Estimation of Downwelling Shortwave and Longwave Radiation in the Tibetan Plateau Under All‐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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Toward the Estimation of All-Weather Daytime Downward Longwave Radiation over the Tibetan Plateau

Atmosphere ◽

10.3390/atmos12121692 ◽

2021 ◽

Vol 12 (12) ◽

pp. 1692

Author(s):

Zhiyong Long ◽

Lirong Ding ◽

Ji Zhou ◽

Tianhao Zhou

Keyword(s):

Climate Change ◽

Tibetan Plateau ◽

Energy Budget ◽

Water Cycle ◽

Longwave Radiation ◽

Radiation Balance ◽

The Tibetan Plateau ◽

Clear Sky ◽

Downward Longwave Radiation ◽

Sky Conditions

Downward longwave radiation (DLR) is a critical parameter for radiation balance, energy budget, and water cycle studies at regional and global scales. 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, 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 DLR over the Tibetan Plateau, which is a focus area of climate change study, this study tests eight methods for clear-sky conditions and six methods for cloudy conditions based on ground-measured data. It is found that the Dilley and O’Brien model and the Lhomme model are most suitable for clear-sky conditions and cloudy conditions, respectively. For the Dilley and O’Brien model, the average root mean square error (RMSE) of DLR under clear-sky conditions is approximately 22.5 W/m2 for 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), hourly all-weather daytime DLR with a 0.0625° resolution over the Tibetan Plateau is estimated. Results demonstrate that the average RMSE of the estimated hourly all-weather DLR is approximately 26.4 W/m2. With the combined all-weather DLR model, the hourly all-weather daytime DLR dataset with a 0.0625° resolution from 2008 to 2016 over the Tibetan Plateau is generated. This dataset can contribute to studies associated with the radiation balance and energy budget, water cycle, and climate change over the Tibetan Plateau.

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Outgoing longwave radiation and cloud radiative forcing of the Tibetan Plateau

Journal of Geophysical Research Atmospheres ◽

10.1029/2000jd900201 ◽

2000 ◽

Vol 105 (D11) ◽

pp. 14863-14872 ◽

Cited By ~ 3

Author(s):

Wenying Su ◽

Jietai Mao ◽

Fei Ji ◽

Yu Qin

Keyword(s):

Tibetan Plateau ◽

Outgoing Longwave Radiation ◽

Radiative Forcing ◽

Longwave Radiation ◽

The Tibetan Plateau ◽

Cloud Radiative Forcing

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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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The Properties and Formation of Cirrus Clouds over the Tibetan Plateau Based on Summertime Lidar Measurements

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-12-0171.1 ◽

2013 ◽

Vol 70 (3) ◽

pp. 901-915 ◽

Cited By ~ 21

Author(s):

Q. S. He ◽

C. C. Li ◽

J. Z. Ma ◽

H. Q. Wang ◽

G. M. Shi ◽

...

Keyword(s):

Tibetan Plateau ◽

Large Scale ◽

Longwave Radiation ◽

Mean Value ◽

Cirrus Clouds ◽

The Tibetan Plateau ◽

Mean Values ◽

Upper Troposphere ◽

Lidar Ratio ◽

Highly Correlated

Abstract As part of the Tibet Ozone, Aerosol and Radiation (TOAR) project, a micropulse lidar was operated in Naqu (31.5°N, 92.1°E; 4508 m MSL) on the Tibetan Plateau to observe cirrus clouds continuously from 19 July to 26 August 2011. During the experiment, the time coverage of ice clouds only was 15% in the upper troposphere (above 9.5 km MSL). The cirrus top/bottom altitudes (mean values of 15.6/14.7 km) are comparable to those measured previously at tropical sites but relatively higher than those measured at midlatitude sites. The majority of the cloud layers yielded a lidar ratio between 10 and 40 sr, with a mean value of 28 ± 15 sr, characterized by a bimodal frequency distribution. Subvisible, thin, and opaque cirrus formation was observed in 16%, 34%, and 50% of all cirrus cases, respectively. A mean cirrus optical depth of 0.33 was observed over the Tibetan Plateau, slightly higher than those in the subtropics and tropics. With decreasing temperature, the lidar ratio increased slightly, whereas the mean extinction coefficient decreased significantly. The occurrence of clouds is highly correlated with the outgoing longwave radiation and the strong cold perturbations in the upper troposphere. Deep convective activity and Rossby waves are important dynamical processes that control cirrus variations over the Tibetan Plateau, where both anvil cirrus outflowing from convective cumulonimbus clouds and large-scale strong cold perturbations in the upper troposphere should play an important role in cirrus formation.

