Relationship between the Subtropical Anticyclone and Diabatic Heating

2004 ◽  
Vol 17 (4) ◽  
pp. 682-698 ◽  
Author(s):  
Yimin Liu ◽  
Guoxiong Wu ◽  
Rongcai Ren
Keyword(s):  
Diabatic Heating ◽  
Subtropical Anticyclone

scholarly journals The influence of direct radiative forcing versus indirect sea surface temperature warming on southern hemisphere subtropical anticyclones under global warming

2021 ◽  
Author(s):  
Abdullah A. Fahad ◽  
Natalie J. Burls
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Southern Hemisphere ◽  
Radiative Forcing ◽  
Diabatic Heating ◽  
Sea Surface ◽  
Atmospheric Response ◽  
Austral Winter ◽  
Subtropical Anticyclone ◽  
Surface Temperature Warming

AbstractSouthern hemisphere subtropical anticyclones are projected to change in a warmer climate during both austral summer and winter. A recent study of CMIP 5 & 6 projections found a combination of local diabatic heating changes and static-stability-induced changes in baroclinic eddy growth as the dominant drivers. Yet the underlying mechanisms forcing these changes still remain uninvestigated. This study aims to enhance our mechanistic understanding of what drives these Southern Hemisphere anticyclones changes during both seasons. Using an AGCM, we decompose the response to CO2-induced warming into two components: (1) the fast atmospheric response to direct CO2 radiative forcing, and (2) the slow atmospheric response due to indirect sea surface temperature warming. Additionally, we isolate the influence of tropical diabatic heating with AGCM added heating experiments. As a complement to our numerical AGCM experiments, we analyze the Atmospheric and Cloud Feedback Model Intercomparison Project experiments. Results from sensitivity experiments show that slow subtropical sea surface temperature warming primarily forces the projected changes in subtropical anticyclones through baroclinicity change. Fast CO2 atmospheric radiative forcing on the other hand plays a secondary role, with the most notable exception being the South Atlantic subtropical anticyclone in austral winter, where it opposes the forcing by sea surface temperature changes resulting in a muted net response. Lastly, we find that tropical diabatic heating changes only significantly influence Southern Hemisphere subtropical anticyclone changes through tropospheric wind shear changes during austral winter.

scholarly journals Mechanisms of Meridional Teleconnection Observed between a Summer Monsoon System and a Subtropical Anticyclone. Part I: The Pacific–Japan Pattern

2010 ◽  
Vol 23 (19) ◽  
pp. 5085-5108 ◽  
Author(s):  
Yu Kosaka ◽  
Hisashi Nakamura
Keyword(s):  
Energy Conversion ◽  
Diabatic Heating ◽  
Lower Troposphere ◽  
The Philippines ◽  
Convective Activity ◽  
Mean Flow ◽  
Subtropical Anticyclone ◽  
The Pacific ◽  
Monsoon System ◽  
Dynamical Mode

Abstract Summertime atmospheric circulation over the midlatitude western North Pacific (WNP) is influenced by anomalous convective activity near the Philippines. This meridional teleconnection, observed in monthly anomalies and known as the Pacific–Japan (PJ) pattern, is characterized by zonally elongated cyclonic and anticyclonic anomalies around the enhanced convection center and to its northeast, respectively, in the lower troposphere, with an apparent poleward phase tilt with height. The authors’ idealized two-layer linear model, whose basic state consists of a zonal subtropical jet and a pair of a monsoon system and a subtropical anticyclone, can simulate a PJ-like response against diabatic heating located between the pair. Each of the observed and simulated patterns can gain energy through barotropic and baroclinic conversions from the zonally varying baroclinic mean flow, in an efficiency comparable with that of energy generation due to the anomalous diabatic heating, indicating a characteristic of the pattern as a dry dynamical mode. In fact, the conversion efficiency is sensitive to the location of the anomaly pattern relative to the climatological-mean flow. Furthermore, the second-least damped mode identified in the idealized model bears certain resemblance with the observed PJ pattern, indicating its modal characteristics as well as a critical importance of these features in the mean field for the pattern. In addition to the PJ pattern, another meridional teleconnection pattern with high efficiency for its energy conversion is identified observationally in association with anomalous convection near the Bonin Islands. The anomalous circulation of the PJ pattern, in turn, can intensify the anomalous convective activity near the Philippines through enhancing evaporation and moisture convergence and dynamically inducing anomalous ascent. It is thus hypothesized that the PJ pattern can be regarded as a moist dynamical mode that sustains itself both via dry energy conversion and interaction with moist processes.

scholarly journals Responses of the Summertime Subtropical Anticyclones to Global Warming

