著者

Rimpei Kamamoto Kenji Suzuki Tetsuya Kawano Hiroshi Hanado Katsuhiro Nakagawa Yuki Kaneko

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-020, (Released:2020-06-03)

---

Two products from the Global Precipitation Measurement (GPM) Dual-frequency Precipitation Radar (DPR) algorithms, a flag of intense solid precipitation above the −10°C height (“flagHeavyIcePrecip”) and a classification of precipitation type (“typePrecip”) were validated by ground-based hydrometeor measurements and X-band multi-parameter (X-MP) radar observations of snow clouds on 4 February 2018. Contoured frequency by altitude diagrams of the X-MP radar reflectivity exhibited a significant difference between footprints flagged and unflagged by the “flagHeavyIcePrecip” algorithm, which indicated that the algorithm is reasonable. The hydrometeor classification (HC) by the X-MP radar, which was confirmed by microphysical evidence from ground-based hydrometeor measurements, suggested the existence of graupel in the footprints with “flagHeavyIcePrecip”. In addition, according to the information of the GPM DPR, the “flagHeavyIcePrecip” footprints were characterized by not only graupel but also large snowflakes. According to the information of X-MP radar HC, the “typePrecip” algorithm by the detection of “flagHeavyIcePrecip” was effective in classifying precipitation types of snow clouds, whereas it seems that there is room for improvement in the “typePrecip” algorithms based on the extended-DPRm-method and H-method.

著者

Masato Sugi Yohei Yamada Kohei Yoshida Ryo Mizuta Masuo Nakano Chihiro Kodama Masaki Satoh

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-012, (Released:2020-03-19)

被引用文献数

31

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In relation to projections of tropical cyclone (TC) frequency in a future warmer climate, there is a debate on whether the global frequency of TC seeds (weak pre-storm vortices) will increase or not. We examined changes in the frequency of TC seeds by occurrence frequency analysis (OFA) of vortex intensity (vorticity or maximum wind speed). We directly counted the number of vortices with various intensities in high resolution global atmospheric model simulations for present and future climates. By using the OFA we showed a clear reduction of the occurrence frequency of TC seeds and relatively weak (category 2 or weaker) TCs in a future warmer climate, with an increase in the frequency of the most intense (category 5) TCs. The results suggest that the OFA is a useful method to estimate the future changes in TC frequency distribution ranging from TC seeds to the most intense TCs.

著者

Yanjie Li Jin Feng Jianping Li Sen Zhao

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.121-125, 2018 (Released:2018-09-04)

参考文献数

25

被引用文献数

1

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Rossby wave propagation theory is reviewed under two kinds of non-uniform basic flows: the zonal mean (ZM) and horizontally non-uniform (HN) flows in this study. The diagrams in the wavenumber domain for stationary and non-stationary waves embedded in the ZM flow are given and discussed in comparison with previous studies. Then a circle diagram in the group velocity domain for waves embedded in the HN flow is derived from the formulas in forms of three vectors: the wavenumber, background wind and gradient of basic-state absolute velocity. Given the basic state, we can identify the maximum and minimum magnitude of group velocity and its departure from the background wind. These results provide insights into Rossby wave propagation behaviors in the real atmosphere.

著者

Akihiro Hashimoto Hiroki Motoyoshi Narihiro Orikasa Ryohei Misumi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.51-56, 2020 (Released:2020-03-25)

参考文献数

36

---

We have developed a new method of diagnosing the characteristics of ice particles using a bulk microphysics model. Our model tracked the mass compositions of different classes of ice particles, using their microphysical process of origin, such as water vapor deposition and riming. The mass composition from depositional growth was further divided into six components by the temperature and humidity ranges corresponding to the typical growth habits of ice crystals. In test simulations, the new framework successfully revealed the influences of riming and depositional growths of ice particles within clouds and on surface snowfall. The new approach enables weather prediction models to provide much more information on the characteristics of ice particles regarding crystal habits and the extent of riming.

