Sources, Sinks and Processing of Newly Formed Particles in the Remote Free Troposphere: Comparing In Situ-Measurements from the Nasa Atmospheric Tomography Mission with Chemistry Climate Models
Abstract
Aerosols nucleated in the free troposphere may account for 35% of cloud condensation nuclei (CCN) in global low-level clouds, yet the relative importance of different particle formation mechanisms remains poorly understood . The spatial distribution, concentration and fate of newly formed particles is controlled by nucleation mechanisms, availability of condensable vapors, and coagulation and condensation sinks. Constraining these factors in models is particularly important for pre-industrial aerosol-climate interactions, where the effect of newly formed particles on climate is amplified compared with the present day.
We present in-situ measurements of the global distribution of newly formed particles and coagulation and condensation sinks from the NASA Atmospheric Tomography Mission (ATom). Flights covered the Pacific and Atlantic basins from 80°N to 86°S latitude, constantly profiling between 0.2 and 13km altitude over different seasons. The DC-8 aircraft was equipped with instrumentation for measuring various aerosol properties as well as greenhouse, reactive and trace gases. We compare these measurements with output from several global models with online aerosol microphysics. Our measurements reveal a pattern of high nucleation mode aerosol concentrations at altitudes > 9 km over the tropics, coincident with convective influence and low coagulation sinks. Size distributions over this region show a continuous increase in modal diameter with decreasing altitude between the upper troposphere and top of the boundary layer, demonstrating that these particles grow to CCN sizes and can influence planetary albedo and radiation balance in the remote atmosphere. This process spans from 30°S to 30°N, representing half of the Earth's global oceanic surface area, and persists through seasonal changes. We assess how this process is represented in each of the models, and use the models' output to examine the roles of sinks, nucleation mechanisms and availability of condensable vapors in the formation and growth of these particles.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A51Q2478K
- Keywords:
-
- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSESDE: 3337 Global climate models;
- ATMOSPHERIC PROCESSESDE: 3359 Radiative processes;
- ATMOSPHERIC PROCESSES