著者

Masayoshi Ishii Yoshikazu Fukuda Shoji Hirahara Soichiro Yasui Toru Suzuki Kanako Sato

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.13, pp.163-167, 2017 (Released:2017-09-14)

参考文献数

31

被引用文献数

102

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The simplest global mapping method and dense data coverage for the global oceans by the latest observation network ensure an estimate of global ocean heat content (OHC) within a satisfactory uncertainty for the last 60 years. The observational database conditionally presented a level high enough for practical use for the global OHC estimation when applying bias corrections of expendable bathythermograph, assuming that the other severe observational biases are not included in the database. Uncertainties in annual global mean temperatures averaged vertically from the surface to 1,500 m are within 0.01 K for the period from 1955 onward, when only sampling errors are taken into account. Those in annual mean global OHC of an improved objective analysis for 0-1,500 m depth is 16ZJ on average throughout the period. Compared to previous studies, the new objective analysis provides a higher estimation of the global 0-1,500 m OHC trend for a longer period from 1955 to 2015, which is an increase of 350 ± 57ZJ with a 95% confidence interval.

著者

Yukie Moroda Kazuhisa Tsuboki Shinsuke Satoh Katsuhiro Nakagawa Tomoo Ushio Hiroshi Kikuchi

出版者

公益社団法人 日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.18, pp.110-115, 2022 (Released:2022-06-08)

参考文献数

16

---

A rapid rise of the lightning activity center in the upper part of a cloud is called a lightning bubble (LB). It remains unclear how LBs occur in thunderstorm clouds. Recently, high-spatiotemporal resolution data obtained by a phased array weather radar enabled observation of temporal changes in the three-dimensional structure of precipitation cores in a precipitation cell. To understand the mechanism by which LBs occur, we examined the relationship between the time-evolution of precipitation cores and the flash initiation points. After a precipitation core developed in an isolated thundercloud, the top height of the core reached its highest altitude and then started to descend. Meanwhile, the echo tops above the core continued to rise, which is termed an upward reflectivity pulse (URP). Over an hour, nine URPs were successively observed in the thundercloud. The average tracking period of the URPs was 3.9 minutes. Flash initiation points appeared near the highest points of the URPs and continued to rise with time. These observational results suggest that URPs cause LBs by enhancing the electric field, via the separation of graupel and ice crystals near the highest points of ascending URPs.

著者

Kohei Fukuda Kazuaki Yasunaga Ryo Oyama Akiyoshi Wada Atsushi Hamada Hironori Fudeyasu

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-019, (Released:2020-05-25)

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This study examined the diurnal cycles of brightness temperature (TB) and upper-level horizontal winds associated with tropical cyclones (TCs) over the western North Pacific basin, making use of data retrieved from geostationary-satellite (Himawari-8) observations that exhibited unprecedented temporal and spatial resolutions. The results of a spectral analysis revealed that diurnal cycles prevail in TB variations over the outer regions of TCs (300-500 km from the storm center). The dominance of the diurnal cycle was also found in variations in the radial wind (Vr) in intensive TCs, although there was no dominant cycle in tangential wind variation. In addition, coherence spectra demonstrated that the diurnal cycles of TB and Vr are significantly coherent in intensive TCs. The migration speed of TB and Vr anomalies exceeded the time-mean Vr, and it was speculated that diurnal cycle signals propagate (i.e., are not advected) toward the outer regions of TCs.

著者

Hiroaki Ueda Mikihiro Yokoi Masaya Kuramochi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17B, no.Special_Edition, pp.14-18, 2021 (Released:2021-09-09)

参考文献数

28

被引用文献数

7

---

During the early summer of 2020, a stagnation of the Meiyu-Baiu front brought torrential rainfall over East Asia. Meanwhile, the anticyclone was much enhanced over the subtropical western Pacific (SWP), which contributed abundant moisture to the Meiyu-Baiu rainband along the western rim of the anticyclone. Based on the sensitivity experiments of the linear baroclinic model by prescribing the observed diabatic heating anomalies, a combination of anomalous convection over the Indian Ocean and reduced rainfall over the western Pacific can account for the maintenance of zonally elongated SWP anticyclone. Interestingly, this period corresponded to the developing stage of La Niña, while the convective activities were notably suppressed over the warmed western Pacific. The sensitivity experiments to SST anomalies using the atmospheric general circulation model shows that the attenuated convection over the western Pacific can be ascribed to the warmed Indian Ocean associated with an atmospheric Kelvin wave wedge from the Indian Ocean. Overall, the suppressant SST effect of the Indian Ocean opposes and is greater than that of tropical Pacific. We issue a caveat regarding the additivity of the remote influence across the maritime continent. These results have important implications for the predictability of early summer rainfall over East Asia.

