An Investigation of Clouds and Precipitation for the Texas High Plains Page: 9
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0.4 altocumulus is reported as 0.6 altocumulus. In some instances the most
significant, rather than the predominant, cloud type is reported. Thus,
cumulonimbus may be reported even though another type of less significance
may be predominant. This recording procedure makes it extremely difficult
to determine the true individual cloud frequencies or amounts. Only the
frequency with which a cloud type is a predominating type in its layer can
be determined. In addition to these data limitations, there are several
others worth noting (Changnon, 1957; DesJardins, 1958; Sellers, 1958):
1. Cloud identification at night : It is obvious that visual
cloud observations are severely limited by darkness. In
many instances, cloud types and amounts at upper levels
may be difficult to detect and thus go unreported. Cirri-
form clouds are especially difficult to detect at night,
even when they are the only cloud type present. A sharp
rise in the frequency of occurrence of cirrus in the early
morning may be due simply to the fact that the sun has
risen and observation is possible. A study by Braham (1955)
in Arizona indicates the number of reports of cirriform
clouds increased directly with the lunar altitude. Cloud
amounts in all layers are subject to error under conditions
of darkness.
2. Obscuration by lower layers: In some instances, low-level
clouds may serve to obscure clouds at upper Lerelo. Smoke
and haze also contribute to the obscuration pr blem. This
probably causes middle and high clouds to be underestimated.
3. Observer error: Even though the observations are made by trained
observers, there is an error introduced in the recording of
types by different observers. A particular cloud type may have
a variable appearance and may be difficult to differentiate
from another type under certain conditions.
All of these limitations should be kept in mind when reviewing the
results rf this census.
No attempt has been made to differentiate between the four layers
reported. A particular cloud type is recorded and tabulated without regard
to the layer in which it occurred. Once a cloud type has been recorded at
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Haragan, Donald R. An Investigation of Clouds and Precipitation for the Texas High Plains, report, March 1970; Austin, Texas. (https://texashistory.unt.edu/ark:/67531/metapth839452/m1/21/: accessed July 16, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu; crediting UNT Libraries Government Documents Department.