scholarly journals The Wavelength Dependence of the Gross Moist Stability and the Scale Selection in the Instability of Column-Integrated Moist Static Energy

2011 ◽  
Vol 68 (1) ◽  
pp. 61-74 ◽  
Author(s):  
Zhiming Kuang
Keyword(s):  
Large Scale ◽  
Theoretical Models ◽  
Wavelength Dependence ◽  
Convective Heating ◽  
Moist Static Energy ◽  
Scale Selection ◽  
Temperature Anomalies ◽  
Divergent Flow ◽  
Gross Moist Stability ◽  
Static Energy

Abstract Gross moist stability (GMS), a measure of how efficiently divergent flow exports column-integrated moist static energy (MSE), is a widely used quantity in current simplified models of the tropical mean circulation and intraseasonal variabilities such as the Madden–Julian oscillation (MJO), where it is often assumed to be constant. In this paper, it is shown, with cloud-system-resolving model experiments that incorporate feedback from the large-scale flow, that the GMS is smaller at longer wavelengths. The reason for this wavelength dependence is that temperature anomalies required to maintain a given divergent flow increase with wavelength. At long wavelengths, the required temperature anomalies become sufficiently strong to affect the shape of convective heating. As a consequence, the divergent flow is forced to be less top heavy in order to maintain the balance of momentum, heat, and moisture, as well as consistency with the behavior of cumulus convection. A simple model is constructed to illustrate this behavior. Given the ongoing theoretical efforts that view the MJO as resulting from instability in column-integrated MSE, the results presented here provide a planetary-scale selection for such instability, which is absent in current theoretical models that assume a constant GMS.

A Moist Static Energy Budget Analysis of Quasi-2-Day Waves Using Satellite and Reanalysis Data

2016 ◽  
Vol 73 (2) ◽  
pp. 743-759 ◽  
Author(s):  
Yukari Sumi ◽  
Hirohiko Masunaga
Keyword(s):  
Large Scale ◽  
Deep Convection ◽  
Reanalysis Data ◽  
Convective Heating ◽  
Moist Static Energy ◽  
Wave Dynamics ◽  
Vertical Advection ◽  
Budget Analysis ◽  
Static Energy ◽  
Thermodynamic Processes

Abstract A moist static energy (MSE) budget analysis is applied to quasi-2-day waves to examine the effects of thermodynamic processes on the wave propagation mechanism. The 2-day waves are defined as westward inertia–gravity (WIG) modes identified with filtered geostationary infrared measurements, and the thermodynamic parameters and MSE budget variables computed from reanalysis data are composited with respect to the WIG peaks. The composite horizontal and vertical MSE structures are overall as theoretically expected from WIG wave dynamics. A prominent horizontal MSE advection is found to exist, although the wave dynamics is mainly regulated by vertical advection. The vertical advection decreases MSE around the times of the convective peak, plausibly resulting from the first baroclinic mode associated with deep convection. Normalized gross moist stability (NGMS) is used to examine the thermodynamic processes involving the large-scale dynamics and convective heating. NGMS gradually decreases to zero before deep convection and reaches a maximum after the convection peak, where low (high) NGMS leads (lags) deep convection. The decrease in NGMS toward zero before the occurrence of active convection suggests an increasingly efficient conversion from convective heating to large-scale dynamics as the wave comes in, while the increase afterward signifies that this linkage swiftly dies out after the peak.

scholarly journals Gross Moist Stability Assessment during TOGA COARE: Various Interpretations of Gross Moist Stability

2015 ◽  
Vol 72 (11) ◽  
pp. 4148-4166 ◽  
Author(s):  
Kuniaki Inoue ◽  
Larissa E. Back
Keyword(s):  
Life Cycle ◽  
Large Scale ◽  
Convective System ◽  
Stability Assessment ◽  
Moist Static Energy ◽  
Toga Coare ◽  
Gross Moist Stability ◽  
Static Energy ◽  
Diabatic Forcing ◽  
Drying Efficiency

