Joint Seminar: Increased Large-Scale Convective Aggregation in Climate Projections: Mechanisms and implications for tropical radiative fluxes
Deep convection in the tropics organize across a wide range of spatial- and temporal scales and includes a broad spectrum of convective events ranging from isolated and transient mesoscale convective systems O(100-1000 km) up to long-lived super-clusters and planetary envelopes (tropical-scale). The spatial organization of deep convection (Degree of Organization of Convection - DOC) on large scales plays an important role in shaping the hydrological cycle, moisture distribution, large-scale circulation, and radiative feedbacks. Therefore, changes to large-scale DOC in a warming climate may have important implications for precipitation extremes and equilibrium climate sensitivity. State-of-the-art GCMs have a wide range of climatological DOC and increase DOC uniformly through a clustering of large-scale convective events in a warming climate. While a general trend of aggregation of convection with warming has been identified, the regions and convective events most important to describe the model differences in DOC across timescales are unknown. Here we present how tendencies for increasing DOC on timescales of weather (daily and monthly anomalies) shape the climatological DOC, and what large-scale features explain most of the variance across model climatologies and in projections of DOC. Further, we assess the associated radiative and cloud-radiative effect from changes in DOC across timescales. In line with results from observational studies on tropical DOC, we find that monthly anomalies in tropical large-scale DOC are positively correlated with outgoing longwave radiation and low clouds in subsidence regions and negatively correlated with anvil cloud amount in regions of ascent with R^2 ranging from 0.1-0.5 in models and 0.1-0.3 from observational estimates. While clear relationships emerge in current climate conditions, tendencies on timescales of weather cannot explain the tendencies in climatological radiative fluxes for an increase in DOC in a warming climate.
Date
14.01.2025
Time
15:15 h
Place
- Bundesstr. 53, room 022/023
- Seminar Room 022/023, Ground Floor, Bundesstrasse 53, 20146 Hamburg, Hamburg