Ja-Jz

 

jackknife method

A statistical procedure in which, in its simplest form, estimates are formed of a parameter based on a set of N observations by deleting each observation in turn to obtain, in addition to the usual estimate base d on N observations, N estimates each based on N-1 observations. Combinations of these give estimates of both bias and variance valid under a wide range of parent distributions. This method has deposed distribution-based methods in many applications due to its simplicity, its applicability in complicated situations, and its lack of distributional assumptions, resulting in greater reliability in practice. An elementary review can be found in Efron and Gong (1983) and the extension of such methods to time series analysis (with several geophysical examples) is reviewed in Thomson and Chave (1991).

 

Jacobsen's method

A method suggested by Jacobsen (1927) to compute eddy coefficients using T-S diagrams. See Neumann and Pierson (1966).

 

Japan Sea

A marginal sea of the western Pacific Ocean bounded on the east by the Japanese islands, the west and southwest by Korea, and the north and northwest by the former Soviet Union. It is connected to the East China Sea in the south, the Okhotsk Sea in the north, and the Pacific Ocean in the east via narrow passages whose sill depths don't exceed 100 m. It comprises the Japan Basin (with depths exceeding 3500 m) north of about 40 deg. N, and the Yamato Basin (with depths around 2500 m) south of 40 deg. N, the the basins separated by the Yamato Ridge. The area is 978,000 km2, the average depth 1750 m, and the greatest depth about 4050 m.

Prominent circulation features in the Japan Sea include the Tshushima Current, the Tsugaru Current, the Liman Current, the North Korea Current and the Mid-Japan Sea or Maritime Province Current. Water masses found there include Japan Sea Middle Water (or Intermediate Water) and Japan Sea Proper Water.

The Japan Sea is a meeting place for warm currents from the south and cold currents from the north, with the confluence being the Polar Front.

 

Japan Sea Bottom Water

See Japan Sea Proper Water.

 

Japan Sea Deep Water

See Japan Sea Proper Water.

 

Japan Sea Middle Water

A water mass found in the Japan Sea. It is found in the depth range 25-200 m and characterized by a rapid drop in temperature from 17 to 2 deg. C as well as an oxygen maximum of 8 ml/l near 200 m depth. The warmer layers are advected in by the Kuroshio and the colder layers formed by sinking at the Polar Front and on the shelf to the north.

 

Japan Sea Proper Water

A water mass in the Japan Sea that comprises all the water below 200 m (and thus the overlying Japan Sea Middle Water). It is characterized by uniform temperature (1-2 deg. C) and salinity (34.1) which result from its isolation from other basins by shallow sills. It is formed via winter convection facilitated by the salt imported by the Tsushima Current, with the instabilities in the Polar Front serving to transport this salt into the northern formation regions. Some authors differentiate Japan Sea Deep Water (200 - 2000 m) and Japan Sea Bottom Water (2000 m - bottom), and occasionally the entire water mass is referred to as Japan Sea Deep Water. See Tomczak and Godfrey (1994).

 

Japan Stream

See Kuroshio Current.

 

Jaramillo Magnetic Event

Short-term normal polarity time interval about 0.95 million years ago within the Matuyama Reverse Epoch. See Bowen (1991).

 

JASIN

Acronym for the Joint Air-Sea Interaction experiment. See Nicholls et al. (1983).

 

JavaSea

A shallow body of water located in the southwestern part of the Australasian Mediterranean Sea. Centered at about 114 deg. E and 5 deg. S, it has average depths of around 40-50 m. It is connected to the Sulawesi Sea to the northeast by the Makassar Strait, adjoins the Flores Sea to the east, connects to the South China Sea to the northwest via the Karimata Strait, abuts the Bali Sea to the south and Kalimantan to the north.

The Java Sea was formed when two large river systems, now forming shallow channels in the shallow sea floor, were drowned out at the end of the last ice age. The circulation and hydrography are determined by the annual cycle of monsoons winds, with currents flowing westward from June to August and eastward during the rest of the year. During this latter period a tongue of high salinity water from the South China Sea pushes salinity values of 32 as far east as 112 deg. E. See Tomczak and Godfrey (1994).

 

JEBAR

In oceanography, an acronym for the Joints Effects of Baroclinicity And Relief. See Mertz and Wright (1992).

 

JEDA

Acronym for Joint Environmental Data Center, a joint venture between SIO and NODC with the purpose of providing quality control on upper ocean temperature and salinity observations over the global ocean. See the JEDA Web site.

 

Jeffreys' theorem

A theorem that concerns the conditions under which hydrostatic equilibrium obtains. It states that hydrostatic equilibrium is impossible if density variaitons occur on level surfaces. See Hide (1978).

 

Jerlov water types

A scheme for classifying the optical properties of various waters based on their irradiance transmissivity in the upper 10 m. The scheme divides them into oceanic (Types I to III) and coastal (Types 1 to 9) categories. See Jerlov (1976).

 

jet stream

A well-defined core of strong wind, ranging from 200-300 miles (320-480 km) wide with wind speeds up to 200 mph (320 kph), that occurs in the vicinity of the tropopause. See Reiter (1963).

 

JGOFS

Acronym for Joint Global Ocean Flux Study, a subprogram of the IGBP whose goal is to improve our knowledge of the processes controlling carbon fluxes between the atmosphere, surface ocean, ocean interior and its continental margins, and the sensitivity of these fluxes to climate changes. See the JGOFS Web site.

 

JOIDES

Acronym for Joint Oceanographic Institutions for Deep Earth Sampling, a program to obtain cores of deep ocean sediments. See the JOIDES Web site.

 

JONSWAP

Acronym for JOint North Sea WAve Project.

 

joule

The unit of work or energy in the mks system of units. It is the work done by a force of one newton in moving its point of application one meter in the direction of the force. Some equivalences are: 1 joule = watt sec = ergs; 1 calorie = 4.1868 joules.

 

JPL

Abbreviation for Jet Propulsion Laboratory.

 

JPO

1. Abbreviation for Journal of Physical Oceanography. 2. See GCOS.

 

JPOP

Abbreviation for Japanese Polar Orbiting Platform.

 

JSTC

See GCOS.

 

Julian calendar

A system of keeping years and months for civil purposes based on a tropical year of 365.25 days. It was instituted by Julius Caeser in 45 BC and is still the basis of the calendar, although it was modified and improved to create the Gregorian calendar.

 

Julian date

The number of days which have elapsed since 12:00 GMT on Jan. 1, 4713 BC. This system of numbering by consecutive days gives a calendar independent of month and year and is used for analyzing periodic phenomena. This system, devised in 1582 by J. Julius Scaliger and used most extensively by astronomers, has no connection with the Julian calendar other than the similar name.

 

Junge layer

A layer in the lower stratosphere that is enriched in sulfate aerosols. See Woodwell (1995b).

 

Jurassic

The second and penultimate period of the Mesozoic era, lasting from 208 to 144 Ma. It precedes the Cretaceous period and follows the Triassic period, and is comprised of the Early (208-187 Ma), Middle (187-163) and Late (163-144 Ma) epochs. It is named from the Jura mountains in France.

 

Jutland Current

See North Sea and Skagerrak.