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.

 

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.

 

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.

 

magnetic declination

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

 

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 the inferred periodic polarity 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. This 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 and polarity superchrons (previously called polarity events).

 

magnetostratigraphy

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

 

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.

 

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

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.

 

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).

 

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 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).

 

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.

 

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.

 

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.

 

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.

 

MCA

Abbreviation for moist convective adjustment.

 

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 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

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.

 

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.

 

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 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 deg. 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).

 

MEDOC

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

 

meiobenthos

See benthos.

 

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.

 

MESA

Acronym for Maximum Entropy Spectral Analysis.

 

mesopelagic

The oceanic 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 is the middle of three layers in the pelagic zone, the other two being the upper euphotic the lower bathypelatic zones.

 

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.

 

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.

 

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.

 

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.

 

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).

 

MILDEX

Acronym for MIxed Layer Dynamics EXperiment.

 

MILE

Acronym for MIxed Layer Experiment.

 

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

See MindanaoEddy.

 

Mindanao Eddy

A cyclonic circulation gyre or eddy to the east of Mindanao centered at about 8 deg. N and 135 deg. E. The southward flowing section near the coast is called the Mindanao Current with the southward flow not extending beyond a depth of 250 m. A deep western boundary current flows northward below this (from 250 to 500 m) at a rate of 16-18 Sv. The transport is estimated at around 25-35 Sv with strong interannual variations.

 

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.

 

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 60 to 100 m depth caused by wind stirring and convection.

 

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.

 

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.