The lake level dynamics of the Qinghai–Tibetan Plateau (QTP, also called the ‘Third Pole’) are a crucial indicator of climate change and human activities; however, they remain poorly measured due to extremely high elevation and cold climate. The existing satellite altimeters also suffer from relatively coarse temporal resolution or low spatial coverage, preventing effective monitoring of lake level change at such a large spatial scale. The recently launched surface water and ocean topography (SWOT) mission is expected to greatly enhance the current lake level monitoring capabilities. However, a systematic evaluation is still lacking in the region. To elucidate this potential, here, we generated SWOT-like lake products for 38 major lakes (>150 km2) over the QTP during 2000–2018 using a large-scale SWOT hydrology simulator with the input of satellite altimetry and water mask databases. The comparative assessments between the satellite altimetry data and SWOT simulations using various statistical metrics and decomposed time series components demonstrate that SWOT can successfully monitor both short-term dynamics and long-term trends. Extended experiments to derive SWOT-like data of 783 lakes (>1 km2) based on the synthetic lake level series present the spatial pattern of SWOT performance that tends to improve with the increasing lake area. Our findings provide comprehensive inferences and confidence for lake level monitoring in the Third Pole in the early period of the SWOT satellite.

A large portion of lakes on the Tibetan Plateau (TP) have experienced considerable expansion in the past decades. However, how the lake surface area expansion has influenced regional precipitation, especially its underlying mechanism, has not been investigated. By selecting the most dramatically expanded lake on the TP as a case study, this paper investigates the magnitude and extent of the precipitation response to lake expansion and its underlying mechanism using twin Weather Research and Forecasting (WRF) simulations with and without lake expansion. The results show that the precipitation response to the lake expansion exhibits pronounced spatial and seasonal variations and is generally more intense in the downwind direction than in the upwind direction. During the wet season (the South Asian summer monsoon, SASM), precipitation decreases in the downwind area by −25% ± 16% and −13% ± 15% in the 0–50 km and 50–100 km intervals (from the lake’s center), respectively. Conversely, the precipitation increases in the downwind area during the dry season (before the freeze and after the SASM) by 27% ± 36% in the 0–50 km interval. The thermal and evaporative effects, which are generated by lake expansion and propagate in the downwind direction, are the key factors responsible for the precipitation changes. The cooling effect, which generally occurs in the daytime, stabilizes the atmosphere and triggers downward motion, consequently inhibiting precipitation. The warming effect has the opposite effect, and the additional water vapor strengthens this process. However, the effects vary with the seasons, causing seasonal variations in the precipitation response.