Determining dew and hoar frost formation for a low mountain range and alpine grassland site by weighable lysimeter

Groh, Jannis; Slawitsch, Veronika; Herndl, Markus; Graf, Alexander; Vereecken, Harry; Pütz, Thomas

doi:10.1016/j.jhydrol.2018.06.009

Cited by 63 publications

(57 citation statements)

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“…The analysis shows that dew corresponds on average to 5.1% and 6.2% of the total annual amount of precipitation at Wüstebach and Rollesbroich, respectively. This is in line with previous investigations at Rollesbroich (Groh, Slawitsch, et al, 2018), Wüstebach (Groh, Stumpp, et al, 2018), and other grasslands sites under humid climate conditions, which showed that dew contributes between 4.5% and 6.9% of the total annual precipitation (Heusinger & Weber, 2015;Jacobs et al, 2006;Xiao et al, 2009). The different parameterized PM models were also used to predict dew formation.…”

Section: Water Resources Researchsupporting

confidence: 92%

Quantification and Prediction of Nighttime Evapotranspiration for Two Distinct Grassland Ecosystems

Groh

Pütz

Gerke

et al. 2019

Water Resources Research

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Evapotranspiration (ET) is, after precipitation, the second largest flux at the land surface in the water cycle and occurs mainly during daytime. Less attention has been given to water fluxes from the land surface into the atmosphere during nighttime (i.e., between sunset and sunrise). The nighttime ET (ETN) may be estimated based on models that use meteorological data; however, due to missing experimental long‐term data, the verification of ETN estimates is limited. In this paper, the amount of ETN for two grassland ecosystems was determined from highly temporally resolved and precise weighing lysimeter data. We found that annual ETN ranged between 3.5% and 9.5% of daytime annual ET (ETD) and occurred mainly during wet soil and canopy surface conditions, which suggests that ETN is largely related to evaporation. ETN was positively correlated with wind speed. Dew formation, ranging from 4.8% to 6.4% of annual precipitation, was in absolute terms larger than ETN. The prediction of ETN with the Penman‐Monteith model improved if the aerodynamic and surface resistance parameters were based on vegetation height observations and the nighttime stomatal resistance parameter was assumed to be zero. The occurrence of hot days during the observation period showed to increase average ETN rates. Our results suggest that ETN can be observed with precision weighing lysimeters, was a not negligible component in the water balance of the grassland ecosystems, and thus needs more attention when simulating land surface hydrological processes.

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Section: Water Resources Researchsupporting

confidence: 92%

Quantification and Prediction of Nighttime Evapotranspiration for Two Distinct Grassland Ecosystems

Groh

Pütz

Gerke

et al. 2019

Water Resources Research

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“…We find that higher air temperature, vapor pressure deficit, wind speed, soil moisture, and downward longwave radiation tend to favor higher NWL, although the correlations are rather low. Similar results were reported by Groh et al (2019) at two sites in Germany. In addition, Dawson et al (2007) found clear positive relationships between these conditions and nocturnal sap flow in woody plant species from different ecosystems; however, nocturnal sap flow could occur with no NWL, e.g., for capacitance refilling.…”

Section: Discussionsupporting

confidence: 89%

“…Water is not only lost from the surface during night, but it can also be gained by dew formation. For example, dew and hoar frost comprise 4.2 %-6.4 % of annual precipitation at three humid grass sites in Austria and Germany (Groh et al, 2018(Groh et al, , 2019 and were found to occur on approximately 30 % of the nights in a forest in central Colorado (Berkelhammer et al, 2013) and 70 % of the nights in a grassland in the Netherlands (Jacobs et al, 2006). ET and dew formation correspond to a latent heat flux and might both occur, e.g., within the same hour, which makes it difficult to quantify them separately if the temporal resolution of the data is insufficient.…”

Section: Introductionmentioning

confidence: 99%

Terrestrial water loss at night: global relevance from observations and climate models

Padrón

Gudmundsson

Michel

et al. 2020

Hydrol. Earth Syst. Sci.