2017 ◽  
Vol 30 (16) ◽  
pp. 6465-6479 ◽  
Author(s):  
Chao He ◽  
Bo Wu ◽  
Liwei Zou ◽  
Tianjun Zhou
Keyword(s):  
Global Warming ◽  
North Atlantic ◽  
North Pacific ◽  
Diabatic Heating ◽  
South Pacific ◽  
Static Stability ◽  
Subtropical Anticyclone ◽  
The North ◽  
The North Atlantic ◽  
The North Pacific

Subtropical anticyclones dominate the subtropical ocean basins in summer. Using the multimodel output from phase 5 of the Coupled Model Intercomparison Project (CMIP5), the future changes of the subtropical anticyclones as a response to global warming are investigated, based on the changes in subsidence, low-level divergence, and rotational wind. The subtropical anticyclones over the North Pacific, South Atlantic, and south Indian Ocean are projected to become weaker, whereas the North Atlantic subtropical anticyclone (NASA) intensifies, and the South Pacific subtropical anticyclone (SPSA) shows uncertainty but is likely to intensify. Diagnostic analyses and idealized simulations suggest that the projected changes in the subtropical anticyclones are well explained by the combined effect of increased tropospheric static stability and changes in diabatic heating. Increased static stability acts to reduce the intensity of all the subtropical anticyclones, through the positive mean advection of stratification change (MASC) over the subsidence regions of the subtropical anticyclones. The pattern of change in diabatic heating is dominated by latent heating associated with changes in precipitation, which is enhanced over the western North Pacific under the “richest get richer” mechanism but is reduced over subtropical North Atlantic and South Pacific due to a local minimum of SST warming amplitude. The change in the diabatic heating pattern substantially enhances the subtropical anticyclones over the North Atlantic and South Pacific but weakens the North Pacific subtropical anticyclone.

scholarly journals Subseasonal relationship between Arctic and Eurasian surface air temperature

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hye-Jin Kim ◽  
Seok-Woo Son ◽  
Woosok Moon ◽  
Jong-Seong Kug ◽  
Jaeyoung Hwang
Keyword(s):  
Air Temperature ◽  
Diabatic Heating ◽  
Surface Air Temperature ◽  
Significant Negative Correlation ◽  
Cold Season ◽  
Reanalysis Data ◽  
Necessary Condition ◽  
Sea Level Pressure ◽  
Blocking High ◽  
Pressure Anomaly

AbstractThe subseasonal relationship between Arctic and Eurasian surface air temperature (SAT) is re-examined using reanalysis data. Consistent with previous studies, a significant negative correlation is observed in cold season from November to February, but with a local minimum in late December. This relationship is dominated not only by the warm Arctic-cold Eurasia (WACE) pattern, which becomes more frequent during the last two decades, but also by the cold Arctic-warm Eurasia (CAWE) pattern. The budget analyses reveal that both WACE and CAWE patterns are primarily driven by the temperature advection associated with sea level pressure anomaly over the Ural region, partly cancelled by the diabatic heating. It is further found that, although the anticyclonic anomaly of WACE pattern mostly represents the Ural blocking, about 20% of WACE cases are associated with non-blocking high pressure systems. This result indicates that the Ural blocking is not a necessary condition for the WACE pattern, highlighting the importance of transient weather systems in the subseasonal Arctic-Eurasian SAT co-variability.

scholarly journals Diabatic heating governs the seasonality of the Atlantic Niño

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hyacinth C. Nnamchi ◽  
Mojib Latif ◽  
Noel S. Keenlyside ◽  
Joakim Kjellsson ◽  
Ingo Richter
Keyword(s):  
Feedback Loop ◽  
Diabatic Heating ◽  
Seasonal Migration ◽  
Equatorial Atlantic ◽  
Bjerknes Feedback ◽  
Atlantic Sector ◽  
Inter Tropical Convergence Zone ◽  
Sst Variability ◽  
Leading Mode ◽  
Atlantic Niño

AbstractThe Atlantic Niño is the leading mode of interannual sea-surface temperature (SST) variability in the equatorial Atlantic and assumed to be largely governed by coupled ocean-atmosphere dynamics described by the Bjerknes-feedback loop. However, the role of the atmospheric diabatic heating, which can be either an indicator of the atmosphere’s response to, or its influence on the SST, is poorly understood. Here, using satellite-era observations from 1982–2015, we show that diabatic heating variability associated with the seasonal migration of the Inter-Tropical Convergence Zone controls the seasonality of the Atlantic Niño. The variability in precipitation, a measure of vertically integrated diabatic heating, leads that in SST, whereas the atmospheric response to SST variability is relatively weak. Our findings imply that the oceanic impact on the atmosphere is smaller than previously thought, questioning the relevance of the classical Bjerknes-feedback loop for the Atlantic Niño and limiting climate predictability over the equatorial Atlantic sector.

