the cloud seeding research plan that Roelof developed

1. 1. OPERATIONAL PROCEDURES FOR BRRAA KING AIR RESEARCH
1.1 Objectives Summary
In summary, any field program provides a unique opportunity to validate physical chain of
events of the hygroscopic and glaciogenic seeding conceptual models through the ability to seed
and measure storms at the same time (using one or more aircraft), to document microphysical
characteristics and development remotely (using polarimetric radar). Concurrent physical
measurements with a cloud seeding experiment could help scientists to either confirm or discard
aspects of the seeding conceptual model and strengthen any statistical results from a randomized
cloud seeding experiment.
Aircraft operations are emphasized here. Radar operations in general will focus on documenting
the variability and range of radar responses to natural precipitation development, the area of
which is unconstrained outside of aircraft operations. During aircraft operations, the radar will
be operated similarly but concentrated on clouds and storms being studied or seeded by the
aircraft.
The detailed objectives can be summarized into five basic areas for aircraft studies:
(1) Aerosol, particularly CCN, characterization. This includes information on aerosol types,
concentrations, size distributions that may affect the CCN character of particulates.
Understanding the origins, transports, and natural variability of CCN are key to
documenting the background CCN which cloud seeding attempts to perturb. This
objective requires boundary layer flights – low level (~500’ AGL) to cloud base
altitudes. The primary instruments in these studies are the PCASP, DMA, CCN counter
and the FFSSP.
(2) Cloud droplet characterization. Hygroscopic seeding attempts to broaden the droplet
distribution, which needs to be assessed along with natural variability. These studies
typically require cloud penetrations near cloud base – cloud base to roughly 1000’ above
cloud base. The primary instruments in these studies are the FFSSP, 2D-Stereo, and CPI
probes in addition to the Total LWC probe.
(3) Development of drizzle-sized drops. A largely undocumented link in the hygroscopic
seeding hypothesis is the development of drizzle and its circulation within a treated cloud
and into surrounding cloud regions (other developing updrafts and downdrafts).
Coordination with polarimetric radar coverage is important for this study. Flight altitudes
are variable, following the growth of cloud top on occasion but usually concentrating on
repeated penetrations at the 0° C level. The primary instruments are the FFSSP, 2D-
Stereo, CPI and TWC probes.
(4) Ice phase processes. Monitoring graupel formation and detecting evidence of ice
multiplication will help tie hygroscopic seeding to cold cloud processes (and help assess
glaciogenic seeding potential). This study also requires close coordination with CP2 for
comparison with particle type classification from polarimetric variables. The flight
altitudes of interest are at the cloud base, 0°, -5°, -10°, and (occasionally) -15° C levels,
with a flight profile of both repeated penetrations at one level and multiple penetrations in
rising turrets. The primary instruments are the FFSSP, 2D-Stereo, CPI and TWC.

2. (5) Drop size distributions (DSD) in rain shafts. An issue that remains unresolved is whether
seeding changes the DSD such that past seeding experimental results based on
reflectivity alone overestimated the change in rain flux at cloud base. This is an ideal
experiment for CP2, and some flights in rain shafts may provide “ground truth” for
comparison with the radar. These flights would normally take place within 1000’ below
the original cloud base. The primary instruments are the 2D-Stereo and HVPS.
1.2 Flight strategies overview
Flight operations will be undertaken to accomplish a range of observation needs, including:
1. Instrumentation tests and intercomparisons. These operations will utilize tower fly-bys,
flights in close spatial coordination with rawinsondes.
2. Ambient aerosol research survey flights required to document and understand the aerosol
content of the lower atmosphere under a variety of synoptic and regional weather
conditions.
3. Cloud and aerosol research flights required to document and understand the microstructure
of clouds and the effectiveness of natural precipitation processes. These studies will
address both convective and stratiform clouds in non-precipitating and precipitating form.
4. Exploratory cloud seeding flights required to establish and maintain effective ATC
coordination, refine project direction and communication protocols, and test preliminary
seeding hypotheses and methods (seeding aircraft only).
5. Coordinated cloud physics and seeding research flights required to explicitly test and
evaluate hypotheses regarding cloud precipitation processes, seeding hypotheses and
seeding trials. These flight operations will utilize the research aircraft and one of the
seeding aircraft operating in spatial and temporal coordination.
6. Compare in situ airborne measurements of clouds, aerosol, and precipitation with radar and
satellite observations. These are required to better explain regional variations of cloud,
aerosol, and precipitation characteristics and to validate satellite retrievals of cloud
microphysical properties.
1.2.1 Flight plans for research and experimental seeding
Coordination of profiling and seeding objectives
The research aircraft cloud and aerosol profiling objectives are critical to the diagnosis of
seeding potential in the cloud systems discussed below. Profiling objectives are also critical to
subsequent refinement of appropriate seeding strategies for these systems. Consequently, trial
seeding early in the project will proceed in parallel with profiling flights, but will be conducted
so as not to influence clouds to be profiled in their natural state.
Potential seeding strategies
A seeding operation is initiated when the forecast calls for clouds containing supercooled liquid
water to be passing just upwind or over the target area. Under these conditions aircraft are
launched. The objective is to intercept the desirable cloud liquid water regions in clouds with
concentrated plumes of silver iodide. It is critical to properly time the releases and correctly

