Instrument Descriptions



Calculated Dew Point (from air temperature and rel humidity) (DEW_CALC)

Computed from relative humidity and air temperature every sampling
interval (15 seconds).

DEWPOINT AND VAPOR PRESSURE DEFICIT EQUATIONS
From 'Tetens Equation'for the relation between temperature and the
partial pressure of water vapor:
e(millibars)=6.1078 exp((17.269*T)/(237.3+T))
T is temperature in degrees C
and the equation for relative humidity:
Rh=(ea/es)*100
ea is the actual vapor pressure or vapor pressure at dewpoint
temp.
es is the saturation vapor pressure or vapor pressure at air
temp
it can be shown that:
Tdew=(237.3*X)/(17.269-X)
where X=ln(Rh/100)+((17.269*Tair)/(237.3+Tair)).

Vapor Pressure Deficit = es-ea = es-(Rh*es/100) at any instant.

********************************


DEFINITIONS:

SATURATION VAPOR PRESSURE: water evaporating and condensing
through
the air-water interface yields zero net transport.

Ideal gas law to sat vap pr:
e = pRT
e=vapor pressure in millibars
p=vapor density in mass/unit volume (g/cubic meter)
T=absolute temperature (degrees Kelvin)
R=vapor gas constant

If we use the universal gas constatant for R, the formula becomes
e = 1.61pRT

which becomes
p = 0.622e/RT

This is known as VAPOR DENSITY or ABSOLUTE HUMIDITY of the
atmosphere.

RELATIVE HUMIDITY is the ratio of the vapor density (or pressure)
to
the saturation vapor density (or pressure) at the same
temperature.

--------------

APPROXIMATIONS:

For sat vap pr in temperature range 25-55 deg Fahrenheit:
e == 6.11 + 0.339(D-32)
e = sat vap pr in millibars
D = dew point temperature in Fahrenheit

For sat vap pr in temperature range 25-55 deg Fahrenheit:
e == 0.18 + 0.01(D-32)
e = sat vap pr in inches of mercury
D = dew point temperature in Fahrenheit

Relative humidity can be approximated from air and dewpt by
rh = 100 ((112 - 0.1T + D) / 112 + 0.9T)**8
T = temperature
D = dew point
(Range of valid temperatures is unknow).

Dewpt can be approximated in temp range -40 to 50 deg C by
T - D = (14.55+0.114T)x + ((2.5+0.007T)x)**3 +
((15.9+0.117T)x)**14
T = temperature
D = dewpt
x = complement of rh in dec form, ie. x = 1.0 - (rh/100)


Rustrak strip chart and dewpoint sensor (DEW_CHT1)

Precision: +/- 1 degree C

Dewpoint temperature measured with a heated lithium-chloride dewpoint
sensor. The sensor temperature is measured with a thermistor and
recorded continuously on a separate 30-day Rustrak strip chart scaled
from -5 degrees C to 20 degrees C with and accuracy and resolution of 1 degree C. This sensor was often very unreliable. Datalogger is the
Interface Instrument M-2 or M-3.


Interface Instrument hygrometer with linear thermister (DEW_HYG1)

Precision: +/- 0.5 degrees C

Dewpoint temperature measured indirectly by a heated Interface
Instrument lithium-chloride hygrometer with a linear thermistor. The
accuracy is +/-0.5 degrees C with a resolution of 0.1 degrees C, and range of -14 to 29 degrees C. Data logger is the Interface Instrument
M-4.


No Instrument (NO_INSTR)

No instrument located at the site. Records are estimated from other
sites or is missing.


Heated raingage 8" diameter, A-35 chart recorder (PPT_A35R)

The gage sits on top of a shelter and is heated with a propane heater.
Continuous precipitation is recorded with depth measurements using a
Stevens A-35 chart recorder.


Heated raingage 8" diameter, A-35 chart recorder, w/standard (PPT_A35S)

Recording rain gage record is adjusted to a nearby 8"standard gage
(PNUSWB). The gage sits on top of a shelter and is heated with a
propane heater. Continuous precipitation is recorded with depth
measurements using a Stevens A-35 chart recorder.


