Analyzing El Nino Influence on MSLP


All months in the control run (nw_cntrl_03, 21 years) where the Southern Oscillation Index (SOI) is less than -1.0 (El Nino conditions, n = 43 months) are averaged together to create a composite of the effect of El Nino on global mean sea level pressure and wind patterns. Below is the mean sea level pressure (hPa, contours) and mean sea level pressure anomaly (hPa, shaded) and the wind vectors are the 850 hPa wind anomaly (U,V components included, m/s). High pressure is observed over the maritime continent and low pressure is observed in much of the eastern Pacific Ocean, helping to drive anomalously westerly winds across the Pacific, kickstarting an El Nino. Strong easterly wind anomalies are observed west of the maritime continent, which can be found as far westward as Africa.



Control Run: Mean Sea Level Pressure and Wind Anomaly during JJA (left, n = 13) and DJF (right, n = 9) months with El Nino conditions.

Mean Sea Level Pressure and 850 hPa Wind Anomaly following May 15th 150 Tg injection of soot: JJA Year 0(left) and DJF Year 1(right)


It's clear that there are anomalous westerly winds as soon as 150 Tg of soot is injected into the upper troposphere and stratosphere. These winds are far stronger than in the control composite El Nino figures. The ultimate question is why. The MSLP anomalies are also far greater than during the control El Nino composites, across entire ocean basins. The entirety of eastern Asia is 5+ hPa higher than the control during DJF.