The Scenario Analysis On Tropical Cyclone Activities In Western North Pacific Using PRECIS

Using the UKMO (UK Met Office) regional climate modeling system PRECIS with the driving oflateral boundary conditions provided by ERA-Interim reanalysis data and6Global Climate Model(GCM) outputs (e.i. ECHAM5, HadCM3Q0, HadCM3Q1, HadCM3Q7, HadCM3Q10andHadCM3Q13) respectively, this research firstly probe the PRECIS’ capability in simulating tropicalcyclone (TC) acitivities and large-scale processes controlling TCs over Western North Pacific (WNP).The projection of TC genesis and its uncertainties by different TC identification methods wereanalysed by using the ECHAM5-PRECIS’ SRES A1B scenario data, in which we applied3differentTC identification methods and analysed the cause of projection differences of TC identifications. ThePRECIS outputs by multi-GCM drives were used to project the future WNP TC activities and analyseits uncertainties.Comparison to the observation indicated that PRECIS is capable in effectively simulating theTC-controlled thermodynamic and dynamic large-scale environmental fields and the frequencydistribution of genesis and tracks of WNP TCs. Significant correlation was found between simulatedand observed annual genesis numbers. The simulated high value area of genesis distributionconsistently corresponded to the observation, and the distribution of simulated track frequency showedsimilarities compared to the observation. But the simulated TC genesis in South China Sea is morethan the observations, and the simulated track density is over-concentrated in the northeast of SouthChina Sea. The northward track number and intensities are underestimated in PRECIS simulation.The simulated TC genesis identified by the3different TC genesis identification methods showedsimilarities between CYGP and TRACK, which both derived close30yr mean values of simulatedannual genesis numbers of WNP TCs in the baseline period (1961-1990) while YGP overestimated theWNP TC genesis number. In the projection of2020s future period (2011-2040), the TRACK andCYGP both indicated decrease trends of TC numbers, while a significant increase trend is showed byYGP. Thermal factors are the possible main cause of differences in projection results.The simulation of PRECIS drived by multi-GCM derived reasonable spatial and temporaldistributions of TC genesis and tracks in the baseline period (1961-1990). In the projection of2020sfuture period, most of PRECIS outputs suggested decreases of WNP TC genesis number, eastwarddrifts of TC genesis area, eastward drifts of high value areas of track frequency and decreases of thetrack frequency at South China Sea. These outputs also indicated that TCs would become morelong-lasting and more intense in future period. A very likely increase of TC precipitation was showedin every GCM’s driving outputs.