Selection of climate models for projection of spatiotemporal changes in temperature of Iraq with uncertainties

We developed an updated nonstationary bias-correction method for a monthly global climate model of temperature and precipitation. The proposed method combines two widely used quantile mapping bias-correction methods to eliminate potential illogical values of the variable. Instead of empirical parameter estimation in the more-common quantile mapping method, our study compared bias-correction performance when parametric or nonparametric procedures were used to estimate the probability distribution. The results showed our proposed bias-correction method to be very effective in reducing the model bias: it removed over 80% and 83% of model bias for surface air temperature and precipitation, respectively, during the validation period. Compared with a widely used method of bias correction (delta change), our proposed technique demonstrates improved correction of the distribution of variables. In addition, nonparametric estimation procedures further reduced the mean absolute errors in temperature and precipitation during the validation period by approximately 2% and 0.4%, respectively, compared with parametric procedures. The proposed method can remove over 40% and 60% of the uncertainty from model temperature and precipitation projections, respectively, at the global land scale.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2015JD024159

A nonstationary bias-correction technique to remove bias in GCM simulations

The systemic biases of Regional Climate Models (RCMs) impede their application in regional hydrological climate-change effects analysis and lead to errors. As a consequence, bias correction has become a necessary prerequisite for the study of climate change. This paper compares the performance of available bias correction methods that focus on the performance of precipitation and temperature projections. The hydrological effects of these correction methods are evaluated by the modelled discharges of the Kaidu River Basin. The results show that all used methods improve the performance of the original RCM precipitation and temperature simulations across a number of levels. The corrected results obtained by precipitation correction methods demonstrate larger diversities than those produced by the temperature correction methods. The performance of hydrological modelling is highly influenced by the choice of precipitation correction methods. Furthermore, no substantial differences can be identified from the results of the temperature-corrected methods. The biases from input data are often greater from the works of hydrological modelling. The suitability of these approaches depends upon the regional context and the RCM model, while their application procedure and a number of results can be adapted from region to region.

https://biblio.ugent.be/publication/8583792/file/8583793.pdf

Comparing bias correction methods used in downscaling precipitation and temperature from regional climate models : a case study from the Kaidu River Basin in Western China

Hydrological response to expected future changes in land use and climate in the Samin catchment (278 km2) in Java, Indonesia, was simulated using the Soil and Water Assessment Tool model. We analys...

https://www.tandfonline.com/doi/pdf/10.1080/02626667.2018.1511054

Hydrological response to future land-use change and climate change in a tropical catchment

Using regionally downscaled and adjusted outputs of three global climate models (GCMs), meteorological drought analysis was accomplished across Ankara, the capital city of Turkey. To this e...

/pdf/climate-change-impacts-on-meteorological-drought-using-spi-3y2sp4j7g9.pdf

Climate change impacts on meteorological drought using SPI and SPEI: case study of Ankara, Turkey

. Water resources are essential to the ecosystem and social economy in the desert and oasis of the arid Tarim River basin, northwestern China, and expected to be vulnerable to climate change. It has been demonstrated that regional climate models (RCMs) provide more reliable results for a regional impact study of climate change (e.g., on water resources) than general circulation models (GCMs). However, due to their considerable bias it is still necessary to apply bias correction before they are used for water resources research. In this paper, after a sensitivity analysis on input meteorological variables based on the Sobol' method, we compared five precipitation correction methods and three temperature correction methods in downscaling RCM simulations applied over the Kaidu River basin, one of the headwaters of the Tarim River basin. Precipitation correction methods applied include linear scaling (LS), local intensity scaling (LOCI), power transformation (PT), distribution mapping (DM) and quantile mapping (QM), while temperature correction methods are LS, variance scaling (VARI) and DM. The corrected precipitation and temperature were compared to the observed meteorological data, prior to being used as meteorological inputs of a distributed hydrologic model to study their impacts on streamflow. The results show (1) streamflows are sensitive to precipitation, temperature and solar radiation but not to relative humidity and wind speed; (2) raw RCM simulations are heavily biased from observed meteorological data, and its use for streamflow simulations results in large biases from observed streamflow, and all bias correction methods effectively improved these simulations; (3) for precipitation, PT and QM methods performed equally best in correcting the frequency-based indices (e.g., standard deviation, percentile values) while the LOCI method performed best in terms of the time-series-based indices (e.g., Nash–Sutcliffe coefficient, R2); (4) for temperature, all correction methods performed equally well in correcting raw temperature; and (5) for simulated streamflow, precipitation correction methods have more significant influence than temperature correction methods and the performances of streamflow simulations are consistent with those of corrected precipitation; i.e., the PT and QM methods performed equally best in correcting flow duration curve and peak flow while the LOCI method performed best in terms of the time-series-based indices. The case study is for an arid area in China based on a specific RCM and hydrologic model, but the methodology and some results can be applied to other areas and models.

https://hess.copernicus.org/articles/19/2547/2015/hess-19-2547-2015.pdf

Yn Chen

Papers

Comparing bias correction methods in downscaling meteorological variables for a hydrologic impact study in an arid area in China