AGES+ Coordinating Activities

Ground Sites: La Jolla

Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE)

Science Objectives

The focus of the EPCAPE is to characterize the extent, radiative properties, aerosol interactions, and precipitation characteristics of stratocumulus clouds in the Eastern Pacific across all four seasons at a coastal location, the Scripps Pier and the Scripps Mt. Soledad sites in La Jolla, California. The planned data record will start 15 February 2023 and continue until 14 February 2024, with two intensive operation periods (April-June; July-September). Coastal cities provide the opportunity to characterize marine clouds and the substantial effects of manmade particles on cloud properties and processes. The large dynamic range of aerosol particle concentrations combined with the multi-hour to multi-day persistence of stratocumulus cloud layers makes the site ideal for investigating the seasonal changes in cloud and aerosol properties as well as the quantitative relationships between cloud and aerosol properties. An important enhancement to this study will be the collection of simultaneous in-cloud aerosol and droplet measurements to investigate the differences in these cloud properties during regional polluted and clean marine conditions at the Mt. Soledad location. The combined observations will provide an unprecedented set of constraints for the following questions:

Each of these questions reflects a topic of current controversy in the literature that cannot be addressed without the type of comprehensive data set that this project is expected to provide.

Potential Instrumentation

site aerials
Overview (top left) of Scripps sites in La Jolla, CA, with enlarged details for Mt. Soledad (top right) and pier (bottom).

EPCAPE will locate most of the AMF1 instrumentation at the main site at Scripps Pier and a few additional instruments at the Scripps Mt. Soledad site. Below-cloud instrumentation, including cloud, precipitation, radiation, and aerosol instruments will be situated on the Scripps pier. Additional instrumentation (scanning radar) will be located at the Mt. Soledad site, located less than 2 km inland (250 m above sea level), which will allow for sampling downwind of the pier below, in, and above clouds depending on conditions. Statistics are not available on how frequently the Soledad location is below, in, and above cloud (other than the seasonally limited prior study), as that will be an important outcome of this 12-month data set.

The resources from ARM for this campaign are AMF1, including standard meteorological instrumentation, a broadband and spectral radiometer suite, and remote-sensing measurements including lidars and radars, plus the AOS system for aerosol observations. AMF1 is well suited for this deployment.

ARM Instruments Requested

* ARM instrument that is not currently part of AMF1 but it is requested to be added if it becomes available, because it would enhance the scientific objectives of this project.

Russell will provide filter sampling for organic functional groups (FTIR) and elements (XRF) at the Scripps pier to complement the chemical analysis available from the AMF1 ACSM. This sampling will be housed in an AMF1 AOS van at the pier. Dan Lubin will contribute a shortwave spectroradiometer for measurement of shortwave spectral irradiance between 350 and 1700 nm complements the mid-infrared AERI radiance measurements, in that cloud optical properties (optical depth and effective radius) can be retrieved under thicker clouds that emit in the longwave as blackbodies (with no spectral sensitivity to microphysics). Delphine Farmer will measure particle fluxes at Scripps pier.

UCSD (Russell), UCLA (Suzanne Paulson), and NCSU (Markus Petters) will deploy instruments at Mt. Soledad for in-cloud sampling of detailed aerosol chemical composition, including offline filter analysis. The Mt. Soledad measurements will include aerosol size distributions, SP2, CCN, and aqueous OH radical measurements, as well as a high-resolution, time of flight, event-enabled Aerodyne AMS to provide aerosol composition and concentration for comparison to the AOS ACSM deployed at the pier. Rachel Chang (Dalhousie) plans to deploy the fog droplet monitor at this site to characterize the droplet size distribution in cloud. Environment and Climate Change Canada (John Liggio, Jeremy Wentzell, Michael Wheeler, Alex Lee) is providing a Brechtel ground-based CVI for deployment at the Mt. Soledad site to enable in-cloud composition sampling of droplet residuals. Liggio has support to bring a chemical ionization mass spectrometer, which has previously demonstrated at Mt. Soledad that cloud water chemistry was likely responsible for enhancements in low molecular weight polar organics such as isocyanic (HNCO) and formic acids in cloud droplets, with scavenging efficiencies beyond what can be expected from Henry's Law solubility. Smith will also be measuring ultrafine particles at Mt. Soledad.

Potential instrumentation for Mt. Soledad between February 2023 and February 2024

Inlet column indicates isokinetic (aerosol), CVI, switched between inlets, or duplicated on both inlets.

