scholarly journals Climatic features of the Mediterranean Sea detected by the analysis of the longwave radiative bulk formulae

2000 ◽  
Vol 18 (11) ◽  
pp. 1482-1487 ◽  
Author(s):  
M. E. Schiano ◽  
M. Borghini ◽  
S. Castellari ◽  
C. Luttazzi
Keyword(s):  
Mediterranean Sea ◽  
Longwave Radiation ◽  
Radiation Budget ◽  
Clear Sky ◽  
Radiative Processes ◽  
Direct Measurements ◽  
Climatic Regime ◽  
The Mediterranean ◽  
Sky Conditions ◽  
Climatic Features

Abstract. Some important climatic features of the Mediterranean Sea stand out from an analysis of the systematic discrepancies between direct measurements of longwave radiation budget and predictions obtained by the most widely used bulk formulae. In particular, under clear-sky conditions the results show that the surface values of both air temperature and humidity over the Mediterranean Sea are larger than those expected over an open ocean with the same amount of net longwave radiation. Furthermore, the twofold climatic regime of the Mediterranean region strongly affects the downwelling clear-sky radiation. This study suggests that a single bulk formula with constant numerical coefficients is unable to reproduce the fluxes at the surface for all the seasons.Key words: Meteorology and Atmospheric dynamics (radiative processes) – Oceanography: general (marginal and semienclosed seas; marine meteorology)

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.

Migratory directions of free-flying birds versus orientation in registration cages

1999 ◽  
Vol 202 (16) ◽  
pp. 2225-2231 ◽  
Author(s):  
F. Nievergelt ◽  
F. Liechti ◽  
B. Bruderer
Keyword(s):  
Species Composition ◽  
Mediterranean Sea ◽  
Clear Sky ◽  
Flight Direction ◽  
Northern Border ◽  
Migratory Season ◽  
Directional Preference ◽  
The Mediterranean ◽  
Sky Conditions ◽  
Tracking Radar

Good conditions for migration may promote offshore flights in nocturnal autumn migrants at the northern border of the Mediterranean Sea, whereas unfavourable conditions may induce flights along the coast. These predictions were tested by performing orientation cage experiments and making simultaneous observations of free-flying birds using a tracking radar. The flight directions of free-flying birds were mainly towards southwest and did not differ between overcast and clear sky conditions. The caged birds, however, tended towards southwest under clear sky and showed a more scattered distribution in the southwest and southeast quadrants under overcast conditions. Similar directional scatter occurred when the cage experiments were performed late at night. In contrast, free-flying birds shifted their flight direction towards west as night progressed to avoid flights across the sea. Flight directions observed by radar shifted slightly towards west as the season progressed owing to more frequent southeasterly winds. In orientation cages, however, directional preference was scattered towards southwest and southeast in the early migratory season and became unimodal (southwest) at the peak of the season; this change was not caused by different species composition. Consequently, there is a general coincidence of flight directions and directional preferences in orientation cages, but interpretations of results from orientation cages must allow for the possibility that experimental directions are different from migratory directions of free-flying birds, particularly under suboptimal migratory conditions.

Longwave radiation budget in the Mediterranean Sea

1995 ◽  
Vol 100 (C2) ◽  
pp. 2501 ◽  
Author(s):  
F. Bignami ◽  
S. Marullo ◽  
R. Santoleri ◽  
M. E. Schiano
Keyword(s):  
Mediterranean Sea ◽  
Longwave Radiation ◽  
Radiation Budget ◽  
The Mediterranean

Evaluation of net shortwave radiation over China with a regional climate model

2020 ◽  
Vol 80 (2) ◽  
pp. 147-163
Author(s):  
X Liu ◽  
Y Kang ◽  
Q Liu ◽  
Z Guo ◽  
Y Chen ◽  
...  
Keyword(s):  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Radiant Energy ◽  
Energy System ◽  
Radiation Budget ◽  
Shortwave Radiation ◽  
Monsoon Region ◽  
Clear Sky ◽  
Sky Conditions

The regional climate model RegCM version 4.6, developed by the European Centre for Medium-Range Weather Forecasts Reanalysis, was used to simulate the radiation budget over China. Clouds and the Earth’s Radiant Energy System (CERES) satellite data were utilized to evaluate the simulation results based on 4 radiative components: net shortwave (NSW) radiation at the surface of the earth and top of the atmosphere (TOA) under all-sky and clear-sky conditions. The performance of the model for low-value areas of NSW was superior to that for high-value areas. NSW at the surface and TOA under all-sky conditions was significantly underestimated; the spatial distribution of the bias was negative in the north and positive in the south, bounded by 25°N for the annual and seasonal averaged difference maps. Compared with the all-sky condition, the simulation effect under clear-sky conditions was significantly better, which indicates that the cloud fraction is the key factor affecting the accuracy of the simulation. In particular, the bias of the TOA NSW under the clear-sky condition was <±10 W m-2 in the eastern areas. The performance of the model was better over the eastern monsoon region in winter and autumn for surface NSW under clear-sky conditions, which may be related to different levels of air pollution during each season. Among the 3 areas, the regional average biases overall were largest (negative) over the Qinghai-Tibet alpine region and smallest over the eastern monsoon region.

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 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.

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 &gt; 20 W m−2) during any type of cloud occurrence, and negative LW↓ biases when LBCLs are observed (bias magnitudes &gt;15 W m−2 in tenuous LBCL cases and &gt;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.

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

&lt;p&gt;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&amp;#8217;Brien model and the Lhomme model are most suitable under clear-sky conditions and cloudy conditions, respectively. For the Dilley and O&amp;#8217;Brien model, the average root mean square error (RMSE) of the DLR under clear-sky conditions is approximately 22.5 W/m&lt;sup&gt;2&lt;/sup&gt; at nine ground sites; for the Lhomme model, the average RMSE is approximately 23.2 W/m&lt;sup&gt;2&lt;/sup&gt;. 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&amp;#176; 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&lt;sup&gt;2&lt;/sup&gt;. With the combined all-weather DLR model, the hourly all-weather daytime DLR dataset with a 0.0625&amp;#176; 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.&lt;/p&gt;

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;

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