Role Of Diabatic Heating Research Articles

Diagnostic Analysis of Diabatic Heating in an Extreme Rainfall Event in Shandong Province, China

This study utilizes data from national ground meteorological observation stations in Shandong province, Fengyun-4 satellite data, and ERA5 reanalysis data. Through the calculation of atmospheric heat source changes, the role of diabatic heating in the occurrence and development of heavy rainfall is revealed. The widespread heavy-to-torrential rainfall event in Shandong province on 25 June 2018 is analyzed as a case study. It was found that a deep and robust southwest jet stream was the key system for the formation of this rainfall event. Satellite cloud images during the peak rainfall period showed vigorous development in the rainfall cloud region. During the concentrated rainfall period and when the low-altitude jet stream strengthened, there was mostly cold advection overhead at the observation station. The low-altitude jet stream transported moisture, increasing the humidity gradient, thus enhancing frontogenesis. The warm advection in the low-altitude jet stream was not the main energy supplier during heavy rainfall, and local temperature variations were the primary contributors to the thermodynamic conditions during the peak rainfall period. The rate of warming caused by the condensation and release of heat from water vapor significantly increased during the concentrated rainfall period. This warming effect played a heating role in the middle and lower layers, and the positive feedback from the latent heat release of water vapor condensation intensified the weather system affecting the rainfall, providing strong thermodynamic and dynamic conditions for heavy rainfall.

Diabatic Heat Effects on the Generation of Energy for Evolution of a SACZ Event: A Perspective from the Lorenz Energy Cycle

Abstract Here we used meteorological datasets from ERA5 to study the dynamic and thermodynamic characteristics of a SACZ event that occurred between 12 and 26 December 2013. This is an atypical SACZ episode with considerable variations in cloudiness band positioning and high rainfall amounts, causing enormous problems for society. We study this case through the Lorenz energy cycle (LEC), focusing mainly on the role of diabatic heating in energy generation and consequently in circulation aspects, analyzing the event in three stages (formation, development, and dissipation), and discussing it according to the convection localization pattern. The diabatic heat rate has a large impact on the energy generation of SACZ events at midlevels south of 24°S and below 900 hPa in the tropics. In LEC, the generation terms in the SACZ area were larger at the beginning (12–15 December) and smaller at the ending periods (23–26 December), with means of 21.23 and −7.62 W m−2, respectively. The conversion terms follow the LEC directions, except for barotropic instability [C(KE, KM) < 0] that dominates throughout the analyzed periods. The convection area expansion to the north between 16 and 22 December was reflected by the most intense heating in the tropics and weaker barotropic instability. The friction term did not favor the event decay; therefore, we concluded that the cooling through a negative covariance between Q and T contributed to the event decay. We find that these results were largely influenced by a midlatitude wave train configuration that acted to favor the persistence, expansion, and decay of the event.

Formation of the northern East Asian low: role of diabatic heating

The northern East Asian low (NEAL), characterized by a mid-latitude closed low (or trough) in the lower troposphere, is an important component of the East Asian summer monsoon system. This study investigates formation mechanism of the summer NEAL, with emphasis on the roles of diabatic heating and transient eddy forcing, using a linear baroclinic model (LBM) with prescribed forcing derived from the National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) dataset during the 1979–2010 period. The LBM simulations show that the formation of NEAL is induced by the diabatic heating, and the effect of transient eddy forcing is negligible. Further investigation indicates that the diabatic heating over northern East Asia (NEA) is the key factor for the NEAL’s formation, in which the latent heating and radiative cooling in concert to play a major role and the vertical diffusion sensible heating plays a secondary role. In response to the NEA diabatic heating (latent and sensible heating), a local northerly is induced that advects cold air to partially balance the diabatic heat source and forms a low to the east. On the other hand, the radiative cooling induces a southerly anomaly over NEA, shaping the position and intensity of the low induced by the latent and sensible heating. The total effect of the diabatic heating and radiative cooling causes a closed NEAL. Results are similar for the NEAL’s formation in June, July, and August, respectively. Moreover, we further investigate sub-seasonal change of the NEAL in summer. The weakened intensity of the NEAL in August, relative to that in June and July, is contributed to mainly by the enhanced offset effect of the radiative cooling over NEA and partially by the weakened impact of the latent and diffusion sensible heating.

The Role of Diabatic Heating in Ferrel Cell Dynamics

AbstractThe Ferrel cell consists of the zonal mean vertical and meridional winds in the midlatitudes. The continuity of the Ferrel circulation and the zonal mean momentum and heat budgets imply a collocation of the eddy‐driven jet and poleward eddy heat flux maxima, under certain assumptions, including the negligibility of diabatic heating. The latter assumption is questioned, since midlatitude storms are associated with latent heating in the midtroposphere. In this study, the heat budget of the Ferrel cell in both hemispheres is examined, using the JRA55 reanalysis data set. The diabatic heating rate is significant close to the center of the Ferrel cell during winter and at the ascending branch during summer in both hemispheres. The interannual variability shows a positive correlation between the diabatic heating rate in the midlatitude midtroposphere and the latitudinal separation between the eddy heat flux and the eddy‐driven jet maxima during winter in both hemispheres.

