Estimation of the terms acting on local surface one-hour temperature variations in Paris region: the specific contribution of clouds

Abstract. Local temperature variations at the surface are mainly dominated by small-scale processes coupled through the surface energy budget terms, which depend mostly on radiation availability and thus cloud processes. A method to determine each of these terms based almost exclusively on observations is presented in this paper, with the main objective to estimate their importance in hourly surface temperature variations at the SIRTA observatory, near Paris. Almost all terms are estimated from the multi-year dataset SIRTA-ReOBS, following a few parametrizations. The four main terms acting on temperature variations are radiative forcing (separated into clear-sky and cloud radiation), atmospheric heat exchange, ground heat exchange, and advection. Compared to direct measurements of hourly temperature variations, it is shown that the sum of the four terms gives a good estimate of the hourly temperature variations, allowing a better assessment of the contribution of each term to the variation, with an accurate diurnal and annual cycles representation, especially for the radiative terms. A random forest analysis shows that whatever the season, clouds are the main modulator of the clear sky radiation for 1-hour temperature variations during the day, and mainly drive these 1-hour temperature variations during the night. Then, the specific role of clouds is analyzed exclusively in cloudy conditions considering the behavior of some classical meteorological variables along with lidar profiles. Cloud radiative effect in shortwave and longwave and lidar profiles show a consistent seasonality during the daytime, with a dominance of mid- and high-level clouds detected at the SIRTA observatory, which also affects surface temperatures and upward sensible heat flux. During the nighttime, despite cloudy conditions and having a strong cloud longwave radiative effect, temperatures are the lowest and are therefore mostly controlled by larger-scale processes at this time.

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Estimation of the terms acting on local 1 h surface temperature variations in Paris region: the specific contribution of clouds

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-15699-2021 ◽

2021 ◽

Vol 21 (20) ◽

pp. 15699-15723

Author(s):

Oscar Javier Rojas Muñoz ◽

Marjolaine Chiriaco ◽

Sophie Bastin ◽

Justine Ringard

Keyword(s):

Heat Exchange ◽

Surface Temperature ◽

Radiative Forcing ◽

Small Scale ◽

Radiative Effect ◽

Near Surface ◽

Temperature Variations ◽

Clear Sky ◽

Hourly Temperature ◽

Specific Contribution

Abstract. Local short-term temperature variations at the surface are mainly dominated by small-scale processes coupled through the surface energy balance terms, which are well known but whose specific contribution and importance on the hourly scale still need to be further analyzed. A method to determine each of these terms based almost exclusively on observations is presented in this paper, with the main objective being to estimate their importance in hourly near-surface temperature variations at the SIRTA observatory, near Paris. Almost all terms are estimated from the multi-year dataset SIRTA-ReOBS, following a few parametrizations. The four main terms acting on temperature variations are radiative forcing (separated into clear-sky and cloudy-sky radiation), atmospheric heat exchange, ground heat exchange, and advection. Compared to direct measurements of hourly temperature variations, it is shown that the sum of the four terms gives a good estimate of the hourly temperature variations, allowing a better assessment of the contribution of each term to the variation, with an accurate diurnal and annual cycle representation, especially for the radiative terms. A random forest analysis shows that whatever the season, clouds are the main modulator of the clear-sky radiation for 1 h temperature variations during the day and mainly drive these 1 h temperature variations during the night. Then, the specific role of clouds is analyzed exclusively in cloudy conditions considering the behavior of some classical meteorological variables along with lidar profiles. Cloud radiative effect in shortwave and longwave and lidar profiles show a consistent seasonality during the daytime, with a dominance of mid- and high-level clouds detected at the SIRTA observatory, which also affects near-surface temperatures and upward sensible heat flux. During the nighttime, despite cloudy conditions and having a strong cloud longwave radiative effect, temperatures are the lowest and are therefore mostly controlled by larger-scale processes at this time.

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Aerosol properties and aerosol–radiation interactions in clear sky conditions over Germany

10.5194/acp-2021-517 ◽

2021 ◽

Author(s):

Jonas Witthuhn ◽

Anja Hünerbein ◽

Florian Filipitsch ◽

Stefan Wacker ◽

Stefanie Meilinger ◽

...

