Ha-Hm

 

habitat

The space used by an organism together with the other organisms with which it co-exists and the landscape and climate elements that affect it. See Heywood (1995).

 

haboob

A name applied to lens-shaped dust walls generated from the surface outflow (i.e. downburst) portion of a mature thunderstorm cell. They last about three hours with an average maximum wind velocity of about 30 mph and dust rising to heights exceeding 1000 meters. These are found in SW North America from May through September, most frequently in June. They are also found in the Sudan north of about 13 N and occur from about May to September, most frequently in the afternoon and evening. The name is derived from the Arabic habb meaning wind.

 

hadal

More later.

 

Hadley Cell

A part of the atmospheric circulation system extending from the Equator to 30 latitude on both sides of the Equator. It is a thermally-driven system in which heated air rises at the Equator, flows poleward, cools and descends at subtropical latitudes, and then flows back towards the Equator. This description was suggested by Hadley in the 18th century.

 

hadopelagic zone

One of five vertical ecological zones into which the deep sea is sometimes divided. The is the lowest of the levels and is separated from the overlying abyssopelagic zone at about 6000 meters. See Bruun (1957).

 

Haida Current

A narrow, poleward flowing surface current over the continental slope of northwestern British Columbia and southwestern Alaska. It is seasonal, occuring predominantly between October and April with maximal flow taking place in midwinter from November through February. Its characteristics include a minimal length of 200-300 km, a width of 20-30 km, a depth scale of 500 m, a near-surface speed typically around 0.1 m s , and a near-surface temperature signature about 1 C greater than ambient. The temporal variability is not well known, although it evinces spatial variability in the form of large-amplitude (around 10 km) mesoscale waves and eddies. The primary driving mechanisms are wind stress and alongshore sea surface slope. See Thomson and Emery (1986).

 

Hale cycle

A 22-year cycle in solar activity which is a combination of the 11-year cycle in sunspot number and the reversal of the magnetic polarity of adjacent pairs of sunspots between alternate cycles. See Burroughs (1992).

 

half-life

The time in which half of the atoms of a given quantity of radioactive nuclide undergo at least one disintegration.

 

haline

Related to salinity.

 

Halmahera Sea

A regional sea located in the central eastern part of the Australasian Mediterranean Sea. It is centered at about 1 S and 129 E and is bordered by the Pacific Ocean to the north, Halmahera to the west, Waigeo and Irian Jaya to the east, and the Seram Sea to the south. It covers about 95,000 km and the topography comprises a number of separate basins and ridges, the chief of which is the Halmahera Basin reaching a depth of 2039 m. Other prominent geographic features include Kau Bay (between the two northward pointing lobes of Halmahera), Buli Bay (between the two eastward pointing lobes), Weda Bay (between the two southward point lobes), the Jailolo, Bougainville and Dampier Straits connecting it to the Pacific, and the Obi Strait connecting it to the Molucca Sea.

The surface salinities range from 34 (March through May) to 34.6 (September through November) and the temperatures from 25.7 C in August to 28.6 in May. The surface currents are variable with the seasonal monsoon winds. The deep water in the Halmahera Basin is renewed by water from the Pacific which passes from north to south over sills 700 m and 940 m deep. The surface waters are a mixture of oxygen rich Pacific water and oxygen poor water from the Seram Sea. See Fairbridge (1966).

 

Halobates

An entirely marine genus (Hemiptera: Heteroptera) of thirty-nine known species of wingless bugs commonly known as ocean-striders. These are related to the more familiar pond-skaters found in inland waters and the only known insects to have successfully invaded the open ocean hundreds of miles away from shore. Thirty-two of the species live in nearshore habitats with limited distributions (with some endemic to specific groups of islands), while the other seven species are known to occur only on the open ocean far from land. These latter species live exclusively on the sea surface, a stratum occupied by no other marine animals. See Cheng (1973).

 

halocarbon

Any of several radiatively-active (i.e. greenhouse) gases that are compounds of carbon with fluorine and chlorine.

 

halocline

In oceanography, a relatively sharp change in salinity with depth.

