scholarly journals Evaluation of Six High-Spatial Resolution Clear-Sky Surface Upward Longwave Radiation Estimation Methods with MODIS

2020 ◽  
Vol 12 (11) ◽  
pp. 1834
Author(s):  
Boxiong Qin ◽  
Biao Cao ◽  
Hua Li ◽  
Zunjian Bian ◽  
Tian Hu ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Hybrid Methods ◽  
Longwave Radiation ◽  
Surface Radiation ◽  
Radiation Budget ◽  
Estimation Methods ◽  
Mean Bias Error ◽  
Clear Sky ◽  
Surface Radiation Budget

Surface upward longwave radiation (SULR) is a critical component in the calculation of the Earth’s surface radiation budget. Multiple clear-sky SULR estimation methods have been developed for high-spatial resolution satellite observations. Here, we comprehensively evaluated six SULR estimation methods, including the temperature-emissivity physical methods with the input of the MYD11/MYD21 (TE-MYD11/TE-MYD21), the hybrid methods with top-of-atmosphere (TOA) linear/nonlinear/artificial neural network regressions (TOA-LIN/TOA-NLIN/TOA-ANN), and the hybrid method with bottom-of-atmosphere (BOA) linear regression (BOA-LIN). The recently released MYD21 product and the BOA-LIN—a newly developed method that considers the spatial heterogeneity of the atmosphere—is used initially to estimate SULR. In addition, the four hybrid methods were compared with simulated datasets. All the six methods were evaluated using the Moderate Resolution Imaging Spectroradiometer (MODIS) products and the Surface Radiation Budget Network (SURFRAD) in situ measurements. Simulation analysis shows that the BOA-LIN is the best one among four hybrid methods with accurate atmospheric profiles as input. Comparison of all the six methods shows that the TE-MYD21 performed the best, with a root mean square error (RMSE) and mean bias error (MBE) of 14.0 and −0.2 W/m2, respectively. The RMSE of BOA-LIN, TOA-NLIN, TOA-LIN, TOA-ANN, and TE-MYD11 are equal to 15.2, 16.1, 17.2, 21.2, and 18.5 W/m2, respectively. TE-MYD21 has a much better accuracy than the TE-MYD11 over barren surfaces (NDVI < 0.3) and a similar accuracy over non-barren surfaces (NDVI ≥ 0.3). BOA-LIN is more stable over varying water vapor conditions, compared to other hybrid methods. We conclude that this study provides a valuable reference for choosing the suitable estimation method in the SULR product generation.

scholarly journals Estimation of Long-Term Surface Downward Longwave Radiation over the Global Land from 2000 to 2018

2021 ◽  
Vol 13 (9) ◽  
pp. 1848
Author(s):  
Chunjie Feng ◽  
Xiaotong Zhang ◽  
Yu Wei ◽  
Weiyu Zhang ◽  
Ning Hou ◽  
...  
Keyword(s):  
Water Vapor ◽  
Spatial Resolution ◽  
Land Surface ◽  
Longwave Radiation ◽  
Surface Radiation ◽  
Radiation Budget ◽  
Mean Bias Error ◽  
Downward Longwave Radiation ◽  
Global Land

It is of great importance for climate change studies to construct a worldwide, long-term surface downward longwave radiation (Ld, 4–100 μm) dataset. Although a number of global Ld datasets are available, their low accuracies and coarse spatial resolutions limit their applications. This study generated a daily Ld dataset with a 5-km spatial resolution over the global land surface from 2000 to 2018 using atmospheric parameters, which include 2-m air temperature (Ta), relative humidity (RH) at 1000 hPa, total column water vapor (TCWV), surface downward shortwave radiation (Sd), and elevation, based on the gradient boosting regression tree (GBRT) method. The generated Ld dataset was evaluated using ground measurements collected from AmeriFlux, AsiaFlux, baseline surface radiation network (BSRN), surface radiation budget network (SURFRAD), and FLUXNET networks. The validation results showed that the root mean square error (RMSE), mean bias error (MBE), and correlation coefficient (R) values of the generated daily Ld dataset were 17.78 W m−2, 0.99 W m−2, and 0.96 (p < 0.01). Comparisons with other global land surface radiation products indicated that the generated Ld dataset performed better than the clouds and earth’s radiant energy system synoptic (CERES-SYN) edition 4.1 dataset and ERA5 reanalysis product at the selected sites. In addition, the analysis of the spatiotemporal characteristics for the generated Ld dataset showed an increasing trend of 1.8 W m−2 per decade (p < 0.01) from 2003 to 2018, which was closely related to Ta and water vapor pressure. In general, the generated Ld dataset has a higher spatial resolution and accuracy, which can contribute to perfect the existing radiation products.

