Climatology and Variability of the Evaporative Stress Index and Its Suitability as a Tool to Monitor Australian Drought

The seasonal cycle of the evaporative stress index (ESI) over Australia, and its relationship to observed rainfall and temperature, is examined. The ESI is defined as the standardized anomaly of the ratio of actual evapotranspiration to potential evapotranspiration, and as such, is a measure of vegetation moisture stress associated with agricultural or ecological drought. The ESI is computed using the daily output of version 6 of the Bureau of Meteorology’s landscape water balance model [Australian Water Resource Assessment Landscape (AWRA-L)] on a 5-km horizontal grid over a 45-yr period (1975–2019). Here we show that the ESI exhibits marked spatial and seasonal variability and can be used to accurately monitor drought across Australia, where ESI values less than negative one indicate drought. While the ESI is highly correlated with rainfall as expected, its relationship with temperature only becomes significant during the warmer seasons, suggesting a threshold above which temperature may affect vegetation stress. Our analysis also shows that the ESI tends to be strongly negative (i.e., indicating drought) during El Niño and positive phases of the Indian Ocean dipole (IOD), when conditions tend to be anomalously hot and dry. A negative phase of the southern annular mode also tends to drive negative ESI values during austral spring with a one-month delay.

The environmental effects of global changes on northeast central Europe in the case of non-modified agricultural management

Climate impact scenarios for agriculture usually consider yield development, landscape water balance, nutrient dynamics or the endangerment of habitats separately. Scenario results are further limited by roughly discriminated land use types at low spatial resolution or they are restricted to single sites and isolated crops. Here, we exemplify a well data based comprehensive sensitivity analysis of a drought endangered agrarian region in Northeast Germany using a 2050 climate scenario. Coherently modelled results on water balance and yields indicate that agricultural production may persist, whereas wetlands and groundwater production will be negatively affected. The average percolation rate decreases from 143 mm a-1 to 12 mm a-1, and the average yield decline broken down by crops ranges from 4% for summer wheat to 14% for potatoes (main cereals: 5%).