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September 2015 - August 2017
April 2015 - present
April 2013 - March 2015
Publications
Publications (101)
Physical processes responsible for tropospheric adjustment to increasing carbon dioxide concentration are investigated using abrupt CO2 quadrupling experiments of a general circulation model (GCM) called the model for interdisciplinary research on climate version 5 with several configurations including a coupled atmosphere–ocean GCM, atmospheric GC...
Factors and possible constraints to extremely large spread of effective climate sensitivity (ECS) ranging about 2.1–10.4 K are examined by using a large-member ensemble of quadrupling CO2 experiments with an atmospheric general circulation model (AGCM). The ensemble, called the multiparameter multiphysics ensemble (MPMPE), consists of both parametr...
AbstractAtmospheric rivers (ARs), conduits of intense water vapor transport in the middle latitudes, are critically important for water resources and heavy rainfall events over the west coast of North America, Europe and Africa. ARs are also frequently observed over the Northwestern Pacific (NWP) during boreal summer but have not been studied compr...
Eddy transport of atmospheric water vapor from the tropics is important for rainfall and related natural disasters in the middle latitudes. Atmospheric rivers (ARs), intense moisture plumes typically associated with extratropical cyclones, often produce heavy precipitation upon encountering topography on the west coasts of mid-latitude North Americ...
Land–sea surface air temperature (SAT) contrast, an index of tropospheric thermodynamic structure and dynamical circulation, has shown a significant increase in recent decades over East Asia during the boreal summer. In Part I of this two-part paper, observational data and the results of transient warming experiments conducted using coupled atmosph...
In 2017/18 winter, the Siberian High intensified significantly, leading to a severe cold winter in central Eurasia. Here, we apply the event attribution methods using two types of historical large-ensemble simulations from an atmospheric general circulation model to quantify the influence of human activities on this event. The 2017/18 winter was do...
The Sea of Okhotsk, between northern Japan and Siberia, is the southernmost sea region of the Northern Hemisphere with seasonal sea ice cover. During early spring, occasional rapid reduction in sea ice cover observed in the southern Sea of Okhotsk can lead to anomalously early disappearance of sea ice along the Hokkaido coast (northern Japan). This...
Understanding orbital-scale changes in East Asian summer monsoon (EASM) precipitation is a fundamental issue in paleoclimate research as it helps assess the response of the East Asian monsoon to different climatic forcings, such as insolation, ice volume, and greenhouse gases. However, due to inconsistencies between different proxies, the fundament...
Sri Lanka has a tropical monsoon climate. The first intermonsoon (FIM) season is one of four rainfall seasons. Previous investigations have explored the concurrent ramifications of the El Niño Southern Oscillation (ENSO); however, its impact on seasonal rainfall patterns in the country in the post-El Niño years remains unexplored. This study aims t...
Heavy rainfall due to tropical cyclones (TCs) in the North Indian Ocean (NIO) adversely impacts nations frequently. Though extensive research has focused on TCs in the NIO, less attention has been given to the connection between TCs and extreme events in Sri Lanka. This study examined atmospheric characteristics during sixteen extreme events, focus...
Understanding orbital-scale changes in East Asian summer monsoon (EASM) precipitation is a fundamental issue in paleoclimate research for assessing the response of the East Asian monsoon to different climate forcings, such as insolation, ice volume, and greenhouse gases. However, owing to the inconsistencies between different proxies, the fundament...
The Maritime Continent (MC) forms the western boundary of the tropical Pacific Ocean, and relatively small changes in this region can impact the climate locally and remotely. In the mid-Piacenzian warm period of the Pliocene (mPWP; 3.264 to 3.025 Ma) atmospheric CO2 concentrations were ∼ 400 ppm, and the subaerial Sunda and Sahul shelves made the l...
Radiative feedbacks over interannual timescales can be potentially useful for global warming estimation. However, the diversity of the lead–lag relationships in global mean surface temperature (GMST) and net radiation flux at the top of the atmosphere (GMTOA) create uncertainty during the estimation of radiative feedbacks. In this study, key physic...
Accurate understanding of permafrost dynamics is critical for evaluating and mitigating impacts that may arise as permafrost degrades in the future; however, existing projections have large uncertainties. Studies of how permafrost responded historically during Earth's past warm periods are helpful in exploring potential future permafrost behavior a...
