WMOD00439

• Title: HIPLEX-1: Experimental Design and Response Variables
• Date: 4/4/1984
• Weather Modification - Doc Type: Report

506 JOURNAL OF CLIMATE AND APPLIED METEOROLOGY VOLUME 23
TABLE 4. H1PLEX-l cloud selection variables.
Selection
pass Aircraft
Test time altitude Temp AWCO AICO MICO VVLO BOYO LPNO CTTO CBTO Cloud
case Date (CUT) (km) (0C) (g m-3) (L-1) (L-') (m S-I) (0C) (km) (0C) (oC) class SINS
I 21 Jun 79 213023 4.56 -7.8 0.79 0.02 0.02 7.46 1.86 3.29 -15.0 3.0 B NS
2 22 Jun 79 201236 4.53 -8.0 1.79 0.06 0.06 6.17 2.68 6.51 -12.5 8.0 B S
3 22 Jun 79 222111 4.52 -7.6 1.09 0.00 0.02 2.57 0.41 2.60 -11.3 7.3 A-I NS
4 11 Jul 79 203802 5.21 -8.8 0.52 0.02 0.17 4.14 0.69 4.00 -15.5 2.0 B ' S
5 II Jul 79 212522 5.25 -7.4 0.98 0.02 1.81 4.40 0.34 3.09 -14.0 2.0 B NS
6 12 Jul 79 185842 5.20 -8.0 0.68 0.00 0.00 2.45 0.42 3.31 -10.5 7.7 A-I S
7 16 Jul 79 183142 4.42 -7.0 2.51 0.69 0.69 -0.53 -0.51 2.84 -10.5 8.5 A-I NS
8 16 Jul 79 205037 4.45 -7.1 0.93 0.00 0.00 -1.35 -0.24 3.41 -12.9 5.6 B S
9 22 Jul 79 211139 5.57 -7.0 1.02 0.09 ,0.12 10.36 1.57 3.70 -14.0 5.4 B S
10 23 Jul 79 195959 5.20 ,-5.9 1.71 0.11 0.25 6.66 1.04 3.02 -11.0 11.0 A-I S
II 24 Jul 79 193330 5.21 -8.1 0.89 0.00 0.00 6.39 -0.08 2.92 -17.0 7.0 B NS ~
12 24 Jul 79 203110 5.23 -9.1 0.56 0.00 0.05 5.24 0.22 3.16 -17.9 5.6 B S --
13 16 May 80 202254 4.31 -8.7 0.75 0.02 0.06 0.97 0.65 2.03 -12.8 2.0 B S
14 16 May 80 221412 4.29 -8.0 0.56 0.02 0.28 2.35 0.31 7.88 -15.0 1.5 B S
15 7 Jun 80 212250 3.86 -8.8 0.81 0.09 0.34 4.08 0.00 2.83 -11.0 3.4 A-I S
16 16 Jun 80 180357 4.50 -8.4 1.13 0.02 0.02 -4.16 -0.16 2.59 -10.0 10.0 A-I NS
17 2 Jul 80 184552 5.19 -7.1 1.09 0.02 0.02 7.45 0.70 3.48 -13.5 10.8 B NS
18 2 Jul 80 200724 5.18 -7.9 0.59 0.00 0.02 3.87 0.64 2.68 -13.0 6.8 B NS
19 2 Jul 80 215559 5.19 -7.1 1.67 0.00 0.00 6.29 2.13 2.84 -9.5 6,8 A-I S
20 15 Jul 80 193920 4.62 -9.1 0.97 0.00 0.04 7.99 0.76 4.26 -16.0 2.3 B S

(1981) and Cooper et al. (1982). The latter scheme
was too complex to include in the real-time program,
so there were some minor discrepancies; for example,
Test Case 8 had a measured initial vertical wind
(VVLO) of -0.8 m S-I from the real-time system, but
-1.35 m S-l from the improved post-flight processing.
This type of discrepancy could not be avoided with
the system in use, but the discrepancy for Test Case
16 is so large that the real-time system would surely
have rejected the cloud had it been functioning prop-
erly. Thus, the open circuit breaker caused the erro-
neous inclusion of this cloud in the experiment. The
error was not discovered until after the flight, and the
fact that the proper vertical wind was negative was not
realized until late 1982. The seed/no-seed decision en-
velope for Case 16 was taken from the Class A-I se-
quence, so this case has been included in that class
for all evaluations of the HIPLEX-I experiment to
date, in spite of the error.
Another error occurred in Case 9 (22 July 1979)
when the wrong dry-ice dispenser was inadvertently
activated by the crew of the seeding aircraft. Because
there was no bias involved, as they had no knowledge
of which dispenser had been disabled, the case was
simply assigned to the actual category (seeded).
For Case 9 and one other Class B seeded cloud (Case
20), the cloud physics aircraft followed the procedure
calling for descent from the -50C level prior to 17
min after treatment, after making one pass through a
radar echo found at that level (see discussion of TFPI
in Appendix). However, the particles observed on the
last -50C pass did not satisfy the qualifications for
TFPI, so the default value of 17 min (1020 s) was

assigned. It had been thought that the airborne radar
sensitivity was low enough that only particles sufficient
to met the TFPI qualifications would give a detectablt~
echo. While events bore out that expectation in seven
other cases, it turned out not to be true in these two
cases. Graupel particles sufficient to give a radar echo
appeared, but in concentrations too low to meet tht~
0.1 L -I threshold forTFPI. The SWR-75 radar verified
the early appearance of an echo in both cases (cf. Tabk
6 below).
Supplemental cloud physics data obtained by a Twin
Otter research aircraft operated by the National
Aeronautics Establishment and the Atmospheric En..
vironment Service of Canada are available for somt:
of the HIPLEX-I test cases. The statistical evaluation
plan included no provision for using these data, be-,
cause the aircraft was not available for all of the teslt
cases. However, the data (mostly from near cloud base)
are useful for the physical evaluation of the experiment.

7. Calculation of response variables

The response variables were calculated from data
acquired by instrumentation on board the cloud phys..
ics aircraft arid the SWR-75 radar. Table 5 lists tht:
instruments used to determine the primary responst:
variables. The aircraft-derived variables were calculated
according to procedures described in Section VIII of
the design document (Bureau of Reclamation, 1979)
and summarized in the Appendix. The procedures
generally involved taking average values along specified
segments of the flight path for the indicated cloud
penetrations. A concerted effort was made to specify