William J. Capehart

A new look at the simplified method for remote sensing of daily evapotranspiration

Abstract A modification of the so-called “Simplified Method” used to obtain the integrated daily evapotranspiration from surface radiant temperature over variable vegetation cover is proposed. Mathematically, the simplified equation takes the form Rn 24 − LE 24 =(T o13 − T a13 ) n , where Rn24 and LE24 are, respectively, the integrated net radiation and evapotranspiration over a 24-h period and T013 and Ta13 are, respectively, the surface radiant and the 50-m air temperatures at 1300 local time. B and n are pseudo constants given as functions of the normalized difference vegetation index (NDVI), expressed as a scaled index N*. Both N* and Ta13 are obtained with the aid of remotely determined measurements, which are viewed on scatterplots of T013 versus NDVI.

DECOUPLING OF SURFACE AND NEAR-SURFACE SOIL WATER CONTENT : A REMOTE SENSING PERSPECTIVE

Inconsistencies between remotely sensed (thermal infrared), in situ, and modeled values of soil water content are examined. First, an important hydraulic parameter in a soil water profile model is varied by one standard deviation to simulate a reasonable degree of spatial variability within a given soil texture class. This results in a large range of drying rates at the soil surface and the formation of a sharp vertical soil water gradient at the surface. The formation of this gradient is dependent upon the soil properties. Thermal infrared remote sensing, which detects soil moisture at the soil surface, is then discussed in this context. Because of the “decoupling” of the soil water profile, we conclude that soil moisture derived from surface radiant temperatures is probably not useful in knowing the column-average soil water content but may provide some insight into the spatial variations in soil texture and hydraulic properties at the surface.

Initialization of Soil-Water Content in Regional-Scale Atmospheric Prediction Models

The purpose of this study is to demonstrate the feasibility of determining the soil-water content fields required as initial conditions for land surface components within atmospheric prediction models. This is done using a model of the hydrologic balance and conventional meteorological observations, land cover, and soils information. A discussion is presented of the subgrid-scale effects, the integration time, and the choice of vegetation type on the soil-water content patterns. Finally, comparisons are made between two The Pennsylvania State University/National Center for Atmospheric Research mesoscale model simulations, one using climatological fields and the other one using the soil-moisture fields produced by this new method.

Using a Soil Hydrology Model to Obtain Regionally Averaged Soil Moisture Values

Abstract The Soil Hydrology Model (SHM) was modified, and daily simulations of soil volumetric water content were made at 38 Oklahoma Mesonet sites for July 1997. These model results were compared with soil moisture observations made at the mesonet sites at depths of 5, 25, 60, and 75 cm. This work is believed to be the first time that a hydrological model has been evaluated with in situ soil moisture measurements over such an extensive area spanning several climate zones. Comparisons of time series between the observed and modeled domain-averaged volumetric water content at 5 cm revealed similar phase and amplitude changes, a coefficient of determination (R2) of 0.64, and small mean bias and root-mean-square errors (MBE and rmse) of 0.03 and 0.09, respectively. At 25, 60, and 75 cm, the model performance was slightly worse, with R2 values between 0.27 and 0.40, MBE between −0.01 and 0.02, and rmse between 0.11 and 0.13. The model response to changes in soil water at these levels was sluggish, possibly be...

The Pacific quasi‐decadal oscillation (QDO): An important precursor toward anticipating major flood events in the Missouri River Basin?

Measurements taken by the Gravity Recovery and Climate Experiment satellites indicated a continued water storage increase over the Missouri River Basin (MRB) prior to the 2011 flood event. An analysis of the major hydrologic variables in the MRB, i.e., those of soil moisture, streamflow, groundwater storage, and precipitation, show a marked variability at the 10–15 year time scale coincident with the water storage increase. A climate diagnostic analysis was conducted to determine what climate forcing conditions preceded the long-term changes in these variables. It was found that precipitation over the MRB undergoes a profound modulation during the transition points of the Pacific quasi-decadal oscillation and associated teleconnections. The results infer a prominent teleconnection forcing in driving the wet/dry spells in the MRB, and this connection implies persistence of dry conditions for the next 2 to 3 years.

C-Lock-A Method to Maximize Carbon Sequestration Value to Agro-forestry Producers and Purchasers

Publisher Summary This chapter provides a detailed description of C-Lock, a patent-pending Web-based carbon sequestration accounting and marketing tool. C-Lock, developed by Dr. Zimmerman and his colleagues at the South Dakota School of Mines and Technology, aggregates carbon emission reduction offsets from individual land parcels and prepares certified units for sale in the marketplace. The C-Lock process allows agricultural producers to quantify the impact of specific land-use management practices for specific agricultural land parcels on the sequestration of carbon in soil and vegetation. It also aggregates carbon emission reduction offsets for individual land parcels into units that can be efficiently marketed. This comprehensive tool has been designed to serve as an interface to link agricultural producers, carbon sequestration science and policy, and those who wish to purchase carbon emission reduction offsets. The C-Lock process incorporates three levels of data validation. Level I validation compares producer input data with lookup data for regional land use. Level II verification consists of a random audit to compare satellite data for a land parcel with reported data. Level III verification consists of submitting all data to a third party to operate the model and confirm the results. The C-Lock system must account for the variability in carbon accounting that results from a wide range of sources.

Coupled Model simulation of snowfall events over the Black Hills

Abstract Numerical simulations of two snowfall events over the Black Hills of South Dakota are made to demonstrate the use and potential of a coupled atmospheric and land surface model. The Coupled Atmospheric–Hydrologic Model System was used to simulate a moderate topographic snowfall event of 10–11 April 1999 and a blizzard event of 18–23 April 2000. These two cases were chosen to provide a contrast of snowfall amounts, locations, and storm dynamics. The model configuration utilized a nested grid with an outer grid of 16-km spacing driven by numerical forecast model data and an inner grid of 4 km centered over the Black Hills region. Simulations for the first case were made with the atmospheric model, the Advanced Regional Prediction System (ARPS) alone, and with ARPS coupled with the National Center for Atmospheric Research Land Surface Model (LSM). Results indicated that the main features of the precipitation pattern were captured by ARPS alone. However, precipitation amounts were greatly overpredicte...