scholarly journals Application of Oceanic Heat Content Estimation to Operational Forecasting of Recent Atlantic Category 5 Hurricanes

2008 ◽  
Vol 23 (1) ◽  
pp. 3-16 ◽  
Author(s):  
Michelle Mainelli ◽  
Mark DeMaria ◽  
Lynn K. Shay ◽  
Gustavo Goni
Keyword(s):  
Tropical Cyclone ◽  
Positive Impact ◽  
Thermal Structure ◽  
Heat Content ◽  
Intensity Change ◽  
Upper Ocean ◽  
Average Intensity ◽  
Hurricane Intensity ◽  
Structure Information ◽  
Maximum Improvement

Abstract Research investigating the importance of the subsurface ocean structure on tropical cyclone intensity change has been ongoing for several decades. While the emergence of altimetry-derived sea height observations from satellites dates back to the 1980s, it was difficult and uncertain as to how to utilize these measurements in operations as a result of the limited coverage. As the in situ measurement coverage expanded, it became possible to estimate the upper oceanic heat content (OHC) over most ocean regions. Beginning in 2002, daily OHC analyses have been generated at the National Hurricane Center (NHC). These analyses are used qualitatively for the official NHC intensity forecast, and quantitatively to adjust the Statistical Hurricane Intensity Prediction Scheme (SHIPS) forecasts. The primary purpose of this paper is to describe how upper-ocean structure information was transitioned from research to operations, and how it is being used to generate NHC’s hurricane intensity forecasts. Examples of the utility of this information for recent category 5 hurricanes (Isabel, Ivan, Emily, Katrina, Rita, and Wilma from the 2003–05 hurricane seasons) are also presented. Results show that for a large sample of Atlantic storms, the OHC variations have a small but positive impact on the intensity forecasts. However, for intense storms, the effect of the OHC is much more significant, suggestive of its importance on rapid intensification. The OHC input improved the average intensity errors of the SHIPS forecasts by up to 5% for all cases from the category 5 storms, and up to 20% for individual storms, with the maximum improvement for the 72–96-h forecasts. The qualitative use of the OHC information on the NHC intensity forecasts is also described. These results show that knowledge of the upper-ocean thermal structure is fundamental to accurately forecasting intensity changes of tropical cyclones, and that this knowledge is making its way into operations. The statistical results obtained here indicate that the OHC only becomes important when it has values much larger than that required to support a tropical cyclone. This result suggests that the OHC is providing a measure of the upper ocean’s influence on the storm and improving the forecast.

Oceanic Heat Content Variability in the Eastern Pacific Ocean for Hurricane Intensity Forecasting

2010 ◽  
Vol 138 (6) ◽  
pp. 2110-2131 ◽  
Author(s):  
Lynn K. Shay ◽  
Jodi K. Brewster
Keyword(s):  
Pacific Ocean ◽  
Heat Content ◽  
Ocean Basin ◽  
Eastern Pacific ◽  
Intensity Change ◽  
Upper Ocean ◽  
Eastern Pacific Ocean ◽  
Hurricane Intensity ◽  
Tropical Ocean

Abstract Recent evidence supports the premise that the subsurface ocean structure plays an important role in modulating air–sea fluxes during hurricane passage, which in turn, affects intensity change. Given the generally sparse in situ data, it has been difficult to provide region-to-basin-wide estimates of isotherm depths and upper-ocean heat content (OHC). In this broader context, satellite-derived sea surface height anomalies (SSHAs) from multiple platforms carrying radar altimeters are blended, objectively analyzed, and combined with a hurricane-season climatology to estimate isotherm depths and OHC within the context of a reduced gravity model at 0.25° spatial intervals in the eastern Pacific Ocean where tropical cyclone intensity change occurs. Measurements from the Eastern Pacific Investigation of Climate in 2001, long-term tropical ocean atmosphere mooring network, and volunteer observing ship deploying expendable bathythermograph (XBT) profilers are used to carefully evaluate satellite-based measurements of upper-ocean variability. Regression statistics reveal small biases with slopes of 0.8–0.9 between the subsurface measurements compared with isotherm depths (20° and 26°C), and OHC fields derived from objectively analyzed SSHA field. Root-mean-square differences in OHC range between 10 and 15 kJ cm−2 or roughly 10%–15% of the mean signals. Similar values are found for isotherm depth differences between in situ and inferred satellite-derived values. Blended daily values are used in the Statistical Hurricane Intensity Prediction Scheme (SHIPS) forecasts as are OHC estimates for the Atlantic Ocean basin. An equivalent OHC variable is introduced that incorporates the strength of the thermocline at the base of the oceanic mixed layer using a climatological stratification parameter  /No, which seems better correlated to hurricane intensity change than just anomalies as observed in Hurricane Juliette in 2001.

