Introducing a new metrics for the atmospheric pressure adjustment to
thermal structures at the ocean surface
Abstract
Thermal structures at the sea surface are known to affect the overlying
atmospheric dynamics over various spatio-temporal scales, from hourly
and sub-kilometric to annual and O(1000 km). The relevant mechanisms at
play are generally identified by means of correlation coefficients (in
space or time) or by linear regression analysis using appropriate
couples of variables. For fine spatial scales, where SST gradients get
stronger, the advection might disrupt these correlations and, thus, mask
the action of such mechanisms, just because of the chosen metrics. For
example, at the oceanic sub-mesoscale, around 1-10 km and hourly time
scales, the standard metrics used to identify the pressure adjustment
mechanism (that involves sea surface temperature, SST, Laplacian and
wind divergence) may suffer from this issue, even for weak wind
conditions. By exploiting high-resolution realistic numerical
simulations with ad hoc SST forcing fields, we introduce some new
metrics to evaluate the action of the pressure adjustment atmospheric
response to the surface oceanic thermal structures. It is found that the
most skillful metrics is based on the wind divergence and SST second
spatial derivative evaluated in the across direction of a locally
defined background wind field.