Levno bullet-shaped precip gage (PPT_BULL)


Heated raingage, 8" diameter, with pressure transducer (PPT_PT08)

... with Campbell Scientific data logger


Heated raingage, 12" diameter, with pressure transducer (PPT_PT12)

Gage is a standing pipe employing an Alter shield with water depth
measured by a pressure transducer. Gage is heated with a propane
heater controlled by the datalogger and thermistor. Gage has a 12"
orifice which is slanted where the slant is equal to the site's slope. Gage was tipped over and subsequently rebuilt in Oct 1994 with
a shortened stand pipe. An MTS magneto strictive float gage replaced
the pressure transducer.


PVC Standard Raingage (PPT_PVC1)

The standard gage used is made from 2' sections of schedule 26 PVC
pipe, wall thickness of _5/16". The bottom is capped and the top edge
beveled to prevent rain from splashing in. The average inside
diameter is _7 7/8". These have 30" holding capacity. Water from
these gages is weighed and calibrated into inches.


Leupold-Stevens Q-12 snow-rain recording gage (PPT_Q12R)


Leupold-Stevens Q-12 snow-rain gage adjusted to standard (PPT_Q12S)

Recording rain gage record is adjusted to a nearby 8"standard gage
(PPT_USWB).


Sacramento Storage Gage (PPT_SACR)

Sacramento Storage Gage is 8" with approximately 200 inches storage
capacity and is mounted on platforms. Water depth is measured with
tapes and calibrated to inches through individual rating tables for
each gage.

The Sacramento Storage Gage consists of a 15-gal oil drum and a sheet
metal cone assembly. The oil drum serves as the storage can. The cone
assembly has three parts. The cone and inner skirt are cut from 24
gage and the catch ring from 22 gage galvanized sheet metal. The top
of the catch ring is beveled from the outside to form a cutting edge.
The inner skirt prevents loss of precipitation between the cone and
can. The complete gage is mounted on a tower to keep the top of the
gage well above maximum snow depth. The amount of precip. is the
difference between the weight of the charge and the weight of the
contents at the end of the period.


Stand Alone Raingage w/ Valdais windshield (PPT_SAR1)

Stand Alone Raingage with Valdais wind shield.

A New Type of Heated Orifice Raingage
by
Frederick Bierlmaier

A new type of raingage at the Upper Lookout Weather Station is
constructed in two sections:
1) a heated orifice section
2) an unheated stand pipe section.
A Valdais-style wind break fence surrounds the gages at UPLMET and CENMET. A natural tree break surrounds the gages at VANMET and PRIMET.
This gage is designed to work with a Campbell Scientific model
CR10 or CR21X datalogger. Some other brand would also work if it
had control outputs.

The heated orifice section is a 20" diameter stainless steel
funnel with copper tubing wrapped around it and clamped to it.
The tubing is thermally coupled to the funnel with heat sink
compound. A skin consisting of a layer of Reflectrix (tm)
insulation and an outer layer of fiber-glass covers the entire
outside of the funnel over the tubing to make an efficient heat
exchanger. This heat exchanger is plumbed to a DC pump and an
Aquastar (tm) tankless propane hot water heater in a closed loop.
The plumbing is filled with automotive anti-freeze solution.
The pump is wired to a 12 volt battery through a 12 volt normally
open power relay. The battery is kept charged by means of a 45
watt solar panel.

A temperature probe located near the lip of the funnel inside the
heat exchanger feeds temperature information to the datalogger.
When temperature falls below a programable setpoint the
datalogger turns on the pump via the relay with one of its
control outputs. The pump in turn turns on the heater. When the
temperature rises above another setpoint the pump and heater turn
off.

The entire orifice section is coated with Vellox (tm) hydrophobic
coating. This coating keeps moisture from clinging to the inside
of the funnel thus reducing evaporation losses. It also keeps
snow build up off the outside of the funnel.

The entire orifice section is coated with Vellox (tm) hydrophobic
coating. This coating keeps moisture from clinging to the inside
of the funnel thus reducing evaporation losses. It also keeps
snow build up off the outside of the funnel.

