Determination of transpiration in irrigated grapevines: comparison of the heat-pulse technique with gravimetric and micrometeorological methods

The use of a heat-pulse technique to monitor sap flow from which transpiration can be deduced was evaluated in ungrafted grapevines (Vitis vinifera L., cv. Sultana) under glasshouse and field conditions. There was a significant degree of agreement between daily transpiration deduced from heat-pulse velocity (T _hp) and that determined directly by gravimetry in the glasshouse and by calibration using the Penman-Monteith equation in the field. Comparison throughout the growing season of T _hp to transpiration calculated with the full Penman-Monteith equation produced a high coefficient of determination (r ²=0.69). A similar comparison of T _hp with transpiration calculated with only the aerodynamic component of the Penman-Monteith equation produced a non-linear relationship, due to the equation over-estimating transpiration relative to T _hp at high vapour pressure deficits (i.e. above 2.5 kPa). Values for total seasonal transpiration measured with heat-pulse sensors or calculated with either the full Penman-Monteith equation or with only the modified aerodynamic component of the equation were within 10% of each other. Transpiration (T _hp) in grapevines with an adequate supply of soil water was shown to be coupled to ambient air conditions. Received: 20 July 1998     

An improved Lewis-Milne equation for the advance phase of border irrigation

Summary The Lewis-Milne (LM) equation has been widely applied for design of border irrigation systems. This equation is based on the concept of mass conservation while the momentum balance is replaced by the assumption of a constant surface water depth. Although this constant water depth depends on the inflow rate, slope and roughness of the infiltrating surface, no explicit relation has been derived for its estimation. Assuming negligible border slope, the present study theoretically treats the constant depth in the LM equation by utilizing the simple dam-break wave solution along with boundary layer theory. The wave front is analyzed separately from the rest of the advancing water by considering both friction and infiltration effects on the momentum balance. The resulting equations in their general form are too complicated for closed-form solutions. Solutions are therefore given for specialized cases and the mean depth of flow is presented as a function of the initial water depth at the inlet, the surface roughness and the rate of infiltration. The solution is calibrated and tested using experimental data.Abbreviations a (t) advance length - c mean depth in LM equation - c _f friction factor - c _h Chezy's friction coefficient - g acceleration due to gravity - h(x, t) water depth - h ₀ water depth at the upstream end - i() rate of infiltration - f(x, t) discharge - q₀ constant inflow discharge - S _f energy loss gradient or frictional slope - S₀ bed slope - t time - u(x, t) mean velocity along the water depth - x distance - Y() cumulative infiltration - (t) distance separating two flow regions - infiltration opportunity time     

Minimizing instrumentation requirement for estimating crop water stress index and transpiration of maize

Research was conducted in northern Colorado in 2011 to estimate the crop water stress index (CWSI) and actual transpiration (T _a) of maize under a range of irrigation regimes. The main goal was to obtain these parameters with minimum instrumentation and measurements. The results confirmed that empirical baselines required for CWSI calculation are transferable within regions with similar climatic conditions, eliminating the need to develop them for each irrigation scheme. This means that maize CWSI can be determined using only two instruments: an infrared thermometer and an air temperature/relative humidity sensor. Reference evapotranspiration data obtained from a modified atmometer were similar to those estimated at a standard weather station, suggesting that maize T _a can be calculated based on CWSI and by adding one additional instrument: a modified atmometer. Estimated CWSI during four hourly periods centered on solar noon was largest during the 2 h after solar noon. Hence, this time window is recommended for once-a-day data acquisition if the goal is to capture maximum stress level. Maize T _a based on CWSI during the first hourly period (10:00–11:00) was closest to T _a estimates from a widely used crop coefficient model. Thus, this time window is recommended if the goal is to monitor maize water use. Average CWSI over the 2 h after solar noon and during the study period (early August to late September, 2011) was 0.19, 0.57, and 0.20 for plots under full, low-frequency deficit, and high-frequency deficit irrigation regimes, respectively. During the same period (50 days), total maize T _a based on the 10:00–11:00 CWSI was 218, 141, and 208 mm for the same treatments, respectively. These values were within 3 % of the results of the crop coefficient approach.     

