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Changes in diurnal temperature range and national cereal yields

机译：昼夜温度范围和国家谷物产量的变化

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Models of yield responses to temperature change have often considered only changes in average temperature (Tavg) with the implicit assumption that changes in the diurnal temperature range (DTR; the difference between daily maximum and minimum temperature) can safely be ignored. The goal of this study was to evaluate this assumption using a combination of historical datasets and climate model projections. Data on national crop yields for 1961-2002 in the ten leading producers of wheat (Triticum spp.), rice (Oryza spp.) and maize (Zea mays) were combined with datasets on climate and crop locations to evaluate the empirical relationships between Tavg, DTR and crop yields. In several rice and maize growing regions, including the two major nations for each crop, there was a clear negative response of yields to increased DTR. This finding reflects a nonlinear response of yields to temperature, which likely results from greater water and heat stress during hot days. In many other cases, the effects of DTR were not statistically significant, in part because correlations of DTR with other climate variables, and the relatively short length of the time series resulted in wide confidence intervals for the estimates. To evaluate whether future changes in DTR are relevant to crop impact assessments, yield responses to projected changes in Tavg and DTR by 2046-2065 from 11 climate models were estimated. The mean of climate model projections indicated an increase in DTR in most seasons and locations where wheat is grown, mixed projections for maize, and a general decrease in DTR for rice. These mean projections were associated with wide ranges that included zero in nearly all cases. The estimated impacts of DTR changes on yields were generally small (<5% change in yields) relative to the consistently negative impact of projected warming of Tavg. However, DTR changes did significantly affect yield responses in several cases, such as in reducing US maize yields and increasing India rice yields. Because DTR projections tend to be positively correlated with Tavg, estimates of yield changes for extreme warming were particularly affected by including DTR (up to 10%). Finally, based on the relatively poor performance of climate models in reproducing the magnitude of past DTR trends, it is possible that future DTR changes and associated yield responses will exceed the ranges considered here..
机译：产量对温度变化的响应模型通常只考虑平均温度（Tavg）的变化，而隐含的假设是可以安全地忽略昼夜温度范围（DTR;每日最高和最低温度之间的差异）的变化。这项研究的目的是结合历史数据集和气候模型预测来评估这一假设。将十个主要小麦生产国（Triticum spp。），水稻（Oryza spp。）和玉米（Zea mays）1961-2002年全国作物产量的数据与气候和作物位置数据集相结合，以评估Tavg之间的经验关系。 ，DTR和农作物产量。在几个稻米和玉米种植区，包括每种作物的两个主要国家，单产对增加的DTR有明显的负面反应。这一发现反映了产量对温度的非线性响应，这很可能是由于炎热天气中更大的水分和热应力导致的。在许多其他情况下，DTR的影响在统计上并不显着，部分原因是DTR与其他气候变量的相关性以及相对较短的时间序列长度导致了较大的置信区间。为了评估DTR的未来变化是否与作物影响评估相关，估计了从11种气候模式到2046-2065年Tavg和DTR预测变化的产量响应。气候模式预测的平均值表明，在小麦种植的大多数季节和地区，DTR均增加，玉米的混合预测与水稻的DTR总体下降有关。这些平均预测与几乎在所有情况下都为零的宽范围相关。与预期的塔夫格变暖的持续负面影响相比，DTR变化对单产的估计影响通常很小（单产变化<5％）。但是，DTR的变化确实在一些情况下显着影响了产量响应，例如降低了美国玉米的产量并增加了印度大米的产量。由于DTR预测值往往与Tavg呈正相关，因此，包括DTR（最多10％）会特别影响极端变暖的产量变化估计。最后，基于气候模型在再现过去DTR趋势的幅度方面相对较差的性能，未来DTR的变化和相关的产量响应可能会超出此处考虑的范围。

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