Evaporates cloud droplets and provides residual particles to other instrumentsBrechtel Counterflow Virtual Impactor (CVI)N/AMichael WheelerECCC
Number distribution of particles (0.02-0.9 µm)Brechtel Differential Mobility Analyzer (DMA)SwitchedLynn RussellUCSD
CCN number concentration and supersaturation spectra of particles
for 0.07-0.6% supersaturation
DMT Cloud Condensation Nuclei (CCN) CounterSwitchedMarkus PettersNCSU
CCN number concentration and supersaturation spectra of particles
for 0.1-1% supersaturation
Mini Handix CCN (5)BothMarkus PettersNCSU
Aerosol number distribution (0.15-3 µm)Printed Optical Particle Spectrometer (POPS)SwitchedMarkus PettersNCSU
Number distribution of particles (0.5-10 µm)TSI Aerodynamic Particle Sizer (APS)IsokineticMarkus RussellNCSU
NR organic, sulfate, nitrate, chloride,
ammonium mass fragment concentrations (0.07-0.8 µm) every 5 min
Aerodyne High-Resolution Aerosol Mass Spectrometer (HR-AMS) with Event Trigger (ET)SwitchedLynn RussellUCSD
BC mass and number distribution (0.08-1 µm)DMT Single-Particle Soot Photometer (SP2)SwitchedMichael WheelerECCC
Gas-phase compounds ionized by IodideAerodyne Chemical Ionization Mass Spectrometer (CIMS)SwitchedJohn LiggioECCC
Number size distribution of fog (cloud) dropletsFog Droplet MonitorN/ARachel ChangDalhousie
BC and aerosol light scattering/absorption coefficientsDMT Photoacoustic Extinctiometer (PAX)SwitchedAlex LeeECCC
Hydroxyl radical formation by particles using direct-to-liquid sampling and fluorescenceDirect-to-Liquid Cloud Droplet OH Burst (DtL-OH)SwitchedSuzanne PaulsonUCLA
Soluble metals by ICPMS and OH burstFilters for transition metals and OH burstSwitchedSuzanne PaulsonUCLA
Chemical composition, hygroscopicity, and volatility of ultrafine particlesTDCIMS, UHPLC-HRMS, and H/VTDMAIsokineticJames SmithUCI
Organic functional group and element concentrationsFilters for FTIR and XRFBothLynn RussellUCSD
Aerosol source for sized calibration particlesTSI Atomizer with DMA for size selectionN/ALynn RussellUCSD
CO, NO, and NOx concentrationTeledyne CO, NO, NOxIsokineticLynn RussellUCSD
Temperature, relative humidity, winds, pressureWeather StationN/ALynn RussellUCSD

Aircraft: NPS Twin Otter

Southern California Interactions of Low cloud and Land Aerosol (SCILLA) Experiment

The Naval Postgraduate School (NPS, formerly CIRPAS) Twin Otter aircraft, led by Mikael Witte, will deploy to San Diego for the Southern California Interactions of Low cloud and Land Aerosol (SCILLA) experiment. Flights will span a four week intensive observational period during June 2023, the month of climatological maximum low cloud cover, and are designed to sample aerosol, microphysics, and meteorological state upwind of the Scripps Pier during the mesoscale eddy events that typically accompany "June gloom" low cloud occurrence at the coast. SCILLA science objectives are to 1) investigate dynamical controls on aerosol transport into, and distribution within, the Southern California Bight; 2) quantify the impact of aerosol-cloud interactions on PBL structure and evolution; and 3) characterize gradients in atmospheric properties across the PBL-capping inversion to constrain vertical mixing/turbulent transport hypotheses. In-cloud sampling of cloud droplet residuals will be performed with a counterflow virtual impactor inlet (Brechtel model 1204 CVI). Finally, the Twin Otter will be equipped to measure surface fluxes over the ocean that can be used to constrain Lagrangian modeling studies of air masses arriving at the ground-based measurement sites.

Potential NPS Twin Otter instrument payload for SCILLA

Meteorology (T, RH, P, 3-D wind)Thermistor, chilled mirror hygrometer, P transducers, radome/flow angle probeMikael WitteNPS
Dry particle size distribution (0.02<Dp<0.5 µm)Brechtel SEMS 2100Andrew MetcalfClemson
Dry particle size distribution (0.1<Dp<3.0 µm)PMS PCASP SPP200Andrew MetcalfClemson
Dry particle concentration Dp>0.003 µm)Aerosol Devices MAGIC CPC, TSI UFCPC 3025Don CollinsUC Riverside
CCN concentrationDMT CCN-100 (x2)Don CollinsUC Riverside
Non-refractory aerosol compositionAerodyne C-ToF-mAMS Roya BahreiniUC Riverside
Refractory black carbonDMT SP2Andrew MetcalfClemson
Fast gas analyzer (CO2, H2O)LI-COR 7500DSMikael WitteNPS
Trace gases (NOx, O3, CO)Teledyne-APi T200U, T400; Ecotech EC9830TDon Collins / Andrew MetcalfUC Riverside / Clemson
Water vapor isotopic analyzerLGR WVIA-911Lisa WelpPurdue
Secondary aerosol formationOxidation flow reactor with dedicated SMPSDon CollinsUC Riverside
Bulk liquid water contentGerber PVM-100AMikael WitteNPS
Cloud and drizzle drop size distribution (2<Dp<1000 µm)Artium dual range PDIPatrick ChuangUC Santa Cruz
Cloud and drizzle drop size distribution (3<Dp<1550 µm)DMT CAPS (CDP+CIP)Mikael WitteNPS
Sea surface temperatureHeitronics KT 19.85 pyrometerMikael WitteNPS
Down-/upwelling solar irradianceKipp & Zonen modified CM22 pyranometerMikael WitteNPS
Down-/upwelling infrared irradianceKipp & Zonen modified CG4 pyrgeometerMikael WitteNPS