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N
0
calculator for soil moisture sensors
Calculate the calibration parameter
N
0
based on counting rate and other data. Scale to high latitude sea level if lat/long are provided (optional). See notes below for explanation of variables and constants.
Calibration variables
VWC
(0.02 to 0.50)
N
, cph
(10
0
to 10
5
)
t
, min
(1 to 7200)
P
, mb
(1100 to 500)
P
0
, mb
(1100 to 500)
T
, deg C
(-70 to 140)
RH, %
(0 to 100)
F
sol
(0.2 to 2.0)
Soil constants
ρ
b
, g cm
-3
(0.2 to 2.0)
SOC_eq, g g
-1
(0 to 0.15)
LW, g g
-1
(0 to 0.15)
BM, g g
-1
(0 to 0.15)
Site location (optional)
Latitude
(90°N to -90°N)
Longitude
(0°E to 360°E)
Year
(1900 to 2024)
Calculation took 0 seconds
Explanation:
Calibration variables: all except
f
sol
are usually taken from measurements on-site during calibration.
P
0
is arbitrary but is usually something typical for the site.
N
: Raw counting rate averaged over the nominal calibration period.
P
: Pressure over the nominal calibration period.
P
0
: Reference pressure; must be the same
P
0
used in calculating the soil moisture timeseries. Can be calculated from International Standard Atmosphere
https://crnslab.org/util/atmo.php
T
: Air temperature (for specific humidity correction).
RH
: Relative humidity (for specific humidity correction).
f
sol
: Solar activity factor. This can be obrained from
https://crnslab.org/util/solar.php
Soil constants: these are assumed to be constant soil properties of the site.
ρ
d
: soil bulk density
SOC_eq
: Water equivalent value of soil organic carbon. Generally found by multiplying SOC by 0.5 per Franz et al., 2015, GRL.
LW
: Lattice water.
BM
: Biomass.
Site location (optional): For scaling
N
0
to high latitude/sea level.
Latitude
: site latitude.
Longitude
: site longitude.
Year
: year calibration was performed.
Additional notes:
For simplicity, values of N, P, T and RH represent the mean value over the calibration period. This allows the user to input a single value for each variable rather than an array of hourly values. Such a simplification is justified when the variable, particularly P, does not change much over the averaging period. If the change in pressure is <10mb then the error in N0 will be less than 0.1% and can be safely ignored.
Changes: 07-May-2024: changed SOC to SOC_eq and added explanation.