Mengqian Lu - Academia.edu (original) (raw)
Papers by Mengqian Lu
Bulletin of the American Meteorological Society
Kong government officials, and representatives from industrial communities, gathered to review an... more Kong government officials, and representatives from industrial communities, gathered to review and discuss pressing challenges, positive solutions, and potential opportunities related to climate change, extreme weather events, and water sustainability issues. When: 5
Journal of Climate
This study addresses how moisture in continental precipitation is recycled globally from a moistu... more This study addresses how moisture in continental precipitation is recycled globally from a moisture-tracking perspective. Using a state-of-the-art three-dimensional Lagrangian model and optimized water accounting diagnostics, we complete a 40-yr (1971–2010) tracking of moisture from continental precipitation in the present-day climate. Climatologically, we conclude that 62% of continental precipitation stems from evapotranspiration through Lagrangian tracking—a measure is known as the global “continental precipitation recycling (CPR)” ratio. The result bridges the long-standing gap between the explicit (i.e., moisture trajectory–based) and implicit (i.e., water budget–based) estimates of the global CPR ratio in the literature. On the 1° grid scale, nonlocal terrestrial sources dominate precipitation in almost 70% of the land areas, most prominent in the continental interior. The CPR ratio consistently exhibits a contrasting seasonality between the mid-to-high latitudes and monsoon r...
Scientific Reports, 2019
Popular perception claims that rain following a hot day brings relief, indicating a bio-meteorolo... more Popular perception claims that rain following a hot day brings relief, indicating a bio-meteorological perspective of ‘rainy’ forecasts. However, the hypothesis has rarely been examined on India which experiences distinct pre- and post-monsoon seasons with continuous dry days, occasionally interrupted by thunderstorms or cyclones. The current study analyzes 54 years of observed daily meteorological records across India to assess the impact of shower effect, defined as the amount of change in the temperature on the first day of a wet spell that succeeds a dry spell. Nine combinations of low to high probability rainfall events on the first day of a wet spell and short to prolonged dry spell categories are evaluated. Results indicate that the north, the northeastern, and the eastern states of India witness a decrease in the maximum and minimum temperatures, up to 5 °C during the pre-monsoon season while mostly exhibiting a statistically insignificant long-term temporal trend. During th...
Hydrology and Earth System Sciences, 2017
Rainfall is the primary trigger of landslides in Hong Kong; hence, rainstorm spatial distribution... more Rainfall is the primary trigger of landslides in Hong Kong; hence, rainstorm spatial distribution is an important piece of information in landslide hazard analysis. The primary objective of this paper is to quantify spatial correlation characteristics of three landslide-triggering large storms in Hong Kong. The spatial maximum rolling rainfall is represented by a rotated ellipsoid trend surface and a random field of residuals. The maximum rolling 4, 12, 24, and 36 h rainfall amounts of these storms are assessed via surface trend fitting, and the spatial correlation of the detrended residuals is determined through studying the scales of fluctuation along eight directions. The principal directions of the surface trend are between 19 and 43 • , and the major and minor axis lengths are 83-386 and 55-79 km, respectively. The scales of fluctuation of the residuals are found between 5 and 30 km. The spatial distribution parameters for the three large rainstorms are found to be similar to those for four ordinary rainfall events. The proposed rainfall spatial distribution model and parameters help define the impact area, rainfall intensity and local topographic effects for landslide hazard evaluation in the future.
npj Climate and Atmospheric Science
Three consecutive precipitation extremes emerged in November 2021, including India-Sri Lanka floo... more Three consecutive precipitation extremes emerged in November 2021, including India-Sri Lanka flooding, East Asian blizzard, and Canadian floods. Why the catastrophic events occurred successively and whether they will become more frequent as global warming continues are unknown. Here we show they are organized by an intraseasonal Asian/North American (ANA) teleconnection consisting of two cross-Pacific wave trains fortified by dipolar diabatic heating anomalies (“wet India-dry Philippines”). The dipolar heating anomaly is shaped by multi-scale interaction between a quasi-stationary Madden-Julian Oscillation (MJO) episode and a rapidly developed La Niña over the tropical Asian monsoon region. Numerical experiments suggest that the off-equatorial heating dipole can generate the ANA pattern resembling observations, distinct from the equatorial MJO-induced teleconnection and the La Niña-induced Pacific/North American teleconnection. Philippine cooling stimulates the circum-Pacific wave t...
