daylength

This function computes sunrise time, sunset time and daylength for a
particular location and day of the year (Julian day). This is done using
equations by Spencer (1971) and Almorox et al. (2005).

utility

The phenology of plants (i.e. the timing of their annual life
phases) depends on climatic cues. For temperate trees and many other plants,
spring phases, such as leaf emergence and flowering, have been found to result
from the effects of both cool (chilling) conditions and heat. Fruit tree
scientists (pomologists) have developed some metrics to quantify chilling
and heat (e.g. see Luedeling (2012) <doi:10.1016/j.scienta.2012.07.011>).
'chillR' contains functions for processing temperature records into
chilling (Chilling Hours, Utah Chill Units and Chill Portions) and heat units
(Growing Degree Hours). Regarding chilling metrics, Chill Portions are often
considered the most promising, but they are difficult to calculate. This package
makes it easy. 'chillR' also contains procedures for conducting a PLS analysis
relating phenological dates (e.g. bloom dates) to either mean temperatures or
mean chill and heat accumulation rates, based on long-term weather and phenology
records (Luedeling and Gassner (2012) <doi:10.1016/j.agrformet.2011.10.020>).
As of version 0.65, it also includes functions for generating weather
scenarios with a weather generator, for conducting climate change analyses
for temperature-based climatic metrics and for plotting results from such
analyses. Since version 0.70, 'chillR' contains a function for interpolating
hourly temperature records.

Eike Luedeling

chillR

Statistical Methods for Phenology Analysis in Temperate Fruit
Trees

Lars Caspersen

Eduardo Fernandez

daylength function

<dl><dt>latitude</dt>
<dd>numeric value specifying the geographic latitude
(in decimal degrees) of the location of interest</dd>
<dt>JDay</dt>
<dd>numeric (usually integer) value or vector specifying the
Julian day (day of the year), for which calculations should be done.</dd>
<dt>notimes.as.na</dt>
<dd>parameter to determine whether for days without
sunrise or sunset, na should be returned for Sunset and Sunrise. If
left at FALSE (the default), the function returns -99 and 99 for
sunrise and sunset or polar nights and polar days, respectively.</dd></dl>

Arguments

Author

Compute sunrise and sunset times, and daylength — daylength

<dl>

<dt>latitude</dt>
<dd>numeric value specifying the geographic latitude
(in decimal degrees) of the location of interest</dd>


<dt>JDay</dt>
<dd>numeric (usually integer) value or vector specifying the
Julian day (day of the year), for which calculations should be done.</dd>


<dt>notimes.as.na</dt>
<dd>parameter to determine whether for days without
sunrise or sunset, na should be returned for Sunset and Sunrise. If
left at FALSE (the default), the function returns -99 and 99 for
sunrise and sunset or polar nights and polar days, respectively.</dd>

</dl>

daylength: Compute sunrise and sunset times, and daylength

Description

Usage

Value

Arguments

Author

References

Examples