A Relationship Between ITCZ Organization and Subtropical Humidity
2020
Hohenegger, Cathy | Jakob, Christian
Motivated by the results of idealized studies on the self-aggregation of convection, we investigate a potential relationship between the degree of organization of the Intertropical Convergence Zone (ITCZ) and humidity based on reanalysis data. We focus on the Atlantic ITCZ and use the number of long convergence lines occurring per month to define the degree of organization. The latter shows a weak enhancement during June to August (JJA) and a large interannual variability. On an interannual time scale and particularly during JJA, a relationship exists between organization and humidity: Years with more organized ITCZs are associated with a moister ITCZ region and drier subtropics. Even though we cannot demonstrate any causality and cannot rule out the presence of another agent, we show that these moisture anomalies are not incompatible with an effect of organization. We also note that the annual cycle in sea surface temperature (SST) gradient may contribute to the intra-annual variability in organization.
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