2002 Annual

Monday, 14 January 2002: 2:43 PM
Hydrological Land Surface Response in a Tropical and a Midlatitudinal Regime
Dev dutta S. Niyogi, North Carolina State University, Raleigh, NC; and Y. Xue and S. Raman
Poster PDF (49.4 kB)
A statistical - dynamical study was performed on the role of land surface interactions in the midlatitudes and the semi-arid tropics. For this, observations from two field experiments (called FIFE and HAPEX - Sahel) representative of the midlatitudes and the semi-arid tropical conditions, and simulated results from a land surface model: 'Simplified SiB', were statistically analyzed for direct and interaction effects. The study objectives were to (i) test the hypothesis that there are significant differences in the land surface processes in the semi - arid tropical and mid-latitudinal regimes, and (ii) identify the nature of the differences in the evapotranspiration exchanges for the two biogeographical domains. Results suggest, there are similarities in the direct responses while the interactions or the indirect feedback pathways could be quite different. The arid tropical regimes are dominated through vegetative pathways (via variables such leaf area index, stomatal resistance, and vegetal cover), while the mid-latitudes show soil wetness (moisture) related feedback. Additionally, for the mid-latitudinal case, the vegetation and the soil surface acted in unison, leading to more interactive exchanges between the vegetation and the soil surface. The water stressed semi - arid tropical surface on the other hand, showed response either directly between vegetation and the atmosphere or the soil and the atmosphere with very little interaction between the vegetation and the soil variables. Thus, the semi - arid tropics would require explicit bare ground and vegetation fluxes consideration, while the effective (combined vegetation and soil fluxes) surface representation used in various models may be more valid for the midlatitudinal case. This also implied that, with higher resource (water) availability the surface invested more in the surrounding environment. On the other hand, with poor resource availability (such as water stress in the tropical site), the surface components retain individual resources without sharing.

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