Geography

Natural and anthropogenic sources of CO2 around the globe contribute to mid-tropospheric concentrations, yet it remains unknown how measurements of mid-tropospheric CO2 relate to regional ecosystem dynamics. NASA Atmospheric Infrared Sounder (AIRS) measurements of CO2 concentrations in the mid-troposphere from 2002 to 2010 were examined in relation to precipitation and vegetation phenology across the US Great Plains.

Abstract: A more thorough understanding of the multi-scale spatial structure of land surface heterogeneity will enhance understanding of the relationships and feedbacks between land surface conditions, mass and energy exchanges between the surface and the atmosphere, and regional meteorological and climatological conditions.

A wavelet multi-resolution analysis was conducted using vegetation and radiometric temperature data derived from the Advanced Very High Resolution Radiometer (AVHRR) data from the Southern Great Plains 1997 (SGP97) Hydrology Experiment. The wavelet coefficients were used to investigate whether the Normalized Difference Vegetation Index (NDVI) and radiometric temperature fields exhibit self-similar scaling behaviour.

Abstract: As a system is moved away from a state of thermodynamic equilibrium, spatial and temporal heterogeneity is induced. A possible methodology to assess these impacts is to examine the thermodynamic entropy budget and assess the role of entropy production and transfer between the surface and the atmosphere.

Abstract. Monarch butterflies (Danaus plexippus) have a unique yearly life cycle, in which successive generations breed and move northward from the southern USA in spring to the northern US and southern Canada by late summer; they overwinter in extremely restricted areas in central Mexico and along the California coast. Mexican overwintering populations have experienced significant mortality events recently, which have been hypothesized as increasing in frequency owing to climate change.

Abstract: The role of land-atmosphere interactions under heterogeneous surface conditions is investigated in order to identify mechanisms responsible for altering surface heat and moisture fluxes. Twelve coupled land surface–large eddy simulation scenarios with four different length scales of surface variability under three different horizontal wind speeds are used in the analysis. The base case uses Landsat ETM imagery over the Cloud Land Surface Interaction Campaign (CLASIC) field site for 3 June 2007.

The assimilation or interpretation of hydrological or related fields (eg, vegetation) between models such as MM5 and those derived from remote sensing is complicated by the fact that the scales of the data are generally not commensurate--this often necessitates some form of aggregation. However, methods for aggregation need to consider the inherent non-linearities that affect the surface energy balance and so, the water balance at the land surface.

Abstract The effect of emissivity on the estimation of evaporation is investigated using an emissivity estimate based upon the fractional vegetation coverage. An atmospherically corrected image that does not incorporate emissivity is used for comparison purposes. The evaporation is derived as a function of a scaling of the surface radiant temperature field. The mean difference in evaporation between the emissivity corrected and uncorrected temperature images is 3 W irr.

Abstract Future climates are forecast to include greater precipitation variability and more frequent heat waves, but the degree to which the timing of climate variability impacts ecosystems is uncertain. In a temperate, humid grassland, we examined the seasonal impacts of climate variability on 27 y of grass productivity. Drought and high-intensity precipitation reduced grass productivity only during a 110-d period, whereas high temperatures reduced productivity only during 25 d in July.

Hydrological processes in the humid tropics differ from other regions in having greater energy inputs and faster rates of change, including human-induced change. Human influences on population growth, land use and climate change will profoundly influence tropical hydrology, yet understanding of key hydrological interactions is limited. We propose that efforts to collect tropical data should explicitly emphasize characterizing moisture and energy fluxes from below the ground surface into the atmosphere.

Soil moisture affects land-atmosphere interactions at multiple temporal and spatial scales; including boundary layer convection and energy balance partitioning. A study of soil moisture control on carbon and water cycling was conducted in a brome grass field experiencing woody-encroachment at the Nelson Environmental Research Area (NESA) near Lawrence, KS.

Due to complex microclimatic interactions, a biannual phenological cycle, and the generally small scale of coffee plantations, there have been few applications of satellite observations to examine coffee yield. Using 2001-2006 data, surface precipitation and air temperature are related to MODIS surface temperature and fractional vegetation. Using lagged correlation analysis and deviations from the annual cycle, yield is related to accumulated deviations in fractional vegetation.

Despite their fame, Ebola and Marburg viruses (family Filoviridae) remain mysterious. Filovirus outbreaks are restricted to tropical Africa, but their likely geographic extent has been outlined only recently, and their natural reservoir host (s) remains unidentified. If environmental conditions associated with outbreaks in space and time can be identified precisely, much could be learned about the ecology, evolution and transmission of these viruses.

The Large Aperture Scintillometer (LAS) has emerged as one of the best tools for quantifying areal averaged fluxes over heterogeneous land surfaces. This is particularly useful as a validation of surface energy fluxes derived from satellite sources. We examine how changes in surface source area contributing to the scintillometer and eddy covariance measurements relate to satellite derived estimates of sensible heat flux.

Abstract The issue of incorporating surface emissivity into a thermal atmospheric correction of thermal remotely sensed data is addressed. The Normalized Difference Vegetation Index (NDVI) is derived using atmospherically corrected surface reflectance values, which is subsequently used to estimate the percent of vegetation cover. Surface emissivity is approxihated by a linear interpolation between a minimum bare soil emissivity and a maximum vegetation value of emissivity.

Abstract The University of Oklahoma's Advanced Regional Prediction System (ARPS) was used to examine the impacts of varying mean soil moisture and model resolution on the magnitude and frequency of precipitation events in the US Central Plains and to determine whether modeled soil moisture and precipitation fields exhibit scale invariance using the statistical moments.

Abstract: Fluxes across the land surface directly influence predictions of ecological processes, atmospheric dynamics, and terrestrial hydrology. However, many simplifications are made in numerical models when considering terrestrial hydrology from the viewpoint of the atmosphere and vice versa. While this may be a necessity in the current generation of operational models used for forecasting, it can create obstacles to the advancement of process understanding.

On global and local scales, a number of factors change the climate. Some of these factors (such as the power of the sun) change very slowly over billions of years. Other factors (such as the number of sunspots) affect solar output over about an eleven year cycle. The total power from the sun clearly influences the energy received by the planet, and thus the climate.