Tropospheric warming

Since ROS are formed from the absorption of UVR by DOM and its subsequent photochemical decay, any changes in the atmosphere such as tropospheric warming or stratospheric ozone depletion should affect steady state concentrations of ROS in the water column. Initial studies with H2O2 suggest that the formation of an ozone hole will increase production rates by 20-50%. Changes in atmospheric ozone levels are also expected to affect production rates of other... 

H20 Greenhouse Feedback. As the lower atmosphere (the troposphere) warms, it can hold more water vapor. The enhanced water vapor traps more IR radiation and amplifies the greenhouse effect. Ramanathan [36] indicates that, based on studies with one-dimensional climate models, this feedback amplifies the air temperature by a factor of about 1.5 and the surface warming by a factor of about 3. The IPCC [23] determined a surface temperature amplification factor of 1.6 for water vapor feedback. 

An analysis of the annual air temperature data from 1929 to 1993 shows a positive temperature trend at all levels (Fig. 2). The Kurgan-Tube temperature increase is 1.9°C/100 years. At 803 m above sea level the temperature increase is 1.72°C/100 years. Data from the Kharamkul station show a temperature increase of 1.33°C/100 years. A temperature increase of 0.7°C/100 years is found at 4169 m above sea level. The data show that troposphere warming decreases with elevation, leading to increased vertical gradients of temperature (Table 1). The vertical gradient increases by 3.3% per 70 years between levels 1 and 4. This should reduce tiie stability of the atmosphere and result in a stronger vertical mixing. 

Recent estimates indicate that the level of carbon dioxide in the atmosphere has increased by a third since the beginning of the industrial age, and that it contributes significantly to global warming. Other major contributors include methane, tropospheric ozone, and nitrous oxide. Methane is the principal component of natural gas, but it is also produced by other sources such as rice paddies and farm animals. Tropospheric ozone is generated naturally and by the sunlight-... 

The warming climate is likely to induce changes in the hydrological cycle that will lead to further climate change. Increased heating should increase the rate of evaporation and, hence, the amount of water vapor, which is a GHG. The IPCC s Fourth Assessment Report, published in 2007, finds that the average atmospheric water vapor content has increased since at least the 1980s over land and ocean as well as in the upper troposphere. ... 

Nitrous oxide (N2O) is an important greenhonse gas with a radiative forcing effect 310 times that of CO2 and a lifetime in the troposphere of approximately 120 years. Part of the N2O is converted to NO in the stratosphere, and so contributes to depletion of ozone. Nitric oxide (NO) is very reactive in the atmosphere and has a lifetime of only 1-10 days. It contribntes to acidification and to reactions leading to the formation of ozone in the troposphere, and so also to global warming. 

In a normal troposphere that has a positive lapse rate, i.e., where the temperature is falling with altitude, warm air close to the earth s surface, being less dense, rises and is replaced by cooler air from higher elevations. This results in mixing within the troposphere. 

As air is transported rapidly upward, for example in a convective system, cooling occurs (see Chapter 2), leading to the condensation of water as ice crystals. Because of this removal of water as moist tropospheric air rises, air in the stratosphere is very dry, of the order of a few ppm. Some water is also produced directly in the stratosphere from the oxidation of CH4 and H2. The so-called extratropical pump then moves the air poleward and downward at higher latitudes (Path I), warming the air as it descends. 

In addition, there is an obseived correlation between total column ozone and the El Nino Southern Oscillation (ENSO) in the tropical troposphere, with decreases in total ozone in middle and sometimes polar latitudes following the ENSO by several months the period associated with the ENSO is 43 months (Zerefos et al., 1992). While the association between the ENSO and ozone is not well understood, it has been proposed that the warming of the troposphere in the tropics over the Pacific Ocean causes increases in the upper troposphere air temperatures and tropopause height and an upwelling in the lower stratosphere. If sufficiently large, this could have more widespread impact than just in the tropics (e.g., see Zerefos et al., 1992 and Kalicharran et al., 1993). 

As discussed earlier, although C02 warms the troposphere, it cools the stratosphere since it efficiently radiates infrared out to space. This effect can contribute to changes in the temperature profile in the stratosphere and potentially have a signficant impact... 

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