How the clear-sky angle of polarization pattern continues underneath clouds: full-sky measurements and implications for animal orientation.

PubMed

Pomozi, I; Horváth, G; Wehner, R

2001-09-01

One of the biologically most important parameters of the cloudy sky is the proportion P of the celestial polarization pattern available for use in animal navigation. We evaluated this parameter by measuring the polarization patterns of clear and cloudy skies using 180 degrees (full-sky) imaging polarimetry in the red (650 nm), green (550 nm) and blue (450 nm) ranges of the spectrum under clear and partly cloudy conditions. The resulting data were compared with the corresponding celestial polarization patterns calculated using the single-scattering Rayleigh model. We show convincingly that the pattern of the angle of polarization (e-vectors) in a clear sky continues underneath clouds if regions of the clouds and parts of the airspace between the clouds and the earth surface (being shady at the position of the observer) are directly lit by the sun. The scattering and polarization of direct sunlight on the cloud particles and in the air columns underneath the clouds result in the same e-vector pattern as that present in clear sky. This phenomenon can be exploited for animal navigation if the degree of polarization is higher than the perceptual threshold of the visual system, because the angle rather than the degree of polarization is the most important optical cue used in the polarization compass. Hence, the clouds reduce the extent of sky polarization pattern that is useful for animal orientation much less than has hitherto been assumed. We further demonstrate quantitatively that the shorter the wavelength, the greater the proportion of celestial polarization that can be used by animals under cloudy-sky conditions. As has already been suggested by others, this phenomenon may solve the ultraviolet paradox of polarization vision in insects such as hymenopterans and dipterans. The present study extends previous findings by using the technique of 180 degrees imaging polarimetry to measure and analyse celestial polarization patterns.

Sensitivity of Downward Longwave Surface Radiation to Moisture and Cloud Changes in a High-elevation Region

NASA Technical Reports Server (NTRS)

Naud, Catherine M.; Chen, Yonghua; Rangwala, Imtiaz; Miller, James R.

2013-01-01

Several studies have suggested enhanced rates of warming in high-elevation regions since the latter half of the twentieth century. One of the potential reasons why enhanced rates of warming might occur at high elevations is the nonlinear relationship between downward longwave radiation (DLR) and specific humidity (q). Using ground-based observations at a high-elevation site in southwestern Colorado and coincident satellite-borne cloud retrievals, the sensitivity of DLR to changes in q and cloud properties is examined and quantified using a neural network method. It is also used to explore how the sensitivity of DLR to q (dDLR/dq) is affected by cloud properties. When binned by season, dDLR/dq is maximum in winter and minimum in summer for both clear and cloudy skies. However, the cloudy-sky sensitivities are smaller, primarily because (1) for both clear and cloudy skies dDLR/dq is proportional to 1/q, for q>0.5 g/kg, and (2) the seasonal values of q are on average larger in the cloudy-sky cases than in clear-sky cases. For a given value of q, dDLR/dq is slightly reduced in the presence of clouds and this reduction increases as q increases. In addition, DLR is found to be more sensitive to changes in cloud fraction when cloud fraction is large. In the limit of overcast skies, DLR sensitivity to optical thickness decreases as clouds become more opaque. These results are based on only one high-elevation site, so the conclusions here need to be tested at other high-elevation locations.

Cloudy-sky Longwave Downward Radiation Estimation by Combining MODIS and AIRS/AMSU Measurements

NASA Astrophysics Data System (ADS)

Wang, T.; Shi, J.

2017-12-01

Longwave downward radiation (LWDR) is another main energy source received by the earth's surface except solar radiation. Its importance in regulating air temperature and balancing surface energy is enlarged especially under cloudy-sky. Unfortunately, to date, a large number of efforts have been made to derive LWDR from space under only clear-sky conditions leading to difficulty in utilizing space-based LWDR in most models due to its spatio-temporal discontinuity. Currently, only few studies focused on LWDR estimation under cloudy-sky conditions, while their global application is still questionable. In this paper, an alternative strategy is proposed aiming to derive high resolution(1km) cloudy-sky LWDR by fusing collocated satellite multi-sensor measurements. The results show that the newly developed method can work well and can derive LWDR at better accuracy with RMSE<27 W/m2 and bias < 10 W/m2 even under cloudy skies and at 1km scales. By comparing to CALIPSO-CloudSat-CERES-MODIS (CCCM) and SSF products of CERES, MERRA, ERA-interim and NCEP-CSFR products, the new approach demonstrates its superiority in terms of accuracy, temporal variation and spatial distribution pattern of LWDR. The comprehensive comparison analyses also reveal that, except for the proposed product, other four products (CERES, MERRA, ERA-interim and NCEP-CSFR) also show a big difference from each other in the LWDR spatio-temporal distribution pattern and magnitude. The difference between these products can still up to 60W/m2 even at the monthly scale, implying large uncertainties in current LWDR estimations. Besides the higher accuracy of the proposed method, more importantly, it provides unprecedented possibilities for jointly generating high resolution global LWDR datasets by connecting the NASA's Earth Observing System-(EOS) mission (MODIS-AIRS/AMSU) and the Suomi National Polar-orbiting Partnership-(NPP) mission (VIIRS-CrIS/ATMS). Meanwhile, the scheme proposed in this study also gives some clues for multiple data fusing in the remote sensing community.

Analysis of photosynthetically active radiation under various sky conditions in Wuhan, Central China.

PubMed

Wang, Lunche; Gong, Wei; Lin, Aiwen; Hu, Bo

2014-10-01

Observations of photosynthetically active radiation (PAR) and global solar radiation (G) at Wuhan, Central China during 2005-2012 were first reported to investigate PAR variability at different time scales and its PAR fraction (F(p)) under different sky conditions. Both G irradiances (I(g)) and PAR irradiances (I(p)) showed similar seasonal features that peaked in values at noon during summer and reached their lower values in winter. F(p) reached higher values during either sunrise or sunset; lower values of F p appeared at local noon because of the absorption effects of water vapor and clouds on long-wave radiation. There was an inverse relationship between clearness index (K(t)) and F(p); the maximum I(p) decreased by 22.3 % (39.7 %) when sky conditions changed from overcast to cloudless in summer (winter); solar radiation was more affected by cloudiness than the seasonal variation in cloudy skies when compared with that in clear skies. The maximum daily PAR irradiation (R(p)) was 11.89 MJ m⁻² day⁻¹ with an annual average of 4.85 MJ m⁻² day⁻¹. F p was in the range of 29-61.5 % with annual daily average value being about 42 %. Meanwhile, hourly, daily, and monthly relationships between R p and G irradiation (R g) under different sky conditions were investigated. It was discovered that cloudy skies were the dominated sky condition in this region. Finally, a clear-sky PAR model was developed by analyzing the dependence of PAR irradiances on optical air mass under various sky conditions for the whole study period in Central China, which will lay foundations for ecological process study in the near future.

A Neural Network Based Intelligent Predictive Sensor for Cloudiness, Solar Radiation and Air Temperature

PubMed Central

Ferreira, Pedro M.; Gomes, João M.; Martins, Igor A. C.; Ruano, António E.

2012-01-01

Accurate measurements of global solar radiation and atmospheric temperature, as well as the availability of the predictions of their evolution over time, are important for different areas of applications, such as agriculture, renewable energy and energy management, or thermal comfort in buildings. For this reason, an intelligent, light-weight and portable sensor was developed, using artificial neural network models as the time-series predictor mechanisms. These have been identified with the aid of a procedure based on the multi-objective genetic algorithm. As cloudiness is the most significant factor affecting the solar radiation reaching a particular location on the Earth surface, it has great impact on the performance of predictive solar radiation models for that location. This work also represents one step towards the improvement of such models by using ground-to-sky hemispherical colour digital images as a means to estimate cloudiness by the fraction of visible sky corresponding to clouds and to clear sky. The implementation of predictive models in the prototype has been validated and the system is able to function reliably, providing measurements and four-hour forecasts of cloudiness, solar radiation and air temperature. PMID:23202230

Digital all-sky polarization imaging of partly cloudy skies.

PubMed

Pust, Nathan J; Shaw, Joseph A

2008-12-01

Clouds reduce the degree of linear polarization (DOLP) of skylight relative to that of a clear sky. Even thin subvisual clouds in the "twilight zone" between clouds and aerosols produce a drop in skylight DOLP long before clouds become visible in the sky. In contrast, the angle of polarization (AOP) of light scattered by a cloud in a partly cloudy sky remains the same as in the clear sky for most cases. In unique instances, though, select clouds display AOP signatures that are oriented 90 degrees from the clear-sky AOP. For these clouds, scattered light oriented parallel to the scattering plane dominates the perpendicularly polarized Rayleigh-scattered light between the instrument and the cloud. For liquid clouds, this effect may assist cloud particle size identification because it occurs only over a relatively limited range of particle radii that will scatter parallel polarized light. Images are shown from a digital all-sky-polarization imager to illustrate these effects. Images are also shown that provide validation of previously published theories for weak (approximately 2%) polarization parallel to the scattering plane for a 22 degrees halo.

The Impact of Cross-track Infrared Sounder (CrIS) Cloud-Cleared Radiances on Hurricane Joaquin (2015) and Matthew (2016) Forecasts

NASA Astrophysics Data System (ADS)

Wang, Pei; Li, Jun; Li, Zhenglong; Lim, Agnes H. N.; Li, Jinlong; Schmit, Timothy J.; Goldberg, Mitchell D.

2017-12-01

Hyperspectral infrared (IR) sounders provide high vertical resolution atmospheric sounding information that can improve the forecast skill in numerical weather prediction. Commonly, only clear radiances are assimilated, because IR sounder observations are highly affected by clouds. A cloud-clearing (CC) technique, which removes the cloud effects from an IR cloudy field of view (FOV) and derives the cloud-cleared radiances (CCRs) or clear-sky equivalent radiances, can be an alternative yet effective way to take advantage of the thermodynamic information from cloudy skies in data assimilation. This study develops a Visible Infrared Imaging Radiometer Suite (VIIRS)-based CC method for deriving Cross-track Infrared Sounder (CrIS) CCRs under partially cloudy conditions. Due to the lack of absorption bands on VIIRS, two important quality control steps are implemented in the CC process. Validation using VIIRS clear radiances indicates that the CC method can effectively obtain the CrIS CCRs for FOVs with partial cloud cover. To compare the impacts from assimilation of CrIS original radiances and CCRs, three experiments are carried out on two storm cases, Hurricane Joaquin (2015) and Hurricane Matthew (2016), using Gridpoint Statistical Interpolation assimilation system and Weather Research and Forecasting-Advanced Research Version models. At the analysis time, more CrIS observations are assimilated when using CrIS CCRs than with CrIS original radiances. Comparing temperature, specific humidity, and U/V winds with radiosondes indicates that the data impacts are growing larger with longer time forecasts (beyond 72 h forecast). Hurricane track forecasts also show improvements from the assimilation of CrIS CCRs due to better weather system forecasts. The impacts of CCRs on intensity are basically neutral with mixed positive and negative results.

Effective cloud optical depth and enhancement effects for broken liquid water clouds in Valencia (Spain)

NASA Astrophysics Data System (ADS)

Marín, M. J.; Serrano, D.; Utrillas, M. P.; Núñez, M.; Martínez-Lozano, J. A.

2017-10-01

Partly cloudy skies with liquid water clouds have been analysed, founding that it is essential to distinguish data if the Sun is obstructed or not by clouds. Both cases can be separated considering simultaneously the Cloud Modification Factor (CMF) and the clearness index (kt). For partly cloudy skies and the Sun obstructed the effective cloud optical depth (τ) has been obtained by the minimization method for overcast skies. This method was previously developed by the authors but, in this case, taking into account partial cloud cover. This study has been conducted for the years 2011-2015 with the multiple scattering model SBDART and irradiance measurements for the UV Erythemal Radiation (UVER) and the broadband ranges. Afterwards a statistical analysis of τ has shown that the maximum value is much lower than for overcast skies and there is more discrepancy between the two spectral ranges regarding the results for overcast skies. In order to validate these results the effective cloud optical depth has been correlated with several transmission factors, giving similar fit parameters to those obtained for overcast skies except for the clearness index in the UVER range. As our method is not applicable for partly cloudy skies with the visible Sun, the enhancement of radiation caused by clouds when the Sun is visible has been studied. Results show that the average enhancement CMF values are the same for both ranges although enhancement is more frequent for low cloud cover in the UVER and medium-high cloud cover in the broadband range and it does not depend on the solar zenith angle.

Validation and Improvement of CERES Surface Radiation Budget Algorithms: Extension of Dusty and Cloudy Scenes

NASA Technical Reports Server (NTRS)

Ramanathan, V.; Inamdar, Anand K.

2005-01-01

Our main task was to validate and improve the generation of surface long wave fluxes from the CERES TOA window channel flux measurements. We completed this task successfully for the clear sky fluxes in the presence of aerosols including dust during the first year of the project. The algorithm we developed for CERES was remarkably successful for clear sky fluxes and we have no further tasks that need to be performed past the requested termination date of December 31, 2004. We found that the information contained in the TOA fluxes was not sufficient to improve upon the current CERES algorithm for cloudy sky fluxes. Given this development and given our success in clear sky fluxes, we do not see any reason to continue our validation work beyond what we have completed. Specific details are given.

Success of sky-polarimetric Viking navigation: revealing the chance Viking sailors could reach Greenland from Norway

NASA Astrophysics Data System (ADS)

Száz, Dénes; Horváth, Gábor

2018-04-01

According to a famous hypothesis, Viking sailors could navigate along the latitude between Norway and Greenland by means of sky polarization in cloudy weather using a sun compass and sunstone crystals. Using data measured in earlier atmospheric optical and psychophysical experiments, here we determine the success rate of this sky-polarimetric Viking navigation. Simulating 1000 voyages between Norway and Greenland with varying cloudiness at summer solstice and spring equinox, we revealed the chance with which Viking sailors could reach Greenland under the varying weather conditions of a 3-week-long journey as a function of the navigation periodicity Δt if they analysed sky polarization with calcite, cordierite or tourmaline sunstones. Examples of voyage routes are also presented. Our results show that the sky-polarimetric navigation is surprisingly successful on both days of the spring equinox and summer solstice even under cloudy conditions if the navigator determined the north direction periodically at least once in every 3 h, independently of the type of sunstone used for the analysis of sky polarization. This explains why the Vikings could rule the Atlantic Ocean for 300 years and could reach North America without a magnetic compass. Our findings suggest that it is not only the navigation periodicity in itself that is important for higher navigation success rates, but also the distribution of times when the navigation procedure carried out is as symmetrical as possible with respect to the time point of real noon.

