The Impact of Surface Properties on Downward Surface Shortwave Radiation over the Tibetan Plateau

The complexity of inhomogeneous surface-atmosphere radiation transfer is one of the foremost problems in the field of atmospheric physics and atmospheric radiation. To date, the influence of surface properties on shortwave radiation has not been well studied. The daily downward surface shortwave radiation of the latest FLASHFlux/CERES （Fast Longwave And Shortwave Fluxes_Time Interpolated and Spatially Averaged/Clouds and the Earth＇s Radiant Energy System） satellite data was evaluated against in situ data. The comparison indicated that the differences between the two data sets are unstable and large over rugged terrain compared with relatively flat terrain, and the mean absolute error of the satellite products reaches 31.4 W m-2 （12.3%） over rugged terrain. Based on the SSF （single satellite footprint）/CERES product, the influence of surface properties on the distribution of downward surface shortwave radiation （DSSR） was analyzed. The influence of surface properties on DSSR over the Tibetan Plateau is about twice as large as that in two other regions located at the same latitude （eastern China-western Pacific and subtropical North Pacific）. A simulation was carried out with the help of the I3RC （International Intercomparision of Three-Dimensional Radiation Code） Monte Carlo 3D radiative transfer community model. The results showed that DSSR increases as surface albedo increases. Moreover, the impact of surface albedo on DSSR is larger if the spatial distribution of clouds is more non-uniform. It is hoped that these results will contribute to the development of 3D radiative transfer models and the improvement of satellite inversion algorithms.

Contributions of shortwave radiation to the formation of temperature inversions in the Bay of Bengal and eastern equatorial Indian Ocean:A modeling approach

Variations in incoming shortwave radiation influence the net surface heat flux,contributing to the formation of a temperature inversion.The effects of shortwave radiation on the temperature inversions in the Bay of Bengal and eastern equatorial Indian Ocean have never been investigated.Thus,a high-resolution(horizontal resolution of 0.07°×0.07° with 50 vertical layers) Regional Ocean Modeling System(ROMS) model is utilized to quantify the contributions of shortwave radiation to the temperature inversions in the study domain.Analyses of the mixed layer heat and salt budgets are performed,and different model simulations are compared.The model results suggest that a 30% change in shortwave radiation can change approximately 3% of the temperature inversion area in the Bay of Bengal.Low shortwave radiation reduces the net surface heat flux and cools the mixed layer substantially;it also reduces the evaporation rate,causing less evaporative water vapor losses from the ocean than the typical situation,and ultimately enhances haline stratification.Thus,the rudimentary outcome of this research is that a decrease in shortwave radiation produces more temperature inversion in the study region,which is primarily driven by the net surface cooling and supported by the intensive haline stratification.Moreover,low shortwave radiation eventually intensifies the temperature inversion layer by thickening the barrier layer.This study could be an important reference for predicting how the Indian Ocean climate will respond to future changes in shortwave radiation.

Accurate Shortwave Radiation Simulation with a Two-Layer Aerosol Model in Xinjiang Region

To harness the rich solar energy resources in Xinjiang Region of Northwest China,this study tries to address the issue of lack of downward surface shortwave radiation(DSSR)observations and the need to improve the accuracy of satellite retrieval and numerical simulation of DSSR under varied sky and meteorological conditions.(1)A two-layer aerosol model specific to Xinjiang was developed to capture the vertical distributions of aerosols based on multiple data sources including lidar,GPS sounding,ground meteorological observations,and profiles from the ECMWF reanalysis version 5(ERA5)data.The results show that the ERA5/PBLH(planetary boundary layer height)and ERA5/ALH(aerosol layer height)could be used to establish the two-layer aerosol model and characterize the vertical distribution of aerosols in Xinjiang Region.(2)Using the Santa Barbara Discrete Atmospheric Radiative Transfer(SBDART)model,a localized inverse model of clear-sky DSSR was established.After parameter adjustment and using the optimal combination of input parameters for DSSR simulation together with the two-layer aerosol model,the model-simulated DSSR(DSSRSBD)under clear-sky conditions improved significantly compared to the initial results,with all fitting indices greatly improved.(3)In addition,the study demonstrated that the impact of the two-layer aerosol model on DSSR was more pronounced under dust conditions than clear-sky conditions.(4)Using the localized clear-sky DSSR inversion model and its required parameters,simulations were also conducted to capture the spatiotemporal distribution of DSSR under clear-sky conditions in Xinjiang from 2017 to 2019.The annual average DSSR_(SBD)under clear-sky conditions in Xinjiang during 2017–2019 was 606.78 W m^(-2),while DSSR from CERES(DSSR_(CER))under the same conditions was generally higher(703.95 W m^(-2)).(5)It is found that satellite remote sensing products experienced data loss in high-altitude snow areas,where numerical simulation technology could serve as a valuable complement.

