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

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

10.5194/egusphere-egu2020-6648 ◽

2020 ◽

Author(s):

Genhou Sun ◽

Zeyong Hu ◽

Yaoming Ma ◽

Song Yang

Keyword(s):

Soil Moisture ◽

Tibetan Plateau ◽

Rainy Season ◽

Surface Fluxes ◽

Underlying Surface ◽

The Tibetan Plateau ◽

Spatial Distributions ◽

Initial Soil Moisture ◽

Initial Soil ◽

The Relationship

The Local land atmosphere coupling (LoCo) focuses on the interactions between soil conditions, surface fluxes, PBL growth, and the formations of convective clouds and precipitations, and a study of LoCo over the Tibetan Plateau (TP) is of great significance to understand its role of &#8220;Asian Water Tower&#8221;. This study investigates the LoCo characteristics over a typical underlying surface in central TP in the rainy season based on a series of real case simulations using Weather Research and Forecasting Model (WRF) with different combinations of land surface model (LSM) schemes and planetary boundary layer (PBL) schemes based on in-situ measurements. Then the LoCo characteristics over a typical underlying surface in central TP are analyzed using a mixing diagram. The simulations results indicates that WRF simulations using Noah with BouLac, MYNN, and YSU produce much better results in terms of curves of Cp*theta and Lv*q, surface fluxes (Hsfc and LEsfc), entrainment fluxes (Hent and LEent) at site BJ/Nagqu that those using CLM with BouLac, MYNN, and YSU do. The frequency distributions of Hsfc, LEsfc, Hent, and LEent in the study area confirmed 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 show a good 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 contents (QCloud) reveals that the grids with small Hent and large LEent are likely to have high QCloud and Hsfc. This means that high Hsfc is conductive to convective cloud formations, which lead to small Hent and large LEent. Sensitivity analysis of LoCo to the soil moisture at site BJ/Nagqu indicates that in a sunny day, an increase in soil moisture leads to an increase in LEsfc but a decrease in Hsfc, Hent, and LEent. The sensitivity of the relationship between simulated max daytime PBLH and mean daytime EF in the study area to soil moistures indicates that the rate at which the max daytime PBLH decrease with the mean EF increases as the initial soil moisture goes up. The analysis of simulated Hsfc, LEsfc, Hent, and LEent under different soil moisture conditions reveals that the frequencies of Hent ranging from 80 W/m2 and over 240 W/m2 and frequency of LEent ranging from -240 W/m2 to -90 W/m2 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 increase in soil moisture lead to an increase in cloud amounts but a decrease in QCloud.

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Simulation analysis of local land atmosphere coupling in rainy season over a typical underlying surface in the Tibetan Plateau

Hydrology and Earth System Sciences ◽

10.5194/hess-24-5937-2020 ◽

2020 ◽

Vol 24 (12) ◽

pp. 5937-5951

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) investigates the interactions between soil conditions, surface fluxes, planetary boundary layer (PBL) growth, and the formations of convective clouds and precipitation. Studying LoCo over the Tibetan Plateau (TP) is of great significance for understanding the TP's role in the Asian water tower. A series of real-case simulations, using the Weather Research and Forecasting (WRF) model with different combinations of land surface model (LSM) schemes and PBL schemes, has been carried out to investigate the LoCo characteristics over a typical underlying surface in the central TP in the 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, Mellor-Yamada Nakanishi and Niino Level-2.5 PBL (MYNN), and Yonsei University (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 of Nagqu Station (BJ/Nagqu) than those using the Community Land Model (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 conducive to convective cloud formation, which leads to small Hent and large LEent. A 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 (ET) in the study area to soil moisture indicates the rate at which the maximum daytime PBLH decreases with the mean ET 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 m−2 and the frequency of LEent ranging from −240 to −90 W m−2 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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The spatial heterogeneity of land surface conditions and its influence on surface fluxes over a typical underlying surface in the Tibetan Plateau

Theoretical and Applied Climatology ◽

10.1007/s00704-018-2369-9 ◽

2018 ◽

Vol 135 (1-2) ◽

pp. 221-235 ◽

Cited By ~ 5

Author(s):

Genhou Sun ◽

Zeyong Hu ◽

Jiemin Wang ◽

Weiqiang Ma ◽

Lianglei Gu ◽

...