Success of sky-polarimetric Viking navigation: revealing the chance Viking sailors could reach Greenland from Norway.

PubMed

Száz, Dénes; Horváth, Gábor

2018-04-01

According to a famous hypothesis, Viking sailors could navigate along the latitude between Norway and Greenland by means of sky polarization in cloudy weather using a sun compass and sunstone crystals. Using data measured in earlier atmospheric optical and psychophysical experiments, here we determine the success rate of this sky-polarimetric Viking navigation. Simulating 1000 voyages between Norway and Greenland with varying cloudiness at summer solstice and spring equinox, we revealed the chance with which Viking sailors could reach Greenland under the varying weather conditions of a 3-week-long journey as a function of the navigation periodicity Δ t if they analysed sky polarization with calcite, cordierite or tourmaline sunstones. Examples of voyage routes are also presented. Our results show that the sky-polarimetric navigation is surprisingly successful on both days of the spring equinox and summer solstice even under cloudy conditions if the navigator determined the north direction periodically at least once in every 3 h, independently of the type of sunstone used for the analysis of sky polarization. This explains why the Vikings could rule the Atlantic Ocean for 300 years and could reach North America without a magnetic compass. Our findings suggest that it is not only the navigation periodicity in itself that is important for higher navigation success rates, but also the distribution of times when the navigation procedure carried out is as symmetrical as possible with respect to the time point of real noon.

Success of sky-polarimetric Viking navigation: revealing the chance Viking sailors could reach Greenland from Norway

PubMed Central

Száz, Dénes; Horváth, Gábor

2018-01-01

According to a famous hypothesis, Viking sailors could navigate along the latitude between Norway and Greenland by means of sky polarization in cloudy weather using a sun compass and sunstone crystals. Using data measured in earlier atmospheric optical and psychophysical experiments, here we determine the success rate of this sky-polarimetric Viking navigation. Simulating 1000 voyages between Norway and Greenland with varying cloudiness at summer solstice and spring equinox, we revealed the chance with which Viking sailors could reach Greenland under the varying weather conditions of a 3-week-long journey as a function of the navigation periodicity Δt if they analysed sky polarization with calcite, cordierite or tourmaline sunstones. Examples of voyage routes are also presented. Our results show that the sky-polarimetric navigation is surprisingly successful on both days of the spring equinox and summer solstice even under cloudy conditions if the navigator determined the north direction periodically at least once in every 3 h, independently of the type of sunstone used for the analysis of sky polarization. This explains why the Vikings could rule the Atlantic Ocean for 300 years and could reach North America without a magnetic compass. Our findings suggest that it is not only the navigation periodicity in itself that is important for higher navigation success rates, but also the distribution of times when the navigation procedure carried out is as symmetrical as possible with respect to the time point of real noon. PMID:29765673

All sky imaging observations in visible and infrared waveband for validation of satellite cloud and aerosol products

NASA Astrophysics Data System (ADS)

Lu, Daren; Huo, Juan; Zhang, W.; Liu, J.

A series of satellite sensors in visible and infrared wavelengths have been successfully operated on board a number of research satellites, e.g. NOAA/AVHRR, the MODIS onboard Terra and Aqua, etc. A number of cloud and aerosol products are produced and released in recent years. However, the validation of the product quality and accuracy are still a challenge to the atmospheric remote sensing community. In this paper, we suggest a ground based validation scheme for satellite-derived cloud and aerosol products by using combined visible and thermal infrared all sky imaging observations as well as surface meteorological observations. In the scheme, a visible digital camera with a fish-eye lens is used to continuously monitor the all sky with the view angle greater than 180 deg. The digital camera system is calibrated for both its geometry and radiance (broad blue, green, and red band) so as to a retrieval method can be used to detect the clear and cloudy sky spatial distribution and their temporal variations. A calibrated scanning thermal infrared thermometer is used to monitor the all sky brightness temperature distribution. An algorithm is developed to detect the clear and cloudy sky as well as cloud base height by using sky brightness distribution and surface temperature and humidity as input. Based on these composite retrieval of clear and cloudy sky distribution, it can be used to validate the satellite retrievals in the sense of real-simultaneous comparison and statistics, respectively. What will be presented in this talk include the results of the field observations and comparisons completed in Beijing (40 deg N, 116.5 deg E) in year 2003 and 2004. This work is supported by NSFC grant No. 4002700, and MOST grant No 2001CCA02200

Relationship between high daily erythemal UV doses, total ozone, surface albedo and cloudiness: An analysis of 30 years of data from Switzerland and Austria

NASA Astrophysics Data System (ADS)

Rieder, H. E.; Staehelin, J.; Weihs, P.; Vuilleumier, L.; Maeder, J. A.; Holawe, F.; Blumthaler, M.; Lindfors, A.; Peter, T.; Simic, S.; Spichtinger, P.; Wagner, J. E.; Walker, D.; Ribatet, M.

2010-10-01

This work investigates the occurrence frequency of days with high erythemal UV doses at three stations in Switzerland and Austria (Davos, Hoher Sonnblick and Vienna) for the time period 1974-2003. While several earlier studies have reported on increases in erythemal UV dose up to 10% during the last decades, this study focuses on days with high erythemal UV dose, which is defined as a daily dose at least 15% higher than for 1950s clear-sky conditions (which represent preindustrial conditions with respect to anthropogenic chlorine). Furthermore, the influence of low column ozone, clear-sky/partly cloudy conditions and surface albedo on UV irradiance has been analyzed on annual and seasonal basis. The results of this study show that in the Central Alpine Region the number of days with high UV dose increased strongly in the early 1990s. A large fraction of all days with high UV dose occurring in the period 1974-2003 was found especially during the years 1994-2003, namely 40% at Davos, 54% at Hoher Sonnblick and 65% at Vienna. The importance of total ozone, clear-sky/partly cloudy conditions and surface albedo (e.g. in dependence of snow cover) varies strongly among the seasons. However, overall the interplay of low total ozone and clear-sky/partly cloudy conditions led to the largest fraction of days showing high erythemal UV dose. Furthermore, an analysis of the synoptic weather situation showed that days with high erythemal UV dose, low total ozone and high relative sunshine duration occur at all three stations more frequently during situations with low pressure gradients or southerly advection.

The National Solar Radiation Database (NSRDB): A Brief Overview

DOE Office of Scientific and Technical Information (OSTI.GOV)

Habte, Aron M; Sengupta, Manajit; Lopez, Anthony

This poster presents a high-level overview of the National Solar Radiation Database (NSRDB). The NSRDB uses the physics-based model (PSM), which was developed using: adapted PATMOS-X model for cloud identification and properties, REST-2 model for clear-sky conditions, and NREL's Fast All-sky Radiation Model for Solar Applications (FARMS) for cloudy-sky Global Horizontal Irradiance (GHI) solar irradiance calculations.

Infrared Sky Imager (IRSI) Instrument Handbook

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morris, Victor R.

2016-04-01

The Infrared Sky Imager (IRSI) deployed at the Atmospheric Radiation Measurement (ARM) Climate Research Facility is a Solmirus Corp. All Sky Infrared Visible Analyzer. The IRSI is an automatic, continuously operating, digital imaging and software system designed to capture hemispheric sky images and provide time series retrievals of fractional sky cover during both the day and night. The instrument provides diurnal, radiometrically calibrated sky imagery in the mid-infrared atmospheric window and imagery in the visible wavelengths for cloud retrievals during daylight hours. The software automatically identifies cloudy and clear regions at user-defined intervals and calculates fractional sky cover, providing amore » real-time display of sky conditions.« less

An Improved Algorithm for Retrieving Surface Downwelling Longwave Radiation from Satellite Measurements

NASA Technical Reports Server (NTRS)

Zhou, Yaping; Kratz, David P.; Wilber, Anne C.; Gupta, Shashi K.; Cess, Robert D.

2006-01-01

Retrieving surface longwave radiation from space has been a difficult task since the surface downwelling longwave radiation (SDLW) are integrations from radiation emitted by the entire atmosphere, while those emitted from the upper atmosphere are absorbed before reaching the surface. It is particularly problematic when thick clouds are present since thick clouds will virtually block all the longwave radiation from above, while satellites observe atmosphere emissions mostly from above the clouds. Zhou and Cess developed an algorithm for retrieving SDLW based upon detailed studies using radiative transfer model calculations and surface radiometric measurements. Their algorithm linked clear sky SDLW with surface upwelling longwave flux and column precipitable water vapor. For cloudy sky cases, they used cloud liquid water path as an additional parameter to account for the effects of clouds. Despite the simplicity of their algorithm, it performed very well for most geographical regions except for those regions where the atmospheric conditions near the surface tend to be extremely cold and dry. Systematic errors were also found for areas that were covered with ice clouds. An improved version of the algorithm was developed that prevents the large errors in the SDLW at low water vapor amounts. The new algorithm also utilizes cloud fraction and cloud liquid and ice water paths measured from the Cloud and the Earth's Radiant Energy System (CERES) satellites to separately compute the clear and cloudy portions of the fluxes. The new algorithm has been validated against surface measurements at 29 stations around the globe for the Terra and Aqua satellites. The results show significant improvement over the original version. The revised Zhou-Cess algorithm is also slightly better or comparable to more sophisticated algorithms currently implemented in the CERES processing. It will be incorporated in the CERES project as one of the empirical surface radiation algorithms.

Broadband Heating Rate Profile Project (BBHRP) - SGP ripbe370mcfarlane

DOE Data Explorer

Riihimaki, Laura; Shippert, Timothy

2014-11-05

The objective of the ARM Broadband Heating Rate Profile (BBHRP) Project is to provide a structure for the comprehensive assessment of our ability to model atmospheric radiative transfer for all conditions. Required inputs to BBHRP include surface albedo and profiles of atmospheric state (temperature, humidity), gas concentrations, aerosol properties, and cloud properties. In the past year, the Radiatively Important Parameters Best Estimate (RIPBE) VAP was developed to combine all of the input properties needed for BBHRP into a single gridded input file. Additionally, an interface between the RIPBE input file and the RRTM was developed using the new ARM integrated software development environment (ISDE) and effort was put into developing quality control (qc) flags and provenance information on the BBHRP output files so that analysis of the output would be more straightforward. This new version of BBHRP, sgp1bbhrpripbeC1.c1, uses the RIPBE files as input to RRTM, and calculates broadband SW and LW fluxes and heating rates at 1-min resolution using the independent column approximation. The vertical resolution is 45 m in the lower and middle troposphere to match the input cloud properties, but is at coarser resolution in the upper atmosphere. Unlike previous versions, the vertical grid is the same for both clear-sky and cloudy-sky calculations.

Broadband Heating Rate Profile Project (BBHRP) - SGP 1bbhrpripbe1mcfarlane

DOE Data Explorer

Riihimaki, Laura; Shippert, Timothy

2014-11-05

The objective of the ARM Broadband Heating Rate Profile (BBHRP) Project is to provide a structure for the comprehensive assessment of our ability to model atmospheric radiative transfer for all conditions. Required inputs to BBHRP include surface albedo and profiles of atmospheric state (temperature, humidity), gas concentrations, aerosol properties, and cloud properties. In the past year, the Radiatively Important Parameters Best Estimate (RIPBE) VAP was developed to combine all of the input properties needed for BBHRP into a single gridded input file. Additionally, an interface between the RIPBE input file and the RRTM was developed using the new ARM integrated software development environment (ISDE) and effort was put into developing quality control (qc) flags and provenance information on the BBHRP output files so that analysis of the output would be more straightforward. This new version of BBHRP, sgp1bbhrpripbeC1.c1, uses the RIPBE files as input to RRTM, and calculates broadband SW and LW fluxes and heating rates at 1-min resolution using the independent column approximation. The vertical resolution is 45 m in the lower and middle troposphere to match the input cloud properties, but is at coarser resolution in the upper atmosphere. Unlike previous versions, the vertical grid is the same for both clear-sky and cloudy-sky calculations.

Broadband Heating Rate Profile Project (BBHRP) - SGP ripbe1mcfarlane

DOE Data Explorer

Riihimaki, Laura; Shippert, Timothy

2014-11-05

The objective of the ARM Broadband Heating Rate Profile (BBHRP) Project is to provide a structure for the comprehensive assessment of our ability to model atmospheric radiative transfer for all conditions. Required inputs to BBHRP include surface albedo and profiles of atmospheric state (temperature, humidity), gas concentrations, aerosol properties, and cloud properties. In the past year, the Radiatively Important Parameters Best Estimate (RIPBE) VAP was developed to combine all of the input properties needed for BBHRP into a single gridded input file. Additionally, an interface between the RIPBE input file and the RRTM was developed using the new ARM integrated software development environment (ISDE) and effort was put into developing quality control (qc) flags and provenance information on the BBHRP output files so that analysis of the output would be more straightforward. This new version of BBHRP, sgp1bbhrpripbeC1.c1, uses the RIPBE files as input to RRTM, and calculates broadband SW and LW fluxes and heating rates at 1-min resolution using the independent column approximation. The vertical resolution is 45 m in the lower and middle troposphere to match the input cloud properties, but is at coarser resolution in the upper atmosphere. Unlike previous versions, the vertical grid is the same for both clear-sky and cloudy-sky calculations.

