Abstract
Abstract As a response to strong radiative heating, the fruit temperature of apples may rise significantly above the air temperature. This may result in damage to the skin tissue and the epidermal and hypodermal cell layers. To avoid economic losses induced by sunburn symptoms on the skin, apple growers need forecasts of the fruit temperature, which will allow them to organize sun-protection measures in time. The temperatures of detached apples, which had been exposed to incident radiation and wind, were measured in order to quantify the extent of fruit heating under the climate conditions of northern Germany. On average, the daily maximum skin temperatures measured on the sunlit south side of the fruit during selected sunny and warm days were about 7 °C above the daily maximum air temperature. However, skin temperatures of more than 40 °C (the predefined warning threshold) were rarely detected, indicating that sunburn is still an uncommon phenomenon in northern Germany. Maximum apple-core temperatures were on average 4 °C higher than the maximum temperatures of ambient air. Based on energy balance principles, a simple model has been developed to predict the diurnal cycle of the sky- and ground-facing hemispherical apple temperatures. Focusing on fruit growers’ needs, daily temperature maxima of the modeled sky-facing hemisphere were compared with skin temperatures measured on the sunlit south side, resulting in a mean absolute error (MAE) of 1.7 °C. Comparison between daily maxima of total sphere temperatures and apple core temperatures provided better correlations (MAE = 0.8 °C).
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Claims 5
Claim · model-written summary
Daily maximum apple skin temperatures on the sunlit south side were on average about 7 °C above the daily maximum air temperature.
- Taxon
- apples
Malus domesticae1 - Outcome
- daily maximum skin temperaturese2
- Value
- 7 °Ce2
- Comparator
- daily maximum air temperaturee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“the fruit temperature of apples may rise significantly above the air temperature”
e2“On average, the daily maximum skin temperatures measured on the sunlit south side of the fruit during selected sunny and warm days were about 7 °C above the daily maximum air temperature”
Claim · model-written summary
Skin temperatures above 40 °C were rarely detected, indicating that sunburn is still uncommon in northern Germany.
- Taxon
- applesMalus domesticae1
- Outcome
- skin temperatures of more than 40 °Ce3
- Qualifier
- rarely detectede3
- Setting
- northern Germanye3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“the fruit temperature of apples may rise significantly above the air temperature”
e3“skin temperatures of more than 40 °C (the predefined warning threshold) were rarely detected, indicating that sunburn is still an uncommon phenomenon in northern Germany”
Claim · model-written summary
Maximum apple-core temperatures were on average 4 °C higher than the maximum ambient air temperatures.
- Taxon
- applesMalus domesticae1
- Outcome
- Maximum apple-core temperaturese4
- Value
- 4 °Ce4
- Comparator
- maximum temperatures of ambient aire4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“the fruit temperature of apples may rise significantly above the air temperature”
e4“Maximum apple-core temperatures were on average 4 °C higher than the maximum temperatures of ambient air”
Claim · model-written summary
The simple energy-balance model predicted sky-facing apple temperature maxima with a mean absolute error of 1.7 °C against measured sunlit skin temperatures.
- Taxon
- applesMalus domesticae1
- Outcome
- mean absolute error (MAE)e5
- Value
- 1.7 °Ce5
- Comparator
- skin temperatures measured on the sunlit south sidee5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“the fruit temperature of apples may rise significantly above the air temperature”
e5“daily temperature maxima of the modeled sky-facing hemisphere were compared with skin temperatures measured on the sunlit south side, resulting in a mean absolute error (MAE) of 1.7 °C”
Claim · model-written summary
Daily maxima of total sphere temperatures gave better correlations with apple core temperatures (MAE 0.8 °C) than the sky-facing model.
- Taxon
- applesMalus domesticae1
- Outcome
- correlationse6
- Value
- MAE = 0.8 °Ce6
- Comparator
- apple core temperaturese6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“the fruit temperature of apples may rise significantly above the air temperature”
e6“Comparison between daily maxima of total sphere temperatures and apple core temperatures provided better correlations (MAE = 0.8 °C)”