Abstract Daily averaged TOGA COARE data are analyzed to investigate the convective amplification/decay mechanisms. The gross moist stability (GMS), which represents moist static energy (MSE) export efficiency by large-scale circulations associated with the convection, is studied together with two quantities, called the critical GMS (a ratio of diabatic forcing to the convective intensity) and the drying efficiency [a version of the effective GMS (GMS minus critical GMS)]. The analyses reveal that convection intensifies (decays) via negative (positive) drying efficiency. The authors illustrate that variability of the drying efficiency during the convective amplifying phase is predominantly explained by the vertical MSE advection (or vertical GMS), which imports MSE via bottom-heavy vertical velocity profiles (associated with negative vertical GMS) and eventually starts exporting MSE via top-heavy profiles (associated with positive vertical GMS). The variability of the drying efficiency during the decaying phase is, in contrast, explained by the horizontal MSE advection. The critical GMS, which is moistening efficiency due to the diabatic forcing, is broadly constant throughout the convective life cycle, indicating that the diabatic forcing always tends to destabilize the convective system in a constant manner. The authors propose various ways of computing quasi-time-independent “characteristic GMS” and demonstrate that all of them are equivalent and can be interpreted as (i) the critical GMS, (ii) the GMS at the maximum precipitation, and (iii) a combination of feedback constants between the radiation, evaporation, and convection. Those interpretations indicate that each convective life cycle is a fluctuation of rapidly changing GMS around slowly changing characteristic GMS.

Quantifying the interplay of clouds and their environment through an energetic lens during EUREC4A

2021 ◽  
Author(s):  
Anna Lea Albright ◽  
Sandrine Bony ◽  
Bjorn Stevens ◽  
Raphaela Vogel
Keyword(s):  
Large Scale ◽  
Hydrological Cycle ◽  
Trade Wind ◽  
Energy Budgets ◽  
Moist Static Energy ◽  
Radiative Effect ◽  
The North ◽  
Cloud Radiative Effect ◽  
Moist Static Energy Budget ◽  
Static Energy

<p>The trades form an important link in the atmospheric energy supply, transporting moisture and momentum to the deep tropics and influencing the global hydrological cycle. Trade-wind cumuli are the most ubiquitous cloud type over tropical oceans, yet models disagree in simulating their response to warming. Our study takes advantage of extensive in-situ soundings performed during the EUREC4A campaign, which took place in the downstream trades of the North Atlantic in winter 2020. We employ 1068 dropsondes made in a ca. 2deg x 2deg area to close the moisture and energy budgets of the subcloud layer and atmospheric column. Our motivation for closing moisture and energy budgets using EUREC4A data is two-fold. First, we try to understand which large-scale environmental factors control variability in subcloud layer moisture and moist static energy, given their influence on setting convective potential. Second, we quantify the interplay between clouds and their environment through an energetic lens. The cloud radiative effect emerges as a residual from the total column moist static energy budget, yielding an energetic estimate of clouds. We quantify how this cloud radiative effect compares with coincident satellite and geometric (i.e. cloud fraction) estimates of cloudiness, varies on different scales, and relates to large-scale environmental conditions.</p>

Linkage of Arctic Sea Ice and Energy Transport

2021 ◽  
Author(s):  
Ines Höschel ◽  
Dörthe Handorf ◽  
Christoph Jacobi ◽  
Johannes Quaas
Keyword(s):  
Sea Ice ◽  
Large Scale ◽  
Energy Transport ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Moist Static Energy ◽  
Large Scale Circulation ◽  
Arctic Sea ◽  
Rossby Wave Propagation ◽  
Static Energy

<p>The loss of Arctic sea ice as a consequence of global warming is changing the forcing of the atmospheric large-scale circulation.  Areas not covered with sea ice anymore may act as an additional heat source.  Associated changes in Rossby wave propagation can initiate tropospheric and stratospheric pathways of Arctic - Mid-latitude linkages.  These pathways have the potential to impact on the large-scale energy transport into the Arctic.  On the other hand, studies show that the large-scale circulation contributes to Arctic warming by poleward transport of moist static energy. This presentation shows results from research within the Transregional Collaborative Research Center “ArctiC Amplification: Climate Relevant Atmospheric and SurfaCe Processes, and Feedback Mechanisms (AC)3” funded by the Deutsche Forschungsgemeinschaft.  Using the ERA interim and ERA5 reanalyses the meridional moist static energy transport during high ice and low ice periods is compared.  The investigation discriminates between contributions from planetary and synoptic scale.  Special emphasis is put on the seasonality of the modulations of the large-scale energy transport.</p>

scholarly journals Large-Scale Environmental Characteristics of MJOs that Strengthen and Weaken over the Maritime Continent