Assessment of the Effect of Air Pollution Controls on Trends in Shortwave Radiation over the United States from 1995 through 2010 from Multiple Observation Networks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gan, Chuen-Meei; Pleim, Jonathan; Mathur, Rohit

2014-02-14

Long term datasets of total (all-sky) and clear-sky downwelling shortwave (SW) radiation, cloud cover fraction (cloudiness) and aerosol optical depth (AOD) are analyzed together with aerosol concentration from several networks (e.g. SURFRAD, CASTNET, IMPROVE and ARM) in the United States (US). Seven states with varying climatology are selected to better understand the effect of aerosols and clouds on SW radiation. This analysis aims to test the hypothesis that the reductions in anthropogenic aerosol burden resulting from substantial reductions in emissions of sulfur dioxide and nitrogen oxides over the past 15 years across the US has caused an increase in surfacemore » SW radiation. We show that the total and clear-sky downwelling SW radiation from seven sites have increasing trends except Penn State which shows no tendency in clear-sky SW radiation. After investigating several confounding factors, the causes can be due to the geography of the site, aerosol distribution, heavy air traffic and increasing cloudiness. Moreover, we assess the relationship between total column AOD with surface aerosol concentration to test our hypothesis. In our findings, the trends of clear-sky SW radiation, AOD, and aerosol concentration from the sites in eastern US agree well with our hypothesis. However, the sites in western US demonstrate increasing AOD associated with mostly increasing trends in surface aerosol concentration. At these sites, the changes in aerosol burden and/or direct aerosol effects alone cannot explain the observed changes in SW radiation, but other factors need to be considered such as cloudiness, aerosol vertical profiles and elevated plumes.« less

Automatic Mosaicking of Satellite Imagery Considering the Clouds

NASA Astrophysics Data System (ADS)

Kang, Yifei; Pan, Li; Chen, Qi; Zhang, Tong; Zhang, Shasha; Liu, Zhang

2016-06-01

With the rapid development of high resolution remote sensing for earth observation technology, satellite imagery is widely used in the fields of resource investigation, environment protection, and agricultural research. Image mosaicking is an important part of satellite imagery production. However, the existence of clouds leads to lots of disadvantages for automatic image mosaicking, mainly in two aspects: 1) Image blurring may be caused during the process of image dodging, 2) Cloudy areas may be passed through by automatically generated seamlines. To address these problems, an automatic mosaicking method is proposed for cloudy satellite imagery in this paper. Firstly, modified Otsu thresholding and morphological processing are employed to extract cloudy areas and obtain the percentage of cloud cover. Then, cloud detection results are used to optimize the process of dodging and mosaicking. Thus, the mosaic image can be combined with more clear-sky areas instead of cloudy areas. Besides, clear-sky areas will be clear and distortionless. The Chinese GF-1 wide-field-of-view orthoimages are employed as experimental data. The performance of the proposed approach is evaluated in four aspects: the effect of cloud detection, the sharpness of clear-sky areas, the rationality of seamlines and efficiency. The evaluation results demonstrated that the mosaic image obtained by our method has fewer clouds, better internal color consistency and better visual clarity compared with that obtained by traditional method. The time consumed by the proposed method for 17 scenes of GF-1 orthoimages is within 4 hours on a desktop computer. The efficiency can meet the general production requirements for massive satellite imagery.

User Observed Estimates of Cloud Fraction for Modifying a Cloud-free UV Index for Use in an Educational Smart-phone Application on Erythema

NASA Astrophysics Data System (ADS)

Lantz, K. O.; Long, C. S.; Buller, D.; Berwick, M.; Buller, M.; Kane, I.; Shane, J.

2012-12-01

The UV Index (UVI) is a measure of the skin-damaging UV radiation levels at the Earth's surface. Clouds, haze, air pollution, total ozone, surface elevation, and ground reflectivity affect the levels of UV radiation reaching the ground. The global UV Index was developed as a simple tool to educate the public for taking precautions when exposed to UV radiation to avoid sun-burning, which has been linked to the development of skin cancer. The purpose of this study was to validate an algorithm to modify a cloud-free UV Index forecast for cloud conditions as observed by adults in real-time. The cloud attenuation algorithm is used in a smart-phone application to modify a clear-sky UV Index forecast. In the United States, the Climate Prediction Center of the National Oceanic and Atmospheric Administration's (NOAA) issues a daily UV Index Forecast. The NOAA UV Index is an hourly forecast for a 0.5 x 0.5 degree area and thus has a degree of uncertainty. Cloud cover varies temporally and spatially over short times and distances as weather conditions change and can have a large impact on the UV radiation. The smart-phone application uses the cloud-based UV Index forecast as the default but allows the user to modify a cloud-free UV Index forecast when the predicted sky conditions do not match observed conditions. Eighty four (n=84) adults were recruited to participate in the study through advertisements posted online and in a university e-newsletter. Adults were screened for eligibility (i.e., 18 or older, capable to traveling to test site, had a smart phone with a data plan to access online observation form). A sky observation measure was created to assess cloud fraction. The adult volunteers selected from among four photographs the image that best matched the cloud conditions they observed. Images depicted no clouds (clear sky), thin high clouds, partly cloudy sky, and thick clouds (sky completely overcast). When thin high clouds or partly cloudy images were selected, adults estimated the percentage of the sky covered by clouds. Cloud fraction was calculated by assigning 0% if the clear-sky image was selected, 100% if the overcast thick cloud image was selected, and 10% to 90% as indicated by adults, if high thin clouds or partly cloudy images were selected. The observed cloud fraction from the adult volunteers was compared to the cloud fraction determined by a Total Sky Imager. A cloud modification factor based on the observed cloud fraction was applied to the cloud-free UV Index forecast. This result was compared to the NOAA cloudy sky UV Index forecast and to the concurrent UV Index measurements from three broadband UV radiometers and a Brewer spectrophotometer calibrated using NIST traceable standards.

Optimizing UV Index determination from broadband irradiances

NASA Astrophysics Data System (ADS)

Tereszchuk, Keith A.; Rochon, Yves J.; McLinden, Chris A.; Vaillancourt, Paul A.

2018-03-01

A study was undertaken to improve upon the prognosticative capability of Environment and Climate Change Canada's (ECCC) UV Index forecast model. An aspect of that work, and the topic of this communication, was to investigate the use of the four UV broadband surface irradiance fields generated by ECCC's Global Environmental Multiscale (GEM) numerical prediction model to determine the UV Index. The basis of the investigation involves the creation of a suite of routines which employ high-spectral-resolution radiative transfer code developed to calculate UV Index fields from GEM forecasts. These routines employ a modified version of the Cloud-J v7.4 radiative transfer model, which integrates GEM output to produce high-spectral-resolution surface irradiance fields. The output generated using the high-resolution radiative transfer code served to verify and calibrate GEM broadband surface irradiances under clear-sky conditions and their use in providing the UV Index. A subsequent comparison of irradiances and UV Index under cloudy conditions was also performed. Linear correlation agreement of surface irradiances from the two models for each of the two higher UV bands covering 310.70-330.0 and 330.03-400.00 nm is typically greater than 95 % for clear-sky conditions with associated root-mean-square relative errors of 6.4 and 4.0 %. However, underestimations of clear-sky GEM irradiances were found on the order of ˜ 30-50 % for the 294.12-310.70 nm band and by a factor of ˜ 30 for the 280.11-294.12 nm band. This underestimation can be significant for UV Index determination but would not impact weather forecasting. Corresponding empirical adjustments were applied to the broadband irradiances now giving a correlation coefficient of unity. From these, a least-squares fitting was derived for the calculation of the UV Index. The resultant differences in UV indices from the high-spectral-resolution irradiances and the resultant GEM broadband irradiances are typically within 0.2-0.3 with a root-mean-square relative error in the scatter of ˜ 6.6 % for clear-sky conditions. Similar results are reproduced under cloudy conditions with light to moderate clouds, with a relative error comparable to the clear-sky counterpart; under strong attenuation due to clouds, a substantial increase in the root-mean-square relative error of up to 35 % is observed due to differing cloud radiative transfer models.

Method for validating cloud mask obtained from satellite measurements using ground-based sky camera.

PubMed

Letu, Husi; Nagao, Takashi M; Nakajima, Takashi Y; Matsumae, Yoshiaki

2014-11-01

Error propagation in Earth's atmospheric, oceanic, and land surface parameters of the satellite products caused by misclassification of the cloud mask is a critical issue for improving the accuracy of satellite products. Thus, characterizing the accuracy of the cloud mask is important for investigating the influence of the cloud mask on satellite products. In this study, we proposed a method for validating multiwavelength satellite data derived cloud masks using ground-based sky camera (GSC) data. First, a cloud cover algorithm for GSC data has been developed using sky index and bright index. Then, Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data derived cloud masks by two cloud-screening algorithms (i.e., MOD35 and CLAUDIA) were validated using the GSC cloud mask. The results indicate that MOD35 is likely to classify ambiguous pixels as "cloudy," whereas CLAUDIA is likely to classify them as "clear." Furthermore, the influence of error propagations caused by misclassification of the MOD35 and CLAUDIA cloud masks on MODIS derived reflectance, brightness temperature, and normalized difference vegetation index (NDVI) in clear and cloudy pixels was investigated using sky camera data. It shows that the influence of the error propagation by the MOD35 cloud mask on the MODIS derived monthly mean reflectance, brightness temperature, and NDVI for clear pixels is significantly smaller than for the CLAUDIA cloud mask; the influence of the error propagation by the CLAUDIA cloud mask on MODIS derived monthly mean cloud products for cloudy pixels is significantly smaller than that by the MOD35 cloud mask.

An All Sky Instantaneous Shortwave Solar Radiation Model for Mountainous Terrain

NASA Astrophysics Data System (ADS)

Zhang, S.; Li, X.; She, J.

2017-12-01

In mountainous terrain, solar radiation shows high heterogeneity in space and time because of strong terrain shading effects and significant variability of cloud cover. While existing GIS-based solar radiation models simulate terrain shading effects with relatively high accuracy and models based on satellite datasets consider fine scale cloud attenuation processes, none of these models have considered the geometrical relationships between sun, cloud, and terrain, which are important over mountainous terrain. In this research we propose sky cloud maps to represent cloud distribution in a hemispherical sky using MODIS cloud products. By overlaying skyshed (visible area in the hemispherical sky derived from DEM), sky map, and sky cloud maps, we are able to consider both terrain shading effects and anisotropic cloud attenuation in modeling instantaneous direct and diffuse solar radiation in mountainous terrain. The model is evaluated with field observations from three automatic weather stations in the Tizinafu watershed in the Kunlun Mountains of northwestern China. Overall, under all sky conditions, the model overestimates instantaneous global solar radiation with a mean absolute relative difference (MARD) of 22%. The model is also evaluated under clear sky (clearness index of more than 0.75) and partly cloudy sky (clearness index between 0.35 and 0.75) conditions with MARDs of 5.98% and 23.65% respectively. The MARD for very cloudy sky (clearness index less than 0.35) is relatively high. But these days occur less than 1% of the time. The model is sensitive to DEM data error, algorithms used in delineating skyshed, and errors in MODIS atmosphere and cloud products. Our model provides a novel approach for solar radiation modeling in mountainous areas.

An evaluation of skylight polarization patterns for navigation.

PubMed

Ma, Tao; Hu, Xiaoping; Zhang, Lilian; Lian, Junxiang; He, Xiaofeng; Wang, Yujie; Xian, Zhiwen

2015-03-10

Skylight polarization provides a significant navigation cue for certain polarization-sensitive animals. However, the precision of the angle of polarization (AOP) of skylight for vehicle orientation is not clear. An evaluation of AOP must be performed before it is utilized. This paper reports an evaluation of AOP of skylight by measuring the skylight polarization patterns of clear and cloudy skies using a full-sky imaging polarimetry system. AOP measurements of skylight are compared with the pattern calculated by the single-scattering Rayleigh model and these differences are quantified. The relationship between the degree of polarization (DOP) and the deviation of AOP of skylight is thoroughly studied. Based on these, a solar meridian extracted method is presented. The results of experiments reveal that the DOP is a key parameter to indicate the accuracy of AOP measurements, and all the output solar meridian orientations extracted by our method in both clear and cloudy skies can achieve a high accuracy for vehicle orientation.

An Evaluation of Skylight Polarization Patterns for Navigation

PubMed Central

Ma, Tao; Hu, Xiaoping; Zhang, Lilian; Lian, Junxiang; He, Xiaofeng; Wang, Yujie; Xian, Zhiwen

2015-01-01

Skylight polarization provides a significant navigation cue for certain polarization-sensitive animals. However, the precision of the angle of polarization (AOP) of skylight for vehicle orientation is not clear. An evaluation of AOP must be performed before it is utilized. This paper reports an evaluation of AOP of skylight by measuring the skylight polarization patterns of clear and cloudy skies using a full-sky imaging polarimetry system. AOP measurements of skylight are compared with the pattern calculated by the single-scattering Rayleigh model and these differences are quantified. The relationship between the degree of polarization (DOP) and the deviation of AOP of skylight is thoroughly studied. Based on these, a solar meridian extracted method is presented. The results of experiments reveal that the DOP is a key parameter to indicate the accuracy of AOP measurements, and all the output solar meridian orientations extracted by our method in both clear and cloudy skies can achieve a high accuracy for vehicle orientation. PMID:25763652

On the existence of tropical anvil clouds

NASA Astrophysics Data System (ADS)

Seeley, J.; Jeevanjee, N.; Langhans, W.; Romps, D.

2017-12-01

In the deep tropics, extensive anvil clouds produce a peak in cloud cover below the tropopause. The dominant paradigm for cloud cover attributes this anvil peak to a layer of enhanced mass convergence in the clear-sky upper-troposphere, which is presumed to force frequent detrainment of convective anvils. However, cloud cover also depends on the lifetime of cloudy air after it detrains, which raises the possibility that anvil clouds may be the signature of slow cloud decay rather than enhanced detrainment. Here we measure the cloud decay timescale in cloud-resolving simulations, and find that cloudy updrafts that detrain in the upper troposphere take much longer to dissipate than their shallower counterparts. We show that cloud lifetimes are long in the upper troposphere because the saturation specific humidity becomes orders of magnitude smaller than the typical condensed water loading of cloudy updrafts. This causes evaporative cloud decay to act extremely slowly, thereby prolonging cloud lifetimes in the upper troposphere. As a consequence, extensive anvil clouds still occur in a convecting atmosphere that is forced to have no preferential clear-sky convergence layer. On the other hand, when cloud lifetimes are fixed at a characteristic lower-tropospheric value, extensive anvil clouds do not form. Our results support a revised understanding of tropical anvil clouds, which attributes their existence to the microphysics of slow cloud decay rather than a peak in clear-sky convergence.

EAULIQ: The Next Generation

NASA Technical Reports Server (NTRS)

Randall, David A.; Fowler, Laura D.

