Typical Appearance In Vertical Cross Sections

NWP parameters that describe the vertical structure of the Conceptual Model

  • ITCZ Cross Section
  • ITCZ Ocean Cross Section
  • Easterly Lows Cross Section
  • Continental Tropical Lows Cross Section

ITCZ over the ocean

Wind divergence and vertical motion

Longitudinal vertical cross section of wind divergence (*105) and omega (negative values upward motion) at 3° N at 1200Z on 15 January 2013.
Longitudinal vertical cross section of wind divergence (*105) and omega (negative values upward motion) at 5° S at 1200Z on 15 January 2013.

At 3° north and west of Greenwich, lower level convergence is displaced by mid level divergence resulting in upward motion in the same area as the convective cloud. There is also large values of upward motion at around 10° E over the continent.

At 5° degrees south of the equator the upward motion is restricted to east of 10° E over the continent of Africa.


Latitudinal vertical cross section of wind divergence (*105) and omega (negative values upward motion) at Greenwich at 1200Z on 15 January 2013.
Latitudinal vertical cross section of relative vorticity (*10^5) and winds (in knots) at Greenwich at 1200Z on 15 January 2013.

Strong uplift exist near the equator with general upward motion present in the area north of the equator and subsidence towards the south in the vicinity of the extra-tropical high.

The lower level northeasterly winds north of the equator and southeasterly winds south of the equator results in in wind convergence at around 5° N. On the equator there is little directional wind shear but large directional shear away from the equator. The North African Jet Stream is visible in the 300-200 hPa layer.



Total Static Energy

Longitudinal vertical cross section of TSE at 3° N at 1200Z on 15 January 2013.
Longitudinal vertical cross section of TSE at 5° S at 1200Z on 15 January 2013.

In the vicinity of the ITCZ the TSE values at the surface approaches 350 J/kg. The atmosphere is convectively unstable west of Greenwich with minimum TSE values at around 800 hPa. Over the continent of Africa at 15 E, the surface values of TSE are lower and the atmosphere remains convectively unstable but minimum values now occur at 600 hPa.

Away from the equator at 5° S surface values of TSE remain high but the atmosphere is not as convectively unstable as further north close to the African continent. West of Greenwich over the Atlantic Ocean the atmosphere remains convectively unstable.



ITCZ over the continent

Total Static Energy

Longitudinal vertical cross section of TSE at 15° S at 1200Z on 15 January 2013.

High values of TSE is present over the continent and although the atmosphere is convectively unstable the minimum values in the mid-troposphere are much higher than the example over the ocean.



Easterly Lows

Longitudinal vertical cross section (10° E to 40° E) of vertical velocity at 20° S and winds (in knots). The blue shades are upward motion and the red shades downward motion.
Longitudinal vertical cross section (10° E to 40° E) of divergence (brown shades are divergence and magenta shades convergence) and vertical velocity (contours) at 14° S on 8 January 2013 at 0000 Z.

The largest values of omega occurred in the mid and upper troposphere in the vicinity of the convective development.



Continental Tropical Lows

Longitudinal vertical cross section (15° E to 35° E) of relative vorticity (values multiplied by 105) at 21° S and winds (in knots). The green shades are anticyclonic vorticity and the yellow shades cyclonic vorticity.
Longitudinal vertical cross section (15° E to 35° E) of vertical velocity at 21° S and winds (in knots). The blue shades are upward motion and the red shades downward motion.

The tropical low standing upright with height is clearly visible at 25° E.


Longitudinal vertical cross section (15° E to 35° E) of divergence (brown shades are divergence and magenta shades convergence) and vertical velocity (contours) at 21° S.
Longitudinal vertical cross section (15° E to 35° E) of TSE at 21° S.
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