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Abstract. Nocturnal water loss (NWL) from the surface into the atmosphere is often overlooked because of the absence of solar radiation to drive evapotranspiration and the measuring difficulties involved. However, growing evidence suggests that NWL – and particularly nocturnal transpiration – represents a considerable fraction of the daily values. Here we provide a global overview of the characteristics of NWL based on latent heat flux estimates from the FLUXNET2015 dataset, as well as from simulations of global climate models. Eddy-covariance measurements at 99 sites indicate that NWL represents 6.3 % of total evapotranspiration on average. There are six sites where NWL is higher than 15 %; these sites comprise mountain forests with considerable NWL during winter that is related to snowy and windy conditions. Higher temperature, vapor pressure deficit, wind speed, soil moisture, and downward longwave radiation are related to higher NWL, although this is not consistent across all of the sites. On the other hand, the global multi-model mean of terrestrial NWL is 7.9 % of the total evapotranspiration. The spread of the model ensemble, however, is greater than 15.8 % over half of the land grid cells. Finally, NWL is projected to increase everywhere with an average of 1.8 %, although with a substantial inter-model spread. Changes in NWL contribute substantially to projected changes in total evapotranspiration. Overall, this study highlights the relevance of water loss during the night and opens avenues to explore its influence on the water cycle and the climate system under present and future conditions.

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“…Dew forms when the temperature of a surface is lower than or equal to the dewpoint temperature, such that water vapor in the air condenses on the colder surface [11,12]. Dew is usually attached to the leaves of plants and the soil surface or in shallow soil.…”

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confidence: 99%

“…The difficulty of dew measurement is both in the definition of dew and in its actual measurement. However, scholars have developed various dew measurement instruments or methods in the past 70 years, including dew gauge [23], electrical resistance sensor [24], hiltner-type dew balance method [25], soil moisture sensor [1], leaf wetness sensor [26][27][28][29][30], artificial condensation surface method [31][32][33][34], and weighing method [6,12,35,36]. The last three items of the methods mentioned above are widely used.…”

mentioning

confidence: 99%

Dew Yield and Its Influencing Factors at the Western Edge of Gurbantunggut Desert, China

Jia

Zhao

2019

Water

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Dew is a significant water resource in arid desert areas. However, information regarding dew is scarce because it is difficult to measure due to the harsh environment of locations such as Gurbantunggut Desert, China. In this study, a non-destructive field experiment was conducted from 2015 to 2018 at a desert test station located in the western edge of the Gurbantunggut Desert, using a calibrated leaf wetness sensor (LWS) to measure dew yield. The results are as follows: (1) Dew formed after sunset with the atmospheric temperature gradually dropping and evaporated after sunrise with the temperature increasing in the second morning. (2) Dew was featured as ‘high frequency and low yield’. The average daily dew yield during dew days was 0.10 mm with a daily maximum of 0.62 mm, while dew days accounted for 44% of the total monitoring days, with a monthly maximum of 25 days. Compared with rainfall, dew days were two times as frequent as rainy days, while the average annual dewfall (12.21 mm) was about 1/11th of the average annual rainfall (134.6 mm), which indicates the dew contribution to regional water balance is about 9%. (3) March–April and October–November are the main periods of dew occurrence in this region because accumulated snow begins to melt slowly in March–April, providing sufficient vapor for dew formation, and the air temperature difference between day and night in October–November is the highest in the year, meaning that the temperature drops rapidly at night, making it easier to reach the dewpoint for vapor condensation. (4) Daily dew yield (D) was positively correlated to relative humidity (RH) and the difference between soil temperature at 10 cm below the ground and surface soil temperature (Tss), and negatively correlated to wind speed (V), air temperature (Ta), surface soil temperature (Ts), cloud cover (N), dewpoint temperature (Td) and the difference between air temperature and dewpoint temperature (Tad). It should be noted that the measured values of all factors above were the average value of the overnight period. The multivariate regression equation, D = −0.705 + 0.011 ×RH− 0.006 ×N− 0.01 × V, can estimate the daily dew yield with the thresholds of the parameters, i.e., RH > 70%, N < 7 (oktas) and V < 6 m/s.

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Determining dew and hoar frost formation for a low mountain range and alpine grassland site by weighable lysimeter

Cited by 63 publications

References 64 publications

Quantification and Prediction of Nighttime Evapotranspiration for Two Distinct Grassland Ecosystems

Quantification and Prediction of Nighttime Evapotranspiration for Two Distinct Grassland Ecosystems

Terrestrial water loss at night: global relevance from observations and climate models

Dew Yield and Its Influencing Factors at the Western Edge of Gurbantunggut Desert, China

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