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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May 2007 UNIVERSITY OF ATHENS FACULTY OF PHYSICS DEP. OF APPLIED PHYSICS LAB. OF METEOROLOGY Sensitivity tests in the dynamical and thermal part of the MRF-urban PBL scheme Sensitivity tests in the dynamical and thermal part of the MRF-urban PBL scheme in the MM5 model in the MM5 model Aggeliki Dandou, Maria Tombrou

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May 2007 Meteorological Model MM5 (Version 3-6) The Penn State/NCAR Mesoscale Model MM5 (Grell et al., 1994) is a terrain following numerical weather prediction model, with a multiple-nest capability, nonhydrostatic dynamics and a four-dimensional data assimilation capability. simple ice Hsie et al. (1984), for the moisture parameterization cloud-radiation scheme Dudhia (1989), for the radiation parameterization Grell (1993), for the clouds parameterization Five-Layer Soil model (Dudhia, 1996), for the soil parameterization Parameterization schemes considered: 1

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May 2007 Meteorological Model MM5 (Version 3-6) MRF (Hong and Pan, 1996): high resolution non-local scheme based on Troen and Mahrt (1986) representation of counter gradient term and K profile in the well mixed PBL MRF-urban (Dandou et al., 2005): a modified version of MRF whereby urban features were introduced both in the thermal part and the dynamical part: Anthropogenic heat: as a temporal and spatial function of the diurnal variation of the anthropogenic emissions Heat storage: the OHM scheme (Grimmond et al., 1991) PBL parameterization schemes: Heat and momentum fluxes (under unstable conditions): according to Akylas et al. (2003) Diffusion coefficients (under stable conditions): according to King et al. (2001) Updated field for the roughness length: based on literature values in combination with satellite detailed information on land use (spatial resolution 30 m) 2 MRF-not urban: a modified version of MRF, whereby the city of Athens is replaced by dry cropland and pasture surface, as the surrounding area

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May 2007 Area of application Meteorological data ECMWF (0.5 o x 0.5 o ) every 6 hours Sea Surface Temperature SST (1 o x1 o ) every 6 hours USGS data (25 categories) (30 x 30) for topography and land use Two-way nesting Input data 3 Ground stations National Observatory of Athens (NOA), an urban station (4 km inland from the shore), located in a park, on top of a hill (107 m asl), with urban characteristics 85% and z 0 =0.8 m Marousi, a suburban station (13 km inland from the shore), inside a grove surrounded by buildings of different heights, with urban characteristics 52% and z 0 =0.5 m Peiraias, an urban station at the harbor, with urban characteristics 100% and z 0 =1 m

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Available measurements 14 September 1994 (MEDiterranean CAmpaign of PHOtochemical Evolution MEDCAPHOT-TRACE experiment, Ziomas, 1998) Air temperature Air temperature Sensible heat flux (sonic anemometer) Sensible heat flux (sonic anemometer) Friction velocity (sonic anemometer) Friction velocity (sonic anemometer) Wind velocityWind velocity NOA, Marousi NOA, Marousi, Peiraias Landsat TM satellite image (acquisition date: 13 Joune 1993)Landsat TM satellite image (acquisition date: 13 Joune 1993)

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Results Surface fluxes Surface fluxes Air Temperature Air Temperature Diffusion coefficients Diffusion coefficients PBL height PBL height Surface fluxes Surface fluxes

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Diurnal variation of surface fluxes (MRF-urban scheme) Q*- net all wave radiation QH-sensible heat flux QE-latent heat flux QF-anthropogenic heat ΔQs-heat storage (urban, downtown) (urban, at the harbor) (semi-urban)

