Diagnostic Analysis of the Generative Mechanism of Extratropical Cyclones in the Northwest Pacific and Northwest Atlantic

Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1326
Author(s):  
Qinglong Gong ◽  
Yina Diao ◽  
Ruipeng Sun ◽  
Xuejun Xiong ◽  
Jilin Sun
Keyword(s):  
Early Stage ◽  
Vertical Motion ◽  
Temperature Fields ◽  
Northwest Pacific ◽  
Northwest Atlantic ◽  
Cold Zone ◽  
Westerly Jet ◽  
Warm Core ◽  
Generative Mechanism ◽  
Cold Core

We investigated the early-stage development of cyclones occurring in the strong baroclinic regions in the Northwest Pacific and the Northwest Atlantic based on European Center for Medium-range Weather Forecasts Re-Analysis-Interim (ERA-Interim) data. The composite background conditions corresponding to the cyclones on the onset day are characterized by upper troposphere divergence of westerly jet ahead of a trough, low troposphere convergence of westerly jet behind a trough, and strong meridional air temperature gradient (baroclinicity) both in the Northwest Pacific and the Northwest Atlantic, but with stronger baroclinicity in the Northwest Pacific. The composite velocity and temperature fields of the cyclone on the onset day show a clear horizontal front and a westward and northward vertical tilting of cyclonic circulation to the cold zone. The composite Northwest Pacific cyclone filed on the onset day has a warm core, whereas the composite Northwest Atlantic cyclone field has a cold core in the low troposphere. The leading adiabatic processes that contribute to the developing of the cold core cyclone in the Northwest Atlantic on the onset day is the temperature advection, while stronger vertical motion induces stronger adiabatic warming in the Northwest Pacific cyclones, which has a significant contribution to the development of warm core cyclones on the onset day.

scholarly journals Effects of the Cold Core Eddy on Tropical Cyclone Intensity and Structure under Idealized Air–Sea Interaction Conditions

2013 ◽  
Vol 141 (4) ◽  
pp. 1285-1303 ◽  
Author(s):  
Zhanhong Ma ◽  
Jianfang Fei ◽  
Lei Liu ◽  
Xiaogang Huang ◽  
Xiaoping Cheng
Keyword(s):  
Lower Troposphere ◽  
Vertical Motion ◽  
Ocean Model ◽  
Warm Core ◽  
Budget Analysis ◽  
Ocean Coupling ◽  
Negative Impacts ◽  
Core Height ◽  
Water Vapor Mixing Ratio ◽  
Cold Core

Abstract The impacts of ocean feedback on tropical cyclones (TCs) are investigated using a coupled atmosphere–ocean model under idealized TC and cold core eddy (CCE) conditions. Results reveal negative impacts of the ocean coupling on TC development. The cold wake induced by a TC not only weakens the TC intensity but also limits the expansion of the storm circulation. The presence of CCE has boosted the TC-induced sea surface temperature cooling, which conversely inhibits the TC development. The TC appears to be weakened as it encounters the CCE edge. The intensity reduction attains a maximum shortly after the TC passes over the CCE center, and simultaneously the CCE-induced asymmetry of the storm structure is most significant as well. The TC undergoes a period of recovery after departure from the CCE, lasting about 36–48 h. During this time the residual asymmetry caused by the CCE is smoothed gradually by storm axisymmetrization. The CCE has induced smaller TC size throughout the simulation even after the TC intensity has completely recovered, an indication of longer recovery time for the TC size. Notably cooler and moister eye air in the lower troposphere, just under the warm-core height, is found in the experiment with CCE. The water vapor mixing ratio budget analysis indicates that it is primarily attributed to changes in vertical advection that occurred in the eye, that is, the undermined eye subsidence associated with the suppressed eyewall convection. The horizontal patterns of vertical motion in the boundary layer are also distinctly changed by the CCE.

scholarly journals Statistical Characteristics of Cyclonic Warm-Core Eddies and Anticyclonic Cold-Core Eddies in the North Pacific Based on Remote Sensing Data

2019 ◽  
Vol 11 (2) ◽  
pp. 208 ◽  
Author(s):  
Wenjin Sun ◽  
Changming Dong ◽  
Wei Tan ◽  
Yijun He
Keyword(s):  
Remote Sensing ◽  
North Pacific ◽  
Kuroshio Extension ◽  
Remote Sensing Data ◽  
Statistical Characteristics ◽  
The North ◽  
Warm Core ◽  
Spatio Temporal ◽  
Cold Core ◽  
The North Pacific

