1. OPERATIONAL PROCEDURES FOR BRRAA KING AIR RESEARCH1.1 Objectives SummaryIn summary, any field program provides a unique opportunity to validate physical chain ofevents of the hygroscopic and glaciogenic seeding conceptual models through the ability to seedand measure storms at the same time (using one or more aircraft), to document microphysicalcharacteristics and development remotely (using polarimetric radar). Concurrent physicalmeasurements with a cloud seeding experiment could help scientists to either confirm or discardaspects of the seeding conceptual model and strengthen any statistical results from a randomizedcloud seeding experiment.Aircraft operations are emphasized here. Radar operations in general will focus on documentingthe variability and range of radar responses to natural precipitation development, the area ofwhich is unconstrained outside of aircraft operations. During aircraft operations, the radar willbe operated similarly but concentrated on clouds and storms being studied or seeded by theaircraft.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.
(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 overviewFlight 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 seedingCoordination of profiling and seeding objectivesThe research aircraft cloud and aerosol profiling objectives are critical to the diagnosis ofseeding potential in the cloud systems discussed below. Profiling objectives are also critical tosubsequent refinement of appropriate seeding strategies for these systems. Consequently, trialseeding early in the project will proceed in parallel with profiling flights, but will be conductedso as not to influence clouds to be profiled in their natural state.Potential seeding strategiesA seeding operation is initiated when the forecast calls for clouds containing supercooled liquidwater to be passing just upwind or over the target area. Under these conditions aircraft arelaunched. The objective is to intercept the desirable cloud liquid water regions in clouds withconcentrated plumes of silver iodide. It is critical to properly time the releases and correctly
select and design flight patterns in order for the plume-cloud intercept to occur. Although theOperations Director will generally vector the pilot to the most promising area, it will be theresponsibility of the pilot and/or flight scientist to select the individual cloud features to beseeded.For reference, generalized seeding hypotheses are briefly summarized below. More specifichypotheses and methods will be developed as field research proceeds, as will a more definitiveunderstanding 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.
The characteristics of flares used for seeding and a reference guide for planned seeding actions ina variety of meteorological situations are summarized in Tables 8.1 and 8.2 below. Table 8.1: Characteristics of Flares Used in SeedingAgI 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.
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 20Generally 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 AircraftMay 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.
1.3 Flight missions 1.3.1 Regional aerosol survey missionsResearch questions regarding aerosol structureWhat is the range of background aerosol conditions under different meteorological regimes andcorresponding wind field structures? What is the contribution from biomass burning, dust, localpollution, or sea-salt? What is the corresponding vertical profile of aerosol structure from nearthe surface through the top of the mixed (boundary) layer? What are typical sub-cloud spatialvariations in aerosol characteristics? Do seasonal differences exist?Flight plans – King AirObjective: Obtain the horizontal transects and vertical profile of aerosol content from minimumallowable altitude through the top of the mixed (boundary) layer. Document any horizontalgradients or inhomogeneities in aerosol content through multiple profiles spaced (perhaps 10 to50 NM, as appropriate) and through just below cloud base horizontal transects across a samplingregion. 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 varietyAscent rate 300-400 ft/min. of regimes include clear day, fair- weather Cu day, stratiform, others.Begin missedapproach Flight plan details: See section 8.4.5. Surface 1.3.2 Small to moderate non-precipitating cumulus missionsThe structure and processes of non-precipitating cumulus in a region must be well understood inorder to effectively diagnose the seeding opportunity of convective clouds.Research questions affecting non-precipitating Cu seeding strategiesWhat are the key Cumulus characteristics, typical cloud base heights and temperatures of theclouds, their droplet concentrations, and the growth of the droplet spectrum with height abovecloud base. Do drizzle or rain drops form in them via collision and coalescence? What are thedeepest non-precipitating clouds in a region as a function of season and space? Are they deepenough, and their bases close enough to the ground, to form seeding targets? Does pollution,
sea-salt alter their microstructure? What are the CCN and IN concentrations in the inflow air atcloud base?Flight plansObjective: Survey the sub-cloud aerosol and cloud structure of small to moderate Cumulus asneeded to address the research questions outlined above. The needed surveys are bestaccomplished through horizontal transects consisting of 10 km legs over areas where the air isfairly 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.