 

HALOE

Abbreviation for Halogen Occultation Experiment, an ozone measuring experiment performed using UARS. See Russell and et al. (1993).

 

halophytes

Plants which find their optimum growth condition in saline soils.

 

HAMOCC

Acronym for Hamburg Model of the Ocean Carbon Cycle.

 

HAPEX-MOBILHY

Acronym for the Hydrological Atmospheric Pilot Experiment-Modelisation du Bilan Hydrique. See Noilhan et al. (1991).

 

HAPEX-Sahel

Acronym for Hydrological and Atmospheric Pilot Experiment in the Sahel, a land-surface-atmosphere observation program that was undertaken in western Niger in the west African Sahel region. The goals of the project were to improve understanding of the role of the Sahel on the general circulation, in particular the effects of the large interannual fluctuations of land surface conditions in this region and, in turn, to develop ideas about how the general circulation is related to the persistent droughts that have affected the Sahel during the last 25 years. The field program measured atmospheric, surface and sub-surface properties in a 1 by 1 grid that incorporated examples of many of the major land surface types found throughout the Sahel. See the HAPEX-Sahel Web site.

 

Happel, Eberhard (1647-1690)

A German writer of epics, romance and adventure who published a book entitled Groste Denkwurdigkeiten der Welt oder Sogenannte Relationes Curiosae in 1985 which contained the second chart ever to depict the global ocean circulation. His chart and explanations were very similar to those of Kircher's previous and first-published chart. He also favored the explanation for the tides that had water being withdrawn from the oceans through the north pole and expelled from the south pole, although differing slightly from Kircher on the matter of timing. Happel had the water being withdrawn and discharged at special hours rather than just being rhythmically passed through the earth. See Peterson et al. (1996).

 

harbor wave

A type of seiche found in harbors. The Japanese word ``tsunami'' means ``harbor wave'' but is a misnomer for what is really a seismic sea wave, more popularly (and even more incorrectly) known as a tidal wave.

 

harmattan

A dry wind blowing from a northeast or sometimes easterly direction over northwest Africa. The southern limit is about 5 N in January and 18 N in July. It is dry and cool and thus a welcome relief from the steady damp heat of the tropics, and as such is is known locally as ``the doctor'' for its supposed health-giving powers. This is in spite of the fact that it carries with it great quantities of dust from the desert, often carried in sufficient quantity to form a thick haze and impede navigation on the rivers.

 

harmonic

A frequency that is a simple multiple of a fundamental frequency. A second harmonic, for example, would have twice the frequency of the fundamental.

 

Haro Strait Experiment

See the Haro Strait Experiment Web site.

 

HaRP

Acronym for Hawaiian Rainband Experiment. The planning phase took place during 1988-89.

 

Harrison, John (1693-1776)

See Peterson et al. (1996), p. 53.

 

Hartley bands

The spectral bands in which solar radiation is most strongly absorbed by ozone. These cover the region from 2000 to 3000 Angstroms and are centered at 2553 Angstroms. The absorption of solar flux in these bands takes place primarily in the upper stratosphere and the mesosphere. See Liou (1992).

 

Hauterivian

The third of six ages in the Early Cretaceous epoch, lasting from 131 to 124 Ma. It is preceded by the Valanginian age and followed by the Barremian age.

 

Hawaii-Tahiti Shuttle Experiment

See Wyrtki et al. (1981).

 

HCFC

Abbreviation for hydrochlorofluorocarbon.

 

HDP

Abbreviation for Human Dimensions of Global Environmental Change Programme, an ISSC program.

 

Heard Island Feasibility Test (HIFT)

An ocean acoustical tomography experiment in which computed geodesics (minimum paths) for acoustics transmissions were compared with observations. The acoustic source was suspended from the R/V Cory Chouest 50 km southeast of Heard Island located about halfway between Africa and Australia at about 50 S in the South Indian Ocean. Receiver arrays were located on various research vessels throught the oceans as well as at South Africa, Bermuda, India, Christmas Island, Samoa, Hobart (Tasmania) and Monterey (California). See Baggeroer and Munk (1992) and Munk et al. (1995).

 

heat capacity

The heat capacity of a body is the product of its mass and its specific heat.

