THE ARM UAV Program: Past, Present and Future Greg M. McFarquhar 1 and Will Bolton 2 1 University of Illinois, Urbana, IL 2 Sandia National Laboratories, Livermore, CA Funded by ARM UAV Program

Outline Overview of ARM UAV Program Instruments for Cloud Research New Science Issues UAVs can address

ARM UAV Program Objectives The ARM-UAV Program was established by DOE to address the largest source of uncertainty in global warming: the interaction of clouds and solar/thermal energy support the climate change community with valuable data sets develop measurement techniques and instruments suitable for use with the new class of high altitude, long endurance UAVs demonstrate these instruments and measurement techniques in field measurement campaigns

ARM-UAV has conducted ten major field campaigns Field Campaigns to date: Fall 1993, Edwards AFB, CA Spring 1994, Northern OK Fall 1995, Northern OK Spring 1996, Northern OK Fall 1996, Northern OK Fall 1997, Northern OK Spring 1999, PMRF Kauai, HI Summer 1999, Monterey, CA Winter 2000, Northern OK Fall 2002, Northern OK GA-ASI “GNAT 750” (F93, S94) Grob “Egrett” (F95, S96) GA-ASI “Altus I” (F96, F97) GA-ASI “Altus II” (Su99) Twin Otter (F93, S94, F95, S96, F96, F97, Sp99, Su99, W00)

Currently using Proteus, available from Scaled Composites, in piloted mode; flies to over 50 kft; 6900 kg payload; ~20 h duration

Current Suite of Instruments Passive remote sensing (14 instruments) Active remote sensing (2 instruments) In-situ Microphysics (4 instruments) Atmospheric State (5 instruments)

Broadband Radiometers Package (BRP) CM-22 pyranometers, 0.3 – 4um (zenith level, zenith fixed, nadir, nadir covered) CG-4 pyrgeometers, 4 – 40 um (zenith level, nadir, nadir covered) Spectral Radiance Package (SRP) nadir mounted, NFOV VIS um, 2nm res, A-Band um, 0.07nm res NIR um, 2nm res Solar Spectral Flux Radiometer (SSFR) nadir & zenith, hemispheric FOV 300–1700 nm The Diffuse Field Camera (DFC) VIS: 1300 x 1030 pixels x 12 bit, 645 nm center with 50 nm total bandpass NIR: 320 X 256 pixels x 12 bit, 1610 nm center with 60 nm total bandpass Scanning High-Resolution Interferometer Sounder (S-HIS) scanning interferometer, high spectral resolution (0.5 cm -1 ) Spectral Coverage between 3.3 and 18.0 µm Proteus Payload - Passive Remote Sensing

Stabilized Platform for High Altitude Remote Sensing Location of Stabilized platform First flown in 2002 Level to ±.02 o Improved data quality and data range (±2 to ±5 o ) Significantly reduces post processing time

Stabilized platform roll less than ±0.02 o Aircraft roll ±3 o

Platform was stabilized until 18 hours

Proteus Payload - Active Remote Sensing 95 GHz Compact Millimeter Wave Radar (CMR) sensitivity of –42 dBZ at 1 km Cloud Detection Lidar (CDL) µm at 5 kHz, 48 µJ/pulse CMR CDL

Example of Lidar Data

Proteus Payload - In-situ Instrumentation MET Package Buck Research CR-2 Cryogenic Hygrometer, -100 o C, 20 s response Near-ir laser absorption spectrometery, 1 ppmv, 50 Hz response Micro Air Data Transducer (MADT) static pressure, differential pressure, total air temp, static air Temp, dh/dt, height, true air speed, indicated air speed Best Aircraft Turbulence Probe measured wind speed and direction at 50 Hz Cloud, Aerosol, and Precipitation Spectrometer cloud and aerosol spectrometer (CAS: 0.35 – 50 µm) cloud imaging probe (CIP: 25 – 1550 µm) liquid water content detector (LWC: 0.01 – 3 gm-3) Cloud Integrating Nephelometer (CIN) measures asymmetry parameter and extinction coefficient Video Ice Particle Sampler (VIPS) sizes between μm Nevzorov Probe (NEV), LWC, TWC – 3 gm -3, sensitivity: gm -3 NEV pitot VIPS CR-2 TAT CIN CAPS

VIPS: Measuring Crystal Shape & Size Distributions Size distribution generated through automatic particle recognition from NIH software

Future Missions Fall 04, North Slope Alaska (NSA) vertical structure of mixed-phase clouds Winter 06, Tropical western Pacific (TWP) cirrus/radiative interactions associated with monsoon convection

Have UAVs reached full potential? No: UAV cost, reliability/maintenance, availability, and airspace access need to improve BUT: UAVs offer unique capabilities for important science applications Equipment and operational capabilities have been developed

Science Issues for UAVs What can be done if we had routine long duration UAV flights that we cannot do now?

Aerosol/Cloud Vertical Profiles Representing vertical distributions of aerosols, their mixing scenarios, size distributions & single- scattering properties crucial for different regions –Includes measurements in cloud layers! Observations needed in many different regions –Different vertical profiles & meteorological forcing Critical for radiative and thermodynamic forcing of aerosols How representative are surface aerosol measurements of aerosol properties in cloud layers?

Complete Life Cycles/Parcel Studies Satellites have at best hourly resolution and can’t resolve fine-scale phenomena –Trade wind cumuli have pretty short life cycles Field observations don’t allow us to track complete life cycle (e.g., evolution of anvil associated with deep convection in Tropics) Long duration platform might allow to track Saharan dust event, or brown cloud from Asia as it transits Pacific

Scaling Issues Need to go from ground-based measurements to long space/time scales of satellites Field experiments last only hours; satellites years long More routine observations in several locations would be helpful E.g., UAV spectral radiance measurements above ground-station would help scale between MODIS type retrievals and ground-based cloud retrievals

Summary 1.Unique set of instruments for airborne in-situ and remote sensing capabilities 2.Upcoming experiments offer unique opportunity for acquiring data on cloud-radiation interactions 3.Ongoing activities will attempt to further take advantage of UAV technology Long duration platform for tracking whole life cycle More routine climate tropospheric interactions not currently available

UW Scanning HIS: 1998-Present (HIS: High-resolution Interferometer Sounder, ) Longwave Midwave Shortwave CO 2 CO N2ON2O H2OH2O H2OH2O CH 4 /N 2 O CO 2 O3O3 Characteristics Spectral Coverage: 3-17 microns Spectral Resolution: 0.5 cm -1 Resolving power: Footprint Diam: km Cross-Track Scan: Programmable including uplooking zenith view u Radiances for Radiative Transfer u Temp & Water Vapor Retrievals u Cloud Radiative Prop. u Surface Emissivity & T u Trace Gas Retrievals Applications:

Proteus performance characteristics Altitude record (10/25/00): 62,786 feet (peak) 61,919 feet (sustained) 55,786 feet (w/1000 kg payload) Stall speed: 65 knots Top speed: 250 knots/M=0.6 Loiter (14,000 lb takeoff wt): nmi radius nmi

Canard station, CIN Canard station, CAPS Iridium satellite phone Payload pod Iridium satellite data link Boom extension, S-HIS Stable radiometer platform ARM-UAV/Proteus payload arrangement