Diurnal Variation of GPS Precipitable Water at Lhasa in Premonsoon and Monsoon Periods

Takagi, Tetsuro; Kimura, Fujio; Kono, S.

doi:10.2151/jmsj1965.78.2_175

Cited by 29 publications

(22 citation statements)

References 5 publications

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“…Diurnal variations in PW have been observed by GPS at Lhasa during the pre-monsoon and monsoon (Takagi et al 2000). During the summer monsoon, PW decreases from morning until 15 LST and then increases until 21 LST.…”

Section: Characteristics Of Diurnal Variations In Convection and Precmentioning

confidence: 96%

Characteristics of Diurnal Variations in Convection and Precipitation over the Southern Tibetan Plateau during Summer

Fujinami

Nomura

Yasunari

2005

SOLA

103

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This study investigated diurnal cycles in convection and precipitation over the complex mountain-valley terrain of the southern Tibetan Plateau (TP) during the mature phase of the summer monsoon. Cloud-cover frequency (CCF) for high cloud increased after 13 LST (07 UTC) over the mountain ranges along 28.5°N and 30.2°N, reaching a maximum near 18 LST (12 UTC). Areas of high CCF subsequently moved towards the valley area along 29.3°N; relatively high CCF persisted there until early morning. Tropical Rainfall Measuring Mission (TRMM) PR data show a nearly identical variation in rainfall frequency. Formation and development of convective-type clouds and phase differences in the diurnal cycle were strongly affected by TP topography. Possible mechanisms for convective enhancement over the southern TP are also discussed.

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Section: Characteristics Of Diurnal Variations In Convection and Precmentioning

confidence: 96%

Characteristics of Diurnal Variations in Convection and Precipitation over the Southern Tibetan Plateau during Summer

Fujinami

Nomura

Yasunari

2005

SOLA

103

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“…Kuwagata et al (2001) discussed the horizontal transport of moisture by thermally induced local circulation in the major topography of the Tibetan Plateau after showing that most observation stations are located in valley regions. By analyzing GPS precipitable water, Takagi et al (2000) demonstrated that precipitable water decreases in the daytime at Lhasa, which is located at the bottom of a valley (shown in Fig. 1b).…”

Section: Introductionmentioning

confidence: 99%

Relationship between Topography and Daytime Cloud Activity around Tibetan Plateau.

Kurosaki

Kimura

2002

Journal of the Meteorological Society of Japan

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The relationship between topography and daytime cloud activity over the Tibetan Plateau and surrounding areas was examined by using Geostationary Meteorological Satellite (GMS) Visible (VIS) and Infrared (IR) images during the premonsoon, and monsoon periods in 1998. Previous studies using IR images have already confirmed the strong diurnal variation of convective activity over the Tibetan Plateau. This study relies primarily on VIS images to analyze daytime cloud distribution because VIS images are more adaptable to low-level clouds and they offer better spatial resolution than IR images. IR images are used to judge whether cloud tops are high or low. High-level clouds are prominent over the large-scale (100-300 km) mountain ranges, but fewer clouds are observed in the major valleys in the plateau during premonsoon and monsoon periods at 15 Local Solar Time (LST), when the amount of cloud cover is at its maximum from 09 LST to 15 LST. However, the relationship between cloud distribution and topography is not always clear when the horizontal scale of the topography is less than 100 km.Less cloud coverage was observed over the plateau in the morning during the premonsoon period. On the contrary, clouds frequently appeared over the southeastern part of the plateau in the morning during the monsoon period. Low-level clouds often cover the southern slope of the Himalayas, and the frequency of cloud coverage exceeds 75% at 15 LST in the monsoon period. While the cloud tops are growing high elevation in the afternoon over the plateau, low-level clouds cover the southern slope of the Himalayas through the daytime (09-15 LST).

