The Relationship between Precipitation and Airflow over the Tibetan Plateau in Boreal Summer

Abstract. We validate Aura Microwave Limb Sounder (MLS) version 3 (v3) and version 4 (v4) retrievals of summertime temperature, water vapour and ozone in the upper troposphere and lower–middle stratosphere (UTLS; 10–316 hPa) against balloon soundings collected during the Study of Ozone, Aerosols and Radiation over the Tibetan Plateau (SOAR-TP). Mean v3 and v4 profiles of temperature, water vapour and ozone in this region during the measurement campaigns are almost identical through most of the stratosphere (10–68 hPa), but differ in several respects in the upper troposphere and tropopause layer. Differences in v4 relative to v3 include slightly colder mean temperatures from 100–316 hPa, smaller mean water vapour mixing ratios in the upper troposphere (215–316 hPa), and a more vertically homogeneous profile of mean ozone mixing ratios below the climatological tropopause (100–316 hPa). These changes substantially improve agreement between ozonesondes and MLS ozone retrievals in the upper troposphere, but slightly worsen existing cold and dry biases in the upper troposphere. Aura MLS v3 and v4 temperature profiles contain significant cold biases relative to collocated temperature measurements in several layers of the lower–middle stratosphere (mean biases of −1.3 to −1.8 K centered at 10–12 hPa, 26–32 hPa and 68– 83 hPa) and in the upper troposphere (mean biases of approximately −2.3±0.3 K in v3 and −2.6±0.4 K in v4 between 147 and 261 hPa). MLS v3 and v4 profiles of water vapour volume mixing ratio generally compare well with collocated measurements, with a slight dry bias (v4: −8±4%) near 22–26 hPa, a slight wet bias (v4: +12±5%) near 68–83 hPa, and a more substantial dry bias (v4: −32±11%) in the upper troposphere (121–261 hPa). MLS v3 and v4 retrievals of ozone volume mixing ratio are biased high relative to collocated ozonesondes through most of the stratosphere (18–83 hPa), but are biased low at 100 hPa. The largest positive biases in ozone retrievals are located at 83 hPa (approximately +70%); this peak was not identified by earlier validations and may be regionally or seasonally specific. Ozone retrievals are substantially improved in v4 relative to v3, with smaller biases in the tropopause layer, reduced variance below 68 hPa, larger data yields, and smoother gradients in the vertical profile of ozone biases in the upper troposphere.

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Simulation Analysis of Local Land Atmosphere Coupling in Rainy Season over a Typical Underlying Surface in the Tibetan Plateau

10.5194/hess-2020-199 ◽

2020 ◽

Author(s):

Genhou Sun ◽

Zeyong Hu ◽

Yaoming Ma ◽

Zhipeng Xie ◽

Jiemin Wang ◽

...

Keyword(s):