3. select and design flight patterns in order for the plume-cloud intercept to occur. Although the
Operations Director will generally vector the pilot to the most promising area, it will be the
responsibility of the pilot and/or flight scientist to select the individual cloud features to be
seeded.
For reference, generalized seeding hypotheses are briefly summarized below. More specific
hypotheses and methods will be developed as field research proceeds, as will a more definitive
understanding of the optimum techniques to use for cloud systems.
Hygroscopic Techniques
Seeding Hypotheses:
1. Seeding at cloud base may enhance collision/coalescence leading to drizzle formation
that would spread the seeding effect throughout the cloud and result in warm rain precipitation
production.
2. Seeding at cloud base may induce development of large droplets, leading to enhanced ice
production at warmer temperatures, thus invigorating ice phase precipitation development in
the cloud.
Glaciogenic Techniques
Static Seeding Hypothesis:
Depending upon cloud base temperature and cloud depth, there may be insufficient
opportunity for natural development of the ice phase in the cloud. For example, if cloud base
is colder than about -5ºC, or if the cloud is too shallow to develop large (~25 μm) cloud
droplets, the conditions for Hallet-Mossop ice multiplication do not exist. AgI seeding within
the most vigorous updraft regions may be effective toward glaciation and thus induce an
effective ice-phase precipitation process.
Dynamic Seeding Hypothesis:
AgI seeding in regions of significant supercooled cloud water can stimulate updraft growth
through enhanced release of the latent heat of fusion or through beneficial surface outflows
resulting from a precipitation-induced downdraft. This requires a large supercooled liquid
water content and delivery of a high concentration of AgI nuclei.
The assessment of seeding effect will be made on the basis of:
 Physical insight gained from the suite of physical measurements made and from the
interpretation of these data against the knowledge gained from past experiments.
 A number of case studies in which microphysical effects are observed in single-aircraft or
coordinated multiple-aircraft seeding process studies that are clearly attributable to seeding
(so-called seeding signatures).
 Once we have assessed through the above studies that clouds may be amenable to seeding
a number of randomized seeding studies should be conducted in which seeding effects are
sought in the radar data for a range of cloud types. These will be more like the “black box”
experiments. These studies gain statistical strength by collecting a large number of cases,
and the seeding aircraft that do not carry research instruments.
 Indications and insights gained from numerical modeling results.

4. The characteristics of flares used for seeding and a reference guide for planned seeding actions in
a variety of meteorological situations are summarized in Tables 8.1 and 8.2 below.
Table 8.1: Characteristics of Flares Used in Seeding
AgI Ejectables (EJs)
- To promote ice-phase processes through enhanced nucleation.
- Effective only in regions of supercooled liquid water.
- Flare payload: - King Air: 102 flares.
- Burn time ~37 sec while falling approximately 1 km (3-4 k ft).
- Requires 5000 ft safety drop zone below flight level.
- Release rate: Every 4-5 sec. (~ 0.5 km spacing).
- Release duration: Continuous while aircraft is in cloud region meeting seeding criteria (see
Seeding Criteria in following Table). May be used in combination with Endburners (below).
AgI Endburners (EBs)
- To promote ice-phase processes through enhanced nucleation.
- Effective only in regions of supercooled liquid water.
- Seeding target zone at flight level.
- Flare payload: - King Air: 72 total (can be comprised of Endburners and/or HBIPs).
- Burn time ~6 min. each.
Always multiple burns (3 burns in sequence)
(3 burns) X (1 per burn) = 3 flares per event
= ~18 minutes total burn per event.
= up to 8 seeding events per flight.
Hygroscopic Burn-in-Place (HBIPs)
Flares comprised of KCl and NaCl.
To enhance collision-coalescence processes through development of large cloud droplets.
Flare payload: - King Air: 36 total (can be comprised of HBIPs and/or Endburners)
Burn time ~ 4 min, each.
Always burned in pairs.
Always multiple burns (4 burns in sequence)
(4 burns) X (2 per burn) = 8 flares per event
= ~16 minutes total burn per event.
= up to 3 seeding events per flight.

