Predictability and dynamical processes Heini Wernli Institute for Atmosphere and Climate Science ETH Zurich HIW Workshop, Karlsruhe 18 March 2013

Key points the dynamics of high-impact weather is often complex and closely related to basic/fundamental research questions, relevant processes range from large-scale to microscale; from Rossby wave dynamics to deep convection, cloud microphysics and turbulence, occasionally, forecast uncertainties are still large for various of these processes and their interaction, field experiments, together with dedicated modeling/diagnostic research activities, are important for bringing the community together to work jointly on important issues, important pillars of a future HIW project should be (a) collaboration between universities, research institutes, and weather services, and (b) research projects like, e.g., DIAMET and PANDOWAE.

  High-impact wet snowfall Poor forecasts for wet snowfall event in NW Germany in Nov 2005  transition from rain to wet snow poorly predicted by ECMWF and COSMO models issue of correctly predicting position of surface cyclone  Frick and Wernli 2012 (WaF)

 Sting jets: high-impact winds in cyclones Complex dynamical & physical processes on various scales Frontal structure of cyclone Conditional symmetric instability? Sublimation of ice particles? Stability of BL and vertical momentum transport  Clark et al. 2005 (QJ) Sting jet within cyclone Friedhelm (8 Dec 2011), observed during the DIAMET field experiment

Heavy precipitation events: Stability vs. transport Role of conditional instability (CAPE) and horizontal moisture flux varies for different events Nuissier et al. 2008 (QJ)

 Heavy precipitation events and long-range moisture transport Flooding event in Bernese Oberland in October 2011  plume of moisture extending from the tropics to central Europe (cf. atmospheric river, tropical moisture export) link to ET of Philipp from Nicolas Piaget

Pfahl et al., in preparation Relevance of synoptic systems for precipitation extremes % of HPE associated with cyclone or WCB HPE defined as >99 percentile in ERA-Interim dataset Pfahl et al., in preparation

Case study of major forecast bust 5-day ECMWF forecast from 12 UTC 13 Jan 2005 SLP average over C. Europe analysis 1003 hPa deterministic fc 1024 hPa EPS 1012 – 1037 hPa !!  what happened meteorologically?

Case study of major forecast bust T850 and SLP ana +3.5 ana +5 fc +3.5 fc +5

Case study of major forecast bust PV on 320 K ana +3.5 ana +5 T1 R1 T1 R1 fc +3.5 fc +5 T1 T1 R1 R1

- - Hypothesis: errors in WCBs amplify downstream + generation of a positive PV anomaly (downstream trough) WCB  amplified upper-level ridge  downstream trough WCB triggers / enhances downstream Rossby wave activity

Warm conveyor belts Microphysical processes diagnosed in COSMO simulation Joos and Wernli 2012 (QJ)

T-NAWDEX-Falcon: IOP3 (19/20 Oct 2012) In-situ observations in warm conveyor belts from Maxi Böttcher

Tropopause polar cyclones Long-lived mesoscale vortices associated with diabatic processes radiative heating latent heating TPCs are frequent and fairly long-lived (> week) TPCs can trigger / amplify waves along jet TPCs are associated with characteristic pattern of radiative and latent heating Kew et al. 2010 (MWR) Cavallo & Hakim 2010 (MWR)

Longer time scales: cold winters & hot summers Cold winter 2005/06 in Europe: five events of upstream blocking blocking events blocking cold temperature influence from upstream weather systems Croci Maspoli & Davies 2009 (MWR)

HIW-related research projects T-PARC, DIAMET, PANDOWAE, Prevassemble, … strong (international) collaboration collaboration between weather services & universities linkage of observational & modeling research strengthen research with benefit for operational forecasting at universities education of next generation of “weather scientists”  key component of future WWRP HIW Project

Scientific challenges for future HIW project Scale-interactions of dynamical and physical processes including large-scale, mesoscale & microscale Non-linear processes & thresholds Upscale and downscale forecast error propagation Interaction of atmospheric water cycle and dynamics Interaction of cloud microphysics and dynamics Specific model evaluation for HIW events Quantify benefit from convection-permitting models for HIW Link communities from nowcasting to (sub)seasonal prediction