A review and comparison of surface incident shortwave radiation from multiple data sources: satellite retrievals, reanalysis data and GCM simulations

Surface incident shortwave radiation(Rs)can promote the circulation of substance and energy,and the accuracy of its estimation is of great significance for climate studies.The Rs can be acquired from satellite retrievals,reanalysis predictions and general circulation model(GCM)simulations.Although Rs estimates have been evaluated and compared in previous studies,most of them focus on evaluating the Rs estimates over specific regions using ground measurements from limited stations.Therefore,it is essential to comprehensively validate Rs estimates from multiple data sources.In this study,ground measurements of 690 stations from BSRN,GEBA,CMA,GC-NET and buoys were employed to validate the Rs estimates from seven representative products(GLASS,GEWEX-SRB,CERES-EBAF,ERA5,MERRA2,CFSR and CMIP6).The validation results indicated that the selected products overestimated Rs globally,with biases ranged from 0.48 to 21.27 W/m^(2).The satellite retrievals showed relatively better accuracy among seven datasets compared to ground measurements at the selected stations.Moreover,the selected seven products were all in poor accuracy at high-latitude regions with RMSEs greater than 50 W/m^(2).The long-term variation trends were also analyzed in this study.

Shortwave radiation balance modulates potential evapotranspiration over China

Shortwave radiation is an influential driver of global hydrological cycle,as its variation will alter evapotranspiration(ET).While climate change discussion extensively examined ET response to temperature,wind speed and land use/cover variations,little is known about the contribution of shortwave radiation balance on ET partly because of data availability.In this study,we applied the newly-released Global LAnd Surface Satellite(GLASS)products to detect changes in shortwave radiation and albedo for 2003–2018 over China,and quantified their contributions on potential evapotranspiration(PET)which is the upper limit of ET and generally the basis to estimate it.The results showed that downward shortwave radiation declined,together with a slight decrease in albedo,causing a decrease of net shortwave radiation.While climate change affected PET,the decreased net shortwave radiation reduced PET during the period.We identified a hotspot area in the north China plain that is one of the main agricultural production regions,as the radiation balance induced a contrasting effect on PET for the warm and the cold seasons.Our study indicates that it is important to consider shortwave radiation balance when estimating PET and ET to make reliable evaluation of climate change on hydrological cycle and ecosystem response.

Time-series variation and attribution analysis of downward shortwave radiation over the Yunnan-Kweichow plateau from 1984 to 2018

The downward shortwave radiation(DSR)is a key input parameter for land surface models and climate models.Based on the daily averaged Global Land Surface Satellite downward shortwave radiation(GLASS-DSR)dataset over the Yunnan-Kweichow Plateau(YKP)from 1984 to 2018,this paper analyzes variation trend and breakpoints of DSR.The results show that:annual averaged DSR decreases at a decreasing rate of-1.84 W·m^(-2)·decade^(-1) over the YKP from 1984 to 2018;the overall distribution of interannual averaged DSR shows higher in the mid-west,and gradually decreasing from west to northeast over the YKP;the estimated averaged DSR is larger in spring than in summer due to the influence of the monsoon;monthly averaged DSR reaches its maximum in May and its minimum in December;breakpoints are found in the seasonal and trend components of daily averaged DSR.Eleven driving factors are examined for their effects on DSR variation,including annual average temperature,precipitation,10 m wind speed,aerosol optical thickness(AOT),total cloud cover,elevation,slope,aspect,longitude,latitude,and climate zones.According to thefindings,AOT predominates in the spatio-temporal distribution of DSR over the YKP.This study will contribute to studies related to climate change and highland radiation.

