Pedro Berliner

A mono-window algorithm for retrieving land surface temperature from Landsat TM data and its application to the Israel-Egypt border region

Remote sensing of land surface temperature (LST) from the thermal band data of Landsat Thematic Mapper (TM) still remains unused in comparison with the extensive studies of its visible and near-infrared (NIR) bands for various applications. The brightness temperature can be computed from the digital number (DN) of TM6 data using the equation provided by the National Aeronautics and Space Administration (NASA). However, a proper algorithm for retrieving LST from the only one thermal band of the sensor still remains unavailable due to many difficulties in the atmospheric correction. Based on thermal radiance transfer equation, an attempt has been made in the paper to develop a mono-window algorithm for retrieving LST from Landsat TM6 data. Three parameters are required for the algorithm: emissivity, transmittance and effective mean atmospheric temperature. Method about determination of atmospheric transmittance is given in the paper through the simulation of atmospheric conditions with LOWTRAN 7 program. A practicable approach of estimating effective mean atmospheric temperature from local meteorological observation is also proposed in the paper when the in situ atmospheric profile data is unavailable at the satellite pass, which is generally the case in the real world especially for the images in the past. Sensitivity analysis of the algorithm indicates that the possible error of ground emissivity, which is difficult to estimate, has relatively insignificant impact on the probable LST estimation error i T, which is sensible to the possible error of transmittance i 6 and mean atmospheric temperature i T a . Validation of the simulated data for various situations of seven typical atmospheres indicates that the algorithm is able to provide an accurate LST retrieval from TM6 data. The LST difference between the retrieved and the simulated ones is less than 0.4°C for most situations. Application of the algorithm to the sand dunes across the Israel-Egypt border results in a reasonable LST estimation of the region. Based on this LST estimation, spatial variation of the interesting thermal phenomenon has been analysed for comparison of LST difference across the border. The result shows that the Israeli side does have significantly higher surface temperature in spite of its denser vegetation cover than the Egyptian side where bare sand is prevalent.

Derivation of split window algorithm and its sensitivity analysis for retrieving land surface temperature from NOAA-advanced very high resolution radiometer data

Retrieval of land surface temperature (LST) from advanced very high resolution radiometer (AVHRR) data is an important methodology in remote sensing. Several split window algorithms have been proposed in last two decades. In this paper we intend to present a better algorithm with less parameters and high accuacry. The algorithm involves only two essential parameters (transmittance and emissivity). The principle and method for the linearization of Plancks radiance equation, the mathematical derivation process of the algorithm, and the method for determining the atmospheric transmittance are discussed with details. Sensitivity analysis of the algorithm has been performed for evaluation of probable LST estimation error due to the possible errors in transmittance and emissivity. Results from the analysis indicate that the proposed algorithm is able to provide an accurate estimation of LST from AVHRR data. Assuming an error of 0.05 in atmospheric transmittance estimate and 0.01 in ground emissivity for the two AVHRR thermal channels, the average LST error with the algorithm is 1.1°C. Two methods have been used to validate the proposed algortihm. Comparison has also been done with the existing 11 algorithms in literature. Results from validation and comparison using the standard atmospheric simulation for various situations and the ground truth data sets demonstrate the applicability of the algorithm. According to the root mean square (RMS) errors of the retrieved LSTs from the measured or assumed LSTs, the proposed algorithm is among the best three. Considering the insignificant RMS error difference among the three, the proposed algorithm is better than the other two because they require more parameters for LST retrieval. Validation with standard atmospheric simulation indicates that this algorithm can achieve the accuacry of 0.25°C in LST retrieval for the case without error in both transmittance and emissivity estimates. The accuary of this algorithm is 1.75°C for the ground truth data set without precise in situ atmospheric water vapor contents. The accuracy increases to 0.24°C for another ground truth data set with precise in situ atmospheric water vapor contents. The much higher accuracy for this data set confirms the appplicability of the proposed algorithm as an alternative for the accurate LST retrieval from AVHRR data.

