Unidata Regional Workshop - 2004

at Millersville University

An IDV Vertical Cross Section of Temperature Anomaly

(updated to version 1.1)

by

Bill Fingerhut

Lyndon State College

A vertical cross section of temperature does not show as much structure as possible because the vertical temperature gradient is much larger than the horizontal temperature gradient. One way to solve this problem is to subtract the U. S. Standard Atmosphere from the temperature field, and create a vertical cross section of temperature anomaly.

Below is an example using ETA forecast data for 0 GMT on March 13, 2002.







A vertical cross section of temperature anomaly can discern:
  • the vertical level of temperature anomalies,
  • the horizontal location of large horizontal temperature gradients, and
  • the anomaly reversal across the tropopause.

Creating a Vertical Cross Section of Temperature Anomaly

Using the IDV

http://apollo.lsc.vsc.edu/~fingerhutb/UserWshop2004/W2004_IDV_LabF.html

  • Create Jython Method and Formula
  • Identify a Data Source
  • Create Vertical Cross Section Display
Create Jython Method and Formula
  • Start the IDV
  • Create Jython method
    • in the, Data Selector, window: choose, Edit, Formulas, Jython Library
      • choose the, DefaultIdv/default.py, tab
      • copy (exactly) and paste the following jython method after the last line of Jython:
        • def tempAnom(t):
    """ temperature anomaly from U.S. Standard Atmosphere """
    # get pressure levels of temperature grids
    p=extractPressureFromNWPGrid(t)
    # calculate temperature for a constant lapse rate (6.5 C/km) atmosphere
    tstd=288.15*(p/1013.25)**(287.05*.0065/9.806)
    # change temperature in stratosphere to isothermal (216.65 K)
    for i in range(len(p)):
      if p[i] < 225.0: 
        tstd[i]=216.65
    # calculate the temperature anomaly
    tanom=t-tstd
    return tanom
      • click the, Save, button
      • click the, OK, button
  • Create Formula
    • in the, Data Selector, window: choose, Edit, Formulas, Create Formula
      • In the, Formula Editor, window enter the following data:
        • Name: anomaly of temperature
        • Description: anomaly of temperature
        • Group: standard atmosphere
        • Formula: tempAnom(temperature)
        • check the, Use all displays, box
        • click the, Add formula, button
Identify a Data Source

Data sources (data sets) can be identified in several different ways in the IDV. Two are presented below. The first method accesses a Netcdf grid file on a remote server, and the second accesses real-time model data on a remote server. Try one or both if you have time.

  • Netcdf grid file on a remote server
    • In the, Data Selector, window click the, Add New Data Source, button
      • In the, Data Source Selector, window choose the, URLs, tab
        • choose, Data Source Type: Netcdf grid files
        • copy (exactly) and paste in the, URL:, box, http://apollo.lsc.vsc.edu/~fingerhutb/UserWshop2004/2002031200_eta.nc
        • click the, Add Source, button
    • In the, Data Selector, window the selected data source should appear in the, Data Sources, pane

  • or, Real-time model data on a remote server
    • In the, Data Selector, window click the, Add New Data Source, button
      • In the, Data Source Selector, window
        • choose the, Catalogs, tab
        • open the folder of the desired NCEP model and choose the model run desired
        • Click the, Add Source, button
    • In the, Data Selector, window the selected data source should appear in the, Data Sources, pane
Create Vertical Cross Section Display
  • In the, Data Selector, window
    • In the, Data Sources, pane click, Formulas
    • In the, Fields, pane
      • open the, standard atmosphere, folder
      • choose, anomaly of temperature
    • In the, Displays, pane
      • open the, Cross sections, folder
      • choose, Contour Vertical Cross Section
    • Click the, Create Display, button
  • In the, Field Selector, window
    • open the desired data source folder
    • open the, 3D grid, folder
    • select, temperature (at isobaric levels)
    • click the, OK, button

The display should appear soon. In the, Unidata IDV, window you will see a map and a line that represents the location of the vertical cross section. The ends of the cross section can be moved by dragging with the left mouse button.

  • In the, Unidata IDV, window
    • use the left mouse button to slowly drag the right edge of the cross section to the center of Hudson's Bay
    • use the left mouse button to slowly drag the left edge of the cross section to the center of Cuba
  • In the, anomaly of temperature Contour Cross Section, window: use the left mouse button to slowly drag a corner of the window to enlarge the window
After you successfully create a vertical cross section of temperature anomaly, explore other geographical locations, forecast times, and models. North-south cross sections from pole to pole, and east-west cross sections across a front are often nice. If you find an interesting pattern, please let me know. It would be fun to see what turns up !