Update on doctoral dissertation research: lake models application and comparison in Lake Taihu

Transcription

1 Yale-NUIST Center on Atospheric Environent Update on doctoral dissertation research: lake odels application and coparison in Lake Taihu ZHANG Zhen

2 Outline Background Model principle Motivation Experiental design Model odification Preliinary results Future work 2

3 Background Models for wind ixing and stratification of lakes have included integral energy odels (Mironov 2005, 2008, 2010), turbulent diffusion based odels (Hostetler 1990, 1993, 1994; Subin 2012) and turbulent closure odels (Goudsit 2002; Peeters 2002; JOHNK 2005). Surface energy and radiation balance odule is critical to surface flux calculation and lake body energy distribution. Especially surface flux calculation is relied on robust siulation of surface teperature. Vertical turbulent ixing is an iportant role in lakes, Production of TKE by wind shear (forced convection) and an unstable density stratification is produced in the water colun (natural convection) are two ain drivers. 3

4 Model principle Sun Air Water Soil 4

5 CLM4-LISSS odel k-ε odel Sun Bulk odel 2 Conservation of Energy T s 1 Epirical odel 2 Air T s 2 Surface Flux 1 Paraeterization 3 Heat Transfer Equation 3 3 TKE Equation Water Teperature diffusivity TKE 3 Soil 5

6 Motivation CLM4-LISSS odel does integrated preparation on conservation of surface energy and surface flux calculation, Dose this odel perfor better in this respect? k-ε odel owns heat transfer equation and TKE equation, how about the turbulent diffusivity siulation results copared with CLM4-LISSS odel? Find out the distribution of surface eddy diffusivity (K e ) in different season and different weather condition. The diurnal variation of K e? which eteorological factor affect variation of K e? 6

7 Experiental design CNR4 HMP155A 8.5 EC150+CSAT3A Input data: Ta, q, P, WS, DLR, Rn Verified data: Tw, H, LE Data: acquired fro The Taihu Eddy Flux Network, BFG site fro 2012 to 2015 T109 20c 50c 100c 150c 7 sedient

8 Model odification on eddy diffusivity k- ε odel: K z = C k Z E CLM4-LISSS odel: K z = d k + k e ; d =0.02 K e = K e0 f(r i ) f R i = (1 + 37R 2 i ) 1 Neutral condition: 0 Depth (d) K e0 = ku z u = u 0 exp( k z) k = 6.6U sinφ D D d d 8

9 Model odification on Paraeter adjustent k- ε odel: Table 2 k-ε odel paraeter values Paraeter Description Noinal Value (units) K wc light attenuation coefficient for water 1 1 K specific light attenuation coefficient for acrophytes gdw 1 d water depth 2 C k ixing length coefficient 0.1(Herb [2005]) C D drag coefficient 1.0 (Finnigan [2000]) K h hypolinetic diffusivity d 1 (Herb [2005]) C w wind correction coefficient 1.0 nz nuber of discrete depth increents 50 t tie increent 30in onth Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Bioass (gdw/ 3 ) Plant height () CLM4-LISSS odel: Paraeter setting is roughly sae with Deng s Paper 9

10 Model odification on freezing teperature 10

11 CLM4-LISSS odel: About spin up 11

12 k- ε odel: 12

13 Surface Teperature Perforance 13

14 14

15 Sensible Heat Surface Flux Perforance n represents the total nuber of half-hourly observations 15

16 Latent Heat 16

17 Turbulent diffusivity Perforance 2012 CLM4-LISSS odel k- ε odel The dotted line represents winter, spring, suer and autun

18 2013 CLM4-LISSS odel k- ε odel The dotted line represents winter, spring, suer and autun

19 2014 CLM4-LISSS odel k- ε odel The dotted line represents winter, spring, suer and autun

20 2015 CLM4-LISSS odel k- ε odel The dotted line represents winter, spring, suer and autun

21 Case analysis: DOY Year 2012 Water teperature profile perforance (CLM4-LISSS odel, k-ε odel, observation ) 21

22 22

23 CLM-LISSS odel Variation rate (T) -30% -20% -10% 10% 20% 30% K e 3.9% 2.8% 1.5% -1.6% -2.8% -4% Variation rate (DR) -30% -20% -10% 10% 20% 30% K e 0.13% 0.04% 0.01% -0.02% -0.07% -0.12% Variation rate (U) -30% -20% -10% 10% 20% 30% K e -33% -22% -11% 11% 21% 32% k-ε odel Variation rate (T) -30% -20% -10% 10% 20% 30% K e 6% 3.9% 1.9% -1.9% -3.2% -4.2% Variation rate (DR) -30% -20% -10% 10% 20% 30% K e 2.21% 1.42% 0.67% -0.75% -1.43% -1.91% Variation rate (U) -30% -20% -10% 10% 20% 30% K e -38% -25% -13% 13% 26% 40% 23

24 Suary Both CLM4-LISSS odel and k-ε odel have been applied in Lake Taihu, CLM4-LISSS odel have better perforance in siulation of surface teperature and surface energy flux. Two odels have siilar siulation trend on turbulent diffusivity. But there exists agnitude difference of vertical turbulent diffusivity and difference expend with depth. Wind variation sees to be leading factor of turbulent kinetic energy distribution. 24

25 Future work It is still doubtful that the result of spring and winter s predicted water teperature, turbulent kinetic energy and the agnitude of vertical turbulent diffusivity. Ai to quantify the contribution of turbulent kinetic energy distribution. Try to establish lake surface flux dataset based on BCC_AGCM s future scenarios cliate data and verify it. 25

26 Upcoing 26

27 Thank you 27 Photographer: Cao zhengda