scholarly journals Cloud Influence on ERA5 and AMPS Surface Downwelling Longwave Radiation Biases in West Antarctica

2019 ◽  
Vol 32 (22) ◽  
pp. 7935-7949 ◽  
Author(s):  
Israel Silber ◽  
Johannes Verlinde ◽  
Sheng-Hung Wang ◽  
David H. Bromwich ◽  
Ann M. Fridlind ◽  
...  
Keyword(s):  
Longwave Radiation ◽  
Surface Energy Budget ◽  
Polar Regions ◽  
Model Errors ◽  
Microphysics Scheme ◽  
Clear Sky ◽  
Radiation Component ◽  
West Antarctic ◽  
Downwelling Longwave Radiation ◽  
Sky Conditions

Abstract The surface downwelling longwave radiation component (LW↓) is crucial for the determination of the surface energy budget and has significant implications for the resilience of ice surfaces in the polar regions. Accurate model evaluation of this radiation component requires knowledge about the phase, vertical distribution, and associated temperature of water in the atmosphere, all of which control the LW↓ signal measured at the surface. In this study, we examine the LW↓ model errors found in the Antarctic Mesoscale Prediction System (AMPS) operational forecast model and the ERA5 model relative to observations from the ARM West Antarctic Radiation Experiment (AWARE) campaign at McMurdo Station and the West Antarctic Ice Sheet (WAIS) Divide. The errors are calculated separately for observed clear-sky conditions, ice-cloud occurrences, and liquid-bearing cloud-layer (LBCL) occurrences. The analysis results show a tendency in both models at each site to underestimate the LW↓ during clear-sky conditions, high error variability (standard deviations > 20 W m−2) during any type of cloud occurrence, and negative LW↓ biases when LBCLs are observed (bias magnitudes >15 W m−2 in tenuous LBCL cases and >43 W m−2 in optically thick/opaque LBCLs instances). We suggest that a generally dry and liquid-deficient atmosphere responsible for the identified LW↓ biases in both models is the result of excessive ice formation and growth, which could stem from the model initial and lateral boundary conditions, microphysics scheme, aerosol representation, and/or limited vertical resolution.

scholarly journals On the Contribution of Longwave Radiation to Global Climate Model Biases in Arctic Lower Tropospheric Stability

2014 ◽  
Vol 27 (19) ◽  
pp. 7250-7269 ◽  
Author(s):  
Neil P. Barton ◽  
Stephen A. Klein ◽  
James S. Boyle
Keyword(s):  
Surface Temperature ◽  
Global Climate ◽  
Longwave Radiation ◽  
Reanalysis Data ◽  
The Arctic ◽  
Transfer Model ◽  
Polar Night ◽  
Clear Sky ◽  
Lower Tropospheric Stability ◽  
Downwelling Longwave Radiation

Abstract Previous research has found that global climate models (GCMs) usually simulate greater lower tropospheric stabilities compared to reanalysis data. To understand the origins of this bias, the authors examine hindcast simulations initialized with reanalysis data of six GCMs and find that four of the six models simulate within five days a positive bias in Arctic lower tropospheric stability during the Arctic polar night over sea ice regions. These biases in lower tropospheric stability are mainly due to cold biases in surface temperature, as very small potential temperature biases exist aloft. Similar to previous research, polar night surface temperature biases in the hindcast runs relate to all-sky downwelling longwave radiation in the models, which very much relates to the cloud liquid water. Also found herein are clear-sky longwave radiation biases and a fairly large clear-sky longwave radiation bias in the day one hindcast. This clear-sky longwave bias is analyzed by running the same radiation transfer model for each model’s temperature and moisture profile, and the model spread in clear-sky downwelling longwave radiation with the same radiative transfer model is found to be much less, suggesting that model differences other than temperature and moisture are aiding in the spread in downwelling longwave radiation. The six models were also analyzed in Atmospheric Model Intercomparison Project (AMIP) mode to determine if hindcast simulations are analogous to free-running simulations. Similar winter lower tropospheric stability biases occur in four of the six models with surface temperature biases relating to the winter lower tropospheric stability values.

scholarly journals Cloud effects on the surface energy and mass balance of Brewster Glacier, New Zealand

2015 ◽  
Vol 9 (1) ◽  
pp. 975-1019 ◽  
Author(s):  
J. P. Conway ◽  
N. J. Cullen
Keyword(s):  
Surface Energy ◽  
Mass Balance ◽  
Air Temperature ◽  
Longwave Radiation ◽  
Heat Fluxes ◽  
Glacier Surface ◽  
Surface Mass ◽  
Clear Sky ◽  
Climate Interactions ◽  
Sky Conditions

