Special Issue

Biogeochemical Cycles in Atomosphre, Terrestrial Ecosystem and Maring Environments

Original Paper

Evaluation of global atomospheric transport model using Radon 222

Shoichi.TAGUCHI (Inter-Spheric Environment Div., Environmental Assessment Dept., NIRE)

Abstract
Horizontal and vertical advection in a global chemical transport model are investigated using radon 222 emitted from continental soil. Horizontal advection is tested using continuous observations at three islands in Indian Ocean. Vertical advection is tested using aircraft measurements. A model successfully reproduced radonic storm observed at the islands. Emission from ocean surface is required to reproduce observed mean concentrations there. The model tends to underestimate the concentrations at upper troposphere if monthly averages are compared with the observations. Simulated concentrations are both higher and lower than the observed values if they are compared with instantaneous values. The model tends to overestimate those at lower troposphere. Vertical flux due to moist convection is a possible cause of this deficiency but another model using this flux showed a similar tendency. Therefore the cause of higher concentrations in model simulations at lower troposphere is unknown.

Key words : Radon, Chemical Transport Model, Reanalysis Meteorological Data

(Language:Japanese)

Original Paper

Preliminary Results on the Greenhouse Gas Measurements by IMG Sensor aboard ADEOS Satellite

Ryoichi. IMASU (Inter-Spheric Environment Div., Environmental Assessment Dept., NIRE)

Abstract
Interferometric Monitor for Greenhouse gases (IMG) aboard AdvancedEarth Observing Satellite (ADEOS) is a Fourier Transform-type Spectrometer (FT-IR) which has been developed for measuring the greenhouse gases in the atmosphere, particularly in the troposphere. It was operated for about 7 months from November 1996 up to the end of the lifetime of the ADEOS on June 1997. During the operational period IMG had measured over 138000 terrestrial thermal emission spectra of which the signal to noise ratio is sufficiently large for retrieving the atmospheric parameters such as temperature and gas concentrations. As most of the data had been obtained during the 4-day operational period scheduled twice in each REQQ period, we have obtained about 15 global data sets of the IMG data during the whole IMG operational period.

Preliminary results from IMG retrieval analyses show the relationship between the stratospheric ozone depression and low temperature field over the arctic region in the northern hemispheric spring of 1997. On the other hand, the analyses for the troposphere show that the methane concentration in the northern hemisphere was relatively higher than that in the southern hemisphere in the 1997 spring. In future analysis, we would try to raise the accuracy of the data analysis by customizing the 'a priori' data and constraint parameters used in the retrieval analyses, and would validate these retrieved results using routinely obtained meteorological data such as rewin and ozone sonde data.

Key words : IMG, ADEOS, Greenhouse gas, FT-IR, Remote sensing

(Language:Japanese)

Review

An Introduction to Terrestrial Ecosystem Modeling

Nobuko. SAIGUSA (Atmospheric Environment Div., Environmental Assessment Dept., NIRE)

Abstract
Energy, water, and carbon cycles between terrestrial ecosystem and the atmosphere are controlled by such biological processes as photosynthesis, respiration, transpiration, and decomposition of organic soil matter. Terrestrial ecosystem models have been developed by many researchers in biology, agriculture, meteorology, and fluid mechanics. These models cover several spatial scales such as leaf, individual, and plant canopy. In this review, some recent studies on terrestrial ecosystem modeling for energy, water, and carbon cycles are introduced. It is necessary to develop and improve models from canopy scale to global scale, in order to understand the global carbon cycle and the response of ecosystems to the earth's environmental change.

Key words : Terrestrial ecosystem, Modeling, Photosynthesis, Transpiration

(Language:Japanese)

Original Paper

Uptake rates of carbon dioxide by forest ecosystems

Susumu. YAMAMOTO (Atmospheric Environment Div., Environmental Assessment Dept., NIRE)
Shohei. MURAYAMA (Atmospheric Environment Div., Environmental Assessment Dept., NIRE)
Nobuko. SAIGUSA (Atmospheric Environment Div., Environmental Assessment Dept., NIRE)
Hiroaki. KONDO (Atmospheric Environment Div., Environmental Assessment Dept., NIRE)
Noboru. NISHIMURA (Institute for Basin Ecosystem Studies, Gifu University)

Abstract
The objectives of this research are to estimate the uptake rates of CO₂ between the atmosphere and a temperate deciduous forest in Japan, and to compare the results with uptake rates obtained in the several forest ecosystems throughout the world.

