||Pressure (force per unit area) exerted by the
atmosphere on any surface by virtue of its weight;
it is equivalent to the weight of a vertical column
of air extending above a surface unit area to the
outer limit of the atmosphere.
||The number of hours of temperature below
a threshold temperature.
|Chilling Hours Calculator
||Tool to calculate number of chilling hours for
a period specified by user and compared to previous
||Difference between the mean temperature of a
particular day and a pre-determined reference temperature. GDD are calculated by subtracting a base temperature from the average daily temperature (°F). If the resulting value is less than 0, then it is set to 0. Thus GDD are always 0 or greater.
GDD = (Tmax+Tmin)/2 - Tbase
|Degree Day Model
||Tool to calculate number of degree days for
period specified by user and compared to previous
||Temperature to which a volume of air must be
cooled at constant pressure and constant moisture
in order to reach saturation; any further cooling
The amount of water required to grow a crop consists of transpiration by the plant (T) due to water uptake and the water evaporated from the soil surface (E). Combined these two are called evapotranspiration (ET) and is also referred to as crop water use. ET is measured in inches (or mm) of water used per day. ETr is the estimated evapotranspiration of a reference surface of fully grown alfalfa crop and is calculated from measured weather parameters. These include solar radiation, air temperatures, relative humidity, and wind speed. The reference ET for alfalfa (ETr) is calculated with the ASCE standardized Penman-Monteith Equation (ASCE - EWRI, 2005)
||An index that combines air temperature and relative
humidity to determine apparent temperature—how it
||Water vapor content of air.
||Tool to calculate total rainfall in inches and
number of rainy days for a period specified by the
user and compared to past years and climatological
||A ratio, expressed in percent, of the amount
of atmospheric moisture present relative to the
amount that would be present if the air were saturated.
||Moisture contained in that portion of the soil
which lies above the water table, including water
vapor contained in the soil pores.
||Temperature at variable depths in the soil.
||A measure of the intensity of the sun's radiation
reaching the earth's surface. Radiation with wavelengths
from 0.3 to about 4um
||The degree of hotness or coldness of a substance
as measured by a thermometer.
||The comparison of actual and potential evapotranspiration
with amount of precipitation
||Air motion relative to the Earth's surface.
Unless otherwise specified, only the horizontal
component is considered.
||The combined effect of wind and temperature
on exposed human flesh.