著者

Arata Amemiya Takumi Honda Takemasa Miyoshi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.6-11, 2020 (Released:2020-01-28)

参考文献数

18

被引用文献数

7

---

The observation operator for the Phased Array Weather Radar in the SCALE-LETKF data assimilation system is revisited, and the impact of its improvement on the analyses and forecasts is examined. The observation operator provides a functional relationship between equivalent radar reflectivity factor (Ze) and hydrometeor mass density (W) of each precipitation particle category. The W–Ze relationship is obtained by a radar simulator. This study performs a radiation code calculation with the parameters regarding particle size distribution of graupel consistent with the cloud microphysics scheme in the SCALE model. The newly obtained observation operator provides much stronger sensitivity of graupel mixing ratio to observed Ze compared to the operator originally used in the model. To examine the impact on the SCALE-LETKF analyses and forecasts, an experiment on a 13 July 2013 heavy rain case is performed with the new observation operator and is compared with the previous study. The forecast initiated by the analysis using the new operator shows much more realistic evolution of Ze in the middle troposphere, where a large amount of graupel is located. The overestimation of forecast Ze is significantly alleviated by the new observational operator. The 30-minute forecast of surface precipitation rate is also improved.

著者

Junya Fukuda Munehiko Yamaguchi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.250-256, 2019 (Released:2019-12-26)

参考文献数

19

被引用文献数

2

---

The effectiveness of multiple ensembles to determine 70% probability-circle radii of operational tropical cyclone (TC) track forecasts in the Japan Meteorological Agency (JMA) is investigated. The ensembles used in this study are global ensembles from JMA, the European Centre for Medium-Range Weather Forecasts (ECMWF), the National Centers for Environmental Prediction (NCEP) and the Met Office in the United Kingdom (UKMO). The verification for all TCs from 2016 to 2018 reveals that the multiple ensemble-based method has stronger correlation with operational TC track forecast errors and the clearer degree of separation among confidence levels derived from the ensemble spreads than the conventional statistical and single ensemble-based methods. It indicates that the multiple ensemble method provides situation-dependent forecast uncertainty most appropriately. As the effectiveness of the multiple ensemble method has been confirmed, JMA started to operate the multiple ensemble-based 70% probability-circle radii for its operational TC track forecasts for all forecast times up to 120 hours in June 2019. The radii are based solely on confidence levels derived from cumulative ensemble spreads of the multiple ensemble from the 4 centers. This is a good example of successful research to operation transfer of The International Grand Global Ensemble (TIGGE) project.

著者

Kazuaki Yasunaga Atsushi Hamada Kazuaki Nishii

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.238-243, 2019 (Released:2019-11-30)

参考文献数

21

被引用文献数

2

---

This study examines the factors responsible for the long-term changes of winter monsoonal flow around Japan in association with increasing precipitation trends in December along the coastal areas of Honshu (the main island of Japan) facing the Sea of Japan. The precipitation around the tropical eastern Indian Ocean and maritime continent has significantly increased in recent years. Thus, a packet of the stationary Rossby wave associated with the anomalous heating deflects the subtropical jet to the south over the eastern edge of the Eurasian continent. The deflection of the jet gives favorable conditions for the development of a low pressure trough in the lower level on the eastern side, leading to the formation of negative height anomalies near the surface around Japan.Although tropical precipitation also increases in November and January, the anomalous heating induces negative height anomalies and cyclonic circulations over the inland region of China and eastern offshore region of Japan (to the further west and east in comparison with those in December) in these months. As a result, monsoonal flow around Japan (and precipitation along the coastal areas of the Sea of Japan) shows no long-term trends in November or January.