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Diurnal variation of sensible heat flux Diurnal variation of sensible heat flux NOA : larger values due toNOA : larger values due to soil characteristics (bare rocks) and surface cover (olive tree plantation) Marousi: turbulence characteristics of the grove and not the surrounded built-up areaMarousi: turbulence characteristics of the grove and not the surrounded built-up area Model results versus measurements MRF: substantially higher values than the measurementsMRF: substantially higher values than the measurements MRF-urban: in better agreement with the measurementsMRF-urban: in better agreement with the measurements Decrease MANGE 40% Decrease MANGE 29% Schemes intercomparison During the night: increase (absolute values) due to the thermal partDuring the night: increase (absolute values) due to the thermal part During the day: decrease due to the smaller temperature gradients produced by the thermal part and the z 0During the day: decrease due to the smaller temperature gradients produced by the thermal part and the z 0 Measurements (Batchvarova and Gryning, 1998) temperature gradients (higher location) - predicted values - observed values (Mean Absolute Normalized Gross Error)

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May W/m 2 Spatial distribution of the sensible heat flux Spatial distribution of the sensible heat flux MRF 3:00 LST 14:00 LST MRF MRF-dyn MRF-ther MRF-urban

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Diurnal variation of friction velocity Diurnal variation of friction velocity Max values ~0.5 m/s at both sites, although V NOA (~4 m/s) > V MAROUSI (~2 m/s), due to its higher locationMax values ~0.5 m/s at both sites, although V NOA (~4 m/s) > V MAROUSI (~2 m/s), due to its higher location Marousi: the nonhomogeneity of the surrounding buildings, interchanged with the green areas cause higher valuesMarousi: the nonhomogeneity of the surrounding buildings, interchanged with the green areas cause higher values Decrease MANGE 6% Decrease MANGE 2% Measurements (Batchvarova and Gryning, 1998)Model results versus measurements During the night: any comparison with the measurements is meaningless (<0.1 m/s, the models threshold)During the night: any comparison with the measurements is meaningless (<0.1 m/s, the models threshold) During the day: decrease in the MRF-urban, closer to the measurementsDuring the day: decrease in the MRF-urban, closer to the measurements Marousi: smaller decrease because the z 0 did not change significantly. Higher values at noon due to the wind speed increaseMarousi: smaller decrease because the z 0 did not change significantly. Higher values at noon due to the wind speed increase Schemes intercomparison Differences due to the different profile functions and z 0Differences due to the different profile functions and z 0 During the night: increase due to the increase of instabilityDuring the night: increase due to the increase of instability increase of z 0 increase in the diffusion processes decrease in the wind speed increase of u * normalization in temperature gradients decrease of u * During the day:During the day:

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Spatial distribution of the friction velocity Spatial distribution of the friction velocity MRF 3:00 LST 14:00 LST MRF MRF-dyn MRF-ther MRF-urban m/s

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Results Surface fluxes Surface fluxes Air Temperature Air Temperature Diffusion coefficients Diffusion coefficients PBL height PBL height Surface fluxes Surface fluxes Air Temperature Air Temperature

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Diurnal variation of air temperature (at 10 m agl) Diurnal variation of air temperature (at 10 m agl)Measurements During the night: development of an urban heat islandDuring the night: development of an urban heat island During the day: lower maximum values at the urban stations (NOA and Peiraias), compared to the suburban station (Marousi) During the day: lower maximum values at the urban stations (NOA and Peiraias), compared to the suburban station (Marousi) MRF-urban: decrease in the temperature amplitude wave, in better accordance with the measurementsMRF-urban: decrease in the temperature amplitude wave, in better accordance with the measurements NOA: differences with measurements due to its location on top of the hill, not resolved by the models spatial resolution (2 km)NOA: differences with measurements due to its location on top of the hill, not resolved by the models spatial resolution (2 km) Decrease MANGE 53% Decrease MANGE 38% Decrease MANGE 41% Schemes intercomparison During the nightDuring the night: increase due to the thermal part increase due to the dynamical part decrease due to the thermal part total decrease During the day:During the day: Model results versus measurements

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Spatial distribution of the air temperature (at 2m agl) Spatial distribution of the air temperature (at 2m agl) MRF-urban MRF-dyn - MRF MRF-ther - MRF MRF-urban - MRF oCoCΔΤ ( o C) Spatial distribution of the air temperature differences (at 2m agl) Spatial distribution of the air temperature differences (at 2m agl) 3:00 LST 14:00 LST 3:00 LST 14:00 LST

