Challenges in reanalysis products to assess extreme weather impacts on agriculture: Study case in southern Sweden

Conclusion

The study presented in this paper showed clearly that the frequency and intensity of dry and wet spells returned can differ widely between RPs. For our three sites, it appears overall that RPs overestimate the number of rainy days and therefore wet spells but underestimate dry spells. A noteworthy finding here was for also the substantial divergence regarding long dry spells (>15 days), i.e., Meteorological events that are likely to increase the risk of agricultural drought, and imply yield and food security implications at local or even regional level. When RP data are used in agricultural models, this divergence in representation of dry and wet spells can generate substantial differences in impact analysis of crop yields and quality. There are also implications for strategies and investments in agricultural water management (drainage and irrigation), as system design, precision, and cost-benefit must be conducted at high spatial and temporal resolution in order to be meaningful for local farmers and beneficiaries. Our findings indicate that agro-hydrologists and agro-meteorologists need to exercise caution when choosing climate RPs for agricultural research. This paper focused only on the occurrence of dry and wet days i.e. meteorological events that can potentially trigger agricultural events. The importance of a good representation of those dry and wet meteorological periods in agronomical studies are becoming more and more important if we consider also the global temperature rise—so evaporative fluxes—which could cause faster transfer from meteorological event to agricultural event.

Representation of meteorological events resulting in dry and wet spells, which is not generally considered when evaluating RP quality, is a future challenge for agro-climatic research. The scientific community should work to improve representations of important agro-climatic features, in particular the distribution of wet and dry spells, in evaluations of soil moisture and yield responses in agro-climatic investigations. Of the four RPs investigated, MESAN (available until 2013) best depicted dry and wet days and spells at our study sites. MESAN was developed over a more limited area (northern Europe) than the other RPs (European or global scale), which could explain its better representation of agro-climatic parameters at the Swedish field site. It is however important for the authors to highlight that this study was not aiming to point out which RP is better. The aim was to show the divergence that can result in using one RP or another. The goodness of RP is somehow depending upon the location considered. This comparison of RPs was conducted in a region with a dense observation data network, on which the RPs are based. Divergence between available RPs may be even stronger in poorly monitored regions, such as sub-Saharan Africa. The issue of accurate representation of dry and wet spells may also arise in results generated by climate models, which are widely used to project food production over the next century.

This extract is taken from: Grusson Y, Barron J (2022) Challenges in reanalysis products to assess extreme weather impacts on agriculture: Study case in southern Sweden. PLOS Climate 1(9): e0000063. https://doi.org/10.1371/journal.pclm.0000063