PV/Humidity precursors

Gwendal Rivière, Karine Maynard, Philippe Arbogast GAME; CNRM/GMAP/RECYFCNRS; Météo-France

Rationale: upper-level features are associated to stratospheric intrusions into the upper troposphere that can be identified using satellite data (WV, ozone…). There

are : • Dry patterns

• High PV patterns

Tools : sensitivity studies

• To humidity (corrections)

• To PV(inversion)

• Within ARPEGE (global, 23km resolution over western Europe)+Aladin (Lam, 10km)+AROME (LAM over France, 2.5km resolution, NH)

Iso-PV

Iso-q

PV/q

PV/q correction (z) after 1D-var

x

y

z

Methodology PV/specific humidity modifications

Case studies

• Sensitivity to PV and humidity in the case of a Mediterranean MCS

• Sensitivity of Klaus windstorm to humidity

• Sensitivity of Klaus windstorm to PV. Application of initial condition improvement.

NOS (PV modification)

NOHUS(Hu modification)

NOHUC(Hu modification)

CTRL NOS

NOHUS NOHUC

Case studies

• Sensitivity to PV and humidity in the case of a Mediterranean MCS

• Sensitivity of Klaus windstorm to humidity

• Sensitivity of Klaus windstorm to PV. Application of initial condition improvement.

Case studies

• Sensitivity to PV and humidity in the case of a Mediterranean MCS

• Sensitivity of Klaus windstorm to humidity

• Sensitivity of Klaus windstorm to PV. Application of initial condition improvement.

PV+column ozone (METEOSAT)

ARPEGE +27h ARPEGE +24h (with modified PV) MSLP

ARPEGE +27h ARPEGE +24h (with modified PV) ARPEGE +21h wind gusts > 35 m/s

Conclusions (1)

• In the case of the Mediterranean MCS (05 Sept 2005) the precipitating activity seems to be sensitive to mid to upper-level moisture and to PV.

• Upper-level PV, as it triggers a low-level southerly flow over the gulf of Lion, indirectly contributes to convective activity.

• Moisture gradients are likely area for convective initiation and also seem to help the stationarity (crucial to understand since it is associated with strong accumulated precipitations

Conclusions (2)• Klaus windstorm activity is weakly sensitive to initial

condition humidity• On the one hand, it is not possible to recognize the diabatic

Rossby wave behaviour in that case• On the other hand, diabatic processes are reduced for about 6h.

Afterwards remnants of diabatic processes may be found in the vicinity of the tropopause downstream wrt the cyclone

• Klaus windstorm behaves like a type-B cyclone development since it is sensitive to upper-PV.

• IC failures may be corrected by experts (forecasters) and the subsequent forecast may be eventually improved .