The role of the ocean in convective burst initiation: implications for tropical cyclone intensification

The upper ocean significantly influences tropical cyclone structure and intensity. These effects, however, are not well understood mostly due to a lack of oceanic and atmospheric boundary layer observations within the inner-core region. This study relates ocean-atmosphere energy exchange processes to mid-to-upper tropospheric latent heating using mesoscale inner-core convective burst events.

A multivariate Lagrangian time series of the inner-core SST, the inner-core-wake SST, the ahead-of-storm SST, and measures of spatial variability of these variables for 30 tropical cyclones was constructed using an objectively interpolated SST tropical cyclone cold-wake climatology. Latent and sensible heat flux estimates and a measure of upper-ocean energy utilization were calculated for the inner-core (<.5° radius) and the near-core (.5° - 1° radius).

This along-track ocean-atmosphere analysis was compared to estimates of atmospheric latent heating calculated using a combined active and passive TRMM PR and TMI retrieval algorithm (Grecu and Olsen, 2005). Results show strong positive space and time correlations between ocean-air fluxes and mid-upper tropospheric latent heating.

Additionally, the 30 storms analyzed were categorized by the presence or absence of convective burst events during the storm lifecycle. Composite atmospheric latent heating profiles constructed for each group show a two-fold release in energy for the storms with convective burst events compared to storms with no convective burst event.