Quantitative relationship between Meteosat WV data and positive potential vorticity anomalies: a case study over the Mediterranean

Abstract

dry air (see e.g. Fischer et al., 1981). Meteosat WV data are disseminated in high resolution image (HRI) formats coded in 256 digital values (0-255) that we shall call simply WV counts.

Cloud systems leading to flood events in Europe: an overview and classification

“…Deepening cyclones are associated with tropopause folding, where there are high PV values in the upper troposphere as a result of PV conservation (Georgiev 1999). Generally, such high PV values in the upper and middle troposphere are considered to be potential vorticity anomalies (PVa).…”

Use of potential vorticity fields, Meteosat water vapour imagery and pseudo water vapour images for evaluating numerical model behaviour

“…However, the agreement between the shape and intensity of the PV anomaly and the WV pattern is complex since various mechanisms of cyclogenesis are possible. Also, the variable WV channel sensitivity is a maximum within the middle and the upper troposphere (see Georgiev, 1999). Forcing of cyclogenesis is usually associated with a positive upper-level PV anomaly indicated by a dry slot in the WV imagery but it can occur at lower levels associated with PV anomalies within the moist air.…”

“…(b) Absolute vorticity at the 2 PVU surface (Carroll, 1997;COST-78, 1998). (c) Positive PV anomalies at 400 hPa (Georgiev, 1999). (d) Positive PV anomalies at 500 hPa (Georgiev 1998(Georgiev , 1999.…”

“…As the latter field is most easily interpreted, this was the preferred dynamical field, though it was agreed that the physical basis for the relationship of absolute vorticity on a PV surface with the imagery should be clarified. (c) The field of positive PV anomalies (PPVAs) at 500 hPa gives quite a good correspondence to WV image dry slots (Georgiev, 1999). It has also been recommended that using this PV field may be a way of helping to solve the problem of verifying and validating numerical output (Georgiev, 1998(Georgiev, , 1999.…”

“…(c) The field of positive PV anomalies (PPVAs) at 500 hPa gives quite a good correspondence to WV image dry slots (Georgiev, 1999). It has also been recommended that using this PV field may be a way of helping to solve the problem of verifying and validating numerical output (Georgiev, 1998(Georgiev, , 1999.…”