Cloud, Aerosol, and Complex Terrain Interactions (CACTI)

1 October 2018 - 30 April 2019

Lead Scientist: Adam Varble

Observatory: AMF, COR

General circulation models and downscaled regional models exhibit persistent biases in deep convective initiation location and timing, cloud top height, stratiform area and precipitation fraction, and anvil coverage. Despite important impacts on the distribution of atmospheric heating, moistening, and momentum, nearly all climate models fail to represent convective organization, while system evolution is not represented at all. Improving representation of convective systems in models requires characterization of their predictability as a function of environmental conditions, and this characterization depends on observing many cases of convective initiation, non-initiation, organization, and non-organization.

The Cloud, Aerosol, and Complex Terrain Interactions (CACTI) field campaign in the Sierras de Córdoba mountain range of north-central Argentina is designed to improve understanding of cloud life cycle and organization in relation to environmental conditions so that cumulus, microphysics, and aerosol parameterizations in multiscale models can be improved. The Sierras de Córdoba has a high frequency of orographic boundary layer clouds, many reaching congestus depths, many initiating into deep convection, and some organizing into mesoscale systems uniquely observable from a single fixed site. Some systems even grow upscale to become among the deepest, largest, and longest-lived in the world. These systems likely contribute to an observed regional trend of increasing extreme rainfall, and poor prediction of them likely contributes to a warm, dry bias in climate models downstream of the Sierras de Córdoba in a key agricultural region.

Many environmental factors influence the convective life cycle in this region, including orographic, low-level jet, and frontal circulations, surface fluxes, synoptic vertical motions influenced by the Andes, cloud detrainment, and aerosol properties. Local and long-range transport of smoke resulting from biomass burning, as well as blowing dust, is common in the austral spring. Changes in land surface properties as the wet season progresses impact surface fluxes and boundary layer evolution on daily and seasonal time scales that feed back to cloud and rainfall generation. This range of environmental conditions and cloud properties coupled with a high frequency of events makes the Sierras de Córdoba an ideal location to improve understanding of cloud-environment interactions.

The following primary science questions will be addressed through coordinated ARM Climate Research Facility and guest instrumentation observations:

  • How are the properties and life cycles of orographically generated cumulus humilis, mediocris, and congestus clouds affected by environmental kinematics, thermodynamics, aerosols, and surface properties? How do these cloud types alter these environmental conditions?
  • How do environmental kinematics, thermodynamics, and aerosols impact deep convective initiation, upscale growth, and mesoscale organization?
  • How are soil moisture, surface fluxes, and aerosol properties altered by deep convective precipitation events and seasonal accumulation of precipitation?

The ARM Aerial Facility Gulfstream-159 (G-1) aircraft will be deployed near the first ARM Mobile Facility (AMF1) location for approximately six weeks—November 1 to December 15, 2018—to support the CACTI science goals. The G-1 flight measurements will provide information on orographic cumulus clouds and deep convective systems.

For orographic cumulus clouds, the G-1 measurements will characterize in-cloud dynamics, microphysics, and aerosols, as well as the environmental variability around the clouds focusing on conditions upstream and downstream of clouds at multiple altitudes in the vicinity of the AMF1 site. In situations of significant aerosol heterogeneity, emphasis will be placed on observations in and out of aerosol plumes in the vicinity of the clouds.

For deep convective systems, the G-1 measurements will focus on characterizing the environmental conditions that lead to convective initiation and the vertical profiles of environmental properties around the growing deep convection and in adjacent regions that are not initiating deep convection so that the differences in environment can be compared. Convective inflow and free tropospheric properties from the G-1 aircraft will be important for putting AMF1 observations into context and for providing input to numerical simulations.

Co-Investigators

Eldo Avila Sonia Kreidenweis Paola Salio
Paul DeMott L. Ruby Leung Sue van den Heever
David Gochis Greg McFarquhar Christopher Williams
Robert Houze Steve Nesbitt Edward Zipser
Michael Jensen Kristen Rasmussen
Pavlos Kollias David Romps

COR Data Sources

Name Full Name Browse Data
ACSM Aerosol Chemical Speciation Monitor Browse Data
AERI Atmospheric Emitted Radiance Interferometer Browse Data
AOS Aerosol Observing System Browse Data
AOSMET Meteorological Measurements associated with the Aerosol Observing System Browse Data
APS Aerodynamic Particle Sizer Browse Data
CCN Cloud Condensation Nuclei Particle Counter Browse Data
CEIL Ceilometer Browse Data
CO-ANALYZER Carbon Monoxide Analyzer Browse Data
CPC Condensation Particle Counter Browse Data
DL Doppler Lidar Browse Data
ECOR Eddy Correlation Flux Measurement System Browse Data
GNDRAD Ground Radiometers on Stand for Upwelling Radiation Browse Data
IRT Infrared Thermometer Browse Data
LDIS Laser Disdrometer Browse Data
MAWS Automatic Weather Station Browse Data
MET Surface Meteorological Instrumentation Browse Data
MPL Micropulse Lidar Browse Data
MWR Microwave Radiometer Browse Data
MWRHF Microwave Radiometer - High Frequency Browse Data
MWRP Microwave Radiometer Profiler Browse Data
NEPHELOMETER Nephelometer Browse Data
OZONE Ozone Monitor Browse Data
PSAP Particle Soot Absorption Photometer Browse Data
RAIN Rain Gauge Browse Data
RWP Radar Wind Profiler Browse Data
SASHE Shortwave Array Spectroradiometer-Hemispheric Browse Data
SASZE Shortwave Array Spectroradiometer-Zenith Browse Data
SEBS Surface Energy Balance System Browse Data
SKYRAD Sky Radiometers on Stand for Downwelling Radiation Browse Data
SMPS Scanning mobility particle sizer Browse Data
SODAR Mini Sound Detection and Ranging Browse Data
SONDE Balloon-Borne Sounding System Browse Data
SP2RBC Single Particle Soot Photometer Refractory Black Carbon Browse Data
TSI Total Sky Imager Browse Data
UHSAS Ultra-High Sensitivity Aerosol Spectrometer Browse Data
WB Weighing Bucket Precipitation Gauge Browse Data