Potential Evaporation – A Matter of Definition

1993 ◽  
Vol 24 (5) ◽  
pp. 359-364 ◽  
Author(s):  
Anders Lindroth
Keyword(s):  
Evaporation Rate ◽  
Vapour Pressure Deficit ◽  
Open Water ◽  
Dry Forest ◽  
Water Evaporation ◽  
Good Representation ◽  
Large Scatter ◽  
Potential Evaporation ◽  
The Difference ◽  
Forest Conditions

The aim of this paper is to discuss the concept of potential evaporation and its use in runoff models. The potential evaporation for forest is defined on basis of estimated minimum canopy resistances for a well-watered spruce forest. The difference between the Penman open water evaporation, commonly used as “potential” evaporation, and a more realistic estimate of the potential evaporation from a dry forest showed a large scatter and a systematic seasonal deviation. Part of the differences were explained by differences in vapour pressure deficit. It was also shown that the evaporation rate of a completely wet forest was typically four times higher than the rate predicted by the Penman equation. The conclusion was that Penman open water evaporation did not give a good representation of forest conditions.

scholarly journals Evapotranspiration from a riparian fen wetland

2005 ◽  
Vol 36 (2) ◽  
pp. 121-135 ◽  
Author(s):  
H.E. Andersen ◽  
S. Hansen ◽  
H. E. Jensen
Keyword(s):  
Driving Forces ◽  
Radiant Energy ◽  
Vapour Pressure Deficit ◽  
Open Water ◽  
Absolute Magnitude ◽  
Growing Season ◽  
Agricultural Landscapes ◽  
Water Evaporation ◽  
Evaporative Demand ◽  
Fine Grained

Evapotranspiration rates were measured in a riparian fen wetland dominated by vascular vegetation and surrounded by open agricultural areas and forests. The wetland is situated on a floodplain in central Denmark. Measurements were taken throughout the growing season (April–September) of 1999. Evapotranspiration rates were higher than those published for most other wetland types, with an average of 3.6 mm d−1 during the growing season and a peak rate of 5.6 mm d−1. Daily average evapotranspiration was 110% of Penman's potential open water evaporation. Evapotranspiration was the dominant sink in the energy balance of the wetland studied. During the day, evapotranspiration accounted for 82% of the available radiant energy, Rn. Due to the presence of deposited fine-grained sediments, soil-water availability was kept high at all times which resulted in moderate canopy resistances, rc (overall mean =32 s m−1). Evapotranspiration was controlled by a combination of driving forces: Rn, saturation vapour pressure deficit, D, and rc. It is hypothesized that the results presented in this study are conditioned by the proximity of the wetland to drier upland areas. During periods with high evaporative demand and low precipitation, warm, dry air is formed over the upland areas and wetland evapotranspiration rates are enhanced by local advection. Indicative evidence for the hypothesis is presented. Although the absolute magnitude of the results reported is only directly relevant to similar sites in Denmark, the processes and controls described are considered to be representative of riparian wetlands subjected to frequent flooding and/or with a high groundwater table, with vascular vegetation, and which are narrow corridors in open agricultural landscapes.

scholarly journals New lessons on the Sudd hydrology learned from remote sensing and climate modeling

2006 ◽  
Vol 10 (4) ◽  
pp. 507-518 ◽  
Author(s):  
Y. A. Mohamed ◽  
H. H. G. Savenije ◽  
W. G. M. Bastiaanssen ◽  
B. J .J. M. van den Hurk
Keyword(s):  
Remote Sensing ◽  
Regional Climate Model ◽  
Land Surface ◽  
Evaporation Rate ◽  
Climate Model ◽  
Regional Climate ◽  
Remote Sensing Data ◽  
Open Water ◽  
Groundwater Table ◽  
Water Evaporation

