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<pubdate>1992</pubdate>
<title>
Nevada: Monthly station normals of temperature,
precipitation, and heating and cooling degree days
1961-1990
</title>
<serinfo>
<sername>Climatography of the United States</sername>
<issue>81</issue>
</serinfo>
</citeinfo>
</srccite>
<typesrc>paper</typesrc>
<srctime>
<timeinfo>
<sngdate>
<caldate>1992</caldate>
</sngdate>
</timeinfo>
<srccurr>publication date</srccurr>
</srctime>
<srccitea>NCDC 61-90 M NV</srccitea>
<srccontr>
Data used to calculate mean annual temperature (MAT) and
mean annual precipitation (MAP) at dust trap sites
</srccontr>
</srcinfo>
<srcinfo>
<srccite>
<citeinfo>
<origin>U.S. Department of Commerce (Weather Bureau)</origin>
<pubdate>1964</pubdate>
<title>
California: Climatic summary of the United States--
Supplement for 1951 through 1960
</title>
<serinfo>
<sername>Climatography of the United States</sername>
<issue>86-4</issue>
</serinfo>
</citeinfo>
</srccite>
<typesrc>paper</typesrc>
<srctime>
<timeinfo>
<sngdate>
<caldate>1964</caldate>
</sngdate>
</timeinfo>
<srccurr>publication date</srccurr>
</srctime>
<srccitea>DOC 51-60 CA</srccitea>
<srccontr>
Data used to calculate mean annual temperature (MAT) and
mean annual precipitation (MAP) at dust trap sites
</srccontr>
</srcinfo>
<srcinfo>
<srccite>
<citeinfo>
<origin>U.S. Department of Commerce (Weather Bureau)</origin>
<pubdate>1964</pubdate>
<title>
Nevada: Climatic summary of the United States--
Supplement for 1951 through 1960
</title>
<serinfo>
<sername>Climatography of the United States</sername>
<issue>86-4</issue>
</serinfo>
</citeinfo>
</srccite>
<typesrc>paper</typesrc>
<srctime>
<timeinfo>
<sngdate>
<caldate>1964</caldate>
</sngdate>
</timeinfo>
<srccurr>publication date</srccurr>
</srctime>
<srccitea>DOC 51-60 NV</srccitea>
<srccontr>
Data used to calculate mean annual temperature (MAT) and
mean annual precipitation (MAP) at dust trap sites
</srccontr>
</srcinfo>
<procstep>
<procdesc>
The most important factors that influenced dust-trap
design in this study were:  (1) measuring the amount of
dust added to soils; (2) sampling on an annual basis; (3)
no protection other than being hard to find; and (4) the
cost and ready availability of components that might have
to be replaced from sources in small towns.  The original
design consists of a single-piece Teflon-coated angel-food
cake pan (see note 1) painted flat black on the outside to
maximize water evaporation and mounted on a steel fence
post about 2 m above the ground.  A circular piece of 1/4-
inch-mesh galvanized hardware cloth is fitted into the pan
so that it rests 3-4 cm below the rim, and glass marbles
fill the upper part of the pan above the hardware cloth.
The Teflon coating is non-reactive and adds no mineral
contamination to the dust sample should it flake.  The
hardware cloth resists weathering under normal
conditions.  The 2-m height eliminates most sand-sized
particles that travel by saltation rather than by
suspension in air; sand grains are not generally pertinent
to soil genesis because they are too large to be
translocated downward into soil profiles.  The marbles
imitate the effect of a gravelly fan surface and prevent
dust that has filtered or washed into the bottom of the
pan from being blown away.  The empty space below the
hardware cloth provides a reservoir that prevents water
from overflowing the pan during large storms.  This basic
design was modified in 1986 in two ways.  In many areas,
the traps became favored perching sites for a wide variety
of birds.  As a result, significant amounts of non-eolian
sediment were locally added to the samples (as much as
five times the normal amount of dust at some sites).   All
dust traps were fitted with two metal straps looped in an
inverted basket shape over the top and the top surfaces of
the straps were coated with Tanglefoot.  [Use of trade
names by the U.S. Geological Survey does not constitute an
endorsement of the product.] This sticky material never
dries (although it eventually becomes saturated with dust
and must be reapplied) and effectively discourages birds
from roosting.  In addition, extra dust traps surrounded
by alter-type wind baffles were constructed at four sites
characterized by different plant communities.   These
communities and sites are:  blackbrush (Coleogyne
ramosissima), creosote bush (Larrea divaricata), and other
low brushy plants at sites 1-5 on Fortymile Wash; Joshua
tree (Yucca brevifolia), other tall yucca species, and
blackbrush at site 18 on the Kyle Canyon fan; pinyon-
juniper (Pinus monophylla-Juniperus sp) at site 7 on
Pahute Mesa; and acacia (acacia sp), creosote bush, and
blackbrush at site 26 near the McCoy Mountains.  The wind
baffles imitate the effect of ground-level wind speed at
the 2-m height of the dust trap and permit comparison of
the amount of dust caught by an unshielded trap with the
amount that should be caught at ground level where
vegetation breaks the wind.
