scholarly journals Enhanced MJO-like Variability at High SST

2013 ◽  
Vol 26 (3) ◽  
pp. 988-1001 ◽  
Author(s):  
Nathan P. Arnold ◽  
Zhiming Kuang ◽  
Eli Tziperman
Keyword(s):  
Intraseasonal Variability ◽  
Lower Troposphere ◽  
Longwave Radiation ◽  
Positive Contribution ◽  
Physical Processes ◽  
Tropical Variability ◽  
Community Atmosphere Model ◽  
The Mean ◽  
Static Energy ◽  
The Relationship

Abstract The authors report a significant increase in Madden–Julian oscillation (MJO)–like variability in a superparameterized version of the NCAR Community Atmosphere Model run with high sea surface temperatures (SSTs). A series of aquaplanet simulations exhibit a tripling of intraseasonal outgoing longwave radiation variance as equatorial SST is increased from 26° to 35°C. The simulated intraseasonal variability also transitions from an episodic phenomenon to one with a semiregular period of 25 days. Moist static energy (MSE) budgets of composite MJO events are used to diagnose the physical processes responsible for the relationship with SST. This analysis points to an increasingly positive contribution from vertical advection, associated in part with a steepening of the mean vertical MSE profile in the lower troposphere. The change in MSE profile is a natural consequence of increasing SST while maintaining a moist adiabat with a fixed profile of relative humidity. This work has implications for tropical variability in past warm climates as well as anthropogenic global warming scenarios.

MJO Intensification with Warming in the Superparameterized CESM

2015 ◽  
Vol 28 (7) ◽  
pp. 2706-2724 ◽  
Author(s):  
Nathan P. Arnold ◽  
Mark Branson ◽  
Zhiming Kuang ◽  
David A. Randall ◽  
Eli Tziperman
Keyword(s):  
Intraseasonal Variability ◽  
Dominant Mode ◽  
Positive Contribution ◽  
Vertical Advection ◽  
Tropical Variability ◽  
Surface Latent Heat Flux ◽  
Future Global Warming ◽  
Community Earth System Model ◽  
The Mean ◽  
Static Energy

Abstract The Madden–Julian oscillation (MJO) is the dominant mode of tropical intraseasonal variability, characterized by an eastward-propagating envelope of convective anomalies with a 30–70-day time scale. Here, the authors report changes in MJO activity across coupled simulations with a superparameterized version of the NCAR Community Earth System Model. They find that intraseasonal OLR variance nearly doubles between a preindustrial control run and a run with 4×CO2. Intraseasonal precipitation increases at a rate of roughly 10% per 1 K of warming, and MJO events become 20%–30% more frequent. Moist static energy (MSE) budgets of composite MJO events are calculated for each scenario, and changes in budget terms are used to diagnose the physical processes responsible for changes in the MJO with warming. An increasingly positive contribution from vertical advection is identified as the most likely cause of the enhanced MJO activity. A decomposition links the changes in vertical advection to a steepening of the mean MSE profile, which is a robust thermodynamic consequence of warming. Surface latent heat flux anomalies are a significant sink of MJO MSE at 1×CO2, but this damping effect is reduced in the 4×CO2 case. This work has implications for organized tropical variability in past warm climates as well as future global warming scenarios.

scholarly journals The Role of Moisture–Convection Feedbacks in Simulating the Madden–Julian Oscillation

2011 ◽  
Vol 24 (11) ◽  
pp. 2754-2770 ◽  
Author(s):  
Walter M. Hannah ◽  
Eric D. Maloney
Keyword(s):  
Intraseasonal Variability ◽  
Substantial Reduction ◽  
Entrainment Rate ◽  
Madden Julian Oscillation ◽  
Moisture Sensitivity ◽  
Community Atmosphere Model ◽  
The Mean ◽  
Gross Moist Stability ◽  
Static Energy

