Land surface impacts on precipitation in the Netherlands

Abstract

Land surface impacts on precipitation in the NetherlandsThe Netherlands is a small and relatively flat coastal country with a temperate maritime climate and annual mean precipitation that varies spatially from 675 to 925 mm. Like in many regions of the world, there is ongoing urbanization. In fact, urban areas have increased from about 2% in 1900, to 13% in 2000, and are projected to increase to 24% in 2040. Other important land cover changes in the last century were the creation of new land in Lake Yssel and agricultural intensification (e.g. conversion of large heather areas into grassland). This thesis addresses the effects of historic and projected land use changes on precipitation in the Netherlands with data analyses and a mesoscale model.The thesis first deals with the observed increase in precipitation in the last century and indicates that this is most likely attributable to an increase in sea surface temperature (Chapter 2). It is also found that along the West coast (the Randstad) precipitation is enhanced by urban areas (Chapter 3). Both chapters make use of daily gauge measurements. The observed precipitation increase from 1951 to 2009 is about 20% in the first 45 km from the coast and decreases by about 10% per 100 km thereafter progressing to the southeast/land inwards. The largest increases in precipitation are found from November through April, while the largest differences between precipitation near the coast and precipitation further inland are observed in May and June. At the same time, it is observed that precipitation amounts downwind of major urban areas are on average about 7% higher than the surrounding area. This increase was found to vary throughout the year with values of 9, 10, 3 and 8% in spring, summer, autumn and winter, respectively. The enhancement was detected over the entire distribution of precipitation, so both in the mean as well as the extremes. These results are comparable with studies from around the globe and show that the influence of relatively small fragmented urban areas, as are vi present in the Netherlands, can be similar to the influence of large metropolitan areas on precipitation.Next, the atmospheric Weather Research and Forecasting (WRF) model was used to investigate the sensitivity of precipitation to the land surface in the Netherlands in spring and summer. For a 4-day case study in spring (Chapter 4), a consistent positive soil moisture-precipitation feedback was found. That is, wet (dry) soils increase (decrease) the amount of precipitation. The expansion of urban areas and other projected land use changes resulted in an increase of the sensible heat flux and a deeper planetary boundary layer. Similar changes occur after reducing soil moisture. The strength of the soil moisture-precipitation feedback (measured as the ratio of evaporation to precipitation) was weaker in the urbanization experiments, because the reduction in evaporation was partly compensated by enhanced triggering of precipitation. In all, the reduction of moisture in urban areas ...

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Towards sustainable drinking water supply in the Netherlands

“…In the Netherlands the projected climate change can be broadly characterised as an increase in precipitation in winter and an increase in summer drought due to higher temperatures and a change in summer precipitation patterns (Van den Hurk et al, 2014). This trend is already visible in the meteorological data (Daniëls, 2016). In the Netherlands the increase of precipitation surplus in winter will partially discharge through the surface water system and therefore only partially recharge the groundwater system.…”

“…The increase is probably caused by higher sea surface temperatures and changes in circulation, but could also be influenced by land use change and urbanisation (Daniëls, 2016).…”