Ma-Mm

 

MAA

Abbreviation for Moist Adiabatic Adjustment.

 

Maastrichtian

The last of six ages in the Late Cretaceous epoch, lasting from 74.5 to 66.4 Ma. It is preceded by the Campanian age and followed by the Danian age of the Paleocene epoch. It is characterized by chalk limestones throughout western Europe.

 

MAB

Abbreviation for Man and the Biosphere program, a UNESCO project.

 

MACAWS

Acronym for Multi-center Airborne Coherent Atmospheric Wind Sensor, an airborne, pulsed, scanning, coherent, Doppler laser radar (lidar) that directly measures wind velocity and aerosol backscatter distribution in a 3-D volume in the troposphere and lower stratosphere. It flies on the NASA DC-8 research aircraft. See the MACAWS Web site.

 

Mach number

More later.

 

MACISS

Acronym for the Meteorological and Climatological Information Server Searcher, a suite of software that collects the addresses of servers, extracts information from the servers, and adds this information to a searchable database. MACISS searches servers that are thought to contain a meteorological, climatological, or atmospheric science component. See the MACISS Web site.

 

macrobenthos

See benthos.

 

macroevolution

Evolution above the species level.

 

macrofossil

See microfossil.

 

MACS

Acronym for Middle Atmosphere in the Climate System, an IAGA program.

 

MADAM

Acronym for Mediterranean Assistance and Data Management in Oceanography, an initiative to set up and run an infrastructure to provide assistance in the field of oceanographic data management to the MTP, including the different subprojects and associated MAST projects. The general objective of MADAM is to compile and produce an up-to-date dataset, the MTP Data Set, comprising data from the MTP as well as a set of basic tools for the scientific use of the data. Secondary objectives include managing and making available the data set during the course of MTP, set up and running a network to provide links between associated scientists, and providing support for subprojects for specific data handling problems. See the MADAM Web site.

 

Madeira Mode Water

A type of Mode Water formed north of Madeira in the North Atlantic Ocean. It is characterized by a summer thermostad at 70-150 m depth and provides a major contribution to the formation of North Atlantic Central Water (NACW). See Siedler et al. (1987).

 

MAESA

Acronym for Measurements for Assessing the Effects of Stratospheric Aircraft, a program whose focus was to provide information about stratospheric photochemistry and transport for assessing the potential environmental effects of stratospheric aircraft. It was conducted in concert with ASHOE in four phases through the Antarctic winter of 1994. See the MAESA Web site.

 

maestro

A northwesterly wind in the Adriatic, most frequent on the western shore and in summer. This is also applied to northwesterly winds in other parts of the Mediterranean.

 

MAGE

Acronym for Marine Aerosol and Gas Exchange, an IGAC activity.

 

magnetic declination

The difference between Magnetic North (South) and Geographical North (South).

 

magnetic field reversals

Cooling lava flows acquire a direction of magnetization parallel to that of the earth's magnetic field as the iron-rich particles within align themselves parallel to that field. The discovery of this effect by Bernard Brunhes in 1906 led to the measurement of the direction of magnetization of many ancient lava flows and, eventually, to the realization that the earth's magnetic field must have reversed itself in the past and, indeed, many times.

Skepticism concerning the multiple and worldwide nature of these reversals was eventually allayed by the use of potassium-argon dating methods to date lava flows above and below reversals in samples from widespread locations and demonstrate the synchroneity of the events. These fixed dates provided a framework on which to build a magnetostratigraphic time scale for the previous 4.5 million years.

 

Magnetic North

The direction in which the North pole of a pivoted magnet will point. It differs from Geographical North by an angle called the magnetic declination.

 

Magnetic South

The direction in which the South pole of a pivoted magnet will point. It differs from Geographical South by an angle called the magnetic declination.

 

magnetostratigraphic time scale

A time scale based on inferred periodic magnetic field reversals in the Earth's geomagnetic field. If a rock contains suitable minerals, then it will retain the magnetic orientation induced by this field at its time of formation, the orientation being described as either a normal or reversed state of the field. The correlation of these normal and reversed patterns among many different successions of rocks at widespread geographic locations has resulted in a sequence of orientations that, when combined with a dating method such as potassium-argon dating, provides a magnetostratigraphic time scale measured in units of normal or reversed polarity. The scale presently extends back to the Early Jurassic (about 200 Ma).

The basic unit for this scale is the polarity epoch or, more recently (and officially), polarity chron and represents a time period over which the magnetic field is constantly or predominantly of one polarity. Smaller and larger units are called, respectively and unsurprisingly, polarity subchrons (previously called polarity events). and polarity superchrons.

 

magnetostratigraphy

Stratigraphy based on the geomagnetic polarity reversals on which the magnetostratigraphic time scale is based.

 

MAGNETT

Acronym for Measurements of Anthropogenic Gases and Natural Emissions from Tall Towers, a NOAA CMDL program which uses existing tall (> 400 meters) towers as sampling platforms for in situ and flask sample analyses of atmospheric trace gases. The program began in June 1992. See the MAGNETT Web site.

