MJO in the NCAR CAM2 with the Tiedtke Convective Scheme*

2005 ◽  
Vol 18 (15) ◽  
pp. 3007-3020 ◽  
Author(s):  
Ping Liu ◽  
Bin Wang ◽  
Kenneth R. Sperber ◽  
Tim Li ◽  
Gerald A. Meehl
Keyword(s):  
Climate Model ◽  
Convective Available Potential Energy ◽  
Intraseasonal Variability ◽  
Power Spectra ◽  
Boreal Winter ◽  
Central Pacific ◽  
Standard Version ◽  
Central Pacific Ocean ◽  
Model Version ◽  
Convective Scheme

Abstract The boreal winter Madden–Julian oscillation (MJO) remains very weak and irregular in the National Center for Atmospheric Research (NCAR) Community Atmosphere Model version 2 (CAM2) as in its direct predecessor, the Community Climate Model version 3 (CCM3). The standard version of CAM2 uses the deep convective scheme of Zhang and McFarlane, as in CCM3, with the closure dependent on convective available potential energy (CAPE). Here, sensitivity tests using several versions of the Tiedtke convective scheme are conducted. Typically, the Tiedtke convection scheme gives an improved mean state, intraseasonal variability, space–time power spectra, and eastward propagation compared to the standard version of the model. Coherent eastward propagation of MJO-related precipitation is also much improved, particularly over the Indian–western Pacific Oceans. A composite life cycle of the model MJO indicates that over the Indian Ocean wind-induced surface heat exchange (WISHE) functions, while over the western/central Pacific Ocean aspects of frictional moisture convergence are evident in the maintenance and eastward propagation of the oscillation.

scholarly journals Tropical Intraseasonal Variability in the MRI-20km60L AGCM*

2009 ◽  
Vol 22 (8) ◽  
pp. 2006-2022 ◽  
Author(s):  
Ping Liu ◽  
Yoshiyuki Kajikawa ◽  
Bin Wang ◽  
Akio Kitoh ◽  
Tetsuzo Yasunari ◽  
...  
Keyword(s):  
Intraseasonal Variability ◽  
Power Spectra ◽  
Cumulus Parameterization ◽  
Boreal Summer ◽  
Boreal Winter ◽  
Loose Coupling ◽  
Low Level ◽  
Mature Phase ◽  
The Mean ◽  
Ceof Analysis

Abstract This study documents the detailed characteristics of the tropical intraseasonal variability (TISV) in the MRI-20km60L AGCM that uses a variant of the Arakawa–Schubert cumulus parameterization. Mean states, power spectra, propagation features, leading EOF modes, horizontal and vertical structures, and seasonality associated with the TISV are analyzed. Results show that the model reproduces the mean states in winds realistically and in convection comparable to that of the observations. However, the simulated TISV is less realistic. It shows low amplitudes in convection and low-level winds in the 30–60-day band. Filtered anomalies have standing structures. Power spectra and lag correlation of the signals do not propagate dominantly either in the eastward direction during boreal winter or in the northward direction during boreal summer. A combined EOF (CEOF) analysis shows that winds and convection have a loose coupling that cannot sustain the simulated TISV as realistically as that observed. In the composited mature phase of the simulated MJO, the low-level convergence does not lead convection clearly so that the moisture anomalies do not tilt westward in the vertical, indicating that the low-level convergence does not favor the eastward propagation. The less realistic TISV suggests that the representation of cumulus convection needs to be improved in this model.

EXPLORING INLAND TROPICAL CYCLONE RAINFALL AND TORNADOES UNDER FUTURE CLIMATE CONDITIONS THROUGH A CASE STUDY OF HURRICANE IVAN

2020 ◽  
Author(s):  
Dereka Carroll-Smith ◽  
Robert J. Trapp ◽  
James M. Done
Keyword(s):  
Climate Change ◽  
Tropical Cyclone ◽  
Climate Models ◽  
Climate Model ◽  
Convective Available Potential Energy ◽  
Track Length ◽  
Geophysical Fluid Dynamics Laboratory ◽  
Climate System Model ◽  
Hurricane Ivan ◽  
Model Version