Keyword(s):

Radiative Transfer ◽

Aerosol Optical Depth ◽

Optical Depth ◽

Kernel Method ◽

Detection Algorithm ◽

Surface Energy Budget ◽

Radiative Effect ◽

Clear Sky ◽

Observational Network ◽

Level Of Agreement

Abstract. The clear-sky radiative effect of aerosol-radiation interactions is of relevance for our understanding of the climate system. The influence of aerosol on the surface energy budget is of high interest for the renewable energy sector. In this study, the radiative effect is investigated in particular with respect to seasonal and regional variations for the region of Germany and the year 2015 at the surface and top of atmosphere using two complementary approaches. First, an ensemble of clear-sky models which explicitly consider aerosols is utilized to retrieve the aerosol optical depth and the surface direct radiative effect of aerosols by means of a clear sky fitting technique. For this, short-wave broadband irradiance measurements in the absence of clouds are used as a basis. A clear sky detection algorithm is used to identify cloud free observations. Considered are measurements of the shortwave broadband global and diffuse horizontal irradiance with shaded and unshaded pyranometers at 25 stations across Germany within the observational network of the German Weather Service (DWD). Clear sky models used are MMAC, MRMv6.1, METSTAT, ESRA, Heliosat-1, CEM and the simplified Solis model. The definition of aerosol and atmospheric characteristics of the models are examined in detail for their suitability for this approach. Second, the radiative effect is estimated using explicit radiative transfer simulations with inputs on the meteorological state of the atmosphere, trace-gases and aerosol from CAMS reanalysis. The aerosol optical properties (aerosol optical depth, Ångström exponent, single scattering albedo and assymetrie parameter) are first evaluated with AERONET direct sun and inversion products. The largest inconsistency is found for the aerosol absorption, which is overestimated by about 0.03 or about 30 % by the CAMS reanalysis. Compared to the DWD observational network, the simulated global, direct and diffuse irradiances show reasonable agreement within the measurement uncertainty. The radiative kernel method is used to estimate the resulting uncertainty and bias of the simulated direct radiative effect. The uncertainty is estimated to −1.5 ± 7.7 and 0.6 ± 3.5 W m−2 at the surface and top of atmosphere, respectively, while the annual-mean biases at the surface, top of atmosphere and total atmosphere are −10.6, −6.5 and 4.1 W m−2, respectively. The retrieval of the aerosol radiative effect with the clear sky models shows a high level of agreement with the radiative transfer simulations, with an RMSE of 5.8 W m−2 and a correlation of 0.75. The annual mean of the REari at the surface for the 25 DWD stations shows a value of −12.8 ± 5 W m−2 as average over the clear sky models, compared to −11 W m−2 from the radiative transfer simulations. Since all models assume a fixed aerosol characterisation, the annual cycle of the aerosol radiation effect cannot be reproduced. Out of this set of clear sky models, the largest level of agreement is shown by the ESRA and MRMv6.1 models.

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Regional and monthly and clear-sky aerosol direct radiative effect (and forcing) derived from the GlobAEROSOL-AATSR satellite aerosol product

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-393-2013 ◽

2013 ◽

Vol 13 (1) ◽

pp. 393-410 ◽

Cited By ~ 9

Author(s):

G. E. Thomas ◽

N. Chalmers ◽

B. Harris ◽

R. G. Grainger ◽

E. J. Highwood

Keyword(s):

