Instructions for the WRIT Monthly Timeseries webpage

Topics:
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.

Variable Selection

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. for reanalyses. Note that the MERRA dataset is not defined for values below the surface. There is a new option for users to choose a climate time-series such as a PNA index or else upload their own timeseries. Choose Pre-generated Time Series and then either choose a time-series or select User Uploaded and enter the pathname and a title. See the use your own timeseries directions.

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. There are also single level variables. If you select "Pre-generated Time Series" you will not see the variable list. All variables are converted to use a common unit.

Dataset 2

(Optional)

You can select a second datasets/variable similarly to Dataset 1 above.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. here are also single level variables. If you select "Pre-generated Time Series" you will not see the variable list. 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, anomalies, or long term mean (climatology). 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.

Grid Point/Region

Foe time-series created from gridded datasets, 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.

Plotting Options

Output Type

There are 5 types:

    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.

    Timeseries Difference Plot
    Plots the timeseries of the difference between the two selected timeseries.

  1. 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.

  2. 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 lags.

  3. Scatter Plot
    Plots one timeseries vs. another.
  4. Wavelets
    For one timeseries, the technique decomposes a timeseries into time/frequency space simultaneously. One gets information on both the amplitude of any "periodic" signals within the series, and how this amplitude varies with time. See a more complete description of wavelets for this analysis page and how to cite their use. Note, currently, only monthly time-series with no missing are allowed for this page.

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 Year 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.

Show Plot markers

Markers for each point can be added to the plot.

Legend Location

By default, the legend is on the top right. This can be moved which is helpful if it overlaps the line 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 PSD 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, or additional datasets or index time-series.

WRIT is supported in part by NOAA/ESRL Physical Sciences Division, the NOAA Climate Program Office, and the US Department of Energy's Office of Science (BER). WRIT contributes to the Atmospheric Circulation Reconstructions over the Earth (ACRE) Initiative.