Including Tropical Croplands in a Terrestrial Biosphere Model

1
Including Tropical Croplands in a Terrestrial
Biosphere Model

• A.Berg (1), N. de Noblet (2), B. Sultan (1)
• (1) Laboratoire dOcéanographie et du Climat
  Expérimentation et Approches Numériques (IPSL),
• (2) Laboratoire des Sciences du Climat et de
  lEnvironnement (IPSL)

2
The climate / crop system

• Studying the relationships between climate and
  agriculture rises two different issues
• Agriculture is the most climate-dependant human
  activity. Impacts are particularly severe in
  developing countries of tropical regions with low
  levels of crop management, and exposed to high
  variability in climate (monsoon systems, el Niño)
• It is crucial to increase our
  understanding of how large-scale crop production
  responds to seasonal and year-to-year large-scale
  climate variability.
• Agriculture on a large-scale plays a role in the
  climate system. Croplands account for 10 to 15
  of the global land surface differing from
  natural vegetation regarding phenology (sowing,
  cycle duration) and growth condition (tillage,
  fertilization,...), they modify surface carbon,
  water and energy budgets, thus causing feedbacks
  to climate.
• It is necessary to account for
  croplands when modeling climate-biosphere
  interactions in the climate system.

3

• A relevant framework to consistently address
  this twofold issue is the extension of existing
  Dynamic Global Vegetation Models (DGVMs) to
  include an accurate representation of croplands
  (e.g, Betts et al. 2005, Osborne al., 2007)
• In ORCHIDEE work initiated by S.Gervois,
  continued by P.Smith, to develop ORCHIDEE-STICS,
  a coupling between ORCHIDEE and the crop model
  STICS (Inra). However
• more or less limited to temperate crops (for
  now)
• numerical consistency, and cost, of this
  approach ?

Need to rapidly include a simpler and more direct
formulation of croplands in ORCHIDEE
particularly for tropical crops.
4

• What has already been done
• West Africa well illustrates the interactions
  between crops and climate - in the frame of the
  AMMA project - we derive parameterizations for
  tropical crops from the crop model SARRAH (CIRAD-
  Dingkuhn et al., 2003), which is already well
  calibrated and validated over the West African
  region for tropical cereal (eg, millet and
  sorghum) and we include them in ORCHIDEE.

5

• What needs to be done
• Further validate (develop ?) this  ORCH-mil 
  version over W.A. (paper to be submitted ?)
• Some pb millet hydrology landcover
  map-dependant ! Separate bqsbs ? Second sowing ?
• Outlooks application to seasonal prediction
  analysis of the effects of ALCC on the WA
  Monsoon.
• In a more generic approach of croplands (rice,
  maize, sugarcane), define how many Crop
  functionnal Types  (CFT) are needed -
  particularly if vegetation types parameters in
  ORCHIDEE can be spatialized ? Can  Orch-mil be
  degraded into a more or less generic crop scheme
  (vegetative growth / grain filling ) ?
• ex temperate/tropical maize.
• Then analysis of production surface budgets
  feedbacks at global scale.
• Collaboration N.Vuichard (biofuels), N.Viovy,
  post-doc.