The local atmosphere and the turbulent heat transfer in the Eastern Himalayas

Wang

2022

Remote Sensing

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To promote Tibetan meteorological research, the third Tibetan Plateau (TP) Experiment for atmospheric sciences (TIPEX III) has been carried out over the plateau region since 2014, with near-surface heat fluxes measured at different sites. Using the observational data of near-surface heat fluxes measured at 8 plateau stations in TIPEX III, as well as the ECMWF ERA Interim reanalysis data, the land-atmosphere heat transfers over different regions of TP and their responses to the South Asian summer monsoon (SASM) during active/break periods were investigated. Inhomogeneity was found in the land-atmosphere heat transfers over the plateau, with large differences among plateau stations. During the observation period, the daily averaged total heat transfer (the sum of sensible and latent heat flux) varied from 70.2 to 101.2 Wm−2 among the 8 plateau stations, with the sensible heat flux from 18.8 to 60.1 Wm−2 and the latent heat flux from 10.1 to 74.7 Wm−2. These heat transfers were strongly affected by the SASM evolution, but with strong inhomogeneities over the plateau stations. Overall, the more southern station locations exhibited more SASM impacts. The land-atmosphere heat transfers (the total, sensible and latent heat fluxes) were greatly weakened/strengthened during the SASM active/break period at Namco (southeast plateau), Baingoin (central plateau), Lhari (central plateau), and Nagqu (central plateau), which were closely related to the weakened/strengthened radiation conditions. However, the SASM impacts were quite small or even negligible for the other plateau stations, which complicated our conclusions, and further investigations are still needed.

Section: Introductionmentioning

confidence: 99%

The Observed Impact of the South Asian Summer Monsoon on Land-Atmosphere Heat Transfers and Its Inhomogeneity over the Tibetan Plateau

Wang

2022

Remote Sensing

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“…Their results show the total turbulent heat transfer over the south, east, west, and central Tibet in a range of 80.0–144.0 W m −2 , with more sensible heat transfer in a range of 43.0–86.0 W m −2 and less latent heat transfer in a range of 28.0–59.0 W m −2 . However, as Zou et al [] measured the surface heat transfer in the Southeast Tibet in the same season, the land to air heat transfer was dominated by the latent heat transfer, different from the other Tibetan regions, with a total heat flux of 86.3 W m −2 , sensible heat flux of 22.9 W m −2 , latent heat flux of 63.4 W m −2 , and a Bowen ratio of 0.36.…”

Section: Introductionmentioning

confidence: 99%

“…The Tibetan atmosphere receives great amount of water vapor from the Bay of Bengal through the Yarlung Tsangpo water vapor pass in the Southeast Tibet [ Gao et al , ; Zhou et al , ]. The local atmosphere and the near‐surface energy exchange in the Southeast Tibet are distinct from the other Tibetan regions due to the impacts of the warm and wet flow of the South Asian summer monsoon [ Zou et al , ]. As the other Tibetan regions, the Southeast Tibet is characterized with steep topography and inhomogeneous land cover.…”

Section: Introductionmentioning

confidence: 99%

“…The inhomogeneous landscape introduces multiscale local circulations and complicated near‐surface energy exchange, and therefore makes great difficulty to the observational studies in this region. Although study has been conducted with one‐site observation in this region [ Zou et al , ], the results could not precisely describe the surface energy exchange process occurring over the inhomogeneous land surface.…”

Section: Introductionmentioning

confidence: 99%

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The observed impacts of South Asian summer monsoon on the local atmosphere and the near‐surface turbulent heat exchange over the Southeast Tibet

Han

et al. 2015

JGR Atmospheres

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The Southeast Tibet is an important region of the Tibetan Plateau bearing the interaction between the Tibetan and the neighbor atmospheric systems. The South Asian summer monsoon (SASM) as a basic climate system in Asia could impact the local atmosphere and the near‐surface heat exchange process in the Southeast Tibet. An observational campaign, Observation on the Surface‐to‐air Exchange Processes in Southeast Tibet (OSEP2013), was carried out in this region during SASM in 2013. The atmospheric parameters and turbulent heat fluxes were observed and averaged over three different land surfaces of the inhomogeneous landscape during the observation campaign. Results show clear SASM impacts on the local atmosphere and near‐surface heat exchange in the Southeast Tibet. The South Asian summer monsoon was onset on 1 June 2013 and experienced a south phase and north phase during OSEP2013. The convection and humidity were increased in the Southeast Tibet by SASM, especially during the north phase. The observation domain received low radiation energy due to the convective clouds brought by SASM, and the soil and air temperatures were lowered as consequence. In addition, the air humidity was increased over this region by the wet air transportation of SASM circulation. The sensible and latent heat transfers were decreased by the low land‐air temperature difference and high air humidity during SASM. The latent heat transfer dominated the total heat transfer in the Southeast Tibet due to the low sensible heat transfer in the SASM situation, and the domination was increased as the sensible heat transfer was further decreased during the SASM north phase.

“…They showed the total turbulent heat fluxes from the surface to the air in the range of 80.0-144.0 W/m 2 , with more sensible heat transfer in the range of 43.0-86.0 W/m 2 and less latent heat transfer in the range of 28.0-59.0 W/m 2 . Zou et al (2012) measured the near-surface heat transfer in southeastern Tibet in early summer and found that the land-air heat transfer differed from the previous regions, with a total heat flux of 86.3 W/m 2 , a sensible heat flux of 22.9 W/m 2 , and a latent heat flux of 63.4 W/m 2 ; that is, latent heat transfer dominates the land-air heat exchange with a Bowen ratio of 0.36 in this region. These measurements exhibit a large variability in the land-air heat exchange from region to region across the Tibetan Plateau, with an 80 percent difference in total heat transfer, a 275 percent difference in sensible heat transfer, and a 125 percent difference in latent heat transfer.…”

Section: Introductionmentioning

confidence: 99%

Observed heterogeneity in the local atmosphere and land–air heat exchange across complex terrain in the Tibetan mountains

Han

Arctic, Antarctic, and Alpine Research

et al. 2018

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Surface heating is important in terms of the thermal effect of the Tibetan Plateau on atmospheric systems in Asia. The complex mountain terrain across the Tibetan Plateau introduces small-scale heterogeneity in the local atmosphere and land-air heat exchange that biases our understanding of the Tibetan thermal effect and misleads boundary-layer parameterization for numerical studies and predictions. It is therefore essentially important to evaluate heterogeneity in the Tibetan mountains. An observational experiment was conducted in a small region with a complex landscape in the eastern Himalayas from June 9 to July 9, 2013. This study analyzes the observations of three major land covers and discusses the observed heterogeneity of the local atmosphere and land-air heat exchange. A heterogeneity rate is defined to approximately quantify the heterogeneity observed in the atmospheric properties and land-air heat exchange. Obvious heterogeneity is found in the local atmosphere across the complex terrain of the Eastern Himalayas, which could introduce uncertainties up to 33.3 percent in our knowledge related to the local weather and climate. A large heterogeneity is revealed in the land-air heat exchange, which would bias our understanding of total surface heating in this region up to 16 percent and of heating properties up to 62 percent. Therefore, attention should be given to the uncertainties introduced by small-scale heterogeneity in any weather and climate studies across a complex terrain, such as the eastern Himalayas. In addition, the heterogeneity rate provided could be a useful measure to generally identify the uncertainties in our understanding of the local atmosphere and land-air heat exchange across a complex terrain.