Impact of Argo Sampling and Cloud Cover on Ocean Mixed Layer Property Estimates

Dimitris Menemenlis, Jet Propulsion Laboratory, Pasadena, CA, United States, Daria J Halkides, Earth and Space Research, Seattle, WA, United States, Christopher N Hill, Massachusetts Institute of Technology, Earth Atmosphere and Planetary Science, Cambridge, MA, United States and Hong Zhang, NASA Jet Propulsion Laboratory, Pasadena, CA, United States
Abstract:
Ocean mixed layer properties are of critical interest across several
disciplines, including air-sea exchange of heat, momentum, freshwater, carbon
dioxide and other trace gases; theoretical and operational considerations of
weather and climate prediction (e.g., tropical cyclones, monsoons, and ENSO);
and biological productivity and ocean ecosystems. Subsurface ocean data needed
for these applications, however, are sparse and can lead to high uncertainties
in mixed layer heat, momentum, salt, gas, nutrient content, and in the
contributions of physical processes to these quantities. Here we use output
from a high-resolution numerical ocean simulation to examine impact of
observational sampling on mixed layer property estimates.

The simulation is based on a global ocean and sea ice configuration of the
Massachusetts Institute of Technology general circulation model (MITgcm) with
1/24-degree horizontal grid spacing and 90 vertical levels. The vertical
levels have 1-m thickness near the surface in order to better resolve the
diurnal cycle. The MITgcm simulation is concurrently driven by atmospheric
fields from the European Center for Medium-Range Weather Forecasts (ECMWF)
atmospheric operational model analysis, starting in 2011, and by astronomical
tidal potential, hence representing tidal energetics not normally represented
in global calculations.

Two sets of mixed layer property observation system simulation experiments are
carried out. In a first step we sample the simulation according to available
Argo observation in 2011-2013 and compare 10-day and monthly averages of mixed
layer depth and heat content on a 1-degree global grid obtained from the Argo
samples to the full model averages. In a second step we sample the simulation
according to a hypothetical mixed layer lidar that is flown in a 10-day TOPEX/Jason
orbit but can only obtain mixed layer depth in cloud-free and ice-free
conditions and has a depth-dependent noise profile. The above experiments
allow us to examine in a quantitative way the impact of a hypothetical mixed
layer lidar instrument on improving the accuracy of observationally-derived
estimates of mixed layer properties.

Back to: The Ocean Surface Boundary Layer: Physical Processes and Roles in Weather, Climate, and Biogeochemistry I