Gang Chen

Gang Chen
University of California, Los Angeles | UCLA · Department of Atmospheric and Oceanic Sciences (AOS)

PhD

About

96
Publications
13,823
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
2,310
Citations
Introduction
I am a professor in the department of atmospheric and oceanic sciences at University of California, Los Angeles. My primary interests are atmospheric and climate dynamics, focusing on 1) global atmospheric circulation and regional weather extremes in a changing climate and 2) dynamics and transport of atmospheric moisture and chemical species. You can find more at my website: http://www.gchenpu.com

Publications

Publications (96)
Article
Full-text available
While there is substantial evidence for tropospheric jet shift and Hadley cell expansion in response to greenhouse gas increases, quantitative assessments of individual mechanisms and feedback for atmospheric circulation changes remain lacking. We present a new forcing-feedback analysis on circulation response to increasing CO 2 concentration in an...
Article
Full-text available
Atmospheric rivers (ARs), narrow intense moisture transport, account for much of the poleward moisture transport in midlatitudes. While studies have characterized AR features and the associated hydrological impacts in a warming climate in observations and comprehensive climate models, the fundamental dynamics for changes in AR statistics (e.g., fre...
Article
Full-text available
Plain Language Summary It has been hypothesized that Arctic sea ice loss can influence midlatitude weather extremes. Atmospheric rivers (ARs), a type of extreme weather, are characterized by intense water vapor transport in the atmosphere. When these “rivers” in the sky make landfall and encounter mountain barriers, they can produce torrential rain...
Article
Large meridional excursions of a jet stream are conducive to blocking and related midlatitude weather extremes, yet the physical mechanism of jet meandering is not well understood. This paper examines the mechanisms of jet meandering in boreal winter through the lens of a potential vorticity (PV)-like tracer advected by reanalysis winds in an advec...
Article
Full-text available
Plain Language Summary A weak polar vortex in the winter stratosphere is likely associated with cold spells at the surface, yet there are large uncertainties in predicting surface cold events based on stratospheric signals. This study introduces a new method to separate stratospheric variability into the leading modes of zonally symmetric and asymm...
Article
The relative roles of upper- and lower-level thermal forcing in shifting the eddy driven jet are investigated using a multi-level nonlinear quasi-geostrophic channel model. The numerical experiments show that the upper-level thermal forcing is more efficient in shifting the eddy-driven jet. The finite-amplitude wave activity diagnostics of numerica...
Article
To better understand the role of atmospheric dynamics in modulating surface concentrations of fine particulate matter (PM2.5), we relate the anticyclonic wave activity (AWA) metric and PM2.5 data from the Interagency Monitoring of Protected Visual Environment (IMPROVE) data for the period of 1988–2014 over the US. The observational results are comp...
Article
Full-text available
Purpose of Review: Review our current understanding of how precipitation is related to its thermodynamic environment, i.e., the water vapor and temperature in the surroundings, and implications for changes in extremes in a warmer climate. Recent Findings: Multiple research threads have i) sought empirical relationships that govern onset of strong...
Article
Full-text available
Based on daily data from Japanese 55-year Reanalysis (JRA-55), and daily interpolated outgoing longwave radiation (OLR) data from the National Oceanic and Atmospheric Administration (NOAA), this study examines the formation and maintenance mechanisms of the Pacific-Japan (PJ) pattern as an intraseasonal variability mode. Results show that the PJ pa...
Article
The non-normality of temperature probability distributions and the physics that drive it are important due to their relationships to the frequency of extreme warm and cold events. Here we use a conditional mean framework to explore how horizontal temperature advection and other physical processes work together to control the shape of daily temperat...
Preprint
To better understand the role of atmospheric dynamics in modulating surface concentrations of fine particulate matter (PM2.5), we relate the anti-cyclone wave activity (AWA) metric and PM2.5 data from the Interagency Monitoring of Protected Visual Environment (IMPROVE) data for the period of 1988–2014 over the US. The observational results are comp...
Article
Full-text available
Plain Language Summary The Northern Hemisphere stratosphere during boreal winter and early spring 2020 had multiple outstanding features. The period showed the strongest ozone depletion on record for the hemisphere accompanied by very low temperatures. The stratospheric evolution included an episode of polar warming at upper levels in March. These...
