I recently created a simple wine quality index to compare the vintage notes of the Chateau Montelena to daily weather records from St. Helena, CA. In the post, I used the variables of primary importance from Ashenfelter et al. 1995. Since I did not have market pricing data to estimate the value of regression coefficients, I created simple weights from normalized weather data. The normalized values were:
- Accumulated Winter Season Rainfall
- Average Growing Season Temperature
- Assumulated Harvest Season Rainfall
The index result in a time series displayed below:
A Wince Quality Index for Northern Napa Valley
In this post, I add a new component to the index and compare the results.
As an example, the 1972 notes state “Record heat in July caused considerable damage”.
I’ve seen other reports of heat damamge or heat injury. I recently created a quick post on heat damage as well. So, it seems only logical to add to the index a term that measures the likelyhood of heat damage.
The eqaution for the Quality index is:
I modified the equation to include a term that counts the number of days during the growing season that a daily maximum temperature of 95 oF is exceeded. As before, this time series is normalized, and only exceedances greather than average are applied. The equation then takes the form:
The “Temperature Excedance” variable is a normalized time series of a count of the number of times daily maximum temperature execeeds 95 oF during the growing season.
The Wine Quaility Index based on the temperature exceedance (a measure of the potential for heat injury) and the original Quality Index is displayed below.
A Heat Index based Wine Quality Index for Northern Napa Valley
In general there are no drastic changes to the quality index when heat index is added. This is not unexpected since it’s wieght is only -0.25. But, it may “fine tune” a few of the values.
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