The role of dew in the water and heat balance of bare loess soil in the Negev Desert: quantifying the actual dew deposition on the soil surface

During nighttime, latent heat fluxes to or from the soil surface are usually very small and the absolute amounts of dew deposition are accordingly very small. The detection of such small fluxes poses serious measurement difficulties. Various methods for measuring dew have been described in the literature and most of them rely on the use of artificial condensing plates with physical properties that are very different from those of soil surfaces. A system that detects the actual dew deposition on the soil surface under natural conditions would be advantageous and microlysimeters (MLs) appear to be the obvious answer. The objectives of this work were to test the adequacy of microlysimeters to estimate condensation amounts, and to compare these amounts with those measured by a Hiltner dew balance in order to validate the long term data collected using the latter. The research was carried out at the Wadi Mashash Experimental Farm in the Northern Negev, Israel, during two measurement periods. A micro-meteorological station was installed in the field next to a modified Hiltner balance. A microlysimeter with an undisturbed soil sample was placed nearby. During the first period, the depth of the microlysimeter was 15 cm while at the second period it was 55 cm. The results show that for measuring dew, the minimum depth of a microlysimeter should exceed the depth at which the diurnal temperature is constant, which for a dry loess soil in the Negev Desert is 50 cm.

Diurnal Water Content Changes in the Bare Soil of a Coastal Desert

Abstract The deposition of dew is a common meteorological phenomenon that has been recognized as an important ecosystem element, especially in arid areas. There is some evidence that indicates that there is an increase in the water content of the topsoil during nights in which no dew deposition was observed. The purpose of this study is to describe the daily pattern of changes in water content in the upper soil layers and to identify the mechanism by which water is added to the soil (deposition or direct absorption). Moreover, the gains in soil water content during the night are compared to the dew amounts recorded by the Hiltner balance, and the losses and gains of water in terms of easily measurable environmental parameters are parameterized. Nine 24-h field campaigns took place during the dry season of 2002. During each campaign, the 100-mm topsoil was sampled hourly, and water content at 10-mm increments was obtained. Micrometeorological measurements included incoming and reflected shortwave radiation...

A model for numerical simulating of evaporation from bare saline soil

A mathematical model for the computation of evaporation from bare saline soils is presented. Moisture flow and heat transport equations in the partially saturated zone of the soil are coupled at the soil surface with a lower atmosphere boundary layer model. The transport model considers multicomponent salt migration. The flow equation accounts for osmotic flux due to the presence of ion species in the soil solution. Nonlinear one-dimensional equations were solved using fully implicit finite difference schemes. The soil part of the model was tested using experimental data of water and solute redistribution under temperature gradients in sealed soil columns. In order to demonstrate the effect of soil salinity on the evaporation, the problem of water infiltration into soil with initially low water content and its subsequent evaporation was considered. Results show a significant effect of osmotic pressure gradients on predicted evaporation.

Evaluation of Urban Surface Energy Fluxes Using an Open-Air Scale Model

Abstract The thermal behavior of an urban surface is crucial to understand, but it is difficult to predict using conventional measurement or modeling approaches. In this study, an integrated method is proposed for evaluating urban energy exchanges with an open-air scale model of a building–street canyon surface array. The technique, which potentially combines the flexibility of modeling with the reliability of empirical observation under natural turbulence and radiative loading, is tested in hot, arid summer conditions to gauge its ability for reproducing surface–atmosphere energy fluxes that are representative of diurnal patterns in actual urban settings. After identifying the inertial sublayer, which is created above the scaled roughness array at a point near its downwind edge, roughness parameters utilized in the calculation of turbulent sensible heat flux are determined for two different array configurations of varying frontal area density and compared with existing data from field studies and morphom...

Numerical solution of a complete surface energy balance model for simulation of heat fluxes and surface temperature under bare soil environment

