JDay_earlier

For two Julian dates, this function checks whether the first date
is earlier than the second date within a user-defined phenological season.
This is particularly useful for seasons that start in one year and end
in the next, because simple &gt; or &lt; operations can produce wrong results
then.

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_earlier function

<dl><dt>check_date</dt>
<dd>integer ranging from 1 to 366, indicating a Julian date.
This is the date for which to check whether it is before the reference date.
If this is a vector, all elements are checked against the reference date.</dd>
<dt>ref_date</dt>
<dd>integer ranging from 1 to 366, indicating a Julian date.
This is the reference date.</dd>
<dt>season</dt>
<dd>integer vector of length 2, specifying the beginning and end
of the phenology season, respectivcely.</dd></dl>

Arguments

Author

Check whether a Julian date is before or after another one — JDay_earlier

<dl>

<dt>check_date</dt>
<dd>integer ranging from 1 to 366, indicating a Julian date.
This is the date for which to check whether it is before the reference date.
If this is a vector, all elements are checked against the reference date.</dd>


<dt>ref_date</dt>
<dd>integer ranging from 1 to 366, indicating a Julian date.
This is the reference date.</dd>


<dt>season</dt>
<dd>integer vector of length 2, specifying the beginning and end
of the phenology season, respectivcely.</dd>

</dl>

JDay_earlier: Check whether a Julian date is before or after another one

Description

Usage

Value

Arguments

Author

Examples