The role of topography and diabatic heating in the formation of dipole blocking in the atmosphere

1989 ◽  
Vol 6 (2) ◽  
pp. 173-185 ◽  
Author(s):  
Luo Dehai ◽  
Ji Liren
Keyword(s):  
Diabatic Heating

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.

scholarly journals A numerical modelling investigation of the role of diabatic heating and cooling in the development of a mid-level vortex prior to tropical cyclogenesis – Part 1: The response to stratiform components of diabatic forcing

2018 ◽  
Vol 18 (19) ◽  
pp. 14393-14416 ◽  
Author(s):  
Melville E. Nicholls ◽  
Roger A. Pielke Sr. ◽  
Donavan Wheeler ◽  
Gustavo Carrio ◽  
Warren P. Smith
Keyword(s):  
Numerical Modelling ◽  
Diabatic Heating ◽  
Tropical Cyclogenesis ◽  
Minor Role ◽  
Microphysics Scheme ◽  
Heating And Cooling ◽  
Physics Simulation ◽  
Diabatic Forcing ◽  
Convective Cells

Abstract. Mid-tropospheric mesoscale convective vortices have been often observed to precede tropical cyclogenesis. Moreover, recent cloud-resolving numerical modelling studies that are initialized with a weak cyclonic mid-tropospheric vortex sometimes show a considerable intensification of the mid-level circulation prior to the development of the strong cyclonic surface winds that characterize tropical cyclogenesis. The objective of this two-part study is to determine the processes that lead to the development of a prominent mid-level vortex during a simulation of the transformation of a tropical disturbance into a tropical depression, in particular the role of diabatic heating and cooling. For simplicity simulations are initialized from a quiescent environment. In this first part, results of the numerical simulation are described and the response to stratiform components of the diabatic forcing is investigated. In the second part, the contribution of diabatic heating in convective cells to the development of the mid-level vortex is examined. Results show that after a period of intense convective activity, merging of anvils from numerous cells creates an expansive stratiform ice region in the upper troposphere, and at its base a mid-level inflow starts to develop. Subsequently conservation of angular momentum leads to strengthening of the mid-level circulation. A 12 h period of mid-level vortex intensification is examined during which the mid-level tangential winds become stronger than those at the surface. The main method employed to determine the role of diabatic forcing in causing the mid-level inflow is to diagnose it from the full physics simulation and then impose it in a simulation with hydrometeors removed and the microphysics scheme turned off. Removal of hydrometeors is achieved primarily through artificially increasing their fall speeds 3 h prior to the 12 h period. This results in a state that is in approximate gradient wind balance, with only a weak secondary circulation. Then, estimates of various components of the diabatic forcing are imposed as source terms in the thermodynamic equation in order to examine the circulations that they independently induce. Sublimation cooling at the base of the stratiform ice region is shown to be the main factor responsible for causing the strong mid-level vortex to develop, with smaller contributions from stratiform heating aloft and low-level melting and evaporation. This contrasts with the findings of previous studies of mid-latitude vortices that indicate sublimation plays a relatively minor role. An unanticipated result is that the central cool region that develops near the melting level is to a large degree due to compensating adiabatic ascent in response to descent driven by diabatic cooling adjacent to the central region, rather than in situ diabatic cooling. The mid-level inflow estimated from stratiform processes is notably weaker than for the full physics simulation, suggesting a moderate contribution from diabatic forcing in convective cells.

scholarly journals Hurricane Eyewall Evolution in a Forced Shallow-Water Model

2014 ◽  
Vol 71 (5) ◽  
pp. 1623-1643 ◽  
Author(s):  
Eric A. Hendricks ◽  
Wayne H. Schubert ◽  
Yu-Han Chen ◽  
Hung-Chi Kuo ◽  
Melinda S. Peng
Keyword(s):  
Shallow Water ◽  
Diabatic Heating ◽  
Nonlinear Evolution ◽  
Unstable Mode ◽  
Relative Vorticity ◽  
Stable Region ◽  
Water Model ◽  
Barotropic Instability ◽  
Shallow Water Model