5. Table 8.2: Seeding actions for a variety of meteorological conditions.
Meteorological Seeding Criteria
(assumes 10 nm / 20 km target Seeding Action
Situation spacing criterion is met)
AgI Endburner (EB) Seeding
Seeding zone: region of LW (see left) at
flight level in -5 to -10 oC range.
Widespread 1 EB at a time; 3 total per case.
Stratiform Cloud Yields ~18 minutes seeding; allow 20
Generally associated with a For Instrumented Aircraft minutes for event.
tropical system. Cloud LW ≥ 0.2 g m-3 over 3 km path in Optional: Concurrent AgI Ejectable (EJ)
Accompanying precipitation is cloud. Seeding Aloft
mesoscale in dimension and Targets embedded convection aloft if present.
For Non-Instrumented Aircraft
typically shows a radar bright EB and EJ seeding in combination is
band. Identifiable cloud base
acceptable.
Typically can contain embedded Indications of supercooled LW (e.g. a/c
Flt level in zone from -5 to -10 oC.
convection. riming, water on wind screen)
EJ drops made every 4-5 sec while aircraft is
in updraft / LW zone at -19C level..
Duration: as long as aircraft can find and
remain in LW zone aloft, but event is not to
exceed 20 min.
AgI Ejectable (EJ) Seeding Aloft AgI Ejectable (EJ) Seeding Aloft
Cloud Selection Procedure: Pilot Flight level in zone between -5 and
encouraged to select by visual cues (solid -10 oC.
cloud base at least 2km in diameter EJ drops made every 4-5 sec while aircraft is
without inspection pass when able. in updraft / LW zone.
Cloud Conditions Obs: Pilot obs on
updraft & LW especially important when Duration: as long as seeding criteria at left are
visual selection (above) used. Can note met, but not to exceed 20 min.
on logs and/or envelope.
For Non-Instrumented Aircraft
Indications of light to mod icing.
Cloud tops above -8 oC.
Cauliflower appearance if visible.
Convection
For Instrumented Aircraft
May be isolated or organized
Seeding criteria above, plus:
convection.
Cloud LW ≥ 0.5 g m-3 for 10 sec.
Cloud depth > 3000 ft.
Hygro (HBIP) Seeding at Base Hygro (HBIP) Seeding at Base
For Instrumented Aircraft Flight level at or just below cloud base.
Updraft at base ≥ 200 ft min-1 and should 2 HBIPS at a time; 8 total per event.
be persistent enough to remain in Duration: as long as seeding criteria at left are
updraft. met, but not to exceed 20 min.
Solid visual cloud base at least 2km in Instrumented aircraft: Follow with a pass just
diameter. above cloud base to detect drop spectrum
Flight level (cloud base) temperature > 0 spreading.
o
C. Optional Concurrent AgI Ejectable Seeding
Aloft
For Non-Instrumented Aircraft
Procedure as in EJ Seeding above.
Same.

6. 1.3 Flight missions
1.3.1 Regional aerosol survey missions
Research questions regarding aerosol structure
What is the range of background aerosol conditions under different meteorological regimes and
corresponding wind field structures? What is the contribution from biomass burning, dust, local
pollution, or sea-salt? What is the corresponding vertical profile of aerosol structure from near
the surface through the top of the mixed (boundary) layer? What are typical sub-cloud spatial
variations in aerosol characteristics? Do seasonal differences exist?
Flight plans – King Air
Objective: Obtain the horizontal transects and vertical profile of aerosol content from minimum
allowable altitude through the top of the mixed (boundary) layer. Document any horizontal
gradients or inhomogeneities in aerosol content through multiple profiles spaced (perhaps 10 to
50 NM, as appropriate) and through just below cloud base horizontal transects across a sampling
region.
Spiral ascent to 15K’ Figure 1.1: King Air: Measure vertical
or top of mixed layer. profile and horizontal transects of
aerosol structure through the mixed
layer starting at minimum possible flight
level. One profile per location.
Domain: Multiple profile locations
enable regional characterization.
Spiral diameter 1 to 2 km. Mixed
Layer
Choice of Conditions: Sample a variety
Ascent rate 300-400 ft/min. of regimes include clear day, fair-
weather Cu day, stratiform, others.
Begin missed
approach Flight plan details: See section 8.4.5.
Surface
1.3.2 Small to moderate non-precipitating cumulus missions
The structure and processes of non-precipitating cumulus in a region must be well understood in
order to effectively diagnose the seeding opportunity of convective clouds.
Research questions affecting non-precipitating Cu seeding strategies
What are the key Cumulus characteristics, typical cloud base heights and temperatures of the
clouds, their droplet concentrations, and the growth of the droplet spectrum with height above
cloud base. Do drizzle or rain drops form in them via collision and coalescence? What are the
deepest non-precipitating clouds in a region as a function of season and space? Are they deep
enough, and their bases close enough to the ground, to form seeding targets? Does pollution,

7. sea-salt alter their microstructure? What are the CCN and IN concentrations in the inflow air at
cloud base?
Flight plans
Objective: Survey the sub-cloud aerosol and cloud structure of small to moderate Cumulus as
needed to address the research questions outlined above. The needed surveys are best
accomplished through horizontal transects consisting of 10 km legs over areas where the air is
fairly homogenous.
Figure 1.2: King Air sub-cloud Profiling: Perform aerosol and CCN measurements
just below cloud base.
g
- Sub-cloud aerosol profiling.
- ‘Just above cloud base’ cloud pass.
- In-cloud passes at -5 C, -10 C, -15 C…
reaching cloud top.
- Tracks parallel to shear vector.
Upshear
Downshear
Figure 1.3: King Air sub- and in-cloud Profiling: Combined sub-cloud aerosol
pass and in-cloud microstructure profile with multiple passes along shear. AgI
seeding may occur by dropping ejectables into water-rich growing turrets at -5 C
level. Hygroscopic seeding may occur beneath cloud base.

