SEA-AIR INTERACTION LABORATORY (SAIL)
The laboratory’s goal is to advocate that the study of weather and climate would be incomplete without studying the ocean.
Sea Air Land Interaction
“The ocean remembers, being the memory of the climate system”.
Upper ocean dynamics
The dynamics of the upper ocean is important in understanding the weather systems as it is within the bounds of the interface of the ocean and atmosphere. One of the interesting dynamical features of the ocean near the Philippines is the bifurcation of the North Equatorial Current located at the eastern side of the Philippines.
The Acoustic Doppler Current Profiler (ADCP) is one of the devices used for measuring ocean current velocities through the doppler effect of scattered sound waves in the water column.
Wind and waves
Wave generation is greatly influenced by the force of wind. The image shows the wind intensity of a passing cyclone, in this case Typhoon Yolanda of 2013, were the intense wind generated huge waves and storm surges.
Models are decision support systems that transform complex physical phenomena to simplified versions that can explain, to some extent, the said phenomena.
Wave exposure maps
Wave exposure maps are proactive response to the impacts of battering waves that constantly affects our coastal communities.
Image Source: Vulnerability Assessment Tools for Coastal Ecosystems: A Guidebook 2013
Topographic sills are underwater geologic formations that influence the dynamics of the water column in terms of current velocities, current directions, salinity, temperature, etc.
The Flow Through System device is comprised of several interdependent devices/sensors used for ocean optics data acquisition. This is a standard device in the sea-air interaction laboratory.
Phytoplankton pigments and productivity
Chlorophyll in phytoplankton is one of the photosynthetic pigment in the ocean. SAIL is also interested in studying phytoplankton pigments as a productivity indicator of the ocean waters.
Source: Barrier Layer Control of Entrainment and Upwelling in the Bohol Sea, Philippines (Cabrera et al. 2011)
Rodrigo, S.M.T., Villanoy, C.L., Briones, J.C., Bilgera, P.H.T., Cabrera, O.C.C., Narisma, G.T.T., The mapping of storm surge-prone areas and characterizing surge-producing cyclones in Leyte Gulf, Philippines. Natural Hazards (2018) 92: 1305.
Historically, Leyte Gulf in central eastern Philippines has received catastrophic damage due to storm surges, the most recent of which was during Typhoon Haiyan in 2013. A city-level risk assessment was performed on Leyte Gulf through synthetic storm generation, high-resolution ocean modeling, and decision tree analyses. Cyclones were generated through a combination of a Poisson point process and Monte Carlo simulations. Wind and pressure fields generated from the cyclones were used in a storm surge model of Leyte Gulf developed on Delft3D. The output of these simulations was a synthetic record of extreme sea level events, which were used to estimate maximum surge heights for different return periods and to characterize surge-producing storm characteristics using decision tree analyses. The results showed that the area most prone to surges is the Tacloban–Basey area with a 2.8 ± 0.3 m surge occurring at a frequency of every 50 years. Nearby Palo area will likely receive a surge of 1.9 ± 0.4 m every 50 years while Giporlos–Salcedo area a surge of 1.0 ± 0.1 m. The decision tree analysis performed for each of these areas showed that for surges of 3–4 m, high-velocity winds (> 30 m/s) are consistently the main determining factor. For the areas, Tacloban, Basey, and Giporlos–Salcedo, wind speed was also the main determining factor for surge > 4 m.
J.L.A. Soria, A.D. Switzer, C.L. Villanoy, H.M. Fritz, P.H.T. Bilgera, O.C. Cabrera, F. Siringa, Y.Yacat-Sta. Maria, R. D. Ramos, and I.Q. Fernandez. 2016: Repeat Storm Surge Disasters of Typhoon Haiyan and Its 1897 Predecessor in the Philippines. Bull. Amer. Meteor. Soc., 97, 31-48.
On 8 November 2013, Typhoon Haiyan impacted the Philippines with estimated winds of approximately 314 km h-1 and an associated 5–7-m-high storm surge that struck Tacloban City and the surrounding coast of the shallow, funnel-shaped San Pedro Bay. Typhoon Haiyan killed more than 6,000 people, superseding Tropical Storm Thelma of November 1991 as the deadliest typhoon in the Philippines. Globally, it was the deadliest tropical cyclone since Nargis hit Myanmar in 2008. Here, we use field measurements, eyewitness accounts, and video recordings to corroborate numerical simulations and to characterize the extremely high velocity flooding caused by the Typhoon Haiyan storm surge in both San Pedro Bay and on the more open Pacific Ocean coast. We then compare the surge heights from Typhoon Haiyan with historical records of an unnamed typhoon that took a similar path of destruction in October 1897 (Ty 1897) but which was less intense, smaller, and moved more slowly. The Haiyan surge was about twice the height of the 1897 event in San Pedro Bay, but the two storm surges had similar heights on the open Pacific coast. Until stronger prehistoric events are explored, these two storm surges serve as worst-case scenarios for this region. This study highlights that rare but disastrous events should be carefully evaluated in the context of enhancing community-based disaster risk awareness, planning, and response.