著者

Kenichi Kusunoki Ken-ichiro Arai Hanako Y. Inoue Chusei Fujiwara

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.234-237, 2019 (Released:2019-11-15)

参考文献数

23

---

On 11 December 2012, a wind gust caused an F0-intensity wind damage in the Shonai area, Yamagata Prefecture, Japan. This paper provides an overview of an anticyclonic misocyclone (i.e., anticyclonic circulation in the Doppler velocity) related to a wind gust from X-band Doppler radar data. The anticyclonic misocyclone was embedded within a cell with a spiral echo diameter of approximately 3-4 km. The misocyclone over the Sea of Japan moved southeastward at a speed of 11 m s−1, made landfall, and passed over the damaged area; this timing is consistent with the Japan Meteorological Agency (JMA) wind damage assessment. Over the damaged area, the diameter of the misocyclone in the Doppler velocity was estimated to be smaller than 893 m, and the peak tangential wind speed and the vorticity of the vortex were estimated to be at least 8 m s−1 and −3.6 × 10−2 sec−1, respectively. This study discusses various possible explanations for the relationship between the misocyclone and wind gust and provides a first overview of a wintertime anticyclonic misocyclone associated with a surface wind gust on the coast of the Sea of Japan and may provide useful insights to the understanding of wintertime vortices.

著者

Hanako Y. Inoue Kenichi Kusunoki Toru Adachi Chusei Fujiwara Naoki Ishitsu Ken-ichiro Arai

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.228-233, 2019 (Released:2019-11-12)

参考文献数

24

---

The characteristics and finescale evolution of misovortices within a snowband were examined using low-level high-resolution single- and dual-Doppler radar analysis. From 02:00 to 06:00 JST on 17 January 2017, many misovortices developed within three snowbands in the Japan Sea coastal region. The vortices developed along the shear line between the offshore north-northwesterly and the coastal northeasterly. As discussed in several previous studies of misovortices along airmass boundaries, horizontal shearing instability was considered to be a possible mechanism responsible for misovortex formation. A detailed investigation was performed on the most distinct snowband and misovortices embedded within it. Dual-Doppler analysis revealed a detailed behavior of vortex during merger, such as the morphological change from quasi-circular to elliptical shape, and the counterclockwise rotation which caused high-amplitude inflection of the shear line in less than 10 minutes. During the decay stage, the vortices weakened along with weakening convergence. The results suggest that evolution of the misovortex appears to have been closely tied to the low-level convergence within the vortex.

著者

Kazuo Saito

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.222-227, 2019 (Released:2019-11-12)

参考文献数

27

被引用文献数

8

---

It is well known that northward winds are often observed at southern coastal areas of Japan when a developed tropical cyclone is located off the south coast of Japan. These northward winds have been frequently referred to the northward emission of warm and humid air from the typhoon which cause pre-typhoon rainfalls, but their mechanism has not been clarified. In this paper, we show that the northward wind can be explained by the ageostrophic wind components dynamically induced by acceleration vector round the tropical cyclone. On 7 October 2009, when a developed typhoon (T0918 Melor) approached Japan, distinct northward winds were observed at aerological observations over western Japan. Using numerical simulations with the Japan Meteorological Agency nonhydrostatic model, we reproduced the observed northward wind and their mechanism were examined by numerical experiments. The origin of the northward winds is explained by the ageostrophic winds dynamically induced by the acceleration vectors. When a typhoon approaches a baroclinic zone from south, northeastward ageostrophic winds are induced by southeastward acceleration vectors. Other possible causes (diabatic heating and orographic effect) are examined by sensitivity experiments. Diabatic heating by moist process acts to enhance the ageostrophic winds but the role is not primary. Orography has little effect on the observed ageostrophic wind. Non-axisymmetric features of the upper level divergence flow of a tropical cyclone near a baroclinic zone can also be elucidated by the similar mechanism of the ageostrophic winds.