 

MAGS

Acronym for the Mackenzie River GEWEX Study, a series of large-scale hydrological and related atmospheric and land-atmosphere studies to be conducted within the Mackenzie Basin in Canada. More information can be found at the MAGS Web site.

 

MAHLOVS

Acronym for Middle and High Latitude Ocean Variability Study.

 

Makaroff Deep

See Guiana Basin.

 

Maluku Sea

See Molucca Sea.

 

Malvinas Current

A jet-like northward looping extension of the Antarctic Circumpolar Current located in the southwest Atlantic Ocean. The cold waters of this current form an intense front with the warm waters of the Brazil Current as it separates from the continental shelf at around 35 S. This is also called the Falkland Current. See Tomczak and Godfrey (1994).

 

MAMBO

Acronym for Mediterranean Association of Marine Biological Oceanography, an ICSU project.

 

mammal

A member of the class Mammalia.

 

Mammalia

A class of the subphylum Vertebrata of the phylum Chordata. These are warm-blooded, air-breathing animals with hair and mammary glands. The orders that include marine mammals include Carnivora, Pinnipedia, Sirenia and Cetacea. Members of this class include sea otters, seals, walruses, sea cows, manatees, whales and dolphins.

 

MAMS

Acronym for Multispectral Atmospheric Mapping Sensor, a multispectral scanner which measures reflected radiation from the Earth's surface and clouds in eight visible/near-infrared bands, and thermal emission from the Earth's surface, clouds and atmospheric constituents (primarily water vapor) in four infrared bands. It is an airborne sensor developed and flown in 1985 to verify small-scale water vapor features observed in VAS imagery aboard GOES. The data collected from MAMS will be used to identify mesoscale atmospheric moisture variations and provide visible and infrared measurements of thunderstorms. The data will also be used to characterize the structure of these features and to derive integrated water content (precipitable water) measurements for these features. See the MAMS Web site.

 

map projections

Any of an extremely large number of methods for mapping, or projecting, the spherical (well, almost) Earth onto a two-dimensional surface. An overview of map projections is available on the Web.

 

MAPS

1. Acronym for Measurement of Air Pollution from Satellites, an experiment to measure the global distribution of carbon monoxide in the free troposphere. See the MAPS Web site. 2. Acronym for Mesoscale Analysis and Prediction System, a NOAA FSL regional data assimilation and forecast system which provides high-frequency (i.e. at least every 3 hours) analyses of conventional and new data sources over the contiguous U.S. and short-range forecasts (out to 12 hours) in support of aviation and other mesoscale forecast users. See the MAPS Web site.

 

MAPSS

Abbreviation for Mapped Atmosphere-Plant-Soil System, a global biome model including resource limitation and competitive balance effects, i.e. a so-called ``second-generation'' model. See Neilson (1994).

 

marginal ice zone

An area between solid sea ice and the open ice-free sea that is only partially covered by dispersed ice floes. This can represent a large portion of the total sea area covered by ice.

 

MARGINEX

Acronym for Margin Experiment, an Antarctic CRC experiment along the continental shelf and slope region of Antarctica from 80 to 165 E whose objectives include: (1) estimating the rate of formation of surface and Antarctic Bottom Water (AABW) masses; (2) defining the evolution and modification of Antarctic water masses along the shelf and slope in this region; (3) estimating the relative importance of air-sea interaction and advection of surface and deep waters on property changes in the major water masses; and (4) constructing numerical models of the formation and dynamics of water masses south of the Antarctic Convergence over the full seasonal cycle. See the MARGINEX Web site.

 

Margules' equation

In physical oceanography, an equation that allows the estimation of the slope of the surface density discontinuity associated with geostrophic motions in the sea and of fronts in the atmosphere from a knowledge of the component speeds of geostrophic motion along the interface and the density difference across the interface. The equation is given by

where is a finite increment of vertical distance, a finite increment of horizontal distance along the dip of the interfacial slope, f the Coriolis parameter, g the gravitational acceleration, the density, and c the geostrophic velocity parallel with one side of the interface, and the primed variables the values of corresponding properties on the other side. This equation is helpful in clarifying the sometimes confusing problem of estimating the change of frontal slope as a function of latitude or a change in density contrast across the front at the same latitude but with different velocities of flow. See Von Arx (1962).

 

marine biogeography

See Hedgpeth (1957a).

 

marine bioluminescence

See Tett and Kelly (1973).

 

marine palynology

The study of pollen deposits in marine sediment records. See Stanley (1969).

 

marine pollution

See Duursma and Marchand (1974).

 

marine snow

Oceanic particles which are amorphous, heterogeneous aggregates greater than 500 m and composed of detrital material, living organisms and inorganic matter. See Alldredge and Silver (1988).

 

Marine Technology Society (MTS)

An international, interdisciplinary society devoted to ocean and marine engineering, science and policy. Its objectives are to disseminate marine science and technical knowledge, promote and aid education of scientists and other involved in marine fields, and advance the development of tools to explore, study, preserve and exploit the oceans. MTS publishes the ``MTS Journal.'' See the MTS Web site.

 

MARIS

Acronym for the MARine Information Service, a project in the Netherlands to improve the overview of and access to marine expertise, information, and data related to the sea and its uses. See the MARIS Web site.