Regional calibration of Hargreaves equation for estimating reference ET in a semiarid environment

The Hargreaves equation provides reference evapotranspiration (ET_o) estimates when only air temperature data are available, although it requires previous local calibration for acceptable performance. This equation has been evaluated under semiarid conditions in Southern Spain using data from 86 meteorological stations, comparing daily estimates against those from the FAO-56 Penman–Monteith equation, which was used as standard. Variability of results among location was clearly apparent, with MBE ranging from 0.74 to −1.13 mm d⁻¹ and RMSE from 0.46 to 1.65 mm d⁻¹. Maxima under- and overestimation amounted to 24.5 and 22.5%, respectively. In general, larger under- and overestimations occurred in stations located close to the coast and at inland areas, respectively. Yearly means of windspeed (V) and daily temperature range (ΔT) fairly influenced the accuracy of the equation. It was more accurate for windy locations with large ΔT, and for locations with light wind conditions combined with low to moderate values of ΔT. According to the values taken by V and ΔT, the stations were represented by points on the ΔT–V coordinate plane, in which four regions were delimited. A regional calibration was carried out considering only temperature and wind conditions. Correction was not necessary for stations located within two of them; for the other two regions, new values for the empirical coefficient of the equation are suggested (0.0027 and 0.0021). After correction, average RMSE and maximum and minimum MBE decreased substantially (12, 24 and 41%, respectively), and 74 out of the 86 locations gave quite accurate results, with relative values of MBE lower than 10% in most cases. Alternatively, another method based on kriging interpolation was proposed to obtain, for each individual station, locally adjusted values for the empirical coefficient as a function of the same variables. This second correction procedure behaved even better than the first one. There was a 15% improvement in the average RMSE, and maximum and minimum MBE values decreased 50 and 70%, respectively. At all locations, relative values of MBE were less than 10% and in 70% of them were lower than 5%. Validation was done by using data from 14 meteorological stations for other Spanish regions, and the consequences from the application of the corrections proposed for an irrigation district are discussed.     

Improved calibration of Cutthroat flumes

An analysis of laboratory data for a 0.914-m (3-ft) length Cutthroat flume with four different throat widths is presented. Significant differences with previously published calibration parameters were found. Special attention was given to non-hydrostatic pressures at the upstream and downstream piezometer taps, and the variations are presented in a series of three-dimensional plots. Variation in relative pressure at different tap heights was observed and was concluded to represent a shift from a concave to a convex flow profile between the 0.305- and 0.203-m throat widths. This significant alteration in the flow profile correlates with a sharp change in the n _f calibration parameter, describing a non-linear relationship with flume throat width. Alternative equation forms were explored in an attempt to increase the predictive accuracy of the calculated flow rates for free- and submerged-flow regimes. The alternative equations showed a decrease in the percent error, in the submerged-flow regime, by more than 50%. Transition submergence was observed to vary not only due to flume size, but also to flow rate. An empirically fitted equation was developed to calculate the transition submergence as a function of throat width and flow rate. In addition, a separate calibration for free-flow parameters was defined based on measurements from an upstream point gauge. The flow measurement accuracy of existing Cutthroat flumes can be significantly increased, especially for submerged-flow regimes.     

Alternative models for predicting the foliage—Air temperature difference of well irrigated wheat under variable meteorological conditions. I. Derivation of parameters II. Accuracy of predictions

Summary One means of using infrared measurements of foliage temperature (T _f ) for scheduling irrigations requires the use of meteorological data to predict the foliage-air temperature difference for a comparable well-watered crop (T _f ^* – T _a ). To determine the best method for making this prediction, parameters for models of increasing complexity for predicting (T _f ^* – T _a ) were derived for wheat using two sets of field data collected in 1982 and 1983.The simplest model with vapor pressure deficit (VPD) as the sole predictor accounted for 64% of observed variance in (T _f ^* – T _a ). The next model with both VPD and net radiation (R _n ) as predictors accounted for 74%. The most complex model predicted (T _f ^* – T _a ) from the crop energy balance. In addition to VPD and R _n it included parameters for the effects of air temperature (T _a ), aerodynamic resistance (r _a ) and the canopy resistance of a well-watered crop (r _cp ) and accounted for 70% of the variance.Accuracy of these alternative models was tested against an independent set of field data collected in 1984. The single variable model with VPD as sole predictor accounted for 17% of the variance in observed values of (T _f ^* – T _a ). This increased to 47% when the effect of R _n was included by using the two variable model and was increased further to 65% when the additional variables of T _a , r _a and r _cp were included by use of the energy balance model. When the complexity of the model was measured by its number of variables there was a close relationship between complexity and the accuracy of the predictions. Reasons for the residual variability are discussed. The need for improved instrumentation for meteorological measurements was indicated.     