npj Climate and Atmospheric Science
East Asia will face a skewed monsoon cycle with soaring flood, drought, and weather whiplash risk... more East Asia will face a skewed monsoon cycle with soaring flood, drought, and weather whiplash risks in a warming climate. In our objective eight-intraseasonal-monsoon-stage framework, we uncover a ‘dry-get-wetter’ paradigm in East Asia, contesting the fallen ‘rich-get-richer’ common belief. On timing, the Mid-summer and Fall periods are stretching at the expense of three delayed, shortened, and weakened winter stages, especially near the end of the twenty-first century. On threats, entire East Asia will experience up to 14–20 more heavy precipitation days during the rainy Spring to Mid-summer stages. Specifically, the Yangtze basin will suffer from an earlier pluvial period with escalating flood risks. Moreover, societal security and ecosystem resilience in the Huai-Yellow basin, South Japan, and the Korean Peninsula will be challenged by more frequent weather whiplash. Under the monsoon-stage framework, a complete moisture budget decomposition sheds light on the causes of a slower p...
Atmospheric moisture channels and pre-existing weather regimes for rain belt events during East Asian summer monsoon season
This study aims to advance the understanding of the pre-existing weather regimes up to two weeks ... more This study aims to advance the understanding of the pre-existing weather regimes up to two weeks ahead of rain belt events during the East Asian summer monsoon season. To this end, we backtrack the...
Streamflow forecasts on seasonal and interannual time scales for reservoir management
Multi-time scale Climate Informed Stochastic Hybrid Simulation-Optimization Model (McISH model) for Multi-Purpose Single Reservoir System
npj Climate and Atmospheric Science
Rain belts in East Asia frequently pose threats to human societies and natural systems. Advances ... more Rain belts in East Asia frequently pose threats to human societies and natural systems. Advances in a skillful forecast on heavy precipitation require a deeper understanding of the preconditioned environments and the hydrologic cycle. Here, we disentangle 15 dominant moisture channels along four corridors reaching the Somali Jet, South Asia, Bay of Bengal, and Pacific basin for the warm-season rain belts. Among them, the Somali and South Asian channels were underappreciated in the literature. The results also highlight the importance of terrestrial moisture sources, and the close relationship between the moisture pathways and rain belts’ characteristics. Back-tracing the weather within a 2-week lead time reveals the pre-existing weather systems and circumglobal wave trains, that govern the moisture channels. Findings from this work develop a better understanding of East Asian rain belts’ water cycle, and may offer insights into model evaluation and heavy rainfall prediction at a lon...
Spatiotemporal structure of Tropical Moisture Exports and their Precursors associated with High Precipitation induced Floods over the Continental United States
Nonstationarity of flood risk has emerged as an important issue and progress in addressing this c... more Nonstationarity of flood risk has emerged as an important issue and progress in addressing this concern can only come from an improved understanding of the associated climate dynamics. An understanding of the dynamical mechanisms and statistics associated with the frequency and structure of heavy precipitation induced floods events can aid exploration of the key sources of uncertainties that challenge extreme hydrometerological forecasts, and improve reliability of streamflow forecasts for realtime applications. Although the climate mechanisms governing precipitation vary by location, extreme precipitation events in the mid-latitudes are typically associated with anomalous atmospheric moisture from warmer tropical or subtropical oceanic areas. Tropical moisture exports (TMEs) to the Northern Hemispheric extratropics are an important feature of the general circulation of the atmosphere and link tropical moisture sources with extratropical precipitation and occasionally with explosive...
