Urban air quality simulation Vivien Mallet 1 , 2 With contributions - PowerPoint PPT Presentation

Urban air quality simulation Vivien Mallet 1 , 2 With contributions by Anne Tilloy 1 , 2 Raphaël Périllat 1 , 2 David Poulet 3 Fabien Brocheton 3 Frédéric Mahé 4 Pierre Pernot 4 Fabrice Joly 4 1 INRIA 2 CEREA, joint laboratory École des Ponts ParisTech - EDF R&D, Université Paris-Est 3 Numtech 4 Airparif Berkeley–Inria–Stanford Workshop, Stanford University, May 2013 V. Mallet Urban air quality simulation May 2013 1 / 67

Quick introduction to urban air quality simulation Simulation of pollutant concentrations over a city with street resolution. V. Mallet Urban air quality simulation May 2013 2 / 67

Urban air quality simulation: what for? Objectives 1 Evaluating the air concentrations of NO 2 , PM 10 , O 3 , . . . Analyzing: exposure of population for one or several past years Forecasting: for the next few days 2 Supporting decision making Characterizing: emission sources, local versus regional pollution Testing: scenarios of emissions reduction, new roads or industrial facilities V. Mallet Urban air quality simulation May 2013 3 / 67

Simulation tools: numerical models with street resolution Classical model: ADMS Urban 1 Computing the stationary solution of the reactive transport equation Every point source creates a plume, with Gaussian shape crosswind Parameterization for the standard deviations depending on meteorological variables Special treatment within the streets 2 Inputs Time-dependent: spatial distribution of emissions, background pollutant concentrations, meteorological variables (one value for the whole domain) Time-independent: street network 3 High computational costs ∼ 10 min of computations for a single date, i.e., ∼ 4 h for a full day V. Mallet Urban air quality simulation May 2013 4 / 67

Simulation tools: numerical models with street resolution Output points of ADMS Urban for Paris (east part) 2434000 2432000 2430000 2428000 2426000 2424000 596000 598000 600000 602000 604000 606000 608000 V. Mallet Urban air quality simulation May 2013 5 / 67

An important source of information: observations 2434000 2432000 2430000 2428000 2426000 2424000 596000 598000 600000 602000 604000 606000 608000 V. Mallet Urban air quality simulation May 2013 6 / 67

Merging model outputs and field observations Data assimilation classical assumptions The error on the simulated concentration vector x b has mean 0 and variance B The observation vector y can be compared with H x b where H is called the observation operator The error on the observation vector y has mean 0 and variance R No correlation between simulation and observational errors BLUE: best linear unbiased estimator BLUE is the linear estimator x a = L x b + K y whose error has mean 0 and variance A , so that A has minimal trace BLUE reads x a = x b + K ( y − H x b ) , with K = BH ⊤ ( HBH ⊤ + R ) − 1 V. Mallet Urban air quality simulation May 2013 7 / 67

Parameterization for the error variances Observational error Observational error variance: R = r I Simulation error � � � � − d ij − | P i − P j | Simulation error covariance: B ij = b exp exp L p ( i , j ) L d d ij : distance, along the network, between the projections on the network of the output points i and j P i : distance to the road network L d and L p ( i , j ) = L p + α min ( P i , P j ) : decorrelation lengths Determination of the parameters Statistical study of y − H x b , whose variance should be HBH ⊤ + R Leave-one-out cross-validation V. Mallet Urban air quality simulation May 2013 8 / 67

Simulation error covariances With respect to a traffic station 2434000 450 400 2432000 350 2430000 300 250 2428000 200 150 2426000 100 50 2424000 0 598000 600000 602000 604000 606000 V. Mallet Urban air quality simulation May 2013 9 / 67

Simulation error covariances With respect to a background station 2434000 450 400 2432000 350 2430000 300 250 2428000 200 150 2426000 100 50 2424000 0 598000 600000 602000 604000 606000 V. Mallet Urban air quality simulation May 2013 10 / 67

Before and after assimilation (preliminary result) 2434000 2434000 80 80 2432000 2432000 70 70 60 60 2430000 2430000 50 50 40 40 2428000 2428000 30 30 2426000 2426000 20 20 10 10 2424000 2424000 0 0 596000 598000 600000 602000 604000 606000 608000 596000 598000 600000 602000 604000 606000 608000 V. Mallet Urban air quality simulation May 2013 11 / 67

Before and after assimilation (preliminary result) 2434000 2434000 80 80 2432000 2432000 70 70 60 60 2430000 2430000 50 50 2428000 40 2428000 40 30 30 2426000 2426000 20 20 10 10 2424000 2424000 0 0 596000 598000 600000 602000 604000 606000 608000 596000 598000 600000 602000 604000 606000 608000 V. Mallet Urban air quality simulation May 2013 12 / 67

