Reflection Of Shortwave Radiation Research Articles

Aerosol-cloud-precipitation interaction during some convective events over southwestern Iran using the WRF model

Four convective precipitation events in southwestern Iran are examined in this study using the aerosol-aware bulk microphysical scheme implemented in the Weather Research and Forecasting (WRF) model. Two simulations were conducted for each of the events, which included the control and polluted simulations. In the control simulation, the concentration of aerosols in the current climate is considered, while the concentration of aerosols was increased by a factor of 5 at all grid points in the polluted simulation. The aim of this research is to evaluate the effects of aerosols on cloud microphysics and precipitation. During the convective events, southerly to southwesterly warm and dry winds dominated, causing a substantial transport of aerosols and humidity. Relatively high values of planetary boundary-layer height (PBLH) are simulated in the polluted simulations, which indicate a higher convective activity and more efficient transport of aerosols and moisture in the vertical. Also, the convective available potential energy (CAPE) increases in polluted simulations, implying that an increase in the concentration of aerosols is associated with more favorable thermodynamic conditions for convection. In all simulations, the reflection of shortwave radiation by clouds increases, indicating that the first indirect effect of aerosols plays a key role in the energy budget of the Earth. On the other hand, an increase in the concentration of aerosols only slightly influences longwave radiation. Altitudes of the lifting condensation level (LCL) and the level of free convection (LFC) increase in all polluted compared to control simulations. This indicates that the air parcel needs to rise to a higher altitude to get saturated. The impact of an increase in the concentration of aerosols on cloud development is substantial in a simulation that contains a higher convergence of vertical moisture flux and stronger winds over the region. The convergence of the vertical moisture flux in the three simulations indicates that more water vapor is available in these simulations to be condensed on aerosols, which increases the cloud water content. Thus, the number density of cloud droplets is higher in the polluted compared to control simulations. The altitude of the maximum mass density of cloud droplets is nearly the same in the simulation (between 3 and 6 km). Due to higher specific humidity in these altitudes, higher water vapor can be condensed on condensation nuclei. An increase in ice and snow, which indicates a higher lifting of droplets to the freezing level, is seen in the simulations with the negative convergence of vertical moisture flux. This indicates that these regions may help the large-scale collection of moisture and its lifting. In simulations with a divergence of moisture in the northern and the whole domain, the cloud water content decreases. In simulations with a higher moisture difference, there is higher precipitation in the polluted compared to control simulations because, in the humid atmosphere, there is enough water vapor to be condensed on aerosols, which leads to the formation of larger cloud droplets. Thus, the collision of cloud droplets is more efficient, and precipitation increases. In addition, due to a lower cloud base, there is less chance for the evaporation and melting of precipitation.

Estimates of broadband upwelling irradiance from GOES-16 ABI

Satellite-derived estimates of the Earth’s radiation budget are crucial for understanding and predicting the weather and climate. However, existing satellite products measuring broadband outgoing longwave radiation (OLR) and reflected shortwave radiation (RSR) have spatio-temporal resolutions that are too coarse to evaluate important radiative forcers like aircraft condensation trails. We present a neural network which estimates OLR and RSR based on narrowband radiances, using collocated Cloud and Earth’s Radiant Energy System (CERES) and GOES-16 Advanced Baseline Imager (ABI) data. The resulting estimates feature strong agreement with the CERES data products (R2 = 0.977 for OLR and 0.974 for RSR on CERES Level 2 footprints), and we provide open access to the collocated satellite data and model outputs on all available GOES-16 ABI data for the 4 years from 2018–2021.

