農業気象
Online ISSN : 1881-0136
Print ISSN : 0021-8588
ISSN-L : 0021-8588
71 巻, 1 号
選択された号の論文の4件中1~4を表示しています
Full Paper
  • Ari MARYADI, Kikuro TOMINE, Koji NISHIYAMA
    2015 年 71 巻 1 号 p. 1-14
    発行日: 2015年
    公開日: 2015/03/10
    ジャーナル フリー
     Artificial cloud seeding is currently being explored as a method for mitigating drought in certain regions of the Indonesian archipelago. Most ongoing projects have performed hygroscopic seeding using sodium chloride (NaCl) as the seeding agent. Although some positive effects have been observed, the statistical results of previous hygroscopic seeding experiments have generally been inconclusive. Given concerns related to the effectiveness of glaciogenic cloud seeding in tropical areas such as Indonesia, a new seeding approach must be devised from the standpoint of precipitation enhancement. As such, this study introduces a glaciogenic cloud seeding method using liquid carbon dioxide as an alternative technique.
     Since numerical modeling is a key component of weather modification research, this paper reports a numerical simulation conducted using the Weather Model Forecasting version 3.1.1 to investigate glaciogenic seeding experiments over the Kupang region in Indonesia's Nusa Tenggara Province, located on the island of Timor. Simulation results indicate that the rainfall enhancement induced could be separated into two stages, the first of which concerns the direct effects of cloud seeding that enhance the intensity of rainfall from the seeded cloud.
     During the second stage, the interaction of the remaining cloud ice and activated convective cells under the seeded cloud that emerged after the seeding treatment enhanced precipitation in the study area by approximately 40%. The activated convective cells are thought to be strongly influenced by the sea-breeze convergence zone over Timor, indicating that the interaction of the sea-breeze convergence zone and remaining cloud ice caused by glaciogenic seeding are crucial to enhancing rainfall.
Short Paper
  • Neelam NIROULA, Kazuhiko KOBAYASHI, Jianqing XU
    2015 年 71 巻 1 号 p. 15-23
    発行日: 2015年
    公開日: 2015/03/10
    ジャーナル フリー
     We analyzed temporal changes of sunshine duration (SSD) and number of rainy days (NRD) in Nepal across its three physiographic regions: plains, low-hills, and high-hills and mountains for the period from 1987 to 2010 from records at 13 meteorological stations. We found declining trends in SSD (i.e., solar dimming) across Nepal at a rate of -0.20% per year, with the highest decline occurring during the post-monsoon season (-0.33% per year), followed by the pre-monsoon season (-0.24% per year). A close look at individual stations indicated that declines in pre- and post-monsoon seasons are common regional phenomena. By region, dimming was pronounced (-0.56% per year) in the plains at 0-300 m above sea level and gradually diminished as elevation rose. The NRD for the same 13 stations showed a significant declining trend (-0.20% per year), which suggests that the change in NRD is not a major driver of the decreased SSD in Nepal. We argue that the decline in SSD might be influenced by transboundary air pollution from the Indian subcontinent and biomass burning across the region as suggested by other studies.
  • Daitaro ISHIKAWA, Gerrit HOOGENBOOM, Susumu HAKOYAMA, Etsuji ISHIGURO
    2015 年 71 巻 1 号 p. 24-31
    発行日: 2015年
    公開日: 2015/03/10
    ジャーナル フリー
     The present study was carried out for the fundamental suggestion of the physical and chemical insight of the spectral change due to the phenological stage by using chlorophyll absorption bands in the 400-1100 nm region. The time-series spectra data during the cultivation period were measured at several sites in situ. The peak of the time-series second derivative spectra in the 660-700 nm region arose around the Day of Year (DOY): 220-230 and DOY:240-250 periods. These periods agree well with the active tillering stage and the heading, respectively. Additionally, the negative peak of the second derivative spectra in the DOY:230-240 accommodates the maximum tiller number stage. The time-series behavior of band shifts of peak wavelength in the 650-700 nm region corresponded to that of the intensity of second derivative spectra. These results indicate a possibility that the aggregation of chlorophyll molecules become stronger in the DOY:220-255 region with the increase of the chlorophyll concentration. Simultaneously, the blue shift of the DOY:255-260 period indicates that the aggregation becomes weaker according to the senescence of leaves. The result of band shift thus provides the insights of the change in the time-series intensities from the view of the chemical interaction of chlorophyll molecules in the rice leaf.
Full Paper
  • Wonsik KIM, Akira MIYATA, Ali ASHRAF, Atsushi MARUYAMA, Amnat CHIDTHAI ...
    2015 年 71 巻 1 号 p. 32-50
    発行日: 2015年
    公開日: 2015/03/10
    ジャーナル フリー
     To understand how terrestrial ecosystems respond to global climate change, researchers have globally measured the energy, water and carbon dioxide flux densities (F) globally over various types of vegetation by the eddy covariance (EC) method. However, the process of F calculation and the method of quality control and quality assurance (QCQA) are complex and site specific. Moreover, instantly maintaining remote EC flux measurement sites against instrumentation problems and administrative difficulties is laborious. To overcome these issues, particularly those of realtime F monitoring and prompt site management, FluxPro was created.
     FluxPro consists of three functional systems: 1) a gathering system that transports EC measurements from various sites to the FluxPro management server; 2) a cooking system that computes F and its frictional uncertainty (ε) together with micrometeorological variables (V); and 3) a serving system that presents the results of the gathering and cooking systems as charts to be distributed over the internet in realtime. Consequently, FluxPro could become an appropriate system for realtime-multi-site management, since it not only automatically monitors F with ε and V but also continuously surveils EC sites, including copious information and an email alert system.
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