EPCAPE-CCC-CCN

COASTAL CLOUD CHEMISTRY DURING EPCAPE

15 January 2023 - 31 October 2023

Lead Scientist: Markus Petters

Observatory: AMF (ARM Mobile Facility 1) - EPC

Observations of cloud chemistry in the atmosphere are needed to support the relevance of past and
future laboratory and modeling studies, as measurements may change how cloud formation is
represented in climate models, alter interpretation of correlations between aerosol and meteorological
properties, and affect which emissions are regulated. The DOE-funded Eastern Pacific Cloud Aerosol
Precipitation Experiment (EPCAPE) campaign will be conducted in La Jolla, California from February 2023 to January
2024, siting an array of cloud, aerosol, and precipitation instrumentation at the Scripps Pier and nearby
Mt. Soledad. EPCAPE will provide unprecedented characterization of coastal clouds, their seasonal
changes, and their diurnal evolution. This campaign augments these meteorological observations with a
suite of measurements at Mt. Soledad to document the differences from the ARM instruments at the
Scripps Pier.
Specifically, for the campaign AFC010121, PI Petters will deploy a suite of instruments inside a van
provided by PI Russell that is sited at Mt. Soledad. The rack includes a differential mobility analyzer, a
condensation particle counter, a printed particle optical spectrometer, a continuous flow diffusion cloud
condensation nuclei (CCN) counter, and four new mini cloud condensation nuclei instruments. The
instruments will sample from a counterflow virtual impactor inlet and an isokinetic inlet. The
measurements will provide the aerosol size distribution, size-resolved CCN activity, and denuded versus
undenuded CCN activity of aerosols and cloud drop residuals. In addition to replicating some of the ARM
measurements at the Scripps Pier at a location closer to cloud base, these measurements are designed
to address the following two science questions.
(1) Does removing the gas-phase components by denuding affect drop activation in clean or polluted
conditions at Mt. Soledad?
(2) Does removing the gas-phase components by denuding affect the growth rate of cloud droplets?