Article
Full-text available
The leading interannual mode of winter surface air temperature over the North American (NA) sector, characterized by a “Warm Arctic, Cold Continents” (WACC) pattern, exerts pronounced influences on NA weather and climate, while its underlying mechanisms remain elusive. In this study, the relative roles of surface boundary forcing versus internal at...
Article
Full-text available
While the relationship between the Arctic sea ice loss and midlatitude winter climate has been well discussed, especially on the seasonal mean scale, it remains unclear whether the Arctic sea ice condition affects the predictability of North American cold weather on the subseasonal time scale. Here we find that, in the presence of low Barents-Kara...
Article
Full-text available
Plain Language Summary Atmospheric rivers (ARs) are “rivers” in the sky that carry a huge amount of water vapor equivalent to the world's largest rivers on the ground. Because of the amount of water vapor they carry, ARs can cause extreme rainfall and floods upon landfall when the moisture is condensed out by mountain barriers or other favorable co...
Article
Full-text available
Plain Language Summary Long‐range transport plays a crucial role in determining the distribution of pollutants in the Arctic, as many pollutants have their sources in northern middle latitudes. Recent studies show large differences in transport into the Arctic among models, and it has been suggested that this is related to differences in the northe...
Article
Full-text available
In this study, detailed characteristics of the leading intraseasonal variability mode of boreal winter surface air temperature (SAT) over the North American (NA) sector are investigated. This intraseasonal SAT mode, featured by two anomalous centers with an opposite sign, one over central NA and another over East Siberia (ES) / Alaska, bears great...
Article
Full-text available
Land use and land cover change (LULCC) is one of the most important forcings affecting climate in the past century. This study evaluates the global and regional LULCC impacts in 1950-2015 by employing an annually updated LULCC map in a coupled land-atmosphere-ocean model. The difference between LULCC and control experiments shows an overall land su...
Article
Full-text available
Extreme and persistent haze events frequently occur during wintertime China. While recent emissions reductions reduced annual mean fine particulate matter (PM2.5) concentrations over eastern China, their effectiveness on wintertime PM2.5 trend remains uncertain. We use observations and model simulations to quantify seasonal differences in PM2.5 tre...
Article
Full-text available
Projected precipitation changes in a warming climate vary considerably, spatially, and between intensities. The changes can be greater or less than the ∼7% K⁻¹ Clausius‐Clapeyron (CC) prediction, owing to dynamic effects. Using two global‐climate‐model large ensembles, we quantify the dynamically induced changes to precipitation extremes from the p...
Article
Full-text available
While the observed decline of sea ice over the Chukchi‐Bering Sea (CBS) has coincided with the “warm‐Arctic, cold‐continent” (WACC) pattern over the North America (NA) sector, there is a debate on the causes of the WACC pattern. Here we present a very similar WACC pattern over the NA sector on both interannual and subseasonal time scales. Lead‐lag...
Article
Full-text available
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Article
Full-text available
Winter extreme weather events receive major public attention due to their serious impacts1, but the dominant factors regulating their interdecadal trends have not been clearly established2,3. Here, we show that the radiative forcing due to geospatially redistributed anthropogenic aerosols mainly determined the spatial variations of winter extreme w...
Article
Full-text available
Understanding what physically sets the shape of temperature distributions will enable more robust predictions of local temperature with global warming. We derive the relationship between the temperature distribution shape and the advection of temperature conditionally averaged at each temperature percentile. This enables quantification of the shift...
Article
Full-text available
The latitude of the westerly jet stream is influenced by a variety of climate forcings, but their effects on the jet latitude often manifest as a tug of war between tropical forcing (e.g., tropical upper‐tropospheric warming) and polar forcing (e.g., Antarctic stratospheric cooling or Arctic amplification). Here we present a unified forcing‐feedbac...
Article
Full-text available
Based on a newly developed observational dataset and a suite of climate model simulations, we evaluate changes in summer mean wet bulb globe temperature (WBGT) in China from 1961 through 2080. We show that summer mean WBGT has increased almost everywhere across China since 1961 due to human-induced climate change. Consequently, hot summers as measu...