The Maritime Continent (MC) forms the western boundary of the tropical Pacific Ocean, and relatively small changes in this region can impact the climate locally and remotely. In the mid-Pliocene (from 3.264 to 3.025 million years before present), atmospheric CO2 concentrations were ~ 400 ppm, and the subaerial Sunda and Sahul shelves made the land-...
During the recent years, synoptic-scale water vapor flows have frequently caused widespread intense precipitation events over East Asia, including the heavy rain event of mid-August 2021. The elongated water vapor transport bands over the middle latitudes are called as "atmospheric rivers (ARs)". Previous studies found the relationship between the...
Wintertime sea ice cover in the Okhotsk Sea (OS) exhibits strong interaction with the atmosphere over the Far East and the North Pacific. Previous studies identified that interannual variability of sea ice cover in the OS is associated with large-scale atmospheric circulations. However, the atmospheric processes responsible for rapid changes in sea...
The El Niño/Southern Oscillation (ENSO), the dominant driver of year-to-year climate variability in the equatorial Pacific Ocean, impacts climate pattern across the globe. However, the response of the ENSO system to past and potential future temperature increases is not fully understood. Here we investigate ENSO variability in the warmer climate of...
Using reanalysis and high-resolution ensemble simulations, we characterize cold season (December−March) North Atlantic (NA) atmospheric river (AR) tracks by grouping them into four distinct clusters; then for each cluster, we link the year-to-year variations in track count to large-scale climate variability and examine the climatological effects of...
The sea surface temperature (SST)-forced and internal variability in cold-season (December–March) atmospheric river (AR) occurrence frequency during 1951–2010 over the North Atlantic (NA) basin are examined using a 30-member ensemble of high-resolution atmospheric simulations. The first leading mode of the forced variability features a north–south...
Portions of East Asia often experienced extremely heavy rainfall events over the last decade. Intense atmospheric rivers (ARs), eddy transports of moisture over the middle latitudes, contributed significantly to these events. Although previous studies pointed out that landfalling ARs will become more frequent under global warming, the extent to whi...
The mid-Pliocene warm period (3.264–3.025 Ma) is the most recent geological period during which atmospheric CO2 levels were similar to recent historical values (∼400 ppm). Several proxy reconstructions for the mid-Pliocene show highly reduced zonal sea surface temperature (SST) gradients in the tropical Pacific Ocean, indicating an El Niño-like mea...
The mid-Pliocene warm period (mPWP; ∼3.2 million years ago) is seen as the most recent time period characterized by a warm climate state, with similar to modern geography and ∼400 ppmv atmospheric CO2 concentration, and is therefore often considered an interesting analogue for near-future climate projections. Paleoenvironmental reconstructions indi...
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 south...
Atmospheric rivers (ARs) are an important concern in regional water management; however, little is known about the AR impacts on hydrology in East Asia (EA). This study analyzes the characteristics of storms, precipitation (P), streamflow (Q), and runoff coefficient (R) in the Namgang-dam basin in Korea related to ARs for 2000–2013, as well as the...
Cloud feedback remains the largest source of uncertainty in equilibrium climate sensitivity (ECS). Many studies have attempted to narrow uncertainties in cloud feedback and ECS by proposing observable metrics with high skill at predicting future climate, referred to as emergent constraints. These constraints are often associated with clouds, convec...
Using a high-resolution atmospheric general circulation model simulation of unprecedented ensemble size, we examine potential predictability of monthly anomalies under El Niño–Southern Oscillation (ENSO) forcing and background internal variability. This study reveals the pronounced month-to-month evolution of both the ENSO forcing signal and intern...
The mid-Pliocene warm period (3.264–3.025 Ma) is the most recent geological period during which atmospheric CO2 levels were similar to recent historical values (~400 ppm). Several proxy reconstructions for the mid-Pliocene show highly reduced zonal sea surface temperature (SST) gradients in the tropical Pacific Ocean, indicating an El Niño-like mea...
The El Niño Southern Oscillation (ENSO) is the strongest pattern of year-to-year climate variability found in the equatorial Pacific Ocean with global impacts. However, it is not fully understood how ENSO responds to different warming scenarios. In the warmer climate (~2-3K) of the mid-Pliocene Warm Period (~3 Ma BP), models consistently suggest a...
