JDay_count

This function counts the days between two Julian dates, taking into
account whether the season extends past the end of a calender year and
whether the count is to be done for a leap year.

date

Phenology

season

Julian

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

JDay_count function

<dl><dt>start_date</dt>
<dd>integer ranging from 1 to 366, indicating a Julian date.
This is the start date of the interval of interest.</dd>
<dt>end_date</dt>
<dd>integer ranging from 1 to 366, indicating a Julian date.
This is the end date of the interval of interest.</dd>
<dt>season</dt>
<dd>integer vector of length 2, specifying the beginning and end
of the phenology season, respectivcely. If this is not specified, the
start_date and end_date are used to define the season.</dd>
<dt>leap_year</dt>
<dd>either a Boolean parameter indicating whether the count
should be done for a leap year, or an integer specyfing the year, for
which the calculation is to be done. The function then determines
automatically, whether this is a leap year.</dd></dl>

Arguments

Author

Count days between two Julian dates — JDay_count

<dl>

<dt>start_date</dt>
<dd>integer ranging from 1 to 366, indicating a Julian date.
This is the start date of the interval of interest.</dd>


<dt>end_date</dt>
<dd>integer ranging from 1 to 366, indicating a Julian date.
This is the end date of the interval of interest.</dd>


<dt>season</dt>
<dd>integer vector of length 2, specifying the beginning and end
of the phenology season, respectivcely. If this is not specified, the
start_date and end_date are used to define the season.</dd>


<dt>leap_year</dt>
<dd>either a Boolean parameter indicating whether the count
should be done for a leap year, or an integer specyfing the year, for
which the calculation is to be done. The function then determines
automatically, whether this is a leap year.</dd>

</dl>

JDay_count: Count days between two Julian dates

Description

Usage

Value

Arguments

Author

Examples