著者

Masaya Kuramochi Hiroaki Ueda Chiaki Kobayashi Youichi Kamae Koutarou Takaya

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17B, no.Special_Edition, pp.9-13, 2021 (Released:2021-08-26)

参考文献数

29

被引用文献数

5

---

The anomalous warm winter from December 2019 to February 2020 over East Asia, particularly the anticyclonic anomaly around Japan, was examined from the teleconnection perspective anchored by a warmed Indian Ocean and the El Niño Modoki. In the upper troposphere, high–low–high wave patterns progressing from the Arabian Sea toward Japan via the southern region of China, coupled with the wave-activity flux diagnosis, implicate the propagation of stationary Rossby waves caused by enhanced convection in the western Indian Ocean and suppressed convection around the Maritime Continent. These anomalous convective activities could be responsible for the northward displacement of the subtropical jet and the ensuing warm conditions over East Asia. The atmospheric response to the observed diabatic heating by means of the linear baroclinic model well reproduced the observations. Moreover, sensitivity experiments of the atmospheric general circulation model to sea surface temperature (SST) anomalies, especially in the warmed western Indian and central Pacific oceans, can help understand the anomalous subsidence over the Maritime Continent sector and subsequently weakened convection. The warmer SST observed around the Maritime Continent alone reproduces the enhancement of rainfall and subsequent cold anomalies around Japan, suggesting the importance of trans-basin interaction for teleconnection towards East Asia.

著者

Masaki Katsumata Kyoko Taniguchi Tomoaki Nishizawa

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16A, no.Special_Edition, pp.6-11, 2020 (Released:2020-06-20)

参考文献数

30

被引用文献数

2

---

A shipboard lidar system was examined the capability to retrieve detailed variation of the water vapor mixing ratio in and above the marine atmospheric boundary layer (MABL). The water vapor mixing ratio is retrieved from the ratio of Raman lidar signals by water vapor and by nitrogen, with the help of radiosonde data beside. Data obtained during two special observations, Pre-YMC and YMC-Sumatra, off the west coast of Sumatra island were examined.The mixing ratio was retrieved in the nighttime over 1 km height with the resolution of 10-minutes in temporal and 120-meters in vertical. The root mean square difference from the radiosonde data is about or less than 1 g/kg in MABL. A case study demonstrates that the retrieved spatiotemporal variation of water vapor mixing ratio captures meso-scale drying and moistening in detail. The capabilities of the retrieved data were well demonstrated, while number of improvements are expected in future work.

著者

Noriko N. Ishizaki Motoki Nishimori Toshichika Iizumi Hideo Shiogama Naota Hanasaki Kiyoshi Takahashi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.80-85, 2020 (Released:2020-05-13)

参考文献数

25

被引用文献数

24

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Bias corrected climate scenarios over Japan were developed using two distinct methods, namely, the cumulative distribution function-based downscaling method (CDFDM) and Gaussian-type Scaling approach (GSA). We compared spatial distribution, monthly variation, and future trends. The seasonal distribution of bias-corrected data using CDFDM closely followed the original general circulation model (GCM) outputs. GSA overestimated the amount of precipitation by 12-18% in every season because of an unsuitable assumption on the probability distribution. We also examined the contributions of each source of the uncertainty in daily temperature and precipitation indices. For daily temperature indices, GCM selection was the main source of uncertainty in the near future (2026-2050), while different Representative Concentration Pathways (RCPs) resulted in large variability at the end of the 21st century (2076-2100). We found large uncertainty using the bias-correction (BC) methods for daily precipitation indices even in the near future. Our results indicated that BC methods are an important source of uncertainty in climate risk assessments, especially for sectors where precipitation plays a dominant role. An appropriate choice of BC, or use of different BC methods, is encouraged for local mitigation and adaptation planning in addition to the use of different GCMs and RCPs.

著者

Masahiro Shiozaki Takeshi Enomoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.12-16, 2020 (Released:2020-01-31)

参考文献数

11

被引用文献数

1

---

The 2015/16 El Niño is compared with the two previous strongest events, the 1982/83 and 1997/98 El Niño. The 2015/16 winter features a basin warming in the Indian Ocean, a negative sea surface temperature (SST) anomaly shifted to the north in the western Pacific Ocean in addition to a positive SST anomaly shifted to the west in the eastern Pacific Ocean. These SST distributions lead to suppressed convection in the Maritime Continent, and to a weakened Hadley circulation in the western Pacific Ocean. The eastern Asian monsoon in the 2015/16 winter was also weakened due to the dominance of the western Pacific (WP) pattern. On the other hand, the third and fourth centers of action of Pacific/North American (PNA) pattern in the 2015/16 case are obscure. This may be due to weak divergence in the eastern Pacific Ocean.