The standpipe section is a 10" diameter schedule 40 aluminum pipe
14' long with a 2' square piece of aluminum plate welded on one
end as an end cap. Triangular stiffeners are also welded between
the plate and the pipe. The stand-pipe is bolted to a 4' square
concrete pad. A drain valve is located near the bottom and a
filling tube near the top. One inch diameter threaded nipples
welded to the pipe in line 3'6" and 12'6" from the bottom are for
attachment of a 3" diameter pvc measurement tube to the side of
the aluminum pipe. An MTS Level Plus (tm) model LT420 (105"
range) magnetostrictive tank gage measures the fluid level and
transmits it to the datalogger. It is mounted in the measurement
tube. Originally, the gage was charged with 17 gallons of anti-freeze
solution, but this led to fluid level fluctuations with temperature.
The solution was a 50-50 mixture of propylene glycol and alcohol.
Currently, a thermistat controls a propane heater which keeps the
fluids from freezing. A layer of turbine oil covers the surface.

In this gage 1 inch of precipitation causes a rise of 3.67" in
the standpipe. Thus the gage can measure about 28" of
precipitation before it needs to be recharged.



Stand Alone Raingage (PPT_SAR2)


Shelter Raingage with Alter wind shield (PPT_SHL1)


Heated raingage 8" diameter, PAT with data logger (PPT_SHL2)

The gage sits on top of a shelter and is heated with a propane heater.
Continuous precipitation is recorded with depth measurements using a
PAT with Campbell data logger.


Tipping bucket gage, 8" diameter orifice, with data logger (PPT_TBR1)

Precision: +/- .254 mm

Texas Electronics tipping bucket raingage located on 1 m. high
platform. 8" orifice. Campbell Scientific data logger.


Tipping bucket,8" diameter, punch tape, w/standard (PPT_TBS1)

Tipping Bucket Recording rain gage record is adjusted to a nearby
8"standard gage (PPT_USWB). Recording gage description:
Propane-heated rain and snow gage, Model 6041, 8"diameter from WeatherMeasure WEATHERtronics. Uses a catalytic propane burner to melt
frozen precipitation in the collection funnel and to keep it from
refreezing inside the gage. The melted precipitation is funneled into
one of two tipping buckets. Accuracy is at 0.5% at 0.5"/hr.


Universal Recording rain and snow gage (PPT_UNIR)

Belfort Universal Recording Rain Gage, Cat No. 5-780 Series. 8"
diameter, 12" capacity. Accuracy of 1/3 of 1%. Meets National Weather
Service specifications.


Universal Recording rain and snow gage w/std (PPT_UNIS)

Belfort Universal Recording Rain Gage, Cat No. 5-780 Series
8"diameter, 12" capacity. Accuracy of 1/3 of 1%. Non-Recording
Precipitation Gage Cat No. 5-400, accuracy of .01" of ppt. Both meet
National Weather Service specfications


U.S.Weather Bureau Standard, 8"dia (PPT_USWB)


Mt Rose snow core sampler (SNO_COR1)

Mt Rose snow core sampler. Note that a new snow core sampler was put
into use on
approximately March 1, 1999. The new scale is capable of measuring
greater weights,
and generally weigh less on the new scale in comparison to the older
one.

At the meteorological stations, 5 snow core samples are taken along a
transect, and
average depth, water equivalence and density are calculated.
Snow moisture and snow depth are measured with snow cores at 5 points
across a transect. This station snow course (transect) is near the
station and tries to follow a single countour. The average depth,
water equivalence and density are calculated for these 5 points and
provide a check of the snow pillow and snow depth sensor.


Mt Rose snow core samples around snow pillow (SNO_COR2)

Snow cores were taken at each corner of the station's snow pillow.
Snow water equivalence, depth, and density were derived from the
average of these measurements. This method was modified because of
disruption around the snow pillow, and the method was changed so that
only snow depth is measured from installed stakes. Since the snow
density calculated from the snow course was similar to that at the
snow pillow, future calculations of snow water equivalence are
calculated using the snow course snow density along with the average
snow depth at the snow pillow.