A (an) cyclonic (anticyclonic) eddy is usually associated with a cold (warm) core caused by the eddy-induced divergence (convergence) motion. However, there are also some cyclonic (anticyclonic) eddies with warm (cold) cores in the North Pacific, named cyclonic warm-core eddies (CWEs) and anticyclonic cold-core eddies (ACEs) in this study, respectively. Their spatio-temporal characteristics and regional dependence are analyzed using the multi-satellite merged remote sensing datasets. The CWEs are mainly concentrated in the northwestern and southeastern North Pacific. However, besides these two areas, the ACEs are also concentrated in the northeastern Pacific. The annual mean number decreases year by year for both CWEs and ACEs, and the decreasing rate of the CWEs is about two times as large as that of the ACEs. Moreover, the CWEs and ACEs also exhibit a significant seasonal variation, which are intense in summer and weak in winter. Based on the statistics of dynamic characteristics in seven subregions, the Kuroshio Extension region could be considered as the most active area for the CWEs and ACEs. Two possible mechanisms for CW-ACEs generation are discussed by analyzing two cases.

scholarly journals Warm-Core Formation in Tropical Storm Humberto (2001)

2012 ◽  
Vol 140 (4) ◽  
pp. 1177-1190 ◽  
Author(s):  
Klaus Dolling ◽  
Gary M. Barnes
Keyword(s):  
Energy Content ◽  
Early Stage ◽  
Deep Convection ◽  
Lower Troposphere ◽  
Mesoscale Convective System ◽  
Tropical Storm ◽  
Central Pressure ◽  
Convective System ◽  
Warm Core ◽  
Mesoscale Convective

At 0600 UTC 22 September 2001, Humberto was a tropical depression with a minimum central pressure of 1010 hPa. Twelve hours later, when the first global positioning system dropwindsondes (GPS sondes) were jettisoned, Humberto’s minimum central pressure was 1000 hPa and it had attained tropical storm strength. Thirty GPS sondes, radar from the WP-3D, and in situ aircraft measurements are utilized to observe thermodynamic structures in Humberto and their relationship to stratiform and convective elements during the early stage of the formation of an eye. The analysis of Tropical Storm Humberto offers a new view of the pre-wind-induced surface heat exchange (pre-WISHE) stage of tropical cyclone evolution. Humberto contained a mesoscale convective vortex (MCV) similar to observations of other developing tropical systems. The MCV advects the exhaust from deep convection in the form of an anvil cyclonically over the low-level circulation center. On the trailing edge of the anvil an area of mesoscale descent induces dry adiabatic warming in the lower troposphere. The nascent warm core at low levels causes the initial drop in pressure at the surface and acts to cap the boundary layer (BL). As BL air flows into the nascent eye, the energy content increases until the energy is released from under the cap on the down shear side of the warm core in the form of vigorous cumulonimbi, which become the nascent eyewall. This series of events show one possible path in which a mesoscale convective system may evolve into a warm-cored structure and intensify into a hurricane.

scholarly journals Tropical Transition of an Unnamed, High-Latitude, Tropical Cyclone over the Eastern North Pacific

2016 ◽  
Vol 144 (2) ◽  
pp. 713-736 ◽  
Author(s):  
Alicia M. Bentley ◽  
Nicholas D. Metz
Keyword(s):  
Life Cycle ◽  
Tropical Cyclone ◽  
Cross Sections ◽  
North Pacific ◽  
Lower Troposphere ◽  
Sea Surface ◽  
The West ◽  
Warm Core ◽  
Cold Core ◽  
North Pacific Basin

Abstract In early November 2006, an unnamed tropical cyclone (TC) formed via the tropical transition (TT) process at 42°N over the eastern North Pacific. An extratropical cyclone (EC), developing downstream of a thinning upper-tropospheric trough over the eastern North Pacific, served as the precursor disturbance that would ultimately undergo TT. The TT of the unnamed TC was extremely unusual—occurring over ~16°C sea surface temperatures in a portion of the eastern North Pacific basin historically devoid of TC activity. This paper 1) identifies the upper- and lower-tropospheric features linked to the formation of the EC that transitions into the unnamed TC, 2) provides a synoptic overview of the features and processes associated with the unnamed TC’s TT, and 3) discusses the landfall of the weakening cyclone along the west coast of North America. As observed in previous studies of TT, the precursor EC progresses through the life cycle of a marine extratropical frontal cyclone, developing a bent-back warm front on its northern and western sides and undergoing a warm seclusion process. Backward air parcel trajectories suggest that air parcels isolated in the center of the transitioning cyclone were warmed in the lower troposphere via sensible heating from the underlying sea surface. Vertical cross sections taken through the center of the cyclone during its life cycle reveal its transformation from an asymmetric, cold-core, EC into an axisymmetric, warm-core, TC during TT. Ensemble reforecasts initialized after TT highlight the relatively low forecast skill associated with the landfall of the weakening cyclone.

scholarly journals Typhoon Warm-Core Structures Derived from FY-3D MWTS-2 Observations

