Analysis of the Radiation Fluxes over Complex Surfaces on the Tibetan Plateau

Analysis of long-term, ground-based observation data on the Tibetan Plateau help to enhance our understanding of land-atmosphere interactions and their influence on weather and climate in this region. In this paper, the daily, monthly, and annual averages of radiative fluxes, surface albedo, surface temperature, and air temperature were calculated for the period of 2006 to 2019 at six research stations on the Tibetan Plateau. The surface energy balance characteristics of these six stations, which include alpine meadow, alpine desert, and alpine steppe, were then compared. The downward shortwave radiation at stations BJ, QOMS, and NAMORS was found to decrease during the study period, due to increasing cloudiness. Meanwhile, the upward shortwave radiation and surface albedo at all stations were found to have decreased overall. Downward longwave radiation, upward longwave radiation, net radiation, surface temperature, and air temperature showed increasing trends on inter-annual time scales at most stations. Downward shortwave radiation was maximum in spring at BJ, QOMS, NADORS, and NAMORS, due to the influence of the summer monsoon. Upward shortwave radiation peaked in October and November due to the greater snow cover. BJ, QOMS, NADORS, and NAMORS showed strong sensible heat fluxes in the spring while MAWORS showed strong sensible heat fluxes in the summer. The monthly and diurnal variations of surface albedo at each station were “U” shaped. The diurnal variability of downward longwave radiation at each station was small, ranging from 220 to 295 W·m−2.The diurnal variation in surface temperature at each station slightly lagged behind changes in downward shortwave radiation, and the air temperature, in turn, slightly lagged behind the surface temperature.

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Numerical study on the response of the largest lake in China to climate change

Hydrology and Earth System Sciences ◽

10.5194/hess-23-2093-2019 ◽

2019 ◽

Vol 23 (4) ◽

pp. 2093-2109 ◽

Cited By ~ 5

Author(s):

Dongsheng Su ◽

Xiuqing Hu ◽

Lijuan Wen ◽

Shihua Lyu ◽

Xiaoqing Gao ◽

...

Keyword(s):

Climate Change ◽

Heat Flux ◽

Tibetan Plateau ◽

Surface Temperature ◽

Air Temperature ◽

Longwave Radiation ◽

Shortwave Radiation ◽

Qinghai Lake ◽

Observation Data ◽

Lake Surface

Abstract. Lakes are sensitive indicators of climate change. There are thousands of lakes on the Tibetan Plateau (TP), and more than 1200 of them have an area larger than 1 km2; they respond quickly to climate change, but few observation data of lakes are available. Therefore, the thermal condition of the plateau lakes under the background of climate warming remains poorly understood. In this study, the China regional surface meteorological feature dataset developed by the Institute of Tibetan Plateau Research, Chinese Academy of Sciences (ITPCAS), MODIS lake surface temperature (LST) data and buoy observation data were used to evaluate the performance of lake model FLake, extended by simple parameterizations of the salinity effect, for brackish lake and to reveal the response of thermal conditions, radiation and heat balance of Qinghai Lake to the recent climate change. The results demonstrated that the FLake has good ability in capturing the seasonal variations in the lake surface temperature and the internal thermal structure of Qinghai Lake. The simulated lake surface temperature showed an increasing trend from 1979 to 2012, positively correlated with the air temperature and the downward longwave radiation while negatively correlated with the wind speed and downward shortwave radiation. The simulated internal thermodynamic structure revealed that Qinghai Lake is a dimictic lake with two overturn periods occurring in late spring and late autumn. The surface and mean water temperatures of the lake significantly increased from 1979 to 2012, while the bottom temperatures showed no significant trend, even decreasing slightly from 1989 to 2012. The warming was the strongest in winter for both the lake surface and air temperature. With the warming of the climate, the later ice-on and earlier ice-off trend was simulated in the lake, significantly influencing the interannual and seasonal variability in radiation and heat flux. The annual average net shortwave radiation and latent heat flux (LH) both increase obviously while the net longwave radiation and sensible heat flux (SH) decrease slightly. Earlier ice-off leads to more energy absorption mainly in the form of shortwave radiation during the thawing period, and later ice-on leads to more energy release in the form of longwave radiation, SH and LH during the ice formation period. Meanwhile, the lake–air temperature difference increased in both periods due to shortening ice duration.

