Meridional wind

TABLE 5.1 Seasonal Cycles of Sea Level Air Pressure, Zonal ( , Positive Eastward) and Meridional Wind Component (v, Positive Northward), Wind Speed Ivl and Its Squared and Cubic Values Representing the So-Called Energy and Turbulence Indices Where Available, the Standard Deviation is Given Behind the Mean Peak Values of Each Row Are Given in Bold... 

Fig. 9 Data from the mooting station installed in the strait connecting the western and the eastern basins in October, 2005, Survey 5(2). The current meter and the level gauge at the mooring station were deployed at the depth of 4 m, about 1.5 m above the bottom in the deep channel at the western outlet of the strait. The meteorological station was installed at the northern bank of the strait, some 3 km north of the mooring. From top to bottom atmospheric pressure relative humidity zonal and meridional wind stress components zonal and meridional components of the current velocity surface level anomaly as derived from the pressure gauge...

Vertical and meridional winds in the stratosphere can be estimated from theoretical studies, which are usually based on solutions to the equations of atmospheric dynamics, as will be described below. In the mesosphere, however, the meridional wind (wind speed in the latitudinal direction) has been measured at particular points, usually with radar techniques (see Figure 3.6 from Nastrom et al., 1982) and derived from space observations (see, e.g., Lieberman et al., 2000). Meridional winds are denoted by a positive velocity when they are directed from the south to the north. In the vertical, wind speeds are positive when they are directed upwards. 

Figure 3.6. Velocity of meridional winds observed in the mesosphere at Poker Flat, Alaska (m s-1). The air flow at 88 km is directed southwards during summertime. From Nastrom et al. (1982).

Figure 3.15c. Amplitude of the meridional wind variation at 95 km and 20° N between October 1991 and April 1995 produced by the diurnal component of the migrating tides. From Burrage et oil., 1996.

The special case of zonal asymmetries should also be mentioned. The vector wind is generally aligned along latitude circles in summer, but in winter the influence of planetary waves can cause the vector wind to flow across latitude lines (see Figure 3.13). Under these zonally asymmetric conditions, the local wind speed in the meridional direction is much greater than the mean meridional wind. Indeed, winds of zonal speeds (tens of meters per second) can flow across latitude lines, and any species exhibiting a latitude gradient will be affected. 

Nastrom, G.D., B.B. Balsley, and D.A. Carter, Mean meridional winds in the mid and high latitude mesosphere. Geophys Res Lett 9, 139, 1982. 

Figure 5.27. Photochemical lifetime of odd hydrogen radicals, as well as the time constants for transport by the zonal and meridional winds, and a onedimensional diffusive time constant.

At mid- and low-latitudes, the ionospheric plasma is strongly affected by the motion of the earth s upper atmosphere (neutral wind). In general, this neutral wind blows away from the subsolar point on the dayside and around to the nightside. The ionospheric plasma at midlatitudes is confined to move along magnetic field lines therefore the meridional wind exerts a major influence on the ionosphere. On the dayside, this wind blows toward the poles, and the ionization is driven downward. On the nightside, the meridional wind blows toward the equator, and the ionization is driven up field lines. 

Meridional wind The component of the wind along the meridional, or north-south, direction. 

FIGURE 12 Schematic representation of the horizontal structure of an equatorial Kelvin wave. The contours denote geopotential anomalies, while the arrows denote zonal wind perturbations. Note that the Kelvin wave has no meridional wind perturbation. [From Andrews etal. (1987). Middle Atmosphere Dynamics, Academic Press, New York.]... 

The constraint imposed by geostrophic equilibrium im-phes that the zonal-mean circulation of the stratosphere tends to follow longitude circles zonal-mean motion in the meridional and vertical directions is then due to srrtall depattitres from geostrophy. As noted previously, zorral-mean zonal winds are typically 10-100 times larger than zonal-mean meridional winds, and the latter in tom exceed vertical motions by another a factor of at least 100 (compare Fig. 6 and 13). 

The analytical approach used in Section IV.A.2 is not applicable to the tropical circulations, even though these are low-frequency phenomena, with time scales comparable to or longer than that of the extratropical circulation. The weakness of the Coriolis force in the tropics tends to decouple the zonal and meridional wind fields, so even at very low frequencies the EP-flux divergence acts mainly... 

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