著者

Michiya Hayashi Masahiro Watanabe

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.12, pp.42-45, 2016 (Released:2016-02-25)

参考文献数

36

被引用文献数

1 2

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Westerly (WWEs) and easterly (EWEs) wind events, short-lived anomalous westerly and easterly surface winds, are known to occur with unusual large magnitude over the equatorial Pacific. As their relative frequency of occurrence and dependence on background conditions are yet to be fully clarified, we analyzed daily surface winds for 1982-2013 from which WWEs and EWEs are detected. Both types of events appear over the Pacific warm pool, where sea surface temperature (SST) is sufficiently high for active deep convection, and favorably occur with increasing Niño4 SST. However, the frequency of occurrence of EWEs is less than that of WWEs, resulting in asymmetry in wind amplitude. Local and remote anomalous convections are equally important in exciting these events, but different local development processes cause the asymmetry in the frequency of occurrence. These results can also be seen in wind stress anomalies, albeit obscured due to nonlinearity therein.

著者

Yuki Nishikawa Masaki Satoh

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.12, pp.232-236, 2016 (Released:2016-08-31)

参考文献数

26

被引用文献数

3

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As nonhydrostatic models have higher resolution, a topographical representation scheme is desirable as an alternative to the terrain-following approach, which is unstable for steep topography. We developed a conserved topographical representation scheme using a thin-wall approximation in z-coordinates (the CT scheme). This scheme is formulated by the flux-form finite-volume method with a flux limiter, so that the total integrals over the entire domain of prognostic variables are conserved: this is advantageous compared to the conventional thin-wall approximation method. The CT scheme is easily implemented for existing models that use the finite-volume method. We constructed the scheme to satisfy conservation of mass, horizontal momentum, and total energy. We compared the results of the CT scheme for an isolated mountain case with those of a step-mountain (SM) method. The CT scheme represents the propagation of gravity waves more accurately than the SM method. The upward flux of horizontal momentum becomes more vertically uniform for the CT scheme than for the SM method over time. In addition, the horizontal momentum budget shows that the total momentum is reduced by reaction force at the lower boundary with changes due to numerical damping in the upper layers and numerical filters in the free layers.

著者

Shuhei Maeda Yusuke Urabe Kazuto Takemura Tamaki Yasuda Youichi Tanimoto

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.12, pp.17-21, 2016 (Released:2016-02-11)

参考文献数

19

被引用文献数

2 10

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We investigated features of the atmosphere and ocean to seek a possible candidate that suppressed the growth of the El Niño event in 2014. In the boreal summer-fall season, equatorially antisymmetric sea surface temperature (SST) anomalies with a positive (negative) sign to the north (south) of the equator prevailed in the central and eastern tropical Pacific. In association with the SST anomalies, cumulus convective activity was enhanced in the region of the climatological Intertropical Convergence Zone (ITCZ). Anomalous southerly surface winds flowing across the equator toward the ITCZ induced upward latent heat flux anomalies and lowered SST in the near-equatorial region. These coherent spatial patterns between SST, wind, and latent heat flux anomalies suggested that the wind-evaporation-SST (WES) feedback sustained the suppression of the El Niño growth. A linear baroclinic model experiment indicated that the enhanced convective heating in the ITCZ also contributed to sustain the anomalous surface southerlies across the equator by the intense meridional atmospheric circulation over the equator. These results indicate that the anomalous southerlies across the equator sustained by the WES feedback and intense convective heating in the ITCZ contributed to the suppression of the El Niño growth.

著者

Seiji KATO Norman G. LOEB David A. RUTAN Fred G. ROSE

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.93, no.6, pp.597-612, 2015 (Released:2016-01-13)

参考文献数

107

被引用文献数

11

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NASA’s Clouds and the Earth’s Radiant Energy System (CERES) project integrates CERES, Moderate Resolution Imaging Spectroradiometer (MODIS), and geostationary satellite observations to provide top-of-atmosphere (TOA) irradiances derived from broadband radiance observations by CERES instruments. It also uses snow cover and sea ice extent retrieved from microwave instruments as well as thermodynamic variables from reanalysis. In addition, these variables are used for surface and atmospheric irradiance computations. The CERES project provides TOA, surface, and atmospheric irradiances in various spatial and temporal resolutions. These data sets are for climate research and evaluation of climate models. Long-term observations are required to understand how the Earth system responds to radiative forcing. A simple model is used to estimate the time to detect trends in TOA reflected shortwave and emitted longwave irradiances.

