Assessment of NA-CORDEX regional climate models, reanalysis, and in-situ
gridded-observational against U.S. Climate Reference Network datasets
Abstract
Climate models still need to be improved in their capability of
reproducing the present climate at both global and regional scale. The
assessment of their performance depends on the datasets used as
comparators. Reanalysis and gridded (homogenized or not homogenized)
observational datasets have been frequently used for this purpose.
However, none of these can be considered a reference dataset. Here, for
the first time, using in-situ measurements from NOAA U.S. Climate
Reference Network (USCRN), a network of 139 stations with high-quality
instruments deployed across the continental U.S, daily temperature, and
precipitation from a suite of dynamically downscaled regional climate
models (RCMs; driven by ERA-Interim) involved in NA-CORDEX are assessed.
The assessment is extended also to the most recent and modern widely
used reanalysis (ERA5, ERA-Interim, MERRA2, NARR) and gridded
observational datasets (Daymet, PRISM, Livneh, CPC). Results show that
biases for the different datasets are mainly seasonal and subregional
dependent. On average, reanalysis and in-situ-based datasets are
generally warmer than USCRN year-round, while models are colder (warmer)
in winter (summer). In-situ-based datasets provide the best performance
in most of the CONUS regions compared to reanalysis and models, but
still have biases in regions such as the Midwest mountains and the
Northwestern Pacific. Results also highlight that reanalysis does not
outperform RCMs in most of the U.S. subregions. Likewise, for both
reanalysis and models, temperature and precipitation biases are also
significantly depending on the orography, with larger temperature biases
for coarser model resolutions and precipitation biases for reanalysis.