The interactions between airflow and trees and forest stands are diverse. They include the reduction in nearsurface wind speed and production of turbulence by trees. Near-surface wind conditions affect physiological processes in trees, tree growth, and survival (Ennos 1997; Eugster 2008). Turbulent components of the flow field dominate the tree response behaviour (Mayer 1987; Gardiner 1995; Schindler et al. 2010) and drive the scalar exchange at the forest–atmosphere interface (Finnigan 2000). Wind–tree interactions take place at a wide range of temporal and spatial scales (de Langre 2008). Aerodynamic drag at all surfaces of the aerial parts of trees—from individual leaves (Vogel 1989) to whole tree crowns (Kane et al. 2008)—perturbs the airflow inside forest canopies (Shaw et al. 1974; Baldocchi and Meyers 1988; Turnipseed et al. 2003). Therefore, detailed information on forest structure is an essential precondition for understanding wind–tree interactions and the successful application of flow models to tall canopies. In flow models, forest structure is often represented by the mean vertical profile of the plant area density. Queck et al. (2011, this issue) present a method that can be used to record detailed 3D stand structure from terrestrial laser scanning. They investigated the relationship between wind speed, aerodynamic drag, and plant area density and show how 3D laser scanner data can be used to derive turbulence parameters for flow models. The structure of windward forest edges (Mitscherlich 1973; Dupont and Brunet 2008a, b) as well as the stand structure (Gardiner et al. 1997; Marcolla et al. 2003; Dupont and Brunet 2008b, c; Queck and Bernhofer 2010) affects the flow field within and above forests. In the nearedge region, pronounced gradients of flow quantities provoke high wind load on trees (Stacey et al. 1994; Peltola 1996; Gardiner et al. 1997), which may trigger damage in strong wind conditions. Although Gardiner and Stacey (1996) as well as Dupont and Brunet (2008a) report that tapered forest edges reduce wind loading and related bending moments of trees near the edge, it is still not completely clear, how changes in edge and stand structure affect the flow field at the canopy near forest edges, and whether these changes can contribute to the mitigation of damage in high wind conditions. In a detailed wind tunnel study, Ruck et al. (2011, this issue) investigated the effect of changes in taper angle of windward forest edges on the flow field for different stand densities. Their results demonstrate the impact of edge shape and stand density on quantities of the flow field near the canopy top, the region most relevant for tree failure in strong wind conditions. The aerial parts of trees start to vibrate in response to wind excitation (Sellier and Fourcaud 2005; Rodriguez et al. 2008). In forests, dynamic tree responses are not only observed at the single tree level (Mayer 1987; Gardiner 1995; Peltola 1996; Flesch and Wilson 1999; Rudnicki et al. 2008; Schindler et al. 2010) but also at the tree group level (Rudnicki et al. 2001, 2003; Schindler et al. 2011, this issue). At both levels, the resulting tree response patterns are complex and complicated. So far, even in horizontally homogeneous terrain, not all physical and biological This article belongs to the special issue ‘Wind Effects on Trees’.

https://link.springer.com/content/pdf/10.1007%2Fs10342-011-0582-5.pdf

Wind effects on trees

Rapid industrialization in East Asia is causing adverse effects due to atmospheric deposition in terrestrial and freshwater ecosystems. Decreasing stream pH and alkalinity and increasing NO3
 − concentrations were observed throughout the 1990s in the forested Lake Ijira catchment in central Japan. We investigated these changes using data on atmospheric deposition, soil chemistry, stream water chemistry, and forest growth. Average atmospheric depositions (wet + dry) of 0.83, 0.57, and 1.37 kmol ha−1 year−1 for hydrogen, sulfur, and nitrogen, respectively, were among the highest levels in Japan. Atmospheric deposition generally decreased before 1994 and increased thereafter. The catchment was acid-sensitive; stream alkalinity was low (134 μmolc l−1) and pH in surface mineral soils decreased from 4.5 in 1990 to 3.9 in 2003. Stream NO3
 − concentration nearly doubled (from 22 to 42 μmolc l−1) from the late 1980s to the early 2000s. Stream NO3
 − concentration was controlled primarily by water temperature before 1996/1997 and by stream discharge thereafter. Stream NO3
 − concentrations decreased during the growing season before 1996/1997, but this seasonality was lost thereafter. The catchment became nitrogen-saturated (changing from stage 1 to 2) in 1996/1997, possibly because of declining forest growth rates due to the 1994 summer drought, defoliation of Japanese red pine by pine wilt disease, maturation of Japanese cedar stands, and stimulation of nitrogen mineralization and nitrification due to alkalinization of soils (increased exchangeable Ca2+ and soil pH) after the summer drought. Stream pH and alkalinity began decreasing in 1996/1997. The enhanced growing-season NO3
 − discharge since 1996/1997 appeared to be the major cause of stream acidification. Increased atmospheric deposition since 1994 may have contributed to this change.

