都市気候に及ぼす河川水の熱的影響に関する実測研究

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1 OBRVATIO O TH THRMAL FFCT OF RIVR ATR O URBA CLIMAT tudy on heat budget on water surface and its effects on surrounding areas of umida River * ** *** Ken-ichi ARITA, Akiko UMURA and Ikusei MIAKA ater bodies in urban area have been expected to mitigate the urban heat island as well as green space. In this paper, we showed the results of observations about heat budget at river water and moving observations to clarify horizontal extent of its thermal effects. Diurnal variations of sensible heat flux estimated by several methods corresponded closely with each other., though these values didn t exceed /m even in the peak about midday. stimated heat storage term occupied more than 9% of net radiation during daytime. According to the numerical simulation, observed water temperature variation required equivalent heat conductivity for actual stirred water about forty times as much as that of stagnant water. This heat balance is completely different from that of green space characterized large latent heat flux. On the other hand, horizontal sensible heat flux from adjacent built-up area to the river space also estimated by eddy correlation method at riverside terrace. Turbulent heat flux across the river-edge amounted to /m in daytime, which greatly surpassed vertical sensible heat flux at water surface. The horizontal limits of river-effect along the street crossing the river were about m from river-edge, and there was no clear relation between this limits and wind speed. Keywords : heat island, urban rivers, sensible heat flux, advection, urban canyon, heat storage )) ) ) ) 6)7) 8) 9) ) )-) ) * Prof., Dept. of Architecture, Faculty of ng., ippon Institute of Technology, Dr. ng. ** Technical High chool of Ohmagari., M. ng. *** Research & Development Institute of Takenaka Co., M. ci.

2 km m m m km () m (Q ) (Q ) (I ) Q Q m I.m Q.m cm Hz.m 9m.7.9m m ().m.8m 7 9 ( 6 ) cm.8m Hz に河岸テラスで実測された (Q ) (I ) 9 I /m km 6 7m/s m/s. 7

3 放射フラックス (/m ) 9 風速 (m/s) ( 風速 (m/s) ( 気温水温 ( ) 気温差 ( ) ) Q I アルベド大手町アメダス中央定点大手町との差風速風速大手町風向両国橋風向両国橋水温水位風向風向水位 [ 親水テラスより ](cm) アルベド吹上角度 ( 度 ) 蒸気圧.(hPa) 河岸テラス橋上定点水面飽和 m/s w ) 6) - - 橋上定点 Hz PC H c p w t H / m c p J/kg K kg/m t K w H/ρc p =C H U (T -T) /ρ=c U(q -q)

4 顕熱潜熱フラックス (/m ) C H C T q Ts kg/kg (kg/m s) U(m/s) T q kg/kg C H C ) = { /( ( +..)} =(T s -T)/[U {..+log (/z)} ] Ts T< C HD C HD 顕熱 ( シンチレーション法 ) 顕熱 ( バルク法 ) 顕熱 ( 渦相関法 )[ 河岸テラス ] 顕熱 ( 渦相関法 )[ 橋上定点 ] 潜熱 ( シンチレーション法 ) 潜熱 ( バルク法 ) /m *) (L L) L HD / C H C D / C exp.9exp(.8.8) HD C D D.. D *) z U (m) m 対流熱伝達率 (/m K) K) シンチレーション法シンチレーション法バルク係数バルク係数渦相関法橋上定点渦相関法 [ 橋上定点 ] 橋上風速 (m/s) 橋上風速 (m/s) フラックス (/m ) m/s. 8) /m (Rn Rn) (9) Q Rn. H(bulk).9 L(bulk).8 G.7 G/Rn G/Rn

5 水平熱フラックス ( /m ) 表面水温 ( ) 静止 (λ=.6) 倍 (λ=6.) 8 倍 (λ=8.) 倍 (λ=.) 6 倍 (λ=6) 実測水温 Ts 市街地から河川へ向かう方向 ( 北から 7 度方向 ) を正とする Q I T ε.96 (G) H L (8) *) Rn=H+L L+G Rn=Q - -Q + +I -εσ -εσt G/Rn.9 Rn.9 ) Rn 8 G G m *).6/m K () ( ) /m *) point point point point point 9 point 9 point 9 point point

6 point point point 9.9. point.8 point m point point 日本橋川定点 point 6 point 7. point point point..6 隅田川.7 point.6. point o point....6 風速比.8 ( ) ( ) ( ) ( ) ( ) m, hpa,hpa 温度差湿度差両国橋温度差比湿度差比温度差比湿度差比 V.P. ratio 西橋中央からの距離 (m) 東両国橋 est distance from the center of bridge ast 西橋中央からの距離 (m) 東 ~ (m/s) ~ (m/s) ~ (m/s) ~ 6(m/s) 6(m/s)~ 6

7 m 8 6 両国橋 m/s *) c C.8 x ) c [/m.k] C[J/(kg.K)] x : [kg/(m.s.(kg/kg ))] *)Q *)..9 *) C H or C. U=m/s. U=m/s. U=6m/s Ts-T ( ) () () () () m () (6) C 66 *) () (7) ) ) ),9-6,999. ) Mellor-Yamada ) ) ) ) ) ) pp ) ) ) A Climatological tudy of the Cooling ffects of River in Urban Heat Island ( ). 7

8 ) ) Kaimal. J. C., J. J. Finnigan Atmospheric Boundary Layer Flows, Oxford, pp89, 99 6) Thiermann. V, H. Grassl The measurement of turbulent surface-layer flux by use of bichromatic scintillation Boundary-Layer Meteorol ) vol. o ) Green. A.., Y. Hayashi Use of cintillometer Technique over a Rice Paddy J. Agric. Meteorol. () ) )

LAGUNA LAGUNA 8 p Saline wedge at River Gonokawa, Shimane Pref., Japan Saline water intrusion at estuary r

LAGUNA LAGUNA 8 p Saline wedge at River Gonokawa, Shimane Pref., Japan Saline water intrusion at estuary r LAGUNA8 67 78 2001 3 LAGUNA 8 p.67 78 2001 1 1 2 3 4 5 6 7 8 Saline wedge at River Gonokawa, Shimane Pref., Japan Saline water intrusion at estuary river and its relation to the underground water Observation