Abstract. Despite its local and regional importance, hydro-meteorological data on the Sudd (one of Africa's largest wetlands) is very scanty. This is due to the physical and political situation of this area of Sudan. The areal size of the wetland, the evaporation rate, and the influence on the micro and meso climate are still unresolved questions of the Sudd hydrology. The evaporation flux from the Sudd wetland has been estimated using thermal infrared remote sensing data and a parameterization of the surface energy balance (SEBAL model). It is concluded that the actual spatially averaged evaporation from the Sudd wetland over 3 years of different hydrometeorological characteristics varies between 1460 and 1935 mm/yr. This is substantially less than open water evaporation. The wetland area appears to be 70% larger than previously assumed when the Sudd was considered as an open water body. The temporal analysis of the Sudd evaporation demonstrated that the variation of the atmospheric demand in combination with the inter-annual fluctuation of the groundwater table results into a quasi-constant evaporation rate in the Sudd, while open water evaporation depicts a clear seasonal variability. The groundwater table characterizes a distinct seasonality, confirming that substantial parts of the Sudd are seasonal swamps. The new set of spatially distributed evaporation parameters from remote sensing form an important dataset for calibrating a regional climate model enclosing the Nile Basin. The Regional Atmospheric Climate Model (RACMO) provides an insight not only into the temporal evolution of the hydro-climatological parameters, but also into the land surface climate interactions and embedded feedbacks. The impact of the flooding of the Sudd on the Nile hydroclimatology has been analysed by simulating two land surface scenarios (with and without the Sudd wetland). The paper presents some of the model results addressing the Sudd's influence on rainfall, evaporation and runoff of the river Nile, as well as the influence on the microclimate. The paper presents a case study that confirms the feasibility of using remote sensing data (with good spatial and poor temporal coverage) in conjunction with a regional climate model. The combined model provides good temporal and spatial representation in a region characterized by extremely scarce ground data.

scholarly journals Comparison of evaporation rate on open water bodies: energy balance estimate versus measured pan

2017 ◽  
Vol 9 (1) ◽  
pp. 101-111 ◽  
Author(s):  
Yohannes Yihdego ◽  
John A. Webb
Keyword(s):  
Wind Speed ◽  
Evaporation Rate ◽  
Meteorological Data ◽  
Open Water ◽  
Combination Method ◽  
Shortwave Radiation ◽  
Water Evaporation ◽  
Seasonal Adjustment ◽  
Budget Analysis ◽  
Rate Of Evaporation

Abstract Much attention has been paid to establish accurately open water evaporation since the lake itself is the largest consumer of water. The aim of this study is to assess the discrepancy in the measured (pan evaporation) and estimated (Penman) evaporation rate, seasonally, based on the results from a 37-year energy budget analysis of Lake Burrumbeet, Australia. The detailed analysis of meteorological data showed that evaporation is fully radiation driven and that the effect of wind is minimal. Sensitivity analysis shows that evaporation estimation is more sensitive to shortwave radiation followed by relative humidity. An increase or decrease of estimated shortwave radiation by 10% could result in an increase or decrease of estimated evaporation up to 18%. The Penman combination method is relatively the least sensitive to wind speed but could bring a significant effect on the lake level fluctuation since a 10% increase of wind speed increases the estimated evaporation by 2.3%. The current analysis highlights the relative roles of radiation, temperature, humidity, and wind speed in modulating the rate of evaporation from the lake surface, by employing an inter-monthly seasonal adjustment factor to the estimated evaporation in the lake water budget analysis, with implications for the inter-monthly variability and short-term trends assessment of water resource through various meteorological parameters.

Prediction of the water evaporation rate of wet textile materials in a pre-defined environment

2020 ◽  
Vol 32 (3) ◽  
pp. 356-365
Author(s):  
Song-Rui Liu ◽  
Xiao-Qun Dai ◽  
Yan Hong
Keyword(s):  
Evaporation Rate ◽  
Water Evaporation ◽  
Material Surface ◽  
Wind Condition ◽  
Temperature Decrease ◽  
Content Type ◽  
Textile Materials ◽  
Maximum Water ◽  
The Difference ◽  
Practical Implications

