Development of an Integrated Earthquake Early Warning System in Taiwan - Case for the Hualien Area Earthquakes

The purpose of this paper is to document the climate characteristics ofthe Global Forecast System(GFS),which is an atmospheric general circulationmodel developed at the Central Weather Bureau(CWB),Taiwan.This paper documents the winter(December-February)and summer(June-August)climate characteristics of simulated hydrological processes andatmospheric circulation from a 2-year control simulation conducted withthe GFS using an annually repeating prescribed sea surface temperatureclimatology.In most regards,the climate characteristics of hydrological processesand atmospheric circulation are reproduced reasonably well by the GFSwhen compared to observations and analyses of the atmosphere.As for theclimate characteristics of hydrological processes,the major features of observedprecipitation,such as the Intertropical Convergence Zone(ITCZ),the Asian monsoon regimes,and the extratropical storm tracks,are wellcaptured in the GFS simulation.Similarly,other climate features of observedprecipitation,namely the regions of low precipitation rates over thesubtropical subsidence zones and polar areas,are also well defined by theGFS.The simulated precipitation pattern,however,exhibits some obviousdiscrepancies from the observed in the tropics.Excessive precipitation issimulated by the GFS over some tropical regions where there are complextopographic variations among oceans and lands.Otherwise,the GFS precipitationin the remaining tropical regions is generally underestimated.Inparticular,the underestimate of model precipitation over the tropical easternPacific results in a local ITCZ that is less organized in spatial structurethan the observed.This model precipitation deficiency is linked to underestimatesof precipitable water content and water vapor convergence overthe tropical eastern Pacific in the GFS simulation.Regarding the climate characteristics of the zonal mean state,the zonalmean climatologies of temperature and zonal wind are adequately simulatedby the GFS when compared to analyses.The major difference betweenthe simulated and analyzed zonal mean temperatures is a systematiccold bias in the model troposphere.This cold bias is generally within 4°K ofthe analyses for most of the tropospheric domain bounded by 40°S and40°N.The modal cold bias becomes significant at the polar tropopause,wherethe simulated zonal mean temperature can be from 8°K to 18°K colderthan the analyzed.Also noteworthy is the spatial relationship between thezonal mean temperature bias and zonal mean zonal wind bias.This is foundto be consistent with the spatial relationship between the real temperatureand the real zonal wind fields known as the thermal wind relationship.Thisfinding suggests that interactions between the thermal and dynamic fieldsin the GFS simulation must be to a great extent consistent with analyseswith regard to the thermal wind relationship.Regarding the climate characteristics of atmospheric circulation,theprimary circulation features associated with the summer monsoon systemand winter teleconnection pattern are well represented in the GFS simulationwhen compared with analyses.Nevertheless,in winter,major differencesbetween the analyzed and simulated circulation fields include theunderestimate of the East Asia subtropical jet features and the overestimateof the North America subtropical jet features in the GFS simulation.In the summer simulation,the major circulation bias is that the zonalwavenumber-2 component of the Northern-Hemisphere stationary eddy issimulated with larger amplitude than analyses.This circulation bias is accompaniedby excessive precipitation biases over the subtropical centralNorth Pacific west of the date line and the Central America/Caribbean Searegion.

並列關鍵字

Earthquake ； Earthquake Early Warning ； Real-Time Seismic System

國際替代計量

全文下載

主題瀏覽