Preface

**Section 2 Tropical Cyclones and Remote Sensing 135**

Song Yang and Joshua Cossuth

**Eyewalls 171**

**VI** Contents

Krishna Vissa

**Rainfall Forecast 217**

and Xingbao Wang

**Cyclones 233** Yuriy Kuleshov

Chapter 7 **Satellite Remote Sensing of Tropical Cyclones 137**

**Section 3 Tropical Cyclones, Modeling and Prediction 191**

**the North Indian Ocean Region 193**

Chapter 8 **Satellite Climatology of Tropical Cyclone with Concentric**

Chapter 9 **Progress in Tropical Cyclone Predictability and Present Status in**

Chapter 10 **An Operational Statistical Scheme for Tropical Cyclone-Induced**

Chapter 11 **Climate Risk Early Warning System for Island Nations: Tropical**

Kasturi Singh, Jagabandhu Panda, Krishna K. Osuri and Naresh

Qinglan Li, Hongping Lan, Johnny C.L. Chan, Chunyan Cao, Cheng Li

Yi-Ting Yang, Hung-Chi Kuo, Eric A. Hendricks and Melinda S. Peng

There has been a large amount of research on tropical cyclones, one of nature's most de‐ structive phenomena. This research has resulted in recent improvements for forecasting the arrival, path, and intensity of these storms. Today, however, tropical cyclones can still strike with little warning. Tropical cyclones continue to bring destruction, as well as disruption, to societies that are exposed to their threat. These storms cause as many problems for devel‐ oped nations as for less developed nations, a good example being Hurricane Katrina (2005).

Of course RADAR and satellite technology and numerical models continue to increase our understanding of the structure and dynamics of tropical cyclones. The monitoring of tropi‐ cal systems continues to improve in all the world's ocean basins. We are now at the point of understanding the climatological occurrence of tropical cyclones and also the interannual and interdecadal variations in their occurrences. We can also see climatological trends in tropical cyclone occurrence for each ocean basin and can make reasonable assessments about the frequency of its occurrence in the future. Concern about climate change and the change in frequency of extreme events often invoke projections about how tropical storm intensity may change as well. As stated in the book"Recent Hurricane Research - Climate, Dynamics, and Societal Impacts", we understand that these powerful storms represent the cooperative interaction between atmospheric and oceanic conditions and that they will oc‐ cur only when conditions in both are favorable.

The book represents a compilation of more cutting-edge research on tropical cyclones and their impacts from researchers at many institutions around the world. Each contribution has been reviewed. This book has been divided into three sections, and each is organized by topic. The first section, Tropical Cyclone Dynamics, contains contributions that explore the physical factors contributing to storm development and maintenance. This includes the use of traditional diagnostics as well as statistics in explaining their occurrence. The first chapter examines the impact of tropical cyclone occurrence on the characteristics of the Western North Pacific. Traditionally, studies have examined the impact of the ocean on tropical cy‐ clone characteristics. The second chapter explores the influence of the synoptic scale on the rapid development of tropical cyclones using principal component analysis. The outcome gives insight into which variables are important in forecasting rapid development.

The next chapter in section 1 performs a thorough analysis of the synoptic considerations for understanding tornadogenesis in land-falling storms and the improvement of recognition of these conditions by the operational community. The dynamics and biological response of the upper ocean are the subject of the fourth chapter in this section. Examining a case study (Typhoon Cimaron, 2006), the authors demonstrate that the ocean is restored to the prestorm equilibrium in two to three weeks. They also demonstrate that phytoplankton blooms can occur within days of a storm's passage. The next chapter examines the planetary-scale low-level dynamics in the rapid development of Hurricane Wilma (2005). The authors show that large-scale low-level circulations associated with midlatitude troughs play an important role in rapid tropical cyclogenesis. The final chapter in this section explores the interaction of mesoscale convective systems and latent heat release associated with deep convection in the rapid development of two tropical cyclones.

The second section presents the use of satellite-based remote sensing in the detection and climatology of tropical cyclones. The first chapter presents a review of satellite-based techni‐ ques in examining the location, structure, and intensity of tropical cyclones using many dif‐ ferent platforms. This also includes a discussion of their detection and their precipitation patterns. The advent of remote sensing has greatly helped to reduce the ability to forecast these events. The second chapter presents a satellite-based climatology of concentric eyewall occurrence in tropical cyclones. They looked at the frequency with which eyewall replace‐ ment happened with the inner wall relative to the outer wall, as well as the maintenance of concentric eyewalls for some time. They find that the inner (outer) eyewall replacement is associated with internal (environmental) dynamics. They find significant variability related to El Niño and Southern Oscillation in the West Pacific Ocean Basin, but no corresponding variability in the Atlantic.

