scholarly journals Water in a warmer world – is atmospheric evaporative demand changing in viticultural areas?

2019 ◽  
Vol 12 ◽  
pp. 01011
Author(s):  
H.R. Schultz

The predicted developments in climate are region-specific and adaptation can only be successful considering the regional characteristics with its diverse technical, environmental, economic and social implications. One of the key concerns for many regions is the availability of water through precipitation, the distribution of precipitation throughout the year, and possible changes in evaporative demand of the atmosphere and thus water use. From rising temperatures it is mostly assumed that water holding capacity of the atmosphere will increase in the future as a function of the Clausius-Clapeyron law, which predicts an increase in the saturation vapour pressure of the atmosphere of 6–7% per degree Celsius. As a consequence, a simultaneous increase in potential evapotranspiration (ETp, the amount of water that could potentially be evaporated from soils and transpired by plants due to changes in climatic factors such as temperature, vapour pressure deficit, radiation and wind speed) is assumed in many cases, which would alter soil and plant water relations. However, the same underlying principles also predict an increase in precipitation by 1–2% per degree warming. Additionally, model predictions for many regions forecast altered precipitation patterns and thus in combination with the possibility of increased ETp, farmers around the world fear an increase in the likelyhood of water deficit and a reduction in the availability of water for irrigation. Contrary to expectations, there have been reports on a reduction in evaporative demand worldwide despite increasing temperatures. In many cases this has been related to a decrease in solar radiation observed for many areas on earth including wine growing regions in Europe until the beginning of the 80th (global dimming) of the last century. However, since then, solar radiation has increased again, but ETp did not always follow and a worldwide decrease in wind speed and pan evaporation has been observed. In order to evaluate different grape growing regions with respect to observed changes on precipitation patterns and ETp, the data of seven wine-growing areas in five countries in the Northern and Southern hemisphere across a large climatic trans-sect were analyzed (Rheingau, Germany, Burgundy, Rhone Valley, France, Napa Valley, USA, Adelaide Hills, Tasmania, Australia, Marlborough, New Zealand) were analyzed. Precipitation patterns differed vastly between locations and showed very different trends over observation periods ranging from 23 to 60 years. The ETp has increased continuously in only two of the seven wine growing areas (Rheingau and Marlborough). In most other areas, ETp has been stable during winter and summer for at least 22 years (Rhone Valley, Napa Valley, Tasmania), sometimes much longer (45 years Adelaide Hills), and has been declining in Burgundy after a period of strong increase for the last 13 years. The potential underlying factors are discussed in relation to observed shifts in precipitation patterns.

2021 ◽  
Vol 53 (2) ◽  
pp. 182-199
Author(s):  
Rusmawan Suwarman ◽  
Novitasari Novitasari ◽  
I Dewa Gede Agung Junnaedhi

This study aims to understand the characteristic of evaporation and to evaluate the evaporation estimation methods to be employed in Bandung by using observation data at three different land cover characteristics sites, namely, densely vegetated area (Baleendah), densely built-up area (Ujung Berung), and mix of buildings and vegetation area (ITB). Observation data used are hourly evaporation, vapour pressure deficit, temperature, relative humidity, wind speed, and radiation. The analysis was done mostly by using statistical methods such as regression analysis and error comparison. The result shows the dominant weather factor affecting the evaporation in ITB and Ujung Berung is vapour pressure deficit, and in Baleendah is solar radiation. The methods of evaporation estimations used in this study are Trabert, Schendel, Turc, and CIMIS-Penman methods. The result shows that the original constant values of those methods are significantly correlated. However, the Schendel is found the most overestimated, and the second is Turc. The best estimated evaporation in Baleendah, ITB, and Ujung Berung is calculated using CIMIS-Penman with one hour lag of radiation, Trabert, and Calibrated Schendel, respectively. The improvement of constant value was applied to Schendel and the result is better than the original constants.


2021 ◽  
Vol 53 (2) ◽  
pp. 182-199
Author(s):  
Rusmawan Suwarman ◽  
I Dewa Gede Agung Junnaedhi ◽  
Novitasari Novitasari

This study aims to understand the characteristic of evaporation and to evaluate the evaporation estimation methods to be employed in Bandung by using observation data at three different land cover characteristics sites, namely, densely vegetated area (Baleendah), densely built-up area (Ujung Berung), and mix of buildings and vegetation area (ITB). Observation data used are hourly evaporation, vapour pressure deficit, temperature, relative humidity, wind speed, and radiation. The analysis was done mostly by using statistical methods such as regression analysis and error comparison. The result shows the dominant weather factor affecting the evaporation in ITB and Ujung Berung is vapour pressure deficit, and in Baleendah is solar radiation. The methods of evaporation estimations used in this study are Trabert, Schendel, Turc, and CIMIS-Penman methods. The result shows that the original constant values of those methods are significantly correlated. However, the Schendel is found the most overestimated, and the second is Turc. The best estimated evaporation in Baleendah, ITB, and Ujung Berung is calculated using CIMIS-Penman with one hour lag of radiation, Trabert, and Calibrated Schendel, respectively. The improvement of constant value was applied to Schendel and the result is better than the original constants.