scholarly journals IR Radiation from Trees to a Ski Run: A Case Study

2013 ◽  
Vol 52 (7) ◽  
pp. 1525-1539 ◽  
Author(s):  
Rosie Howard ◽  
Roland Stull
Keyword(s):  
Meteorological Data ◽  
Longwave Radiation ◽  
Surface Radiation ◽  
Radiation Budget ◽  
Ir Radiation ◽  
Clear Sky ◽  
Brightness Temperatures ◽  
Point Of Interest ◽  
Surface Radiation Budget ◽  
Downwelling Longwave Radiation

AbstractAccurately calculating the surface radiation budget of a groomed ski run is crucial when determining snow surface temperature and other snow-related variables, knowledge of which is important for ski racing. Downwelling longwave radiation can compose a large part of the surface radiation budget in mountainous terrain. At a location on a ski run, a portion of the downwelling longwave radiation comes from the sky and a portion comes from tall evergreen trees. Infrared photographs taken during daytime at a ski run on Whistler Mountain, British Columbia, Canada, for a clear-sky day in February 2012 show that trees can enhance the downwelling longwave radiation at the center of the ski run considerably, with a maximum estimated enhancement of 75.6 ± 16.8 W m−2 for trees in direct sunlight. The average needle and trunk brightness temperatures from the IR photographs were correlated with measured meteorological data. Regressions were found to allow estimation of longwave radiation from trees using nearby routine meteorological data. Absolute errors in tree longwave radiation estimations using the derived trunk and needle temperatures did not exceed 4 W m−2. The effect of the intervening air upon longwave radiative transfer between trees and the point of interest on the ski run was found to be small for these very short pathlengths of 50 m or less. These results can be used to improve calculations of the surface radiation budget of a groomed ski run under clear skies.

Estimation of Daily Mean Photosynthetically Active Radiation under All-Sky Conditions Based on Relative Sunshine Data

2012 ◽  
Vol 51 (1) ◽  
pp. 150-160 ◽  
Author(s):  
Jun Qin ◽  
Kun Yang ◽  
Shunlin Liang ◽  
Wenjun Tang
Keyword(s):  
Photosynthetically Active Radiation ◽  
Sunshine Duration ◽  
Surface Radiation ◽  
Radiation Budget ◽  
Mean Bias Error ◽  
Bias Error ◽  
Active Radiation ◽  
Clear Sky ◽  
Surface Radiation Budget ◽  
Sky Conditions

AbstractPhotosynthetically active radiation (PAR) is absorbed by plants to carry out photosynthesis. Its estimation is important for many applications such as ecological modeling. In this study, a broadband transmittance scheme for solar radiation at the PAR band is developed to estimate clear-sky PAR values. The influence of clouds is subsequently taken into account through sunshine-duration data. This scheme is examined without local calibration against the observed PAR values under both clear- and cloudy-sky conditions at seven widely distributed Surface Radiation Budget Network (SURFRAD) stations. The results indicate that the scheme can estimate the daily mean PAR at these seven stations under all-sky conditions with root-mean-square error and mean bias error values ranging from 6.03 to 6.83 W m−2 and from −2.86 to 1.03 W m−2, respectively. Further analyses indicate that the scheme can estimate PAR values well with globally available aerosol and ozone datasets. This suggests that the scheme can be applied to regions for which observed aerosol and ozone data are not available.

scholarly journals Modeling the Downwelling Longwave Radiation over a Groomed Ski Run under Clear Skies

2013 ◽  
Vol 52 (7) ◽  
pp. 1540-1553 ◽  
Author(s):  
Rosie Howard ◽  
Roland Stull
Keyword(s):  
Longwave Radiation ◽  
Liquid Water Content ◽  
Surface Radiation ◽  
Radiation Budget ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Clear Sky ◽  
Surface Radiation Budget ◽  
Flux Model ◽  
Downwelling Longwave Radiation