The mid-Pliocene Warm Period (mPWP; ~3.2 million years ago) is seen as the most recent time period characterized by a warm climate state, with similar modern geography and ~400 ppmv atmospheric CO2 concentration, and is therefore often considered an interesting analogue for near-future climate projections. Paleoenvironmental reconstructions indicat...
This chapter reviews a recently developed idea of the Indo-western Pacific Ocean capacitor (IPOC) mode. Its positive phase features an anomalous low-level anticyclone anchored by weaker atmospheric convection over the tropical western North Pacific and extending to Indian subcontinent from boreal spring to summer. However, its key air-sea feedback...
Palaeoclimate simulations improve our understanding of the climate, inform us about the performance of climate models in a different climate scenario, and help to identify robust features of the climate system. Here, we analyse Arctic warming in an ensemble of 16 simulations of the mid-Pliocene Warm Period (mPWP), derived from the Pliocene Model In...
The Pliocene epoch has great potential to improve our understanding of the long-term climatic and environmental consequences of an atmospheric CO2 concentration near ∼400 parts per million by volume. Here we present the large-scale features of Pliocene climate as simulated by a new ensemble of climate models of varying complexity and spatial resolu...
Thermodynamic arguments imply that global mean rainfall increases in a warmer atmosphere; however, dynamical effects may result in more significant diversity of regional precipitation change. Here we investigate rainfall changes in the mid-Pliocene Warm Period (~ 3 Ma), a time when temperatures were 2–3ºC warmer than the pre-industrial era, using o...
Abstract. Palaeoclimate simulations improve our understanding of the climate, inform us about the performance of climate models in a different climate scenario, and help to identify robust features of the climate system. Here, we analyse Arctic warming in an ensemble of 16 simulations of the mid-Pliocene Warm Period (mPWP), derived from the Pliocen...
Atmospheric rivers (ARs), narrow water vapor transport bands over the mid-latitudes, often cause great socio-economic impacts over East Asia. While it has been shown that summertime AR activity over East Asia is strongly induced by preceding-winter El Niño development, it remains unclear the extent to which seasonal transitions of El Niño Southern...
The influence of eastern tropical Pacific (EPAC: 10ºS-10ºN, 140ºW-80ºW) wind
anomalies on El Niño is investigated using observations and model experiments.
Extreme and moderate El Niños exhibit contrasting anomalous wind patterns in the
EPAC during the peak and decay phases: westerly wind anomalies during extreme El
Niño and southeasterly (southwes...
The Pliocene epoch has great potential to improve our understanding of the long-term climatic and environmental consequences of an atmospheric CO2 concentration near ~ 400 parts per million by volume. Here we present the large-scale features of Pliocene climate as simulated by a new ensemble of climate models of varying complexity and spatial resol...
The Earth’s solar reflectance is reduced through rapid climate adjustments to increasing CO2, via a decrease in total cloud cover over ocean. Perturbations to marine boundary-layer clouds are essentially important for the global radiative balance at the top of the atmosphere. However, the physical robustness of low cloud adjustments to increasing C...
Atmospheric rivers (ARs), intense water vapor transports associated with extra-tropical cyclones, frequently bring heavy rainfalls over mid-latitudes. Over East Asia, landfalling ARs result in major socio-economic impacts including widespread floods and landslides; for example, western Japan heavy rainfall in July 2018 killed more than 200 people....
Variability of North Atlantic annual hurricane frequency during 1951–2010 is studied using a 100-member ensemble of climate simulations by a 60-km atmospheric general circulation model that is forced by observed sea surface temperatures (SSTs). The ensemble mean results well capture the interannual-to-decadal variability of hurricane frequency in b...
The record low sunshine over Japan during August 2017 was mainly attributed to a blocking high and Pacific-Japan pattern. Anthropogenic warming and decaying El Niño contributed to an increase in the probability of occurrence.
Equilibrium climate sensitivity (ECS) and hydrological sensitivity describe the global mean surface temperature and precipitation responses to a doubling of atmospheric CO2. Despite their connection via the Earth’s energy budget, the physical linkage between these two metrics remains controversial. Here, using a global climate model with a perturbe...
The response of tropical cyclone (TC) activity to the El Niño-Southern Oscillation (ENSO) and coherent sea surface temperate (SST) anomaly in the Indian Ocean (IO) is investigated with a particular focus on the decaying phase of El Niño. The TC anomalies are obtained from the database for Policy Decision making for Future climate change (d4PDF). Th...
