| dc.description.abstract |
<p>The hydrologic cycle may be described in essence as the process of water rising
and falling in its various phases between land and atmosphere. In this minimal description
of the hydrologic cycle two features come into focus: intermittency and irreversibility.
In this dissertation intermittency and irreversibility are investigated broadly in
the soil-plant-atmosphere system. The theory of intermittency and irreversibility
is addressed here in three ways: (1) through its effect on components of the soil-plant-atmosphere
system, (2) through development of a measure of the degree of irreversibility in time-series,
and (3) by the investigation of the dynamical sources of this intermittency. First,
soil infiltration and spring frost risk are treated as two examples of hydrologic
intermittency with very different characters and implications for the soil plant system.
An investigation of the water budget in simplified soil moisture models reveals that
simple bucket models of infiltration perform well against more accurate representation
of intra-storm infiltration dynamics in determining the surface water partitioning.
Damaging spring frost is presented as a ``biologically-defined extreme event'' and
thus as a more subtle form of hydrologic intermittency. This work represents the first
theoretical development of a biologically-defined extreme and highlights the importance
of the interplay between daily temperature mean and variance in determining the changes
in damaging frost risk in a warming climate. Second, a statistical measure of directionality/asymmetry
is developed for stationary time-series based on analogies with the theory of nonequilibrium
thermodynamics. This measure is then applied to a set of DNA sequences as an example
of a discrete sequence with limited state-space. The DNA sequences are found to be
statistically asymmetric and further that the local degree of asymmetry is a reliable
indicator of the coding/noncoding status of the DNA segment. Third, the phenomenology
of rainfall occurrence is compared with canonical examples of dynamical intermittency
to determine whether these simple dynamical features may display a dominant signature
in rainfall processes. Summer convective rainfall is found to be broadly consistent
with Type-III intermittency. Following on this result we studied daytime atmospheric
boundary layer dynamics with a view toward developing simplified models that may further
elucidate the interaction the interaction between land surface conditions and convective
rainfall triggering.</p>
|
|
