Details and instructions on the Sub-Daily Compositing Page

Variables  |  Levels  |  Dates |  Use Date File |  Type of Plot  |  Contour range/interval
Plotting Regions | How Page was Created | Feedback/suggestions | How to Reference

Variables are from the 20th Century Reanalysis V2c and V2. 20CRV2c starts Jan 1 1851 and 20CRV2 starts Jan 1 1871.

*Enter Level

Levels are analysis levels. Geopotential height and specific humidity are not available at the surface. For pressure or SLP, specify surface.

*Enter date(s)

Individual Dates Enter yyyy, mm, dd for the days you desire. For long-term means, use a fake year and enter the month,day. Years are from Jan 1 1851 to Dec 31, 2011 . To subtract one set of days from another, use a negative sign in front of the year. If there are an unequal number of positive and negative years, the years are normalized. For example, the years:
will be calculated as
Date range
Enter the starting and ending day of the year. Also enter the year of the data. The year corresponds to the year of the last day of the range. That is, Dec 31 1999 to Jan 4 2000 should be entered as Dec 31 to Jan 4 2000. For the days to be used, a year must be entered. If a year is entered, it overrides anything in the individual date entry boxes.


Use your own date-time File 
There is a limit of 1000 date-time values. Please upload the data or use openDAP if that isn't sufficient

Create a text file in the following format

Where "hh" can be "00", "06", "12", or "18" and, for some variables,
it can also be "03", "09", "15", or "21".


Make sure there is no miscellaneous text at the top of the file like headers. Put the file in our anonymous ftp directory. ftp and then cd /Public/incoming/dates/ and then put yourfilename. You will not be able to delete or rename the file. We may run a scrubber to delete files over 3 days old so you may need to re-ftp a file. Then, type in the filename /Public/incoming/dates/yourfilename and type in a plot label. If the plot label is blank, all the days will be written which may not fit.

*Enter Color

Color or Black and White. Color ranges are chosen arbitrarily by the developer (and may be subject to change).

*Enter Shading

Shaded or contour levels are available.

*Enter Plot Type


Average of the days specified.


The anomaly based on the 1968-1996 climatology is calculated for each day. The average of all days is then calculated. For vector wind, the anomaly of the u and v components are calculated separately for each day. They are each averaged and then the resulting u and v anomalies are plotted. The wind speed is the wind speed of the anomalies. If the u anomaly component is -4 and the v component is -3 then the resulting wind anomaly vector points southwest and has a magnitude of +5.

Long-term mean

The 1981-2010 climatology is calculated for each day (year ignored). The days are then averaged.

*Enter Output Type

Ensemble Mean

Average of the 56 individual ensemble members.

Ensemble Spread

Standard Deviation of the 56 individual ensemble members.

*(Optionally) Enter Contour range/interval option

A desired contour interval and range can be input instead of the default being used. Different plots can be easily compared (and the resulting gifs could be animated). For this option to work, the interval AND the range must be input. There must be at least 2 and less than 33 contours. The contour interval must be positive and the range must go from low to high.

*Plotting Regions

To plot over the dateline, use values from 0 to 720. For example, to plot 180W eastward to 180W, use 180 to 540. Be sure that the western most longitude is less than the eastern., For example, to plot 100W to 70W, use -100 to -70 or 260 to 290 and NOT 100 to 70.
There are 6 custom projections:
Northern Hemisphere: 0-90N, 0-360W in using a polar stereographic projection
Globe: 90S-90N 0E-360W
United States: 20N-65N; 235-285 polar stereographic projection
Tropics: 60S-60N
Tropical Pacific: 35N-35S 100E to 60W
4-corner States of the Western US:31-42.5N, 244.5-258.5W CO,UT,AZ,NM
Indio-Pacific (20S-20N,60E-160W)
To rotate polar stereographic plots

To rotate map, choose "custom" map projection and then choose either northern or southern polar stereographic projection. For lat range, enter 0 to 90 (for northern hemisphere) or -90 to 0 for southern. For longitude, the center of the longitude range input will be at the bottom of the plot. To center along 0E, choose -180 to 180, for example. To center at 90E, choose -90 to 270. You can plot sectors as well. The longitudes -90 to 90 in the NH will plot the half hemisphere from the US across the Atlantic to Europe.

*How this page was created

The main interface for this page is an html form. The data that are input into this form are processed by a Perl script. The script reads the inputs, tests for bad inputs and then executes a FORTRAN code that produces a composite file (in netCDF). This file is what is processed by a GrADS script. The GrADS script is run as a batch job with the plot created in a virtual frame buffer (to increase the quality of the gif output). Plot options are input into the GrADS script at this time. The plot in the frame buffer is converted to gif and this gif is displayed as part of a html document. The netCDF file and the gif file are kept in a directory where the files are periodically deleted.


Please let us know if find the page useful. Likewise, let us know if you think any instructions are unclear, if you think there are bugs or if you have any suggestions for improvements of any type. We would particularly like to know if you use these pages for teaching purposes and if so, how. We can be reached by email at

*How to reference

Find out how to reference plots and datasets in publications.