著者

Akira Yamazaki Meiji Honda Akira Kuwano-Yoshida

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.11, pp.59-64, 2015 (Released:2015-05-11)

参考文献数

12

被引用文献数

1 16

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The influence of large-scale atmospheric blocking over the northwestern Pacific on heavy snowfall events in the Kanto area and on the Pacific Ocean side of northern Japan (PNJ) within the time scale of ∼10 days was examined through blocking case studies. The past 14 blocking cases over the Pacific, including the blocking during early- to mid-February 2014 that influenced a record-breaking snowfall over the Kanto area, were analyzed using a long-term reanalysis dataset and local meteorological observation station data. Results reveal that blocking over the Pacific causes large precipitation over the Kanto area and the PNJ by shifting cyclone (storm) tracks towards the east coast of Japan from their usual eastward course across the mid-Pacific via the south coast of Japan. Excessive passing of cyclones caused large precipitation in the Kanto area and snowfall in the PNJ. In the blocking cases with heavy snowfall events in the Kanto area, a strong cold-air inflow over Japan also existed in the lower troposphere originating from east Siberia, which initiated synoptic ground cold-air environments in the Kanto area.

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.93, no.1, pp.1-2, 2015 (Released:2015-03-18)

参考文献数

5

著者

土屋 清

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.47, no.6, pp.457-465, 1969 (Released:2008-05-27)

参考文献数

14

被引用文献数

26

---

約4時間の時間間隔で撮影した気象衛星エッサ7号と8号の写真に現われた済州島風下のKarman鋤うず列状の雲を解析した結果,次のことがわかった.雲のうず列から得られた無次元パラメーターは,これまで2次元流の流体実験から得られたKarman鋤うず列発生の限界値を満足しており,Karmanうず列の理論で説明できる.島の抵抗とうず列のwakeによる抵抗を考慮して,うず列の間隔と個々のうずの間隔の比だけから,うず列の移動速度を求める計算式を導いた.結果実況とかなりよく合い,比が0.332のとき.一般流の約76%であった.済州島の風下に,このような雲のうず列のできるのは,晩秋から初春にかけて,比較的強い(10ノット以上)北風が持続し,1000m付近(島の中央部の山の高さの半分)に顕著な逆転のある時である.

著者

Hiroshige TSUGUTI Teruyuki KATO

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.2, pp.163-183, 2014 (Released:2014-05-16)

参考文献数

32

被引用文献数

4 22

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On 20 October 2010, a heavy rainfall event occurred on Amami-Oshima Island, Japan, delivering a record 622 mm of rainfall in one day. To clarify the factors underlying this event, the supply mechanism and formation process of low-level humid air and the formation and maintenance mechanisms of the precipitation systems causing the heavy rainfall were examined using observation data, objective analysis data, and numerical simulation results. These investigations showed that low-level humid air, carried to Amami-Oshima Island during the rainfall event by strong east-northeasterly winds, originated more than 500 km to the east-northeast as low-level dry air on the northern side of a stationary front. This dry air was transformed into humid air on the way to the island by receiving large latent heat flux from the sea surface (air-parcel transformation). Warm sea surface temperatures around Amami-Oshima Island, about 2°C higher than the annual mean, contributed to this air-parcel transformation. At Amami-Oshima Island, the collision of the humid flows with a cold pool formed under earlier precipitation systems contributed significantly to the formation and maintenance of the precipitation systems, supplemented by topographic effects of the island.

著者

Kensuke NAKAJIMA Eizi TOYODA Masaki ISHIWATARI Shin-ichi TAKEHIRO Yoshi-Yuki HAYASHI

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.82, no.6, pp.1483-1504, 2004 (Released:2005-03-02)

