scholarly journals Sensitivity of Tropical Cyclone Track Simulation over the Western North Pacific to Different Heating/Drying Rates in the Betts–Miller–Janjić Scheme

2015 ◽  
Vol 143 (9) ◽  
pp. 3478-3494 ◽  
Author(s):  
Yuan Sun ◽  
Zhong Zhong ◽  
Hong Dong ◽  
Jian Shi ◽  
Yijia Hu
Keyword(s):  
Tropical Cyclone ◽  
Large Scale ◽  
Lower Troposphere ◽  
Western Pacific Subtropical High ◽  
Cumulus Parameterization ◽  
Weather Research And Forecasting ◽  
Upper Troposphere ◽  
Steering Flow ◽  
Correct Representation ◽  
Drying Rates

Abstract The Weather Research and Forecasting Model is employed to examine the sensitivity of simulated tropical cyclone (TC) motion and associated intensity of the western Pacific subtropical high (WSPH) to different heating and drying rates in the Betts–Miller–Janjić (BMJ) cumulus parameterization (CP) scheme. A case study of Tropical Cyclone Megi (2010) is performed. Results indicate that the simulated WPSH strengthens as the heating/drying effects of the BMJ decrease. A strong WPSH subsequently leads to changes in the large-scale steering flow in its southern edge and delays the northward turning of the simulated storm. The associated physical mechanism is revealed. As the heating/drying is overestimated in the BMJ, the model produces unrealistic drying below 500 hPa whereas the atmosphere becomes moist above 500 hPa. Drying in the lower troposphere hinders the activation of the microphysics while moistening in the upper troposphere facilitates the microphysics. As a result, the model generates extensive anvil clouds that extend far away from the TC center and reach the upper troposphere over the WPSH. This leads to a warming in the upper troposphere due to condensation in the anvil clouds, and a cooling in the lower troposphere due to precipitation evaporation below the anvil clouds. Subsequently, the WPSH weakens and the large-scale steering flow becomes anomalously northward, leading to an early recurvature of TC Megi. Results of this study emphasize the importance of a correct representation of anvil clouds in simulating the WPSH and TC track. This study also implies that correcting the heating/drying can be an effective way to reduce errors in simulating the WPSH and TC motion.

scholarly journals Why Are Tropical Cyclone Tracks over the Western North Pacific Sensitive to the Cumulus Parameterization Scheme in Regional Climate Modeling? A Case Study for Megi (2010)

2014 ◽  
Vol 142 (3) ◽  
pp. 1240-1249 ◽  
Author(s):  
Yuan Sun ◽  
Zhong Zhong ◽  
Wei Lu ◽  
Yijia Hu
Keyword(s):  
Tropical Cyclone ◽  
Climate Modeling ◽  
Deep Convection ◽  
Regional Climate ◽  
Lower Troposphere ◽  
Western Pacific Subtropical High ◽  
Regional Climate Modeling ◽  
Cumulus Parameterization ◽  
Parameterization Schemes ◽  
Cumulus Parameterization Schemes

Abstract The Weather Research and Forecasting Model is employed to simulate Tropical Cyclone (TC) Megi (2010) using the Grell–Devenyi (GD) and Betts–Miller–Janjić (BMJ) cumulus parameterization schemes, respectively. The TC track can be well reproduced with the GD scheme, whereas it turns earlier than observations with the BMJ scheme. The physical mechanism behind different performances of the two cumulus parameterization schemes in the TC simulation is revealed. The failure in the simulation of the TC track with the BMJ scheme is attributed to the overestimation of anvil clouds, which extend far away from the TC center and reach the area of the western Pacific subtropical high (WPSH). Such extensive anvil clouds, which result from the excessively deep convection in the eyewall, eventually lead to a large bias in microphysics latent heating. The warming of the upper troposphere due to the condensation in anvil clouds coupled with the cooling of the lower troposphere due to precipitation evaporation cause a weakening of the WPSH, which in turn is favorable for the early recurvature of Megi.

scholarly journals An Initiation Process of Tropical Depression-type Disturbances under the Influence of Upper-level Troughs

