Potato injury risk and weed control from reduced rates of PPO inhibitor herbicides

The ability to use the protoporphyrinogen oxidase (PPO) inhibitor herbicides fomesafen, flumioxazin, and sulfentrazone in potato is limited regionally or by soil texture largely because of crop injury noted in research in the 1990s. With that in mind, we evaluated if reducing the herbicide rates could maintain weed control while providing more consistent crop safety. Studies were conducted on a silt loam and a coarse-textured loamy sand soil. Soil texture played a greater than anticipated role in PPO inhibitor herbicide injury risk as it relates to high precipitation events. For example, in 2020 at the silt loam location, there were five precipitation events across the season that exceeded 2.5 cm, including one 6 days after treatment (DAT), and a seasonal total precipitation that was over 10 cm greater than the previous year. Despite excessive moisture and initial potato injury as high as 27% where flumioxazin was applied at the high rate with s-metolachlor, by 29 DAT injury was less than 10% in all treatments and marketable tuber yield was similar among treatments. In contrast, in 2020 at the loamy sand location there were four precipitation events across the season that exceeded 2.5 cm and potato injury was as much as 60%. In 2020 the high amount of injury from flumioxazin was hypothesized to be caused by precipitation prior to herbicide application and not after, suggesting a need for more research in this area. This work documents the fine line between yield reduction presumably caused by reduced weed control and yield reduction assumed to be related to herbicide injury. This delineation between adequate weed control and consistent crop safety may differ by soil texture and environmental conditions, supporting the notion that custom-tailored weed management may become more necessary as high precipitation events become more common in Upper Midwest USA agricultural systems.

Hydrological Analysis of Extreme Rain Events in a Medium-Sized Basin

The hydrological response of a medium-sized watershed with both rural and urban characteristics was investigated through event-based modeling. Different meteorological event conditions were examined, such as events of high precipitation intensity, double hydrological peak, and mainly normal to wet antecedent moisture conditions. Analysis of the hydrometric features of the precipitation events was conducted by comparing the different rainfall time intervals, the total volume of water, and the precedent soil moisture. Parameter model calibration and validation were performed for rainfall events under similar conditions, examined in pairs, in order to verify two hydrological models, the lumped HEC-HMS (Hydrologic Engineering Center’s Hydrologic Modeling System model) and the semi-distributed HBV-light (a recent version of Hydrologiska Byråns Vattenbalansavdelning model), at the exit of six individual gauged sub-basins. Model verification was achieved by using the Nash–Sutcliffe efficiency and volume error index. Different time of concentration (Tc) formulas are better applied to the sub-watersheds with respect to the dominant land uses, classifying the Tc among the most sensitive parameters that influence the time of appearance and the magnitude of the peak modeled flow through the HEC-HMS model. The maximum water content of the soil box (FC) affects most the peak flow via the HBV-light model, whereas the MAXBAS parameter has the greatest effect on the displayed time of peak discharge. The modeling results show that the HBV-light performed better in the events that had less precipitation volume compared to their pairs. The event with the higher total precipitated water produced better results with the HEC-HMS model, whereas the rest of the two high precipitation events performed satisfactorily with both models. April to July is a flood hazard period that will be worsened with the effect of climate change. The suggested calibrated parameters for severe precipitation events can be used for the prediction of future events with similar features. The above results can be used in the water resources management of the basin.

Aerosol-enhanced high precipitation events near the Himalayan foothills

Particulate emissions can alter the physical and dynamical properties of cloud systems and, in turn, amplify rainfall events over orographic regions downwind of highly polluted urban areas. The Indo-Gangetic Plain, one of the most polluted regions of the world, is located upwind of the Himalayan foothills. The region, therefore, provides an opportunity for studying how aerosol effects, in connection with orographic forcing, affect extreme rainfall events. This study uses 17 years (2001–2017) of observed rain rate, aerosol optical depth (AOD), meteorological reanalysis fields and outgoing long-wave radiation to investigate high precipitation events on the foothills of the Himalayas. Composite analysis of all these co-located data sets for high precipitation events (daily rainfall > 95th percentile) is done to understand the inherent dynamics and linkages between the AOD and extreme events. Clear and robust associations are found between high precipitation events, high aerosol loading and high moist static energy values. Results show an average increase in AOD by 36 %, along with an average increase in low-level moist static energy (1000–850 hPa) by ≈ 1500 J kg−1 inside the selected domain for high precipitation events. The finding highlights the crucial role of the aerosol direct radiative effect on high precipitation events over the Himalayan region.

Assessment of Extremes in Global Precipitation Products: How Reliable Are They?