Predicting 30 Days Extreme Precipitation using a Global SST-SLP Correlation Network
The Spatiotemporal Characteristics of Summer Rainfall in the Southeast China Coast and Hydrometeorological Diagnosis of its Predictability
Journal of Climate
This study aims to construct a novel source–receptor (SR) network to study the atmospheric water ... more This study aims to construct a novel source–receptor (SR) network to study the atmospheric water cycle associated with the East Asian summer monsoon (EASM) circulation. Using a dynamical recycling model (DRM), 68%–74% of the wet season (April–September) precipitation in six EASM land regions is attributed. The results reveal that terrestrial sources can be equally or more competitive than oceans for several sink regions downwind in East Asia. Terrestrial sources, such as the Indian subcontinent, Indochina, Southwest China, and the eastern Tibetan Plateau, are sustained by southwesterly monsoons and contribute to appreciable fractions of precipitation in the East Asian subregions downwind. Further, southwesterly and southeasterly sources for a sink region alternately dominate the moisture supply in the early and late wet season, respectively, referred to as the “SW–SE source swing.” The SR network is found to be largely governed by the zonal oscillation of the western North Pacific s...
Define East Asian Monsoon Annual Cycle via a Self‐Organizing Map‐Based Approach
Geophysical Research Letters
Journal of Geophysical Research: Atmospheres
The spatiotemporal variation and characteristics of heatwave in Northeastern Asia are investigate... more The spatiotemporal variation and characteristics of heatwave in Northeastern Asia are investigated on both a grid basis and an event basis. We find that persistent, extensive, and intense heatwave has become more frequent during the last four decades. Such trend is found significantly correlated with the increase of temperature. The association between heatwave and blocking is also analyzed using two leading blocking indices, examining 500-hPa geopotential height (TM index) and vertically averaged potential vorticity anomaly (PV index), respectively. A discrepancy between blocking climatology of TM index and PV index is exhibited, with the former displaying two high-frequency zonal bands at the north and south regions, while the latter only showing one high frequency band in the north. However, grid-based concurrence analysis using the two blocking indices agreeably suggests that blocking favors the occurrence of heatwave, especially in the north region where blocking often occurs. We further explicitly investigate their temporal association with time lags, which has not been done before in the literatures. It reveals that heatwave mostly occurs after or on the onset day of blocking and ends after or at the end of blocking. It indicates that blocking is more of a favorable environmental condition to trigger heatwave than maintain it. Lastly, the impact of blocking on the characteristics of heatwave events is explored on an event basis using a 3-D spatiotemporal object model. Blocking-related heatwave events are more likely to be more persistent, extensive, and intense than unrelated events.
East Asia Atmospheric River catalog: Annual Cycle, Transition Mechanism, and Precipitation
Geophysical Research Letters
Investigating Spatiotemporal Variation of Heatwave and its Association with Blocking in the Northeastern Asia
<p>... more <p>Severe heatwaves in recent decades caused tremendous financial loss and even deaths. And both the occurrence and characteristics of heatwave are changing under global warming. The spatiotemporal variation and characteristics of heatwave in Northeastern Asia are investigated on both grid and event bases in this study. We find that persistent, extensive and intense heatwave has become more frequent during the last four decades. Such trend is found significantly correlated with the increase of temperature.</p><p>As most dreadful heatwaves are reported to be accompanied by blocking, we also thoroughly analyze the association between heatwave and blocking using two leading blocking indices, examining 500hpa geopotential height (TM index) and vertically averaged potential vorticity anomaly (PV index), respectively. A discrepancy between blocking climatology of TM index and PV index is exhibited, with the former displaying two high-frequency zonal bands at the south and north regions, while the latter only showing one high frequency band in the north. However, grid-based concurrence analysis using the two blocking indices agreeably suggests that blocking favors the occurrence of heatwave, especially in the north region where blocking often occurs. We further explicitly investigate their extended temporal association with time lags, which has not been done before in the literatures. It reveals that heatwave mostly occurs after or on the onset day of blocking and ends after or at the end of blocking. It indicates that blocking is more of a favorable environmental condition to trigger heatwave than maintain it. Lastly, the impact of blocking on the characteristics of heatwave events is explored on an event basis, using the 3D object model newly proposed by this study. Blocking related heatwave events are more likely to be more persistent, extensive and intense than unrelated events.</p>
