scholarly journals Comparison of Four Cloud Schemes in Simulating the Seasonal Mean Field Forced by the Observed Sea Surface Temperature

2008 ◽  
Vol 136 (7) ◽  
pp. 2557-2575 ◽  
Author(s):  
Akihiko Shimpo ◽  
Masao Kanamitsu ◽  
Sam F. Iacobellis ◽  
Song-You Hong
Keyword(s):  
Relative Humidity ◽  
Cloud Amount ◽  
Atmospheric Model ◽  
Global Precipitation Climatology Project ◽  
Cloud Water ◽  
Department Of Energy ◽  
Surface Radiation ◽  
Radiation Budget ◽  
Strong Interactions ◽  
Stratiform Cloud

Abstract The impacts of four stratiform cloud parameterizations on seasonal mean fields are investigated using the global version of the Experimental Climate Prediction Center (ECPC) global-to-regional forecast system (G-RSM). The simulated fields are compared with the International Satellite Cloud Climatology Project (ISCCP) data for clouds, the Global Precipitation Climatology Project data for precipitation, the Earth Radiation Budget Experiment and the Surface Radiation Budget data for radiation, and the National Centers for Environmental Prediction (NCEP)–Department of Energy (DOE) Atmospheric Model Intercomparison Project (AMIP-II) Reanalysis (R-2) for temperature. Compared to observations, no stratiform cloud parameterization performed better in simulating all aspects of clouds, temperature, precipitation, and radiation fluxes. There are strong interactions between parameterized stratiform clouds and boundary layer clouds and convection, resulting in changes in low-level cloudiness and precipitation in the simulations. When the simulations are compared with ISCCP cloudiness and cloud water, and the NCEP/DOE R-2 relative humidity, the cloud amounts simulated by all four cloud schemes depend mostly on relative humidity with less dependency on the model’s cloud water, while the observed cloud amount is more strongly dependent on cloud water than relative humidity, suggesting that cloud parameterizations and the simulation of cloud water require further improvement.

scholarly journals TURAC—A New Instrument Package for Radiation Budget Measurements and Cloud Detection

2005 ◽  
Vol 22 (10) ◽  
pp. 1473-1479 ◽  
Author(s):  
C. Ruckstuhl ◽  
R. Philipona
Keyword(s):  
Numerical Algorithms ◽  
Cloud Amount ◽  
Longwave Radiation ◽  
Surface Radiation ◽  
Radiation Budget ◽  
Cloud Detection ◽  
Radiation Fluxes ◽  
New Instrument ◽  
Temperature And Humidity ◽  
Flux Measurements

Abstract Atmospheric radiation flux measurements and the resulting surface radiation budget are important quantities for greenhouse effect and climate change investigations. Accurate net shortwave and longwave fluxes, in conjunction with numerical algorithms, also allow monitoring of the radiative effect of clouds and the nowcasting of the cloud amount. To achieve certain advantages on the accuracy of flux measurements a new instrument is developed that measures downward and upward shortwave and longwave radiation with the same sensors. Two high-quality instruments—a pyranometer for shortwave and a pyrgeometer for longwave measurements—are mounted on a pivotable sensor head, which is rotated up and down in 10-min intervals. To keep the instrument domes free from dew and ice, and to minimize the pyranometer thermal offset, both sensors are ventilated with slightly heated air. Additionally, a ventilated temperature and humidity sensor is integrated in the new instrument. The combination of measurements of radiation fluxes, temperature, and humidity allows for instrument use for autonomous and automatic cloud amount detection. The Temperature, Humidity, Radiation and Clouds (TURAC) sensor has been successfully tested under harsh alpine winter conditions, as well as under moderate lowland conditions. Comparisons to reference instruments showed all radiation fluxes to be within a maximum bias and rms difference of 1.6% or 1.4 W m−2 on daily averages.

