Jozsef Szilagyi

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Budapest University of Technology and Economics · Department of Hydraulic and Water Resources Engineering

An important scaling consideration is introduced into the formulation of the complementary relationship (CR) of land surface evapotranspiration (ET) by specifying the maximum possible evaporation rate (Epmax) of a small water body (or wet patch) as a result of adiabatic drying from the prevailing near-neutral atmospheric conditions. In dimensionles...

Trends in monthly evapotranspiration (ET) rates across three watersheds covering the Central Valley in California were calculated by the latest calibration-free version of the complementary relationship of evaporation for 1979–2015. While a recent study concluded that ET rates of the irrigated fields in the Central Valley were declining in 1981–200...

Having recognized the limitations in spatial representativeness and/or temporal coverage of (i) current ground ETa observations and (ii) land surface model‐ and remote sensing‐based ETa estimates due to uncertainties in soil and vegetation parameters, a calibration‐free nonlinear complementary relationship (CR) model is employed with inputs of air...

Monthly evapotranspiration (ET) rates for 1979–2015 were estimated by the latest, calibration‐free version of the complementary relationship (CR) of evaporation over the conterminous United States. The results were compared to similar estimates of three land surface models (Noah, VIC, Mosaic), two reanalysis products (National Centers of Environmen...

Long-term tendencies in annual, seasonal, and monthly (March) precipitation, evapotranspiration, and air- and dew-point temperature values were correlated with county-level changes in irrigated area across Nebraska over the 1979–2015 period. A statistically significant linear relationship (slope of − 1.65 ± 0.33 mm decade−1 per % decadal change in...

Evaporation rates and land surface temperatures can be modified by planned water availability as well as land use and land cover changes. In general, a higher evaporation rate via its associated latent heat flux yields a cooler surface. Here we demonstrate that increasing energy at the land surface necessitates more intense latent heat fluxes for t...

Surprising significant underperformance of the polynomial complementary relationship (PCR) of evaporation (Szilagyi et al., 2017, https://doi.org/10.1002/2016jd025611) by Wang et al. (2023, https://doi.org/10.1029/2023jd038683) is caused by the (a) station‐by‐station application of a grid‐based estimation procedure of the Priestley‐Taylor parameter...

A szerző a területi párolgás komplementáris összefüggésén alapuló becslési módszerek szakértője. Az itt, magyar nyelven először ismertetett termodinamikai alapú, rugalmas, minimális adatigényű (léghőmérséklet, légnedvesség, szélsebesség, sugárzási egyenleg) becslési eljárás huszonkét év kutatási munkájának eredménye. A módszer előnye, hogy mindössz...

Changes and trends in the climatic water balance of the Danube river basin. Water is a key to success in mitigating climate change and for sustainability. Temperature, radiation, and evaporation trends in the Danube River basin show significant changes! Evaporation is not a loss, but a vital environmental service! Water is the key medium for the di...

This study compares four different hypotheses regarding the nature of the Priestley–Taylor parameter α. They are as follows: α is a universal constant. The Bowen ratio (H/LE, where H is the sensible heat flux, and LE is the latent heat flux) for equilibrium (i.e., saturated air column near the surface) evaporation is a constant times the Bowen rati...

The series of severe droughts in Europe from the beginning of this century may have a root cause to which we do not pay enough attention. The key function of the water cycle-energy, and water distribution-is directly influenced by climate change. Analyzing the trends of ERA5-Land gridded meteorological data for Central-Europe confirms significant t...

Key Points The evaporation model of Szilagyi et al. (2017, https://doi.org/10.1002/2016JD025611) is less restrictive than the one employed by Tu et al. (2023, https://doi.org/10.1029/2022WR033763)

Severe droughts of 2022 in Europe raise the question if one has sufficient knowledge and tools to predict and prevent such events. Analysis of 40 years of meteorological data for Hungary between 1981 and 2020 confirms significant upward trends with p = 0.05 in temperature, relative humidity, and net radiation. Shortwave net radiation has increased...

The linear form of the nondimensional complementary relationship (CR) follows from an isenthalpic process of evaporation under a constant surface available energy and unchanging wind. Mixing of external moisture into the boundary layer (BL) alters the dry‐end second‐type boundary condition yielding a polynomial that can be further generalized into...

This study compares four different hypotheses regarding the nature of the Priestley-Taylor parameter α. They are: 1) α is a universal constant; 2) the Bowen ratio (H/LE, where H is the sensible and LE is the latent heat flux) for equilibrium (i.e. saturated air column near the surface) evaporation is a constant times the Bowen ratio at minimal adve...

