scholarly journals Boreal Summer Synoptic-Scale Waves over the Western North Pacific in Multimodel Simulations

2016 ◽  
Vol 29 (12) ◽  
pp. 4487-4508 ◽  
Author(s):  
Haikun Zhao ◽  
Xianan Jiang ◽  
Liguang Wu
Keyword(s):  
Spatial Pattern ◽  
North Pacific ◽  
General Circulation ◽  
Western North Pacific ◽  
Climate Model ◽  
Climate Modeling ◽  
Active Role ◽  
General Circulation Models ◽  
Boreal Summer ◽  
Synoptic Scale

During boreal summer, vigorous synoptic-scale wave (SSW) activity, often evident as southeast–northwest-oriented wave trains, prevails over the western North Pacific (WNP). In spite of their active role for regional weather and climate, modeling studies on SSWs are rather limited. In this study, a comprehensive survey on climate model capability in representing the WNP SSWs is conducted by analyzing simulations from 27 recent general circulation models (GCMs). Results suggest that it is challenging for GCMs to realistically represent the observed SSWs. Only 2 models out of the 27 GCMs generally well simulate both the intensity and spatial pattern of the observed SSW mode. Plausible key processes for realistic simulations of SSW activity are further explored. It is illustrated that GCM skill in representing the spatial pattern of the SSW is highly correlated to its skill in simulating the summer mean patterns of the low-level convergence associated with the WNP monsoon trough and conversion from eddy available potential energy (EAPE) to eddy kinetic energy (EKE). Meanwhile, simulated SSW intensity is found to be significantly correlated to the amplitude of 850-hPa vorticity, divergence, and conversion from EAPE to EKE over the WNP. The observed modulations of SSW activity by the Madden–Julian oscillation are able to be captured in several model simulations.

scholarly journals The cloud–aerosol–radiation (CAR) ensemble modeling system

2013 ◽  
Vol 13 (16) ◽  
pp. 8335-8364 ◽  
Author(s):  
X.-Z. Liang ◽  
F. Zhang
Keyword(s):  
Radiative Forcing ◽  
General Circulation ◽  
Climate Model ◽  
Climate Modeling ◽  
General Circulation Models ◽  
Climate Impacts ◽  
Sensitivity Analyses ◽  
General Description ◽  
Ensemble Modeling ◽  
Uncertainty Range

Abstract. A cloud–aerosol–radiation (CAR) ensemble modeling system has been developed to incorporate the largest choices of alternate parameterizations for cloud properties (cover, water, radius, optics, geometry), aerosol properties (type, profile, optics), radiation transfers (solar, infrared), and their interactions. These schemes form the most comprehensive collection currently available in the literature, including those used by the world's leading general circulation models (GCMs). CAR provides a unique framework to determine (via intercomparison across all schemes), reduce (via optimized ensemble simulations), and attribute specific key factors for (via physical process sensitivity analyses) the model discrepancies and uncertainties in representing greenhouse gas, aerosol, and cloud radiative forcing effects. This study presents a general description of the CAR system and illustrates its capabilities for climate modeling applications, especially in the context of estimating climate sensitivity and uncertainty range caused by cloud–aerosol–radiation interactions. For demonstration purposes, the evaluation is based on several CAR standalone and coupled climate model experiments, each comparing a limited subset of the full system ensemble with up to 896 members. It is shown that the quantification of radiative forcings and climate impacts strongly depends on the choices of the cloud, aerosol, and radiation schemes. The prevailing schemes used in current GCMs are likely insufficient in variety and physically biased in a significant way. There exists large room for improvement by optimally combining radiation transfer with cloud property schemes.

scholarly journals Influences of the Pacific–Japan Teleconnection Pattern on Synoptic-Scale Variability in the Western North Pacific

2014 ◽  
Vol 27 (1) ◽  
pp. 140-154 ◽  
Author(s):  
Richard C. Y. Li ◽  
Wen Zhou ◽  
Tim Li
Keyword(s):  
North Pacific ◽  
General Circulation ◽  
Western North Pacific ◽  
Wave Train ◽  
Circulation Model ◽  
Environmental Parameters ◽  
Teleconnection Pattern ◽  
Convective Heating ◽  
Synoptic Scale ◽  
The Pacific