参考文献数

23

被引用文献数

6 9 7

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For the purpose of examining the initial development of the atmospheric response to a warm SST anomaly placed at the equator, an ensemble switch-on experiment is conducted with an aqua-planet GCM. An ensemble average of the size of 128 significantly reduces the transient noises caused by both small scale convective activity and large scale intraseasonal variability.In the first three days after the switch-on of the SST anomaly, a convection center develops above the warm SST area. As a barotropic response to the heating of convection center, a global increase of surface pressure occurs outside the low pressure region around the warm SST area. The response after the emergence of the high pressure anomaly is consistent with Gill (1980); a warm Kelvin wave-like anomaly is emitted to the east of the convection center, while a warm Rossby wave-like anomaly is emitted to the west.The Kelvin wave-like signal propagates at a speed slower than that of free Kelvin wave expected from its vertical wavelength, suggesting that the signal is a “moist” Kelvin wave. Transient decrease of precipitation occurs at the moist Kelvin wave front; a decrease of convection associated with the downward motion at the wave front is consistent with its slow propagation. After several days, precipitation recovers and is even intensified because of the surface frictional convergence associated with the Kelvin wave-like equatorial low pressure anomaly. To the west of the warm SST area, on the other hand, precipitation decreases monotonically. The continuous reduction of precipitation is caused by the equatorial surface frictional divergence associated with the relatively high pressure anomaly at the equator of the Rossby wave structure.Finally, there appears a slow zonally symmetric response within the Hadley cell characterized with surface pressure rise in the tropics and westerly wind anomaly in the troposphere. The change of eddy zonal momentum transport, together with the transport toward the lower level by the Hadley circulation and the geostrophic adjustment to the resulting low level westerly acceleration, seems to be responsible for the response.

著者

Trismidianto Tri Wahyu Hadi Sachinobu Ishida Qoosaku Moteki Atsuyoshi Manda Satoshi Iizuka

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.12, pp.6-11, 2016 (Released:2016-01-25)

参考文献数

26

被引用文献数

23

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This study analyzed the oceanic convective systems that induced heavy rainfall over the western coast of Sumatra on 28 October 2007. The convective systems that satisfied the definition of a mesoscale convective complex (MCC), as identified by infrared satellite imagery, developed repeatedly for 16 hours over the Indian Ocean near Sumatra. The MCC developed from midnight on 27 October until the early morning of 28 October, and it was intensified by the land breeze from Sumatra. New convective systems around the decaying MCC were generated during the daytime of 28 October, and they propagated to the western coast of Sumatra in the evening because of a divergent outflow from a cold pool. The combination of the land breeze from Sumatra and cold pool outflows from the decaying MCC was a significant factor in the formation of the convective system that induced strong rainfall up to 46 mm h−1 over the western coast of Sumatra.

著者

Ahoro ADACHI Takahisa KOBAYASHI Hiroshi YAMAUCHI

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.93, no.3, pp.359-388, 2015 (Released:2015-07-10)

参考文献数

78

被引用文献数

1 8

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A method for estimating three parameters of a gamma raindrop size distribution (DSD) model and the rainfall rate from polarimetric radar at attenuating frequency was developed. The algorithm was developed based on the self-consistency principle but was expanded to consider the attenuation effect by describing the interrelation between polarimetric measurements along the range profile. The proposed method does not require any assumptions of relation among DSD parameters or simplifications of equations that describe the relation between the axis ratio and diameter of raindrops, which have been used in previous studies. Moreover, the proposed algorithm needs no external reference data such as two-dimensional video disdrometer measurements for attenuation corrections because it retrieves the co-polar and differential specific attenuation from the interrelation among the polarimetric measurements. The performance of this algorithm was evaluated by comparison with optical disdrometers and a weighing precipitation gauge. The evaluation of the algorithm showed that the retrieved three DSD parameters of raindrops, reflectivity, and differential reflectivity from actual C-band polarimetric radar data have fairly good agreement with those obtained by surface measurements. Moreover, rainfall rates retrieved using this algorithm have comparable precision with those estimated from the specific differential phase, and outperform those estimated through the so-called Z-R relation, particularly during heavy rainfall. Furthermore, the effects of raindrop temperature and shape parameter on the retrieval of the rainfall rate were examined. The results show that for radar operating at C-band, a raindrop temperature error of 10°C may be negligible in rainfall rate estimations, whereas a shape parameter error of 2 may increase the error of the rainfall rate estimation by 10 %.