著者

Tetsuya Takemi Takashi Unuma

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-006, (Released:2020-01-21)

被引用文献数

33

---

This study investigated the environmental factors responsible for the development of heavy rainfall in eastern Japan during the passage of Typhoon Hagibis (2019) by using mesoscale gridded analysis data as well as observed data. Environmental indices for diagnosing stability and moisture conditions were examined. It was found that the whole troposphere is almost saturated and the column total water vapor content is extremely large. In the lower troposphere we identified layers of moist absolutely unstable states with the thickness deeper than 2 km. Such deep moist absolutely unstable layers as well as abundant moisture content and almost saturated troposphere set a high potential for convective development. Under these favorable environmental conditions, the fact that the heights of the absolutely unstable layers' bottom are comparable to the mountain elevations is considered to be favorable for topographic lifting of unstable, moist air, which will trigger and activate strong convection and hence heavy rainfall. In spite of a moderate amount of convective available potential energy and a nearly moist-adiabatic lapse rate, moist absolute instability, abundant moisture, and high humidity jointly play a key role to increase the potential for generating the present heavy rainfalls.

著者

Kazuto Takemura Shunya Wakamatsu Hiroki Togawa Akihiko Shimpo Chiaki Kobayashi Shuhei Maeda Hisashi Nakamura

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15A, pp.49-54, 2019 (Released:2019-08-09)

参考文献数

21

被引用文献数

1 28

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This study investigates the influence of strong southerly moisture flux on an extreme rainfall event over western Japan in early July 2018, by using a global atmospheric reanalysis dataset. During its peak period from 5 to 7 July, extensive and unprecedented rainfall observed along the well-defined quasi-stationary Baiu front was attributed to two branches of extremely moist inflow from the southern confluence into western Japan. One was a shallow southerly airstream enhanced by the surface North Pacific Subtropical High, and the other was a deeper southwesterly airstream accompanying enhanced convection over the East China Sea. Both the vertically integrated moisture flux from the south and its convergence into western Japan reached the highest levels for 60 years due to an overwhelming contribution from the intensified southerlies. Anomalous diabatic heating associated with the active convection over the East China Sea acted to maintain the southwesterly moisture flux by inducing low-level cyclonic potential vorticity anomalies. During the rainfall event, a strong meander of the upper-level subtropical jet associated with the intensified surface North Pacific Subtropical High accompanied an amplified upper-level trough over the Korean Peninsula, which acted to induce ascent dynamically along the Baiu front.

著者

Akifumi Nishi Hiroyuki Kusaka

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.17-21, 2019 (Released:2019-02-05)

参考文献数

34

被引用文献数

17

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In this study, we use observational data and numerical models to reveal whether foehn wind affects the record-breaking high-temperature event (41.1°C) at Kumagaya on July 23, 2018. On this day, the weather conditions at Kumagaya satisfied the conditions described in Takane et al. (2014) for a likely extreme high temperature (EHT) day: a “whale-tail” pressure pattern, no precipitation for 6 days, a high potential temperature at 850 hPa, and northerly surface winds. Our back-trajectory analysis shows that the air parcels came to Kumagaya from heights up to 3.0 km above sea level over the Sea of Japan. The Lagrangian energy budget analysis shows that adiabatic heating accounts for about 87.5% of the increase of the thermal energy given to the air parcel, with the rest from diabatic heating. The diabatic heating is caused by heating associated with surface sensible heat flux and the mixing by turbulent diffusion. The adiabatic and diabatic heating are calculated to have raised the temperature of air parcel by 14 and 2.0 K, respectively, for this EHT event. We conclude that the dynamic foehn effect and diabatic heating from the surface, together with mixing in the atmospheric boundary layer, affected the formation of this EHT event.

著者

Daisuke Matsuoka Shiori Sugimoto Yujin Nakagawa Shintaro Kawahara Fumiaki Araki Yosuke Onoue Masaaki Iiyama Koji Koyamada

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.154-159, 2019 (Released:2019-07-23)

参考文献数

19

被引用文献数

7

---

In this study, a stationary front is automatically detected from weather data using a U-Net deep convolutional neural network. The U-Net trained the transformation process from single/multiple physical quantities of weather data to detect stationary fronts using a 10-year data set. As a result of applying the trained U-Net to a 1-year untrained data set, the proposed approach succeeded in detecting the approximate shape of seasonal fronts with the exception of typhoons. In addition, the wind velocity (zonal and meridional components), wind direction, horizontal temperature gradient at 1000 hPa, relative humidity at 925 hPa, and water vapor at 850 hPa yielded high detection performance. Because the shape of the front extracted from each physical quantity is occasionally different, it is important to comprehensively analyze the results to make a final determination.

