EUMeTrain: Cold front over middle Europe

Derived Meteorological Parameters

Basic parameters are not sufficient for understanding the whole physical background of a situation. So, in this chapter some derived meteorological parameters will be discussed.

Parameters which are helpful in diagnosis of a cold front and the substructures on a cold front are:


Theoretical aspects of the mentioned parameters can be found in the SATMANU - Manual of Synoptic Satellite Meteorology in the chapter BASIC.


Thermal Front Parameter

A widely used parameter for frontal analysis is TFP and in the following sequence this parameter is superimposed on the IR satellite images so one could better see the connection between cloud distribution and the front location.


Temperature Advection at 700 hPa

Front lies at the interface of two air masses of a different density and temperature. Temperature advection can be an indicator of upward or downward motion occuring. Upward motion exists in maxima of warm advection. The cold advection, in contrast, contributes to the sinking motion.


Isotachs at 300 hPa

Isotachs at 300 hPa show the distribution of the wind speed and the location of the jet streak and the zero line of shear vorticity indicates the location of the jet axis.

In this chapter the cloud configurations seen in the IR images are related to the isotachs. Sequence of images with 6-hour intervals is shown.


Height of PV=1 PVU  

Very useful parameter for wave diagnosis is potential vorticity (PV). Maxima of PV indicate stratospheric air protruding downward into the troposphere.

In this chapter the cloud configurations seen in the WV images are related to the height of PV=1 PVU.


Airmass + Height of PV=1 PVU

In this chapter the cloud configurations seen in Airmass RGB images are related to the height of PV=1 PVU. Sequence of images with 6-hour intervals is shown.


Positive Vorticity Advection at 500 hPA

In this chapter the cloud configurations seen in IR images are related to the Positive vorticity advection (PVA).


Summary of the investigations in this chapter

Scaning the chapters above several conclusions can be made. First of all, the cold front is developing under a cold advection. This can be seen in the chapter Temperature Advection. The zero line of TA is in advance of the frontal cloud band which is a key parameter for a cold front in cold advection. The TFP distribution, which shows high values of parameter within the whole cloud band, reveals that this front is of an Ana type.

The distribution of temperature field is suitable for wave growth on the cold front. In this case there were two waves developing during the day. The first one developed in early morning and in few hours, due to a suitable conditions, it becomes a cloud spiral. The second one starts to develop in the middle of the day and shows strong enhancement in the afternoon hours. The reason for that can be found in distribution of several parameters.

Behind the cold front there is strong cold advection taking place and dry air from the stratosphere is protruded into the lower parts of troposphere . Location of jet streak together with high values of PVA contributed to further growth and enhancemend of the system.