simon's

peer-reviewed papers

all 183 of them


2024

We explore how changing weather patterns, driven by global warming, impact North America's extreme weather and the winter dipole. We found the noticeable role of human activities in altering teleconnection in North America over the past 70 years, emphasizing the need to understand the dynamic effects of global warming in shaping winter climate variations. 

We show that as the globe warms, there will be a decline in the warm arctic-cold continent patterns. The cold air that usually hits East Asia and North America is moving north, suggesting less frequent cold spells in these regions in the future. This change could mean we need to rethink how we predict and prepare for winter weather, emphasizing the need for updated climate models.

The CESM, adept at capturing the Southern US climate, often misses extreme weather predictions. This study upgrades the model with detailed, convective-resolving local climate data, boosting its ability to forecast severe weather. When initiated weeks ahead, the model more precisely anticipates wet and dry extremes. It also indicates that varying upper atmospheric wind patterns could play a role in Texas's atypical seasonal rainfall or drought conditions. 

The unexpected bounty of the Colorado River Basin's snowpack in the winter of 2022–2023 defied predictions, revealing the tenuous link between tropical sea temperatures and regional rainfall. As a critical water lifeline for the Western US, this season's atypical snowfall patterns underscore the prevailing role of stochastic forces on water availability. This reinforces the imperative for a multi-faceted approach to forecasting in water management strategies.

The severe drought in Taiwan halted carbon sequestration in its subtropical forests. The analysis uncovers a significant correlation between carbon uptake, radiative factors, groundwater levels, and wildfires, indicating that the severity of droughts leads to a shift from carbon absorption to emission in these forests, thereby inviting a broader examination of the climate-carbon nexus.

Given the recent increases in drought and wildfire, this study anticipates that, under severe climate scenarios, the subtropical island of Taiwan could see a dramatic rise in wildfires, with some regions potentially experiencing up to 90% more fires by the end of the century.

2023

This paper examines the intricate relationship between climate risks and Taiwan's financial system, stressing the importance of data-driven strategies for resilience and policy making. It highlights Taiwan's unique challenges in managing climate-related financial risks and suggests using Data Assisted Techniques for Adaptation (D.A.T.A) for policy intervention, focusing on effective climate data collection and analysis to bolster the financial system against climate extremes.

The study explores how socioeconomic factors like education, age, and financial limitations impact farmers' decisions in crop production in Northwest India from 2016-2021. It emphasizes the role of government policies and communication from agricultural scientists in improving crop yields.

Recent studies show a 17% increase in East Asia's summer monsoon frontal rainfall from 1958–2015, with anthropogenic warming contributing to a 5.8% intensification from 1991–2015. The findings highlight the role of human-induced climate change in intensifying future rainfall patterns.

The authors tried to understand how regional climate variability in peninsular Southeast Asia affects springtime biomass-burning aerosol emissions and transport. Four key climatic factors and their correlation with El Niño events are identified to improve aerosol-climate models.

The authors explore the complexities of actionable climate information and its utilization in decision-making. Through four years of co-production engagements, the study empirically derives typologies that map the landscape of climate information and its various uses. These typologies aim to streamline the knowledge production process, making it more time and cost-efficient for producers and users.

This study explores South American extratropical cyclones, unveiling the influence of Andes' dynamics on cyclogenesis. Coastal and lee-side cyclogenesis respond differently to temperature anomalies, affecting their frequency. Enhanced understanding of these mechanisms is crucial amid climate change-induced variability.

Two spatial groups of explosive cyclones (ECs) are identified, with high latitude EC frequency linked to the North Atlantic Oscillation and coastal EC frequency associated with an atmospheric wave-train from the North Pacific. Model experiments highlight the influence of tropical and North Pacific oceans on this atmospheric wave train.

Palm oil is vital for Thailand's economy, but its productivity is influenced by climate and ENSO events. Dynamic models integrating local and large-scale climate variables can enhance prediction accuracy. Future research should explore measures to safeguard yield based on skillful seasonal prediction.

Nepal's 2020 monsoon was the wettest in 40 years. The Western North Pacific Anticyclone and an intense Indian Ocean warming caused the unusually high precipitation. The Indo-western Pacific Ocean Capacitor may have played a role, and anthropogenic warming may have further tipped the balance.

The APCSW 2021 brought together over 200 people from 11 countries to Taipei to discuss climate change and climate services. Participants agreed that climate action is urgently needed in the Asia-Pacific region, and that climate services are essential to building climate-resilient societies.

This study investigates the impact of climate change on the relationship between a cold western North Pacific phase and El Niño development, finding that enhanced warming intensifies surface convergence and anomalous advection in the equatorial Pacific, leading to an increase in the amplitude and frequency of El Niño events and a strengthened three-way link between the western North Pacific, Pacific Meridional Mode, and El Niño.

Summertime air quality in Northern Utah is highly correlated with the number of dry-hot days, wildfire size, and an upper atmospheric ridge over the Northwestern United States, with climate model simulations confirming increasing trends in these factors, highlighting the need for longer-term monitoring and seasonal forecasting for air quality and its compounding factors.

Since 1850, anthropogenic climate warming has strengthened the relationship between ENSO and both the Asian and Australian summer monsoons, leading to synchronized variations in monsoon precipitation.

The Warm Arctic Cold Continent (WACC) pattern contributes to increasingly extreme cold winters in interior Eurasia and North America, and although WACC will continue in the future, cold extremes may slightly weaken due to overall warming, reducing the predictability of midlatitude winter anomalies.

The record wildfire season in Nepal during spring 2021 was driven by both climate variability and climate change-induced drought conditions, and the analysis suggests a likelihood of recurring droughts and increased wildfire activity throughout the 21st century; this information can help forest managers to develop strategies based on monitoring and projecting climate anomalies at sub-seasonal to decadal timescales.

