Toward the Estimation of All-Weather Daytime Downward Longwave Radiation over the Tibetan Plateau

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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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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A revisiting of the parametrization of downward longwave radiation in summer over the Tibetan Plateau based on high-temporal-resolution measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-4415-2020 ◽

2020 ◽

Vol 20 (7) ◽

pp. 4415-4426 ◽

Cited By ~ 1

Author(s):

Mengqi Liu ◽

Xiangdong Zheng ◽

Jinqiang Zhang ◽

Xiangao Xia

Keyword(s):

Climate Change ◽

Tibetan Plateau ◽

Longwave Radiation ◽

Radiation Budget ◽

Cloud Base ◽

The Tibetan Plateau ◽

Climate Change Research ◽

Clear Sky ◽

Downward Longwave Radiation ◽

Mean Square Errors

Abstract. The Tibetan Plateau (TP) is one of the research hot spots in the climate change research due to its unique geographical location and high altitude. Downward longwave radiation (DLR), as a key component in the surface energy budget, has practical implications for radiation budget and climate change. A couple of attempts have been made to parametrize DLR over the TP based on hourly or daily measurements and crude clear-sky discrimination methods. This study uses 1 min shortwave and longwave radiation measurements at three stations over the TP to parametrize DLR during summer months. Three independent methods are used to discriminate clear sky from clouds based on 1 min radiation and lidar measurements. This guarantees the strict selection of clear-sky samples that is fundamental for the parametrization of clear-sky DLR. A total of 11 clear-sky and 4 cloudy DLR parametrizations are examined and locally calibrated. Compared to previous studies, DLR parametrizations here are shown to be characterized by smaller root-mean-square errors (RMSEs) and higher coefficients of determination (R2). Clear-sky DLR can be estimated from the best parametrization with a RMSE of 3.8 W m−2 and R2>0.98. Systematic overestimation of clear-sky DLR by the locally calibrated parametrization in one previous study is found to be approximately 25 W m−2 (10 %), which is very likely due to potential residual cloud contamination on previous clear-sky DLR parametrization. The cloud base height under overcast conditions is shown to play an important role in cloudy DLR parametrization, which is considered in the locally calibrated parametrization over the TP for the first time. Further studies on DLR parametrization during nighttime and in seasons except summer are required for our better understanding of the role of DLR in climate change.

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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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Estimation of Downwelling Shortwave and Longwave Radiation in the Tibetan Plateau Under All‐Sky Conditions

Journal of Geophysical Research Atmospheres ◽

10.1029/2019jd030763 ◽

2019 ◽

Vol 124 (21) ◽

pp. 11086-11102 ◽

Cited By ~ 2

Author(s):

Lei Zhong ◽

Mijun Zou ◽

Yaoming Ma ◽

Ziyu Huang ◽

Kepiao Xu ◽

...

Keyword(s):

Tibetan Plateau ◽

Longwave Radiation ◽

The Tibetan Plateau ◽

Sky Conditions

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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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Downward longwave radiation estimates for clear-sky conditions over northeast Brazil

Revista Brasileira de Meteorologia ◽

10.1590/s0102-77862011000300010 ◽

2011 ◽

Vol 26 (3) ◽

pp. 443-450 ◽

Cited By ~ 14

Author(s):

Carlos Antonio Costa dos Santos ◽

Bernardo Barbosa da Silva ◽

Tantravahi Venkata Ramana Rao ◽

Prakki Satyamurty ◽

Antonio Ocimar Manzi

Keyword(s):

Arid Regions ◽

Longwave Radiation ◽

Radiation Budget ◽

Semiarid Region ◽

Northeast Brazil ◽

Hydrological Models ◽

Experimental Site ◽

Clear Sky ◽

Downward Longwave Radiation ◽

Sky Conditions

The main objective of this paper is to assess the performance of nine downward longwave radiation equations for clear-sky condition and develop a locally adjusted equation using the observed vapor pressure and air temperature data. The radiation and atmospheric parameters were measured during the months of October 2005 to June 2006 at a micrometeorological tower installed at the experimental site in a banana orchard in the semiarid region of Northeast Brazil. The comparative statistics for the performance of the downward longwave radiation calculation models during daytime and nighttime compared to measured data have shown that the parameterizations with more physical foundations have the best results. The locally adjusted equation and Sugita and Brutsaert model developed in 1993 showed errors less than 1.0% in comparison with measured values. Downward longwave radiation is one of the most expensive and difficult component of the radiation budget to be monitored in micrometeorological studies. Hence, the locally adjusted equation can be used to estimate downward longwave energy, needed as input to some agricultural and hydrological models, in semi-arid regions of the Northeast Brazil, where this component is not monitored.

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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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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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