Welcome to the North American Drought Atlas, an HTML web browser
program that provides access to 286 annual drought reconstructions
extending as far back as 1,992 years into the past. The reconstructions
are derived from 835 exactly dated, annual tree-ring chronologies. A
description of the Palmer Drought Severity Index (PDSI), the network of
tree-ring chronologies used, and the method by which the reconstructions
were built, is given in the "Methods" chapter of this Atlas.
This chapter describes how to configure one's HTML web browser to
download and properly view the PDSI reconstruction plots, maps and
annimations. All the data and images within this Atlas are freely
available for responsible use without modification. The citation for these
data is:
Cook, E.R. and P.J. Krusic. 2004. The North American Drought Atlas.
Lamont-Doherty Earth Observatory and the National Science Foundation.
This Atlas was developed by Paul J. Krusic and Edward R. Cook,
Tree-Ring Laboratory, Lamont-Doherty Earth Observatory of Columbia
University, Palisades, NY USA through support from the National
Science Foundation, Division of Atmospheric Sciences, Award
ATM 03-22403. Questions, comments, or suggestions may be sent to:
Edward R. Cook or Paul J. Krusic (when we're around).
I. Software Requirements
As with any web-based information service the appearance of HTML
text and images will vary depending on the platform one is working on.
This Atlas was originally written on a Macintosh computer running
OS X 10.2 and the new, "Safari" (1.0 v85) web browser. The Atlas has
been tested to read well with a limited number of other configurations,
particularly "Internet Explorer". In each case, the font size was set
to 14 points in the browser "Preferences". That is our suggestion for
you as well.
The following browsers and "Helper" applications (or "Plug-ins") will
properly display the Atlas' pages:
Macintosh OS X 10.2 - Safari (1.0v85 or higher) using QuickTime
Player to display animations and .pdf files. Netscape (7.1) using
Adobe Acrobat Reader to view .pdf files and QuickTime Player to
view animations. - Explorer (5.2) for Macintosh using QuickTime
Player to view both .pdf files and animations.
Windows XP - Explorer (6.0) configured to use the QuickTime (for
Windows) Player to open .pdf files and animations.
II. Configuring Your Browser
All browsers, within their "Preferences" menu, have a means to
associate certain file types, e.g., .pdf, .avi, .txt, with a specific
application. The majority of images within the pages of this Atlas
are in .pdf format. PDF files are not instantly recognizable by all
browsers especially their older versions. We have found that installing
helper applications after installing a browser often configures the
browser to automatically choose the proper helper application. If you
are experiencing difficulty viewing any of the pages in this Atlas the
most likely explanation is your browser does not know what application
or to use for displaying the page or image. If this is the case, it may be
necessary to first go to the download page of this chapter and install
the suggested programs on your computer, or open the files directly
within any of the above mentioned the helper applications.
III. Window Managing
The Atlas is designed to display properly on a screen as small as 12
inches, however, the area needed to see a whole page may vary on the
platform used. Scroll bars are provided to permit the reader to see all
options and links when the size of the browser's window or frame is
too small.
We do not recommend leaving too many pages open at a time. Resizing
windows will have a different effect depending on the browser. For the
browser configurations mentioned above, we found, the resizing of
pages and frames behaves well.
IV. Downloading Files and Archives
Most of the data and images available for download are stored in
compressed archives containing all the grid-point or annual map files.
These collections are quite large and are compressed to conserve space.
All archives are in .zip format and may be decompressed by programs
such as Stuffit, for both Macintosh and Windows environments or
WinZip for Windows machines only.
The exception to the rule are the individual grid-point reconstruction
data files, including the grid-point validation statistics. These grid-
point files are ASCI text files and may be opened directly with a text
editor such as Simple Text, or BBedit for Macintosh users or Windows
Notepad for PC users.
Text File Format of Individual Grid-Point Files:
Consider the 100th grid point file (file name: 110.0W_45.0N_100.txt),
which is located at 110 degrees west longitude and 45 degrees north
latitude. A row of an Individual Grid-Point File may be read with the
following FORTRAN format specification (i5,2i7,8f8.3). Each row
represents a year of data and the number of rows defines the length
of the grid-point reconstruction. The columns are defined as follows:
Column #1: YEAR the calendar years of the reconstruction
Column #2: NREC the number of grid point reconstructions used
to optimally extend the reconstruction back
as far a possible, based on a Queen's Case
design
Column #3: NCRN the number of chronologies avaible for use in
the reconstruction for each calendar year
Column #4: RECON the summer PDSI reconstruction itself
Column #5: 20LP 20-year low-pass filtered version of the
reconstruction
Column #6: CRSQ the calibration period R-square over time
Column #7: VRSQ the verification period R-square over time
Column #8: RE the reduction of error verification over time
Column #9: CE the coefficient of efficiency verification over
time
Column #10: ACT actual summer PDSI data used for calibration
and verification
Column #11: 20LP 20-year low-pass filtered version of the actual
data
The grid point PDSI records over the coterminous USA extend out to
2003. All other grid point records end in 1990, with -99.999 used as a
missing data flag. Also be advised that all PDSI estimates in the
reconstruction are based on instrumental data after 1978.
Text File Format of the Complete Grid-Point Data Matrix Files:
These complete files contain the information for all 286 grid-points
in one large martrix. There is a matrix for NCRN, RECON, CRSQ, VRSQ,
RE, and CE, with the beginning year being -1 and the outer year 2003
in every case. As before, missing values are indicated by -99.999 flags.
The columns represent the grid point and the rows represent years. The
following FORTRAN format specification will read these files correctly
(i5,286f8.3).