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 missionsCumulonimbus clouds are particularly important to this study because their natural processes aresuccessful in producing precipitation that reaches the ground.Research questions affecting isolated Cumulonimbus seeding strategiesWhat are the natural precipitation processes in Cb clouds and how do they relate to seedinghypotheses? What is the source of those rainshafts that reach the ground? Are they comprisedmainly of graupel or can they also arise from the aggregation of snow crystals? What are theconcentrations of natural ice particles in these clouds? How rapidly do ice crystals form inthem? How much supercooled liquid water is in them, and how long does it last? Do drizzle andraindrops form in them? Can the precipitation from these clouds be augmented by seeding witheither silver iodide or hygroscopic agents? How does seeding alter the natural formation of iceand precipitation? How are they affected by aerosols?Flight plansObjectives: Document the sub-cloud aerosol and in-cloud microstructure of cumulonimbusacross the full range of lifecycle stages (e.g., developing, mature, dissipating) as needed todocument the natural precipitation processes at work. Special attention should be paid to the sizedistributions of liquid and solid cloud particles, locations and amounts of liquid water, andevidence for details of riming growth.King Air Profiling: Survey aerosol and cloud structure of Cb. Define evolution of ice and waterfrom precipitation below cloud base upward through cloud top. Characterize differences incloud structure and apparent ice/water processes as clouds age from early precipitation stagethrough dissipation. Survey aerosol structure in the sub-cloud inflow zone including CCN andIN measurements. Obtain cloud droplet spectra above cloud base.AgI Seeding (any aircraft): Determine potential for invigorating cloud dynamics through AgIejectable seeding of maximum liquid water zones expected within the -5 to -10 C region. AgI
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 asshown. 1.3.4 Shallow and Deep Tropical Stratiform Rain SystemsShallow and deep tropical rain systems produce the largest overall amounts of rain in Thailandand surrounding regions and they come in several forms especially during the rainy season. Thissection deals with the study and seeding of these rain systems that typically show a very moistlow and/or deep atmosphere (wet adiabatic) with slowly rising air.Research questions affecting shallow and deep tropical rain seeding strategiesWhat is the natural process of precipitation formation? How much of the rain at the ground isdue solely to the convection and how much is due to the stratiform regions in these clouds? Isthe rain that reaches the ground solely due to warm rain, graupel, or do aggregates of snowcrystals also play a role and how effective are the warm rain and ice processes? How widespreadis supercooled water in these clouds? Can seeding augment the rain from these bands? Do theyoriginate in the boundary layer or are they the result of conveyor-belt type lifting?Flight plansObjectives:King Air Profiling: Survey aerosol and cloud structure of tropical rain systems. Defineevolution 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 asclose 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 throughburn-in-place AgI seeding in Supercooled liquid water regions and/or hygroscopic seeding in airinflow regions in warmer parts of the cloud.Aerosol CharacterizationMap advection and diffusion from known source regions. Aerosol characterization below cloudbase (or near the top of the boundary layer on clear days). Repeated legs or circling for adequatesampling with slow responding instrumentation. Make slow ascent soundings in specific areas –upwind and downwind of sources, over areas of interest.Cloud Droplet MeasurementsObjective: Document the cloud droplet size distribution near cloud base before, during, andimmediately after seeding. The impact of seeding on the cloud base droplet distribution shouldbe evident within seconds of the onset of seeding.