Keyword(s):

Tibetan Plateau ◽

Spatial Heterogeneity ◽

Land Surface ◽

Surface Fluxes ◽

Underlying Surface ◽

The Tibetan Plateau ◽

Surface Conditions

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Research on Occurrence and Development of Pasture Drought Events in Alpine Grassland using the Drought Threshold

10.5194/nhess-2018-305 ◽

2018 ◽

Author(s):

Tiaofeng Zhang ◽

Lin Li ◽

Hongbin Xiao ◽

Hongmei Li

Keyword(s):

Soil Moisture ◽

Alpine Grassland ◽

Soil Drought ◽

Severe Drought ◽

Drought Event ◽

Drought Intensity ◽

Quantitative Expression ◽

Initial Soil Moisture ◽

Initial Soil ◽

The Relationship

Abstract. Pasture is vital to livestock husbandry development in Qinghai and even in North China. Drought is the primary meteorological disaster that affects pasture, but insufficient soil moisture is the most prominent cause of pasture drought. Timely and accurate determination of the soil moisture threshold of pasture is important for objective recognition and monitoring of the occurrence and development of pasture drought. This study aims at investigating pasture responses to soil drought as well as quantitative expression of soil drought degree and drought threshold. Test plots were selected from the pasture test station. Five testing groups were set according to coverage rate (0–100 %) at the initiation the pasture growth period. The impacts of profile moisture characteristics, drought threshold, and precipitation on duration of pasture drought were studied. Research results have demonstrated that moisture in the soil profile below 20 cm decreases slightly throughout drought events in alpine grassland. Changes of soil moisture in the 0–20 cm layer can generally reflect drought stress of the pasture. In the process of a drought event, the relationship between soil water storage and cumulative relative water loss can be expressed via a logarithmic linear equation. Quantitative expression of drought degree in grasslands can be realized by transforming the slope of this equation into the index D with an interval of [0, 1]. The occurrence rates of mild drought,moderate drought, and severe drought were 0.36, 0.45, and 0.70, respectively. The duration of severe drought was closely related with initial soil moisture. The relationship between duration of drought and the necessary minimum precipitation can be expressed by an exponential equation. Values of the D index can express soil drought intensity and pasture drought intensity. The durations for different grades of drought events were correlated with both initial soil moisture and previous precipitation. The conclusions of this study can provide scientific references for the objective understanding onoccurrence, development, monitoring, and early warning of pasture drought.

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Sensitivity of Numerical Weather Forecasts to Initial Soil Moisture Variations in CFSv2

Weather and Forecasting ◽

10.1175/waf-d-16-0049.1 ◽

2016 ◽

Vol 31 (6) ◽

pp. 1973-1983 ◽

Cited By ~ 25

Author(s):

Paul A. Dirmeyer ◽

Subhadeep Halder

Keyword(s):

Boundary Layer ◽

Soil Moisture ◽

Time Scales ◽

Land Surface ◽

Forecast Model ◽

Surface Fluxes ◽

Near Surface ◽

Weather Forecasts ◽

Initial Soil Moisture ◽

Initial Soil

Abstract When initial soil moisture is perturbed among ensemble members in the operational NWS global forecast model, surface latent and sensible fluxes are immediately affected much more strongly, systematically, and over a greater area than conventional land–atmosphere coupling metrics suggest. Flux perturbations are likewise transmitted to the atmospheric boundary layer more formidably than climatology-based metrics would indicate. Impacts are not limited to the traditional land–atmosphere coupling hot spots, but extend over nearly all ice-free land areas of the globe. Key to isolating this effect is that initial atmospheric states are identical among quantities correlated, pinpointing soil moisture and snow cover. A consequence of this high sensitivity is that significant positive impacts of realistic land surface initialization on the skill of deterministic near-surface temperature and humidity forecasts are also immediate and nearly universal during boreal spring and summer (the period investigated) and persist for at least 3 days over most land areas. Land surface initialization may be more broadly important for weather forecasts than previously realized, as the research focus historically has been on subseasonal-to-seasonal time scales. This study attempts to bridge the gap between climate studies with their associated coupling assessments and weather forecast time scales. Furthermore, errors in land surface initialization and shortcomings in the parameterization of atmospheric processes sensitive to surface fluxes may have greater consequences than previously recognized, the latter exemplified by the lack of impact on precipitation forecasts even though the simulation of boundary layer development is shown to be greatly improved with realistic soil moisture initialization.

