Crop Risk

The crop climate risk analysis diagram shows the drought, heat, or frost risk for a selected crop at a selected location as calculated from a selected period from 1985 to today.

Note: This diagram assumes the viewer is familiar with the concept of growing degree days and crop growth stages.

The vertical coloured strips in the background indicate the growing stages of the selected crop. The growth stage names (phenologic development stages) on the colour bar are positioned at the end of each growing stage (right).

The crop weather risk prediction diagram indicates the risk to a selected crop based on drought, heat, or frost in the current season at a selected location, based on a 7-day and a seasonal forecast.

Note: This diagram assumes the viewer is familiar with the concept of growing degree days and crop growth stages.

The colour bar below the diagram indicates the selected crop’s growth stages. The growth stage names (phenologic development stages) on the colour bar below the diagram are positioned at the end of each growth stage.

Season start month: The month in which the selected crop is typically planted in Europe. Adjust the season start month as needed. In Settings (top right) you can also specify the day within the season start month to indicate the planting date.

Season end month: The month in which the selected crop is typically harvested in Europe. Adjust the season end month as needed.

Reference period start year: The calculated risk is based on the weather observed in the reference period. You can adjust the start year between 1985 and last year.

Reference period end year: The calculated risk is based on the weather observed in the reference period. You can adjust the end year between 1986 and last year.

Reference period 2 - start year: The average value of the weather variable driving the risk during the reference period 2. You can adjust the start year between 1985 and last year.

Reference period 2 - end year: The average value of the weather variable, which causes the risk, during the reference period 2. You can adjust the end year between 1986 and last year.

Note: For locations in the southern hemisphere season start and end dates are shifted by six months.

The crop’s growth stages are derived from cumulated growing degree days as found in literature and listed in the table below. How much a weather event impacts a crop depends on the crop’s growing stage, shown in the table below as well. Impact values are derived from literature and expressed as values between 0.0 and 1.0, with low values meaning low impact.

The vertical axis is the likelihood of the selected event (drought, frost, heat) occurring. The likelihood is based on historical statistics for the selected reference period.

By default, events are defined as follows: during a drought event available soil water falls below 3mm, during a frost event the temperature falls below 0 °C for 3 hrs or more, and during a heat event the temperature rises above 30 °C for 3 hrs or more. These parameters can be adjusted on the Settings panel.

Tip: Choose a reference period at least 5 years long to obtain a useful diagram.

Depending on whether looking at drought, frost, or heat risk, the blue curve shows an estimate of available soil water, daily minimum temperature, or daily maximum temperature, respectively, based on the weather up to the current date. The magenta curve shows a 7-day forecast, and the tan curves show various seasonal forecasts published by the European Centre for Medium-Range Weather Forecasts (ECMWF) and various national weather services.

Tip: You can switch curves on and off by clicking in the legend below the diagram.

Note: You won`t see part or all of the forecast curves if the current date is outside the growth season of the chosen crop.

The black and grey curves show the weather’s (average) behaviour in reference periods that you can define. In addition, the grey area covers two standard deviations of the past 35 years’ mean value of the selected weather variable.

Tip: Choose one past year with high yields and one with low yields as reference periods. This allows you to compare the current year with those. For crops planted in one year and harvested in the next, specify the harvest year.

The vertical axis is the value of the weather variable that drives the selected event: available soil water for drought events, daily maximum temperature for heat events, and daily minimum temperature for frost events. Variable values are categorized in five classes, one beyond the event threshold value, and four before the event threshold value. Each class is associated with a defined likelihood between 0.0 and 1.0 such that the likelihood value increases as the threshold is approached and is set to 1.0 once the threshold value is passed.

Note: This simple model of likelihood can be further improved but even in its present form allows the diagram to (1) highlight when the threshold values are passed and (2) express risk as the product of likelihood of an event and its impact in each crop growth stage.

Dot colours indicate the level of risk to the crop according to the colour scale on the right. The risk level is calculated as the product of likelihood of a drought, frost, or heat event occurring and its impact on the crop.

Tip: For additional detail see this white paper on crop risk.

The level of risk due to drought, heat, or frost to the crop in its various growth stages is the product of likelihood and impact, represented graphically by the diagram’s background colours.

Tip: For additional detail see this white paper on crop risk.