The topic of the third section is contributions to modeling tropical cyclones as well as their prediction. The first chapter presents an in-depth look at the climatology of Northern Indian Ocean region cyclones. Detailed records for this region are less than 40 years old. The authors examine the occurrence, movement, structure, and intensification of tropical cyclones in the region. They also look at the relative role of the atmospheric and oceanic influences on these, with the goal of improving predictability in this region of the world. The second chapter ex‐ amines the occurrence and prediction of heavy rainfall associated with land-falling tropical cyclones in the southwest part of the West Pacific Ocean Basin. The authors use nonparamet‐ ric statistical methods. They develop and test statistical models of the probability of heavy rainfalls and show the success of their methods in improving forecasts. The last chapter uses statistical techniques to model the behavior of tropical cyclone activity in the Southern Hemi‐ sphere. Using linear multivariable and support sector regression techniques, the authors dem‐ onstrate they can reasonably model the regional annual and temporal occurrence of tropical cyclones. These methods could potentially improve current forecast techniques.

In closing, the research presented here adds to the current database on what is known about tropical cyclone behavior and has the potential to lead to the development of better forecast‐ ing methods, which will save lives and property. This book would make a great supplement to any course on tropical meteorology, which highlights current research. I would like to thank all those that made this book possible including the publication staff at InTech pub‐ lishers and the authors who chose to publish their work in this volume.

> **Professor Anthony R. Lupo** University of Missouri Columbia, MO, USA

**Tropical Cyclone Dynamics**

can occur within days of a storm's passage. The next chapter examines the planetary-scale low-level dynamics in the rapid development of Hurricane Wilma (2005). The authors show that large-scale low-level circulations associated with midlatitude troughs play an important role in rapid tropical cyclogenesis. The final chapter in this section explores the interaction of mesoscale convective systems and latent heat release associated with deep convection in

The second section presents the use of satellite-based remote sensing in the detection and climatology of tropical cyclones. The first chapter presents a review of satellite-based techni‐ ques in examining the location, structure, and intensity of tropical cyclones using many dif‐ ferent platforms. This also includes a discussion of their detection and their precipitation patterns. The advent of remote sensing has greatly helped to reduce the ability to forecast these events. The second chapter presents a satellite-based climatology of concentric eyewall occurrence in tropical cyclones. They looked at the frequency with which eyewall replace‐ ment happened with the inner wall relative to the outer wall, as well as the maintenance of concentric eyewalls for some time. They find that the inner (outer) eyewall replacement is associated with internal (environmental) dynamics. They find significant variability related to El Niño and Southern Oscillation in the West Pacific Ocean Basin, but no corresponding

The topic of the third section is contributions to modeling tropical cyclones as well as their prediction. The first chapter presents an in-depth look at the climatology of Northern Indian Ocean region cyclones. Detailed records for this region are less than 40 years old. The authors examine the occurrence, movement, structure, and intensification of tropical cyclones in the region. They also look at the relative role of the atmospheric and oceanic influences on these, with the goal of improving predictability in this region of the world. The second chapter ex‐ amines the occurrence and prediction of heavy rainfall associated with land-falling tropical cyclones in the southwest part of the West Pacific Ocean Basin. The authors use nonparamet‐ ric statistical methods. They develop and test statistical models of the probability of heavy rainfalls and show the success of their methods in improving forecasts. The last chapter uses statistical techniques to model the behavior of tropical cyclone activity in the Southern Hemi‐ sphere. Using linear multivariable and support sector regression techniques, the authors dem‐ onstrate they can reasonably model the regional annual and temporal occurrence of tropical

cyclones. These methods could potentially improve current forecast techniques.

lishers and the authors who chose to publish their work in this volume.

In closing, the research presented here adds to the current database on what is known about tropical cyclone behavior and has the potential to lead to the development of better forecast‐ ing methods, which will save lives and property. This book would make a great supplement to any course on tropical meteorology, which highlights current research. I would like to thank all those that made this book possible including the publication staff at InTech pub‐

> **Professor Anthony R. Lupo** University of Missouri Columbia, MO, USA

the rapid development of two tropical cyclones.

variability in the Atlantic.