Global atmospheric moisture transport associated with precipitation extremes: Mechanisms and climate change impacts
WIREs Water
Tropical cyclone genesis and trajectory characteristics in the western north Pacific
<p&amp... more <p>The western North Pacific (WNP) is one of the most active tropical cyclone (TC) regions, which can inflict enormous death and massive property damage to surrounding areas. Although many studies about tropical cyclone activities on multi-timescales have been done, most of them focus on the entire basin, variations within the basin deserve more investigations. Besides TC characteristics on different timescales, to investigate the impacts of environment variables on TC and provide informative factors for prediction is another concern in the research community. In this study, we adopt several data science techniques, including Gaussian kernel estimator, wavelet, cross-wavelet coherence and regression analyses, to explore the spatiotemporal variations of TC genesis and associated environmental conditions. Significant semiannual and annual variations of TC genesis have been found in the northern South China Sea (NSCS) and oceanic areas east of the Philippines (OAEP). In the southeast part of WNP (SEWNP), TC genesis shows prominent variations on ENSO time scale. With reconstructed TC series on those frequencies, we further quantify the influences of environmental variables on the primary TC signals over WNP. About 40% of the identified TC variance over NSCS and OAEP can be explained by variability in vertical shear of zonal wind and relative humidity. In the SEWNP, TC genesis reveals strong nonlinear and non-stationary relationships with vertical shear of zonal wind and absolute vorticity. Besides, A probabilistic clustering algorithm is used to describe the TC tracks in the WNP. The best track dataset from JMA is decomposed into three clusters based on genesis location and curvature. For each cluster, we analyze the relationships between TC properties, such as genesis location, trajectory and intensity, and associated environmental conditions using the self-organizing map. The spatial patterns of sea surface temperature have huge impacts on TC genesis location, while the trajectory is largely influenced by geopotential height.</p>
Bulletin of the American Meteorological Society
Kong government officials, and representatives from industrial communities, gathered to review an... more Kong government officials, and representatives from industrial communities, gathered to review and discuss pressing challenges, positive solutions, and potential opportunities related to climate change, extreme weather events, and water sustainability issues. When: 5
Journal of Climate
This study addresses how moisture in continental precipitation is recycled globally from a moistu... more This study addresses how moisture in continental precipitation is recycled globally from a moisture-tracking perspective. Using a state-of-the-art three-dimensional Lagrangian model and optimized water accounting diagnostics, we complete a 40-yr (1971–2010) tracking of moisture from continental precipitation in the present-day climate. Climatologically, we conclude that 62% of continental precipitation stems from evapotranspiration through Lagrangian tracking—a measure is known as the global “continental precipitation recycling (CPR)” ratio. The result bridges the long-standing gap between the explicit (i.e., moisture trajectory–based) and implicit (i.e., water budget–based) estimates of the global CPR ratio in the literature. On the 1° grid scale, nonlocal terrestrial sources dominate precipitation in almost 70% of the land areas, most prominent in the continental interior. The CPR ratio consistently exhibits a contrasting seasonality between the mid-to-high latitudes and monsoon r...
Scientific Reports, 2019
Popular perception claims that rain following a hot day brings relief, indicating a bio-meteorolo... more Popular perception claims that rain following a hot day brings relief, indicating a bio-meteorological perspective of ‘rainy’ forecasts. However, the hypothesis has rarely been examined on India which experiences distinct pre- and post-monsoon seasons with continuous dry days, occasionally interrupted by thunderstorms or cyclones. The current study analyzes 54 years of observed daily meteorological records across India to assess the impact of shower effect, defined as the amount of change in the temperature on the first day of a wet spell that succeeds a dry spell. Nine combinations of low to high probability rainfall events on the first day of a wet spell and short to prolonged dry spell categories are evaluated. Results indicate that the north, the northeastern, and the eastern states of India witness a decrease in the maximum and minimum temperatures, up to 5 °C during the pre-monsoon season while mostly exhibiting a statistically insignificant long-term temporal trend. During th...