This study evaluated the loss of forest ecosystem services due to mining operations in two Taiwanese mines over 20 years, finding significant losses in forest production, carbon sequestration, water conservation, and forest recreation benefits, highlighting the need to incorporate these losses into mining-related expenses and compensation for ecological damage.


2022

This study examines the impact of extratropical transitioning cyclones (ETCs) on North American fire weather, finding that ETCs consistently result in both suppressed and enhanced fire weather in specific areas through their interaction with the jet stream, providing a first holistic understanding of ETCs' influence on fire weather amid increasing concerns about wildfires in the Western United States.

The study modifies the Meiyu onset index using ERA5 reanalysis data, resulting in better alignment with maximum precipitation events during the Meiyu season, offering operational forecasters and water resource managers an improved method for anticipating Meiyu rainfall and managing water resources in Taiwan.

Climate warming affects rice cultivation in Taiwan, leading to shorter vegetative phases, earlier maturation, reduced yields, and increased yield variability.

The CFS-Super Resolution, a hybrid prediction system combining a weather forecast model and deep learning, significantly improves fire weather forecasting up to 7 days in advance with enhanced spatial resolution, providing county-level information for better resource allocation and wildfire mitigation.

Integrating Twitter data with meteorological records using machine learning techniques can improve drought detection and progression tracking. Twitter-based model outperformed the control model without social media input, suggesting its potential in predicting drought severity and aiding in future drought monitoring efforts.

The population change of rice planthoppers in Taiwan, which has declined since the mid-2000s, is strongly linked to multi-decadal climate variability, and a future reversal of this climate pattern may lead to a resurgence in planthopper populations.

The study emphasizes that the increased summertime midlatitude waviness in the Northern Hemisphere over the past 40 years is primarily driven by cooling trends in the tropical Eastern Pacific, rather than Arctic amplification, highlighting the need for accurate tropical Pacific SST predictions to project weather extremes.

The study highlights pronounced climatological changes in the 1990s, with shifts in Northern Hemisphere dry and wet patterns occurring more rapidly in winter than summer, driven by factors such as jet stream shifts and weakened westerly flows above Asian and African monsoons.


2021

The study identifies five weather types and finds that a general drying trend in the western U.S. is more significantly associated with fewer troughs rather than more ridges, with attribution analysis suggesting that this decrease in wetter and colder weather is likely due to anthropogenic forcing.

Historical trends in probable maximum precipitation (PMP) for Utah's watersheds show a significant increase, with varying magnitudes depending on the dataset and its spatial resolution, suggesting a need to consider these trends in future PMP estimates, particularly when using coarse-resolution data.

Keen et al. identifies potential early warning signals for drought-related mortality in ponderosa pine forests, derived from measurements of tree-ring growth and carbon isotope discrimination, which may provide land managers with more time to mitigate the extent or severity of forest mortality in advance of droughts caused by climate warming.

This study investigates the influences of local hydroclimate and remote large-scale circulation on tree-ring δ18O in monsoon Asia, and finds that South Asian summer monsoon precipitation and El Niño–Southern Oscillation are the main factors controlling a common signal of tree-ring δ18O across Monsoon Asia.

Historical wildfire events in California occur every five to seven years, linked to a sequence of anomalous large-scale climate patterns with an eastward propagation in both the ocean and atmosphere, suggesting the semi-cyclical hydrological behavior as a climate driver for wildfire variability in California.

This study analyzed questionnaires collected from 17 cities in Taiwan to assess the public's understanding of climate change and its impact on forests, finding that most respondents recognized the need to adjust forest management for climate change, establish mixed forests, and monitor forest damage, and called for the government to raise forest owners’ understanding on climate change and adaptation policies.

The frequency of atmospheric rivers affecting wet and dry periods in Northern California is driven by the position and intensity of the Aleutian Low, which is forced by the tropical Pacific and modulates moisture transport towards California on decadal time scales.

This study highlights the significance of eastward propagating waves in the U.S. Great Plains for initiating four types of summer mesoscale convective systems (MCSs), with 30% of mid-tropospheric perturbations related to MCS initiation, leading to increased rainfall, larger affected areas, and stronger convective intensity.

The ability of NA-CORDEX regional climate model ensembles to reproduce the precipitation climatology of hydrologically-important western US regions is evaluated. Results indicate over-simulated wintertime precipitation over mountainous regions, but improvements to the Desert Southwest's summertime precipitation. The higher resolution showed better performance metrics than the lower resolution.

This study assesses the impact of 1.5 °C and 2.0 °C increases in global temperature on fire weather, indicating that the half-degree difference between these two thresholds may significantly increase the hazard of wildfire in certain parts of the world, particularly the Amazon, African savanna, and Mediterranean, and limiting global warming to 1.5 °C would alleviate some risk in these regions.

We analyzed tropical easterly waves in the Western North Pacific during May-September of 1979–2017 and shows that most of the waves dissipate when encountering the monsoon trough and associated westerlies, while a small number move westward due to total vortex stretching in the lower troposphere, highlighting the importance of interaction with the monsoon trough or a monsoon gyre for development into a typhoon.

This study presents the first tree ring oxygen isotope record from southwestern Greenland, showing a positive correlation with ice core δ18O and January-August mean temperatures, as well as a negative correlation with the North Atlantic Oscillation (NAO), suggesting the potential for using tree rings to extend the NAO reconstruction.


2020

The study explores how climate and water policy interact to influence water availability for cannabis in California, and how public discourse frames these interactions, and suggests that water policy should better represent growers' voices and explicitly address stakeholder controversies to promote a socially, politically, and environmentally viable cannabis industry.

In September 2020, three western Pacific typhoons undergoing extratropical transition over Korea within 12 days amplified an atmospheric wave train across the Pacific Ocean, intensifying winds and contributing to the western U.S. fire outbreak by enhancing the ridge over the west coast and deepening the trough in central Canada.