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Air pollution slows down surface warming over the Tibetan Plateau

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-881-2020 ◽

2020 ◽

Vol 20 (2) ◽

pp. 881-899 ◽

Cited By ~ 1

Author(s):

Aolin Jia ◽

Shunlin Liang ◽

Dongdong Wang ◽

Bo Jiang ◽

Xiaotong Zhang

Keyword(s):

Climate Change ◽

Air Pollution ◽

Tibetan Plateau ◽

Air Temperature ◽

Surface Radiation ◽

Shortwave Radiation ◽

Cmip5 Models ◽

The Tibetan Plateau ◽

Anthropogenic Aerosols ◽

Surface Warming

Abstract. The Tibetan Plateau (TP) plays a vital role in regional and global climate change. The TP has been undergoing significant surface warming starting from 1850, with an air temperature increase of 1.39 K and surface solar dimming resulting from decreased incident solar radiation. The causes and impacts of solar dimming on surface warming are unclear. In this study, long-term (from 1850 to 2015) surface downward radiation datasets over the TP are developed by integrating 18 Coupled Model Intercomparison Project phase 5 (CMIP5) models and satellite products. The validation results from two ground measurement networks show that the generated downward surface radiation datasets have a higher accuracy than the mean of multiple CMIP5 datasets and the fused datasets of reanalysis and satellite products. After analyzing the generated radiation data with four air temperature datasets, we found that downward shortwave radiation (DSR) remained stable before 1950 and then declined rapidly at a rate of −0.53 W m−2 per decade, and that the fastest decrease in DSR occurs in the southeastern TP. Evidence from site measurements, satellite observations, reanalysis, and model simulations suggested that the TP solar dimming was primarily driven by increased anthropogenic aerosols. The TP solar dimming is stronger in summer, at the same time that the increasing magnitude of the surface air temperature is the smallest. The cooling effect of solar dimming offsets surface warming on the TP by 0.80±0.28 K (48.6±17.3 %) in summer since 1850. It helps us understand the role of anthropogenic aerosols in climate warming and highlights the need for additional studies to be conducted to quantify the influence of air pollution on regional climate change over the TP.

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Air pollution slows down surface warming over the Tibetan Plateau

10.5194/acp-2019-553 ◽

2019 ◽

Author(s):

Aolin Jia ◽

Shunlin Liang ◽

Dongdong Wang ◽

Bo Jiang ◽

Xiaotong Zhang

Keyword(s):

Climate Change ◽

Air Pollution ◽

Tibetan Plateau ◽

Air Temperature ◽

Surface Radiation ◽

Shortwave Radiation ◽

Cmip5 Models ◽

The Tibetan Plateau ◽

Anthropogenic Aerosols ◽

Surface Warming

Abstract. The Tibetan Plateau (TP) plays a vital role in regional and global climate change. The TP has been undergoing significant surface warming since 1850, with an air temperature increase of 1.39 K and surface solar dimming resulting from decreased incident solar radiation. The causes and impacts of solar dimming on surface warming are unclear. In this study, long-term (from 1850–2015) surface downward radiation datasets over the TP are developed by integrating 18 Coupled Model Intercomparison Project Phase 5 (CMIP5) models and satellite products. The validation results from two ground measurement networks show that the generated downward surface radiation datasets have higher accuracy than the mean of multiple CMIP5 and the fused datasets of reanalysis and satellite products. After analyzing the generated radiation data with four air temperature datasets, we found that downward shortwave radiation (DSR) remained stable before 1950 and then declined rapidly at a rate of −0.53 W m−2 per decade and that the fastest decrease in DSR is in the southeastern TP. Evidence from site measurements, satellite observations, reanalysis, and model simulations suggested that TP solar dimming was primarily driven by increased anthropogenic aerosols. The TP solar dimming is stronger in summer, at the same time that the increasing magnitude of the surface air temperature is the smallest. The cooling effect of solar dimming offsets surface warming on the TP by 0.80 ± 0.28 K (48.6 ± 17.3 %) in summer. It helps us understand the role of anthropogenic aerosols in climate warming, and highlights the need for additional studies to be conducted to quantify the influence of air pollution on regional climate change over the TP.

