WMOD00176

• Project Name: Annual Report
• Title: Seeding Operations & Atmospheric Research, 2005 Annual Report
• Prepared By: Duncan Axisia
• Date: 12/31/2005
• Weather Modification - Doc Type: Report

contmental regime is typtcally populated with
much smaller nuclei and of a more uniform
nature, This acts to inhibit coalescence
processes tn continental clouds as the
requirement of broad droplet sizes is not met.
Oceanic douds do not expenence the same
barrier to coalescence as giant sa" nuclei act to
broaden the distnbution of CCN sizes and
therefore imtiate coalescence at a much faster
rate and at much warmer temperatures As one
might expect, the addition of larger nudei in
continental clouds may therefore help to initiate
coalescence processes whereas the same
administration to an oceanIC cloud may actually
be detrimental, The actual CCN sIZe
distnbutlOns have never been sampled
systematically across Texas to denbfy regions
that are typically continental versus mantime in
their cloud microphysical structure, Therefore
Phase I of the SPECTRA project was devoted to
sampling convective douds across various
weather regimes and locations in Texas, eastern
New Mexioo. and Oklahoma to typify doud
structures seen in these regIOns By doing so, an
effective strategy for seeding may be developed
based upon the regional tendencies of CCN
spectra,

Cloud physics measurements in Texas

The SOAR cloud physics aircraft equipped with
state-of.the.art doud microphysics
instrumentation. was deployed within and in
proximity to operational rain-enhancement
"target" areas in semi-arid West and South Texas
during the 2-month time frame beginning on
August 4, 2004 (SPECTRA I). Measurements of
CCN were also made in western and southern
Oklahoma. as well as in other sectors of Texas
where cloud seeding has not been performed in
recent years. In all. the research aircraft
conducted 34 missions during the 9-week field
program. logging a total of 75 hours.

The baSIC measurements consisted of CCN data.
aerosol concentratIons (0,1 to 311m). cloud
droplet size distribution (3 to 5011m) and
precipitation hydrometeor distributions (2Sj.Lm to
1 Smm) The data were plotted for each of the 34
missions Figure 17 b through e is a sample of
the data for a case on the 191'1 August 2004 in
San Angelo, Texas

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F'9"'" 1 7 1'1 ... SOAR Cteyonre II doud 1*1,.."
aircraft: (b) CCN concef1traboos 00I0w doud base plotted
as a function of supersaturalllXl (55): (c) doud droplel
(COP) coocentralioos as a function of height.

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