Article
Over the past 15 years, numerous studies have suggested that the sinking branches of Earth’s Hadley circulation and the associated subtropical dry zones have shifted poleward over the late 20 th century and early 21 st century. Early estimates of this tropical widening from satellite observations and reanalyses varied from 0.25° to 3° latitude per...
Article
Full-text available
Plain Language Summary Narrow intense bands of water vapor transport in the atmosphere, known as atmospheric rivers, are expected to become more frequent and intense along the North American west coast, resulting in an intensification of precipitation over this region. We investigated the physical mechanisms associated with these storms in both the...
Article
Full-text available
Using a global space-time diagram of column water vapor (CWV) at 30° N latitude from daily reanalysis data, we find two quasi-stationary parts of atmospheric rivers (QSARs) that feature locally enhanced CWV and evolve from the Eastern Pacific/Atlantic basins in the winter to the Western Pacific/Atlantic in the summer. East Asian Summer Monsoon onse...
Article
Full-text available
Local finite-amplitude wave activity (LWA) measures the waviness of the local flow. In this work we relate the anticyclonic part of LWA, AWA (anticyclonic wave activity), to surface ozone in summertime over the US on interannual to decadal timescales. Interannual covariance between AWA diagnosed from the European Centre for Medium-Range Weather For...
Article
Full-text available
Abstract The frequent episodes of severe air pollution over China during recent years have posed serious health threats to densely populated eastern China. Although several studies investigated the linkage between enhanced severity and frequency of air pollution and the large‐scale weather patterns over China, the day‐to‐day covariability between t...
Article
Full-text available
Plain Language Summary Climate models project that extreme precipitation events will intensify during the 21st century at large spatial scales, with several studies suggesting that the most extreme events will exhibit the highest rate of intensification. Identification of the causes of this phenomenon nevertheless remains tenuous, partly because es...
Article
Full-text available
Projected changes in the frequency of major precipitation accumulations (hundreds of millimeters), integrated over rainfall events, over land in the late twenty-first century are analyzed in the Community Earth System Model (CESM) Large Ensemble, based on the RCP8.5 scenario. Accumulation sizes are sorted by the local average recurrence interval (A...
Article
Full-text available
Local finite-amplitude wave activity (LWA) measures the waviness of the local flow. In this work we relate the anticyclonic part of LWA, AWA (Anticyclonic Wave Activity), to surface ozone in summertime over the U.S. on interannual to decadal scales. Interannual covariance between AWA diagnosed from the European Centre for Medium-Range Weather Forec...
Preprint
Full-text available
Global climate models project that extreme precipitation events will increase in intensity during the 21st century at large spatial scales, with several studies suggesting that the most extreme events will exhibit the highest rate of intensification. The identification of the causes of this phenomenon nevertheless remains tenuous, in part because s...
Article
Full-text available
Precipitation changes in a warming climate have been examined with a focus on either mean precipitation or precipitation extremes, but changes in the full probability distribution of precipitation have not been well studied. This paper develops a methodology for the quantile-conditional column moisture budget of the atmosphere for the full probabil...
Article
Full-text available
The moisture budget is evaluated as a function of the probability distribution of precipitation for the end of the twentieth century and projected end of the twenty-first century in the Community Earth System Model Large Ensemble. For a given precipitation percentile, a conditional moisture budget equation relates precipitation minus evaporation (P...
Article
Full-text available
Observed surface temperature distributions are non-Gaussian, which has important implications for the likelihood of extreme events in a changing climate. We use a two-dimensional advection-diffusion model of temperature stirred by stochastically generated Rossby waves with a sustained background temperature gradient to explore non-Gaussian temperat...
Preprint
Full-text available
Precipitation changes in a warming climate have been examined with a focus on either mean precipitation or precipitation extremes, but changes in the full probability distribution of precipitation have not been well studied. This paper develops a methodology for quantile-conditional column moisture budget of the atmosphere for the full probability...
Article
Full-text available
The sensitivity of stratospheric polar vortex variability to the basic-state stratospheric temperature profile is investigated by performing a parameter sweep experiment with a dry dynamical core GCM where the equilibrium temperature profiles in the polar lower and upper stratosphere are systematically varied. It is found that stratospheric variabi...
