DYCOMS-II Model: NCEP AVN Model Column Imagery (GIF) 1.0 General Information The NCEP AVN Model Column Imagery (GIF) is one of several model products collected as part of the Dynamics and Chemistry of Marine Stratocumulus Phase II: Entrainment Studies (DYCOMS-II) project field catalog operated by the University Corporation for Atmospheric Research/Joint Office for Science Support (UCAR/JOSS; http://www.joss.ucar.edu/dycoms/catalog/). The plots are National Oceanic and Atmospheric Administration (NOAA) National Centers for Environmental Prediction (NCEP) Aviation (AVN) data for model columns over the DYCOMS-II target area. Two types of plots are included, contour plots of height time data (C, for contour), and line (L, for line) plots of surface variables versus time. For each type there are area averaged data (A plots) and data from an individual column (P plots). The products cover the period from 1 - 31 July 2001 and cover the DYCOMS-II region. All images are in GIF format. 2.0 Data Contact Bjorn Stevens, UCLA (bstevens@atmos.ucla.edu) 3.0 Product Information The data are plotted for model columns over the target area. Two types of plots are created, contour plots of height time data (C, for contour), and line (L, for line) plots of surface variables versus time. For each type we plot area averaged data (A plots) and data from an individual column (P plots). Thus for any given forecast time we generate four plots: CA: Time-height plot of basic variables averaged over target area CP: Time-height plot of basic variables at center of target area LA: Line plot of surface variables averaged over target area LP: Line plot of surface variables at center of target area For the line plots the scales are fixed. Two vertical green lines are on each of the plots, these indicate the time windows for possible night-time flights. Also on each line plot three different forecasts are plotted, successive forecasts start 24 hours earlier. This gives an illustration as to how the forecasts had to adjust to the subsequent analyses. From left to right and top to bottom the plots are: (a) pbl height in meters (b) 2m air temperature and surface temperature (quasi-straight lines) (c) Total cloud fraction (Low cloud for NCEP) (d) Surface Pressure (e) 2m specific humidity and surface saturation specific humidity (f) Low cloud fraction (g) Zonal wind at 10m (h) Sensible Heat Flux (i) Net Solar Radiation into surface (h) Meridional Wind at 10m (k) Latent Heat Flux (l) Net IR into surface For the contour plots the scales are variable. From left to right and top to bottom we plot: (a) Temperature (b) Zonal Wind (c) Meridional Wind (d) Specific Humidity (e) Cloud water (if any) (f) Cloud fraction (if any, omitted for NCEP) (g) Relative Humidity (h) Vertical velocity (i) Potential Temperature NCEP forecasts extend 48 hours and are made twice daily, at 00Z and 12Z, both are processed and sent to the archive at about 14Z on the day of the forecast. All plots are preliminary, the data is being archived for re-examination should the data behave anonomously. In particular the cloud variables from NCEP are uncertain. 4.0 Quality Control Procedures UCAR/JOSS conducted no quality checks on these data. 5.0 File Naming Convention The file names are structured as follows: NCEP.yyyymmddhhmm.AVN-LP.gif Where NCEP is the data type yyyy is the four digit year mm is the two digit month dd is the two digit day hh is the hour (UTC) mm is the minute AVN-LP represents the type of plot other possibilities include AVN-CA, AVN-CP, and AVN-LA. 6.0 References None.