Lucy Bricheno

Effect of High-Resolution Meteorological Forcing on Nearshore Wave and Current Model Performance

Accurate representation of wind forcing and mean sea level pressure is important for modeling waves and surges. This is especially important for complex coastal zone areas. The Weather Research and Forecasting (WRF) model has been run at 12-, 4-, and 1.33-km resolutionfor a storm event over the Irish Sea. The outputs were used to force the coupled hydrodynamic and the Proudman Oceanographic Laboratory Coastal Ocean Modeling System (POLCOMS)‐Wave Model (WAM) and the effect on storm surge and waves has been assessed. An improvement was observed in the WRF model pressure and wind speed when moving from 12- to 4-km resolution with errors in wind speed decreasing more than 10% on average. When moving from 4 to 1.33km no further significant improvement was observed. The atmospheric model results at 12 and 4km were then applied to the ocean model. Wave direction was seen to improve with increased ocean model resolution,andhigher-resolutionforcingwasfoundtogenerallyincreasethewaveheightovertheIrishSeaby up to 40cm in places. Improved clustering of wave direction was observed when 4-km meteorological forcing was used. Large differences were seen in the coastal zone because of the improved representation of the coastline and, in turn, the atmospheric boundary layer. The combination of high-resolution atmospheric forcing and a coupled wave‐surge model gave the best result.

Modeling daily soil salinity dynamics in response to agricultural and environmental changes in coastal Bangladesh

Understanding the dynamics of salt movement in the soil is a prerequisite for devising appropriate management strategies for land productivity of coastal regions, especially low-lying delta regions, which support many millions of farmers around the world. At present, there are no numerical models able to resolve soil salinity at regional scale and at daily time steps. In this research, we develop a novel holistic approach to simulate soil salinization comprising an emulator-based soil salt and water balance calculated at daily time steps. The method is demonstrated for the agriculture areas of coastal Bangladesh (∼20,000 km2). This shows that we can reproduce the dynamics of soil salinity under multiple land uses, including rice crops, combined shrimp and rice farming, as well as non-rice crops. The model also reproduced well the observed spatial soil salinity for the year 2009. Using this approach, we have projected the soil salinity for three different climate ensembles, including relative sea-level rise for the year 2050. Projected soil salinity changes are significantly smaller than other reported projections. The results suggest that inter-season weather variability is a key driver of salinization of agriculture soils at coastal Bangladesh.

Modelling Tidal River Salinity in Coastal Bangladesh

Understanding how changing climate may affect future salinity levels is important for ecosystem services within the delta. Observations of tidal river salinity in Bangladesh are limited so a field survey of salinity levels and river soundings were undertaken providing calibration for a hydrodynamic model. Modelled changes in salinity levels have a pronounced spatial pattern. The saltiest river waters continue to be found in the western section of the delta, including the Sundarbans. The largest changes are projected in the central estuaries, where rising sea levels move the saltwater front further inland, increasing salinity levels. In the eastern section, increased river flow and rising sea levels are more balanced, and little change is anticipated in future salinity at the mouth of the Meghna River.