Dew amounts and its correlations with meteorological factors in urban landscapes of Guangzhou, China

Atmospheric Research 86 (2007) 21 – 29 www.elsevier.com/locate/atmos

Dew amounts and its correlations with meteorological factors in urban landscapes of Guangzhou, China Youhua Ye a , Kai Zhou b , Liying Song a , Jianhua Jin a , Shaolin Peng a,⁎ a

State Key Laboratory of Biocontrol/School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China b South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China Received 23 August 2006; received in revised form 10 February 2007; accepted 7 March 2007

Abstract The aim of this study was to investigate dew amounts in different urban landscapes and to examine the correlations between dew amounts and meteorological factors in Guangzhou, China. Results indicated that the dew amounts at fine night were different from landscapes to landscapes. A significant difference was found in average dew amounts between forest landscape and residential landscape (forest landscape and commercial landscape, industrial landscape and residential landscape). The highest mean dew amounts in urban area were observed in forest landscape (0.034 mm night− 1), followed by industrial landscape (0.022 mm night− 1), commercial landscape (0.013 mm night− 1) and residential landscape (0.009 mm night− 1), respectively. For maximum dew amounts, a similar relationship like the mean dew mounts was found in urban measured landscapes, whose values in turn were 0.104 mm, 0.08 mm, 0.03 mm and 0.109 mm, respectively. Both the mean dew amounts night− 1 and maximum dew amounts in urban landscapes were significantly less than those (0.077 mm in mean value and 0.224 mm in maximum value) in their countryside. The mean dew amounts correlated positively with mean relative humidity; meanwhile it correlated negatively with daily evaporation and urban heat island, respectively. It was therefore concluded that urban forest landscape was an important site for dew deposit, urban environment was not favorable for dew condensation, and relative humidity, daily evaporation and urban heat island might be the most important three meteorological factors responsible for the dew amounts in urban area. © 2007 Elsevier B.V. All rights reserved. Keywords: Urban dew; Dew amounts; Urban landscapes; Meteorological factors

1. Introduction Dew is the condensation of water vapor on a surface, whose temperature is reduced by radiate cooling to below the dew point of the clear air in contact with it (WMO, 1966; HMSO, 1991). It is important and helpful for plants and animals (Stone, 1957a,b; Wallin, 1967; Jacobs et al., 1999; Liu et al., 2001; Li, 2002), and is a key limiting ⁎ Corresponding author. Tel.: +86 20 84039571; fax: +86 20 84115356. E-mail address: [email protected] (S. Peng). 0169-8095/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.atmosres.2007.03.001

factor in arid and semi-arid ecosystem (Malek et al., 1999; Kidron, 1999, 2000; Ninari and Berliner, 2002). Most observations and simulations of dew were carried out in rural area (Richards, 2004; Ye et al., 2006), while urban dew, a potential source of water, was often neglected (Beysens, 1995) and has rarely been reported. However, it is also necessary and important for urban vegetation system and urban ecological environment, especially in arid season or dry months with less fresh water. Previous researches on urban dew mainly focused on the analysis of its chemical components and amino acids, model construction of its ecological process, and

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simulation (Yaalon and Ganor, 1968; Nikolayev et al., 1996, 2001; Jiries, 2001; Takeuchi et al., 2001, 2002; Muselli et al., 2002; Richards, 2002; Pitelli and Amorim, 2003), while only a few observations focused on urban dew amounts (Monteith, 1963; Garratt and Segal, 1988; Chiwa et al., 2003; Richards, 2002, 2004, 2005). Due to the fact that only a few researches addressed urban dew, the impact factors for dew amounts were still not clear. Meanwhile, seldom researches have referred to the effect of different landscapes on dew. Studies on dew amounts in different urban landscapes and their correlations with meteorological factors are essential for understanding the ecological effect of urban dew. Therefore, the objective of this study is to quantify the dew amounts in urban landscapes including residential landscape, commercial landscape, industrial landscape and forest landscape, and to examine the relationships between dew amounts and some meteorological factors. 2. Materials and methods 2.1. Study site Guangzhou (112°57′–114°3′E, 22°26′–23°56′N) lies at the north of Pearl River delta area. It is an important political, economical and cultural center in