Sea Surface Temperature Variability in Hurricanes: Implications with Respect to Intensity Change

2003 ◽  
Vol 131 (8) ◽  
pp. 1783-1796 ◽  
Author(s):  
Joseph J. Cione ◽  
Eric W. Uhlhorn
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Heat Content ◽  
Sea Surface ◽  
Intensity Change ◽  
Upper Ocean ◽  
High Wind ◽  
Ocean Energy ◽  
Upper Ocean Heat Content ◽  
Ocean Environment

Abstract Scientists at NOAA's Hurricane Research Division recently analyzed the inner-core upper-ocean environment for 23 Atlantic, Gulf of Mexico, and Caribbean hurricanes between 1975 and 2002. The interstorm variability of sea surface temperature (SST) change between the hurricane inner-core environment and the ambient ocean environment ahead of the storm is documented using airborne expendable bathythermograph (AXBT) observations and buoy-derived archived SST data. The authors demonstrate that differences between inner-core and ambient SST are much less than poststorm, “cold wake” SST reductions typically observed (i.e., ∼0°–2°C versus 4°–5°C). These findings help define a realistic parameter space for storm-induced SST change within the important high-wind inner-core hurricane environment. Results from a recent observational study yielded estimates of upper-ocean heat content, upper-ocean energy extracted by the storm, and upper-ocean energy utilization for a wide range of tropical systems. Results from this analysis show that, under most circumstances, the energy available to the tropical cyclone is at least an order of magnitude greater than the energy extracted by the storm. This study also highlights the significant impact that changes in inner-core SST have on the magnitude of air–sea fluxes under high-wind conditions. Results from this study illustrate that relatively modest changes in inner-core SST (order 1°C) can effectively alter maximum total enthalpy (sensible plus latent heat) flux by 40% or more. The magnitude of SST change (ambient minus inner core) was statistically linked to subsequent changes in storm intensity for the 23 hurricanes included in this research. These findings suggest a relationship between reduced inner-core SST cooling (i.e., increased inner-core surface enthalpy flux) and tropical cyclone intensification. Similar results were not found when changes in storm intensity were compared with ambient SST or upper-ocean heat content conditions ahead of the storm. Under certain circumstances, the variability associated with inner-core SST change appears to be an important factor directly linked to the intensity change process.

Further Improvements to the Statistical Hurricane Intensity Prediction Scheme Using Tropical Cyclone Rainfall and Structural Features

2018 ◽  
Vol 33 (6) ◽  
pp. 1587-1603 ◽  
Author(s):  
Udai Shimada ◽  
Hiromi Owada ◽  
Munehiko Yamaguchi ◽  
Takeshi Iriguchi ◽  
Masahiro Sawada ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Real Time ◽  
Heat Content ◽  
Absolute Error ◽  
Structural Features ◽  
Japan Meteorological Agency ◽  
Intensity Change ◽  
Hurricane Intensity ◽  
Intensity Prediction ◽  
Prediction Scheme

Abstract The Statistical Hurricane Intensity Prediction Scheme (SHIPS) is a multiple regression model for forecasting tropical cyclone (TC) intensity [both central pressure (Pmin) and maximum wind speed (Vmax)]. To further improve the accuracy of the Japan Meteorological Agency version of SHIPS, five new predictors associated with TC rainfall and structural features were incorporated into the scheme. Four of the five predictors were primarily derived from the hourly Global Satellite Mapping of Precipitation (GSMaP) reanalysis product, which is a microwave satellite-derived rainfall dataset. The predictors include the axisymmetry of rainfall distribution around a TC multiplied by ocean heat content (OHC), rainfall areal coverage, the radius of maximum azimuthal mean rainfall, and total volumetric rain multiplied by OHC. The fifth predictor is the Rossby number. Among these predictors, the axisymmetry multiplied by OHC had the greatest impact on intensity change, particularly, at forecast times up to 42 h. The forecast results up to 5 days showed that the mean absolute error (MAE) of the Pmin forecast in SHIPS with the new predictors was improved by over 6% in the first half of the forecast period. The MAE of the Vmax forecast was also improved by nearly 4%. Regarding the Pmin forecast, the improvement was greatest (up to 13%) for steady-state TCs, including those initialized as tropical depressions, with slight improvement (2%–5%) for intensifying TCs. Finally, a real-time forecast experiment utilizing the hourly near-real-time GSMaP product demonstrated the improvement of the SHIPS forecasts, confirming feasibility for operational use.