 

Maritime Province Current

See Mid-Japan Sea Current.

 

Marmara Sea

A marginal sea centered near 28.5 E and 40.5 N whose primary significance is to serve as part of the connection between the Black Sea and the Mediterranean Sea. It reaches 75 km in width, 250 km in length, has a surface area of about 11,500 km , and a maximum depth of 1390 m. It is located between the Bosporus Strait to the northeast (which connects to the Black Sea) and the and the Dardanelles to the west (which connects to the Aegean Sea).

The northern part of the Marmara comprises three topographic depressions. The eastern (1240 m), central (1389 m) and western (1097 m) basins are connected by sills about 750 m and widths (from west to east) of 20 km and 40 km. The southern continental shelf is shallow (100 m) and wide (30 km), while the northern shelf is much narrower (< 10 km).

The mean upper layer circulation is a basin scale anticyclonic gyre driven mainly by the sea level differences between the Black Sea and the Aegean Sea. This gyre is modified by the Bosphorous jet during high outflow conditions in spring and early summer and by the wind stress during the winter. See Besiktepe et al. (1994).

 

MARSEN

See Hasselmann and Shemdin (1982).

 

Count Marsigli (1658-1730)

See Peterson et al. (1996), p. 32.

 

Marsipobranchii

See Agnath.

 

MARVOR

Abbreviation for Marvor float, a multicycle RAFOS type float developed by IFREMER and TEKELEC (now MARTEC). A MARVOR float cycles several times between the surface and its planned depth during its mission. When it surfaces it sends the data collected to the ARGOS satellite which relays it to land-based stations. It is equipped with a hydraulic system that controls its depth by transferring oil from an internal reservoir to the external ballast. See Ollitrault and et al. (1994) and the MARVOR Web page at the IFREMER Web site.

 

MAS

Acronym for Millimeter-wave Atmospheric Sounder, an instrument designed to study the formation and distribution of ozone by measuring emission lines of ozone, water vapor, and chlorine monoxide from the Space Shuttle. The MAS scans the limb of the earth to produce maps of the global distribution of these trace molecules as a function of altitude. See the MAS Web site.

 

MASIG

Abbreviation for Mesoscale Air-Sea Interaction Group.

 

masl

Abbreviation for meters above sea level.

 

Massenerhebung effect

The tendency for mountains to significantly modify the prevailing climate. See Collinson (1988).

 

mass spectrometry

A method for making isotope abundance measurements on gases in geochemical work. The instrument separates and detects ions on the basis of the motions of charged particles with different masses in magnetic or electrical fields.

 

MAST

Acronym for MArine Science and Technology, a research program of the European Union. THe aim of this program is to develop the scientific and technological bases for the sustainable exploitation of marine systems and determine their precise role in global change. See the MAST Web site.

 

MATE

Acronym for the Midocean Acoustic Transmission Experiment, a project of the APL of the University of Washington Department of Oceanography. It was conducted near Cobb Seamount in the Northeast Pacific Ocean about 450 km off the coast of Washington during June-July 1977. In this experiment simultaneous measurements of temperature and velocity time series, vertical and horizontal temperature profiles, and acoustic transmissions were performed to attempt to ascertain the effects of internal waves on acoustic transmissions. See Ewart and Reynolds (1984).

 

Matuyama Magnetic Epoch

Reverse polarity time interval extending from 0.6 to 2.4 million years ago. See Bowen (1991).

 

Maunder butterly

A graph of the distribution of sunspots showing heliographic latitude with time that is shaped not unlike the wings of a butterfly. See Burroughs (1992).

 

Maunder Minimum

An extended period of limited sunspot activity lasting from 1645 to 1715. It is named after the British astronomer who first called attention to it in 1890. See Eddy (1976) specifically and Foukal (1990) and Wigley (1988) generally.

 

Maury, Matthew Fontaine (1806-1873)

See Peterson et al. (1996), p. 79.

 

MAW

Abbreviation for Modified Atlantic Water.

 

Maximum Entropy Spectral Analysis

A method of analyzing time series which uses autoregressive methods to extract the maximum amount of information from the available data.

 

Mayr's Rules

These are ecogeographical rules that apply to birds. In colder climates, the number of eggs in a clutch are larger, the wings longer, and migratory behavior is more developed than in warmer climates. These were published by Ernst Mayr in 1942.

 

MBL

1. Abbreviation for Marine Biology Laboratory, located at WHOI. 2. Abbreviation for marine boundary layer.

 

MCA

Abbreviation for moist convective adjustment.

 

MCM

Abbreviation for mechanical current meter.

 

MCSST

Abbreviation for multichannel sea surface temperature, a satellite data set derived from the TIROS-N/NOAA series satellite AVHRR. See Wick et al. (1992).

 

mean

A statistical property of n numbers that is their sum divided by m. The mean of a probability distribution is called its expected value. Constrast with median and mode.

 

mean meridional circulation

An average circulation feature or cell defined to consist of the zonal-mean meridional and vertical velocities. In the tropics and subtropics this mean meridional circulation cell is known as the Hadley cell and in midlatitudes as the Ferrel cell.