South China, with a population of 8.99 million and a total area of 3718.5 km2 in urban area. It has a subtropical oceanic monsoon climate with an average annual temperature of 21.7–22.9 °C, an annual average precipitation ranges from 1385.5 mm to 1619.5 mm (Guangzhou Statistical Bureau, 2005). 2.2. Methodology In order to quantify the dew amounts in urban area, Zhongda residential landscape (ZRL), Tianhe commercial landscape (TCL), Fangcun industrial landscape (FIL) and Baiyunshan forest landscape (BFL) were chosen as a representative of urban residential landscape, commercial landscape, industrial landscape and forest landscape, respectively. Conghua landscape (CCL), a country of Guangzhou city, was chosen as a contrast of urban landscapes. The detailed characteristics of the landscapes were presented in Table 1. Dew sample collections were performed on lawn in all landscapes except BFL where the collecting site was set on the canopy of the forest. Dew collection was started in early August and ended in early November for the following two reasons. Firstly, previous information suggested that most dew events occurred in late summer and early autumn (Li and Liu, 2001). Secondly, the climate data of Guangzhou from

Table 1 Characteristics of all measured landscapes in Guangzhou Landscapes

Mean T Mean RH Mean UHI Mean E Mean WS Substrates (°C) (%) (°C) (mm) (m/s)

Others

Zhongda residential landscape (ZRL) Tianhe commercial landscape (TCL) Fangcun industrial landscape (FIL) Baiyunshan forest landscape (BFL) Conghua countryside landscape (CCL)

26.2

69

2.0

5.0

0.8

26.5

70

2.8

5.5

0.9

25.0

75

0.6

4.9

1.7

25.8

76

0.8

3.1

0.7

With a total area of 21.98 km2; sub-tropic evergreen broad leafed forest

North of Guangzhou; 100 m above the sea level

25.3

84

0.0

3.2

1.0

High vegetation coverage rate and low concrete surface, mass farmland

50 km far from the city in the northeast of Guangzhou city

Alternate lawn, trees, and paved road around the Buildings in 6–7 m buildings; low vegetation coverage rate and high interval and over 60 m concrete surface, especially in TCL; no stable height water area Prosperous commercial belts; buildings stand in great number Traditional industrial area with lots of factories

T—nocturnal temperature; RH—nocturnal relative humidity; UHI—nocturnal urban heat island; E—daily evaporation; WS—nocturnal wind speed. The data in the table were measured during the collecting period.

