著者

MORODA Yukie TSUBOKI Kazuhisa SATOH Shinsuke NAKAGAWA Katsuhiro USHIO Tomoo SHIMIZU Shingo

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2021-038, (Released:2021-03-16)

被引用文献数

3

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A phased array weather radar (PAWR) can complete one volume scan in 30 seconds, thus enabling us to obtain high spatiotemporal resolution echo intensities and wind fields of storms. Using its rapid scanning capability, we investigated the evolution of a convective storm in detail. To describe evolution of convective storms, we used the following definitions. The precipitation cell is defined as a three-dimensionally contiguous region of 40 dBZ or greater. The precipitation core is defined by a threshold of positive deviation greater than 7 dBZ, which is a difference from the average reflectivity during the mature stage of the cell. An updraft core is defined as an updraft region of 1 m s−1 or stronger at a height of 2 km. An isolated convective storm was observed by two PAWRs on 7 August 2015 in the Kinki District, western Japan. The storm was judged as a single cell, according to the above definition. We identified nine precipitation cores and five updraft cores within 49 minutes in the mature stage of the cell. A long-lasting updraft core and its branches moved southwestward or southeastward. Around these updraft cores, the precipitation cores were generated successively. The updraft core with the longest duration lasted 73.5 minutes; in contrast, the lifetimes of precipitation cores were from 4.5 to 14.5 minutes. The precipitation cell was maintained by the successive generations of updraft cores which lifted humid air associated with a low-level southwesterly inflow. The total amounts of water vapor inflow supplied by all the identified updraft cores were proportional to the volumes of the precipitation cell, with a correlation coefficient of 0.75. Thus, the extremely high spatiotemporal resolution of the PAWR observations provides us with new evidence that an isolated convective storm can be formed by multiple precipitation cores and updraft cores.

著者

YAMADA Yoshinori

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2021-036, (Released:2021-03-12)

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This paper presents an efficient, practical post-processing algorithm for the quality control of dual-pulse repetition frequency (dual-PRF) Doppler velocity data observed in Plan Position Indicator (PPI) mode. Quality control refers to the enhancement of the quality of the Doppler velocities through the re-assignment of an appropriate Nyquist interval number to an erroneous velocity datum and the elimination of unreliable data. The proposed algorithm relies on the local continuity of velocity data, as do most of the preexisting algorithms. Its uniqueness, however, lies both in the preparation of more reliable reference velocity data and its applicability to PPI data at higher elevation angles. The performance of the proposed algorithm is highlighted by its application to observed data from C- and X-band Doppler radars. This algorithm is practical, efficient, and not time consuming. It may be of great help in the derivation of accurate wind information from dual-PRF Doppler velocities.

著者

CUI Ye RUAN Zheng WEI Ming LI Feng GE Runsheng HUANG Yong

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2021-032, (Released:2021-01-21)

被引用文献数

1

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This study applied the C-band vertically pointing radar with frequency-modulation continuous-wave technology to obtain the continuous observation data of four shallow and two deep snow events during the winter of 2015-2016 in the midlatitudes of China. Generating cells (GCs) were found near the echo tops in every event. The ice particle number concentration (N), ice water content (IWC), and median mass diameter (Dm) retrieved from radar Doppler spectra were used to analyze the microphysical properties in the snow clouds. The clouds were divided into upper GC and lower stratiform (St) regions according to their vertical structure. The fall streaks (FSs) associated with GCs were embedded in the St regions. In the GC regions, the N values in shallow events were smaller compared with deep events, while Dm and IWC were larger. In the St regions, N decreased compared with the GC regions, while the Dm and IWC increased, implying the existence of aggregation and deposition growth. The growth of particle size and mass mainly occurred in the St regions. The increases of N were usually observed near −5°C accompanied by bimodal Doppler spectra, which might be caused by ice multiplication. The average ratios of the median N, Dm, and IWC inside GCs to those outside GCs are 2, 1.3, and 2.5 respectively for shallow events, with 1.7, 1.2, and 2.3 respectively for deep events. These values were basically the same as those for the FSs, implying the importance of GCs to the enhanced ice growth subsequently found in FSs. The larger values of N, Dm, and IWC inside GCs could be related to the upward air motions inside GCs. The first Ze–IWC relationship suitable for snow clouds in the midlatitudes of China was also established.