This new study presents a 260-year-long record of temperature and soil moisture over inner East Asia that reveals an abrupt shift to hotter and drier conditions in the past 20 years, which are unprecedented in earlier records, caused by a positive feedback loop between soil moisture deficits and surface warming that may represent the start of an irreversible trend.

During the 2012-2015 California drought, surviving ponderosa pines had higher growth rates and were found in areas with lower basal area, indicating that trees more resistant to drought stress and beetle attacks were among the top performers within a stand and across the landscape.

Snow cover in northern Eurasia, La Niña-like sea surface temperature anomalies, and sea ice loss in the Barents and Kara seas can influence winter cooling events in Eurasia and North America by modulating Arctic Oscillation circulation and North American surface air temperature.

Decadal climate prediction system using a fully coupled climate model demonstrates the predictability of the annual water supply of the Colorado River up to several years in advance, showing that prolonged shortages of water supply are linked to sea surface temperature precursors, making multi-year predictions of severe water shortages useful as early indicators of subsequent agricultural loss and wildfire risk.

Winter cloud seeding suitability in Utah's mountains may decrease under future climate change, with the projected decline in precipitating clouds suitable for seeding dropping from 60% to 40% statewide due to rising temperatures and reduced precipitation frequency.

The study combines phenological models to predict bloom dates of tart cherries in Utah and Michigan, improving the estimation of chill units and exhibiting subseasonal performance in predicting bloom dates for 6 weeks in advance, providing growers with a way to mitigate extreme climate anomalies.

Equatorial Atlantic cooling is the primary cause of weakened equatorial zonal winds in the Indo-Pacific and subsequent warming in the tropical Pacific, affecting the interbasin climate seesaw between the Atlantic and Pacific through an atmospheric zonal Wavenumber 1 pattern.

There has been a long-term increase of stagnant air conditions over East Asia, with a decrease in near-surface wind speed and an increase in static stability, which is likely driven by global warming caused by greenhouse gases and has negative implications for air quality in the future.

The East Asian summer monsoon (EASM) has intensified, resulting in a shorter but stronger rainy season, according to observational datasets and historical simulations of CMIP6, while CMIP6 models generally underestimated the observed intensification of the EASM lifecycle and the monsoon precipitation.

The 2019 Asia Pacific Climate Service Workshop in Taiwan aimed to develop climate services in the region by fostering communication, policy steering, and information sharing among government agencies, private companies, and academia to address risk reduction, management issues, and create economic opportunities related to weather and climate phenomena.

This study reveals that PDO variability stems from 12-29% Atlantic Ocean influence, 40-44% tropical Pacific influence, and the remainder from other processes like North Pacific ocean-atmosphere interactions and Indian Ocean teleconnections.

The compound effects of atmospheric aerosols and regional climate warming on tropical cyclone Fani in the Bay of Bengal were analyzed using a quantitative attribution analysis, showing that aerosol and its interaction with the atmosphere mitigated the strengthening effect of anthropogenic warming on Fani, but was not strong enough to entirely counteract it.

The study finds that the long-term intraseasonal δ18Oc values in tree rings from the southeastern Tibetan Plateau correlate with the onset and mature phase of summer monsoon precipitation, enabling reconstruction of the Asian summer monsoon's intraseasonal variations.

ENSO influences on north central India rainfall are changing, with Atlantic Niño overtaking La Niña-like conditions and affecting pressure anomalies over northwest Europe, subsequently affecting the upper-troposphere high pressure anomaly in north India.

Sea surface temperature anomalies in the Western North Pacific (WNP) have been found to have a significant impact on the development of El Niño Southern Oscillation events in the eastern Pacific, with the removal of SST variability in the WNP leading to the increased likelihood of central Pacific ENSO events developing.

In Tanzania, maximum rainfall during the long rainy season is decreasing, and the short rainy season in the northwest is experiencing increasing precipitation trends, with warmer temperatures in the western Indian Ocean having a stronger correlation with rainfall variability than ENSO, and the IOD having a greater effect on rainfall variability.

This study examines intense diurnal precipitation beneath the South Asian High during the summer monsoon season using observational data from 2010 to 2015 and found that warmer air, increased moisture, and stronger upward velocity can enhance the potential for diurnal convection, supporting the nighttime peak of rainfall, which persists until the South Asian High retreats.

The study evaluates and diagnoses model skill for the East Asian summer monsoon in Taiwan, identifying a substantial increase in precipitation for the Meiyu season in both high and low skill model groups, projected to occur through the extension of a strengthened North Pacific anticyclone and Clausius–Clapeyron relationship.

2019

The NAWD has exhibited both marked natural variability and a warming-induced amplification trend in recent years, with a significant increase in the number of billion-dollar freeze and drought disasters in eastern and western states respectively, and identified changes to the circulation patterns of the winter planetary waves over North America from pre- to post-1980 periods.

Observational studies overwhelmingly support that Arctic amplification (AA) is contributing to winter continental cooling, but divergent conclusions between model and observational studies continue to obfuscate a clear understanding of how AA is influencing midlatitude weather.

Using multi-year prediction of the Great Salt Lake water level to forecast the Colorado River water supply could aid in management decision-making in the face of near-future water shortages.

High-resolution data shows increased extreme precipitation and decreased seasonal mean precipitation in Nepal leading to reduced dry-season stream flow and increased flash flood risk, with CMIP5 models suggesting a reversal of this trend due to Indian Ocean warming.

A series of extreme precipitation events in coastal Peru during Jan-March 2017 resulted from strong recurrent patterns of atmospheric and oceanic conditions, including warm sea surface temperatures and weakened trade winds, which led to an increased precipitation frequency and intensity.

