Abstract The weather and climate of the Western Ghats have a significant role in the distribution of monsoon rainfall, which in turn influences the nation’s economic performance. To improve the understanding of regional climate and atmospheric processes governing the interaction between Western Ghats orography and monsoon clouds, the National Centre for Earth Science Studies established a High Altitude Cloud Physics Observatory (HACPO; 10°9′ 19.94′′ N, 77°1′ 6.65′′ E, 1820 m above MSL) at Rajamallay in Munnar, in the Idukki district of Kerala. The strategic location of the observatory in the Western Ghats region enables accurate cloud measurements from the onset to the withdrawal stage of the southwest monsoon, thereby aiding improved model parameterizations. The observatory region receives moderate rainfall ~40% of monsoon days, with a pronounced diurnal cycle and frequent mid-level clouds, irrespective of seasons. The preliminary study on the chemical composition and morphological analysis of PM10 and PM2.5 indicates the presence of anthropogenic aerosols over this pristine environment of the Western Ghats, potentially influencing cloud microphysics and regional rainfall patterns. This article highlights the observatory’s overview, scientific objectives, and contributions to understanding atmospheric processes while supporting climate adaptation and societal resilience. Research Highlights <UnorderedList Mark="Bullet"> <ItemContent> A High Altitude Cloud Physics Observatory (HACPO) is established in the southern part (10°9′ 19.94′′ N, 77°1′ 6.65′′ E) of the Western Ghats to study orographic precipitation and cloud–aerosol interactions. </ItemContent> <ItemContent> Located ~1820m above MSL, close to the typical height of monsoon low level westerly, the observatory provides continuous observation of cloud processes from monsoon onset to withdrawal phases. </ItemContent> <ItemContent> Integrated measurements from co-located instruments enable a comprehensive microphysical and thermodynamical process level investigation of orographic precipitation. </ItemContent> <ItemContent> The long term observations will advance understanding and improving aerosol–cloud–precipitation parameterization in numerical models over complex terrain. </ItemContent> </UnorderedList>

Studying the developments of clouds and rainfall over Western Ghats, India: High Altitude Cloud Physics Observatory in Rajamallay, Munnar

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发表日期：

2026年2月25日

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E A Resmi,
R K Sumesh,
V C Mobin Raj,
G R Malavika,
A R Aswini,
C T Tejavath,
P P Leena,
S Nita,
C K Unnikrishnan,
K Sreelash,
S Sneha,
D Jash,
S Kumar,
A Andrews,
S Abhinav

摘要

Abstract

The weather and climate of the Western Ghats have a significant role in the distribution of monsoon rainfall, which in turn influences the nation’s economic performance. To improve the understanding of regional climate and atmospheric processes governing the interaction between Western Ghats orography and monsoon clouds, the National Centre for Earth Science Studies established a High Altitude Cloud Physics Observatory (HACPO; 10°9′ 19.94′′ N, 77°1′ 6.65′′ E, 1820 m above MSL) at Rajamallay in Munnar, in the Idukki district of Kerala. The strategic location of the observatory in the Western Ghats region enables accurate cloud measurements from the onset to the withdrawal stage of the southwest monsoon, thereby aiding improved model parameterizations. The observatory region receives moderate rainfall ~40% of monsoon days, with a pronounced diurnal cycle and frequent mid-level clouds, irrespective of seasons. The preliminary study on the chemical composition and morphological analysis of PM₁₀ and PM_2.5 indicates the presence of anthropogenic aerosols over this pristine environment of the Western Ghats, potentially influencing cloud microphysics and regional rainfall patterns. This article highlights the observatory’s overview, scientific objectives, and contributions to understanding atmospheric processes while supporting climate adaptation and societal resilience.

Research Highlights

A High Altitude Cloud Physics Observatory (HACPO) is established in the southern part (10°9′ 19.94′′ N, 77°1′ 6.65′′ E) of the Western Ghats to study orographic precipitation and cloud–aerosol interactions.

Located ~1820m above MSL, close to the typical height of monsoon low level westerly, the observatory provides continuous observation of cloud processes from monsoon onset to withdrawal phases.

Integrated measurements from co-located instruments enable a comprehensive microphysical and thermodynamical process level investigation of orographic precipitation.

The long term observations will advance understanding and improving aerosol–cloud–precipitation parameterization in numerical models over complex terrain.