VIII Preface

#### **Influence of Tropical Cyclones in the Western North Pacific Influence of Tropical Cyclones in the Western North Pacific**

Wen-Zhou Zhang, Sheng Lin and Xue-Min Jiang Wen-Zhou Zhang, Sheng Lin and Xue-Min Jiang

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/64009

#### **Abstract**

The Western North Pacific (WNP) is the most favorable area in the world for the generation of tropical cyclones (TCs). As the most intense weather system, TCs play an important role in the change of ocean environment in the WNP. Based on many investigations published in the literature, we obtained a collective and systematic understanding of the influence of TCs on ocean components in the WNP, including sea temperature, ocean currents, mesoscale eddies, storm surges, phytoplankton (indicated by chlorophyll *a*). Some ocean responses to TCs are unique in the WNP because of the existence of the Kuroshio and special geographical configurations such as the South China Sea.

**Keywords:** tropical cyclone, typhoon, influence, ocean response, Western North Pacif‐ ic

### **1. Introduction**

The Western North Pacific (WNP), including its marginal seas (similarly hereafter), is the most favorable area in the world for the generation of tropical cyclones (TCs) since more TCs are born in this area than in any other region every year. The TCs in the WNP account for about one‐third of TCs born in the world oceans [1, 2]. According to the data during the period of 1971–2000, the annual generation rate of TCs is 27.2 in the WNP [2]. For the activity of TCs, the South China Sea (SCS) is the most important marginal sea of the WNP where many TCs pass through and some locally form every year. Averaged from 1968 to 1988, the annual mean number of TCs in the WNP is 25.7 among which the numbers of the TCs passing over the SCS and the TCs forming in the SCS are 10.3 and 3.5, respectively [3]. The TCs in

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

the WNP can occur in any month of the year but most of them are generated in the boreal summer (June‐August) and autumn (September‐November). Strong TCs are traditionally called typhoons in the WNP.

As the most intense weather system which usually causes drastic air‐sea interaction, TCs play an important role in the change of ocean environment in the WNP and attract many researches focusing on this topic. By reviewing these researches, we aim to get a collective and systematic understanding of the influence of TCs in the WNP.

## **2. Temperature response to TCs**

#### **2.1. In the open ocean**

Sea surface temperature (SST) response to TCs has been widely noticed and extensively investigated in the world oceans (e.g., [4, 5]). TCs usually cause SST to drop (SST cooling) via vertical mixing, air‐sea heat flux, and advection. Vertical mixing is regarded as the most important mechanism of the cooling within the initial mixed layer and meanwhile it is responsible for the warming below the initial mixed layer [4]. Owing to the asymmetry of both wind stress and its rotation with time, the strongest SST cooling is shifted to the right of TC track in the Northern Hemisphere [4, 6]. In addition, this rightward shift or bias depends on the TC translation speed [4, 7]. Upwelling (vertical advection) enhances the SST cooling associated with TCs, especially slowly moving ones, and tends to reduce its rightward shift [4]. The exclusion of upwelling may result in the underestimation of the SST cooling as shown in Chiang et al. [8]. The cooling caused by upwelling may overwhelm the warming due to vertical mixing, resulting in a subsurface cooling, in the subsurface layer where the vertical gradient of temperature is large [6].

Mei et al. [9] demonstrated that stronger, slower‐moving, and higher‐latitude TCs usually cause a larger magnitude of SST anomaly. Slowly moving typhoons tend to induce larger SST drop than fast moving typhoons for the former have relatively longer residence time, producing a stronger vertical mixing and more heat loss from ocean to air. The magnitude of the SST cooling depends not only on the intensity and translation speed of typhoon, but also on the preceding thermal structure (i.e., mixed layer depth and upper‐ocean stratifica‐ tion) of the upper ocean. Lin et al. [5] showed that a typhoon causes quite smaller SST cooling under the condition with a thicker warm upper layer than it does under the climatological condition. The scope of the SST cooling is related to the typhoon size. D'Asaro et al. [7] observed that among several TC‐induced cold wakes, the smallest typhoon, Megi in Philippine Sea, produced a narrowest wake, indicating that the width of the cold wake depends on the TC size.