Evaluation and intercomparison of multiple satellite-derived and reanalysis downward shortwave radiation products in China

Downward shortwave radiation(DSR)is a critical variable in energy balance driving Earth’s surface processes.Satellite-derived and reanalysis DSR products have been developed and continuously improved during the last decades.However,as those products have different temporal resolutions,their performances in different time scales have not been well-documented,particularly in China.This study intended to evaluate several DSR products across multiple time scales(i.e.instantaneous,1-hourly,daily,and monthly average)and ecosystems in China.Six DSR products,including GLASS,BESS,CLARA-A2,MCD18A1,ERA5 and MERRA-2,were evaluated against ground measurements at Chinese Ecosystem Research Network(CERN)and integrated land-atmosphere interaction observation(TPDC)sites from 2009 to 2012.The instantaneous DSR of MCD18 showed a root mean square error(RMSE)of 146.02 W/m^(2).The hourly RMSE of ERA5(155.52 W/m^(2))was largely smaller than MERRA-2(188.53 W/m^(2)).On the daily and monthly scale,BESS had the most optimized accuracy among the six products(RMSE of 36.82 W/m^(2)).For the satellite-derived DSR products,the monthly accuracy at CERN can meet the threshold accuracy requirement set by World Meteorological Organization(WMO)for Global Numerical Weather Prediction(20 W/m^(2)).

High-speed performance self-powered short wave ultraviolet radiation detectors based onκ(ε)-Ga_(2)O_(3)

High-speed solar-blind short wavelength ultraviolet radiation detectors based onκ(ε)-Ga_(2)O_(3)layers with Pt contacts were demonstrated and their properties were studied in detail.Theκ(ε)-Ga_(2)O_(3)layers were deposited by the halide vapor phase epitaxy on patterned GaN templates with sapphire substrates.The spectral dependencies of the photoelectric properties of struc-tures were analyzed in the wavelength interval 200-370 nm.The maximum photo to dark current ratio,responsivity,detectiv-ity and external quantum efficiency of structures were determined as:180.86 arb.un.,3.57 A/W,1.78×10^(12) Hz^(0.5)∙cm·W^(-1) and 2193.6%,respectively,at a wavelength of 200 nm and an applied voltage of 1 V.The enhancement of the photoresponse was caused by the decrease in the Schottky barrier at the Pt/κ(ε)-Ga_(2)O_(3)interface under ultraviolet exposure.The detectors demon-strated could functionalize in self-powered mode due to built-in electric field at the Pt/κ(ε)-Ga_(2)O_(3)interface.The responsivity and external quantum efficiency of the structures at a wavelength of 254 nm and zero applied voltage were 0.9 mA/W and 0.46%,respectively.The rise and decay times in self-powered mode did not exceed 100 ms.

Performance of surface radiation products of Greenland Ice Sheet using in-situ measurements