 

mean noon

The instant at which the mean Sun crosses the meridian at upper culmination at any place. The meridian of Greenwich is usually meant.

 

mean sea level

See Lisitzin (1963).

 

mean solar day

The interval, perfectly constant, between two successive transits of the mean Sun across the meridian.

 

mean solar time

Time as measured by the hour angle of the mean Sun. It is counted from midnight, and when referred to the meridian of Greenwich is called Greenwich Mean Time.

 

mean Sun

A fictitious reference point which has a constant rate of motion and is used in timekeeping in preference to the non-uniform motion of the real Sun. The mean Sun is imagined to follow a circular orbit along the celestial equator and is used to measure mean solar time.

 

MECCA

1. Acronym for Model for Estuarine and Coastal Circulation Assessment. 2. Acronym for Model Evaluation Consortium for Climate Assessment, created in 1991 with the goals of performing numerical experiments that will identify and quantify the uncertainties associated with predictions of greenhouse gas-induced climate change for models used to advise public policy, to create a protocol for analyzing the experimental results and applying them to policy, and to communicate findings in order to advance model development. See the MECCA Web site.

 

MEDALPLEX

Acronym for the Mediterranean Alpine Experiment, a part of the GARP subprogram on airflow over and around mountains. The primary function of MEDALPLEX was to study the response of the western part of the Mediterranean to wind forcing. See the MEDALPLEX Web site.

 

MEDALUS

An international research project to investigate the effects of desertification on land use in Mediterranean Europe. See the MEDALUS Web site.

 

MEDATLAS

A project to create a hydroraphic data bank for the Mediterranean Sea. The objectives are to create a data project which includes an update of currently available data sets, a quality control of the data set in conformance with IOC and MAST recommendations, revised climatological statistics for the Mediterreanean Sea, and making the final product available electronically. See the MEDATLAS Web site.

 

meddy

A subsurface lense of Mediterranean Water. These rotating lenses serve to transport the Mediterranean Water in their cores as far afield as the Sargasso Sea. Over the long term these meddies, each slowly releasing its surplus of heat and salt, inject their contents into and serve to partially form the upper part of North Atlantic Deep Water (NADW).

 

MEDEA

Acronym for Measurements of Earth Data for Environmental Analysis.

 

median

The value of the middle item of a group of data arranged according to size. The median of a probability distribution is the value on the horizontal scale through which a vertical line dividing the area into two equal parts passes. Contrast with mean and mode.

 

Medieval Maxima

A period of increased sunspot activity lasting from approximately 1120 to 1280. See Foukal (1990) and Wigley (1988).

 

Medieval Warm epoch

See Little Climatic Optimum.

 

mediolittoral zone

The second (from the surface) of seven zones into which the benthos has been divided. In this zone organisms are more or less regularly emerged and submerged, usually by the action of the tides. Species are here adapted to resist prolonged emersion and are generally incapable of living if continually emerged. See Fairbridge (1966).

 

mediterranean sea

A generic term used to describe a class of ocean basins that have limited communication with the major ocean basins and in which the circulation is dominated by thermohaline forcing. This causes a circulation that is the reverse of that found in the major basins, i.e. it is driven by salinity and temperature differences and only modified by wind action. Mediterranean seas exhibit the dynamics of estuaries rather than those of open oceans. Examples include the Arctic Mediterranean Basin, Australasian Mediterreanan Basin, and of course the Mediterranean Sea.

Mediterranan seas can be further distinguished by their balance of precipitation and evaporation. If evaporation exceeds precipitation, the deep vertical convection occurs and the water below the sill depth is frequently renewed. The open ocean connection features inflow in the upper layer and outflow in the lower layer since the inflow is driven by the freshwater loss in the upper layer. This is called a concentration basin.

If precipitation exceeds evaporation, then the surplus of fresh water in the upper layer drives an outflow of surface water into the connecting major basin. The decrease in surface density also results in an increased pressure difference at the connecting sill which in turn results in inflow in the lower layer and even more outflow in the upper layer. A very sharp pycnocline is established which inhibits the renewal of the deep waters. This type of basin can be depleted in oxygen even to the point of anoxia in the lower layer. This is known as a dilution basin.

 

Mediterranean Sea

See Robinson et al. (1992).

 

Mediterranean Surface Water

See Perkins and Pistek (1990).

 

Mediterranean Water

In physical oceanography, a water mass formed in the arid eastern Mediterranean Sea that flows westward and sinks in the Algero-Ligurian and Alboran basins to depth of about 500 m due to its relatively high salinity of 36.5 to 39.1. It continues westward into the Atlantic Ocean through the shallow Straits of Gibraltar (at depths below 150 m) where it sinks to about 1000 m, forming a distinctive water mass with a temperature of 11-12 C and a salinity of 36.0-36.2. It can be recognized as a salinity and temperature maximum near 1000 m. This is also denoted as EMW or Eurafrican MW to distinguish it from Australasian MW. See Tomczak and Godfrey (1994).

 

MEDMEX

Acronym for Mediterranean Models Evaluation Experiment, whose aim is to achieve an intercomparison of existing models that have been applied to the Mediterranean Sea. See the MEDMEX Web site.