1999-01-01

This report summarizes the design of a new version of the stratiform cloud parameterization called Eauliq; the new version is called Eauliq NG. The key features of Eauliq NG are: (1) a prognostic fractional area covered by stratiform cloudiness, following the approach developed by M. Tiedtke for use in the ECMWF model; (2) separate prognostic thermodynamic variables for the clear and cloudy portions of each grid cell; (3) separate vertical velocities for the clear and cloudy portions of each grid cell, allowing the model to represent some aspects of observed mesoscale circulations; (4) cumulus entrainment from both the clear and cloudy portions of a grid cell, and cumulus detrainment into the cloudy portion only; and (5) the effects of the cumulus-induced subsidence in the cloudy portion of a grid cell on the cloud water and ice there. In this paper we present the mathematical framework of Eauliq NG; a discussion of cumulus effects; a new parameterization of lateral mass exchanges between clear and cloudy regions; and a theory to determine the mesoscale mass circulation, based on the hypothesis that the stratiform clouds remain neutrally buoyant through time and that the mesoscale circulations are the mechanism which makes this possible. An appendix also discusses some time-differencing methods.

Estimates of radiative flux divergence in the atmosphere from satellite data

NASA Technical Reports Server (NTRS)

Smith, G. L.; Charlock, Thomas P.; Bess, T. D.; Gupta, Shashi; Rutan, David; Rose, Fred G.

1990-01-01

Several options for the inference of the atmospheric radiative flux divergence (ARD) on the basis of satellite data are discussed. Attention is given to the clear-sky case and the cloudy-sky case. LW ARD profiles for different climatological regimes are presented and the effect of cloud base height on LW ARD divergence at various heights is illustrated.

Clear-sky remote sensing in the vicinity of clouds: what can be learned about aerosol changes?

NASA Astrophysics Data System (ADS)

Marshak, Alexander; Varnai, Tamas; Wen, Guoyong

2010-05-01

Studies on aerosol direct and indirect effects require a precise separation of cloud-free and cloudy air. However, separation between cloud-free and cloudy areas from remotely-sensed measurements is ambiguous. The transition zone in the regions around clouds often stretches out tens of km, which are neither precisely clear nor precisely cloudy. We study the transition zone between cloud-free and cloudy air using MODerate-resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) measurements. Both instruments show enhanced clear-sky reflectance (MODIS) and clear-sky backscatterer (CALIPSO) near clouds. Analyzing a large dataset of MODIS observations we examine the effect of three-dimensional (3D) radiative interactions between clouds and cloud-free areas, also known as a cloud adjacency effect. Comparing with CALIPSO clear-sky backscatterer measurements, we show that the cloud adjacency effect may be responsible for a large portion of the enhanced clear sky reflectance observed by MODIS. While aerosol particles are responsible for a large part of the near-cloud enhancements in CALIPSO observations, misidentified or undetected cloud particles are also likely to contribute. As a result, both the nature of these particles (cloud vs. aerosol) and the processes creating them need to be clarified using a quantitative assessment of remote sensing limitations in particle detection and identification. The width and ubiquity of the transition zone near clouds imply that studies of aerosol-cloud interactions and aerosol direct radiative effects need to account for aerosol changes near clouds. Not accounted, these changes can cause systematic biases toward smaller aerosol radiative forcing. On the other hand, including aerosol products near clouds despite their uncertainties may overestimate aerosol radiative forcing. Therefore, there is an urgent need for developing methods that can assess and account for remote sensing challenges and thus allow for including the transition zone into the study. We describe a simple model that estimates the cloud-induced enhanced reflectances of cloud-free areas in the vicinity of clouds. The model assumes that the enhancement is due entirely to Rayleigh scattering and is therefore bigger at shorter wavelengths, thus creating a so-called apparent "bluing" of aerosols in remote sensing retrievals.

Clear-sky remote sensing in the vicinity of clouds: what we learned from MODIS and CALIPSO

NASA Astrophysics Data System (ADS)

Marshak, Alexander; Varnai, Tamas; Wen, Guoyong; Cahalan, Robert

Studies on aerosol direct and indirect effects require a precise separation of cloud-free and cloudy air. However, separation between cloud-free and cloudy areas from remotely-sensed measurements is ambiguous. The transition zone in the regions around clouds often stretches out tens of km, which are neither precisely clear nor precisely cloudy. We study the transition zone between cloud-free and cloudy air using MODerate-resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) measurements. Both instruments show enhanced clear-sky reflectance (MODIS) and clear-sky backscatterer (CALIPSO) near clouds. Analyzing a large dataset of MODIS observations we examine the effect of three-dimensional (3D) radiative interactions between clouds and cloud-free areas, also known as a cloud adjacency effect. Comparing with CALIPSO clear-sky backscatterer measurements, we show that the cloud adjacency effect may be responsible for a large portion of the enhanced clear sky reflectance observed by MODIS. While aerosol particles are responsible for a large part of the near-cloud enhancements in CALIPSO observations, misidentified or undetected cloud particles are also likely to contribute. As a result, both the nature of these particles (cloud vs. aerosol) and the processes creating them need to be clarified using a quantitative assessment of remote sensing limitations in particle detection and identification. The width and ubiquity of the transition zone near clouds imply that studies of aerosol-cloud interactions and aerosol direct radiative effects need to account for aerosol changes near clouds. Not accounted, these changes can cause systematic biases toward smaller aerosol radiative forcing. On the other hand, including aerosol products near clouds despite their uncertainties may overestimate aerosol radiative forcing. Therefore, there is an urgent need for developing methods that can assess and account for remote sensing challenges and thus allow for including the transition zone into the study. We describe a simple model that estimates the cloud-induced enhanced reflectances of cloud-free areas in the vicinity of clouds. The model assumes that the enhancement is due entirely to Rayleigh scattering and is therefore bigger at shorter wavelengths, thus creating a so-called apparent "bluing" of aerosols in remote sensing retrievals.

Effect of clouds on UV and total irradiance at Paradise Bay, Antarctic Peninsula, from a summer 2000 campaign

NASA Astrophysics Data System (ADS)

Luccini, E.; Cede, A.; Piacentini, R. D.

The analysis of ground-based measurements of solar erythemal ultraviolet (UV) irradiance with a Solar Light 501 biometer, and total (300-3000nm) irradiance with an Eppley B&W pyranometer at the Argentine Antarctic Base ``Almirante Brown'', Paradise Bay (64.9°S, 62.9°W, 10ma.s.l.) is presented. Measurement period extends from February 16 to March 28 2000. A relatively high mean albedo and a very clean atmosphere characterise the place. Sky conditions were of generally high cloud cover percentage. Clear-sky irradiance for each day was estimated with model calculations, and the effect of the cloudiness was studied through the ratio of measured to clear-sky value (r). Two particular cases were analysed: overcast sky without precipitation and overcast sky with rain or slight snowfall, the last one presenting frequently dense fog. Total irradiance was more attenuated than UV by the homogeneous cloudiness, obtaining mean r values of 0.54 for erythemal irradiance and 0.30 for total irradiance in the first case (without precipitation) and 0.27 and 0.17 respectively in the second case (with precipitation). Mean r values for the complete period were 0.58 for erythemal irradiance and 0.43 for total irradiance. Erythemal and total daily insolations reduce quickly at this epoch due to the increase of the noon solar zenith angle and the decrease of daylight time. Additionally, they were strongly modulated by cloudiness. Measured maxima were 2.71kJ/m2 and 18.42MJ/m2 respectively. Measurements were compared with satellite data. TOMS-inferred erythemal daily insolation shows the typical underestimation with respect to ground measurements at regions of high mean albedo. Measured mean total daily insolation agrees with climatological satellite data for the months of the campaign.

Improved Estimates of Clear Sky Longwave Flux and Application to the Tropical Greenhouse Effect

NASA Technical Reports Server (NTRS)

Collins, W. D.

1997-01-01

The first objective of this investigation is to eliminate the clear-sky offset introduced by the scene-identification procedures developed for the Earth Radiation Budget Experiment (ERBE). Estimates of this systematic bias range from 10 to as high as 30 W/sq m. The initial version of the ScaRaB data is being processed with the original ERBE algorithm. Since the ERBE procedure for scene identification is based upon zonal flux averages, clear scenes with longwave emission well below the zonal mean value are mistakenly classified as cloudy. The erroneous classification is more frequent in regions with deep convection and enhanced mid- and upper-tropospheric humidity. We will develop scene identification parameters with zonal and/or time dependence to reduce or eliminate the bias in the clear- sky data. The modified scene identification procedure could be used for the ScaRaB-specific version of the Earth-radiation products. The second objective is to investigate changes in the clear-sky Outgoing Longwave Radiation (OLR) associated with decadal variations in the tropical and subtropical climate. There is considerable evidence for a shift in the climate state starting in approximately 1977. The shift is accompanied by higher SSTs in the equatorial Pacific, increased tropical convection, and higher values of atmospheric humidity. Other evidence indicates that the humidity in the tropical troposphere has been steadily increasing over the last 30 years. It is not known whether the atmospheric greenhouse effect has increased during this period in response to these changes in SST and precipitable water. We will investigate the decadal-scale fluctuations in the greenhouse effect using Nimbus-7, ERBE, and ScaRaB measurements spaning 1979 to the present. The data from the different satellites will be intercalibrated by comparison with model calculations based upon ship radiosonde observations. The fluxes calculated from the radiation model will also be used for validation of the ScaRaB fluxes.

A Method for Deriving All-Sky Evapotranspiration From the Synergistic Use of Remotely Sensed Images and Meteorological Data

NASA Astrophysics Data System (ADS)

Leng, Pei; Li, Zhao-Liang; Duan, Si-Bo; Tang, Ronglin; Gao, Mao-Fang

2017-12-01

Evapotranspiration (ET) is an important component of the water and energy cycle. The present study develops a practical approach for generating all-sky ET with the synergistic use of satellite images and meteorological data. In this approach, the ET over clear-sky pixels is estimated from a two-stage land surface temperature (LST)/fractional vegetation cover feature space method where the dry/wet edges are determined from theoretical calculations. For cloudy pixels, the Penman-Monteith equation is used to calculate the ET where no valid remotely sensed LST is available. An evaluation of the method with ET collected at ground-based large aperture scintillometer measurements at the Yucheng Comprehensive Experimental Station (YCES) in China is performed over a growth period from April to October 2010. The results show that the root-mean-square error (RMSE) and bias over clear-sky pixels are 57.3 W/m2 and 18.2 W/m2, respectively, whereas an RMSE of 69.3 W/m2 with a bias of 12.3 W/m2 can be found over cloudy pixels. Moreover, a reasonable overall RMSE of 65.3 W/m2 with a bias of 14.4 W/m2 at the YCES can be obtained under all-sky conditions, indicating a promising prospect for the derivation of all-sky ET using currently available satellite and meteorological data at a regional or global scale in future developments.

Psychophysical study of the visual sun location in pictures of cloudy and twilight skies inspired by Viking navigation.

PubMed

Barta, András; Horváth, Gábor; Meyer-Rochow, Victor Benno

2005-06-01

In the late 1960s it was hypothesized that Vikings had been able to navigate the open seas, even when the sun was occluded by clouds or below the sea horizon, by using the angle of polarization of skylight. To detect the direction of skylight polarization, they were thought to have made use of birefringent crystals, called "sun-stones," and a large part of the scientific community still firmly believe that Vikings were capable of polarimetric navigation. However, there are some critics who treat the usefulness of skylight polarization for orientation under partly cloudy or twilight conditions with extreme skepticism. One of their counterarguments has been the assumption that solar positions or solar azimuth directions could be estimated quite accurately by the naked eye, even if the sun was behind clouds or below the sea horizon. Thus under partly cloudy or twilight conditions there might have been no serious need for a polarimetric method to determine the position of the sun. The aim of our study was to test quantitatively the validity of this qualitative counterargument. In our psychophysical laboratory experiments, test subjects were confronted with numerous 180 degrees field-of-view color photographs of partly cloudy skies with the sun occluded by clouds or of twilight skies with the sun below the horizon. The task of the subjects was to guess the position or the azimuth direction of the invisible sun with the naked eye. We calculated means and standard deviations of the estimated solar positions and azimuth angles to characterize the accuracy of the visual sun location. Our data do not support the common belief that the invisible sun can be located quite accurately from the celestial brightness and/or color patterns under cloudy or twilight conditions. Although our results underestimate the accuracy of visual sun location by experienced Viking navigators, the mentioned counterargument cannot be taken seriously as a valid criticism of the theory of the alleged polarimetric Viking navigation. Our results, however, do not bear on the polarimetric theory itself.

Psychophysical study of the visual sun location in pictures of cloudy and twilight skies inspired by Viking navigation

NASA Astrophysics Data System (ADS)

Barta, András; Horváth, Gábor; Benno Meyer-Rochow, Victor

2005-06-01

In the late 1960s it was hypothesized that Vikings had been able to navigate the open seas, even when the sun was occluded by clouds or below the sea horizon, by using the angle of polarization of skylight. To detect the direction of skylight polarization, they were thought to have made use of birefringent crystals, called "sunstones," and a large part of the scientific community still firmly believe that Vikings were capable of polarimetric navigation. However, there are some critics who treat the usefulness of skylight polarization for orientation under partly cloudy or twilight conditions with extreme skepticism. One of their counterarguments has been the assumption that solar positions or solar azimuth directions could be estimated quite accurately by the naked eye, even if the sun was behind clouds or below the sea horizon. Thus under partly cloudy or twilight conditions there might have been no serious need for a polarimetric method to determine the position of the sun. The aim of our study was to test quantitatively the validity of this qualitative counterargument. In our psychophysical laboratory experiments, test subjects were confronted with numerous 180° field-of-view color photographs of partly cloudy skies with the sun occluded by clouds or of twilight skies with the sun below the horizon. The task of the subjects was to guess the position or the azimuth direction of the invisible sun with the naked eye. We calculated means and standard deviations of the estimated solar positions and azimuth angles to characterize the accuracy of the visual sun location. Our data do not support the common belief that the invisible sun can be located quite accurately from the celestial brightness and/or color patterns under cloudy or twilight conditions. Although our results underestimate the accuracy of visual sun location by experienced Viking navigators, the mentioned counterargument cannot be taken seriously as a valid criticism of the theory of the alleged polarimetric Viking navigation. Our results, however, do not bear on the polarimetric theory itself.

