Tom Murphree

The Northern Oscillation Index (NOI): a new climate index for the northeast Pacific

Abstract We introduce the Northern Oscillation Index (NOI), a new index of climate variability based on the difference in sea level pressure (SLP) anomalies at the North Pacific High (NPH) in the northeast Pacific (NEP) and near Darwin, Australia, in a climatologically low SLP region. These two locations are centers of action for the north Pacific Hadley–Walker atmospheric circulation. SLPs at these sites have a strong negative correlation that reflects their roles in this circulation. Global atmospheric circulation anomaly patterns indicate that the NEP is linked to the western tropical Pacific and southeast Asia via atmospheric wave trains associated with fluctuations in this circulation. Thus the NOI represents a wide range of tropical and extratropical climate events impacting the north Pacific on intraseasonal, interannual, and decadal scales. The NOI is roughly the north Pacific equivalent of the Southern Oscillation Index (SOI), but extends between the tropics and extratropics. Because the NOI is partially based in the NEP, it provides a more direct indication of the mechanisms by which global-scale climate events affect the north Pacific and North America. The NOI is dominated by interannual variations associated with El Nino and La Nina (EN/LN) events. Large positive (negative) index values are usually associated with LN (EN) and negative (positive) upper ocean temperature anomalies in the NEP, particularly along the North American west coast. The NOI and SOI are highly correlated, but are clearly different in several respects. EN/LN variations tend to be represented by larger swings in the NOI. Forty percent of the interannual moderate and strong interannual NOI events are seen by the SOI as events that are either weak or opposite in sign. The NOI appears to be a better index of environmental variability in the NEP than the SOI, and NPH SLP alone, suggesting the NOI is more effective at incorporating the influences of regional and remotely teleconnected climate processes. The NOI contains alternating decadal-scale periods dominated by positive and negative values, suggesting substantial climate shifts on a roughly 14-year ‘cycle’. The NOI was predominantly positive prior to 1965, during 1970–1976 and 1984–1991, and since 1998. Negative values predominated in 1965–1970, 1977–1983, and 1991–1998. In the NEP, interannual and decadal-scale negative NOI periods (e.g. EN events) are generally associated with weaker trade winds, weaker coastal upwelling-favorable winds, warmer upper ocean temperatures, lower Pacific Northwest salmon catch, higher Alaska salmon catch, and generally decreased macrozooplankton biomass off southern California. The opposite physical and biological patterns generally occur when the index is positive. Simultaneous correlations of the NOI with north Pacific upper ocean temperature anomalies are greatest during the boreal winter and spring. Lagged correlations of the winter and spring NOI with subsequent upper ocean temperatures are high for several seasons. The relationships between the NOI and atmospheric and physical and biological oceanic anomalies in the NEP indicate this index is a useful diagnostic of climate change in the NEP, and suggest mechanisms linking variations in the physical environment to marine resources on interannual to decadal climate scales. The NOI time series is available online at: http://www.pfeg.noaa.gov.

The evolution of oceanic and atmospheric anomalies in the northeast Pacific during the El Niño and La Niña events of 1995-2001

Abstract From late 1995 through early 2001, three major interannual climate events occurred in the tropical Pacific; the 1995–97 La Nina (LN), 1997–98 El Nino (EN), and 1998–2001 LN. We analyze atmospheric and upper oceanic anomalies in the northeast Pacific (NEP) during these events, and compare them to anomalies both elsewhere in the north and tropical Pacific, and to typical EN and LN anomaly patterns. The atmospheric and oceanic anomalies varied strongly on intraseasonal and interannual scales. During the 1995–97 LN and 1997–98 EN, the Northeast Pacific was dominated by negative SLP and cyclonic wind anomalies, and by upper ocean temperature and sea surface height (SSH) anomalies. The latter were positive along the North American west coast and in the NEP thermal anomaly pool (between Hawaii, Vancouver Island, and Baja California), and negative in the central north Pacific. This atmospheric/oceanic anomaly pattern is typical of EN. An eastward shift in the atmospheric teleconnection from east Asia created EN-like anomalies in the NEP during the 1995–97 LN, well before the 1997–98 EN had begun. The persistence of negative sea-level pressure (SLP) and cyclonic wind anomalies in the NEP during the 1997–98 EN intensified pre-existing upper oceanic anomalies. Atmospheric anomalies were shifted eastward during late 1996–early 1998, leading to a similar onshore shift of oceanic anomalies. This produced exceptionally strong positive upper ocean temperature and SSH anomalies along the west coast during the 1997–98 EN, and explains the unusual coastal occurrences of several species of large pelagic warm-water fishes. The growth and eastward shift of these pre-existing anomalies does not appear to have been linked to tropical Pacific EN anomalies until late 1997, when a clear atmospheric teleconnection between the two regions developed. Prior to this, remote atmospheric impacts on the NEP were primarily from east Asia. As the 1998–2001 LN developed, NEP anomalies began reversing toward the typical LN pattern. This led to predominantly negative SLP and cyclonic wind anomalies in the NEP, and upper ocean temperature and SSH anomalies that were mainly negative along the west coast and positive in the central north Pacific. The persistence of these anomalies into mid-2001, and a number of concurrent biological changes in the NEP, suggest that a decadal climate shift may have occurred in late 1998. During 1995–2001, NEP oceanic anomalies tracked the overlying atmospheric anomalies, as indicated by the maintenance of a characteristic spatial relationship between these anomalies. In particular, wind stress curl and SSH anomalies in the NEP maintained an inverse relationship that strengthened and shifted eastward toward the west coast during late 1996–early 1998. This consistent relationship indicates that anomalous Ekman transport driven by regional atmospheric forcing was an important contributor to temperature and SSH anomalies in the NEP and CCS during the 1997–98 EN. Other studies have shown that coastal propagations originating from the tropical Pacific also may have contributed to coastal NEP anomalies during this EN. Our results indicate that at least some of this coastal anomaly signal may have been generated by regional atmospheric forcing within the NEP.