Variable upper and lower crop water stress index baselines for corn and soybean

Upper and lower crop water stress index (CWSI) baselines adaptable to different environments and times of day are needed to facilitate irrigation scheduling with infrared thermometers. The objective of this study was to develop dynamic upper and lower CWSI baselines for corn and soybean. Ten-minute averages of canopy temperatures from corn and soybean plots at four levels of soil water depletion were measured at North Platte, Nebraska, during the 2004 growing season. Other variables such as solar radiation (R _s), air temperature (T _a), relative humidity (RH), wind speed (u), and plant canopy height (h) were also measured. Daily soil water depletions from the research plots were estimated using a soil water balance approach with a computer model that used soil, crop, weather, and irrigation data as input. Using this information, empirical equations to estimate the upper and lower CWSI baselines were developed for both crops. The lower baselines for both crops were functions of h, vapor pressure deficit (VPD), R _s, and u. The upper baselines did not depend on VPD, but were a function of R _s and u for soybean, and R _s, h, and u for corn. By taking into account all the variables that significantly affected the baselines, it should be possible to apply them at different locations and times of day. The new baselines developed in this study should facilitate the application of the CWSI method as a practical tool for irrigation scheduling of corn and soybean.     

Flow over rectangular sharp-crested weirs

Sharp-crested weirs are the simplest form of over-flow spillway that commonly used to determine the flow rate in hydraulic laboratories, industry and irrigation systems, where highly accurate discharge measurements are needed. In this study, the experimental upper and lower nappe profiles in rectangular sharp-crested weirs are fitted by quadratic and cubic equations, respectively. In addition, free-vortex theory is used to simulate flow over this kind of weirs and determine discharge coefficient. Physical models of sharp-crested weirs with various widths and heights were considered. The proposed method agrees well with the experimental observations. Also, the experimental data indicate that the suggested equation presents reasonable results for the range of 0 < h/P < 9.     

Evaluation of the surface renewal method to estimate wheat evapotranspiration

The performance of the surface renewal method to estimate latent heat fluxes (LE) over a wheat crop was evaluated by comparison against values of LE measured independently using a weighing lysimeter. High-frequency temperature readings were taken at 1.5 m above ground from 29 April to 7 June 2000 over a 0.7–0.8 m high wheat crop. Surface renewal analysis was applied for two time lags r (0.75 and 0.25 s) to estimate half-hour sensible heat flux (H) and, subsequently, LE by solving the energy balance equation, using concurrent measurements of net radiation and soil heat flux. When H was estimated using sensor measurement height (z) in the computations, indices of agreement (IA) between lysimeter and surface renewal LE were above 0.94 and relative errors varied between 8.5 and 14.9% for time lag r=0.75 s for all analyzed days but 7 June. Results were slightly poorer for time lag r=0.25 s. When z−h_c or z−d (h_c being the crop height and d being the zero plane displacement) were used instead of z to compute H, surface renewal LE estimates slightly improved, particularly for the z−d case. The improvement was particularly noticeable for 7 June. The use of z−h_c or z−d was thus more appropriate for these measurements, with the result that it was not necessary to calibrate the weighing factor α, as required by the standard surface renewal method. Unfortunately, although of similar magnitude than those reported for other micrometeorological methods, surface renewal errors found in this paper were biased and LE was underestimated. Further research and testing of the surface renewal method is therefore required to remove biases from the estimates of LE.     

Intercepted radiation by apple canopy can be used as a basis for irrigation scheduling

Improved approaches for irrigation scheduling require specific protocols for adaptation to different growing conditions. We assessed crop intercepted radiation as the main factor for decision on irrigation scheduling. Over two growing seasons (2007-2008), apple trees growing in a large weighing lysimeter were used to measure daily canopy transpiration (T_d). Seasonal patterns of daily canopy intercepted photosynthetically active radiation (IPAR_d) and midday stem water potential were also measured. In 2007, irrigation was withheld in two different times to study T_d responses to midday stem water potential. Before harvest, under full irrigation, T_d increased linearly with IPAR_d (R² = 0.81 in 2007 and 0.84 in 2008). With the two year data combined, R² increased from 0.74 to 0.80 when VPD was considered as a second variable. When irrigation was withheld in 2007 the ratio between T_d and IPAR_d, which is defined here as transpiratory radiation use efficiency (TRUE), decreased linearly (R² = 0.49) as midday stem water potential decreased. Due to the highly significant effect of IPAR_d and VPD on T_d, TRUE showed potential applications in estimating the amount of irrigation water.     