Article
Full-text available
This study uses a set of idealized aquaplanet model experiments to investigate the linkage between the Asian summer monsoon circulation and tropopause fold activity. It is found that folds tend to occur on the northwestern side of the upper-level anticyclone associated with the monsoon circulation and are generated due to intensified monsoon circul...
Article
Full-text available
Understanding how regional hydrological extremes would respond to warming is a grand challenge to the community of climate change research. A novel diagnostic framework based on the wave activity is developed for column integrated water vapor (CWV) to afford the probe into the higher moments of the hydrological cycle. Applying the CWV wave activity...
Article
Full-text available
Diagnostics of finite-amplitude local wave activity (LWA) are applied to the 500-hPa geopotential height field to diagnose persistent synoptic weather events of anomalously large wave activity in the Northern Hemisphere. By considering the cyclonic and anticyclonic components of LWA separately, persistent weather systems associated with large-ampli...
Article
Full-text available
In an attempt to resolve the controversy as to whether Arctic sea ice loss leads to more mid-latitude extremes, a metric of finite-amplitude wave activity is adopted to quantify the midlatitude wave activity and its change during the observed period of the drastic Arctic sea ice decline in both ERA Interim reanalysis data and a set of AMIP-type of...
Article
Full-text available
While the importance of the seasonal migration of the zonally averaged Hadley circulation on interhemispheric transport of trace gases has been recognized, few studies have examined the role of the zonally asymmetric monsoonal circulation. This study investigates the role of monsoon-like zonally asymmetric heating on interhemispheric transport usin...
Article
Full-text available
Building on the recent advent of the concept of finite-amplitude wave activity, a contour-following diagnostics for column water vapor (CWV) is developed and applied to a pair of aquaplanet model simulations to understand and quantify the higher moments in the global hydrological cycle. The Lagrangian nature of the diagnostics leads to a more tract...
Article
Full-text available
The response of the atmospheric circulation to greenhouse gas-induced SST warming is investigated using large ensemble experiments with two AGCMs, with a focus on the robust feature of the poleward shift of the eddy driven jet. In these experiments, large ensembles of simulations are conducted by abruptly switching the SST forcing on from January 1...
Article
Full-text available
Studies have suggested that the persistence in the meridional vacillation of the midlatitude jet (i.e., annular mode timescale) in comprehensive climate models is related to the model biases in climatological jet latitude, with important implications for projections of future climates and midlatitude weather events. Through the use of the recently...
Article
There is increased evidence that stratosphere-troposphere exchange (STE) of ozone has a significant impact on tropospheric chemistry and radiation. Traditional diagnostics of STE consider the ozone budget in the lowermost stratosphere (LMS) as a whole. However, this can only render the hemispherically-integrated ozone flux, and therefore does not d...
Article
Wind-blown dunes are a record of the climatic history in Titan’s equatorial region. Through modeling of the climatic conditions associated with Titan’s historical orbital configurations (arising from apsidal precessions of Saturn’s orbit), we present evidence that the orientations of the dunes are influenced by orbital forcing. Analysis of 3 Titan...
Article
Full-text available
Midlatitude extreme weather events are responsible for a large part of climate-related damage, yet our understanding of these extreme events is limited, partly due to the lack of a theoretical basis for midlatitude extreme weather. In this letter, the local finite-amplitude wave activity (LWA) of Huang and Nakamura [2015] is introduced as a diagnos...
Article
Full-text available
Observations and climate models have shown that the midlatitude eddy-driven jet can exhibit an evident latitudinal shift in response to lower-tropospheric thermal forcing (e.g., the tropical SST warming during El Nino or extratropical SST anomalies associated with the atmosphere-ocean-sea ice coupling). In addition to the direct thermal wind respon...
Article
Full-text available
Systematic sensitivity of the jet position and intensity to horizontal model resolution is identified in several aquaplanet AGCMs, with the coarser resolution producing a more equatorward eddy-driven jet and a stronger upper-tropospheric jet intensity. As the resolution of the models increases to 50 km or finer, the jet position and intensity show...
Article
Full-text available
Previous studies have suggested that Southern Hemisphere (SH) summertime trends in the atmospheric circulation in the second half of the twentieth century are mainly driven by stratospheric ozone depletion in spring. Here, the authors show that the pattern and timing of observed trends, characterized by downward propagation of signals, can be appro...