Hydrology and Earth System Sciences, 2017
Rainfall is the primary trigger of landslides in Hong Kong; hence, rainstorm spatial distribution... more Rainfall is the primary trigger of landslides in Hong Kong; hence, rainstorm spatial distribution is an important piece of information in landslide hazard analysis. The primary objective of this paper is to quantify spatial correlation characteristics of three landslide-triggering large storms in Hong Kong. The spatial maximum rolling rainfall is represented by a rotated ellipsoid trend surface and a random field of residuals. The maximum rolling 4, 12, 24, and 36 h rainfall amounts of these storms are assessed via surface trend fitting, and the spatial correlation of the detrended residuals is determined through studying the scales of fluctuation along eight directions. The principal directions of the surface trend are between 19 and 43 • , and the major and minor axis lengths are 83-386 and 55-79 km, respectively. The scales of fluctuation of the residuals are found between 5 and 30 km. The spatial distribution parameters for the three large rainstorms are found to be similar to those for four ordinary rainfall events. The proposed rainfall spatial distribution model and parameters help define the impact area, rainfall intensity and local topographic effects for landslide hazard evaluation in the future.
npj Climate and Atmospheric Science
Three consecutive precipitation extremes emerged in November 2021, including India-Sri Lanka floo... more Three consecutive precipitation extremes emerged in November 2021, including India-Sri Lanka flooding, East Asian blizzard, and Canadian floods. Why the catastrophic events occurred successively and whether they will become more frequent as global warming continues are unknown. Here we show they are organized by an intraseasonal Asian/North American (ANA) teleconnection consisting of two cross-Pacific wave trains fortified by dipolar diabatic heating anomalies (“wet India-dry Philippines”). The dipolar heating anomaly is shaped by multi-scale interaction between a quasi-stationary Madden-Julian Oscillation (MJO) episode and a rapidly developed La Niña over the tropical Asian monsoon region. Numerical experiments suggest that the off-equatorial heating dipole can generate the ANA pattern resembling observations, distinct from the equatorial MJO-induced teleconnection and the La Niña-induced Pacific/North American teleconnection. Philippine cooling stimulates the circum-Pacific wave t...
npj Climate and Atmospheric Science
East Asia will face a skewed monsoon cycle with soaring flood, drought, and weather whiplash risk... more East Asia will face a skewed monsoon cycle with soaring flood, drought, and weather whiplash risks in a warming climate. In our objective eight-intraseasonal-monsoon-stage framework, we uncover a ‘dry-get-wetter’ paradigm in East Asia, contesting the fallen ‘rich-get-richer’ common belief. On timing, the Mid-summer and Fall periods are stretching at the expense of three delayed, shortened, and weakened winter stages, especially near the end of the twenty-first century. On threats, entire East Asia will experience up to 14–20 more heavy precipitation days during the rainy Spring to Mid-summer stages. Specifically, the Yangtze basin will suffer from an earlier pluvial period with escalating flood risks. Moreover, societal security and ecosystem resilience in the Huai-Yellow basin, South Japan, and the Korean Peninsula will be challenged by more frequent weather whiplash. Under the monsoon-stage framework, a complete moisture budget decomposition sheds light on the causes of a slower p...
Atmospheric moisture channels and pre-existing weather regimes for rain belt events during East Asian summer monsoon season
This study aims to advance the understanding of the pre-existing weather regimes up to two weeks ... more This study aims to advance the understanding of the pre-existing weather regimes up to two weeks ahead of rain belt events during the East Asian summer monsoon season. To this end, we backtrack the...