Dependence of Land Surface Albedo on Solar Zenith Angle: Observations and Model Parameterization

2008 ◽  
Vol 47 (11) ◽  
pp. 2963-2982 ◽  
Author(s):  
Fanglin Yang ◽  
Kenneth Mitchell ◽  
Yu-Tai Hou ◽  
Yongjiu Dai ◽  
Xubin Zeng ◽  
...  
Keyword(s):  
Great Plains ◽  
Zenith Angle ◽  
Land Surface ◽  
Solar Zenith Angle ◽  
Surface Albedo ◽  
Geographical Location ◽  
Department Of Energy ◽  
Surface Radiation ◽  
Radiation Budget ◽  
Direct Beam

Abstract This study examines the dependence of surface albedo on solar zenith angle (SZA) over snow-free land surfaces using the intensive observations of surface shortwave fluxes made by the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Program and the National Oceanic and Atmospheric Administration Surface Radiation Budget Network (SURFRAD) in 1997–2005. Results are used to evaluate the National Centers for Environmental Prediction (NCEP) Global Forecast Systems (GFS) parameterization and several new parameterizations derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) products. The influence of clouds on surface albedo and the albedo difference between morning and afternoon observations are also investigated. A new approach is taken to partition the observed upward flux so that the direct-beam and diffuse albedos can be separately computed. The study focused first on the ARM Southern Great Plains Central Facility site. It is found that the diffuse albedo prescribed in the NCEP GFS matched closely with the observations. The direct-beam albedo parameterized in the GFS is largely underestimated at all SZAs. The parameterizations derived from the MODIS product underestimated the direct-beam albedo at large SZAs and slightly overestimated it at small SZAs. Similar results are obtained from the analyses of observations at other stations. It is also found that the morning and afternoon dependencies of direct-beam albedo on SZA differ among the stations. Attempts are made to improve numerical model algorithms that parameterize the direct-beam albedo as a product of the direct-beam albedo at SZA = 60° (or the diffuse albedo), which varies with surface type or geographical location and/or season, and a function that depends only on SZA. A method is presented for computing the direct-beam albedos over these snow-free land points without referring to a particular land-cover classification scheme, which often differs from model to model.

scholarly journals The Impacts of Smoke Emitted from Boreal Forest Wildfires on the High Latitude Radiative Energy Budget—A Case Study of the 2002 Yakutsk Wildfires

Atmosphere ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 410 ◽  
Author(s):  
Zheng Lu ◽  
Irina Sokolik
Keyword(s):  
Energy Budget ◽  
Cloud Water ◽  
Surface Radiation ◽  
Radiation Budget ◽  
Radiative Energy ◽  
Fire Season ◽  
Smoke Particles ◽  
Smoke Plumes ◽  
Induced Changes ◽  
Water Amount

We examine the 2002 Yakutsk wildfire event and simulate the impacts of smoke aerosols on local radiative energy budget, using the WRF-Chem-SMOKE model. When comparing satellite retrievals (the Surface Radiation Budget (SRB) dataset) with model simulations, we found that the agreement is generally good, except for the regions where the model predicts too few clouds or SRB misclassifies strong smoke plumes as clouds. We also found that the smoke-induced changes in upward shortwave fluxes at top of atmosphere (TOA) vary under different burning and meteorological conditions. In the first period of the fire season (9–12 August), smoke particles cause a warming effect around 3 W/m2, mainly through functioning as ice nuclei, which deplete the cloud water amount in the frontal system. At the beginning of the second period of the fire season (19–20 August), large amounts of pre-existing smoke particles cause a strong cooling effect of −8 W/m2. This is offset by the warming effect caused by relatively small amounts of cloud condensation nuclei increases, which promotes the rain formation and depletes the cloud water amount. After the cloud decks are well mixed with smoke plumes (21–22 August), the first indirect and direct effects of smoke together lead to a cooling of −10 W/m2. These results highlight the importance of meso-scale modeling efforts in estimating the smoke-induced changes in the radiative energy budget over high latitudes.

Linking Cloud Variability with Surface Radiation Budget over the Continental United States Using NASA CERES Satellite Observations and CMIP6 Model Simulations

2020 ◽  
Author(s):  
Danning Fu
Keyword(s):  
United States ◽  
21St Century ◽  
Radiant Energy ◽  
Cloud Amount ◽  
Surface Energy Budget ◽  
Surface Radiation ◽  
Radiation Budget ◽  
Model Simulations ◽  
Surface Radiation Budget ◽  
Cloud Water Content