AbstractThe overarching purpose of this study is to investigate the impacts of anthropogenic climate change both on the rainfall and tornadoes associated with tropical cyclones (TCs) making landfall in the U.S. Atlantic Basin. The “pseudo-global” warming (PGW) approach is applied to Hurricane Ivan (2004), a historically prolific tropical cyclone tornado (TCT)-producing storm. Hurricane Ivan is simulated under its current climate forcings using the Weather Research and Forecasting model. This control simulation (CTRL) is then compared to PGW simulations in which the current forcings are modified by climate-change differences obtained from the Community Climate System Model version 4 (NCAR), Model for Interdisciplinary Research on Climate version 5 (MIROC), and Geophysical Fluid Dynamics Laboratory Climate Model version 3 (GFDL) climate models. Changes in TC intensity, TC rainfall, and TCT production, identified for the PGW-modified Ivan are documented and analyzed.Compared to CTRL, all three PGW simulations show an increase in TC intensity and generate substantially more accumulated rainfall over the course of Ivan’s progression overland. However, only one of the TCs under PGW (MIROC) produced more TCTs than the control. Evidence is provided that in addition to favorable environmental conditions, TCT production is related to the TC track length and to the strength of the interaction between the TC and an environmental mid-level trough. Enhanced TCT generation at landfall for MIROC and GFDL is attributed to increased values of convective available potential energy, low level shear and storm relative environmental helicity.

Impact of ENSO on stratospheric ozone

2021 ◽  
Author(s):  
Samuel Benito-Barca ◽  
Natalia Calvo ◽  
Marta Abalos
Keyword(s):  
Climate Model ◽  
Southern Oscillation ◽  
Global Climate ◽  
Stratospheric Ozone ◽  
Boreal Winter ◽  
Residual Circulation ◽  
Central Pacific ◽  
Large Variability ◽  
Enso Events ◽  
Middle Latitudes

<p>El Niño‐Southern Oscillation (ENSO) is the main source of interannual variability in the global climate. Previous studies have shown ENSO has impacts on stratospheric ozone concentrations through changes in stratospheric circulation. The aim of this study is to extend these analysis by examining the anomalies in residual circulation and mixing associated with different El Niño flavors (Eastern Pacific (EP) and Central Pacific (CP)) and La Niña in boreal winter. For this purpose, we use four 60-year ensemble members of the Whole Atmospheric Community Climate Model version 4, reanalysis and satellite data.</p><p>Significant ozone anomalies are identified in both tropics and extratropics. In the northern high-latitudes (70-90N), significant positive ozone anomalies appear in the middle stratosphere in early winter during both CP and EP El Niño, which propagates downward during winter to the lower stratosphere only during EP-El Niño events. Anomalies during La Niña events are opposite to EP-El Niño. The analysis of the different terms in the continuity equation for zonal-mean ozone concentration reveals that Arctic ozone changes during ENSO events  are mainly driven by advection due to residual circulation, although contributions of mixing and chemistry are not negligible, especially in upper stratosphere.</p><p>The ENSO impact on total ozone column (TOC) is also investigated. During EP-El Niño, a significant reduction of TOC appears in the tropics and an increase in the middle latitudes. During La Niña the response is the opposite. The TOC response to CP El Niño events is not as robust. In the Northern Hemisphere polar region the TOC anomalies are not significant, probably due to its large variability associated with sudden stratospheric warmings in this region.</p>

Tropical Instability Waves as a Resonance between Equatorial Rossby Waves*

2005 ◽  
Vol 35 (2) ◽  
pp. 232-254 ◽  
Author(s):  
John M. Lyman ◽  
Dudley B. Chelton ◽  
Roland A. deSzoeke ◽  
Roger M. Samelson
Keyword(s):  
Rossby Waves ◽  
Climate Model ◽  
The State ◽  
State Variables ◽  
Central Pacific ◽  
Instability Waves ◽  
Tropical Instability Waves ◽  
Central Pacific Ocean ◽  
Ocean Climate Model ◽  
Equatorial Rossby Waves

Abstract To understand the characteristics of sea surface height signatures of tropical instability waves (TIWs), a linearized model of the central Pacific Ocean was developed in which the vertical structures of the state variables are projected onto a set of orthogonal baroclinic eigenvectors. In lieu of in situ current measurements with adequate spatial and temporal resolution, the mean current structure used in the model was obtained from the Parallel Ocean Climate Model (POCM). The TIWs in the linear model have cross-equatorial structure and wavenumber–frequency content similar to the TIWs in POCM, even when the vertical structures of the state variables are projected onto only the first two orthogonal baroclinic eigenvectors. Because this model is able to reproduce TIWs with relatively simple vertical structure, it is possible to examine the mechanism for the formation of TIWs. TIWs are shown to form from a resonance between two equatorial Rossby waves as the strength of the background currents is slowly increased.

scholarly journals Predictable mode of tropical intraseasonal variability in boreal summer

2020 ◽  
pp. 1
Author(s):  
Xiaojing Li ◽  
Youmin Tang
Keyword(s):  
Critical Role ◽  
Intraseasonal Variability ◽  
Western Indian Ocean ◽  
Seasonal Prediction ◽  
Boreal Summer ◽  
Central Pacific ◽  
Tropical Ocean ◽  
Weather Forecasts ◽  
Central Pacific Ocean ◽  
Negative Center