Global gridded precipitation products have proven essential for many applications ranging from hydrological modeling and climate model validation to natural hazard risk assessment. They provide a global picture of how precipitation varies across time and space, specifically in regions where ground-based observations are scarce. While the application of global precipitation products has become widespread, there is limited knowledge on how well these products represent the magnitude and frequency of extreme precipitation—the key features in triggering flood hazards. Here, five global precipitation datasets (MSWEP, CFSR, CPC, PERSIANN-CDR, and WFDEI) are compared to each other and to surface observations. The spatial variability of relatively high precipitation events (tail heaviness) and the resulting discrepancy among datasets in the predicted precipitation return levels were evaluated for the time period 1979–2017. The analysis shows that 1) these products do not provide a consistent representation of the behavior of extremes as quantified by the tail heaviness, 2) there is strong spatial variability in the tail index, 3) the spatial patterns of the tail heaviness generally match the Köppen–Geiger climate classification, and 4) the predicted return levels for 100 and 1000 years differ significantly among the gridded products. More generally, our findings reveal shortcomings of global precipitation products in representing extremes and highlight that there is no single global product that performs best for all regions and climates.

Aerosol-induced high precipitation events near the Himalayan foothills

Particulate emissions can alter the physical and dynamical properties of cloud systems and in turn amplify rainfall events over orographic regions downwind of highly polluted urban areas. The Indo-Gangetic Plains, one of the most polluted regions of the world, is located upwind of Himalayan foothills. The region, therefore, provides an opportunity for studying how aerosol effects in connection with orographic forcing affect extreme rainfall events. This study uses 17-years (2001–2017) of observed rain rate, aerosol optical depth (AOD), meteorological re-analysis fields, and outgoing longwave radiation to investigate high precipitation events at the foothills of the Himalayas. Composite analysis of all these collocated datasets for high precipitation events (daily rainfall > 95 percentile) is done to understand the inherent dynamics and linkages between AOD and extreme events. Clear and robust associations are found between high precipitation events, high aerosol loading and high moist static energy values. This finding highlights the crucial role of the aerosol direct radiative effect on high precipitation events over the Himalayan region.

Evaluation of the GPM IMERG v5 and TRMM 3B42 v7 Precipitation Products in the Yangtze River Basin, China

The purpose of this study is to quantitatively evaluate the accuracy of the GPM IMERG v5 and the TRMM 3B42 v7, with the reference of 224 rain gauge stations over the Yangtze River basin in China from April 2014 to December 2017. The results showed that: (1) The changing pattern of IMERG v5 was similar to the 3B42 v7, and higher correlations can be found between the satellite-based precipitation products (SPPs) and observed precipitation for the monthly and annual time scale; (2) the IMERG v5 tended to overestimate the distribution range of the main rain band while the 3B42 v7 underestimated the precipitation in Sichuan basin, and the largest differences were found for the precipitation less than 1 mm/d for two SPPs; (3) both of the IMERG v5 and 3B42 v7 overestimated the precipitation in the lower elevation areas (<3000 m), while the opposite was true for areas ≥ 3000 m (RBIMERG v5 = −5.42%, RB3B42 v7 = −1.87%), and the retrieved results of PPDFc index and average precipitation at different altitudes for IMERG v5 were better than 3B42 v7. This study highlighted that IMERG v5 performed generally better than 3B42 v7 in detecting precipitation, especially light precipitation in the Yangtze River basin, indicating the great potential utility in hydrological applications. However, its poor skills when retrieving data for high precipitation events and for detecting complex terrain environments remains, leaving room for IMERG v5 to improve its inversion algorithm.

Evaluation of Seasonal and Synoptic Changes in Snow Accumulation in Antarctica between Five Reanalyses Products and In Situ Observations

The performance of recent reanalysis products (i.e., ERA-Interim, NCEP2, MERRA, CFSR, and JRA-55) was evaluated based on in situ observations from nine automatic weather stations and one stake network to investigate the monthly and seasonal variability of the surface mass balance in Antarctica. Synoptic precipitation simulations were also evaluated by an investigation of high precipitation events. The seasonal variations showed large fluctuations and were inconsistent at each station, probably owing to the large interannual variability of snow accumulation based on the short temporal coverage of the data. The ERA-Interim and JRA-55 datasets revealed better simulated precision, with the other three models presenting similar simulations at monthly and seasonal timescales. The JRA-55 dataset captured a greater number of synoptic high precipitation events at four of the nine stations. Such events at the other five stations were mainly captured by ERA and CFSR. The NCEP2 dataset was more weakly correlated with each station on all timescales. These results indicate that significant monthly or seasonal correlations between in situ observations and the models had little effect on the capability of the reanalyses to capture high precipitation events. The precision of the five reanalysis datasets widely fluctuated in specific regions or at specific stations at different timescales. Great caution is needed when using a single reanalysis dataset to assess the surface mass balance over all of Antarctica.