Abstract This study investigates the influences of the Pacific–Japan (PJ) teleconnection pattern on synoptic-scale variability (SSV) in the western North Pacific (WNP). The PJ pattern exhibits salient intraseasonal variations, with a dominant peak at 10–50 days. During positive PJ phases, strengthened SSV is found in the WNP, with a much stronger and better organized synoptic wave train structure. Such a synoptic-scale wave train, however, is greatly weakened during negative PJ phases. Examination of the vertical profiles of the observational data suggests that environmental parameters are generally more (less) favorable for the growth of synoptic disturbances under positive (negative) PJ conditions. Observational results are further verified with an anomaly atmospheric general circulation model, which reveals faster (slower) growth of the synoptic-scale wave train when the environmental anomalies associated with positive (negative) PJ phases are incorporated into the summer mean state of the model. In addition, sensitivity experiments indicate that thermodynamic parameters of the planetary boundary layer (PBL) play a determining role in controlling the development of synoptic disturbances in the WNP. The increase (decrease) in background PBL moisture during positive (negative) PJ phases enhances (suppresses) perturbation moisture convergence and thus the convective heating associated with SSV, leading to strengthened (weakened) synoptic-scale activity in the WNP. Serving as potential seed disturbances for cyclogenesis, the strengthened (weakened) synoptic-scale activity may also contribute to the enhancement (suppression) in intraseasonal TC frequency during positive (negative) PJ phases.

Interactions between Boreal Summer Intraseasonal Oscillations and Synoptic-Scale Disturbances over the Western North Pacific. Part II: Apparent Heat and Moisture Sources and Eddy Momentum Transport*

2011 ◽  
Vol 24 (3) ◽  
pp. 942-961 ◽  
Author(s):  
Pang-Chi Hsu ◽  
Tim Li
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Wave Train ◽  
Intraseasonal Oscillation ◽  
Momentum Transport ◽  
Boreal Summer ◽  
Synoptic Scale ◽  
Mean Flow ◽  
The North ◽  
Intraseasonal Oscillations

Abstract The interactions between the boreal summer intraseasonal oscillation (ISO) and synoptic-scale variability (SSV) are investigated by diagnosing the atmospheric apparent heat source (Q1), apparent moisture sink (Q2), and eddy momentum transport. It is found that the synoptic Q1 and Q2 heating (cooling) anomalies are in phase with cyclonic (anticyclonic) vorticity disturbances, aligned in a southeast–northwest-oriented wave train pattern over the western North Pacific (WNP). The wave train is well organized and strengthened (loosely organized and weakened) during the ISO active (suppressed) phase. The nonlinearly rectified Q1 and Q2 fields due to the eddy–mean flow interaction account for 10%–30% of the total intraseasonal Q1 and Q2 variabilities over the WNP. During the ISO active (suppressed) phase, the nonlinearly rectified intraseasonal Q1 and Q2 heating (cooling) appear to the northwest of the ISO enhanced (suppressed) convection center, favoring the northwestward propagation of the ISO. A diagnosis of the zonal momentum budget shows that the eddy momentum flux convergence forces an intraseasonal westerly (easterly) tendency to the north of the ISO westerly (easterly) center during the ISO active (suppressed) phase. As a result, the eddy momentum transport may contribute to the northward propagation of the boreal summer ISO over the WNP.

Changes in spring and Mei-yu extreme precipitation in the Western North Pacific and East Asia in the warmer climate in two high-resolution AGCMs

2020 ◽  
Author(s):  
Chao-An Chen ◽  
Huang-Hsiung Hsu
Keyword(s):  
High Resolution ◽  
Spatial Pattern ◽  
East Asia ◽  
Extreme Events ◽  
North Pacific ◽  
Extreme Precipitation ◽  
General Circulation ◽  
Western North Pacific ◽  
Future Climate Change ◽  
Sst Warming

<p>In this study, we estimate the changes in extreme precipitation indices over the western North Pacific and East Asia region (WNP-EA) during the spring and Mei-yu seasons in the warmer climate. Our analyses are based on two high-resolution atmospheric general circulation model simulations. The high-resolution atmospheric Model (HiRAM) was used in a series of simulations, which were forced by 4 sets of sea surface temperature (SST) changes under Representative Concentration Pathways 8.5 (RCP8.5) scenario. The Database for Policy Decision-Making for Future Climate Change (d4PDF) consists of global warming simulation outputs from MRI-AGCM3.2 with large ensemble members and multiple SST warming scenarios.</p><p>In the spring season, the changes in the spatial pattern of SDII, RX1day, and PR99 demonstrate greater enhancement over the northern flank of the climatological rainy region in both HiRAM and d4PDF, implying a northward extension of spring rain band. Besides, the changes in probability distribution display a shifting tendency that heavier extreme events occur more frequently in the warmer climate. The above changes are larger than the internal variability and uncertainty associated with SST warming patterns, indicating the robustness of the projected enhancement in precipitation intensity in the WNP-EA region. The spatial pattern for changes in CDD and total rainfall occurrence are less consistent between two datasets. In the Mei-yu season, the tendency toward more frequent extreme events in the probability distributions are consistently found in HiRAM and d4PDF. However, the changes in the spatial pattern of all indices are less consistent between HiRAM and d4PDF, implying larger uncertainty in the projection of extreme precipitation in the Mei-yu period in the warmer climate.</p>

scholarly journals The global impact of supersaturation in a coupled chemistry-climate model

