TITLE: 2 km resolution 3dVOM forecast images AUTHOR: Simon Vosper email: simon.vosper@metoffice.gov.uk Met Office, FitzRoy Road, Exeter EX1 3PB UK DATA SET OVERVIEW: 3dVOM forecasts for the Sierra Nevada (2 km resolution) 3dVOM (3-D Velocities over Mountains) is a finite-difference numerical model designed for high-resolution simulations of lee waves generated by flow over complex terrain. The model is based on a set of simplified equations of motion, the linearised shallow Boussinesq equations of motion for a dry atmosphere. The equations of motion are linearised about an upwind profile of wind and temperature (assumed to be dependent on height only) and are integrated forward in time until a quasi-steady lee-wave field is obtained. The model includes a 1st-order (mixing-length) turbulence closure scheme. Because the equations of motion are greatly simplified (relative to those in a full NWP forecast model) solutions can be generated relatively quickly. The 3dVOM code was used to generate high-resolution detailed forecasts of lee-wave fields and associated near-surface winds. Met Office Unified Model (UM) global forecast data were used to generate forecast profiles of wind and temperature for the Sierra Nevada range (at 118 W, 36.6 N) and the 3dVOM wave forecasts are based on these profiles. Note that over the lower portion of the forecast profiles (below 1500 m above ground level) the UM wind data are replaced by a wind profile which varies logarithmically with height. This approach was adopted to avoid uncertainties connected with the sub-grid flow blocking drag parametrisation applied in the UM, which may affect the quality of the low-level forecast winds in regions of significant orography. The horizontal resolution is approx. 2 km. The image "org.png" shows the model domain and terrain heights (in metres). Also shown are lines labelled W-E, S-N, NW-SE, SW-NE, Track A, Track B and Track C. These show the orientations of the available vertical cross sections. The latter three are the aircraft tracks of the NCAR Hiaper, FAAM BAe-146 and University of Wyoming King Air during the T-REX campaign. Forecasts at 2 km resolution were available from the period 13 February to 4 May 2006. 3dVOM forecasts were run once per day during this period, based on profiles obtained from the UM global 00 UTC forecast run. 2 km resolution wave forecasts were made for T+06 h, T+12 h, T+18 h, T+24 h, T+30 h, T+36 h, T+42 h, T+48 h, T+54 h, T+60 h, T+66 h and T+72 h. Note that due to system problems, no forecasts were made during the periods 17-18 February and 19-20 March inclusive. DATA FORMAT: All files are PNG images. Forecast images are available in directories with the naming convention: YYYYMMDD_AA_T+HH, where YYYY, MM, DD and AA are the year, month, day, UM analysis time in hours (always 00) and AA refers to the forecast validity time in hours (06, 12, ..., 72). Within each directory the following images are available: profil.png - The UM profiles used as the background state. Quantities shown are wind speed, direction, potential temperature and N^2/U^2, where N is the Brunt Vaisala frequency and U is the wind speed. A second set of panels (bottom row) shows the same quantities over the lowest 8 km only. u_00010m_agl.png - The wind speed and horizontal wind vectors at 10 m above ground level (AGL). u_00100m_agl.png - As above but for 100 m AGL. u_00300m_agl.png - As above but for 300 m AGL. u_00500m_agl.png - As above but for 500 m AGL. u_00010m_agl_zoom.png - The wind speed and horizontal wind vectors at 10 m above ground level (AGL) in the Owens Valley area only. u_00100m_agl_zoom.png - As above but for 100 m AGL. u_00300m_agl_zoom.png - As above but for 300 m AGL. u_00500m_agl_zoom.png - As above but for 500 m AGL. w_01000m.png - Vertical velocity and horizontal wind vectors at 1000 m above sea level (ASL). w_02000m.png - As above but for 2000 m ASL. w_03000m.png - As above but for 3000 m ASL. w_04000m.png - As above but for 4000 m ASL. w_05000m.png - As above but for 5000 m ASL. w_06000m.png - As above but for 6000 m ASL. w_07000m.png - As above but for 7000 m ASL. w_08000m.png - As above but for 8000 m ASL. w_09000m.png - As above but for 9000 m ASL. w_10000m.png - As above but for 10000 m ASL. w_11000m.png - As above but for 11000 m ASL. w_12000m.png - As above but for 12000 m ASL. w_13000m.png - As above but for 13000 m ASL. w_14000m.png - As above but for 14000 m ASL. w_15000m.png - As above but for 15000 m ASL. w_i002-244_j126-102.png - The vertical velocity and potential temperature contours (5 K interval) on track A (see org.png). w_i002-256_j110-110.png - The vertical velocity and potential temperature contours (5 K interval) on the W-E vertical section. w_i002-256_j240-028.png - The vertical velocity and potential temperature contours (5 K interval) on the NW-SE vertical section. w_i008-248_j060-144.png - The vertical velocity and potential temperature contours (5 K interval) on track B (see org.png). w_i022-256_j002-198.png - The vertical velocity and potential temperature contours (5 K interval) on the SW-NE vertical section. w_i044-200_j002-160.png - The vertical velocity and potential temperature contours (5 K interval) on track C (see org.png). w_i152-152_j002-256.png - The vertical velocity and potential temperature contours (5 K interval) on the S-N vertical section. u_W-E.png - The zonal wind component and potential temperature contours (5 K interval) on a Owens Valley zoom of the W-E vertical section. w_W-E.png - The vertical velocity and potential temperature contours (5 K interval) on a Owens Valley zoom of the W-E vertical section. wprofil.png - A vertical profile of the maximum value of |w(x,y)|, where w is the vertical velocity, at each height. Note: The orientations of the vertical cross sections are shown in the image org.png.