scholarly journals Upper-Ocean Thermal Structure and the Western North Pacific Category 5 Typhoons. Part II: Dependence on Translation Speed

2009 ◽  
Vol 137 (11) ◽  
pp. 3744-3757 ◽  
Author(s):  
I-I. Lin ◽  
Iam-Fei Pun ◽  
Chun-Chieh Wu
Keyword(s):  
Mixed Layer ◽  
North Pacific ◽  
Western North Pacific ◽  
Thermal Structure ◽  
Subsurface Layer ◽  
Heat Content ◽  
Correlation Coefficients ◽  
Upper Ocean ◽  
Translation Speed

Abstract Using new in situ ocean subsurface observations from the Argo floats, best-track typhoon data from the U.S. Joint Typhoon Warning Center, an ocean mixed layer model, and other supporting datasets, this work systematically explores the interrelationships between translation speed, the ocean’s subsurface condition [characterized by the depth of the 26°C isotherm (D26) and upper-ocean heat content (UOHC)], a cyclone’s self-induced ocean cooling negative feedback, and air–sea enthalpy fluxes for the intensification of the western North Pacific category 5 typhoons. Based on a 10-yr analysis, it is found that for intensification to category 5, in addition to the warm sea surface temperature generally around 29°C, the required subsurface D26 and UOHC depend greatly on a cyclone’s translation speed. It is observed that even over a relatively shallow subsurface warm layer of D26 ∼ 60–70 m and UOHC ∼ 65–70 kJ cm−2, it is still possible to have a sufficient enthalpy flux to intensify the storm to category 5, provided that the storm can be fast moving (typically Uh ∼ 7–8 m s−1). On the contrary, a much deeper subsurface layer is needed for slow-moving typhoons. For example at Uh ∼ 2–3 m s−1, D26 and UOHC are typically ∼115–140 m and ∼115–125 kJ cm−2, respectively. A new concept named the affordable minimum translation speed Uh_min is proposed. This is the minimum required speed a storm needs to travel for its intensification to category 5, given the observed D26 and UOHC. Using more than 3000 Argo in situ profiles, a series of mixed layer numerical experiments are conducted to quantify the relationship between D26, UOHC, and Uh_min. Clear negative linear relationships with correlation coefficients R = −0.87 (−0.71) are obtained as Uh_min = −0.065 × D26 + 11.1, and Uh_min = −0.05 × UOHC + 9.4, respectively. These relationships can thus be used as a guide to predict the minimum speed a storm has to travel at for intensification to category 5, given the observed D26 and UOHC.

scholarly journals Restratification of the Upper Ocean after the Passage of a Tropical Cyclone: A Numerical Study

2012 ◽  
Vol 42 (9) ◽  
pp. 1377-1401 ◽  
Author(s):  
Wei Mei ◽  
Claudia Pasquero
Keyword(s):  
Tropical Cyclone ◽  
Water Column ◽  
Numerical Study ◽  
Baroclinic Instability ◽  
Relative Size ◽  
Heat Content ◽  
Heat Fluxes ◽  
Upper Ocean ◽  
Regional Ocean Modeling System ◽  
Eddy Structures

Abstract The role of baroclinic instability in the restratification of the upper ocean after the passage of a tropical cyclone (TC) is determined by means of numerical simulations. Using a regional ocean model, the Regional Ocean Modeling System (ROMS), a high-resolution three-dimensional simulation that includes the process of baroclinic instability and is initialized with moderate-amplitude eddy structures reproduces the satellite-observed decay rate of the TC-induced sea surface temperature (SST) anomaly and is also in qualitative agreement with published observations after the passage of Hurricane Fabian in 2003 that showed decaying cold and warm anomalies located in the climatological mixed layer (CML) and upper thermocline, respectively. The model ocean is restratified after approximately one month with a net heat gain in the water column due to anomalous air–sea heat fluxes. The model shows, however, that vertical heat fluxes associated with baroclinic instability dominate over air–sea heat fluxes in restoring the CML heat content during the first month. A comparison with two-dimensional simulations that exclude baroclinic adjustment further highlights the importance of baroclinic instability: it can not only input a considerable amount of heat into the CML, but also establish strong stratification there, inhibiting the downward penetration of heat contributed by diabatic heating at the surface; both effects hasten the recovery of the SST. Additional experiments were performed to examine the sensitivity of the model results to changes in Newtonian cooling rate, changes in the magnitude of the eddy structures used to initialize the simulation, and changes in poststorm wind strength; the results indicate that, although some of them may have a significant effect on the recovery time of the SST, their influence on the contribution of baroclinic instability to the recovery of the CML heat content is modest. However, the contribution of baroclinic instability exhibits pronounced positive dependence on the depth of the mixing layer relative to the CML depth and the relative size of the area with unperturbed water. Its dependence on the shape of the spatial variation of the mixing depth is relatively weak but in a more complicated manner. These dependencies are consistent with those predicted by a simple front adjustment model, whereas the latter also suggest that the contribution of baroclinic instability is independent of the prestorm stratification below the CML. Overall, the idealized simulations in this study suggest that, for a typical situation in the real ocean, baroclinic instability can account for approximately 50% of the full recovery of the CML heat content, whereas under specific conditions the contribution can be significantly smaller. Those estimates provide a limit to the maximum net warming of the water column after the initial mixing event and thus have important implications regarding estimating the long-term effect of TCs on the upper-ocean heat budget.