2021 ◽  
Author(s):  
Yuya Hamaguchi ◽  
Yukari N. Takayabu
Keyword(s):  
Large Scale ◽  
Convective Available Potential Energy ◽  
Three Dimensional ◽  
Lower Troposphere ◽  
Dimensional Structure ◽  
Convective Heating ◽  
Upper Troposphere ◽  
Tropical Depression ◽  
Upper Level ◽  
Extratropical Forcing

AbstractIn this study, the statistical relationship between tropical upper-tropospheric troughs (TUTTs) and the initiation of summertime tropical-depression type disturbances (TDDs) over the western and central North Pacific is investigated. By applying a spatiotemporal filter to the 34-year record of brightness temperature and using JRA-55 reanalysis products, TDD-event initiations are detected and classified as trough-related (TR) or non-trough-related (non-TR). The conventional understanding is that TDDs originate primarily in the lower-troposphere; our results refine this view by revealing that approximately 30% of TDDs in the 10°N-20°N latitude ranges are generated under the influence of TUTTs. Lead-lag composite analysis of both TR- and non-TR-TDDs clarifies that TR-TDDs occur under relatively dry and less convergent large-scale conditions in the lower-troposphere. This result suggests that TR-TDDs can form in a relatively unfavorable low-level environment. The three-dimensional structure of the wave activity flux reveals southward and downward propagation of wave energy in the upper troposphere that converges at the mid-troposphere around the region where TR-TDDs occur, suggesting the existence of extratropical forcing. Further, the role of dynamic forcing associated with the TUTT on the TR-TDD-initiation is analyzed using the quasi-geostrophic omega equation. The result reveals that moistening in the mid-to-upper troposphere takes place in association with the sustained dynamical ascent at the southeast side of the TUTT, which precedes the occurrence of deep convective heating. Along with a higher convective available potential energy due to the destabilizing effect of TUTTs, the moistening in the mid-to-upper troposphere also helps to prepare the environment favorable to TDDs initiation.

Effect of TC–Trough Interaction on the Intensity Change of Two Typhoons

2005 ◽  
Vol 20 (2) ◽  
pp. 199-211 ◽  
Author(s):  
Hui Yu ◽  
H. Joe Kwon
Keyword(s):  
Tropical Cyclone ◽  
Wind Shear ◽  
Large Scale ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Intensity Change ◽  
Eddy Flux ◽  
Upper Troposphere ◽  
Shallow Layer ◽  
Upper Level

Abstract Using large-scale analyses, the effect of tropical cyclone–trough interaction on tropical cyclone (TC) intensity change is readdressed by studying the evolution of upper-level eddy flux convergence (EFC) of angular momentum and vertical wind shear for two TCs in the western North Pacific [Typhoons Prapiroon (2000) and Olga (1999)]. Major findings include the following: 1) In spite of decreasing SST, the cyclonic inflow associated with a midlatitude trough should have played an important role in Prapiroon’s intensification to its maximum intensity and the maintenance after recurvature through an increase in EFC. The accompanied large vertical wind shear is concentrated in a shallow layer in the upper troposphere. 2) Although Olga also recurved downstream of a midlatitude trough, its development and maintenance were not strongly influenced by the trough. A TC could maintain itself in an environment with or without upper-level eddy momentum forcing. 3) Both TCs started to decay over cold SST in a large EFC and vertical wind shear environment imposed by the trough. 4) Uncertainty of input adds difficulties in quantitative TC intensity forecasting.

scholarly journals A Study on the Reduction of Forecast Error Variance by Three Adaptive Observation Approaches for Tropical Cyclone Prediction

2011 ◽  
Vol 139 (7) ◽  
pp. 2218-2232 ◽  
Author(s):  
Xiaohao Qin ◽  
Mu Mu
Keyword(s):  
Tropical Cyclone ◽  
Large Scale ◽  
Forecast Error ◽  
Error Variance ◽  
Northwest Pacific ◽  
Optimal Perturbation ◽  
Observational Network ◽  
Steering Flow ◽  
Forecast Error Variance ◽  
Cyclone Prediction