Cloud cover classification through simultaneous ground-based measurements of solar and infrared radiation

NASA Astrophysics Data System (ADS)

Orsini, Antonio; Tomasi, Claudio; Calzolari, Francescopiero; Nardino, Marianna; Cacciari, Alessandra; Georgiadis, Teodoro

2002-04-01

Simultaneous measurements of downwelling short-wave solar irradiance and incoming total radiation flux were performed at the Reeves Nevè glacier station (1200 m MSL) in Antarctica on 41 days from late November 1994 to early January 1995, employing the upward sensors of an albedometer and a pyrradiometer. The downwelling short-wave radiation measurements were analysed following the Duchon and O'Malley [J. Appl. Meteorol. 38 (1999) 132] procedure for classifying clouds, using the 50-min running mean values of standard deviation and the ratio of scaled observed to scaled clear-sky irradiance. Comparing these measurements with the Duchon and O'Malley rectangular boundaries and the local human observations of clouds collected on 17 days of the campaign, we found that the Duchon and O'Malley classification method obtained a success rate of 93% for cirrus and only 25% for cumulus. New decision criteria were established for some polar cloud classes providing success rates of 94% for cirrus, 67% for cirrostratus and altostratus, and 33% for cumulus and altocumulus. The ratios of the downwelling short-wave irradiance measured for cloudy-sky conditions to that calculated for clear-sky conditions were analysed in terms of the Kasten and Czeplak [Sol. Energy 24 (1980) 177] formula together with simultaneous human observations of cloudiness, to determine the empirical relationship curves providing reliable estimates of cloudiness for each of the three above-mentioned cloud classes. Using these cloudiness estimates, the downwelling long-wave radiation measurements (obtained as differences between the downward fluxes of total and short-wave radiation) were examined to evaluate the downwelling long-wave radiation flux normalised to totally overcast sky conditions. Calculations of the long-wave radiation flux were performed with the MODTRAN 3.7 code [Kneizys, F.X., Abreu, L.W., Anderson, G.P., Chetwynd, J.H., Shettle, E.P., Berk, A., Bernstein, L.S., Robertson, D.C., Acharya, P., Rothman, L.S., Selby, J.E.A., Gallery, W.O., Clough, S.A., 1996. In: Abreu, L.W., Anderson, G.P. (Eds.), The MODTRAN 2/3 Report and LOWTRAN 7 MODEL. Contract F19628-91-C.0132, Phillips Laboratory, Geophysics Directorate, PL/GPOS, Hanscom AFB, MA, 261 pp.] for both clear-sky and cloudy-sky conditions, considering various cloud types characterised by different cloud base altitudes and vertical thicknesses. From these evaluations, best-fit curves of the downwelling long-wave radiation flux were defined as a function of the cloud base height for the three polar cloud classes. Using these relationship curves, average estimates of the cloud base height were obtained from the three corresponding sub-sets of long-wave radiation measurements. The relative frequency histograms of the cloud base height defined by examining these three sub-sets were found to present median values of 4.7, 1.7 and 3.6 km for cirrus, cirrostratus/altostratus and cumulus/altocumulus, respectively, while median values of 6.5, 1.8 and 2.9 km were correspondingly determined by analysing only the measurements taken together with simultaneous cloud observations.

Diurnal Differences in OLR Climatologies and Anomaly Time Series

NASA Technical Reports Server (NTRS)

Susskind, Joel; Lee, Jae N.; Iredell, Lena; Loeb, Norm

2015-01-01

AIRS (Atmospheric Infrared Sounder) Version-6 OLR (Outgoing Long-Wave Radiation) matches CERES (Clouds and the Earth's Radiant Energy System) Edition-2.8 OLR very closely on a 1x1 latitude x longitude scale, both with regard to absolute values, and also with regard to anomalies of OLR. There is a bias of 3.5 watts per meter squared, which is nearly constant both in time and space. Contiguous areas contain large positive or negative OLR difference between AIRS and CERES are where the day-night difference of OLR is large. For AIRS, the larger the diurnal cycle, the more likely that sampling twice a day is inadequate. Lower values of OLRclr (Clear Sky OLR) and LWCRF (Longwave Cloud Radiative Forcing) in AIRS compared to CERES is at least in part a result of AIRS sampling over cold and cloudy cases.

Observation of the spectrally invariant properties of clouds in cloudy-to-clear transition zones during the MAGIC field campaign

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Weidong; Marshak, Alexander; McBride, Patrick J.

2016-12-01

We use the spectrally invariant method to study the variability of cloud optical thickness τ and droplet effective radius reff in transition zones (between the cloudy and clear sky columns) observed from Solar Spectral Flux Radiometer (SSFR) and Shortwave Array Spectroradiometer-Zenith (SASZe) during the Marine ARM GPCI Investigation of Clouds (MAGIC) field campaign. The measurements from the SSFR and the SASZe are different, however inter-instrument differences of self-normalized measurements (divided by their own spectra at a fixed time) are small. The spectrally invariant method approximates the spectra in the cloud transition zone as a linear combination of definitely clear andmore » cloudy spectra, where the coefficients, slope and intercept, character-ize the spectrally invariant properties of the transition zone. Simulation results from the SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer) model demonstrate that (1) the slope of the visible band is positively correlated with the cloud optical thickness τ while the intercept of the near-infrared band has high negative cor-relation with the cloud drop effective radius reff even without the exact knowledge of τ; (2) the above relations hold for all Solar Zenith Angle (SZA) and for cloud-contaminated skies. In observations using redundant measure-ments from SSFR and SASZe, we find that during cloudy-to-clear transitions, (a) the slopes of the visible band de-crease, and (b) the intercepts of the near-infrared band remain almost constant near cloud edges. The findings in simulations and observations suggest that, while the optical thickness decreases during the cloudy-to-clear transition, the cloud drop effective radius does not change when cloud edges are approached. These results sup-port the hypothesis that inhomogeneous mixing dominates near cloud edges in the studied cases.« less

Observation of the spectrally invariant properties of clouds in cloudy-to-clear transition zones during the MAGIC field campaign

DOE PAGES

Yang, Weidong; Marshak, Alexander; McBride, Patrick J.; ...

2016-08-11

We use the spectrally invariant method to study the variability of cloud optical thickness τ and droplet effective radius r eff in transition zones (between the cloudy and clear sky columns) observed from Solar Spectral Flux Radiometer (SSFR) and Shortwave Array Spectroradiometer-Zenith (SASZe) during the Marine ARM GPCI Investigation of Clouds (MAGIC) field campaign. The measurements from the SSFR and the SASZe are different, however inter-instrument differences of self-normalized measurements (divided by their own spectra at a fixed time) are small. The spectrally invariant method approximates the spectra in the cloud transition zone as a linear combination of definitely clearmore » and cloudy spectra, where the coefficients, slope and intercept, characterize the spectrally invariant properties of the transition zone. Simulation results from the SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer) model demonstrate that (1) the slope of the visible band is positively correlated with the cloud optical thickness τ while the intercept of the near-infrared band has high negative correlation with the cloud drop effective radius r eff even without the exact knowledge of τ; (2) the above relations hold for all Solar Zenith Angle (SZA) and for cloud-contaminated skies. In observations using redundant measurements from SSFR and SASZe, we find that during cloudy-to-clear transitions, (a) the slopes of the visible band decrease, and (b) the intercepts of the near-infrared band remain almost constant near cloud edges. The findings in simulations and observations suggest that, while the optical thickness decreases during the cloudy-to-clear transition, the cloud drop effective radius does not change when cloud edges are approached. Furthermore, these results support the hypothesis that inhomogeneous mixing dominates near cloud edges in the studied cases.« less

Observation of the Spectrally Invariant Properties of Clouds in Cloudy-to-Clear Transition Zones During the MAGIC Field Campaign

NASA Technical Reports Server (NTRS)

Yang, Weidong; Marshak, Alexander; McBride, Patrick; Chiu, J. Christine; Knyazikhin, Yuri; Schmidt, K. Sebastian; Flynn, Connor; Lewis, Ernie R.; Eloranta, Edwin W.

2016-01-01

We use the spectrally invariant method to study the variability of cloud optical thickness tau and droplet effective radius r(sub eff) in transition zones (between the cloudy and clear sky columns) observed from Solar Spectral Flux Radiometer (SSFR) and Shortwave Array Spectroradiometer-Zenith (SASZe) during the Marine ARM GPCI Investigation of Clouds (MAGIC) field campaign. The measurements from the SSFR and the SASZe are different, however inter-instrument differences of self-normalized measurements (divided by their own spectra at a fixed time) are small. The spectrally invariant method approximates the spectra in the cloud transition zone as a linear combination of definitely clear and cloudy spectra, where the coefficients, slope and intercept, characterize the spectrally invariant properties of the transition zone. Simulation results from the SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer) model demonstrate that (1) the slope of the visible band is positively correlated with the cloud optical thickness t while the intercept of the near-infrared band has high negative correlation with the cloud drop effective radius r(sub eff)even without the exact knowledge of tau; (2) the above relations hold for all Solar Zenith Angle (SZA) and for cloud-contaminated skies. In observations using redundant measurements from SSFR and SASZe, we find that during cloudy-to-clear transitions, (a) the slopes of the visible band decrease, and (b) the intercepts of the near-infrared band remain almost constant near cloud edges. The findings in simulations and observations suggest that, while the optical thickness decreases during the cloudy-to-clear transition, the cloud drop effective radius does not change when cloud edges are approached. These results support the hypothesis that inhomogeneous mixing dominates near cloud edges in the studied cases.

Earth Observation

NASA Image and Video Library

2014-05-31

Earth Observation taken during a day pass by the Expedition 40 crew aboard the International Space Station (ISS). Folder lists this as: CEO - Arena de Sao Paolo. View used for Twitter message: Cloudy skies over São Paulo Brazil

A speeded-up saliency region-based contrast detection method for small targets

NASA Astrophysics Data System (ADS)

Li, Zhengjie; Zhang, Haiying; Bai, Jiaojiao; Zhou, Zhongjun; Zheng, Huihuang

2018-04-01

To cope with the rapid development of the real applications for infrared small targets, the researchers have tried their best to pursue more robust detection methods. At present, the contrast measure-based method has become a promising research branch. Following the framework, in this paper, a speeded-up contrast measure scheme is proposed based on the saliency detection and density clustering. First, the saliency region is segmented by saliency detection method, and then, the Multi-scale contrast calculation is carried out on it instead of traversing the whole image. Second, the target with a certain "integrity" property in spatial is exploited to distinguish the target from the isolated noises by density clustering. Finally, the targets are detected by a self-adaptation threshold. Compared with time-consuming MPCM (Multiscale Patch Contrast Map), the time cost of the speeded-up version is within a few seconds. Additional, due to the use of "clustering segmentation", the false alarm caused by heavy noises can be restrained to a lower level. The experiments show that our method has a satisfied FASR (False alarm suppression ratio) and real-time performance compared with the state-of-art algorithms no matter in cloudy sky or sea-sky background.

New challenges in solar energy resource and forecasting in Greece

NASA Astrophysics Data System (ADS)

Kazantzidis, A.; Nikitidou, E.; Salamalikis, V.; Tzoumanikas, P.; Zagouras, A.

2018-05-01

Aerosols and clouds are the most important constituents in the atmosphere that affect the incoming solar radiation, either directly through absorbing and scattering processes or indirectly by changing the optical properties and lifetime of clouds. Under clear skies, aerosols become the dominant factor that affect the intensity of solar irradiance reaching the ground. Under cloudy skies, the high temporal and spatial variability of cloudiness is the key factor for the estimation of solar irradiance. In this study, recent research activities related to the climatology and the prediction of solar energy in Greece are presented with emphasis on new challenges in the climatology of global horizontal irradiance (GHI) and direct normal irradiance (DNI), the changes of DNI due to the decreasing aerosol optical depth and the short-term (15-240 min) forecasts of solar irradiance with the collaborative use of neural networks and satellite images.

Quantifying and Modelling the Effect of Cloud Shadows on the Surface Irradiance at Tropical and Midlatitude Forests

NASA Astrophysics Data System (ADS)

Kivalov, Sergey N.; Fitzjarrald, David R.

2018-02-01

Cloud shadows lead to alternating light and dark periods at the surface, with the most abrupt changes occurring in the presence of low-level forced cumulus clouds. We examine multiyear irradiance time series observed at a research tower in a midlatitude mixed deciduous forest (Harvard Forest, Massachusetts, USA: 42.53{°}N, 72.17{°}W) and one made at a similar tower in a tropical rain forest (Tapajós National Forest, Pará, Brazil: 2.86{°}S, 54.96{°}W). We link the durations of these periods statistically to conventional meteorological reports of sky type and cloud height at the two forests and present a method to synthesize the surface irradiance time series from sky-type information. Four classes of events describing distinct sequential irradiance changes at the transition from cloud shadow and direct sunlight are identified: sharp-to-sharp, slow-to-slow, sharp-to-slow, and slow-to-sharp. Lognormal and the Weibull statistical distributions distinguish among cloudy-sky types. Observers' qualitative reports of `scattered' and `broken' clouds are quantitatively distinguished by a threshold value of the ratio of mean clear to cloudy period durations. Generated synthetic time series based on these statistics adequately simulate the temporal "radiative forcing" linked to sky type. Our results offer a quantitative way to connect the conventional meteorological sky type to the time series of irradiance experienced at the surface.

Bridging the Radiative Transfer Models for Meteorology and Solar Energy Applications

NASA Astrophysics Data System (ADS)

Xie, Y.; Sengupta, M.

2017-12-01

Radiative transfer models are used to compute solar radiation reaching the earth surface and play an important role in both meteorology and solar energy studies. Therefore, they are designed to meet the needs of specialized applications. For instance, radiative transfer models for meteorology seek to provide more accurate cloudy-sky radiation compared to models used in solar energy that are geared towards accuracy in clear-sky conditions associated with the maximum solar resource. However, models for solar energy applications are often computationally faster, as the complex solution of the radiative transfer equation is parameterized by atmospheric properties that can be acquired from surface- or satellite-based observations. This study introduces the National Renewable Energy Laboratory's (NREL's) recent efforts to combine the advantages of radiative transfer models designed for meteorology and solar energy applictions. A fast all-sky radiation model, FARMS-NIT, was developed to efficiently compute narrowband all-sky irradiances over inclined photovoltaic (PV) panels. This new model utilizes the optical preperties from a solar energy model, SMARTS, to computes surface radiation by considering all possible paths of photon transmission and the relevent scattering and absorption attenuation. For cloudy-sky conditions, cloud bidirectional transmittance functions (BTDFs) are provided by a precomputed lookup table (LUT) by LibRadtran. Our initial results indicate that FARMS-NIT has an accuracy that is similar to LibRadtran, a highly accurate multi-stream model, but is significantly more efficient. The development and validation of this model will be presented.