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1996–2004 (offered by Guangdong Meteorological Bureau, China) showed that dew events occurred mainly from July to November with the number of dewy days amount to more than 50% in a month. There are no standard internationally methods or instruments for measuring dew amounts so far (Zangvil, 1996; Li, 2002; Richards, 2004). Optical sensor, lysimeter, mini-lysimeter, glass fiber, polyethylene plastic, filter paper and cloth-method and others were used to evaluate dew (Popov et al., 1996; Grimmond et al., 1992; Takeuchi et al., 2001; Kidron, 2005; Yan et al., 2004). For this experiment, we chose to measure dew amounts using cloth-plate method (Kidron, 1998). This method has been used to measure dew amounts in semi-arid area and was proved to be appropriate (Kidron, 1998, 1999, 2000, 2005; Kidron et al., 2000, 2002). The materials used in this experiment include plywood (100 × 100 × 0.5 cm, the size of length, width and height, the same meaning as follow), synthetic velvet cloth (100 × 90 × 0.15 cm), polyethylene plate (100 × 100 × 0.05 cm), polyethylene bottles and 15 cm height stakes. Compared to Kidron's method, the height of the setting and the collecting material were changed in this experiment. Artificial surface with 0.7 cm height in cloth-plate method sounded favorable, but in order to obey the rule of urban management and protect the lawn, we had to choose about 15 cm height to collect dew. Glass is an ideal material for the formation of dew, but the substrates in urban area are not covered by glass, so we chose “cloth + polyethylene plate” surface. This artificial surface is therefore more close to the real surface than “cloth + glass” surface to some extent. The cloths were attached to polyethylene plate affixed on the plywood (polyethylene plate face to the sky) half an hour after sunset in the evening, and were collected half an hour before sunrise early the next morning at different sites synchronously. This strict collecting time has been used by some experts (Yan et al., 2004), and it could insure that most of dew condensed at night was collected. Once collected, the cloths were transferred to separate pre-weighed polyethylene bottles and sealed immediately, and then weighed as soon as possible by Electronic Balance (Guangzhou Pubo instrument Co., Ltd., China) with an accuracy of about ± 0.1 g m− 2 in a nearby laboratory. Mass data were later converted to units of mm depth (accuracy = ± 0.0001 mm night− 1), so that they could be coherent with the unit of rainfall and evaporation. Per millimeter dew amounts equal to 1 l dew amounts per square meter. The dew amounts night− 1 showed in this paper meant the dew amounts condensed on per square centimeter.

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In all measured landscapes, surface air temperature (T) and relative humidity (RH) were measured using a ZJ1-2A auto-recording hygrothermograph (accuracy = ±0.1 °C and ±5% RH) (Shanghai Meteorological Instrument Factory Co., Ltd., China), and wind speed (WS) was measured using a FYF-1, a portable auto-recording wind detecting instrument (accuracy = 0.1 m/s) (Shanghai Fengyun Meteorological Instrument Management Factory, China). The three parameters were measured at 1.5 m height above the lawn from eighteen o'clock in the evening to 6 o'clock early next morning. Hourly data of T and RH, and two-hourly data of WS were obtained. The mean value of T, RH, and WS was used in this paper. Evaporation (E) was measured using an AM3 pan (a rarefied steel pan in 20 cm diameter) (Shanghai Meteorological Instrument Factory Co., Ltd., China) in all landscapes at 0.7 m height from 6 o'clock in the day time to 6 o'clock early next morning. The value of evaporation could be expressed as: E ¼ PW þ RF  LW; where E was the daily evaporation, PW was the poured clean water (20 mm), RF was the concurrent rainfall (rainfall was measure by an ombrometer, RF was zero when no rain event occurred), and LW was the left water in the pan after a day. All terms in the equation had the same unit (mm). Urban heat island (UHI), a very popular phenomenon in urban area, was chosen as a parameter to assess its effect on dew amounts. According to the definition of UHI from Kim and Baik (2004), UHI could be expressed as: UHI ¼ Tu  Tc ; where UHI was the mean urban heat island, Tu was the mean temperature of the measured urban landscapes, and Tc was the mean temperature of Conghua countryside. 2.3. Statistical analysis In this paper, dewy days with rain and fog (a time characterized by b1000 m visibility, lasting for at least half an hour, was recorded as foggy time) were not calculated for the following three reasons. Shower and the foggy events that occurred at landscapes were different for the influence of urban regional climate. Urban dew is much small, and it is difficult to distinguish dew from rain and fog. Dew amounts were measured during the whole night not hour by hour. One should note that some dewy events would be ignored based on above mentioned statistic method, which

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consequently affected the number of dew days as well as the maximum dew amounts. Therefore, the results in this paper only reflected the dew events at fine night. Abundance data of dew amounts in urban landscapes and their surrounding countryside were evaluated by oneway analysis of variance (ANOVA) and LSD multiple comparison at 0.01 and 0.05level. The correlations between dew amounts and all measured factors were determined by

Regression Analysis. All statistical analyses were performed using SPSS 11.5 software package (SPSS Inc, USA). 3. Results The fine night dew amounts at each landscape were shown in Fig. 1. Comparison of mean and maximum dew amounts measured at each landscape was showed

Fig. 1. Dewy days and the dew amounts during the collecting period at landscapes of Guangzhou (ZRL: Zhongda residential landscape; BFL: Baiyunshan forest landscape; TCL: Tianhe commercial landscape; FIL: Fangcun industrial landscape; CCL: Conghua countryside landscape).