Abstract A forced shallow-water model is used to understand the role of diabatic and frictional effects in the generation, maintenance, and breakdown of the hurricane eyewall potential vorticity (PV) ring. Diabatic heating is parameterized as an annular mass sink of variable width and magnitude, and the nonlinear evolution of tropical storm–like vortices is examined under this forcing. Diabatic heating produces a strengthening and thinning PV ring in time due to the combined effects of the mass sink and radial PV advection by the induced divergent circulation. If the forcing makes the ring thin enough, then it can become dynamically unstable and break down into polygonal asymmetries or mesovortices. The onset of barotropic instability is marked by simultaneous drops in both the maximum instantaneous velocity and minimum pressure, consistent with unforced studies. However, in a sensitivity test where the heating is proportional to the relative vorticity, universal intensification occurs during barotropic instability, consistent with a recent observational study. Friction is shown to help stabilize the PV ring by reducing the eyewall PV and the unstable-mode barotropic growth rate. The radial location and structure of the heating is shown to be of critical importance for intensity variability. While it is well known that it is critical to heat in the inertially stable region inside the radius of maximum winds to spin up the hurricane vortex, these results demonstrate the additional importance of having the net heating as close as possible to the center of the storm, partially explaining why tropical cyclones with very small eyes can rapidly intensify to high peak intensities.

The role of diabatic heating in maintaining the upper-tropospheric baroclinic zone in the South Pacific

1989 ◽  
Vol 115 (490) ◽  
pp. 1253-1271 ◽  
Author(s):  
Franklin R. Robertson ◽  
Dayton G. Vincent ◽  
Deirdre M. Kann
Keyword(s):  
Diabatic Heating ◽  
South Pacific ◽  
The South ◽  
Baroclinic Zone

scholarly journals Evidence for the role of the diabatic heating in synoptic scale processes: a case study example

1997 ◽  
Vol 15 (4) ◽  
pp. 487-493 ◽  
Author(s):  
M. L. Martin ◽  
M. Y. Luna ◽  
F. Valero
Keyword(s):  
Diabatic Heating ◽  
Potential Temperature ◽  
Principal Component ◽  
Phase Changes ◽  
Synoptic Scale ◽  
Thermodynamic Variable ◽  
Dynamic Forcing ◽  
Diabatic Forcing

Abstract. The quasigeostrophic theory is used to address the role of diabatic forcing in synoptic scale processes over Iberia. A parametrization of diabatic heating is obtained in terms of a thermodynamic variable called the ice-liquid water potential temperature which is conservative under all phase changes of water. A case study objectively selected by means of a rotated principal component analysis over the diabatic field is analyzed to test the proposed parametrization. This study highlights the fact that the magnitudes of diabatic forcing and dynamic forcing are very nearly the same throughout the troposphere. The results also show that the composite diabatic heating is a better representation for both cloudiness and precipitation fields than the dynamic forcing.

scholarly journals African Easterly Wave Dynamics in a Mesoscale Numerical Model: The Upscale Role of Convection

2012 ◽  
Vol 69 (4) ◽  
pp. 1267-1283 ◽  
Author(s):  
Gareth J. Berry ◽  
Chris D. Thorncroft
Keyword(s):  
Composite Structures ◽  
Diabatic Heating ◽  
Weather Prediction ◽  
Phase Speed ◽  
Lower Troposphere ◽  
Life Cycles ◽  
Large Contribution ◽  
African Easterly Wave ◽  
Easterly Wave

Abstract To examine the dynamical role of convection in African easterly wave (AEW) life cycles the Weather Research and Forecasting (WRF) model is used to simulate the evolution of a single AEW from September 2004. The model simulations are validated against corresponding numerical weather prediction analyses and the mean fields closely resemble composite structures from previous studies. A potential vorticity (PV) thinking approach is used to highlight the interactions between dynamics and convection. Organized deep convection embedded within the AEW has a large contribution to the synoptic-scale mean PV and energetics of the AEW. The PV tendency is maximized in the lower troposphere, consistent with the vertical gradient in diabatic heating rates in the areas of convection. By examining terms in the Lorenz energy cycle, it is shown that diabatic heating associated with convection is as important as adiabatic energy conversion in producing eddy available potential energy of the synoptic AEW, implying that AEWs are best described as hybrid adiabatic and diabatic structures. The net effect of convection is succinctly described using a simulation whereby the parameterizations associated with convection are switched off at the midpoint of the model run. This perturbation experiment shows that, although the AEW continues to propagate westward with a similar phase speed, the net PV value continually weakens with time. This result proves that convection is vital for the maintenance of the AEW as it propagates across West Africa and suggests that without active convection the synoptic AEW cannot persist for an extended length of time.

