WMOD00311

• Title: Harold D. Orville Symposium - Forty Years of Modeling Clouds and Weather Modification
• Date: 4/26/2003
• Weather Modification - Doc Type: Report

copy of David Letterman's top ten list).

i. Qualitative and quantitative understanding of
how ice is initiated in clouds for all ranges of
temperature, moisture, height, and other
salient input conditions.

ii. Qualitative and quantitative understanding of
ice multiplication mechanisms in clouds. A
better understanding of the occurrence of very
high numbers of ice particles observed in
tropical convective systems (Houze and
Churchill, 1987; Gamache, 1990), hurricanes
(Black and Hallett, 1986), and maritime
cumulus clouds (e.g., Hobbs and Rangno,
1990).

Hi. A better understanding of the habits and
particle size spectra of ice in the convective,
transition, and stratiform components of
mesoscale convective systems. Recent
results from the TRMM field campaigns are
beginning to shed some insight on this,
particularly in areas of cirrus and light
stratiform precipitation (Heymsfield et a/.,
2002).

iv. Improved quantitative understanding of the
collection efficiencies and fracturing rates
between colliding ice particles, at least to
where there is reasonable consensus within
the community.

v. Interpreting aircraft observations of rapidly
evolving, smaller-scale convective events into
appropriate time- and volume-averaged
quantities useful for model evaluation.

vi. Using more sophisticated schemes to improve
simpler, faster schemes.

9. CURRENT AND FUTURE RESEARCH
INITIATIVES

There is great promise in. the foreseeable
future that cloud microphysical modeling will play
an ever-increasing role in enhancing the remote
sensing capability of our planet. Many of the new
instruments on NOAA and NASA satellites are
designed to gain a better understanding of cloud,
precipitation, and radiation processes (e.g.,
passive-microwave channels, TRMM radar,
CERES, MODIS), in which microphysical models
coupled with radiative transfer models are used in
algorithm development, validation exercises, and

data assimilation. These models are also used in
a wide variety of conventional and multiparameter
radar applications, Iidar retrievals, and other
remote sensing platforms. Several groups have
been working on assimilating radar reflectivity data
into numerical models (e.g., at Univ. Oklahoma,
NSSL, NCAR), requiring the use of cloud
microphysical models. This is a rapidly growing
effort in the community, and plans are to begin a
similar effort at EMC in assimilating reflectivity data
into operational models. The total volume of data
received at NCEP has increased by two orders of
magnitude during the past three years (of which
-10% is assimilated into the models), and this data
volume is expected to increase by three orders of
magnitude by the end of this decade. Some of this
will involve improved cloud measurements, where
microphysics models will be used at various points
in the data flow between satellite observations and
model assimilation.

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There are several exciting community-based
research initiatives. One is the ongoing GEWEX
Cloud Systems Studies (GCSS), which has been in
existence for over a decade. It is composed of five
working groups focusing on (1) boundary-layer
clouds, (2) cirrus clouds, (3) extratropical (frontal)
clouds, (4) deep convection, and (5) polar clouds.
The primary mission is to improve the cloud
parameterizations in climate models, with a
secondary emphasis on improving global models.

Another major community modeling initiative is
the WRF model. It is a non hydrostatic modeling
system designed for cloud-scale and regional-
scale modeling at grid resolutions between 1 km
and 10 km. The WRF model system is intended to
bridge the gap between research and operational
modeling efforts by providing a common modeling
infrastructure with unified coding standards. It is a
joint effort between NCEP, NCAR, FSL, and the
Univ. of Oklahoma, as well as involving other
institutions and the university community. Multiple
dynamic cores and physics packages will be
available as options for the user to select. When I
attended an international workshop last year in
Europe, I realized that most of the European
countries have created their own WRF-Iike efforts
involving multi-national consortiums designed for
improved regional scale modeling.

What is exciting about WRF is that cloud
microphysics will play an important role in both
research and operational NWP communities. The
WRF model will be a true community model with
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