著者

平山 操

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.16, no.11, pp.421-430, 1938-11-05 (Released:2009-02-05)

参考文献数

6

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Recently, Dellinger's phenomena which make the transmission of short waves impossible, attract the attentions of those who are engaged in the wireless-communication or in the observation of the earth's magnetic field and many studies have been made in the ionospheric conditions and magnetic and electric fields. The author investigated the magnetic field of the phenomena occurred during 1935-36, and found that the disturbance in the ionosphere not far from Japan causes the magnetic changes (De) so as to increase the amplitude of the diurnal variation. On comparatively quiet days, we obtained 0.2-0.9 for the ratio De/Ω0, where Ω0 is the departure from the preceding and following midnight.The author calc_??_lated the magnetic potential of the disturbing field by the increase of electrons in the ionosphere. When the increase is constant in the area Se, where σ0+σs and σ0 are the total conductivities when the ionosphere is disturbed and when it is not disturbed respectively, where [φ0]m is the mean normal current function in Se, α the ratio of current in the external and internal portions (Si) induced in the earth-core, and ωe or ωi are the solid angles subtended by Se and Si respectively. From these studies we see that the dynamo-theory is appropriate for interpreting De and the drift current and diamagnetic theories are not, since De is always produced in the sense to decrease the permanent field in the latter theories

著者

Masuo NAKANO Teruyuki KATO Syugo HAYASHI Sachie KANADA Yoshinori YAMADA Kazuo KURIHARA

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.90A, pp.339-350, 2012 (Released:2012-06-07)

参考文献数

32

被引用文献数

14 34

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A 5-km-mesh nonhydrostatic cloud-system-resolving regional climate model (NHM-5km) has been developed at the Meteorological Research Institute (MRI) of the Japan Meteorological Agency (JMA) by improving upon the JMA operational mesoscale model (MSM). Three major changes have been made to MSM: the Kain-Frisch convective parameterization scheme has been improved to reduce the incidence of false predictions of rainfall areas along coastlines during the warm season, a spectral nudging method has been introduced to avoid phase-gap between the inner model (NHM-5km) and the outer model, and a Simple Biosphere model has been applied for sophisticated representation of land surface processes. This article presents details of the first two of these modifications.A present-day climate simulation is performed using NHM-5km by nesting within the results of a 20-kmmesh atmospheric global climate model (MRI-AGCM3.2S). Taylor’s skill score is used to compare the performances of NHM-5km and MRI-AGCM3.2S in terms of reproducing the spatial pattern of precipitation-based extreme indices over the Japanese Islands. The comparison shows that NHM-5km yields a significant improvement in reproducing the present-day climatology (e.g., the maximum number of consecutive dry days and the simple daily precipitation intensity index), suggesting that NHM-5km is a reliable tool for accurately predicting future changes in extreme weather at a fine spatial resolution.

著者

Philippe BARON Shoken ISHII Kozo OKAMOTO Kyoka GAMO Kohei MIZUTANI Chikako TAKAHASHI Toshikazu ITABE Toshiki IWASAKI Takuji KUBOTA Takashi MAKI Riko OKI Satoshi OCHIAI Daisuke SAKAIZAWA Masaki SATOH Yohei SATOH Taichu Y. TANAKA Motoaki YASUI

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.95, no.5, pp.319-342, 2017 (Released:2017-10-04)

参考文献数

42

被引用文献数

10

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A feasibility study of tropospheric wind measurements using a coherent Doppler lidar aboard a super low altitude satellite is being conducted in Japan. The considered lidar uses a 2.05 μm laser light source of 3.75 W. In order to assess the measurement performances, simulations of wind measurements were conducted. The mission definition is presented in a companion paper (Part 1) while, in this paper, we describe the measurement simulator and characterize the errors on the retrieved line-of-sight (LOS) winds. Winds are retrieved from the Doppler-shift of the noisy backscattered signal with a horizontal resolution of 100 km along the orbit track and a vertical resolution between 0.5 and 2 km. Cloud and wind fields are the pseudo-truth of an Observing System Simulation Experiment while aerosol data are from the Model-of-Aerosol-Species-IN-the-Global-AtmospheRe (MASINGAR) constrained with the pseudo-truth wind. We present the results of the analysis of a full month of data in summer time for a near-polar orbiting satellite and a LOS nadir angle of 35°. Below ≈ 8 km, the ratio of good retrievals is 30-55 % and the median LOS wind error is better than 0.6 m s−1 (1.04 m s−1 for the horizontal wind). In the upper troposphere, the ratio is less than 15 % in the southern hemisphere and high-latitudes. However, the ratio is still 35 % in the northern Tropics and mid-latitudes where ice-clouds frequently occur. The upper-tropospheric median LOS-wind measurement error is between 1-2 m s−1 depending on the latitude (1.74-3.5 m s−1 for the horizontal wind). These errors are dominated by uncertainties induced by spatial atmospheric inhomogeneities.