8. AgI Seeding
- Near -5 to -10 C level.
- Target supercooled
LWC maximum.
- LWC > ~ 0.2 g m-3 Older Hygroscopic Seeding
turret.
Lower
- Direct to updraft at
LWC. cloud base.
- Target isolated,
LWC-rich narrower Cu.
growing
turret.
Figure 1.4: Seeding: Initial seeding is considered ‘exploratory’ until analyses of
regional survey/profiling flights allows development of a more fully refined set of
seeding hypotheses for a variety of meteorological situations. Seeding during the latter
part of the field phase will more specifically reflect and test emerging seeding
hypotheses focused on the characteristics of regional clouds.
1.3.3 Isolated cumulonimbus missions
Cumulonimbus clouds are particularly important to this study because their natural processes are
successful in producing precipitation that reaches the ground.
Research questions affecting isolated Cumulonimbus seeding strategies
What are the natural precipitation processes in Cb clouds and how do they relate to seeding
hypotheses? What is the source of those rainshafts that reach the ground? Are they comprised
mainly of graupel or can they also arise from the aggregation of snow crystals? What are the
concentrations of natural ice particles in these clouds? How rapidly do ice crystals form in
them? How much supercooled liquid water is in them, and how long does it last? Do drizzle and
raindrops form in them? Can the precipitation from these clouds be augmented by seeding with
either silver iodide or hygroscopic agents? How does seeding alter the natural formation of ice
and precipitation? How are they affected by aerosols?
Flight plans
Objectives: Document the sub-cloud aerosol and in-cloud microstructure of cumulonimbus
across the full range of lifecycle stages (e.g., developing, mature, dissipating) as needed to
document the natural precipitation processes at work. Special attention should be paid to the size
distributions of liquid and solid cloud particles, locations and amounts of liquid water, and
evidence for details of riming growth.
King Air Profiling: Survey aerosol and cloud structure of Cb. Define evolution of ice and water
from precipitation below cloud base upward through cloud top. Characterize differences in
cloud structure and apparent ice/water processes as clouds age from early precipitation stage
through dissipation. Survey aerosol structure in the sub-cloud inflow zone including CCN and
IN measurements. Obtain cloud droplet spectra above cloud base.
AgI Seeding (any aircraft): Determine potential for invigorating cloud dynamics through AgI
ejectable seeding of maximum liquid water zones expected within the -5 to -10 C region. AgI

9. seeding may occur by dropping ejectables into water-rich growing turrets at -5 to -10 C level.
These are expected on the upshear side.
King Air Profiling: Cloud microstructure profile via multiple passes along shear vector as
shown.
1.3.4 Shallow and Deep Tropical Stratiform Rain Systems
Shallow and deep tropical rain systems produce the largest overall amounts of rain in Thailand
and surrounding regions and they come in several forms especially during the rainy season. This
section deals with the study and seeding of these rain systems that typically show a very moist
low and/or deep atmosphere (wet adiabatic) with slowly rising air.
Research questions affecting shallow and deep tropical rain seeding strategies
What is the natural process of precipitation formation? How much of the rain at the ground is
due solely to the convection and how much is due to the stratiform regions in these clouds? Is
the rain that reaches the ground solely due to warm rain, graupel, or do aggregates of snow
crystals also play a role and how effective are the warm rain and ice processes? How widespread
is supercooled water in these clouds? Can seeding augment the rain from these bands? Do they
originate in the boundary layer or are they the result of conveyor-belt type lifting?
Flight plans
Objectives:
King Air Profiling: Survey aerosol and cloud structure of tropical rain systems. Define
evolution of ice and water from precipitation below cloud base upward through cloud top.
Define ice particle concentrations and forms (single crystals, aggregates, pellets, etc.).
Characterize aerosol content of inflow air and obtain air truth precipitation measurements as
close to the surface as possible. Survey aerosol characteristics in the sub-cloud inflow zone.
Obtain CCN and IN measurements. Obtain cloud droplet spectra near and above cloud base.
AgI Seeding (Seeding aircraft): Utilizing results from tropical rain systems profiling studies,
examine potential for enhancing ice crystal and/or invigorating precipitation production through
burn-in-place AgI seeding in Supercooled liquid water regions and/or hygroscopic seeding in air
inflow regions in warmer parts of the cloud.
Aerosol Characterization
Map advection and diffusion from known source regions. Aerosol characterization below cloud
base (or near the top of the boundary layer on clear days). Repeated legs or circling for adequate
sampling with slow responding instrumentation. Make slow ascent soundings in specific areas –
upwind and downwind of sources, over areas of interest.
Cloud Droplet Measurements
Objective: Document the cloud droplet size distribution near cloud base before, during, and
immediately after seeding. The impact of seeding on the cloud base droplet distribution should
be evident within seconds of the onset of seeding.