Cabrera, O.C., C.L. Villanoy, I.D. Alabia, and A.L. Gordon. 2015. Shifts in chlorophyll a off eastern Luzon, Philippines, associated with the North Equatorial Current bifurcation latitude. Oceanography 28(4): 46-53
The Bohol Sea is a relatively unstudied marginal sea located in the southern part of the Philippines. Hydrographic data from the Philippine Straits Dynamics Experiment (PhilEx) cruises reveal a complex three-dimensional circulation composed of two overturning cells that may be referred to as “double-estuarine type.” This type of overturning circulation promotes upwelling of cold, nutrient-rich waters within the Bohol Sea associated with entrainment and eddy processes that promote phytoplankton blooms. Evidence from ocean color imagery supports entrainment in the eastern basin and eddy formation in the southwestern basin. However, PhilEx researchers found that the cyclonic Iligan Bay Eddy in the southwestern basin did not conform to the paradigm of cyclonic eddy upwelling. Although upwelling was evident through doming isotherms within the water column, the surface projection of this signal was suppressed by the presence of a thick barrier layer, particularly during cruises in December 2007 and January 2008, a known La Niña period. Long-term trends in chlorophyll data followed trends in rainfall and the ENSO 3.4 index, with elevated (reduced) chlorophyll during dry El Niño years (wet La Niña years). By promoting stability of surface layer stratification and preventing vertical transport of nutrients, the barrier layer is thus a mechanism by which the El Niño-Southern Oscillation influences phytoplankton biomass in the Bohol Sea.
M.S. Samson, S.S. Mamauag, L.T. David, R.Borja-Del Rosario, M.C.C. Quibilan, F.P. Siringan, M.Y.Y. Sta Maria, N.B. España, C.L. Villanoy, R.C. Geronimo, O.C. Cabrera, R.J.S. Martinez, P.M. Aliño (2015). I-C-SEA Change: A participatory tool for rapid assessment of vulnerability of tropical coastal communities to climate change impacts. AMBIO A Journal of the Human Environment 06/2015
We present a synoptic, participatory vulnerability assessment tool to help identify the likely impacts of climate change and human activity in coastal areas and begin discussions among stakeholders on the coping and adaptation measures necessary to minimize these impacts. Vulnerability assessment tools are most needed in the tropical Indo-Pacific, where burgeoning populations and inequitable economic growth place even greater burdens on natural resources and support ecosystems. The Integrated Coastal Sensitivity, Exposure, and Adaptive Capacity for Climate Change (I-C-SEA Change) tool is built around a series of scoring rubrics to guide non-specialists in assigning scores to the sensitivity and adaptive capacity components of vulnerability, particularly for coral reef, seagrass, and mangrove habitats, along with fisheries and coastal integrity. These scores are then weighed against threat or exposure to climate-related impacts such as marine flooding and erosion. The tool provides opportunities for learning by engaging more stakeholders in participatory planning and group decision-making. It also allows for information to be collated and processed during a "town-hall" meeting, facilitating further discussion, data validation, and even interactive scenario building.
Pullen, J., Gordon, A. L., Flatau, M., Doyle, J. D., Villanoy, C., & Cabrera, O. (2015). Multiscale influences on extreme winter rainfall in the Philippines. Journal of Geophysical Research: Atmospheres, 1–18. doi:10.1002/2014JD022645
During 2007–2008, the Philippines experienced the greatest rainfall in 40 winters. We use a combination of observations (including 48 meteorological stations distributed throughout the islands, Tropical Rainfall Measuring Mission satellite-sensed precipitation, and shipboard measurements) along with a high-resolution two-way coupled ocean/atmosphere model (3 km Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS)®) to examine this anomalous season. As expected from climatology, rainfall was greatest on the eastern side of the archipelago, with seasonal totals exceeding 4000 mm in some locations. A moderate to strong La Niña increased the rainfall across the region. But discrete precipitation events delivered the bulk of the rain to the area and coincided with intense Madden-Julian oscillation activity over the archipelago and a late February cold surge. General patterns and magnitudes of rainfall produced by the two-way coupled model agreed with observations from land and from space. During the discrete events, the 3 km COAMPS also produced high amounts of precipitation in the mountainous parts of central Philippines. Direct observations were limited in this region. However, the government reported river flooding and evacuations in Mindoro during February 2008 as a result of significant rainfall. In addition, shipboard measurements from late January 2008 (collected by the Philippines Straits Dynamics Experiment) reveal a fresh lens of water to the west of the island of Mindoro, consistent with high freshwater discharge (river runoff) into the coastal area.
