Satellite detection of red tide in Ariake Sound, 1998–2001

High resolution SeaWiFS data was used to detect red tide events that occurred in the Ariake Sound, Japan, a small embayment known as one of the most productive areas in Japan. SeaWiFS chlorophyll data clearly showed that a large red tide event, which damaged seaweed (Nori) cultures, started early in December 2000 in Isahaya Bay, expanded to the whole sound and persisted to the end of February 2001. The monthly average of SeaWiFS data from May 1998 to December 2001 indicated that the chlorophyll peaks appeared twice a year, in early summer and in fall, after the peaks of rain and river discharge. The SeaWiFS data showed that the red tide event during 2000–2001 winter was part of the fall bloom; however, it started later and continued significantly longer than other years. Satellite ocean color data is useful to detect the red tide; however the algorithms require improvement to accurately estimate chlorophyll in highly turbid water and in red tide areas.     

Size-Fractionated Primary Production Estimated by a Two-Phytoplankton Community Model Applicable to Ocean Color Remote Sensing

In order to estimate primary production from ocean color satellite data using the Vertical Generalized Production Model (VGPM; Behrenfeld and Falkowski, 1997), we propose a two-phytoplankton community model. This model is based on the two assumptions that changes in chlorophyll concentration result from changes of large-sized phytoplankton abundance, and chlorophyll specific productivity of phytoplankton tends to be inversely proportional to phytoplankton size. Based on the analysis of primary production data, P _opt ^B , which was one parameter in the VGPM, was modeled as a function of sea surface temperature and sea surface chlorophyll concentration. The two-phytoplankton community model incorporated into the VGPM gave good estimates in a relatively high productive area. Size-fractionated primary production was estimated by the two-phytoplankton community model, and P _opt ^B of small-sized phytoplankton was 4.5 times that of large-sized phytoplankton. This result fell into the ranges observed during field studies.     

A simple model to estimate monthly forest evapotranspiration in Japan from monthly temperature

The estimation of evapotranspiration (E) in forested areas is required for various practical purposes (e.g. evaluation of drought risks) in Japan. This study developed a model that estimates monthly forest E in Japan with the input of monthly temperature (T). The model is based on the assumptions that E equals the equilibrium evaporation rate (E_eq) and that E_eq is approximated by a function of T. The model formulates E as E (mm month⁻¹) = 3·48 T ( °C) + 32·3. The accuracy of the model was examined using monthly E data derived using short‐term water balance (WB) and micrometeorological (M) methods for 15 forest sites in Japan. The model estimated monthly E more accurately than did the Thornthwaite and Hamon equations according to regression analysis of the estimated E and E derived using the WB and M methods. Although the model tended to overestimate monthly E, the overestimation could be reduced by considering the effect of precipitation on E. As T data are commonly available all over Japan, the model would be a useful tool to estimate forest E in Japan. Copyright © 2010 John Wiley & Sons, Ltd.     

Characteristics of canopy interception loss in Moso bamboo forests of Japan

In recent years, Moso bamboo (Phyllostachys pubescens) forests have rapidly expanded in Japan by replacing surrounding coniferous and/or broadleaved forests. To evaluate the change in water yield from forested areas because of this replacement, it is necessary to examine evapotranspiration for Moso bamboo forests. However, canopy interception loss, one of the major components of evapotranspiration in forested areas, has been observed in only two Moso bamboo forests in Japan with relatively high stem density (~7000 stems/ha). There are, in fact, many Moso bamboo forests with much lower stem density. Thus, we made precipitation (Pr), throughfall (Tf) and stemflow (Sf) observations for 1 year in a Moso bamboo forest with stem density of 3611 stems/ha and quantified canopy interception loss (Ic). Pr and Ic for the experimental period were 1636 and 166 mm, respectively, and Ic/Pr was 10%. The value was approximately the same as values for the other two Moso bamboo forests and lower than values for coniferous and broadleaved forests. On the other hand, Tf/Pr and Sf/Pr for our forest (86% and 4%, respectively) were approximately 10% of Pr larger and smaller than values for the other two Moso bamboo forests. These results suggest that the difference in stem density greatly affects precipitation partitioning (i.e. Tf/Pr and Sf/Pr) but does not greatly change Ic/Pr. Copyright © 2012 John Wiley & Sons, Ltd.     

