High-Resolution Simulations of Freezing Drizzle and Freezing Rain and Comparisons to Observations

High-resolution simulations of freezing drizzle and freezing rain and comparisons to observations

Greg Thompson

Research Applications Laboratory National Center for Atmospheric Research

additional contributions by:

Roy Rasmussen, Trude Eidhammer, Kyoko Ikeda, Changhai Liu, Pedro Jimenez, Mei Xu, Stan Benjamin

Winterwind 7 Feb 2017, Skelleftea, Sweden Outline • Brief History • High-Resolution Forecasts o Supercooled water drops aloft o Ground icing • Verification o Weather Research & Forecasting, WRF o High Resolution Rapid Refresh, HRRR • Next steps o Time-lag ensemble average o Making clouds better o WISLINE project and AROME model With respect to Numerical Weather Prediction

The microphysics scheme is a component in a weather model responsible for:

• Condensing water vapor into droplets

• Model collisions with other droplets to become drizzle/rain

• Creating ice crystals via droplet freezing or vapor-to-ice conversion

• Growing ice crystals to snow size

• Letting snow collect cloud water droplets (riming or accretion)

• Large drops freeze into hail, snow rimes heavily to create graupel

• Making rain, snow, and graupel fall to earth

• etc.

The treatment of processes going between water vapor, liquid water, and ice. Cloud physics & precipitation NCAR-RAL microphysics scheme

Scheme version/generation Research or operational model

Reisner, Rasmussen, Bruintjes (1998MWR) MM5 Rapid Update Cycle (RUC) Thompson, Rasmussen, Manning (2004MWR) MM5 WRF RUC Thompson, Field, Rasmussen, Hall (2008MWR) MM5 WRF & HWRF RUC Rapid Refresh (RAP) High-Res Rapid Refresh (HRRR) Model for Prediction Across Scales (MPAS) CM1 – G. Bryan COAMPS (Navy) Thompson & Eidhammer (2014JAS) WRF “aerosol-aware” RAP* HRRR* MPAS (in progress) NEMS-NMMB (NCEP) GFS (NCEP; in progress) CM1 COAMPS AROME (Europe; in progress)

*major milestone: 23Aug2016 operational RAPv3/HRRRv2 WRF – ConUS 13-year simulation (Dx = 4km)

WRF model • 4-km grid spacing • 50 vertical levels • Single model run, non-stop for 13 years • 15 October 2001 to 15 April 2002 … 2012 (60 months analyzed) • 3-hourly WRF output (~100 TB of data) • Thompson & Eidhammer (2014JAS) “aerosol-aware” microphysics

Analysis • comparison to FAA database of icing research flights • ~280,000 pilot reports of icing (~half indicate non-icing) • ~4 million surface observations (METARs): • FZRA/FZDZ, RA/DZ, SG/GR/GS, PL, SN, FG, FZFG • horizontal and vertical matching process ~ 24 x 24 km2 (6x6 box) • explicit prediction of supercooled water and, more importantly FZRA/FZDZ WRF – ConUS 13-year simulation

WRF model • 4-km grid spacing • 50 vertical levels • Single model run, non-stop for 13 years • 15 October 2001 to 15 April 2002 … 2012 (60 months analyzed) • 3-hourly WRF output (28 TB of data) • Thompson & Eidhammer (2014JAS) “aerosol-aware” microphysics

References: Ikeda et al, 2010 Rasmussen et al, 2011 Liu et al, 2011 (MWR, in press)

Thompson, G., M. K. Politovich, and R. M. Rasmussen, 2017: A numerical weather model's ability to predict the characteristics of aircraft icing environments. Weather and Forecasting, 32, 207–221. Verification: WRF surface and aircraft icing forecasts

Surface reports: METARs (4 million) • RA or DZ • FZRA or FZDZ • SN • GR/GS/SG • PL • FG • FZFG

References: Ikeda et al, 2010 Rasmussen et al, 2011 Voice PIlot REPortsLiu et al, 2011(PIREPs) (MWR, in press) (280,000) • Icing intensity: “TRC,” “LGT,” “MDT,” “SEV” • Explicit report of “Negative” icing • Implicit, clear-sky icing Verification: WRF surface weather forecasts

