James Edson

(Ph.D., Penn State University) Professor of Marine Sciences, emeritus

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I am a marine meteorologist conducting interdisciplinary research that investigates how the atmosphere and ocean interact i.e., air-sea interactions.  I am part the Atmopsheric Sciences Group (ASG) at UConn, which is a growing group of colleagues specializing in the atmospheric and climate sciences.  My specific research interests lie in boundary layer meteorology with a focus on the turbulent exchange (or flux) of momentum, heat, and water vapor to and form the ocean surface. I am particularly interested in how waves affect the transfer of momentum and heat across the air-sea interface.  These investigations have led to the development of new measurement techniques, instrumentation, motion correction algorithms, flux parameterizations, drag and transfer coefficients, and models of evaporating sea-spray. Over longer timescales, I am also involved with research aimed at improving our predictive capabilities of climate change.  Specifically,we have designed a system that is capable of directly measuring the exchange of CO₂ between the ocean and atmosphere.  The data from this system is being used to improve the way this exchange is simulated in climate models.  I have also been actively involved in the development of new ocean observing systems such as the Martha’s Vineyard Coastal Observatory (MVCO).

SO GASEX: The Southern Ocean Gas Exchange (SO GASEX) program is the 3rd of a series of open ocean experiments that are designed to quantify and model the exchange of CO₂ and other climate relevant gases between the ocean and atmosphere. During SO GASEX, we made direct measurements of air-sea heat, momentum and mass (including CO₂, DMS and water vapor) fluxes using the direct covariance method over the open ocean from the NOAA R/V Ronald H. Brown.  My NSF funded research focused the wind speed dependency of the transfer velocity, k, used to model the CO₂ flux between the atmosphere and ocean. A quadratic dependence of k on wind speed based on dual tracer experiments is most frequently encountered in the literature. However, in recent years, bubble-mediated enhancement of k, which exhibits a cubic relationship with wind speed, has emerged as a key issue for flux parameterization in high wind regions (Ho et al. 2011; Fairall et al. 2011). Therefore, a major question addressed in SO GasEx is whether the transfer velocities obey a quadratic or cubic relationship with wind speed. After significant correction to the flux estimates (primarily due to moisture contamination), the direct covariance CO₂ fluxes predict a significant enhancement of the transfer velocity at high winds compared with previous quadratic formulations. Regression analysis suggests that a cubic relationship provide a more accurate parameterization over a wind speed range of 0 to 18 ms-1 (Edson et al. 2011). The Southern Ocean results are in good agreement with the 1998 GasEx experiment in the North Atlantic and a recent separate field program in the North Sea.

CLIMODE:  The Clivar Mode Water Dynamics Experiment (CLIMODE) is designed to investigate the formation and subsequent evolution of subtropical mode water in the North Atlantic (Marshall et al. 2009) funded by NSF.   It collected a large data set of air-sea heat and momentum fluxes provided by three highly instrumented platforms during the field programs: a moored 3-m discus buoy, a research vessel for surveys, and a drifting Air-Sea Interaction Spar (ASIS). A direct covariance flux system was successfully deployed for 15 months on the discus buoy that was generally in the Gulf Stream (Weller et al. 2012; Bigorre et al. 2013).  High wind events drove surface stresses that routinely exceeded 1.0 N/m² and combined latent and sensible heat fluxes from the ocean into the atmosphere that exceed 1300 W/m² during cold air outbreaks (e.g., Skyllingstad and Edson,  2009). The CLIMODE data has been used to modify the wind-speed dependent Charnock coefficient in the COARE 3.0 algorithm, which is shown to give better agreement with the stress estimates from a variety of the field programs at all winds speeds with significant improvement for wind speeds over 13 m/s.  The data is also used to develop wave-age and wave-slope dependent parameterizations of the surface roughness, which give good agreement with the directly measured momentum fluxes over a wide range of sea-states and wave-ages.   These formulations are included in a new version of the algorithm named COARE 3.5 (Edson et al. 2013).