Combining FAO-56 model and ground-based remote sensing to estimate water consumptions of wheat crops in a semi-arid region

This study was performed to test three methods based on the FAO-56 “dual” crop coefficient approach to estimate actual evapotranspiration (AET) for winter wheat under different irrigation treatments in the semi-arid region of Tensift Al Haouz, Marrakech (center of Morocco). The three methods differ in the calculation of the basal crop coefficient (K_cb) and the fraction of soil surface covered by vegetation (f_c). The first approach strictly follows the FAO-56 procedure, with K_cb given in the FAO-56 tables and f_c calculated from K_cb (No-Calibration method). The second method uses local K_cb and f_c values estimated from field measurements (Local-Calibration method) and the last approach uses a remotely-sensed vegetation index to estimate K_cb and f_c (NDVI-Calibration method). The analysis was performed on three fields using actual (AET) measured by Eddy Correlation systems. It was shown that the Local-Calibration approach gave best results. Accurate estimates of K_cb and f_c were necessary for FAO-56 “dual” crop coefficient application. The locally derived K_cb for winter wheat taken at initial, mid-season, and maturity crop growth were 0.15, 0.90 and 0.23, respectively. The K_cb value at the mid-season stage was found to be considerably less than that suggested by the FAO-56.     

A distributed agro-hydrological model for irrigation water demand assessment

The actual irrigation water demand in a district in Sicily (Italy) was assessed by the spatially distributed agro-hydrological model SIMODIS (SImulation and Management of On-Demand Irrigation Systems). For each element with homogeneous crop and soil conditions, in which the considered area can be divided, the model numerically solves the one-dimensional water flow equation with vegetation parameters derived from Earth Observation data. In SIMODIS, the irrigation scheduling is set by means of two parameters: the threshold value of soil water pressure head in the root zone, h_m, and the fraction of soil water deficit to be re-filled, Δ. This study investigated the possibility of identifying a couple of irrigation parameters (h_m, Δ) which allowed to reproduce the actual irrigation water demand, given that the study area was adequately characterized with regard to the spatial distribution of the soil hydraulic properties and the vegetation conditions throughout the irrigation season. The spatial distribution of the soil and vegetation properties of the study area, covering an irrigation district of approximately 800 ha, was accurately characterized during the summer of 2002. The soil hydraulic properties were identified by an intensive undisturbed soil sampling, while the vegetation cover was characterized in terms of leaf area index, surface albedo and fractional soil cover by analysing multispectral LandSat TM imageries. Irrigation volumes were monitored at parcel scale.A reference scenario with h_m = −700 cm and Δ = 50% (corresponding to a mean actual to potential transpiration ratio of 0.95) allowed to reproduce the spatial and temporal distribution of the actual irrigation demand at the district scale. The spatial variability of the crop conditions in the considered area had much more influence to assess the irrigation water demand than the soil hydraulic spatial variability. The proposed approach showed that, under the agro-climatic conditions typical for the Mediterranean region, SIMODIS may be a valuable tool in managing irrigation to increase water productivity.     

Night-time sap flow is parabolically linked to midday water potential for field-grown almond trees

To quantify night-time (S _n) and diurnal (S _d) tree water uptake, two sets of sap flow sensors (heat-pulse compensated) were installed per tree in the north-east and south-west sides of the trunk in three trees per treatment. There were two treatments: (1) control, irrigated with 100 % ETc (T₁₀₀), and (2) deficit, irrigated at 60 % ETc (T₆₀) with daily irrigations at the peak atmospheric demand (December–January). Normalised S _n by trees was in the range of 15–25 % throughout the season, compared to normalised S _d, for T₁₀₀ and T₆₀, respectively. Furthermore, S _n was parabolically correlated to plant water status from the previous day, measured as midday stem water potential. We also found strong correlations between S _n and nocturnal vapour pressure deficit for T₁₀₀ and T₆₀, indicating that nocturnal transpiration was significant for both treatments. Differences in S _n were observed for the NE and SW sensors for T₆₀, being significantly less for the NE side (sunny side) compared to the SW side (more shaded). No differences were observed for T₁₀₀ regarding probe positioning.     