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Recent Trends in Land Surface Temperature on the Tibetan Plateau

Journal of Climate ◽

10.1175/jcli3811.1 ◽

2006 ◽

Vol 19 (12) ◽

pp. 2995-3003 ◽

Cited By ~ 29

Author(s):

Yuichiro Oku ◽

Hirohiko Ishikawa ◽

Shigenori Haginoya ◽

Yaoming Ma

Keyword(s):

Tibetan Plateau ◽

Surface Temperature ◽

Air Temperature ◽

Land Surface Temperature ◽

Land Surface ◽

Precipitation Amount ◽

Surface Air Temperature ◽

The Tibetan Plateau ◽

Near Surface ◽

Diurnal Range

Abstract The diurnal, seasonal, and interannual variations in land surface temperature (LST) on the Tibetan Plateau from 1996 to 2002 are analyzed using the hourly LST dataset obtained by Japanese Geostationary Meteorological Satellite 5 (GMS-5) observations. Comparing LST retrieved from GMS-5 with independent precipitation amount data demonstrates the consistent and complementary relationship between them. The results indicate an increase in the LST over this period. The daily minimum has risen faster than the daily maximum, resulting in a narrowing of the diurnal range of LST. This is in agreement with the observed trends in both global and plateau near-surface air temperature. Since the near-surface air temperature is mainly controlled by LST, this result ensures a warming trend in near-surface air temperature.

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Estimation of All-weather Downward Longwave Radiation over the Tibetan Plateau

10.5194/egusphere-egu21-14096 ◽

2021 ◽

Author(s):

Lirong Ding ◽

Zhiyong Long ◽

Ji Zhou ◽

Shaofei Wang ◽

Xiaodong Zhang

Keyword(s):

Climate Change ◽

Tibetan Plateau ◽

Energy Budget ◽

Water Cycle ◽

Longwave Radiation ◽

Radiation Balance ◽

The Tibetan Plateau ◽

Clear Sky ◽

Downward Longwave Radiation ◽

Sky Conditions

The downward longwave radiation (DLR) is a critical parameter for radiation balance, energy budget, and water cycle studies at regional and global scales. The accurate estimation of the all-weather DLR with a high temporal resolution is important for the estimation of the surface net radiation and evapotranspiration. However, the most DLR products involve instantaneous DLR estimates based on polar orbiting satellite data under clear-sky conditions. To obtain an in-depth understanding of the performances of different models in the estimation of the DLR over the Tibetan Plateau, which is a focus area of climate change study, this study tested eight methods under clear-sky conditions and six methods under cloudy conditions based on ground-measured data. The results show that the Dilley and O&#8217;Brien model and the Lhomme model are most suitable under clear-sky conditions and cloudy conditions, respectively. For the Dilley and O&#8217;Brien model, the average root mean square error (RMSE) of the DLR under clear-sky conditions is approximately 22.5 W/m2 at nine ground sites; for the Lhomme model, the average RMSE is approximately 23.2 W/m2. Based on the estimated cloud fraction and meteorological data provided by the China land surface data assimilation system (CLDAS), the hourly all-weather daytime DLR with 0.0625&#176; over the Tibetan Plateau was estimated. The results show that the average RMSE of the estimated hourly all-weather DLR was approximately 26.4 W/m2. With the combined all-weather DLR model, the hourly all-weather daytime DLR dataset with a 0.0625&#176; resolution from 2008 to 2016 over the Tibetan Plateau was generated. This dataset can better contribute to studies associated with the radiation balance and energy budget, water cycle, and climate change over the Tibetan Plateau.

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Causes of the 1985-2014 Surface Warming over the Sanjiangyuan Region of the Tibetan Plateau from the Perspective of Energy Transport

10.5194/egusphere-egu2020-6744 ◽

2020 ◽

Author(s):

Yinglin Tian ◽

Deyu Zhong

Keyword(s):

Heat Flux ◽

Tibetan Plateau ◽

Heat Source ◽

Energy Transport ◽

Longwave Radiation ◽

Warming Trend ◽

The Tibetan Plateau ◽

Heat Sources ◽

The South ◽

Downward Longwave Radiation

The Tibetan Plateau (TP), known as the &#8220;World Roof&#8221;, has significant influences on hydrological and atmospheric circulation at both regional and global scale. As the Sanjiangyuan Region (SJY) supplies water resources to the adjacent river basin and the TP could exert strong thermal forcing on the atmosphere over Asian monsoon region, adequate understand of the climate change over this region and its underlying mechanisms is of great importance. Based on gridded data provided by China Meteorological Administration (CMA), a continuous warming trend higher than that over elsewhere in China has been observed over the TP during 1985-2014, especially in the cold season (0.69 K/decade) and over the SJY (1.0 K/decade). On the basis of ERA interim reanalysis datasets, this paper analyzed the factors facilitating this warming trend in the SJY from the perspective of energy transport. At first, the local processes involved were investigated by calculating partial temperature changes using the surface energy budget equation. Then the horizontal convection of heat was quantified by summing the heat flux across the boundaries of the SJY. Finally, a Lagrangian heat source diagnostic method was developed to identify the major heat source. As the results indicating, among all the local heat sources, the enhanced downward longwave radiation reflected to surface air and the increasing upward longwave radiation emitted by warmer land surface were responsible for the pronounced surface air warming. However, the changes in surface sensible and latent heat fluxes had a reduced warming effect on the surface air. As for the non-local horizontal heat sources, rising horizontal heat flux from the south, west and east boundaries into the SJY contributed to the higher surface temperature of the SJY. In winter season, the heat flows stemmed from the South Himalayan vein into the SJY played a dominant role. Moreover, the higher the temperature over the SJY was, the more inclined this heat source was to Nepal.

