Toby Carlson

• Pennsylvania State University

A simple version of the triangle model is proposed, that of a right triangle, which allows one to estimate from remote thermal/optical measurements the evapotranspiration fraction and surface soil moisture availability without reference to external variables even in the absence of a full range of vegetation cover and soil dryness. To date however,...

This essay distills the thoughts of the author who has spent over 30 years developing land surface models, including those for use in remote sensing. The latter includes models whose function is to serve both as a mathematical interface between remotely sensed optical/thermal measurements and land surface evapotranspiration and soil water content a...

Simsphere, a soil/vegetation/atmosphere/transfer (SVAT) model developed at Penn State, can be downloaded from the web for use by students and researchers. In existence for several decades, Simsphere has figured in both the classroom and in research at several universities. As such, Simsphere has been supported by a knowledgeable group of academic u...

20 Imagery acquired from Unmanned Aerial Vehicles (UAVs) is used nowadays more 21 often than ever before in a wide range of disciplines and research fields. In this work 22 we explored the use of UAV data in deriving very high spatial resolution maps of 23 evaporative fraction (EF) and surface soil moisture (SSM) by applying the so-called 24 "simpl...

There is great interest in wind-borne mineral dust because of the role that dust plays in climate by modulating solar radiation and cloud properties. Today, much research focuses on North Africa because it is Earth’s largest and most persistently active dust source. Moreover, this region is expected to be greatly impacted by climate change, which w...

The present study investigates the ability of SimSphere, a soil vegetation atmosphere transfer model, to predict key parameters in characterising land surface interactions. In particular, the model's performance in predicting Net Radiation (Rnet), Latent Heat (LE) and Sensible Heat (H) was examined. For this purpose, concurrent in-situ measurements...

2020): Exploring the use of Unmanned Aerial Vehicles (UAVs) with the simplified 'triangle' technique for soil water content and evaporative fraction retrievals in a Mediterranean setting, International Journal of Remote Sensing, ABSTRACT Information acquired from Unmanned Aerial Vehicles (UAVs) is frequently used nowadays in a variety of discipline...

The well-known triangle method in optical/thermal remote sensing, its construction, uncertainties, and the significance of its products are first discussed. These topics are then followed by an outline of how the method can be implemented operationally for practical use, including a suggestion for constructing a dynamic crop moisture index.

Earth Observation (EO) makes it possible to obtain information on key parameters characterizing interactions among Earth’s system components, such as evaporative fraction (EF) and surface soil moisture (SSM). Notably, techniques utilizing EO data of land surface temperature (Ts) and vegetation index (VI) have shown promise in this regard. The prese...

In this study a new method for predicting soybean yield over large spatial scales, overcoming the difficulties of scalability, is proposed. The method is based on the so-called “simplified triangle” remote sensing technique which is coupled with a crop prediction model of Doorenbos and Kassam 1979 (DK) and the climatological water balance model of...

We assess the validity of the surface moisture availability parameter (Mo) derived from satellite-based optical/thermal measurements using the simplified triangle method. First, we show that Mo values obtained from the simplified triangle method agree closely with those generated from a soil/vegetation/atmosphere/transfer (SVAT) model for scenes ov...

Earth Observation (EO) provides a promising approach towards deriving accurate spatiotemporal estimates of key parameters characterizing land surface interactions, such as latent (LE) and sensible (H) heat fluxes as well as soil moisture content. This paper proposes a very simple method to implement, yet reliable to calculate evapotranspiration fra...

announcement to remote sensing community to submit papers to a special issue of Remote Sensing.

Papers accepted for special issue of Remote Sensing on subject of practical applications from optical/thermal remote sensing from satellite or aircraft.

Earth Observation (EO) provides a promising approach towards deriving accurate spatiotemporal estimates of key parameters characterizing land surface interactions, such as latent (LE) and sensible (H) heat fluxes as well as soil moisture content. This paper proposes a very simple method to implement, yet reliable to calculate evapotranspiration fra...

SimSphere is a land biosphere model that provides a mathematical representation of vertical ‘views’ of the physical mechanisms controlling Earth's energy and mass transfers in the soil/vegetation/atmosphere continuum. Herein, we present recent advancements introduced to SimSphere code, aiming at making its use more integrated to the automation of p...