Radiation is the direct energy source of the surface natural environment and the main driving force of climate change.It has increasingly become an important meteorological factor affecting the surface heat exchange and glacier mass balance,especially in the glacier changes of the Greenland Ice Sheet(Gr IS).Due to the harsh climatic conditions of Gr IS and sparse observed data,it has become an important way to obtain radiation data from reanalysis datasets.However,the applicability of these radiation data on Gr IS is uncertain and worth exploring.In this work,we evaluate five reanalysis datasets(the fifth generation of European Centre for Medium-Range Weather Forecasts(ERA5),European Centre for Medium-Range Weather Forecasts Interim Reanalysis(ERA-Interim),Japanese 55-year Reanalysis(JRA55),National Centers for Environmental Prediction Reanalysis II(NCEP2)and Modern-Era Retrospective analysis for Research and Applications,Version 2(MERRA-2))during 1997-2022 using observations from 26 Program for Monitoring the Greenland Ice Sheet(PROMICE)automatic weather stations(AWSs)and 3 K-transect AWSs on Gr IS.The conclusions are as follows:ERA5 has the best performances in downward shortwave radiation(SWD)as well as downward and upward longwave radiation(LWD and LWU),but the performance is not the best in upward shortwave radiation(SWU).Based on the radiation budget analysis with ERA5 during 1979-2022,the fluctuation of longwave radiation is greater than that of shortwave radiation.The seasonal variation of shortwave radiation is obvious,while that of longwave radiation is small.The increasing trend of longwave radiation may result from global warming,in which ice sheets absorb more solar radiation and the surface heats up significantly,emitting more LWU.

A review of the estimation of downward surface shortwave radiation based on satellite data:Methods, progress and problems

The estimation of downward surface shortwave radiation(DSSR)is important for the Earth’s energy budget and climate change studies.This review was organised from the perspectives of satellite sensors,algorithms and future trends,retrospects and summaries of the satellite-based retrieval methods of DSSR that have been developed over the past 10 years.The shortwave radiation reaching the Earth’s surface is affected by both atmospheric and land surface parameters.In recent years,studies have given detailed considerations to the factors which affect DSSR.It is important to improve the retrieval accuracy of cloud microphysical parameters and aerosols and to reduce the uncertainties caused by complex topographies and high-albedo surfaces(such as snow-covered areas)on DSSR estimation.This review classified DSSR retrieval methods into four categories:empirical,parameterisation,look-up table and machine-learning methods,and evaluated their advantages,disadvantages and accuracy.Further efforts are needed to improve the calculation accuracy of atmospheric parameters such as cloud,haze,water vapor and other land surface parameters such as albedo of complex terrain and bright surface,organically combine machine learning and other methods,use the new-generation geostationary satellite and polar orbit satellite data to produce highresolution DSSR products,and promote the application of radiation products in hydrological and climate models.

Estimation of Net Surface Shortwave Radiation from Land Surface Temperature in Regional Scale

The method to estimate NSSR （net surface shortwave radiation） from LST （land surface temperature） in regional scale is discussed. First, an elliptical model between the time series of normalized LST and NSSR was developed using the daily evolution of LST and NSSR. Second, time series of LST and NSSR were simulated by common land model （CoLM） and were proved to be of high accuracy. On the basis of these, a non-linear least square ellipse fitting using the genetic algorithm method was used to fit the normalized LST and NSSR. Finally, LST was inverted using MODIS （moderate resolution imaging spectroradiometer） data with the split-window algorithm, and the regional NSSR was then estimated with LST and an elliptical model. The validation result shows that the derived average NSSR of 50×50 pixels of MODIS data was quite close to the observed data, and the distribution was reasonable, which indicates that the proposed method was capable of estimating NSSR on a regional scale.

THEORETICAL CALCULATION MODEL OF SHORTWAVE RADIATION FOR THE EARTH-ATMOSPHERE SYSTEM AND ITS TESTING RESULTS

On the basis of radiation transfer theory,adopting improved two-stream algorithm incorporated with addingalgorithm,we build up a theoretical calculation model of shortwave radiation for the earth-atmosphere system whichcan be applied with satellite data.The model can calculate direct solar radiation,scattering solar radiation,heating rateand other physical quantities of radiation field at every layer of the atmosphere and on the earth’s surface,if the under-ground reflectance or the planetary albedo obtained from satellite can be known.The model can be used in clear orcloudy atmosphere,and its calculating speed is fairly fast.We think that the model can be incorporated into large-scaleand mesoscale climatic models for the consideration of radiation calculation,and also it is useful for the utilization of so-lar energy.