The uptake rates of CO₂ from October, 1993 to December, 1996 were estimated from field measurements using a tower in the temperate forest at Takayama, Japan. The average of integrated uptake of CO₂ from 1994 to 1996 was 390 gCO₂/m²/year (1.1 tC/ha/year), but they had notable inter-annual variation due to the differences in averaged insolation and temperature each summer. This value of uptake rate was less than the results obtained in other temperate deciduous forests.

According to the CO₂ flux measurements in several forests including the present one, the uptake rates by forest ecosystems were from 1 to 5 tC/ha/year. Adopting these data to the protected forests in the world (aera=530Mha), we estimated that the uptake amounts of CO₂ ranged from 0.6 to 2.2 GtC/year. Moreover, the capability of CO₂ uptake by future plantations was evaluated. These results indicated that the forest ecosystems could be a large sink of CO₂, however, more data of the CO₂ flux in the various forests and latitudes are needed to reduce the uncertainty in estimating the CO₂ uptake on a global scale.

Key words : Carbon cycle, CO₂ flux, Uptake rate of CO₂ ,Forest ecosystem, Plantation

(Language:Japanese)

Original Paper

Classification of arid regions of the world by vegetation index and aridity index

M. GAMO (Inter-Spheric Environment Div., Environmental Assessment Dept.,NIRE)
T. MAEDA (Inter-Spheric Environment Div., Environmental Assessment Dept., NIRE)
M. HAYASHI (Environmental Assessment Dept., NIRE)
R. IMASU (Inter-Spheric Environment Div., Environmental Assessment Dept., NIRE)
M. SHINODA (Tokyo Metropolitan Univ.)

Abstract
Arid and semi-arid regions in the world are classified by the yearly maximum of normalized difference vegetation index NDVIymax. Histogram of area of NDVIymax has two peaks at severe deserts and areas where vegetation is rich, and between two peaks there exist semi-arid regions. According to the standard deviation of NDVIymax, which shows degree of variability of year-to-year changes of NDVIymax, very unstable regions for vegetation exist near deserts where standard deviation is very small. There is a linear relationship between annual precipitaion and NDVIymax in the sub-tropical arid and semi-arid regions. While, there is no relationship between them in the high-latitude dry regions. On the other hand, there is a relatively good relationship between aridity index and vegetation index for both arid and semi-arid regions above. Dry regions of the world are divided into seven categories, including regions where vegetation is relatively abundant in spite of severe dryness, and regions where vegetation is poor in spite of relatively humid conditions.

Key words :desertification, vegetation index, aridity index, desert, seni-arid region

(Language:Japanese)

Review

Recent Studies on the Global Ocean General Circulation Model

Minoru. NAKATA (Marine Environment Div., Environmental Assessment Dept.,NIRE)

Abstract
There are many trials to improve the general circulation model for oceans, due to the fact that the supercomputers for science and technology are just recently developing. New parameterizations for the diffusive process, which are recently introduced into the ocean general circulation model (O-GCM), are explained. Tracer studies with the O-GCM and the simulations by the model which are combined with the simple biogeochemical processes are briefly mentioned. And finally, the problems for the O-GCM, which are clarified by the above new processes added into the model, are discussed.

Key words : ocean general circulation model, parameterization of diffusive process

(Language:Japanese)

Original Paper

Carbon Cycle in the North Pacific-Role in the Global Ocean

Joji. ISHIZAKA (Marine Environment Div., Environmental Assessment Dept.,NIRE)
Yutaka. WATANABE (Marine Environment Div., Environmental Assessment Dept.,NIRE)
Akio. ISHIDA (Kansai Environmental Engineering Center, Japan Marine Science and Technology Center)
Shigeaki. AOKI (Marine Environment Div., Environmental Assessment Dept.,NIRE)
Akira. HARADA (Marine Environment Div., Environmental Assessment Dept.,NIRE)
Kisaburo. NAKATA (School of Marine Science and Technology, Tokai University)
Kimitoshi. ISHIKAWA (Environmental Assessment Dept.,NIRE)
Hiroyuki. TSUBOTA (Hiroshima University)

Abstract
Carbon contents of resoviors and flux between the resoviors were estimated in the North Pacific and compared with the values of global ocean. Rates of biological pump and accumulation of anthropogenic carbon seem to be fast in the North Pacific. However, most of the estimates were uncertain and further study is required.

Key words :North Pacific, Carbon Cycle

(Language:Japanese)