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evaporation were negatively related to dew amounts, respectively (p b 0.0001) (Fig. 3c and e). In addition, no significant relationships were found between dew amounts and temperature as well as wind speed, respectively (p N 0.05) (Fig. 3b and d). 4. Discussions

Fig. 2. Mean and maximum dew amounts condensed at landscapes of Guangzhou. CCL: Conghua countryside landscape; BFL: Baiyunshan forest landscape; FIL: Fangcun industrial landscape; TCL: Tianhe commercial landscape; ZRL: Zhongda residential landscape. Similar letters indicate non-significant differences while different letters indicated significant differences between landscapes. Bars represent one standard error.

in Fig. 2. Thirty-seven dewy days were obtained in FIL, TCL, and BFL, while forty-six dewy days and fortynine dewy days were observed in ZRL and CCL, respectively. The average dew amounts night− 1 for BFL, FIL, TCL and ZRL were 0.034 mm, 0.022 mm, 0.013 mm and 0.009 mm, respectively, and the maximum dew amounts were 0.104 mm in BFL, 0.08 mm in FIL, 0.03 mm in TCL and 0.019 mm in ZRL. Based on the mean and maximum values measured at urban landscapes, the highest dew value was found in BFL, followed by FIL, TCL and ZRL, respectively. Significant differences in mean dew amounts night− 1 were found between ZRL and FIL (BFL and ZRL, BFL and TCL) (Fig. 2). Theses results implied that, urban forest landscape was an important site for dew deposit in urban area. Significant differences (p b 0.05) characterized urban landscapes and the countryside, with the former receiving a mean dew amounts night− 1 no more than 0.034 mm (maximum dew amounts no more than 0.104 mm) as compared to the mean dew amounts of 0.077 mm (maximum dew amounts of 0.224 mm) of the latter (Figs. 1 and 2). These data demonstrated that it was more difficult for dew to condense in urban area than in the countryside, and urban environment was not favorable for dew condensation. Relationships between dew amounts and meteorological factors measured in urban area were shown in Fig. 3. It was found that there was a positive correlation between dew amounts and nocturnal mean relative humidity (Fig. 3a), while nocturnal mean UHI and daily

Dew is a natural phenomenon, and its condensation is a natural physical process. Some experts have tried to discuss the formation process of dew in previous researches (Beysens, 1995; Li, 2002; Richards, 2005). Actually, the impact factors for dew amounts in city are complicated. Generally, the formation of dew is linked to aerodynamics and thermodynamics, especially the near surface meteorological parameters and surface properties. Our results showed that urban dew amounts would increase with the increasing relative humidity, which was consistent with other investigations (Zangvil, 1996; Liu et al., 1998). It is well known that, based on a certain air pressure, the air water vapor is related to the dew point, dew can form at a relative higher temperature if more water vapor is in surface air where a higher relative humidity could be evaluated. Though 100% relative humidity is not necessary for dew formation, a relative humidity of 91–99% would be favorable (Monteith, 1956; Liu et al., 1998). A result from Richards (2005) indicated that the depleted near-surface humidity in rural areas was attributed to nocturnal dew precipitation, while the small urban moisture excess observed on fine nights was linked to reduced urban dew, meaning that relative humidity is a quite important factor for dew. The differences in dew amounts between landscapes could be explained by the differences of relative humidity. For example, the mean dew amounts were higher in BFL (0.034 mm) than in TCL (0.013 mm) and in ZRL (0.009 mm), which might be attributed to higher relative humidity in BFL (76%) than in TCL (70%) and in ZRL (69%) (Table 1 and Fig. 2). The lower relative humidity might be an important reason for the smaller dew amounts in urban landscapes than in countryside landscape. Temperature or urban heat island may be expected as another kind of impact factors on dew. However, no significant relationships were found between dew amounts and temperature in present study. This result was not consistent with some previous researches (Hage, 1975; Ackerman, 1987), which demonstrated that dew was highly influenced by temperature. Some researches also indicated an absence, delay or reduction of dew in cities under the warmer temperature (Oke, 1987; Richards, 2004, 2005). There is an evident positive relationships between temperature and relative

