Scientific Theme: Advanced Modeling and Observing Systems

Scientific Theme: Regional Processes
ACCOMPLISHMENTS FOR PSD12.4:
This project involves the repackaging of fast CO2 sensors to permit continuous, unattended deployment on the
NOAA R/V Ronald H. Brown. The goal is to obtain an extensive database of CO2 flux and transfer velocity for a
variety of verification and parameterization development objectives. The project has been underway for about a
year. A system has been designed, sensors acquired, and tested at the pier at Duck, NC. The system was field tested
on a Norwegian ship in the summer of 2006. The data are presently being evaluated. An improved version of the
sensor will be deployed on the GOMECC cruise in July 2007.
MILESTONE PSD12.5:
Create a multi-year global oceanic data set of near-surface temperature and humidity using a
multi-sensor satellite retrieval method recently developed at the ESRL Physical Sciences
Division.
ACCOMPLISHMENTS FOR PSD12.5:
A 12-year (1993-2004) global oceanic data set of near-surface humidity has been developed using SSM/I and
SSM/T-2 satellite sensors, and a 7-year (1999-2005) data set of both near-surface humidity and temperature has
been developed combining AMSU-A and SSM/I satellite sensors. Updated regression coefficients using an
enhanced training data set generally provide less bias than the previous version and particularly improve the Qa
retrievals exceeding 16 g/kg. A stability correction was introduced to the humidity retrieval to repair wet biases in
the summertime North Pacific observations that often exceeded 3 g/kg. Multi-year comparison with I-COADS
indicates a smaller bias and rms difference when compared with existing single-sensor SSM/I retrieval methods.
Ultimately, improvements in these Ta and Qa products will help improve retrievals of latent and sensible heat fluxes
derived from air-sea bulk turbulent flux models. Heat fluxes derived using these products and the COARE version 3
bulk model are currently being conducted. Products include:
A 12-year near-surface humidity data set of daily mean 1-degree data derived from SSM/I and SSM/T-2
observations
A 7-year near-surface humidity and temperature data set of daily mean 1-degree data from AMSU-A and
SSM/I observations.
0.5 degree/3-hourly grid data are currently available for 1999 but will be extended to the same time periods
as the 1 degree/daily averaged data given above.
MILESTONE PSD12.6:
Study and parameterization of stable boundary-layers as part of the NOAA/NSF Polar Programs.
ACCOMPLISHMENTS FOR PSD12.6:
Structure of the stable boundary layer (SBL) in the Arctic has been examined based on measurements made during
the Surface Heat Budget of the Arctic Ocean experiment (SHEBA). Turbulent and mean meteorological data
collected at five levels on a 20-m tower over the Arctic pack ice during eleven months of measurements cover a
wide range of stability conditions, from the weakly unstable regime to very stable stratification. According to
SHEBA data, stratification and the Earth‘s rotation control the SBL over a flat rough surface. Traditional Monin-
Obukhov similarity theory works well in the weakly stable regime. As stability increases, the near-surface
turbulence is affected by the turning effects of the Coriolis force (the turbulent Ekman layer). In this regime, the
surface layer, where the turbulence is continuous, may be very shallow (less than 5 m). Turbulent transfer near the
―critical Richardson number‖ is characterized by small but still significant heat flux and negligible stress. The
supercritical stable regime where the bulk Richardson number exceeds a critical value 0.2 is associated with
collapsed turbulence and the strong influence of the Earth‘s rotation, even near the surface. The comprehensive data
set collected during SHEBA allows study of the profile stability functions of momentum (nondimensional gradient
of wind-speed), sensible heat (non-dimensional gradient of temperature), and derivative quantities such as the
turbulent Prandtl number and the gradient Richardson number in detail, including the very stable case.
New parameterizations for the profile stability functions in stable conditions are proposed to describe the SHEBA
data; these cover the entire range of the stability parameter z/L from neutral to very stable conditions, where L is the
Obukhov length and z is the measurement height. In the limit of very strong stability, stability functions of
momentum follows the ―1/3‖ dependence in the very stable regime (in log-log coordinates), whereas stability
functions of sensible heat flux initially increases with increasing z/L, reaches a maximum at about z/L=10, and then
tends to level off with increasing z/L
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