1979 ◽  
Vol 27 (2) ◽  
pp. 251 ◽  
Author(s):  
MM Campbell ◽  
DS Kettle

Numbers of C. brevitarsis on cattle in south-east Queensland increased rapidly from zero at 0.5 h before sunset, to a peak during the half hour after sunset, then decreased to zero in the following 5-6 h and remained at zero throughout the day. On standing animals abundance was greatest on the ridgeline at the tail, decreasing rapidly down the flank and less rapidly towards the head. On mature animals abundance after sunset halved with each increase of 0.53 m s-1 in wind speed, each increase of 6.4�C, each decrease of 158 Pa vapour pressure deficit, and each additional 38 min after sunset. Only females were collected from cattle; 97% of nullipars were mated. They did not always feed at their first attempt and were much less likely to feed on some hosts than others. Close shaving did not alter the number of flies on small areas and did not prevent feeding. Before sunset C. brevitarsis were observed more frequently on hosts in the absence of direct sunlight. In direct sunlight, abundance was influenced most by wind speed (positive), minutes before sunset (negative) and temperature (negative), in order of decreasing importance. Without direct sunlight, the factors were minutes before sunset (negative), temperature (positive), and wind speed (negative); after sunset the factors were wind speed (negative), vapour pressure deficit (positive), minutes after sunset (negative) and minor effects from time of year and temperature.


1993 ◽  
Vol 171 (5) ◽  
pp. 336-342 ◽  
Author(s):  
V. Bala Subramanian ◽  
S. Venkateswarlu ◽  
M. Maheswari ◽  
M. Narayana Reddy

1998 ◽  
Vol 16 (4) ◽  
pp. 470-476 ◽  
Author(s):  
A. Sellin

Abstract. Where there is sufficient water storage in the soil the water potential (Ψx) in shoots of Norway spruce [Picea abies (L.) Karst.] is strongly governed by the vapour pressure deficit of the atmosphere, while the mean minimum values of Ψx usually do not drop below –1.5 MPa under meteorological conditions in Estonia. If the base water potential (Ψb) is above –0.62 MPa, the principal factor causing water deficiency in shoots of P. abies may be either limited soil water reserves or atmospheric evaporative demand depending on the current level of the vapour pressure deficit. As the soil dries the stomatal control becomes more efficient in preventing water losses from the foliage, and the leaf water status, in turn, less sensitive to atmospheric demand. Under drought conditions, if Ψb falls below –0.62 MPa, the trees' water stress is mainly caused by low soil water availability. Further declines in the shoot water potential (below –1.5 MPa) can be attributed primarily to further decreases in the soil water, i.e. to the static water stress.Key words. Hydrology (evapotranspiration · plant ecology · soil moisture).


1997 ◽  
Vol 24 (3) ◽  
pp. 381 ◽  
Author(s):  
João P. Maroco ◽  
João S. Pereira ◽  
M. Manuela Chaves

Stomatal response to leaf-to-air vapour pressure deficit (LAVPD) was studied in the annual arid zone C4 grasses Schoenefeldia gracilis, Dactyloctenium aegyptium and Eragrostis tremula and in the C3 species, convolvulus, Ipomoea pes-tigridis and Ipomoea vagans. Stomatal responses to LAVPD were consistent with the drought survival strategies adopted by the different species. In drought resistant species (S. gracilis, I. vagansand I. pes-tigridis) stomatal conductance showed a negative response to increasing LAVPD whereas, in drought escaping species (D. aegyptium and E. tremula), stomatal conductance was independent of LAVPD. These observations suggest that resistance to drought was associated with stomatal closure as LAVPD increased, thus reducing the negative effect of a higher evaporative demand on water use efficiency, whereas in drought escaping species stomata showed no response to increasing evaporative demand in the atmosphere.


2004 ◽  
Vol 55 (9) ◽  
pp. 931 ◽  
Author(s):  
Youssef Rouphael ◽  
Giuseppe Colla

In Mediterranean climates, high temperatures and vapour pressure deficits are currently observed in greenhouses during summer. These conditions are responsible for a high transpiration rate leading to greater water consumption. Measuring and modelling transpiration can be useful for efficient irrigation management by allowing prediction of short-term water demand. The rate of transpiration of zucchini crops (Cucurbita pepo L.) grown in soilless culture was measured in a greenhouse located at Viterbo, central Italy, during spring–summer 2002. The Penman-Monteith equation was used to predict the potential transpiration of the plants averaged over 30-min intervals using different approaches in the calculation of aerodynamic resistance. The values obtained were compared with transpiration measured by a gravimetric method by weighing plants on an electronic balance. Leaf temperature was lower (up to 5°C) than air temperature on clear summer days owing to high transpiration rates. Stomatal resistance was computed and found to be exponentially related to solar radiation. The best fit in transpiration between the Penman-Monteith calculated and those measured was achieved when the heat transfer in the former was obtained as a process of mixed convection, where the slope of the regression was 1, and there was improvement of the coefficient of determination (R2 = 0.96). A simplified model of daytime transpiration based on easily measured variables (solar radiation and vapour pressure deficit) was developed and produced strong agreement with the gravimetric method (R2 = 0.93).


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