Schematic Skew-T soundings can be used to estimate the depth of elevated mixed layers and their origins thousands of kilometers downstream from their source regions. Focus is on the elevated mixed layer from the Sahara, the Saharan Air Layer (SAL), and its relationship to aerosol optical depth. Aerosol optical depth (AOD) measurements and SAL depth...

With current predicted climate change, there is an increased requirement to gain knowledge on the terrestrial biosphere, for numerous agricultural, hydrological and meteorological applications. To this end, Soil Vegetation Atmospheric Transfer (SVAT) models are quickly becoming the preferred scientific tool to monitor, at fine temporal and spatial...

Sensitivity analysis (SA) consists of an integral and important validatory check of a computer simulation model before it is used to perform any kind of analysis. In the present work, we present the results from a SA performed on the SimSphere Soil Vegetation Atmosphere Transfer (SVAT) model utilising a cutting edge and robust Global Sensitivity An...

Being able to accurately estimate parameters characterising land surface interactions is currently a key scientific priority due to their central role in the Earth's global energy and water cycle. To this end, some approaches have been based on utilising the synergies between land surface models and Earth observation (EO) data to retrieve relevant...

This chapter discusses the contribution of field spectroradiometry and hyperspectral remote sensing in extracting information related to land cover mapping. It provides an overview on the use of field spectroradiometry in examining the spectral discrimination between different land cover targets. An overview on the main statistical approaches emplo...

Being able to accurately estimate parameters characterising land surface interactions is of key scientific priority today due to their central role in the Earth's global energy and water cycle. To this end, some approaches have been based on utilising the synergies between land surface models and Earth Observation (EO) data to retrieve relevant par...

Use of Earth Observation (EO) data combined with land surface process models has played an imperative role in extending our abilities to studying land surface interaction processes and enhancing our understanding on how different components of the Earth system interplay. These techniques aim at improving estimates of key parameters characterising l...

Use of simulation process models has played a key role in extending our abilities to study Earth system processes and enhancing our understanding on how different components of it interplay. Use of such models combined with Earth Observation (EO) data provides a promising direction towards deriving accurately spatiotemporal estimates of key paramet...

Earth Observation (EO) has played an imperative role in extending our abilities for obtaining information on the spatio-temporal distribution of surface soil moisture (SSM). A wide range of techniques have been proposed for this purpose, utilising spectral information acquired from remote sensing instruments operating in different regions of the el...

An assessment of stream health within the Chesapeake Bay Basin can be made using the Stream Health and Runoff Potential (SHARP) model, which is based solely on the relationship between land cover and stream constituents: Total phosphorus (TP), total nitrogen (TN), and total suspended sediment (TSS). While not intended to compete with more complex m...

Comparison of model simulations versus corresponding validated in situ observations forms an integral and important validatory check of a computer simulation model before the developed code is used in performing any kind of analysis or other operation. The present study presents the results pertaining to the accuracy assessment of a 1D SVAT model n...

Accurate information on spatially explicit distributed estimates of key land-atmosphere fluxes and related land surface parameters is of key importance in a range of disciplines including hydrology, meteorology, agriculture and ecology. Estimation of those parameters from remote sensing frequently employs the integration of such data with mathemati...

The technique of relative-flow analysis on isentropic surfaces is used to examine the large- (“synoptic”-) scale situations associated with selected severe local storms near southern England and over the mid-western U.S.A. (including the Horsham, Wokingham, and Geary storms whose behaviour has been described in several previous publications). The s...

Sensitivity analysis consists of an integral and important validatory check of a computer simulation model before the code is used in performing any kind of analysis operation. The present paper demonstrates the use of a relatively new method and tool for conducting global sensitivity analysis (GSA) for environmental models, providing simultaneousl...

Imagery from remote sensing systems, often combined with ancillary ground information, is able to provide repetitive, synoptic views of key parameters characterizing land surface interactions, including surface energy fl uxes and surface soil moisture. Differing methodologies using a wide range of remote sensing data have been developed for this pu...

Estimation of land-atmosphere fluxes and related land surface parameters is of key importance in many disciplines including hydrology, meteorology and agriculture. Remote sensing alone or often combined with land surface simulation process models, such as Soil Vegetation Atmosphere Transfer (SVAT) models, has generally shown a promising avenue in t...

