springpheno (version 0.5.0)

chillh: Chill Hours Calculator

Description

This function calculates the chill hours for a given day and plant given the high and low temperature, plant base temperature, and day length (from the daylength function). Still in development, but based on Schwarz et al. (2006 and 2013)

Usage

chillh(tmax, tmin, daylen, baset)

Arguments

tmax

Scalar - daily high temperature in degrees Fahrenheit

tmin

Scalar - daily low temperature in degrees Fahrenheit

daylen

Scalar - day length in hours

baset

Scalar - base temperature for determining chill hours. Typically this is 44.96 degrees Fahrenheit, but can be plant specific.

Value

CHOUR - total chill hours for a given day. That is, number of hours the temperature fell below baset.

References

Schwarz, M., R. Ahas and A. Aasa, 2006: Onset of spring starting earlier across the Northern Hemisphere, 12, DOI: 10.1111/j.1365-2486.2005.01097.x

Schwarz, M., T.R. Ault and J.L. Betancourt, 2013: Spring onset variations and trends in the continental United States: Past and regional assessment using temperature-based indices. International Journal of Climatology, 33, DOI: 10.1002/joc.3625

Examples

# NOT RUN {
 daystop <- 366
lat <- 35.476 # latitude for OKC
daylen <- daylength(daystop=daystop,lat=lat)

tmax <- 65
tmin <- 42
dlen <- daylen[60]
bt <- 44.96

result <- chillh(tmax,tmin,dlen,bt)

# }