It is argued here that the wet‐surface temperature (Tws) estimation method employed by Tu and Yang for their potential evaporation estimates yields physically unreachable low values not only during dry, but frequently under wet environmental conditions as well. For these reasons it is claimed that the wet‐surface temperature estimation method of Sz...

The estimation of catchment response time (Tr) plays an important role in several hydrological and civil engineering design problems. The non-linear relationship between Tr and rainfall intensity necessitates the estimation of an event-based set of Tr values instead of a characteristic constant value. However, there is no generally accepted method...

Several versions of the Complementary Relationship (CR) between actual regional evaporation and apparent potential evaporation have recently been proposed. Few studies have compared multiple CR versions side-by-side using datasets spanning various climates and land surfaces. Filling this lack is one purpose of this project. It also investigates how...

Study region 61 catchments located in Hungary, with drainage areas from 8.74 to 810 km². Study focus Many engineering tasks require the estimation of the catchment response time (Tr). The most frequently used Tr parameters are the time of concentration and the lag time. At ungauged catchments, they are usually estimated by empirical equations that...

While large-scale terrestrial evapotranspiration (ET) information is essential for our understanding of the Earth's water and energy cycles, substantial differences exist in current global ET products due partly to uncertainties in soil- and vegetation-related parameters and/or precipitation forcing. Here a calibration-free complementary relationsh...

A rescaling of variables changes the Priestley‐Taylor parameter value in the complementary relationship of evaporation for optimal performance.

The simultaneous thermodynamic pathways (i.e., isenthalps) of the air at the measurement height and at the vegetated land surface under isobaric and adiabatic wetting/drying cycles of the environment make it possible to define the actual evaporation rate with the help of three (one measured and two derived) vapor pressure (and corresponding tempera...

The paper by Han and Tian (2020) reviews the history of developments in the complementary relationship (CR) between actual and potential evaporation and introduces the generalized complementary principle (GCP) developed by the authors. This comment assesses whether the GCP: (1) can give reasonable results from a wide range of surfaces worldwide; (2...

No solid methodology is available to estimate the true value of catchment response time parameters based on measured time-series. The theoretical differences between time parameters, such as the lag time, time of concentration (Tc), time to peak and time to equilibrium are emphasized, based on the results of a comprehensive analysis of 8 different...

Most large-scale evapotranspiration (ET) estimation methods require detailed information of land use, land cover, and/or soil type on top of various atmospheric measurements. The complementary relationship of evaporation (CR) takes advantage of the inherent dynamic feedback mechanisms found in the soil-vegetation-atmosphere interface for its estima...

The paper by Han and Tian reviews the history of developments in the complementary relationship (CR) between actual and potential evaporation and introduces the generalized complementary principle (GCP) developed by the authors. This comment assesses whether the GCP: 1) Can give reasonable results from a wide range of surfaces worldwide; 2) is supp...

Watershed-scale annual evapotranspiration (ET) is routinely estimated by a simplified water balance as the difference in catchment precipitation (P) and stream discharge (Q). With recent developments in ET estimation by the calibration-free generalized complementary relationship, the water balance equation is employed to estimate watershed/basin P...

Liu et al. (2020, https://doi.org/10.1029/2019WR026292) provide comments on two papers introducing the rescaled Complementary Relationship (CR) of evaporation. Four concerns regarding the rescaled CR were raised and are addressed herein. Specifically, it is shown here that (1) the rescaled CR is not simply an asymmetric advection‐aridity model; (2)...

Forest ecosystems typically have a large leaf-area index both within the crown level and on the ground as litter, making interception a very important element of the forest water balance. Broad information exists about crown interception, but relatively few data are available regarding litter interception. The litter layer is able to change the qua...

From an analysis of 3,738 river gauging stationsof catchments ranging from 5 to 100,000 km2, Blöschl et al. constructed a map that depicts trends of annual maximum discharges across Europe for the 1960-2010 period. On that map Hungary, one of the most flood-prone countries in Europe, appears with nearly unanimously decreasing flood discharges which...

Kim et al. (2019) proposed to scale the generalized complementary-relationship-obtained daily evapotranspiration (ETGCR) rate by the wet-environment ET value (ETw) as an index (Ks) of soil water stress but they did not tie their index-values to any soil moisture data. With daily measurements from the same study area (Mead, Nebraska) and period (200...

Key Points The exact functional form of the nondimensional complementary relationship (CR) of evaporation remains unknown Application of a sigmoid function leads to physical contradictions The slope of the CR function at the upper boundary must be constrained by the slope of the Priestley‐Taylor limit line

Total irrigated land area has been expanding in Nebraska over the last 40 years, propelling the state into a leading position within the US in terms of irrigated acreages. Typically, those counties which display the largest degree of irrigation development had a significant portion of their land area already irrigated in 1978. Large-scale irrigatio...