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“…Several previous studies have reported decreases in PWV in the daytime over inland, mountainous, and coastal areas and have concluded that local circulations are important to this process (Takagi et al 2000;Bastin et al 2007). Under such conditions, convective activity might be closely related to a local circulation.…”

Section: Discussionmentioning

confidence: 98%

“…Recent progress in collecting in situ observation variables has made it possible to measure precipitable water vapor (PWV) at a high time resolution (e.g., Takagi et al 2000). Passive microwave radiometry, which was adopted in this study, is an efficient method to retrieve continuous profiles of atmospheric humidity and temperature (Lohnert et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Diurnal Variation of Water Vapor Mixing between the Atmospheric Boundary Layer and Free Atmosphere over Changwu, the Loess Plateau in China

Takahashi

Hiyama

Nishikawa

et al. 2008

SOLA

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We investigated the diurnal variation of water vapor mixing between the atmospheric boundary layer (ABL) and the free atmosphere over the Loess Plateau in China. Water vapor and wind velocity in the troposphere were observed using a ground-based microwave radiometer and a wind profiler radar in 2005 and 2006. On sunny days in early summer, a strong vertical wind was generated in the afternoon followed by ABL development. Strong convection was enhanced when active cumulus convection developed in the afternoon. In such cases, water vapor decreased in the lower atmosphere from the early morning until late afternoon, while water vapor increased in the upper atmosphere. This finding suggests that water vapor was exchanged diurnally between the ABL and the free atmosphere. The strong convection in the ABL, which was developed by sensible heat from the land surface, played critical roles with link to cumulus convection in such vertical mixing of water vapor. Influences of other processes such as a local circulation and advection of cloud systems were also discussed. IntroductionWater plays an important role in the Earth's climate by transporting energy over long distances, forming clouds and rainfall, and thereby influencing biological and ecological activities worldwide. Water is also crucial for human lives and activities. It is especially critical in arid and semi-arid regions where water resources are limited.In East Asia, vast areas of such severe climate regimes are distributed across northern China. Located in the middle part of the Yellow River basin, the Loess Plateau significantly affects the water cycle in the Yellow River basin (Zhang and Liu 2005).The Loess Plateau experiences dry conditions in most periods of the year. Over the dry surface exposed to intense solar radiation, the atmospheric boundary layer (ABL) can develop to high altitudes (Gamo 1996). A strong vertical wind, which can reach the free atmosphere, develops in the ABL over the plateau in early summer . Over the Tibetan Plateau, dry convection in the ABL and cumulus convection have been shown to play significant roles in heating the upper troposphere in spring (Taniguchi and Koike 2007). Thus, the developments of the ABL and clouds are critical factors in atmospheric dynamics and water cycles.To clarify the role of cloud activity, it is necessary to investigate the temporal variation of the atmospheric thermodynamic state. Recent progress in collecting in situ observation variables has made it possible to measure precipitable water vapor (PWV) at a high time resolution (e.g., Takagi et al. 2000). Passive microwave radiometry, which was adopted in this study, is an efficient method to retrieve continuous profiles of atmospheric humidity and temperature (Lohnert et al. 2007). In this study, data were also obtained using a wind profiler radar to assess the kinematic structures of the ABL and the free atmosphere.The aims of this study were 1) to clarify the diurnal variation of the atmospheric water vapor over the Loess Plateau in early ...

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Diurnal Variation of GPS Precipitable Water at Lhasa in Premonsoon and Monsoon Periods

Cited by 29 publications

References 5 publications

Characteristics of Diurnal Variations in Convection and Precipitation over the Southern Tibetan Plateau during Summer

Characteristics of Diurnal Variations in Convection and Precipitation over the Southern Tibetan Plateau during Summer

Relationship between Topography and Daytime Cloud Activity around Tibetan Plateau.

Diurnal Variation of Water Vapor Mixing between the Atmospheric Boundary Layer and Free Atmosphere over Changwu, the Loess Plateau in China

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