Irrigation scheduling of plastic greenhouse vegetable crops based on historical weather data

Irrigation scheduling based on the daily historical crop evapotranspiration (ET_h) data was theoretically and experimentally assessed for the major soil-grown greenhouse horticultural crops on the Almería coast in order to improve irrigation efficiency. Overall, the simulated seasonal ET_h values for different crop cycles from 41 greenhouses were not significantly different from the corresponding values of real-time crop evapotranspiration (ET_c). Additionally, for the main greenhouse crops on the Almería coast, the simulated values of the maximum cumulative soil water deficit in each of the 15 consecutive growth cycles (1988–2002) were determined using simple soil-water balances comparing daily ET_h and ET_c values to schedule irrigation. In most cases, no soil-water deficits affecting greenhouse crop productivity were detected, but the few cases found led us to also assess experimentally the use of ET_h for irrigation scheduling of greenhouse horticultural crops. The response of five greenhouse crops to water applications scheduled with daily estimates of ET_h and ET_c was evaluated in a typical enarenado soil. In tomato, fruit yield did not differ statistically between irrigation treatments, but the spring green bean irrigated using the ET_h data presented lower yield than that irrigated using the ET_c data. In the remaining experiments, the irrigation-management method based on ET_h data was modified to consider the standard deviation of the inter-annual greenhouse reference ET. No differences between irrigation treatments were found for productivity of pepper, zucchini and melon crops.     

Shallow groundwater contribution to pistachio water use

Pistachio can be grown in the central desert of Islamic Republic (I.R.) of Iran with adverse conditions such as shallow saline groundwater tables. The contribution of water from shallow, saline groundwater to crop water use may be important in such conditions. The objectives of this study were to determine the contributions from shallow, saline groundwater to water use of pistachio seedlings, and how this contribution was affected by groundwater depth, salinitiy, and irrigation conditions. The results indicated that an increase in groundwater depth resulted in significant increase in root depth and significant decrease in seasonal evapotranspiration (ET), transpiration, and groundwater contribution to the plant water use. Non-saline shallow (30–120 cm depth) groundwater under irrigated and non-irrigated conditions contributed 72.4–89.7% and 90.7–100.0% of plant water use, respectively. However, these contributions were 57.2–74.8% and 79.3–100.0% for irrigated and non-irrigated conditions, respectively for saline shallow (30–120 cm depth) groundwater. The effect of groundwater depths (D, cm) on groundwater contributions (q, %) was found to be influenced by the salinity levels of the groundwater (EC, dS m⁻¹). The linear multiple regression equations were q = 97.5 − 1.24(EC) − 0.194(D) and q = 105.9 − 0.48(EC) − 0.154(D) for irrigated and non-irrigated conditions, respectively. The maximum reductions in relative plant dry weight of 80.3% and 44.8% were occurred under non-irrigated condition and saline groundwater depth of 30 cm and non-saline water depth of 60 cm, respectively. Root depth analysis indicated that vertical root growth caused the root to reach a moist layer near the groundwater. A very close to 1:1 relationship between relative reduction in top dry weight (1 − y/y_m) and relative reduction in transpiration (1 − T/T_m) was obtained.     

Combined effect of technical, meteorological and agronomical factors on solid-set sprinkler irrigation: II. Modifications of the wind velocity and of the water interception plane by the crop canopy