scholarly journals The Quasigeostrophic Omega Equation: Reappraisal, Refinements, and Relevance

2015 ◽  
Vol 143 (1) ◽  
pp. 3-25 ◽  
Author(s):  
Huw C. Davies
Keyword(s):  
Diabatic Heating ◽  
Weather Prediction ◽  
Phase Relationship ◽  
General Utility ◽  
Forcing Function ◽  
Flow Features ◽  
Nwp Model ◽  
Omega Equation ◽  
Q Vector

Abstract A two-component study is undertaken of the classical quasigeostrophic (QG) omega equation. First, a reappraisal is undertaken of extant formulations of the equation’s so-called forcing function. It pinpoints shortcomings of various formulations and prompts consideration of alternative forms. Particular consideration is given to the contribution of flow deformation to the forcing function, and to the role of the advection of the geostrophic flow by the thermal wind (the R vector). The latter is closely related to the Q vector, the horizontal component of the ageostrophic vorticity, and the forcing function itself. The reexamination promotes further examination of the physical interpretation and diagnostic use of the omega equation particularly for assessing richly structured subsynoptic flow features. Second, consideration is given to the dynamics associated with the equation and its more general utility. It is shown that the R vector is intrinsic to a quasigeostrophic cascade to finer-scaled flow, and that a fundamental feature of the QG omega equation—the in-phase relationship between cloud-diabatic heating and the attendant vertical velocity—has important potential ramifications for the assimilation of data in numerical weather prediction (NWP) models. Finally, it is shown that, in the context of considering NWP model output, mild generalizations of the quasigeostrophic R vector retain interpretative value for flow settings beyond geostrophy and warrant consideration when addressing some contemporary NWP challenges.

scholarly journals A dynamic and thermodynamic coupling view of the linkages between Eurasian cooling and Arctic warming

2021 ◽  
Author(s):  
Yongkun Xie ◽  
Guoxiong Wu ◽  
Yimin Liu ◽  
Jianping Huang ◽  
Hanbin Nie
Keyword(s):  
Sea Ice ◽  
Interannual Variability ◽  
Diabatic Heating ◽  
The Arctic ◽  
Sensible Heat ◽  
Arctic Warming ◽  
Enhanced Absorption ◽  
Subsurface Ocean ◽  
Thermodynamic Coupling

AbstractInvestigating the contrast between wintertime warming in the Arctic and cooling in Eurasia is of great importance for understanding regional climate change. In this study, we propose a dynamic and thermodynamic coupling view of the linkages between wintertime Arctic warming and Eurasian cooling since 1979. The key factors are the energy budget at the Earth’s surface, the diabatic heating and baroclinicity of the atmosphere, and subsurface ocean heat. A summertime origin of wintertime Arctic warming suggests a partial driving role of the Arctic in wintertime Eurasian cooling. The reasons for this finding are as follows. First, there is a dipole pattern in the diabatic heating change in winter over the Arctic Ocean corresponding to the anticyclonic circulation that links Eurasian cooling and Arctic warming. Second, the change in diabatic heating of the atmosphere is determined by sensible heat at the Earth’s surface through vertical diffusion. Third, the positive sensible heat change in the eastern Arctic sector in winter originates from the summertime enhanced absorption of solar radiation by the subsurface ocean over the sea ice loss region. Meanwhile, the negative sensible heat change in the western Arctic sector and wide Arctic warming can be explained by the circulation development triggered by the change in the east. Additionally, the background strong baroclinicity of the atmosphere in mid-high latitudes and corresponding two-way Arctic and mid-latitude interactions are necessary for circulation development in winter. Furthermore, the seasonality of the changes indicates that Eurasian cooling occurs only in winter because the diabatic heating change in the Arctic is strongest in winter. Overall, the comprehensive mechanisms from the summertime Earth’s surface and subsurface ocean to the wintertime atmosphere suggest a driving role of the Arctic. Note that the situation in interannual variability is more complex than the overall trend because the persistence of the influence of summertime sea ice is weakly established in terms of interannual variability.

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