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Oceanography and Atmospheric Sciences and Meteorology Commons™
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- CFS Prediction (1)
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- California drought;ENSO precursor;teleconnection;anthropogenic warming (1)
- Central U. S. (1)
Articles 1 - 30 of 36
Full-Text Articles in Oceanography and Atmospheric Sciences and Meteorology
Pacific Decadal Oscillation Remotely Forced By The Equatorial Pacific And The Atlantic Oceans, Zachary F. Johnson, Yoshimitsu Chikamoto, Shih-Yu Simon Wang, Michael J. Mcphaden, Takashi Mochizuki
Pacific Decadal Oscillation Remotely Forced By The Equatorial Pacific And The Atlantic Oceans, Zachary F. Johnson, Yoshimitsu Chikamoto, Shih-Yu Simon Wang, Michael J. Mcphaden, Takashi Mochizuki
Plants, Soils, and Climate Faculty Publications
The Pacific Decadal Oscillation (PDO), the leading mode of Pacific decadal sea surface temperature variability, arises mainly from combinations of regional air-sea interaction within the North Pacific Ocean and remote forcing, such as from the tropical Pacific and the Atlantic. Because of such a combination of mechanisms, a question remains as to how much PDO variability originates from these regions. To better understand PDO variability, the equatorial Pacific and the Atlantic impacts on the PDO are examined using several 3-dimensional partial ocean data assimilation experiments conducted with two global climate models: the CESM1.0 and MIROC3.2m. In these partial assimilation experiments, …
Climatology And Change Of Extreme Precipitation Events In Taiwan Based On Weather Types, Yi-Chao Wu, Shih-Yu (Simon) Wang, Yi-Chiang Yu, Chu-Ying Kung, An-Hsiang Wang, Sebastian A. Los, Wan-Ru Huang
Climatology And Change Of Extreme Precipitation Events In Taiwan Based On Weather Types, Yi-Chao Wu, Shih-Yu (Simon) Wang, Yi-Chiang Yu, Chu-Ying Kung, An-Hsiang Wang, Sebastian A. Los, Wan-Ru Huang
Plants, Soils, and Climate Faculty Publications
Taiwan's most significant natural hazards are caused by hydrological extremes resulting from excessive precipitation. The threat of extreme precipitation is posed by several different types of weather patterns that affect Taiwan. This study examined the bi‐decadal changes in rainfall by defining an extreme precipitation occurrence (EPO) for a range of event durations from 1 to 24 hr. Three major weather types affecting EPO in Taiwan were identified from 1993 to 2015: the front type consisting of either a frontal zone or convective systems developing with an apparent Meiyu cloudband, diurnal rainfall events when no apparent synoptic features are present, and …
The Influence Of Arctic Amplification On Mid-Latitude Summer Circulation, Dim Coumou, Giorgia Di Capua, Steve Vavrus, Lei Wang, Shih-Yu (Simon) Wang
The Influence Of Arctic Amplification On Mid-Latitude Summer Circulation, Dim Coumou, Giorgia Di Capua, Steve Vavrus, Lei Wang, Shih-Yu (Simon) Wang
Plants, Soils, and Climate Faculty Publications
Accelerated warming in the Arctic, as compared to the rest of the globe, might have profound impacts on mid-latitude weather. Most studies analyzing Arctic links to mid-latitude weather focused on winter, yet recent summers have seen strong reductions in sea-ice extent and snow cover, a weakened equator-to-pole thermal gradient and associated weakening of the mid-latitude circulation. We review the scientific evidence behind three leading hypotheses on the influence of Arctic changes on mid-latitude summer weather: Weakened storm tracks, shifted jet streams, and amplified quasi-stationary waves. We show that interactions between Arctic teleconnections and other remote and regional feedback processes could …
Ocean Impacts On Australian Interannual To Decadal Precipitation Variability, Zachary F. Johnson, Yoshimitsu Chikamoto, Jing-Jia Luo, Takashi Mochizuki
Ocean Impacts On Australian Interannual To Decadal Precipitation Variability, Zachary F. Johnson, Yoshimitsu Chikamoto, Jing-Jia Luo, Takashi Mochizuki
Plants, Soils, and Climate Faculty Publications
In Australia, successful seasonal predictions of wet and dry conditions are achieved by utilizing the remote impact of sea surface temperature (SST) variability in tropical oceans, particularly the Pacific Ocean, on the seasonal timescale. Beyond seasonal timescales, however, it is still unclear which processes and oceans contribute to interannual-to-decadal wet/dry conditions in Australia. This research examines the interannual-to-decadal relationship between global SST anomalies (SSTAs) and Australian wet/dry variability by analyzing observational data and global climate model experiments conducted with the NCAR Community Earth System Model (CESM) and the Model for Interdisciplinary Research on Climate (MIROC). A 10-member ensemble simulation suite …