 

MEDOC

Acronym for MEDiterranean Ocean Circulation. See Group (1970).

 

MEDS

Acronym for Marine Environmental Data Service, a branch of Canada's DFO whose mandate is to manage and archive physical and chemical oceanographic data collected by DFO regions or acquired through various arrangements from Canadian researchers and from foreign research conducted in the major ocean areas adjacent to Canada. See the MEDS Web site.

 

MEHALICE

Acronym for Methane and Halocarbons Intercalibrations Experiment, and IGAC task.

 

meiobenthos

See benthos.

 

MEL

Acronym for the Master Environmental Library, a distributed environmental data access system which allows users to search for, browse, and retrieve environmental data from distributed sources. This project, sponsored by the U.S. Navy's Defense Modeling and Simulation Office (DMSO), allows users to access the available environmental data by region, date, databases and keywords. See the MEL Web site.

 

meltemi

See etesian.

 

Menard, Henry

A marine geologist at Scripps who in 1958 suggested a continuous process of mid-ocean ridge development.

 

MER

Acronym for the Marine Ecosystem Response program, a research initiative jointly supported by NOAA and NSF geared toward the generation of quantitative scenarios for the impact of the climate system on marine ecosystems such as the economically significant fisheries in the northeast U.S. See the MER Web site.

 

Merian's formula

In the study of seiches and harbor resonance, this is an equation that gives the natural period of a long and narrow basin in terms of its length and depth for the various modes of oscillation. It is given by

where T is the period, a is the length of the basin, n is the mode number, g gravitational acceleration, and h the basin depth. See Raichlen (1966).

 

meridian

The great circle passing through the poles of the celestial sphere which cuts the observer's horizon in the north and south points and also passes through his zenith angle.

 

MERIS

Acronym for Medium Resolution Imaging Spectrometer, an ocean color sensor. It is a push-broom instrument that measures the radiation reflected from the Earth's surface and from clouds in the visible and near-infrared range during the daytime. The 1150 km wide swatch of the instrument is divided into 5 segments covered by 5 identical cameras having corresponding fields of view with slight overlap between adjacent cameras. The geophysical parameters derived from MERIS measurements include ocean color in open and coastal waters, e.g. chlorophyll, gelbstoffe, and other pigments, qualitative parameters such as presence ofclouds and emerged land, and atmospheric parameters like aerosol optical thickness, cloud albedo, Angstrom exponent, top pressure, and water vapor column contents. See the MERIS Web site.

 

meristic

In heterochrony, meristic characters are individual structures produced during an organism's ontogeny.

 

MERLIN

Acronym for the Multi-source EnviRonmental dispLay for INternet archives, a software system that provides access, fusion, intercomparison, interpretation and visualization of a wide variety of environmental data and derived products for researchers investigating climate and global change issues. It was developed at SSEC and further details can be found at the MERLIN Web site.

 

MERMAIDS

Acronym for Mediterreanean Eddy Resolving Modeling and Interdisciplinary Studies, a study whose main goal is to assess the internal variability of the Mediterranean thermohaline circulation as induced by deep and intermediate water formation processes and the inflow/outflow system at Gibraltar on the seasonal and interannual time scales. See the MERMAIDS Web site.

 

MESA

Acronym for Maximum Entropy Spectral Analysis.

 

mesopelagic zone

One of five vertical ecological zones into which the deep sea is sometimes divided. This is the uppermost aphotic zone from 200 to 1000 m deep where little light penetrates and the temperature gradient is even and gradual with little seasonal variation. This zone contains an oxygen minimum layer and usually the maximum concentrations of the nutrients nitrate and phosphate. This overlies the bathypelagic zone and is overlain by the epipelagic zone. See Bruun (1957).

 

mesophytes

Plants which can withstand wilting for short periods.

 

mesoscale

To be completed.

 

Mesozoic

The middle of three eras of the Phanerozoic eon, lasting from 245 to 66.4 Ma. It is preceded by the Paleozoic era and followed by the Cenozoic era and consists of the Triassic, Jurassic, and Cretaceous periods. It was characterized by great terrestrial disturbances such as the formation of mountains and much volcanic activity. The fauna was notable for the number, variety, and enormous size of the reptiles on land and in the sea, which occasionally leads to it being called "The Age of Reptiles". Flowering plants, deciduous trees, and the first birds appeared in the middle of this era.

 

Messinian

The last of six ages in the Miocene epoch (the second of two in the Late Miocene), lasting from 6.5 to 5.3 Ma. It is preceded by the Tortonian age and followed by the Zanclean age of the Pliocene epoch.

 

MESSR

Abbreviation for Multispectral Electronic Self-Scanning Radiometer.

 

metadata

Information describing a data set, including data user guide, descriptions of the data set in directories, catalogs, and inventories, and any additional information required to define the relationships among these.

 

Meteo-France

The French national weather service. See the Meteo-France Web page for more information.

 

meteoric water

Water produced by or derived from the atmosphere. Meteoric waters start as precipitation in the hydrologic cycle, and the source thereof is evaporation from oceanic surfaces.