10. Primary Cloud Physics Instrumentation: SPEC 2D-Stereo, SPEC CPI, SPEC HVPS and SPEC
FFSSP, Total Liquid Water Content sensor, PCASP, DMA counter, CCN counter, state
parameters
Procedure:
During times when there are no suitable clouds available for the randomized experiment but
convective clouds with bases lower than 5,000 ft (1500 m) and a vertical depth of at least 1-2 km
exist or when storms exist outside the radar coverage area, airborne observations to measure the
effects of seeding on droplet broadening and drizzle formation would be desirable. In these
situations it is suggested that both the research aircraft and a seeding aircraft take off to conduct
these experiments.
Prior to starting the seeding, the research aircraft should measure the natural aerosol size
distribution and CCN entering cloud base by performing an elongated racetrack pattern
approximately 1000 ft below cloud base. This will most likely take approximately 15 minutes,
depending on the CCN cycle. During this time, the seeding aircraft can be looking for suitable
updrafts. Once the below cloud aerosol measurements are completed, the cloud base
measurement phase can begin.
A measurement of cloud base (height, pressure, and temperature) is obtained with the seeder
aircraft flying straight and level at cloud base without penetrating any cloud. After the cloud base
measurements the research aircraft will ascend to 1000 ft above cloud base and conduct a
penetration in an actively growing convective cloud. It is important to note that the cloud base
measurements should be taken just below cloud base without penetrating cloudy regions.
Drizzle Studies
The research aircraft will subsequently conduct three to four penetrations through the updraft
core at 500-1000 ft above cloud base to document the droplet size distributions and in seeding
cases to detect the initial effects on the droplet size distribution. Following the cloud base
passes, it will conduct repeated penetrations to higher altitudes (at about 2000-3000’ vertical
intervals but not higher than the 0°C level) to detect the onset of coalescence and drizzle
formation in the cloud. Make repeated passes at the 0°C level.
Ice-phase Microphysical Measurements
Objective: Measurement of drop freezing, graupel growth, and possible secondary ice generation
by conducting repeated penetrations at the –5°C level with Research Aircraft.
Primary Cloud Physics Instrumentation: SPEC 2D-Stereo, SPEC CPI and SPEC HVPS, SPEC
FFSSP, Total Liquid Water Content sensor, state parameters
Procedure:
The research aircraft should ascend to the altitude with a temperature of approximately –5° C.
The seeding aircraft should be near cloud base to search for an updraft and keep the research
aircraft informed of its general location.

11. The location of the seeding aircraft should be communicated to the research aircraft at the
decision time. Penetrations at the –5° C level of the seeded cloud should be performed
continuously from the decision time until 30 minutes past the end of the seeding experiment.
This time should also be communicated to the research aircraft. The research aircraft will cease
penetrations if the cloud dissipates or penetrations become unsafe prior to the completion of the
30 minutes.
The recommended flight pattern for a single turret is a ‘figure 8’ pattern. If the selected cloud is
embedded in more organized convection, this pattern may be modified to allow the aircraft to
penetrate as far into the core of the cloud (where high liquid water exists) as safety will allow
and then exit before penetrating the next cell. Measurements in the core of the cloud will allow
for study of ice and mixed phase formation and growth processes while the data from the side
regions should help explain recirculation patterns. The combination of the two will provide a
more complete picture of the cloud microphysics at this level.
1.4 Sampling Strategies for the Research Aircraft
The following paragraphs details flight profiles that are recommended to be flown in a region
based on previous scientific campaigns. These profiles are guidelines for the pilots and
instrumentation PIs and will be followed at the discretion of the Pilot-In-Command (PIC).
The numerical order of the flight plans is indicative of the measurement priorities.
1.4.1 Flight Plan 0 – Experimental Seeding Case
The main scientific objective of cloud seeding experiments is to assess the potential for seeding
to enhance rainfall and to quantify these results. To support this objective, the research aircraft
will conduct seeding for high priority targets. The research aircraft should be launched early
when conditions are forecast to be favorable for such high priority targets. Once the research
aircraft is launched on an Experimental Seeding Case flight plan, the second seeding aircraft
should be launched in succession or placed on stand-by at the airport.
The research aircraft will not conduct seeding unless the seeding is being done as part of a
“hygroscopic seeding process study” or a “glaciogenic seeding process study”. Flight plans for
these cases are given below. At no time will the research aircraft conduct seeding at night.
Note: Bold text highlights Flight Scientist decision points.
CCN table 1: 0.2 (4min), 0.5 (3min), 0.8 (3min)
Task A: Characterize the atmospheric conditions before seeding.
Fly to target area at 16000 ft ascending at 500ft/min at airspeeds not to exceed 200kts. Observe
the cloud layer structure. Decide if it is a hygroscopic seeding or glaciogenic seeding case.
Hygroscopic Seeding Case:

12. Descend to cloud base at 500 ft/min. Descend at 1000 ft/min if Operations Director has
indications of a good possible target. Fly below cloud base and search for updraft/inflow. Search
for updrafts for at least 10 minutes. Determine if it is a seeding conditions case, if there are
other possible targets, or proceed to a different research flight plan. The Flight Scientist’s
decision will depend on the measurement priorities as they are perceived at the seeding location.
If the Flight Scientists or Operations director decides to proceed to a different research flight
plan, then a seeder aircraft has to be available to resume with the seeding operations.
Seeding Conditions Case:
Request/confirm that ground operation launch stand-by seeding aircraft. After seeding
experiment case concludes, decide if it is necessary to proceed to new possible target or to
characterize the seeded cloud.
Characterize the Seeded Cloud Case:
Immediately after seeding, ascend through the cloud base at 500 ft/min up to 2000 ft above the
cloud formation level and circle in the updraft drifting downshear but staying away from
precipitating cloud. Continue to characterize the cloud as described in flight plan Flight Plan B
Task C.
Other Possible Targets Case:
Proceed to next possible target at airspeeds not exceeding 200kts.
Different Research Flight Plan Case:
Proceed to conduct another flight plan as outlined in the operational plan. May be able to start
a different research plan in the middle. For example, the “Hygroscopic Seeding Process Study”
or “Aerosol/cloud Interactions and Cloud Microphysical Properties” flight plan.
Glaciogenic Seeding Case:
Penetrate cloud tops between -15 °C and -5 °C; and 200 to 500 ft. below the tops of high super
cooled liquid water areas that contain updraft. Determine if it is a seeding condition case, if
there is other possible target, or proceed to a different research flight plan.
Seeding Conditions Case:
Request/confirm that ground operation launch stand-by seeding aircraft. After seeding
experiment case concludes, decide if it is necessary to proceed to new possible target or to
characterize the seeded cloud.
Proceed to New Possible Target Case:
Proceed to next possible target at airspeeds not exceeding 200kts.
Characterize the Seeded Cloud Case:
Immediately after seeding, conduct cloud top penetrations between -10 °C and -0 °C for at least
10 minutes.
Other Possible Targets Case:
Proceed to next possible target at airspeeds not exceeding 200kts.
Different Research Flight Plan Case:

13. Proceed to conduct another flight plan as outlined in the operational plan. May be able to start
a different research plan in the middle. For example, the “Glaciogenic Seeding Process Study”
flight plan.
1.4.2 Flight plan 1 – Hygroscopic seeding process study
The objective is to characterize the microphysical changes that occur following hygroscopic
seeding at cloud base.
CCN table 1: 0.2 (4min), 0.5 (3min), 0.8 (3min)
Task A: Seeding process study with the research aircraft
Penetrate the cloud base at 1000ft above the cloud formation level starting in the updraft area and
continuing in a direction upshear to downshear. Stay away from the precipitating core.
Descend to cloud base at a fast rate of descent (2000 ft/min) and start seeding the updraft.
Seeding rate should be at least 2 HBIP every 3.5 minutes.
Immediately after seeding, ascend through the cloud base at 500 ft/min up to 2000 ft above the
cloud formation level and circle in the updraft drifting downshear but staying away from
precipitating cloud
Task B: Simultaneous aircraft measurements
Coordinate with the seeder aircraft and penetrate the cloud base 1000-2000ft above the seeder,
first perpendicular to the upshear vector then turning out of cloud to penetrate along the upshear
vector (upshear to downshear). Stay away from the precipitation core.
Penetrate the cloud along the same vector multiple times until seeding stops.
1.4.3 Flight plan 2 – Glaciogenic seeding process study
The objective is to characterize the microphysical changes that occur following glaciogenic
seeding at cloud top.
CCN table 1: 0.2 (4min), 0.5 (3min), 0.8 (3min)
Penetrate cloud tops between -5ºC and -10ºC 500 to 1000ft below the tops of high SLWC areas
that contain updraft. Pick young visibly growing towers.
Continue cloud top penetrations at -5ºC to -10ºC 500 to 1000ft below the tops following seeding
with ejectable flares. Continue for 10 minutes after the last seeding event. Repeat the
penetrations as quickly as possible.
1.4.4 Flight plan 3 – Aerosol/cloud interactions and cloud microphysical
properties
The objective is to characterize the aerosol size distribution and the CCN activity (out of cloud)
and aerosol-cloud interactions at the precipitating cloud base level (cloud layering may be
present below the precipitating cloud base).

14. CCN table 1: 0.2 (4min), 0.5 (3min), 0.8 (3min)
Task A: Characterize the sub-cloud aerosol layer (remain out of cloud and out of rain)
Climb at 500ft/min as soon as possible after takeoff and throughout the aerosol profile. Maintain
around 80m/s (~155kts).
Observe any aerosol layering or stratification. Pick 2 intermediate altitudes from the surface to
the cloud base.
Fly for at least 10 minutes in straight and level flight (or standard rate turns) at each of the
intermediate altitudes (one CCN SS cycle).
If a dusty layer is located below cloud base, the aircraft should fly for 15 minutes at constant
altitude flight while orbiting in a standard rate turn and maintaining 80m/s (filters).
A clean slot may be present immediately below the precipitating cloud base. This is usually a
very shallow layer (100 to 200ft thick). If possible to sample this shallow layer while staying out
of the cloud base, this should be done for 10 minutes (one CCN SS cycle).
Avoid areas where precipitation may fall on the aircraft as much as possible
Task B: Characterize the cloud droplet spectra at about 1000ft above the base
Note the cloud base altitude
Pick an altitude (1000ft above the cloud formation level) where the ground is not visible in the
cloud throughout the cloud base penetration
Penetrate the cloud perpendicular to the upshear vector to avoid any cloudy areas where
precipitation may be falling from above (often clouds are moving from west to east, so the
penetrations should be oriented north to south or south to north)
Task C: Characterize cloud droplet growth and the evolution of cloud hydrometeors
Penetrate the cloud perpendicular to the upshear vector at 2000ft intervals (depending on cloud
depth) from cloud base to cloud top. Avoid cloudy regions where precipitation may fall from
above. If precipitation falling from above is observed during the penetration, repeat the
penetration.
Note the cloud top altitude
In addition, flight scientists may focus on the following specific objectives:
Objective: Characterize the vertical structure of the different cloud layers
Climb through the layered cloud at 500 ft/min
Objective: Characterize the cloud microphysics with radar first echo
Find altitude of cloud with radar echo from ground radar
Penetrate the cloud at 500-1000ft intervals (depending on cloud depth) starting from the altitude
of the first radar echo
Objective: Characterize cloud turrets that pushes into dry air (bubble pushing above the layered
cloud deck)
Penetrate the cloud top at 500 to 1000ft below the top