Primary Cloud Physics Instrumentation: SPEC 2D-Stereo, SPEC CPI, SPEC HVPS and SPECFFSSP, Total Liquid Water Content sensor, PCASP, DMA counter, CCN counter, stateparametersProcedure:During times when there are no suitable clouds available for the randomized experiment butconvective clouds with bases lower than 5,000 ft (1500 m) and a vertical depth of at least 1-2 kmexist or when storms exist outside the radar coverage area, airborne observations to measure theeffects of seeding on droplet broadening and drizzle formation would be desirable. In thesesituations it is suggested that both the research aircraft and a seeding aircraft take off to conductthese experiments.Prior to starting the seeding, the research aircraft should measure the natural aerosol sizedistribution and CCN entering cloud base by performing an elongated racetrack patternapproximately 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 suitableupdrafts. Once the below cloud aerosol measurements are completed, the cloud basemeasurement phase can begin.A measurement of cloud base (height, pressure, and temperature) is obtained with the seederaircraft flying straight and level at cloud base without penetrating any cloud. After the cloud basemeasurements the research aircraft will ascend to 1000 ft above cloud base and conduct apenetration in an actively growing convective cloud. It is important to note that the cloud basemeasurements should be taken just below cloud base without penetrating cloudy regions.Drizzle StudiesThe research aircraft will subsequently conduct three to four penetrations through the updraftcore at 500-1000 ft above cloud base to document the droplet size distributions and in seedingcases to detect the initial effects on the droplet size distribution. Following the cloud basepasses, it will conduct repeated penetrations to higher altitudes (at about 2000-3000’ verticalintervals but not higher than the 0°C level) to detect the onset of coalescence and drizzleformation in the cloud. Make repeated passes at the 0°C level.Ice-phase Microphysical MeasurementsObjective: Measurement of drop freezing, graupel growth, and possible secondary ice generationby conducting repeated penetrations at the –5°C level with Research Aircraft.Primary Cloud Physics Instrumentation: SPEC 2D-Stereo, SPEC CPI and SPEC HVPS, SPECFFSSP, Total Liquid Water Content sensor, state parametersProcedure: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 researchaircraft informed of its general location.
The location of the seeding aircraft should be communicated to the research aircraft at thedecision time. Penetrations at the –5° C level of the seeded cloud should be performedcontinuously 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 ceasepenetrations if the cloud dissipates or penetrations become unsafe prior to the completion of the30 minutes.The recommended flight pattern for a single turret is a ‘figure 8’ pattern. If the selected cloud isembedded in more organized convection, this pattern may be modified to allow the aircraft topenetrate as far into the core of the cloud (where high liquid water exists) as safety will allowand then exit before penetrating the next cell. Measurements in the core of the cloud will allowfor study of ice and mixed phase formation and growth processes while the data from the sideregions should help explain recirculation patterns. The combination of the two will provide amore complete picture of the cloud microphysics at this level.1.4 Sampling Strategies for the Research AircraftThe following paragraphs details flight profiles that are recommended to be flown in a regionbased on previous scientific campaigns. These profiles are guidelines for the pilots andinstrumentation 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 CaseThe main scientific objective of cloud seeding experiments is to assess the potential for seedingto enhance rainfall and to quantify these results. To support this objective, the research aircraftwill conduct seeding for high priority targets. The research aircraft should be launched earlywhen conditions are forecast to be favorable for such high priority targets. Once the researchaircraft is launched on an Experimental Seeding Case flight plan, the second seeding aircraftshould 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 forthese 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. Observethe cloud layer structure. Decide if it is a hygroscopic seeding or glaciogenic seeding case.Hygroscopic Seeding Case:
Descend to cloud base at 500 ft/min. Descend at 1000 ft/min if Operations Director hasindications of a good possible target. Fly below cloud base and search for updraft/inflow. Searchfor updrafts for at least 10 minutes. Determine if it is a seeding conditions case, if there areother possible targets, or proceed to a different research flight plan. The Flight Scientist’sdecision 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 flightplan, 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 seedingexperiment case concludes, decide if it is necessary to proceed to new possible target or tocharacterize 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 thecloud formation level and circle in the updraft drifting downshear but staying away fromprecipitating cloud. Continue to characterize the cloud as described in flight plan Flight Plan BTask 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 starta 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 supercooled liquid water areas that contain updraft. Determine if it is a seeding condition case, ifthere 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 seedingexperiment case concludes, decide if it is necessary to proceed to new possible target or tocharacterize 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 least10 minutes.