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Fig. 3. Relationships between dew amounts and coherent nocturnal mean relative humidity (a), temperature (b), urban heat island (c), wind speed (d) and daily evaporation (e).

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humidity (Li and Liu, 2001; Richards, 2005), meaning that relative humidity or other factors might play a key role on the formation of dew from 23 °C to 27.5 °C (Fig. 3b). However, the associations between urban heat island and dew amounts indicated that higher temperature might influence the dew amounts through having an effect on humidity or evaporation or dew point or others. A situation with higher temperature or strong urban heat island may make the surface air retain a temperature higher than the dew point, and constraint the dew formation. Higher temperature would result in an increase of evaporation and a decrease of near surface relative humidity, and with a consequence of reduced dew precipitation. Some experts considered low temperature as an important parameter for the formation of dew (Monteith, 1956; Angus, 1958; Duvdevani, 1964; Li, 2002). As a matter of fact, the definition of dew indicates the importance effect of temperature on dew. Surface radiate cooling accelerates the condensation, but the radiation inversion and the heat transition may weaken the cooling and lead to a decrease of dew amounts. In our measured landscapes, the urban heat island in BFL (0.8 °C) and FIL (0.6 °C) was lower than those in ZRL (2.0 °C) and TCL (2.8 °C), respectively, which was coherent with the results that dew amounts condensed in BFL (0.034 mm) and FIL (0.022 mm) were higher than those in TCL (0.013 mm) and ZRL (0.009 mm) (Table 1 and Fig. 2). The mean dew amounts in the countryside (0.077 mm) were higher than those in urban measured landscapes (no more than 0.034 mm), which might partly be related to no urban heat island in the countryside. Therefore, urban heat island might be one of an important meteorological factor responsible for dew amounts. Most of dew events occurred at a wind speed below 2 m/s, but no significant relationships were found between dew amounts and wind speed in our research (Fig. 3d), which was consistent with Richards' (2004). However, other studies supported that the formation of dew benefited from light winds (Chen et al., 1993; Li and Liu, 2001). The function of wind for dew deposit is complicated. Wind is beneficial to enhance the transition of water vapor and heat in horizontal and vertical direction. On the process of wind which is a main factor for vapor diffusion, the near surface water vapor is supplemented and thus the probability of dew deposit increases. When wind is weak or even closed to zero, a boundary layer forms, the molecules of water diffuse over this quiet layer and hit randomly the droplet where they are incorporate, then a concentration gradient of water molecules forms around the drop (Beysens, 1995), and the volume of dew might accumulated. Due to the

