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  • 1
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    The CBLAST-Hurricane program and the next-generation fully coupled atmosphere–wave–ocean models for hurricane research and prediction (2010)
    American Meteorological Society
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    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2007. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 88 (2007): 311-317, doi:10.1175/bams-88-3-311.
    Description: The record-setting 2005 hurricane season has highlighted the urgent need for a better understanding of the factors that contribute to hurricane intensity, and for the development of corresponding advanced hurricane prediction models to improve intensity forecasts. The lack of skill in present forecasts of hurricane intensity may be attributed, in part, to deficiencies in the current prediction models—insufficient grid resolution, inadequate surface and boundary-layer formulations, and the lack of full coupling to a dynamic ocean. The extreme high winds, intense rainfall, large ocean waves, and copious sea spray in hurricanes push the surface-exchange parameters for temperature, water vapor, and momentum into untested regimes. The Coupled Boundary Layer Air–Sea Transfer (CBLAST)-Hurricane program is aimed at developing improved parameterizations using observations from the CBLAST-Hurricane field program that will be suitable for the next generation of hurricane-prediction models. The most innovative aspect of the CBLAST-Hurricane modeling effort is the development and testing of a fully coupled atmosphere–wave–ocean modeling system that is capable of resolving the eye and eyewall at ~1-km grid resolution, which is consistent with a key recommendation for the next-generation hurricane-prediction models by the NOAA Science Advisor Board Hurricane Intensity Research Working Group. It is also the National Centers for Environmental Prediction (NCEP) plan for the new Hurricane Weather Research and Forecasting (HWRF) model to be implemented operationally in 2007–08.
    Description: The CBLAST-Hurricane is a research program supported by a departmental research initiative at the Office of Naval Research (ONR). The research is supported by ONR Research Grants N00014-01-1-0156, N00014-04-1-0109, N00014-01-F-0052, and SBIR for the EM-APEX development and deployment.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    An ocean coupling potential intensity index for tropical cyclones (2013)
    John Wiley & Sons
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    Publication Date: 2022-05-25
    Description: © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 40 (2013): 1878–1882, doi:10.1002/grl.50091.
    Description: Timely and accurate forecasts of tropical cyclones (TCs, i.e., hurricanes and typhoons) are of great importance for risk mitigation. Although in the past two decades there has been steady improvement in track prediction, improvement on intensity prediction is still highly challenging. Cooling of the upper ocean by TC-induced mixing is an important process that impacts TC intensity. Based on detail in situ air-deployed ocean and atmospheric measurement pairs collected during the Impact of Typhoons on the Ocean in the Pacific (ITOP) field campaign, we modify the widely used Sea Surface Temperature Potential Intensity (SST_PI) index by including information from the subsurface ocean temperature profile to form a new Ocean coupling Potential Intensity (OC_PI) index. Using OC_PI as a TC maximum intensity predictor and applied to a 14 year (1998–2011) western North Pacific TC archive, OC_PI reduces SST_PI-based overestimation of archived maximum intensity by more than 50% and increases the correlation of maximum intensity estimation from r2 = 0.08 to 0.31. For slow-moving TCs that cause the greatest cooling, r2 increases to 0.56 and the root-mean square error in maximum intensity is 11 m s−1. As OC_PI can more realistically characterize the ocean contribution to TC intensity, it thus serves as an effective new index to improve estimation and prediction of TC maximum intensity.
    Description: This work is supported by Taiwan’s National Science Council and National Taiwan University (grant numbers: NSC 101- 2111-M-002-002-MY2; NSC 101-2628-M-002-001-MY4; 102R7803) and US Office of Naval Research (ONR) under the Impact of Typhoons on Pacific (ITOP) program. PB’s support is provided by ONR under PE 0601153N through NRL Contract N00173-10-C-6019.
    Keywords: Tropical cyclones ; Potential intensity index ; Ocean cooling
    Repository Name: Woods Hole Open Access Server
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  • 3
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    Aircraft Observations of Dry Air, the ITCZ, Convective Cloud Systems, and Cold Pools in MJO during DYNAMO (2016)
    American Meteorological Society
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    Publication Date: 2016-03-01
    Description: One of the most challenging problems in predicting the Madden–Julian oscillation (MJO) is the initiation of large-scale convective activity associated with the MJO over the tropical Indian Ocean. The lack of observations is a major obstacle. The Dynamics of the MJO (DYNAMO) field campaign collected unprecedented observations from air-, land-, and ship-based platforms from October 2011 to February 2012. Here we provide an overview of the aircraft observations in DYNAMO, which captured an MJO initiation event from November to December 2011. The National Oceanic and Atmospheric Administration (NOAA) WP-3D aircraft was stationed at Diego Garcia and the French Falcon 20 aircraft on Gan Island in the Maldives. Observations from the two aircraft provide a unique dataset of three-dimensional structure of convective cloud systems and their environment from the flight level, airborne Doppler radar, microphysics probes, ocean surface imaging, global positioning system (GPS) dropsonde, and airborne expendable bathythermograph (AXBT) data. The aircraft observations revealed interactions among dry air, the intertropical convergence zone (ITCZ), convective cloud systems, and air–sea interaction induced by convective cold pools, which may play important roles in the multiscale processes of MJO initiation. This overview focuses on some key aspects of the aircraft observations that contribute directly to better understanding of the interactions among convective cloud systems, environmental moisture, and the upper ocean during the MJO initiation over the tropical Indian Ocean. Special emphasis is on the distinct characteristics of convective cloud systems, environmental moisture and winds, air–sea fluxes, and convective cold pools during the convectively suppressed, transition/onset, and active phases of the MJO.