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 starta different research plan in the middle. For example, the “Glaciogenic Seeding Process Study”flight plan. 1.4.2 Flight plan 1 – Hygroscopic seeding process studyThe objective is to characterize the microphysical changes that occur following hygroscopicseeding at cloud base.CCN table 1: 0.2 (4min), 0.5 (3min), 0.8 (3min)Task A: Seeding process study with the research aircraftPenetrate the cloud base at 1000ft above the cloud formation level starting in the updraft area andcontinuing 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 thecloud formation level and circle in the updraft drifting downshear but staying away fromprecipitating cloudTask B: Simultaneous aircraft measurementsCoordinate 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 upshearvector (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 studyThe objective is to characterize the microphysical changes that occur following glaciogenicseeding 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 areasthat contain updraft. Pick young visibly growing towers.Continue cloud top penetrations at -5ºC to -10ºC 500 to 1000ft below the tops following seedingwith ejectable flares. Continue for 10 minutes after the last seeding event. Repeat thepenetrations as quickly as possible. 1.4.4 Flight plan 3 – Aerosol/cloud interactions and cloud microphysical propertiesThe 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 bepresent below the precipitating cloud base).
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. Maintainaround 80m/s (~155kts).Observe any aerosol layering or stratification. Pick 2 intermediate altitudes from the surface tothe cloud base.Fly for at least 10 minutes in straight and level flight (or standard rate turns) at each of theintermediate altitudes (one CCN SS cycle).If a dusty layer is located below cloud base, the aircraft should fly for 15 minutes at constantaltitude 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 avery shallow layer (100 to 200ft thick). If possible to sample this shallow layer while staying outof 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 possibleTask B: Characterize the cloud droplet spectra at about 1000ft above the baseNote the cloud base altitudePick an altitude (1000ft above the cloud formation level) where the ground is not visible in thecloud throughout the cloud base penetrationPenetrate the cloud perpendicular to the upshear vector to avoid any cloudy areas whereprecipitation may be falling from above (often clouds are moving from west to east, so thepenetrations should be oriented north to south or south to north)Task C: Characterize cloud droplet growth and the evolution of cloud hydrometeorsPenetrate the cloud perpendicular to the upshear vector at 2000ft intervals (depending on clouddepth) from cloud base to cloud top. Avoid cloudy regions where precipitation may fall fromabove. If precipitation falling from above is observed during the penetration, repeat thepenetration.Note the cloud top altitudeIn addition, flight scientists may focus on the following specific objectives:Objective: Characterize the vertical structure of the different cloud layersClimb through the layered cloud at 500 ft/minObjective: Characterize the cloud microphysics with radar first echoFind altitude of cloud with radar echo from ground radarPenetrate the cloud at 500-1000ft intervals (depending on cloud depth) starting from the altitudeof the first radar echoObjective: Characterize cloud turrets that pushes into dry air (bubble pushing above the layeredcloud deck)Penetrate the cloud top at 500 to 1000ft below the top
Repeat several times until cloud top collapses (Updraft velocity, typical lifetime, evolution ofcloud 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 theaerosol boundary layer. The descending profile should be in a different region to characterizespatial 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 theaerosol profile. Maintain around 80m/s (~155kts). Continue the climb to 2000ft above the top ofthe aerosol boundary layer. Fly for 10 minutes above the aerosol boundary layer whilemaintaining standard rate turns. Aerosol scientist should check CCN supersaturation (SS) cycleto 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 tothe 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 theintermediate altitudes (one CCN SS cycle)If a polluted layer is located, the aircraft should fly for 15 minutes at constant altitude flightwhile 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 thecity 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. Ifpossible 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 flightwhile 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 PlansObjectives:Extend airborne observations to satellite measurements over the region to better explain regionalvariations of cloud, aerosol, and precipitation characteristics.