Regional Trends In Early-Monsoon Rainfall Over Vietnam And Ccsm4 Attribution, Rong Li, S.-Y. Simon Wang, Robert R. Gillies, Brendan Buckley, Jin-Ho Yoon, Changrae Cho
Regional Trends In Early-Monsoon Rainfall Over Vietnam And Ccsm4 Attribution, Rong Li, S.-Y. Simon Wang, Robert R. Gillies, Brendan Buckley, Jin-Ho Yoon, Changrae Cho
Plants, Soils, and Climate Faculty Publications
The analysis of precipitation trends for Vietnam revealed that early-monsoon precipitation has increased over the past three decades but to varying degrees over the northern, central and southern portions of the country. Upon investigation, it was found that the change in early-monsoon precipitation is associated with changes in the low-level cyclonic airflow over the South China Sea and Indochina that is embedded in the large-scale atmospheric circulation associated with a “La Niña-like” anomalous sea surface temperature pattern with warming in the western Pacific and Indian Oceans and cooling in the eastern Pacific. The Community Climate System Model version 4 (CCSM4) …
Multidecadal Variability In The Subseasonal Peak Of Low-Level Convergence Over The Pacific Warm Pool, Yen-Heng Lin, Shih-Yu (Simon) Wang
Multidecadal Variability In The Subseasonal Peak Of Low-Level Convergence Over The Pacific Warm Pool, Yen-Heng Lin, Shih-Yu (Simon) Wang
Plants, Soils, and Climate Faculty Publications
In the Western North Pacific (WNP), the atmospheric low-level convergence is one of the main factors that influences the genesis of tropical cyclones (TC). It has been observed that the timing of the seasonal maxima in the low-level convergence and TC genesis has shifted since the mid-1990s from mid-August to late-July, with this shift having also affected the number of TC. A multidecadal frequency of 20 years was revealed in the timing variation of the tropical intraseasonal oscillation (ISO) in the Western Pacific, in which a weak WNP low-level convergence in spring may trigger an advanced ISO phase in summer …
Gridded Snow Water Equivalent Reconstruction For Utah Using Forest Inventory And Analysis Tree-Ring Data, Daniel Barandiaran, Shih-Yu (Simon) Wang, R. Justin Derose
Gridded Snow Water Equivalent Reconstruction For Utah Using Forest Inventory And Analysis Tree-Ring Data, Daniel Barandiaran, Shih-Yu (Simon) Wang, R. Justin Derose
Plants, Soils, and Climate Faculty Publications
Snowpack observations in the Intermountain West are sparse and short, making them difficult for use in depicting past variability and extremes. This study presents a reconstruction of April 1 snow water equivalent (SWE) for the period of 1850–1989 using increment cores collected by the U.S. Forest Service, Interior West Forest Inventory and Analysis program (FIA). In the state of Utah, SWE was reconstructed for 38 snow course locations using a combination of standardized tree-ring indices derived from both FIA increment cores and publicly available tree-ring chronologies. These individual reconstructions were then interpolated to a 4-km grid using an objective analysis …
Future Changes In Propagating And Non-Propagating Diurnal Rainfall Over East Asia, Wan-Ru Huang, Shih-Yu (Simon) Wang
Future Changes In Propagating And Non-Propagating Diurnal Rainfall Over East Asia, Wan-Ru Huang, Shih-Yu (Simon) Wang
Plants, Soils, and Climate Faculty Publications
The characteristics of diurnal rainfall in the East Asian continent consist of a propagating regime over the Yangtze River and a non-propagating regime in southeast China. Simulations of these two diurnal rainfall regimes by 18 CMIP5 models were evaluated from the historical experiment of 1981–2005. The evaluation led to the identification of one model, the CMCC-CM that replicated the key characteristics of diurnal rainfall regimes including the propagation of moisture convergence. Using the CMCC-CM to assess the future (2076–2100) change of diurnal evolution and propagation projected by the RCP4.5 experiment, it was found that propagating diurnal rainfall will enhance and …
Role Of The Strengthened El Nino Teleconnection In The May 2015 Floods Over The Southern Great Plains, S.-Y. Wang, W.-R. Huang, H.-H. Hsu, R. R. Gillies
