Faculty Profiles - KOTANI, Ayumi

Papers - KOTANI, Ayumi

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Spatial variations in evapotranspiration over East Asian forest sites. II Surface conductance and aerodynamic conductance Reviewed

Khatun R, Ohta T, Kotani A, Asanuma J, Gamo M, Han S, Hirano T, Nakai Y, Saigusa N, Takagi K, Wang H, Yoshifuji N

Hydorological Rearch Letters ( 5 ) page： 88-92 2011

Spatial variations in evapotranspiration over East Asian forest sites. I. Evapotranspiration and decoupling coefficient Reviewed

Khatun R, Ohta T, Kotani A, Asanuma J, Gamo M, Han S, Hirano T, Nakai Y, Saigusa N, Takagi K, Wang H, Yoshifuji N

Hydorological Rearch Letters ( 5 ) page： 83-87 2011

Spatial variations in evapotranspiration over East Asian forest sites. I. Evapotranspiration and decoupling coefficient

Khatun Rehana, Ohta Takeshi, Kotani Ayumi, Asanuma Jun, Gamo Minoru, Han Shijie, Hirano Takashi, Nakai Yuichiro, Saigusa Nobuko, Takagi Kentaro, Wang Huimin, Yoshifuji Natsuko

Hydrological Research Letters Vol. 5 ( 5 ) page： 83 - 87 2011

Language：English Publishing type：Research paper (scientific journal) Publisher：Japan Society of Hydrology and Water Resources (JSHWR) / Japanese Association of Groundwater Hydrology (JAGH) / Japanese Association of Hydrological Sciences (JAHS) / Japanese Society of Physical Hydrology (JSPH)

Evapotranspiration (ET) is not only a vital component of water budget, but also plays an important role in the energy budget of the earth-atmospheric system, ultimately driving many regional and global scale climatological processes. This paper describes the ET characteristics and factors controlling ET across the 17 forest sites in East Asia (2°S to 64°N latitude). ET was measured using the eddy covariance technique at each site. Daytime dry-canopy data for the growing season were used in this study. Growing season mean ET gradually decreased as latitude increased, with a range of 4.4 to 1.2 mm d−1. The growing season mean decoupling coefficient (Ω) ranged from 0.42 to 0.11 across the studied sites. At low-latitude forest sites, Ω was close to 0.50, indicating that the bulk surface was partially decoupled from the atmosphere and ET was strongly controlled by net radiation and vapour pressure deficit. At high-latitude forest sites, Ω was low (∼0.12), indicating that the bulk surface was well coupled to the atmosphere and ET was mainly controlled by surface conductance. The value of Ω was determined mainly by the ratio of aerodynamic conductance to surface conductance across the studied forests of East Asia.

DOI： 10.3178/hrl.5.83

CiNii Research

Evapotranspiration over larch forest in southern area of eastern Siberia

Kotani Ayumi, Ohta Takeshi, Maximov Trofim

The Japanese Forest Society Congress Vol. 123 ( 0 ) page： Pb083 - Pb083 2011

Spatial variations in evapotranspiration over East Asian forest sites. II. Surface conductance and aerodynamic conductance

Khatun Rehana, Ohta Takeshi, Kotani Ayumi, Asanuma Jun, Gamo Minoru, Han Shijie, Hirano Takashi, Nakai Yuichiro, Saigusa Nobuko, Takagi Kentaro, Wang Huimin, Yoshifuji Natsuko

Hydrological Research Letters Vol. 5 ( 5 ) page： 88 - 92 2011

Evapotranspiration over forest surfaces is mainly constrained by environmental and forest structural components through their influence on surface conductance (Gs) and aerodynamic conductance (Ga). Tower based eddy covariance data from 16 forest sites in East Asia (2°S to 64°N) were used to examine the sensitivity of Matsumoto and Nakai models for predicting Gs and Ga, respectively. Daytime dry-canopy data for the growing season were used in this study. Comparisons between model predictions and observed Gs and Ga showed good agreement, suggesting that the models were suitable for predicting Gs and Ga with reasonable accuracy. However, the model for Gs was unable to predict Gs accurately when soil water content was low (∼10%). In this circumstance, effective soil water content and a more comprehensive method for modelling the soil water content function must be used. Gs in East Asia was largely depended on vapour pressure deficit and secondarily on soil water content. Ga was largely affected by leaf area index compared with stand density.

DOI： 10.3178/hrl.5.88

CiNii Research

Environmental factors controlling forest evapotranspiration and surface conductance on a multi-temporal scale in growing seasons of a Siberian larch forest

Yoshida Megumi, Ohta Takeshi, Kotani Ayumi, Maximov Trofim

JOURNAL OF HYDROLOGY Vol. 395 ( 3-4 ) page： 180 - 189 2010.12

Environmental factors controlling forest evapotranspiration and surface conductance on a multi-temporal scale in growing seasons of a Siberian larch forest Reviewed

Yoshida, M., Ohta, T., Kotani, A., and Maximov,T.