The intensified Baiu rainband in Japan in 2018 was a result of a stationary short-wave train and energized tropical intraseasonal oscillation (TISO), with typhoons Prapiroon and Maria playing a role, and the authors call for an integrated view of the amplified East Asian summer monsoon "lifecycle" that influences extreme rainfall and subsequent heat waves.

This study explores the connection between Pacific-North American climate patterns and the natural gas market in the US, and finds that understanding the impact of climate variability on natural gas storage and consumption is crucial for economic adaptation to extreme winter weather conditions.

This study examines the changes in extreme precipitation occurrence (EPO) in Taiwan The study from 1993-2015 identifies three major weather types affecting EPO, with overall increase, but with variability and interannual variations associated with the TC season before an ENSO event.

ENSO modulates Chao Phraya River peak season streamflow, with Pacific Decadal Oscillation modulating ENSO-streamflow correlations, as shown in a 202-year reconstruction using tree ring δ18O series, providing insight for water resource management planning in Thailand.

A study found that the dipole index explains the greatest fraction of multivariate variability in co-occurring California wintertime temperature and precipitation extremes, with co-occurring extremes having a greater impact on human and ecological systems than any single extreme.

Tree-ring isotopes from white pine trees by Lake Superior could produce a winter-specific paleoclimate reconstruction with inter-annual resolution for the first time, and potentially reconstruct variability in winter minimum temperatures, ice cover, and atmospheric circulation patterns.

India's reduction in wheat yield during 2002-2010 in Punjab and Haryana was due to high temperatures during maturity stage, less monsoon rainfall, depletion of groundwater, reduced surface water for irrigation, and irregular irrigation.

ERWs are planetary-scale waves that modulate convective activity in South Asia and the Maritime Continents, with recent observations suggesting their intensification in the upper troposphere due to the strengthening and westward shift of the Walker circulation.

A tree-ring chronology was developed for southwestern China to reconstruct precipitation, revealing a drying trend since 1840 and more frequent droughts since 1970, modulated by the El Niño-Southern Oscillation and Indian Ocean Dipole on an interannual timescale.


2018

The study revealed that small, mid-tropospheric perturbations in large-scale ridge patterns drive severe weather outbreaks, and climate change in North America may cause a significant subseasonal shift in MP climatology, leading to increased frequency and convective precipitation.

Arctic warming may weaken storm tracks by reducing temperature gradient, but the implications for weather persistence and extremity are uncertain, emphasizing the need to assess future high-end risks by disentangling and quantifying non-linear interactions.

The study explores the role of the Indochina Peninsula's topography in modulating the seasonality of nearby monsoons and driving rapid monsoonal transitions, emphasizing its impact on East Asian precipitation and the asymmetric seasonal variation.

Decadal prediction models for autumn rainfall in Central Vietnam are found to be feasible by utilizing tree-ring data and Pacific sea surface temperature variability, indicating that multi-year forecasts can be achieved with a time series model.

Low-level convergence variability over the Pacific Warm Pool influences tropical cyclone genesis in the Western North Pacific, with a 20-year frequency shift in the tropical intraseasonal oscillation affecting the timing and number of tropical cyclones due to stochastic low-frequency atmospheric variability.

Hurricane Harvey's extreme rainfall, which caused vast devastation in Texas in 2017, was potentially exacerbated by post-1980 climate warming, contributing to an estimated 20% increase in precipitation, while global climate model analysis indicates a rise in stalling storm frequency and intensity over southeast Texas through the mid-21st century.

Large-ensemble simulations project that both intense drought and excessive precipitation in Texas will increase by the mid-21st century, with a strengthened connection to the El Niño–Southern Oscillation, potentially leading to decreased groundwater storage despite increased precipitation in the southern Great Plains.

The extreme flooding in Missouri in December 2015 was influenced by the Madden Julian Oscillation and El Niño, and climate change may have impacted the relationship between ENSO and precipitation in several central US states, as seen in 17 CMIP5 models.

The Colorado River Basin water supply has a 10-20-year oscillation, and its connection with the Great Salt Lake (GSL) elevation suggests a cross-basin connection in climate and hydrometeorological variations, making the 160-year-long GSL elevation record an effective indicator for the Colorado water supply that has not been accounted for in climate models used for future water supply projections.

Increased early-monsoon precipitation in Vietnam is linked to low-level cyclonic airflow changes and atmospheric circulation. Greenhouse gases and natural forcing contribute to this increase across different regions of the country.

Increased winter crop losses in Taiwan are linked to extreme wet-and-cold events. The study developed an empirical model using various indices, which accurately predicts these events up to 6 months in advance, helping forecast winter crop damage in northwestern Taiwan.


2017

The Arabian Sea monsoon inversion is connected to a larger-scale monsoon evolution across the African Sahel, South Asia, and East Asia-Western North Pacific. Peak Sahel rainfall and equatorial Indian Ocean heating strengthen the Arabian Sea thermal inversion, while the broad monsoon plays a secondary role.

Interdecadal variations of Lake Qinghai's water levels are influenced by water vapor flux divergence related to the North Pacific and Pacific decadal oscillation modes, and greenhouse gas forcing significantly increases precipitation, contributing to the lake's water level changes.

The dramatic switch from extreme drought to severe flooding in California, and the accompanying flip from atmospheric ridge to trough in the northeastern Pacific, exemplifies the pathways to an intensified water cycle under a warming climate.

This study reconstructs April 1 snow water equivalent (SWE) from 1850-1989 using tree-ring data, providing water resource managers with better spatial resolution to examine past snowpack variability in the context of climate change.

A regime change around 1960 was observed, where Taiwan's precipitation became more synchronized with the Pacific quasi-decadal oscillation (QDO), potentially due to increased sea surface temperatures and a strengthened anticyclone in the subtropical western Pacific.