Snow depth around snow pillow adjusted to snowcourse density (SNO_COR3)

Snow depth is measured at each corner of the station snow pillow using
a permanently set graduated stake (pvc pipe).
The average depth is converted to snow water equivalence using the
density calculated from the station snow course (the snow course consists of 5 snow core samples along a transect near
the snow pillow).


Tipping Bucket snow lysimeter with A-35 chart recorder (SNO_LYS1)

The lysmeter collection pan was constructed from 2x12s and plywood.
The pan was covered with hyplon (black plastic/vinyl polymer), and a
bathtub drain installed in one corner. The pan was installed on the
ground surface and was leveled such that the collected water would
flow to the corner with the drain. The water is then directed to a tipping bucket (TB) in the basement of the structure by pvc pipe which
is buried to prevent freezing. The final deminsions of the lysmeter
pan are 92"x93"x12", so a volume of water equal to .01" of ppt is
1.4032L.

The TB is a custom design. Each side of the bucket will hold about 3L
of water. TB tips were recorded by pen which makes a tic mark on the
margin of the A-35 chart and a mechanical counter. The event recorder
is a 12v recording pen element from an Esterline-Angus event recorder
which was altered slightly to mount inside the A-35 and leave a pen
trace on the chart. The counter is an old 12v mechanical counter. The
TB was first calibrated to tip for each .02" of ppt collected, however, after problems it was recalibrated to .01" per tip on 910815.
The A-35 clock scale was set to 9.6"/day and then later changed to
2.4"/day.


Tipping Bucket snow lysimeter with Campbell data logger (SNO_LYS2)

The CR-10 records the Tipping Bucket snow lysimeter tips (.01" of ppt/snowmelt input). Electro magnetic counter acts as a check to CR10
recorded tips. Sensors are connected to the CR10 or data logger
through a Campbell CR10WP wiring panel.

General installation: The lysmeter collection pan was constructed
from 2x12s and plywood. The pan was covered with hyplon (white vinyl
polymer), and a bathtub drain installed in one corner. The pan was
installed on the ground surface and was leveled such that the
collected water would flow to the corner with the drain. The water is
then directed to a tipping bucket (TB) in the basement of the
structure by pvc pipe which is buried to prevent freezing. The final
deminsions of the lysimeter pan are 92"x93"x12", so a volume of water
equal to .01" of ppt is 1.4032L.



Snow pressure pillow with pressure transducer (SNO_PIL1)

Snow moisture measured with a Park Mechanical pressure pillow and
Druck pressure trandsducer. Campbell Scientific data logger.


Snow pressure pillow w/prs.transducer and snow depth sensor (SNO_PIL2)

Precision: +/- 0.1mm depth

Snow moisture is measured with a Park Mechanical pressure pillow and
Druck pressure trandsducer and snow depth with a Campbell Scientific SR50 sonic ranging snow depth sensor. The snow depth sensor takes up
to 10 readings, performs error checking and outputs a reading in mm every 5 minutes. Depth sensor measurement range is 0.5 to 10 meters. The snow sensor iis mounted on a long pipe extending from the shelter.
Campbell Scientific data logger. Snow moisture and snow depth are
merged in the output files.


Snow pressure pillow w/prs.transducer and snow depth sensor (SNO_PIL3)

Precision: +/- 3 mm depth

Snow moisture is measured with a Park Mechanical pressure pillow and
Druck pressure transducer and snow depth with a Judd communications
snow depth sensor. The snow depth sensor takes up to 10 readings,
performs error checking and outputs a reading in mm every 5 minutes.
Depth sensor measurement range is 0.5 to 10 meters. The snow sensor
is mounted on a long pipe extending from the shelter. Campbell
Scientific data logger. Snow moisture and snow depth are merged in
the output files.


Campbell Scientific snow depth sensor (SNO_SDS1)

Campbell Scientific model SR50 sonic ranging snow depth sensor.


Campbell Scientific soil Moisture gypsum block (SOI_GYP1)

Campbell Scientific model 223 gypsum soil moisture block. Units are (-) Bars. A polynomial equation relates changes in soil moisture with
changes in block resistence. The manufacturer supplied equation is calibrated from -.1 to -15 bars. Values less than -15 bars are listed
as out of range. Data logger is Campbell Scientific.