    Print ISSN: 0003-0007
    Electronic ISSN: 1520-0477
    Topics: Geography , Physics
    Published by American Meteorological Society
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  • 4
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    Reducing TC Position Uncertainty in an Ensemble Data Assimilation and Prediction System: A Case Study of Typhoon Fanapi (2010) (2018)
    American Meteorological Society
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    Publication Date: 2018-04-01
    Description: Ensemble-based data assimilation (EDA) has been used for tropical cyclone (TC) analysis and prediction with some success. However, the TC position spread determines the structure of the TC-related background error covariance and affects the performance of EDA. With an idealized experiment and a real TC case study, it is demonstrated that observations in the core region cannot be optimally assimilated when the TC position spread is large. To minimize the negative impact from large position uncertainty, a TC-centered EDA approach is implemented in the Weather Research and Forecasting (WRF) Model–local ensemble transform Kalman filter (WRF-LETKF) assimilation system. The impact of TC-centered EDA on TC analysis and prediction of Typhoon Fanapi (2010) is evaluated. Using WRF Model nested grids with 4-km grid spacing in the innermost domain, the focus is on EDA using dropsonde data from the Impact of Typhoons on the Ocean in the Pacific field campaign. The results show that the TC structure in the background mean state is improved and that unrealistically large ensemble spread can be alleviated. The characteristic horizontal scale in the background error covariance is smaller and narrower compared to those derived from the conventional EDA approach. Storm-scale corrections are improved using dropsonde data, which is more favorable for TC development. The analysis using the TC-centered EDA is in better agreement with independent observations. The improved analysis ameliorates model shock and improves the track forecast during the first 12 h and landfall at 72 h. The impact on intensity prediction is mixed with a better minimum sea level pressure and overestimated peak winds.
    Print ISSN: 0882-8156
    Electronic ISSN: 1520-0434
    Topics: Geography , Physics
    Published by American Meteorological Society
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  • 5
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    Predictability and Dynamics of Tropical Cyclone Rapid Intensification Deduced from High-Resolution Stochastic Ensembles (2016)
    American Meteorological Society
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    Publication Date: 2016-10-25
    Description: Rapid intensification (RI) of tropical cyclones (TCs) remains one of the most challenging issues in TC prediction. This study investigates the predictability of RI, the uncertainty in predicting RI timing, and the dynamical processes associated with RI. To address the question of environmental versus internal control of RI, five high-resolution ensembles of Hurricane Earl (2010) were generated with scale-dependent stochastic perturbations from synoptic to convective scales. Although most members undergo RI and intensify into major hurricanes, the timing of RI is highly uncertain. While environmental conditions including SST control the maximum TC intensity and the likelihood of RI during the TC lifetime, both environmental and internal factors contribute to uncertainty in RI timing. Complex interactions among environmental vertical wind shear, the mean vortex, and internal convective processes govern the TC intensification process and lead to diverse pathways to maturity. Although the likelihood of Earl undergoing RI seems to be predictable, the exact timing of RI has a stochastic component and low predictability. Despite RI timing uncertainty, two dominant modes of RI emerged. One group of members undergoes RI early in the storm life cycle; the other one later. In the early RI cases, a rapidly contracting radius of maximum wind accompanies the development of the eyewall during RI. The late RI cases have a well-developed eyewall prior to RI, while an upper-level warm core forms during the RI process. These differences indicate that RI is associated with distinct physical processes during particular stages of the TC life cycle.
