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Volume 76, Issue 4
Displaying 1-5 of 5 articles from this issue
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Full Paper
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Xiang GAO, Fengxue GU, Daozhi GONG, Weiping HAO, Jianmin CHU, Ha ...2020 Volume 76 Issue 4 Pages 155-163
Published: 2020
Released on J-STAGE: October 10, 2020
JOURNAL FREE ACCESSAccurate estimates of the rain-fed field evapotranspiration (ET) in the Loess Plateau of Northwest China is critical for predicting hydrologic processes, crop yield formation, and climate change. We simulated the ET variation in a rain-fed spring maize field in the eastern Loess Plateau using the Penman-Monteith (PM), Shuttleworth-Wallace (SW), and modified Priestley-Taylor (PTm) models. Then we compared their results with the observed ET using the eddy covariance (EC) method. Generally, the diurnal variation in estimated ET from the three models was similar to that of observed ET by the EC method. However, the PM model significantly underestimated ET. The ET estimates obtained from the SW and PTm models were approximately equal to the observed ET by the EC method. Considering the PTm model’s simplicity, we finally recommend it for rain-fed spring maize fields in the Loess Plateau. After precipitation, the estimated ET from the three models was significantly smaller than measured ET by the EC method, especially the PM model. After a frost, all three models failed to reflect the dramatic decrease in crop transpiration, and thus significantly overestimated ET.View full abstractDownload PDF (1188K) -
Keach MURAKAMI, Tomoyoshi HIROTA, Seiji SHIMODA, Tomotsugu YAZAKI2020 Volume 76 Issue 4 Pages 164-173
Published: 2020
Released on J-STAGE: October 10, 2020
JOURNAL FREE ACCESS
Supplementary materialInteractions between boundary layer wind and topography form non-uniform air temperature distributions in cold and snow-covered regions. Because of this heterogeneity, spatially interpolated air temperatures sometimes deviate from observed values. To evaluate the quality of spatially interpolated daily mean temperatures (Tint) provided by a 1 km gridded meteorological data service (Ohno et al., 2016), we collected observed temperatures (Tobs) obtained at meteorological observation sites located near farmland in the Tokachi and Okhotsk regions—in eastern Hokkaido, Japan—in winter (October-March) and revisited the bias in the interpolated temperatures (dT). The root-mean-square error (RMSE) of Tint obtained at 88 sites was 1.16°C, and the absolute median dT values were greater than 1°C at 14 sites. The variance of dT was greater on cold and calm days, suggesting the involvement of radiative cooling and the accumulation of cold air parcels. To correct Tint by estimating dT at a given site by considering the formation mechanisms of the temperature distributions, we attempted to develop a multimodal machine learning model that had four predictors: surface and boundary layer meteorological data and topographical and geographical features around each site. To analyze the influence of the spatial extent of the topography and geography around each site, we compared models having these predictors with various sizes of the region of interest (ROI). By training the models and applying them to an independent test dataset, it has been shown that bias correction using models with a small topographical ROI (30×30 km or smaller) reduced the RMSE. The RMSE of the test dataset decreased by ~0.1°C via the application of a nested model, suggesting the potential usefulness of the presented approach for locally confined meteorological events. However, the biases were increased at several sites by application of the models, thus implying that further improvement is essential for practical use.View full abstractDownload PDF (3500K)
Short Paper
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Naru TAKAYAMA, Hiroyuki HORI, Hidekazu WATANABEArticle type: Short Paper
2020 Volume 76 Issue 4 Pages 174-179
Published: 2020
Released on J-STAGE: October 10, 2020
Advance online publication: July 28, 2020JOURNAL FREE ACCESSWe compared the difference of heatstroke risk of marathon runners in the Summer Olympics on the basis of the percentage of weight decrease due to sweating using potential effective sweating, between Tokyo and Sapporo. For the women’s marathon, the difference in the rate of decrease in body weight was 0.42% when the start time was 11:00, with 7.51% loss for Tokyo and 7.09% for Sapporo. Nevertheless, when the start time was 7:00, as planned, the difference decreased to 0.28%, with a 6.94% loss for Tokyo and 6.66% for Sapporo. The estimated thermal load on runners when starting the race at 7:00 on August 8 in Sapporo was equivalent to starting at 5:30 or at 16:00 on August 2 in Tokyo. For the men’s marathon, the start time with the maximum rate of decrease in weight was 10:00, with a 6.91% loss for Sapporo and 7.42% for Tokyo. If the race started at 7:00, the rate of decrease in body weight was 6.50% for Sapporo and 7.00% for Tokyo, a 0.50% difference. However, as a result of the analysis based on the relation between wet bulb globe temperature and M-lE s (equivalent to the thermal load to the human body by net radiation and sensible heat exchange), severe weather conditions might place a large thermal load on runners, even if the race venue is changed to Sapporo.View full abstractDownload PDF (1544K) -
Ji-Yoon LEE, Akimasa SHIMANO, Shoko HIKOSAKA, Yasuhiro ISHIGAMI, Eiji ...2020 Volume 76 Issue 4 Pages 180-187
Published: 2020
Released on J-STAGE: October 10, 2020
JOURNAL FREE ACCESSOphiorrhiza pumila is a medicinal plant distributed on the floors of humid inland forests in subtropical areas and accumulates camptothecin (CPT) in whole plant organs. To elucidate the proper light and air temperature conditions for plant growth and CPT yield, we conducted two experiments under controlled environments. In experiment 1, we measured the net photosynthetic rate (Pn) and transpiration rate (E) of the whole plant O. pumila using an open-type assimilation chamber under different photosynthetic photon flux densities (PPFDs) and air temperatures. The result showed that the combination of an air temperature of 28 °C and a PPFD of 100 μmol m-2 s-1 was a good condition for photosynthesis and transpiration. In experiment 2, O. pumila was cultivated for 35 days under three PPFDs and three light periods at an air temperature of 28 °C. At a PPFD of 100 μmol m-2 s-1 and a light period of 16 h, growth was accelerated by the generating the lateral shoots and branches, and total CPT content per plant was the highest among these treatments. The present study revealed that the proper PPFD and light period conditions could enhance growth and CPT accumulation of O. pumila.View full abstractDownload PDF (1769K) -
Yuta OHASHI, Taiki TORII, Yasuhiro ISHIGAMI, Eiji GOTO2020 Volume 76 Issue 4 Pages 188-193
Published: 2020
Released on J-STAGE: October 10, 2020
JOURNAL FREE ACCESSWe constructed 3D models of the greenhouse (168 m2) and tomato plants (plant height: 150 cm). The point cloud data of tomato plants was acquired by a 3D scanner and converted to the 3D model, which was constructed using polygons. The canopy 3D model was installed in the greenhouse 3D model. In addition, the date, time, latitude, longitude, global solar radiation, and optical properties of objects, such as plants and covering material, were used as input values to estimate the amount of solar radiation received by canopy models using the ray tracing. The amount of solar radiation received by the canopy models at different layers under different furrow distances (60-160 cm) was calculated every 1 h. The lower layer and the middle layer of tomato plants were saturated with solar radiation at furrow distances of 120 cm and 100 cm, respectively. However, the radiation received by the upper layer of tomato plants did not change across the range (60-160 cm) of investigated furrow distances. This investigation has provided a visual demonstration of the relationship between the arrangement of cultivated fruit and vegetable plants, such as tomato, in the greenhouse and the amount of solar radiation received.View full abstractDownload PDF (1723K)
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