<p>The surface radiation budget is defined by the difference between the downward and upward components of shortwave and thermal infrared longwave radiation at the surface. The instability of the surface radiation budget plays a significant role in climate change and variability through the modulation of temperature, precipitation, atmospheric circulation, etc. Clouds are believed to be a key factor to regulate such energy imbalance at the surface, as they generally reflect shortwave radiation from the sun and emit infrared radiation. Specifically, we are going to focus on the continental United States and answer the following questions: How is the surface radiation budget varied with time and space in the observations? How do clouds impact variations of surface radiation budget? How do state-of-the-art global climate models capture these observed features? What can they tell us about future changes in the surface radiation budget?</p><p>To investigate these questions, the NASA Clouds and the Earth's Radiant Energy System (CERES) observations will be used, along with model simulations from Phase 6 of the Coupled Model Intercomparison Project (CMIP6). We will first focus on the surface radiation budget from CERES observations in the 21st century, and examine their seasonal cycles, spatial patterns, long-term trends, and interannual variations over the continental United States. More importantly, we are going to investigate how cloud variability, including cloud types, cloud amount and cloud water content, influences the surface radiation budget. Then the CMIP6 historical simulations will be compared with CERES observations over the same time period. In addition, the CMIP6 future scenario simulations will be used to investigate how the surface radiation budget changes from the middle and late 21st century to the early 21st century. Overall, this study will help us to better understand the cloud and radiation variations in the past, as well as build credibility in the hindcast and future projections of surface energy budget over the continental United States.</p>

scholarly journals Evaluation of cloud fraction and its radiative effect simulated by IPCC AR4 global models against ARM surface observations

2012 ◽  
Vol 12 (4) ◽  
pp. 1785-1810 ◽  
Author(s):  
Y. Qian ◽  
C. N. Long ◽  
H. Wang ◽  
J. M. Comstock ◽  
S. A. McFarlane ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Probability Distribution ◽  
Vertical Structure ◽  
Cloud Amount ◽  
Cloud Fraction ◽  
Department Of Energy ◽  
The Arctic ◽  
Radiative Fluxes ◽  
The Tropics ◽  
Ipcc Ar4

Abstract. Cloud Fraction (CF) is the dominant modulator of radiative fluxes. In this study, we evaluate CF simulated in the IPCC AR4 GCMs against ARM long-term ground-based measurements, with a focus on the vertical structure, total amount of cloud and its effect on cloud shortwave transmissivity. Comparisons are performed for three climate regimes as represented by the Department of Energy Atmospheric Radiation Measurement (ARM) sites: Southern Great Plains (SGP), Manus, Papua New Guinea and North Slope of Alaska (NSA). Our intercomparisons of three independent measurements of CF or sky-cover reveal that the relative differences are usually less than 10% (5%) for multi-year monthly (annual) mean values, while daily differences are quite significant. The total sky imager (TSI) produces smaller total cloud fraction (TCF) compared to a radar/lidar dataset for highly cloudy days (CF > 0.8), but produces a larger TCF value than the radar/lidar for less cloudy conditions (CF < 0.3). The compensating errors in lower and higher CF days result in small biases of TCF between the vertically pointing radar/lidar dataset and the hemispheric TSI measurements as multi-year data is averaged. The unique radar/lidar CF measurements enable us to evaluate seasonal variation of cloud vertical structures in the GCMs. Both inter-model deviation and model bias against observation are investigated in this study. Another unique aspect of this study is that we use simultaneous measurements of CF and surface radiative fluxes to diagnose potential discrepancies among the GCMs in representing other cloud optical properties than TCF. The results show that the model-observation and inter-model deviations have similar magnitudes for the TCF and the normalized cloud effect, and these deviations are larger than those in surface downward solar radiation and cloud transmissivity. This implies that other dimensions of cloud in addition to cloud amount, such as cloud optical thickness and/or cloud height, have a similar magnitude of disparity as TCF within the GCMs, and suggests that the better agreement among GCMs in solar radiative fluxes could be a result of compensating effects from errors in cloud vertical structure, overlap assumption, cloud optical depth and/or cloud fraction. The internal variability of CF simulated in ensemble runs with the same model is minimal. Similar deviation patterns between inter-model and model-measurement comparisons suggest that the climate models tend to generate larger biases against observations for those variables with larger inter-model deviation. The GCM performance in simulating the probability distribution, transmissivity and vertical profiles of cloud are comprehensively evaluated over the three ARM sites. The GCMs perform better at SGP than at the other two sites in simulating the seasonal variation and probability distribution of TCF. However, the models remarkably underpredict the TCF at SGP and cloud transmissivity is less susceptible to the change of TCF than observed. In the tropics, most of the GCMs tend to underpredict CF and fail to capture the seasonal variation of CF at middle and low levels. The high-level CF is much larger in the GCMs than the observations and the inter-model variability of CF also reaches a maximum at high levels in the tropics, indicating discrepancies in the representation of ice cloud associated with convection in the models. While the GCMs generally capture the maximum CF in the boundary layer and vertical variability, the inter-model deviation is largest near the surface over the Arctic.