著者

KOBAYASHI Takahisa NOMURA Mitsuharu ADACHI Ahoro SUGIMOTO Soichiro TAKAHASHI Nobuhiro HIRAKUCHI Hiromaru

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2021-030, (Released:2021-02-24)

被引用文献数

3

---

A new method that retrieves attenuation profiles using a Dual-Frequency Precipitation Radar (DPR) equipped on the Global Precipitation Mission (GPM) is proposed. The DPR operates at Ka and Ku-bands and provides profiles of a differential frequency ratio, which is the difference of the measured or attenuated reflectivity in decibel scale between Ka and Ku bands. For accurate measurements of precipitation, hydrometeor classification is essential. Attenuation of radio wave due to precipitation is closely related to microphysical properties and available for hydrometeor classification. The proposed method estimates range variations of relative values of differential attenuation between two frequencies and can be used for identifying hydrometeor types along the radar propagation path. Numerical simulations indicate that the proposed method performs well for rain, melted snow, mixed-phase precipitation, and some cases of the melting layer. The method was also evaluated for GPM DPR measurements. Results indicate that the method works well for identifying rain and snow and also provides useful information for melting layer detection and attenuation, even for the melting layer in which no enhancement of reflectivity is observed.

著者

Syono S. Hamuro M.

出版者

公益社団法人 日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.40, no.1, pp.1-12, 1962

被引用文献数

5

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この覚書ではオブコフ・モーニンの一般関数望に関する山本・パノフスキーの方程式φ4+ξφ3-1=0を厳密に解いた。弱非断熱的,非常に不安定,非常に安定な三つの場合について,厳密解より近似解を導いたところ,第一次近似においてカザンスキー・モーニンおよび山本の解と一致することがわかつた。これらの解を用いて熱および水蒸気の流束を求める式を出した。これはソーンスウエイト・ホルツマンの公式を特別の場合として含んでいる。不安定大気の減率はモーニンやプリストリーの式と一致する。

著者

Michael E. McIntyre

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.60, no.1, pp.37-65, 1982 (Released:2007-10-19)

参考文献数

101

被引用文献数

208 252

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成層圏突然昇温に関する Matsuno の朱駆的な数値実験が成功して以来,この荘大な自然現象が力学的な原因に由来するものであることは疑いをはさむ余地のないところである。しかし,その理論的なモデル化や衛星観測に基づく諸研究は,昇温現象の詳細にわたる理解や適切な予測に関してある程度の見通しが得られた段階に到ったばかりである。本論文では,この現象に関する最近の研究の進展ぶりを自由に論じ,あわせて,数値モデル化に際して対流圏の運動を先駆的に与えることによって生ずる偽の共鳴を避ける方法など,将来の研究のあり方についても示唆を与える。

著者

LI Zhenghui LUO Yali DU Yu CHAN Johnny C. L.

出版者

公益社団法人 日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.98, no.1, pp.213-233, 2020

被引用文献数

36

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<p>In this study, the climatological characteristics of pre-summer (April to June) rainfall over South China (SC) and the associated synoptic conditions are examined using 1980–2017 hourly rainfall observations and reanalysis data. The amount, frequency, and intensity of rainfall show pronounced regional variations and substantial changes between pre- and post-monsoon-onset periods. Owing to the more favorable thermodynamic conditions after monsoon onset over the South China Sea (SCS), rainfall intensifies generally over SC irrespective of the rainfall-event durations. Increased rainfall amounts in longer-duration (> 6 h) events were found over a designated west-inland region (west of 111°E), which are partially attributed to enhanced dynamic instability. In addition, rainfall events occur more frequently over the west-inland region, as well as coastal regions to the west of 118°E, but less over a designated east-inland region. Inland-region rainfall is closely linked to dynamic lifting driven by subtropical synoptic systems (low pressure and an associated front or shearline). The westward extension of the western North Pacific high and the eastward extension/movement of the front or shearline, interacting with the intra-period intensification of the southwesterly monsoonal flows, play important roles in providing high-<i>θ</i>_e (equivalent potential temperature) air to the west- and east-inland regions, respectively. Warm-sector coastal rainfall is closely related to the deceleration of the southerly boundary layer (BL) air flow over the northern SCS and associated convergence of BL high-<i>θ</i>_e air near the coast. Meanwhile, the southwesterly synoptic-system-related low-level jet in the lower-to-middle troposphere to the south of the inland cold front can contribute to the coastal rainfall occurrence by providing divergence above the BL convergence near the coast. The BL flow often simultaneously strengthens with the lower-troposphere horizontal winds, suggesting a close association between the BL flow and the synoptic systems. The quantitative statistics provided in this study complement previous case studies or qualitative results and, thus, advance our understanding about pre-summer rainfall over SC.</p>