</procdesc>
<procdate>1984</procdate>
</procstep>
<procstep>
<procdesc>
Samples were obtained from the dust traps by carefully
washing the marbles, screen, and pan with distilled water
into plastic liter bottles. In the laboratory, the sample
was gradually dried at about 35&deg;C in large evaporating
dishes; coarse organic material is removed during this
process.  Subsequent analyses on dust samples included, in
the order they were performed:  (1) moisture, (2) organic
matter, (3) soluble salts and gypsum, (4) total carbonate
(calcite plus dolomite), (5) grain size, (6) major-oxide
chemistry, and (7) mineralogy (sand, silt, and clay
fractions).  The database for any given site commonly
contains gaps depending on how far the sample for a
particular year could be stretched through the analytical
cascade.  In some cases, samples from different years at
the same site or adjacent sites were combined to obtain
enough material for measuring grain size.
A sample was commonly retrieved and used in more than one
analysis if the first analytical procedure used was non-
destructive.  These sequential analytical techniques
included: (1) Moisture and organic-matter content (Walkley-
Black procedure in Black, 1965)  were measured on the same
split using 0.05 g.  (2) The entire sample was used to
extract the solution to measure soluble salts (Jackson,
1958) and was then dried and recovered; thus, subsequent
analyses were performed on samples without soluble
salts.  (3)  A 0.25-g split was used to analyze total
carbonate (Chittick procedure in Singer and Janitzky,
1986).   This split, free of carbonate after the analysis,
was recovered and used to analyze for major oxides and
zirconium.  (4) When sufficient sample (0.4 g) existed to
obtain grain size using the Sedigraph rather than by
pipette analysis, the clay and silt fractions were saved
and used to analyze mineralogy by X-ray diffraction.
Most of the laboratory analyses were performed in the
Sedimentation Laboratory of the Institute of Arctic and
Alpine Research in Boulder, Colorado, using standard
laboratory techniques for soil samples (see Black, 1965,
and Singer and Janitzky, 1986) that we adapted for use on
very small samples (the non-organic content of a dust
sample collected from one trap typically weighs less than
1 g/yr).  These adaptations generally result in larger
standard errors than normal for the results of different
techniques because the amount of sample used is smaller
than the recommended amount.
</procdesc>
<procdate>1985</procdate>
</procstep>
<procstep>
<procdesc>
Total dust flux is calculated by multiplying the mineral
weight times the fraction less than 2 mm times the pan
area times the fraction of year during which the sample
accumulated (in file labdust.xls, number of days divided
by 365).  Other dust-flux values for various components (i.
e. silt flux) are calculated by multiplying the total dust
flux by the percentage of the component.
Preliminary examination of the flux data indicated that
samples from some sites collected in 1985 and 1986, before
the trap design was modified to discourage birds from
roosting, were anomalously large (50-500% greater)
compared to those collected in later years.  All of the
anomalous samples had been recorded as having significant
amounts of bird feces at the time of collection.
Consultations with bird biologists confirmed that bird
droppings can contain significant amounts of mineral
matter, mostly derived from cropstones; the amount varies
with the species and with the diet of local populations of
individual species.  Moreover, perching birds can
contaminate the sample with material from their feet.  In
some cases, we have evidence of near-deliberate
contamination in the form of one or two pebble-sized
clasts of local rocks that were found in samples, possibly
dropped (or swapped for marbles) by large birds such as
ravens. Data from samples with large amounts of bird
droppings were discarded from further analysis and were
excluded from the computations of &quot;selected average&quot; flux
values.
</procdesc>
<procdate>1987</procdate>
</procstep>
<procstep>
<procdesc>
Major elements were measured in U.S. Geological Survey
laboratories on a split of the less-than-2mm fraction
remaining after analysis and removal of carbonate by the
Chittick method.  Major elements and zirconium were
analyzed by induction-coupled plasma spectroscopy (Lichte
and others, 1987).  In some cases, samples from different
years at the same site or adjacent sites were combined to
obtain enough material for measuring major-oxide
composition.