Subdiurnal to Interannual Frequency Analysis of Observed and Modeled Reflected Shortwave Radiation From Earth

AbstractEstimates of global top‐of‐atmosphere radiation on monthly, seasonal, annual, and longer time‐scales require estimates of the diurnal variability in both insolation and surface and atmospheric reflection. We compare Earth Polychromatic Imaging Camera (EPIC) and National Institute of Standards and Technology Advanced Radiometer (NISTAR) observations from the Deep Space Climate Observatory (DSCOVR) satellite with Clouds and Earth’s Radiant Energy System (CERES) hourly synoptic fluxes, which are diurnally filled through geostationary observations, and find that their power spectral density functions substantially agree, showing strong relative power at subdiurnal, diurnal, seasonal, and annual time‐scales, and power growing from diurnal to seasonal time‐scales. Frequency analysis of fluxes from several coupled model intercomparison project 5 model (CMIP5) and CMIP6 models shows that they distribute too much power over periods greater than 1 day but less than one year, indicating that a closer look is needed into how models achieve longer‐term stability in reflected shortwave radiation. Model developers can consider using these datasets for time‐varying energetic constraints, since tuning parameter choices will impact modeled planetary shortwave radiation across timescales ranging from subdiurnal to decadal.

Low clouds link equilibrium climate sensitivity to hydrological sensitivity

Equilibrium climate sensitivity (ECS) and hydrological sensitivity describe the global mean surface temperature and precipitation responses to a doubling of atmospheric CO2. Despite their connection via the Earth’s energy budget, the physical linkage between these two metrics remains controversial. Here, using a global climate model with a perturbed mean hydrological cycle, we show that ECS and hydrological sensitivity per unit warming are anti-correlated owing to the low-cloud response to surface warming. When the amount of low clouds decreases, ECS is enhanced through reductions in the reflection of shortwave radiation. In contrast, hydrological sensitivity is suppressed through weakening of atmospheric longwave cooling, necessitating weakened condensational heating by precipitation. These compensating cloud effects are also robustly found in a multi-model ensemble, and further constrained using satellite observations. Our estimates, combined with an existing constraint to clear-sky shortwave absorption, suggest that hydrological sensitivity could be lower by 30% than raw estimates from global climate models. The connections between global mean temperature and precipitation responses to CO2 doubling (equilibrium climate and hydrological sensitivity) are driven through low-cloud responses to surface warming, according to MIROC5 perturbation experiments.

Retrieval of Reflected Shortwave Radiation at the Top of the Atmosphere Using Himawari-8/AHI Data

This study developed a retrieval algorithm for reflected shortwave radiation at the top of the atmosphere (RSR). This algorithm is based on Himawari-8/AHI (Advanced Himawari Imager) whose sensor characteristics and observation area are similar to the next-generation Geostationary Korea Multi-Purpose Satellite/Advanced Meteorological Imager (GK-2A/AMI). This algorithm converts the radiance into reflectance for six shortwave channels and retrieves the RSR with a regression coefficient look-up-table according to geometry of the solar-viewing (solar zenith angle, viewing zenith angle, and relative azimuth angle) and atmospheric conditions (surface type and absence/presence of clouds), and removed sun glint with high uncertainty. The regression coefficients were calculated using numerical experiments from the radiative transfer model (SBDART), and ridge regression for broadband albedo at the top of the atmosphere (TOA albedo) and narrowband reflectance considering anisotropy. The retrieved RSR were validated using Terra, Aqua, and S-NPP/CERES data on the 15th day of every month from July 2015 to February 2017. The coefficient of determination (R2) between AHI and CERES for scene analysis was higher than 0.867 and the Bias and root mean square error (RMSE) were −21.34–5.52 and 51.74–59.28 Wm−2. The R2, Bias, and RMSE for the all cases were 0.903, −2.34, and 52.12 Wm−2, respectively.

Can Top-of-Atmosphere Radiation Measurements Constrain Climate Predictions? Part II: Climate Sensitivity

A large number of perturbed-physics simulations of version 3 of the Hadley Centre Atmosphere Model (HadAM3) were compared with the Clouds and the Earth's Radiant Energy System (CERES) estimates of outgoing longwave radiation (OLR) and reflected shortwave radiation (RSR) as well as OLR and RSR from the earlier Earth Radiation Budget Experiment (ERBE) estimates. The model configurations were produced from several independent optimization experiments in which four parameters were adjusted. Model–observation uncertainty was estimated by combining uncertainty arising from satellite measurements, observational radiation imbalance, total solar irradiance, radiative forcing, natural aerosol, internal climate variability, and sea surface temperature and that arising from parameters that were not varied. Using an emulator built from 14 001 “slab” model evaluations carried out using the climateprediction.net ensemble, the climate sensitivity for each configuration was estimated. Combining different prior probabilities for model configurations with the likelihood for each configuration and taking account of uncertainty in the emulated climate sensitivity gives, for the HadAM3 model, a 2.5%–97.5% range for climate sensitivity of 2.7–4.2 K if the CERES observations are correct. If the ERBE observations are correct, then they suggest a larger range, for HadAM3, of 2.8–5.6 K. Amplifying the CERES observational covariance estimate by a factor of 20 brings CERES and ERBE estimates into agreement. In this case the climate sensitivity range is 2.7–5.4 K. The results rule out, at the 2.5% level for HadAM3 and several different prior assumptions, climate sensitivities greater than 5.6 K.