著者

BARREYAT Marylis CHAMBON Philippe MAHFOUF Jean-François FAURE Ghislain IKUTA Yasutaka

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2021-050, (Released:2021-04-30)

被引用文献数

3

---

The assimilation of cloudy and rainy microwave observations is under investigation at Météo-France with a method called ‘1D-Bay+3D/4D-Var’. This method consists of two steps: (i) a Bayesian inversion of microwave observations and (ii) the assimilation of the retrieved relative humidity profiles in a 3D/4D-Var framework. In this paper, two estimators for the Bayesian inversion are used: either a weighted average (WA) or the maximum likelihood (ML) of a kernel density function. Sensitivity studies over the first step of the method are conducted for different degrees of freedom: the observation error, the channel selection and the scattering properties of frozen hydrometeors in the observation operator. Observations over a two-month period of the Global Precipitation Measurement (GPM) Microwave Imager (GMI) on-board the GPM-Core satellite and forecasts of the convective scale model Application of Research to Operations at Mesoscale (AROME) have been chosen to conduct these studies. Two different meteorological situations are analysed: those predicted cloudy in AROME but clear in the observations and, on the contrary, those predicted clear in AROME but cloudy in the observations.Main conclusions are as follows. First, low observational errors tend to be associated with the profiles with the highest consistency with the observations. Second, the validity of the retrieved profiles varies vertically with the set of channels used. Third, the radiative properties used in the radiative transfer simulations have a strong influence on the retrieved atmospheric profiles. Finally, the ML estimator has the advantage of being independent of the observation error but is less constrained than the WA estimator when few frequencies are considered. While the presented sensitivities have been conducted to incorporate the scheme in a data assimilation system, the results may be generalized for geophysical retrieval purposes.

著者

岡田 武松

出版者

Meteorological Society of Japan

雑誌

氣象集誌. 第1輯 (ISSN:00261165)

巻号頁・発行日

vol.24, no.3, pp.en5-en12, 1905-03-28 (Released:2009-02-05)

参考文献数

3

著者

Matthew H. HITCHMAN 余田 成男 Peter H. HAYNES Vinay KUMAR Susann TEGTMEIER

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.99, no.2, pp.239-267, 2021 (Released:2021-04-14)

参考文献数

108

被引用文献数

27

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成層圏準2年周期振動(QBO)が熱帯・亜熱帯の上部対流圏・下部成層圏(UTLS)に与える影響に関する観測的研究の歴史をレビューする。観測解析能力の段階に応じて、その展開を順次説明する。QBOの西風(W)と東風(E)の位相は下部成層圏の帯状風によって定義される。1960~1978年の間には、ラジオゾンデ観測データでUTLSのQBO変調が示され、QBO W位相時に熱帯では暖かい偏差、南緯30度と北緯30度付近では冷たい偏差であることが明らかにされた。このことは、熱帯と亜熱帯の間のコヒーレントで逆位相的な応答を予言していたQBOに伴う平均子午面循環(MMC)の理論と一致していた。1978~1994 年の間には、人工衛星によるエアロゾルと気温の観測により、QBO MMCの存在が確認された。1994年~2001年の間には、全球データセットにより、対流圏界面温度の帯状平均QBO変動の解析が可能となった。そして、2001年には、1958~2000年の42年間の全球NCEP再解析により、圏界面温度、気圧、帯状風のQBO W-E位相差の季節的・地理的な違いが明らかにされた。今では、38年間のMERRA-2データと40年間のERA-Interimデータによる最新の更新により、季節的・地理的変動をより完全に把握することができる。 熱帯のQBO変動幅は、圏界面の気温は約0.5~2K、高度は約100~300m、気圧は約1~3hPaであり、QBO E位相時に、特に北半球の冬から春にかけて、寒く、高くなる。QBO温度シグナルは、深い対流が多い地域で大きくなる傾向がある。南半球亜熱帯のQBOシグナルは南半球の冬に強まる。QBO W位相時には、亜熱帯の偏西風ジェットが発達する一方でWalker循環は弱くなり、特に北半球の春には弱くなる。ERA-Interimのデータを用いて、気温、帯状風、MMCの帯状平均QBO偏差の新しい気候学を提示する。QBO E位相はUTLSでの静的安定度と帯状風シアーの両方を低下させることで対流を促進させる可能性がある。