Trends in monthly evapotranspiration (ET) rates across Nebraska, the most intensely irrigated state within the US, were calculated by the calibration-free version of the nonlinear complementary relationship of evaporation over the 1979–2015 period utilizing North American Regional Reanalysis (NARR) net radiation, 10-m wind velocity, as well as Para...

Continuous simulation of monthly evapotranspiration rates for 1979–2015 was performed by the latest, calibration-free version of the complementary relationship of evaporation over the conterminous United States. The results were compared to similar estimates of the WREVAP program and the North American Regional Reanalysis (NARR) project. Validation...

A mathematically correct form of the linear storage element’s routing equation is specified requiring only a slight modification of the existing HEC-HMS routine. The new formulation, unlike the current version in use, is unconditionally stable as long as the time step and the storage coefficient values are trivially specified as positive numbers.

Ma and Zhang (2017) note a concern they have with our rescaled Complementary Relationship (CR) for land surface evaporation when daily average wind speeds are very low (perhaps less than 1 m/s). We discuss conditions and specific formulations that lead to this concern, but ultimately argue that under these conditions, a key assumption behind the CR...

Recent research into the complementary relationship (CR) between actual and apparent potential evaporation has resulted in numerous alternative forms for the CR. Inspired by Brutsaert [2015], who derived a general CR in the form y=function(x), where x is the ratio of potential evaporation to apparent potential evaporation and y is the ratio of actu...

The original and revised versions of the generalized complementary relationship (GCR) of evaporation (ET) were tested with six-digit Hydrologic Unit Code (HUC6) level long-term (1981–2010) water-balance data (sample size of 334). The two versions of the GCR were calibrated with Parameter-Elevation Regressions on Independent Slopes Model (PRISM) mea...

Despite the importance of groundwater recharge (GR), its accurate estimation still remains one of the most challenging tasks in the field of hydrology. In this study, with the help of inverse modeling, long-term (6years) soil moisture data at 34 sites from the Automated Weather Data Network (AWDN) were used to estimate the spatial distribution of G...

Thirty year normal (1981-2010) monthly latent heat fluxes (ET) over the conterminous United States were estimated by a modified Advection-Aridity model from North American Regional Reanalysis (NARR) radiation and wind as well as Parameter-Elevation Regressions on Independent Slopes Model (PRISM) air and dew-point temperature data. Mean annual ET va...

Quantitative estimation of actual evapotranspiration (ETa) by in-situ measurements and mathematical modeling is a fundamental task for physical understanding of ETa as well as the feedback mechanisms between land and the ambient atmosphere. However, the ETa information in the Tibetan Plateau (TP) has been greatly impeded by the extremely sparse gro...

New research suggests that the Priestley-Taylor (PT) parameter, α, displays a temperature dependency with a significant increase in its generally accepted constant value of 1.26 as air temperature (T) drops. Multi-year water-balance data from two humid, cool climate experimental watersheds –Hubbard Brook in New Hampshire and Lookout Creek in Oregon...

Theoretical considerations and empirical evidence indicate a linear relationship between the land surface temperature (Ts) and the corresponding evapotranspiration (ET) rate under spatially constant wind and net energy conditions at a homogeneous vegetated surface. Such a relationship lies at the core of the popular surface energy balance algorithm...

The Priestley-Taylor parameter α of wet surface evaporation is investigated using daily, 0.75-degree ERA-Interim reanalysis data for the winter hemispheres of. Published ERA-Interim sensible and latent heat fluxes over sea and land yield two distinct best-fit curves for α as a function of air temperature (T a). When the wet land surface temperature...

The complementary relationship (CR) of evapotranspiration allows the estimation of the actual evapotranspiration rate (ETa) of the land surface using only routine meteorological data, which is of great importance in the Tibetan Plateau (TP) due to its sparse observation network. With the highest in-situ automatic climate observation system in a typ...

The Priestley–Taylor equation (PTE) is frequently applied in actual areal evapotranspiration (ET) estimation methods for obtaining the maximum daily rate of evaporation with data from sub-humid conditions. Since PTE was parameterized under humid conditions, a temperature correction is necessary to avoid overestimation of the maximum rate of ET. Wet...

Deep drainage of water below plant root zones (potential groundwater recharge) will become groundwater recharge (GR) after a delay (or lag time) in which soil moisture traverses the vadose zone before reaching the water table. Depending on the thickness of the vadose zone, the magnitude of deep drainage, and soil hydraulic properties, lag times wil...