Surface energy balance model is an essential approach for heat flux and evaporation estimation in applied meteorology and hydrology. Due to the complexity of soil-air interface system, the model has been simplified for different purposes in many researches. A complete model with full description of its complex factor relationships and its numerical solution has not been yet implemented in practical use. This paper presents a complete surface energy balance model with its inner relations cited from different researches. The model couples soil temperature change simultaneously with soil moisture movement, which makes the solution of the model uneasy. A detailed methodology of numerical approximation to the complete model is presented in the study for practical use. Soil heat and latent heat fluxes in the model are determined according to both soil temperature change and soil moisture movement, which are described as two differential equations. Crank-Nicolson implicit method is used to expand the differential equations into two sets of simultaneous linear equations, which are then solved by applying Gausss elimination method. Latent heat flux is determined at the balance when evaporation from the surface is equal to the soil water loss. And surface temperature is estimated as the heat fluxes of the surface reaching the status of balance. The iterative computation of Newton-Raphson method is used to approximate latent heat flux and surface temperature from the balances. Based on this complexity of the models relationships, a detailed computation procedure of the model is proposed. The methodology has been validated through application to south Israeli desert for heat flux and surface temperature estimation. A good matching of the simulated soil temperature to the measured one proves the validity of the model and method used for its numerical solution.

Calibration of minirhizotron readings against root length density data obtained from soil cores

The minirhiozotron (MR) root observation method was studied versus root length density (RLD) obtained from soil cores. Two plant species, acacia (Acacia saligna) and wheat (Triticum aestivum L.) were grown in a 1-m3 container on Silt Loam (Typic Torrifluvent) and on fine dune sand (Typic Torripsamment), respectively. Roots of both plants were measured periodically by the two methods. The MR observation tubes (MROT) were inserted, either vertically or at 45°. The correlation between the number of roots obtained by the MR and RLD was significant for the entire profile. However, an appreciable error in root estimation by the MR root observation method at the upper 10-cm soil might occur. No significant difference was obtained from MROT oriented vertically or at 45°. The differences between the correlation coefficients of the two methods were not significant, for both plants and soils, indicating that this correlation expresses the geometry of the two measurement systems, not affected by plant or soil types. We concluded that the MR method may be used as an in situ, non-destructive root measuring method with reasonable confidence.

Runoff agroforestry in arid lands

Abstract Biomass production in arid zones may be increased without irrigation by using runoff farming techniques. The salient feature of this technique is that large amounts of water are collected a few times per year and percolate deep into the soil. The combined cultivation of shallow rooting annuals and deep rooting perennials (agroforestry) was proposed as a method by which fodder and firewood could be simultaneously produced and stored water used efficiently. As a first step to test the feasibility of this proposal, Acacia salicina and Eucalyptus occidentalis were grown at two densities (625 and 1250 trees ha −1 ) in runoff catchment basins in the Northern Negev Desert of Israel (average rainfall: 115 mm a −1 ). Biomass, soil moisture content and some plant physiological parameters were periodically recorded. Total above-ground dry matter after three years was 15 and 19 t ha −1 for A. salicina and 25 and 28 t ha −1 for E. occidentalis at low and high density, respectively. Soil water balance studies during the growing season indicate that for the conditions under which this trial was carried out, tree roots do not explore the upper soil layers efficiently and that relatively high leaf water potential can be maintained by taking up water from deeper layers. These results suggest that water from surface layers could be used by annual crops without affecting production of the perennial crop.

Evaluating the performance of the MODIS Leaf Area Index (LAI) product over a Mediterranean dryland planted forest

The launch of the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Terra and Aqua satellites improved the ability to evaluate several surface biophysical parameters, including Leaf Area Index (LAI), which is provided as an operational MODIS product, available at 1-km spatial resolution and at 8-day intervals. However, for heterogeneous and sparse planted forests that are common to the semi-arid eastern Mediterranean region, the data at low spatial resolution may be significantly biased by the contribution of different background elements to the total surface reflectance received by the sensor and cannot therefore correctly reflect the real forest phenology. In the current paper the performance of the MODIS LAI product was examined over a dryland Mediterranean forest in southern Israel. The study found a significant discrepancy between ground-based and MODIS LAI datasets. In general, MODIS LAI values were c.51% of the ground-based LAI measurements. In addition ground based LAI peaked in the summer due to the natural growth cycle of the pine trees, while MODIS values peaked in the winter. The MODIS seasonal course could be explained by the development of annuals and crypto- and micro-phytes in the understorey and the clearing areas during the mid winter months that are included in the MODIS LAI product but not in the ground based measurements. However, for that period MODIS estimates should have exceeded ground-based estimates while in fact they were still lower. The relationship between MOD12C1 Land Cover Type 3 and MOD15A2 products is discussed.