著者

Abd. Rahman As-syakur Keiji Imaoka Kakuji Ogawara Manabu D. Yamanaka Tasuku Tanaka Yuji Kashino I Wayan Nuarsa Takahiro Osawa

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.216-221, 2019 (Released:2019-11-08)

参考文献数

28

被引用文献数

7

---

We analyzed 3-hourly Tropical Rainfall Measuring Mission multi-satellite analysis (TRMM 3B42) version-7 data for the 17-year period 1998-2014 to investigate seasonal and geographic characteristics of the diurnal rainfall cycle (DRC) over Sumatera, Indonesia. Dividing Sumatera into north, central, and south regions approximately perpendicular to the west coast, we point out for the first time early-afternoon initiation of daily rainfall not only in the Barisan Mountains but also in the east-coastal small islands (ECSIs) such as Bangka and Belitung. Westward and eastward migrations of rainfall areas from the Barisan Mountains are varied with seasons and regions, with the most remarkable being westward during September-October-November (SON) in the central region and the least remarkable occurring during June-July-August (JJA) in the southern region. In the central region, the DRC reaches a distance of ∼700 km off the west coast during SON and of only 200 km during March-April-May (MAM). The other westward migrations from the ECSIs in the central and southern regions (except for JJA) have been confirmed by 5-year hourly Multi-functional Transport Satellite-1R (MTSAT-1R) cloud-top data. The results shown in this paper suggest that the rainfall distribution with respect to coastal distance, varying geographically and seasonally.

著者

Yan Nie Lijuan Li Yanli Tang Bin Wang

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.211-215, 2019 (Released:2019-10-29)

参考文献数

31

被引用文献数

11

---

External forcings among the different phases of the Coupled Model Intercomparison Project (CMIP) vary considerably, but their impacts have not been extensively investigated yet. This study compares the impacts of CMIP5 and CMIP6 forcings on model stability and the 20th-century global warming and El-Niño Southern Oscillation (ENSO) based on the Pre-Industrial control (PI-control) and historical runs of the Flexible Global Ocean–Atmosphere–Land System Model: Grid-point Version 2 (FGOALS-g2). Results indicate that CMIP6 forcings result in a larger climate drift and a lower climatological global average surface temperature (GAST) than those of CMIP5 in PI-control runs. In historical runs, stronger 20th-century warming trends occur during the periods 1910-1940 and 1970-2005 using CMIP6 forcings, which are closer to the HadCRUT than those of the CMIP5 forcings simulation. A stronger spurious warming trend in the CMIP6 results in an evolution of GAST that is less consistent with the HadCRUT dataset than that in the CMIP5 during 1940-1970. Among all forcings, GHGs and aerosol forcings play the dominant roles in differences in GAST, particularly in the Northern Hemisphere. In both the PI-control and historical runs, a larger ENSO amplitude and smaller seasonality are simulated in CMIP6 than in CMIP5.

著者

Hidekazu Matsueda Rebecca R. Buchholz Kentaro Ishijima Helen M. Worden Dorit Hammerling Toshinobu Machida

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.205-210, 2019 (Released:2019-09-27)

参考文献数

36

被引用文献数

6

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We analyzed temporal variations of carbon monoxide (CO) in the upper troposphere from 30°N to 30°S observed using instruments aboard commercial airliner flights between Japan and Australia over the period 1993-2016. Here we focused on the CO variations in the Southern Hemisphere (SH) that showed a unique seasonal cycle with an increased CO around October-November every year. The seasonal CO peaks in the SH showed significant interannual variability (IAV), and are notably enhanced in strong El Niño years, especially 1997. The CO enhancements are proportionally associated with CO emissions from Indonesian fires, when compared to the Global Fire Emissions Database (GFED). The IAV of the CO peak anomalies relative to the mean seasonal cycle was assessed by a statistical regression model that uses a combination of multiple climate indices and their interaction terms. We found that over 80% of the CO IAV observed in the upper troposphere could be explained by the model. The largest anomaly in 1997 showed a different CO-climate relationship than the other periods, which could be due to amplification during synchronized climate modes, or include additional influence from other factors such as human activities.

