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

275 m Williams Tower on the west side of
Houston_ A room on the 59tn Roor of that building
was used fO{ sampling during thiS campaign. A
ground~based version of the DMNTDMA system
operated on board the Cheyenne was used to
characterize submiaon aerosol sIZe distnbutJOns
and size-resolved hygroscopic growth. The size
distnbution of supermaon partides was
measured using a TSI. Inc. Model 3321
Aerodynamic PartICle Sizer (APS). Direct
measurements of CCN concentration at a single
supersaturation were measured W11h the same
model DMT counter as that used on board the
Cheyenne Whereas the TOMA and CCN
counter were operated in parallel on the
Cheyenne to maximize time resolution. they were
intermittently operated in series at the surface
site to examine the relatIonship between particle
size. hygroscopic behavlOl". and activation
efficiency

The measurements dunng the HEAT campaign
can best be demonstrated by desCl1bing one of
the flights. A summary of the aerosol
measurements conducted on August 23. 2004 is
given in here. Traverses upwind (to the south of
the city) and downwind (on the north side of the
city) were made at doud base to document the
aerosols being ingested by the douds. This was
followed by in-doud measurements at
progressively higher elevations to document the
effect of the aerosols on the cloud properties.
The subdoud measurements for this flight are
provided in the figure.

The data suggests that Houston emissions may
have a significant impact on CCN concentrations
even when mass concentrallon measurements.
which are more sensitive to larger particles. are
largely unaffected

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Figure 20: Data collected by the SOAR Cheyenne II dunng
a fllQhl Ol::PMIwIrd and upwmd of Houston. CaIo.;lated
backtra.f€ClCreS are represented by !he five yellow lines
that terrnnate alcng lhe ~ue leg ollhe flight traclI. The hne
colors used in the top gra~ sha.w1g measured CeN
concentratlcll at 0.5% reflect !he ~boo along the ft~hl
track shown on the map CeN coocentraOOris In'Yl'1(!(bately
dowrrwind of Houston 'M!fe observed to be as mud1 as 10
bmes higher than that measured on the east west, and
south sides of !he urban plLrne. The cause of the
brrodality In concentration IS not kno'-Nn. althoug1 Slrnlar
obsefvalions were made dunng lhe TexAQS study in
2000

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