2018 ◽  
Vol 31 (14) ◽  
pp. 5731-5748 ◽  
Author(s):  
Casey D. Burleyson ◽  
Samson M. Hagos ◽  
Zhe Feng ◽  
Brandon W. J. Kerns ◽  
Daehyun Kim
Keyword(s):  
Seasonal Cycle ◽  
Large Scale ◽  
Longwave Radiation ◽  
Sea Surface ◽  
Madden Julian Oscillation ◽  
Moist Static Energy ◽  
Maritime Continent ◽  
New Finding ◽  
Field Campaigns ◽  
Static Energy

Abstract The characteristics of Madden–Julian oscillation (MJO) events that strengthen and weaken over the Maritime Continent (MC) are examined. The real-time multivariate MJO (RMM) index is used to assess changes in global MJO amplitude over the MC. The MJO weakens at least twice as often as it strengthens over the MC, with weakening MJOs being twice as likely during El Niño compared to La Niña years and the reverse for strengthening events. MJO weakening shows a pronounced seasonal cycle that has not been previously documented. During the Northern Hemisphere (NH) summer and fall the RMM index can strengthen over the MC. MJOs that approach the MC during the NH winter typically weaken according to the RMM index. This seasonal cycle corresponds to whether the MJO crosses the MC primarily north or south of the equator. Because of the seasonal cycle, weakening MJOs are characterized by positive sea surface temperature and moist-static energy anomalies in the Southern Hemisphere (SH) of the MC compared to strengthening events. Analysis of the outgoing longwave radiation (OLR) MJO index (OMI) shows that MJO precipitation weakens when it crosses the MC along the equator. A possible explanation of this based on previous results is that the MJO encounters more landmasses and taller mountains when crossing along the equator or in the SH. The new finding of a seasonal cycle in MJO weakening over the MC highlights the importance of sampling MJOs throughout the year in future field campaigns designed to study MJO–MC interactions.

scholarly journals A Vertically Resolved MSE Framework Highlights the Role of the Boundary Layer in Convective Self-Aggregation

2021 ◽  
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Mathematical Formulation ◽  
Detailed Comparison ◽  
Moist Static Energy ◽  
Uniform Temperature ◽  
Static Energy ◽  
Global And Local ◽  
Self Aggregation

Abstract Convective self-aggregation refers to a phenomenon in which random convection can self-organize into large-scale clusters over an ocean surface with uniform temperature in cloud-resolving models. Previous literature studies convective aggregation primarily by analyzing vertically integrated (VI) moist static energy (MSE) variance. That is the global MSE variance, including both the local MSE variance at a given altitude and the covariance of MSE anomalies between different altitudes. Here we present a vertically resolved (VR) MSE framework that focuses on the local MSE variance to study convective self-aggregation. Using a cloud-resolving simulation, we show that the development of self-aggregation is associated with an increase of local MSE variance, and that the diabatic and adiabatic generation of the MSE variance is mainly dominated by the boundary layer (BL, the lowest 2 km). The results agree with recent numerical simulation results and the available potential energy analyses showing that the BL plays a key role in the development of self-aggregation. Additionally, we find that the lower free troposphere (2 - 4 km) also generates significant MSE variance in the first 15 days. We further present a detailed comparison between the global and local MSE variance frameworks in their mathematical formulation and diagnostic results, highlighting their differences.

scholarly journals Satellite Perspectives of Sea Surface Temperature Diurnal Warming on Atmospheric Moistening and Radiative Heating During MJO

2020 ◽  
pp. 1-56
Author(s):  
Kyle Itterly ◽  
Patrick Taylor ◽  
J. Brent Roberts
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Large Scale ◽  
Active Phase ◽  
Radiative Heating ◽  
Sea Surface ◽  
Integrated Analysis ◽  
Moist Static Energy ◽  
Diurnal Warming ◽  
Static Energy

AbstractDiurnal air-sea coupling affects climate modes such as the Madden-Julian Oscillation (MJO) via the regional moist static energy budget. Prior to MJO initiation, large-scale subsidence increases (decreases) surface shortwave insolation (winds). These act in concert to significantly warm the uppermost layer of the ocean over the course of a single day and the ocean mixed layer over the course of 1-2 weeks. Here, we provide an integrated analysis of multiple surface, top-of-atmosphere, and atmospheric column observations to assess the covariability related to regions of strong diurnal sea surface temperature (dSST) warming over 44 MJO events between 2000-2018 to assess their role in MJO initiation. Combining satellite observations of evaporation and precipitation with reanalysis moisture budget terms, we find 30-50% enhanced moistening over high dSST regions during late afternoon using either ERA5 or MERRA-2 despite large model biases. Diurnally developing moisture convergence, only modestly weaker evaporation, and diurnal minimum precipitation act to locally enhance moistening over broad regions of enhanced diurnal warming, which rectifies onto the larger scale. Field campaign ship and sounding data corroborate that strong dSST periods are associated with reduced middle tropospheric humidity and larger diurnal amplitudes of surface warming, evaporation, instability, and column moistening. Further, we find greater daytime increases in low cloud cover and evidence of enhanced radiative destabilization for the top 50th dSST percentile. Together, these results support that dSST warming acts in concert with large-scale dynamics to enhance moist static energy during the suppressed to active phase transition of the MJO.