DYNAMO: The Dynamics of the Madden-Julian Oscillation (DYNAMO) program is the U.S. led component of the international CYNDY2011 program. The Madden-Julian Oscillation (MJO) is a quasi-period disturbance with a period between 30-90 days that propagates eastward from the Indian Ocean to the Central Pacific at an average speed of 5 m/s. The MJO is characterized by an active phase with strong deep convection and precipitation and an inactive phase with weaker deep convection and less precipitation. It has a strong impact on the timing of the Indian monsoon season and rainfall variability in the regions. The rainfall patterns and zonal wind anomalies that develop under these disturbances affect ocean waves, currents and air-sea interaction. The objective of my research (funded by ONR) is to improve our understanding of heat and moisture exchange in the tropics through direct estimates of the fluxes and their related mean variables. The flux of heat across the coupled boundary layers is mainly accomplished by small-scale processes that are parameterized in numerical models. A primary goal of this research is to improve the surface flux parameterization for latent and sensible heat used in these models and observational process studies. The principle hypothesis of this research is that improved observations and parameterizations of latent and sensible heat fluxes, which is a primary source of energy for these convective systems, will improve our ability to simulate and predict the MJO.

SPURS:  The Salinity Processes Upper-ocean Regional Study (SPURS) program is the process study associated with NASA’s Aquarius satellite mission.  The satellite is designed to provide global maps of salinity from space and was successfully launched in July of 2011.   Our primary research goal is accurate estimates of the variables governing the evolution of upper-ocean salinity, to allow improved understanding of processes affecting both the large-scale salinity field and the shallow, high-frequency variations in surface salinity. To meet this objective, an oceanographic surface mooring was successfully deployed by colleagues at the Woods Hole Oceanographic Institution (WHOI) on September 14, 2012 during the SPURS cruise aboard the R/V Knorr. The mooring’s surface buoy carries state-of-the-art instruments for measuring surface meteorology and subsurface temperature, salinity, and velocity, with specific focus on making accurate estimates of the surface freshwater fluxes (evaporation and precipitation), which are of particular importance to this program.  Therefore, we deployed a technically innovative system for making autonomous, direct measurements of the turbulent fluxes of heat, moisture, and momentum in the atmospheric surface layer. We expect that this combination of measurements will provide the best possible estimate of the surface fluxes in the SPURS study region and allow development a regionally appropriate set of bulk formulas to improve indirect estimates of the evaporation from research buoys and global evaporation products derived from satellite data or other sources.  The buoy will be recovered in October, 2013.

Research Projects

Southern Ocean Air-Sea CO2 Exchange – A component of the SO GASEX Program. – National Science Foundation, Chemical Oceangraphy

Air-sea Interaction in the 18 degree C Water Formation Area – A component of the CLIMODE Program – National Science Foundation, Physical Oceanography

An Investigation of Turbulent Heat Exchange in the Subtropics – A component of the DYNAMO Program – Office of Naval Research, Marine Meteorology & Physical Oceanography

A Surface Mooring for the Direct Measurements of Air-Sea Fluxes, Evaporation and Precipitation – A component of the SPURS Program – NASA, Physical Oceangraphy

Oceanography Students

Raymond Graham – M.Sc. Student

Oceanography Alumni

Alejandro Cifuentes – Ph.D. 2013

Aaron Rosenberg – M.Sc. 2016

Former Postdoctoral Fellow

Aaron Paget

Courses Taught

MARN 5064 Air-Sea Interaction (University of Connecticut, Avery Point, Spring 2014)

PHYS 1401Q General Physics with Calculus I (University of Connecticut, Avery Point, Fall 2005-2010; Fall 2011-present)

PHYS 1402Q General Physics with Calculus II (University of Connecticut, Avery Point, Spring 2005-2010)

MARN 3001 Coastal Systems II (University of Connecticut, Avery Point, Fall 2012)

MARN 2002 Coastal Systems I (University of Connecticut, Avery Point, Spring 2012)

MARN 5898 Air-sea Interaction (University of Connecticut, Avery Point, Spring 2006; 2012)

MARN 5898 Marine Boundary Layers (University of Connecticut, Avery Point, Fall 2007)

Air-sea Interaction Course (MIT/WHOI, co-taught course, Spring 1995, 1997, 2000; Fall 1997, 2003)

Air-sea Interaction Laboratory (MIT/WHOI, co-taught lab, Spring 1992)

Micrometeorology (Penn State, Fall 1988)