The objective of this project is to assess quantitatively the capability and limitations of the Argo float array for the investigation of basin-to-global scale upper ocean response to hurricanes based on the comparison between the Argo observation and numerical model results. The Argo array measures subsurface temperature and salinity profiles before and after storms, and so provides a unique dataset to study the impact of the storms in a basin-to-global scale and for the subsurface as well as the sea surface.
To properly understand the basin-to-global scale impact of tropical storms, a sustained global observational network with a resolution sufficient to observe the impact of tropical storms is needed for surface as well as the subsurface ocean. On the other hand, our understanding on the upper ocean response to the storms has progressed mostly based on the studies focused on individual storms. Successful use of the global observational network of Argo array in conjunction with satellite observations would allow the investigators to extrapolate our understanding to basin-to-global scale consequences. However, despite the unique opportunity provided by the near-global and subsurface coverage of the Argo array, the uncontrolled sampling in space with a relatively sparse 10 day interval produces substantial uncertainty primarily due to the inability to filter out near-inertial pumping and random position uncertainties with respect to the storm and the background flow. Therefore, a method to quantify uncertainty in the Argo sampling of ocean response to the hurricane is needed as a prerequisite to address the scientific questions using the dataset.
The main strategy is to use a realistic numerical ocean simulation under a given initial background condition and hurricane forcing to perform an observation sampling experiment. During the experiments, virtual floats will be deployed in the model to mimic Argo floats in the real ocean. The data sampled by virtual float profiles will be used to estimate the uncertainty against the simulated full response. The 3-dimensional Price-Weller-Pinkel model will be used to perform observation sampling experiment.
Intellectual Merit: Assessing uncertainty of the uncontrolled Argo observation in a statistically robust fashion with respect to the response to hurricane is unprecedented (as far as we are aware of). The proposed activity will not only advance the community's capability to apply statistical methods to scattered observations, but also enable it to use the Argo observations to address the fundamental scientific questions associated with the basin-scale ocean response to the hurricane, such as what is the contribution of tropical storms to the vertical mixing and the meridional transport of heat in the upper ocean.
Broader Impacts Our proposed work will provide the broader oceanography and atmospheric science community with a statistically robust tool to use the Argo observations to study the upper ocean response to an extreme event such as the hurricane and associated air-sea interaction, an application of Argo array that is well beyond its original vision. Argo has been a long-term international community effort that benefited many areas from the large-scale oceanography to the interannual-to-decadal predictability efforts. Broadening the use of Argo array will be very desirable and beneficial to justify the extension and expansion of this community asset. The project will also contirubte to the careeer development of two promising new NSF investigators.