著者

LI Tsung-Han WANG Yuqing

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2021-028, (Released:2021-01-15)

被引用文献数

9

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In Part I of this series of studies, we demonstrated that the intensification rate of a numerically simulated tropical cyclone (TC) during the primary intensification stage is insensitive to surface drag coefficient. This leads to the question of what is the role of the boundary layer in determining the TC intensification rate given sea surface temperature and favorable environmental conditions. This part attempts to answer this question based on both a boundary layer model and a full-physics model as used in Part I. Results from a boundary layer model suggest that TCs with a smaller radius of maximum wind (RMW) or of lesser strength (i.e., more rapid radial decay of tangential wind outside the RMW) can induce stronger boundary-layer inflow and stronger upward motion at the top of the boundary layer. This leads to stronger condensational heating inside the RMW with higher inertial stability, and thus favorable for higher intensification rate. Results from full-physics model simulations show that the TC vortex initially with a smaller RMW or of lesser strength has a shorter initial spinup stage due to faster moistening of the inner core and intensifies more rapidly during the primary intensification stage. This is because the positive indirect effect of boundary layer dynamics depends strongly on vortex structure but the dissipation effect of surface friction depends little on vortex structure. As a result, the intensification rate of the simulated TC is very sensitive to the initial TC structure.

著者

LI Tsung-Han WANG Yuqing

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2021-027, (Released:2021-01-15)

被引用文献数

11

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This study examines the role of boundary layer dynamics in tropical cyclone (TC) intensification by numerical simulations. The hypothesis is that although surface friction has a negative effect on TC intensification because of frictional dissipation (direct effect), it contributes positively to TC intensification by determining the amplitude and radial location of eyewall updrafts/convection (indirect effect). Results from a boundary layer model show that TCs with larger surface drag coefficient (CD) can induce stronger and more inwardly penetrated boundary-layer inflow and upward motion at the top of the boundary layer. This can lead to stronger and more inwardly located condensational heating inside the radius of maximum wind with higher inertial stability, and is favorable for more rapid intensification. Results from full-physics model simulations using the TC Model version 4 (TCM4) demonstrate that the intensification rate of a TC during the primary intensification stage is insensitive to CD if CD is changed in a reasonable range. This is because the increased/reduced positive contribution by the indirect effect of surface friction to TC intensification due to increased/reduced CD is roughly offset by the increased/reduced negative (direct) dissipation effect due to surface friction. However, greater surface friction can significantly shorten the initial spin-up period through stronger frictional moisture convergence and Ekman pumping and thus faster moistening of the inner core column of the TC vortex, but would lead to a weaker storm in the mature stage.

著者

澤田 壮弘 上野 健一

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.99, no.2, pp.473-496, 2021 (Released:2021-04-22)

参考文献数

65

被引用文献数

6

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気象庁137地点の2日積算降水量を使い,2014―2019年寒候期における多降水事例を選出した。全球降水観測(GPM)主衛星に搭載された二周波降水レーダー(DPR)のプロダクツおよびヨーロッパ中期予報センター再解析データを使用した流跡線解析により、閉塞過程の温帯低気圧構造が多降水を引き起こす仕組みを解析した。多降水についての上位の事例のほとんどは温帯低気圧により発生し、その多くが成熟段階であった。上位50事例の中から、3つの南岸低気圧を抽出し、メソスケールの降水系と気流系の関係を集中的に診断した。多降水が発生した観測地点における時間降水量変化は、基本的にウォームコンベアーベルト(WCB)、コールドコンベアーベルト(CCB)、ドライイントルージョン(DI)の組み合わせの影響を受けていた。低気圧中心の東側に広がる層状降水域はCCB上の下層WCBと上層WCBから構成され、低気圧中心付近の対流性降水域はWCB上に上層からのDIを伴い、線状降水帯の形成とともに地上で強い降水強度をもたらした。対流性の降水活動は、停滞性の層状降水域上空に上層WCBとして湿潤な大気を移流させる働きを担った。さらに、DPRプロダクツは、低気圧中心の後面に延びる雲域(クラウドヘッド)での背の高い層状降水、中層(地上付近)での潜熱開放(吸収)、及び低気圧の発達を可能にするCCBに沿った渦位増加を確認した。