著者

Shion Sekizawa Takafumi Miyasaka Hisashi Nakamura Akihiko Shimpo Kazuto Takemura Shuhei Maeda

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15A, pp.25-30, 2019 (Released:2019-06-22)

参考文献数

10

被引用文献数

34

---

During a torrential rainfall event in early July 2018, profound enhancement of moisture influx from the south and its convergence occurred over western Japan, which is investigated in this study on the basis of objective analysis and forecast data from the Japan Meteorological Agency Meso-Scale Model. The heavy rainfall over western Japan is found to accompany enhanced oceanic evaporation extensively around Japan, especially around the Kuroshio and entirely over the Sea of Japan. Linear decompositions of the anomalous moisture flux and surface latent heat flux anomalies applied to the high-resolution data reveal that the intensified speed of the low-level southerlies was the primary factor for the pronounced enhancement of both the moisture transport into the heavy rainfall region, especially in its western portion, and evaporation around the Kuroshio into the southerlies. An additional contribution is found from positive sea-surface temperature anomalies to the enhanced southerly moisture inflow into the eastern portion of the rainfall region. These findings have been confirmed through a backward trajectory analysis, which suggests that anomalous moisture supply to air parcels into the rainfall region primarily through the enhanced wind-forced evaporation roughly corresponds to about 10% of the precipitable water anomaly over western Japan.

著者

Koji Terasaki Shunji Kotsuki Takemasa Miyoshi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.41-46, 2019 (Released:2019-02-28)

参考文献数

29

被引用文献数

7

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This study investigates the long-term stability of the global atmospheric data assimilation system, incorporating the Local Ensemble Transform Kalman Filter (LETKF) with the Nonhydrostatic ICosahedral Atmospheric Model (NICAM). The NICAM-LETKF system assimilates conventional observations, advanced microwave sounding unit–A (AMSU-A) radiances, and global satellite mapping of precipitation (GSMaP) data. The long-term stability of the data assimilation system can be investigated only by running an expensive long-term experiment. This study successfully performed a data assimilation experiment with more than 2 years of data, using the relaxation to prior spread (RTPS) method for covariance inflation. Analysis fields indicate a stable physical performance compared with the ERA-interim data for the entire experimental period.

著者

Haruka Ishizaki Hiroshi Matsuyama

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.192-196, 2018 (Released:2018-12-14)

参考文献数

23

被引用文献数

10

---

Radar/Raingauge-Analyzed Precipitation (RA) represents 1 km-grid precipitation after 2006 created by combining radar precipitation and ground precipitation, i.e., Automated Meteorological Data Acquisition System (AMeDAS) of Japan Meteorological Agency along with ground data observed by other organizations. Although RA is slightly greater than ground precipitation, no earlier studies investigated the spatial distribution of this accuracy across Japan using 1 km grid data, as clarified in this study. We selected hourly data of RA and AMeDAS located closest each other, for which miss rates were less than 10% in 2006-2010. We then investigated the distribution of the annual precipitation ratio (RA/AMeDAS). The ratio diverged in the smaller annual precipitation, but converged to ca. 1.2 for larger annual precipitation. By setting the observational area of 46 radars across Japan using Thiessen method, we investigated the relation between the annual precipitation ratio and the distance from the radar to AMeDAS station. We found only negative relation was statistically significant. As a possible reason for this relation, we considered that RA far from the radar is affected by the attenuating and shadowing effect of heavy rainfall near the radar.

著者

Masatake E. Hori Kazuhiro Oshima

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.69-73, 2018 (Released:2018-06-26)

参考文献数

15

被引用文献数

3

---

We use two groups of 100-member ensemble AGCM experiment to investigate the robustness and probabilistic nature of the Warm Arctic/Cold Eurasian (WACE) pattern with or without strong warming SST trend and sea-ice reduction. Model ensembles successfully simulate a distribution of trend coefficients close to that of observation. Results show that the recent trend in WACE pattern is driven by the warming of the Arctic SST, but the pattern itself is not amplified between the warming and non-warming experiment and cannot explain the current cooling trend of the mid-latitudes. We argue that the difference in sea-ice condition regulates the more extreme cases of the pattern thereby contributing to the positive trend in WACE pattern similar to that of observation.