Abstract The sensitivity of a simulated Madden–Julian oscillation (MJO) was investigated in the NCAR Community Atmosphere Model 3.1 with the relaxed Arakawa–Schubert convection scheme by analyzing the model’s response to varying the strength of two moisture sensitivity parameters. A higher value of either the minimum entrainment rate or rain evaporation fraction results in increased intraseasonal variability, a more coherent MJO, and enhanced moisture–convection feedbacks in the model. Changes to the mean state are inconsistent between the two methods. Increasing the minimum entrainment leads to a cooler and drier troposphere, whereas increasing the rain evaporation fraction causes warming and moistening. These results suggest that no straightforward correspondence exists between the MJO and the mean humidity, contrary to previous studies. Analysis of the mean column-integrated and normalized moist static energy (MSE) budget reveals a substantial reduction of gross moist stability (GMS) for increased minimum entrainment, while no significant changes are found for an increased evaporation fraction. However, when considering fluctuations of the normalized MSE budget terms during MJO events, both methods result in negative GMS prior to the deep convective phase of the MJO. Intraseasonal fluctuations of GMS, rather than the mean, appear to be a better diagnostic quantity for testing a model’s ability to produce an MJO.

scholarly journals Impacts of Shallow Convection on MJO Simulation: A Moist Static Energy and Moisture Budget Analysis

2013 ◽  
Vol 26 (8) ◽  
pp. 2417-2431 ◽  
Author(s):  
Qiongqiong Cai ◽  
Guang J. Zhang ◽  
Tianjun Zhou
Keyword(s):  
Boundary Layer ◽  
Deep Convection ◽  
Lower Troposphere ◽  
Longwave Radiation ◽  
Reanalysis Data ◽  
Specific Humidity ◽  
Moist Static Energy ◽  
Shallow Convection ◽  
Budget Analysis ◽  
Static Energy

Abstract The role of shallow convection in Madden–Julian oscillation (MJO) simulation is examined in terms of the moist static energy (MSE) and moisture budgets. Two experiments are carried out using the NCAR Community Atmosphere Model, version 3.0 (CAM3.0): a “CTL” run and an “NSC” run that is the same as the CTL except with shallow convection disabled below 700 hPa between 20°S and 20°N. Although the major features in the mean state of outgoing longwave radiation, 850-hPa winds, and vertical structure of specific humidity are reasonably reproduced in both simulations, moisture and clouds are more confined to the planetary boundary layer in the NSC run. While the CTL run gives a better simulation of the MJO life cycle when compared with the reanalysis data, the NSC shows a substantially weaker MJO signal. Both the reanalysis data and simulations show a recharge–discharge mechanism in the MSE evolution that is dominated by the moisture anomalies. However, in the NSC the development of MSE and moisture anomalies is weaker and confined to a shallow layer at the developing phases, which may prevent further development of deep convection. By conducting the budget analysis on both the MSE and moisture, it is found that the major biases in the NSC run are largely attributed to the vertical and horizontal advection. Without shallow convection, the lack of gradual deepening of upward motion during the developing stage of MJO prevents the lower troposphere above the boundary layer from being preconditioned for deep convection.

The Moist Static Energy Budget of a Composite Tropical Intraseasonal Oscillation in a Climate Model

2009 ◽  
Vol 22 (3) ◽  
pp. 711-729 ◽  
Author(s):  
Eric D. Maloney
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Climate Model ◽  
Intraseasonal Variability ◽  
Lower Troposphere ◽  
Specific Humidity ◽  
Horizontal Advection ◽  
Moisture Advection ◽  
Static Energy

Abstract The intraseasonal moist static energy (MSE) budget is analyzed in a climate model that produces realistic eastward-propagating tropical intraseasonal wind and precipitation variability. Consistent with the recharge–discharge paradigm for tropical intraseasonal variability, a buildup of column-integrated MSE occurs within low-level easterly anomalies in advance of intraseasonal precipitation, and a discharge of MSE occurs during and after precipitation when westerly anomalies occur. The strongest MSE anomalies peak in the lower troposphere and are, primarily, regulated by specific humidity anomalies. The leading terms in the column-integrated intraseasonal MSE budget are horizontal advection and surface latent heat flux, where latent heat flux is dominated by the wind-driven component. Horizontal advection causes recharge (discharge) of MSE within regions of anomalous equatorial lower-tropospheric easterly (westerly) anomalies, with the meridional component of the moisture advection dominating the MSE budget near 850 hPa. Latent heat flux anomalies oppose the MSE tendency due to horizontal advection, making the recharge and discharge of column MSE more gradual than if horizontal advection were acting alone. This relationship has consequences for the time scale of intraseasonal variability in the model. Eddies dominate intraseasonal meridional moisture advection in the model. During periods of low-level intraseasonal easterly anomalies, eddy kinetic energy (EKE) is anomalously low due to a suppression of tropical synoptic-scale disturbances and other variability on time scales shorter than 20 days. Anomalous moistening of the equatorial lower troposphere occurs during intraseasonal easterly periods through suppression of eddy moisture advection between the equator and poleward latitudes. During intraseasonal westerly periods, EKE is enhanced, leading to anomalous drying of the equatorial lower troposphere through meridional advection. Given the importance of meridional moisture advection and wind-induced latent heat flux to the intraseasonal MSE budget, these findings suggest that to simulate realistic intraseasonal variability, climate models must have realistic basic-state distributions of lower-tropospheric zonal wind and specific humidity.

