Research in Marine Sciences 13 Investigating short-term variations of some parameters during the selected typhoons in the South China Sea Tahereh Haghroosta1, 2, ∗, and Wan Ruslan Ismail3, 4 1Iranian Coastal and Marine Structural Engineering Association, Tehran, Iran 2Arman Darya Research-based Company, Tehran, Iran 3Section of Geography, School of Humanities, Universiti Sains Malaysia, 11800 Minden, Pulau Pinang, Malaysia 4Centre for Global Sustainability Studies, Universiti Sains Malaysia, 11800 Minden, Pulau Pinang, Malaysia Received: 2016-07-22 Accepted: 2016-08-18 Abstract Different parameters of sea surface temperature (SST), latent heat flux (LHF), sensible heat flux (SHF), sea level pressure (SLP), and precipitation rate were compared with their own related anomalies during different typhoons in the South China Sea, to determine the effect of the typhoon on the parameters. These effects were examined based on the archived data from the National Centers for Environmental Prediction and the National Center for Atmospheric Research to compute the anomaly of the parameters. The data of the typhoons obtained from the International Best Track Archive for Climate Stewardship. Two series of maps were considered, one for the first day and one for the strongest day of the typhoon occurrence. Using eyeball analysis of the maps showed the SST in the day that the typhoon had high intensity reduced relative to the first day due to cooling effect. The SLP anomaly reduction from the first day to the extreme day was obvious in all cases that could be connected to the typhoon strengthening. Furthermore, variations of LHF values between the first day and the extreme day increased, and their anomalies changed from negative val- ues to positive values. The results also indicated a positive correlation between SHF and typhoon intensity. Keywords: Sea surface temperature; Latent heat flux; Sensible heat flux; Sea level pressure; Pre- cipitation rate; South China Sea. 1. Introduction cording to the study by Zhou and Cui (2011), ty- phoons are a synoptic phenomenon over warm Typhoons are important events in the South Chi- waters. They often generate rainstorms and storm na Sea as it can generate large-scale damage. They surges, which are caused many financial and human cause strong winds, heavy precipitation, and storm losses in countries. More research about typhoons surge, which are significant natural disasters. Ac- can improve understanding on their mechanisms, *Corresponding Author: [email protected] key element for climate studies, and they have an essential role in developing and 14 Investigating short-term variations of some parameters.../ 13-21 maintaining of the cyclones (Yu and Weller, 2007). However, operational predicting of typhoon intensity variation is still a challenging task. and provide a scientific foundation for short-term Dare and McBride (2011) investigated the re- forecasting, increasing capability for defending sponse of sea surface temperature (SST) to TCs us- against this kind of disasters, and reducing losses. ing SST dataset and global cyclone tracks during 2. Data In particular, latent heat flux (LHF) and sensible the years of 1981–2008. The temperature time se- heat2.1. fluxStudy (SHF) area have important roles during a ty- ries were averaged before and after cyclone occur- phoon (Shay et al., 2000). rence at individual cyclone positions. The results TheTyphoons South Chinaobtain theirSea energyis the largest from warm marginal water, sea showedplaced atthat the maximum western north cooling of Pacificeffect occurredOcean andextending ocean provides from theenergy equator for typhoon’s to 23 °N strength latitude- andmostly from a99 day ºE after to 125 storm ºE passage. longitude Their (Figure study 1).stat - ening (Emanuel, 1991; Lin et al., 2009). The TC ed that the minimum SST anomaly was 20.98 ˚C intensityThe area is caused is a bysemi-closed the interaction ocean with basinwarm wasurrounded- and the by data South of SST China, anomalies Vietnam, were recovered Cambodia, with ter,Thailand, which provides Peninsular fuel. As Malaysia, the TC strengthens, Borneo Island, the 44%Indonesia, within fivethe Philippines,days and with Taiwan,88% in 30 anddays. the This evaporation rate grows because of the increase in means that the SST reactions, and the recovery time Indo-China Peninsula (Ho et al., 2000; Wang, 2008). The area connects with the east of surface wind speed. The enhancement of the mois- were related to the cyclone strength and its speed. tureChina supply Sea, from the the Indian ocean Ocean, leads toand an theincrease Pacific of OceanFurthermore, through the atTaiwan the ocean-atmosphere Straits, the Straits interface, of theMalacca, latent heat and energy the thatLuzon drives Straits, the