The SST cooling reaches a peak during the day following a TC passage and the surface cold wake restores to normal in an e‐folding time of 5–20 days [9, 10]. In the WNP, Mrvaljevic et al. [11] found that a cold wake induced by Typhoon Fanapi (2010) extended to more than 80 m depth and four days later a thin and warm surface layer was formed above the cold wake. The capped wake (defined as the layer of 26–27°C) returned to normal after an e‐folding time of 23 days, almost twice that of the corresponding SST cooling. Similar phenomenon has also been observed in the WNP by D'Asaro et al. [7] and their observations showed that the subsurface wake commonly occurred after the passage of several typhoons.

#### **2.2. In the Kuroshio region**

the WNP can occur in any month of the year but most of them are generated in the boreal summer (June‐August) and autumn (September‐November). Strong TCs are traditionally

As the most intense weather system which usually causes drastic air‐sea interaction, TCs play an important role in the change of ocean environment in the WNP and attract many researches focusing on this topic. By reviewing these researches, we aim to get a collective and systematic

Sea surface temperature (SST) response to TCs has been widely noticed and extensively investigated in the world oceans (e.g., [4, 5]). TCs usually cause SST to drop (SST cooling) via vertical mixing, air‐sea heat flux, and advection. Vertical mixing is regarded as the most important mechanism of the cooling within the initial mixed layer and meanwhile it is responsible for the warming below the initial mixed layer [4]. Owing to the asymmetry of both wind stress and its rotation with time, the strongest SST cooling is shifted to the right of TC track in the Northern Hemisphere [4, 6]. In addition, this rightward shift or bias depends on the TC translation speed [4, 7]. Upwelling (vertical advection) enhances the SST cooling associated with TCs, especially slowly moving ones, and tends to reduce its rightward shift [4]. The exclusion of upwelling may result in the underestimation of the SST cooling as shown in Chiang et al. [8]. The cooling caused by upwelling may overwhelm the warming due to vertical mixing, resulting in a subsurface cooling, in the subsurface layer where the vertical gradient

Mei et al. [9] demonstrated that stronger, slower‐moving, and higher‐latitude TCs usually cause a larger magnitude of SST anomaly. Slowly moving typhoons tend to induce larger SST drop than fast moving typhoons for the former have relatively longer residence time, producing a stronger vertical mixing and more heat loss from ocean to air. The magnitude of the SST cooling depends not only on the intensity and translation speed of typhoon, but also on the preceding thermal structure (i.e., mixed layer depth and upper‐ocean stratifica‐ tion) of the upper ocean. Lin et al. [5] showed that a typhoon causes quite smaller SST cooling under the condition with a thicker warm upper layer than it does under the climatological condition. The scope of the SST cooling is related to the typhoon size. D'Asaro et al. [7] observed that among several TC‐induced cold wakes, the smallest typhoon, Megi in Philippine Sea, produced a narrowest wake, indicating that the width of the cold wake

The SST cooling reaches a peak during the day following a TC passage and the surface cold wake restores to normal in an e‐folding time of 5–20 days [9, 10]. In the WNP, Mrvaljevic et al. [11] found that a cold wake induced by Typhoon Fanapi (2010) extended to more than 80 m depth and four days later a thin and warm surface layer was formed

called typhoons in the WNP.

**2.1. In the open ocean**

of temperature is large [6].

depends on the TC size.

understanding of the influence of TCs in the WNP.

4 Recent Developments in Tropical Cyclone Dynamics, Prediction, and Detection

**2. Temperature response to TCs**

As a famous western boundary current originating from the North Equatorial Current, the Kuroshio has unique properties, characterized by high temperature, high salinity, and large velocity. In the Kuroshio region, the mixed layer as well as the thermocline is usually deeper than that in the neighboring ocean water [12, 13], which restrains the typhoon‐induced SST cooling. Based on satellite remote sensing data, Wu et al. [12] found that Typhoon Nari (2001) did not induce a significant SST cooling near the Kuroshio axis where the thermocline depth is 80–100 m, while a significant SST cooling occurred in the shelf region north of the Kuroshio where the thermocline depth is 20–30 m. In addition to the deep thermocline, they suggested that the strong advection of heat along the Kuroshio also contributed to weak SST cooling near the Kuroshio axis. Analyzing the SST responses to 22 typhoons which went across the Kuroshio in the East China Sea (ECS) from 2001 to 2010, Liu and Wei [13] demonstrated that the SST cooling (averaged within 150 km on the right of each typhoon track) in the Kuroshio region ranged from 0.61°C to 4.93°C with a mean of 2.09°C while the mean SST cooling in the neighboring ocean region was 2.68°C. Wei et al. [14] reported that a SST cooling of about 3°C in the Kuroshio was produced by Typhoon Megi (2004). Their results indicated that vertical mixing is mainly responsible for the SST cooling and the kinetic energy drawn from the Kuroshio baroclinic potential energy may contribute to the cooling by enhancing local vertical mixing.