Optical Properties ◽

Radiative Forcing ◽

Radiative Effect ◽

Mean Values ◽

Clear Sky ◽

Aerosol Loading ◽

Uncertainty Estimates ◽

Wide Range ◽

Aerosol Radiative ◽

Radiation Scheme

Abstract. Using the GlobAEROSOL-AATSR dataset, estimates of the instantaneous, clear-sky, direct aerosol radiative effect and radiative forcing have been produced for the year 2006. Aerosol Robotic Network sun-photometer measurements have been used to characterise the random and systematic error in the GlobAEROSOL product for 22 regions covering the globe. Representative aerosol properties for each region were derived from the results of a wide range of literature sources and, along with the de-biased GlobAEROSOL AODs, were used to drive an offline version of the Met Office unified model radiation scheme. In addition to the mean AOD, best-estimate run of the radiation scheme, a range of additional calculations were done to propagate uncertainty estimates in the AOD, optical properties, surface albedo and errors due to the temporal and spatial averaging of the AOD fields. This analysis produced monthly, regional estimates of the clear-sky aerosol radiative effect and its uncertainty, which were combined to produce annual, global mean values of (−6.7 ± 3.9) W m−2 at the top of atmosphere (TOA) and (−12 ± 6) W m−2 at the surface. These results were then used to give estimates of regional, clear-sky aerosol direct radiative forcing, using modelled pre-industrial AOD fields for the year 1750 calculated for the AEROCOM PRE experiment. However, as it was not possible to quantify the uncertainty in the pre-industrial aerosol loading, these figures can only be taken as indicative and their uncertainties as lower bounds on the likely errors. Although the uncertainty on aerosol radiative effect presented here is considerably larger than most previous estimates, the explicit inclusion of the major sources of error in the calculations suggest that they are closer to the true constraint on this figure from similar methodologies, and point to the need for more, improved estimates of both global aerosol loading and aerosol optical properties.

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Evaluation of clear sky models to estimate the surface direct aerosol radiative effect over Germany

10.5194/egusphere-egu21-7294 ◽

2021 ◽

Author(s):

Jonas Witthuhn ◽

Anja Hünerbein ◽

Hartwig Deneke ◽

Florian Filipitsch ◽

Stefan Wacker

Keyword(s):

Radiative Forcing ◽

Power Plants ◽

Climate System ◽

Radiation Budget ◽

Radiative Effect ◽

Clear Sky ◽

A Value ◽

Reference Simulation ◽

One Year ◽

Aerosol Radiative

The radiation budget of the earth and its climate system is driven by the solar radiation, which interacts with gases, aerosol particles and clouds. Focusing on aerosol, a fundamental measure is the radiative forcing resulting from aerosol-radiation interactions (RFari) which is also known as the aerosol direct radiative effect. Quantifying the surface RFari on regional scales aids the understanding of the role of aerosol in the climate system and is important for the planning of solar energy systems.This study is based on a one year dataset (2015) of shortwave broadband global and diffuse horizontal irradiance measured with shaded and unshaded pyranometers at 26 station across Germany within the German Weather Service (DWD) observational network. A variety of clear-sky models are utilized to quantify RFari with a clear sky fitting technique. Clear sky models used are MMAC, MRM v.6.1, METSTAT, ESRA, Heliosat-1, CEM and the simplified Solis model. As these models have not been designed to estimate the clear sky irradiance without the presence of aerosol, we evaluated the accuracy of RFari with an reference simulation.The reference RFari is simulated using the TROPOS (Leibniz Institute of Tropospheric Research) Cloud and Aerosol Radiative Simulator (T-CARS) utilizing the offline version of the ECMWF radiation scheme (ecRad) with input data of meteorological state of the atmosphere, trace-gases and aerosol from CAMS reanalysis.The clear sky fitting approach for this set of clear sky models agrees well with T-CARS, showing an RMSE of 6.7 Wm-2 and an correlation of 0.75. The annual mean of surface RFari over the observation stations in Germany shows a value of -13.2 Wm-2 as an average over all clear sky models, compared to -13.4 Wm-2 from T-CARS. Out of this set of clear sky models, best performance is shown by the ESRA and MRM v6.1 models. Although, the accuracy of the annual mean RFari from the clear sky fitting approach is strongly depended on the number available clear-sky irradiance measurements and its distribution over the year. Therefore, this approach is not recommended for climatological studies, but may serve as valuable information for e.g. the evaluation of power generation and the influence by aerosol of photo-voltaic power plants.

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“Solar panels forest” and its radiative forcing effect: preliminary results from the Arava Desert

10.5194/egusphere-egu2020-18924 ◽

2020 ◽

Author(s):

Rafael Stern ◽

Madi Amer ◽

Jonathan Müller ◽

Fyodor Tatarinov ◽

Lior Segev ◽

...