 

Meteoric Water Line

An equation expressing a correlation between deuterium and oxygen-18 in meteoric waters. The equation is expressed as del D = 8 * del oxygen-18 + 10. See Bowen (1991).

 

meteorological equator

The latitude of the mean annual position of the equatorial trough. This is located at about N rather than on the geographical equator. See Riehl (1954).

 

Meteosat

A European geostationary meteorological satellite operated by EUMETSAT.

 

meter

The SI fundamental unit of length. It was defined (in 1983) as the distance travelled by light in a vaccum during the time interval of 1/299,792,458 of a second. The meter was originally defined as 1/10**7 of the distance on the Earth's surface between the North Pole and Equator, but later defined as in the above.

 

methane

This atmospheric trace gas is also a greenhouse gas, and a particularly effective one. It has a warming effect that is 21 time more on a molecule-for-molecule basis and 58 times more on a pound-for-pound basis than does carbon dioxide. The concentration of this in the atmosphere (1.72 ppm in 1990) has doubled since the advent of the industrial age, and has increased in concentration about 8 times faster than carbon dioxide. On the plus side, its atmospheric lifetime is only about 11 years, much less than most other greenhouse gases.

It is produced naturally by geologic sources such as venting by volcanoes and other breaks in the Earth's crust, although much of atmospheric methane is biological in origin. A large source is produced by bacteria decomposing plant and animal refuse in natural wetlands, which is estimated to produce about one-fifth of the annual emissions. Another source is intestinal gas produced by ruminant (vegetation-eating) livestock, which produces about one-sixth as much as natural wetlands. Other anthropogenic sources include rice paddies (i.e. artificial wetlands), fossil fuel extraction, animal wastes, sewage treatment, landfills, and biomass burning.

 

methanogenesis

The production of CH4 in organic soils as a result of anaerobic respiration. See Schlesinger (1995).

 

methanotrophy

The oxidation of CH4 by bacteria in the upper, aerobic layers of the soil. See Schlesinger (1995).

 

method of dynamic sections

See dynamic method.

 

methyl bromide

A broad spectrum pesticide which is a significant ozone depleting substance. This is at least 50 times more effective at destroying ozone than chlorine from CFCs on a per molecule basis, with an ozone depletion potential (ODP) of 0.6. See the EPA Methyl Bromide Web site.

 

METLA

Acronym for the Finnish Forest Research Institute, a state research organization with the duty to furnish research results for use by forest policy decision makers. See the METLA Web site.

 

Metonic cycle

A period of 19 years over which the phases of the Moon recur on the same days of the year as during the previous period. This cycle was introduced by the Greek astronomer Meton in 433 BC and is very nearly equal to 235 synodic months.

 

MEU

Abbreviation for Marine Environment Unit, a part of the Space Applications Institute at the European Commission Joint Research Center. Its purpose is to develop, demonstrate, and validate methodologies for the use of data from space and airborne platforms in both operational applications and scientific investigations related to the marine environment. The MEU is mainly involved in analyzing ocean color data collected by the CZCS, investigating the sea surface temperature of the Northwest African upwelling area, and developing hydrodynamic models to assimilate remote sensing data for process studies and as a contribution to global modeling. See the MEU Web site.

 

MF

Abbreviation for medium frequency, an electromagnetic spectrum waveband ranging from 300 kHz to 3 MHz.

 

MFRSR

Abbreviation for Multifilter Rotating Shadowband Radiometer, an instrument used in the ARM program to measure direct normal, diffuse horizontal, and total horizontal solar irradiances. The optical depth of the atmosphere at various wavelengths can be inferred from these measurements and, in turn, the optical depths can be used to derive information about column abundances of ozone and water vapor as well as atmospheric aerosols. See the MFRSR Web site.

 

MGBC

Abbreviation for Modeling Global Biogeochemical Cycles, an IGBP project.

 

MICE

Acronym for Man's Impact on Coastal and Estuarine Systems, an MAB-COMAR project.

 

MICOM

Acronym for the Miami Isopycnic Coordinate Ocean Model, a ocean circulation model that uses isopycnic coordinates in the vertical. See the MICOM Web site.

 

microfossil

A small htmlreffossilfossil. A quasi-arbitrary distinction is made between these and macrofossils by restricting the former to those discrete remains whose study requires the use of a microscope.

 

MICROFRONTS

A boundary-layer micrometeorology measurement program designed to study radiation and dissipation properties in frontal regions. The objectives were to: (1) determine the dissipation of kinetic energy in the surface layer under varying conditions; (2) determine the kinetic energy dissipation in a frontal zone as a check on previous estimates; (3) examine the nature of the coherent structures and microfronts for the case of surface heating; (4) study and modify the bulk aerodynamic relationship for use with the surface radiative temperature; (5) study the dynamic and thermodynamic effects on the atmosphere from the contrast between a small lake and the surrounding land; (6) observe the occurrences of breakdowns of the stable boundary layer and the occurrences of atmospheric gravity waves. See the MICROFRONTS Web site.

 

micropaleontology

The study of microfossils.. This term is sometimes restricted to studies of mineral-walled microfossils to distinguish it from palynology.

 

microplankton

Phytoplankton whose lengths range from 50 to 500 m. Compare to nanoplankton and ultraplankton.