15. Repeat several times until cloud top collapses (Updraft velocity, typical lifetime, evolution of
cloud particles, surrounding humidity profile)
1.4.5 Flight plan 4 – Aerosol profile (no cloud present or forecast)
The objective is to characterize the aerosol size distribution and the CCN activity through the
aerosol boundary layer. The descending profile should be in a different region to characterize
spatial homogeneity. .
CCN table 1: 0.2 (4min), 0.5 (3min), 0.8 (3min)
Climb at 500ft/min as soon as possible after takeoff and maintain 500ft/min throughout the
aerosol profile. Maintain around 80m/s (~155kts). Continue the climb to 2000ft above the top of
the aerosol boundary layer. Fly for 10 minutes above the aerosol boundary layer while
maintaining standard rate turns. Aerosol scientist should check CCN supersaturation (SS) cycle
to make sure that a full SS cycle is flown at a constant altitude.
Observe any aerosol layering or stratification. Pick 2 intermediate altitudes from the surface to
the top of the aerosol boundary layer.
Descend at 500 ft/min maintaining a standard rate turn to the lowest possible altitude.
Fly for at least 10 minutes in straight and level flight (or standard rate turns) at each of the
intermediate altitudes (one CCN SS cycle)
If a polluted layer is located, the aircraft should fly for 15 minutes at constant altitude flight
while orbiting in a standard rate turn and maintaining 80m/s (filters).
Return To Base (RTB) at the lowest possible altitude.
1.4.6 Flight plan 5 - Pollution plume survey flight (no cloud present or forecast)
CCN table 2: 0.5 (continuously)
Plan 2 or 3 (40nm) flight legs oriented perpendicular to the wind direction and <30nm from the
city center.
Climb at 500ft/min as soon as possible after takeoff and maintain 500ft/min and 80m/s (155kts).
Continue the climb to 500 to 2000ft AGL. Intercept one end point of your planned flight track. If
possible do not change the altitude for the duration of the track.
Repeat the track for the second time at an altitude 1000ft above the first track.
If a polluted layer is located, the aircraft should fly for 15 minutes at constant altitude flight
while orbiting in a standard rate turn and maintaining 80m/s (filters).
RTB at the lowest possible altitude.
1.4.7 Flight plan 6 and 7: CloudSat/CALIPSO Overpass Flight Plans
Objectives:
Extend airborne observations to satellite measurements over the region to better explain regional
variations of cloud, aerosol, and precipitation characteristics.

16. Compare in situ airborne measurements of clouds, aerosol, and precipitation with satellite
observations.
Validation of conceptual model of precipitation formation.
Background Information:
CLOUDSAT
http://www.nasa.gov/mission_pages/cloudsat/main/index.html
http://cloudsat.atmos.colostate.edu/home
CALIPSO
http://www.nasa.gov/mission_pages/calipso/main/index.html
Based on the orbit predictor, a possible mission could exist every 4-5 days. Flights will be during
overpasses
CLOUDSAT/CALIPSO overpasses.
5-10 successful missions for CALIPSO and for CLOUDSAT will be sufficient.
Pre-mission Procedures:
Forecasters should determine when there will be a possible CLOUDSAT/CALIPSO overpass
(daytime) near preferred location (< 200 km). This can be predicted well-in advance using the
orbit predictor:
http://www-angler.larc.nasa.gov/cgi-bin/predict/predict.cgi
Note: The orbit of the satellites will change frequently. It is recommended to only use orbit
predictions < 5 days in advance (e.g. update orbit predictions every 5 days or less). Provide an
update of the next possible CLOUDSAT/CALIPSO flight 2-3 days in advance
Forecast if conditions will be conducive for a mission:
CLOUDSAT: Clouds along the orbit track: They can be precipitating or non-precipitating, but
not deep convection
CALIPSO: Stable Conditions and very little to no existing clouds (especially cirrus) along the
orbit track
Provide forecast 1 day in advance with an update on the day of the mission (2-3 hours before
overpass time)
Provide pilots/flight scientists latitude/longitude coordinates of orbit track to setup flight leg
1.4.8 Flight plan 6 - Satellite overpass with CP2 polarimetric particle ID
(Cloudsat)
For each flight, it is important to be in-cloud at the time of CloudSat orbit overpass.
Flight Plan 6.1: Sampling of liquid phase of precipitating and non-precipitating cloud. Fly in
cloud, but at altitudes below 0° C along orbit track.
Goal: To better understand the partitioning of liquid water between rain and non-precipitating
cloud.
Flight Plan 6.2: Sampling of the ice phase of cloud. Fly in cloud, at a variety of altitudes (e.g. -5,
-10°, -15° C, etc) along the orbit track.
Goal: To better understand of the ice water path (IWP), crystal shape, and particle size
distributions (PSD) in the precipitating ice above the melting layer.

