Abstract
Abstract. Two new remotely sensed leaf area index (LAI) and surface soil moisture (SSM) satellite-derived products are compared with two sets of simulations of the ORganizing Carbon and Hydrology In Dynamic EcosystEms (ORCHIDEE) and Interactions between Soil, Biosphere and Atmosphere, CO2-reactive (ISBA-A-gs) land surface models. We analyse the interannual variability over the period 1991–2008. The leaf onset and the length of the vegetation growing period (LGP) are derived from both the satellite-derived LAI and modelled LAI. The LGP values produced by the photosynthesis-driven phenology model of ISBA-A-gs are closer to the satellite-derived LAI and LGP than those produced by ORCHIDEE. In the latter, the phenology is based on a growing degree day model for leaf onset, and on both climatic conditions and leaf life span for senescence. Further, the interannual variability of LAI is better captured by ISBA-A-gs than by ORCHIDEE. In order to investigate how recent droughts affected vegetation over the Euro-Mediterranean area, a case study addressing the summer 2003 drought is presented. It shows a relatively good agreement of the modelled LAI anomalies with the observations, but the two models underestimate plant regrowth in the autumn. A better representation of the root-zone soil moisture profile could improve the simulations of both models. The satellite-derived SSM is compared with SSM simulations of ISBA-A-gs only, as ORCHIDEE has no explicit representation of SSM. Overall, the ISBA-A-gs simulations of SSM agree well with the satellite-derived SSM and are used to detect regions where the satellite-derived product could be improved. Finally, a correspondence is found between the interannual variability of detrended SSM and LAI. The predictability of LAI is less pronounced using remote sensing observations than using simulated variables. However, consistent results are found in July for the croplands of the Ukraine and southern Russia.
Highlights
The Global Climate Observing System (GCOS) has defined a list of atmospheric, oceanic and terrestrial essential climate variables (ECVs) which can be monitored at a global scale from satellites
While an attempt was made in a previous work (Szczypta et al, 2012) to simulate the hydrological droughts over the Euro-Mediterranean area, this study focuses on the monitoring of agricultural droughts and complements the joint evaluation of the ORCHIDEE and ISBAA-gs land surface model performed by Lafont et al (2012) over France using satellite-derived leaf area index (LAI)
ORCHIDEE and ISBA-Ags were used to assess the seasonal and interannual vegetation phenology derived from GEOV1
Summary
The Global Climate Observing System (GCOS) has defined a list of atmospheric, oceanic and terrestrial essential climate variables (ECVs) which can be monitored at a global scale from satellites. Terrestrial ECV products consisting of long time series are needed to evaluate the impact of climate change on environment and human activities. They have high impact on the requirements of the Intergovernmental Panel on Climate Change (IPCC). Soil moisture is a key ECV in hydrological and agricultural processes. It constrains plant transpiration and photosynthesis (Seneviratne et al, 2010) and is one of the limiting factors of vegetation development and growth (Champagne et al, 2012), especially in water-limited regions such as the Mediterranean zone, from spring to autumn. Land Surface Models (LSMs) are generally able to Published by Copernicus Publications on behalf of the European Geosciences Union
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