著者

瀬戸 心太 井口 俊夫 Robert MENEGHINI 阿波加 純 久保田 拓志 正木 岳志 高橋 暢宏

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.99, no.2, pp.205-237, 2021 (Released:2021-04-19)

参考文献数

50

被引用文献数

51

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全球降水観測(GPM)計画主衛星搭載二周波降水レーダ(DPR)の降水強度推定アルゴリズムを開発した。DPRは、Ku帯レーダ(KuPR; 13.6GHz)およびKa帯レーダ(KaPR; 35.5GHz)から構成される。KuPRアルゴリズムは、熱帯降雨観測衛星(TRMM)搭載の降雨レーダ(PR)のアルゴリズムと同様であるが、降水強度Rと質量重み付き平均粒径Dmの関係(R-Dm関係)を、減衰係数kと有効レーダ反射因子Zeの関係(k-Ze関係)の代わりに使用している。R-Dm関係は、KaPRアルゴリズムおよび二周波アルゴリズムにも使用できる。一周波アルゴリズムおよび二周波アルゴリズムともに、R-Dm関係の修正係数εに暫定値を仮定した前進法によりプロファイルを推定し、その結果を評価して最適なεを選択する。二周波アルゴリズムの利点は、εの決定のために二周波表面参照法およびZfKa法(KaPRの減衰補正反射強度Zfを用いる手法)を用いること、およびKuPRまたはKaPRの観測を選択的に利用できることである。また本論文では、R-Dm関係と散乱テーブルの導出およびビーム内非一様性補正手法を詳細に説明している。さらに、アルゴリズムの出力結果を統計的に解析し、各アルゴリズムの特性を示している。

著者

TAKEMURA Kazuto ENOMOTO Takeshi MUKOUGAWA Hitoshi

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2021-016, (Released:2020-12-02)

被引用文献数

2

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This study examines the predictability of an enhanced monsoon trough, which is accompanied by a large-scale cyclone in the lower troposphere, south of Japan seen in late August 2016. The monsoon trough is found to be enhanced by a meandering of the Asian jet and a consequent southwestward intrusion of upper-level high potential vorticity associated with a Rossby wave breaking east of Japan. JMA's operational one-month ensemble prediction during the forecast period of a week underestimates intensity of the Rossby wave breaking and fails to predict the enhanced monsoon trough. A simple sensitivity analysis based on ensemble singular vectors indicates that initial perturbations over the Bering sea and near the Asian jet entrance region can efficiently grow and propagate toward the region to the south of Japan, contributing to maximize the perturbations of the enhanced monsoon trough. The time evolution of the perturbations propagating toward the region to the south of Japan is consistent with that of the ensemble spread during the forecast period. Perturbed hindcast experiments were conducted with the initial perturbations obtained from the simple sensitivity analysis. The monsoon trough to the south of Japan in the perturbed experiment is significantly more enhanced than the unperturbed experiment, supporting the simple sensitive analysis. These results indicate crucial contribution of the initial perturbations associated with the Rossby wave breaking and near the Asian jet entrance region to the limited predictability of the enhanced monsoon trough in late August 2016.

著者

肥沼 寛一

出版者

公益社団法人 日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.8, no.1, pp.29-32, 1930

著者

Timothy J LANG Ana P BARROS

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.82, no.3, pp.829-844, 2004 (Released:2004-09-27)

参考文献数

28

被引用文献数

134 185

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Based on observations from a hydrometeorological network on the eastern slopes of the Annapurna Range, nearly all the annual precipitation at low elevations ( 3000 m MSL) can receive up to 40% of their annual precipitation as snowfall during the winter, with the highest altitude stations (∼4000 m MSL and above) having the most total winter precipitation (which can exceed 100 cm). Significant snowstorms are associated with terrain-locked low-pressure systems that form when an upper-level disturbance passes over the notch formed by the Himalayas and Hindu Kush mountains (the so-called Western Disturbances), causing upper-level SW flow over central Nepal and orographically forced precipitation. Based on these results, a 30-year (1973-2002) climatology of these notch depressions is developed and reveals that significant interannual variability in central Himalayan winter storms exists. Weak but statistically significant correlation between notch depressions and the Polar/Eurasia teleconnection pattern was found, suggesting that the strength of the circumpolar vortex may affect the number of depressions passing through the Himalayan region. A typical snow event (11 February 2000) was the subject of an observational and modeling case study. Local precipitation (snow and rain) and other meteorological observations, as well as satellite (Meteosat-5 and TRMM) and NCEP/NCAR Reanalysis data were used, along with a cloud-resolving model with realistic topography. This study shows that significant wintertime precipitation only occurs in the central Himalayas when the large-scale flow evolves to a favorable geometry with respect to the mountains.

