Downscaling over Vietnam using the stretched-grid CCAM: verification of the mean and interannual variability of rainfall

Abstract

Rainfall over Vietnam is highly variable from north to south, due to the interaction of the monsoonal winds with the terrain. There is high rainfall from April to September, and little rainfall from October to March (except along the central Vietnam coast). In order to study the ability of the Commonwealth Scientific and Industrial Research Organisation stretched-grid Conformal Cubic Atmospheric Model (CCAM) to capture the climatic and interannual variability of rainfall, downscaled simulations at approximately 20 km horizontal resolution over the region were produced for the period 1979-2001. A scaleselective digital filter was used to force the winds, temperature and sea-level pressure from the ERA-Interim reanalysis for length scales greater than about 700 km. For wind and temperature, the forcing is applied for pressuresigma levels above about 0.9. ERA-Interim sea surface temperatures were used over the oceans. The simulations were primarily validated against the gridded Asian Precipitation Highly Resolved Observational Data Integration Toward Evaluation of the Water Resources rainfall dataset and station observations using standard statistical methods. It was found that CCAM reproduces well the amount and spatial variability of rainfall, with an area-averaged bias for the entire study domain of less than 1 mm day -1 ; CCAM is also able to capture the rainfall pattern under different El Niño Southern Oscillation phases reasonably well for the dry season. For interannual variability, the simulation generally performed better for North and Central Vietnam than for South Vietnam, where rainfall variability was overestimated.

Statistical‐dynamical downscaling of precipitation for Vietnam: methodology and evaluation for the recent climate

“…Compared with previous studies, we found similar results to Nguyen et al (2014b) and Katzfey et al (2016), which used two RCMs as a downscaling tool for precipitation for this area. In their studies, simulations show generally lower rainfall amounts at the north central coast of Vietnam compared with observational datasets and an overestimation of rainfall in south Vietnam, which corresponds to the findings of our study.…”

“…Compared with previous studies, we found similar results to Nguyen et al . () and Katzfey et al . (), which used two RCMs as a downscaling tool for precipitation for this area.…”

Interference of natural and anthropogenic forcings on variations in continental freshwater discharge from the Red River (Vietnam) to sea

“…Moreover, the continental freshwater discharge of the Red River is strongly influenced by the South Asia Summer Monsoon (SASM) (Isupova and Mikhailov, 2011) with seasonal characteristics (Simonovic and Carson, 2003). EI Niño Southern Oscillation (ENSO) can also trigger occurrence of some extreme hydroclimatological events in rivers, such as floods, droughts and precipitation anomalies (Zhang et al, 2013a;Nguyen et al, 2014).…”

An assessment of CSIRO Conformal Cubic Atmospheric Model simulations over Sri Lanka

“…A number of recent studies (Kim et al 2014;Dosio et al 2015;Kotlarski et al 2014;Nguyen et al 2014) focused on the assessment of model simulations over different spatial and temporal scales are already available in the literature. Simulations performed for the Coordinated Regional Climate Downscaling Experiment (CORDEX) were evaluated by Kim et al (2014) over the African region using gridded station data from the Climate Research Unit (CRU).…”

“…They noted that seasonally and regionally averaged temperature biases are small while precipitation biases are large. Nguyen et al 2014 evaluated interannual variability of rainfall produce by CCAM simulations over the Vietnam region by comparing with APHRODITE data. They found that the CCAM simulations performed better for North and Central Vietnam than for South Vietnam.…”