Diabatic Heating and Convective Asymmetries During Rapid Intensity Changes of Tropical Cyclones Over North Indian Ocean

ABSTRACT Rapid changes in Tropical Cyclone (TC) structure and intensity are the most difficult aspects of TC forecasting. The intensity and structural changes associated with rapid intensification (RI) and rapid weakening (RW) instances of TCs of North Indian Ocean (NIO) are analysed based on 5 cases each for RI and RW. The vertical profiles of heat (Q1) and moisture (Q2) based on heat and moisture budget equations are analysed to bring out the role of diabatic heating during the RI and RW processes. The associated structural changes are analysed based on the Fourier first order wave number-1 asymmetry in the precipitation patterns associated with RI and RW instances. During RI process, there are 2 predominant Q1 maxima associated with latent heat release near the TC centre, one in the upper troposphere and the other in the lower troposphere. During RW process, there is a single dominant Q1 and Q2 maxima in the mid-troposphere. Regarding the structural changes, there is a pronounced front-back asymmetry in both RI and RW cases. The asymmetry amplitude in the inner core is lower in the case of RI events but, is quite high for RW events. Thus, RW events are characterised by large convective asymmetry.

North Atlantic Extratropical Rossby Wave Breaking during the Warm Season: Wave Life Cycle and Role of Diabatic Heating

This study investigates the life cycle of anticyclonic Rossby wave breaking during the extended warm season (July–October) over the North Atlantic basin. It was found that upper-tropospheric breaking waves are coupled with lower-level perturbations and can be traced back to a wave train that extends from the North Pacific. The overturning of potential vorticity (PV) contours during wave breaking is associated with the rapid development of an upper-level ridge, which occurs along the east coast of North America and over a warm and moist airstream. The ridge development is investigated using the PV budget analysis and trajectory analysis. The PV budget analysis suggests that the horizontal advection of PV by the perturbed flow dictates the movement and the later decay of the ridge. The ridge amplification, opposed by the horizontal advection of PV, is driven by the vertical advection and the diabatic production of PV, both of which are connected to diabatic heating. The vital role of diabatic heating in the ridge amplification is corroborated by the trajectory analysis. The analysis suggests that diabatic heating reduces the static stability near the tropopause and contributes to the ridge-related negative PV anomalies. The role of diabatic heating in anticyclonic and cyclonic wave breaking in other regions is also discussed. The findings suggest that moist diabatic processes, which were often excluded from the earlier studies of wave breaking, are crucial for Rossby wave breaking during the warm season. The updated understanding of wave breaking may benefit weather forecasting and climate predictions.

Equatorial Mean Zonal Wind in a Global Nonhydrostatic Aquaplanet Experiment

Timeaveraged zonalmean equatorial winds in an aquaplanet experiment were investigated using 30day simulation data from a global 7km mesh nonhydrostatic experiment with explicit moist physics. The simulated mean winds included equatorial easterly (westerly) in the lower (upper) troposphere and Hadley cells with a single upward branch on the equator. The mean zonal wind in the equatorial region, where moist convection was abundant, was investigated in detail. Each term of the momentum equation for the mean zonal wind was diagnosed. The advection terms were the major components that maintained the simulated mean wind.The advection terms were divided into those associated with mean (zonal and temporal) and deviation winds. In the equatorial region (1°N-1°S), the advection due to deviation winds led to westerly acceleration, which was balanced by the vertical transport of lowlevel easterly through mean upward motion. To identify the primary source of the westerly acceleration, deviation winds were decomposed into several classes by zonal scales, and momentum flux divergence was calculated for each class. The role of diabatic heating was also examined in a similar way. It was found that the momentum transport associated with planetaryscale disturbances was the primary source in the upper troposphere, of which moist Kelvin wave modes accounted for a significant part. In the middle to lower troposphere, synopticscale and mesoscale components were responsible for the westerly acceleration. It was also found that the westerly acceleration in the upper (middle to lower) troposphere by deviation winds mainly occurred on cloudfree (convective) grid points.

The Role of diabatic heating, torques and stabilities in forcing the radial- vertical circulation within cyclones part iii: case study of lee-side cyclones

Two phases of extratropical cyclone development identified in previous mass and angular momentum budget studies have been confirmed through the numerical simulations of the azimuthally-averaged mass-weighted radial motion within two leeside cyclones: a Mediterranean and an Alberta cyclone. In the Mediterranean cyclone, a moist baroclinic phase is identified with inward (outward) mass and storm angular momentum transport in the lower (higher) value isentropic layers. The mass and storm angular momentum are then transported diabatically from lower to higher value isentropic layers through latent heat release. In addition, storm angular momentum is transferred horizontally across the inclined isentropic surfaces by pressure stresses due to the paired negative and positive pressure torque in lower and higher value isentropic layers respectively. A dry-leeside baroclinic phase is identified in the early stage of the Alberta cyclone with inward (outward) transport of mass and angular momentum in the higher (lower) value isentropic layers. The redistribution of angular momentum is associated with the virtual transfer by torques. A transition from dry to moist phase is identified in the life cycle of the Alberta cyclone.