Abstract. A thorough understanding of the influence of clouds on glacier surface energy balance (SEB) and surface mass balance (SMB) is critical for forward and backward modelling of glacier–climate interactions. A validated 22 month time series of SEB/SMB was constructed for the ablation zone of the Brewster Glacier, using high quality radiation data to carefully evaluate SEB terms and define clear-sky and overcast conditions. A fundamental change in glacier SEB in cloudy conditions was driven by increased effective sky emissivity and surface vapour pressure, rather than the minimal change in air temperature and wind speed. During overcast conditions, positive net longwave radiation and latent heat fluxes allowed melt to be maintained through a much greater length of time compared to clear-sky conditions, and led to similar melt in each sky condition. The sensitivity of SMB to changes in air temperature was greatly enhanced in overcast compared to clear-sky conditions due to more frequent melt and the occurrence of precipitation, which enabled a strong accumulation–albedo feedback. During the spring and autumn seasons, the sensitivity during overcast conditions was strongest. There is a need to include the effects of atmospheric moisture (vapour, cloud and precipitation) on melt processes when modelling glacier–climate interactions.

Estimation of All-weather Downward Longwave Radiation over the Tibetan Plateau

2021 ◽  
Author(s):  
Lirong Ding ◽  
Zhiyong Long ◽  
Ji Zhou ◽  
Shaofei Wang ◽  
Xiaodong Zhang
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
Energy Budget ◽  
Water Cycle ◽  
Longwave Radiation ◽  
Radiation Balance ◽  
The Tibetan Plateau ◽  
Clear Sky ◽  
Downward Longwave Radiation ◽  
Sky Conditions

<p>The downward longwave radiation (DLR) is a critical parameter for radiation balance, energy budget, and water cycle studies at regional and global scales. The accurate estimation of the all-weather DLR with a high temporal resolution is important for the estimation of the surface net radiation and evapotranspiration. However, the most DLR products involve instantaneous DLR estimates based on polar orbiting satellite data under clear-sky conditions. To obtain an in-depth understanding of the performances of different models in the estimation of the DLR over the Tibetan Plateau, which is a focus area of climate change study, this study tested eight methods under clear-sky conditions and six methods under cloudy conditions based on ground-measured data. The results show that the Dilley and O’Brien model and the Lhomme model are most suitable under clear-sky conditions and cloudy conditions, respectively. For the Dilley and O’Brien model, the average root mean square error (RMSE) of the DLR under clear-sky conditions is approximately 22.5 W/m<sup>2</sup> at nine ground sites; for the Lhomme model, the average RMSE is approximately 23.2 W/m<sup>2</sup>. Based on the estimated cloud fraction and meteorological data provided by the China land surface data assimilation system (CLDAS), the hourly all-weather daytime DLR with 0.0625° over the Tibetan Plateau was estimated. The results show that the average RMSE of the estimated hourly all-weather DLR was approximately 26.4 W/m<sup>2</sup>. With the combined all-weather DLR model, the hourly all-weather daytime DLR dataset with a 0.0625° resolution from 2008 to 2016 over the Tibetan Plateau was generated. This dataset can better contribute to studies associated with the radiation balance and energy budget, water cycle, and climate change over the Tibetan Plateau.</p>

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

2011 ◽  
Vol 26 (3) ◽  
pp. 443-450 ◽  
Author(s):  
Carlos Antonio Costa dos Santos ◽  
Bernardo Barbosa da Silva ◽  
Tantravahi Venkata Ramana Rao ◽  
Prakki Satyamurty ◽  
Antonio Ocimar Manzi
Keyword(s):  
Arid Regions ◽  
Longwave Radiation ◽  
Radiation Budget ◽  
Semiarid Region ◽  
Northeast Brazil ◽  
Hydrological Models ◽  
Experimental Site ◽  
Clear Sky ◽  
Downward Longwave Radiation ◽  
Sky Conditions

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

scholarly journals Characteristics of Downward and Upward Longwave Radiation at Athalassa, an Inland Location of the Island of Cyprus

2021 ◽  
Vol 11 (2) ◽  
pp. 719
Author(s):  
Stelios Pashiardis ◽  
Soteris A. Kalogirou
Keyword(s):  
Normal Distribution ◽  
Control Process ◽  
Ground Surface ◽  
Longwave Radiation ◽  
Surface Radiation ◽  
Normal Distribution Function ◽  
Clear Sky ◽  
Quality Control Process ◽  
Sky Conditions ◽  
Mean Square Errors

