Primary biological aerosol particles (PBAPs), such as bacteria, fungal spores, and micro-algae, are significant natural sources of atmospheric particles, abundant in various ecosystems. They are dispersed over long distances and high altitudes by wind, playing a crucial role in spreading microorganisms, and affecting nutrient cycles, agriculture, and public health. Additionally, PBAPs act as cloud condensation nuclei (CCN) or ice nuclei (IN), impacting cloud and precipitation formation, radiation budget, and Earth's hydrological cycle and climate.
The terrestrial emission flux of PBAP is estimated at 50 to 1000 Tg/yr, with a high uncertainty. Definitions of PBAPs vary across literature, leading to discrepancies in reported emission fluxes. The role of PBAPs in ice formation and climate impact remains uncertain due to limited measurements, especially over marine environments.
Understanding PBAPs-cloud interactions is essential for climate research, aligning with Sustainable Development Goal 13 and the Paris Agreement. The BIOAAT project aims to address key scientific questions regarding PBAPs:
1. Global distribution and emission variations of PBAPs, affecting mass, surface concentration, deposition, and atmospheric lifetime.
2. Parametrization of PBAPs' ice nucleation activity considering their unique features.
3. Assessment of PBAPs' climatic impacts, especially in cloud formation scenarios.
Key conclusions from BIOAAT include:
1. Development of the GISS-E2.1 climate model incorporating PBAPs emissions for investigating their climatic impacts.
2. PBAPs emissions contribute to cooling effects, particularly evident with increased emissions.
3. Recognition of the importance of PBAPs emissions from marine environments, often overlooked in previous studies.
4. Emphasis on the necessity of additional experimental data to refine PBAPs emission estimates and validate modeling studies.
5. Importance of considering PBAPs' molecular features, such as proteins attached to cell membranes, in parametrizing their ice nucleation activity.
6. Acknowledgment of the significant impact of PBAPs-cloud interactions on cloud radiative forcings, highlighting the need for comprehensive modeling.
In summary, the BIOAAT project advances understanding of PBAPs' role in climate dynamics, emphasizing the complexity of their interactions with clouds and the atmosphere.