AbstractThis work uses a 19-year ensemble hindcast of the European Centre for Medium-Range Weather Forecasts (ECMWF) and the average predictable time (APT) method to detect the most predictable tropical intraseasonal variability (ISV) mode. The first and most predictable mode (APT1) of tropical ISV is similar to a joint merger of the two Madden–Julian Oscillation (MJO) modes with more weight on the second mode and is characterized by a triple pattern with two positive centers in the equatorial western Indian Ocean and central Pacific Ocean and a negative center over the Maritime Continent. The APT1 doubles the skillful prediction period made by the MJO defined by a correlation skill of 0.5 (approximately 25 days in the ECMWF model), demonstrating its potential to become a skillful prediction target and to offer powerful sub-seasonal prediction sources.The underlying physical process and predictability source of the APT1 are further analyzed. The APT1 is very similar to the pattern triggered by the most predictable tropical intraseasonal sea surface temperature (SST) anomalies mode, suggesting its oceanic origin. Tropical ocean-atmosphere interaction plays a critical role in the APT1 by enhancing the evolution of tropical convection cells under WES (Wind-Evaporation-SST) and Bjerknes feedbacks. The internal atmospheric processes also have an important impact on the formation and maintenance of the APT1.

scholarly journals Future Changes in Tropical Cyclone Activity Projected by the New High-Resolution MRI-AGCM

2012 ◽  
Vol 25 (9) ◽  
pp. 3237-3260 ◽  
Author(s):  
Hiroyuki Murakami ◽  
Yuqing Wang ◽  
Hiromasa Yoshimura ◽  
Ryo Mizuta ◽  
Masato Sugi ◽  
...  
Keyword(s):  
High Resolution ◽  
Tropical Cyclone ◽  
General Circulation ◽  
Climate Model ◽  
Global Climate Model ◽  
General Circulation Models ◽  
Central Pacific ◽  
Model Version ◽  
Mesh Model ◽  
Basin Scale

New versions of the high-resolution 20- and 60-km-mesh Meteorological Research Institute (MRI) atmospheric general circulation models (MRI-AGCM version 3.2) have been developed and used to investigate potential future changes in tropical cyclone (TC) activity. Compared with the previous version (version 3.1), version 3.2 yields a more realistic simulation of the present-day (1979–2003) global distribution of TCs. Moreover, the 20-km-mesh model version 3.2 is able to simulate extremely intense TCs (categories 4 and 5), which is the first time a global climate model has been able to simulate such extremely intense TCs through a multidecadal simulation. Future (2075–99) projections under the Intergovernmental Panel on Climate Change (IPCC) A1B scenario are conducted using versions 3.1 and 3.2, showing consistent decreases in the number of TCs globally and in both hemispheres as climate warms. Although projected future changes in basin-scale TC numbers show some differences between the two versions, the projected frequency of TC occurrence shows a consistent decrease in the western part of the western North Pacific (WNP) and in the South Pacific Ocean (SPO), while it shows a marked increase in the central Pacific. Both versions project a future increase in the frequency of intense TCs globally; however, the degree of increase is smaller in version 3.2 than in version 3.1. This difference arises partly because version 3.2 projects a pronounced decrease in mean TC intensity in the SPO. The 20-km-mesh model version 3.2 projects a northward shift in the most intense TCs (category 5) in the WNP, indicating an increasing potential for future catastrophic damage due to TCs in this region.

scholarly journals The role of tropical volcanic eruptions in exacerbating Indian droughts

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Suvarna Fadnavis ◽  
Rolf Müller ◽  
Tanusri Chakraborty ◽  
T. P. Sabin ◽  
Anton Laakso ◽  
...  
Keyword(s):  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
Volcanic Eruptions ◽  
Summer Monsoon Rainfall ◽  
Indian Region ◽  
Volcanic Plume ◽  
Kelvin Wave ◽  
Central Pacific ◽  
Climate Model Simulations

AbstractThe Indian summer monsoon rainfall (ISMR) is vital for the livelihood of millions of people in the Indian region; droughts caused by monsoon failures often resulted in famines. Large volcanic eruptions have been linked with reductions in ISMR, but the responsible mechanisms remain unclear. Here, using 145-year (1871–2016) records of volcanic eruptions and ISMR, we show that ISMR deficits prevail for two years after moderate and large (VEI > 3) tropical volcanic eruptions; this is not the case for extra-tropical eruptions. Moreover, tropical volcanic eruptions strengthen El Niño and weaken La Niña conditions, further enhancing Indian droughts. Using climate-model simulations of the 2011 Nabro volcanic eruption, we show that eruption induced an El Niño like warming in the central Pacific for two consecutive years due to Kelvin wave dissipation triggered by the eruption. This El Niño like warming in the central Pacific led to a precipitation reduction in the Indian region. In addition, solar dimming caused by the volcanic plume in 2011 reduced Indian rainfall.