Keyword(s):

Solar Radiation ◽

Radiative Forcing ◽

Power Efficiency ◽

Sensible Heat Flux ◽

Surface Energy Budget ◽

Spatial Average ◽

Sensible Heat ◽

Solar Panels ◽

High Background ◽

Preliminary Results

&#160;&#160;&#160;&#160;&#160;&#160; The production of electricity from solar radiation should replace power production by burning fossil fuel and help reduce atmospheric concentrations of CO2. However, large photovoltaic (PV) fields can also influence the climate in more direct ways. The albedo of solar panels is low to allow efficient light absorption, but actual conversion efficiency is below &#160;20%. The remaining 80% of the energy is reflected, re-emitted as thermal radiation or dissipated as sensible heat (H). These effects can heat the surface, influence local air circulations, and lead to the formation of &#8220;heat-islands&#8221;. Such effects are particularly significant in desert areas with high radiation load and high background albedo. The ultimate objective of this study will be to estimate the cost (in number of years) of CO2 emission suppression of a PV power generation (a &#8220;cooling effect&#8221;) associated with the albedo radiative forcing and the surface "warming effects" and the partitioning to its components.&#160;&#160;&#160;&#160;&#160;&#160; We used a state-of-the-art field laboratory to carry out eddy covariance flux measurements of sensible and latent heat, and the radiative balance of incoming and outgoing short- and long-wave radiations. A research drone equipped with a thermal and a multi-spectral camera was used to estimate the spatial average reflected and emitted radiation from the solar panels field. Measurements were carried out on campaign basis during 2018-2019, both inside and outside a PV field in the Arava desert in southern Israel.&#160;&#160;&#160;&#160;&#160;&#160; The preliminary results indicated that summer noon incoming solar radiation (S) is ~1000 Wm-2 and the desert surface albedo is on average 0.40. The mean solar panel field albedo is 0.23 (with panels projected area about 1/3rd of the PV field area), which is translated to ~170 Wm-2 higher S absorption by the PV field. A large fraction of the energy is converted to sensible heat flux with mid-day H values of 450 Wm-2, compared with 250 Wm-2 in the desert, or about 200 Wm-2 of extra heating above the PV field. A first approximation of the summer daily carbon suppression (assuming 12h daily average sunlight of ~500 Wm-2, PV efficiency of 0.2, and conventional power efficiency of ~200 gC/KWh) indicated ~0.08 Kg C per day per m-2 PV area. These preliminary results are being extended to include thermal emission effects and the annual scale perspective to assess the &#8220;PV forest&#8221; radiative forcing effect. But it is evident that the land use change examined here has a large impact on the surface energy budget and its surrounding environments.

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Regional and monthly and clear-sky aerosol direct radiative effect (and forcing) derived from the GlobAEROSOL-AATSR satellite aerosol product

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-18459-2012 ◽

2012 ◽

Vol 12 (7) ◽

pp. 18459-18497 ◽

Cited By ~ 3

Author(s):

G. E. Thomas ◽

N. Chalmers ◽

B. Harris ◽

R. G. Grainger ◽

E. J. Highwood

Keyword(s):

Optical Properties ◽

Radiative Forcing ◽

Radiative Effect ◽

Mean Values ◽

Clear Sky ◽

Aerosol Loading ◽

Uncertainty Estimates ◽

Wide Range ◽

Aerosol Radiative ◽

Radiation Scheme

Abstract. Using the GlobAEROSOL-AATSR dataset, estimates of the instantaneous, clear-sky, direct aerosol radiative effect and radiative forcing have been produced for the year 2006. Aerosol Robotic Network sun-photometer measurements have been used to characterise the random and systematic error in the GlobAEROSOL product for 22 regions covering the globe. Representative aerosol properties for each region have been derived from the results of a wide range of literature sources and, along with the de-biased GlobAEROSOL AODs, were used to drive an offline version of the Met Office unified model radiation scheme. In addition to the mean AOD, best-estimate run of the radiation scheme, a range of additional calculations were done to propagate uncertainty estimates in the AOD, optical properties, surface albedo and errors due to the temporal and spatial averaging of the AOD fields. This analysis produced monthly, regional estimates of the clear-sky aerosol radiative effect and its uncertainty, which produce annual, global mean values of (−6.7 ± 3.9) W m−2 at the top of atmosphere (TOA) and (−12 ± 6) W m−2 at the surface. These results were then used to produce estimates of regional, clear-sky aerosol direct radiative forcing, using modelled pre-industrial AOD fields for 1750 calculated for the AEROCOM PRE experiment. However, as it was not possible to quantify the uncertainty in the pre-industrial aerosol loading, these figures can only be taken as indicative and their uncertainties as lower bounds on the likely errors. Although the uncertainty on aerosol radiative effect presented here is considerably larger than most previous estimates, the explicit inclusion of the major sources of error in the calculations suggest that they are closer to the true constraint on this figure from similar methodologies, and point to the need for more, improved estimates of both global aerosol loading and aerosol optical properties.