Impacts of the Diurnal Cycle of Radiation on Tropical Cyclone Intensification and Structure

To investigate the impacts of the diurnal cycle on tropical cyclones （TCs）,a set of idealized simulations were conducted by specifying different radiation （i.e.,nighttime-only,daytime-only,full diurnal cycle）.It was found that,for an initially weak storm,it developed faster during nighttime than daytime.The impacts of radiation were not only on TC intensification,but also on TC structure and size.The nighttime storm tended to have a larger size than its daytime counterparts.During nighttime,the radiative cooling steepened the lapse rate and thus reduced the static stability in cloudy regions,enhancing convection.Diabatic heating associated with outer convection induced boundary layer inflows,which led to outward expansion of tangential winds and thus increased the storm size.

Impacts of the Diurnal Cycle of Solar Radiation on Spiral Rainbands

Based on idealized numerical simulations, the impacts of the diurnal cycle of solar radiation on the diurnal variation of outer rainbands in a tropical cyclone are examined. It is found that cold pools associated with precipitation-driven downdrafts are essential for the growth and propagation of spiral rainbands. The downdrafts result in surface outflows, which act as a lifting mechanism to trigger the convection cell along the leading edge of the cold pools. The diurnal cycle of solar radiation may modulate the diurnal behavior of the spiral rainbands. In the daytime, shortwave radiation will suppress the outer convection and thus weaken the cold pools. Meanwhile, the limited cold pool activity leads to a strong modification of the moisture field, which in turn inhibits further convection development.

SOME CHARACTERISTICS OF THE SURFACE RADIATION COMPONENTS AT ZHONGSHAN STATION

A preliminary analysis of some characteristics of the radiation components is made by using the surface radiation data obtained from February 1990 to January 1991 at Zhongshan Station. The result shows that the fluxes of direct radiation and global radiation are strong with higher atmospheric transparency, and the surface can absorb large amount of radiation energy in warm season. The surface loses heat energy in cold season due to the seasonal variations of the surface albedo and shortwave radiation. The variation of net longwave radiation is related to cloud amount and surface air temperature. The property of net radiation is similar to other Antarctic coastal stations but differs greatly from Antarctic inland area.

Improvement of Coding for Solar Radiation Forecasting in Dili Timor Leste—A WRF Case Study

This paper investigates the accuracy of weather research and forecasting by improving coding for solar radiation forecasting for location in Dili Timor Leste. Weather Research and Forecasting (WRF) model version 3.9.1 is used in this study for improvement purposes. The shortwave coding of WRF is used to improve in order to decrease error simulation. The importance of improving WRF coding at a specific region will reduce the bias and root mean square root when comparing to the observed data. This study uses high resolution based on the WRF modeling to stabilize the performance of forecasting. The decrease in error performance will be expected to enhance the value of renewable energy. The results show the root mean square error of the WRF default is 233 W/m2 higher compared to 205 W/m2 from the WRF improvement model. In addition, the Mean Bias Error (MBE) of the WRF default is obtained value 0.06 higher than 0.03 from the WRF improvement in rainy days. Meanwhile, on sunny days, the performance Root Mean Square Error (RMSE) of WRF default is 327 W/m2 higher than 223 W/m2 from the WRF improvement. The MBE of WRF improvement obtained 0.13 lower compared to 0.21 of WRF default coding. Finally, this study concludes that improving the shortwave code under the WRF model can decrease the error performance of the WRF simulation for local weather forecasting.

