Collaborative Research: AGS-FIRP Track 2--Process Investigation of Clouds and Convective Organization over the atLantic Ocean (PICCOLO)

The deep, rain-bearing convective clouds of the tropics are often found clumped into clusters with multiple cumulus towers topped by spreading anvils. These clusters come in a variety of shapes and sizes including squall lines and mesoscale convective systems like the ones found over the US Great Plains. Convective organization is clearly a concern for severe weather and it could also play important roles in Earth's energy balance, the distribution of moisture in the tropical atmosphere, and the ability of convection to drive the global atmospheric circulation. A key issue for understanding the role of convective organization in the climate system is the extent to which organization occurs spontaneously, driven by the clouds themselves, or is forced by large-scale environmental factors such as winds and sea surface temperature (SST) contrasts. Spontaneous organization has been found in idealized simulations, with substantial impacts on tropical climate and energetics, but the organization happens slowly in an otherwise quiescent and uniform environment. These simulations are compelling but their relevance to the real-world tropics, where conditions are never quiescent or uniform, has not been fully established. Work performed under this award seeks to understand the role of self-organization in the development of real-world convective cloud clusters observed over the tropical Atlantic Ocean. The effects of the clusters on the surrounding environment is also examined.Specifically, the award supports a field campaign called PICCOLO, which stands for Process Investigation of Clouds and Convective Organization Over the atLantic Ocean. The primary activity of PICCOLO is the deployment of SEA-POL, a stabilized C-band polarimetric weather radar, on the German research vessel Meteor. The campaign is part of a joint international effort called ORCESTRA, ORganized Convection ExperimentS in the TRopical Atlantic, in which the Meteor will sail from Cape Verde to Barbados over six weeks starting in August 2024. The ship will cross the Atlantic at 7 degrees north with interruptions for several north-south transects across the Intertropical Convergence Zone (ITCZ), a band of organized convection typically found north of the equator over the tropical oceans. The SEA-POL radar observations will be combined with data from a variety of other observing systems aboard the Meteor, including weather balloons, a W-band cloud radar, a microwave radiometer, and two lidars. The ORCESTRA effort also includes measurements from the German HALO and French SAFIRE research aircraft.The work is of societal as well as scientific interest given the role of convective organization in extreme precipitation and hurricane formation, as well as the fact that organized convection contributes nearly half of the total precipitation in the tropics. The role of convective organization in Earth's energy balance is also of interest given recent studies suggesting that the rising temperature of the Earth could affect the extent of convective organization, which could in turn affect the amount of warming produced by increasing greenhouse levels. Beyond this societal relevance the work has broader impacts through the support and training of seven graduate students and two postdoctoral fellows. The campaign also participates in the SEA-POL PLUS program, which facilitates participation by students from underrepresented groups, and conducts local outreach to communities in Barbados and Cape Verde in collaboration with partners in the international ORCESTRA effort.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.