Observed Spectral Invariant Behavior of Zenith Radiance in the Transition Zone Between Cloud-Free and Cloudy Regions

NASA Technical Reports Server (NTRS)

Marshak, A.; Knyazikhin, Y.; Chiu, C.; Wiscombe, W.

2010-01-01

The Atmospheric Radiation Measurement Program's (ARM) new Shortwave Spectrometer (SWS) looks straight up and measures zenith radiance at 418 wavelengths between 350 and 2200 nm. Because of its 1-sec sampling resolution, the SWS provides a unique capability to study the transition zone between cloudy and clear sky areas. A surprising spectral invariant behavior is found between ratios of zenith radiance spectra during the transition from cloudy to cloud-free atmosphere. This behavior suggests that the spectral signature of the transition zone is a linear mixture between the two extremes (definitely cloudy and definitely clear). The weighting function of the linear mixture is found to be a wavelength-independent characteristic of the transition zone. It is shown that the transition zone spectrum is fully determined by this function and zenith radiance spectra of clear and cloudy regions. This new finding may help us to better understand and quantify such physical phenomena as humidification of aerosols in the relatively moist cloud environment and evaporation and activation of cloud droplets.

Studies in the parameterization of cloudiness in climate models and the analysis of radiation fields in general circulation models

NASA Technical Reports Server (NTRS)

HARSHVARDHAN

1990-01-01

Broad-band parameterizations for atmospheric radiative transfer were developed for clear and cloudy skies. These were in the shortwave and longwave regions of the spectrum. These models were compared with other models in an international effort called ICRCCM (Intercomparison of Radiation Codes for Climate Models). The radiation package developed was used for simulations of a General Circulation Model (GCM). A synopsis is provided of the research accomplishments in the two areas separately. Details are available in the published literature.

Measuring high-resolution sky luminance distributions with a CCD camera.

PubMed

Tohsing, Korntip; Schrempf, Michael; Riechelmann, Stefan; Schilke, Holger; Seckmeyer, Gunther

2013-03-10

We describe how sky luminance can be derived from a newly developed hemispherical sky imager (HSI) system. The system contains a commercial compact charge coupled device (CCD) camera equipped with a fish-eye lens. The projection of the camera system has been found to be nearly equidistant. The luminance from the high dynamic range images has been calculated and then validated with luminance data measured by a CCD array spectroradiometer. The deviation between both datasets is less than 10% for cloudless and completely overcast skies, and differs by no more than 20% for all sky conditions. The global illuminance derived from the HSI pictures deviates by less than 5% and 20% under cloudless and cloudy skies for solar zenith angles less than 80°, respectively. This system is therefore capable of measuring sky luminance with the high spatial and temporal resolution of more than a million pixels and every 20 s respectively.

Observational evidence of fire-driven changes to tropical cloudiness

NASA Astrophysics Data System (ADS)

Tosca, Michael; Diner, David; Garay, Michael; Kalashnikova, Olga

2014-05-01

Anthropogenic fires in the tropics emit smoke aerosols that affect cloud dynamics, meteorology and climate (Tosca et al., 2013). We developed a new technique to observationally quantify the cloud response to biomass burning aerosols using aerosol retrievals from the Multi-angle Imaging SpectroRadiometer (MISR) and non-coincident cloud retrievals from the MODerate resolution Imaging Spectroradiometer (MODIS) from collocated morning and afternoon overpasses. The Global Fire Emissions Database, version 3 and Level 2 data from scenes acquired between 2006 and 2010 were used to quantify changes in cloud fraction from morning (10:30am local time) to afternoon (1:30pm local time) in the presence of varying fire-aerosol burdens. This temporal offset allowed for analysis of the evolution of clouds in the presence of aerosols, something that previous methods using coincident observations could not produce. We controlled for large-scale meteorological differences between scenes using reanalysis data from the ERA-interim product and matching scenes with fire smoke to those with no smoke and similar initial (morning) meteorological conditions. Elevated aerosol optical depths (AODs) reduced cloud fraction from morning to afternoon in the Southeast Asia, Central America and northern Africa burning regions. In mostly cloudy conditions, aerosols significantly reduced cloud fraction, but in clear skies, cloud fraction increased. These results support the general hypothesis of a positive feedback loop between anthropogenic burning and cloudiness in tropical regions, and are consistent with previous studies linking smoke aerosols to convective cloud reduction. Tosca, M.G., J.T. Randerson and C.S. Zender (2013), Global impact of smoke aerosols from landscape fires on climate and the Hadley circulation, Atmos. Chem. Phys., 13, 5227-5241, doi: 10.5194/acp-13-5227-2013.

Tracking the dynamics of skyglow with differential photometry using a digital camera with fisheye lens

NASA Astrophysics Data System (ADS)

Jechow, Andreas; Ribas, Salvador J.; Domingo, Ramon Canal; Hölker, Franz; Kolláth, Zoltán; Kyba, Christopher C. M.

2018-04-01

Artificial skyglow is dynamic due to changing atmospheric conditions and the switching on and off of artificial lights throughout the night. Street lights as well as the ornamental illumination of historical sites and buildings are sometimes switched off at a certain time to save energy. Ornamental lights in particular are often directed upwards, and can therefore have a major contribution towards brightening of the night sky. Here we use differential photometry to investigate the change in night sky brightness and illuminance during an automated regular switch-off of ornamental light in the town of Balaguer and an organized switch-off of all public lights in the village of Àger, both near Montsec Astronomical Park in Spain. The sites were observed during two nights with clear and cloudy conditions using a DSLR camera and a fisheye lens. A time series of images makes it possible to track changes in lighting conditions and sky brightness simultaneously. During the clear night, the ornamental lights in Balaguer contribute over 20% of the skyglow at zenith at the observational site. Furthermore, we are able to track very small changes in the ground illuminance on a cloudy night near Àger.

Climatological Data For Clouds Over the Globe From Surface Observations, 1982-1991: The Total Cloud Edition (1994) (NDP-026a)

DOE Data Explorer

Hahn, Carole J. [Univ. of Colorado, Boulder, CO (United States). Cooperative Inst. for Research in Environmental Sciences (CIRES); Warren, Stephen G. [Department of Atmospheric Sciences, University of Colorado, Boulder, CO; London, Julius [Department of Astrophysical, Planetary, and Atmospheric Sciences, University of Colorado, Boulder, CO

1994-01-01

Routine, synoptic surface weather reports from ships and land stations over the entire globe, for the10-year period December 1981 through November 1991, were processed for total cloud cover and the frequencies of occurrence of clear sky, sky-obscured due to precipitation, and sky-obscured due to fog. Archived data, consisting of various annual, seasonal and monthly averages, are provided in grid boxes that are typically 2.5° × 2.5° for land and 5° × 5° for ocean. Day and nighttime averages are also given separately for each season. Several derived quantities, such as interannual variations and annual and diurnal harmonics, are provided as well. This data set incorporates an improved representation of nighttime cloudiness by utilizing only those nighttime observations for which the illuminance due to moonlight exceeds a specified threshold. This reduction in the night-detection bias increases the computed global average total cloud cover by about 2%. The impact on computed diurnal cycles is even greater, particularly over the oceans where it is found (in contrast to previous surface-based climatologies), that cloudiness is often greater at night than during the day.

Influence of cloud fraction and snow cover to the variation of surface UV radiation at King Sejong station, Antarctica

NASA Astrophysics Data System (ADS)

Lee, Yun Gon; Koo, Ja-Ho; Kim, Jhoon

2015-10-01

This study investigated how cloud fraction and snow cover affect the variation of surface ultraviolet (UV) radiation by using surface Erythemal UV (EUV) and Near UV (NUV) observed at the King Sejong Station, Antarctica. First the Radiative Amplification Factor (RAF), the relative change of surface EUV according to the total-column ozone amount, is compared for different cloud fractions and solar zenith angles (SZAs). Generally, all cloudy conditions show that the increase of RAF as SZA becomes larger, showing the larger effects of vertical columnar ozone. For given SZA cases, the EUV transmission through mean cloud layer gradually decreases as cloud fraction increases, but sometimes the maximum of surface EUV appears under partly cloudy conditions. The high surface EUV transmittance under broken cloud conditions seems due to the re-radiation of scattered EUV by cloud particles. NUV transmission through mean cloud layer also decreases as cloud amount increases but the sensitivity to the cloud fraction is larger than EUV. Both EUV and NUV radiations at the surface are also enhanced by the snow cover, and their enhancement becomes higher as SZA increases implying the diurnal variation of surface albedo. This effect of snow cover seems large under the overcast sky because of the stronger interaction between snow surface and cloudy sky.

Spectral Invariant Behavior of Zenith Radiance Around Cloud Edges Observed by ARM SWS

NASA Technical Reports Server (NTRS)

Marshak, A.; Knyazikhin, Y.; Chiu, J. C.; Wiscombe, W. J.

2009-01-01

The ARM Shortwave Spectrometer (SWS) measures zenith radiance at 418 wavelengths between 350 and 2170 nm. Because of its 1-sec sampling resolution, the SWS provides a unique capability to study the transition zone between cloudy and clear sky areas. A spectral invariant behavior is found between ratios of zenith radiance spectra during the transition from cloudy to cloud-free. This behavior suggests that the spectral signature of the transition zone is a linear mixture between the two extremes (definitely cloudy and definitely clear). The weighting function of the linear mixture is a wavelength-independent characteristic of the transition zone. It is shown that the transition zone spectrum is fully determined by this function and zenith radiance spectra of clear and cloudy regions. An important result of these discoveries is that high temporal resolution radiance measurements in the clear-to-cloud transition zone can be well approximated by lower temporal resolution measurements plus linear interpolation.

Cloudy Sounding and Cloud-Top Height Retrieval From AIRS Alone Single Field-of-View Radiance Measurements

NASA Technical Reports Server (NTRS)

Weisz, Elisabeth; Li, Jun; Li, Jinlong; Zhou, Daniel K.; Huang, Hung-Lung; Goldberg, Mitchell D.; Yang, Ping

2007-01-01

High-spectral resolution measurements from the Atmospheric Infrared Sounder (AIRS) onboard the EOS (Earth Observing System) Aqua satellite provide unique information about atmospheric state, surface and cloud properties. This paper presents an AIRS alone single field-of-view (SFOV) retrieval algorithm to simultaneously retrieve temperature, humidity and ozone profiles under all weather conditions, as well as cloud top pressure (CTP) and cloud optical thickness (COT) under cloudy skies. For optically thick cloud conditions the above-cloud soundings are derived, whereas for clear skies and optically thin cloud conditions the profiles are retrieved from 0.005 hPa down to the earth's surface. Initial validation has been conducted by using the operational MODIS (Moderate Resolution Imaging Spectroradiometer) product, ECMWF (European Center of Medium range Weather Forecasts) analysis fields and radiosonde observations (RAOBs). These inter-comparisons clearly demonstrate the potential of this algorithm to process data from 38 high-spectral infrared (IR) sounder instruments.

Systematic measurements of the night sky brightness at 26 locations in Eastern Austria

NASA Astrophysics Data System (ADS)

Posch, Thomas; Binder, Franz; Puschnig, Johannes

2018-05-01

We present an analysis of the zenithal night sky brightness (henceforth: NSB) measurements at 26 locations in Eastern Austria focussing on the years 2015-2016, both during clear and cloudy to overcast nights. All measurements have been performed with 'Sky Quality Meters' (SQMs). For some of the locations, simultaneous aerosol content measurements are available, such that we were able to find a correlation between light pollution and air pollution at those stations. For all locations, we examined the circalunar periodicity of the NSB, seasonal variations as well as long-term trends in the recorded light pollution. The latter task proved difficult, however, due to varying meteorological conditions, potential detector 'aging' and other effects. For several remote locations, a darkening of the overcast night sky by up to 1 magnitude is recorded - indicating a very low level of light pollution -, while for the majority of the examined locations, a brightening of the night sky by up to a factor of 15 occurs due to clouds. We present suitable ways to plot and analyze huge long-term NSB datasets, such as mean-NSB histograms, circalunar, annual ('hourglass') and cumulative ('jellyfish') plots. We show that five of the examined locations reach sufficiently low levels of light pollution - with NSB values down to 21.8 magSQM/arcsec2 - as to allow the establishment of dark sky reserves, even to the point of reaching the 'gold tier' defined by the International Dark Sky Association. Based on the 'hourglass' plots, we find a strong circalunar periodicity of the NSB in small towns and villages ( < 5.000 inhabitants), with amplitudes of up to 5 magnitudes. Using the 'jellyfish' plots, on the other hand, we demonstrate that the examined city skies brighten by up to 3 magnitudes under cloudy conditions, which strongly dominate in those cumulative data representations. Nocturnal gradients of the NSB of 0.0-0.14 magSQM/arcsec2/h are found. The long-term development of the night sky brightness was evaluated based on the 2012-17 data for one of our sites, possibly indicating a slight ( 2%) decrease of the mean zenithal NSB at the Vienna University Observatory.

Reconstructing daily clear-sky land surface temperature for cloudy regions from MODIS data

USDA-ARS?s Scientific Manuscript database

Land surface temperature (LST) is a critical parameter in environmental studies and resource management. The MODIS LST data product has been widely used in various studies, such as drought monitoring, evapotranspiration mapping, soil moisture estimation and forest fire detection. However, cloud cont...

Imaging and mapping the impact of clouds on skyglow with all-sky photometry.

PubMed

Jechow, Andreas; Kolláth, Zoltán; Ribas, Salvador J; Spoelstra, Henk; Hölker, Franz; Kyba, Christopher C M

2017-07-27

Artificial skyglow is constantly growing on a global scale, with potential ecological consequences ranging up to affecting biodiversity. To understand these consequences, worldwide mapping of skyglow for all weather conditions is urgently required. In particular, the amplification of skyglow by clouds needs to be studied, as clouds can extend the reach of skyglow into remote areas not affected by light pollution on clear nights. Here we use commercial digital single lens reflex cameras with fisheye lenses for all-sky photometry. We track the reach of skyglow from a peri-urban into a remote area on a clear and a partly cloudy night by performing transects from the Spanish town of Balaguer towards Montsec Astronomical Park. From one single all-sky image, we extract zenith luminance, horizontal and scalar illuminance. While zenith luminance reaches near-natural levels at 5 km distance from the town on the clear night, similar levels are only reached at 27 km on the partly cloudy night. Our results show the dramatic increase of the reach of skyglow even for moderate cloud coverage at this site. The powerful and easy-to-use method promises to be widely applicable for studies of ecological light pollution on a global scale also by non-specialists in photometry.

