Resolution Dependence of Regional Hydro-Climatic Projection: A Case-Study for the Johor River Basin, Malaysia

Abstract

High resolution models from the High-Resolution Model Intercomparison Project (HighResMIP), part of CMIP6, have the capacity to allow a better representation of the climate system in tropical regions, but how different model resolutions affect hydrological outputs remains unclear. This research aims to evaluate projections of hydro-climatic change of the Johor River Basin (JRB) in southern Peninsular Malaysia between 1985 to 2015 and 2021 to 2050, focusing on uncertainty quantification of hydrological outputs from low (>1°), medium (0.5° to 1°) and high (≤0.5°) horizontal resolution models. These projections show future increases in annual precipitation of 0.4 to 3.1%, minimum and maximum temperature increases of 0.8 to 0.9 °C and 0.9 to 1.1 °C, respectively. These projected climate changes lead to increases in annual mean streamflow of 0.9% to 7.0% and surface runoff of 7.0% to 20.6% in the JRB. These annual mean changes are consistent with those during the wet period (November to December), e.g., streamflow increases of 4.9% to 10.8% and surface runoff of 28.8 to 39.9% in December. Disagreement in the direction of change is found during the dry seasons, (February to March and May to September), where high resolution models project a decrease in future monthly precipitation and streamflow, whilst increases are projected by the medium- and low-resolution models.

Projected near-term changes in monsoon precipitation over Peninsular Malaysia in the HighResMIP multi-model ensembles

“…This paper has evaluated the role of model spatial resolution in projected changes in precipitation over Peninsular Malaysia in a set of state-of-the-art GCMs. Such a resolution dependence can strongly influence the result of watershedscale hydrological modeling driven by the GCM simulations (Tan et al 2021). However, this impact has not been thoroughly investigated, especially the role of vertical resolution, since previous research has typically focused on the effect of improving horizontal resolution.…”

Irregularity and time series trend analysis of rainfall in Johor, Malaysia

“…Johor is one of Malaysia's states, located in Peninsular Malaysia's southern region(1°48′N, 103°76′E) with the total land area of 19,102 km 2 [ 39 ]. According to the Köppen climate classification, Johor has a tropical rainforest climate, characterized by high mean annual temperatures, small temperature variations, and received year-round rainfall [ 25 ]. Both monsoonal and convective rainfall systems have a strong correlation with Johor's rainfall.…”

“…Numerous hydrological and climatic parameter studies employing a variety of methodologies have been conducted. Evaluation of these climatic and hydrological changes is substantially aided by trend analysis [ 24 , 25 ]. In order to reduce uncertainty in trend analysis summaries, complex methods including parametric models (deterministic trend), non-parametric methods, and stochastic trend are utilized [ 15 ].…”

Analyzation of water demand projection for Johor River Basin

“…According to Pak, Chuah, Yong & Snyder, 2021 [6], the Johor River Basin (JRB) are occupied with four different districts in Johor state which was the Kluang, Kota Tinggi, Kulai and Pasir Gudang. Based on paper from Tan et al, 2021 [7], the JRB are quite important to Malaysia and Singapore for the consumers to consume the water from JRB and it is very crucial when it comes to pollution matters and any other concerns, it might affect the whole entire ecosystem level whether from human being lifestyle, the life for animals and plants or even for the economic values.…”