Aerosol breezes drive cloud and precipitation increases.

Aerosol-cloud interactions are a major source of uncertainty in weather and climate models. These interactions and associated precipitation feedbacks are modulated by spatial distributions of aerosols on global and regional scales. Aerosols also vary on mesoscales, including around wildfires, industrial regions, and cities, but the impacts of variability on these scales are understudied. Here, we first present observations of covarying mesoscale aerosol and cloud distributions on the mesoscale. Then, using a high-resolution process model, we show that horizontal aerosol gradients of order 100 km drive a thermally-direct circulation we call an "aerosol breeze". We find that aerosol breezes support initiation of clouds and precipitation over the low-aerosol portion of the gradient while suppressing their development on the high-aerosol end. Aerosol gradients also enhance domain-wide cloudiness and precipitation, compared with homogenous distributions of the same aerosol mass, leading to potential biases in models that do not adequately represent this mesoscale aerosol heterogeneity.

The future of Earth system prediction: Advances in model-data fusion.

Predictions of the Earth system, such as weather forecasts and climate projections, require models informed by observations at many levels. Some methods for integrating models and observations are very systematic and comprehensive (e.g., data assimilation), and some are single purpose and customized (e.g., for model validation). We review current methods and best practices for integrating models and observations. We highlight how future developments can enable advanced heterogeneous observation networks and models to improve predictions of the Earth system (including atmosphere, land surface, oceans, cryosphere, and chemistry) across scales from weather to climate. As the community pushes to develop the next generation of models and data systems, there is a need to take a more holistic, integrated, and coordinated approach to models, observations, and their uncertainties to maximize the benefit for Earth system prediction and impacts on society.

Cold Pool-Land Surface Interactions in a Dry Continental Environment.

Cold pools influence convective initiation and organization, dust lofting, and boundary layer properties, but little is known about their interactions with the land surface, particularly in dry continental environments. In this study, two-way cold pool-land surface interactions are investigated using high-resolution idealized simulations of an isolated, transient cold pool evolving in a dry convective boundary layer. Results using a fully interactive land surface demonstrate that sensible heat fluxes are suppressed at the center of the cold pool but enhanced at the edge due to the spatial patterns of land surface cooling and the air temperature and wind speed perturbations. This leads to cold pool dissipation from the edge inward. Latent heat fluxes are primarily suppressed within the cold pool, and the magnitude of this suppression is controlled by competition between atmospheric and land surface effects. By comparing the fully interactive land surface simulation to a simulation with imposed surface fluxes, the land surface-cold pool feedbacks are shown to reduce the cold pool lifetime, extent, and intensity by up to 50% and influence the pattern of boundary layer turbulent kinetic energy recovery, which have significant implications for cold pool-induced convective initiation.