Difference between revisions of "Growing Degree Day"

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Growing Degree Days (GDD), also called Growing Degree Units (GDU) or Heat Units (HU), are based on the observation that within limits, plants grow faster when warm and more slowly when cold. Below a base temperature (T<sub>base</sub>), the plant is dormant and little growth occurs.   Plants grow in a cumulative stepwise manner which is strongly influenced by the ambient temperature.  Since growth depends on the accumulation of specific quantities of heat, by using Growing Degree Days is possible to predict when events such as bud break should occur during a growing season regardless of differences in temperatures from year to year.
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==Introduction==
 +
Plants grow in a cumulative stepwise manner which is strongly influenced by ambient temperature.  Growing Degree Days (GDD), also called Growing Degree Units (GDU) or Heat Units (HU), are based on the observation that within limits, plants grow faster when warm and more slowly when cold. Below a base temperature (T<sub>base</sub>), the plant is dormant and little growth occurs.   Since growth depends on the accumulation of specific quantities of heat, by accumulating Growing Degree Days it is possible to predict when events such as bud break (nectar flows) will occur during a growing season regardless of differences in temperatures from year to year.
  
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A simple theoretical formula for GDD at time t is:
 
[[File:GDD integral.png|frameless|center|400px]]
 
[[File:GDD integral.png|frameless|center|400px]]
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where: <br>
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T<sub>t</sub> = temperature at time t<br>
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T<sub>base</sub> = temperature below which plant growth is zero.<br>
  
At temperatures above an upper limit, (T<sub>max</sub>), the plant does not grow any faster.
 
  
Each plant species has  its  own  lower  air  temperature  threshold  and  upper
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In addition to the value of T<sub>base</sub>, the selection of the start date (t=0) will also change the value of accumulated GDD. Common start dates are:
air temperature threshold. This temperature range varies for each plant.
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#Coldest day of the year
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#Shortest day of the year
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#Arbitrary Gregorian calendar date (e.g. January 1)
  
Different methods exist for calculating heat units depending on a) the crop or biological
 
organism of interest and b) the whim or personal preference of the researcher.
 
Growing  degree  day  units  are  calculated  by  using  the  maximum  daily  air
 
temperature,  the  minimum  daily  air  temperature  and  the  crop’s  lower
 
temperature  threshold. 
 
  
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Each plant species has it's own upper air temperature threshold, T<sub>cap</sub>. 
 +
At temperatures above T<sub>cap</sub> the plant does not grow any faster.  T<sub>cap</sub> varies for each species.
  
The base temperature is that temperature below which plant growth is zero.
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In addition to selection of T<sub>base</sub>, T<sub>cap</sub> and and when t=0,
 +
different methods exist for calculating heat units depending on a) the crop or biological
 +
organism of interest and b) the whim or personal preference of the researcher.
  
The method most commonly used in the U.S. for determining heat unit accumulation relative to corn phenology is the formula first suggested by the National Oceanic and Atmospheric Administration. The “modified growing degree day formula” calculates daily accumulation of GDD’s as the average daily temperature minus 50° F.
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==NOAA Modified Growing Degree Day Formula==
 +
The method most commonly used in the U.S. for approximating GDD for phenology is the formula first suggested by the National Oceanic and Atmospheric Administration. The “modified growing degree day formula” calculates daily accumulation of GDD’s as the average daily temperature minus 50° F.
  
 +
This method of approximating GDD for each day is the average of the daily maximum and minimum temperatures above T<sub>base</sub>.
  
Calculate [http://en.wikipedia.org/wiki/Growing_degree_day Growing Degree Day (GDD)] for each hive and add to database.
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[[File:GDD average.png|frameless|center|400px]]
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Before calculating the average:
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*Any temperature below T<sub>base</sub> is set to T<sub>base</sub>.  
 +
*Any temperature above T<sub>cap</sub> is set to T<sub>cap</sub>.
 +
 
 +
If the mean daily temperature is lower than the base temperature then GDD=0.
 +
 
 +
Some warm temperate and tropical plants have significant requirements for days above 30 °C to mature fruit or seeds.  
 +
 
 +
When comparing GDD numbers from different sources, one must consider:
 +
#Are the base temperatures (T<sub>base</sub>) and the cap temperatures (T<sub>cap</sub>) the same?
 +
#Are the start dates (t<sub>0</sub>) for the accumulation the same?
 +
#Are the equations used to calculate the daily GDD the same?
 +
#Are the temperatures used in degrees Celsius or Fahrenheit?
 +
 
 +
==SQL calculation of GDD==
  
  
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   (least(greatest(max(wx_temp_c),10),30) - least(greatest(min(wx_temp_c),10),30))/2 AS gdd
 