scholarly journals Southern Hemisphere Jet Variability in the IPSL GCM at Varying Resolutions

2012 ◽  
Vol 69 (12) ◽  
pp. 3788-3799 ◽  
Author(s):  
Ara Arakelian ◽  
Francis Codron
Keyword(s):  
Southern Hemisphere ◽  
Intraseasonal Variability ◽  
Co2 Concentration ◽  
Southern Annular Mode ◽  
Horizontal Resolution ◽  
Dominant Mode ◽  
The Mean ◽  
Jet Variability ◽  
The Relationship ◽  
Mean State

Abstract Fluctuations of the Southern Hemisphere eddy-driven jet are studied in a suite of experiments with the Laboratoire de Météorologie Dynamique, version 4 (LMDZ4) atmospheric GCM with varying horizontal resolution, in coupled mode and with imposed SSTs. The focus is on the relationship between changes in the mean state brought by increasing resolution, and the intraseasonal variability and response to increasing CO2 concentration. In summer, the mean jet latitude moves poleward when the resolution increases in latitude, converging toward the observed one. Most measures of the jet dynamics, such as skewness of the distribution or persistence time scale of jet movements, exhibit a simple dependence on the mean jet latitude and also converge to the observed values. In winter, the improvement of the mean-state biases with resolution is more limited. In both seasons, the relationship between the dominant mode of variability—the southern annular mode (SAM)—and the mean state remains the same as in observations, except in the most biased winter simulation. The jet fluctuations—latitude shifts or splitting—just occur around a different mean position. Both the model biases and the response to increasing CO2 project strongly onto the SAM structure. No systematic relation between the amplitude of the response and characteristics of the control simulation was found, possibly due to changing dynamics or impacts of the physical parameterizations with different resolutions.

scholarly journals Physical Processes Associated with the Tropical Atlantic SST Gradient during the Anomalous Evolution in the Southeastern Ocean

2007 ◽  
Vol 20 (14) ◽  
pp. 3366-3378 ◽  
Author(s):  
Zeng-Zhen Hu ◽  
Bohua Huang
Keyword(s):  
Heat Flux ◽  
Sensible Heat Flux ◽  
Longwave Radiation ◽  
Damping Factor ◽  
Positive Contribution ◽  
Tropical Atlantic ◽  
Sensible Heat ◽  
Gulf Of Guinea ◽  
Physical Processes ◽  
Sst Anomalies

Abstract This work is focused on the evolution of the dominant air–sea coupled mode in the equatorial and southeastern tropical Atlantic and the associated physical processes. It is shown that in June–August (JJA) the evolution of the dominant mode is mainly dynamically driven and displays a coherent warming or cooling pattern extending from the Angola coast toward the equator in the Gulf of Guinea. For anomalies peaking in JJA, the warming (cooling) is initiated near the Angola coast in March–May. It is suggested that SST anomalies along the coast and near the equator are physically connected. The air–sea interaction along the coast may be a major factor in triggering the development of SST anomalies near the equator, which is intensified by local positive feedbacks that may include Bjerknes and Ekman processes. In return, the warming or cooling near the equator weaken the SST anomalies along the coast by changing the direction of anomalous wind. Slow westward Rossby wave propagation may also play a role in stimulating the equatorial feedback. The thermodynamic processes affect the evolution of this mode. On average, the net surface latent heat flux anomalies are the leading damping factor, and the net surface sensible heat flux plays the same role on a smaller scale, while the net surface shortwave (longwave) radiation heating has a negative (positive) contribution to the SST variation. However, although on average the surface heat flux damps the SST anomalies, the role played by the heat flux varies with regions and components. Spatially, the latent and sensible heat flux as well as the longwave radiation damp air–sea coupling in the eastern South Atlantic near the Gulf of Guinea and amplify the coupling in the western equatorial ocean. The situation is opposite for the solar radiation.