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Seasonal thermal regime and climatic trends in lakes of the Tibetan highlands

Hydrology and Earth System Sciences ◽

10.5194/hess-21-1895-2017 ◽

2017 ◽

Vol 21 (4) ◽

pp. 1895-1909 ◽

Cited By ~ 13

Author(s):

Georgiy Kirillin ◽

Lijuan Wen ◽

Tom Shatwell

Keyword(s):

Tibetan Plateau ◽

High Altitude ◽

Air Temperature ◽

Thermal Regime ◽

Mixed Boundary ◽

Reanalysis Data ◽

Shortwave Radiation ◽

The Tibetan Plateau ◽

Seasonal Temperature ◽

High Altitude Lakes

Abstract. The hydrology of the lake-rich Tibetan Plateau is important for the global climate, yet little is known about the thermal regime of Tibetan lakes due to scant data. We (i) investigated the characteristic seasonal temperature patterns and recent trends in the thermal and stratification regimes of lakes on the Tibetan Plateau and (ii) tested the performance of the one-dimensional lake parameterization scheme FLake for the Tibetan lake system. For this purpose, we combined 3 years of in situ lake temperature measurements, several decades of satellite observations, and the global reanalysis data. We chose the two largest freshwater Tibetan lakes, Ngoring and Gyaring, as study sites. The lake model FLake faithfully reproduced the specific features of the high-altitude lakes and was subsequently applied to reconstruct the vertically resolved heat transport in both lakes during the last 4 decades. The model suggested that Ngoring and Gyaring were ice-covered for about 6 months and stratified in summer for about 4 months per year with a short spring overturn and a longer autumn overturn. In summer the surface mixed boundary layer extended to 6–8 m of depth and was about 20 % shallower in the more turbid Gyaring. The thermal regime of the transparent Ngoring responded more strongly to atmospheric forcing than Gyaring, where the higher turbidity damped the response. According to the reanalysis data, air temperatures and humidity have increased, whereas solar radiation has decreased, since the 1970s. Surprisingly, the modeled mean lake temperatures did not change, nor did the phenology of the ice cover or stratification. Lake surface temperatures in summer increased only marginally. The reason is that the increase in air temperature was offset by the decrease in radiation, probably due to increasing humidity. This study demonstrates that air temperature trends are not directly coupled to lake temperatures and underscores the importance of shortwave radiation for the thermal regime of high-altitude lakes.

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A revisit of parametrization of summer downward longwave radiation over the Tibetan Plateau from high temporal resolution measurements

10.5194/acp-2019-397 ◽

2019 ◽

Cited By ~ 2

Author(s):

Mengqi Liu ◽

Xiangdong Zheng ◽

Jinqiang Zhang ◽

Xiangao Xia

Keyword(s):

Tibetan Plateau ◽

Temporal Resolution ◽

Longwave Radiation ◽

Surface Energy Budget ◽

Coefficient Of Determination ◽

Cloud Base ◽

High Temporal Resolution ◽

The Tibetan Plateau ◽

Clear Sky ◽

Downward Longwave Radiation

Abstract. The Tibetan Plateau (TP) is one of hot spots in the climate research due to its unique geographical location, high altitude, highly sensitive to climate change as well potential effects on climate in East Asia. Downward longwave radiation (DLR), as a key component in the surface energy budget, is of practical implications for many research fields. Several attempts have been made to measure hourly or daily DLR and then model it over the TP. This study uses 1-minute radiation and meteorological measurements at three stations over the TP to parameterize DLR during summer months. Three independent methods are used to discriminate clear-sky observations by making maximal use of collocated measurements of downward shortwave and longwave radiation as well as Lidar backscatter measurements with high temporal resolution. This guarantees a reliable separation of clear-sky and cloudy samples that favors for proper parameterizations of DLR under these two contrast conditions. Clear-sky and cloudy DLR models with original parameters are firstly assessed. These models are then locally calibrated based on 1-minute observations. DLR estimation is notably improved since specific conditions over the TP are accounted for by local calibration, which is indicated by smaller root mean square error (RMSE) and larger coefficient of determination (R2). The best local parametrization can estimate clear-sky DLR with RMSE of 3.8 W⸱m-2. Overestimation of clear-sky DLR by previous study is evident, likely due to potential residue cloud contamination on the clear-sky samples. Cloud base height under overcast conditions is shown to be intimately related to cloudy DLR parameterization, which is considered by this study in the locally calibrated parameterization over the TP for the first time.