Role Of The Strengthened El Nino Teleconnection In The May 2015 Floods Over The Southern Great Plains, S.-Y. Wang, W.-R. Huang, H.-H. Hsu, R. R. Gillies
Plants, Soils, and Climate Faculty Publications
The climate anomalies leading to the May 2015 floods in Texas and Oklahoma were analyzed in the context of El Niño teleconnection in a warmer climate. A developing El Niño tends to increase late-spring precipitation in the southern Great Plains, and this effect has intensified since 1980. Anthropogenic global warming contributed to the physical processes that caused the persistent precipitation in May 2015: Warming in the tropical Pacific acted to strengthen the teleconnection toward North America, modification of zonal wave 5 circulation that deepened the stationary trough west of Texas, and enhanced Great Plains low-level southerlies increasing moisture supply from …
The 2011 Great Flood In Thailand: Climate Diagnostics And Implications From Climate Change, Parichart Promchote, S. -Y. Simon Wang, Paul G. Johnson
The 2011 Great Flood In Thailand: Climate Diagnostics And Implications From Climate Change, Parichart Promchote, S. -Y. Simon Wang, Paul G. Johnson
Plants, Soils, and Climate Faculty Publications
Severe flooding occurred in Thailand during the 2011 summer season, which resulted in more than 800 deaths and affected 13.6 million people. The unprecedented nature of this flood in the Chao Phraya River basin (CPRB) was examined and compared with historical flood years. Climate diagnostics were conducted to understand the meteorological conditions and climate forcing that led to the magnitude and duration of this flood. Neither the monsoon rainfall nor the tropical cyclone frequency anomalies alone was sufficient to cause the 2011 flooding event. Instead, a series of abnormal conditions collectively contributed to the intensity of the 2011 flood: anomalously …
The North American Winter 'Dipole' And Extremes Activity: A Cmip5 Assessment, Shih-Yu (Simon) Wang, Wan-Ru Huang, Jin-Ho Yoon
The North American Winter 'Dipole' And Extremes Activity: A Cmip5 Assessment, Shih-Yu (Simon) Wang, Wan-Ru Huang, Jin-Ho Yoon
Plants, Soils, and Climate Faculty Publications
The 2013–2014 winter in North America brought intense drought in the West and severe cold in the East. The circulation anomalies were characterized as a dipole: an amplified upper-level ridge over the West Coast and a deepened trough over the central-eastern United States. A previous study using a single model has linked the dipole to the El Niño precursor and found that this link has strengthened in recent years. Here, 17 models from the Coupled Model Intercomparison Project Phase 5 are used to examine the dipole activity. Most models capture the dipole and its association with El Niño precursor and …
A Combined Dynamical And Statistical Downscaling Technique To Reduce Biases In Climate Projections: An Example For Winter Precipitation And Snowpack In The Western United States, R. Li, Shih-Yu (Simon) Wang, R. R. Gillies
A Combined Dynamical And Statistical Downscaling Technique To Reduce Biases In Climate Projections: An Example For Winter Precipitation And Snowpack In The Western United States, R. Li, Shih-Yu (Simon) Wang, R. R. Gillies
Plants, Soils, and Climate Faculty Publications
Large biases associated with climate projections are problematic when it comes to their regional application in the assessment of water resources and ecosystems. Here, we demonstrate a method that can reduce systematic biases in regional climate projections. The global and regional climate models employed to demonstrate the technique are the Community Climate System Model (CCSM)and the Weather Research and Forecasting (WRF) model. The method first utilized a statistical regression technique and a global reanalysis dataset to correct biases in the CCSM-simulated variables (e.g., temperature, geopotential height, specific humidity, and winds) that are subsequently used to drive the WRF model. …
Decadal Oscillation Of Autumn Precipitation In Central Vietnam Modulated By The East Pacific-North Pacific (Ep-Np), R. Li, Shih-Yu (Simon) Wang, R. R. Gillies, B. Buckley, L. H. Troung, C. Cho
Decadal Oscillation Of Autumn Precipitation In Central Vietnam Modulated By The East Pacific-North Pacific (Ep-Np), R. Li, Shih-Yu (Simon) Wang, R. R. Gillies, B. Buckley, L. H. Troung, C. Cho
Plants, Soils, and Climate Faculty Publications