Campbell Scientific soil moisture reflectometer (SOI_WCR1)

Precision: +/- 2%

Campbell Scientific CS615 Water Content Reflectometer.


LI-COR PAR (photosynthetically active radiation) sensor (SOL_PAR1)

LI-COR PAR (photosynthetically active radiation) quantum sensor,
Campbell Scientific model LI190SB. The output of the PAR sensor is a daily average, daily maximum and 15 minute averages, and the units are
in micromoles/sec/meter2.


Kipp and Zonen solar radiation pyranometer, model CM-5 (SOL_PYR1)

Precision: +/- .05 Langley

Kipp and Zonen, Inc. model CM-5 pyranometer with thermopile type sensor. Located on 1 meter high platform at Primary Met. Data logger
is the Campbell Scientific CR21X or earlier Instrument Interface M4
data logger.


Kipp and Zonen solar radiation pyranometer, model CM-6B (SOL_PYR2)

Precision: +/- .05 Langley

Kipp and Zonen, Inc. model CM-6B pyranometer located on top of the
shelter. Data logger is Campbell Scientific.


Lintronic dome solarimeter (SOL_SLR1)

Precision: 0.1 cal/cm_/min

Solar radiation measured with a Lintronic dome solarimeter. The signal is recorded continuously on a 30-day Rustrak strip chart scaled
from 0 to 2.0 cal/cm2/min with a resolution of 0.1 cal/cm2/min. This
sensor was often unreliable. Data logger is the Interface Instrument
M-2 or M-3.


Vaisala Relative Humidity/Temperature (TMP_35C1)

Precision: +/-2% RH

Temperature and relative humidity is sampled by a Campbell Model
HMP35C probe containing a Vaisala capacitive relative humidity sensor
and a Fenwal Electronics UUT51J1 thermistor. The probe is housed in a
locally designed PVC radiation shield. Data logger is a Campbell
Scientific.


Vaisala Relative Humidity probe (TMP_35C2)

Precision: +/-2% RH

Relative humidity is sampled by a Campbell Model HMP35C probe containing a Vaisala capacitive relative humidity sensor. The Vanilla
Leaf station probes are housed in a locally designed PVC radiation
shield. The Primet station sensor was housed in a Cotton Region
Shelter. Data logger is the Campbell Scientific CR21X.


Vaisala Relative Humidity/Temperature (TMP_45C1)

Precision: +/-2% RH

Temperature and relative humidity is sampled by a Campbell Model
HMP45C probe containing a Vaisala capacitive relative humidity sensor
and a platinum resistance thermometer. Data logger is a Campbell
Scientific model.


Rustrak strip chart with thermister (TMP_CHT1)

Precision: +/- 1 degree C

Air temperature is measured by a thermistor in a standard Cotton
Region Shelter and continuously recorded on a separate 30-day Rustrak strip chart scaled from -10 degrees C to 40 degrees C. Data logger is
the Interface Instrument M-2 or M-3.


Partlow chart, mercury bulb thermometers (TMP_CHT2)

Dual Recording Thermometer Model RFHTT. Records temperatures from two
separate locations (air and soil) simultaneously on a single chart.
Each of the two thermometer mechanisms operate with a mercury-filled
sensing bulb which expands or contracts in response to temperature
changes and in turn moves the recording pen along the calibrated
chart. To prevent interference between the two pens, the right-hand
pen records 1/12 revolution behind the left-hand pen. The recorder
uses 10" 30 and 31 day Partlow charts that have ranges from -30F -
170F or 20F - 120F.


Cole Parmer hygrothermograph chart (TMP_HYG1)

Precision: +/-1% RH

Cole Parmer hygrothermograph chart. The Hi-Q hygrothermograph is a
precision self-contained recording instrument that measures and
records ambient temperature and relative humidity simultaneously on a
double scale chart. A specially treated bundle of human hair is used
to measure relative humidity over the full range of 0 to 100%. The
hair expands and contracts with increasing or decreasing amounts of
water vapor in the air. The Belfort Maximum Minimum Thermometer Cat
No. 5-484 indicates the temperature extremes reached over a 24 hour
period and is the standard for adjusting chart temperature readings.
The chart is installed on a self-contained brass clock which is
spring-wound. Accuracy is +/- 1%.