scholarly journals Tropical Cyclones and Transient Upper-Ocean Warming

2008 ◽  
Vol 21 (1) ◽  
pp. 149-162 ◽  
Author(s):  
Claudia Pasquero ◽  
Kerry Emanuel
Keyword(s):  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
Heat Content ◽  
Ocean Model ◽  
Ocean Heat Content ◽  
Upper Ocean ◽  
Cyclone Activity ◽  
Upper Ocean Heat Content ◽  
Vertical Temperature Profile ◽  
Thermodynamic Conditions

Abstract Strong winds affect mixing and heat distribution in the upper ocean. In turn, upper-ocean heat content affects the evolution of tropical cyclones. Here the authors explore the global effects of the interplay between tropical cyclones and upper-ocean heat content. The modeling study suggests that, for given atmospheric thermodynamic conditions, regimes characterized by intense (with deep mixing and large upper-ocean heat content) and by weak (with shallow mixing and small heat content) tropical cyclone activity can be sustained. A global general circulation ocean model is used to study the transient evolution of a heat anomaly that develops following the strong mixing induced by the passage of a tropical cyclone. The results suggest that at least one-third of the anomaly remains in the tropical region for more than one year. A simple atmosphere–ocean model is then used to study the sensitivity of maximum wind speed in a cyclone to the oceanic vertical temperature profile. The feedback between cyclone activity and upper-ocean heat content amplifies the sensitivity of modeled cyclone power dissipation to atmospheric thermodynamic conditions.

scholarly journals Upper Oceanic Energy Response to Tropical Cyclone Passage

2013 ◽  
Vol 26 (8) ◽  
pp. 2631-2650 ◽  
Author(s):  
John A. Knaff ◽  
Mark DeMaria ◽  
Charles R. Sampson ◽  
James E. Peak ◽  
James Cummings ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Energy Content ◽  
Energy Conditions ◽  
Upper Ocean ◽  
Ocean Energy ◽  
Translation Speed ◽  
Structure Information ◽  
Sst Cooling ◽  
Ocean Response ◽  
Upper Ocean Response

Abstract The upper oceanic temporal response to tropical cyclone (TC) passage is investigated using a 6-yr daily record of data-driven analyses of two measures of upper ocean energy content based on the U.S. Navy’s Coupled Ocean Data Assimilation System and TC best-track records. Composite analyses of these data at points along the TC track are used to investigate the type, magnitude, and persistence of upper ocean response to TC passage, and to infer relationships between routinely available TC information and the upper ocean response. Upper oceanic energy decreases in these metrics are shown to persist for at least 30 days—long enough to possibly affect future TCs. Results also indicate that TC kinetic energy (KE) should be considered when assessing TC impacts on the upper ocean, and that existing TC best-track structure information, which is used here to estimate KE, is sufficient for such endeavors. Analyses also lead to recommendations concerning metrics of upper ocean energy. Finally, parameterizations for the lagged, along-track, upper ocean response to TC passage are developed. These show that the sea surface temperature (SST) is best related to the KE and the latitude whereas the upper ocean energy is a function of KE, initial upper ocean energy conditions, and translation speed. These parameterizations imply that the 10-day lagged SST cooling is approximately 0.7°C for a “typical” TC at 30° latitude, whereas the same storm results in 10-day (30-day) lagged decreases of upper oceanic energy by about 12 (7) kJ cm−2 and a 0.5°C (0.3°C) cooling of the top 100 m of ocean.

scholarly journals Improving Ocean Model Initialization for Coupled Tropical Cyclone Forecast Models Using GODAE Nowcasts

2008 ◽  
Vol 136 (7) ◽  
pp. 2576-2591 ◽  
Author(s):  
G. R. Halliwell ◽  
L. K. Shay ◽  
S. D. Jacob ◽  
O. M. Smedstad ◽  
E. W. Uhlhorn
Keyword(s):  
Tropical Cyclone ◽  
Thermal Energy ◽  
Prediction Models ◽  
Three Dimensional ◽  
Heat Content ◽  
Ocean Model ◽  
Upper Ocean ◽  
Cold Bias ◽  
Sst Cooling ◽  
Free Running