Autumn precipitation over Central Vietnam is associated with an increase in the occurrence of tropical cyclones that lead to frequent flooding and pose a significant threat to lives and property. The present analyses reveal a pronounced decadal oscillation of autumn precipitation in Central Vietnam within the 8-11 year frequency band that is modulated by the East Pacific-North Pacific (EP-NP) teleconnection. The negative phase of the EP-NP pattern is associated with a positive sea surface temperature (SST) anomaly in the South China Sea (SCS) that induces low-level convergence, enhances convection, and increases precipitation over Central Vietnam and adjacent islands including Hainan …
Anthropogenic Footprint Of Climate Change In The June 2013 Northern India Flood, C. Cho, R. Li, Shih-Yu (Simon) Wang, J. -H. Yoon, R. R. Gillies
Anthropogenic Footprint Of Climate Change In The June 2013 Northern India Flood, C. Cho, R. Li, Shih-Yu (Simon) Wang, J. -H. Yoon, R. R. Gillies
Plants, Soils, and Climate Faculty Publications
During 13-17 June 2013, heavy rainfall occurred in the northern Indian state of 15 Uttarakhand and led to one of the worst floods in history and massive landslides, 16 resulting in more than 5,000 casualties and a huge loss of property. In this study, 17 meteorological and climatic conditions leading up to this rainfall event in 2013 and 18 similar cases were analyzed for the period of 1979-2012. Attribution analysis was 19 performed to identify the natural and anthropogenic influences on the climate anomalies 20 using the historical single-forcing experiments in the Coupled Model Intercomparison 21 Project Phase 5 (CMIP5). …
Observing The Quantumbehavior Of Light In An Undergraduate Laboratory, M. S. Neel, J. J. Thorn, V. W. Donato, G. S. Bergreen, Robert E. Davies, M. Beck
Observing The Quantumbehavior Of Light In An Undergraduate Laboratory, M. S. Neel, J. J. Thorn, V. W. Donato, G. S. Bergreen, Robert E. Davies, M. Beck
Plants, Soils, and Climate Faculty Publications
While the classical, wavelike behavior of light (interference and diffraction) has been easily observed in undergraduate laboratories for many years, explicit observation of the quantum nature of light (i.e., photons) is much more difficult. For example, while well-known phenomena such as the photoelectric effect and Compton scattering strongly suggest the existence of photons, they are not definitive proof of their existence. Here we present an experiment, suitable for an undergraduate laboratory, that unequivocally demonstrates the quantum nature of light. Spontaneously downconverted light is incident on a beamsplitter and the outputs are monitored with single-photon counting detectors. We observe a near …
Probable Causes Of The Abnormal Ridge Accompanying The 2013-14 California Drought: Enso Precursor And Anthropogenic Warming Footprint, Shih-Yu (Simon) Wang
Probable Causes Of The Abnormal Ridge Accompanying The 2013-14 California Drought: Enso Precursor And Anthropogenic Warming Footprint, Shih-Yu (Simon) Wang
Plants, Soils, and Climate Faculty Publications
The 2013–2014 California drought was initiated by an anomalous high-amplitude ridge system. The anomalous ridge was investigated using reanalysis data and the Community Earth System Model (CESM). It was found that the ridge emerged from continual sources of Rossby wave energy in the western North Pacific starting in late summer and subsequently intensified into winter. The ridge generated a surge of wave energy downwind and deepened further the trough over the northeast U.S., forming a dipole. The dipole and associated circulation pattern is not linked directly with either El Niño–Southern Oscillation (ENSO) or Pacific Decadal Oscillation; instead, it is correlated …
Coupling Of Pre-Monsoon Tropical Cyclones With The Monsoon Onset In Myanmar, B. O. Fosu, Shih-Yu (Simon) Wang
Coupling Of Pre-Monsoon Tropical Cyclones With The Monsoon Onset In Myanmar, B. O. Fosu, Shih-Yu (Simon) Wang
Plants, Soils, and Climate Faculty Publications
The pre-monsoon tropical cyclone (TC) activity and the monsoon evolution in the Bay of Bengal (BoB) are both influenced by the Madden–Julian Oscillation (MJO), but the two do not always occur in unison. This study examines the conditions that allow the MJO to modulate the monsoon onset in Myanmar and TC activity concurrently. Using the APHRODITE gridded precipitation and the ERA-Interim reanalysis datasets, composite evolutions of monsoon rainfall and TC genesis are constructed for the period of 1979–2010. It is found that the MJO exhibits a strong interannual variability in terms of phase and intensity, which in some years modulate …
