著者

和達 清夫

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.12, no.9, pp.496-497, 1934 (Released:2009-02-05)

参考文献数

5

著者

Masanori OIGAWA Eugenio REALINI Hiromu SEKO Toshitaka TSUDA

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.92, no.3, pp.189-205, 2014 (Released:2014-07-04)

参考文献数

24

被引用文献数

4

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A simulation study was conducted to investigate the retrieval of meso-γ scale precipitable water vapor (PWV) distribution with the Quasi-Zenith Satellite System (QZSS) using output from a non-hydrostatic model (JMA NHM). The evaluation was performed on PWV values obtained by simulating three different methods: using all GPS satellites above an elevation angle higher than 10° (PWVG) (conventional Global Navigation Satellite System (GNSS) meteorology method), using only the QZSS satellite at the highest elevation (PWVQ), and using only the GPS satellite at the highest elevation (PWVHG). The three methods were compared by assuming the vertically integrated water vapor amounts of the model as true PWV. As a result, the root mean square errors of PWVG, PWVQ, and PWVHG were 2.78, 0.13, and 0.59 mm, respectively, 5 min before the rainfall. The time series of PWVHG had a large discontinuity (˜ 2 mm) when the GPS satellite with the highest elevation changed, while that of PWVQ was small because the elevation at which the highest QZSS satellites change was much higher. The standard deviation of PWVQ was smaller than those of PWVG and PWVHG, which vary significantly depending on GPS satellite geometry. When the spatial distributions of PWVG and PWVQ were compared to the meso-γ scale distribution of the reference PWV, PWVG smoothed out the PWV fluctuations, whereas PWVQ captured them well, due to the higher spatial resolution achievable using only high-elevation slant paths. These results suggest that meso-γ scale water vapor fluctuations associated with a thunderstorm can be retrieved using a dense GNSS receiver network and analyzing PWV from a single high-elevation GNSS satellite. In this study, we focus on QZSS, since this constellation would be especially promising in this context, and it would provide nearly continuous PWV observations as its highest satellite changes, contrary to using the highest satellites from multiple GNSS constellations.

著者

Hong-Li REN Fei-Fei JIN Malte F. STUECKER Ruihuang XIE

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.91, no.6, pp.835-842, 2013 (Released:2014-01-10)

参考文献数

30

被引用文献数

8 37

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During the late 1970s, the El Niño-Southern Oscillation (ENSO) experienced a notable regime change, manifested by a change in amplitude, dominant ENSO period, and sea surface temperature anomaly (SSTA) propagation characteristics. The present study shows that these features of the ENSO regime change are associated with property changes of the canonical ENSO, i.e., cold-tongue (CT) type ENSO. Another signature of the ENSO regime change is manifested in the frequent occurrence of a warm-pool (WP) type ENSO that accompanies SSTAs centered over the central Pacific near the WP edge and exhibits characteristics differing from those of the CT ENSO. The distinct manifestations of the two types of ENSO detected in this ENSO regime change are clearly identifiable with the removal of the strong background decadal signal. Since the late 1970s, the WP ENSO has featured a weak eastward (westward) propagation of the SSTA center in the developing (decaying) phase, which makes no net contribution to the observed eastward propagation, and a 2-3 yr period compared to the 4-5 yr period of the CT ENSO. Observations strongly suggest that the WP and CT ENSO are independent quasi-biennial and quasi-quadrennial modes, respectively, of the tropical Pacific climate variability. Our observations also suggest that these two ENSO modes have coexisted actively since the late 1970s when either El Niño or La Niña can be separated into the two types.