How Well Can Infrared Sounders Observe the Atmosphere and Surface Through Clouds?

NASA Technical Reports Server (NTRS)

Zhou, Daniel K.; Larar, Allen M.; Liu, Xu; Smith, William L.; Strow, L. Larrabee; Yang, Ping

2010-01-01

Infrared sounders, such as the Atmospheric Infrared Sounder (AIRS), the Infrared Atmospheric Sounding Interferometer (IASI), and the Cross-track Infrared sounder (CrIS), have a cloud-impenetrable disadvantage in observing the atmosphere and surface under opaque cloudy conditions. However, recent studies indicate that hyperspectral, infrared sounders have the ability to detect cloud effective-optical and microphysical properties and to penetrate optically thin clouds in observing the atmosphere and surface to a certain degree. We have developed a retrieval scheme dealing with atmospheric conditions with cloud presence. This scheme can be used to analyze the retrieval accuracy of atmospheric and surface parameters under clear and cloudy conditions. In this paper, we present the surface emissivity results derived from IASI global measurements under both clear and cloudy conditions. The accuracy of surface emissivity derived under cloudy conditions is statistically estimated in comparison with those derived under clear sky conditions. The retrieval error caused by the clouds is shown as a function of cloud optical depth, which helps us to understand how well infrared sounders can observe the atmosphere and surface through clouds.

Assessment of clear sky radiative fluxes in CMIP5 climate models using surface observations from BSRN

NASA Astrophysics Data System (ADS)

Wild, M.; Hakuba, M. Z.; Folini, D.; Ott, P.; Long, C. N.

2017-12-01

Clear sky fluxes in the latest generation of Global Climate Models (GCM) from CMIP5 still vary largely particularly at the Earth's surface, covering in their global means a range of 16 and 24 Wm-2 in the surface downward clear sky shortwave (SW) and longwave radiation, respectively. We assess these fluxes with monthly clear sky reference climatologies derived from more than 40 Baseline Surface Radiation Network (BSRN) sites based on Long and Ackermann (2000) and Hakuba et al. (2015). The comparison is complicated by the fact that the monthly SW clear sky BSRN reference climatologies are inferred from measurements under true cloud-free conditions, whereas the GCM clear sky fluxes are calculated continuously at every timestep solely by removing the clouds, yet otherwise keeping the prevailing atmospheric composition (e.g. water vapor, temperature, aerosols) during the cloudy conditions. This induces the risk of biases in the GCMs just due to the additional sampling of clear sky fluxes calculated under atmospheric conditions representative for cloudy situations. Thereby, a wet bias may be expected in the GCMs compared to the observational references, which may induce spurious low biases in the downward clear sky SW fluxes. To estimate the magnitude of these spurious biases in the available monthly mean fields from 40 CMIP5 models, we used their respective multi-century control runs, and searched therein for each month and each BSRN station the month with the lowest cloud cover. The deviations of the clear sky fluxes in this month from their long-term means have then be used as indicators of the magnitude of the abovementioned sampling biases and as correction factors for an appropriate comparison with the BSRN climatologies, individually applied for each model and BSRN site. The overall correction is on the order of 2 Wm-2. This revises our best estimate for the global mean surface downward SW clear sky radiation, previously at 249 Wm-2 infered from the GCM clear sky flux fields and their biases compared to the BSRN climatologies, now to 247 Wm-2 including this additional correction. 34 out of 40 CMIP5 GCMs exceed this reference value. With a global mean surface albedo of 13 % and net TOA SW clear sky flux of 287 Wm-2 from CERES-EBAF this results in a global mean clear sky surface and atmospheric SW absorption of 214 and 73 Wm-2, respectively.

Effects of Cloudiness on the Daily and Annual Radiation Balance: Elaboration on the Shartwave and Longwave Radiation

NASA Astrophysics Data System (ADS)

Malek, E.

2007-12-01

Clouds are visible masses of condensed droplets and frozen crystals of water in the atmosphere above the Earth. They make changes in the energy balance at local, regional, and planetary scales. They affect the climate by positive and negative feedback. To study these effects at local scale, we set up a radiation station which uses two CM21 Kipp & Zonen pyranometers (one inverted), and two CG1 Kipp & Zonen pyrgeometers (one inverted) in a semi-arid mountainous valley in Logan, Utah, U.S.A. The pyranometers and pyrgeometers were ventilated using four CV2 Kipp & Zonen ventilation systems. Ventilation of pyranometers and pyrgeometers prevents dew and frost and snow accumulation which otherwise would disturb the measurement. All sensors were installed at about 3 m above the ground, which is covered with natural vegetation during the growing season (May - September). The incoming (Rsi) and outgoing (Rso) solar or shortwave radiation, the incoming (Rli, atmospheric) and outgoing (Rlo, terrestrial) longwave radiation, along with the 2-m air temperature, humidity, and pressure have been continuously measured since 1995. We also measured the 3-m wind speed and direction, the surface temperature (using an IR thermometer) and precipitation (using a heated rain gauge). These parameters have been measured every 2 seconds and averaged into 20 minutes. For this study we chose three days: 6 April (a partially cloudy day), 29 July (a cloudless day), and 29 November (an overcast day), 2005, along with continuous study throughout the year 2005. We developed an algorithm for evaluation of cloudless-sky incoming (atmospheric) longwave radiation. Equations for cloudless-sky incoming shortwave and atmospheric longwave radiation were applied to compare the cloud-free measurements with the actual ones. Cloudless - measured incoming shortwave (solar) radiation is an indication of how much less radiation was received due to cloudiness (if any). Measured - cloudless incoming longwave (atmospheric) radiation shows the cloud (if any) contribution to the radiation budget. The results indicate that for the partial cloudy day of 6 April, 2005, cloudiness caused less shortwave radiation 23.29 - 13.76 = 9.53 MJ m-2 d-1 received at the surface. On the same day cloud contributed an additional radiation of 25.44 - 23.44 = 2.00 MJ m-2 d-1. On 29 November, 2005, these values were 9.37 - 1.98 = 7.39 and 28.82 - 23.86 = 4.96 MJ m-2 d-1, respectively. On the annual basis, the 2005 cloudiness caused a reduction of 7279 - 5800 = 1479 MJ m-2 y-1 for the shortwave radiation, while the additional longwave radiation due to cloudiness amounted to 9976 - 9573 = 403 MJ m-2 y-1. The cloudiness in 2005 caused a negative feedback on the climate in this valley.

Validation of a weather forecast model at radiance level against satellite observations allowing quantification of temperature, humidity, and cloud-related biases

NASA Astrophysics Data System (ADS)

Bani Shahabadi, Maziar; Huang, Yi; Garand, Louis; Heilliette, Sylvain; Yang, Ping

2016-09-01

An established radiative transfer model (RTM) is adapted for simulating all-sky infrared radiance spectra from the Canadian Global Environmental Multiscale (GEM) model in order to validate its forecasts at the radiance level against Atmospheric InfraRed Sounder (AIRS) observations. Synthetic spectra are generated for 2 months from short-term (3-9 h) GEM forecasts. The RTM uses a monthly climatological land surface emissivity/reflectivity atlas. An updated ice particle optical property library was introduced for cloudy radiance calculations. Forward model brightness temperature (BT) biases are assessed to be of the order of ˜1 K for both clear-sky and overcast conditions. To quantify GEM forecast meteorological variables biases, spectral sensitivity kernels are generated and used to attribute radiance biases to surface and atmospheric temperatures, atmospheric humidity, and clouds biases. The kernel method, supplemented with retrieved profiles based on AIRS observations in collocation with a microwave sounder, achieves good closure in explaining clear-sky radiance biases, which are attributed mostly to surface temperature and upper tropospheric water vapor biases. Cloudy-sky radiance biases are dominated by cloud-induced radiance biases. Prominent GEM biases are identified as: (1) too low surface temperature over land, causing about -5 K bias in the atmospheric window region; (2) too high upper tropospheric water vapor, inducing about -3 K bias in the water vapor absorption band; (3) too few high clouds in the convective regions, generating about +10 K bias in window band and about +6 K bias in the water vapor band.

Ultraviolet and visible radiation at Barrow, Alaska: Climatology and influencing factors on the basis of version 2 National Science Foundation network data

NASA Astrophysics Data System (ADS)

Bernhard, Germar; Booth, Charles R.; Ehramjian, James C.; Stone, Robert; Dutton, Ellsworth G.

2007-05-01

Spectral ultraviolet (UV) and visible irradiance has been measured near Barrow, Alaska (71°N, 157°W), between 1991 and 2005 with a SUV-100 spectroradiometer. The instrument is part of the U.S. National Science Foundation's UV Monitoring Network. Here we present results based on the recently produced "version 2" data release, which supersedes published "version 0" data. Cosine error and wavelength-shift corrections applied to the new version increased biologically effective UV dose rates by 0-10%. Corrected clear-sky measurements of different years are typically consistent to within ±3%. Measurements were complemented with radiative transfer model calculations to retrieve total ozone and surface albedo from measured spectra and for the separation of the different factors influencing UV and visible radiation. A climatology of UV and visible radiation was established, focusing on annual cycles, trends, and the effect of clouds. During several episodes in spring of abnormally low total ozone, the daily UV dose at 305 nm exceeded the climatological mean by up to a factor of 2.6. Typical noontime UV Indices during summer vary between 2 and 4; the highest UV Index measured was 5.0 and occurred when surface albedo was unusually high. Radiation levels in the UV-A and visible exhibit a strong spring-autumn asymmetry. Irradiance at 345 nm peaks on approximately 20 May, 1 month before the solstice. This asymmetry is caused by increased cloudiness in autumn and high albedo in spring, when the snow covered surface enhances downwelling UV irradiance by up to 57%. Clouds reduce UV radiation at 345 nm on average by 4% in March and by more than 40% in August. Aerosols reduce UV by typically 5%, but larger reductions were observed during Arctic haze events. Stratospheric aerosols from the Pinatubo eruption in 1991 enhanced spectral irradiance at 305 nm for large solar zenith angles. The year-to-year variations of spectral irradiance at 305 nm and of the UV Index are mostly caused by variations in total ozone and cloudiness. Changes in surface albedo that may occur in the future can have a marked impact on UV levels between May and July. No statistically significant trends in monthly mean noontime irradiance were found.

Student Recruitment and Retention Efforts in PETE: Cloudy Skies or Silver Linings

ERIC Educational Resources Information Center

Bulger, Sean M.; Braga, Luciana; DiGiacinto, Kacey; Jones, Emily M.

2016-01-01

This article addresses current issues and trends related to teacher candidate recruitment in physical education teacher education programs. It highlights the efforts of program leaders in three different higher education institutions to recruit and retain well-qualified physical education majors. The key lessons learned from these cases serve as a…

Photosynthetically active sunlight at high southern latitudes.

PubMed

Frederick, John E; Liao, Yixiang

2005-01-01

A network of scanning spectroradiometers has acquired a multiyear database of visible solar irradiance, covering wavelengths from 400 to 600 nm, at four sites in the high-latitude Southern Hemisphere, from 55 degrees S to 90 degrees S. Monthly irradiations computed from the hourly measurements reveal the character of the seasonal cycle and illustrate the role of cloudiness as functions of latitude. Near summer solstice, the combined influences of solar elevation and the duration of daylight would produce a monthly irradiation with little latitude dependence under clear skies. However, the attenuation associated with local cloudiness varies geographically, with the greatest effect at the most northern locations, Ushuaia, Argentina and Palmer Station on the Antarctic Peninsula. Near summer solstice, the South Pole experiences the largest monthly irradiation of the sites studied, where relatively clear skies contribute to this result. Scaling factors derived from radiative-transfer calculations combined with the measured 400-600 nm irradiances allow estimating irradiances integrated over the wavelength band 400-700 nm. This produces a climatology of photosynthetically active radiation for each month of the year at each site.

Predicting Ground Illuminance

NASA Astrophysics Data System (ADS)

Lesniak, Michael V.; Tregoning, Brett D.; Hitchens, Alexandra E.

2015-01-01

Our Sun outputs 3.85 x 1026 W of radiation, of which roughly 37% is in the visible band. It is directly responsible for nearly all natural illuminance experienced on Earth's surface, either in the form of direct/refracted sunlight or in reflected light bouncing off the surfaces and/or atmospheres of our Moon and the visible planets. Ground illuminance, defined as the amount of visible light intercepting a unit area of surface (from all incident angles), varies over 7 orders of magnitude from day to night. It is highly dependent on well-modeled factors such as the relative positions of the Sun, Earth, and Moon. It is also dependent on less predictable factors such as local atmospheric conditions and weather.Several models have been proposed to predict ground illuminance, including Brown (1952) and Shapiro (1982, 1987). The Brown model is a set of empirical data collected from observation points around the world that has been reduced to a smooth fit of illuminance against a single variable, solar altitude. It provides limited applicability to the Moon and for cloudy conditions via multiplicative reduction factors. The Shapiro model is a theoretical model that treats the atmosphere as a three layer system of light reflectance and transmittance. It has different sets of reflectance and transmittance coefficients for various cloud types.In this paper we compare the models' predictions to ground illuminance data from an observing run at the White Sands missile range (data was obtained from the United Kingdom's Meteorology Office). Continuous illuminance readings were recorded under various cloud conditions, during both daytime and nighttime hours. We find that under clear skies, the Shapiro model tends to better fit the observations during daytime hours with typical discrepancies under 10%. Under cloudy skies, both models tend to poorly predict ground illuminance. However, the Shapiro model, with typical average daytime discrepancies of 25% or less in many cases, performed somewhat better than the Brown model during daytime hours. During nighttime hours under cloudy skies, both models produced erratic results.