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fact that surface long wave radiation makes a lower temperature in near surface air than its upper air, hence the heat transition or turbulence brought by wind may result in a symmetrical temperature between the near surface air and the upper air. The symmetrical temperature weakened the radiate cooling, and then the formation of dew is held back. Therefore, the result about dew and wind in present research is an integrated influence of wind. In addition, evaporation is also a non-neglected parameter. Previous research referred to the relationships between dew and evaporation is rare. Our results implied that the increasing evaporation did not facilitate the formation of dew. In urban measured landscapes, the dew amounts were higher in a relatively low evaporation situation than those in a relatively high evaporation situation. For example, BFL and CCL, whose evaporation were lower than other landscapes, had more dew amounts than other measured landscapes which was in agreement with the correlations between dew and evaporation (Table 1 and Fig. 2). Xu et al. (2006) found that evaporation was related to temperature which would accelerate evaporation, and consequently result in a decrease of dew. Meanwhile, there is a significant and negative relationships between evaporation and surface relative humidity (Zuo et al., 2006), meaning that the increasing evaporation will make the near surface relative humidity decrease, and eventually lead to a reduction of dew. Except the impact of meteorological factors, substrates may have an effect on the formation of dew. The temperature and wetting properties of the substrate are two key parameters which can control dew and these two factors can be easily changed by treatment (Beysens, 1995). For example, trees and lawn make for an increase of near surface water vapor and a decrease of absorbed sun radiation, which would be helpful for the formation of dew. Water area or farmland could provide water vapor directly and benefit the formation of dew. Concrete surface will result in an increase of near surface air temperature for absorbing mass sun radiation, and then has a negative effect on dew. On the canopy of urban forest landscape, the water vapor was higher than that in other urban landscapes for mass transpiration from forest plants. In addition, the velocity of radiate cooling at forest landscape is bigger than that at other urban landscapes. More dew formed with the increasing water vapor and radiate cooling. Though the vegetation coverage rate In ZRL was slightly higher than that in FIL and TCL, dew amounts condensed in ZRL were less than that in FIL and TCL, especially in FIL. It might be related to mass sprinkling irrigation in FIL. In order to make the dust which loaded on and in the

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surface dissolve in water and flow through the cloacae, mass sprinkling irrigation was performed by the management department. With this measurement carried out, not only the dust and the temperature decreased, but also the water vapor and the dew mounts increased. In TCL, the concrete surface was larger than that in other urban landscapes, which absorbed more sun radiation than any kinds of surfaces. The sun radiation, together with mass energy released by human activities, heats the near surface air, increases the surface evaporation, and consequently induces a decrease of dew amounts. On the contrary, the substrate was not destroyed by human being in the countryside. The number of trees and the areas of lawn was bigger in the countryside than those in urban landscapes. Besides, there exist lots of farmlands near the sample collecting site. These surfaces are very important reason for more dew condensed in the countryside than in urban landscapes. 5. Conclusion The dew amounts in urban area were different from landscapes to landscapes. The highest dew amounts were observed in urban forest, followed by industrial landscape, commercial landscape and residential landscape, respectively. Urban dew amounts were significantly less than those in the countryside. There existed a positive correlation between dew amounts and mean relative humidity, while mean urban heat island and daily evaporation were negatively related to mean dew amounts, respectively. It was therefore concluded that urban forest landscape was an important site for dew deposit, urban environment was not favorable for dew condensation, and relative humidity, daily evaporation and urban heat island might be the most important three meteorological factors responsible for the dew amounts in urban area. Our experiment was performed in a metropolis of low sub-tropic delta area, if nearby cities have similar results are not clear. Due to the fact that our research only addressed the dew amounts at fine night, hence this result cannot be applied in other time. More researches on urban dew amounts in other time and other landscapes are valuable. Besides, the quantity of dew was also linked to collecting methodology, different dew amounts may be presented under different types of dew collectors, so more methods should be attempted to use to measure urban dew amounts in further researches. Acknowledgements This study was supported by National Natural Science Foundation of China (30670385 and 40672017), the Key