scholarly journals Primary Production in the Water Column as Major Structuring Element of the Biogeographical Distribution and Function of Archaea in Deep-Sea Sediments of the Central Pacific Ocean

Archaea ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Franziska Wemheuer ◽  
Avril Jean Elisabeth von Hoyningen-Huene ◽  
Marion Pohlner ◽  
Julius Degenhardt ◽  
Bert Engelen ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Primary Production ◽  
Deep Sea ◽  
Archaeal Community ◽  
Central Pacific ◽  
Central Pacific Ocean ◽  
Deep Sea Sediments ◽  
And Function ◽  
Functional Profiles ◽  
Archaeal Communities

Information on environmental conditions shaping archaeal communities thriving at the seafloor of the central Pacific Ocean is limited. The present study was conducted to investigate the diversity, composition, and function of both entire and potentially active archaeal communities within Pacific deep-sea sediments. For this purpose, sediment samples were taken along the 180° meridian of the central Pacific Ocean. Community composition and diversity were assessed by Illumina tag sequencing targeting archaeal 16S rRNA genes and transcripts. Archaeal communities were dominated by CandidatusNitrosopumilus(Thaumarchaeota) and other members of theNitrosopumilaceae(Thaumarchaeota), but higher relative abundances of the Marine Group II (Euryarchaeota) were observed in the active compared to the entire archaeal community. The composition of the entire and the active archaeal communities was strongly linked to primary production (chlorophyll content), explaining more than 40% of the variance. Furthermore, we found a strong correlation of the entire archaeal community composition to latitude and silicic acid content, while the active community was significantly correlated with primary production and ferric oxide content. We predicted functional profiles from 16S rRNA data to assess archaeal community functions. Latitude was significantly correlated with functional profiles of the entire community, whereas those of the active community were significantly correlated with nitrate and chlorophyll content. The results of the present study provide first insights into benthic archaeal communities in the Pacific Ocean and environmental conditions shaping their diversity, distribution, and function. Additionally, they might serve as a template for further studies investigating archaea colonizing deep-sea sediments.

scholarly journals Changes in Spread and Predictability Associated with ENSO in an Ensemble Coupled GCM

2006 ◽  
Vol 19 (17) ◽  
pp. 4378-4396 ◽  
Author(s):  
Renguang Wu ◽  
Ben P. Kirtman
Keyword(s):  
Surface Pressure ◽  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
La Niña ◽  
Boreal Summer ◽  
Boreal Winter ◽  
Central Pacific ◽  
La Nina ◽  
Signal Change

Abstract The present study documents the influence of El Niño and La Niña events on the spread and predictability of rainfall, surface pressure, and 500-hPa geopotential height, and contrasts the relative contribution of signal and noise changes to the predictability change based on a long-term integration of an interactive ensemble coupled general circulation model. It is found that the pattern of the El Niño–Southern Oscillation (ENSO)-induced noise change for rainfall follows closely that of the corresponding signal change in most of the tropical regions. The noise for tropical Pacific surface pressure is larger (smaller) in regions of lower (higher) mean pressure. The ENSO-induced noise change for 500-hPa height displays smaller spatial scales compared to and has no systematic relationship with the signal change. The predictability for tropical rainfall and surface pressure displays obvious contrasts between the summer and winter over the Bay of Bengal, the western North Pacific, and the tropical southwestern Indian Ocean. The predictability for tropical 500-hPa height is higher in boreal summer than in boreal winter. In the equatorial central Pacific, the predictability for rainfall is much higher in La Niña years than in El Niño years. This occurs because of a larger percent reduction in the amplitude of noise compared to the percent decrease in the magnitude of signal from El Niño to La Niña years. A consistent change is seen in the predictability for surface pressure near the date line. In the western North and South Pacific, the predictability for boreal winter rainfall is higher in El Niño years than in La Niña years. This is mainly due to a stronger signal in El Niño years compared to La Niña years. The predictability for 500-hPa height increases over most of the Tropics in El Niño years. Over western tropical Pacific–Australia and East Asia, the predictability for boreal winter surface pressure and 500-hPa height is higher in El Niño years than in La Niña years. The predictability change for 500-hPa height is primarily due to the signal change.

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