Aerosol forecast verification at ECMWF

Transcription

1 Aerosol forecast verfcaton at ECMWF Luke Jones Angela Benedett ECMWF Acknowledgements: Jean-Jacques Morcrette and Johannes Kaser

2 Quck overvew of the MACC/ECMWF aerosol analyss and forecastng system Forward model 2 aerosol-related prognostc varables: * 3 bns of sea-salt ( µm) * 3 bns of dust ( µm) * Black carbon (hydrophlc and phobc) * Organc carbon (hydrophlc and phobc) * SO 2 -> SO 4 Physcal processes nclude: emsson sources (some of whch updated n NRT,.e.fres), horzontal and vertcal advecton by dynamcs, vertcal advecton by vertcal dffuson and convecton aerosol specfc parameterzatons for dry deposton, sedmentaton, wet deposton by large-scale and convectve precptaton, and hygroscopcty (SS, OM, BC, SU) Analyss Integrated n the ECMWF ncremental 4D-Var Control varable s formulated n terms of the total aerosol mxng rato. Soon to come: fne and coarse mode. Increments n total mass are reparttoned nto the sngle speces accordng to ther fractonal contrbuton to the total. Background error statstcs have been computed usng forecasts errors as n the NMC method (48h-24h forecast dfferences). Assmlated observatons are the MODIS Aerosol Optcal Depths (AODs) at 550 nm over land and ocean. Observaton errors are prescrbed fxed values as a result of nvestgaton to mplement the varatonal bas correcton (not actve).

3 MACC NRT aerosol forecasts Anthropogenc Natural

4 Verfcaton Based on AERONET mult-wavelength Aerosol Optcal Depths (AOD) Forecast felds are retreved and nterpolated to all known AERONET ste locatons usng b-lnear nterpolaton. To obvate the problem of an uneven dstrbuton of the AERONET stes around the globe, wth a hgh densty of statons n Europe and North Amerca but far fewer n less developed regons and vrtually none oceanc, an attempt s made to pck a subset of the stes by fndng pars of stes whch are less than a crtcal dstance apart (typcally between 500km and 000km) and rejectng the one whch has fewer data at a gven set of wavelengths over a gven perod. For NRT experments the ste-lst s fxed. For reanalyses the lst of selected stes needs to be a functon of tme to mantan data volume AERONET data s averaged over the number of hours between model output steps, and t s compared wth the NRT forecast output at the gven archvng tme (every three hours) ( F O ) Tme-seres of bas (or mean error, F-O) and Root Mean Square Error ( N ) are computed by averagng over the selected stes. Due to nature of AERONET the statstcs are not always computed over the same number of stes (N s varable). The number of stes s plotted separately to check that the statstcs are meanngful. 2

5 Plot type : Bas and RMSE maps As a functon of space, meaned over tme N ( F O ) N s represented by the symbol-sze For multple: months wavelengths areas N ( F O 2 )

6 Plot type 2: Bas and RMSE As a functon of tme, meaned over space N ( F O ) N s shown on a separate plot For multple: months wavelengths areas N ( F O 2 )

7 Multple forecast ranges & 24-hour meanng Day Day 2 Day 3 Day 4 Daly-meaned values more stable & meanngful Multple forecast days supermposed Bas ncreases wth forecast range Less notceable on the RMS

8 Plot type 3: Sngle-ste tme-seres Comparson of model (f93) and MODIS AOT at 550nm and L.5 Aeronet AOT at 500nm over Solar_Vllage (24.9 N, 46.4 E). Model: 00UT, -28 Feb 200, T+3 to T+24. Aeronet AOT MODIS AOT Total FC AOT Sulphate Sea Salt Dust Organc Matter Black Carbon FEB MAR 200 For multple: stes, months, wavelengths

9 NRT Verfcaton on the Web From the man web page Clck on Global atmospherc composton Clck on Montorng and Forecastng of Global Atmospherc Composton Clck on aerosol verfcaton plots under the header Verfcaton Or go drectly to Comparson of model (f93) and MODIS AOT at 550nm and L.5 Aeronet AOT at 500nm over Alta_Floresta (9.87 S, 56. W). Model: 00UT, -30 Sep 200, T+3 to T+24. Aeronet AOT MODIS AOT Total FC AOT Sulphate Sea Salt Dust Organc Matter Black Carbon FC-OBS Bas. Model (f93) AOT at 550nm aganst L.5 Aeronet AOT at 500nm. Meaned over 64 stes globally. Perod=-30 Sep 200. FC start hrs=0z from T+3. Tme-seres of bas over approx 64 unformly-dstrbuted AERONET statons SEP 200 Plots updated daly RMS Error. Model (f93) AOT at 550nm aganst L.5 Aeronet AOT at 500nm. Meaned over 64 stes globally. Perod=-30 Sep 200. FC start hrs=0z from T Sngle ste plots SEP OCT 200 RMS SEP 200

10 Aerosol verfcaton wth A-Tran data Model now outputs smulated Aerosol Attenuated Backscatter Allows drect numercal comparson between CALIPSO & model statstcs can be computed What statstcs? ~ on-gong research Soon to come: new NRT level-.5 CALIPSO product

11 graphcs by M. Raznger Aerosol verfcaton wth PM0 Sngle case-study: 200 fres n Russa PM0 (μg/m 3 ) Sammaltuntur, Fnland Observed MACC Aug Vrolaht, Fnland FRP on 4 August 200, graphcs by S. Semen Ar-qualty observatons show hgh values over parts of Fnland on 8 August (y-axs labels not publc) MACC 0-96-hour forecasts predct the smoke plume overpass well Due to aerosol assmlaton & fre source PM0 s a useful aerosol verfcaton measure Vrolaht four forecast days

12 Summary and future plans Currently, all verfcaton for the aerosol analyss/forecasts wth the ECMWF/MACC system s based on INDEPENDENT observatons of multwavelength AOD from AERONET and ldar backscatterng from CALIPSO. Verfcaton actvtes have beneftted greatly from the provson of near realtme data (AERONET typcal data latency s day, thanks to NASA/GSFC). Other teams dealng wth aerosol observatons are developng NRT data provson capabltes (.e. CALIPSO, thanks to NASA/LaRC). Research data (level 2.0 AERONET, CALIPSO, ground-based ldars, GAW statons, other n-stu observatons, arcraft and feld experments) s very valuable for R&D and model assessment, even f does not meet the NRT requrements Future plans to nclude also model-based verfcaton lookng forward to the outcomes of today s dscusson!