Program of Ministry of Education of China (403037) and the Scientific Research Fund, Hongda Zhang, Sun Yat-sen University. The authors would like to thank Wang Bo-sun, Zhang Hai-qing, Chen Bao-ming, Li Jin-tian, Luo Lian and Li Huang-di for their advice in writing. Special thanks are owed to reviewers for their encouragement and fruitful suggestions to the improvement of the manuscript. References Ackerman, B., 1987. Climatology of Chicago area urban–rural differences in humidity. J. Clim. Appl. Meteorol. 26, 427–430. Angus, D.E., 1958. Measurements of dew. Arid Zone Res. II, 301–303. Beysens, D., 1995. The formation of dew. Atmos. Res. 39, 215–237. Chen, S.X., Chen, C.M., Lin, Y.H., 1993. Meteorology. Sun Yat-sen University Press, Guangzhou, pp. 219–223 (in Chinese). Chiwa, M., Oshiro, N., Miyake, T., et al., 2003. Dry deposition washoff and dew on the surfaces of pine foliage on the urban- and mountain-facing sides of Mt. Gokurakuji, western Japan. Atmos. Environ. 37, 327–337. Duvdevani, S., 1964. Dew in Israel and its effect on plants. Soil Sci. 2, 14–21. Garratt, J.R., Segal, M., 1988. On the contribution of atmospheric moisture to dew formation. Boundary - Layer Meteorol. 45, 209–236. Grimmond, C.S.B., Isard, S.A., Belding, M.J., 1992. Development and evaluation of continuously weighing mini-lysimeters. Agric. For. Meteorol. 62, 205–218. Guangzhou Statistical Bureau, 2005. Guangzhou Statistical Yearbook. Guangzhou Statistical Bureau Press, Guangzhou, pp. 175–191 (in Chinese). Hage, K.D., 1975. Urban–rural humidity differences. J. Appl. Meteorol. 14, 1277–1283. HMSO, 1991. Meteorological Glossary. Meteorological Office, HMSO, London, p. 335. Jacobs, A.F.G., Heusinkveld, B.G., Berkowicz, S.M., 1999. Dew deposition and drying in a desert system: a simple simulation model. J. Arid Envion. 42, 211–222. Jiries, A., 2001. Chemical composition of dew in Amman, Jordan. Atmos. Res. 57, 261–268. Kidron, G.J., 1998. A simple weighing method for dew and fog measurements. Weather 53, 428–433. Kidron, G.J., 1999. Altitude dependent dew and fog in the Negev Desert, Israel. Agric. For. Meteorol. 96, 1–8. Kidron, G.J., 2000. Analysis of dew precipitation in three habitats within a small arid drainage within a small arid drainage basin, Negev Highlands, Israel. Atmos. Res. 55, 257–270. Kidron, G.J., 2005. Angle and aspect dependent dew and fog precipitation in the Negev desert. J. Hydrol. 301, 66–74. Kidron, G.J., Yair, A., Danin, A., 2000. Dew variability within a small arid drainage basin in the Negev Highlands, Israel. Q. J. R. Meteorol. Soc. 126, 63–80. Kidron, G.J., Herrnstadt, Ilana, Barzilay, Eldad, 2002. The role of dew as a moisture source for sand microbiotic crusts in the Negev Desert, Israel. J. Arid Environ. 52, 517–533. Kim, Y.H., Baik, J.J., 2004. Daily maximum urban heat island intensity in large cities of Korea. Theor. Appl. Climatol. 79 (3–4), 151–164. Li, X.Y., 2002. Effect of gravel and sand mulches on dew deposition in the semiarid region of China. J. Hydrol. 260, 151–160. Li, A.Z., Liu, H.F., 2001. Climatology and Basic Climatology. China Meteorological Press, Beijing, p. 89 (in Chinese).