2021 ◽  
Vol 13 (18) ◽  
pp. 3730
Author(s):  
Zeyi Niu ◽  
Xiaolei Zou ◽  
Wei Huang
Keyword(s):  
Linear Regression ◽  
Multiple Linear Regression ◽  
Three Dimensional ◽  
Detection Algorithm ◽  
Maximum Temperature ◽  
Retrieval Algorithm ◽  
Northwest Pacific ◽  
Cloud Detection ◽  
Warm Core ◽  
Mean Square Errors

In this study, the three-dimensional (3D) warm-core structures of the Northwest Pacific typhoons Francisco, Lekima, and Krosa in August 2019 are retrieved from the Fengyun-3D (FY-3D) microwave temperature sounder-2 (MWTS-2) observations of brightness temperature. Due to the lack of two window channels at 23.8 GHz and 31.4 GHz, an empirical cloud detection algorithm based on 50.3 GHz bias-corrected observations-minus-backgrounds is applied to obtain clear-sky observations for the multiple linear regression retrieval algorithm. The MWTS-2 cloud-affected channels 3–5 are not used to retrieve temperatures under cloudy conditions to eliminate low-tropospheric cold anomalies. The multiple linear regression coefficients are obtained based on MWTS-2 brightness temperatures and the temperatures from the European Centre for Medium-Range Weather Forecasts Reanalysis-5 (ERA5) in the training period of three weeks before the month of targeted typhoons. The proposed MWTS-2 warm-core retrieval can well capture the radial and vertical temporal evolutions of the temperature anomalies of the typhoons Francisco, Lekima, and Krosa. The sizes of the warm-core anomalies of typhoons Lekima and Krosa retrieved by the MWTS-2 are horizontally and vertically similar to and stronger than those of the ERA5. Compared with the ERA5 reanalysis in August 2019, the biases for MWTS-2 temperature retrievals are smaller than ±0.25 K, with root-mean-square errors (RMSEs) smaller than and 2.0 K at all altitudes. Additionally, the location of the 250-hPa maximum temperature anomaly retrieved by the MWTS-2 is closer to the best track than that of the ERA5. A weak warm-core around 200 hPa and a cold-core anomaly in the middle troposphere are also found in the outer rain bands region due to the effect of evaporation of rainfall.

Moisture and Energy Budget Perspectives on Summer Drought in North China

2020 ◽  
Vol 33 (23) ◽  
pp. 10149-10167
Author(s):  
Lan Dai ◽  
Jonathon S. Wright ◽  
Rong Fu
Keyword(s):  
Energy Budget ◽  
Large Scale ◽  
North China ◽  
Static Stability ◽  
Summer Drought ◽  
Warm Core ◽  
Budget Analysis ◽  
Moisture Advection ◽  
Upper Level ◽  
Cold Core

AbstractWe investigate the physical processes behind summer drought in North China by evaluating moisture and energy budget diagnostics and linking them to anomalous large-scale circulation patterns. Moisture budget analysis reveals that summer drought in North China was caused dynamically by reduced vertical moisture advection due to anomalous subsidence and reduced horizontal moisture advection due to anomalous northeasterly winds. Energy budget analysis shows that reduced latent heating was balanced dynamically by decreased dry static energy (DSE) divergence in the middle-to-upper troposphere. Linking these results to previous work, we suggest that summer drought in North China was predicated on co-occurrence of the positive phases of the Eurasian (EU) and Pacific–Japan (PJ) teleconnection patterns, potentially modulated by the circumglobal teleconnection (CGT). In the typical case, the negative phase of the CGT intensified the positive EU-related upper-level cyclone. Resulting upper-level cooling and positive surface feedback imposed a cold-core surface anticyclone that weakened with height. By contrast, when the positive phase of the CGT occurred in tandem with the positive EU and PJ patterns, the anticyclone had a warm core and intensified with height. The two cases were unified by strong subsidence but exhibited opposite meridional advection anomalies. In the cold-core cases, meridional moisture inflow was reduced but meridional DSE export was enhanced, further limiting precipitation while maintaining negative thermal anomalies. In the warm-core case, which only occurred once, enhanced meridional inflow of water vapor supplied moisture for sporadic precipitation while reduced meridional DSE export helped to maintain strong static stability.

scholarly journals Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oceans: estimates based on in-situ chemical and optical measurements and chemical transport modeling

2006 ◽  
Vol 6 (6) ◽  
pp. 1657-1732 ◽  
Author(s):  
T. S. Bates ◽  
T. L. Anderson ◽  
T. Baynard ◽  
T. Bond ◽  
O. Boucher ◽  
...  
Keyword(s):  
Climate Change ◽  
Radiative Transfer ◽  
Chemical Transport ◽  
Climate Forcing ◽  
Northwest Pacific ◽  
Anthropogenic Aerosols ◽  
Northwest Atlantic ◽  
Clear Sky ◽  
Aerosol Properties