Soil Vegetation Atmosphere Transfer (SVAT) models consist of deterministic mathematical representations of the physical processes involved between the land surface and the atmosphere and of their interactions, at time-steps acceptable for the study of land surface processes. The present article provides a comprehensive and systematic review of one...

Sensitivity analysis consist an integral validatory check of an all-inclusive validation of any multi-level code computer simulation model before the latter is used in performing any kind of analysis of operation, particularly so if a model is going to be used on an operational basis. A software platform/tool called GEM SA developed for performing...

Sensitivity analysis consist an integral validatory check of an all-inclusive validation of any multi-level code computer simulation model before the latter is used in performing any kind of analysis of operation, particularly so if a model is going to be used on an operational basis. A software platform/tool called GEM SA developed for performing...

A new approach to simulating the urban environment with a mesocale model has been developed to identify efficient strategies for mitigating increases in surface air temperatures associated with the urban heat island (UHI). A key step in this process is to define a "global" roughness for the cityscape and to use this roughness to diagnose 10-m tempe...

Money is trumping creativity in academic science. This statement was previously given substance in an article I published, along with a companion paper by Mark Roulston in the Bulletin of the American Meteorological Society ( Carlson, 2006a; >Roulston, 2006) and in a subsequent address I gave to the Heads and Chairs meeting in Boulder, Colorado (Ca...

Many studies can be found in the literature pertaining to the effects of urbanization on surface runoff in small watersheds and the hydrologic response of undeveloped watersheds. However, an extensive literature review yielded few published studies that illustrate differing hydrologic responses from multiple source areas within a watershed. The con...

The success rate in proposal submissions among university faculty has decreased considerably over the years. This unhappy situation is the result of several factors: national funding has decreased relative to inflation and research costs; more PhD's are on the market who are writing grants; universities continue to grow as they did during the Cold...

Use of satellite remote sensing data for the estimation of surface evapotranspiration (ET) is emerging as a promising approach with a range of application potentials. Unlike traditional point-based approaches, some of these satellite-based approaches have been shown to have bounded error. This is a significant advantage of such ET estimation approa...

This study examined the relationship between land cover and three solute (chloride, total organic carbon (TOC), and lead) concentrations during winter rainstorms in 10 subbasins of Spring Creek, Pennsylvania, USA at two spatial scales. Despite similar percent land cover at both scales, correlations between water quality and land cover were stronger...

Accurate estimation of surface energy fluxes is essential for various hydrological, meteorological, agricultural, and ecological applications. Over the years, a wide variety of instrument systems and estimation methodologies have been developed to measure and estimate surface fluxes. Comparisons of various scale field experimental data and differen...

As part of an ongoing class project at the Pennsylvania State University, measurements of phosphorus (P) and nitrate-N (N) concentrations were determined from samples in three small Central Pennsylvania gauged streams and in surface runoff over urban areas during late winter rainstorms from 2000 to 2003. Results suggest that a flushing effect for P...

This paper demonstrates how satellite image data [e.g., from Landsat 5 Thematic Mapper (TM)], in conjunction with an urban growth model and simple runoff calculations, can be used to estimate future surface runoff and, by implication, water quality within a watershed. To illustrate the method, predictions of land use change and surface runoff are s...

Urban development is shown to induce predictable changes in satellite-based measures of radiant surface temperature and evapotranspiration fraction—as long as certain features of the development are known. Specifically, the vegetation changes that accompany the development and the initial climatic state of the land parcel must be noted. Techniques...

The Hydrologic Model System (HMS), a physically based distributed model, was used to simulate the soil moisture variation during a storm event in the Upper West Branch, a subbasin of the Susquehanna River Basin. The model was calibrated by comparing the simulated temporal daily variation in soil moisture with field data. Data from the Mahantango Wa...

A correlation between housing lot size and impervious surface area (ISA), previously published by the Soil Conservation Service (SCS), is re‐examined using satellite (Landsat 5 Thematic Mapper) image data and a new method for determining ISA from remote measurements. ISA is determined for each pixel using two criteria: an image classification and t...

Increasing levels of atmospheric CO2 concentration [CO2] has caused a debate in the scientific community over how vegetation responds to this increase — specifically in the stomatal resistance increase (SRincrease) and the transpiration decrease (TRdecrease). This paper presents results in changes of stomatal resistance and transpiration from two c...

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...

