A Parameterization for Land Surface Physical Characteristics of Burning Areas for Weather and Climate Models. Yihua Wu & Michael Ek

Transcription

1 A Parameterization for Land Surface Physical Characteristics of Burning Areas for Weather and Climate Models Yihua Wu & Michael Ek 8/19/ WWOSC Montreal, Canada

2 Wildfire Effects Wildfires can affect weather/climate systems in three ways: (1) atmospheric circulations, (2) aerosols and clouds, and (3) land physical properties which have impacts on energy budget, and PBL structure. We will focus on (3) the effects on land physical properties. 2

3 Short Term Effects on Land Surface Direct effects Greenness fraction reduction Roughness length reduction Surface albedo reduction Surface temperature increase Top layer soil temperature increase Top layer soil moisture reduction Gas and particle emissions Indirect effects Energy/Radiation Budget Water balance Wind Organic Matter 3

4 Simple Parameterization Surface physical property changes due to burning effects in NMM model are updated based on satellite derived burning products as the following: Albedo is reduced by half Greenfrac = (1-FireFrac/100)* Greenfrac Roughness (Zom) is reduced by half SfcTemp = sfctemp+15 Tsoil1 = Tsoil1+15 Msois1 = 0.25*Msoil1 References: Kenji Yoshikawa et al., 2003; Thomas Torika Bagamsah, 2005; J. Beringer et al., 2003; Daniel G. Neary et al.,

5 Burning Area Products Two fire burning area products are available from NOAA/NESDIS/STAR team : 1 km resolution data twice a day, covers the area between 20 N and 70 N 12 km resolution data four times a day, covers the area from the equator to the north pole. Lambert conformal projection GRIB2 Format with unit in percent 5

6 Numerical Experiments Four runs were conducted with the NMMB model for the Wallon Fire in Arizona in 2011 The effects of the fire induced changes of GVF, albedo and Zom in the parameterization on the energy budget were investigated in these series runs. More tests on the other three changes in the parameterization will be conducted soon. CTL: Control Run RUN1: Reductions of Green Fraction RUN2: Run1 plus reduction albedo by half RUN3: Run2 Plus reduction of Zom by half 6

7 fire timeline.php 7

8 The Wallon Fire Burning Area Satellite derived burning area Ground Observed burning area 8

9 GVF reduction slightly increased upward short wave radiation; Albedo reduction clearly reduced upward short wave radiation; Reduction of roughness did not have any impact on upward short wave radiation; 9

10 GVF reduction slightly increased upward long wave radiation; Albedo reduction clearly increased upward long wave radiation; Reduction of roughness had negative impact on upward long wave radiation; 10

11 GVF reduction clearly reduced latent heat fluxes; Albedo reduction had small impact on latent heat fluxes; Reduction of roughness had little impact on latent heat fluxes; 11

12 GVF reduction slightly increased sensible heat fluxes; Albedo reduction clearly increased sensible heat fluxes; The effect of reduction of roughness on sensible heat fluxes is positive. 12

13 GVF reduction increased ground heat fluxes; Albedo reduction also increased ground heat fluxes; Reduction of roughness had slight negative effect on ground heat fluxes; 13

14 GVF reduction slightly increased 2 meter air temperature; Albedo reduction clearly increased 2 meter air temperature; Reduction of roughness slightly decreased 2 meter air temperature. 14

15 GVF reduction slightly increased the temperature; Albedo reduction clearly increased the temperature; Reduction of roughness decreased the temperature; 15

16 Summary The reduction of Vegetation green fraction leads to the reduction of evapotranspiration/latent heat fluxes which result in higher soil temperature. The reduction of the albedo leads to the reduction of the upward short wave radiation. Both above lead to warmer temperatures of the and first soil layer, which results in an increase of upward long wave radiation, sensible heat flux and downward ground heat fluxes. More case studies and full tests on the parameterization will be conducted. Cycling real time land physical characteristics in model runs will be conducted 16

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