 

microtektite

Tiny particles of glassy material probably formed by the collision between a planetisimal and the Earth.

 

Mid-Japan Sea Current

A slow southward cold water movement into the Polar Front in the Japan Sea. This is also known as the Maritime Province Current.

 

Milankovitch forcing

The name given to the changes in the amount or seasonal distribution of solar radiation that reaches the Earth as caused by the orbital changes predicted by Milankovitch theory.

 

Milankovitch theory

The theory that changes in the geographic distribution of solar insolation due to planetary perturbations of the Earth's orbital characteristics are the primary driving force for the cycles of glaciation seen in geological and fossil records. See Berger (1988).

 

mild slope equation

See Mei (1990).

 

MILDEX

Acronym for MIxed Layer Dynamics EXperiment, multi-institutional cooperative experiment which took place in a deep water region (4700 m) about 650 km off Pt. Conception in central California. Two ships and two floating platforms were used to make measurements of the surface meteorological forcing and the temperature and current response of the near-surface layers in the ocean. See Paduan et al. (1989).

 

MILE

Acronym for MIxed Layer Experiment.

 

MILOX

Acronym for Mid-Latitude Ecosystems as Sources and Sinks for Atmospheric Oxidants, and IGAC activity.

 

MIMR

Abbreviation for Multifrequency Imaging Microwave Radiometer, a passive microwave radiometer successor to the Special Sensor Microwave/Imager (SSM/I) that provides greater frequency diversity, improved spatial resolution, increased swatch width, and improved antenna performance. It is used to observe atmospheric and oceanic parameters such as precipitation, soil moisture, global ice and snow cover, SST, wind speed, atmospheric cloud water, and water vapor. See the MIMR Web site.

 

Mindanao Current

A southward flowing boundary current along the Philippine coast (from about 13 to 8 N at about 127 W) that closes the counterclockwise wind-driven gyre of which the North Equatorial Current (NEC) and the North Equatorial Countercurrent (NECC) are the northern and southern limbs, respectively. The westward flowing NEC splits at the Philippine coast and the Mindanao Current (MC) flows southward, carrying North Pacific subtropical thermocline and surface waters toward a region of confluence with South Pacific waters near 5 N. Part of the flow continues along the Philippines and on into the Celebes Sea, with the remainder turning eastward at the confluence and contributing to the aforementioned NECC as well as the Equatorial Undercurrent and the Northern Subsurface Countercurrent. This eastward turn also serves to spin-up a recirculation feature historically called the Mindanao Eddy, although the Eddy may be an intermittent rather than a persistent feature.

The MC is an energetic coastally trapped jet with speeds reaching over 0.9 m s at the shelf break, with a standard deviation of measured velocities of less than 0.1 m s indicating low current variability. It is broadest at the surface and narrows to a width of 150 km at 300 m depth. The average transport above the thermocline has been estimated from direct measurements to be kg s , with the estimate from hydrographic surveys virtually identical.

The MC contains distinct cores of high salinity North Pacific Central Water (NPCW) and low-salinity North Pacific Intermediate Water (NPIW), with each salinity core associated with elevated concentrations of dissolved oxygen indicative of the source connection with the subtropical gyre. See Wijffels et al. (1995).

 

Mindanao Dome

See Mindanao Eddy.

 

Mindanao Eddy

A cyclonic circulation gyre or eddy sometimes found to the east of Mindanao centered at about 8 N and 135 E. The southward flowing section near the coast is part of the Mindanao Current, and the Eddy can be thought of as the recirculation cell of this current. The southward flow does not extend beyond a depth of 250 m and is underlain by a deep western boundary current flowing northward (from about 250 to 500 m) at a rate of 16-18 Sv. The transport has been estimated at around 25-35 Sv with strong interannual variations. At least one investigation of the Mindanao Current at 8 N noted the absence of the Eddy, and as such it may be an intermittent feature of the circulation field. This has also been called the Mindanao Dome. See Tomczak and Godfrey (1994) and Wijffels et al. (1995).

 

Mindanao Sea

See Bohol Sea.

 

Mindanao Undercurrent

A northward flowing current beneath and offshore of the Mindanao Current. This has been estimated by some investigators to have speeds ranging from 0.15 to 0.30 m s and transports between 8 and 22 kg s , although others have found it to be more of a transient phenomena than a permanent circulation feature. See Wijffels et al. (1995).

 

Mindel

The Alpine name given to the Kansan glacial period.

 

Miocene

The fourth of five epochs in the Tertiary period, lasting from 23.7 to 5.3 Ma. It is preceded by the Oligocene epoch followed by the Pliocene epoch, and comprised of the Aquitanian, Burdigalian, Langhian, Serravalian, Tortonian, and Messinian ages.

 

MIPAS

Acronym for Michelson Inteferometer for Passive Atmospheric Sounding. See the MIPAS Web site.

 

MIRAGE

Acronym for Migration of Radioisotopes in the Geosphere.

 

MISR

Abbreviation for Multi-Angle Imaging Spectro-Radiometer, an EOS instrument planned for the AM satellite platforms. Nine CCD cameras fixed at nine viewing angles in four spectral bands provide top-of-atmosphere, cloud, and surface angular reflectance functions. See Diner (1991) and the MISR Web site.

