Ventilation Climate Information System products

aka Climatological Ventilation Index Point Statistics

• Direct link to Product Listing (remember to set your location)
  

Available Output

Output variables (available as climatological statistical summaries):
[click name for definition]

• Mixing height
• Surface wind speed and direction
  
• Ventilation index

Notes:  Separated "am" and "pm" periods.  Available in several formats for either calendar month or annually

General Discussion

• The Ventilation Climate Information System (VCIS) is a climatology of model interpolated surface wind, mixing height, and ventilation index.
• VCIS is available for 30-40 years depending on location.
  
• VCIS is available on a 5-km grid across CONUS.
• Mixing heights were interpolated from the historical soundings database.
• Surface winds were calculated using the WINFLO mass conserving wind model connected to a very high resolution terrain database.  As a result the VCIS winds are heavily terrain influenced.
  
• Ventilation Index is calculated as surface wind * mixing height.  This is somewhat different from typical ventilation indexes (which use transport winds averaged through the mixed layer).   This was done because the WINFLO model, which was used to generate winds at a horizontal resolution of 5 km, outputs surface winds rather than transport winds.  Because of this, VCIS ventilation indices are typically about 1/2 of standard ventilation indices in absolute terms, providing a conservative estimate of ventilation.  The categories of "Poor", "Marginal", "Fair", and "Good" ventilation index values have been appropriately modified.
  

How to use

• VCIS is designed to provide information on the atmosphere's ability to remove smoke from the area by lofting and advection.  While the ultimate measure of this is the ventilation index, by providing the component pieces as well (winds and mixing height) users can get a better feel for the atmospheric state (in a climatological sense) at the selected location and date.
  
• Note that VCIS is provided on a 5-km grid across CONUS.  Users can move their location on the site or through the portal.
  
• In general, users start with ventilation index and then examine mixing height, and finally winds.
  

Navigating the product

• 

  When first arriving within VCIS, you will see a page with a table of colored circles (see figure to the right).  The rows list calendar months, and the columns are for surface wind, mixing height, ventilation index, and summary table outputs.
•   Clicking on a given circle will fetch the appropriate graphic.  The graphic will initially appear full-size but within the table cell;  clicking on the graphic again will toggle its size in order to enable easier navigation of the table when many graphics are shown.   Note that graphics are generated at the time of the request, so retrieving a particular graphic may take up to 1 minute of processing time.
•  
  Example of the wind rose product.  Colors represent wind speeds per the key.  Within each direction, the relative length of the color bar represents the amount of time the wind was from that direction in that speed range.  The scale for % time is shown by the % numbers on the light grey circles.  The time of day (AM vs PM, corresponding to 12UTC and 00UTC) and month are listed in title.
  

• 

  Example of mixing height graphic.  Statistics of mixing height are shown as a series of vertical box plots, with the mixing height scale shown in vertical axes.  Within each vertical box plot, a heavier center line represents the median value, and the surrounding solid line box shows the 25th percentile (lower end of the box) and 75th percentile (upper end of the box) values.  Dashed lines extend out from each box to show the full (0th percentile to 100th percentile) range of the data.
  
  The statistics are presented 2 ways.  The left portion of the plot shows the statistics per calendar day (e.g. all data from Jan 4th regardless of year) for all 40 years.  The right portion of the plot show the statistics per year (e.g. all data from 1977 for all days in Jan).  Thus the left portion of the plot shows how the statistics vary throughout the calendar month, while the right portion of the plot shows how the statistics vary year to year.

• 

  Example of Ventilation Index graphic.  Presented as vertical box plots similar to the mixing height graphic.  See the mixing height graphic discussion for further explanation of the box plots.  The Ventilation Index axes are labeled in numeric values (m^2/s) and color coded into categories as Poor (red), Marginal (yellow), and Good (green to grey).    These categories are defined as 0-1175 m^2/s = Poor;  1176-2350 = Marginal;  2351-3525 = Fair;  3525+ = Good.  The category definitions are derived from commonly used values but adjusted to reflect the use of 10m surface winds rather than 40m or mixed layer average winds typically used in calculating Ventilation Index;  in this way the categories are "normalized" to this methodology.

• Example summary table.  The table lists the max, min, and mean of the monthly average values (i.e. each year's January is averaged and the table lists the highest average, lowest average, and average of the averages ).   These values can give a quick look at the general conditions and interannual variability that pertains at this location, however more detail is provided by the previous (wind rose, mixing height, and ventilation index) graphics.  
• Graphics are located within the page table.  Clicking on any graphic in the table will make it smaller to enable navigation within the table. 

Expected improvements

• Navigation system for setting alternate locations within the VCIS website is being updated.