Shmengie posted this question here:http://forum.arctic-sea-ice.net/index.php/topic,1805.msg96253.html#msg96253
Does moisture content of atmospheric layers (troposphere/stratosphere) change or affect their height at the poles?
Funny, I was just reviewing "Observational Evidence for Aerosols Increasing Upper Tropospheric Humidity" by Riuttanen et al. see: http://www.atmos-chem-phys.net/16/14331/2016/acp-16-14331-2016.pdf
I have been analyzing regional impacts of SO2 emission reductions on the tropopause height. A known effect, though the granual regional impacts are not well known, only a global average which is next to useless.
however, seeing the movement of tropical water vapor from the West extratropics all the way to the arctic this year makes me even more confirmed that we are seeing a great shift in the tropopause height, which produces a stronger meridional (North-South) gradient to move tropical water vapor and heat further into the arctic than ever before. (edit note: this appears to be a function of high temperature industrial process Aerosols which move more rapidly into the mid/upper troposphere as opposed to open fire (coal/biomass) aerosols which appear - during Winter especially - to stay predominantly in the lower/mid troposphere)
This paper was a bit of a Surprise to me though, The significant increase in upper tropospheric water vapor (humidity) would seem (at first glance) to cool this region. I think the real issue here is that the expansion of the tropics is happening at the tropical edge, and the upper tropospheric (humidity) dynamics are limited there, while the boundary layer impacts of reduced AOD and cloud reflectivity levels are impacted more directly with reductions in SO2 emissions. Not sure though.
So yeah, I would figure that, in the tropics at least, increased humidity at the upper troposphere would lead to a lowering of the tropopause height
post edit, the effect of increased rainfall in the upper troposphere of the tropics would work to effectively move latent heat from the upper altitudes to the lower altitudes, greatly increasing lower troposphere temperatures and cooling upper troposphere temperatures (in the tropics) this effect has been observed quite clearly in the MSU channel temp analyses.
By cooling the upper troposphere this way, the expansion of tropical waves of heat and water vapor in the meridional are reduces since the Coriolis effect is moderated by the lower tropopause heights.
This is the primary reason that we are currently seeing greater expansions of tropical moisture into the mid latitudes since the last two weeks of 2015 (though it has been evidence since China slowed it's coal consumption growth in early 2013.