I imagine that all of us are looking into our respective locations to see how much chill we are accumulating this winter season. As a brief review and for anyone that is new to this business, we have our traditional models:

1) The Weinberger Model (# hours below 45F) and

2) The Modified Weinberger Model (# hours between  32F and 45F).

The data corresponding to these two models is easily accessible in our UGA Weather Network or in Agroclimate. In both sites, you will find a drop down menu or you will be able to select a specific weather station (close to your location) and see how much chill has been accumulated. We normally select the dates between October 1st to February 10th. There are two options for the chill degree model to be selected as described above (these are the traditional data that we have been using for a long time).

Sadly we don’t have access in UGA Weather Network website to 3) the Dynamic model. We have found in the last years that the dynamic model is proving to be better suited for our temperature variations accounting for gain and losses of chill. The site that I have been using for obtaining the data for chill portions is https://climatetoolbox.org/tool/historical-climate-dashboard. You will need to add your location. So, click on choose location. Next, you can choose your data option. There are four panels. You need to add in two of those panels the chill calculation options. Click on the drop down menu and you will be able to see an option for the Modified Weinberger model and one for chill portion (Dynamic model). The nice thing about this tool is that you don not have to look for station IDs. Climatetoolbox is based on NWS (NOAA National Weather Service data). Again, I need to state what Dr. Knox (UGA Agricultural Climatologist) has mentioned before: “The data source for the calculator appeared to be a grid based on NWS data supplemented with some other networks (but not the UGA network) and I believe it should be a reasonable source of data. Keep in mind that there are going to be some variations in local microclimate at your sites due to slope, soil type, and other factors which may make the values different than what the grid is predicting, but it’s the only place I know that you can find a chill portion calculator now”.

Another tool that was recently added in the climatetoolbox site is the Historical Climate tracker. In the drop-down menu for variable you can find the different chill models (including now chill portions). Select dates from Oct to Feb and you will get a graph with bars above the average as a default. There is an option in that drop-down menu to change it to scatter plot. I personally prefer that option. I think this will be a great tool to allow you to see what happened years back and relate that information to what you saw in your orchards.

Now, one exciting new option that was added last month is in the Agroclimate website. This is a chill tool that includes the traditional models, but also the Dynamic model. The website for this new tool is http://agroclimate.org/chill-calculator-tool/. The use of this tool is similar to the traditional tool in Agroclimate, but with the new added feature of providing us with the chill portion data for a location. I think this is quite exciting as we didn’t have such an option before with the UGA site or agroclimate.

Hope this helps you to see how are we doing with chill this year.

Please if you have any questions, comments, and suggestions, or if you would like to have a conversation about our current situation please feel free to contact me at 352-871-3981 or dchavez@uga.edu.

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