Forecasting and future work - Severe Convective Storms and Tornadoes: Observations and Dynamics - page 422

perature gradient will decrease which, according to the thermal wind relation, will
lead to a decrease in deep-layer vertical shear. Since supercells are probably more
sensitive to the amount of vertical shear in the atmosphere than CAPE, it might
be that the likelihood of severe weather associated with supercells will decrease,
while the likelihood of heavy rain from mesoscale convective systems will increase.
The models, however, do not tell us anything about the change, if any, in the
likelihood that convective storms will actually be triggered and it is possible that
there could be fewer storms even if CAPE is higher. Furthermore, it is possible
that future distributions of CAPE and shear could have significant regional
differences. Moreover, while the long-range mean values of CAPE and shear may
change, it is possible that there could be increased variability, such that there
could be more instances when CAPE and shear deviate significantly from the
long-term mean: there could be major outbreaks in spite of an unfavorable
environment in the mean.
Using a technique known as ''dynamical downscaling'', Jeff Trapp at Purdue
University and collaborators have undertaken an exercise in which a large-scale
model is run for short time periods and then a non-hydrostatic, fine-grid cloud
model is run to produce forecasts given larger scale forecasts as initial conditions.
Using such a procedure, one can assess regional changes in severe convection.
Currently, efforts have been undertaken to look at non-hydrostatic model runs
based on decades of reanalysis data to find statistics on the relation between
actual severe weather events and model output.
7.3 FUTURE RESEARCH
There are several areas of research that are evolving now and several that are just
emerging. The current areas of evolving research include advancing our ability to
probe severe convective storms by remote sensing with Doppler radars, especially
those dealing with rapid-scan, polarimetric radar technology. The development of
electronic scanning using phased array technology, imaging radar technology, and
spaced antenna technology, should have the potential for improving our ability to
map the wind and hydrometeor fields in severe convective storms and tornadoes
on short time scales with high spatial resolution. If these advances could be
adapted for high-frequency radars, then tornadoes could be much better observed
when attenuation is not too great. In the far future, it would be advantageous to
mount these radars, when made small and lightweight, on mobile, airborne plat-
forms, such as helicopters in particular, which can hover safely near tornadoes and
not be restricted to road networks necessary for ground-based vehicles, and do not
require longer update times as do aircraft, which must fly by at some minimum
speed necessary to keep the aircraft airborne. Developing airborne radars likely
requires solid state, low-power transmitters, which will have to make use of pulse
compression techniques to enhance their sensitivity. NASA has already begun this
area of technology development with their radar on the Global Hawk UAV, and
Gerry Heymsfield and colleagues have used it to collect data in hurricanes over