Mesoscale models for urban air quality research with high resolution

Transcription

1 This work is supported by the Russian Foundation for Basic Research, grant N Mesoscale models for urban air uality research with high resolution Starchenko Alexander V., Bart A.A., Belikov D.A., Danilkin E.A. Tomsk State University, Tomsk, Russia International Conference CITES29, July 29, Krasnoyarsk

2 Introduction Increases in environmental problems linked to urbanization and increases in computational power are proposed as the main mechanisms behind positive feedbacks between experimental investigation and numerical modelling in mesoscale urban studies Urban canopy influences the airflow in ABL, turbulent transfer, heat and moisture exchange and pollution transport, particulate t dispersion i and deposition.

3 Mesoscale model The mesoscale ranges from a few kilometres to several hundred kilometers in the horizontal and tens of meteres to the depth of the troposphere in the vertical, with a time scale of about 1 to 12 h (Pielke, 1984). Circulations such as land/sea breezes, mountain/valley flows,and urban breezes fall within this scale. The pollutant dispersion is strongly dependent of the structure of the boundary layer developing over the city and of its interactions with the rural boundary layer.

4 Mesoscale model includes, as a rule, unsteady three-dimensional euations of hydro- thermodynamics and differ by various approaches of parameterisation of atmospheric processes and have a good representation of the urban effects.

5 Mesoscale model It is assumed, that t Taking into account moisture exchange and short-wave and long- wave radiation in atmosphere with explicit representation and with parameterization of urban sublayer Parameterization of urban sublayer is based on modelling of influence of urban obstacles on flow, turbulence level and heat and moisture exchange. Every surface computational ti cell is divided id d on f urb part of urbanized surface (f urb =f con +f roof )

6 Tomsk city Urban land use is divided to: Urban1 low rise Urban2 low to medium rise Urban3 four and more stories Urban1 Urban2 Urban 3 Building height, m 1m 2m 4m Roof fraction f roof,33,33,33 Drag coef Cd,5,1,2 Heat flux, W/m

7 Mesoscale model Basic euations (continuity and momentum) ( u ) x ( v ) y ( w ) z 2 2 u u u u p u u m u u v w fvkh K 2 2 Z t x y z x x y z z f f C A ( z) u( u v ) urb roof D f v v v v p v v v m u v w fukh K 2 2 Z t x y z y x y z z f f C A ( z )( v u v ) urb roof D f w t w u x w v y w w z p z g K 2 2 w w 2 x y H 2 K z m Z w z

8 Mesoscale model Mesoscale model Basic euations (heat and moisture exchange) (1 ) (1 ) h H Z urb NC Nr urb rad urb urb cnyn roof w u v w K K t x y z x y z z R R f Q f f f f L T ( a ) cloud v h Z H H z K z y K y x K x z w y v x u t ( ) ( ) urb rad urb urb cnyn roof w p f Q f f f f c T z z z W y K y x K x z w y v x u t rain H rain H rain rain rain rain ) ( R R RT p 1 z W z K z rain rain rain rain h Z ) ( O air M H M R R RT, p 2

9 Mesoscale model Basic euations (turbulence) 2 2 k k k k m u v g h u v w KZ KZ t x y z z z z 1,5 k k k CDk 1, 2 kl 1, 2 kl 1, 2 kl x x y y z z l f f C A ( z )( u v w ) urb roof D f /2 K Cf kl mh, Z m, h K H cl 2 u 2 x 2 u y v x 2 v 2 y 2,5

10 Boundary conditions On the lateral boundaries C t u, v,, S C S n t n Mesoscale model w ; ; n On the top boundary z u z v z w z On the ground k z l z H ; z 1 sat 1 G (1 f )((1 A) F F F ) H E f (1 f ) F s urb S A L s s urb roof uc z z 1 U z : v* f u * * cos ; V f sin ; f ( ); 1 v u 1 k 1 k z Monin-Obukhov Similarity Theory (MOST)

11 Simulation case Research domain: 5x5km2 with Tomsk city in the center; Date: 1-11 July 25; Cloudiness 9/1 on and 4/1 on ; South-West wind 1..3 m/sec; Computational grid: 5x5x Water, Few vegetation, Farmland, Deciduous forest, Mixed forest, Evergreen forest, Urban area; parameters of LU categories correspond to 24USGS classification

12 Results of 1m-wind predictions /s wind, m/ direction, deg time, hrs Observ. at Tomsk_South Observ. at TOR Pred. at Tomsk_South, MLayer Pred. at TOR, MLayer Pred. at TOR, MOST Pred. at Tomsk_South, MOST time, hrs

13 Results of 2m-temperature predictions i 4 Te emperatur re, deg time, hrs

14 Results of 1m-wind predictions at : LST

15 Results of 1m-wind predictions at 6: LST

16 Results of 1m-wind predictions at 12: LST

17 Results of 1m-wind predictions at 18: LST

18 Microscale model M2U (CFD) &MUST experiment

19 Microscale model M2U (CFD) &MUST experiment Averaged on research domain vertical profiles of velocity, turbulent energy and g p y gy scale of turbulence

20 Vertical profiles of wind at the center of ftomsk city z, m :LST 6:LST 12:LST 18:LST Solid line MOST; dashed line Multilayer model

21 Vertical profiles of TKE at the center of ftomsk city z, m :LST :LST Solid line MOST; dashed line Multilayer model

22 Vertical profiles of temperature at the center of Tomsk city z, m :LST 6:LST 12:LST Solid line MOST; dashed line Multilayer model 18:LST

23 г.томск, г., маршрут «змейка» The route of mobile meteo-station of IAO SB RAS through Tomsk city on 11 July

24 Simulation of formation of secondary pollutants in urban atmosphere 12 Concentration of near surface ozone, observed in Tomsk on O3,ppb 8 4 CO,ppb May time, hrs time, hrs NO2,ppb Legend TOR-station Prediction time, hrs Eulerian photochemical model with high resolution predicts distribution of 12 gaseous chemical species above considered domain during hours with using supercomputer TSU SKIF Cyberia. Point, linear and areal pollution sources are taken into account. r.tom

25 Comparison of measurements and predictions Near surface concentration of carbon monoxide, mg/m Observations Predictions

26 Comparison of measurements and predictions Near surface concentration of nitric dioxide, mkg/m Observations Predictions

27 Comparison of measurements and predictions Near surface concentration of nitric monoxide, mkg/m Observations Predictions

28 Comparison of measurements and predictions Near surface concentration of ozone, mkg/m Observations Predictions 2

29 Conclusion -For research of urban meteorology and pollution transport we developed mesoscale model with high resolution based on multilayer approach of parameterisation of influence of urban buildings on air flow, turbulent structure, heat and mass exchange -Some results of its application for Tomsk city conditions show perspectives of considered approach and its importance for the further investigations on model validation -Based on predicted urban meteorology simulation of distribution of primary and secondary pollutants, such as CO, NO, NO2, O3, also shows a good correspondence between observed and calculated concentrations