# PM10 and PM25 global products **URL:** \ **Category:** CAMS - Datasets and Usage\ **Tags:** cams, cams\_global\_forecast\ **Created:** [24 September 2019 14:55 UTC](https://forum.ecmwf.int/t/pm10-and-pm25-global-products/1084 "2019-09-24T14:55:55Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Michela](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/m/898d66/32.png) [@Michela](https://forum.ecmwf.int/u/Michela)\ **Post date:** [24 September 2019 14:55 UTC](https://forum.ecmwf.int/t/pm10-and-pm25-global-products/1084/1 "2019-09-24T14:55:55Z")
How are PM10 and PM25 in CAMS global products calculated? ---
**Author:** ![Antje\_Inness](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/a/eb8c5e/32.png) [@Antje\_Inness](https://forum.ecmwf.int/u/Antje_Inness)\ **Post date:** [26 September 2019 12:46 UTC](https://forum.ecmwf.int/t/pm10-and-pm25-global-products/1084/2 "2019-09-26T12:46:29Z")
## For CAMS NRT forecasts up to and including January 23rd 2017 (model cycle 41r1) The formulae used are:   PM10 = RHO \* ( 1 \* SS1 + 1 \* SS2 + 1 \* DD1 + 1 \* DD2 + 0.55 \* DD3 + 0.85 \* OM1 + 0.85 \* OM2 + 0.85 \* SU1 + 1\* BC1 + 1 \* BC2 )   PM2.5 = RHO \* ( 1 \* SS1 + 0.4 \* SS2 + 1 \* DD1 + 1 \* DD2 + 0.11 \* DD3 + 0.7 \* OM1 + 0.7 \* OM2 + O.7 \* SU1 + 1 \* BC1 + 1 \* BC2 ) Where RHO: air density (around 1.2 KG/M3 at altitude 0), which can be computed from pressure P and temperature T as RHO = P/R\*T, R is the specific gas constant for dry air, 287.058 J/(kg·K). SS1: seal salt (bin 1) SS2: seal salt (bin 2) DD1: desert dust (bin 1) DD2: desert dust (bin 2) DD3: desert dust (bin 3) OM1: organic matter (bin 1) OM2: organic matter (bin 2) SU1: sulphur (bin 1) BC1: black carbon (bin 1) BC2: black carbon (bin 2) Sea salt bins: [0.03-0.5], [0.5- 5], [5-20 microns] radius Desert dust bins: [0.03-0.55], [0.55-0.9], [0.9-20 microns] radius Notes: - SS3 does not contribute to PM10 and PM2.5, on the basis that SS3 particles are \>5µm in radius (10µm  diameter), thus too large. - The above formulae are subject to an overestimation of the sea salt contribution to PM by a factor of 4.3 [as described here](https://confluence.ecmwf.int/display/CKB/CAMS+global+sea+salt+aerosol+mixing+ratios).  This mostly affects PM in cleaner (especially coastal) environments with background aerosol, rather than the PM peaks in polluted regions, which are probably of most concern to users. See also: Morcrette, J.-J., and Coauthors, 2009: Aerosol analysis and forecast in the European Centre for Medium-Range Weather Forecasts Integrated Forecast System Forward modeling, _J. Geo. Res._, **114** , D06206, [doi:10.1029/2008JD011235](https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2008JD011235) ## For CAMS NRT forecasts from January 24th 2017 (model cycle 43r1) and the CAMS Reanalysis (based on model cycle 42r1): The formulae used are:   PM10 = RHO \* ( 1 \* SS1 / 4.3 + SS2 / 4.3 + 1 \* DD1 + 1 \* DD2 + 0.4 \* DD3 + 1 \* OM1 + 1 \* OM2 + 1 \* SU1 + 1 \* BC1 + 1 \* BC2 )   PM2.5 = RHO \* ( 1 \* SS1 / 4.3 + 0.5 \* SS2 / 4.3 + 1 \* DD1 + 1 \* DD2 + 0.7 \* OM1 + 0.7 \* OM2 + O.7 \* SU1 + 1 \* BC1 + 1 \* BC2 ) Where RHO: air density (around 1.2 KG/M3 at altitude 0), which can be computed from pressure P and temperature T as RHO = P/R\*T, R is the specific gas constant for dry air, 287.058 J/(kg·K). SS1: seal salt (bin 1) SS2: seal salt (bin 2) DD1: desert dust (bin 1) DD2: desert dust (bin 2) DD3: desert dust (bin 3) OM1: organic matter (bin 1) OM2: organic matter (bin 2) SU1: sulphur (bin 1) BC1: black carbon (bin 1) BC2: black carbon (bin 2) Sea salt bins: [0.03-0.5], [0.5- 5], [5- 20 microns] radius Desert dust bins: [0.03-0.55], [0.55-0.9], [0.9-20 microns] radius Notes: - SS3 does not contribute to PM10 and PM2.5, on the basis that SS3 particles are \>5µm in radius (10µm  diameter), thus too large. This may need revisiting in future as a result of correcting for [the 80% humidity issue](https://confluence.ecmwf.int/display/CKB/CAMS+global+sea+salt+aerosol+mixing+ratios), which means the particles now look smaller than before. - DD3 (large dust particles) does not contribute PM2.5. ## For CAMS NRT forecasts from July 9th 2019 (model cycle 46r1) with additional Nitrate and Ammonium aerosols The formulae used are:   PM10 = RHO \* ( 1 \* SS1 / 4.3 + SS2 / 4.3 + 1 \* DD1 + 1 \* DD2 + 0.4 \* DD3 + 1 \* OM1 + 1 \* OM2 + 1 \* SU1 + 1 \* BC1 + 1 \* BC2 +  1 \* NI1 + 1 \* NI2  + 1 \* NH3 )   PM2.5 = RHO \* ( 1 \* SS1 / 4.3 + 0.5 \* SS2 / 4.3 + 1 \* DD1 + 1 \* DD2 + 0.7 \* OM1 + 0.7 \* OM2 + O.7 \* SU1 + 1 \* BC1 + 1 \* BC2  +  0.7 \* NI1 + 0.25  \* NI2  + 0.7 \* NH3  ) RHO: air density (around 1.2 KG/M3 at altitude 0), which can be computed from pressure P and temperature T as RHO = P/R\*T, R is the specific gas constant for dry air, 287.058 J/(kg·K). SS1: seal salt (bin 1) SS2: seal salt (bin 2) DD1: desert dust (bin 1) DD2: desert dust (bin 2) DD3: desert dust (bin 3) OM1: organic matter (bin 1) OM2: organic matter (bin 2) SU1: sulphur (bin 1) BC1: black carbon (bin 1) BC2: black carbon (bin 2) NI1: Nitrates fine (bin 1) NI2: Nitrates coarse (bin 2) NH3: Ammonium Sea salt bins: [0.03-0.5], [0.5- 5], [5- 20 microns] radius Desert dust bins: [0.03-0.55], [0.55-0.9], [0.9-20 mic ---
**Author:** ![Johannes\_Flemming](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/j/958977/32.png) [@Johannes\_Flemming](https://forum.ecmwf.int/u/Johannes_Flemming)\ **Post date:** [14 October 2019 10:58 UTC](https://forum.ecmwf.int/t/pm10-and-pm25-global-products/1084/3 "2019-10-14T10:58:49Z")
Please note SU1 is not sulphur but aerosol sulfate (SO4)