Streamflow forecasts on seasonal and interannual time scales for reservoir management
Multi-time scale Climate Informed Stochastic Hybrid Simulation-Optimization Model (McISH model) for Multi-Purpose Single Reservoir System
npj Climate and Atmospheric Science
Rain belts in East Asia frequently pose threats to human societies and natural systems. Advances ... more Rain belts in East Asia frequently pose threats to human societies and natural systems. Advances in a skillful forecast on heavy precipitation require a deeper understanding of the preconditioned environments and the hydrologic cycle. Here, we disentangle 15 dominant moisture channels along four corridors reaching the Somali Jet, South Asia, Bay of Bengal, and Pacific basin for the warm-season rain belts. Among them, the Somali and South Asian channels were underappreciated in the literature. The results also highlight the importance of terrestrial moisture sources, and the close relationship between the moisture pathways and rain belts’ characteristics. Back-tracing the weather within a 2-week lead time reveals the pre-existing weather systems and circumglobal wave trains, that govern the moisture channels. Findings from this work develop a better understanding of East Asian rain belts’ water cycle, and may offer insights into model evaluation and heavy rainfall prediction at a lon...
Spatiotemporal structure of Tropical Moisture Exports and their Precursors associated with High Precipitation induced Floods over the Continental United States
Nonstationarity of flood risk has emerged as an important issue and progress in addressing this c... more Nonstationarity of flood risk has emerged as an important issue and progress in addressing this concern can only come from an improved understanding of the associated climate dynamics. An understanding of the dynamical mechanisms and statistics associated with the frequency and structure of heavy precipitation induced floods events can aid exploration of the key sources of uncertainties that challenge extreme hydrometerological forecasts, and improve reliability of streamflow forecasts for realtime applications. Although the climate mechanisms governing precipitation vary by location, extreme precipitation events in the mid-latitudes are typically associated with anomalous atmospheric moisture from warmer tropical or subtropical oceanic areas. Tropical moisture exports (TMEs) to the Northern Hemispheric extratropics are an important feature of the general circulation of the atmosphere and link tropical moisture sources with extratropical precipitation and occasionally with explosive...
Predicting 30 Days Extreme Precipitation using a Global SST-SLP Correlation Network
The Spatiotemporal Characteristics of Summer Rainfall in the Southeast China Coast and Hydrometeorological Diagnosis of its Predictability
Journal of Climate
This study aims to construct a novel source–receptor (SR) network to study the atmospheric water ... more This study aims to construct a novel source–receptor (SR) network to study the atmospheric water cycle associated with the East Asian summer monsoon (EASM) circulation. Using a dynamical recycling model (DRM), 68%–74% of the wet season (April–September) precipitation in six EASM land regions is attributed. The results reveal that terrestrial sources can be equally or more competitive than oceans for several sink regions downwind in East Asia. Terrestrial sources, such as the Indian subcontinent, Indochina, Southwest China, and the eastern Tibetan Plateau, are sustained by southwesterly monsoons and contribute to appreciable fractions of precipitation in the East Asian subregions downwind. Further, southwesterly and southeasterly sources for a sink region alternately dominate the moisture supply in the early and late wet season, respectively, referred to as the “SW–SE source swing.” The SR network is found to be largely governed by the zonal oscillation of the western North Pacific s...
Define East Asian Monsoon Annual Cycle via a Self‐Organizing Map‐Based Approach
Geophysical Research Letters
Journal of Geophysical Research: Atmospheres
The spatiotemporal variation and characteristics of heatwave in Northeastern Asia are investigate... more The spatiotemporal variation and characteristics of heatwave in Northeastern Asia are investigated on both a grid basis and an event basis. We find that persistent, extensive, and intense heatwave has become more frequent during the last four decades. Such trend is found significantly correlated with the increase of temperature. The association between heatwave and blocking is also analyzed using two leading blocking indices, examining 500-hPa geopotential height (TM index) and vertically averaged potential vorticity anomaly (PV index), respectively. A discrepancy between blocking climatology of TM index and PV index is exhibited, with the former displaying two high-frequency zonal bands at the north and south regions, while the latter only showing one high frequency band in the north. However, grid-based concurrence analysis using the two blocking indices agreeably suggests that blocking favors the occurrence of heatwave, especially in the north region where blocking often occurs. We further explicitly investigate their temporal association with time lags, which has not been done before in the literatures. It reveals that heatwave mostly occurs after or on the onset day of blocking and ends after or at the end of blocking. It indicates that blocking is more of a favorable environmental condition to trigger heatwave than maintain it. Lastly, the impact of blocking on the characteristics of heatwave events is explored on an event basis using a 3-D spatiotemporal object model. Blocking-related heatwave events are more likely to be more persistent, extensive, and intense than unrelated events.