Abstract Three adaptive approaches for tropical cyclone prediction are compared in this study: the conditional nonlinear optimal perturbation (CNOP) method, the first singular vector (FSV) method, and the ensemble transform Kalman filter (ETKF) method. These approaches are compared for 36-h forecasts of three northwest Pacific tropical cyclones (TCs): Matsa (2005), Nock-Ten (2004), and Morakot (2009). The sensitive regions identified by each method are obtained. The CNOPs form an annulus around the storm at the targeting time, the FSV targets areas north of the storm, and the ETKF closely targets the typhoon location itself. The sensitive results of both the CNOPs and FSV collocate well with the steering flow between the subtropical high and the TCs. Furthermore, the regions where the convection is strong are targeted by the CNOPs. Relatively speaking, the ETKF sensitive results reflect the large-scale flow. To identify the most effective adaptive observational network, numerous probes or flights were tested arbitrarily for the ETKF method or according to the calculated sensitive regions of the CNOP and FSV methods. The results show that the sensitive regions identified by these three methods are more effective for adaptive observations than the other regions. In all three cases, the optimal adaptive observational network identified by the CNOP and ETKF methods results in similar forecast improvements in the verification region at the verification time, while the improvement using the FSV method is minor.

scholarly journals Sudden Track Changes of Tropical Cyclones in Monsoon Gyres: Full-Physics, Idealized Numerical Experiments*

2015 ◽  
Vol 72 (4) ◽  
pp. 1307-1322 ◽  
Author(s):  
Jia Liang ◽  
Liguang Wu
Keyword(s):  
Tropical Cyclones ◽  
Numerical Experiments ◽  
Large Scale ◽  
Wrf Model ◽  
Weather Research And Forecasting ◽  
Coalescence Process ◽  
The West ◽  
Steering Flow ◽  
Sharp Turn ◽  
Wind Profiles

Abstract Tropical cyclones (TCs) in the eastern semicircle of large-scale monsoon gyres (MGs) were observed to take either a northward (sudden northward and northward without a sharp turn) or a westward TC turn, but only the northward turn was previously simulated in a barotropic model. To understand what controls TC track types in MGs, idealized numerical experiments are performed using the full-physics Weather Research and Forecasting (WRF) Model. These experiments indicate that TCs initially located in the eastern semicircle of MGs can generally take three types of tracks: a sudden northward track, a westward track, and a northward track without a sharp turn. The track types depend upon the TC movement relative to the MG center. In agreement with barotropic simulations, the WRF simulation confirms that approaching and being collocated with the MG center is crucial to the occurrence of sudden northward TC track changes and that sudden northward track changes can be generally accounted for by changes in the steering flow. TCs that take westward tracks and northward tracks without a sharp turn do not experience such a coalescence process. Westward TCs move faster than MGs and are then located to the west of the MG center, while TCs move more slowly than MGs and then take a northward track without a sharp turn. This study reveals that the specific TC track in the eastern semicircle of an MG is sensitive to the initial wind profiles of both MGs and TCs, suggesting that improvement in the observation of TC and MG structures is very important for predicting TC track types in MGs.

scholarly journals The Development and Assessment of a Model-, Grid-, and Basin-Independent Tropical Cyclone Detection Scheme

2013 ◽  
Vol 26 (15) ◽  
pp. 5493-5507 ◽  
Author(s):  
K. J. Tory ◽  
S. S. Chand ◽  
R. A. Dare ◽  
J. L. McBride
Keyword(s):  
Tropical Cyclone ◽  
Large Scale ◽  
Climate Models ◽  
Climate Model ◽  
Vertical Wind Shear ◽  
Lower Troposphere ◽  
Specific Humidity ◽  
Model Data ◽  
Detector Performance ◽  
Detection Scheme

