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Influence of reanalysis datasets on dynamically downscaling the recent past

Authors :
Jason P. Evans
D.B. Moalafhi
Ashish Sharma
Source :
Climate Dynamics. 49:1239-1255
Publication Year :
2016
Publisher :
Springer Science and Business Media LLC, 2016.

Abstract

Multiple reanalysis datasets currently exist that can provide boundary conditions for dynamic downscaling and simulating local hydro-climatic processes at finer spatial and temporal resolutions. Previous work has suggested that there are two reanalyses alternatives that provide the best lateral boundary conditions for downscaling over southern Africa. This study dynamically downscales these reanalyses (ERA-I and MERRA) over southern Africa to a high resolution (10 km) grid using the WRF model. Simulations cover the period 1981–2010. Multiple observation datasets were used for both surface temperature and precipitation to account for observational uncertainty when assessing results. Generally, temperature is simulated quite well, except over the Namibian coastal plain where the simulations show anomalous warm temperature related to the failure to propagate the influence of the cold Benguela current inland. Precipitation tends to be overestimated in high altitude areas, and most of southern Mozambique. This could be attributed to challenges in handling complex topography and capturing large-scale circulation patterns. While MERRA driven WRF exhibits slightly less bias in temperature especially for La Nina years, ERA-I driven simulations are on average superior in terms of RMSE. When considering multiple variables and metrics, ERA-I is found to produce the best simulation of the climate over the domain. The influence of the regional model appears to be large enough to overcome the small difference in relative errors present in the lateral boundary conditions derived from these two reanalyses.

Details

ISSN :
14320894 and 09307575
Volume :
49
Database :
OpenAIRE
Journal :
Climate Dynamics
Accession number :
edsair.doi...........6ee2c2739559e60bfdcf32affda5776e
Full Text :
https://doi.org/10.1007/s00382-016-3378-y