著者

MENEGHINI Robert KIM Hyokyung LIAO Liang KWIATKOWSKI John IGUCHI Toshio

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2021-010, (Released:2020-11-19)

被引用文献数

11

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Estimation of path attenuation is a critical part of retrieving precipitation parameters using measurements from the Dual-Frequency Precipitation Radar (DPR) on board the Global Precipitation Measurement Mission (GPM) satellite. In this paper, we describe the latest implementation of the Surface Reference Technique that uses surface scattering properties to infer path attenuation through the precipitation. Both single- and dual-frequency versions of this method are available and while the dual-frequency version appears to be more accurate at moderate rain rates, the single-frequency approach at Ku-band is needed when the Ka-band data are not available. Despite improvements afforded by the dual-frequency version of the method, other methods such as the Hitschfeld-Bordan and standard dual-frequency approaches offer advantages particularly at lighter rain rates and at near-nadir incidence angles over land. Weighted averages of the results from these methods appear to offer the best estimate of path attenuation presently available.

著者

楠 昌司 水田 亮

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.99, no.1, pp.79-100, 2021 (Released:2021-03-03)

参考文献数

57

被引用文献数

2

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60km格子の全球大気モデル(60kmモデル)を用いた「地球温暖化施策決定に資する気候再現・予測実験データベース (the database for Policy Decision making for Future climate change : d4PDF)」と呼ばれる約100個の大規模アンサンブル実験により、東アジアの雨期の将来変化を予測した。現在気候は、過去に観測された海面水温(Sea Surface Temperature : SST)を60kmモデルに与えた。産業革命以前の気候に比べて4℃暖かい将来気候では、第5期大気海洋大循環モデル国際比較実験(the Atmosphere–Ocean General Circulation Models of the fifth phase of the Coupled Model Intercomparison Project : CMIP5)に参加した大気海洋大循環モデルで予測された6つの異なるSST分布を60kmモデルに与えた。将来、夏の降水量は東アジアのほとんどの地域で一般に増えるが、西日本で減る。中国、韓国、日本の30-35°N付近で6月に降水量が減る。6月について各格子点において大規模アンサンブル実験から算出した確率密度関数によれば、単純な算術平均による月平均降水量は減るものの、最も強い降水が増える地域がある。西日本では、梅雨入りが遅れ、梅雨明けが早まるので、結果として雨期が短くなる。西日本で6月に降水量が減ることは、北西太平洋亜熱帯高気圧が南に偏ることで、日本の南で水蒸気収束が起こることによる波及効果に起因する。モデルの水平解像度の違い、対流の表現方法の違い、大気海洋の相互作用の有無にかかわらず、一貫して西日本で6月に降水量が減ることを確認した。

著者

YU Tiantian CHANDRASEKAR V. XIAO Hui JOSHIL Shashank S

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2021-004, (Released:2020-10-29)

被引用文献数

5

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Accurate estimation of snowfall rate during snowstorms is crucial. This estimate directly impacts the hydrological and atmospheric models. The density of snow plays a very important role in estimating the snowfall rate. In this paper, the density of snow is investigated during a huge snowstorm event during the International Collaborative Experiment held during the PyeongChang 2018 Olympics and Paralympic winter games (ICE-POP 2018). The density is calculated using the terminal velocities and diameters of the snow particles measured by a disdrometer. In this study, we not only use radar reflectivity factor (Z) for snowfall rate (S) estimation, but also use dual-frequency ratio (DFR). We derive S-Z and S-Z-DFR relations for snowfall estimation during this snowstorm event after considering the density of snow. The comparisons are performed between National Aeronautics and Space Administration (NASA) Dual-frequency Dual-polarization Doppler Radar (D3R) and precipitation gauges using these two power-law relations. The results show that the two relations for snowfall rate estimation agree well with gauges, but the S-Z-DFR method performs the best, which has a lower normalized standard error. The error in the snowfall rate estimates decreases as the time scale becomes large. This shows that the S-Z-DFR algorithm is a promising way for snowfall quantitative precipitation estimation (QPE) and can be used as a ground validation tool for Global Precipitation Measurement (GPM) snowfall production evaluations.