Stratospheric and Tropospheric Flux Contributions to the Polar Cap Energy Budgets

2021 ◽  
pp. 1-49
Author(s):  
Christopher J. Cardinale ◽  
Brian E. J. Rose ◽  
Andrea L. Lang ◽  
Aaron Donohoe
Keyword(s):  
Energy Budget ◽  
Vertical Structure ◽  
Lower Troposphere ◽  
Longwave Radiation ◽  
Surface Energy Budget ◽  
The Arctic ◽  
Energy Budgets ◽  
Polar Regions ◽  
Static Energy ◽  
Arctic Surface

AbstractThe flux of moist static energy into the polar regions plays a key role in the energy budget and climate of the polar regions. While usually studied from a vertically integrated perspective (Fwall), this analysis examines its vertical structure, using the NASA-MERRA-2 reanalysis to compute climatological and anomalous fluxes of sensible, latent, and potential energy across 70°N and 65°S for the period 1980–2016. The vertical structure of the climatological flux is bimodal, with peaks in the mid- to lower-troposphere and mid- to upper-stratosphere. The near zero flux at the tropopause defines the boundary between stratospheric (Fstrat) and tropospheric (Ftrop) contributions to Fwall. Especially at 70°N, Fstrat is found to be important to the climatology and variability of Fwall, contributing 20.9 Wm−2 to Fwall (19% of Fwall) during the winter and explaining 23% of the variance of Fwall. During winter, an anomalous poleward increase in Fstrat preceding a sudden stratospheric warming is followed by an increase in outgoing longwave radiation anomalies, with little influence on the surface energy budget of the Arctic. Conversely, a majority of the energy input by an anomalous poleward increase in Ftrop goes toward warming the Arctic surface. Ftrop is found to be a better metric than Fwall for evaluating the influence of atmospheric circulations on the Arctic surface climate.

scholarly journals The Leading Pattern of Intraseasonal and Interannual Indian Ocean Precipitation Variability and Its Relationship with Asian Circulation during the Boreal Cold Season

2012 ◽  
Vol 25 (21) ◽  
pp. 7509-7526 ◽  
Author(s):  
Andrew Hoell ◽  
Mathew Barlow ◽  
Roop Saini
Keyword(s):  
Indian Ocean ◽  
Time Scales ◽  
Southern Oscillation ◽  
Function Analysis ◽  
Intraseasonal Variability ◽  
Longwave Radiation ◽  
Severe Drought ◽  
Monthly Precipitation ◽  
Southwest Asia ◽  
The Mean

The leading pattern of precipitation for the Indian Ocean, one of the most intense areas of rainfall on the globe, is calculated for November–April 1979–2008. The associated regional circulation and thermodynamic forcing of precipitation over Asia are examined at both intraseasonal and interannual time scales. The leading pattern is determined using both empirical orthogonal function analysis of monthly precipitation data and a closely related index of daily outgoing longwave radiation filtered into intraseasonal (33–105 days) and interannual (greater than 105 days) components. The leading pattern has a maximum in the tropical eastern Indian Ocean, and is closely associated with the Madden–Julian oscillation at intraseasonal time scales and related to the El Niño–Southern Oscillation at interannual time scales. Both time scales are associated with baroclinic Gill–Matsuno-like circulation responses extending over southern Asia, but the interannual component also has a strong equivalent barotropic circulation. Thermodynamically, both time scales are associated with cold temperature advection and subsidence over southwest Asia, with advection of the mean temperature by the anomalous wind more important at lower and midlevels and advection of the anomalous temperature by the mean wind more important at upper levels. For individual months, the intraseasonal variability can overwhelm the interannual variability. Enhanced Indian Ocean convection persisted for almost the entire 2007/08 season in association with severe drought over southwest Asia, but a strong intraseasonal signal in January 2008 reversed the pattern, resulting in damaging floods in the midst of drought.

