My interests in land surface processes lie on the study of the natural and
anthropogenic impacts on the hydrological cycle, particularly the study of
processes and their scales in relation to the availability of water. Water per se promotes interdisciplinary and
inclusive research, as it links the different components of the Earth System.
Water in the soil regulates the exchanges of water between the land surface and
the atmosphere, while in the atmosphere it regulates radiation and precipitates
on the earth's surface affecting the energy and water balances. Exchanges of
water and CO2 between the leaves and the atmosphere represent
physiological processes at the plant-scale but through coupled cycles of water
and carbon represent the variability of available water and carbon
sequestration (or release) at the ecosystem-to-global scales. Further, water is
a key socio-economical element, linked to human activities such as agriculture
and energy production, inherent to the sustainability of human activities and
North American Monsoon System:Land Surface-Atmosphere Interactions and the Water Cycle
In the Southwestern North America water distribution
and variability are influenced by the North American Monsoon (NAM), which
provides 50 to 70% of the annual precipitation during the summer. During the field
experiments Soil Moisture Experiment and the North American Monson Experiment
in 2004 (SMEX04 and NAME, respectively) I was particularly interested in how
the NAM sustains the region's arid to semiarid ecosystems and human activities
within them. Some of these interests were translated into the following
Sustainability of Agriculture and Water Resources
is the main
source of water for agriculture in the Yaqui River Basin (YRB). Its variability
is determined by the monsoon precipitation (and to a lesser extent winter
precipitation), and the impact of human activities. These aspects can also
impact the sustainability of agriculture and ecosystems, and, in consequence,
the region's socio-economical health. I proposed to evaluate how the response
of a hydrological system (YRB) to land use changes could be modulated by
climate variability. I used a macro-scale land surface hydrology model
(Variable Infiltration Capacity model, or VIC), in which the explicit
representation of land use allowed me to simulate streamflow
under natural and land-use-modified conditions. The main finding was that,
at the basin-scale, hydrological regimes were more sensitive to climate
variability than changes in land use (Munoz-Arriola
et al 2009).
Figure 1. a) Changes in land use as described by Hansen et al (2000) and used in VIC (11 vegetation types plus bare soil) for three sub-basins of the Yaqui River Basin (NW-Mexico). b) Spatial distribution of the dominant land-use (top) and the fraction of crop for a 1993 baseline, and 10% and 25% increments in crop surfaces.
Figure 2. Spatial distribution of VIC simulated Baseflow, Soil Moisture (in layer 3), Evapotranspiration, and Runoff for the 1993 baseline and after an increment of 50% in crop surfaces during the monsoon (mn) and nonmonsoon(nm) seasons.
Interdependencies between Land Surface Hydrology and Ecosystems Phenology in the NAM area
As part of my field experience in 2004 I was
fascinated by the "greening" of the local ecosystems in response to the monsoon
onset or, in other words, the inherent reactivation of the local hydrological
cycle. While previous studies made punctual evaluations of the hydrological
response to greening, the intraseasonal and interannual variability of the land-atmosphere interactions
over broader areas and their impact on the ecosystems' phenology was still
unclear. On this basis, we used the land surface hydrology model (VIC) with a
dynamical representation of the changes in the ecosystem derived from remote
sensing (LAI-MODIS)(Tang et al 2012).
Figure 3. "Greening" and dormancy periods.
Figure 4. "Greening" in NW-Mexico.
Development and Evaluation of Datasets with Applications in Hydroclimatology
I worked on two
projects that assessed different measurements of evapotranspiration and
precipitation in Mexico. In the first project, we used remote sensing, land
surface hydrology modeling, atmospheric modeling (Regional Reanalysis), and
field observations to evaluate the uncertainty in the derived evapotraspiration. The main contribution was to quantify
the long-term global ET based on remote sensing (Shefield
et al 2011). The second project assessed the transfer of uncertainty in
precipitation measurements (discrepancy among datasets) to simulate streamflow over the NAM domain. Preliminary results show
that discrepancies among rain gauge, remote sensing, modeling, and merged
products could be doubled by the discrepancy in simulated streamflows.