Regional Climate Change Simulations And Uncertainty Analysis Over CORDEX-East Asia Region

A new gridded daily dataset with the resolution of0.25°/0.5°latitude by0.25°/0.5°longitude, CN05.1, is constructed for the purpose of high resolution climate model validationover China region. The dataset is based on the interpolation from over2400observing stationsin China, includes4variables: daily mean, minimum and maximum temperature, dailyprecipitation. The "anomaly approach" is applied in this interpolation. The climatology is firstinterpolated by thin-plate smoothing splines and then a gridded daily anomaly derived fromangular distance weighting method is added to climatology to obtain the final dataset.Intercomparison of the dataset with other three daily datasets, CN05for temperature, and EA05and APHRO for precipitation is conducted.For multi-annual mean temperature variables, results show small differences over easternChina with dense observation stations, but larger differences (warmer) over western China withless stations between CN05.1and CN05. The temperature extremes are measured by TX3D(mean of the3greatest maximum temperature in a year) and TN3D (mean of the3lowestminimum temperature). CN05.1in general shows a warmer TX3D over China, while a lowerTN3D in the east and greeter TN3D in the west are found compared to CN05. A greater valueof annual mean precipitation compared to EA05and APHRO, especially for the later, is foundin CN05.1. For precipitation extreme of R3D (mean of the3largest precipitation in a year),CN05.1presents lower value of it in western China compared to EA05.Under the frame of Coordinated Regional climate Downscaling Experiment (CORDEX),high resolution regional climate model simulations are performed, driving by different globalmodel outputs to provide climate change information over East and Southeast region for inputto impact/adaptation work and contribute to the IPCC Fifth Assessment Report (AR5). Twosets of simulation are conducted by RegCM4.0, driving by two different global model output(ECHAM5_MPI-OM from Max-Planck Institute for Meteorology and HadCM3from theHadley Centre) respectively, under IPCC SRES A1B scenarios, form1978to2099(hereaftercalled EdR and HdR). The horizontal resolutions of these simulations are50km. For brevity,the four sets of results are called four simulations.Simulations of present climate from1980to1999over China by two global models andRegCM4.0are evaluated against observations. Results show that all of simulations reproducethe general observed spatial patterns of surface air temperature and precipitation. Compared totwo global model simulations, regional model simulations provide more spatial details ofsurface variables. EdR shows improvement in December-January-February (DJF),June-July-August (JJA) and annual mean air temperature simulations, but it's not obvious inHdR. The precipitation simulations don't show any evident improvements in both two RegCM4.0simulations. The EdR simulation is slightly better than ECHAM5, however HdRperforms worse than HadCM3. Different patterns can be found in the interannual variabilityand multi-year-trends of annual mean temperature and precipitation simulations. The abilitiesare not as good as the mean climate. Regional model simulations underestimate the subtropicalhigh and southerwesterly flow, which lead to an underestimation of JJA rainfall over China.The climate change (future-present) projections by the four simulations are analyzed.Significant warming in DJF, JJA and annual mean are simulated by four simulations in themiddle and end of the21st century. RegCM4.0and its driving GCM simulate a consistentchange pattern over China characterized by a greater increasing by HadCM3. The warming areremarkably enhanced in the end of21st century, regional mean increasing of annual meantemperature under A1B scenario simulated by ECHAM5and EdR are4.5°C and4.0°C,HadCM3and HdR increase by4.7°C and3.7°C, respectively.Precipitation change mainly increase in DJF, JJA and annual mean over China by twodriving globle models. The pattern in the end of21st century is similar with the middle of21st's,but for the JJA precipitation by ECHAM5simulation. The two regional model simulationsshow similar distribution in middle and end of21st century. The regional model and its drivingmodel simulation show a consistent DJF precipitation pattern over China, but a quite differentJJA precipitation, while the change patterns differ across the two regional model simulations. Inthe end of21st century, annual mean precipitation increasing under A1B scenario simulated byECHAM5and EdR by3.6%and2.5%, HadCM3and HdR are12.1%and10.5%. A largerdeviation can be found in the JJA precipitation simulation over China by the four simulations.The weak performance can be found in moisture flux and its convergence change simulation,different topographic representations and topography forcing can be dominant factors.The model performances in present climate simulation over Southeast Asia are analyzed.Results show that the distributions of DJF, JJA and annual mean air temperature andprecipitation are reproduced by all simulations. Overall, the two regional model simulationswith higher horizontal resolution provide more spatial details compared to the driving GCMs.Better performance can be found in DJF of each simulation. Both EdR and HdR improve thesimulation of air temperature pattern compared to the GCMs. But the significant improvementcouldn't be found in the precipitation simulations, especially in HdR, which even exhibitsweaker. The abilities of the interannual variability and multi-year-trends of annual meantemperature and precipitation simulations over Southeast Asia are not as good as the meanclimate, while a big discrepancy can be found. Similar results are found in present JJAcirculation simulation comapared to NCEP. The two regional model simulations tend to exhibita poor JJA precipitation. Causes of these differences are explained in terms of the different lowlatitude and ocean circulation and weaker westerly flow over norther equator area in the two simulations.The climate change projections over Southeast Asia by the four simulations are estimated.A predominat increasings in DJF, JJA and annual mean are simulated in the middle of the21stcentury with a greater warming by HadCM3and HdR. The warming is remarkably enhanced inthe end of21st century, especially in JJA simulation of EdR. The seasonal difference oftemperature change is not evident. Regional mean increasing of annual mean temperaturesimulated by all simulations, ECHAM5and EdR are3.3°C and3.5°C, the HadCM3and HdRincrease by3.2°C and2.9°C, respectively. Overall, the increasing values are smaller than theChina region's.Precipitation change simulations in DJF, JJA and annual mean over Southeast Asia arequite different by the four simulations. The pattern of the end of21st century is consistent withthe middle of21st's. But the discrepancy is big between two regional model simulations. Slightincreasing annual mean precipitation in the end of21st century are simulated by two GCMs,with the values of3.8%and3.5%, respectively, while decreasing pattern been found in bothtwo regional model simulations, with the values of-6.0%and-4.2%.