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Results Surface fluxes Surface fluxes Air Temperature Air Temperature Diffusion coefficients Diffusion coefficients PBL height PBL height Surface fluxes Surface fluxes Air Temperature Air Temperature Diffusion coefficients Diffusion coefficients

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Diffusion coefficient profiles Diffusion coefficient profiles During the day:During the day: increase due to the dynamical part decrease due to the thermal part total decrease Schemes intercomparison During the night: increase in the lower atmosphere due to the dynamical and thermal partDuring the night: increase in the lower atmosphere due to the dynamical and thermal part

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Spatial distribution of diffusion coefficients at the surface layer Spatial distribution of diffusion coefficients at the surface layer MRF 3:00 LST 14:00 LST MRF MRF-dyn MRF-ther MRF-urban m 2 /s

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Results Surface fluxes Surface fluxes Air Temperature Air Temperature Diffusion coefficients Diffusion coefficients PBL height PBL height Surface fluxes Surface fluxes Air Temperature Air Temperature Diffusion coefficients Diffusion coefficients PBL height PBL height

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Diurnal variation of the PBL height Diurnal variation of the PBL height Schemes intercomparison During the night: increase due to the thermal partDuring the night: increase due to the thermal part increase due to the dynamical part decrease due to the thermal part total decrease Delay (~1 h) in max value (MRF-urban), due to the delay in the sea-breeze developmentDelay (~1 h) in max value (MRF-urban), due to the delay in the sea-breeze development During the day:During the day:

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Diurnal variation of the PBL height Diurnal variation of the PBL height Tombrou et al. (2006)

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Spatial distribution of the PBL height Spatial distribution of the PBL height MRF 3:00 LST 14:00 LST MRF MRF-dyn MRF-ther MRF-urban m

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Summarizing the results Summarizing the results n=77 (number of grids) t=12 (number of hours for the day and night) Day ( LST ) MRF-dynall - MRF (%) MRF-ther - MRF (%) MRF- urban - MRF (%) Sensible heat Friction velocity Air temperature Diffusion coefficients Wind speed PBL height Night ( LST, LST ) MRF-dynall - MRF (%) MRF-ther - MRF (%) MRF- urban - MRF (%) Sensible heat Friction velocity Air temperature Diffusion coefficients Wind speed PBL height

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May m/s MRF-urban 14:00 LST 3:00 LST 14:00 LST m/s 3:00 LST Spatial distribution of the wind velocity (at 10 m) Spatial distribution of the wind velocity (at 10 m) MRF-urban Spatial distribution of the wind speed differences (at 10m) Spatial distribution of the wind speed differences (at 10m) MRF-urban – MRF-not urban

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Vertical cross sections of the wind velocity along the sea-breeze axis Vertical cross sections of the wind velocity along the sea-breeze axis m/s MRF-urbanMRF-not urban 14:00 LST 3:00 LST 0.4 m/s 4 m/s

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COST-728 Workshop on Model urbanization strategy UKMO, Exeter, UK, 3-4 May Conclusions Both modifications play an important role and improve the models results Both modifications play an important role and improve the models results During the day: During the day: The increase in temperature and diffusion coefficients calculated by the dynamical part is compensated by the decrease in the thermal part, resulting in a total decreaseThe increase in temperature and diffusion coefficients calculated by the dynamical part is compensated by the decrease in the thermal part, resulting in a total decrease A decrease in turbulence and fluxes is calculated by both modificationsA decrease in turbulence and fluxes is calculated by both modifications A slowing in the sea-breeze front and a frictional retard concerning its penetration over the Athens city is calculated due to the increased roughness lengthA slowing in the sea-breeze front and a frictional retard concerning its penetration over the Athens city is calculated due to the increased roughness length During the night: During the night: The total increase in temperature, diffusion coefficients, turbulence and fluxes is due to both modificationsThe total increase in temperature, diffusion coefficients, turbulence and fluxes is due to both modifications The maximum wind speeds calculated in the lower atmosphere is due to the urban heat islandThe maximum wind speeds calculated in the lower atmosphere is due to the urban heat island

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