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Contribution of clouds radiative forcing to the local surface temperature variability

10.5194/egusphere-egu2020-14932 ◽

2020 ◽

Author(s):

Oscar Rojas ◽

Marjolaine Chiriaco ◽

Sophie Bastin ◽

Justine Ringard

Keyword(s):

Heat Exchange ◽

Decision Trees ◽

Radiative Forcing ◽

Temperature Variability ◽

Local Climate ◽

Hourly Temperature ◽

Local Contribution ◽

Bagged Decision Trees ◽

The One ◽

Local Surface Temperature

The local contribution of clouds to the surface energy balance and temperature variability is an important topic in order to apprehend how this intake affects local climate variability and extreme events, how this contribution varies from one place to another, and how it evolves in a warming climate. The scope of this study is to understand how clouds impact temperature variability, to quantify their contribution, and to compare their effects to other surface processes. To do so, we develop a method to estimate the different terms that control temperature variability at the surface (&#8706;T2m /&#8706;t) by using this equation: &#8706;T2m /&#8706;t=R+HA+HG+Adv where R is the radiation that is separated into the cloud term (Rcloud) and the clear sky one (RCS), HA the atmospheric heat exchange, HG the ground heat exchange, and Adv the advection. These terms are estimated hourly, almost only using direct measurements from SIRTA-ReOBS dataset (an hourly long-term multi-variables dataset retrieved from SIRTA, an observatory located in a semi-urban area 20-km South-West of Paris; Chiriaco et al., 2019) for a five-years period. The method gives good results for the hourly temperature variability, with a 0.8 correlation coefficient and a weak residual term between left part (directly measured) and right part of the equation.A bagged decision trees analysis of this equation shows that RCS dominates temperature variability during daytime and is mainly modulated by cloud radiative effect (Rcloud). During nighttime, the bagged decision trees analysis determines that Rcloud is the term controlling temperature changes. When a diurnal cycle analysis (split into seasons) is performed for each term, HA becomes an important negative modulator in the late afternoon, chiefly in spring and summer, when evaporation and thermal conduction are increased. In contrast, HG and Adv terms do not play an essential role on temperature variability at this temporal scale and their contribution is barely considerable in the one-hour variability, but still they remain necessary in order to obtain the best coefficient estimator between the directly measured observations and the method estimated. All terms except advection have a marked monthly-hourly cycle.Next steps consist in characterize the types of clouds and study their physical properties corresponding to the cases where Rcloud is significant, using the Lidar profiles also available in the SIRTA-ReOBS dataset.

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Consequences of the 2019 Greenland Ice Sheet Melt Episode on Albedo

Remote Sensing ◽

10.3390/rs13020227 ◽

2021 ◽

Vol 13 (2) ◽

pp. 227

Author(s):

Arthur Elmes ◽

Charlotte Levy ◽

Angela Erb ◽

Dorothy K. Hall ◽

Ted A. Scambos ◽

...

Keyword(s):

Radiative Forcing ◽

Surface Albedo ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Surface Energy Budget ◽

Landsat 8 ◽

Moderate Resolution ◽

Resolution Imaging ◽

Moderate Resolution Imaging Spectroradiometer ◽

Seasonal Snow Cover

In mid-June 2019, the Greenland ice sheet (GrIS) experienced an extreme early-season melt event. This, coupled with an earlier-than-average melt onset and low prior winter snowfall over western Greenland, led to a rapid decrease in surface albedo and greater solar energy absorption over the melt season. The 2019 melt season resulted in significantly more melt than other recent years, even compared to exceptional melt years previously identified in the moderate-resolution imaging spectroradiometer (MODIS) record. The increased solar radiation absorbance in 2019 warmed the surface and increased the rate of meltwater production. We use two decades of satellite-derived albedo from the MODIS MCD43 record to show a significant and extended decrease in albedo in Greenland during 2019. This decrease, early in the melt season and continuing during peak summer insolation, caused increased radiative forcing of the ice sheet of 2.33 Wm−2 for 2019. Radiative forcing is strongly influenced by the dramatic seasonal differences in surface albedo experienced by any location experiencing persistent and seasonal snow-cover. We also illustrate the utility of the newly developed Landsat-8 albedo product for better capturing the detailed spatial heterogeneity of the landscape, leading to a more refined representation of the surface energy budget. While the MCD43 data accurately capture the albedo for a given 500 m pixel, the higher spatial resolution 30 m Landsat-8 albedos more fully represent the detailed landscape variations.

