Presentation on theme: "The relationship between variation of terrestrial carbon cycle and ENSO Haifeng Qian 05/10/2006 Department of Atmospheric & Oceanic Science University."— Presentation transcript:
The relationship between variation of terrestrial carbon cycle and ENSO Haifeng Qian 05/10/2006 Department of Atmospheric & Oceanic Science University of Maryland Advisor: Prof. Ning Zeng
Outline 1.Background of Carbon Cycle 2. What we concern about 3. Model and Data 4.Results and discussion 5.Conclusion 6.Future plan
Carbon Dioxide in the atmosphere has been steadily rising since regular measurements began in 1958. The graph above shows both the long- term trend and the seasonal variation. http://earthobservatory.nasa.gov/Library/CarbonCycle/carbon_cycle3.html d(co2)/ dt
In any given year, tens of billions of tons of carbon move between the atmosphere, hydrosphere, and geosphere. Human activities add about 5.5 billion tons per year of carbon dioxide to the atmosphere. The illustration above shows total amounts of stored carbon in black, and annual carbon fluxes in purple. http://earthobservatory.nasa.gov/Library/CarbonCycle/carbon_cycle4.html
What we know and don ’ t make sure Bacastow (1976) firstly noticed the relation between CO2 and ENSO. Ocean-atmosphere flux variation is relative modest (Feely 1987;Winguth et al.1994; Francy et al. 1995; Bousquet et al. 2000; Roedenbeck et al. 2003; Zeng et al. 2005) Inverse modeling (Schimel et al. 2001; Gurney et al.,2002; Houghton 2003) long term sink and source & regional uncertainties. Potter et al. did statistical analysis of ENSO, NAO with modeled land_atmosphere flux. Hashimoto et al. (2004) proposed that NPP is related to ENSO. Cao et al. (2005) modeled year to year variation of NEP up to 2.5 PgC/yr, in which 1.4 PgC/yr can be attributed to ENSO cycle Generally, on regional scale, there are still many uncertainties in mechanisms of climate controlling terrestrial carbon cycle.
The questions we concern: What’s kind of terrestrial carbon cycle in response to ENSO cycle. What are their common features during ENSO cycle? How do the climate factors control carbon exchange between land and atmosphere?
Model and Data The VEgetation-Global Atmosphere-Soil Model (VEGAS) (Zeng 2003) and Land surface model(S_Land)( Zeng 2000) 2.5x2.5 Climate forcing: 1. Observed precipitation and Temperature (CRU, GISS, CMAP); 2. Seasonal climatology of radiation, humidity, wind speed; 3. Atmospheric co2 is kept constant at preinustrial level; Manua Loa atmospheric co2 (http://www.cmdl.noaa.gov) Roedenbeck inverse data (Max-Planck-Institut für Biogeochemie ) NDVI data ( http://islscp2.sesda.com/ )
Photosynthesis Autotrophic respiration Carbon allocation Turnover Heterotrophic respiration 4 Plant Functional Types: Broadleaf tree Needleleaf tree C3 Grass (cold) C4 Grass (warm) 3 Vegetation carbon pools: Leaf Root Wood 3 Soil carbon pools: Fast Intermediate Slow Atmospheric CO2 The VEgetation-Global Atmosphere-Soil Model (VEGAS)
Carbon Pool (GtC) and Flux Cleaf (15) Cwood (605) Croot (21) Fast soil ( 307) Med soil ( 610) Slow soil ( 931 ) GPP Ra Rh GPP = NPP + Ra NEP = NPP - Rh NEE = - NEP Total carbon pool Cvege CLeaf + Cwood + Croot Csoil Csfast + Csmed + Csslow Concept of VEGAS
5. Sensitivity simulations To elucidate and quantify the effects of climate factors in controlling the ecosystem, we design other 3 sensitivity simulations as follows: ControlPrecipitation and temperature forcing use observation data. (specified before) Prec-onlyPrecipitation forcing same as Control, while temperature uses seasonal climatology. Ts-onlyTemperature forcing same as Control, while Precipitation uses seasonal climatology. Swet-fixThe same as Ts-only except we fix soil wetness using its seasonal climatology Then, we will do ENSO composite for each sensitivity simulation and compare NEE, NPP, Rh anomalies.
Conclusion and discussion Interannual variability of atmospheric co2 growth rate at Mauna Loa is strongly correlated with ENSO signals with about 6 months lags VEGAS and inverse simulation generally agree well. Tropics plays the dominant role. In the extrotropics, the situation is more complicate due to weaker response to ENSO and regional cancellation. Global NEE anomaly tends to lag –SOI about 7-8 months, 6 months in the tropics. Inverse results show a little less lag. Lag correlation analysis are consistent with ENSO composite analysis. The tropical robust response to ENSO is caused by “conspiracy” of NPP and Rh anomalies induced by climate factors. The sensitivity simulations suggest in the tropics, temperature not only determine Rh, but also has the indirect effect on NPP through soil wetness. Temperature and precipitation effect are comparable in the tropics. NDVI shows general agreement with LAI in the extrotropics, while poor in tropics.
Future plan In last 2 decades, there is a greening in high latitudes, which implies long term of sink(?), but Rh has increased by warming in high latitude. In middle and high latitudes, is it possible that other climatic index has statistically correlated to the interannual and multidecadal variation of sink and source. Land use effect and radiation/co2 effect on the photosynthesis Inter-comparison with other model output.
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