Global Eastward Propagation Signals Associated With The 4-5-Year Enso Cycle, Shih-Yu (Simon) Wang, X. Jiang, B. Fosu
Global Eastward Propagation Signals Associated With The 4-5-Year Enso Cycle, Shih-Yu (Simon) Wang, X. Jiang, B. Fosu
Plants, Soils, and Climate Faculty Publications
Longitude-time evolution of sea surface temperature anomalies (SSTA) reveals a slow southeastward propagation from the western North Pacific (WNP) around 20°N to the Niño-3.4 region in the equatorial Central Pacific. The propagation is manifested as a narrow, southwest-northeast oriented SSTA band across the subtropical North Pacific, and its journey takes about 2–3 years. The propagating SSTA appears to engage the initiation of the El Niño–Southern Oscillation (ENSO). The anomalies of surface winds, sea level pressure, outgoing longwave radiation, and velocity potential all exhibit a concurrent and distinct eastward propagation, one that appears to be circumglobal and is coupled with the …
Could The 2012 Drought In Central U. S. Have Been Anticipated?, Shih-Yu (Simon) Wang, Danny Barandiaran, Kyle Hilburn, Paul Houser
Could The 2012 Drought In Central U. S. Have Been Anticipated?, Shih-Yu (Simon) Wang, Danny Barandiaran, Kyle Hilburn, Paul Houser
Plants, Soils, and Climate Faculty Publications
This paper summarizes research related to the 2012 record drought in the central United States conducted by members of the NEWS (NASA (National Aeronautics and Space Administration) Energy and Water cycle Study) Working Group. Past drought patterns were analyzed for signal coherency with latest drought and the contribution of long-term trends in the Great Plains low-level jet, an important regional circulation feature of the spring rainy season in the Great Plains. Long-term changes in the seasonal transition from rainy spring into dry summer were also examined. Potential external forcing from radiative processes, soil-air interactions, and ocean teleconnections were assessed as …
Significant Impacts Of Radiation Physics In The Wrf Model On The Precipitation And Dynamics Of The West African Monsoon, R. Li, J. Jin, Shih-Yu (Simon) Wang, R. R. Gillies
Significant Impacts Of Radiation Physics In The Wrf Model On The Precipitation And Dynamics Of The West African Monsoon, R. Li, J. Jin, Shih-Yu (Simon) Wang, R. R. Gillies
Plants, Soils, and Climate Faculty Publications
Precipitation from the West African Monsoon (WAM) provides food security and supports the economy in the region. As a consequence of the intrinsic complexities of the WAM’s evolution, accurate simulations of the WAM and its precipitation regime, through the application of regional climate models, are challenging. We used the coupled Weather Research and Forecasting (WRF) and Community Land Model (CLM) to explore impacts of radiation physics on the precipitation and dynamics of the WAM. Our results indicate that the radiation physics schemes not only produce biases in radiation fluxes impacting radiative forcing, but more importantly, result in large bias in …
Identification Of Extreme Precipitation Threat Across Midlatitude Regions Based On Short-Wave Circulations, Shih-Yu (Simon) Wang, Robert E. Davies, Robert R. Gillies
Identification Of Extreme Precipitation Threat Across Midlatitude Regions Based On Short-Wave Circulations, Shih-Yu (Simon) Wang, Robert E. Davies, Robert R. Gillies
Plants, Soils, and Climate Faculty Publications
The most severe thunderstorms, producing extreme precipitation, occur over subtropical and midlatitude regions. Atmospheric conditions conducive to organized, intense thunderstorms commonly involve the coupling of a low-level jet (LLJ) with a synoptic short wave. The midlatitude synoptic activity is frequently modulated by the circumglobal teleconnection (CGT), in which meridional gradients of the jet stream act as a guide for short Rossby waves. Previous research has linked extreme precipitation events with either the CGT or the LLJ but has not linked the two circulation features together. In this study, a circulation-based index was developed by combining (a) the degree of the …
Observational And Synoptic Analyses Of The Winter Precipitation Regime Change Over Utah, Robert R. Gillies, Shih-Yu Wang, Marty R. Booth
Observational And Synoptic Analyses Of The Winter Precipitation Regime Change Over Utah, Robert R. Gillies, Shih-Yu Wang, Marty R. Booth