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Influence of Subfacet Heterogeneity and Material Properties on the Urban Surface Energy Budget

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-13-0286.1 ◽

2014 ◽

Vol 53 (9) ◽

pp. 2114-2129 ◽

Cited By ~ 23

Author(s):

Prathap Ramamurthy ◽

Elie Bou-Zeid ◽

James A. Smith ◽

Zhihua Wang ◽

Mary L. Baeck ◽

...

Keyword(s):

Surface Energy ◽

Energy Budget ◽

Material Properties ◽

Sensible Heat Flux ◽

Role Reversal ◽

Surface Energy Budget ◽

Urban Surface ◽

Urban Site ◽

Peak Time ◽

Sensible Heat

AbstractUrban facets—the walls, roofs, and ground in built-up terrain—are often conceptualized as homogeneous surfaces, despite the obvious variability in the composition and material properties of the urban fabric at the subfacet scale. This study focuses on understanding the influence of this subfacet heterogeneity, and the associated influence of different material properties, on the urban surface energy budget. The Princeton Urban Canopy Model, which was developed with the ability to capture subfacet variability, is evaluated at sites of various building densities and then applied to simulate the energy exchanges of each subfacet with the atmosphere over a densely built site. The analyses show that, although all impervious built surfaces convert most of the incoming energy into sensible heat rather than latent heat, sensible heat fluxes from asphalt pavements and dark rooftops are 2 times as high as those from concrete surfaces and light-colored roofs. Another important characteristic of urban areas—the shift in the peak time of sensible heat flux in comparison with rural areas—is here shown to be mainly linked to concrete’s high heat storage capacity as well as to radiative trapping in the urban canyon. The results also illustrate that the vegetated pervious soil surfaces that dot the urban landscape play a dual role: during wet periods they redistribute much of the available energy into evaporative fluxes but when moisture stressed they behave more like an impervious surface. This role reversal, along with the direct evaporation of water stored over impervious surfaces, significantly reduces the overall Bowen ratio of the urban site after rain events.

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Method Development for Estimating Sensible Heat Flux over the Tibetan Plateau from CMA Data

Journal of Applied Meteorology and Climatology ◽

10.1175/2009jamc2167.1 ◽

2009 ◽

Vol 48 (12) ◽

pp. 2474-2486 ◽

Cited By ~ 28

Author(s):

Kun Yang ◽

Jun Qin ◽

Xiaofeng Guo ◽

Degang Zhou ◽

Yaoming Ma

Keyword(s):

Heat Flux ◽

Tibetan Plateau ◽

Method Development ◽

Sensible Heat Flux ◽

Atmospheric Stability ◽

Surface Energy Budget ◽

New Method ◽

The Tibetan Plateau ◽

Sensible Heat ◽

Hourly Data

Abstract To clarify the thermal forcing of the Tibetan Plateau, long-term coarse-temporal-resolution data from the China Meteorological Administration have been widely used to estimate surface sensible heat flux by bulk methods in many previous studies; however, these estimates have seldom been evaluated against observations. This study at first evaluates three widely used bulk schemes against Tibet instrumental flux data. The evaluation shows that large uncertainties exist in the heat flux estimated by these schemes; in particular, upward heat fluxes in winter may be significantly underestimated, because diurnal variations of atmospheric stability were not taken into account. To improve the estimate, a new method is developed to disaggregate coarse-resolution meteorological data to hourly according to statistical relationships derived from high-resolution experimental data, and then sensible heat flux is estimated from the hourly data by a well-validated flux scheme. Evaluations against heat flux observations in summer and against net radiation observations in winter indicate that the new method performs much better than previous schemes, and therefore it provides a robust basis for quantifying the Tibetan surface energy budget.

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