17. Flight Plan 6.3: Sampling of the melting layer: Fly a spiral pattern ascending through the melting
layer at the time of the overpass.
Goal: To better understand the microphysics through the melting layer.
Flight Plan 6.4: Similar to Flight Plan 6.1 except transitioning between precipitating and non-
precipitating cloud at the time of overpass.
Goal: To better understand the microphysics in the rain/no-rain boundary to improve on
evaluation on the rain/no-rain discrimination algorithms.
CCN table 1: 0.2 (4min), 0.5 (3min), 0.8 (3min)
Climb at 500ft/min immediately after takeoff. Maintain 80 to 100 m/s (155kts to 195kts).
Intercept the satellite track. Continue the climb at 1000 ft/min to the satellite overpass point. Plan
to be in cloud top at the satellite overpass point at the satellite overpass heading and at the
satellite overpass time (layered cloud). If the cloud is convective, penetrate the tops of feeder
towers that are not shielded by any other higher level cloud. Continue cloud penetrations up to
the cloud top as close to the overpass time as possible (convective time scales are much shorter).
Resume navigation and RTB while maintaining a descent rate <1000ft/min.
If a dusty layer is located en-route, the aircraft should fly for 15 minutes at constant altitude
flight while orbiting in a standard rate turn and maintaining 80m/s (filters).
1.4.9 Flight plan 7 - Satellite overpass (CALIPSO, no cloud present or forecast)
CCN table 1: 0.2 (4min), 0.5 (3min), 0.8 (3min)
Climb at 500ft/min immediately after takeoff and throughout the aerosol profile. Maintain 80m/s
(155kts).
Intercept the satellite track. Continue the climb to the middle of the aerosol boundary layer. Fly
for 10 minutes at this altitude.
Resume aircraft climb at 500ft/min and plan to be at the satellite overpass point 2000ft above the
aerosol boundary layer. Fly for 10 minutes at this altitude in standard rate turns around the
satellite overpass point. Aerosol PI should check CCN supersaturation (SS) cycle to make sure
that a full SS cycle is flown at a constant altitude.
Descend at 500 ft/min maintaining a standard rate turn around the satellite overpass point down
to the lowest possible altitude. Plan to be at an altitude in the middle of the aerosol layer at the
satellite overpass time.
Once the profile is complete, RTB at the lowest possible altitude.
If a dusty layer is located en-route, the aircraft should fly for 15 minutes at constant altitude
flight while orbiting in a standard rate turn and maintaining 80m/s (filters).
1.4.10 Flight plan 8 - Sounding comparison flight
Climb at 500ft/min immediately after takeoff and throughout the profile. Maintain 80m/s
(155kts).
Once reaching the point of ascent, climb at 500ft/min up to 20000ft in standard rate turns.
Resume navigation and RTB while maintaining a descent rate <1000ft/min.

18. If a dusty layer is located, the aircraft should fly for 15 minutes at constant altitude flight while
orbiting in a standard rate turn and maintaining 80m/s (filters).
1.4.11 Flight Plan 9 – Hygroscopic Flare Characterization Flight
Requirements: Flight requires clear skies and stable atmosphere. Profile requires a seeding
aircraft in addition to the research aircraft.
Objective: The flight objective is to obtain aerosol distribution measurements of the plume
produced by burning the hygroscopic flares.
CCN table 1: 0.2 (4min), 0.5 (3min), 0.8 (3min)
Task A (Research Aircraft): Characterize the aerosol layer.
Climb at 500 ft/min as soon as possible after takeoff and maintain 500 ft/min up to 16000 ft.
Maintain around 150 kts. Flight direction should be into the 12000 ft wind direction.
Decide on altitude to use to conduct flare sampling. The altitude should be at least 2000 ft above
the top of the aerosol layer. Altitude needs to be 14000 ft or below for good air chemistry
measurements. Altitude should have low turbulence.
Decide on direction to fly for flare sampling. The direction should be with the wind at the flare
sampling altitude.
Relay the altitude and flight direction for flare sampling to the Seeding Aircraft and request that
the seeding aircraft establish a stable flight pattern.
Task B (Research Aircraft): Join up with Seeding Aircraft.
Descent to flare sampling altitude.
Intercept behind the flight tract of the Seeding Aircraft.
When necessary, accelerate to catch up with the Seeding Aircraft.
Match speed and direction.
Task C (Research Aircraft): Engine Exhaust Sampling
Fly behind seeding aircraft for a minimum of 11 minutes.
Task D (Research Aircraft): Flare sampling
Request that the seeding aircraft start to light flares.
Fly behind the seeding aircraft while flares are lit.
Task E (Research Aircraft): Break formation.
Maintain very constant speed (150 knots), altitude (flare sampling altitude) and direction (flare
sampling direction, approximately with the wind).
Task F (Research Aircraft): Clear Air Sampling
Maintain speed, altitude and direction for a minimum of 11 minutes.
Return to base with a 500 ft/min descent.
Task A (Seeding Aircraft): Takeoff and climb
Take off shortly after the Research Aircraft.

19. Follow a similar flight path as the Research Aircraft. Ascent to 12,000 ft (default flare sampling
altitude).
Task B (Seeding Aircraft): Join up with Research Aircraft.
Change to flare sampling altitude if necessary.
Establish aircraft heading to match flare sampling direction.
Slow to 150 knots.
Relay flight position and track to Research King Air.
Maintain very constant speed (150 knots), altitude (flare sampling altitude) and direction (flare
sampling direction, approximately with the wind).
Task C (Seeding Aircraft): Engine Exhaust Sampling
Maintain very constant speed (150 knots), altitude (flare sampling altitude) and direction (flare
sampling direction, approximately with the wind).
Task D (Seeding Aircraft): Flare sampling
Upon request from Research Aircraft, start to light flares. Lit flares 1 on each side (2 at a time)
until all flares have been used.
Task E (Seeding Aircraft): Break formation.
Accelerate until a safe distance ahead of the Research Aircraft and then return to base.
Flight plan 1 – Hygroscopic seeding process study