The succession of distinct Arctic warming events in 2016 allowed for a comparison, revealing an accelerated increase in tropospheric warming events, which may connect to increased midlatitude weather extremes, potentially influenced by reduced Arctic sea ice and tropical oceanic warming.

A strong relationship between winter atmospheric stability and aerosols in the Indo-Gangetic Plains reveals that both greenhouse gas and aerosol forcings contribute to atmospheric stabilization, which can increase aerosol levels even without changes in emission sources.

Tree-ring increment has a wet bias that underestimates extremely wet years, which can be improved by introducing two modified linear regression models to account for this bias, demonstrating that wet bias emerges from nonlinearity of tree-ring chronologies in reconstructing precipitation.


2016

The 2014/15 snowpack drought in Washington resulted from high temperatures despite normal precipitation, a drought type that may recur due to accelerated anthropogenic warming and natural low precipitation.

A persistent upper tropospheric ridge over the Northeastern Pacific caused a major drought in California from 2011 to 2015 by reducing rainy-season precipitation, leading to a decline in snowpack and less water during the dry seasons.

The 2016 Louisiana flood was caused by intense precipitation from a tropical low-pressure system and a midlatitude eastward-moving trough, with increasing potential for similar events due to climate change. Modeling suggests that the August 2016 event's precipitation increased by 20% due to climate warming since 1985, and the Gulf Coast could experience more extreme precipitation in the future.

East Asian diurnal rainfall is characterized by propagating and non-propagating regimes. One model projects propagating rainfall to expand southward by 2076-2100.


This study examines the subseasonal relationships between tropospheric short-waves and regional precipitation anomalies across the continental United States and evaluates the NCEP Climate Forecast System Version 2's capabilities in resolving these relationships.

Since 1979, the active-phase East Asian summer monsoon timing has shifted due to a southward migration of the Meiyu rainband. This is driven by two circulation patterns, enhanced by Western Pacific warming and greenhouse gases, resulting in delayed Meiyu season over Taiwan.

We present a 667-year-long tree ring record from central Vietnam based on Fokienia hodginsii, with significant linkages to regional hydroclimate metrics and the El Niño-Southern Oscillation, and show that cool and warm phase events are linked to regional wet and dry conditions respectively.

Tropical cyclones (TCs) cause a cold wake in the sea surface temperature (SST). In the northwest Pacific, the intensified effect of TC cold wakes has offset the SST warming trend by 37% during the typhoon season, implying that the observed SST warming might be underestimated.

California's recent drought has depleted groundwater supplies, with a continued depletion lasting a year after droughts, which was not observed in earlier records before the 21st century, possibly due to the warming-induced lengthening of droughts and intensification of droughts and pumping.

The unprecedented 2011 flood in Thailand's Chao Phraya River basin was caused by a series of abnormal conditions including high rainfall in the premonsoon season, record-high soil moisture, elevated sea levels, and water management factors. Anthropogenic greenhouse gases were identified as the main external climate forcing behind the rainfall increase.


2015

Global warming is projected to increase both intense drought and excessive flooding in California by at least 50% by the end of the 21st century, with a strengthened relation to El Niño and La Niña events, according to large-ensemble and multi-model simulations.

The 2014 fire season in northern California was the second-largest since 1997 and the highest since 1979 for extreme fire risk across the state. Man-made global warming is expected to exacerbate the frequency and areal extent of extreme fire risk in the future, despite the lack of change in mean fire probability and annual precipitation.

A blizzard and heavy snowfall, leading to avalanches, occurred in Nepal in 2014 due to an unusual coupling of an upper trough with remnants of TC Hudhud. Climate diagnostics suggest a trend for stronger upper troughs and stronger tropical disturbances due to anthropogenic factors, increasing the possibility of similar events in the future. 

To predict fluctuations in the Great Salt Lake level, a statistical model was developed using a 137-year observational record of the lake's elevation and a recently reconstructed 576-year tree-ring record. The model can aid water risk management.

The paper examines the historical properties of winter temperature inversions in Cache Valley, Utah. Although there is no long-term trend in inversion intensity, inversion frequency increased in the early 1980s and decreased by 30% through 2013.

Anthropogenic global warming contributed to the May 2015 floods in Texas and Oklahoma, intensifying the effect of El Niño teleconnection. Attribution analysis showed significant increases in El Niño-induced precipitation anomalies when accounting for increases in greenhouse gases. Climate warming also amplified synoptic waves and strengthened low-level southerlies.

Long-term precipitation decrease during the June-July transition in Central US has intensified since 1979, leading to enhanced spring drought occurrences. This intensified precipitation deficit is accompanied by increased radiation flux, tropospheric subsidence, and elevated planetary boundary layer height, all leading to surface drying. The 2012 record drought showed a similar trend.

Dzud, a mass livestock mortality event, is threatening Mongolian pastoral nomadic herding. Livestock mortality is related to climate variability, with winter temperatures and prior summer drought and precipitation deficit being key triggers. A Mongolian index-based livestock insurance program using a 6% mortality threshold was developed.

The study analyzed the characteristics of decadal-scale changes in summer convective afternoon rainfall activity over Taiwan during 1961-2012. The results showed that the low-frequency variations in rainfall frequency were closely associated with the variations in monsoon southwesterly winds and the Niño-4 region.

This study evaluates historical connectivity between precipitation in the eastern Great Basin and Pacific Ocean sea surface temperatures on interannual to multidecadal timescales for 20 models. The majority of models had simulated connectivity that was too strong for ENSO and too weak for PDO. 

The study analyzed the meteorological and climatic conditions that caused the 2013 Uttarakhand floods. It found that northern India has experienced increasingly heavy rainfall in June since the late 1980s, with a significant contribution from post-1980 climate trends.

A statistical regression technique and global reanalysis dataset were used to correct biases in the CCSM-simulated variables that were subsequently used to drive the WRF model. The bias-corrected CCSM data led to a more realistic regional climate simulation of precipitation, SWE, and associated atmospheric dynamics.

