fraction values in the western Pacific compared to the eastern Pacific from 0005-05 to 0005-06.



The SST gradient finally begins to decline 2 months after the injection, as zonal winds reach a seasonal peak, before they begin to decline. The progression of the SST gradient and zonal winds are opposite of what would be antiicpated. The SST gradient declining should cause a further weakening of the trrade winds, but this is not observed over this short timescale. Over the course of many months, this does occur, but there are other influences on shorter timescales.

CONCLUSION: Ocean Dynamical Thermostat Mechanism does not contribute to westerly wind anomalies, as the atmosphere acts before.