Hilario, M. R. A., L. M. Olaguera, G. T. Narisma, and J. Matsumoto, 2020. Diurnal characteristics of summer precipitation over Luzon Island, Philippines. Asia-Pacific Journal of Atmospheric Sciences. https://link.springer.com/article/10.1007%2Fs13143-020-00214-1
A network of 411 ground stations across Luzon Island, Philippines (12.5–20° N, 119–126.5° E) was used to characterize the diurnal cycles of summer precipitation, in terms of amount (PA), frequency (PF), and intensity (PI), during the southwest monsoon season (SWM; May–September) between 2011 and 2018. In addition to monsoon exposure, the effect of topography on the diurnal cycle of precipitation also was investigated by comparing a valley, plain, west- and east-facing coasts near mountains. Results show that monsoon exposure significantly influenced diurnal precipitation such that PA and PF decreased (PI increased) toward the leeward side of Luzon Island. Most topographies showed late afternoon-early evening peaks; however, the east-facing coast exhibited a late night-early morning peak. Orographic effects led to a high PA over mountains and enhanced the spatiotemporal propagation of PA in monsoon-exposed areas. The first (second) half of the diurnal peak exhibited high PI/low PF (low PI/high PF), suggesting both PI and PF are important indicators of PA. Finally, graded analysis revealed that light precipitation (0.01–2.5 mm h−1) captured overall precipitation trends across Luzon Island, highlighting the importance of this intensity of precipitation. Heavy precipitation (2.5–7.5 mm h−1) peaked in the morning; however, underlying mechanisms remain unknown. The study presents the first examination of the diurnal precipitation cycle in Luzon Island using a dense network of synoptic stations. The study demonstrates the complex effect of topography on precipitation and the importance of the SWM in the diurnal cycle of precipitation.
Nguyen-Thi, T., T. Ngo-Duc, F. T. Tangang, F. Cruz, L. Juneng, J. Santisirisomboon, E. Aldrian, T. Phan-Van, and G. Narisma, 2021. Climate analogue and future appearance of novel climate in Southeast Asia. International Journal of Climatology. https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/joc.6693
This study identified the analogue locations of five big cities and the future appearance of novel climate in Southeast Asia (SEA) at the end of the 21st century under the Representative Concentration Pathways 8.5 (RCP8.5) and 4.5 (RCP4.5) scenarios. A modified version of an existing formulation to estimate climate distance is introduced, using the monthly means of temperature and precipitation from six regional climate experiments and from six global climate models (GCMs). Results showed that regional downscaling allowed a more accurate representation of temperature but displayed a higher variability in rainfall over SEA compared to the GCM performance. The ensemble mean (ENS) experiment had a relatively better performance compared to each individual experiment in representing the monthly time series of temperature and precipitation. The common tendency of climatic relocation towards warmer regions for the five big cities in SEA (Hanoi, Bangkok, Manila, Kuala Lumpur and Jakarta) was prominent with the regional ENS experiment. At the end of the 21st century, the ratio of novel climate areas over SEA, mainly located in low elevation, coastal, equatorial regions, and islands, was less than 2% under RCP4.5, but increased to 24 and 21% under RCP8.5 for the ensemble regional and global experiments, respectively.
Peralta, J. C. Albert C., G. T. T. Narisma, and F. A. T. Cruz, 2020. Validation of High-Resolution Gridded Rainfall Datasets for Climate Applications in the Philippines. Journal of Hydrometeorology. https://journals.ametsoc.org/view/journals/hydr/21/7/jhmD190276.xml
Gridded rainfall products could augment the shortage of available rainfall data in archipelagic countries like the Philippines, where weather stations are still sparsely distributed especially over its remote and less-developed islands. However, these products need to be validated first using ground measurements to determine their ability to represent properties of local rainfall. This study compares four high-resolution, gridded datasets—APHRODITEv1101, CHIRPSv2, TRMM 3B42v7, and PERSIANN-CDR—with respect to 49 synoptic weather stations over the Philippines from 1998 to 2005. The performance of these datasets was assessed in terms of bias, distribution, and different statistical error metrics and skill scores across time scales and climate types. Results show that all the datasets were able to capture the basic climatology and to varying extents, spatial patterns of Philippine rainfall. TRMM 3B42v7 has the least overall average monthly bias and most closely resembles the rainfall distribution observed at weather stations, especially dry days and torrential rain days for the whole Philippines. APHRODITEv1101 performs best in terms of error metrics and skill scores but displays consistent underestimates. CHIRPSv2, on the other hand, best captures the seasonal rainfall peaks in the different climate types in the Philippines but is prone to larger errors. Last, PERSIANN-CDR shows generally poor metrics and rainfall distributions, in comparison to the other datasets. These key findings are used to identify possible research applications in the Philippines that are best suited for each dataset.