Multi-Center Calibration of the Second Reference Material for Thromboplastin, Rabbit, Plain, Coded CRM 149R

1991 ◽  
Vol 65 (03) ◽  
pp. 263-267 ◽  
Author(s):  
A M H P van den Besselaar ◽  
R M Bertina
Keyword(s):  
Reference Material ◽  
Standard Error ◽  
Standard Errors ◽  
Sensitivity Index ◽  
Long Term Stability ◽  
Significant Bias ◽  
The Mean ◽  
The Relationship ◽  
International Sensitivity Index

SummaryIn a collaborative trial of eleven laboratories which was performed mainly within the framework of the European Community Bureau of Reference (BCR), a second reference material for thromboplastin, rabbit, plain, was calibrated against its predecessor RBT/79. This second reference material (coded CRM 149R) has a mean International Sensitivity Index (ISI) of 1.343 with a standard error of the mean of 0.035. The standard error of the ISI was determined by combination of the standard errors of the ISI of RBT/79 and the slope of the calibration line in this trial.The BCR reference material for thromboplastin, human, plain (coded BCT/099) was also included in this trial for assessment of the long-term stability of the relationship with RBT/79. The results indicated that this relationship has not changed over a period of 8 years. The interlaboratory variation of the slope of the relationship between CRM 149R and RBT/79 was significantly lower than the variation of the slope of the relationship between BCT/099 and RBT/79. In addition to the manual technique, a semi-automatic coagulometer according to Schnitger & Gross was used to determine prothrombin times with CRM 149R. The mean ISI of CRM 149R was not affected by replacement of the manual technique by this particular coagulometer.Two lyophilized plasmas were included in this trial. The mean slope of relationship between RBT/79 and CRM 149R based on the two lyophilized plasmas was the same as the corresponding slope based on fresh plasmas. Tlowever, the mean slope of relationship between RBT/79 and BCT/099 based on the two lyophilized plasmas was 4.9% higher than the mean slope based on fresh plasmas. Thus, the use of these lyophilized plasmas induced a small but significant bias in the slope of relationship between these thromboplastins of different species.

Evaluation of the Efficacy of ST2 and NT-proBNP in the Diagnosis and Prediction of Short- Term Prognosis in Heart Failure with Reduced Ejection Fraction

2017 ◽  
Vol 9 (04) ◽  
Author(s):  
Shivananda B Nayak ◽  
Dharindra Sawh ◽  
Brandon Scott ◽  
Vestra Sears ◽  
Kareshma Seebalack ◽  
...  
Keyword(s):  
Heart Failure ◽  
Ejection Fraction ◽  
Cardiac Biomarkers ◽  
Double Blind Study ◽  
Short Term ◽  
Double Blind ◽  
Reduced Ejection Fraction ◽  
The Mean ◽  
Design And Methods ◽  
The Relationship

Purpose: i) To determine the relationship between the cardiac biomarkers ST2 and NT-proBNP with ejection fraction (EF) in heart failure (HF) patients. ii) Assess whether a superiority existed between the aforementioned cardiac markers in diagnosing the HF with reduced EF. iii) Determine the efficacy of both biomarkers in predicting a 30-day cardiovascular event and rehospitalization in patients with HF with reduced EF iv) To assess the influence of age, gender, BMI, anaemia and renal failure on the ST2 and NT-proBNP levels. Design and Methods: A prospective double-blind study was conducted to obtain data from a sample of 64 cardiology patients. A blood sample was collected to test for ST2 and NT-proBNP. An echocardiogram (to obtain EF value), electrocardiogram and questionnaire were also obtained. Results: Of the 64 patients enrolled, 59.4% of the population had an EF less than 40%. At the end of the 30- day period, 7 patients were warded, 37 were not warded, one died and 17 were non respondent. Both biomarkers were efficacious at diagnosing HF with a reduced EF. However, neither of them were efficacious in predicting 30-day rehospitalization. The mean NT-proBNP values being: not rehospitalized (2114.7486) and 30 day rehospitalization (1008.42860) and the mean ST2 values being: not rehospitalized (336.1975), and 30-day rehospitalization. (281.9657). Conclusion: Neither ST2 or NT-proBNP was efficacious in predicting the short- term prognosis in HF with reduced EF. Both however were successful at confirming the diagnosis of HF in HF patients with reduced EF.

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