The eastern tropical Pacific features strong climatic asymmetry across the equator, with the intertropical convergence zone (ITCZ) displaced north of the equator most of time. In February-April (FMA), the seasonal warming in the Southern and cooling in the Northern Hemisphere weaken the climatic asymmetry, and a double ITCZ appears with a zonal rai...
This study discusses how much of the biases in top-of-atmosphere (TOA) radiation and clouds can be removed by parameter tuning in the present-day simulation of a climate model in the Coupled Model Inter-comparison Project phase 5 (CMIP5) generation. We used output of a perturbed parameter ensemble (PPE) experiment conducted with an atmosphere–ocean...
Instrumental and proxy records indicate remarkable global climate variability over the last millennium, influenced by solar irradiance, Earth’s orbital parameters, volcanic eruptions and human activities. Numerical model simulations and proxy data suggest an enhanced Asian summer monsoon during the Medieval Warm Period (MWP) compared to the Little...
The 2016 extreme warmth across Asia would not have been possible without climate change. The 2015/16 El Niño also contributed to regional warm extremes over Southeast Asia and the Maritime Continent.
Natural climate variability contributes to recent decadal climate trends. Specifically the trends during the satellite era since 1979 include Atlantic and Indian Ocean warming and Pacific cooling associated with phase shifts of the Atlantic Multidecadal Oscillation and the Pacific Decadal Oscillation, and enhanced global monsoon (GM) circulation an...
Over the past decade, anomalously hot summers and persistent droughts frequented over the western United States (wUS), the condition similar to the 1950s and 1960s. While atmospheric internal variability is important for mid-latitude interannual climate variability, it has been suggested that anthropogenic external forcing and multidecadal modes of...
This article is a correction to SOLA Vol. 10 (2014) pp. 122-126.
Equilibrium climate sensitivity (ECS) to doubling of atmospheric CO2 concentration is a key index for understanding the Earth’s climate history and prediction of future climate changes. Tropical low cloud feedback, the predominant factor for uncertainty in modeled ECS, diverges both in sign and magnitude among climate models. Despite its importance...
An unprecedentedly large ensemble of climate simulations with a 60 km atmospheric general circulation model and dynamical downscaling with a 20 km regional climate model have been performed to obtain probabilistic future projections of low-frequency local-scale events. The climate of the latter half of the 20th century, the climate 4 K warmer than...
Accumulations of global proxy data are essential steps for improving reliability of climate model simulations for the Pliocene warming climate. In the Pliocene Model Intercomparison Project phase 2 (PlioMIP2), a part project of the Paleoclimate Modelling Intercomparison Project phase 4, boundary forcing data have been updated from the PlioMIP phase...
The correct understanding of the transient response to external radiative perturbation is important for the interpretation of observed climate change, the prediction of near-future climate change, and committed warming under climate stabilization scenarios, as well as the estimation of equilibrium climate sensitivity based on observation data. It h...
Accumulations of global proxy data are essential steps for improving reliability of climate model simulations for the Pliocene warming climate. In the Pliocene Model Intercomprison Project phase 2 (PlioMIP2), boundary forcing data have been updated from phase 1 due to recent advances in understanding of oceanic, terrestrial and cryospheric aspects...
Eight general circulation models have simulated the mid-Pliocene warm period
(mid-Pliocene, 3.264 to 3.025 Ma) as part of the Pliocene Modelling
Intercomparison Project (PlioMIP). Here, we analyse and compare their
simulation of Arctic sea ice for both the pre-industrial period and the
mid-Pliocene. Mid-Pliocene sea ice thickness and extent is redu...
Cloud-related radiative perturbations over land in a warming climate are of importance for human health, ecosystem, agriculture and industry via solar radiation availability and local warming amplification. However, robustness and physical mechanisms responsible for the land cloud feedback were not examined sufficiently because of the limited contr...
Recent research indicates that the cooling trend in the tropical Pacific Ocean over the past 15 years underlies the contemporaneous hiatus in global mean temperature increase. During the hiatus, the tropical Pacific Ocean displays a La Niña-like cooling pattern while sea surface temperature (SST) in the Indian Ocean has continued to increase. This...