References: Ikeda et al, 2010 Rasmussen et al, 2011 Liu et al, 2011 (MWR, in press)

Ikeda, K., M. Steiner, and G. Thompson, 2017: Examination of mixed-phase precipitation forecasts from the High- Resolution Rapid Refresh model using surface observations and sounding data. Weather and Forecasting, in press. Verification: WRF aircraft icing forecasts

References: Ikeda et al, 2010 Rasmussen et al, 2011 Liu et al, 2011 (MWR, in press) Next steps • Time-lag ensemble average

Time-lag-ensemble (TLE) average • Hourly updates with hourly forecasts to 18 hours • A traditional HRRR ensemble forecast system coming in a few years now forecast time

...... 10 11 12 13 14 15 16

9z + 7h 8z + 8h 7z + 9h . . . 80% 22z + 18h 60%

• If now is 09:30 and we consider a forecast valid at 16:00 of detection of • Then we could have as many as 12 forecasts all valid at this time.40%

20%

0.5 1.0 1.5 6 3 Probability Volume of airspace ( x 10 km ) HRRR surface forecast example Observed surface weather conditions HRRR-predicted icing conditions aloft Next steps • Making clouds better Nearly all NWP models predict insufficient clouds

WRF (HRRR)

COSMO (Germany) Sundqvist et al (1989) cloud fraction scheme

*in remembrance: Jon Egill Kristjansson Newly implemented cloud fraction scheme

WRF runs thanks to Pedro Jimenez Analysis thanks to Mei Xu

Thompson, G., P. Jimenez, M. Xu, 2017: A commonly-used cloud fraction scheme applied in a regional model (manuscript in preparation) Next steps • WISLINE project • Wind, Ice, and Snow Impacts on Infrastructure and the Natural Environment Collaborators: • Met.no: Harold McInnes • Oslo Univ: Bjorg Jenny Engdahl • KVT: Bjorn Egil Nygaard, Emilie Iversen • SMHI: Lisa Bengtsson, Karl Ivar Ivarsson WISLINE: AROME & WRF

One week: 01-07Feb2016

WRF

Cloud water content Cloud water AROME

Results courtesy KVT: Bjorn Egil Nygaard IceTroll

WRF

Predicted load ice Predicted AROME One month: Feb2016 “Take home” messages

 NWP (high-resolution) icing forecasts (surface and aloft) are highly skillful

 Add-on methods such as ‘time-lag ensemble’ increase skill

 Model physics matter (AROME vs. WRF) Acknowledgements • Goran Ronsten, WindREN • Research Council of Norway & Harold McInnes (met.no) • FAA Aviation weather research project • NSF Short-term explicit prediction (STEP) project • Developmental Testbed Center • NOAA ESRL/GSD

Additional resources Thompson, G. and T. Eidhammer, 2014: A Study of Aerosol Impacts on Clouds and Precipitation Development in a Large Winter Cyclone, J. Atmos. Sci., 71, 3636–3658. Thompson, G., M. K. Politovich, and R. M. Rasmussen, 2017: A numerical weather model's ability to predict the characteristics of aircraft icing environments. Weather and Forecasting, 32, 207–221. Liu, C., Ikeda, K., Rasmussen, R. et al., 2016: Continental-scale convection-permitting modeling of the current and future climate of North America. Clim. Dyn. doi:10.1007/s00382-016-3327-9. Ikeda, K., M. Steiner, and G. Thompson, 2017: Examination of mixed-phase precipitation forecasts from the High- Resolution Rapid Refresh model using surface observations and sounding data. Wea. and Forecasting, in press. Thompson, G., M. Tewari, K. Ikeda, S. Tessendorf, C. Weeks, J. Otkin and F. Kong, 2016: Explicitly-coupled cloud physics and radiation parameterization and subsequent evaluation in WRF high-resolution convective forecasts. Atmos. Res., 168, 92–104. Thank you!