Abstract. The largest uncertainty in the radiative forcing of climate change over the industrial era is that due to aerosols, a substantial fraction of which is the uncertainty associated with scattering and absorption of shortwave (solar) radiation by anthropogenic aerosols in cloud-free conditions (IPCC, 2001). Quantifying and reducing the uncertainty in aerosol influences on climate is critical to understanding climate change over the industrial period and to improving predictions of future climate change for assumed emission scenarios. Measurements of aerosol properties during major field campaigns in several regions of the globe during the past decade are contributing to an enhanced understanding of atmospheric aerosols and their effects on light scattering and climate. The present study, which focuses on three regions downwind of major urban/population centers (North Indian Ocean (NIO) during INDOEX, the Northwest Pacific Ocean (NWP) during ACE-Asia, and the Northwest Atlantic Ocean (NWA) during ICARTT), incorporates understanding gained from field observations of aerosol distributions and properties into calculations of perturbations in radiative fluxes due to these aerosols. This study evaluates the current state of observations and of two chemical transport models (STEM and MOZART). Measurements of burdens, extinction optical depth (AOD), and direct radiative effect of aerosols (DRE – change in radiative flux due to total aerosols) are used as measurement-model check points to assess uncertainties. In-situ measured and remotely sensed aerosol properties for each region (mixing state, mass scattering efficiency, single scattering albedo, and angular scattering properties and their dependences on relative humidity) are used as input parameters to two radiative transfer models (GFDL and University of Michigan) to constrain estimates of aerosol radiative effects, with uncertainties in each step propagated through the analysis. Constraining the radiative transfer calculations by observational inputs increases the clear-sky, 24-h averaged AOD (34±8%), top of atmosphere (TOA) DRE (32±12%), and TOA direct climate forcing of aerosols (DCF – change in radiative flux due to anthropogenic aerosols) (37±7%) relative to values obtained with "a priori" parameterizations of aerosol loadings and properties (GFDL RTM). The resulting constrained clear-sky TOA DCF is −3.3±0.47, −14±2.6, −6.4±2.1 Wm−2 for the NIO, NWP, and NWA, respectively. With the use of constrained quantities (extensive and intensive parameters) the calculated uncertainty in DCF was 25% less than the "structural uncertainties" used in the IPCC-2001 global estimates of direct aerosol climate forcing. Such comparisons with observations and resultant reductions in uncertainties are essential for improving and developing confidence in climate model calculations incorporating aerosol forcing.

scholarly journals The Dryline on 22 May 2002 during IHOP: Ground-Radar and In Situ Data Analyses of the Dryline and Boundary Layer Evolution

2007 ◽  
Vol 135 (7) ◽  
pp. 2473-2505 ◽  
Author(s):  
Michael S. Buban ◽  
Conrad L. Ziegler ◽  
Erik N. Rasmussen ◽  
Yvette P. Richardson
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Doppler Radar ◽  
Potential Temperature ◽  
Vertical Motion ◽  
Temperature Fields ◽  
Lagrangian Analysis ◽  
Thermodynamic Structure ◽  
In Situ Data ◽  
Water Vapor Mixing Ratio

Abstract On the afternoon and evening of 22 May 2002, high-resolution observations of the boundary layer (BL) and a dryline were obtained in the eastern Oklahoma and Texas panhandles during the International H2O Project. Using overdetermined multiple-Doppler radar syntheses in concert with a Lagrangian analysis of water vapor and temperature fields, the 3D kinematic and thermodynamic structure of the dryline and surrounding BL have been analyzed over a nearly 2-h period. The dryline is resolved as a strong (2–4 g kg−1 km−1) gradient of water vapor mixing ratio that resides in a nearly north–south-oriented zone of convergence. Maintained through frontogenesis, the dryline is also located within a gradient of virtual potential temperature, which induces a persistent, solenoidally forced secondary circulation. Initially quasi-stationary, the dryline retrogrades to the west during early evening and displays complicated substructures including small wavelike perturbations that travel from south to north at nearly the speed of the mean BL flow. A second, minor dryline has similar characteristics to the first, but has weaker gradients and circulations. The BL adjacent to the dryline exhibits complicated structures, consisting of combinations of open cells, horizontal convective rolls, and transverse rolls. Strong convergence and vertical motion at the dryline act to lift moisture, and high-based cumulus clouds are observed in the analysis domain. Although the top of the analysis domain is below the lifted condensation level height, vertical extrapolation of the moisture fields generally agrees with cloud locations. Mesoscale vortices that move along the dryline induce a transient eastward dryline motion due to the eastward advection of dry air following misocyclone passage. Refractivity-based moisture and differential reflectivity analyses are used to help interpret the Lagrangian analyses.

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