</procdesc>
<procdate>1988</procdate>
</procstep>
<procstep>
<procdesc>
Major oxides are calculated from elemental compositions
(file dusticp.txt) using the following equations based on
atomic weights:
SiO2  = Si/0.467
Al2O3 = Al/0.529
Fe2O3 = Fe/0.699
MgO   = Mg/0.603
CaO   = Ca/0.715
Na2O  = Na/0.742
K2O   = K /0.830
TiO2  = Ti/0.599
MnO   = Mn/0.774
ZrO2  = Zr/0.740
The percentages of major oxides and zirconium were then
recalculated to 100%, excluding water, volatiles, and
minor elements, and the ratios of major oxides to ZrO2 are
based on the recalculated values.
</procdesc>
<procdate>1988</procdate>
</procstep>
<procstep>
<procdesc>
Mineralogy was measured in U.S. Geological Survey
laboratories on splits of samples that had been previously
analyzed for grain size.  Samples of sand, silt, and clay
were slurried in water (sand samples were ground to a fine
powder) and mounted dropwise on glass slides.   Minerals
in the sand and silt fractions were identified by
characteristic peaks on X-ray diffractograms and their
relative amounts were estimated by measuring peak
heights.  Minerals in the clay samples were identified by
characteristic peaks obtained after the following
treatments:  air-dried, glycolated, and heated to 300
degrees C and 550 degrees C.  The relative abundances of
clay minerals were estimated by measuring the following
peak heights (in degrees 2 theta) and adjusted for
intensity variations between runs using the peak height of
quartz at 26.65 2 theta:  chlorite, 6.3 on the 550 degrees
C trace; kaolinite, 12.6 on the glycolated trace minus the
amount of chlorite; mica, 8.8 on the glycolated trace;
smectite, 5.2 on the glycolated trace; mixed-layer mica-
smectite, 8.85 on the 550 degrees trace minus the amounts
of mica and smectite.
</procdesc>
<procdate>1988</procdate>
</procstep>
<procstep>
<procdesc>
The National Climatic Data Center no longer publishes mean
climatic data for the entire length of record at weather
stations.  To obtain mean annual temperature (MAT) and
precipitation (MAP) for the weather stations nearest the
dust traps, averages had to be computed from climatic
summaries of the United States (U.S. Department of
Commerce, 1952, 1965), from station normals for 1961-1990
(National Climatic Data Center, 1992), and from various
climatological data annual summaries.  Comparisons could
then be made of the long-term averages with those for the
five years of dust collection (file climate.xls).
</procdesc>
<procdate>1993</procdate>
<srcused>DOC 51-60 CA</srcused>
<srcused>DOC 51-60 NV</srcused>
<srcused>NCDC 61-90 A CA</srcused>
<srcused>NCDC 61-90 M CA</srcused>
<srcused>NCDC 61-90 A NV</srcused>
<srcused>NCDC 61-90 M NV</srcused>
</procstep>
<procstep>
<procdesc>
The dust-trap sites are at different elevations from the
nearest weather stations.  To estimate mean annual
temperature (MAT) and precipitation (MAP) at the sampling
sites, annual climate data for the entire period of record
was obtained for every weather station in the region,
including some that are no longer maintained but excluding
those in coastal California.  The data in this file was
combined from the data in file aveclim.xls, which included
the weather stations nearest the traps, and from climatic
data for other stations.  For many stations with
relatively complete records, this involved computation of
the averages of MAT and MAP (columns under &quot;MAT
calculations&quot; and &quot;MAP calculations&quot;) compiled from
records prior to 1961, the last year in which averages for
the entire length of record were published by the U.S.
Department of Commerce (1965), and from station normals
for 1961-1990 (National Climatic Data Center, 1992).
Normals and averages are not published for stations with
missing data or those which were moved at some time; for
these stations, the computation required hand-entering
data for each year of record from the climatological data
annual summaries (columns under &quot;MAT records&quot; and &quot;MAP
records&quot;).
Linear regression (bottom left of file) was used to obtain
equations that relate temperature and precipitation to
elevation for these weather stations (columns
&quot;Elevation&quot;, &quot;MAT&quot;, and &quot;MAP&quot;) and to estimate these
parameters at sampling sites with different elevations.
For temperature, only one equation was required; it
provides estimates with a standard error (s.e.) of only
1.3 degrees C.  For precipitation, equations were most
useful when the stations were divided into three
geographic regions, including the area of the Mexican
border and the Colorado River-southeast Nevada corridor
(s.e.=2.6 cm), southwestern California east of the
Transverse Ranges (s.e.=8.6 cm), and the interior deserts