2007 ◽  
Vol 7 (6) ◽  
pp. 1629-1643 ◽  
Author(s):  
A. Gettelman ◽  
D. E. Kinnison
Keyword(s):  
Water Vapor ◽  
Radiative Forcing ◽  
General Circulation ◽  
Climate Model ◽  
General Circulation Models ◽  
Boreal Summer ◽  
Boreal Winter ◽  
Strong Impact ◽  
Small Component ◽  
Enhanced Production

Abstract. Ice supersaturation is important for understanding condensation in the upper troposphere. Many general circulation models however do not permit supersaturation. In this study, a coupled chemistry climate model, the Whole Atmosphere Community Climate Model (WACCM), is modified to include supersaturation for the ice phase. Rather than a study of a detailed parameterization of supersaturation, the study is intended as a sensitivity experiment, to understand the potential impact of supersaturation, and of expected changes to stratospheric water vapor, on climate and chemistry. High clouds decrease and water vapor in the stratosphere increases at a similar rate to the prescribed supersaturation (20% supersaturation increases water vapor by nearly 20%). The stratospheric Brewer-Dobson circulation slows at high southern latitudes, consistent with slight changes in temperature likely induced by changes to cloud radiative forcing. The cloud changes also cause an increase in the seasonal cycle of near tropopause temperatures, increasing them in boreal summer over boreal winter. There are also impacts on chemistry, with small increases in ozone in the tropical lower stratosphere driven by enhanced production. The radiative impact of changing water vapor is dominated by the reduction in cloud forcing associated with fewer clouds (~+0.6 Wm−2) with a small component likely from the radiative effect (greenhouse trapping) of the extra water vapor (~+0.2 Wm−2), consistent with previous work. Representing supersaturation is thus important, and changes to supersaturation resulting from changes in aerosol loading for example, might have a modest impact on global radiative forcing, mostly through changes to clouds. There is no evidence of a strong impact of water vapor on tropical tropopause temperatures.

scholarly journals Sensitivity of western north Pacific summertime tropical synoptic- scale disturbances to extratropical forcing – A regional climate model study

2021 ◽  
Author(s):  
Ying Lung Liu ◽  
Chi-Yung Tam ◽  
Andie Yee Man Au-Yeung
Keyword(s):  
Regional Climate Model ◽  
North Pacific ◽  
Western North Pacific ◽  
Climate Model ◽  
Regional Climate ◽  
Wave Activity ◽  
Synoptic Scale ◽  
Low Level ◽  
Zonal Wavenumber ◽  
Extratropical Forcing

Abstract The role of extratropical forcing on the summertime tropical synoptic-scale disturbances (TSDs) in the western north Pacific has been investigated, by conducting parallel integrations of the Regional Climate Model (RegCM). The suite of experiments consists of a control run (CTRL) with European Centre for Medium Range Forecasts (ECMWF) Reanalysis data as boundary conditions, and an experimental run (EXPT) with the same setting, except that signals with zonal wavenumber > 6 were suppressed at the northern boundary (located at 42°N) of the model domain. Comparison between CTRL and EXPT showed that, without extratropical forcing, there is weaker TSD activity in the June-to-August season, with reduced precipitation over the TSD pathway. Associated with suppressed TSD, southeastward-directed wave activity is also reduced, leading to less active mixed Rossby gravity (MRG) waves in the equatorial western Pacific area. Further analysis revealed that extratropical forcing and associated circulation changes can modulate the TSD wavetrain and its coherence structure, in relation to low-level vorticity in far western north Pacific. In CTRL, west of about 140°E, TSD-related circulation tends to be stronger; in EXPT, vorticity signals and vertical motions are found to be slightly more coherent in the more eastern portion of the TSD wavetrain. The latter enhanced coherency of TSD east of 140°E, from the EXPT simulations, might be due to changes in wave activity transport channelled by modulated upper-level mid-latitude westerlies in EXPT. Energetics indicate that changes in low-level background circulation itself can also influence TSD characteristics. Our results serve to quantify how extratropical forcing and related general circulation features influence western north Pacific summertime TSD activities. Implications on understanding the initiation of TSD, as well as their variability on longer time scales, are discussed.

scholarly journals EVALUATION AND BIAS CORRECTION OF MARINE SURFACE WINDS IN THE WESTERN NORTH PACIFIC FROM CMIP5 AND CMIP6 GCMS FOR WAVE CLIMATE MODELLING