 

heat equator

See thermal equator.

 

HEIFE

Acronym for the Heihe River Basin Field Experiment. See Chou et al. (1992).

 

Heinrich Events

This refers to a set of sedimentary layers in cores from the North Atlantic that Heinrich (1988) first conjectured corresponded to the melting of six huge armadas of icebergs during the last 130,000 years. Further investigations Broecker (1994) have suggested that each event triggered a climate response of global extent during the last glaciation.

 

HELCOM

Abbreviation for Helsinki Commission - Baltic Marine Environment Protection Commission, the governing body of the Convention on the Protection of the Marine Environment of the Baltic Sea. The aim of the commission is to protect the marine enviroment of the Baltic Sea from all sources of pollution. See the HELCOM Web site.

 

Helium-3

An isotope of helium that is useful in ocean tracer studies. There are two sources for Helium-3 in the ocean: volcanic sources at mid-ocean ridge crests and the decay of man-made tritium. The former source makes helium-3 a unique tracer due to its being injected into the middle of the water column. This leads, for example, to a stark contrast in helium-3 content between incoming and outgoing deep waters in the Pacific. It also provides a dramatic picture of the relative movement of helium poor NADW and helium rich (due to sources in the Pacific) ACC water. The helium-3 tritium decay (sometimes called trituigenic) source is much larger than the deep sea sources, with the global average of the latter being about 4 at/cm2/s as opposed to a northern hemisphere average of about 32 at/cm2/s for the former.

Helium-3 is used in combination with tritium to date water on timescales of 0-10 years with a resolution of around 0.1 years (in North Atlantic surface waters). It is better to treat them as separate but related tracers on longer timescales or in the presence of extensive mixing. Their relationship is a diagnostic of vertical versus horizontal mixing, and has been used to assess an upper limit to vertical mixing that is consistent with physical estimates. This has also been used to show that horizontal mixing is the dominant mechanism of thermocline ventilation in subtropical gyres. See Sarmiento (1988) and Broecker and Peng (1982).

 

Helland-Hansen, Bjorn

More later.

 

hemipelagic

Or or pertaining to continental margins and the adjacent abyssal plains.

 

Henry's law

To be completed.

 

HESS

Acronym for High Latitude Ecosystems as Sources and Sinks of Trace Gas, and IGAC activity.

 

Hesse's Rule

An ecogeographical rule, also known as the heart-weight rule, that states that extra metabolic work done to maintain heat in a cold environment causes a greater volume and mass of heart in animals living there as compared with their counterparts in warmer regions. This was propounded by Richard Hesse in 1937 and is basically an extension of Bergmann's Rule.

 

heterochrony

In paleobiology, the phenomenon of changes through time in the appearance or rate of development of ancestral characters. It involves the decoupling of the three elements of growth: size, shape, and time, or the extension or contraction of these elements. Temporal changes of size and shape relative to one another produce heterochrony, when either size or shape, or both, are affected by changes in their rate of ontogenetic development. The two basic forms are differentiative and growth heterochrony. See Briggs and Crowther (1990), pp. 111-119, or McKinney and McNamara (1991) for a book-length treatment.

 

heterogeneous nucleation

See GPC.

 

Heteropoda

A superfamily of transparent planktonic animals within the order Mesogastropoda that comprises three families: (1) the Atlantidae which are characterized by a calcareous transparent shell which can contain the entire animal and a laterally flattened fin-like foot with an operculum and a sucker; (2) the Carinariidae with shells very much smaller than the animal whose foot is transformed into a fin and carries a sucker but no an operculum; and (3) the Pterotracheidae with no shell, a flattened and elongate foot without an operculum, and a sucker present in the male. See Thiriot-Quievreux (1973).

 

heterosphere

One of two atmospheric layers in a classification scheme based on homogeneity of composition. This is the atmospheric layer that starts at about 80-90 km in which molecules can be dissociated into atoms and/or ionized by absorption of energetic short-wave radiation. This is almost coincident with the ionosphere, although the ionosphere is usually thought to start a little lower at around 70-85 km. This sits above the homosphere, the lower level in this scheme.