Central Vietnam faces significant risks from climate change, particularly due to the timing of peak rainfall coinciding with tropical cyclone landfall. Analysis of meteorological and tropical cyclone data indicates an intensification of precipitation and tropical cyclones over the region since the early 20th century, with implications for mitigation and adaptation planning.

Autumn precipitation in Central Vietnam is modulated by the East Pacific–North Pacific teleconnection, with a pronounced decadal oscillation within the 8-11 year frequency band. This relationship and shared decadal spectral coherence between the EP–NP index and autumn precipitation might be useful for future climate predictions and flood management.

The 2013-2014 winter in North America had extreme weather with a severe drought in the West and cold temperatures in the East due to a dipole circulation pattern. 17 CMIP5 models revealed the dipole and its association with the El Niño precursor, with the association projected to strengthen.

SSTA propagates southeastward from WNP to Niño-3.4 region in the equatorial Central Pacific, taking 2-3 years, affecting the initiation of ENSO. Anomalies of winds, sea level pressure, and outgoing longwave radiation display a concurrent eastward propagation, coupled with the predominant 4-5 year frequency of the ENSO cycle.

This study presents a 1200-year tree-ring reconstruction of stream flow for the Bear River in the eastern Great Basin, identifying significant periodicity at quasi-decadal, multi-decadal, and centennial scales. The findings highlight the need for water management to account for stream flow variability over the past millennium.

2014

The paper analyzes the 2012 drought in the central United States, examining past drought patterns and potential contributors to the intensity of the drought, finding that the atmospheric Rossby wave activity may be a potential source of predictability for drought onset, and a probabilistic model was evaluated for predicting drought recovery.

This study examines the Madden-Julian Oscillation's (MJO) impact on pre-monsoon tropical cyclone activity and monsoon evolution in the Bay of Bengal, finding that in some years, the MJO modulates the conditions for cyclones and monsoon onset in Myanmar, which could help predict onset and formation.

In the 1980s and 1990s, the U.S. Forest Service collected 11,000 increment cores from the Interior West states for growth model development and biometric analyses. Later, it was found that the finely gridded data could be used to map past climatic patterns with more detail than traditional chronologies. The data confirmed the coupling between wet/dry cycles and Pacific decadal variability.

Radiation physics schemes in regional climate models produce biases in radiation fluxes, resulting in large bias in precipitation of the West African Monsoon (WAM) and variations in the meridional gradient of surface temperature, leading to differences in the WAM precipitation regime both spatially and in intensity, with inferences for predicted climate change both regionally and globally.

The 2013-2014 California drought was caused by an anomalous high-amplitude ridge system, which emerged from Rossby wave energy in the western North Pacific, and the dipole and associated circulation pattern is correlated with an El Niño precursor that has become stronger since the 1970s, indicating a traceable anthropogenic warming footprint.

Significant progress has been made in understanding the variable monsoon climate over the latter Holocene, with the Monsoon Asian Drought Atlas and several speleothem records from China and India providing insight into the prolonged droughts and wet episodes that influenced human history.

A 576-year tree-ring chronology network was developed to reconstruct the Great Salt Lake (GSL) water year level, which showed a 48% correlation with instrumental data from 1876 to 2005 and significant sub-decadal periodicity over six centuries. The study highlights the importance of understanding ocean-atmosphere interactions on precipitation delivery.

A rare bow echo event in the interior west of the United States on 21 April 2011 was studied using available observations and conducted simulations with the Advanced Research Weather Research and Forecasting (WRF) model to understand its development, which could have implications for subsequent regional climate downscaling studies on future extreme weather in the western US.

GRACE satellites detected continued water storage increase over the Missouri River Basin (MRB) before the 2011 flood event. An analysis of hydrologic variables showed marked variability at the 10-15 year timescale, and precipitation over the MRB undergoes a profound modulation during the transition points of the Pacific quasi-decadal oscillation and associated teleconnections, suggesting dry conditions may persist for the next 2-3 years.

The diurnal rainfall in Taiwan is influenced by local forces and the diurnal variation of the large-scale circulation over the East Asia-Western North Pacific. The interaction between two land-sea breeze systems facilitates rainfall, and the post-1998 strengthening of a southerly wind belt intensifies rainfall.

Persistent and recurrent flow patterns in the western US modulate precipitation and result in prolonged surface inversion episodes, which occur about a week later every year and reset every 5-7 years due to the interplay between regional intraseasonal flow patterns and the NAO, modulating the occurrence and timing of persistent ridge/trough events.


2013

We analyzed the trends of the Great Plains low-level jet (GPLLJ) and associated precipitation, revealing a strengthening and northward expansion of GPLLJ, with precipitation decreasing in the Southern Plains and increasing in the Northern Plains. The study discusses these changes in the context of recent droughts and projected climate for the region, indicating the potential to affect drought patterns.

Thunderstorms producing extreme precipitation often involve a coupling of a low-level jet with a synoptic short wave, and are modulated by the circumglobal teleconnection (CGT) in midlatitude regions. A circulation-based index combining the CGT and low-level jet trends was developed, linking them to extreme precipitation events worldwide, with greenhouse gas loadings playing a role. The study provides a method to identify regions at high risk of extreme precipitation events in the future.

A new study explores the link between atmospheric circulations over the North Atlantic and precipitation over the African Sahel. The analysis shows a circulation wave train connected to the Sahel through Rossby wave dispersion, but the Climate Forecast System version 2 fails to depict the connection.

Western Nepal has experienced worsening winter droughts since 2000, with a severe episode in 2008/09. This study showed that they are linked to the Arctic Oscillation and warming of the Indian Ocean, compounded by increased loading of anthropogenic aerosols. Given the declining precipitation and lack of replenishment of groundwater, appropriate water resource management is critical.

