DRIP - DRought ending in Intensified Precipitation

Periods of drought can make the soil hard and cause water repellency which can lead to an increase in flooding and soil erosion in the event of an extreme precipitation event. Compound events with DRoughts ending in Intensified Precipitation -DRIP can therefore cause greater damage to infrastructure and crops than single events with only drought or extreme precipitation. Global warming has intensified both drought periods and extreme precipitation as well as causing them to occur more frequently, compound DRIP event can therefore also intensify and occur more frequently. Although the intensification in drought periods and extreme precipitation with global warming has also been found in the climate model data, there is a large model spread for how much and which areas that may experience more drought and precipitation. The project will investigate actual historical compound DRIP events and find these in weather observations and weather model data to find suitable indices to further analyze how they occur in the climate models. Models on a finer scale do a better job of modeling rainfall. The project will therefore use fine-scale regional climate models as well as the coarser global climate models to see how DRIP events present in these. The models that do well against observations will be identified. Furthermore, the project will study the changes in frequency and intensity of DRIP events with future global warming. One of the identified reasons causing the spread in climate models for rainfall patterns is how evaporation varies over forest and other areas. In the project, we will look at the effect of deforestation and increased forest areas in global models and make our own regional model simulations on a fine scale to see how it affects evaporation. The results of the project are important to mitigate the possible damages caused by compound DRIP events.

Global warming intensifies drought and extreme precipitation. Compound events with droughts ending in intensified precipitation - DRIP can cause large damages but are extremely understudied. This project aims to estimate the change in frequency and intensity of DRIP events with global warming due to changes in the water-cycle. We will identify actual historical compound DRIP events and find indices that are suitable to identify these events in model data. As global climate models show a large spread in precipitation for both historical and the different future climate projections, there is expected to be a spread in model projections of DRIP events as well. We will constrain this spread by identifying global climate models that do a good statistical representation of historical DRIP events and by analyzing large ensembles to evaluate the natural variability. As higher resolution modelling shows a better representation of the water cycle, the project will analyze regional downscaled global models in identified regions of interest. We will also perform in-house regional simulations of identified global models down to convection permitting scale to study the change in DRIP events with model resolution. The project will also target a highlighted uncertainty connected to the water-cycle by exploring how evapotranspiration and the occurrence of DRIP events found in climate models respond to land use change. For this analysis we will extend the regional downscaling to include sensitivity studies which contain deforestation and forestation. Results gained from DRIP will make a large contribution to the knowledge needed on future mitigation measures due to the increase in compound events.