Purpose The water evaporation rate (WER) is not only crucial for fabric drying, but also an important parameter affecting cooling from a body wearing sweat wetted clothing. The purpose of this paper is to predict the WERs of wet textile materials in a pre-defined environment. Design/methodology/approach The maximum water evaporation rate (WERmax) from a saturated surface in a pre-defined environment was first predicted based on the Lewis relationship between the evaporative and the convective heat transfer in this paper. The prediction results were validated by the comparisons with experimental measurements in various environments obtained in this paper and reported in the literature. Findings Experiment results show that the ratios of WERs to WERmax are lower than 100 percent but higher than 50 percent, which confirmed that the prediction of WERmax is reliable. The temperature decrease of the wet material surface due to evaporation was considered to account for the difference between measured WERs and the WERmax, and the WER variation among materials. The lower ratios of WERs to WERmax in the higher wind condition were speculated to be due to the greater temperature decrease caused by the increased evaporation. Practical implications It provides a reliable way to obtain both WERmax and WER (WERmax multiplied by a proper ratio), which can be useful in clothing physiological modeling to predict clothing comfort. Originality/value This study contributes to the understanding of the evaporation process of textile materials.

scholarly journals Modelling the Evaporation Rate in an Impingement Jet Dryer with Multiple Nozzles

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Anna-Lena Ljung ◽  
L. Robin Andersson ◽  
Anders G. Andersson ◽  
T. Staffan Lundström ◽  
Mats Eriksson
Keyword(s):  
Evaporation Rate ◽  
Impinging Jets ◽  
Water Evaporation ◽  
Two Dimensional ◽  
Moist Air ◽  
Dynamics Model ◽  
Computational Fluid Dynamics Model ◽  
Impingement Jet ◽  
Two Component ◽  
The Difference

Impinging jets are often used in industry to dry, cool, or heat items. In this work, a two-dimensional Computational Fluid Dynamics model is created to model an impingement jet dryer with a total of 9 pairs of nozzles that dries sheets of metal. Different methods to model the evaporation rate are studied, as well as the influence of recirculating the outlet air. For the studied conditions, the simulations show that the difference in evaporation rate between single- and two-component treatment of moist air is only around 5%, hence indicating that drying can be predicted with a simplified model where vapor is included as a nonreacting scalar. Furthermore, the humidity of the inlet air, as determined from the degree of recirculating outlet air, has a strong effect on the water evaporation rate. Results show that the metal sheet is dry at the exit if 85% of the air is recirculated, while approximately only 60% of the water has evaporated at a recirculation of 92,5%.

scholarly journals Soil Moisture Dynamics in Response to Precipitation and Thinning in a Semi-Dry Forest in Northern Mexico

Water ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 105
Author(s):  
Argelia E. Rascón-Ramos ◽  
Martín Martínez-Salvador ◽  
Gabriel Sosa-Pérez ◽  
Federico Villarreal-Guerrero ◽  
Alfredo Pinedo-Alvarez ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Forest Management ◽  
Water Availability ◽  
Dry Forest ◽  
Rainfall Events ◽  
Rainfall Characteristics ◽  
Northern Mexico ◽  
The Difference ◽  
The Impact ◽  
Moisture Dynamics

Understanding soil moisture behavior in semi-dry forests is essential for evaluating the impact of forest management on water availability. The objective of the study was to analyze soil moisture based in storm observations in three micro-catchments (0.19, 0.20, and 0.27 ha) with similar tree densities, and subject to different thinning intensities in a semi-dry forest in Chihuahua, Mexico. Vegetation, soil characteristics, precipitation, and volumetric water content were measured before thinning (2018), and after 0%, 40%, and 80% thinning for each micro-catchment (2019). Soil moisture was low and relatively similar among the three micro-catchments in 2018 (mean = 8.5%), and only large rainfall events (>30 mm) increased soil moisture significantly (29–52%). After thinning, soil moisture was higher and significantly different among the micro-catchments only during small rainfall events (<10 mm), while a difference was not noted during large events. The difference before–after during small rainfall events was not significant for the control (0% thinning); whereas 40% and 80% thinning increased soil moisture significantly by 40% and 53%, respectively. Knowledge of the response of soil moisture as a result of thinning and rainfall characteristics has important implications, especially for evaluating the impact of forest management on water availability.

scholarly journals Highly efficient evaporative cooling by all-day water evaporation using hierarchically porous biomass

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jihun Choi ◽  
Hansol Lee ◽  
Bokyeong Sohn ◽  
Minjae Song ◽  
Sangmin Jeon
Keyword(s):  
Porous Structure ◽  
Fiber Length ◽  
Evaporation Rate ◽  
Water Evaporation ◽  
Thickness Direction ◽  
Hierarchically Porous ◽  
Hierarchically Porous Structure ◽  
Length Direction ◽  
Luffa Sponge ◽  
Fiber Thickness

