Possible self‐organizing dynamics for land‐atmosphere interaction

Abstract

Abstract. Land-atmosphere interactions play a central role in the mesoscale evolution of hydrologic fields like rainfall and soil moisture. A water balance model, capturing the essence of such interaction and driven by mesoscale and synoptic processes, was found to self-organize into states showing global scaling features both in space and in time, which we also observed experimentally. Although driving synoptic mechanisms are crucial, a key role was found for the local dynamical rules through which the system self-organizes. The results suggest the possibility of a dynamic origin for the space-time scaling in precipitation from purely local dynamics and may have implications for modeling efforts which involve land-atmosphere interaction. IntroductionThe depth and spatial distribution of precipitation are strongly affected by the landscape heterogeneities which produce significant mesoscale circulations conducive to rainfall Mesoscale circulations resulting from temperature gradients not only transport moisture from one region to the other but also produce an enhancement of precipitation from the local moisture over the drier zone through the magnification of the vertical transport of surface heat and moisture fluxes [Seth and Giorgi, 1996]. The temporal scale of the process is of the order of 1 day because the dynamics results from differential daytime heating. In extended domains, very complex global dynamics may develop from these local phenomena. Thus after rainfall occurs over a previously dry area, new spatial gradients of soil moisture will likely be created and the system will evolve in unforeseen ways. This is further complicated by the evolution of external weather systems that interact with the internal dynamics and which effectively drive the space-time evolution of soil and atmosphere.The general existence and importance of mesoscale circulations induced by the soil moisture gradient needs further studies especially on the field. However, based on the studies mentioned above, we consider it likely that such dynamics takes place. Under this framework, soil moisture is just an overall representative variable for all the landscape heterogeneities (i.e., vegetation, actual evapotranspiration, topography, etc.) responsible for this process.The detailed specification of the dynamics of landatmosphere interactions has recently received considerable attention because of their critical implications on mesoscale and general circulation and on hydrologic balances [Chen and Avissat, 1994; Avissat and Liu, 1996; Seth and Giorgi, 1996]. The state-of-the-art mesoscale atmospheric models used by Avissat and Liu [1996] on simple spatial geometries clearly show that land surface wetness heterogeneity affects the precipitation regime through the development of mesoscale circulations. Other authors have questioned the role of mesoscale fluxes arising from heterogeneous land conditions. Thus Wang et al. [1996], using a three-dimensional stochastic linear model, concluded that synoptic wind strongly inhibits the develop...

Groundwater convergence as a possible mechanism for multi‐year persistence in rainfall

“…In this study we coined the hypothesis that groundwater convergence may have an effect on rainfall persistence and illustrated this hypothesis with a simple model applied to a specific case [i.e., Entekhabi et al , 1992]. We realise that in our simple model many processes are not taken into account, such as seasonality, the connection between continental soil moisture status and Monsoon strength [ Zhu et al , 2005], atmospheric boundary layer dynamics [ Ek and Holtslag , 2004] and the effect of land surface heterogeneity in relation to meso‐scale processes [ Pielke et al , 1998; Rodriguez‐Iturbe et al , 1998]. However, we believe that at the larger temporal and spatial scales at which this model claims to operate, the average effect of increased soil moisture content and evaporation on precipitation will be positive, and that groundwater redistribution can positively influence average soil moisture status.…”

Organization of complexity in water limited ecohydrology

“…Ecohydrological landscapes also exhibit selforganizing tendencies in the horizontal distribution of landscape components Rodriguez-Iturbe et al, 1998;Phillips, 1999;Milne et al, 2002). Across horizontal dimensions much organization can be found in the spatial structure of stream networks (Rodriguez-Iturbe et al, 1994;Stolum, 1996;Phillips, 2001) and soil-moisture patterns (Rodriguez-Iturbe et al, 2006;Ivanov et al, 2010).…”

Self-Organized Critical Behavior of Acid Deposition

“…In the sandpile model, apparently, the critical state refers to the constant angle of repose, at which its slope fluctuates as sand grains are added. The so-called critical state differs according to the subjects studied (Turcotte et al, 2002;Peters et al, 2002;D'Odorico and Rodríguez-Iturbe, 2000;Hergarten and Neugebauer, 1998;Malamud et al, 1998;Ricotta et al, 2001;Rodríguez-Iturbe et al, 1998b;Held, 1990;Stanley et al, 2000). We argue that the critical state of atmospheric acid deposition refers to the normal acidity (pH = 5.0 or 5.6) of water in atmosphere, or the environmental capacity.…”

“…Extensive data analyses in many different regions have detected the existence of signatures of SOC, in the time series and spatial fields of rainfall and of other hydrologic variables (Lovejoy, 1982;Lovejoy and Schertzer, 1985;Over and Gupta, 1996;Peters-Lidard et al, 2001;Rybczynski et al, 2001;Peters et al, 2002;Svensson et al, 1996;Olsson et al, 1993;Rodríguez-Iturbe et al, 1998a, 1998bAegerter, 2003;Zhu and Liu, 2003). Peters et al (2002) proposed that rain is analogous to many other relaxational processes in nature such as earthquakes and avalanches, suggesting the existence of SOC in rainfall.…”

“…SOC was intended to explain the abundance of fractals in nature and has been suggested as a possible explanation for the 1/ f noise and the frequency-size distributions seen in many complex natural phenomena, such as earthquakes, avalanches and various ecosystem properties (Bak and Tang, 1989;Bak et al, 1987;Turcotte et al, 2002). Numerous evidences of different physical characters support that open, dissipative, non-linear systems with many degrees of freedom tend to display critical self-organization with a fractal growth in their global space-time evolution (Rodríguez-Iturbe et al, 1998a, 1998bD'Odorico and Rodríguez-Iturbe, 2000). A set of particular values of the interaction between the units composing the system generates correlations extending throughout the entire system and leads to power-law distributions .…”