Journal of Hydrology 2010.1

Concise formulae for the atmospheric correction of hemisphericalthermal radiation measured near the ground surface Reviewed

A Kotani and M Sugita

Water Resourses Research Vol. 45 page： W07413 2009.8

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

This paper presents the analysis of the atmospheric effects on the measurement of the thermal radiation near the ground surface. The difference of the thermal radiation at surface and L at some height z was evaluated for various atmospheric conditions and for different sensor heights with the LOWTRAN 7 radiation transfer code. It was found that in many cases the effects of transmission of radiation primarily due to the presence of water vapor and secondarily to other minor gases and aerosols are not negligible for the upward component of thermal radiation, whereas they can be neglected for downward component. Based on the results of LOWTRAN 7 calculations, a simple regression equation of atmospheric path transmissivity ta in terms of the total water vapor w within the air layer between the surface and the sensor height and that of
emittance from the air layer between the ground and the sensor height La in terms of w and temperature were obtained; these will then allow the practical estimation of ta and La from measurements of air temperature and humidity near the ground for the atmospheric correction of the upward thermal radiation measured at a certain height. This procedure can be applied to derive net radiation at the ground surface from a four-component radiometer measurement above the ground and also to derive surface radiative temperature from pyrgeometer measurements of the upward long-wave radiation.

How universal is the C function in the bulk atmospheric boundary layer similarity approach for estimating surface sensible heat flux? Reviewed

M. Sugita, H. Kato, A. Kotani, M. Toda

Water resources research Vol. 45 page： W07418 2009.8

How universal is the C function in the bulk atmospheric boundary layer similarity approach for estimating surface sensible heat flux?

Sugita Michiaki, Kato Hidekazu, Kotani Ayumi, Toda Motomu

WATER RESOURCES RESEARCH Vol. 45 ( 7 ) 2009.7

Concise formulae for the atmospheric correction of hemispherical thermal radiation measured near the ground surface

Kotani Ayumi, Sugita Michiaki

WATER RESOURCES RESEARCH Vol. 45 ( 7 ) 2009.7

Response of gross ecosystem productivity, light use efficiency, and water use efficiency of Mongolian steppe to seasonal variations in soil moisture

Li Sheng-Gong, Eugster Werner, Asanuma Jun, Kotani Ayumi, Davaa Gombo, Oyunbaatar Dambaravjaa, Sugita Michiaki

JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES Vol. 113 ( G1 ) 2008.3

Disturbances and their corrections in space observation with GOSAT fourier transform spectrometer

Aoki T.

Proceedings of SPIE - The International Society for Optical Engineering Vol. 6748 2007.12

第4章地表面-大気相互作用

浅沼順, 小谷亜由美, 杉田倫明, 松島大

筑波大学陸域環境研究センター報告, 北東アジア植生変遷域の水循環と生物・大気圏の相互作用 : RAISEプロジェクトで何が分かったか = Bulletin of the Terrestrial Environment Research Center, the University of Tsukuba, Rangelands Atmosphere-Hydrosphere-Biosphere Interaction Study Experiment in Northeastern Asia : Highlights of the RAISE Project Vol. 8 page： 14 - 16 2007.8

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：筑波大学陸域環境研究センター

陽炎から地表面による大気加熱を計る ……14航空機データを用いて推定した地表面から大気への熱輸送量 ……15衛星データとシミュレーションによる土壌水分の推定 ……16

DOI： 10.15068/00147272

CiNii Books

Evapotranspiration from a Mongolian steppe under grazing and its environmental constraints

Li Sheng-Gong, Asanuma Jun, Kotani Ayumi, Davaa Gombo, Oyunbaatar Dambaravjaa

JOURNAL OF HYDROLOGY Vol. 333 ( 1 ) page： 133 - 143 2007.1

Vertical distribution of stable isotopic composition in atmospheric water vapor and subsurface water in grassland and forest sites, eastern Mongolia

Tsujimura Maki, Sasaki Lisa, Yamanaka Tsutomu, Sugimoto Atsuko, Li Sheng-Gong, Matsushima Dai, Kotani Ayumi, Saandar Mijiddorj

JOURNAL OF HYDROLOGY Vol. 333 ( 1 ) page： 35 - 46 2007.1

Variance methods to estimate regional heat fluxes with aircraft measurements in the convective boundary layer

Kotani Ayumi, Sugita Michiaki

JOURNAL OF HYDROLOGY Vol. 333 ( 1 ) page： 68 - 85 2007.1

Variance Methods to Estimate Regional Heat Fluxes with Aircraft Measurements in Convective Boundary Layer Reviewed

Kotani,A. and Sugita,M.

Journal of Hydrology Vol. 333 ( 1 ) page： 68-85 2007

Parameterization of heat transfer for sparse vegetation in the northeathern Mongolia

kotani ayumi, sugita michiaki

Proceeding of Annual Conference Vol. 20 ( 0 ) page： 82 - 82 2007

Energy partitioning and its biophysical controls above a grazing steppe in central Mongolia

Li Sheng-Gong, Eugster Werner, Asanuma Jun, Kotani Ayumi, Davaa Gombo, Oyunbaatar Dambaravjaa, Sugita Michiaki

AGRICULTURAL AND FOREST METEOROLOGY Vol. 137 ( 1-2 ) page： 89 - 106 2006.3

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Papers - KOTANI, Ayumi