Tangang, F., J. Santisirisomboon, L. Juneng, E. Salimun, J. Chung, S. Supari, F. Cruz, S. T. Ngai, T. Ngo-Duc, P. Singhruck, G. Narisma, J. Santisirisomboon, W. Wongsaree, K. Promjirapawat, Y. Sukamongkol, R. Srisawadwong, D. Setsirichok, T. Phan-Van, E. Aldrian, D. Gunawan, G. Nikulin, H. Yang, 2019. Projected future changes in mean precipitation over Thailand based on multi-model regional climate simulations of CORDEX Southeast Asia. International Journal of Climatology. https://doi.org/10.1002/joc.6163
This paper highlights detailed projected changes in rainfall over Thailand for the early (2011–2040), middle (2041–2070) and late (2071–2099) periods of the 21st century under the representative concentration pathways (RCP) 4.5 and RCP 8.5 using the high‐resolution multi‐model simulations of the Coordinated Regional Climate Downscaling Experiment (CORDEX) Southeast Asia. The ensemble mean is calculated based on seven members consisting of six general circulation models (GCMs) and three regional climate models (RCMs). Generally, the ensemble mean precipitation agrees reasonably well with observations, best represented by the Global Precipitation Climatology Center (GPCC) data, over Thailand during the historical period (1976–2005). However, inter‐model variations can be large among ensemble members especially during dry months (December to March) for northern‐central‐eastern parts, and throughout the year for the southern parts of Thailand. Similarly for future projection periods, inter‐model variations in the sign and magnitude of changes exist. The ensemble means of projected changes in rainfall for both RCPs during dry months show distinct contrast between the northern‐central‐eastern parts and the southern parts of Thailand with generally wetter and drier conditions, respectively. The magnitude of change can be as high as 15% of the historical period, which varies depending on the sub‐region, season, projection period, and RCP scenario. In contrast, generally drier conditions are projected during the wet season (June to September) throughout the country for both RCPs where the rainfall reduction can be as high as 10% in some areas. However, the magnitude of projected rainfall changes of some individual models can be much larger than the ensemble means, exceeding 40% in some cases. These projected changes are related to the changes in regional circulations associated with the winter and summer monsoons, which are projected to weaken. The drier (wetter) condition is associated with the enhanced subsidence (rising motion).
Tangang, F., J. X. Chung, L. Juneng, Supari, E. Salimun, S. T. Ngai, A. F. Jamaluddin, M. S. F. Mohd, F. Cruz, G. Narisma, J. Santisirisomboon, T. Ngo-Duc, P. V. Tan, P. Singhruck, D. Gunawan, E. Aldrian, A. Sopaheluwakan, N. Grigory, A. R. C. Remedio, D. V. Sein, D. Hein-Griggs, J. L. McGregor, H. Yang, H. Sasaki, and P. Kumar, 2020. Projected future changes in rainfall in Southeast Asia based on CORDEX-SEA multi-model simulations. Climate Dynamics. https://link.springer.com/article/10.1007/s00382-020-05322-2
This paper examines the projected changes in rainfall in Southeast Asia (SEA) in the twenty-first century based on the multi-model simulations of the Southeast Asia Regional Climate Downscaling/Coordinated Regional Climate Downscaling Experiment–Southeast Asia (SEACLID/CORDEX–SEA). A total of 11 General Circulation Models (GCMs) have been downscaled using 7 Regional Climate Models (RCMs) to a resolution of 25 km × 25 km over the SEA domain (89.5° E–146.5° E, 14.8° S–27.0° N) for two different representative concentration pathways (RCP) scenarios, RCP4.5 and RCP8.5. The 1976–2005 period is considered as the historical period for evaluating the changes in seasonal precipitation of December–January–February (DJF) and June–July–August (JJA) over future periods of the early (2011–2040), mid (2041–2070) and late twenty-first century (2071–2099). The ensemble mean shows a good reproduction of the SEA climatological mean spatial precipitation pattern with systematic wet biases, which originated largely from simulations using the RegCM4 model. Increases in mean rainfall (10–20%) are projected throughout the twenty-first century over Indochina and eastern Philippines during DJF while a drying tendency prevails over the Maritime Continent. For JJA, projections of both RCPs indicate reductions in mean rainfall (10–30%) over the Maritime Continent, particularly over the Indonesian region by mid and late twenty-first century. However, examination of individual member responses shows prominent inter-model variations, reflecting uncertainty in the projections.
