Journal of the Meteorological Society of Japan. Ser. II
Online ISSN : 2186-9057
Print ISSN : 0026-1165
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Volume 92 , Issue 4
Showing 1-7 articles out of 7 articles from the selected issue
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Invited Review Article
  • Atsumu OHMURA
    Volume 92 (2014) Issue 4 Pages 245-285
    Released: September 26, 2014
    JOURNALS FREE ACCESS
     Energy balance climatology emerged from the 19th century thermodynamics and radiation research. Energy balance consideration offered an attractive intellectual ground to apply the conservation principle to a natural process. The climate system was often compared to the processes in a steam engine. Research into this field started with insufficient theory of radiation and turbulence, primitive instruments, and limited observational data. In the course of the last 150 years, energy balance climatology gradually gathered advanced theories, continuously improved instruments, newly acquired observation platforms, such as space, and high performance computational capability. In the present article, the processes of climate formation are examined by going back to the principle of energy conservation. Further, the development of this branch of science is presented in five stages characterized by similar stages of theoretical and technical progress. This review visits important steps in the course of these developments and examines their value in reaching the present stage of knowledge. Although the achievements of the last 150 years are impressive, the present understanding of energy balance is far from sufficient. The main problem stems from the fact that the scientific community has not fully used the outcome of laboratory experiments and precision field observations. As high-quality observations are presently being made throughout the entire world, a new and improved knowledge of energy balance will become available in the near future.
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Articles
  • Hideaki OHTAKE, Masataka MURAKAMI, Narihiro ORIKASA, Akihiro HASHIMOTO ...
    Volume 92 (2014) Issue 4 Pages 287-304
    Released: September 26, 2014
    JOURNALS FREE ACCESS
     Cold rain processes simulated with a nonhydrostatic cloud-resolving model developed by the Japan Meteorology Agency/Meteorological Research Institute and run at 1 km horizontal resolution (1-km-NHM) with a two-moment bulk parameterization scheme are validated using in situ aircraft observations for orographic snow clouds. To statistically validate cold rain processes simulated by the 1-km-NHM, aircraft observations collected during two winter seasons (March and December 2007, a total of 21 flights) over the Echigo Mountains are analyzed and compared with the model.
     For the cases where the differences in the cloud top heights and/or temperatures between the simulations and aircraft observations are small (i.e., the forecast errors are thought to be relatively small), the horizontal wind direction, wind speed, and vertical wind velocity for all three analysis height intervals (2.0-2.5 km, 2.5-3.0 km, and 3.0-3.5 km above sea level) and over all four analysis areas (Toukamachi, Senjyoji, Shimizu, and Naramata) exhibit reasonable agreement between the numerical simulations and aircraft observations, although the 1-km-NHM overestimated the horizontal wind speed in the cloud layer by 2-3 m s-1. The simulated liquid water contents at every height interval and over every analysis area are significantly underestimated compared with the aircraft observations. Taking into account the underestimation of ice water content (IWC) measured with the Nevzorov TWC/LWC probe, the simulated IWCs in the upper and middle parts of the clouds are also slightly underestimated. The simulated total solid particle number concentrations (TNCs) in the upper and middle parts of the clouds were underestimated compared with the aircraft observations, while the simulated TNCs in the lower parts of the clouds are slightly overestimated. The ratios of simulated cloud ice number concentrations to snow number concentrations are less than unity and much smaller than the corresponding ratios obtained from the aircraft observations. This suggests that the overall conversion from cloud ice to snow in the 1-km-NHM, which occurs primarily through depositional growth, is faster than that in real clouds.
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  • Tsuyoshi YAMAURA, Tomohiko TOMITA
    Volume 92 (2014) Issue 4 Pages 305-325
    Released: September 26, 2014
    JOURNALS FREE ACCESS
     This work examines two physical mechanisms that control the interannual variability of Baiu precipitation from late May to mid-July, using objective analysis data of atmospheric parameters including precipitation from 1979 to 2010 and of sea surface temperature (SST) from 1982 to 2010. In late June, of this period, the mean atmospheric circulation that produces Baiu precipitation is altered. In the early Baiu season (May 26-June 24) after a warm El Niño/Southern Oscillation (ENSO) event, an anomalous anticyclone appears in the western North Pacific (WNP) through the Pacific-East Asian teleconnection, which enhances Baiu precipitation. The anomalous anticyclone is maintained by the Rossby wave response to negative SST anomalies (SSTAs) in the WNP, which persist from the preceding winter until this period. On the other hand, the effect of the Indian Ocean capacitor is essential for Baiu precipitation anomalies in the late Baiu season (June 25-July 19) after a warm ENSO event. Positive SSTAs in the tropical Indian Ocean (TIO) induce a specific atmospheric response with the Matsuno-Gill pattern, forcing an anomalous anticyclone in the WNP that increases Baiu precipitation. This effect occurs only in the late Baiu season, because it is necessary for the anomalous tropospheric heating to extend northeastward from the western TIO with intraseasonal development of the Indian summer monsoon.
     Thus, the physical processes producing the interannual variability of Baiu precipitation differ between the early and late Baiu seasons. Based on these differences, more detailed consideration can be given for the indicators of the interannual variability of Baiu precipitation, i.e., the SSTAs in the tropical Pacific and Indian Oceans. The detailed monitoring of SSTAs in these oceans from the preceding winter has the potential to improve predictions of the interannual variability of Baiu precipitation.