著者

Shoken ISHII Philippe BARON Makoto AOKI Kohei MIZUTANI Motoaki YASUI Satoshi OCHIAI Atsushi SATO Yohei SATOH Takuji KUBOTA Daisuke SAKAIZAWA Riko OKI Kozo OKAMOTO Toshiyuki ISHIBASHI Taichu Y. TANAKA Tsuyoshi T. SEKIYAMA Takashi MAKI Koji YAMASHITA Tomoaki NISHIZAWA Masaki SATOH Toshiki IWASAKI

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.95, no.5, pp.301-317, 2017 (Released:2017-10-04)

参考文献数

57

被引用文献数

15

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A working group is studying the feasibility of a future Japanese space-borne coherent Doppler wind lidar (CDWL) for global wind profile observation. This study is composed of two companion papers: an instrumental overview of the space-borne CDWL for global wind profile observation (Part 1), and the wind measurement performance (error and bias) investigated using a full-fledged space-borne CDWL simulator (Part 2). This paper aims to describe the future space-borne CDWL in terms of technical points and observation user requirements. The future mission concept is designed to have two looks for vector wind measurement with vertical resolutions of 0.5 (lower troposphere: 0-3 km), 1 (middle troposphere: 3-8 km), and 2 km (upper troposphere: 8-20 km) and horizontal resolution of < 100 km along a satellite. The altitude and orbit of the satellite are discussed from a scientific viewpoint. The candidate altitude and orbit of the satellite are 220 km and an inclination angle of 96.4° (polar orbit) or 35.1° (low-inclination-angle orbit). The technical requirements of the space-borne CDWL are a single-frequency 2-μm pulse laser with an average laser power of 3.75 W, two effective 40-cm-diameter afocal telescopes, a wide-bandwidth (> 3.4 GHz) detector, a high-speed analog-to-digital converter, and a systematic lidar efficiency of 0.08. The space-borne CDWL looks at two locations at a nadir angle of 35° at two azimuth angles of 45° and 135° (225° and 315°) along the satellite track. The future space-borne CDWL wind profile observation will fill the gap of the current global wind observing systems and contribute to the improvement of the initial conditions for numerical weather prediction (NWP), the prediction of typhoons and heavy rain, and various meteorological studies.

著者

IWABUCHI Hironobu PUTRI Nurfiena Sagita SAITO Masanori TOKORO Yuka SEKIGUCHI Miho YANG Ping BAUM Bryan A.

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

pp.2018-001, (Released:2017-09-15)

被引用文献数

46

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An algorithm for retrieving the macroscopic, physical and optical properties of clouds from thermal infrared measurements is applied to the Himawari-8 multiband observations. A sensitivity study demonstrates that the addition of the single CO2 band of Himawari-8 is effective for the estimation of cloud top height. For validation, retrieved cloud properties are compared systematically with collocated active remote sensing counterparts with small time lags. While retrievals agree reasonably for single-layer clouds, multilayer cloud systems with optically thin upper clouds overlying lower clouds are the major source of error in the present algorithm. Validation of cloud products is critical for identifying the characteristics, advantages and limitation of each product and should be continued in the future. As an application example, data are analyzed for eight days in the vicinity of the New Guinea to study the diurnal cycle of the cloud system. The present cloud property analysis investigates cloud evolution through separation of different cloud types and reveals typical features of diurnal cycles related to the topography. Over land, middle clouds increase from 0900 to 1200 local solar time (LST), deep convective clouds develop rapidly during 1200–1700 LST with a subsequent increase in cirrus and cirrostratus cloud amounts. Over the ocean near coastlines, a broad peak of convective cloud fraction is seen in the early morning. The present study demonstrates the utility of frequent observations by Himawari-8 for life cycle study of cloud systems, owing to the ability to capture their continuous temporal variations.

著者

Toshihisa ITANO Kiyoshi MARUYAMA

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.87, no.4, pp.747-753, 2009 (Released:2009-09-09)

参考文献数

12

被引用文献数

5 11

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The effect of the horizontal component fH of the planetary vorticity on the symmetric stability of zonal flow is investigated using the linearized Boussinesq equations on the f -plane. It is shown that, as in the case of neglecting fH, the stability under full-component Coriolis force is determined by the sign of the potential vorticity. It is also revealed that even in such a generalized situation, the movement associated with the symmetric instability can be decomposed into two independent motions, i.e., the buoyancy oscillation (or instability) modified by the Coriolis force and the inertial oscillation (or instability) modified by the buoyancy. The squared product of their frequencies remains proportional to the potential vorticity of the zonal flow. Meanwhile, the horizontal component of the planetary vorticity is found to exhibit both stabilizing and destabilizing effects, although there is a wide range of stable regions that are not affected by fH. The existence of fH also causes an asymmetry such that the stability changes depending on the sign of the vertical shear of the zonal flow, even if the Richardson number and the dimensionless relative vorticity are maintained constant.