East Asia Atmospheric River catalog: Annual Cycle, Transition Mechanism, and Precipitation
Geophysical Research Letters
Investigating Spatiotemporal Variation of Heatwave and its Association with Blocking in the Northeastern Asia
<p>... more <p>Severe heatwaves in recent decades caused tremendous financial loss and even deaths. And both the occurrence and characteristics of heatwave are changing under global warming. The spatiotemporal variation and characteristics of heatwave in Northeastern Asia are investigated on both grid and event bases in this study. We find that persistent, extensive and intense heatwave has become more frequent during the last four decades. Such trend is found significantly correlated with the increase of temperature.</p><p>As most dreadful heatwaves are reported to be accompanied by blocking, we also thoroughly analyze the association between heatwave and blocking using two leading blocking indices, examining 500hpa geopotential height (TM index) and vertically averaged potential vorticity anomaly (PV index), respectively. A discrepancy between blocking climatology of TM index and PV index is exhibited, with the former displaying two high-frequency zonal bands at the south and north regions, while the latter only showing one high frequency band in the north. However, grid-based concurrence analysis using the two blocking indices agreeably suggests that blocking favors the occurrence of heatwave, especially in the north region where blocking often occurs. We further explicitly investigate their extended temporal association with time lags, which has not been done before in the literatures. It reveals that heatwave mostly occurs after or on the onset day of blocking and ends after or at the end of blocking. It indicates that blocking is more of a favorable environmental condition to trigger heatwave than maintain it. Lastly, the impact of blocking on the characteristics of heatwave events is explored on an event basis, using the 3D object model newly proposed by this study. Blocking related heatwave events are more likely to be more persistent, extensive and intense than unrelated events.</p>
Global atmospheric moisture transport associated with precipitation extremes: Mechanisms and climate change impacts
WIREs Water
Tropical cyclone genesis and trajectory characteristics in the western north Pacific
<p&amp... more <p>The western North Pacific (WNP) is one of the most active tropical cyclone (TC) regions, which can inflict enormous death and massive property damage to surrounding areas. Although many studies about tropical cyclone activities on multi-timescales have been done, most of them focus on the entire basin, variations within the basin deserve more investigations. Besides TC characteristics on different timescales, to investigate the impacts of environment variables on TC and provide informative factors for prediction is another concern in the research community. In this study, we adopt several data science techniques, including Gaussian kernel estimator, wavelet, cross-wavelet coherence and regression analyses, to explore the spatiotemporal variations of TC genesis and associated environmental conditions. Significant semiannual and annual variations of TC genesis have been found in the northern South China Sea (NSCS) and oceanic areas east of the Philippines (OAEP). In the southeast part of WNP (SEWNP), TC genesis shows prominent variations on ENSO time scale. With reconstructed TC series on those frequencies, we further quantify the influences of environmental variables on the primary TC signals over WNP. About 40% of the identified TC variance over NSCS and OAEP can be explained by variability in vertical shear of zonal wind and relative humidity. In the SEWNP, TC genesis reveals strong nonlinear and non-stationary relationships with vertical shear of zonal wind and absolute vorticity. Besides, A probabilistic clustering algorithm is used to describe the TC tracks in the WNP. The best track dataset from JMA is decomposed into three clusters based on genesis location and curvature. For each cluster, we analyze the relationships between TC properties, such as genesis location, trajectory and intensity, and associated environmental conditions using the self-organizing map. The spatial patterns of sea surface temperature have huge impacts on TC genesis location, while the trajectory is largely influenced by geopotential height.</p>