Soil Moisture ◽

Tibetan Plateau ◽

Rainy Season ◽

Surface Fluxes ◽

Underlying Surface ◽

The Tibetan Plateau ◽

Spatial Distributions ◽

Initial Soil Moisture ◽

Initial Soil ◽

The Relationship

Abstract. The Local land atmosphere coupling (LoCo) focuses on the interactions between soil conditions, surface fluxes, planetary boundary layer (PBL) growth, and the formations of convective clouds and precipitations. Study of LoCo over the Tibetan Plateau (TP) is of great significance for understanding TP's role in the Asian Water Tower. A series of real-case simulations using the Weather Research and Forecasting Model (WRF) with different combinations of land surface models (LSM) schemes and PBL schemes has been carried out to investigate the LoCo characteristics over a typical underlying surface in the central TP in rainy season. The LoCo characteristics in the study area are analyzed by applying a mixing diagram to the simulation results. The analysis indicates that the WRF simulations using the Noah with BouLac, MYNN, and YSU produce closer results to the observation in terms of curves of Cp*θ and Lv*q, surface fluxes (Hsfc and LEsfc), entrainment fluxes (Hent and LEent) at site BJ/Nagqu than those using the CLM with BouLac, MYNN, and YSU. The frequency distributions of Hsfc, LEsfc, Hent, and LEent in the study area confirm this result. The spatial distributions of simulated Hsfc, LEsfc, Hent, and LEent using WRF with Noah and BouLac suggest that the spatial distributions of Hsfc and LEsfc in the study area are consistent with that of soil moisture, but the spatial distributions of Hent and LEent are quite different from that of soil moisture. A close examination of the relationship between entrainment fluxes and cloud water content (QCloud) reveals that the grids with small Hent and large LEent tend to have high QCloud and Hsfc, suggesting that high Hsfc is conductive to convective cloud formation, which leads to small Hent and large LEent. Sensitivity analysis of LoCo to the soil moisture at site BJ/Nagqu indicates that on a sunny day, an increase in soil moisture leads to an increase in LEsfc but decreases in Hsfc, Hent, and LEent. The sensitivity of the relationship between simulated maximum daytime PBL height (PBLH) and mean daytime evapotranspiration (EF) in the study area to soil moisture indicates that the rate at which the maximum daytime PBLH decreases with the mean EF increase as the initial soil moisture goes up. The analysis of simulated Hsfc, LEsfc, Hent, and LEent under different soil moisture conditions reveals that the frequency of Hent ranging from 80 to 240 W/m2 and the frequency of LEent ranging from −240 to −90 W/m2 both increase as the initial soil moisture increases. Coupled with the changes in QCloud, the changes in Hent and LEent as the initial soil moisture increases indicate that the rise in soil moisture leads to an increase in the cloud amount but a decrease in QCloud.

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Vertical Structures of Convective and Stratiform Clouds in Boreal Summer over the Tibetan Plateau and Its Neighboring Regions

Advances in Atmospheric Sciences ◽

10.1007/s00376-019-8229-4 ◽

2019 ◽

Vol 36 (10) ◽

pp. 1089-1102 ◽

Cited By ~ 6

Author(s):

Yafei Yan ◽

Yimin Liu

Keyword(s):

Tibetan Plateau ◽

Boreal Summer ◽

The Tibetan Plateau ◽

Stratiform Clouds

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The Dalai Lama and the Nechung Oracle

10.1093/oso/9780197533352.001.0001 ◽

2021 ◽

Author(s):

Christopher Bell

Keyword(s):

Seventeenth Century ◽

Sixteenth Century ◽

Tibetan Plateau ◽

The Tibetan Plateau ◽

Dalai Lama ◽

Administrative Control ◽

The World ◽

Sentient Beings ◽

Relationship Of ◽

The Relationship

This book is about two immortals whose friendship has spanned nearly five hundred years across the Tibetan plateau and beyond. The first immortal is the Dalai Lama, the emanation of a bodhisattva, an enlightened being who voluntarily takes rebirth in the world to benefit sentient beings. The second immortal is a wrathful god named Pehar, who has possessed the Nechung Oracle since the sixteenth century. This book is the first to examine the relationship between these two monolithic figures, which strengthened in the seventeenth century during the reign of the Fifth Dalai Lama (1617–1682). This study is also the first extensive examination of the famed Nechung Oracle and his institution. In the seventeenth century, the protector deity Pehar and his oracle at Nechung Monastery were state-sanctioned by the nascent Tibetan government, becoming the head of an expansive pantheon of worldly deities assigned to protect the newly unified country. While the Fifth Dalai Lama and his government endorsed Pehar as part of a larger unification project, the governments of later Dalai Lamas continued to expand the deity’s influence, and by extension their own, by ritually establishing Pehar at monasteries and temples around Lhasa and across Tibet. Pehar’s cult at Nechung Monastery came to embody the Dalai Lama’s administrative control in a mutually beneficial relationship of protection and prestige, the effects of which continue to reverberate within Tibet and among the Tibetan exile community today.

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