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Impact of Rainfall and Severe Flooding on PM2.5 Dynamics in Hat Yai, Thailand
Organization(s):Srithammaratsuksa School
Country:Thailand
Student(s):Kongpop Suwan, Chutikan Songsoem, Chatmongkhol Dechasak
Jaroonwit Srithip, Parothai Songrung, Suwaphat Kaewklang, Thanaboon Weraprasertsakun
Jiraphat Nookong, Phatsakorn Nongnual, Kanthipha Thipchuai, Pitchaya Chaikong, Chongtham Butpradit, Pharita Khongthongkum, Waritsanun Hemtanon, Thawanrat Wattakeejaroen, Woranittha Pannin, Pitsinee Sirawirod, Sirinat Nuntarat, Phisit Oaksonthong, Phimchanok Kanjanasanhit
Grade Level:Secondary School (grades 9-12, ages 14-18)
GLOBE Member(s):Patipon Thawornnuwong
Contributors:Chatlada Poolsuk, Patipon Thawornnuwong, Assoc.Prof.Dr.Krisanadej Jaorensutasinee, Assoc.Prof.Dr. Mullica Jaroensutasinee, Miss Thunwarut Sutthipun, and Miss Chacha Sattharat
Report Type(s):Virtual Science Symposium Report
Protocols:Clouds, Precipitation, Air Temperature, Relative Humidity
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Language(s):English
Date Submitted:2025-12-16
This study analyzed the relationships between rainfall, air temperature, relative humidity, and fine particulate matter (PM2.5) concentrations during a major flood crisis in Hat Yai District, Songkhla Province, from 1 November to 14 December 2025. This flood event was caused by a rapid and continuous increase in rainfall.
The study divided the analysis period into three main phases: the pre-flood accumulation period (1–18 November), the active flood period (19–26 November), and the post-flood recovery period (27 November–14 December). The results clearly demonstrate significant relationships between rainfall and key meteorological variables. A strong negative relationship was observed between rainfall and air temperature t(43) = 140.107, P<0.001. Substantial increases in rainfall led to a marked decrease in air temperature, primarily due to dense cloud cover and the cooling effects associated with evaporative heat processes. In contrast, rainfall exhibited a strong positive relationship with relative humidity t(43) = 101.921, P<0.001. Very high relative humidity levels, with averages exceeding 90%, were identified as a critical factor promoting heavy and continuous rainfall, reflecting a saturated atmospheric condition. Rainfall also showed a weak negative relationship with PM2.5 concentrations t(43) = 27.513, P<0.001. Rainfall acts as a natural mechanism for removing PM2.5 from the atmosphere through the rain washout effect, resulting in a rapid reduction of particulate concentrations during the flood period. However, after the flood, PM2.5 concentrations increased markedly, reaching a maximum of 23.72 µg/m³ on 28 November. This increase is attributed to dry surface conditions and the re-suspension of dust and sediments, a process known as secondary dust resuspension. In addition, a comparison of cumulative rainfall between Cha-uat District and Hat Yai District in Nakhon Si Thammarat Province revealed that Cha-uat District had a significantly higher average daily rainfall than Hat Yai District t(43) = 3.148, P<0.05, although Hat Yai recorded the highest single-day rainfall during the same period. The study concludes that rainfall is a key meteorological factor exerting significant impacts on both atmospheric conditions and air quality in the study area. Understanding these relationships is essential for improving air quality management, disaster preparedness planning, and post-flood recovery strategies in both the short and long term.