Difference between revisions of "Growing Degree Day"

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Each plant species  has  its  own  lower  air  temperature  threshold  and  upper  
 
Each plant species  has  its  own  lower  air  temperature  threshold  and  upper  
air temperature threshold. It is assumed that no growth occurs outside of this
+
air temperature threshold. This temperature range varies for each plant.
range. This temperature range varies for each plant.
 
  
 
Different methods exist for calculating heat units depending on a) the crop or biological  
 
Different methods exist for calculating heat units depending on a) the crop or biological  

Revision as of 13:41, 25 November 2018

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. At temperatures above an upper limit, (Tmax), the plant does not grow any faster.

Each plant species has its own lower air temperature threshold and upper air temperature threshold. This temperature range varies for each plant.

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.

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.

GDD integral.png

Calculate Growing Degree Day (GDD) for each hive and add to database.


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