ECMWF 數(shù)值預(yù)報(bào)模式簡(jiǎn)介PPT課件

1、.,1,ECMWF 數(shù)值預(yù)報(bào)模式簡(jiǎn)介,.,2,氣象預(yù)報(bào)的四個(gè)方面問(wèn)題,當(dāng)前的天氣或氣候信息完備的綜合觀測(cè)系統(tǒng)完善的觀測(cè)系統(tǒng)；資料信息識(shí)別；資料的綜合處理（同化） 天氣或氣候的演變規(guī)律從資料得到新認(rèn)識(shí)從資料得到新認(rèn)識(shí)；反映大氣運(yùn)動(dòng)數(shù)學(xué)物理規(guī)律的微分方程組。 外力和強(qiáng)迫的變化地形和邊界強(qiáng)迫；太陽(yáng)常數(shù)；引力等 從已知預(yù)報(bào)未來(lái)的手段完備的數(shù)值模 式；承載數(shù)值模式計(jì)算、顯示和通訊平臺(tái) 駕馭觀測(cè)、資料分析和數(shù)值模式發(fā)展和應(yīng) 用的人才隊(duì)伍,.,3,大氣圈,水圈,冰晶圈 /冰凍圈,生物圈,巖石圈,人類(lèi)圈,.,4,紛繁多樣數(shù)值預(yù)報(bào)產(chǎn)品-什么會(huì)有差別？,.,5,分辨率不同 模式的表述的物理過(guò)程有差異 計(jì)算方案、網(wǎng)

2、格、變量分布等 再分析資料分析的初值能代表大氣實(shí)況嗎？,.,6,Orography and Resolutions,GSM T213 (60km),RSM(20km),MSM(10km),Orographic effects are better captured by higher resolution models. The surface parameters such as Tsurf might be predicted more realistically by those models.,.,7,ECMWF 致力于2016-2025 數(shù)值預(yù)報(bào)發(fā)展戰(zhàn)略： 利用集合預(yù)報(bào)方法提前2周預(yù)

3、報(bào)高影響天氣事件 提前4周，無(wú)縫隙地預(yù)報(bào)大尺度系統(tǒng)形勢(shì)和系統(tǒng)移動(dòng) 提前1年預(yù)測(cè)全球范圍的異常狀況,.,8,研究和更豐富的知識(shí) 基于集合預(yù)報(bào)的分析和預(yù)報(bào)技術(shù) 如何實(shí)現(xiàn)目標(biāo)： Observations High resolution ensemble Earth-system Scalability Funding People （引自 Erland Klln，“Earth system modelling for seamless prediction” ECMWF Annual Seminar 2016）,.,9,Future Earth System model and assimilati

4、on developmentsErland Klln, ECMWF,.,10,.,11,Ocean model (NEMO),Wave model (ECWAM),Atmosphericmodel (IFS),Air density,Gustiness,Neutral wind,Roughness,Currents,Sea surface temperature,All configurations,Ensemble FC,Solar and non solar fluxes, E-P,Towards a fully coupled system (currently only operati

5、onal in EPS),ORCA1_Z42,TCo1279/TCo639,14km/28km,9km/18km,Ensemble systems only: - Medium range forecast - Monthly forecast - Seasonal forecast,Every IFS time step,Every coupling time step (1 or 3 hours),Single executable,.,12,Ocean model (NEMO),Wave model (ECWAM),Atmosphericmodel (IFS),Air density,G

6、ustiness,Neutral wind,Roughness,Turbulent energy,Stokes drift,Currents,Sea surface temperature,All configurations,Stress,Ensemble FC,Solar and non solar fluxes, E-P,Towards a coupled system,ORCA1_Z42,TCo1279/TCo639,14km/28km,9km/18km,Single executable,Operational from day 0 since 2013,.,13,Ocean mod

7、el (NEMO),Ice concentration,Wave model (ECWAM),Atmosphericmodel (IFS),Air density,Gustiness,Neutral wind,Roughness,Turbulent energy,Stokes drift,Currents,Ice model (LIM),Sea surface temperature,Ice concentration,All configurations,Stress,Ensemble FC,future operational,Solar and non solar fluxes, E-P

8、,Towards a coupled system,ORCA0.25_Z75,Adding active sea ice model,Implementation: End 2016.,Single executable,.,14,Calling sequence of the single executable,Simplified flow chart of the coupled model, here two time steps are shown. In reality, IFS/WAM coupling every IFS time step, but Call to NEMO

9、every hour (or 3 hours) with averaged accumulated fluxes.,.,15,Impact of Resolution on tropical cyclone forecast,For instance Typhoon Haiyan: forecasts from 4th, 5th and 6th November 2013, 0 UTC all from operational analysis.,Black: estimated from observations Red: old operational Ensemble resolutio