Can Top-of-Atmosphere Radiation Measurements Constrain Climate Predictions? Part I: Tuning

Perturbed physics configurations of version 3 of the Hadley Centre Atmosphere Model (HadAM3) driven with observed sea surface temperatures (SST) and sea ice were tuned to outgoing radiation observations using a Gauss–Newton line search optimization algorithm to adjust the model parameters. Four key parameters that previous research found affected climate sensitivity were adjusted to several different target values including two sets of observations. The observations used were the global average reflected shortwave radiation (RSR) and outgoing longwave radiation (OLR) from the Clouds and the Earth's Radiant Energy System instruments combined with observations of ocean heat content. Using the same method, configurations were also generated that were consistent with the earlier Earth Radiation Budget Experiment results. Many, though not all, tuning experiments were successful, with about 2500 configurations being generated and the changes in simulated outgoing radiation largely due to changes in clouds. Clear-sky radiation changes were small, largely due to a cancellation between changes in upper-tropospheric relative humidity and temperature. Changes in other climate variables are strongly related to changes in OLR and RSR particularly on large scales. There appears to be some equifinality with different parameter configurations producing OLR and RSR values close to observed values. These models have small differences in their climatology with the one group being similar to the standard configuration and the other group drier in the tropics and warmer everywhere.

A comparison of TWP‐ICE observational data with cloud‐resolving model results

Observations made during the TWP‐ICE campaign are used to drive and evaluate thirteen cloud‐resolving model simulations with periodic lateral boundary conditions. The simulations employ 2D and 3D dynamics, one‐ and two‐moment microphysics, several variations on large‐scale forcing, and the use of observationally derived aerosol properties to prognose droplet numbers. When domain means are averaged over a 6‐day active monsoon period, all simulations reproduce observed surface precipitation rate but not its structural distribution. Simulated fractional areas covered by convective and stratiform rain are uncorrelated with one another, and are both variably overpredicted by up to a factor of ∼2. Stratiform area fractions are strongly anticorrelated with outgoing longwave radiation (OLR) but are negligibly correlated with ice water path (IWP), indicating that ice spatial distribution controls OLR more than mean IWP. Overpredictions of OLR tend to be accompanied by underpredictions of reflected shortwave radiation (RSR). When there are two simulations differing only in microphysics scheme or large‐scale forcing, the one with smaller stratiform area tends to exhibit greater OLR and lesser RSR by similar amounts. After ∼10 days, simulations reach a suppressed monsoon period with a wide range of mean precipitable water vapor, attributable in part to varying overprediction of cloud‐modulated radiative flux divergence compared with observationally derived values. Differences across the simulation ensemble arise from multiple sources, including dynamics, microphysics, and radiation treatments. Close agreement of spatial and temporal averages with observations may not be expected, but the wide spreads of predicted stratiform fraction and anticorrelated OLR indicate a need for more rigorous observation‐based evaluation of the underlying micro‐ and macrophysical properties of convective and stratiform structures.

