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Extreme events

Indian downpours are driven more by uplift than extra humidity

Sudharsan N, Karmakar S, Fowler HJ, et al. · Climate dynamics · 2020

Open access · cc by · source: Europe PMC

For monsoon extremes over India, stronger upward motion supplies most of the extra moisture, not the Clausius–Clapeyron humidity increase alone.

Key findings

Dynamics dominate vertical moisture advection in both case studies and contribute more than 90% (mean) across 26 events. Kerala 2018 rain was 40% above normal; Uttarakhand 13–18 June 2013 saw >340 mm (~375% of JJAS normal). CMIP6 also shows Dyn leading Thermo for Indian extremes.

Methodology

The authors decomposed precipitation into dynamic (vertical velocity) and thermodynamic (humidity) moisture-budget terms for Kerala 2018, Uttarakhand 2013, 26 IMD extremes (2005–2018), and 95th-percentile JJAS events in JRA-55/ERA-Interim and six CMIP6 models.

Limitations

Only six CMIP6 models with available omega/humidity fields. Some events fall outside the core monsoon zone or JJAS. Decomposition cannot capture convective-scale triggering. Human impacts cited are not the scientific result.

How this study connects

Role on claims

Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.

  • SupportsExtreme eventsconcept

    For monsoon extremes over India, stronger upward motion supplies most of the extra moisture, not the Clausius–Clapeyron humidity increase alone.

    Evidence for the claim as stated.

  • CMIP is also a catalogue of process fields, not only of warming. Across 26 Indian monsoon extremes, the dynamic (vertical-velocity) moisture-budget term contributed more than 90% on average; six CMIP6 models with omega/humidity agreed that dynamics lead thermodynamics. Twenty-seven CMIP6 models underestimate North American oceanic cyclone depth and overestimate it over land versus ERA5; 12 km CRCM6 has the smallest domain errors even when driven by different CMIP6 models.

    Evidence for the claim as stated.

  • Moisture-budget decompositions of extremes split dynamics from thermodynamics on reanalysis omega and humidity fields. Across 26 Indian events, the dynamic term contributed more than 90% on average; JRA-55/ERA-Interim and six CMIP6 models agreed that dynamics lead thermodynamics for those extremes.

    Evidence for the claim as stated.

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