MS STUDENTS GRADUATED
- Sheila Marie Navarro , MS Meteorology– Modulation of Philippine Rainfall by Convectively Coupled Equatorial Waves
Rainfall is the most prominent climatic event in the Philippines. In this study,the influence of convectively coupled equatorial waves (CCEWs) to rainfall in the Philippines was investigated and quantified using 18-year long daily Outgoing Longwave Radiation (OLR) and rainfall from Tropical Rainfall Measuring Mission(TRMM) from year 1998-2015. Wavenumber-frequency filtering method was employed to isolate and filter the band signal of each CCEWs for a domain covering the Philippines, from 110oE to 130oE and 5oN to 20oN. Variance analysis was used to determine the contributions of CCEWs to rainfall variability for Philippine domain, and for the northern, central, and southern region. Also, the relationship between CCEWs events and ground-based rainfall from Philippine Atmospheric, Geophysical, and Astronomical Service Administration (PAGASA) synoptic station was analyzed for the year 2016.Kelvin, equatorial Rossby (ER), and mixed Rossby gravity (MRG) wave modulated Philippine rainfall variance by 3.36%, 4.19%, and 1.92%, respectively.Kelvin waves dominated the southern Philippines contributing about 3.9% of the total rainfall variance. It has two distinct peaks which occur during May –June, and December – January. The secondary peak of Kelvin waves was weaker compared to the primary peak. On the other hand, ER waves prevailed in the central Philippines with4.6% of the total rainfall variance. ER waves were relatively active throughout the year except for months of September –October. During July –August, the signals of ER waves were shifted to the northern Philippines. Similar to Kelvin waves, MRG waves also had its maximum modulation in southern Philippines with about 2.2% of the total rainfall variance. It also has two distinct peaks which occur during July and November.MRG waves peak during July was extended to northern Philippines. Ground-based data showed rainfall correlating with the OLR signals of the CCEWS. Rain occurred mostly during the passage of waves (i.e, 0 or no lag) particularly Kelvin waves and MRG waves. Active events of ER waves caused a lead to the rainfall in the northern Philippines and a delay in the southern Philippines. This study shows that CCEWs modulated the rainfall variance in the Philippines, with ER (MRG) waves showing greatest (least)influence and with southern Philippines being the most affected collectively by all three studied CCEWs during boreal winter
- Jimmy R. Corong, Jr , MS Meteorology– Use of a forecast atmospheric-ocean-sediment model for assessing the impact of typhoon-induced surge to coastal geomorphology
In the Philippines, intensity of typhoons is measured by maximum wind speed attained, with damage resulting mostly from the ferocious winds and sometimes torrential rains. However, typhoons also inflict damage by changing the onshore and offshore landscape at a faster rate than normal through morphological processes such as erosion and sedimentation. Typhoon Haiyan (Yolanda) is an intense typhoon that devastated the Visayas region in the Philippines on November 8, 2013. The coastal towns along San Pedro Bay were among the most affected when Typhoon Haiyan made landfall. An atmospheric forecast model (WRF) and an ocean model (Delft3D-Flow/Wave) were used to simulate the typhoon surge and sedimentological changes during and immediately after Haiyan. Parameterization of WRF atmospheric model focused on varying microphysics schemes and using the wind and pressure output from the best combination scheme as inputs for the Delft3D ocean model. In Tacloban City, a 2 meter surge was produced using WRF wind, compared to a 5 meter surge produced using input from best-track data of Joint Typhoon Warning Center (JTWC). The difference was due to the significantly weaker wind produced from WRF simulation. There are erosion and sedimentation hotspots in the coasts of San Pedro Bay, with Tacloban and Tanauan as areas with significant erosion and Basey with significant sedimentation. To some extent, hydrodynamic process, coastal erosion and sedimentation that led to the morphological changes in the study area were reproduced and is consistent with previous studies. This study is the first of its kind that tried to couple atmospheric, oceanographic, and sedimentological process in simulating the damage from Typhoon Haiyan.
- Alvin E. Pura, MS Meteorology
- Arra Camille D. Canare, MS Meteorology
- Diana Mae T. Calde, MS Meteorology
- Alyssa Dawn M. Castillo, MS Meteorology
- Noel R. Bangquaio, MS Meteorology
- Macky R. Villa, MS Meteorology
- Angelyn A. General, MS Meteorology
- Regional Scales of Variability in Precipitation (RSVP) Project
- Spatiotemporal Distribution and relative abundance of small cetaceans along southern Tañon Strait in relation to environmental factors
- Benham Rise Potential Productivity Research Project
- National Assessment for the Coral Reef Environmental (NACRE) Project (Watershed and Ocean Parameters for the Assessment of Coral Reef Health [WOPAC])
- Coastal Assessment for Rehabilitation Enhancement:Capability Development and Resiliency of EcoSystems (CARE-CaDRES)