Paper · 2014 · Climatic Change

Comparing the effects of calibration and climate errors on a statistical crop model and a process-based crop model

James Watson; Andrew J. Challinor; Thomas E. Fricker; et al.

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Open access · cc-by

Abstract

Understanding the relationship between climate and crop productivity is a key component of projections of future food production, and hence assessments of food security. Climate models and crop yield datasets have errors, but the effects of these errors on regional scale crop models is not well categorized and understood. In this study we compare the effect of synthetic errors in temperature and precipitation observations on the hindcast skill of a process-based crop model and a statistical crop model. We find that errors in temperature data have a significantly stronger influence on both models than errors in precipitation. We also identify key differences in the responses of these models to different types of input data error. Statistical and process-based model responses differ depending on whether synthetic errors are overestimates or underestimates. We also investigate the impact of crop yield calibration data on model skill for both models, using datasets of yield at three different spatial scales. Whilst important for both models, the statistical model is more strongly influenced by crop yield scale than the process-based crop model. However, our results question the value of high resolution yield data for improving the skill of crop models; we find a focus on accuracy to be more likely to be valuable. For both crop models, and for all three spatial scales of yield calibration data, we found that model skill is greatest where growing area is above 10-15 %. Thus information on area harvested would appear to be a priority for data collection efforts. These results are important for three reasons. First, understanding how different crop models rely on different characteristics of temperature, precipitation and crop yield data allows us to match the model type to the available data. Second, we can prioritize where improvements in climate and crop yield data should be directed. Third, as better climate and crop yield data becomes available, we can predict how crop model skill should improve.

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Claims 5

Method / resourceobservedoriginal resultnegativesignificant (as stated)simulated

Claim · model-written summary

Temperature data errors influenced both crop models significantly more than precipitation errors.

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cropt0
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influence on both modelse0
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strongere0
Comparator
errors in precipitatione0

Verbatim

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“errors in temperature data have a significantly stronger influence on both models than errors in precipitation”

✓ located verbatim in the source · abstract, characters 521–631 · show in text ↑
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“a process-based crop model and a statistical crop model”

✓ located verbatim in the source · abstract, characters 451–506 · show in text ↑
Method / resourceobservedoriginal resultsimulated

Claim · model-written summary

Statistical and process-based model responses differed according to whether synthetic errors overestimated or underestimated inputs.

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cropt0
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model responses differe0
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overestimates or underestimatese0

Not reportedDirection

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“Statistical and process-based model responses differ depending on whether synthetic errors are overestimates or underestimates”

✓ located verbatim in the source · abstract, characters 739–865 · show in text ↑
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“a process-based crop model and a statistical crop model”

✓ located verbatim in the source · abstract, characters 451–506 · show in text ↑
Method / resourceobservedoriginal resultsimulated

Claim · model-written summary

Crop yield calibration scale influenced the statistical model more strongly than the process-based model.

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crope0
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influenced by crop yield scalee0
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more stronglye0
Comparator
process-based crop modele0

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e0

“the statistical model is more strongly influenced by crop yield scale than the process-based crop model”

✓ located verbatim in the source · abstract, characters 1054–1157 · show in text ↑
Method / resourceobservedoriginal resultpositivesimulated

Claim · model-written summary

Model skill was greatest where growing area exceeded 10-15% across both models and all three calibration scales.

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crope0
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model skille0
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greateste0
Value
10-15 %e0
Qualifier
all three spatial scales of yield calibration datae0

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e0

“For both crop models, and for all three spatial scales of yield calibration data, we found that model skill is greatest where growing area is above 10-15 %”

✓ located verbatim in the source · abstract, characters 1331–1486 · show in text ↑
Recommendationauthor interpretationoriginal resultbasis n/a

Claim · model-written summary

The authors prioritize accurate yield data and harvested area information for improving crop models.

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cropt0
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focus on accuracye0

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“we find a focus on accuracy to be more likely to be valuable”

✓ located verbatim in the source · abstract, characters 1269–1329 · show in text ↑
e1

“information on area harvested would appear to be a priority for data collection efforts”

✓ located verbatim in the source · abstract, characters 1493–1580 · show in text ↑
t0

“a process-based crop model and a statistical crop model”

✓ located verbatim in the source · abstract, characters 451–506 · show in text ↑