scholarly journals Systematic Variation in Wintertime Precipitation in East Asia by MJO-Induced Extratropical Vertical Motion

2008 ◽  
Vol 21 (4) ◽  
pp. 788-801 ◽  
Author(s):  
Jee-Hoon Jeong ◽  
Baek-Min Kim ◽  
Chang-Hoi Ho ◽  
Yeon-Hee Noh
Keyword(s):  
East Asia ◽  
Large Scale ◽  
Diabatic Heating ◽  
Daily Precipitation ◽  
Lower Troposphere ◽  
Vertical Motion ◽  
Mean Value ◽  
Asian Countries ◽  
The Indian Ocean ◽  
Omega Equation

Abstract The variations in the wintertime precipitation over East Asia and the related large-scale circulation associated with the Madden–Julian oscillation (MJO) are examined. By analyzing the observed daily precipitation for the period 1974–2000, it is found that the MJO significantly modulates the distribution of precipitation over four East Asian countries; the precipitation rate difference between wet and dry periods over East Asia, when the centers of MJO convective activities are located over the Indian Ocean and western Pacific, respectively, reaches 3–4 mm day−1, which corresponds to the climatological winter-mean value. Composite analysis with respect to the MJO suggests that the MJO–precipitation relation is mostly explained by the strong vertical motion anomalies near an entrance region of the East Asia upper-tropospheric jet and moisture supply in the lower troposphere. To elucidate different dynamic origins of the vertical motion generated by the MJO, diagnostic analysis of a generalized omega equation is adopted. It is revealed that about half of the vertical motion anomalies in East Asia are induced by the quasigeostrophic forcings by the MJO, while diabatic heating forcings explain a very small fraction, less than 10% of total anomalies.

scholarly journals Influential Role of Moisture Supply from the Kuroshio/Kuroshio Extension in the Rapid Development of an Extratropical Cyclone

2015 ◽  
Vol 143 (10) ◽  
pp. 4126-4144 ◽  
Author(s):  
Hidetaka Hirata ◽  
Ryuichi Kawamura ◽  
Masaya Kato ◽  
Taro Shinoda
Keyword(s):  
Diabatic Heating ◽  
Rapid Development ◽  
Kuroshio Extension ◽  
Lower Troposphere ◽  
Active Role ◽  
Conveyor Belt ◽  
Synoptic Scale ◽  
Warm Front ◽  
The Kuroshio

Abstract This study focused on an explosive cyclone migrating along the southern periphery of the Kuroshio/Kuroshio Extension in the middle of January 2013 and examined how those warm currents played an active role in the rapid development of the cyclone using a high-resolution coupled atmosphere–ocean regional model. The evolutions of surface fronts of the simulated cyclone resemble the Shapiro–Keyser model. At the time of the maximum deepening rate, strong mesoscale diabatic heating areas appear over the bent-back front and the warm front east of the cyclone center. Diabatic heating over the bent-back front and the eastern warm front is mainly induced by the condensation of moisture imported by the cold conveyor belt (CCB) and the warm conveyor belt (WCB), respectively. The dry air parcels transported by the CCB can receive large amounts of moisture from the warm currents, whereas the very humid air parcels transported by the WCB can hardly be modified by those currents. The well-organized nature of the CCB plays a key role not only in enhancing surface evaporation from the warm currents but also in importing the evaporated vapor into the bent-back front. The imported vapor converges at the bent-back front, leading to latent heat release. The latent heating facilitates the cyclone’s development through the production of positive potential vorticity in the lower troposphere. Its deepening can, in turn, reinforce the CCB. In the presence of a favorable synoptic-scale environment, such a positive feedback process can lead to the rapid intensification of a cyclone over warm currents.

Modulation of coupled modes of Tibetan Plateau heating and Indian Summer Monsoon on summer rainfall over Central Asia

2021 ◽  
pp. 1-54
Keyword(s):  
Water Vapor ◽  
Tibetan Plateau ◽  
Central Asia ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Diabatic Heating ◽  
Summer Rainfall ◽  
Hadley Cell ◽  
Vapor Transport ◽  
Water Vapor Transport