In this study, two years of hourly longwave downward and upward irradiance measurements at Athalassa, an inland location, are used to analyze and compare them. A detailed quality control process was followed according to the suggested tests proposed by the Baseline Surface Radiation Network (BSRN) group. The criteria involved are based on physically possible, extremely rare and climatological limits. Furthermore, comparison tests were also applied between the two longwave components as well as with air and ground surface temperatures. Additionally, time consistency and persistency tests were applied. All the suspect data were excluded from the analysis. The data showed that the frequency distribution of downward longwave irradiances follows a normal distribution function, while the upward longwave follows an almost normal distribution but with a long positive tail. The annual mean daily downward longwave irradiation is 27.3 MJ m−2 and the annual mean daily upward longwave irradiation is 37.8 MJ m−2. The net longwave irradiation is always negative ranging from −5.9 to −12.1 MJ/m2. Various models were tested to estimate daylight and all day downward and upward longwave irradiances under clear-sky and all-sky conditions. For the comparison of measured and estimated values the root-mean-square errors and linear regression correlations have been used. The results of this comparison showed that Idso’s and Brunt’s models perform well, and they can be used to estimate downward longwave irradiance under clear-sky conditions. Furthermore, both models were extended to estimate the daylight downward longwave irradiance under all-sky conditions by taking into account the ratio of global to the clear-sky global solar irradiance. In this case, the RMSE of the local calibrated coefficients scheme of Idso’s model was 30.6 W m−2, while Brunt’s model showed slightly lower value (29.0 W m−2).

scholarly journals On the use of incoming longwave radiation parameterizations in a glacier environment

2008 ◽  
Vol 2 (4) ◽  
pp. 487-511 ◽  
Author(s):  
J. Sedlar ◽  
R. Hock
Keyword(s):  
Meteorological Data ◽  
Global Radiation ◽  
Correlation Coefficients ◽  
Longwave Radiation ◽  
Near Surface ◽  
Clear Sky ◽  
Radiation Parameterizations ◽  
Cloud Parameterization ◽  
Sky Conditions ◽  
Parameter Values

Abstract. Energy balance based glacier melt models require accurate estimates of incoming longwave radiation since it is generally the largest source of energy input. Multi-year near-surface meteorological data from Storglaciären, northern Sweden, were used to evaluate commonly used longwave radiation parameterizations in a glacier environment under clear-sky, overcast-sky and all-sky conditions. The tested parameterization depending solely on air temperature performed worse than those including also air humidity. Adopting parameter values from the literature instead of fitting them to the data resulted in similar correlation coefficients between modeled and measured radiation, but generated larger biases, emphasizing the need to derive site-specific coefficients. Nearly all models including those fitted to the data tended to overestimate longwave radiation during periods of low longwave radiation, and vice versa when radiation input was high. An attempt was made to parameterize cloud cover using top of atmosphere and measured global radiation. Both hourly and daily calculations of incoming longwave radiation using the cloud parameterization provided similar, or even stronger, correlations to the measurements compared to using observed cloud fraction as input. Using the global radiation cloud parameterization is promising for use in high-latitude regions where global radiation measurements exist but cloud observations do not.

scholarly journals A revisit of parametrization of summer downward longwave radiation over the Tibetan Plateau from high temporal resolution measurements

2019 ◽  
Author(s):  
Mengqi Liu ◽  
Xiangdong Zheng ◽  
Jinqiang Zhang ◽  
Xiangao Xia
Keyword(s):  
Tibetan Plateau ◽  
Temporal Resolution ◽  
Longwave Radiation ◽  
Surface Energy Budget ◽  
Coefficient Of Determination ◽  
Cloud Base ◽  
High Temporal Resolution ◽  
The Tibetan Plateau ◽  
Clear Sky ◽  
Downward Longwave Radiation

Abstract. The Tibetan Plateau (TP) is one of hot spots in the climate research due to its unique geographical location, high altitude, highly sensitive to climate change as well potential effects on climate in East Asia. Downward longwave radiation (DLR), as a key component in the surface energy budget, is of practical implications for many research fields. Several attempts have been made to measure hourly or daily DLR and then model it over the TP. This study uses 1-minute radiation and meteorological measurements at three stations over the TP to parameterize DLR during summer months. Three independent methods are used to discriminate clear-sky observations by making maximal use of collocated measurements of downward shortwave and longwave radiation as well as Lidar backscatter measurements with high temporal resolution. This guarantees a reliable separation of clear-sky and cloudy samples that favors for proper parameterizations of DLR under these two contrast conditions. Clear-sky and cloudy DLR models with original parameters are firstly assessed. These models are then locally calibrated based on 1-minute observations. DLR estimation is notably improved since specific conditions over the TP are accounted for by local calibration, which is indicated by smaller root mean square error (RMSE) and larger coefficient of determination (R2). The best local parametrization can estimate clear-sky DLR with RMSE of 3.8 W⸱m-2. Overestimation of clear-sky DLR by previous study is evident, likely due to potential residue cloud contamination on the clear-sky samples. Cloud base height under overcast conditions is shown to be intimately related to cloudy DLR parameterization, which is considered by this study in the locally calibrated parameterization over the TP for the first time.

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