Search Results (5)

Based on the monthly mean reanalysis data from NCEP/NCAR (National Centers for Environmental Prediction/ National Center for Atmospheric Research) and GPCP (Global Precipitation Climatology Project) (1979–2020), the regional characteristics of precipitation in the warm pool side of the Maritime Continent (MC) and the relationships between different precipitation patterns and atmospheric circulations are studied. The results show that there are significant correlations as well as differences between the precipitation in the east of the Philippines (area A) and that in the Pacific Ocean near the Northern Mariana Islands (area B). Precipitation in area A is closely related to the eastern Pacific ENSO (El Nino-Southern Oscillation) and EAP/PJ (East Asia-Pacific/Pacific-Japan) teleconnection pattern, while precipitation in area B is linked to the Indian Ocean basin-wide and the South China Sea summer monsoon. When the precipitation anomaly in area A is positive, the East Asian summer monsoon is weak. A cyclone appears to the northwest of area A at 850 hPa with convergence airflow. After filtering out the effects of precipitation in area B, the cyclone retreats to the west, and an anticyclone appears to the southeast of area A. When the precipitation is above normal in area B, the circulation and water vapor transportation are similar to that in area A but more to the east. The updraft and downdrafts to both north and south sides of area B form two closed meridional vertical circulations. When the influence of area A is moved out, the circulation center in the warm pool area moves eastward. This research contributes to a better understanding of the regional characteristics of the Maritime Continent and the East Asian summer monsoon. Full article

Intertropical Convergence Zone (ITCZ) primarily governs the convective rainfall potential of the summer monsoon in Asia. In the present study, non-parametric trend test with outgoing longwave radiation (OLR) for the summer monsoon period for the last 42 years (1980–2021) have been analyzed for ITCZ zone, representative zones of Hadley circulation and Walker circulation for exploring trend of the deep convection activity. Besides, various climatic variables like temperature (maximum, minimum, mean), precipitation, and cloud cover dataset are used for exploring trend in major rice growing regions of the world. The results indicate that there is a significantly decreasing trend of OLR in ITCZ zone during summer monsoon season. Contrarily, major rice growing regions of the world have witnessed a significantly increasing trend for the temperature parameter among all the zones. Rainfall and cloud cover have shown a typical trend i.e., increasing rainfall but decreasing cloud cover in the Southeast Asian and Maritime Continent rice growing regions. In rice suitable climate assessment, it has been found that the Maritime Continent rice growing region, the Indo-Gangetic Plain and the Southeast Asian rice growing regions have witnessed better rice suitable climates than other rice growing regions during the last 42 years (1980–2021). Full article

El Niño events vary from case to case with different decaying paces. In this study, we demonstrate that the different El Niño decaying paces have distinct impacts on the East Asian monsoon circulation pattern during post-El Niño summers. For fast decaying (FD) El Niño summers, a large-scale anomalous anticyclone dominates over East Asia and the North Pacific from subtropical to mid-latitude; whereas, the East Asian monsoon circulation display a dipole pattern with anomalous northern cyclone and southern anticyclone for slow decaying (SD) El Niño summers. The difference in anomalous East Asian monsoon circulation patterns was closely associated with the sea surface temperature (SST) anomaly patterns in the tropics. In FD El Niño summers, the cold SST anomalies in the tropical central-eastern Pacific and warm SST anomalies in the Maritime Continent induce the anticyclone anomalies over the Northwest Pacific. In contrast, the warm Kelvin wave anchored over the tropical Indian Ocean during SD El Niño summers plays a crucial role in sustaining the anticyclone anomalies over the Northwest Pacific. In particular, the opposite atmospheric circulation anomaly patterns over Northeast Asia and the mid-latitude North Pacific are mainly modulated by the stationary Rossby wave trains triggered by the opposite SST anomalies in the tropical eastern Pacific during FD and SD El Niño summers. Finally, the effect of distinct summer monsoon circulation patterns associated with the El Niño decay pace on the summer climate over East Asia are also discussed. Full article

The Maritime Continent (MC) is positioned between the Asian and Australian summer monsoons zone. The complex topography and shallow seas around it are major challenges for the climate researchers to model and understand it. It is also the centre of the tropical warm pool of Southeast Asia (SEA) and therefore the MC gets extra attention of the researchers. The monsoon in this area is affected by inter-scale ocean-atmospheric interactions such as the El-Niño Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), and the Madden-Julian Oscillation (MJO). Monsoon rainfall in the MC (especially in Indonesia and Malaysia) profoundly exhibits its variability dependence on ocean-atmospheric phenomena in this region. This monsoon shift often introduces to dreadful events like biomass burning (BB) in Southeast Asia (SEA) in which some led to severe trans-boundary haze pollution events in the past. In this study, the BB episode of 2015 in the MC is highlighted and discussed. Observational satellite datasets are tested by performing simulations with the numerical weather prediction (NWP) model WRF-ARW (Weather Research and Forecast—Advanced research WRF). Observed and model datasets are compared to study the surface air temperature and precipitation (rainfall) anomalies influenced by ENSO, IOD, and MJO. Links amongst these influences have been recognised and the delayed precipitation of the regular monsoon in the MC due to their influence during the 2015 BB episode is explained and accounted for, which eventually led to the intensification of fire and a severe haze. Full article

Satellite precipitation products (SPPs) potentially constitute an alternative to sparse rain gauge networks for assessing the spatial distribution of precipitation. However, applications of these products are still limited due to the lack of robust quality assessment. This study compares daily, monthly, seasonal, and annual rainfall amount at 342 rain gauges over Malaysia to estimations using five SPPs (3B42RT, 3B42V7, GPCP-1DD, PERSIANN-CDR, and CMORPH) and a ground-based precipitation product (APHRODITE). The performance of the precipitation products was evaluated from 2003 to 2007 using continuous (RMSE, R², ME, MAE, and RB) and categorical (ACC, POD, FAR, CSI, and HSS) statistical approaches. Overall, 3B42V7 and APHRODITE performed the best, while the worst performance was shown by GPCP-1DD. 3B42RT, 3B42V7, and PERSIANN-CDR slightly overestimated observed precipitation by 2%, 4.7%, and 2.1%, respectively. By contrast, APHRODITE and CMORPH significantly underestimated precipitations by 19.7% and 13.2%, respectively, whereas GPCP-1DD only slightly underestimated by 2.8%. All six precipitation products performed better in the northeast monsoon than in the southwest monsoon. The better performances occurred in eastern and southern Peninsular Malaysia and in the north of East Malaysia, which receives higher rainfall during the northeast monsoon, whereas poor performances occurred in the western and dryer Peninsular Malaysia. All precipitation products underestimated the no/tiny (<1 mm/day) and extreme (≥20 mm/day) rainfall events, while they overestimated low (1–20 mm/day) rainfall events. 3B42RT and 3B42V7 showed the best ability to detect precipitation amounts with the highest HSS value (0.36). Precipitations during flood events such as those which occurred in late 2006 and early 2007 were estimated the best by 3B42RT and 3B42V7, as shown by an R² value ranging from 0.49 to 0.88 and 0.52 to 0.86, respectively. These results on SPPs’ uncertainties and their potential controls might allow sensor and algorithm developers to deliver better products for improved rainfall estimation and thus improved water management. Full article