Vegetation cover, surface moisture availability (wetness) and radiant surface temperature constitute microclimatic variables derivable from multi-spectral satellite imagery. In addition, fraction impervious surface cover and urban-induced surface runoff (RO) are obtainable from such imagery when it is combined with a conventional image classificati...

The potential for using satellite data in regional planning is suggested by analyses of land cover change for a rapidly urbanizing county in Pennsylvania. Land classification maps can be generated from satellite imagery with relative ease on an annual basis, enabling communities to track the loss of their forested and agricultural lands, and the gr...

The direct effect of elevated carbon dioxide on evapotranspiration over a growing season was investigated by scaling up single-leaf gas exchange measurements on soybean and corn plants grown and measured at three carbon dioxide concentrations. Stomatal conductance decreased markedly with increasing carbon dioxide in these species under most conditi...

Using AVHRR imagery, the effects of urbanization on surface microclimate during a 7-year period in San José, Costa Rica and its surroundings are expressed as changes in fractional vegetation cover, scaled surface temperature, surface wetness, and surface evapotranspiration. Scatterplots of fractional vegetation cover versus scaled surface temperatu...

ABSTRACT Ozone (O3) inhibits plant gas exchange and productivity. Vapour phase (gs) and liquid or hydraulic phase (K) conductances to water flux are often correlated as both change with environmental parameters. Exposure of cotton plants to tropospheric O3 reduces gs through reversible short-term mechanisms and by irreversible long-term disruption...

The regional-scale climatic impact of urbanization is examined using two land cover parameters, fractional vegetation cover (Fr) and surface moisture availability (Mo). The parameters are hypothesized to decrease as surface radiant temperature (To) increases, forced by vegetation removal and the introduction of non-transpiring, reduced evaporating...

We use a simple radiative transfer model with vegetation, soil, and atmospheric components to illustrate how the normalized difference vegetation index (NDVI), leaf area index (LAI), and fractional vegetation cover are dependent. In particular, we suggest that LAI and fractional vegetation cover may not be independent quantitites, at least when the...

An inversion procedure is presented for estimating surface soil water content (as surface moisture availability, Mo), fractional vegetation cover ( Fr), and the instantaneous surface energyuxes, using remote multispectral measure- ments made from an aircraft. The remotely derived values of theseuxes and the soil water content are compared with ® el...

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...

Alfalfa and orchard grass crops were grown at ambient and twice ambient carbon dioxide concentrations in field plots for several years in Beltsville, MD, using semi-open chambers. Canopy conductances throughout many days were determined from water vapour exchange measurements, and indicated significant reductions in canopy conductance to water vapo...

The spatial distribution of ozone uptake by cotton in the field has been determined by micrometeorological, microenvironmental and physiological measurements, and characterized with a model. Ozone damage to intact cotton plants has been determined under controlled exposure conditions. As reported previously, exposure to ozone causes a reduction in...

The diurnal course of photosynthesis and transpiration of different plants can exhibit a dissymmetric behaviour between the morning and the afternoon, a photosynthetic midday depression and a transpiration ‘plateau’. A field experiment conducted in a meditenanean climate allows us to identify these features for a soybean crop undergoing water stres...

Simulations with a soil/vegetation/atmosphere (SVAT) model for normal midlatitude summertime conditions were made for corn and soybeans in order to assess the effect of doubling CO2 concentration on transpiration. A second purpose of this short communication is to emphasize that feedback processes present in the plant canopy but absent in the labor...

Using a new technique referred to as the triangle method, surface soil water content and fractional vegetation cover were derived from surface radiant temperature measurements and normalized difference vegetation index (NDVI). Application of the technique is made with reference to NS001 multispectral scanner measurements made by a C-130 aircraft ov...

This article reviews the major topics discussed at the Thermal Remote Sensing Workshop held at La Londe les Maures, France in 1993 and concludes with a list of new items and concepts suggested during the meeting

The object of this research is to use indirect measurements, notably thermal infrared, to describe urbanization and deforestation with parameters that can be used to assess, as well as predict, the effects of land use changes on local microclimate. More specifically, we use a new approach for the treatment of remotely sensed data; this is referred...

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 , where Rn24 and LE24 are, respectively, the integrated net radiation and evapotranspiration over a 24-h period...

