Message from Dr. Andrew Heymsfield
co-chair of Working Group 2, Aerosol Indirect Effect
INDOEX Workshop, Utrecht, The Netherlands
September 8-10, 1999

Message of Thursday, August 5, 1999

Dear Everybody:

The conveners of the Indirect Aerosol Effects Session at the INDOEX meeting
in  Utrecht (/Desbois/Heymsfield/Twohy) solicit titles and abstracts for
our session. We would like to ask each of you who wishes to present a talk
or poster to send to Andy a brief abstract ASAP.  We will go over them and
try to put together a balanced, focused session that covers the major
findings. The inserts and attachment identifies the C130 flights and their
ranking in terms of  how well they may address the indirect effect. The
highest ranked cases include a combination of gradient flights and
intervals during polluted flights. We ask the Citation group to put
together a similar summary rating of the cases they flew in-cloud with the
FSSP, as well as any cases which may pertain to the indirect effect?

Andy Heymsfield

Ratings (link to Summary of INDOEX Cloud Flights (Non-Gradient):

We rated each  flight  according to  how  well  it  can be used to address
the indirect effect. We felt that CN, CCN, and aerosol composition data in
the  subcloud environment  as  well  as  in-cloud measurements could be
used to establish a linkage in the physical processes which gives rise to
the  indirect  (Twomey)  effect.  We therefore rated highly those cases
which contained measurements  both  in-and  below-cloud at times which were
relatively close. For the gradient flights, good radiation measurements
(usually  on  the  return  leg)  were  of importance  as  they  provide  a
means of inferring the radiative consequences of the indirect effect.

We gave high values to those gradient flights  (a  perfect  score was
assigned a value of 10) that contained sub-cloud and in-cloud data
throughout much of the duration of the N-S transit, and  had radiation
measurements  on  the  return leg; two of the gradient flights had scores
of 10. The  flight  of  24  March,  while  not highly  rated as a gradient
flight, scores high marks for getting clean cloud closure. While we gave
marks of 7 or 8 to several  of the  non-gradient  flights,  we recommend
focusing on 21 March, 7 March followed by 27 Feb and 16 March for the
"polluted" clouds. Note  that on several of  these days, there are discrete
times of interest. Also note that there were several non-gradient flights
whose ratings of "nix" mean that they are of little  interest.

RATINGS 16 Feb  Nix 18 Feb  Nix 20 Feb  10 Gradient flight, possible FSSP problem 24 Feb  10 Gradient 25 Feb  Nix 27 Feb  7--8, particular times: 0945-1030, 1245-1315 28 Feb  Nix 4 March 7 Gradient 7 March 8, particular times: 0730-1115 9 March   Nix 11 March  8 Gradient 13 March 6, Citation intercomparison 16 March 7 18 March 7, multiple penetrations of Cb. 19 March 7, particular times: 0600-0830, 0900-1130 21 March 8, particular times: 0730 to 0915 24 March 6 As a gradient flight, 9 as a characterization of clean clouds 25 March 5
Andrew Heymsfield, Microscale and Mesoscale Meteorology Division NCAR 3450 Mitchell Lane Boulder, Colorado 80301 303-497-8943 (w) 303-497-8171 (fax)