ABSTRACT - DRUM - University of Maryland

eanalysis surface temperature and relative humidity [Kalnay et al., 1996],
interpolated to the specific overshoot locations, as initial conditions for the adiabatic
altitude calculation. In spite of the large ambiguity mentioned above, it is very obvious
that there exist overshoots reaching high enough throughout the TTL. Figure 3.8 also
confirms the result discussed in the section 3.4.1 - the overshoots are warmer than an
adiabatic calculation would predict. This is consistent with the idea that some mixing
is occurring between these clouds and the TTL environment.
3.6 Conclusions
In this chapter, I have calculated the heights of overshooting cloud tops from the
size of the shadows they cast. The existence of high overshoots is important in
understanding the physics of the TTL and has important implications for the
dehydration mechanism of the stratosphere. I measure overshoots going well above
typical tropopause altitudes — about 16.5 km.
These overshoots are warmer than predicted by undiluted adiabatic ascent from
the surface. This suggests that the brightness temperature alone will underestimate the
height of the clouds. Mixing of air with its environment is a possible explanation for
the departure from the adiabatic lapse rate. Because of this mixing, this air will reach
equilibrium at an altitude above the LNB predicted by boundary layer θ e .
I have shown in this paper that convection clearly extends throughout the TTL
and that the overshooting clouds are mixing with the TTL air. This is in agreement
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