The paper analyzes the factors behind the observed intensification of the monsoon trough and associated tropical cyclone activity over the Bay of Bengal in May. Enhanced large-scale monsoon circulation caused by regional warming is identified as the cause for post-1979 increases in pre-monsoon precipitation and TC intensity. Increased aerosol loading and greenhouse gases have contributed to tropospheric warming and a deepening of the monsoon trough.

Tropical intraseasonal oscillations in the western North Pacific, particularly the quasi-biweekly mode, affect the occurrence of diurnal afternoon convection in Taiwan. Analyzing observations and reanalysis data over 18 summers, it was found that the QBW mode plays a significant role in the formation of episodic diurnal convection. The CFSv2 forecast shows an effective lead time ranging from 16 to 24 days for the QBW mode and diurnal convection episodes in Taiwan.

Study finds strengthening link between winter sea surface temperatures (SSTs) in the western North Pacific and the development of ENSO the following year. The correlation has increased since the mid-20th century and is attributed to greenhouse gases. The location of positive SST trends between the subtropical and tropical western Pacific could be influencing low-level circulation, reinforcing the link between the WNP and ENSO.

New tree-ring data from the US Forest Service's Forest Inventory and Analysis Program are a promising climate proxy. They were tested for temporal and spatial coherence, and found to be highly correlated with water year precipitation and the El Niño-Southern Oscillation dipole.

Nepal's monsoon precipitation is uncorrelated with India's, but the quasi-decadal variability is significant. Using reanalysis and observations, a study found that the Pacific Quasi-Decadal Oscillation (QDO) modulates Nepal's precipitation. Moisture fluxes from the Bay of Bengal interact with the southern Himalayan foothills, modulated through the Pacific QDO with a phase shift of 2 years, which explains the low correlation skill between Nepal precipitation and traditional monsoon indices.

Predicting monsoon precipitation in Nepal is challenging due to its strong quasi-decadal oscillation and lack of correlation with ENSO. This study compares five prediction methods, with the P-AR model using past precipitation data performing the best with a <1 mm/day mean absolute error. Time series models appear to be a better alternative than operational numerical models for precipitation prediction in Nepal.

This study examines the effect of rain-snow threshold temperatures on snow depth simulation using the CLM and WRF_CLM models in the French Alps. Results suggest the WRF_CLM is more sensitive to RST temperature changes, which can influence meteorological variables.

2012

De-trended, boreal winter sea surface temperature anomalies in the western North Pacific are a good predictor for the development of the ENSO by the following winter. The WNP is associated with an opposite-signed SSTA dipole located off southeastern Asia and in the western tropical Pacific, which is accompanied by equatorial winds that influence oceanic Kelvin wave activity that precedes ENSO events.

We analyzed the meteorological conditions of multidecadal drought cycles as shown by lake level fluctuations of the Great Salt Lake (GSL). A 6-9 year phase shift was found between wet-dry cycles in the Great Basin and the interdecadal Pacific oscillation (IPO). The IPO modulates local droughts-pluvials in a quarter-phase manner through a teleconnection wave train over the southeastern Gulf of Alaska.

Drifting snow can introduce systematic bias to snow water equivalent (SWE) measurements in Snowpack Telemetry stations, leading to inconsistency between SWE and accumulated precipitation (AP). Regions with drier snow and higher wind speeds are more likely to experience inconsistency.

The study found that integrating remotely sensed lake surface temperature and lake ice cover into the Advanced Research Weather Research and Forecasting model improved simulation of lake-effect precipitation over the Great Lakes region by reducing latent heat and sensible heat fluxes.

This study analyzes the winter precipitation regime in Utah using observation and a synoptic analysis, finding that the proportion of winter precipitation falling as snow has decreased by 9%, accompanied by a decrease in snow depth, cover, and surface albedo, and with weather systems that produce snowfall decreasing at a greater rate, all of which have implications for regional water policy.

A 10-year record of PM2.5 concentrations in Cache Valley, Utah reveals a peak in mid-January; this subseasonal variation is attributed to the displacement of the winter mean ridge, leading to subsidence with local leeside enhancements and mid-level warming over Cache Valley.

Winter precipitation changes in China were studied using observations and the rain-snow threshold temperature (RST) method. The study found a decrease in snowfall and an increase in rainfall, consistent with warming and increased moisture in southeast China. The WRF Model yielded similar results.

The poleward propagation of atmospheric energy is linked to prominent climate oscillations, suggesting the role of the atmospheric circulation change modulated by these patterns from tropical to Arctic and Antarctic regions.


2011

This study investigates the interdecadal variations of the Siberian High and cold surges in the East Asian winter monsoon using six global reanalysis datasets, finding inconsistencies between the datasets and with observations, and discussing potential causes for these discrepancies.

An ensemble of global reanalysis datasets were used to examine the dynamic properties of the recent increase in Sahel rainfall, showing enhancements in both the tropical easterly jet and African easterly jet, as well as positional shifts in African easterly waves accompanying the northward migration of the Sahel rainband.

The meteorological conditions during the 2010 Pakistan floods were examined, revealing that summer precipitation in northern Pakistan is divided into two phases, with the July premonsoon trough phase experiencing an increase in convective activity and heavy rainfall events, and the August monsoon trough phase not experiencing an intensification.

Quasi-decadal peaks in sea surface temperatures (SSTs) in the tropical western Pacific are coherent with western Pacific tropical cyclone threat and may be a precursor for enhanced tropical cyclone threat two years later, with relevant atmospheric fields strongly resembling those observed during El Niño events.

We established a significant relationship between the Great Salt Lake's elevation and central tropical Pacific sea surface temperatures on a 10-15 year timescale, developing a principal component-lagged regression model that was able to predict and replicate changes in the lake's elevation.