著者

Alessandro Damiani Hitoshi Irie Tamio Takamura Rei Kudo Pradeep Khatri Hironobu Iwabuchi Ryosuke Masuda Takashi Nagao

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.198-204, 2019 (Released:2019-09-27)

参考文献数

39

被引用文献数

4

---

We used observations recorded at Chiba University in November 2018 to examine the variability in cloud optical depth (COD) under overcast conditions. First, we conducted a careful evaluation of four COD datasets retrieved from three types of surface observations: i) zenith radiance recorded by two sky radiometers; ii) solar radiation data collected by a pyranometer; and iii) spatial distribution of radiance recorded using a sky camera system. Although the COD retrieved from the pyranometer (camera) slightly (moderately) overestimated the COD from zenith radiance, we found a satisfactory correlation among all surface estimates. This result suggests the efficacy of both pyranometer- and camera-based approaches and supports their broader use when dedicated cloud observations are not available. We then assessed satellite-based COD estimates retrieved from the recently launched Advanced Himawari Imager (AHI) aboard Himawari-8 (H-8) and Second-generation Global Imager (SGLI) on the Global Change Observation Mission for Climate (GCOM-C). Overall, we found good agreement between ground and satellite estimates; their correlation and root mean square error were virtually equivalent to values reported for co-located surface-based instruments. Nevertheless, the AHI-based COD was found to be slightly positively biased with respect to surface datasets.

著者

Takenari Kinoshita Koutarou Takaya Toshiki Iwasaki

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.193-197, 2019 (Released:2019-09-13)

参考文献数

16

---

The mass-weighted isentropic zonal mean (Z-MIM) equations derived by T. Iwasaki are powerful tools for diagnosing meridional circulation and wave-mean interaction, especially for the lower boundary and unstable waves. Recently, some studies have extended the equations to three dimensions by using the time mean instead of the zonal mean. However, the relation between wave activity flux and residual mean flow (not mass-weighed mean flow) is unclear. In the present study, we derive the three-dimensional (3D) wave activity flux and residual mean flow for Rossby waves on the mass-weighted isentropic time mean equations. Next, we discuss the relation between the obtained formulae and 3D transformed Eulerian-mean (TEM) equations.

著者

Jia Liu Xiaofeng Xu Xiangyang Luo

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.189-192, 2019 (Released:2019-09-11)

参考文献数

16

被引用文献数

2

---

Accurate estimation of tropical cyclone (TC) intensity is of great significance for serious natural disasters. A new method is presented to estimate intensity of TC using satellite infrared data. Firstly, TC region is calculated according to the location of TC center. Secondly, 2D-PCA algorithm is used to extract feature of bright temperature image, and historical data of TC intensity is matched with the k-nearest neighbor algorithm. Thirdly, the matching results are analyzed and the intensity information of TC is estimated. In addition, a TC intensity database, which contains historical data during 2006-2010, is developed for estimation of TC intensity. Experiments show that the proposed method is efficient for real-time estimation of TC intensity, average error of estimation is lower than 15 hPa.

著者

Shun-ichi I. Watanabe Hiroyuki Tsujino Akihiko Murata Masayoshi Ishii

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.183-188, 2019 (Released:2019-09-05)

参考文献数

31

被引用文献数

1

---

We evaluated the impact of sea surface temperature (SST) improvement realized by increasing horizontal resolution of an ocean model on dynamical downscaling (DDS) over Japan, focusing on the effects of the Kuroshio on summer precipitation in Japan. Two sets of SSTs were simulated using a high-resolution North Pacific (NP) model and a low-resolution global (GLB) ocean model. Using these SSTs as the lower boundary conditions for the atmosphere, two DDS experiments were conducted (NP-run and GLB-run). In NP-run, summer precipitation increases over the Kuroshio and reduces over Pacific coastal areas of Japan compared with GLB-run. Due to weaker southerly winds north of the Kuroshio in NP-run, the water vapor flux transported to Japan is smaller than in GLB-run. Both the pressure adjustment and the vertical mixing mechanisms weaken the southerly winds, with the latter being slightly more effective. Increasing the horizontal resolution of the ocean model, so that the Kuroshio is more realistically reproduced, improves the accuracy of simulated precipitation over Japan.