著者

Masanori OIGAWA Takafumi MATSUDA Toshitaka TSUDA Noersomadi

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.95, no.4, pp.261-281, 2017 (Released:2017-07-20)

参考文献数

34

被引用文献数

13

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Mechanisms related to the diurnal cycle of tropical deep convection over a complex terrain were investigated in the Bandung basin, West Java, Indonesia. Observational data were analyzed from X-band radar, Global Navigation Satellite System (GNSS) receivers, and radiosondes, in conjunction with high-resolution numerical model data. Significant diurnal variation of GNSS-derived precipitable water vapor (PWV), which peaked in the early evening, was observed from 13 to 19 March 2013. During this period, the X-band radar detected convective initiation at approximately 1200 local time over the southern slope of the basin. A 2-km-mesh model successfully simulated the observed diurnal variations of PWV and rainfall from 15 to 17 March 2013. In the model, moist air was present at the bottom of the basin early in the morning, which was transported to the southern slope of the basin by valley wind circulation after sunrise. In contrast, humidity was lower in the northern part of the basin due to a downward circulating valley wind. The valley wind decreased static stability around the southern slope of the basin by transporting moisture. It also caused a low-level wind convergence, resulting in convective initiation on the southern slope of the basin. The GNSS receiver network also recorded this simulated water vapor variability associated with the valley wind. These results suggest that water vapor in the bottom of the basin during mornings and its advection by the valley wind strongly influences convective initiation in Bandung.

著者

Teppei J. Yasunari Masashi Niwano Yasushi Fujiyoshi Atsushi Shimizu Masamitsu Hayasaki Teruo Aoki Arlindo M. da Silva Brent N. Holben Sumito Matoba Naoto Murao Sadamu Yamagata Kyu-Myong Kim

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.13, pp.96-101, 2017 (Released:2017-06-01)

参考文献数

32

被引用文献数

2

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Monitoring particulate matter is essential to alert the public about health risks. The Terra/MODIS true color image clearly captured a yellow band over Hokkaido prefecture in Japan on 7 March 2016. We investigated whether this event was an Asian dust (Kosa) transport or not with the ground-based observations in Sapporo and Takikawa in Hokkaido and NASA's MERRA-2 re-analysis data. The timing of increased particle number concentrations (PNCs; greater than 0.5 μm) was clearly measured by a low-cost aerosol sensor at Sapporo and Takikawa in the early afternoon. For this particle size range, the PNC by this aerosol sensor had greater agreement with another commercial instrument for the 1-hourly mean data. The lidar data at Takikawa and NASA's AERONET at Sapporo also implied the increased dust particles (i.e., dominance of non-spherical and coarse particles, respectively), which supported that the PNC increase was due to the dust transport. The hourly PM2.5 data in Sapporo significantly increased in the evening rather than around the noon to early afternoon. We concluded that this event was judged as an Asian dust (Kosa) event in Hokkaido starting from the early afternoon, which was, however, not reported by Japan Meteorological Agency (JMA) based on their visible observations.

著者

Yuhji KURODA Kunihiko KODERA

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.95, no.3, pp.171-180, 2017 (Released:2017-04-28)

参考文献数

14

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This paper proposes a new simple method of multivariable maximum covariance analysis (MMCA) for extracting common variability from multiple (more than two) datasets that expands the singular value decomposition analysis method. The method is based on iteration of a recurrence equation derived by a dual relationship between pattern vectors and time coefficients. Two approaches of the method are proposed, one using the extreme of a summation of covariances (sum MMCA) and the other using the product of covariances (product MMCA). Both approaches are demonstrated by successfully extracting the variability related to the Arctic Oscillation from three monthly-mean meteorological datasets. The method is useful because it is easily programmed and is computationally inexpensive. The method can be applied to an arbitrary number of datasets, although a complete set of the product MMCA method cannot be applied to an even number of datasets.