The atmospheric circulation patterns associated with the Pacific quasi-decadal oscillation are investigated, showing that the SST and atmospheric circulation are well coupled, and that the short-wave train emanating from Southeast Asia towards North America is particularly robust in the streamfunction of water vapor flux.

Northwest flow severe weather outbreaks (NWF) are summer convective storms in central US coupled with midtropospheric perturbations (MPs) initiated over the Rocky Mountains. These MPs assist in forming the progressive feature of the associated convective storms and likely generate NWF outbreaks during strong low-level jets.

Midtropospheric perturbations (MPs) over the Rocky Mountains couple with convective storms over the US northern plains, through a zonally propagating vorticity signal that facilitates early-morning MP genesis and Charney-Stern type instability in late afternoon conducive to the formation of baroclinic short waves, revealing the role of the Rocky Mountains in the formation of summer thunderstorms.


2010

Persistent rainfall over the Central Intermountain West of the United States in June 2009 was associated with a circumglobal teleconnection pattern, characterized by a short Rossby wave train along the jet stream waveguide with a wave number 5 structure.

The diurnal wind variation over the East Asian continent is associated with a planetary-scale land-sea breeze coupled with a global-scale diurnal atmospheric pressure tide, leading to different maximum diurnal rainfall times in summer and winter, according to a study of global reanalysis data.

Examination of NAM forecasts during July-August found overprediction of kinematic fields, surface-based CAPE, and precipitable water, contributing to errors in precipitation forecasts, highlighting the need for better depiction of mesoscale convective systems.

Persistent winter inversions in Utah are linked to the dominant intraseasonal mode affecting the Pacific Northwest, and predicting their duration requires combining medium-range forecasts with a longer-term climate diagnostic approach due to the complex interaction between synoptic and intraseasonal variabilities.

A recent study discovered a strong linkage between the intraseasonal oscillation and persistent inversion events in the Intermountain West, and by coupling a simple regression scheme with NCEP's Climate Forecast System, the prediction of these events can be extended up to 4 weeks, improving upon the current 10-day forecasts.

The Great Salt Lake's elevation displays a quasi-decadal oscillation (QDO), closely linked to the Pacific QDO's sea surface temperature anomalies. This study investigates the physical mechanisms behind this coherence, finding that atmospheric circulation patterns in the Gulf of Alaska modulate water vapor flux and impact the hydrological cycle in the Great Basin. This hydrological QDO is integrated into the lake's elevation with a half-phase delay, forming an inverse yet coherent relationship between the two QDOs. Tree-ring records confirm the region's prominent quasi-decadal precipitation signal.

This study examines sudden surface warming events in Taiwan caused by typhoon passages. Preferred warming regions were identified in northwest and southeast Taiwan, with most events occurring during the day and night, respectively. Downslope adiabatic warming and nonprecipitation zone passage contribute to the majority of the warming. The diurnal mode of atmospheric divergent circulation over East Asia–western North Pacific may modulate typhoon arrival times, causing daytime (nighttime) warming in northwest (southeast) Taiwan.

2009

Evaluation of precipitation climatology in the Intermountain Region using NARCCAP's six regional climate models, revealing systematic biases, excessive winter precipitation, and strong annual cycles that may lead to false ENSO signals, necessitating caution when interpreting the results.

The study shows a quadrature phase coupling between the 10-20 year cycles of Pacific Decadal Oscillation (PDO) and Intermountain Region rainfall, with the rainfall cycle lagging by a quarter phase (3-4 years) due to an anomalous circulation dipole, potentially aiding future climate predictions.

The investigation of forecasting summer convective rainfall over the northern plains attributes underpredicted midtropospheric perturbation vorticity, weak ambient flow, and insufficient atmospheric humidity generation. Position errors are corrected and show improved skill scores; however, precipitation amounts remain underpredicted.

The processes behind the late-spring maximum rainfall over the U.S. central plains were examined. The late-spring baroclinic structure and the Great Plains low-level jet contribute to moisture convergence and convective activity. However, the development of an upper-level anticyclone in July reduces convective activity and rainfall.

The study explores the influence of Southeast Asian–western North Pacific monsoon circulation on tropical cyclone tracks, revealing that intraseasonal variations and monsoon conditions impact track characteristics, and accurate predictions of these variations may improve tropical cyclone forecasting.


2008, and earlier

The study investigates the contribution of southern and northern track African easterly waves to North Atlantic tropical cyclones, revealing that southern track waves have a higher conversion rate, with the West African monsoon trough playing a vital role in providing moisture and enhancing vorticity.

The East Asian summer monsoon (EASM) life cycle features active, break, and revival phases, with rainstorms, diurnal convection, and typhoons being the major rainfall contributors in Taiwan, highlighting the importance of understanding these weather systems for climate modeling and water management.

The North Atlantic has a higher percentage of tropical cyclones originating from easterly waves compared to the western North Pacific. The latter has a higher percentage of tropical cyclogeneses due to monsoon gyre formation, and around 25% of easterly waves form tropical cyclones. Over 80% of tropical cyclones in the western North Pacific are found to be formed directly and indirectly from easterly waves.

The summer rainfall maximum in Taipei, Taiwan is largely produced by afternoon/evening thunderstorms on the downwind side and slopes of mountains south of the city, which have increased in frequency due to urbanization, causing temperature rise, rainfall increase, and traffic hazards.

Monsoon depressions propagate westward against monsoon westerlies due to their divergent circulation and the convergence of water vapor transported by the low-level divergent circulation, perpetuated by a vorticity tendency generated by the east–west asymmetric circulation created by the latent heat released by rainfall.

The study analyzes rainfall variation in the East Asian summer monsoon and the relationship between monsoon circulation and synoptic disturbance activity using four datasets, revealing the monsoon's life cycle and two rainfall maxima in the Japanese monsoon.