Combining satellite data and models to estimate cloud radiative effect at the surface and in the atmosphere

AbstractSatellite measurements and numerical forecast model reanalysis data are used to compute an updated estimate of the cloud radiative effect on the global multi‐annual mean radiative energy budget of the atmosphere and surface. The cloud radiative cooling effect through reflection of short wave radiation dominates over the long wave heating effect, resulting in a net cooling of the climate system of − 21 Wm−2. The short wave radiative effect of cloud is primarily manifest as a reduction in the solar radiation absorbed at the surface of − 53 Wm−2. Clouds impact long wave radiation by heating the moist tropical atmosphere (up to around 40 Wm−2 for global annual means) while enhancing the radiative cooling of the atmosphere over other regions, in particular higher latitudes and sub‐tropical marine stratocumulus regimes. While clouds act to cool the climate system during the daytime, the cloud greenhouse effect heats the climate system at night. The influence of cloud radiative effect on determining cloud feedbacks and changes in the water cycle are discussed. Copyright © 2011 Royal Meteorological Society

Evaluation of the Met Office global forecast model using Geostationary Earth Radiation Budget (GERB) data

AbstractSimulations of the top‐of‐atmosphere radiative‐energy budget from the Met Office global numerical weather‐prediction model are evaluated using new data from the Geostationary Earth Radiation Budget (GERB) instrument on board the Meteosat‐8 satellite. Systematic discrepancies between the model simulations and GERB measurements greater than 20 Wm−2in outgoing long‐wave radiation (OLR) and greater than 60 Wm−2in reflected short‐wave radiation (RSR) are identified over the period April–September 2006 using 12 UTC data. Convective cloud over equatorial Africa is spatially less organized and less reflective than in the GERB data. This bias depends strongly on convective‐cloud cover, which is highly sensitive to changes in the model convective parametrization. Underestimates in model OLR over the Gulf of Guinea coincide with unrealistic southerly cloud outflow from convective centres to the north. Large overestimates in model RSR over the subtropical ocean, greater than 50 Wm−2at 12 UTC, are explained by unrealistic radiative properties of low‐level cloud relating to overestimation of cloud liquid water compared with independent satellite measurements. The results of this analysis contribute to the development and improvement of parametrizations in the global forecast model. Copyright © 2007 Royal Meteorological Society

Solar Radiation Transfer Through a Subarctic Shrub Canopy

ABSTRACTMuch of the low Arctic is covered with shrubs that are partially buried by snow in winter and become exposed during melt. This study presents measurements and modeling of shortwave radiation reflection and extinction by a deciduous shrub canopy emerging from a melting snowcover in the mountains of the Yukon Territory, Canada. Shrubs shade most of the snow surface at low solar elevation angles, so only a fraction of the incoming radiation reaches the surface, but there is greater direct shortwave transmission to the surface in gaps between shrubs for higher solar elevations. A simple model is developed to incorporate the changing contributions of sun-lit gaps, shaded gaps, and shrubs to the landscape-averaged (areal) transmission and reflection of shortwave radiation. The areal transmissivity and albedo in this model are lower than in a two-stream approximation that neglects gap shading. A simple shadow parameterization is proposed for calculating shrub tundra snowmelt rates and surface energy balances in hydrological and land-surface models.

Surface fluxes over Goa during Indian monsoon

Variation of surface sensible heat flux over the west coast in the premises of National Center for Antarctic and Ocean Research (NCAOR), Vasco-da-Gama (15° 21' N, 73° 51' E), Goa during Offshore trough (phase-I) and Warm pool campaigns (phase-II) of ARMEX is studied. Sensible heat flux as measured by sonic anemometer at 5 m above surface is -50 to 150 Wm-2 during 13-28 July, 2002 (phase I) and -5 to 350 Wm-2 during 21-24 April, 2003 (phase II). Coastal atmospheric surface layer at Goa during night time is found to be near neutral (nearly zero heat flux) in April 2003 whereas stable (negative heat flux) in July 2002. All components of solar radiation measured by Eppley radiometers at 2 m above surface are used to compute net radiation which is 900 Wm-2 at noon in April 2003. Net solar radiation is nearly equal to incoming short wave radiation during daytime as net long wave radiation (100 Wm-2) compensates the loss due to reflection of short wave radiation (-100 Wm-2) by the ground. High winds in the surface layer are observed during late night hours with calm winds around sunrise and after sunset giving rise to two minima in the diurnal curve. Influence of sea-breeze on the surface layer over land is discussed.