 

heterotroph

Descriptive of a phytoplankton species which obtains the nutrients it needs (e.g. carbon, nitrogen, phosphorous, sulfur, etc.) from dissolved or particulate organic sources. Heterotrophs which feed on phytoplankton or detritus are called phagotrophs.

 

heterotrophic respiration

The form of respiration by which organic matter is converted back into CO2, mainly by soil micro-organisms.

 

heton

To be completed.

 

HEXOS

Acronym for Humidity Exchange Over the Sea, a program to measure water vapor and droplet fluxes from sea to air at moderate to high wind speeds. See Katsaros et al. (1987).

 

HF

Abbreviation for high frequency, an electromagnetic spectrum waveband ranging from 3 to 30 MHz.

 

HFC

Abbreviation for hydrofluorocarbon.

 

HIFT

Acronym for Heard Island Feasibility Test.

 

high

Abbreviated form for high pressure center.

 

high pressure center

In meteorology, a region of relatively high barometric pressure. These are characterized by subsidence at altitude and by divergence near the surface. They predominate at 30 and 90 latitude where the global generation circulation patterns exhibit downward motion. This type of circulation feature is also known as an anticyclone and as such rotates clockwise/counterclockwise in the norther/southern hemisphere. High pressure systems are generally characterized by clear skies and fair weather since cloud development is impeded therein, and winds are also generally light.

 

HiHo HiHo Experiment

Acronym for Harmonious Ice and Hydrographic Observations - Heat In, Halide Out Experiment, a Antarctic CRC experiment to study the Antarctic pack ice during winter. The project aims include: (1) providing a quantitative assessment of the mass budget and Antarctic winter sea ice and to relate this to the rate of water mass modification; (2) providing a quantitative estimate of the surface energy exchanges in the winter Antarctic sea ice zone and, in conjunction with FORMEX, to relate surface vertical energy exchange to the ocean heat budget and advection; and (3) describing the processes by which new ice deforms and thickens and the atmospheric and ocean forcing which determine these processes. See the HiHo Web site.

 

HIMSS

Acronym for High-Resolution Microwave Spectrometer Sounder.

 

HIPP

Acronym for Himalayan Interdisciplinary Paleoclimate Project, an initiative aimed at improving the understanding of past changes in the behavior of the Indian and Plateau monsoons over the past 2000 years, 20,000 years, and beyond through the collection and analysis of high resolution, multivariate paleoclimatic records from the highlands of central Asia. See the HIPP Web site.

 

HIRDLS

Acronym for High-Resolution Dynamics Limb Sounder, an infrared limb-scanning radiometer designed to sound the upper troposphere, stratosphere, and mesosphere to determine temperature; the concentrations of O3, H2O, CH4, N2O, NO2, HNO3, N2O5, CFC11, CFC12, and aerosols; and the locations of polar stratospheric clouds and cloud tops. The goals are to provide sounding observations with horizontal and vertical resolution superior to that previously obtained; to observe the lower stratosphere with improved sensitivity and accuracy; and to improve understanding of atmospheric processes through data analysis, diagnostics, and use of two- and three-dimensional models. This is due to fly on NASA's EOS around the year 2002. See the HIRDLS Web site.

 

HIRIS

Acronym for High Resolution Imaging Spectrometer.

 

HIRLAM

Acronym for HIgh Resolution Limited Area Model, an international project to develop and maintain a numerical short-range weather forecasting for operational use by participating institutes. The project was started in 1985 and is now in the third phase. The HIRLAM model is at version 2.5 (as of 12/95) and the reference or standard version is kept at the ECMWF. See the HIRLAM Web site.

 

HIRS

Abbreviation for High Resolution infrared Sounder, a 20 channel scanning radiometer with infrared channels in the 15 and 4 micrometer regions plus 1 visible channel. The nadir resolution of HIRS is 17.4 km. This is part of the TOVS instrument package.

 

HIS

Acronym for High-resolution Interferometer Sounder, an instrument that obtains vertical profiles of atmopheric temperature and moisture from measurements of upwelling atmospheric radiation. It is currently flown aboard the NASA ER2 aircraft. See the HIS Web site.