MECHANISM ANALYSIS FOR THE DIFFERENCE IN SIMULATED TRACK OF TROPICAL CYCLONE MEGI (2010) WITH TWO PLANETARY BOUNDARY LAYER SCHEMES

Abstract Thermodynamic variables including temperature, humidity, and equivalent potential temperature are obtained and calculated from 88 buoy and C-MAN time series of 38 Atlantic hurricanes. Radial profiles of these variables are compared to the tropical cyclone (TC) boundary layer idealization in potential intensity (PI) theory. For the composite hurricane, temperature decreases by 2.4 K between the environmental far field and the radius of maximum winds (RMW), in contrast to the PI boundary layer profile, which is radially isothermal outside the RMW. Observationally derived moisture and equivalent potential temperature (moist entropy) begin to increase with decreasing radius beyond the RMW, especially for the subset of category 3–5 hurricanes. This suggests the relevance of ocean–air fluxes beyond the RMW to increasing the moist entropy of eyewall updrafts. Ocean–air enthalpy fluxes produced by 85 time series with sea surface temperature data are explored using the bulk aerodynamic flux formulation and two methods that explicitly account for sea spray. Formulations incorporating sea spray produce greater total enthalpy fluxes, especially near the RMW. Total enthalpy fluxes calculated using composite observed conditions differ substantially from fluxes calculated using the idealizations of classic PI theory, though the sign of the difference depends on the calculation method used. Observed conditions may yield higher maximum intensities if maximum intensity is governed by the energy production–frictional dissipation balance under the eyewall. However, if TC intensity is governed by the entropy gained by inflow air, no matter where entropy is acquired, observed conditions may yield lower intensities than the classic PI theory boundary layer.

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Effect of Scale-Aware Planetary Boundary Layer Schemes on Tropical Cyclone Intensification and Structural Changes in the Gray Zone

Monthly Weather Review ◽

10.1175/mwr-d-20-0297.1 ◽

2021 ◽

Author(s):

Xiaomin Chen ◽

Ming Xue ◽

Bowen Zhou ◽

Juan Fang ◽

Jun A. Zhang ◽

...

Keyword(s):

Boundary Layer ◽

Tropical Cyclone ◽

Planetary Boundary Layer ◽

Structural Changes ◽

Prediction Models ◽

Inner Core ◽

Weather Prediction ◽

Turbulent Heat ◽

Gray Zone ◽

Horizontal Grid

AbstractHorizontal grid spacings of numerical weather prediction models are rapidly approaching O (1 km) and have become comparable with the dominant length scales of flows in the boundary layer; within such “gray-zone”, conventional planetary boundary layer (PBL) parameterization schemes start to violate basic design assumptions. Scale-aware PBL schemes have been developed recently to address the gray-zone issue. By performing WRF simulations of Hurricane Earl (2010) at sub-kilometer grid spacings, this study investigates the effect of the scale-aware Shin-Hong (SH) scheme on the tropical cyclone (TC) intensification and structural changes in comparison to the non-scale-aware YSU scheme it is built upon. Results indicate that SH tends to produce a stronger TC with a more compact inner core than YSU. At early stages, the scale-aware coefficients in SH gradually decrease as the diagnosed boundary layer height exceeds the horizontal grid spacing. This scale-aware effect is most prominent for the nonlocal subgrid-scale vertical turbulent fluxes, in the non-precipitation regions radially outside of the convective rainband, and from the early stage through the middle of rapid intensification (RI) phase. Both the scale awareness and different parameterization of the nonlocal turbulent heat flux in SH reduce the parameterized vertical turbulent mixing, which further induces stronger radial inflows and helps retain more water vapor in the boundary layer. The resulting stronger moisture convergence and diabatic heating near the TC center account for the faster inner-core contraction before RI onset and the higher intensification rate during the RI period. Potential issues of applying these two PBL schemes in TC simulations and suggestions for improvements are discussed.

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Effect of the Vertical Diffusion of Moisture in the Planetary Boundary Layer on an Idealized Tropical Cyclone

Advances in Atmospheric Sciences ◽

10.1007/s00376-021-1016-z ◽

2021 ◽

Vol 38 (11) ◽

pp. 1889-1904

Author(s):

Hongxiong Xu ◽

Dajun Zhao

Keyword(s):

Boundary Layer ◽

Tropical Cyclone ◽

Planetary Boundary Layer ◽

Vertical Diffusion

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Sensitivity Study of Planetary Boundary Layer Parameterization Schemes for the Simulation of Tropical Cyclone ‘Fani’ Over the Bay of Bengal Using High Resolution Wrf-Arw Model

Journal of Engineering Science ◽

10.3329/jes.v11i2.50893 ◽

2020 ◽

Vol 11 (2) ◽

pp. 1-18

Author(s):