 

missing carbon

This phrase refers to the difficulty in balancing the fluxes of carbon to the atmosphere via the burning of fossil fuel, forests and other biomass with the known sinks. The total ``missing'' is on the order of 3-5 Pg carbon per year, although the lower bound is within the error margins of recent estiamtes of the net oceanic sink strength, particularly if corrections to the synoptic air-to-sea CO2 influx or enhanced organic carbon sequestration fluxes are included. The upper bound is out of range of current oceanic sink strength estimates, indicating a net terrestrial sink, which implies fertilization of forest ecosystems due to increased atmospheric CO2 levels, eutrophication of terrestrial ecosystems because of fallout of anthropogenic NO3 and NH4 nutrients, aggradation of previously disturbed or undisturbed terrestrial ecosystems, or some combination thereof. See Woodwell (1995b).

 

missing forcing

This refers to possibly important climate forcing mechanisms not yet included in GCMs, whether due to neglect or difficulty. Examples include the indirect effects of sulphate aerosols, the radiative effects of trace gases other than CO2, and the forcings associated with large-scale land-use changes or the carbonaceous aerosols generated by biomass burning.

 

mistral

A northwesterly or northerly wind which blows offshore along the north coast of the Mediterranean from the Ebro to Genoa. In the region of its chief development its characteristics are its frequency, its strength, and its dry coldness. It is most intense on the coasts of Languedoc and Provence, especially near the Rhone delta. Its speeds are usually around 40 knots, but can reach over 75 knots in the delta.

 

mixed layer

In oceanography, a nearly isothermal surface layer of around 40 to 150 m depth caused by wind stirring and convection. In the winter, low surface temperatures and large waves (with their accompanying turbulent mixing) can deepen the mixed layer all the way to the permanent thermoclinethermocline. Higher temperatures and a less energetic wave climate in the summer can lead to the development of a seasonal thermocline at the base of the mixed layer that overlies the permanent thermocline.

 

mixed layer ocean

See slab ocean.

 

mixing length

A concept used in the parameterization of turbulent transport processes. According the this model, fluid masses called eddies, distinguishable from the ambient fluid, spring into existence in some undefined way and then, after moving unchanged over a certain path length, become indistinguishable from the surrounding fluid. This path length, over which the eddy mixes with the surrounding fluid, is called the mixing length. This model is analogous to the mean free path of a molecule or atom between collisions. See Liou (1992), p. 219.

 

mixing ratio

See water vapor mixing ratio.

 

MIZ

Abbreviation for marginal ice zone.

 

MIZEX

Acronym for Marginal Ice Zone Experiment. See Quadfasel et al. (1987).

 

mks system

A system of units in which the basic units are the meter, the kilogram and the second. This is not used as often as the cgs system.

 

ML-ML

Abbrevation for Marine Light-Mixed Layers, a research program designed to study mixed layer dynamics and bioluminescent plankton production. The program focuses on seasonal changes in upper layer physics and the successive populations that are responsible for bioluminescence. See Marra (1989).

 

MLOPEX

Abbreviation for the Mauna Loa Observatory Photochemistry Experiment, a major component of the GTCP. The objective of MLOPEX is to evaluate the budgets and photochemical processes of ozone, odd nitrogen and some odd hydrogen speices and to build a climatology of the distributions of photochemically important short-lived trace species in the remote troposphere. See the MLOPEX Web site.

 

MLS

Abbreviation for the Microwave Limb Sounder, a UARS instrument that provides global maps of ClO, the radical responsible for the Antarctic ozone hole. It scans the atmosphere from top to bottom at the edge, or limb, of the Earth's disc, collecting natural thermal microwave radiation emitted by gases in the atmosphere. It is specifically designed to measure ozone, chlorine monoxide, and water vapor, although it also measures atmospheric temperature and pressure. See the MLS Web site.

 

MMARIE

Acronym for the application of high performance computing techniques for the Modeling of Marine Ecosystems project, whose objectives are to create an interdisciplinary forum for the exhange of information and experience related to the projects carried out by the participants and to facilitate collaboration between the partners. These projects will focus on the implementation of existing models on high performance computers, refining the models and their algorithms, and benchmarking parallel software and validating new models. See the MMARIE Web site.

 

MM5

Abbreviation for the Fifth-Generation NCAR/Penn State Mesoscale Model. See the MM5 Web site.

 

MMM

Abbreviation for Mesoscale and Microscale Meteorology, one of five science divisions at NCAR. The primary focus of this division is on understanding atmospheric phenomena on spatial scales ranging from micrometers to megameters and time scales from seconds to a few days. See the MMM Web site.

 

MMRP

Abbreviation for Marine Mammal Research Program, a project designed to provide information on the hearing capabilities of marine mammals and sea turtles, to study the response of marine mammals and other marine organisms to man-made sounds (from the related ATOC project as well as from other sources such as shipping noise), and to provide information needed to direct policies for the long-term protection and conservation of marine species. See the MMRP Web site.

 

MMS

Abbreviation for Minerals and Management Service.