There are two special cases of temperature cooling associated with typhoons in the Kuroshio region. First, a significant temperature drop of 4°C in the upper layer from the sea surface to about 100 m was observed in the Kuroshio region, near the southeast tip of Taiwan, before Typhoon Morakot (2009) passed over [15]. This was caused by an offshore cool jet which was generated by persistent westerly wind and stretched along the Kuroshio. Secondly, typhoon‐induced inshore transport of Kuroshio subsurface water in the ECS can produce upwelling and cause severe drop in the SST on the shelf beside the Kuroshio. This happened off northeastern Taiwan Island during Typhoons Gerald (1987) and Hai‐Tang (2005) [16–18].

Using 10‐year satellite remote sensing SST data and Argo temperature profiles, Liu and Wei [13] investigated the temperature change (warming) in the surface and subsurface of Kuroshio when the temperature recovered from typhoon‐induced temperature cooling. They found that the surface temperature change (1.24°C) in the Kuroshio region is slightly smaller than that (1.39°C) in the general ocean while the subsurface temperature change (3.52°C) in the former is much larger than that (1.52°C) in the latter. Their numerical simulations indicated that the subsurface temperature change is mostly caused by downwelling related to typhoon‐induced

Ekman pumping. The warm water is extracted into the subsurface from the surface by the downwelling and subsequently moves downstream with Kuroshio current.

#### **2.3. In the SCS**

The SCS is the largest semi‐enclosed marginal sea of the WNP. Many TCs pass through the SCS and some are born in this sea every year [3]. Compared with the open ocean of the WNP, the SCS displays a similar but some different temperature response to typhoons due to its unique hydrological environment and complex topography.

Using the Princeton Ocean Model, Chu et al. [19] showed that Typhoon Ernie (1996) induced a significant SST cooling with a rightward bias in the SCS, similar to that in the open ocean. But it also caused some unique responses such as the SST warming in the region from southwest of Taiwan Island to northwest of Luzon Island because of the convergence between the northward coastal current west of Luzon and the Kuroshio intrusion current through the Luzon Strait.

Owing to the shallow pre‐typhoon mixed layer and thermocline, Typhoons Kai‐Tak (2000), Lingling (2001) and Megi (2010) generated a very large SST drop of 10.8°C, 11°C and 8°C, respectively, in the SCS [8, 20, 21]. Chiang et al. [8] suggested that upwelling (account for 62%) dominated vertical mixing (31%) in producing the SST cooling under the influence of Kai‐Tak, a weak and slowly moving typhoon. Megi's translation speed was 5.5–6.9 m/s over the ocean east of the Philippines, faster than 1.4–2.8 m/s over the SCS, and the pre‐typhoon mixed layer depth in these two regions was about 40 m and 20 m, respectively [22]. As a result, the SST cooling in the former was only 1–2°C, quite smaller than that in the SCS. Based on the mooring observations in the northern SCS during Megi, Guan et al. [23] showed that the temperature cooling occurred in the entire observed water column (60–360 m), which was mainly caused by typhoon‐induced upwelling.

After comparing the temperature responses to TCs in the SCS and in the tropical ocean of the NWP, Mei et al. [24] found that under the influence of TCs with an identical intensity, the SST cooling in the SCS is more than 1.5 times that in the tropical ocean, which could be attributed to the shallower mixed layer and stronger subsurface thermal stratification in the former. Numerical simulations showed that Typhoon Nuri (2008) induced a stronger SST cooling in the SCS than in the open ocean of the WNP when it travelled northwestward from the open ocean to the SCS [25]. Sun et al. [25] indicated that three processes are responsible for the different regional responses. Firstly, the SCS has a thinner mixed layer, which makes it easier to entrain cooler subsurface water into the surface layer. Secondly, the cyclonic background vorticity in SCS allows stronger current shears and turbulent eddy diffusivity to be generated, however, the background vorticity in the open ocean is anticyclonic. Finally, as the typhoon moved to higher latitude in SCS, the larger Coriolis frequency in the SCS is more favorable for producing stronger wind‐current resonance and then stronger inertial amplitudes and turbulence.