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Estimation of surface upward longwave radiation from MODIS and VIIRS clear-sky data in the Tibetan Plateau

Remote Sensing of Environment ◽

10.1016/j.rse.2015.02.021 ◽

2015 ◽

Vol 162 ◽

pp. 221-237 ◽

Cited By ~ 18

Author(s):

Zhonghu Jiao ◽

Guangjian Yan ◽

Jing Zhao ◽

Tianxing Wang ◽

Ling Chen

Keyword(s):

Tibetan Plateau ◽

Longwave Radiation ◽

The Tibetan Plateau ◽

Clear Sky

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Evaluation of Parameterizations of Incoming Longwave Radiation in the High-Mountain Region of the Tibetan Plateau

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-16-0189.1 ◽

2017 ◽

Vol 56 (4) ◽

pp. 833-848 ◽

Cited By ~ 11

Author(s):

Meilin Zhu ◽

Tandong Yao ◽

Wei Yang ◽

Baiqing Xu ◽

Xiaojun Wang

Keyword(s):

Tibetan Plateau ◽

Longwave Radiation ◽

Cloud Base ◽

High Mountain ◽

The Tibetan Plateau ◽

Mountain Regions ◽

Local Conditions ◽

Clear Sky ◽

The Difference ◽

Study Sites

AbstractAccurate evaluations of incoming longwave radiation (Lin) parameterization have practical implications for glacier and river runoff changes in high-mountain regions of the Tibetan Plateau (TP). To identify potential means of accurately predicting spatiotemporal variations in Lin, 13 clear-sky parameterizations combined with 10 cloud corrections for all-sky atmospheric emissivity were evaluated at five sites in high-mountain regions of the TP through temporal and spatial parameter transfer tests. Most locally calibrated parameterizations for clear-sky and all-sky conditions performed well when applied to the calibration site. The best parameterization at five sites is Dilley and O’Brien’s A model combined with Sicart et al.’s A for cloud-correction-incorporated relative humidity. The performance of parameter transferability in time is better than that in space for the same all-sky parameterizations. The performance of parameter transferability in space presents spatial discrepancies. In addition, all all-sky parameterizations show a decrease in performance with increasing altitude regardless of whether the parameters of all-sky parameterizations were recalibrated by local conditions or transferred from other study sites. This may be attributable to the difference between screen-level air temperature and the effective atmospheric boundary layer temperature and to different cloud-base heights. Nevertheless, such worse performance at higher altitudes is likely to change because of terrain, underlying surfaces, and wind systems, among other factors. The study also describes possible spatial characteristics of Lin and its driving factors by reviewing the few studies about Lin for the mountain regions of the TP.

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

Water ◽

10.3390/w13213084 ◽

2021 ◽

Vol 13 (21) ◽

pp. 3084

Author(s):

Chunxiao Wang ◽

Yaoming Ma ◽

Binbin Wang ◽

Weiqiang Ma ◽

Xuelong Chen ◽

...

Keyword(s):

Tibetan Plateau ◽

Surface Temperature ◽

Air Temperature ◽

Surface Albedo ◽

Longwave Radiation ◽

Heat Fluxes ◽

Shortwave Radiation ◽

The Tibetan Plateau ◽

Downward Shortwave Radiation ◽

Downward Longwave Radiation

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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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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