Abstract To simulate tropical cyclone (TC) intensification, coupled ocean–atmosphere prediction models must realistically reproduce the magnitude and pattern of storm-forced sea surface temperature (SST) cooling. The potential for the ocean to support intensification depends on the thermal energy available to the storm, which in turn depends on both the temperature and thickness of the upper-ocean warm layer. The ocean heat content (OHC) is used as an index of this potential. Large differences in available thermal energy associated with energetic boundary currents and ocean eddies require their accurate initialization in ocean models. Two generations of the experimental U.S. Navy ocean nowcast–forecast system based on the Hybrid Coordinate Ocean Model (HYCOM) are evaluated for this purpose in the NW Caribbean Sea and Gulf of Mexico prior to Hurricanes Isidore and Lili (2002), Ivan (2004), and Katrina (2005). Evaluations are conducted by comparison to in situ measurements, the navy’s three-dimensional Modular Ocean Data Assimilation System (MODAS) temperature and salinity analyses, microwave satellite SST, and fields of OHC and 26°C isotherm depth derived from satellite altimetry. Both nowcast–forecast systems represent the position of important oceanographic features with reasonable accuracy. Initial fields provided by the first-generation product had a large upper-ocean cold bias because the nowcast was initialized from a biased older-model run. SST response in a free-running Isidore simulation is improved by using initial and boundary fields with reduced cold bias generated from a HYCOM nowcast that relaxed model fields to MODAS analyses. A new climatological initialization procedure used for the second-generation nowcast system tended to reduce the cold bias, but the nowcast still could not adequately reproduce anomalously warm conditions present before all storms within the first few months following nowcast initialization. The initial cold biases in both nowcast products tended to decrease with time. A realistic free-running HYCOM simulation of the ocean response to Ivan illustrates the critical importance of correctly initializing both warm-core rings and cold-core eddies to correctly simulate the magnitude and pattern of SST cooling.

scholarly journals Eddy-induced Track Reversal and Upper Ocean Physical-Biogeochemical Response of Tropical Cyclone Madi in the Bay of Bengal

2019 ◽  
Author(s):  
Riyanka Roy Chowdhury ◽  
S. Prasanna Kumar ◽  
Arun Chakraborty
Keyword(s):  
Life Cycle ◽  
Tropical Cyclone ◽  
Bay Of Bengal ◽  
Net Primary Productivity ◽  
Heat Content ◽  
Remote Sensing Data ◽  
Fold Increase ◽  
Upper Ocean ◽  
Western Boundary ◽  
Cyclonic Storm

Abstract. The life cycle of the tropical cyclone Madi in the southwestern Bay of Bengal (BoB) during 6th to 12th December 2013 was studied using a suite of ocean and atmospheric data. Madi formed as a depression on 6th December and intensified into a very severe cyclonic storm by 8th December. What was distinct about Madi was its (1) swift weakening from very severe cyclone to a severe cyclone while moving towards north on 9th, (2) abrupt track reversal close to 180-degree in a southwestward direction on 10th, and (3) rapid decay in the open ocean by 12th December while still moving southwestward. Using both in situ and remote sensing data, we show that oceanic cyclonic eddies played a leading role in the ensuing series of events that followed its genesis. The sudden weakening of the cyclone before its track reversal was facilitated by the oceanic cyclonic (cold-core) eddy, which reduced the ocean heat content and cooled the upper ocean through upward eddy-pumping of subsurface waters. When Madi moved over cyclonic eddy-core, its further northward movement was arrested. Subsequently, the prevailing northeasterly winds assisted the slow moving system to change its track to a southwesterly path. While travelling towards southwestward direction, the system rapidly decayed when it passed over the regions of cyclonic eddies located near the western boundary of the BoB. Though Madi was a category-2 cyclone, it had a profound impact on the physical and biogeochemical state of the upper ocean. Cyclone-induced enhancement in the chlorophyll a ranged from 5 to 7-fold, while increase in the net primary productivity ranged from 2.5 to 8-fold. Similarly, the CO2 out-gassing into the atmosphere showed a 3.7-fold increase compared to the pre-cyclone values. Our study points to the crucial role oceanic eddies play in the life cycle of cyclone in the BoB. Eddies being ubiquitous and tropical cyclones occur twice a year in the BoB, there is an urgent need to incorporate them in the models for the better prediction of the cyclone track and intensity.

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