Maize (Zea mays L.) and alfalfa (Medicago sativa L.) were simultaneously irrigated in two adjoining plots with the same sprinkler solid-set system under the same operational and technical conditions. The Christiansen's uniformity coefficient (CUC) and the wind drift and evaporation losses (WDEL) were assessed from the irrigation depth (ID_C) collected into pluviometers above each crop. A network of pluviometers was located above the maize canopy. Two networks of pluviometers were located above the alfalfa, one above the canopy and the other at the same level as that above the maize. The latter was used to analyze the effects of the water collecting plane. The wind velocity (WV) profile was measured above each crop using anemometers located at three levels. Both the CUC and the WDEL differed between maize and alfalfa.The crops modified both the wind velocity above the canopy and the water interception plane. Both effects were related to the height of the crops (h).When h increased, the water interception plane increased, and the overlap of the sprinklers decreased. The CUC of the ID_C increased with the overlap. Because h was greater for maize than for alfalfa, the CUC was noticeably smaller for maize.The WV greatly decreased in proximity to the canopy. The WV at the level of the nozzles was smaller above the maize because the top of the canopy was closer to the nozzles than it was for alfalfa. However, the CUC of the ID_C mainly depended on the WV at higher levels, where the WV was similar above both maize and alfalfa. The logarithmic wind profile overestimated the vertical variation of the WV in the space where the sprinklers distributed the water.The WDEL was greater above the maize than above the alfalfa. This finding was related to the underestimation of the ID_C above maize, especially under windy conditions, because the pluviometers were located very close to the nozzles.     

An alternative to define canopy surface temperature bounds

Canopy temperature, which may be estimated by infrared thermometry (IRT), can serve as an indicator of plant water status. [Idso et al., 1981a] and [Idso et al., 1986] proposed the nowadays much used concept of the crop water stress index, which relates observed canopy surface temperature (T_s) to maxima and minima temperature bounds. Jackson et al. (1981) defined those bounds on the basis of the energy balance. Those bounds vary with the meteorological situation. In this paper a chart is offered for general use with a fixed frame for the upper and lower bound. It relates canopy surface temperatures with r₁(=1 + r_c/r_a)-values (r_c the canopy resistance and r_a the aerodynamic resistance) as a function of a specifically defined temperature sum (S). It links the curved lower bound with the straight upper bound by a bundle of r₁-curves (the T_s-S-r₁-chart). The lower bound can be expressed by an equation, which approximates the energy balance solution with high accuracy. The sensitivity of the upper bound is also discussed. A comparison was made between bounds following Jackson et al. (1981) and the proposed alternative method, which, however, is limited by the short data-set available for this paper.     

An evaluation of common evapotranspiration equations

A comparison is made between the Pruitt and Doorenbos version of an hourly Penman-type equation, the Food and Agriculture Organization (FAO) hourly Penman-Monteith equation, and an independent measure of reference evapotranspiration (ET₀) from lysimeter data. Reducing the canopy resistance improved the hourly FAO Penman-Monteith estimates. Daytime soil heat flux density is estimated as 10% of net radiation in the FAO hourly Penman-Monteith equation; however, the measured soil heat flux density under grass that was never shorter than 0.10 m in this study was between 3% and 5% of net radiation. The daytime totals of hourly ET₀ from the hourly Penman-Monteith and Pruitt-Doorenbos equations and ET₀ from the 24-h FAO Penman-Monteith equation were computed using data from five Italian and five Californian stations. A comparison showed that all of the equations gave acceptable results. The Pruitt-Doorenbos equation may slightly over-estimate ET₀ in conditions of summertime cold air advection. Received: 18 November 1998     

Maximum and Actual Evapotranspiration for Barley (Hordeum vulgare L.) through NOAA Satellite Images in Castilla-La Mancha,Spain

An easy-to-follow methodology is developed for the assessment of regional evapotranspiration in Castilla-La Mancha, a semi-arid region of Spain. The methodology is applied to barley crops to monitor the irrigation scheduling over the region, by using remote sensing techniques supplemented by ground measurements. The methodology can be based on either of two models. In the first one, established by Caselles and Delegido,¹the reference evapotranspiration,ET_o, derives from the expressionET_o=AR_g(T_a)_max+BR_g+CwhereA, BandCare empirical coefficients, depending on climatic parameters and determined for each region;R_gis the daily global radiation; and (T_a)_maxis the maximum air temperature. The second model, proposed by Jacksonet al.,²considers the actual evapotranspirationER=R_n+D(T_a−T_s) whereR_n, is the net radiation,T_aandT_sare the air and crop surface temperatures, respectively, andDis a semi-empirical coefficient. Both methods were compared with the method of Penman (considered standard), and resulted in differences of ±1 mm  d⁻¹. The developed methodology has been applied to map the reference and the actual evapotranspiration over a 10×10 km area, using the thermal-infrared information provided by the AVHRR (advanced very high resolution radiometer) sensor on board the NOAA (national oceanic atmosphere administration) satellite on a selected date.