Before and after assimilation (preliminary result) 2434000 2434000 90 90 2432000 2432000 75 75 2430000 2430000 60 60 2428000 2428000 45 45 30 30 2426000 2426000 15 15 2424000 2424000 0 0 596000 598000 600000 602000 604000 606000 608000 596000 598000 600000 602000 604000 606000 608000 V. Mallet Urban air quality simulation May 2013 13 / 67

Before and after assimilation (preliminary result) 2434000 2434000 120 120 2432000 2432000 105 105 90 90 2430000 2430000 75 75 60 60 2428000 2428000 45 45 2426000 2426000 30 30 15 15 2424000 2424000 0 0 596000 598000 600000 602000 604000 606000 608000 596000 598000 600000 602000 604000 606000 608000 V. Mallet Urban air quality simulation May 2013 14 / 67

Before and after assimilation (preliminary result) 2434000 135 2434000 135 120 120 2432000 2432000 105 105 90 90 2430000 2430000 75 75 2428000 2428000 60 60 45 45 2426000 2426000 30 30 15 15 2424000 2424000 0 0 596000 598000 600000 602000 604000 606000 608000 596000 598000 600000 602000 604000 606000 608000 V. Mallet Urban air quality simulation May 2013 15 / 67

Before and after assimilation (preliminary result) 2434000 2434000 140 140 2432000 2432000 120 120 100 100 2430000 2430000 80 80 2428000 2428000 60 60 2426000 2426000 40 40 20 20 2424000 2424000 0 0 596000 598000 600000 602000 604000 606000 608000 596000 598000 600000 602000 604000 606000 608000 V. Mallet Urban air quality simulation May 2013 16 / 67

Before and after assimilation (preliminary result) 2434000 2434000 180 180 160 160 2432000 2432000 140 140 2430000 120 2430000 120 100 100 2428000 2428000 80 80 60 60 2426000 2426000 40 40 20 20 2424000 2424000 0 0 596000 598000 600000 602000 604000 606000 608000 596000 598000 600000 602000 604000 606000 608000 V. Mallet Urban air quality simulation May 2013 17 / 67

Before and after assimilation (preliminary result) 2434000 2434000 160 160 140 140 2432000 2432000 120 120 2430000 2430000 100 100 80 80 2428000 2428000 60 60 2426000 2426000 40 40 20 20 2424000 2424000 0 0 596000 598000 600000 602000 604000 606000 608000 596000 598000 600000 602000 604000 606000 608000 V. Mallet Urban air quality simulation May 2013 18 / 67

Before and after assimilation (preliminary result) 2434000 160 2434000 160 140 140 2432000 2432000 120 120 2430000 2430000 100 100 80 80 2428000 2428000 60 60 2426000 2426000 40 40 20 20 2424000 2424000 0 0 596000 598000 600000 602000 604000 606000 608000 596000 598000 600000 602000 604000 606000 608000 V. Mallet Urban air quality simulation May 2013 19 / 67

Before and after assimilation (preliminary result) 2434000 160 2434000 160 140 140 2432000 2432000 120 120 2430000 2430000 100 100 80 80 2428000 2428000 60 60 2426000 2426000 40 40 20 20 2424000 2424000 0 0 596000 598000 600000 602000 604000 606000 608000 596000 598000 600000 602000 604000 606000 608000 V. Mallet Urban air quality simulation May 2013 20 / 67

Before and after assimilation (preliminary result) 2434000 2434000 140 140 2432000 2432000 120 120 2430000 100 2430000 100 80 80 2428000 2428000 60 60 2426000 2426000 40 40 20 20 2424000 2424000 0 0 596000 598000 600000 602000 604000 606000 608000 596000 598000 600000 602000 604000 606000 608000 V. Mallet Urban air quality simulation May 2013 21 / 67

Before and after assimilation (preliminary result) 2434000 2434000 135 135 2432000 2432000 120 120 105 105 2430000 2430000 90 90 75 75 2428000 2428000 60 60 45 45 2426000 2426000 30 30 15 15 2424000 2424000 0 0 596000 598000 600000 602000 604000 606000 608000 596000 598000 600000 602000 604000 606000 608000 V. Mallet Urban air quality simulation May 2013 22 / 67

Before and after assimilation (preliminary result) 2434000 2434000 140 140 2432000 2432000 120 120 2430000 2430000 100 100 80 80 2428000 2428000 60 60 2426000 2426000 40 40 20 20 2424000 2424000 0 0 596000 598000 600000 602000 604000 606000 608000 596000 598000 600000 602000 604000 606000 608000 V. Mallet Urban air quality simulation May 2013 23 / 67