Arctic hazes in summer over Greenland and the North American Arctic: II. Nature and concentrations of accumulation-mode and giant particles

Airborne measurements made during August 1985 over Greenland and its environs show that both accumulation-mode (0.1 m D2.0 m) and giant (D2 m) particles were present in relatively high concentrations in arctic haze layers and that the accumulation-mode particles dominated light scattering. Particles with diameters (D) between 1 and 4 m consisted predominately of mixed materials, small and dense inclusions, and probably organic compounds containing sulfur. Many of the particles from 0.1 to 1 m in diameter were also of mixed composition, with sulfuric acid, ammonium sulfate and organics probably the dominant constituents.     

Origin of high-magnesian andesites in the Setouchi volcanic belt,southwest Japan,I. Petrographical and chemical characteristics

High-magnesian andesites of middle Miocene age occur in southwest Japan, forming an obvious volcanic belt. These andesites have low FeO*/MgO ratios (0.546–0.931), and are rich in Ni (101–312 ppm), Co (30.0–45.1 ppm), and Cr (208–756 ppm). They are relatively aphyric (phenocrysts <10 vol.%), and the phenocrysts of magnesian olivine (～Fo₈₈) are in equilibrium with the host high-magnesian andesite magmas on the basis of the Fe-Mg exchange partitioning. These features suggest that the high-magnesian andesites are not differentiated or accumulative; they appear to represent primary andesites generated in the upper mantle. These southwest Japanese high-magnesian andesites are rich in incompatible elements, and show light rare earth enrichment relative to boninites, suggesting that the former is derived from a less depleted mantle source than the latter.     

Preliminary assessment of eutrophication by remotely sensed chlorophyll-a in Toyama Bay,the Sea of Japan

Time series of the chlorophyll-a concentration (Chl-a) observed by ocean color satellites from 1998 to 2009 were used to assess eutrophication in Toyama Bay, the Sea of Japan. An overall mean of Chl-a during the 12-year period was used to divide the study area into “high” or “low” Chl-a areas based on a reference condition of 5 mg m^?3. The annual maximum monthly mean Chl-a trend was estimated pixel-wise and its significance examined by the Sen slope test at a 90 % confidence level. By combining the level and trend of remotely sensed Chl-a, Toyama Bay was then classified into six eutrophication states: high-increasing, high-no trend, high-decreasing, low-increasing, low-no trend and low-increasing. Our study indicates that the combined use of both the level and trend of remotely sensed Chl-a can be an efficient method to preliminarily assess eutrophication of coastal waters after a quality screening process with level 2 flags and validation with in situ Chl-a data.     

Satellite and ship observations of Kuroshio warm-core ring 93A off Sanriku, northwestern North Pacific, in spring 1997

Synoptic ship and satellite observations were performed of the Kuroshio warm-core ring (KWCR) 93A and its adjacent waters, off Sanriku, northwestern North Pacific, between early April and late June 1997. The temporal and spatial distribution of chlorophylla (Chl-a) and sea surface temperature in the study area were analyzed using data from ADEOS Ocean Color and Temperature Scanner (OCTS) and NOAA Advanced Very High Resolution Radiometer (AVHRR). The objective of this study was to describe the temporal and spatial variability of the spring bloom and understand its relationship with the changes in the hydrographic structure of these waters in and around KWCR 93A. The maximum value of Chl-a concentration in the ring was less than 1 mg/m³ during April. The spring bloom in the ring occurred early in May and the relatively high maximum (>1.0 mg/m³) continued from early in May to mid-June. In late June, a ship-observed surface Chl-a concentration of less than 0.4 mg/m³ suggests that the spring bloom had already declined in and around KWCR 93A. Double spiral structures of warm and cold streamers appeared from late April to mid-May, which may have an influence on the occurrence of the spring bloom in and around the ring. In this episodic event, the warm streamer can maintain the available potential energy of the ring and the strength of upwelling around the ring. The cold streamer provided water with a high Chl-a concentration to the surface layer of the ring. In order to understand the temporal and spatial variability of Chl-a distribution in the ring, the behavior of the warm and cold streamers needs to be taken into consideration.