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The performance of CORDEX-EA-II simulations in simulating seasonal temperature and elevation-dependent warming over the Tibetan Plateau

Climate Dynamics ◽

10.1007/s00382-021-05760-6 ◽

2021 ◽

Author(s):

Xiaorui Niu ◽

Jianping Tang ◽

Deliang Chen ◽

Shuyu Wang ◽

Tinghai Ou ◽

...

Keyword(s):

Tibetan Plateau ◽

Radiative Forcing ◽

Regional Climate ◽

Great Influence ◽

Longwave Radiation ◽

Cumulus Parameterization ◽

The Tibetan Plateau ◽

Seasonal Temperature ◽

Temperature Changes ◽

Downward Longwave Radiation

AbstractTo explore the driving mechanisms of elevation-dependent warming (EDW) over the Tibetan Plateau (TP), the output from a suite of numerical experiments with different cumulus parameterization schemes (CPs) under the Coordinated Regional Climate Downscaling Experiments-East Asia (CORDEX-EA-II) project is examined. Results show that all experiments can broadly capture the observed temperature distributions over the TP with consistent cold biases, and the spread in temperature simulations commonly increases with elevation with the maximum located around 4000–5000 m. Such disagreements among the temperature simulations could to a large extent be explained by their spreads in the surface albedo feedback (SAF). All the experiments reproduce the observed EDW below 5000 m in winter but fail to capture the observed EDW above 4500 m in spring. Further analysis suggests that the simulated EDW during winter is mainly caused by the SAF, and the clear-sky downward longwave radiation (LWclr) plays a secondary role in shaping EDW. The models’ inability in simulating EDW during spring is closely related to the SAF and the surface cloud radiative forcing (CRFs). Furthermore, the magnitude and structure of the simulated EDW are sensitive to the choice of CPs. Different CPs generate diverse snow cover fractions, which can modulate the simulated SAF and its effect on EDW. Also, the CPs show great influence on the LWclr via altering the low-level air temperature. Additionally, the mechanism for different temperature changes among the experiments varies with altitudes during summer and autumn, as the diverse temperature changes appear to be caused by the LWclr for the low altitudes while by the SAF for the middle-high altitudes.

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Remotely sensed debris thickness mapping of Bara Shigri Glacier, Indian Himalaya

Journal of Glaciology ◽

10.3189/2015jog14j102 ◽

2015 ◽

Vol 61 (228) ◽

pp. 675-688 ◽

Cited By ~ 27

Author(s):

Simone Schauwecker ◽

Mario Rohrer ◽

Christian Huggel ◽

Anil Kulkarni ◽

Al. Ramanathan ◽

...

Keyword(s):

Surface Temperature ◽

Air Temperature ◽

Thermal Emission ◽

Promising Result ◽

Sensible Heat Flux ◽

Longwave Radiation ◽

Reanalysis Data ◽

Shortwave Radiation ◽

In Situ Data ◽

Energy Balance Approach

AbstractDespite the important role of supraglacial debris in ablation, knowledge of debris thickness on Himalayan glaciers is sparse. A recently developed method based on reanalysis data and thermal band satellite imagery has proved to be potentially suitable for debris thickness estimation without the need for detailed field data. In this study, we further develop the method and discuss possibilities and limitations arising from its application to a glacier in the Himalaya with scarce in situ data. Surface temperature patterns are consistent for 13 scenes of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Landsat 7 imagery and correlate well with incoming shortwave radiation and air temperature. We use an energy-balance approach to subtract these radiation or air temperature effects, in order to estimate debris thickness patterns as a function of surface temperature. Both incoming shortwave and longwave radiation are estimated with reasonable accuracy when applying parameterizations and reanalysis data. However, the model likely underestimates debris thickness, probably due to incorrect representation of vertical debris temperature profiles, the rate of heat storage and turbulent sensible heat flux. Moreover, the uncertainty of the result was found to increase significantly with thicker debris, a promising result since ablation is enhanced by thin debris of 1–2 cm.

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