著者

Youmin TANG Bin YU

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.86, no.6, pp.867-881, 2008 (Released:2009-01-29)

参考文献数

44

被引用文献数

4 10

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Using the Hilbert Singular Value Decomposition (HSVD) and the Nonlinear Canonical Correlation Analysis (NLCCA), we analyzed the statistical relationship of MJO (Madden-Julian Oscillation) and ENSO (El Niño and Southern Oscillation). It was found that while a linear analysis produced no significant relationship between MJO and ENSO, a low-order nonlinear analysis based on the quadratic function of HSVD led to statistically significant lagged correlations. When their nonlinear relationship was further extracted by the NLCCA, stronger correlation was obtained, with the maximum correlation coefficient appearing while the MJO signals preceding the ENSO signals by around 2 months and 5.6 months respectively. The time lags producing the maximum correlation are respectively consistent with the characteristic time of MJO influencing ENSO dominated by two physical processes: the equatorial Kelvin waves and air-sea feedback. Corresponding to the two different physical processes, ENSO shows different features of development. In the former scenario, the westerly winds in the western Pacific excite the equatorial Kelvin waves which propagate eastward and deepen the thermocline in the eastern Pacific, resulting in the sea surface warming at the far eastern Pacific near the coast. In the latter scenario, the westerly anomalies in the western Pacific precede the development of El Niño through bringing surface warm water into the central and eastern Pacific, thus the sea surface warming occurs across the whole eastern Pacific ocean.

著者

藤部 文昭

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.65, no.6, pp.923-929, 1987 (Released:2007-10-19)

参考文献数

15

被引用文献数

1 28

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1961~1985年の地上気象観測資料を使って,東京の都心における気温その他の気象要素の平日と週末の差を調べ,以下の結果を得た。(1) 日曜口(祝日等を含む)の気温は平日よりも低い。気温差は昼間に大きく,昼間の気温差は25年間の平均で約0.2°Cである。(2)気温差は時代とともに増大しており,近年は土曜日の夜にも低温が現れる。(3)気温差は年間を通じて認められるが,値は季節•天気•風速によって多少異なる。(4)日曜日の昼間は気圧が平日よりも0.05mb程度高い。このことから昼間の気温低下は数百 m 上空まで及んでいることが分かる。夜間は気圧差は検出されず,気温低下は地上付近だけに限られると思われる。(5)他の二,三の気象要素にも平日と日曜日の差が認められる。なお,曜日や日付けによる平日同士の気温差は認められない。

著者

穂積 邦彦 孫野 長治

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.62, no.3, pp.522-533, 1984 (Released:2007-10-19)

参考文献数

8

被引用文献数

4 27

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冬の季節風時に日本海中部に発生する収束帯にともなう帯状雲を,日本航空の定期便から写真撮影することにより観測し,その構造を三角測量方法で解析した。山陰地方のレーダー写真や日降雪量の分布も考慮して,収束雲帯の南西側の端に高い雲堤の列があり,これが山陰地方に局地的な大雪をもたらすことがわかったまた収束雲帯の発生機構を議論し,その立体構造のモデルが提案された。

著者

Masato MORI Masahide KIMOTO Masayoshi ISHII Satoru YOKOI Takashi MOCHIZUKI Yoshimitsu CHIKAMOTO Masahiro WATANABE Toru NOZAWA Hiroaki TATEBE Takashi T. SAKAMOTO Yoshiki KOMURO Yukiko IMADA Hiroshi KOYAMA

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.91, no.4, pp.431-452, 2013 (Released:2013-09-06)

参考文献数

54

被引用文献数

5 14

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In line with the experimental design for near-term climate prediction toward the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, we perform ensembles of initialized decadal hindcast and near-future projection using three versions of the coupled atmosphere-ocean model MIROC. In the present study, we explore interannual and multiyear predictability of tropical cyclone (TC) activity in the western North Pacific (WNP) using the initialized hindcasts and examine global warming impacts on TC activity in the near-future on the basis of near-future projections up to 2035. The hindcasts of year-to-year variation in TC number capture the observed values reasonably well. Moreover, interannual variability of TC genesis and occurrence frequency associated with the El Niño Southern Oscillation are found to be predictable, mainly through better prediction of sea surface temperature (SST) and large-scale vorticity anomalies in the lower troposphere. These results indicate that the models can reproduce the major basic mechanisms that link TC genesis with large-scale circulation. Skillful prediction of TC number is likely difficult on multiyear timescales, at least based on our hindcasts, but through initializations, the three-year-mean hindcasts from 1998 onward reasonably capture observed major characteristics of TC activity associated with Pacific climate shift during the late 1990s. Near-future projections (2016-2035) suggest significant reductions (approximately 14%) in TC number, particularly over the western part of the WNP, even under scenarios in which projected global warming is less prominent than that at the end of this century. This reduction is likely due to the suppression of large-scale lower tropospheric vorticity and relative humidity and the enhancement of vertical wind shear. The projected SST exhibits a more pronounced warming over the eastern tropical Pacific than over the western region and accompanies the weakening of Walker circulation via redistribution of tropical convection activity, which appears to be responsible for the change in the large-scale fields in the WNP.