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

10.5194/hess-2020-199-rc1 ◽

2020 ◽

Author(s):

Anonymous

Keyword(s):

Tibetan Plateau ◽

Rainy Season ◽

Simulation Analysis ◽

Underlying Surface ◽

The Tibetan Plateau

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The evaluation of AMSR-E soil moisture data in atmospheric modeling using a suitable time series iteration to derive land surface fluxes over the Tibetan Plateau

10.5194/egusphere-egu2020-2546 ◽

2020 ◽

Author(s):

Weiqiang Ma ◽

Yaoming Ma ◽

Yizhe Han ◽

Wei Hu ◽

Lei Zhong

Keyword(s):

Soil Moisture ◽

Tibetan Plateau ◽

Land Surface ◽

Surface Fluxes ◽

Heat Fluxes ◽

The Tibetan Plateau ◽

Default Model ◽

Model Configuration

Firstly, based on the difference of model and in-situ observations, a serious of sensitive experiments were done by using WRF. In order to use remote sensing products, a land-atmosphere model was initialized by ingesting AMSR-E RS products, and the results were compared with the default model configuration and with in-situ long-term CAMP/Tibet observations.Secondly, a land-atmosphere model was initialized by ingesting AMSR-E products, and the results were compared with the default model configuration and with in-situ long-term CAMP/Tibet observations. The differences between the AMSR-E initialized model runs with the default model configuration and in situ data showed an apparent inconsistency in the model-simulated land surface heat fluxes. The results showed that the soil moisture was sensitive to the specific model configuration. To evaluate and verify the model stability, a long-term modeling study with AMSR-E soil moisture data ingestion was performed. Based on test simulations, AMSR-E data were assimilated into an atmospheric model for July and August 2007. The results showed that the land surface fluxes agreed well with both the in-situ data and the results of the default model configuration. Therefore, the simulation can be used to retrieve land surface heat fluxes from an atmospheric model over the Tibetan Plateau.All of the different methods will clarify the land surface heating field in complex plateau, it also can affect atmospheric cycle over the Tibetan Plateau even all of the global atmospheric cycle pattern.

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The evaluation of AMSR-E soil moisture data in atmospheric modeling using a suitable time series iteration to derive land surface fluxes over the Tibetan Plateau

PLoS ONE ◽

10.1371/journal.pone.0226373 ◽

2019 ◽

Vol 14 (12) ◽

pp. e0226373 ◽

Cited By ~ 2

Author(s):

Weiqiang Ma ◽

Yaoming Ma

Keyword(s):

Time Series ◽

Soil Moisture ◽

Tibetan Plateau ◽

Land Surface ◽

Atmospheric Modeling ◽

Surface Fluxes ◽

The Tibetan Plateau ◽

Soil Moisture Data

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Intraseasonal soil moisture-atmosphere feedbacks on the Tibetan Plateau circulation

Journal of Climate ◽

10.1175/jcli-d-20-0377.1 ◽

2020 ◽

pp. 1-51

Author(s):

Joshua Talib ◽

Christopher M. Taylor ◽

Anmin Duan ◽

Andrew G. Turner

Keyword(s):

Boundary Layer ◽

Soil Moisture ◽

Tibetan Plateau ◽

Rossby Wave ◽

Surface Fluxes ◽

Central China ◽

The Tibetan Plateau ◽

Temperature Anomalies ◽

Upper Level ◽

Heat Low

AbstractSubstantial intraseasonal precipitation variability is observed across the Tibetan Plateau (TP) during boreal summer associated with the subtropical jet location and the Silk Road pattern. Weather station data and satellite observations highlight a sensitivity of soil moisture and surface fluxes to this variability. During rain-free periods of two or more days, skin temperatures are shown to rise as the surface dries, signalling decreased evaporative fraction. Surface fluxes are further enhanced by relatively clear skies. In this study we use an atmospheric reanalysis to assess how this surface flux response across the TP influences local and remote conditions.Increased surface sensible heat flux induced by decreased soil moisture during a regional dry event leads to a deepening of the planetary boundary-layer and the development of a heat low. Consistent with previous studies, heat low characteristics exhibit pronounced diurnal variability driven by anomalous daytime surface warming. For example, low-level horizontal winds are weakest during the afternoon and intensify overnight when boundary-layer turbulence is minimal. The heat low favours an upper-tropospheric anticyclone which induces an upper-level Rossby wave and leads to negative upperlevel temperature anomalies across southern China. The Rossby wave intensifies the upper-level cyclonic circulation across central China, whilst upperlevel negative temperature anomalies across south China extends the west Pacific subtropical high westward. These circulation anomalies influence temperature and precipitation anomalies across much of China. The association between land-atmosphere interactions across the TP, large-scale atmospheric circulation characteristics, and precipitation in east Asia highlights the importance of intraseasonal soil moisture dynamics on the TP.

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