AbstractWe developed a 3D solar steam generator with the highest evaporation rate reported so far using a carbonized luffa sponge (CLS). The luffa sponge consisted of entangled fibers with a hierarchically porous structure; macropores between fibers, micro-sized pores in the fiber-thickness direction, and microchannels in the fiber-length direction. This structure remained after carbonization and played an important role in water transport. When the CLS was placed in the water, the microchannels in the fiber-length direction transported water to the top surface of the CLS by capillary action, and the micro-sized pores in the fiber-thickness direction delivered water to the entire fiber surface. The water evaporation rate under 1-sun illumination was 3.7 kg/m2/h, which increased to 14.5 kg/m2/h under 2 m/s wind that corresponded to the highest evaporation rate ever reported under the same condition. The high evaporation performance of the CLS was attributed to its hierarchically porous structure. In addition, it was found that the air temperature dropped by 3.6 °C when the wind passed through the CLS because of the absorption of the latent heat of vaporization. The heat absorbed by the CLS during water evaporation was calculated to be 9.7 kW/m2 under 1-sun illumination and 2 m/s wind, which was 10 times higher than the solar energy irradiated on the same area (1 kW/m2).

scholarly journals Observations and Simulations of Meteorological Conditions over Arctic Thick Sea Ice in Late Winter during the Transarktika 2019 Expedition

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 174
Author(s):  
Günther Heinemann ◽  
Sascha Willmes ◽  
Lukas Schefczyk ◽  
Alexander Makshtas ◽  
Vasilii Kustov ◽  
...  
Keyword(s):  
Sea Ice ◽  
Climate Models ◽  
Climate Model ◽  
Regional Climate ◽  
Open Water ◽  
The Arctic ◽  
Late Winter ◽  
Good Representation ◽  
Hourly Temperature ◽  
Ice Model

The parameterization of ocean/sea-ice/atmosphere interaction processes is a challenge for regional climate models (RCMs) of the Arctic, particularly for wintertime conditions, when small fractions of thin ice or open water cause strong modifications of the boundary layer. Thus, the treatment of sea ice and sub-grid flux parameterizations in RCMs is of crucial importance. However, verification data sets over sea ice for wintertime conditions are rare. In the present paper, data of the ship-based experiment Transarktika 2019 during the end of the Arctic winter for thick one-year ice conditions are presented. The data are used for the verification of the regional climate model COSMO-CLM (CCLM). In addition, Moderate Resolution Imaging Spectroradiometer (MODIS) data are used for the comparison of ice surface temperature (IST) simulations of the CCLM sea ice model. CCLM is used in a forecast mode (nested in ERA5) for the Norwegian and Barents Seas with 5 km resolution and is run with different configurations of the sea ice model and sub-grid flux parameterizations. The use of a new set of parameterizations yields improved results for the comparisons with in-situ data. Comparisons with MODIS IST allow for a verification over large areas and show also a good performance of CCLM. The comparison with twice-daily radiosonde ascents during Transarktika 2019, hourly microwave water vapor measurements of first 5 km in the atmosphere and hourly temperature profiler data show a very good representation of the temperature, humidity and wind structure of the whole troposphere for CCLM.

scholarly journals Experimental Measurements of the Water Evaporation Rate of a Physical Model

2017 ◽  
Vol 25 (1) ◽  
pp. 19-23 ◽  
Author(s):  
Róbert Turza ◽  
Belo B. Füri
Keyword(s):  
Energy Demand ◽  
Evaporation Rate ◽  
High Water ◽  
Hvac Systems ◽  
Swimming Pool ◽  
Water Evaporation ◽  
Specific Enthalpy ◽  
High Water Content ◽  
Indoor Environments ◽  
Indoor Swimming Pool

Abstract As the number of indoor swimming pools and wellness centers are currently growing, it is necessary to concentrate on the parameters of indoor environments. These parameters are necessary for the design of the HVAC systems that operate these premises. In indoor swimming-pool facilities, the energy demand is large due to ventilation losses from exhaust air. Since water evaporates from a pool’s surface, exhaust air has a high water content and specific enthalpy. In this paper the results of the water evaporation rate measured from swimming pool surfaces at higher thermal water temperatures are described.

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