2020 ◽  
pp. 35
Author(s):  
Mochamad Riam Badriana ◽  
Han Soo Lee
Keyword(s):  
Bias Correction ◽  
North Pacific ◽  
General Circulation ◽  
Western North Pacific ◽  
Coupled Model ◽  
General Circulation Models ◽  
Wave Climate ◽  
Climate Modelling ◽  
Surface Winds ◽  
Marine Surface

For over years, fundamental component and dataset in climate projection had been covered by general circulation models (GCMs) output mainly from the Coupled Model Inter-comparison Project (CMIP). Marine surface winds are an important output of GCMs and they provide input to marine forecasts and warning systems. Their accuracy have direct implications for marine safety, air-sea fluxes, and wave and ocean modellings. Western North Pacific (WNP) is known as a highly vulnerable region to oceanic and atmospheric hazards, such as storm surges, waves and typhoons. Therefore, this study aims to examine the quality of marine surface winds from CMIP5 and CMIP6 GCMs in the WNP and its sub-regions with respect to a reference data, and presents bias correction of marine surface winds for contributing to wave and ocean modelling communities.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/750mqrERbS8

scholarly journals What modulates the intensity of synoptic scale variability over the western North Pacific during boreal summer and fall?

2021 ◽  
pp. 1
Author(s):  
Renguang Wu ◽  
Yuqi Wang ◽  
Xi Cao
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Eastern Pacific ◽  
Propagation Path ◽  
Boreal Summer ◽  
Synoptic Scale ◽  
Mean Flow ◽  
Central Pacific ◽  
Background Fields ◽  
Sst Anomalies

AbstractThe present study investigates the factors that affect the year-to-year change in the intensity of synoptic scale variability (SSV) over the tropical western North Pacific (TWNP) during boreal summer and fall. It is found that the intensity of the TWNP SSV in summer is associated with the equatorial central-eastern Pacific sea surface temperature (SST) anomalies that modulates the background fields through a Rossby wave response both in the source region and along the propagation path of the synoptic scale disturbances. In fall, the intensity of the TWNP SSV is related to an SST anomaly pattern with opposite anomalies in the equatorial central Pacific and TWNP that modulates the background fields from the equatorial central Pacific to TWNP. However, the equatorial central Pacific SST anomalies alone fail to change the intensity of the TWNP SSV as the induced background field changes are limited to the equatorial central Pacific. It is shown that tropical western Pacific SST anomalies may induce notable changes in the intensity of the TWNP SSV. The relation of the TWNP SSV to the equatorial eastern Pacific SST is weak due to opposite SST anomalies in different types of years. Both seasonal mean and intraseasonal flows provide source of barotropic energy for the change in the intensity of the TWNP synoptic scale disturbances in summer. Seasonal mean flow has a main contribution to the barotropic energy conversion for the change in the intensity of the TWNP synoptic scale disturbances in fall.

scholarly journals Attribution of Projected Future Changes in Tropical Cyclone Passage Frequency over the Western North Pacific

2013 ◽  
Vol 26 (12) ◽  
pp. 4096-4111 ◽  
Author(s):  
Satoru Yokoi ◽  
Yukari N. Takayabu ◽  
Hiroyuki Murakami
Keyword(s):  
Tropical Cyclone ◽  
El Niño ◽  
North Pacific ◽  
General Circulation ◽  
Western North Pacific ◽  
Climate Models ◽  
El Nino ◽  
General Circulation Models ◽  
Translation Vector ◽  
Attribution Analysis

Abstract This paper performs an attribution analysis of future changes in the frequency of tropical cyclone (TC) passages over the western North Pacific basin projected by seven general circulation models. The models project increases in the passage frequency over the tropical central North Pacific and decreases in regions to the west and northwest, including East Asian countries. The attribution analysis reveals that while changes of the basinwide TC count would decrease the frequency of passages throughout the basin, the gross horizontal contrast in the passage frequency changes is caused by a projected eastward shift of main TC development regions, probably caused by El Niño–like sea surface temperature changes. The change in the frequency of passages is also caused by changes of TC translation vectors and preferable tracks. In particular, the translation vector would rotate clockwise to point in a more easterly direction over oceanic regions south of Japan, decreasing the passage frequency over the Korean peninsula and western Japan while increasing it over eastern Japan. This change in translation direction may be caused by the southward shift of the subtropical jet axis and resultant intensification of westerly steering flows. The El Niño–like change and westerly steering flow change are consistent not only among the seven models but also among a number of other climate models, which suggests the reliability of these results from the viewpoint of intermodel agreement.

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