Projection Of Sea Surface Wind Speed Under Climate Scenarios Near China

Under the background of global climate change, scientific researches and assessments of marine natural disasters over Chinese costal area have great significance. The most disaster-caused marine systems(storm surge, catastrophic sea wave et al.) are driven by sea surface wind speed(SSWS), which make it necessary and meaningful to assess long-term trends change of SSWS and analyze its correlations with climate factors in future scenarios, accordingly reveal the futrue characteristic of SSWS over the target area.1. Statistical downscaling projection of SSWS near ChinaThe achievement of Coupled Model Intercomparison Project Phase 5(CMIP5) of Intergovermental Panel on Climate Change(IPCC) plays an important role in the research of futrue climate changes. The spatial resolution of global climate model in CMIP5 is too rough to describe the mesoscale characteristic of ocean climate near China’s coast, thus this article ehance the resolution using statistical downscaling model(SDM) based on Empirical Orthogonal Function(EOF) and Multiple Linear Regression(MLR). The SDM is derived from the low resolution ECMWF reanalyzes dataset and the high resolution Cross-Calibrated Multi-Platform(CCMP) SSWS data over an independent period 1992-2011, then tested by using cross-validation method.Finally, the multiple climate models within the CMIP5 under the Historical(HIS)scenario and the Representative Concentration Pathways(RCP26, RCP45, RCP85)scenarios over 2026-2045 are downscaled to assess the SSWS variations.Compare with observed data, the downscaling result of CMIP5 models output under historical scenario(1986-2005) show better performance than directly Bilinear Interpolation result. Comparison between SDM and Regional Climate Model(RCM)show that: under HIS scnario, the SDM exhibits slightly better skill in reproducing simulation of winter SSWS than RCM; when turn to summer, the advantage of SDM simulation was limited to open sea area. The simulation of SSWS under RCP scenario from two RCMs(Had GEM3-RA and Reg CM) is smaller in the east and north sea areas of Taiwan island and larger in south China sea than SDM result, while the same result of YSU-RSM is far larger in most target areas. The downscaling result of 8GCMs in CMIP5 under three RCP scenarios with respect to the reference period1986-2005 show that: the winter mean SSWS strengthens(weakens) in the north(south) of about 25°N under all three RCPs with a minimum increasing area under RCP45, while the maximum of winter SSWS changes little; the summer mean SSWS slightly increases over the Yellow Sea near Shandong Peninsula, the East Sea near the east of Taiwan and certain regions of the south China sea, as well as the maximum of summer SSWS increases over the surrounding sea areas of Hainan island under RCP26, the costal areas in the north of south China sea under RCP45 and the surrounding area of Taiwan island under RCP85.2. Climate Change Projection of the Landfalling Tropical Cyclone in China:Results of CMIP5 ModelsBased on the large-scale circulation features of Tropical Cyclone(TC) simulated by GCM, it is available to assess the future change trends of frequency and intensity of TCs under climate change. Thus, this article firstly investigated the simulated Landfall Tropical Cyclone(LTC) characteristics from 7 CMIP5 GCM outputs under HIS during 1986-2005, subsequently the future changes of LTC under RCP over2026-2045 are detected and projected as well. The result show that, the LTCs from GCMs well reproduce the observed LTC seasonal, geographical position and intensity probability distribution although the frequency of LTCs detected from the GCMs are all less than observed. With respect to the reference period 1986-2005 under HIS, the annual mean occurrence frequency of weak LTCs decrease while strong ones increase under RCP26 and RCP85 scenario. The LTC frequency in high latitude area shows little change under RCP, nevertheless it decreases in low latitude area(15°N-20°N)under all three RCPs, mostly under RCP85. With regard to the average intensity,LTCs under RCP45 and RCP85 are slightly stronger. Additionaly, the connection between the environment field and LTCs feature are also investigated which turns out that the annual mean occurrence frequency of LTCs has a significant negative relationship with the regional average vertical wind shear and sea level pressure between GCMs, while the average landing intensity show a significant positive correlation with sea surface temperature. However, when turn to the ensemble mean of GCMs, the change of LTCs frequency and intensity among each scenarios do not show any consistency with the corresponding environment factors.