Abstract A novel approach to tropical cyclone (TC) detection in coarse-resolution numerical model data is introduced and assessed. This approach differs from traditional detectors in two main ways. First, it was developed and tuned using 20 yr of ECMWF Interim Re-Analysis (ERA-Interim) data, rather than using climate model data. This ensures that the detector is independent of any climate models to which it will later be applied. Second, only relatively large-scale parameters resolvable in climate models are included, in order to minimize any grid-resolution dependence on parameter thresholds. This approach is taken in an attempt to construct a unified TC detection procedure applicable to all climate models without the need for any further tuning or adjustment. Unlike traditional detectors that seek to identify TCs directly, the authors' method seeks to identify conditions favorable for TC formation. Favorable TC formation regions at the center of closed circulations in the lower troposphere to the midtroposphere are identified using a low-deformation vorticity parameter. Additional relative and specific humidity thresholds are applied to ensure the thermodynamic environment is favorable, and a vertical wind shear threshold is applied to eliminate storms in a destructive shear environment. A further requirement is that thresholds for all parameters must be satisfied for at least 48 h before a TC is deemed to have developed. A thorough assessment of the detector performance is provided. It is demonstrated that the method reproduces realistic TC genesis frequency and spatial distributions in the ERA-Interim data. Application of the detector to four climate models is presented in a companion paper.

scholarly journals Mesoscale Horizontal Kinetic Energy Spectra of a Tropical Cyclone

2018 ◽  
Vol 75 (10) ◽  
pp. 3579-3596 ◽  
Author(s):  
Yuan Wang ◽  
Lifeng Zhang ◽  
Jun Peng ◽  
Saisai Liu
Keyword(s):  
Tropical Cyclone ◽  
Kinetic Energy ◽  
Gravity Waves ◽  
Lower Stratosphere ◽  
Wrf Model ◽  
Weather Research And Forecasting ◽  
Physical Processes ◽  
Upper Troposphere ◽  
Mature Period ◽  
Vertically Propagating

A high-resolution cloud-permitting simulation with the Weather Research and Forecasting (WRF) Model is performed to investigate the mesoscale horizontal kinetic energy (HKE) spectra of a tropical cyclone (TC). The spectrum displays an arc-like shape in the troposphere and a quasi-linear shape in the lower stratosphere for wavelengths below 500 km during the mature period of the TC, while they both develop a quasi −5/3 slope. The total HKE spectrum is dominated by its rotational component in the troposphere but by its divergent component in the lower stratosphere. Further spectral HKE budget diagnosis reveals a generally downscale cascade of HKE, although a local upscale cascade gradually forms in the lower stratosphere. However, the mesoscale energy spectrum is not only governed by the energy cascade, but is evidently influenced also by other physical processes, among which the buoyancy effect converts available potential energy (APE) to HKE in the mid- and upper troposphere and converts HKE to APE in the lower stratosphere, the vertically propagating inertia–gravity waves transport the HKE from the upper troposphere to lower and higher layers, and the vertical transportation of convection always transports HKE upward.

scholarly journals Global climate forcing driven by altered BVOC fluxes from 1990–2010 land cover change in maritime Southeast Asia

2018 ◽  
Author(s):  
Kandice L. Harper ◽  
Nadine Unger
Keyword(s):  
Land Cover ◽  
Southeast Asia ◽  
Land Cover Change ◽  
Radiative Forcing ◽  
Large Scale ◽  
Lower Troposphere ◽  
Convective Transport ◽  
Atmospheric Composition ◽  
Land Cover Changes ◽  
Upper Troposphere

Abstract. Over the period 1990–2010, maritime Southeast Asia experienced large-scale land cover changes, including expansion of high-isoprene-emitting oil palm plantations and contraction of low-isoprene-emitting natural forests. The ModelE2-Yale Interactive Terrestrial Biosphere global chemistry–climate model is used to quantify the atmospheric composition changes and, for the first time, the associated radiative forcing induced by the land-cover-change-driven biogenic volatile organic compound (BVOC) emission changes (+6.5 TgC y−1 isoprene, −0.5 TgC y−1 monoterpenes). Regionally, surface-level ozone concentrations largely decreased (−3.8 to +0.8 ppbv). The tropical land cover changes occurred in a region of strong convective transport, providing a mechanism for the BVOC perturbations to affect the composition of the upper troposphere. Enhanced concentrations of isoprene and its degradation products are simulated in the upper troposphere, and, on a global-mean basis, land cover change had a stronger impact on ozone in the upper troposphere (+0.6 ppbv) than in the lower troposphere (

scholarly journals The importance of low-deformation vorticity in tropical cyclone formation