This study outlines a method for the estimation of regional patterns of surface moisture availability (M(sub 0)) and fractional vegetation (Fr) in the presence of spatially variable vegetation cover. The method requires relating variations in satellite-derived (NOAA, Advanced Very High Resolution Radiometer (AVHRR)) surface radiant temperature to a...

Describes a new method for estimating the spatial variation in surface soil water content and the surface energy fluxes. Satisfactory surface energy fluxes can be calculated with the aid of constraints imposed by a visual inspection of the measurements in the form of scatterplots (the “triangle method”). The authors briefly address inherent inabili...

This project addresses the need to improve the surface hydrology component in mesoscale atmospheric prediction models and specifically the temperature and humidity forecasts. One way we did this was to initialize the mesoscale model with continuously updated and reasonable values of soil moisture content. To accomplish this task two approaches were...

This paper presents a simple water budget model for determining the vertical profile of soil water content. The model is driven by conventional meteorological and land use data. The modeled solutions of soil water content become independent of their starting conditions after a few weeks to a few months into a simulation depending on rainfall and ev...

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 i...

A unique relationship between the surface soil moisture availability and the radiant temperature does not exist in the presence of variable vegetation cover. To overcome this ambiguity, the authors present a method which couples a Soil‐Vegetation‐Atmosphere‐Transfer (SVAT) model to satellite derived measurements of surface radiant temperature and N...

This volume provides a descriptive and mathematical account of the underlying processes and behaviour of mid-latitude weather patterns. The mathematics necessary to construct simple models of atmospheric processes are outlined. These are used to model processes such as vorticity, quasi-geostrophic forcing, and quasi-geostrophic energetics. Models a...

Two different bulk stomatal resistance models are compared with measurements of evapotranspiration. We show that a transpiration plateau is more realistically simulated by relating stomatal resistance to leaf water potential, rather than directly to the soil water potential and the leaf vapor pressure difference.

Diagnostic and modeling studies have been performed to improve our understanding of, and skill at forecasting, mesoscale weather systems and circulations, In particular, we have investigated: The effects of entrainment and detrainment on convective cloud heating and moistening profiles, The effects of mesoscale water bodies and ocean currents on th...

Measurements of evapotranspiration and radiometric surface temperature, supplemented by model simulations, illustrate the effect of transient water stress on the evapotranspiration and radiometric surface temperatures over a corn (Zea Mays L) canopy. Transient stress is manifested by a plateau in the evapotranspiration and a warmer radiometric temp...

Better methods for remote sensing of surface evapotranspiration, soil moisture, and fractional vegetation cover were developed. The objectives were to: (1) further develop a model of water movement through the soil/plant/atmosphere system; (2) use this model, in conjunction with measurements of infrared surface temperature and vegetation fraction;...

Remote sensing of substrate moisture and the surface energy balance using surface infrared temperature measurements is much more difficult and complex over vegetation than over bare soil. Unlike those of bare soil, the radiometric temperature of a vegetation canopy is usually close to the air temperature just above the canopy. Leaf temperature does...

A stomatal resistance model is proposed that is specifically designed for use within atmospheric boundary layer models. Stomatal resistance is expressed as a product of linear discontinuous functions of leaf water potential and solar flux; vapor pressure deficit is included indirectly by allowing for a gradient of leaf water potential between the s...

The purpose of this paper is to present a method for using remote measurements to estimate vegetation fraction, surface energy fluxes and the root zone and soil surface water contents for partial vegetation canopies. The primary tools are a boundary layer model with vegetation and substrate components and two image products: the variation of surfac...

Satellite imagery from the Heat Capacity Mapping Mission (HCMM) was analysed for Montreal, Quebec. From this imagery, regional metropolitan maps of day/night surface temperatures are produced for an area of approximately 10 ⁴ km ² . With the implementation of a surface energy budget model coupled with the satellite data, maps of non‐radiative trans...

A method for calculating daily evapotranspiration from the daily surface energy budget using remotely sensed surface temperature and several meteorological variables is presented. Values of the coefficients are determined from simulations with a one-dimensional boundary layer model with vegetation cover. Model constants are obtained for vegetation...

A Conceptual model of the Saharan Air Layer (SAL) and easterly wave disturbance is presented in light of diagnostic analyses of dust outbreaks.Numerical simulations of the SAL were carried out to 5 days for two case studies using the Penn State/NCAR limited-area tropical model. The region of simulations encompasses North Africa and the eastern trop...