Tibay, J., F. Cruz, F. Tangang, L. Juneng, T. Ngo Duc, T. Phan-Van, J. Santisirisomboon, P. Singhruck, D. Gunawan, E. Aldrian, and G. T. Narisma, 2021. Climatological characterization of tropical cyclones detected in the regional climate simulations over the CORDEX-SEA domain. International Journal of Climatology. https://doi.org/10.1002/joc.7070
In this study, a subset of the downscaled simulations of the Southeast Asia Regional Climate Downscaling / Coordinated Regional Climate Downscaling Experiment – Southeast Asia (SEACLID/CORDEX‐SEA) was analyzed to examine the representation of tropical cyclone (TC) climatology over Southeast Asia, in terms of pattern, intensity, frequency, and lifetime. A modified vortex tracking algorithm is used to detect TCs over the SEACLID/CORDEX‐SEA domain in the historical simulations from 1986 to 2005. Sensitivity tests for the detection method criteria, including vorticity, outer core wind strength, sea level pressure anomaly, and temperature anomaly at 300, 500, 700, and 850 hPa, were conducted to determine the optimum threshold configuration for each SEACLID/CORDEX‐SEA simulation used in the study. Comparison with the best track data of the Joint Typhoon Warning Center showed that model simulations underestimated the total number of TCs east of the Philippines for the 1986 – 2005 period but captured the annual cycle of the total number of TCs. This underestimation of TCs is possibly due to the domain used, which does not extend further east to cover most of the TC genesis area in the Western North Pacific. The structure of a typical TC from the regional climate model simulation is comparable to observed TC structure. However, results indicate that the resolution of the simulations is still not sufficient to capture the fine details of the observed TC structure, which could explain in part the lower intensification rate of TCs in the model output.
Trinh-Tuan, L., J. Matsumoto, F. T. Tangang, L. Juneng, F. Cruz, G. Narisma, J. Santisirisomboon, T. Phan-Van, D. Gunawan, E. Aldrian, and T. Ngo-Duc, 2019. Application of quantile mapping bias correction for mid-future precipitation projections over Vietnam, SOLA. https://www.jstage.jst.go.jp/article/sola/15/0/15_2019-001/_article
The Quantile Mapping (QM) bias correction (BC) technique was applied for the first time to address biases in the simulated precipitation over Vietnam from the Regional Climate Model (RegCM) driven by five Coupled Model Intercomparison Project Phase 5 (CMIP5) Global Climate Model (GCM) products. The QM process was implemented for the period 1986-2005, and subsequently applied to the mid-future period 2046-2065 under both Representative Concentration Pathway (RCP) 4.5 and RCP 8.5. Comparison with the original model outputs during the independent validation period shows a large bias reduction from 45% to 3% over Vietnam and significant improvements in representing precipitation indices (PI) after applying the QM technique. Moreover, the ensemble average of the BC products generally performed better than an individual BC member in capturing the spatial distribution of the PIs. A drier condition with a longer rainfall break, and shorter consecutive rainfall events are anticipated over Northern and Central Vietnam during their respective wet seasons in the mid-future. Furthermore, this study showed that the QM method minimally modified the future changes in PIs over most of Vietnam; thus, these corrected projections could be used in climate impacts and adaptation studies.
