Cross-section A-B

ISENTROPES

This is a cross section across the cold front layed from cold to warm air. Backward inclined crowded isentropes represent the frontal zone. However, the appearance of the isentropes in the cross-section is not typical for a cold front. If the cross section is studied carefully it can be seen that the cold front is actually found in upper layers whereas near the ground (under 700 hPa) the isentropes indicate the presence of warmer air.

Coldest cloud tops (depicted here as orange line representing IR pixel values) are clearly connected to the upper level cold front.

Notice also the unstable layer in the left of the cross-section, between 750 and 650 hPa level.

Very common and important feature that can be seen here is the lowering of the tropopause behind the cold front. In the upper left corner og the cross-section it can be seen that the tropopause is lowered down to 300 hPa, whereas ahead of the front (in the upper right corner) the tropopause is obviously outside the scope of the cross-section (above 200 hPa).

RELATIVE HUMIDITY

The highest values of relative humidity can be found ahead of the cold front but there is also another humidity maximum in the layer near the ground behind the front. Again, the distribution of humidity is not typical for the cold front, but it is a more complex system.

TEMPERATURE ADVECTION

Cold advection maximum is found in the region of the cold front, but more in the upper levels. There is another maximum ahead of the front.

WIND SPEED (isotachs)

Jet streak (maximum wind) is located at about 300 hPa, behind the frontal zone.

EUMeTrain: VERTICAL CROSS SECTIONS

CROSS-SECTION A-B