MM Alam

Keyword(s):

Boundary Layer ◽

Tropical Cyclone ◽

Planetary Boundary Layer ◽

Bay Of Bengal ◽

Convective Available Potential Energy ◽

Potential Temperature ◽

Sensitivity Analyses ◽

Track Error ◽

Parameterization Schemes ◽

High Clouds

Comprehensive sensitivity analyses on physical parameterization schemes of WRF-ARW (V3.8.1) model have been carried out for the simulation of Tropical Cyclone (TC) Fani that formed in the Bay of Bengal (BoB) and crossed the Bangladesh and Odisha coast of India on 3rd May 2019. Global Forecasting System (GFS) data 1⁰ and 0.25⁰ from National Centre for Environment Prediction (NCEP) is used as initial and lateral boundary conditions. The six different Planetary Boundary Layer (PBL) schemes used in this research are YSU, BouLac, TEMF, Shin-Hong, GBM and MRF. The meteorological parameters, which have been studied to identify the effect of PBL during the propagation and movement of TC Fani are Estimated Central Pressure (ECP), Maximum Wind Speed (MWS) at 10m height, average relative humidity (%), temperature (⁰C) and potential temperature (0K) at 2m height, Modified Convective Available Potential Energy (MCAP), average PBL height and average high clouds (%). The area considered for these averages are 82-92 ⁰E and 7-22 ⁰N inside the model domain. The simulated ECP by TEMF scheme are 930, 932, 937, 929, 944 and 932 hPa for the Initial Conditions (ICs) at 0000 UTC of 27, 28, 29, 30 April, and 01 May and 02 May, respectively and observed ECP was 932 hPa. The intensity of pressure fall by the TEMF scheme is similar to that observed up to the time of crossing the land of TC Fani. The MWS simulated by the TEMF scheme is almost similar to that of the observed MWS at 10m height and all other schemes have simulated much lower MWS. The temperature at 2m height is positively correlated with the ECP and MWS at 10m height. The TEMF scheme has simulated maximum high clouds for all ICs and for all through the simulation time. The error was systematic for all PBL schemes for the ICs at 0000 UTC of 30 April at 0.25⁰ and 1⁰ GFS data but the track error was much less for 1⁰ GFS data than that of 0.25⁰ GFS data. The TEMF scheme has simulated the most deviated track and MRF scheme has simulated less deviated track for all through the simulation. The study has shown large variations of track and intensity among the different PBL schemes. The PBL schemes have a major impact on the track and intensity of TC Fani. The intensity simulated by the TEMF scheme is better but the track error is higher than that of other schemes. Journal of Engineering Science 11(2), 2020, 1-18

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Assessing CALIOP-Derived Planetary Boundary Layer Height Using Ground-Based Lidar

Remote Sensing ◽

10.3390/rs13081496 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1496

Author(s):

Man-Hae Kim ◽

Huidong Yeo ◽

Soojin Park ◽

Do-Hyeon Park ◽

Ali Omar ◽

...

Keyword(s):

Boundary Layer ◽

Planetary Boundary Layer ◽

Radiosonde Data ◽

Orthogonal Polarization ◽

Aerosol Layer ◽

Planetary Boundary Layer Height ◽

Layer Height ◽

Boundary Layer Height ◽

The Difference ◽

Ground Based Lidar

Coincident profiles from the space-borne and ground-based lidar measurements provide a unique opportunity to estimate the planetary boundary layer height (PBLH). In this study, PBLHs derived from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) were assessed by comparing them with those obtained from the ground-based lidar at Seoul National University (SNU) in Korea for both day and night from 2006 to 2019, and sounding data. CALIOP-derived PBLHs using wavelet covariance transform (WCT) are generally higher than those derived from the SNU lidar for both day and night. The difference in PBLH tends to increase as the signal-to-noise ratio for CALIOP decreases. The difference also increases as aerosol optical depth increases, implying that the PBLH estimated from CALIOP could be higher than that determined from the SNU lidar because of the signal attenuation within the aerosol layer under optically thick aerosol layer conditions. The higher PBLH for CALIOP in this study is mainly attributed to multiple aerosol layers. After eliminating multilayer cases, the PBLHs estimated from both the lidars showed significantly improved agreement: a mean difference of 0.09 km (R = 0.81) for daytime and 0.25 km (R = 0.51) for nighttime. The results from this study suggest that PBL detection using CALIOP is reliable for daytime if multilayer cases are removed. For nighttime, PBLHs derived from the SNU lidar and CALIOP showed a relatively large difference in frequency distribution compared with sounding data. It suggests that further investigations are needed for nighttime PBLHs, such as investigations about discriminating the residual layer and the difference between lidar-derived PBLH based on the aerosol layer and thermally derived PBLH from radiosonde data for the stable boundary layer during the nighttime.

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