Dynamical Processes Related to Cyclone Evolution near Greenland

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1 Dynamical Processes Related to Cyclone Evolution near Greenland Ragnhild B. Skeie a, Jón Egill Kristjánsson a, Haraldur Ólafsson b a Department of Geosciences, University of Oslo b University of Iceland and Icelandic Meteorological Office

2 Motivation General interest in the impact of large scale mountain ranges on weather and climate on all scales Weather vs. climate NWP: Greenland well resolved Climate models: Greenland not as well resolved Forecasts of weather systems influenced by Greenland of very variable quality Some high-impact weather systems are triggered by Greenland

3 Greenland and the weather Greenland is close to the storm-track (jet) Strong temperature gradients (ice-ocean) Exremes in surface forcing: Very stable air (over the sea-ice) Very unstable air (cold air outbreaks over the ocean) Low surface friction (glacier)

4 20 studies 25 authors Studies of flow interaction with Greenland Cases of cyclone tracks

5 Blockings and diversion of low level flow

6 Blockings and diversion of low level flow Low level divergence/convergence

7 Upper level disturbances: gravity waves and larger scale descending motion

8 Blockings and diversion of low level flow Societal impact

9 Pre-THORPEX: Highest ever impact of a wrong forecast? (AD 998) Planned route True route

10 A few examples

11 Shapiro et al., 2002 Nov. 2001: Saltstorm in Iceland, rain in N-Africa

12 Simulations with idealized westerly flow Idealized mountain Greenland speed-up Schwiertz and Davies (Tellus, 2003) Petersen et al. (JAS, 2003)

13 Case study January 1995: Diversion of cold air behind the low NOGREEN DOUBLE Greenland Kristjánsson and McInnes (QJRMS, 1999)

14 No NW-winds in Iceland Wind directions in Iceland Vigurvindáttarós Allar skeytastöðvar, allar athuganir Heildarfjöldi: N % V 1 0 A Fig. from Trausti Jónsson S

15 The Greenland tip jet Doyle & Shapiro (Tellus, 1999)

16 Greenland Tip Jet - DLR Wind Lidar observation Dörnbrack et al. (2004) FL200 z~6.0 km MODIS (Aqua) 14:55 UTC 24 November Greenland Tip Jet

17 South Observed and simulated winds North Lidar Model Dörnbrack et al. (2004) 3. Greenland Tip Jet

18 Case Study Heavy snowfall and sustained winds exceeding 30 m/s over E Greenland and N Iceland on 21 September 2003 What role did Greenland s orography play? What about other factors (latent heat, SST grad., etc.)? Approach: NCAR/PSU MM5 model, 100x100 grid points Resolution: 36 km grid spacing, 23 sigma levels Experiments: CONTROL, NOGREEN, NOLAT, SSTGRAD, SSTWARM

19 High-impact cyclone (September 2003) L Cyclone tracks

20 Forecasts indicating avalanche danger lead to evacuation of houses

21 Sea-level pressure and hpa thickness CONTROL NOGREEN ANA; 00 UTC 18 Sep 2003

22 Sea-level pressure and hpa thickness CONTROL NOGREEN +6h; 06 UTC 18 Sep 2003

23 Sea-level pressure and hpa thickness CONTROL NOGREEN +12 h; 12 UTC 18 Sep 2003

24 Sea-level pressure and hpa thickness CONTROL NOGREEN +18 h; 18 UTC 18 Sep 2003

25 Sea-level pressure and hpa thickness CONTROL NOGREEN +24 h; 00 UTC 19 Sep 2003

26 Sea-level pressure and hpa thickness CONTROL NOGREEN +30 h; 06 UTC 19 Sep 2003

27 Sea-level pressure and hpa thickness CONTROL NOGREEN +36 h; 12 UTC 19 Sep 2003

28 Sea-level pressure and hpa thickness CONTROL NOGREEN +42 h; 18 UTC 19 Sep 2003

29 Sea-level pressure and hpa thickness CONTROL NOGREEN +48 h; 00 UTC 20 Sep 2003

30 Sea-level pressure and hpa thickness CONTROL NOGREEN +54 h; 06 UTC 20 Sep 2003

31 Sea-level pressure and hpa thickness CONTROL NOGREEN +60 h; 12 UTC 20 Sep 2003

32 Sea-level pressure and hpa thickness CONTROL NOGREEN +66 h; 18 UTC 20 Sep 2003

33 Sea-level pressure and hpa thickness CONTROL NOGREEN +72 h; 00 UTC 21 Sep 2003

34 Sea-level pressure and hpa thickness CONTROL NOGREEN +78 h; 06 UTC 21 Sep 2003

35 Sea-level pressure and hpa thickness CONTROL NOGREEN +84 h; 00 UTC 21 Sep 2003

36 Sea-level pressure and hpa thickness CONTROL NOGREEN +90 h; 18 UTC 21 Sep 2003

37 Sea-level pressure and hpa thickness CONTROL NOGREEN +96 h; 00 UTC 22 Sep 2003

38 PV at θ = 316 K Potential Vorticity +48 h; 00 UTC 20 Sep 2003

39 MSLP - CONTROL (isolines); CONTROL -NOGREEN (shaded) +60 h +72 h +84 h +96 h Sea-level pressure dipole

40 Cyclone evolution Sea-level pressure 500 hpa height

41 What is most relevant to THORPEX?

42 Indications of high sensitivity of orographic response to the background flow and its reproduction by NWP Stability at 750 hpa Treatment of gravity waves Position of jet

43 The THORPEX - Greenland connection ongoing and future work Analysis forecast errors in flows from Greenland from large dataset Analysis of situations where a small change in the atmospheric flow may lead to large difference in the orographic response Analysis of forecast errors in flows from Greenland from a large dataset Case studies N-Greenland Easterly flow Downstream development - climatology Synthesis of obtained results

44 Thank you

45 THORPEX an international effort Melvyn A. Shapiro co-king of THORPEX Ólafur. R. Grímsson president of Iceland

1. Greenland Flow Distortion experiment (GFDex)

1. Greenland Flow Distortion experiment (GFDex) (GFDex) is an international fieldwork and modelling-based project to investigate the role that Greenland plays in distorting atmospheric flow over and around