Plants, Soils, and Climate Faculty Publications
Previous studies have indicated a widespread decline in snowpack over Utah accompanied by a decline in the snow–precipitation ratio while anecdotal evidence claims have been put forward that measured changes in Utah’s snowpack are spurious and do not reflect actual change. Using two distinct lines of investigation, this paper further analyzes the winter precipitation regime in the state of Utah. First, by means of observation-based, gridded daily temperature, precipitation, and remotely sensed data, as well as utilizing a climatological rain–snow threshold (RST) temperature method, the precipitation regime of Utah was scrutinized. Second, a comprehensive synoptic analysis was conducted as an …
Connecting Subseasonal Movements Of The Winter Mean Ridge In Western North America To Inversion Climatology In Cache Valley, Utah, Shi-Yu (Simon) Wang, Robert R. Gillies, Randy Martin, Robert E. Davies, Marty R. Booth
Connecting Subseasonal Movements Of The Winter Mean Ridge In Western North America To Inversion Climatology In Cache Valley, Utah, Shi-Yu (Simon) Wang, Robert R. Gillies, Randy Martin, Robert E. Davies, Marty R. Booth
Plants, Soils, and Climate Faculty Publications
A 10-yr record of PM2.5 (particulate matter of aerodynamic diameter ≤ 2.5 μm), collected in Cache Valley near downtown Logan, Utah, reveals a strong peak in the PM2.5 concentration climatology that is tightly localized in mid-January. The cause of this subseasonal variation in the PM2.5 climatology is investigated through dynamical downscaling and large-scale diagnostics. Climatological analysis of the U.S. winter mean ridge reveals a mid-January subseasonal shift in the zonal direction, likely in response to variations in the Rossby wave source over the central North Pacific Ocean. This displacement of the winter mean ridge, in turn, has an impact on …
Multi-Decadal Drought Cycles In The Great Basin Recorded By The Great Salt Lake: Modulation From A Transition-Phase Teleconnection, Shih-Yu (Simon) Wang, Robert R. Gillies, Thomas Reichler
Multi-Decadal Drought Cycles In The Great Basin Recorded By The Great Salt Lake: Modulation From A Transition-Phase Teleconnection, Shih-Yu (Simon) Wang, Robert R. Gillies, Thomas Reichler
Plants, Soils, and Climate Faculty Publications
This study investigates the meteorological conditions associated with multidecadal drought cycles as revealed by lake level fluctuation of the Great Salt Lake (GSL). The analysis combined instrumental, proxy, and simulation datasets, including the Twentieth Century Reanalysis version 2, the North American Drought Atlas, and a 2000-yr control simulation of the GFDL Coupled Model, version 2.1 (CM2.1). Statistical evidence from the spectral coherence analysis points to a phase shift amounting to 6–9 yr between the wet–dry cycles in the Great Basin and the warm–cool phases of the interdecadal Pacific oscillation (IPO). Diagnoses of the sea surface temperature and atmospheric …
Pakistan’S Two-Stage Monsoon And Links With The Recent Climate Change, Shih-Yu (Simon) Wang, Robert Davies, Wan Ru Huang, Robert R. Gillies
Pakistan’S Two-Stage Monsoon And Links With The Recent Climate Change, Shih-Yu (Simon) Wang, Robert Davies, Wan Ru Huang, Robert R. Gillies
Plants, Soils, and Climate Faculty Publications
Meteorological conditions related to the Pakistan floods of 2010 were examined in the context of monsoon dynamics and large‐scale circulations. Case and climatological analyses suggest that summer precipitation in northern Pakistan comprises two distinct phases: (1) a premonsoon trough phase (July) whose rainfall is more episodic and intense, occurring prior to arrival of the monsoon trough, and (2) a monsoon trough phase (August) whose rainfall is persistent, yet less episodic, driven by northward migration of the monsoon trough. Analyses of conditional instability, moisture flux, and circulation features support a persistent increase in conditional instability during the July premonsoon trough phase, …
Observed Change In Sahel Rainfall, Circulations, African Easterly Waves, And Atlantic Hurricanes Since 1979, Shih-Yu (Simon) Wang, Robert R. Gillies
Observed Change In Sahel Rainfall, Circulations, African Easterly Waves, And Atlantic Hurricanes Since 1979, Shih-Yu (Simon) Wang, Robert R. Gillies
Plants, Soils, and Climate Faculty Publications