   (least(greatest(max(wx_temp_c),10),30) - least(greatest(min(wx_temp_c),10),30))/2 AS gdd
 
   from HIVE_DATA group by DATE_FORMAT(`hive_observation_time_local`, '%Y-%m-%d'), hive_id
 
   from HIVE_DATA group by DATE_FORMAT(`hive_observation_time_local`, '%Y-%m-%d'), hive_id
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==References==
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 +
[http://www.hillagric.ac.in/edu/coa/agronomy/lect/agron-640/Advances-in-crop-growth-and-productivity-SSR-RSR-2014.pdf Rana SS and RS Rana. 2014. ''Advances in crop growth and productivity.'' Department of Agronomy, CSK Himachal Pradesh Krishi Vishvavidyalaya, Palampur, pg. 181-186]
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[http://en.wikipedia.org/wiki/Growing_degree_day Wikipedia Growing Degree Day (GDD)]

Latest revision as of 07:53, 26 November 2018

Introduction

Plants grow in a cumulative stepwise manner which is strongly influenced by ambient temperature. Growing Degree Days (GDD), also called Growing Degree Units (GDU) or Heat Units (HU), are based on the observation that within limits, plants grow faster when warm and more slowly when cold. Below a base temperature (Tbase), the plant is dormant and little growth occurs. Since growth depends on the accumulation of specific quantities of heat, by accumulating Growing Degree Days it is possible to predict when events such as bud break (nectar flows) will occur during a growing season regardless of differences in temperatures from year to year.

A simple theoretical formula for GDD at time t is:

GDD integral.png

where:
Tt = temperature at time t
Tbase = temperature below which plant growth is zero.


In addition to the value of Tbase, the selection of the start date (t=0) will also change the value of accumulated GDD. Common start dates are:

  1. Coldest day of the year
  2. Shortest day of the year
  3. Arbitrary Gregorian calendar date (e.g. January 1)


Each plant species has it's own upper air temperature threshold, Tcap. At temperatures above Tcap the plant does not grow any faster. Tcap varies for each species.

In addition to selection of Tbase, Tcap and and when t=0, different methods exist for calculating heat units depending on a) the crop or biological organism of interest and b) the whim or personal preference of the researcher.

NOAA Modified Growing Degree Day Formula

The method most commonly used in the U.S. for approximating GDD for phenology is the formula first suggested by the National Oceanic and Atmospheric Administration. The “modified growing degree day formula” calculates daily accumulation of GDD’s as the average daily temperature minus 50° F.

This method of approximating GDD for each day is the average of the daily maximum and minimum temperatures above Tbase.

GDD average.png


Before calculating the average:

  • Any temperature below Tbase is set to Tbase.
  • Any temperature above Tcap is set to Tcap.

If the mean daily temperature is lower than the base temperature then GDD=0.

Some warm temperate and tropical plants have significant requirements for days above 30 °C to mature fruit or seeds.

When comparing GDD numbers from different sources, one must consider:

  1. Are the base temperatures (Tbase) and the cap temperatures (Tcap) the same?
  2. Are the start dates (t0) for the accumulation the same?
  3. Are the equations used to calculate the daily GDD the same?
  4. Are the temperatures used in degrees Celsius or Fahrenheit?

SQL calculation of GDD

Centigrade
Tbase = 10
Tmax  = 30


SET @gdd_total:=0;
SELECT
  q1.doy,
  q1.gdd,
  round(@gdd_total := @gdd_total + q1.gdd) as gdd_tot
FROM
 (SELECT DAYOFYEAR(DATE_FORMAT(`hive_observation_time_local`, '%Y-%m-%d')) AS doy,
  (least(greatest(max(wx_temp_c),10),30) - least(greatest(min(wx_temp_c),10),30))/2 AS gdd
  from HIVE_DATA 
  where hive_id=10 group by DATE_FORMAT(`hive_observation_time_local`, '%Y-%m-%d') ) AS q1



SELECT hive_id, DAYOFYEAR(DATE_FORMAT(`hive_observation_time_local`, '%Y-%m-%d')) AS doy,
  (least(greatest(max(wx_temp_c),10),30) - least(greatest(min(wx_temp_c),10),30))/2 AS gdd
  from HIVE_DATA group by DATE_FORMAT(`hive_observation_time_local`, '%Y-%m-%d'), hive_id



References

Rana SS and RS Rana. 2014. Advances in crop growth and productivity. Department of Agronomy, CSK Himachal Pradesh Krishi Vishvavidyalaya, Palampur, pg. 181-186


Wikipedia Growing Degree Day (GDD)