Sunday, September 25, 2011
More on the Atmospheric Heat Pipe
Update: I found the issues with the spread sheet so I was able to clean up the chart. This time the invert values of the Stratosphere is in orange, so the trend lines are meaningful.
The Upper Atmosphere impacts are described in the link. There is a lot more going on than just radiative changes due to surface warming.
A while back I was puzzled over the temperature relationship between the mid Troposphere and the Stratosphere. Global warming has predicted that the troposphere should warm and the stratosphere cool. That is the general trend, but there are some oddities when you compare the monthly temperature values. This lead to the tropopause as a heat sink and the heat pipe analogy.
Heat pipes are a good way to remove sensible heat quickly. It involves a liquid to vapor phase change on one end, the cooling end and a vapor to liquid phase change on the other end, the heat sink. To work properly, the heat sink, or thermal reservoir used to pipe the heat to, must be much larger than the cooling load. The upper troposphere, tropopause especially, is an ideal thermal reservoir, because it can easily radiate heat to space except for a narrow band occupied by ozone. Ozone is warmed in the stratosphere by incoming ultraviolet radiation from the sun. It is also warmed by outgoing radiation in its absorption band. Increased CO2 should block a portion of that band reducing the warming due to outgoing radiation (small point in the co2 spectrum shared by ozone and water vapor). There is more to it than that, "In Ramaswamy (2001):
For carbon dioxide the main 15-um band is saturated over quite short distances. Hence the upwelling radiation reaching the lower stratosphere originates from the cold upper troposphere. When the CO2 concentration is increased, the increase in absorbed radiation is quite small and the effect of the increased emission dominates, leading to a cooling at all heights in the stratosphere." From Science of Doom.
Water in all its phases has a spectrum overlap with ozone. So variations in the emitted radiation by water in the upper troposphere can also impact ozone absorption. How significantly I am not sure, but it is possible that variations in the energy emitted to space by water can be causing the odd variations in stratospheric temperature.
Update: To better describe what I am calling the atmospheric heat pump, it is related to convection without precipitation. Warm moist air rising, cooling which condenses the water vapor and producing precipitation is well understood and included in all climate models. Clear sky thermals also move warm moist air higher where it cools the water vapor. Visible clouds may or may not form and clouds that do form may not precipitate, but that does not mean that heat is not being moved from warmer lower levels to colder upper layers where heat from water vapor can be radiated to either space or the atmosphere. Rising air will cause a lower pressure below it that will be replaced eventually by cooler air from above. If you have ever watched buzzards in a kettle, you have seen clear sky thermals.
All clear sky thermals would be "heat pipes" and these thermals from the surface are included in atmospheric models. They gain their energy, heat, from the surface mainly due to sunlight.
My theoretical Atmospheric Heat Pipe would be higher in the atmosphere, at the top of the atmospheric boundary layer, which is the lowest level of the atmosphere between the surface and roughly the base of the low level clouds. Water vapor in the atmosphere absorbs solar energy, not clouds, but water vapor absorbs approximately 10 percent and about half is re-radiated to space as infrared. These are approximations of averages. It is the change in the amount of the absorbed energy re-radiated that may impact climate.
Here is the crackpot part of the theory. During a solar minimum, there is a slight decrease in the overall solar energy spectrum. About 1 W/m^2 out of 1365 at the top of the atmosphere. At the surface, only one quarter of 70 percent of that change on average would be felt due to albedo, geometry and rotation. More of that change would be felt in the mid and upper troposphere. However, it is likely, that the near infrared portion of the solar spectrum varies little between solar minimum and maximum. This light energy imbalance could increase the efficiency of the atmospheric Heat Pump. Water in all its phases, is a strong absorber of infrared which is the power source of the theoretical Atmospheric Heat Pipe.
- ▼ September (4)