Compare in situ airborne measurements of clouds, aerosol, and precipitation with satelliteobservations.Validation of conceptual model of precipitation formation.Background Information:CLOUDSAThttp://www.nasa.gov/mission_pages/cloudsat/main/index.htmlhttp://cloudsat.atmos.colostate.edu/homeCALIPSOhttp://www.nasa.gov/mission_pages/calipso/main/index.htmlBased on the orbit predictor, a possible mission could exist every 4-5 days. Flights will be duringoverpassesCLOUDSAT/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 theorbit predictor:http://www-angler.larc.nasa.gov/cgi-bin/predict/predict.cgiNote: The orbit of the satellites will change frequently. It is recommended to only use orbitpredictions < 5 days in advance (e.g. update orbit predictions every 5 days or less). Provide anupdate of the next possible CLOUDSAT/CALIPSO flight 2-3 days in advanceForecast if conditions will be conducive for a mission:CLOUDSAT: Clouds along the orbit track: They can be precipitating or non-precipitating, butnot deep convectionCALIPSO: Stable Conditions and very little to no existing clouds (especially cirrus) along theorbit trackProvide forecast 1 day in advance with an update on the day of the mission (2-3 hours beforeoverpass 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 incloud, but at altitudes below 0° C along orbit track.Goal: To better understand the partitioning of liquid water between rain and non-precipitatingcloud.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 sizedistributions (PSD) in the precipitating ice above the melting layer.
Flight Plan 6.3: Sampling of the melting layer: Fly a spiral pattern ascending through the meltinglayer 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 onevaluation 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. Planto be in cloud top at the satellite overpass point at the satellite overpass heading and at thesatellite overpass time (layered cloud). If the cloud is convective, penetrate the tops of feedertowers that are not shielded by any other higher level cloud. Continue cloud penetrations up tothe 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 altitudeflight 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. Flyfor 10 minutes at this altitude.Resume aircraft climb at 500ft/min and plan to be at the satellite overpass point 2000ft above theaerosol boundary layer. Fly for 10 minutes at this altitude in standard rate turns around thesatellite overpass point. Aerosol PI should check CCN supersaturation (SS) cycle to make surethat 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 downto the lowest possible altitude. Plan to be at an altitude in the middle of the aerosol layer at thesatellite 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 altitudeflight while orbiting in a standard rate turn and maintaining 80m/s (filters). 1.4.10 Flight plan 8 - Sounding comparison flightClimb 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.
If a dusty layer is located, the aircraft should fly for 15 minutes at constant altitude flight whileorbiting in a standard rate turn and maintaining 80m/s (filters). 1.4.11 Flight Plan 9 – Hygroscopic Flare Characterization FlightRequirements: Flight requires clear skies and stable atmosphere. Profile requires a seedingaircraft in addition to the research aircraft.Objective: The flight objective is to obtain aerosol distribution measurements of the plumeproduced 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 abovethe top of the aerosol layer. Altitude needs to be 14000 ft or below for good air chemistrymeasurements. Altitude should have low turbulence.Decide on direction to fly for flare sampling. The direction should be with the wind at the flaresampling altitude.Relay the altitude and flight direction for flare sampling to the Seeding Aircraft and request thatthe 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 SamplingFly behind seeding aircraft for a minimum of 11 minutes.Task D (Research Aircraft): Flare samplingRequest 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 (flaresampling direction, approximately with the wind).Task F (Research Aircraft): Clear Air SamplingMaintain 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 climbTake off shortly after the Research Aircraft.
Follow a similar flight path as the Research Aircraft. Ascent to 12,000 ft (default flare samplingaltitude).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 (flaresampling direction, approximately with the wind).Task C (Seeding Aircraft): Engine Exhaust SamplingMaintain very constant speed (150 knots), altitude (flare sampling altitude) and direction (flaresampling direction, approximately with the wind).Task D (Seeding Aircraft): Flare samplingUpon 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