My WebLink
|
Help
|
About
|
Sign Out
Home
Browse
Search
WMOD00034
CWCB
>
Weather Modification
>
Backfile
>
WMOD00034
Metadata
Thumbnails
Annotations
Entry Properties
Last modified
7/28/2009 2:27:26 PM
Creation date
10/1/2006 2:11:33 PM
Metadata
Fields
Template:
Weather Modification
Contract/Permit #
#94-6
Applicant
North American Weather
Project Name
Willow Creek Basin
Date
11/1/1994
Weather Modification - Doc Type
Report
There are no annotations on this page.
Document management portal powered by Laserfiche WebLink 9 © 1998-2015
Laserfiche.
All rights reserved.
/
86
PDF
Print
Pages to print
Enter page numbers and/or page ranges separated by commas. For example, 1,3,5-12.
After downloading, print the document using a PDF reader (e.g. Adobe Reader).
Show annotations
View images
View plain text
<br />:-1 <br />-1 <br />I <br />I <br />I <br />1 <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />! I <br />I i <br />I <br />I <br />I <br />I <br /> <br />Perhaps the most commonly employed of these techniques is the "target" and <br />"control" comparison. This technique is based on the selection of a variable that would " <br />be affected by seeding (such as snow). Records of the variable to be tested are acquired <br />for an historical period of several years duration (20 or more if possible) when no <br />seeding occurred. These records are divided into those that lie within the designated <br />"target" area of the project and those in a nearby "control" area. Ideally, the control <br />area should be selected in an area which would be unaffected by the seeding. The <br />historical data, e.g., precipitation!snowpack, in both the target and control areas are <br />taken from past years that have not been subject to cloud seeding activities, since past <br />seeding could affect the development of a relationship between the two areas. Obviously, <br />these data are also taken for the same period of time (usually months) when the seeding <br />will be conducted. These two sets of data are analyzed mathematically to develop a <br />regression equation which predicts the amount of target area precipitation!snowpack, <br />based on precipitation! snowpack in the control area. This equation is then used during <br />the seeded period to estimate what the target area precipitation!snowpack should have <br />been, based on that observed in the control area. A comparison can be made between the <br />predicted target area precipitation!snowpack and that which actually occurred. Any <br />resulting difference can be tested for its significance through statistical tests. This target <br />and control technique works well where a good correlation can be found between target <br />and control area precipitation. Generally, the closer the two areas are together the higher <br />will be the correlation. Areas selected too close together, however, can result in an <br />underestimate of the seeding effect. For precipitation!snowpack assessments, a <br />correlation coefficient (r) of 0.90 or better would be considered excellent, and would <br />indicate that over 80 percent of the variance (r2) in the historical data set would be <br />explained by the regression equation used to predict the variable (expected <br />precipitation!snowpack) in the seeded years. <br /> <br />One of the hazards of this type of analysis is that a "dilution" of the seeding effect <br />is encountered due to the fact that seeding occurs on only some of the stonns during any <br />particular month, and in some instances seeding does not occur on any of these stonns. <br /> <br />5-2 <br />
The URL can be used to link to this page
Your browser does not support the video tag.