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The Atmospheric Valve: How Vegetation‐Controlled Lifting Condensation Level Simultaneously Drives Cloudburst Mortality and Suppresses Water Yield Across Pakistan’s Orographic Ladder

Abstract: Pakistan’s north–south topographic gradient, 0 m to 8,611 m across five ridge systems, defines one of the largest orographic condensation machines on Earth. We show that a single atmospheric variable, the lifting condensation level ﴾LCL﴿, controlled by the surface dewpoint depression ﴾T − Tᵈ﴿, acts as the valve determining whether this machine operates as a distributed water‐production system or as a disaster‐generation system. ERA5 reanalysis ﴾1980–2024﴿ finds mean June dailymaximum LCL over the Indus Plains at 2,727 ± 786 m ﴾domain average; 3,015 ± 1,105 m at five representative inland stations﴿, bypassing the Salt Range ﴾1,520 m﴿ and Margalla Hills ﴾1,600 m﴿ on 94.7% and 93.0% of pre‐monsoon days respectively. A cross‐regional comparison with northeastern India, same Arabian Sea moisture source, comparable ridge heights, but LCL of only 554 ± 262 m due to vegetated land surface maintaining T − Tᵈ at 1.9°C versus Pakistan’s 16.2°C, establishes that the bypass is surface‐controlled, not moisture‐limited ﴾Mann–Whitney p < 10-10﴿.