AbstractThe surface radiation budget of a groomed ski run is important to ski racing. Variables such as snow-surface temperature and liquid water content depend upon the surface radiation budget and are crucial to preparing fast skis. This case study focuses on downwelling longwave radiation, measurements of which were made at a point on a ski run on Whistler Mountain, British Columbia, Canada, throughout a 5-day clear-sky intensive observation period. Tall trees often dominate the horizon of a point on a ski run, and so contributions to total downwelling longwave radiation from trees and sky were treated separately. The “LWRAD” longwave radiative flux model estimated the total downwelling longwave radiation by first calculating thermal contributions from the trees, incorporating regressions for tree temperature that use routine meteorological measurements. Contributions from each azimuth direction were determined with horizon-elevation angles from a theodolite survey. Thermal emissions were weighted accordingly and summed. Sky contributions were estimated using the “libRadtran” radiative transfer model with input of local atmospheric profiles of temperature and humidity and were added to tree emissions. Two clear-sky emissivity parameterizations using screen-height measurements were tested for comparison. LWRAD total downwelling longwave radiation varies between 235 and 265 W m−2 and compares well to measurements, with correlation coefficient squared (r2) of 0.96. These results can be used to improve estimates of downwelling longwave radiation for a groomed ski run.

Validation of Clear-Sky Global LAnd Surface Satellite (GLASS) Longwave Radiation Product

2020 ◽  
Author(s):  
Qi Zeng ◽  
Jie Cheng ◽  
Feng Yang
Keyword(s):  
Land Surface ◽  
Water Cycle ◽  
Radiant Energy ◽  
Remote Sensing Data ◽  
Longwave Radiation ◽  
Energy System ◽  
Surface Radiation ◽  
Radiation Budget ◽  
Clear Sky ◽  
Global Land

&lt;p&gt;Surface longwave (LW) radiation plays an important rolein global climatic change, which is consist of surface longwave upward radiation (LWUP), surface longwave downward radiation (LWDN) and surface longwave net radiation (LWNR). Numerous studies have been carried out to estimate LWUP or LWDN from remote sensing data, and several satellite LW radiation products have been released, such as the International Satellite Cloud Climatology Project&amp;#8208;Flux Data (ISCCP&amp;#8208;FD), the Global Energy and Water cycle Experiment&amp;#8208;Surface Radiation Budget (GEWEX&amp;#8208;SRB) and the Clouds and the Earth&amp;#8217;s Radiant Energy System&amp;#8208;Gridded Radiative Fluxes and Clouds (CERES&amp;#8208;FSW). But these products share the common features of coarse spatial resolutions (100-280 km) and lower validation accuracy.&lt;/p&gt;&lt;p&gt;Under such circumstance, we developed the methods of estimating long-term high spatial resolution all sky&amp;#160; instantaneous LW radiation, and produced the corresponding products from MODIS data from 2000 through 2018 (Terra and Aqua), named as Global LAnd Surface Satellite (GLASS) Longwave Radiation product, which can be free freely downloaded from the website (http://glass.umd.edu/Download.html).&lt;/p&gt;&lt;p&gt;In this article, ground measurements collected from 141 sites in six independent networks (AmerciFlux, AsiaFlux, BSRN, CEOP, HiWATER-MUSOEXE and TIPEX-III) are used to evaluate the clear-sky GLASS LW radiation products at global scale. The bias and RMSE is -4.33 W/m&lt;sup&gt;2 &lt;/sup&gt;and 18.15 W/m&lt;sup&gt;2 &lt;/sup&gt;for LWUP, -3.77 W/m&lt;sup&gt;2 &lt;/sup&gt;and 26.94 W/m&lt;sup&gt;2&lt;/sup&gt; for LWDN, and 0.70 W/m&lt;sup&gt;2 &lt;/sup&gt;and 26.70 W/m&lt;sup&gt;2&lt;/sup&gt; for LWNR, respectively. Compared with validation results of the above mentioned three LW radiation products, the overall accuracy of GLASS LW radiation product is much better. We will continue to improve the retrieval algorithms and update the products accordingly.&lt;/p&gt;

scholarly journals Evaluation of the Surface Radiation Budget in the Atmospheric Component of the Hadley Centre Global Environmental Model (HadGEM1)

2008 ◽  
Vol 21 (18) ◽  
pp. 4723-4748 ◽  
Author(s):  
A. Bodas-Salcedo ◽  
M. A. Ringer ◽  
A. Jones
Keyword(s):  
Land Surface ◽  
Surface Albedo ◽  
Longwave Radiation ◽  
Surface Radiation ◽  
Radiation Budget ◽  
Surface Radiation Budget ◽  
Global Environmental ◽  
Downward Longwave Radiation ◽  
Global Dimming ◽  
Hadley Centre