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  • Keisuke MORI, Tomonori SATO
    Volume 92 (2014) Issue 4 Pages 327-346
    Released: September 26, 2014
    JOURNALS FREE ACCESS
     This study investigated the spatiotemporal characteristics of high-temperature events in Hokkaido, Japan, using observational data of 26 years. Statistical analyses revealed that the annual mean frequency of these events was lower (higher) at stations on the western (eastern) side of Hokkaido. The frequency of these events showed clear seasonal variation with two distinct peaks occurring in January and May. In addition, the local time of the high-temperature onset was strongly dependent on the season; the onset occurred more frequently from 1600 to 0400 Japan Standard Time (JST) in January and from 0700 to 1300 JST in May.
     The seasonal dependence mechanism of the high-temperature onset was investigated in eastern Hokkaido, where the frequencies of both January and May high-temperature events were the highest. In January, an extratropical cyclone passage caused intensified warm advection and increased precipitable water vapor, leading to weakened radiative cooling during the night. In May, the high-temperature events were triggered by two different mechanisms related to solar insolation. The first mechanism is explained by dynamic foehn, which forms the subsidence of the high potential temperature layer on the lee of mountains. However, the nocturnal inversion layer prevented vertical mixing of the foehn-induced warm air aloft and cold air near the ground. The surface air temperature dramatically increased after sunrise when the nocturnal inversion layer disappeared. The second mechanism is explained by the combination of airflow diabatically heated by surface sensible heat flux and dynamic foehn. Therefore, solar insolation is the key factor that controlled the diurnal variation in high-temperature events in May.
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  • Kozo NINOMIYA
    Volume 92 (2014) Issue 4 Pages 347-361
    Released: September 26, 2014
    JOURNALS FREE ACCESS
     Genesis of a weak polar mesoscale cyclone (PMC) over the coastal Pacific south of Honshuu Island (central part of Japan) on 7-8 March 1992 is studied using data obtained at two research vessels and observation stations in Japan, satellite cloud images, and objective-analysis data.
     A cumulus-line that formed over the coastal Pacific south of Honshuu Island developed into a comma-shaped cloud system associated with a weak PMC within several hours. A weak cyclonic circulation with a pressure deficit of ˜1 hPa and precipitation of ˜2 mm h-1 were observed in association with the PMC. Synoptic- and meso-scale analysis showed that the PMC formed in a shear-zone over the coastal Pacific south of Honshuu Island during a period of weak polar-air outbreak. The shear-zone formed between the northwesterly streams passing along the western side of the high-mountains area in Honshuu Island and northeasterly streams passing along the eastern side of the high-mountains area.
     This PMC generated under strong baroclinicity in the low-middle troposphere. However, the PMC did not develop into a significant depression and disappeared within ˜2 days after generation. The synoptic-scale conditions for this non-developed PMC are compared with those for developed PMCs described in previous articles. The conditions for this non-developed PMC were characterized by absence of the associated upper cold trough, background low-level anticyclonic circulation, shallow moist layer, and PMC location outside a zone of maximum sea-surface temperature gradient.
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  • Chih-Hsien WEI, Yao-Chung CHUANG, Tai-Hwa HOR, Chi-Chang LIAO, Nan-Chi ...
    Volume 92 (2014) Issue 4 Pages 363-383
    Released: September 26, 2014
    JOURNALS FREE ACCESS
     Through the analysis of Doppler radar data, this study focuses on the characteristics and evolution of convection embedded within the principal band in Typhoon Morakot (2009) under the impingement of the intense southwesterly (SW) monsoonal flow. The intensity of the SW flow is comparable with the typhoon circulation at the third quadrant. The kinematic analysis shows that the northward component of the SW flow decelerates while approaching the rainband, creating significant convergence zones which results in the initiation and development of convective cells within the principal band.
     The vertical kinematic characteristics of the rainband reveal two types of downdrafts namely inner-edge and low-level downdrafts. The inner-edge downdrafts coupled by the radially inward tilting convection were initiated by the precipitation drag. Dynamically, the existence of the perturbed high at 1.5 km altitude in the inner-edge downdrafts supported the finding. Furthermore, it is evident that the distribution of two perturbation highs in the vicinity of the rainband could lead to SW flow deformation locally and fortify the mechanism of convergence, resulting in the merging of convective cells into the rainband. The maximum vertical vorticity coupled with the horizontal wind maximum at the middle levels of the rainband was also observed.
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  • Paul E. CIESIELSKI, Richard H. JOHNSON, Kunio YONEYAMA, Richard K. TAF ...
    Volume 92 (2014) Issue 4 Pages 385-405
    Released: September 26, 2014
    JOURNALS FREE ACCESS
     During the Dynamics of the MJO (DYNAMO) field campaign in 2011, upper-air soundings were launched in Colombo, Sri Lanka, as part of the enhanced northern sounding array (NSA) of the experiment. The Colombo soundings were affected at low levels by the diurnal heating of this large island and by flow blocking caused by elevated terrain to the east of the Colombo site. Because of the large spacing between sounding sites, these small-scale island effects are aliased onto the larger scale impacting analyses and atmospheric budgets over the DYNAMO NSA. To mitigate these local island effects on the large-scale budgets, a procedure was designed that used low-level ECMWF-analyzed fields in Sri Lanka’s vicinity to estimate open-ocean conditions at Colombo’s location as if the island were not present. These “unperturbed” ECMWF fields at low-levels were then merged with the observed Colombo soundings. Results indicate a beneficial impact of using these adjusted fields on several aspects of the budget analyses.
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