scholarly journals Synoptic-Scale Variability and Its Relationship with Total Ozone and Antarctic Vortex Displacements

2005 ◽  
Vol 133 (8) ◽  
pp. 2374-2386 ◽  
Author(s):  
Paula K. Vigliarolo ◽  
Carolina S. Vera ◽  
Susana B. Díaz
Keyword(s):  
South America ◽  
Total Ozone ◽  
Lower Stratosphere ◽  
Meteorological Data ◽  
Atmospheric Model ◽  
Meridional Wind ◽  
Department Of Energy ◽  
Synoptic Scale ◽  
Austral Spring ◽  
Anomaly Pattern

Abstract The main synoptic-scale circulation anomaly pattern over extratropical South America during the austral spring (September–November) is identified by means of rotated extended empirical orthogonal function techniques, applied to the meridional wind perturbation time series at 300 hPa. The dataset is based on 15 spring seasons (1979–93) of meteorological data from the National Centers for Environmental Prediction–Department of Energy Atmospheric Model Intercomparison Project version-2 daily averaged reanalyses, given in 17 vertical levels from 1000 to 10 hPa. The total-ozone daily measurements for the same period are from the Total Ozone Mapping Spectrometer instrument (version 7). The principal synoptic-scale anomaly pattern is associated with an anticyclone–cyclone pair evolving eastward along subpolar latitudes (and hence it is termed the subpolar mode), with a typical length scale of 5000 km and a phase velocity of 8 m s−1. The subpolar-mode waves, which display the main characteristics of midlatitude baroclinic waves, typically maximize near or above the tropopause and propagate upward into the lower stratosphere, showing large amplitudes even at 50 hPa and above. Subpolar-mode-related circulation anomalies are found to be responsible for large total-ozone daily fluctuations near southern South America and nearby regions. In the positive phase of the subpolar mode, total-ozone fluctuations, which are negative, adopt a sigmoid structure, with a zonal scale as large as the anticyclone–cyclone pair. Moreover, it is herein shown that the associated anticyclone produces a local ozone-column decrease to the north and east of its center, due to adiabatic uplift of air parcels in the upper troposphere and lower stratosphere. At the same time, the downstream cyclonic disturbance is responsible for large negative total-ozone anomalies to the west and south of its center. As the cyclone develops in the lower stratosphere, it promotes the northward incursion of the Antarctic vortex up to about 55°S, along with air masses of highly depleted ozone levels.

scholarly journals CLARA-A2: the second edition of the CM SAF cloud and radiation data record from 34 years of global AVHRR data

2017 ◽  
Vol 17 (9) ◽  
pp. 5809-5828 ◽  
Author(s):  
Karl-Göran Karlsson ◽  
Kati Anttila ◽  
Jörg Trentmann ◽  
Martin Stengel ◽  
Jan Fokke Meirink ◽  
...  
Keyword(s):  
Surface Albedo ◽  
Surface Radiation ◽  
Radiation Budget ◽  
Climate Data ◽  
Ground Segment ◽  
Surface Radiation Budget ◽  
Avhrr Data ◽  
Data Record ◽  
Development And Validation ◽  
Climate Data Record

Abstract. The second edition of the satellite-derived climate data record CLARA (The CM SAF Cloud, Albedo And Surface Radiation dataset from AVHRR data – second edition denoted as CLARA-A2) is described. The data record covers the 34-year period from 1982 until 2015 and consists of cloud, surface albedo and surface radiation budget products derived from the AVHRR (Advanced Very High Resolution Radiometer) sensor carried by polar-orbiting, operational meteorological satellites. The data record is produced by the EUMETSAT Climate Monitoring Satellite Application Facility (CM SAF) project as part of the operational ground segment. Its upgraded content and methodology improvements since edition 1 are described in detail, as are some major validation results. Some of the main improvements to the data record come from a major effort in cleaning and homogenizing the basic AVHRR level-1 radiance record and a systematic use of CALIPSO-CALIOP cloud information for development and validation purposes. Examples of applications studying decadal changes in Arctic summer surface albedo and cloud conditions are provided.

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