Y. Ye et al. / Atmospheric Research 86 (2007) 21–29 Liu, W.J., Li, H.M., Duan, W.P., 1998. An analysis of the dew resource in the xishuangbanna area. J. Nat. Resour. 1, 40–45 (in Chinese). Liu, W.J., Zeng, J.M., Wang, C.M., Li, H.M., Duang, W.P., 2001. On the relationship between forests and occult precipitation (dew and fog precipitation). J. Nat. Resour. 16, 571–575 (in Chinese). Malek, E., McCurdy, G., Giles, B., 1999. Dew contribution to the annual water balances in semi-arid desert valleys. J. Arid Environ. 42, 71–80. Monteith, J.L., 1956. Dew. Q. J. R. Meteorol. Soc. 42, 572–580. Monteith, J.L., 1963. Dew: facts and fallacies. In: Rutter, A.J., Witehead, F.H. (Eds.), The Water Relations of Plants. John Wiley and Sons, New York, pp. 37–56. Muselli, M., Beysens, D., Marcillat, J., et al., 2002. Dew water collector for potable water in Ajaccio (Corsica Island, France). Atmos. Res. 64, 297–312. Nikolayev, V.S., Beysens, D., Gioda, A., et al., 1996. Water recovery from dew. J. Hydrol. 182, 19–35. Nikolayev, V.S., Beysens, D., Muselli, M., 2001. A computer model for assessing dew/frost surface deposition. Proceedings of the 2nd International Conference on Fog and Fog Collection, St John's (Canada), 16–20 July, 2001. The developed interactive computer applications are available from http://www.opur.ubordeaux.fr. Ninari, N., Berliner, P.R., 2002. The role of dew in the water and heat balance of bare loess soil in the Negev Desert: quantifying the actual dew deposition on the soil surface. Atmos. Res. 64, 323–334. Oke, T.R., 1987. Boundary Layer Climates. Routledge, London. Pitelli, R.L.C.M., Amorim, L., 2003. Effects of different dew periods and temperatures on infection of Senna obtusifolia by a Brazilian isolate of Alternaria cassiae. Biol. Control 28, 237–242. Popov, P., Sainov, S., Baeva, M., 1996. Sens. Actuators 51, 199–202. Richards, K., 2002. Hardware scale modelling of summertime patterns of urban dew and surface moisture in Vancouver, BC, Canada. Atmos. Res. 64, 313–321. Richards, K., 2004. Observation and simulation of dew in rural and urban environments. Prog. Phys. Geogr. 28, 76–94.

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Richards, K., 2005. Urban and Rural dewfall, surface moisture, and humidity measurements for Vancouver, Canada. Boundary - Layer Meteorol. 114, 143–163. Stone, E.C., 1957a. Dew as an ecological factor. I. A review of the literature. Ecology 38, 407–413. Stone, E.C., 1957b. Dew as an ecological factor. II. The effects of artificial dew on the survival of Pinus Ponderosa and associated species. Ecology 38, 414–422. Takeuchi, M., Okochi, H., Igawa, M., 2001. Dominant factors of major and minor components and formation of hydroxyl alkane sulfonatein urban dew water. Water Air Soil Pollut. 130, 613–618. Takeuchi, M., Okochi, H., Igawa, M., 2002. Controlling factors of weak acid and base concentrations in urban dew water— comparison of dew chemistry with rain and fog chemistry. Bull. Chem. Soc. Jpn. 75, 757–764. Wallin, G.B., 1967. Agrometeorological aspects of dew. Agric. Meteorol. 4, 85–102. WMO, 1966. International Meteorological Vocabulary. World Meteorological Organization, Geneva, p. 276. Xu, F.M., Yu, W.D., Tang, S.J., et al., 2006. Relationships of the latest 44 years between evaporation and the changing climate in ShangQiu City. Meteorol. J. Henan. 3, 48–49 (in Chinese). Yaalon, D.H., Ganor, E., 1968. Chemical composition of dew and dry fallout in Jerusalem, Israel. Nature 217, 1139–1140. Yan, B.X., Wang, Y.Y., Xu, Z.G., et al., 2004. Study on the dew condensation in the marsh ecosystem in Sangjiang Plain. Wetland Sci. 2, 94–99 (in Chinese). Ye, Y.H., Zhou, K., Li, H.D., et al., 2006. Research advances in urban dew and its ecological effect. Chin. J. Ecol. 25 (12), 1570–1573 (in Chinese). Zangvil, A., 1996. Six years of dew observations in the Negev Desert, Israel. J. Arid Environ. 3, 361–371. Zuo, H.C., Bao, Y., Zhang, C.J., et al., 2006. An analytic and numerical study on the physical meaning of pan evaporation and its trend in recent 40 years. Chin. J. Geophys. 49 (3), 680–688.