scholarly journals Gross Moist Stability Analysis: Assessment of Satellite-Based Products in the GMS Plane

2017 ◽  
Vol 74 (6) ◽  
pp. 1819-1837 ◽  
Author(s):  
Kuniaki Inoue ◽  
Larissa E. Back
Keyword(s):  
Life Cycle ◽  
Phase Plane ◽  
Critical Line ◽  
Time Dependent ◽  
Moist Static Energy ◽  
Geographic Variations ◽  
Moisture Mode ◽  
Gross Moist Stability ◽  
Static Energy ◽  
Diagnostic Applications

Abstract New diagnostic applications of the gross moist stability (GMS) are proposed with demonstrations using satellite-based data. The plane of the divergence of column moist static energy (MSE) against the divergence of column dry static energy (DSE), referred to as the GMS plane here, is utilized. In this plane, one can determine whether the convection is in the amplifying phase or in the decaying phase; if a data point lies below (above) a critical line in the GMS plane, the convection is in the amplifying (decaying) phase. The GMS plane behaves as a phase plane in which each convective life cycle can be viewed as an orbiting fluctuation around the critical line, and this property is robust even on the MJO time scale. This phase-plane behavior indicates that values of the GMS can qualitatively predict the subsequent convective evolution. This study demonstrates that GMS analyses possess two different aspects: time-dependent and quasi-time-independent aspects. Transitions of time-dependent GMS can be visualized in the GMS plane as an orbiting fluctuation around the quasi-time-independent GMS line. The time-dependent GMS must be interpreted differently from the quasi-time-independent one, and the latter is the GMS relevant to moisture-mode theories. The authors listed different calculations of the quasi-time-independent GMS: (i) as a regression slope from a scatterplot and (ii) as a climatological quantity, which is the ratio of climatological MSE divergence to climatological DSE divergence. It is revealed that the latter, climatological GMS, is less appropriate as a diagnostic tool. Geographic variations in the quasi-time-independent GMS are plotted.

Double and Single ITCZs with and without Clouds

2017 ◽  
Vol 30 (22) ◽  
pp. 9147-9166 ◽  
Author(s):  
Max Popp ◽  
Levi G. Silvers
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Convective Available Potential Energy ◽  
Circulation Model ◽  
Hadley Circulation ◽  
Large Scale Circulation ◽  
Low Level ◽  
Convergence Zones ◽  
Gross Moist Stability ◽  
Static Energy

A major bias in tropical precipitation over the Pacific in climate simulations stems from the models’ tendency to produce two strong distinct intertropical convergence zones (ITCZs) too often. Several mechanisms have been proposed that may contribute to the emergence of two ITCZs, but current theories cannot fully explain the bias. This problem is tackled by investigating how the interaction between atmospheric cloud-radiative effects (ACREs) and the large-scale circulation influences the ITCZ position in an atmospheric general circulation model. Simulations are performed in an idealized aquaplanet setup and the longwave and shortwave ACREs are turned off individually or jointly. The low-level moist static energy (MSE) is shown to be a good predictor of the ITCZ position. Therefore, a mechanism is proposed that explains the changes in MSE and thus ITCZ position due to ACREs consistently across simulations. The mechanism implies that the ITCZ moves equatorward if the Hadley circulation strengthens because of the increased upgradient advection of low-level MSE off the equator. The longwave ACRE increases the meridional heating gradient in the tropics and as a response the Hadley circulation strengthens and the ITCZ moves equatorward. The shortwave ACRE has the opposite effect. The total ACRE pulls the ITCZ equatorward. This mechanism is discussed in other frameworks involving convective available potential energy, gross moist stability, and the energy flux equator. It is thus shown that the response of the large-scale circulation to the shortwave and longwave ACREs is a fundamental driver of changes in the ITCZ position.

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