Observing the Ocean’s Interior from the Space
Xiao-Hai YAN
Mary A. S. Lighthipe Chair Professor, College of Earth, Ocean and Environment, Universityof Delaware, Newark, DE 19716, U. S. A.
Also a Distinguished Scholar, Joint-Institute of CRM, State Key Lab of Marine Environmental
Science, Xiamen University, Xiamen, China

Recent ocean remote sensing missions and techniques have produced
remarkable data sets of high accuracy measurements of sea surface height, surface
wind, surface roughness, temperature, pigment concentration, etc. One can nowstudy, on a truly global basis, the fluid ocean and its variability at all periods betweenyears and days, on all spatial scales from the global to about a few meters. Theaccuracy and precision of the measurements are so good, that, with the help of the
newly developed various remote sensing data processing techniques, a huge varietyof phenomena can now be addressed. However, most remotely sensed oceanographic
observations are confined to either the sea surface or to the upper mixed layer due tothe limitations of the sensors. In the past 20 years some of the attempts to break theocean’s surface have already made the headlines. Yan et al. (1990, 1991a, b), and Yanand Okubo (1992) developed methods to infer the upper ocean mixed layer depths
from multi-sensor satellite data. Furthermore, Yan et al (2006) developed method tostudy the variability of the Meddy (Mediterranean Outflow and Eddy) which is atabout 1000m depth. Although these methods break the ocean’s surface from thespace successfully, still many important ocean processes in ocean interior need to beobserved and studied from the space but not yet successful due to the limitations ofthe sensors and difficulties in the methodologies. Such deeper ocean processes
include MOC (Meridional Overturning Circulation), DOC (Deep Ocean Convection),bottom topography, internal waves, some bio-geo-chemical deep ocean processes,
etc, which relate and impact greatly to the global climate changes. This lecture will
review the background and status of the research on breaking the ocean’s surface
from the space, and report some of the recent attempts to combine satellite
altimetry, scatterometry, infrared, ocean color, and SAR with other observations
and techniques, and with general circulation models to infer the three-dimensional,
time varying ocean circulation, air-sea interactions, and global and regional
oceanographic processes at ocean’s interior such as MOC and DOC, which identified
by the recent US National Academy of Sciences’ Decadal Survey Report as one ofurgent and most important research topic.

References:[1] Yan, X.-H., J.R. Schubel, and D.W. Pritchard. 1990. Oceanic upper mixed layer depth
determination from a satellite model. Remote Sensing of Environment, 32(1):55-74.
[2] Yan, X.-H., A. Okubo, J.R. Shubel, and D.W. Pritchard. 1991a. An analytical mixed layer
remote sensing model. Deep Sea Research, 38(3):267-287.
[3] Yan, X.-H., P.P. Niiler and R.H. Stewart. 1991b. Construction and accuracy analysis ofimages of the daily-mean mixed layer depth.International Journal of Remote Sensing,
12(12):2573-2584.
[4] Yan, X.-H. and A. Okubo. 1992. Three-dimensional analytical model for the mixed layer
depth, Journal of Geophysical Research, 97(C12):20,201-20,226[5] Yan, X.-H., Y. Jo, W. T. Liu, and M. He. 2006. A new study of the Mediterranean outflow,
air-sea interactions, and Meddies using multisensor data, J. Physical Oceanogr., Vol. 36,No. 4, pages 691-710