My main research interests are divided between data assimilation and tropical cyclones,
with a focus on the marine boundary layer in both areas.
In data assimilation, I was responsible for implementing the use of scatterometer data
from the QuikScat instrument in the Bureau's operational global NWP system
[paper].
In conjunction with this, I lead a major study which used the QuikScat data to validate
the near-surface winds in the entire NWP suite
[research report]
[paper].
I have also investigated formulation details of the Ensemble Kalman Filter, a relatively
new assimilation method with considerable potential. Specific projects include (i) an examination
of the implications of using perturbed observations to estimate the observation-error
covariance
[paper]
and (ii) an examination of the implications for balance of covariance localisation, and
the development of a new method of localisation with much improved balance properties
[presentation].
Wind energy is a renewable source of energy with a gradually increasing presence in
Australia. A major factor impeding the more extensive use of wind power is that the wind is
highly variable, leading to large fluctuations in electricity output and hence a difficulty
in incorporating these power sources within the electricity grid. I have been closely
involved in the development within BMRC of a new high-resolution
NWP system, WLAPS, developed partly to improve the Bureau's ability to support forecasting of
wind power production. The main innovation in this system is that it assimilates at the native
model resolution of 10 km. Extensive verification has demonstrated that WLAPS produces significantly
superior forecasts to its predecessors.
Recent tropical cyclone work has focussed on the structure of the boundary layer winds,
especially the dynamics and characteristics of the low-level jet that is often found near the top of the
boundary layer, and the factors that determine the strength of the surface winds relative
to those aloft. The approach has been a mix of
analytical modelling,
numerical modelling,
and the analysis of observations, including detailed case studies of the flow and balance
in Hurricanes
Georges and
Mitch using data obtained by the NOAA
Hurricane Research Division from the GPS dropsonde.
These analyses required very accurate location of the cyclone centre, leading to the
development of an objective
new method
for finding the centre of a storm using asynoptic mass data.
Currently, I am attempting to better understand the turbulent structure of the tropical
cyclone boundary layer, using dropsonde data
[presentation].
Earlier work on air-sea interaction at high wind speeds included a demonstration of the roles
of sea spray and rain evaporation in the thermodynamics
of the TCBL, using a slab model which included parameterisations of these effects together
with cloud downdrafts, clear sky and surface fluxes. I also used a turbulent closure
model coupled to a spray dispersion and evaporation model
to explore the transport and
transformations of saline droplets in the full atmospheric boundary layer, and to refine
bulk parameterisations of these effects. A major experimental project, instrumenting two
300 m towers on the tip of North
West Cape, Western Australia, to make detailed boundary layer
measurements during a tropical cyclone passage, ended in 2002.