著者

Takuji SUGIDACHI Masatomo FUJIWARA

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.91, no.3, pp.323-336, 2013 (Released:2013-07-17)

参考文献数

22

被引用文献数

1 3

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Comparisons of relative humidity (RH) measurements between the Meisei RS-06G radiosonde and a chilled-mirror hygrometer revealed that the RS-06G radiosonde shows a stepwise change of ~3% RH at 0°C (drying when air temperature is decreasing). This is due to a discontinuous correction factor in the processing software that compensates for the temperature dependence of the RH sensor. Results from chamber experiments regarding the temperature and RH dependence of RS-06G RH sensors under steady-state conditions showed a wet bias exceeding 7% RH below ~+10°C. As this result contradicted previous in-flight intercomparisons that used the original manufacturer's correction, we investigated a possible additional dry bias caused by a thermal lag in the RH sensor. We speculated that the thermal lag of the RH sensor typically causes a dry bias during a tropospheric ascent, which largely compensates for the wet bias related to the temperature and RH dependence of the RH sensor. We observed that the experimental results of the temperature and RH dependence considering the thermal lag were in agreement with the extrapolation of the original manufacturer's correction. Consequently, we proposed to extrapolate the original manufacturer's correction, which is currently applied at temperatures between −40°C and 0°C, up to +14.5°C to resolve the artificial stepwise change at 0°C. Because the RS-06G radiosonde is a successor to the Meisei RS-01G and RS2-91 radiosondes, which have adopted the same RH sensor material installed since July 1999 and have used the same processing software, the current results should be applied to the data obtained by those radiosondes. The bias of RS-06G RH measurements using this new correction is estimated to be within 7% RH, which is within the manufacturer's specifications, being drier at +40°C and wetter between −40°C and +10°C.

著者

Chiaki KOBAYASHI Kiyotaka SHIBATA

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.89, no.4, pp.363-376, 2011-08-25 (Released:2011-08-31)

参考文献数

35

被引用文献数

1 4

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Dynamical contributions to past long-term changes in the lower stratospheric ozone over the northern mid-latitudes are evaluated using a chemical transport model (CTM) forced by the horizontal wind of the Japanese 25-year Reanalysis (JRA-25). Two simulations (i.e., one is a simulation that prescribes the time-dependent vertical profile of halogens and the other is a simulation which uses the fixed vertical profile of halogens at 1979.) were conducted to estimate chemical and dynamical contributions to the long-term changes in stratospheric ozone during the last three decades. Different from previous similar studies using meteorological data of ECMWF (European Centre for Medium Weather Forecast) 40-year re-analysis (ERA-40), our current simulation does not show a large positive anomaly of simulated total ozone over northern mid-latitudes in the late 1980s, which is consistent with the observation. Because the trend of the fixed halogen simulation amounts to about two-third of that of the time-dependent halogen simulation during 1980–1993 in the northern mid-latitudes, it is evaluated that about two-thirds of the negative trend in total ozone comes from dynamics in the northern mid-latitudes. Since the increasing ozone from 1994 to 1998 is also represented in the fixed halogen simulation, it is considered that the increase of ozone was mainly due to dynamics as pointed out in previous studies. However the dynamical contribution to the trend after 1994 could not be evaluated in our simulation because of simulated ozone gap in 1998. In the same manner, it is evaluated that about two-thirds of the negative ozone trend in the lower stratosphere comes from dynamics in the northern mid-latitudes from 1980 to the mid-1990s. The simulation results indicate that the effect of transport (dynamical influence) is predominant for the negative ozone trend in the lower stratosphere from 1980 to mid-1990s, while the upper stratospheric ozone trend is strongly influenced by long-term changes in halogens (chemical influence).