Separation of Atmospheric Circulation Patterns Governing Regional Variability of Arctic Sea Ice in Summer

In recent decades,Arctic summer sea ice extent(SIE)has shown a rapid decline overlaid with large interannual variations,both of which are influenced by geopotential height anomalies over Greenland(GL-high)and the central Arctic(CA-high).In this study,SIE along coastal Siberia(Sib-SIE)and Alaska(Ala-SIE)is found to account for about 65%and 21%of the Arctic SIE interannual variability,respectively.Variability in Ala-SIE is related to the GL-high,whereas variability in Sib-SIE is related to the CA-high.A decreased Ala-SIE is associated with decreased cloud cover and increased easterly winds along the Alaskan coast,promoting ice-albedo feedback.A decreased Sib-SIE is associated with a significant increase in water vapor and downward longwave radiation(DLR)along the Siberian coast.The years 2012 and 2020 with minimum recorded ASIE are used as examples.Compared to climatology,summer 2012 is characterized by a significantly enhanced GL-high with major sea ice loss along the Alaskan coast,while summer 2020 is characterized by an enhanced CA-high with sea ice loss focused along the Siberian coast.In 2012,the lack of cloud cover along the Alaskan coast contributed to an increase in incoming solar radiation,amplifying ice-albedo feedback there;while in 2020,the opposite occurs with an increase in cloud cover along the Alaskan coast,resulting in a slight increase in sea ice there.Along the Siberian coast,increased DLR in 2020 plays a dominant role in sea ice loss,and increased cloud cover and water vapor both contribute to the increased DLR.

Physical mechanism and numerical simulations of surface layer temperature inversion in tropical ocean

The one-dimensional Kraus- Turner mixed layer model improved by Liu is developed to consider the effect of salinity and the equa- tions of temperature and salinity under the mixed layer. On this basis, the processes of growth and death of surface layer temperature inversion is numerically simulated under different environmental parameters. At the same time, the physical mechanism is preliminari- ly discussed combining the observations at the station of TOGA- COARE 0°N, 156°E. The results indicate that temperature inversion sensitively depends on the mixed layer depth, sea surface wind speed and solar shortwave radiation, etc., and appropriately meteoro- logical and hydrological conditions often lead to the similarly periodical occurrence of this inversion phenomenon.

Radiative forcing over China due to albedo change caused by land cover change during 1990-2010

Land cover change affects surface radiation budget and energy balance by chang- ing surface albedo and further impacts the regional and global climate. In this article, high spatial and temporal resolution satellite products were used to analyze the driving mechanism for surface albedo change caused by land cover change during 1990-2010. In addition, the annual-scale radiative forcing caused by surface albedo changes in China＇s 50 ecological regions were calculated to reveal the biophysical mechanisms of land cover change affecting climate change at regional scale. Our results showed that the national land cover changes were mainly caused by land reclamation, grassland desertification and urbanization in past 20 years, which were almost induced by anthropogenic activities. Grassland and forest area decreased by 0.60% and 0.11%, respectively. The area of urban and farmland increased by 0.60% and 0.19%, respectively. The mean radiative forcing caused by land cover changes during 1990-2010 was 0.062 W/m2 in China, indicating a warming climate effect. However, spatial heterogeneity of radiative forcing was huge among different ecological regions. Farmland conversing to urban construction land, the main type of land cover change for the urban and suburban agricultural ecological region in Beijing-Tianjin-Tangshan region, caused an albedo reduction by 0.00456 and a maximum positive radiative forcing of 0.863 WIm2, which was presented as warming climate effects. Grassland and forest conversing to farmland, the main type of land cover change for the temperate humid agricultural and wetland ecological region in Sanjiang Plain, caused an albedo increase by 0.00152 and a maximum negative radiative forcing of 0.184 W/m2, implying cooling climate effects.

RETRIEVAL OF QINGHAI-XIZANG SASWR WITH ERBE AND ISCCP DATA

In the context of 1985—1988 ERBE and 1984—1988 ISCCP planetary scale albedoes and total cloudiness in combination with Qinghai-Xizang actinometric measurements,investigation was performed of the climatic retrieval of surface absorbed shortwave radiation(SASWR)in the research highland.Evidence suggests that the method has given higher fitting accuracy with mean error of 9.8 W m^(-2),whereupon was calculated the monthly mean SASWR flux density at the gridpoints of 2.5°×2.5°resolution over 25—40°N,75—95°E and 63 stations alongside a set of the distribution maps prepared for its basic features.