著者

Kazuo Saito

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2019-040, (Released:2019-10-10)

被引用文献数

8

---

It is well known that northward winds are often observed at southern coastal areas of Japan when a developed tropical cyclone is located off the south coast of Japan. These northward winds have been frequently referred to the northward emission of warm and humid air from the typhoon which cause pre-typhoon rainfalls, but their mechanism has not been clarified. In this paper, we show that the northward wind can be explained by the ageostrophic wind components dynamically induced by acceleration vector round the tropical cyclone.On 7th October 2009, when a developed typhoon (T0918 Melor) approached Japan, distinct northward winds were observed at aerological observations over western Japan. Using numerical simulations with the Japan Meteorological Agency nonhydrostatic model, we reproduced the observed northward wind and their mechanism were examined by numerical experiments.The origin of the northward winds is explained by the ageostrophic winds dynamically induced by the acceleration vectors. When a typhoon approaches a baroclinic zone from south, northeastward ageostrophic winds are induced by southeastward acceleration vectors. Other possible causes (diabatic heating and orographic effect) are examined by sensitivity experiments. Diabatic heating by moist process acts to enhance the ageostrophic winds but the role is not primary. Orography has little effect on the observed ageostrophic wind.Non-axisymmetric features of the upper level divergence flow of a tropical cyclone near a baroclinic zone can also be elucidated by the similar mechanism of the ageostrophic winds.

著者

Hanako Y. Inoue Kenichi Kusunoki Toru Adachi Chusei Fujiwara Naoki Ishitsu Ken-ichiro Arai

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2019-041, (Released:2019-10-18)

---

The characteristics and finescale evolution of misovortices within a snowband were examined using low-level high-resolution single- and dual-Doppler radar analysis. From 02:00 to 06:00 JST on 17 January 2017, many misovortices developed within three snowbands in the Japan Sea coastal region. The vortices developed along the shear line between the offshore north-northwesterly and the coastal northeasterly. As discussed in several previous studies of misovortices along airmass boundaries, horizontal shearing instability was considered to be a possible mechanism responsible for misovortex formation. A detailed investigation was performed on the most distinct snowband and misovortices embedded within it. Dual-Doppler analysis revealed a detailed behavior of vortex during merger, such as the morphological change from quasi-circular to elliptical shape, and the counterclockwise rotation which caused high-amplitude inflection of the shear line in less than 10 minutes. During the decay stage, the vortices weakened along with weakening convergence. The results suggest that evolution of the misovortex appears to have been closely tied to the low-level convergence within the vortex.

著者

Chiaki Kobayashi Ichiro Ishikawa

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15A, pp.31-36, 2019 (Released:2019-07-03)

参考文献数

11

被引用文献数

7

---

During summer 2018, zonally averaged tropospheric temperatures were higher than normal in the northern mid-latitudes, and this contributed to the extreme warmth experienced in eastern and western Japan. These northern-mid-latitudes warm anomalies, along with enhanced convective activity in the northern subtropics, persisted from autumn 2017 until autumn 2018. This paper demonstrates that both the persistent zonal pattern, and the circulation anomaly pattern, that developed during summer 2018 are well predicted by a reforecast experiment using an operational seasonal prediction system. As variation in zonally averaged convective activity in the northern subtropics is statistically closely related to northern-mid-latitude tropospheric warming in all seasons, we hypothesize that the former is likely to be a key influence on the latter. We found a weakening of northern-mid-latitude tropospheric warming in a sensitivity experiment in which tropical Pacific sea surface temperatures (SSTs) are nudged to the climatology and enhancement of convective activity in the northern tropics is weakened. These results suggest that SST anomalies in the tropical Pacific, which are well predicted by our reforecast experiment, contribute to the successful prediction of northern-mid-latitude tropospheric warming.