United States
Department of
Agriculture
Statistical
Reporting
Service
Statistical
Research
Division
May 1982
Esti mati ng
Daily Advective
Contributions
to
Potential
Evapotranspi ration
Richard G. Stuff
Jerry D. Hill
ESTIMATING
DAILY ADVECTIVE
CONTRIBUTIONS
TO POTENTIAL
EVAPCTRANSPlRATlON
Richard G. Stuff
and
Jerry D. Hill
Climate Assessment
Technology,
Inc.
This research was conducted as part of the
AgRISTARS Yield Model Development
Project.
It was developed
in response to task 5 in
major project element number 3 as identified
in the 1981 Yield Model Development
Project
Implementation
Plan.
As an internal project
documeut,
this report is identified
as
shown below.
AgRISTARS
Yield Model Development
Project
YMD-U2-04245
May 1982
Weather Map Information
fOr Estimating Daily
Potential
Evapotranspiration.
By
Richard
Statistical Reporting Service; u.S. Deparbnent
D.C., 20250. SRS Staff Report No. AGES820428.
ABSTRACT
Advective
Contributions
to
G. Stuff and Jerry Hill;
of Agriculture;
Washington
Wind speeds, local and up-wind
temperatures, and dew-point temperatures
extracted from 1200-GMT surface maps were found to explain 37 to 57 percent of
the variance in the ratios of equivalent latent energy (LE) to net radiation
(RN) for "crop stage" subgroups of soybeans at four site-year combinations in
eastern and central
Nebraska.
The
corresponding
linear
regression
relationships were consistent between subgroups. Differences between subgroup
ratios which were not explained by the data may have resulted from differences
in crop maturity, methodology, or insufficient weather information. A similar
analysis applied
to alfalfa at the same sites was less conclusive.
This
possibly was due to underestimation of advective heat by the Bowen Ratio
Energy Balance method used.
Key words: Advection effects, potential evapotranspiration, synoptic weather
applications
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This paper was prepared for limited distribution to
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the research community outside the Department