Here, we examine the dynamic properties associated with the recent increase in the Sahel rainfall using an ensemble of five global reanalysis datasets (1979–2010). The rainfall that has been observed to be increasing over the Sahel is accounted for by enhancements in both the tropical easterly jet and the African easterly jet, both of which are known to induce wet anomalies. Moreover, positional shifts in the African easterly jet and African easterly waves (AEWs) accompanied the northward migration of the Sahel rainband. Change in the African easterly jet and AEWs are coupled to a northward shift and amplification of convective …
Quasi-Decadal Spectral Peaks Of Tropical Western Pacific Ssts As A Precursor For Tropical Cyclone Threat, Shih-Yu (Simon) Wang, Adam J. Clark
Quasi-Decadal Spectral Peaks Of Tropical Western Pacific Ssts As A Precursor For Tropical Cyclone Threat, Shih-Yu (Simon) Wang, Adam J. Clark
Plants, Soils, and Climate Faculty Publications
A recent study identified significant spectral peaks in sea surface temperatures (SSTs) at quasi‐decadal frequency bands, which were unique to the tropical western Pacific (TWP). Using the multitaper method for spectral and coherence analysis, this study finds that the TWP SSTs at these quasi‐decadal time scales are coherent with western Pacific tropical cyclone threat [as measured by the power dissipation index (PDI)], but that the PDI lags TWP SSTs by about two years. Thus, the quasi‐decadal peaks in TWP SSTs may be a precursor for enhanced tropical cyclone threat two years later. Composite analyses are shown to illustrate how areal …
Nam Model Forecasts Of Warm Season Quasi-Stationary Frontal Environments In The Central U.S., Shih-Yu (Simon) Wang, Adam J. Clark
Nam Model Forecasts Of Warm Season Quasi-Stationary Frontal Environments In The Central U.S., Shih-Yu (Simon) Wang, Adam J. Clark
Plants, Soils, and Climate Faculty Publications
Using a composite procedure, North American Mesoscale Model (NAM) forecast and observed environments associated with zonally oriented, quasi-stationary surface fronts for 64 cases during July–August 2006–08 were examined for a large region encompassing the central United States. NAM adequately simulated the general synoptic features associated with the frontal environments (e.g., patterns in the low-level wind fields) as well as the positions of the fronts. However, kinematic fields important to frontogenesis such as horizontal deformation and convergence were overpredicted. Surface-based convective available potential energy (CAPE) and precipitable water were also overpredicted, which was likely related to the overprediction of the kinematic …
Atmospheric Scale Interaction On Wintertime Intermountain West Low-Level Inversions, Robert R. Gillies, Shih-Yu (Simon) Wang, Marty R. Booth
Atmospheric Scale Interaction On Wintertime Intermountain West Low-Level Inversions, Robert R. Gillies, Shih-Yu (Simon) Wang, Marty R. Booth
Plants, Soils, and Climate Faculty Publications
Persistent winter inversions result in poor air quality in the Intermountain West of the United States. Although the onset of an inversion is relatively easy to predict, the duration and the subsequent breakup of a persistent inversion event remains a forecasting challenge. For this reason and for this region, historic soundings were analyzed for Salt Lake City, Utah, with reanalysis and station data to investigate how persistent inversion events are modulated by synoptic and intraseasonal variabilities. The results point to a close linkage between persistent inversions and the dominant intraseasonal (30 day) mode that characterizes the winter circulation regime over …
Cfs Prediction Of Winter Persistent Inversions In The Intermountain Region, Robert R. Gillies, Shih-Yu (Simon) Wang, Jin Ho Yoon, Scott Weaver
Cfs Prediction Of Winter Persistent Inversions In The Intermountain Region, Robert R. Gillies, Shih-Yu (Simon) Wang, Jin Ho Yoon, Scott Weaver
Plants, Soils, and Climate Faculty Publications
A recent study by Gillies and others of persistent inversion events in the Intermountain West of the United States found a substantive linkage between the intraseasonal oscillation (ISO) and the development of persistent inversion events. Given that NCEP’s Climate Forecast System (CFS) has demonstrated skill in the prediction of the ISO as far out as 1 month, it was decided to examine the CFS forecast’s capability in the prediction of such winter persistent inversions. After initial analysis, a simple regression scheme is proposed that is coupled to the CFS output of geopotential height as a way to predict the occurrence …