Atmospheric Regimes and Drivers of Cloud Variability and Aerosol-Cloud-Radiation Interactions Over the Coastal Northeast Pacific

Atmospheric regimes and drivers of cloud variability and aerosol-cloud-radiation interactions over the coastal northeast Pacific

William L. Smith Jr. (NASA LaRC) and David Painemal (AMA/NASA LaRC)

Marine boundary layer (MBL) clouds have been a topic of active research during past decades owing to their central role in the Earth’s energy budget and challenges in realistically simulating them in climate models. While significant advances have been achieved in identifying large-scale meteorological drivers and boundary layer processes that regulate the MBL cloud evolution, the response of aerosol-cloud interactions

aerosol-cloud interaction

The interaction of airborne particles (aerosols) with clouds. Scientists study how aerosols affect clouds and how these interactions can impact the Earth's climate.

Source: DOE Source

to changes in the local atmospheric conditions are poorly understood. This impedes the ability to isolate the cloud response due to aerosol

aerosols

Small particles or droplets, such as wildfire smoke, volcanic gases, or salty sea spray, that float in the air. They are emitted by both natural events and human activities.

Source: NASA Global Climate Change Source

perturbations from those attributed to meteorological variability. Moreover, the intrinsic difficulty of isolating cloud dynamics

cloud dynamics

The processes and behaviors that occur during the formation, development, movement, and dissipation of clouds in the Earth's atmosphere.

Source: Source

and aerosol indirect effects is further hampered by the lack of long-term observations suitable for statistical analysis.

The northeast Pacific is a region of interest for the study of aerosol-cloud interactions (ACI) due to the presence of a semipermanent stratocumulus cloud

stratocumulus clouds

Low clouds with irregular masses of clouds, rolling or puffy in appearance, sometimes with space between the clouds.

Source: NASA Source

deck that gives rise to a regional enhancement of albedo. this region features relatively high droplet number concentrations, which is likely attributed to ACI, as continental aerosols are transported to the adjacent ocean. The Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE), which primarily consists of the deployment of the ARM Mobile Facility (AMF1) on the Scripps Pier in La Jolla CA, will provide valuable observations to fill gaps in our current understanding of MBL clouds and their interaction with continental pollution. We propose to investigate aerosol, cloud, and radiation interactions in the marine atmospheric boundary layer. More specifically, we endeavor to analyze the meteorological control on stratocumulus clouds, aerosols, and their interactions using ground-based observations being collected during EPCAPE. We hypothesize that a) aerosol-cloud interactions can be better isolated by constraining their study to specific meteorological regimes and that b) differing magnitudes of aerosol-cloud microphysics co-variability for specific synoptic and mesoscale

mesoscale

Size scale referring to weather systems smaller than synoptic-scale systems but larger than storm-scale systems. Horizontal dimensions generally range from around 50 miles to several hundred miles. Squall lines, MCCs, and MCSs are examples of mesoscale weather systems

Source: NOAA Source

regimes are the manifestation of the control of atmospheric circulation, static stability, and cloud-top entrainment. In addition, satellite geostationary retrievals from GOES-West and atmospheric reanalysis will be applied to provide the regional-scale context that will help interpret the ARM observations. Specific objectives of this proposal are to:

1. Characterize the synoptic regimes during the EPCAPE seasonal deployments using an unsupervised neural network method (Kohonen’s self-organizing map) applied to sea level pressure, geopotential height, and wind fields. Define regional modes of variability in the satellite cloud observations based on the unsupervised clustering.
2. Analyze aerosol and cloud variability from the EPCAPE site as a function of atmospheric regimes and boundary layer properties.
3. Compute metrics of aerosol-cloud-precipitation interactions with the use of EPCAPE observations: aerosol and cloud condensation nuclei

cloud condensation nuclei

Tiny airborne particles suspended in the atmosphere that serve as the seeds around which cloud droplets form.

Source: Source

concentration, and cloud microphysics from ground-based remote sensors. Compute the cloud susceptibility to changes in shortwave radiative fluxes

radiative flux

The measurement of the amount of radiant energy that is released from the Earth's atmosphere across specific wavelengths ranging from solar to thermal infrared.

Source: NASA POWER | Docs Source

due to aerosol perturbations with the use of ground-based broadband radiometers and radiative flux calculations.
4. Evaluate the impact of the cloud diurnal cycle in aerosol-cloud-radiation interactions. Examine the role of turbulence, cloud top entrainment, and boundary layer coupling in the cloud microphysical and macrophysical response.