The role of diabatic heating, torques and stabilities in forcing the radial-vertical circulation within cyclones part ii: case study of extratropical and tropical cyclones

Utilizing Eliassen's concepts, the forcing of the isentropic azimuthally-averaged mass-weighted radial-vertical circulation by diabatic heating and torques within an extratropical cyclone and a typhoon was studied through numerical simulations based on the linear diagnostic equation derived previously. The structure of the forcing associated with diabatic heating and torques was determined from quasi-Lagrangian diagnostic analyses of actual case studies. The two cyclones studied were the Ohio extratropical cyclone of 25-27 January 1978 and typhoon Nancy of 18-23 September 1979. The Ohio cyclone, which formed over the Gulf Coast and moved through Ohio and eastern Michigan, was one of the most intense storms with blizzard conditions to ever occur in this region. Typhoon Nancy which occurred over the South China Sea during the FGGE year was selected since relatively high quality assimilated data were available. Within the Ohio cyclone, the dominant internal processes forcing the mean circulation with embedded relatively strong hydrodynamic stability were the pressure torque associated with baroclinic (asymmetric) structure and the horizontal eddy angular momentum transport associated with the typical S-shaped thermal and wind structures of self-development. Within typhoon Nancy, the dominant internal process forcing the mean circulation with embedded weak hydrodynamic stability was the latent heat release. This analysis shows that the simulated azimuthally-averaged mass-weighted radial motions within these two cyclones agree quite well with the “ observed≓ azimuthally-averaged mass-weighted radial motions. This isentropic numerical study also provides insight into the relatively important internal forcing processes and the trade off between forcing and stability within both extratropical and tropical cyclones.

Tropical Cyclone Motion and Evolution in Vertical Shear

Abstract The motion and the evolution of tropical cyclone-like vortices in an environmental flow with vertical shear are investigated using a baroclinic primitive equation model. The study focuses on the fundamental dynamics of a baroclinic vortex in vertical shear, the influence of vortex structure, and the role of diabatic heating. The results show that the initial response of the vortex to the vertical shear is to tilt downshear. As soon as the tilt develops, the upper-level anticyclonic and lower-level cyclonic circulations begin to interact with each other. As a result of these interactions, the tilted axis of the vortex reaches a stable state after an initial adjustment, which varies with the structure of the vortex, its environmental flow shear, and the cumulus convective heating. The motion of an adiabatic vortex in vertical shear is controlled by both the steering of the environmental flow and vertical coupling mechanisms. Most of the vortices move with the environmental flow at about 650 hPa or ...

Factors Affecting Synoptic-Scale Vertical Motions: A Statistical Study Using a Generalized Omega Equation

Abstract Processes affecting synoptic-scale vertical motions are investigated using as the main tool a generalized omega equation that assumes only hydrostatic balance. This equation and the adiabatic quasigeostrophic (QG) omega equation were solved in a global domain for six synoptic times in February 1979 using spectral truncation T63. The results are portrayed in the form of statistical quantities calculated for four latitude belts in the Northern Hemisphere and Tropics. In the mid- and upper troposphere, the average correlation between the QG and generalized vertical motions is near 0.85 in high latitudes (60°–90°N), roughly 0.7 in midlatitudes (30°–60°N), and slightly over 0.6 in the subtropics (15°–30°N). In these zones, ageostrophic temperature and vorticity advections explain an appreciable part of the nonquasigeostrophic vertical motions. In the Tropics (15°S- 15°N), where the role of diabatic heating is dominant, the QG and generalized solutions correlate only very weakly. In the mid- and high l...

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

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

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

AbstractA modified set of ECMWF FGGE level III‐b analyses is used to examine the four‐dimensional structure of the region containing the South Pacific convergence zone (SPCZ) during a period when two cyclones form in the tropics and propagate south‐eastward along the SPCZ into middle latitudes. During this period. 10–18 January 1979, the atmosphere is characterized by a highly baroclinic state which, together with the existence of an upper tropospheric subtropical jet, supports the growth and development of the observed cyclone activity. In a previous study, it was found that convective activity was prominent during the life cycle of each cyclone.The goal of the present study is to examine the significance of kinematic and thermodynamic processes in maintaining the upper baroclinic region coincident with the subtropical jet. This baroclinic zone lies just poleward of the warm core associated with the convectively‐active SPCZ. A partitioned form of the fronto‐genetical function is used to diagnose the adiabatic and diabatic contributions to the maintenance of baroclinicity in the vicinity of the SPCZ. A major balance is found between the frontogenetical contribution by differential diabatic heating and the opposing diabatic tilting processes. In contrast to the results of most mid‐latitude cyclone studies, the adiabatic contributions from the deformation and tilting terms appear to be of lesser importance. Also, the contribution from the deformation associated with the horizontal branch of the diabatically forced circulation is found to be relatively unimportant. The latter finding is in disagreement with some previously reported numerical results concerned with middle latitude moist frontogenesis. Possible reasons for these differences are discussed.