Sunday, April 10, 2011

More on the Troposphere Sink

While I have no clue how strong the troposphere sink may be, it is interesting. The tropopause is an idealized point where the temperature stops falling with an increase in altitude and water vapor is very near zero. For an ideal tropopause, the temperature would remain constant for some distance until it starts warming in the ozone layer of the stratosphere. In the real world, the tropopause tends to wander around a bit so the temperature can change from say -65 C to nearly -95 C. That 30 C change is pretty significant and is not all that dependent on the time of year in the sub-tropics.

Near the poles, things are different. The northern pole can be very entertaining. The wind pattern called the polar vortex can change, reverse direction, split into more than one vortex and move around. That erratic behavior can pass right through the northern tropopause causing different degrees of stratospheric sudden warming. So while conductive heat transfer has less impact above the tropopause, it may not be smart to consider it insignificant. The southern pole is a little more well behaved, but has its moments. In the tropics, convective storms, the tropical jets and the mother of all convective storms, hurricanes or typhoons, complicate things.

One site that I found that has some interesting programs to view the lapse rate is MicroCline Computing. They are skeptical and I have no clue how rigorous their programs may be. They, correctly in my opinion, call the lapse rate, the atmospheric heat pipe. All of the means of heat flow are at work in this heat pipe, pumping heat from the surface to the meandering tropopause.

In my last climate puzzle and the first one that assumes maximum polar warming, what I felt was the correct answer was the upper troposphere and tropopause, where there will always be cold temperatures to generate surface cooling. The bugger of course, is if that heat sink is sufficient to buffer or moderate surface temperatures and to what degree. Several things in question really depend on understanding the strength of the Tropopause. Changes in cloud cover and precipitation in response to some level of surface warming has a dependence on the surface/tropopause heat pipe which may be a better term than the troposphere sink that I use.

Obvious natural impacts on climate are the oscillations or pseudo-periodic cycles that are coupled with Sea Surface Temperatures, like the El Nino Southern Oscillation. It is easy to assume that these oscillations average out over time. It will require stronger math and longer observations to determine if they are actually natural climate drivers. The deep oceans are many orders of magnitude larger as a heat sink than the Tropopause. The thermal inertia of the deep oceans means that there is a lag or lags in its response to surface temperature changes. Since the atmospheric heat pipe has a more rapid response, it is to me similar to an integral or differential control feature. The oceans would be more of a proportional control. Once you complicate a control system with integral and differential controls you can get annoying feedback that requires fine tuning of the weight of each control elements to smooth things out.

When you can't fine tune the controls, there is normally one aspect that dominates. In some cases, conditions can shift dominance to another aspect, creating dual control points. In air conditioning that sucks. In Earth's climate, that could mean an interglacial period. Because of the huge differences in thermal capacity, I am incline to believe that atmospheric heat pipe determines our current set point. The oceans should determine the glaciation set point.

I am probably stating the obvious, but the atmospheric heat pipe will limit the impact of CO2 doubling, with some hysteresis say due to CO2 doubling. It is a puzzle I will never solve, but it is an interesting diversion.

1 comment:

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