Belfort hygrothermograph chart (TMP_HYG2)

TheBelfort hygrothermograph is a precision self-contained recording
instrument that measures and records ambient temperature and relative
humidity simultaneously on a double scale chart. A specially treated
bundle of human hair is used to measure relative humidity over the
full range of 0 to 100%. The hair expands and contracts with
increasing or decreasing amounts of water vapor in the air. The
Belfort Maximum Minimum Thermometer Cat No. 5-484 indicates the temperature extremes reached over a 24 hour period and is the standard
for adjusting chart temperature readings. The chart is installed on a
self-contained brass clock which is spring-wound. Accuracy is +/-
1%.


Thermocouple wire (TMP_THC1)

Probe is type T thermocouple soldered from thermocouple wire. Data
logger is Campbell Scientific, typically CR10, CR21X, CR500, or
CR23X..


Yellow Springs Instruments linear thermistor (TMP_THM1)

Precision: +/- 0.5 degrees C

Air temperature sensor: Yellow Springs Instrument Company YSI44018 linear thermistor in a standard Cotton Region Shelter. Data logger is
the Interface Instrument M-4.


Campbell Scientific thermistor probe (TMP_THM2)

Campbell Scientific model 107 temperature probe (CS107B, CS107B-L)
includes the Fenwal Electronics UUT51J1 thermistor. Data logger is a
Campbell Scientific, typically CR10, CR21X, CR500, or CR23X.

The Mack creek water temperature is measured by a Campbell Scientific
107L
thermistor temperature probe, and recorded on a Campbell CR-10
datalogger.
The temperature probe is housed in a 1/2 inch perforated PVC pipe, so
it
does have shading. The probe was checked weekly with an dial
thermometer or
a Barnant 100 thermocouple thermometer. Though not frequently
calibrated, the
check thermometers are consistantly within 1degree C or better.


Campbell Scientific thermistor probe (TMP_THM3)

Campbell Scientific model 107 temperature probe (CS107B, CS107B-L)
includes the Fenwal Electronics UUT51J1 thermistor. Data logger is a
Campbell Scientific, typically CR10, CR21X, CR500, or CR23X.

Soil temperature without pvc framework....needs description


USGS Maintained instrument (TMP_USGS)


Calculated Water Vapor Pressure Deficit (VPD_CALC)

Vapor Pressure Deficit. Computed from relative humidity and air
temperature
every sampling interval (15 seconds).

DEWPOINT AND VAPOR PRESSURE DEFICIT EQUATIONS
From 'Tetens Equation'for the relation between temperature and the
partial pressure of water vapor:
e(millibars)=6.1078 exp((17.269*T)/(237.3+T))
T is temperature in degrees C
and the equation for relative humidity:
Rh=(ea/es)*100
ea is the actual vapor pressure or vapor pressure at dewpoint
temp.
es is the saturation vapor pressure or vapor pressure at air
temp
it can be shown that:
Tdew=(237.3*X)/(17.269-X)
where X=ln(Rh/100)+((17.269*Tair)/(237.3+Tair)).

Vapor Pressure Deficit = es-ea = es-(Rh*es/100) at any instant.


Cup-type anemometer with M2 data logger (WND_ANE1)

Precision: +/- .25 m/sec

Windspeed: measured with a cup-type anemometer which provides contact closure for every .322 km of air movement. This signal is recorded by
an event marker along the border of the same Rustrak strip chart used
to record dewpoint. Data logger is Interface Instrument M-2.


RM Young 3-cup anemometer with M4 data logger (WND_ANE2)

Precision: +/- .25 m/sec

Wind speed sensors are R.M. Young #6101 tachometer generators mounted
on a tower. Data logger is Interface Instrument M-4.


RM Young Wind Monitor (WND_MON1)

Wind speed and direction is sampled by a RM Young Model 05103 Wind
Monitor mounted to the tower. Potentiometer measures direction,
anemometer measures wind speed. Data logger is a Campbell Scientific
model. Data collected by the Wind Monitor is processed by the
Campbell Wind Vector instruction #69 option #2.