Abstract It has been suggested that summer rainfall over Central Asia (CA) is significantly correlated with the summer thermal distribution of the Tibetan Plateau (TP) and the Indian summer monsoon (ISM). However, relatively few studies have investigated their synergistic effects of different distribution. This study documents the significant correlations between precipitation in CA and the diabatic heating of TP and the ISM based on the results of statistical analysis and numerical simulation. Precipitation in CA is is dominated by two water vapor transport branches from the south which are related to the two primary modes of anomalous diabatic heating distribution related to the TP and ISM precipitation, that is, the “+-” dipole mode in the southeastern TP and the Indian subcontinent (IS), and the “+-+” tripole mode in the southeastern TP, the IS, and southern India. Both modes exhibit obvious mid-latitude Silk Road pattern (SRP) wave trains with cyclone anomalies over CA, but with different transient and stationary eddies over south Asia. The different locations of anomalous anticyclones over India govern two water vapor transport branches to CA, which are from the Arabian Sea and the Bay of Bengal. The water vapor flux climbs while being transported northward and can be transported to CA with the cooperation of cyclonic circulation. The convergent water vapor and ascending motion caused by cyclonic anomalies favor the precipitation in CA. Further analysis corroborates the negative South Indian Ocean Dipole (NSIOD) in February could affect the tripole mode distribution of TP heating and ISM via the atmospheric circulation, water vapor transport and an anomalous Hadley cell circulation. The results indicate a reliable prediction reference for precipitation in CA.

The Intensity- and Size-Dependent Response of Tropical Cyclones to Increasing Vertical Wind Shear

2021 ◽  
Author(s):  
Peter M. Finocchio ◽  
Rosimar Rios-Berrios
Keyword(s):  
Wind Field ◽  
Wind Shear ◽  
Diabatic Heating ◽  
Inner Core ◽  
Potential Temperature ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Rapid Intensification ◽  
Vertical Coupling ◽  
Tangential Wind

AbstractThis study describes a set of idealized simulations in which westerly vertical wind shear increases from 3 to 15 m s−1 at different stages in the lifecycle of an intensifying tropical cyclone (TC). The TC response to increasing shear depends on the intensity and size of the TC’s tangential wind field when shear starts to increase. For a weak tropical storm, increasing shear decouples the vortex and prevents intensification. For Category 1 and stronger storms, increasing shear causes a period of weakening during which vortex tilt increases by 10–30 km before the TCs reach a near-steady Category 1–3 intensity at the end of the simulations. TCs exposed to increasing shear during or just after rapid intensification tend to weaken the most. Backward trajectories reveal a lateral ventilation pathway between 8–11 km altitude that is capable of reducing equivalent potential temperature in the inner core of these TCs by nearly 2°C. In addition, these TCs exhibit large reductions in diabatic heating inside the radius of maximum winds (RMW) and lower-entropy air parcels entering downshear updrafts from the boundary layer, which further contributes to their substantial weakening. The TCs exposed to increasing shear after rapid intensification and an expansion of the outer wind field reach the strongest near-steady intensity long after the shear increases because of strong vertical coupling that prevents the development of large vortex tilt, resistance to lateral ventilation through a deep layer of the middle troposphere, and robust diabatic heating within the RMW.

Why does rapid contraction of the radius of maximum wind precede rapid intensification in tropical cyclones?

2021 ◽  
Author(s):  
Yuanlong Li ◽  
Yuqing Wang ◽  
Yanluan Lin ◽  
Xin Wang
Keyword(s):  
Tropical Cyclones ◽  
Radial Distribution ◽  
Diabatic Heating ◽  
Rate Of Change ◽  
Rapid Intensification ◽  
Absolute Vorticity ◽  
Radial Gradient ◽  
Maximum Wind ◽  
Tangential Wind ◽  
Vorticity Flux

AbstractThe radius of maximum wind (RMW) has been found to contract rapidly well preceding rapid intensification in tropical cyclones (TCs) in recent literature but the understanding of the involved dynamics is incomplete. In this study, this phenomenon is revisited based on ensemble axisymmetric numerical simulations. Consistent with previous studies, because the absolute angular momentum (AAM) is not conserved following the RMW, the phenomenon can not be understood based on the AAM-based dynamics. Both budgets of tangential wind and the rate of change in the RMW are shown to provide dynamical insights into the simulated relationship between the rapid intensification and rapid RMW contraction. During the rapid RMW contraction stage, due to the weak TC intensity and large RMW, the moderate negative radial gradient of radial vorticity flux and small curvature of the radial distribution of tangential wind near the RMW favor rapid RMW contraction but weak diabatic heating far inside the RMW leads to weak low-level inflow and small radial absolute vorticity flux near the RMW and thus a relatively small intensification rate. As RMW contraction continues and TC intensity increases, diabatic heating inside the RMW and radial inflow near the RMW increase, leading to a substantial increase in radial absolute vorticity flux near the RMW and thus the rapid TC intensification. However, the RMW contraction rate decreases rapidly due to the rapid increase in the curvature of the radial distribution of tangential wind near the RMW as the TC intensifies rapidly and RMW decreases.

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