Abstract The partitioning of the earth radiation budget (ERB) between its atmosphere and surface components is of crucial interest in climate studies as it has a significant role in the oceanic and atmospheric general circulation. An analysis of the present-day climate simulation of the surface radiation budget in the atmospheric component of the new Hadley Centre Global Environmental Model version 1 (HadGEM1) is presented, and the simulations are assessed by comparing the results with fluxes derived from satellite data from the International Satellite Cloud Climatology Project (ISCCP) and ground measurements from the Baseline Surface Radiation Network (BSRN). Comparisons against radiative fluxes from satellite and ground observations show that the model tends to overestimate the surface incoming solar radiation (Ss,d). The model simulates Ss,d very well over the polar regions. Consistency in the comparisons against BSRN and ISCCP-FD suggests that the ISCCP-FD database is a good test for the performance of the surface downwelling solar radiation in climate model simulations. Overall, the simulation of downward longwave radiation is closer to observations than its shortwave counterpart. The model underestimates the downward longwave radiation with respect to BSRN measurements by 6.0 W m−2. Comparisons of land surface albedo from the model and estimates from the Moderate Resolution Imaging Spectroradiometer (MODIS) show that HadGEM1 overestimates the land surface albedo over deserts and over midlatitude landmasses in the Northern Hemisphere in January. Analysis of the seasonal cycle of the land surface albedo in different regions shows that the amplitude and phase of the seasonal cycle are not well represented in the model, although a more extensive validation needs to be carried out. Two decades of coupled model simulations of the twentieth-century climate are used to look into the model’s simulation of global dimming/brightening. The model results are in line with the conclusions of the studies that suggest that global dimming is far from being a uniform phenomenon across the globe.

scholarly journals Uncertainties of parameterized near-surface downward longwave and clear-sky direct radiation

2012 ◽  
Vol 12 (1) ◽  
pp. 3357-3407 ◽  
Author(s):  
S. Gubler ◽  
S. Gruber ◽  
R. S. Purves
Keyword(s):  
Mean Squared Error ◽  
Longwave Radiation ◽  
Surface Radiation ◽  
Radiation Budget ◽  
Shortwave Radiation ◽  
Total Output ◽  
Parameter Uncertainties ◽  
Near Surface ◽  
Clear Sky ◽  
Environmental Models

Abstract. As many environmental models rely on simulating the energy balance at the Earth's surface based on parameterized radiative fluxes, knowledge of the inherent uncertainties is important. In this study we evaluate one parameterization of clear-sky incoming shortwave radiation (SDR) and diverse parameterizations of clear-sky and all-sky incoming longwave radiation (LDR). In a first step, the clear-sky global SDR is estimated based measured input variables and mean parameter values for hourly time steps during the year 1996 to 2008, and validated using the high quality measurements of seven Alpine Surface Radiation Budget (ASRB) stations in Switzerland covering different elevations. Then, twelve clear-sky LDR parameterizations are fitted to the ASRB measurements. One of the best performing LDR parameterizations is chosen to estimate the all-sky LDR based on cloud transmissivity. Cloud transmissivity is estimated using measured and modeled global SDR during daytime. For the night, the performance of several interpolation methods is evaluated. Input variable and parameter uncertainties are assigned to estimate the total output uncertainty of the mentioned models, resulting in a mean relative uncertainty of 10% for the clear-sky direct, 15% for diffuse and 2.5% for global SDR, and 2.5% for the fitted all-sky LDR. Further, a function representing the uncertainty in dependence of the radiation is assigned for each model. Validation of the model outputs shows that direct SDR is underestimated (the mean error (ME) is around −33 W m−2), while diffuse radiation is overestimated (ME around 19 W m−2). The root mean squared error (RMSE) scatters around 60 W m−2 for direct, and 40 W m−2 for diffuse SDR. The best behaviour is found, due to the compensating effects of direct and diffuse SDR, for global SDR with MEs around −13 W m−2 and RMSEs around 40 W m−2. The ME of the fitted all-sky LDR is around ±10 W m−2, and the RMSE goes up to 40 W m−2. This is obtained by linearly interpolating the average of the cloud transmissivity of the four hours of the preceeding afternoon and the following morning.

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