Soil and stream water acidification in a forested catchment in central Japan

Air pollution characteristics over the Kathmandu Valley in wintertime were numerically investigated by using a comprehensive transport–chemistry–deposition model of air pollutants together with the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5). In Kathmandu, Nepal, it is known that double-layered local flows, that is, the southwesterly and northwesterly winds, formed as combined valley wind and plain-to-plateau wind, develop every day in the afternoon. In this study, the effect of local flows on air pollution in Kathmandu has been clarified. Detailed analysis of diurnal variation of air pollution transport elucidated the basic nature of the air pollution: 1) the vertical spreading of the pollutants, accumulated during the nighttime, by mixing-layer activity in the late morning, before the intrusion of the two local flows; 2) the late afternoon redevelopment of a shallow polluted layer and the pollutant transport toward the eastern neighboring valley, caused by the doub...

Dynamics of Air Pollution Transport in Late Wintertime over Kathmandu Valley, Nepal: As Revealed with Numerical Simulation

pH monitoring data for public water bodies in Niigata and Gifu prefectures in central Japan were tested by the nonparametric seasonal Mann–Kendall method to evaluate long-term acidification. A significant long-term declining trend in river water pH was found in several watersheds in Niigata and Gifu prefectures. In Niigata, the declining trend was observed only in areas receiving drainage from granitic rocks, and the acid neutralizing capacity of the river waters was in fact low in those areas. In Gifu, a declining trend was observed in some remote watersheds, where there was no clear relationship between the geology and the long-term trends. Since Niigata and Gifu receive the highest level of acid loading from the atmosphere in Japan, river water acidification in several watersheds may be attributable to the effects of the acid deposition. Other factors, such as hot spring drainage, changes in land use, and natural sea salt deposition, cannot adequately explain the acidification phenomena observed in this study.

Long-Term Declining Trends in River Water pH in Central Japan

Since 1983, the Ministry of the Environment of Japan has conducted nation-wide acid deposition surveys. To investigate the effects of acid deposition on surface water, we used the nonparametric Mann–Kendall test to find temporal trends in pH, alkalinity, and electrical conductivity (EC) in more than 10 years of data collected from five lakes and their catchments (Lake Kuttara: northernmost; Lake Kamakita: near Tokyo; Lake Ijira: central; Lake Banryu: western; and Lake Unagiike: southernmost). The pH of Lake Ijira water has declined slightly since the mid-1990s, corresponding with the downward trends seen in the pH and alkalinity of the river water flowing into the lake. There were significant upward trends in the EC of both the lake and stream water; the same trends were also found for \( {\text{NO}}^{ - }_{3} \) concentrations. These trends show evidence of acidification due to atmospheric deposition, and this is the first such finding in Japan based on significant long-term trends. Lake Ijira is located about 40 km north of the Chukyo industrial area near Nagoya. The annual depositions of H+, nss-\( {\text{SO}}^{{2 - }}_{4} \), and \( {\text{NO}}^{ - }_{3} \) in Lake Ijira were among the highest of all deposition monitoring sites, suggesting that this is the main cause of the significant acidification observed in Lake Ijira. No significant trends suggesting acidification were observed in any of the other lake catchments in spite of the significant upward trends in EC. Upward trends in pH and alkalinity at Lake Banryu and upward trends in alkalinity at Lake Kamakita were detected, but no change in pH or alkalinity at Lake Kuttara and Lake Unagiike was observed.

