Details and instructions on the monthly timeseries creation webpage

Year entry box | Variables | Type of Plot (Mean, Long Term Mean and Anomaly)
Plotting Regions | Lagged Maps | Contour interval option | Page Creation | Feedback

Page will plot time series of selected pressure level variables from different reanalysis datasets. Select desired options and hit "create plot". Most options have a default setting so a selection is not required. If you have problems, please email with ALL the options you chose. You will get a plot as well as the data used to create the final plot (in netCDF), a post script image and information on the dataset.

  • Dataset 1
    Access is provided to various global reanalyses. Currently, just pressure level data is available at the following common levels: 1000., 850.,700.,600.,500.,400.,300.,250.,200.,150.,100. mb. Note that the MERRA dataset is not defined for values below the surface.
  • Variable 1
    The following monthly variables are available for each of the reanalyses for the time period of each reanalysis: Geopotential Height, Zonal Wind, Meridional Wind, Air Temperature, Specific Humidity and Relative Humidity. All variables are converted to use a common unit.
  • Dataset 2(Optional)
    You can select a second datasets/variable. If you select a second variable, you must select a second dataset. If you choose a second dataset, the default is 1000mb Geopotential Height. If you choose a second variable, you can plot the difference between the two datasets, plot them on the same time plot, plot a scatter plot or plot a cross-correlation. The correlation and RMS difference will be returned as well as individual statistics on the processed dataset. You cannot plot two distributions.
  • Variable 2(Optional)
    The following monthly variables are available for each of the reanalyses for the time period of each reanalysis: Geopotential Height, Zonal Wind, Meridional Wind, Air Temperature, Specific Humidity and Relative Humidity. All variables are converted to use a common unit.
  • Start/End Year
  • Enter a year range. This will be the timeseries that is plotted/analyzed (e.g. for correlations). You can change the x-axis below to change the dates displayed but that will just affect the plot; not the analysis.
  • Time Averaging
  • You can choose to use the original monthly averages or you can create your own season. If you choose season, enter your starting and ending month for the season. The year of a season that extends over December is the year of the second month. Seasonal values are created by averaging monthly means or monthly anomalies. You cannot yet create seasons that don't average the months together (except for using all 12 months).
  • Statistic
  • You can plot means or anomalies. Anomalies are calculated relative to the climatology range that is input. Monthly anomalies are calculated first and then averaged to create seasonal values.
  • Climatology Range
  • Enter the years to use for the climatology when selecting anomaly or climatology. You can choose a different time range for each dataset if you desire.Plotting Climatologies will be available soon.
  • Grid Point/Region
  • Enter the latitude and longitude ranges (S to N and W to E) for each dataset. You can do a single point or an area average. Note that area averages are area weighted by the cosine of the latitude. NCL obtains the closest grid from a dataset and does not interpolate. To get timeseries averaged over 0E, use a negative longitude for longitude 1.
  • Output Type
  • There are 5 types:
    1. Timeseries
      Plots one or two timeseries. The same Y axis is used for each plot, if there are two. The same statistic and running mean option are also shown. You can plot different grids, variables, levels or datasets. To use a different Y axis, select that later in the options.
    2. Timeseries Difference Plot
      Plots the timeseries of the difference between the two selected timeseries.
    3. Distribution
      Plots the PDF of a single variable. For shorter timeseries, 15 bins are used and for longer, 25 are used. Note you may want to use seasonal values or remove the annual mean, or the distribution will include the annual cycle.
    4. Cross or Auto Correlation
      For single timeseries, the auto-correlation (at zero lag and up to +-12 months/seasons). For two variables, the cross correlation is shown. The first timeseries leads the second for XX lags.
    5. Scatter Plot
      Plots one timeseries vs. another.
  • Y-axis: Same or Different
  • Line plots will use the same Y axis as the second variable unless you choose "different".
  • Plot Type
  • For most plots, you can select a line plot or a bar plot.
  • Running Mean Smoother
  • Selecting "smoothed" will cause a running mean filter to be applied to input timeseries. For monthly data, the smoothing is in months and for season, the smoothing is number of years. The same smoother is applied to two timeseries if you choose two.
  • Override Y Bounds
  • You can input a Y range (low to high). If you select a value outside the range of the data, you will get a blank plot.
  • Override Date Range
  • Date bounds can be adjusted by entering the year range from low to high. This does not change the analysis. Values are calculated using the years in the input date range near the top of the page. It just affects how the plot is plotted and can be useful for matching other plots.
  • 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 NCL is run to read, analyze and plot the data. NetCDF and postscript are also produced. The netCDF file, image and other files are kept in a directory in which the files are periodically deleted.
  • Feedback
    Please let me know if find the page useful. Likewise, let me 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. I would particularly like to know if you use these pages for teaching purposes and if so, how. I can be reached by email at or by phone at (303) 497-6263.