著者

Hiroyuki Yamada Tomoe Nasuno Wataru Yanase 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.203-208, 2016 (Released:2016-08-03)

参考文献数

26

被引用文献数

1 17

---

Typhoon Fengshen (2008) was marked by a persistent track toward the northwest, which was poorly predicted by an operational hydrostatic model, which indicated a significant northward bias. Using a global nonhydrostatic model with finer grid spacing, we have simulated a reliable track of this typhoon. The purpose of this study is to clarify the causes of the northward bias by comparing the output of the two models. This typhoon was marked by the asymmetry of rainfall concentrating in the downshear side. While both models could reproduce the asymmetric structure, a significant difference between them was found in the vertical structure. In the hydrostatic model, the vortex tilted to the downshear side with a displacement from lower to upper levels exceeding 100 km. This tilt was related to weak updrafts of, at most, 0.5 m s−1. Diagnosis using vorticity budget demonstrated that the tilt of the vortex resulted from a lack of vertical coupling that was too weak to withstand differential advection between the lower and upper levels. These results suggest the importance of reproducing inner-core updrafts for better track prediction of a typhoon in an environment with strong vertical shear.

著者

Fumiaki Fujibe Jun Matsumoto Hideto Suzuki

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.144-147, 2018 (Released:2018-10-17)

参考文献数

14

被引用文献数

14

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Relationships between daily heat-stroke mortality and temperature were statistically analyzed using Vital Statistics data for 1999 to 2016, with attention to regional differences related to different climate zones. An analysis based on data categorized for each prefecture has revealed that the daily heat-stroke mortality depends not only on daily temperature but also on the summer mean temperature in a way that a prefecture in a cooler summer climate tends to show a higher mortality for a specified value of daily temperature, implying the effect of acclimatization. Additionally, daily heat-stroke mortality is found to be higher for cases of higher temperature on preceding few days to a week, apparently due to accumulated heat stress, but is lower for cases of higher temperature a few weeks ago, presumably due to acclimatization. As for relative humidity, the mortality on a day of higher humidity tends to be higher for a specified value of daily maximum temperature, but lower for a specified value of daily mean temperature. It is also shown that heat-stroke mortality tends to be high on a day of low wind speed and long sunshine hours.

著者

Yasutaka Hirockawa Teruyuki Kato

出版者

公益社団法人 日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.18, pp.167-172, 2022 (Released:2022-07-27)

参考文献数

21

---

The procedures for identifying and classifying heavy rainfall areas of linear-stationary type (LS-HRAs) from the distributions of radar/raingauge-analyzed precipitation amounts (RAP) were improved to extract “senjo-kousuitai” with elongated and stagnant characteristics that causes localized heavy rainfall in Japan. The improved procedures were verified based on subjective judgments (‘certain’, ‘doubtful’, and ‘suspect’) whether LS-HRAs possess the characteristics of typical senjo-kousuitai. Criteria for excluding LS-HRAs judged to be ‘suspect’, mainly associated with tropical cyclones (TCs) and non-stationary mesoscale convective systems, were introduced to optimally extract senjo-kousuitai events. The criteria were determined by the distance between LS-HRAs and TC centers (DLT), the maximum total RAP of LS-HRA (total RAP), and the properties of each RAP distribution at every hour during the LS-HRA extraction period, e.g., DLT ≤ 500 km and total RAP < 200 mm. By applying these criteria, 372 senjo-kousuitai events were extracted from 452 LS-HRAs during the warm seasons (April–November) in 2009-2020, although approximately 35% of the LS-HRAs judged to be ‘suspect’ were not excluded. The criteria associated with TCs excluded them more effectively than the other factors. The improved procedures for extracting senjo-kousuitai events are expected to be used effectively for their statistical analyses.

著者

Hiroshi Takagi Akihiko Ito Heon-Sook Kim Shamil Maksyutov Makoto Saito Tsuneo Matsunaga

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.213-219, 2021 (Released:2021-12-14)

参考文献数

45

被引用文献数

2

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Numerous wetlands, including the world's two largest contiguous wetlands, lie along the free-flowing Paraná and Paraguay Rivers that travel the length of subtropical South America (SSA) region. These wetlands are floodplains that are inundated with rising river water in flood events; their morphology and area are highly changeable with flooding extent. The long-term variability of methane emission from this wetland hotspot and its sensitivity to meteorological conditions are not well known. We herein explore this unknown using space-based estimates of methane flux for the SSA region between 2009 and 2015 along with data of water balance. We find that methane emission from this region coherently varies with precipitation and inundation areal extent.