Nitrogen Deficiency Detection Using Reflected Shortwave Radiation from Irrigated Corn Canopies

AbstractTechniques that measure the N status of corn (Zea mays L.) can aid in management decisions that have economic and environmental implications. This study was conducted to identify reflected electromagnetic wavelengths most sensitive to detecting N deficiencies in a corn canopy with the possibility for use as a management tool. Reflected shortwave radiation was measured from an irrigated corn N response trial with four hybrids and five N rates at 0, 40, 80, 120, and 160 kg N ha−1 in 1992 and 0, 50, 100, 150, and 200 kg N ha−1 in 1993. A portable spectroradiometer was used to measure reflected radiation (400–1100 nm in 1992, 350–1050 nm in 1993) from corn canopies at approximately the R5 growth stage. Regression analyses revealed that refiected radiation near 550 and 710 nm was superior to refiected radiation near 450 or 650 nm for detecting N deficiencies. The ratio of light reflectance between 550 and 600 nm to light reflectance between 800 and 900 nm also provided sensitive detection of N stress. In 1993, an inexpensive photometricc ell, which has peak sensitivity to light centereda t 550 nm, was also used to measurer eflected radiation from a corn canopy. Photometric ceil readings correlated with relative grain yield (P < 0.001, r2 = 0.74), but more research will be required to develop procedures to account for varying daylight conditions. These results provide information needed for the development of variable‐rate fertilizer N application technology.

Midwinter needle temperature and winter injury of montane red spruce.

To assess the role of solar warming and associated temperature fluctuations in the winter injury of sun-exposed red spruce foliage, we used fine wire thermocouples to monitor midwinter needle temperature in the upper canopy of mature red spruce trees over two winters. In 1989-1990, 15-min mean temperatures were recorded for six needles in a single tree. In 1990-1991, 10-min mean temperatures of six needles in one tree, and 1-min mean temperatures of seven needles in a second tree were recorded during rapid temperature changes. Warming was more frequent and greatest on terminal shoots of branches with a south to southwest aspect. The maximum rise above ambient air temperature exceeded 20 degrees C, and the maximum one minute decrease in temperature was 9 degrees C, with maximum rates of 0.8 and 0.6 degrees C min(-1) sustained over 10- and 15-min intervals, respectively. These data demonstrate that red spruce is subject to rapid temperature fluctuations similar to those known to produce visible injury in American aborvitae, a much hardier species. We concluded that solar warming to temperatures above the freezing point was unlikely to result in dehardening and subsequent freezing injury, because warming was infrequent, of short duration, and did not always raise needle temperature above the freezing point. Parts of branches and some individual shoots were frequently covered by snow or rime that may have prevented injury by reducing the frequency or intensity of needle temperature fluctuations. Radiation load on exposed shoots may have been increased by reflection of short wave radiation from snow and rime deposits on surrounding surfaces, which would exacerbate temperature fluctuations.

The radiation balance of a tropical pasture, I. The reflection of short-wave radiation

Short-wave reflection (albedo) was measured for three agricultural surfaces at Katherine, N. T., Australia, between December 18, 1969 and March 28, 1970. The seasonal albedo value for the pasture legume Townsville stylo was 0.19, for a mixed stand of two annual grass species 0.22, and for bare soil 0.21. Albedo of dry soil varied between 0.20 and 0.22. Wetting could lower albedo to 0.14. Maximum albedos for Townsville stylo and grasses were 0.25 and 0.28. Minimum values (0.13 and 0.15, respectively) were found at plant establishment. Rapid increase in albedo was associated with periods of rapid growth (increasing crop cover and increasing leaf area index). Severe water stress occurred after February 20 and albedo for both vegetative surfaces consequently decreased through reduction in effective crop cover, maturing of inflorescences and gradual senescence. Diurnal variation in albedo for all surfaces can partly be attributed to the sensors used, but part of the increase is due to the nature of the surfaces themselves. The role of specular reflection and internal trapping is discussed.

Water Use by Irrigated Cotton in Sudan. I. Reflection of Short-Wave Radiation

Water Use by Irrigated Cotton in Sudan. I. Reflection of Short-Wave Radiation

The reflection of short‐wave radiation by vegetation

The reflection of short‐wave radiation by vegetation