Long-term Trends in Surface Water Quality of Five Lakes in Japan

The Central Japan has notable topographical features such that high mountains of the Japanese Alps exist at its center, large plains extend in its coastal area, and it is bounded with complex coast lines at the south and north sides facing to the Pacific Ocean and the Sea of Japan, respectively. Thus various types of local flows develop in summer season. In this situation, medium range transport of air pollutants from highly developed urban area to mountainous rural area has attracted concern of many people in applied meteorology and atmospheric environment in Japan, since it occurs in an interesting combination of several types of local winds such as land and sea breezes, mountain and valley winds, and plain-plateau winds, and the transport repeated in summer season probably causes severe damage to eco-systems in the mountainous area. Kurita et al. (1985) pointed out that the pollutants discharged in Tokyo Bay area migrate to the mountains in central Japan, i.e. the travel distance of about 150 km within one day. The distance far exceeded what was expected in simple sea breeze situation in mid-latitudes, and thus the phenomena suggested importance of combined effects of sea breeze, valley wind, and plain to plateau wind for the transport. Later Kondo (1990) numerically verified using meso-scale meteorological model that the presence of the high mountains in the central Japan, which are taller than 2000 m, is a key for the formation of the flow resulting in the medium range transport of pollutants. Kitada et al. (1998) also discussed dominant role of the high mountains of the central Japan in temporal variation of sea breezes over coastal plain area in the Pacific Ocean side, i.e., the Nohbi Plain. It was made clear more than 10 years ago, as noted above, that the pollutants released from huge urban areas in the coastal Japan such as Tokyo can be transported more than 150 km within 12 hours mostly during the daytime and reach to the mountains.

Production and Transport of Ozone in Local Flows over Central Japan-Comparison of Numerical Calculation with Airborne Observation—

Vertical Structures of Land and Sea Breezes in the Nohbi Plain during a Passage of an Anticyclone over the Central Japan

Study on Meteorological Conditions for Severe Air Pollution in Nohbi Plain

To obtain knowledge for urban and regional planning suitable for the prevention of air pollution, the relationship between the high concentration of air pollutants and the meteorological condition was statistically investigated, using hourly SO{sub 2} and NO{sub x} concentration data measured in Nagoya for one year from April 1985 through March 1986. First, the daily average and maximum concentration of SO{sub 2} and NO{sub x} were calculated. Secondly, the {open_quotes}polluted days{close_quotes} were selected for each of warm and cool periods: the polluted days stand for those in which the concentrations at more than 50% of the monitoring stations of all within the highest thirties. Thirdly, for those selected days the diurnal variations of SO{sub 2}, NO{sub x} and meteorological factors such as wind speed, wind direction and atmospheric stability, were analyzed. Results are as follows. In the warm period, there was a clear difference in meteorological condition between the high-SO{sub 2} and high-NO{sub x} days. The high-SO{sub 2} days appeared mainly in {open_quotes}land and sea breezes{close_quotes} situation (hereafter LSB), which occurs in fine weather with light synoptic pressure gradient. In the days, SO{sub 2} concentration at many observation points showed sharp and clear peak in a day. Namely, the SO{submore » 2} concentration reaches its peak value when sea breeze front passes over the observation point, and then decreases rapidly. On the other hand, the high-NO{sub x} concentrations usually occurs in cloudy and rainy days with weak mean wind (hereafter BW, {open_quotes}bad weather{close_quotes}). In these days, NO{sub x} concentration gradually rises to its peak value in the morning, and remains high during daytime. In the cool period, both of the high SO{sub 2} and NO{sub x} concentrations appeared mainly with the BW situation, and sometimes with a fine weather under very weak synoptic-scale pressure gradient conditions.« less

Relationship between high concentration of air pollutants and meteorological condition in Nagoya, a coastal city in central Japan

The central Japan has characteristic topographical features such as highmountains and large plains, and is bounded with complex coast lines of the Pacific Ocean and the Sea of Japan. Thus various types of local flows develop in summer season. It is known that in the daytime, pollutants emitted over the huge coastal-urban areas in the plains such as Tokyo and Nagoya often reach to the central mountainous area within a day, with producing ozone and other products. However, the subsequent behavior and fate of the ozone and others are not clear. In this study, 3D three-days-simulations, during 26-28 July, 1995, of transport/chemistry/deposition of various chemical species were performed to see the behavior of ozone produced in the pollutant rich air mass, which passed over the urban area, particularly Nagoya in the Nohbi Plain, using the calculation domain over the Central Japan. The results were compared with airborne-observation and discussed.

Hiroaki Mori

Papers

Production and Transport of Ozone in Local Flows over Central Japan-Comparison of Numerical Calculation with Airborne Observation—

Vertical Structures of Land and Sea Breezes in the Nohbi Plain during a Passage of an Anticyclone over the Central Japan

Study on Meteorological Conditions for Severe Air Pollution in Nohbi Plain

Relationship between high concentration of air pollutants and meteorological condition in Nagoya, a coastal city in central Japan

Characteristics of o3 production and transport in local winds over central japan in summer season