Villafuerte, M. Q. II, J. C. R. Lambrento, K. I. Hodges, F. T. Cruz, T. A. Cinco, and G. T. Narisma, 2021. Sensitivity of tropical cyclones to convective parameterization schemes in RegCM4. Climate Dynamics. https://link.springer.com/article/10.1007%2Fs00382-020-05553-3
This study investigates the sensitivity of simulated tropical cyclones (TC) affecting the Philippines to convective parameterization schemes (CPS) in the Regional Climate Model Version 4 (RegCM4). Five ERA-Interim driven RegCM4 simulations at 25-km horizontal resolution were conducted utilizing the CPS of Grell with Arakawa–Schubert closure (GR), Emanuel (EM), Kain–Fritsch (KF), Tiedtke (TE), and a combined Grell scheme over land and Emanuel over the ocean (GR-EM). Comparisons made between the observed and RegCM4-simulated TCs covering a 30-year period (1981–2010) indicate that the EM scheme yields an annual-mean TC frequency that is closest to observations. The GR-EM scheme, on the other hand, closely reproduces the observed seasonal patterns of TC tracks, spatial patterns of TC track density and TC-associated rainfall, and TC lifespan. The KF scheme is the only CPS that was able to simulate intense TCs (maximum wind speed > 40 m s–1) within the domain. In contrast, both GR and TE schemes largely underestimated the TC frequency, and were only able to simulate weak TCs. Such underestimation in the TC frequency and intensity in the GR and TE simulations can be attributed to the dry mid-tropospheric environment and the absence of a large area with positive low-level relative vorticity over the Pacific Ocean inhibiting TC formation and further development over the area. These findings would be helpful in selecting the more appropriate CPS for TC-related model simulations over the Philippines and in further model improvements, given the climate modeling imperfections and associated biases.
Bañares, E. N., G. T. T. Narisma, J. B. B. Simpas, F. T. Cruz, G. R. H. Lorenzo, M. O. L. Cambaliza, and R. C. Coronel. Seasonal and diurnal variations of observed convective rain events in Metro Manila, Philippines. Atmospheric Research. https://doi.org/10.1016/j.atmosres.2021.105646
The seasonal and diurnal characteristics of localized convective rain events in Metro Manila, Philippines were examined using observations from 16 automated weather stations in the city during the years 2013–2014. After partitioning total rainfall to determine the proportion that is mainly due to localized convection, the diurnal patterns of frequency and intensity of convective rain were then investigated during the northeast monsoon (from November to March), summer (from April to May), and southwest monsoon (from June to October) seasons. Maximum changes in meteorological variables were used to further verify and characterize localized convective rain events over the city. Results show higher rainfall (by ~500 mm) over northern Metro Manila compared to the southern area throughout the period of study. Although total rainfall was highest during the southwest monsoon season, it was during the summer season, when the total rainfall was least, that the largest proportion of rainfall, i.e. 55%, was attributed to convective rain. Almost 45% of the total convective rain events were identified as localized rain events. During the summer season, localized convective rain events in Metro Manila were prominent and vigorous (i.e. greater change in meteorological variables) in the afternoon, and were noted to move along the direction of the prevailing wind, i.e. from the northeastern side of the city towards the west. Increased understanding of the meteorological characteristics of these localized rain events can help improve rainfall forecasting over Metro Manila, leading to better disaster risk reduction and resilience in the city.
B. Under review
Magnaye, A. M. T., G. T. Narisma, F. T. Cruz, J. M. B. Dado, F. Tangang, L. Juneng, T. Ngo-Duc, T. Phan-Van, J. Santisirisomboon, P. Singhruck, D. Gunawan, and E. Aldrian. Potential influence of sea surface temperature representation in climate model simulations over CORDEX-SEA domain. International Journal of Climatology, under review.
C. In preparation
Antonio, R. L., F. Avila, F. Cruz, G. T. Narisma, L. Olaguera. Climatological analysis of droughts using a novel approach over the Philippines, in preparation.
Lagare, M. C., R. Coronel, J. Tibay, F. Cruz, G. T. Narisma, and M. Villafuerte II. Impacts of PBL parameterization in RegCM4.7 on the intensity and structure of simulated tropical cyclones over the Philippines, in preparation.
Magnaye, A. M. T., L. G. Aragon, J. M. B. Dado, F. T. Cruz, L.M.P. Olaguera, and G. T. Narisma. Process-based analysis on the impact of model SST to model climate using CORDEX-SEA simulations, in preparation.
Ona, B. J., R. A. Marasigan, K. A. Aquino, J. Manalo, T. Cinco, and J. M. Dado. Relationship of climate indices and sea surface temperature variability in the Philippines, in preparation.