2012 ◽  
Vol 12 (7) ◽  
pp. 17539-17581
Author(s):  
K. J. Tory ◽  
R. A. Dare ◽  
N. E. Davidson ◽  
J. L. McBride ◽  
S. S. Chand
Keyword(s):  
Tropical Cyclone ◽  
Solid Body ◽  
Large Scale ◽  
Climate Model ◽  
Lower Troposphere ◽  
Reanalysis Data ◽  
Vertical Shear ◽  
Body Rotation ◽  
Solid Body Rotation ◽  
Tropical Waves

Abstract. Studies of tropical cyclone (TC) formation from tropical waves have shown that TC formation requires a wave-relative quasi-closed circulation: the "marsupial pouch" concept. This results in a layerwise nearly contained region of atmosphere in which the modification of moisture, temperature and vorticity profiles by convective and boundary layer processes occurs undisturbed. The pouch concept is further developed in this paper. TCs develop near the centre of the pouch where the flow is in near solid body rotation. A reference-frame independent parameter is introduced that effectively measures the level of solid-body rotation in the lower troposphere. The parameter is the product of a normalized Okubo-Weiss parameter and absolute vorticity (OWZ). Using 20 yr of ERA-interim reanalysis data and the IBTrACS global TC database, it is shown 95% of TCs including, but not limited to, those forming in tropical waves are associated with enhanced levels of OWZ on both the 850 and 500 hPa pressure levels at the time of TC declaration, while 90% show enhanced OWZ for at least 24 h prior to declaration. This result prompts the question of whether the pouch concept extends beyond wave-type formation to all TC formations world-wide. Combining the OWZ with a low vertical shear requirement and lower troposphere relative humidity thresholds, an imminent genesis parameter is defined. The parameter includes only relatively large-scale fluid properties that are resolved by coarse grid model data (>150 km), which means it can be used as a TC detector for climate model applications. It is also useful as a cyclogenesis diagnostic in higher resolution models such as real-time global forecast models.

scholarly journals The genesis of Typhoon Nuri as observed during the Tropical Cyclone Structure 2008 (TCS08) field experiment – Part 2: Observations of the convective environment

2011 ◽  
Vol 11 (11) ◽  
pp. 31115-31136 ◽  
Author(s):  
M. T. Montgomery ◽  
R. K. Smith
Keyword(s):  
Tropical Cyclone ◽  
Potential Temperature ◽  
Lower Troposphere ◽  
Vertical Profiles ◽  
Upper Troposphere ◽  
Convective Clouds ◽  
Virtual Potential Temperature ◽  
Noticeable Reduction ◽  
Virtual Temperature ◽  
The Tropics

Abstract. Analyses of thermodynamic data gathered from airborne dropwindsondes during the Tropical Cyclone Structure (2008) experiment are presented for the disturbance that became Typhoon Nuri. Although previous work has suggested that Nuri formed within the protective recirculating "pouch" region of a westward-propagating wave-like disturbance and implicated rotating deep convective clouds in driving the inflow to spin up the tangential circulation of the system-scale flow, the nature of the thermodynamic environment that supported the genesis remains a topic of debate. During the genesis phase, vertical profiles of virtual potential temperature show little variability between soundings on a particular day and the system-average soundings likewise show a negligible change. There is a tendency also for the lower and middle troposphere to moisten. However, the data show that on the scale of the recirculating region of the disturbance, there was no noticeable reduction of virtual temperature in the lower troposphere, but a small warming (less than 1 K) in the upper troposphere. Vertical profiles of pseudo-equivalent potential temperature, θe, during the genesis show a modestly decreasing deficit of θe in the vertical between the surface and a height of minimum θe (between 3 and 4 km), from 17.5 K to 15.2 K. The findings reported here are consistent with that found for developing disturbances observed in the Pre-Depression Investigation of Cloud Systems in the Tropics (PREDICT) experiment in 2010. Some implications of the findings are discussed.

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