circulation respectively. of heatThe exchanging South China occurs Sea with is a onenumber of ofthe processes most TCs (Bender et al., 1993). such as: solar radiation, long-wave radiation, SHF importantUsing satellite places observations, of TCs generati the interactionon. In this be study,- by the convection study area and is conduction, limited to andthe LHF1ºN byto 16sea-sur ºN - tweenand fromtropical 100 cyclone ºE to 130Nari ºE,in 2001, in latitude and Kuroshio and longitude. face water evaporation. The distribution of heat flux Current was investigated. Nari crossed the Kuro- over the oceans is a key element for climate studies, shioAccording several times, to the which study caused of Zuki variations and Lupo in ty(2008)- and and they Ariffin have andan essential Moten (2009),role in developing typhoons inand phoonthe westernintensity. PacificThe cooling Ocean effect and (up the to 5South ˚C) was Chin amaintaining Sea may ofhave the cyclonesconsiderable (Yu and effects Weller, on 2007). the observed due to upwelling and vertical mixing in However, operational predicting of typhoon inten- precipitation and cause flooding in surrounding countries. Thus, predicting typhoon intensity the upper ocean some days after the storm passed sity variation is still a challenging task. (Wuis aet challenge al., 2008). in these areas. Figure 1. South China Sea 3 2.2. Selected typhoons The eight selected typhoons originated in the study area, were used in this paper (see Table1), and obtained from International Best Track Archive for Climate Stewardship (IBTrACS) dataset (Knapp et al., 2010). The typhoons were selected based on their generations, development, and dissipation in the study area. Research in Marine Sciences 15 Table1. Selected typhoons in the study area Typhoon Date Affected areas 1 PEIPAH 2007 Philippines- Vietnam Tropical 2 2008 South China Sea- Malaysia Depression 01W 3 NOUL 2008 Philippines- Vietnam- Thailand 4 KUJIRA 2009 Philippines- South China Sea 5 CHAN-HOM 2009 South China Sea- Philippines-Luzon 6 NANGKA 2009 South China Sea- Philippines-Calapan city 7 SONGDA 2011 Philippines-Taiwan 8 WASHI 2011 Philippines- South China Sea 2. Data 2-2 Selected typhoons 2.1.3. StudyMethods area The eight selected typhoons originated in the study To find the relationship between typhoon activities and some important parameters such as The South China Sea is the largest marginal sea area, were used in this paper (see Table1), and obtained placedSST, atLHF, the SHF,western precipitation north of Pacific rate, andOcean sea exlevel- frompressure International (SLP), theBest NCEP-NCAR Track Archive reanalysisfor Climate tendingdata (Kalnay from the etequator al., 1996) to 23 °Navailable latitude from and from the ClimateStewardship Prediction (IBTrACS) Center dataset (CDC) (Knapp are employedet al., 2010). 99 ºE to 125 ºE longitude (Figure 1). The area is a The typhoons were selected based on their generations, semi-closedto compute ocean the basin21-year surrounded (1990-2011) by South mean Chi -anomalydevelopment, of the and para dissipationmeters induring the study the area. selected na,typhoons. Vietnam, Cambodia, Thailand, Peninsular Ma- laysia, Borneo Island, Indonesia, the Philippines, 3. Methods Taiwan,Two series and the of Indo-Chinamaps are considered, Peninsula (Ho one et for al. , the first day of typhoon occurrence and one for 2000;the dayWang, when 2008). the Thetyphoon area wasconnects the strongest.with the UsiTong find eyeball the relationshipanalysis of thebetween maps typhoon shows activithe - east of China Sea, the Indian Ocean, and the Pacif- ties and some important parameters such as SST, variations of the selected parameters during the day and the related anomalies during ic Ocean through the Taiwan Straits, the Straits of LHF, SHF, precipitation rate, and sea level pressure Malacca,different and typhoons the Luzon (i.e., Straits, Noul, respectively. Peipah, TD The 01W, (SLP), Chan-Hom, the NCEP-NCAR Nangka, Kujira,reanalysis Songda, data (Kalnay and et al., 1996) available from the Climate Prediction SouthWashi). China Sea is one of the most important places of TCs generation. In this study, the study area is Center (CDC) are employed to compute the 21- limited to the 1ºN to 16 ºN and from 100 ºE to 130 year (1990-2011) mean anomaly of the parameters ºE, in latitude and longitude. during the selected typhoons. According to the study of Zuki and Lupo Two series of maps are considered, one for the first (2008) and Ariffin and Moten (2009), typhoons in 4 day of typhoon occurrence and one for the day when the western Pacific Ocean and the South China Sea the typhoon was the strongest. Using eyeball analy- may have considerable effects on the precipitation sis of the maps shows the variations of