Climatology Definition of the Myanmar Southwest Monsoon (MSwM): Change Point Index (CPI)

Abstract

Myanmar’s climate is heavily influenced by its geographic location and relief. Located between the Indian summer monsoon (ISM) and the East Asian summer monsoon (EASM), Myanmar’s climate is distinguished by the alternation of seasons known as the monsoon. The north-south direction of peaks and valleys creates a pattern of alternate zones of heavy and scanty precipitation during both the northeast and southwest monsoons. The majority of the rainfall has come from Myanmar’s southwest monsoon (MSwM), which is Myanmar’s rainy season (summer in global terms, June–September). This study explained both threshold-based and nonthreshold-based objective definitions of the onset and withdrawal of large-scale MSwM. The seasonal transitions in MSwM circulation and precipitation are convincingly represented by the new index, which is based on change point detection of the atmospheric moisture flow converging in the MSwM region (10–28 N, 92–102 E). A transition in vertically integrated moisture transport (VIMT), the reversal of surface winds, and an increase in precipitation may also be considered when defining MSwM onset objectively. We also define a change point of the MSwM (CPI) index for MSwM onset and withdrawal dates. The climatological mean onset of MSwM is day 135 (May 14), withdrawal is day 278 (October 4), and the total season length is 144 days. We are investigating spatial patterns of rainfall progression at and after the start of the monsoon, rather than transitions within a single region of the MSwM. The local southwest monsoon duration is well correlated with the CPI duration on interannual timescales, particularly in the peak rainfall regions, with a delay (advance) in large-scale onset or withdrawal associated with a delay (advance) of onset or withdrawal by local index. Hence, the next phase of this research is to study the maintenance and break of the monsoon to understand the underlying physical processes governing the monsoon circulation. The results of this study provide a possibility to reconstruct Myanmar’s monsoon climate dynamics, and the findings of this study can help unravel many remaining questions regarding the greater Asian monsoon system’s variability.

Climate Change Impact on the Trigger of Natural Disasters Over South-Eastern Himalayas Foothill Region of Myanmar: Extreme Rainfall Analysis

“…2. Further analysis examines climatology and rainfall intensity for five periods (1,3,6,12, and 24 hours) results that high intensity has been found over the northern region and monsoon core regions with the maximum values ranging from 35mm to 200mm, while the central region shows less intensity during summer moons. 3.…”

“…Study analysis only during Myanmar's southwest summer monsoon season (MSwM) on the other hand, peak rainfall season and peak floods and earthquakes season by Myanmar Hazard Risk analysis [4]. The mean maximum daily rainfall is less than 5 mm per day in central Myanmar with around 50 mm per day in the northern, southern, and western coastal regions which are also known as monsoon core regions from 1981 to 2020 [5], [6]. In addition to these studies, several other studies have examined various aspects of monsoon rainfall in Myanmar, including its impact on agriculture, hydrology, and the environment.…”

Assessing Future Changes in Variability of Mainland Indochina Southwest Monsoon Rainfall

“…Among the ensemble members, there is notably strong intermodel consensus; at least 95% of models agree on the direction of change at the maximum gridded area, especially in the MSWM monsoon area of the study region (Oo, 2023). Moreover, an in-depth examination of the complete model spread is expanded to cover the regional scale of Mainland Indochina.…”

Bibliography Review of Recent Definition Research on Myanmar Southwest Monsoon

“…Researchers proposed many monsoon indexes to capture the spirit of the monsoon. To de ne the Myanmar southwest monsoon (MSwM) index, some factors, for example, differential heating between land and sea, rainfall intensity, meridional wind, and zonal horizontal wind shear regionally averaged over mainland Indochina were considered in previous research (Htway & Matsumoto, 2011;Oo, 2023; Sen Roy & Kaur, 2000; B. Wang & Ho, 2002).…”

“…Although there will be local research works about the Myanmar monsoon system published only locally these never came out at the international published references level. After the 2000s, the local scholar Tun Lwin, Z. M. M. Sein, Ohnmar Htway, and K. T. Oo introduced and published new methods to study the Myanmar monsoon system (Htway & Matsumoto, 2011;Lwin, 2002;Oo, 2023;Sein & Zhi, 2016). Myanmar meteorologists have recently achieved signi cant advancements in their studies of the Myanmar monsoon's formation mechanisms, onset features, and multiscale variability.…”