Calculating Tropical Winds from Time Mean Sea Level Pressure Fields

Abstract The time-mean tropical surface momentum balance is investigated with a simple model that calculates tropical surface winds from time mean sea level pressure fields. The model domain is the global tropical strip centered on the equator with lateral boundaries at ±30° latitude. Steady state surface winds are numerically calculated from the nonlinear horizontal momentum equations, with forcing from observed climatological monthly mean sea level pressures and prescribed lateral boundary winds. Dissipation is parameterized by linear damping and diffusion. Comparisons of model winds with observed climatological monthly mean winds show realistic simulations in most regions and in all months. The poorest simulations occur in the meridional component of the wind in near-equatorial areas of strongly convergent or weak winds. In these areas, and in the near-equatorial region generally, diffusion processes make a significant positive contribution to the realism of the model winds. Horizontal nonlinear advect...

Observed and simulated Northern Hemisphere intraseasonal circulation anomalies and the influence of model bias

Abstract The ability of an atmospheric general circulation model to simulate the observed primary modes of intraseasonal variability in the Northern Hemisphere upper-tropospheric winds during boreal winter is examined. The model used is the Navy Operational Global Atmospheric Prediction System. The authors examine differences between the observed and modeled modes of variability in the context of various model deficiencies, where the observed modes are derived from the European Centre for Medium-Range Weather Forecasts analyses. Rotated empirical orthogonal function analysis is used to determine the primary modes of variability in the Pacific and Atlantic regions. EOFs are computed for both the zonal and meridional wind components. Time-lagged composite analysis is used to examine the temporal evolution of these modes, as well as their relationship to tropical convection. Wave activity flux vectors are used to examine further the characteristics of these intraseasonal modes and their relationship to tropi...

Certification for Oceanographic Professionals: A Needs Assessment Study

There has been rapid growth in recent years in operational oceanographic activities, especially in association with the growth in ocean observing systems. At the same time, the attention given by the public to ocean issues has greatly increased. These factors along with the increasing complexity and multidisciplinary nature of oceanography suggest that the need for certification of oceanographic professionals may also be increasing (e.g., in association with coastal development, natural disasters, ocean pollution, declining fish stocks). Certification is a way to recognize that an individual has demonstrated professional competence and integrity in an occupational field.

Are we adequately preparing students for ocean occupations

The California Centre for Ocean Science Education Excellence (California COSEE) and the Marine Advanced Technology Education (MATE) Centre services to provide access to accurate information about ocean careers and employment opportunities so they can make informed choices concerning their career, education, and future. The website, www.oceancareers.com, is an extensive relational database composed of information on careers, educational competencies, and professional competencies, and employers, educational competencies and professional societies.

OceanCareers.com: Navigating Your Way to a Better Future

The ocean attracts and inspires thousands of students every year to pursue degrees in science, engineering, and technology. Yet, in spite of all the attention paid to the oceans, students often lack the information needed to make wise decisions about choosing an ocean-related career. The Center for Ocean Science Education Excellence - California 1

MATE Center: Ocean Career Website

OTC 17000, This paper was prepared for presentation at the Offshore Technology Conference held in Houston, Texas, U.S.A. 3-6 May 2004.

MATE Center: A Strategy for Improving Marine Technical Education

OCT 16996, This paper was prepared for presentation at the Offshore Technology Conference held in Houston, Texas, U.S.A., 3-6 May 2004.