10、n (32 km) Blue: old operational HRES configuration (16 km) Green: experimental: new HRES configuration (10km),Typhoon Haiyan at peak intensity on November 7, 2013,.,16,Impact of Coupling on tropical cyclone forecast,For instance Typhoon Neoguri: forecasts from 6 July 2014, 0 UTC,Black: estimated fro

11、m observations Green: old operational HRES configuration (uncoupled) (16km) Red: experimental: 16km coupled to NEMO (ORCA025_Z75) Blue: 16km coupled to NEMO + new physics,min MSLP (hPa),900,950,Neoguri affecting Okinawa on July 8, 2014,Climate reanalyses for the coupled earth model,ECMWF coupled Ear

12、th model for medium-range weather forecasting,New coupled assimilation system (CERA) for the coupled Earth model: atmospheric and ocean observations assimilated simultaneously ocean observations can impact atmospheric estimate and conversely CERA-20C reanalysis in production (1900-2010),Karl and Tre

13、nberth 2003,Coupled assimilation system (CERA),EDA variational approach with a 24-hour window that assimilates simultaneously atmospheric and ocean observations,coupled model computes observation misfits in each outer iteration,atmospheric and ocean increments are computed in parallel to correct the

14、 initial state,SST computed in NEMO and constrained by relaxation,analysis dynamically consistent with respect to the coupled model,.,19,Conclusions:,ECMWF has a coupled atmosphere-wave-ocean circulation forecasting system, currently operational in the Ensemble Prediction System. Work is ongoing on

15、using a higher resolution ocean components (ORCA025z75) planned for end of 2016 in the Ensemble forecasts and later in the High resolution system. There is a clear benefit in coupling the different models, but it creates new challenges in determining what physical parameters need to be exchanged. Fu

16、rthermore, model parameterisations might need revisiting.,.,20,EC模式動(dòng)力框架,垂直采用坐標(biāo)，U=ucos ；V=vcos,.,21,.,22,.,23,對(duì)比球坐標(biāo)系中的基本方程組,曲率項(xiàng),.,24,重力不是指向地心，等位勢(shì)面也不是球面。,.,25,非靜力學(xué)模式 靜力學(xué)模式,靜力學(xué)平衡：運(yùn)動(dòng)的垂直尺度遠(yuǎn)小于水平尺度的情況下成立,模式的分類(lèi),.,26,基于連續(xù)方程的模式分類(lèi),非靜力學(xué)模式根據(jù)模式中是否包含聲波，分為： 滯（非）彈性（anelastic)模式 假定大氣不可壓，濾掉聲波 彈性(elastic)模式 大氣可壓、由散度預(yù)報(bào)氣

17、壓的變化，但聲波 需要特殊的處理,.,27,根據(jù)連續(xù)方程的近似程度， 滯彈性和彈性模式又可進(jìn) 行不同的分類(lèi)：,滯彈性模式,不可壓縮模式,滯彈性模式,彈性模式,準(zhǔn)可壓模式,完全可壓模式,.,28,數(shù)值計(jì)算方案,大氣運(yùn)動(dòng)方程組是一套復(fù)雜的非線(xiàn)性方程組，目前，還沒(méi)有理論解存在，只能借助數(shù)值方法求解。 數(shù)值方法有很多，目前氣象上用的主要用的是差分方法、譜方法、有限元法等。 差分方法：就是在離散的網(wǎng)格點(diǎn)上，以差商代替微商，求解微分方程的方法。,.,29,關(guān)于有限差分與譜方法的圖例,有限差分,譜方法,.,30,.,31,| | | n-1 n n+1,從物理上考慮，差分的精度還與采樣點(diǎn)密即網(wǎng)格，與要素在采

18、樣區(qū)的變化分布有關(guān)。即采樣數(shù)據(jù)是否能有代表性。,中央差,精確值,采樣值,混淆誤差,.,32,離散網(wǎng)格所能表示的最短波長(zhǎng) 上表中當(dāng)L/ x =2時(shí)，即兩倍格距波，R=0，誤差100%，因此，離散網(wǎng)柜完全不能表示兩倍格距以下的短波。如格距為100km，則你只能預(yù)報(bào)出200km以上的天氣系統(tǒng)。,1.5倍格距波,3倍格距波,最短的波，2倍格距波,1.5倍格距波被當(dāng)成3倍格距的波 混淆誤差會(huì)把小于2倍格距的波歪曲為2倍格距以上的波。 因此混淆誤差主要集中在24倍格距間。 預(yù)報(bào)員會(huì)在什么情況下遇到“混淆誤差”？,.,33,拉格朗日和半拉格朗日方法,拉格朗日和半拉格朗日方法是從另外一個(gè)角度來(lái)求取平流方程的解。 有解析解： 不失一般性，考慮 情況下平流方程的解。,可以證明下述兩個(gè)式子是成立的：,Think of