Introduction ◆ The Tibetan Plateau, one of the world's largest plateaus, with an average altitude exceeding 4000 m, is vitally important with regard to the northern hemisphere's climate [Ye and Wu,1998]. Land surface actual evapo-transpiration (ET) from TP plays a significant role in energy-water cycle on a various temporal-spatial scales through t...

[1] Analytical solutions of the 2-D heat and vapor transport equations for a surface-moisture jump are often based on a constant streamwise temperature (Tws) assumption over the wet vegetated surface. By analyzing 90 thermal-infrared images taken over center-pivot irrigated areas in Nebraska, it has been demonstrated for the first time that such an...

Variability in sediment hydraulic properties associated with landscape depositional and erosional features can influence groundwater recharge processes by affecting soil-water storage and transmission. This study considers recharge to aquifers underlying river-incised glaciated terrain where the distribution of clay-rich till is largely intact in u...

Spatially distributed monthly evapotranspiration (ET) rates over the 2000-2009 period were specified for the three states [Colorado (CO), Kansas (KS), Nebraska (NE)] sharing the Republican River basin with the help of a calibration-free ETestimation method using Moderate Resolution (of about one km) Imaging Spectroradiometer (MODIS) data. Mean annu...

Flow-routing at a tributary (Koros River) of the Tisza River in Hungary was achieved by relating the storage coefficient (k) of the state-space formulated discrete linear cascade model (DLCM) to the concurrent discharge rate of the Tisza. As a result, the root mean square error of the 1-day forecasts decreased from 25m3s-1 (k=1.7days-1 and the numb...

In the paper by McMahon et al. (2013, supplementary sections S8 and S19, worked example 8), the Szilagyi-Jozsa advection-aridity model (Szilagyi, 2007; Szilagyi and Jozsa, 2008) was not applied in the worked example as intended by author J. Szilagyi. This commentary seeks to clarify the issue and provide the correct procedure.

In the paper by McMahon et al. (2013, Supplement Sects. S8 and S19 (Worked Example 8)), the Szilagyi-Jozsa Advection-Aridity model (Szilagyi, 2007; Szilagyi and Jozsa, 2008), which is a modification of the original Advection Aridity model of Brutsaert and Strickler (1979), was not applied in the worked example as intended by author J. Szilagyi. Thi...

Evapotranspiration (ET) estimation methods based on diurnal water level (surface or groundwater) fluctuations are sensitive to measurement accuracy ( and ). Water level fluctuations are often measured by pressure transducers of varying design and precision. Available total pressure transducers require a compensation for barometric pressure change s...

Daily and monthly flow-rates of the Little Nemaha River in Nebraska were simulated by the lumped-parameter Jakeman-Hornberger as well as a distributed-parameter water-balance accounting procedure for the 2003-2008 and 2000-2009 periods, respectively, with and without the help of the MODIS-based monthly estimates of evapotranspiration (ET) rates. Wh...

One-km resolution MODIS-based mean annual evapotranspiration (ET) estimates in combination with PRISM precipitation rates were correlated with depth to groundwater (d) values in the wide alluvial valley of the Platte River in Nebraska for obtaining a net recharge (Rn) vs. d relationship. MODIS cells with irrigation were excluded, yielding a mixture...

Monthly evapotranspiration (ET) rates (2000 to 2009) across Nebraska at about 1-km resolution were obtained by linear transformations of the MODIS (MODerate resolution Imaging Spectroradiometer) daytime surface temperature values with the help of the Priestley-Taylor equation and the complementary relationship of evaporation. For positive values of...

Remote-Sensing Based Groundwater Recharge Estimates in the Danube-Tisza Sand Plateau Region of Hungary Mean annual recharge in the Danube-Tisza sand plateau region of Hungary over the 2000-2008 period was estimated at a 1-km spatial resolution as the difference of mean annual precipitation ( P ) and evapotranspiration ( ET ). The ET rates were deri...

Mean annual recharge in the Sand Hills of Nebraska (USA) over the 2000–2009 period was estimated at a 1-km spatial resolution as the difference of mean annual precipitation (P) and evapotranspiration (ET). Monthly P values came from the PRISM dataset, while monthly ET values were derived from linear transformations of the MODIS daytime land-surface...

A calibration-free evapotranspiration mapping technique for spatially-distributed regional-scale hydrologic modeling Monthly evapotranspiration (ET) rates over Hungary for 2000-2008 are mapped at a spatial scale of about 1 km with the help of MODIS daytime land surface temperature as well as sunshine duration, air temperature and humidity data. Map...

Given increasing demands on finite water supplies, accurate estimates of evapotranspiration (LE) from arid shrublands of the Southwestern United States are needed to develop or refine basin water budgets. In this work, a novel approach to estimating the equilibrium (or wet environment) surface temperature (Te) and LE from regionally extensive phrea...