    Print ISSN: 0027-0644
    Electronic ISSN: 1520-0493
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 6
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    Uncertainty Propagation in Coupled Atmosphere–Wave–Ocean Prediction System: A Study of Hurricane Earl (2010) (2018)
    American Meteorological Society
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    Publication Date: 2018-11-05
    Print ISSN: 0027-0644
    Electronic ISSN: 1520-0493
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 7
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    The impact of microphysical schemes on hurricane intensity and track (2011)
    Springer
    Details
    Publication Date: 2011-01-01
    Print ISSN: 1976-7633
    Electronic ISSN: 1976-7951
    Topics: Geosciences , Physics
    Published by Springer
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  • 8
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    Diurnal Cycle of Precipitation and Cloud Clusters in the MJO and ITCZ Over the Indian Ocean (2018)
    American Geophysical Union
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    Publication Date: 2018-09-19
    Description: Satellite observations of the diurnal cycle of precipitation and cloud clusters show a dominant nighttime maximum over the tropical Indian Ocean, similar to other basins. The nighttime maximum is associated with the relatively long lifetime of large convective systems that initiated during the afternoon when the sea surface temperature (SST) reached its diurnal maximum as first showed in Chen and Houze (1997, https://doi.org/10.1002/qj.49712353806). Shipborne and island-based radar data from Dynamics of the Madden-Julian Oscillation show distinct characteristics of the diurnal cycle in the equatorial region and Intertropical Convergence Zone (ITCZ). A secondary afternoon precipitation maximum occurs under light surface winds (〈5 m/s) when the diurnal cycle of SST is large (0.5–1.7 °C) in the equatorial region during the suppressed phase of the Madden-Julian Oscillation (MJO). The afternoon maximum was from short-lived convective systems with rain rates 〉10 mm/hr. In contrast, during the active MJO and in the ITCZ, the secondary afternoon maximum is mostly absent as the surface winds were generally 〉5 m/s and reduced afternoon SST warming to less than 0.5 °C. The Tropical Rainfall Measurement Mission Multiplatform Precipitation Analysis does not resolve the secondary afternoon maximum in heavier rain rates from short-lived small systems, but it suggests a more pronounced night-morning maximum in the ITCZ than in the MJO. Infrared 208-K cloud cluster analysis show that this difference in the morning maximum was due to the greater number of long-lasting, large convective systems (〉~200 km in diameter) persisting into the morning in the ITCZ. ©2018. American Geophysical Union. All Rights Reserved.
    Print ISSN: 2169-897X
    Electronic ISSN: 2169-8996
    Topics: Geosciences , Physics
    Published by American Geophysical Union
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  • 9
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    Prediction of Landfalling Hurricanes with the Advanced Hurricane WRF Model (2008)
    American Meteorological Society
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    Publication Date: 2008-06-01
    Description: Real-time forecasts of five landfalling Atlantic hurricanes during 2005 using the Advanced Research Weather Research and Forecasting (WRF) (ARW) Model at grid spacings of 12 and 4 km revealed performance generally competitive with, and occasionally superior to, other operational forecasts for storm position and intensity. Recurring errors include 1) excessive intensification prior to landfall, 2) insufficient momentum exchange with the surface, and 3) inability to capture rapid intensification when observed. To address these errors several augmentations of the basic community model have been designed and tested as part of what is termed the Advanced Hurricane WRF (AHW) model. Based on sensitivity simulations of Katrina, the inner-core structure, particularly the size of the eye, was found to be sensitive to model resolution and surface momentum exchange. The forecast of rapid intensification and the structure of convective bands in Katrina were not significantly improved until the grid spacing approached 1 km. Coupling the atmospheric model to a columnar, mixed layer ocean model eliminated much of the erroneous intensification of Katrina prior to landfall noted in the real-time forecast.
    Print ISSN: 0027-0644
    Electronic ISSN: 1520-0493
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 10
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    Cloud Clusters and Tropical Cyclogenesis: Developing and Nondeveloping Systems and Their Large-Scale Environment (2013)
    American Meteorological Society
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    Publication Date: 2013-01-01
    Description: Tropical cyclone (TC) genesis occurs only when there is persistent, organized convection. The question of why some cloud clusters develop into a TC and others do not remains unresolved. This question cannot be addressed adequately without studying nondeveloping systems in a consistent manner together with developing systems. This study presents a systematic approach in classifying developing and nondeveloping cloud clusters based on their large-scale environments. Eight years of hourly satellite IR data and global model analysis over the western North Pacific are used. A cloud cluster is defined as an area of ≤208-K cloud-top temperature, generally mesoscale in size. Based on the overlapping area between successive hourly images, they are then tracked in time as time clusters. The initial formations of nearly all TCs during July–October 2003–10 were associated with time clusters lasting at least 8 h (8-h clusters). The occurrence of an 8-h cluster is considered to indicate the minimum degree of convective organization needed for TC genesis. A nondeveloping system is defined as an 8-h cluster that is considered to be a viable candidate for TC genesis, but was not associated with the TC genesis. The large-scale environmental conditions of cyclonic low-level vorticity, low vertical wind shear, low-level convergence, and elevated tropospheric water vapor are statistically more favorable for developing systems. Generally, the environment became more (less) favorable with time for the developing (nondeveloping) systems. Nevertheless, many developing (nondeveloping) systems formed (dissipated) in seemingly unfavorable (favorable) environments within a lead time of
    Print ISSN: 0027-0644
    Electronic ISSN: 1520-0493
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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