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Title: The influence of water table depth and the free atmospheric state on convective rainfall predisposition

Here, we report a mechanistic model for the soil-plant system is coupled to a conventional slab representation of the atmospheric boundary layer (ABL) to explore the role of groundwater table (WT) variations and free atmospheric (FA) states on convective rainfall predisposition (CRP) at a Loblolly pine plantation site situated in the lower coastal plain of North Carolina. Predisposition is quantified using the crossing between modeled lifting condensation level (LCL) and convectively grown ABL depth. The LCL-ABL depth crossing is necessary for air saturation but not sufficient for cloud formation and subsequent convective rainfall occurrence. However, such crossing forms the main template for which all subsequent dynamical processes regulating the formation (or suppression) of convective rainfall operate on. If the feedback between surface fluxes and FA conditions is neglected, a reduction in latent heat flux associated with reduced WT levels is shown to enhance the ABL-LCL crossing probability. When the soil-plant system is fully coupled with ABL dynamics thereby allowing feedback with ABL temperature and humidity, FA states remain the leading control on CRP. However, vegetation water stress plays a role in controlling ABL-LCL crossing when the humidity supply by the FA is within an intermediate range of values. When FAmore » humidity supply is low, cloud formation is suppressed independent of surface latent heat flux. Similarly, when FA moisture supply is high, cloud formation can occur independent of surface latent heat flux. In an intermediate regime of FA moisture supply, the surface latent heat flux controlled by soil water availability can supplement (or suppress) the necessary water vapor leading to reduced LCL and subsequent ABL-LCL crossing. Lastly, it is shown that this intermediate state corresponds to FA values around the mode in observed humidity lapse rates γ w (between -2.5 × 10 -6 and -1.5 × 10 -6 kg kg -1m -1), suggesting that vegetation water uptake may be controlling CRP at the study site.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [1]
  1. Duke Univ., Durham, NC (United States). Nicholas School of the Environment and Pratt School of Engineering
  2. Duke Univ., Durham, NC (United States). Nicholas School of the Environment and Pratt School of Engineering; University of Padova (Italy). Department of Mathematics
  3. North Carolina State Univ., Raleigh, NC (United States). Department of Forestry and Environmental Resources; University of Bordeaux, Gradignan (France). Bordeaux Sciences Agro UMR 1391 INRA-ISPA
  4. University of Padova (Italy). Department of Mathematics
  5. Duke Univ., Durham, NC (United States). Nicholas School of the Environment and Pratt School of Engineering; University of Padova (Italy). Department of Civil, Architectural and Environmental Engineering
Publication Date:
Grant/Contract Number:
SC0006967; SC-0006700-ER65189; IS-4374-11C
Type:
Accepted Manuscript
Journal Name:
Water Resources Research
Additional Journal Information:
Journal Volume: 51; Journal Issue: 4; Journal ID: ISSN 0043-1397
Publisher:
American Geophysical Union (AGU)
Research Org:
Duke Univ., Durham, NC (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 54 ENVIRONMENTAL SCIENCES; groundwater; rainfall; convection; optimization theory; transpiration; CATHY
OSTI Identifier:
1454929
Alternate Identifier(s):
OSTI ID: 1402297