Fast All-Sky Radiation Model for Solar Applications (FARMS): A Brief Overview of Mechanisms, Performance, and Applications: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Yu; Sengupta, Manajit

Solar radiation can be computed using radiative transfer models, such as the Rapid Radiation Transfer Model (RRTM) and its general circulation model applications, and used for various energy applications. Due to the complexity of computing radiation fields in aerosol and cloudy atmospheres, simulating solar radiation can be extremely time-consuming, but many approximations--e.g., the two-stream approach and the delta-M truncation scheme--can be utilized. To provide a new fast option for computing solar radiation, we developed the Fast All-sky Radiation Model for Solar applications (FARMS) by parameterizing the simulated diffuse horizontal irradiance and direct normal irradiance for cloudy conditions from the RRTMmore » runs using a 16-stream discrete ordinates radiative transfer method. The solar irradiance at the surface was simulated by combining the cloud irradiance parameterizations with a fast clear-sky model, REST2. To understand the accuracy and efficiency of the newly developed fast model, we analyzed FARMS runs using cloud optical and microphysical properties retrieved using GOES data from 2009-2012. The global horizontal irradiance for cloudy conditions was simulated using FARMS and RRTM for global circulation modeling with a two-stream approximation and compared to measurements taken from the U.S. Department of Energy's Atmospheric Radiation Measurement Climate Research Facility Southern Great Plains site. Our results indicate that the accuracy of FARMS is comparable to or better than the two-stream approach; however, FARMS is approximately 400 times more efficient because it does not explicitly solve the radiative transfer equation for each individual cloud condition. Radiative transfer model runs are computationally expensive, but this model is promising for broad applications in solar resource assessment and forecasting. It is currently being used in the National Solar Radiation Database, which is publicly available from the National Renewable Energy Laboratory at http://nsrdb.nrel.gov.« less

Influence of clouds on UV-B penetration to the earth's surface

NASA Technical Reports Server (NTRS)

Green, A. E. S.

1979-01-01

Radiometric measurements of cloud influence on ultraviolet B radiation (UV-B) were obtained. Mathematical models of the influence were defined to lay the groundwork for the construction of the global UV-B climatology from satellite determined ozone data. More refined measurements comparing UV-B radiation with total solar radiation were carried out. The cloudy case is referred to the cloudless sky irradiance and convenient transmission ratios are given An approach to the inversion of scattering data is summarized. An improved characterization of the UV-B radiation from a cloudless sky is also presented.

Cloud Properties Derived From GOES-7 for Spring 1994 ARM Intensive Observing Period Using Version 1.0.0 of ARM Satellite Data Analysis Program

NASA Technical Reports Server (NTRS)

Minnis, Patrick; Smith, William L., Jr.; Garber, Donald P.; Ayers, J. Kirk; Doelling, David R.

1995-01-01

This document describes the initial formulation (Version 1.0.0) of the Atmospheric Radiation Measurement (ARM) program satellite data analysis procedures. Techniques are presented for calibrating geostationary satellite data with Sun synchronous satellite radiances and for converting narrowband radiances to top-of-the-atmosphere fluxes and albedos. A methodology is documented for combining geostationary visible and infrared radiances with surface-based temperature observations to derive cloud amount, optical depth, height, thickness, temperature, and albedo. The analysis is limited to two grids centered over the ARM Southern Great Plains central facility in north-central Oklahoma. Daytime data taken during 5 Apr. - 1 May 1994, were analyzed on the 0.3 deg and 0.5 deg latitude-longitude grids that cover areas of 0.9 deg x 0.9 deg and 10 deg x 14 deg, respectively. Conditions ranging from scattered low cumulus to thin cirrus and thick cumulonimbus occurred during the study period. Detailed comparisons with hourly surface observations indicate that the mean cloudiness is within a few percent of the surface-derived sky cover. Formats of the results are also provided. The data can be accessed through the World Wide Web computer network.

CMSAF products Cloud Fraction Coverage and Cloud Type used for solar global irradiance estimation

NASA Astrophysics Data System (ADS)

Badescu, Viorel; Dumitrescu, Alexandru

2016-08-01

Two products provided by the climate monitoring satellite application facility (CMSAF) are the instantaneous Cloud Fractional Coverage (iCFC) and the instantaneous Cloud Type (iCTY) products. Previous studies based on the iCFC product show that the simple solar radiation models belonging to the cloudiness index class n CFC = 0.1-1.0 have rRMSE values ranging between 68 and 71 %. The products iCFC and iCTY are used here to develop simple models providing hourly estimates for solar global irradiance. Measurements performed at five weather stations of Romania (South-Eastern Europe) are used. Two three-class characterizations of the state-of-the-sky, based on the iCTY product, are defined. In case of the first new sky state classification, which is roughly related with cloud altitude, the solar radiation models proposed here perform worst for the iCTY class 4-15, with rRMSE values ranging between 46 and 57 %. The spreading error of the simple models is lower than that of the MAGIC model for the iCTY classes 1-4 and 15-19, but larger for iCTY classes 4-15. In case of the second new sky state classification, which takes into account in a weighted manner the chance for the sun to be covered by different types of clouds, the solar radiation models proposed here perform worst for the cloudiness index class n CTY = 0.7-0.1, with rRMSE values ranging between 51 and 66 %. Therefore, the two new sky state classifications based on the iCTY product are useful in increasing the accuracy of solar radiation models.

Getting Students to Observe the Night Sky, Even When Your Sky is Cloudy Half the Time

NASA Astrophysics Data System (ADS)

Shipman, Harry L.

2010-01-01

Teachers of introductory astronomy classes often wish to get our students to look at the night sky However, most educational institutions in America are located in regions where cloudy nights are relatively common. This paper describes a low cost way to integrate observations into a course which lacks a dedicated astronomy lab. Students in two large. general science classes in fall 2008 and spring 2009 were asked to participate in one of two global star-counting projects. The fall project was coordinated by UCAR and asked for observations of the constellation Cygnus (http://www.windows.ucar.edu/citizen_science/starcount/results.html). The spring project was run by Project Globe and asked for observations of the constellation Orion. (http://www.globe.gov/GaN/ ). In both cases, students simply find the constellation, match the star pattern to charts that go to different limiting magnitudes, and report the data to the coordinating organization. A copy of the report is sent to the course instructor. The instructor can ask for additional information. Did it work? The success of this project was evaluated by analyzing the e-mail messages that students returned in response to the assignment. In both courses, a very large majority of the students actually did the exercise and submitted a report. Students reported that observing the sky in this way was satisfying to them., and sometimes the reports were quite enthusiastic. In spring 2009, some preparatory activies were conducted during class that were designed to sensitize students to the beauty of the sky. Analysis of student reports indicated that these preparatory activities were helpful, but not as helpful as the instructor would like. This research is part of the Teacher Professional Continuum project at the University of Delaware, which is supported by the National Science Foundation.

Design of a device for sky light polarization measurements.

PubMed

Wang, Yujie; Hu, Xiaoping; Lian, Junxiang; Zhang, Lilian; Xian, Zhiwen; Ma, Tao

2014-08-14

Sky polarization patterns can be used both as indicators of atmospheric turbidity and as a sun compass for navigation. The objective of this study is to improve the precision of sky light polarization measurements by optimal design of the device used. The central part of the system is composed of a Charge Coupled Device (CCD) camera; a fish-eye lens and a linear polarizer. Algorithms for estimating parameters of the polarized light based on three images are derived and the optimal alignments of the polarizer are analyzed. The least-squares estimation is introduced for sky light polarization pattern measurement. The polarization patterns of sky light are obtained using the designed system and they follow almost the same patterns of the single-scattering Rayleigh model. Deviations of polarization angles between observation and the theory are analyzed. The largest deviations occur near the sun and anti-sun directions. Ninety percent of the deviations are less than 5° and 40% percent of them are less than 1°. The deviations decrease evidently as the degree of polarization increases. It also shows that the polarization pattern of the cloudy sky is almost identical as in the blue sky.

Design of a Device for Sky Light Polarization Measurements

PubMed Central

Wang, Yujie; Hu, Xiaoping; Lian, Junxiang; Zhang, Lilian; Xian, Zhiwen; Ma, Tao

2014-01-01

Sky polarization patterns can be used both as indicators of atmospheric turbidity and as a sun compass for navigation. The objective of this study is to improve the precision of sky light polarization measurements by optimal design of the device used. The central part of the system is composed of a Charge Coupled Device (CCD) camera; a fish-eye lens and a linear polarizer. Algorithms for estimating parameters of the polarized light based on three images are derived and the optimal alignments of the polarizer are analyzed. The least-squares estimation is introduced for sky light polarization pattern measurement. The polarization patterns of sky light are obtained using the designed system and they follow almost the same patterns of the single-scattering Rayleigh model. Deviations of polarization angles between observation and the theory are analyzed. The largest deviations occur near the sun and anti-sun directions. Ninety percent of the deviations are less than 5° and 40% percent of them are less than 1°. The deviations decrease evidently as the degree of polarization increases. It also shows that the polarization pattern of the cloudy sky is almost identical as in the blue sky. PMID:25196003

The Moon and Mars in August

NASA Astrophysics Data System (ADS)

Paice, P.

2003-10-01

The naked-eye view of the full Moon and Mars together was captured by Peter Paice, Belfast, on 2003 August 12/13 at midnight UT using an Olympus 730 Ultra Zoom digital camera, with no additional processing applied. In a partly cloudy sky, the secret was to wait until clouds partly occluded the power of the Moon, and Mars was in a clear patch.

[Atmospheric Influences Analysis on the Satellite Passive Microwave Remote Sensing].

PubMed

Qiu, Yu-bao; Shi, Li-juan; Shi, Jian-cheng; Zhao, Shao-jie

2016-02-01

Passive microwave remote sensing offers its all-weather work capabilities, but atmospheric influences on satellite microwave brightness temperature were different under different atmospheric conditions and environments. In order to clarify atmospheric influences on Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E), atmospheric radiation were simulated based on AMSR-E configuration under clear sky and cloudy conditions, by using radiative transfer model and atmospheric conditions data. Results showed that atmospheric water vapor was the major factor for atmospheric radiation under clear sky condition. Atmospheric transmittances were almost above 0.98 at AMSR-E's low frequencies (< 18.7 GHz) and the microwave brightness temperature changes caused by atmosphere can be ignored in clear sky condition. Atmospheric transmittances at 36.5 and 89 GHz were 0.896 and 0.756 respectively. The effects of atmospheric water vapor needed to be corrected when using microwave high-frequency channels to inverse land surface parameters in clear sky condition. But under cloud cover or cloudy conditions, cloud liquid water was the key factor to cause atmospheric radiation. When sky was covered by typical stratus cloud, atmospheric transmittances at 10.7, 18.7 and 36.5 GHz were 0.942, 0.828 and 0.605 respectively. Comparing with the clear sky condition, the down-welling atmospheric radiation caused by cloud liquid water increased up to 75.365 K at 36.5 GHz. It showed that the atmospheric correction under different clouds covered condition was the primary work to improve the accuracy of land surface parameters inversion of passive microwave remote sensing. The results also provided the basis for microwave atmospheric correction algorithm development. Finally, the atmospheric sounding data was utilized to calculate the atmospheric transmittance of Hailaer Region, Inner Mongolia province, in July 2013. The results indicated that atmospheric transmittances were close to 1 at C-band and X-band. 89 GHz was greatly influenced by water vapor and its atmospheric transmittance was not more than 0.7. Atmospheric transmittances in Hailaer Region had a relatively stable value in summer, but had about 0.1 fluctuations with the local water vapor changes.

Parameterizing Grid-Averaged Longwave Fluxes for Inhomogeneous Marine Boundary Layer Clouds

NASA Technical Reports Server (NTRS)

Barker, Howard W.; Wielicki, Bruce A.

1997-01-01

This paper examines the relative impacts on grid-averaged longwave flux transmittance (emittance) for Marine Boundary Layer (MBL) cloud fields arising from horizontal variability of optical depth tau and cloud sides, First, using fields of Landsat-inferred tau and a Monte Carlo photon transport algorithm, it is demonstrated that mean all-sky transmittances for 3D variable MBL clouds can be computed accurately by the conventional method of linearly weighting clear and cloudy transmittances by their respective sky fractions. Then, the approximations of decoupling cloud and radiative properties and assuming independent columns are shown to be adequate for computation of mean flux transmittance. Since real clouds have nonzero geometric thicknesses, cloud fractions A'(sub c) presented to isotropic beams usually exceed the more familiar vertically projected cloud fractions A(sub c). It is shown, however, that when A(sub c)less than or equal to 0.9, biases for all-sky transmittance stemming from use of A(sub c) as opposed to A'(sub c) are roughly 2-5 times smaller than, and opposite in sign to, biases due to neglect of horizontal variability of tau. By neglecting variable tau, all-sky transmittances are underestimated often by more than 0.1 for A(sub c) near 0.75 and this translates into relative errors that can exceed 40% (corresponding errors for all-sky emittance are about 20% for most values of A(sub c). Thus, priority should be given to development of General Circulation Model (GCM) parameterizations that account for the effects of horizontal variations in unresolved tau, effects of cloud sides are of secondary importance. On this note, an efficient stochastic model for computing grid-averaged cloudy-sky flux transmittances is furnished that assumes that distributions of tau, for regions comparable in size to GCM grid cells, can be described adequately by gamma distribution functions. While the plane-parallel, homogeneous model underestimates cloud transmittance by about an order of magnitude when 3D variable cloud transmittances are less than or equal to 0.2 and by approx. 20% to 100% otherwise, the stochastic model reduces these biases often by more than 80%.

Optimizing countershading camouflage.

PubMed

Cuthill, Innes C; Sanghera, N Simon; Penacchio, Olivier; Lovell, Paul George; Ruxton, Graeme D; Harris, Julie M

2016-11-15

Countershading, the widespread tendency of animals to be darker on the side that receives strongest illumination, has classically been explained as an adaptation for camouflage: obliterating cues to 3D shape and enhancing background matching. However, there have only been two quantitative tests of whether the patterns observed in different species match the optimal shading to obliterate 3D cues, and no tests of whether optimal countershading actually improves concealment or survival. We use a mathematical model of the light field to predict the optimal countershading for concealment that is specific to the light environment and then test this prediction with correspondingly patterned model "caterpillars" exposed to avian predation in the field. We show that the optimal countershading is strongly illumination-dependent. A relatively sharp transition in surface patterning from dark to light is only optimal under direct solar illumination; if there is diffuse illumination from cloudy skies or shade, the pattern provides no advantage over homogeneous background-matching coloration. Conversely, a smoother gradation between dark and light is optimal under cloudy skies or shade. The demonstration of these illumination-dependent effects of different countershading patterns on predation risk strongly supports the comparative evidence showing that the type of countershading varies with light environment.

Local effects of partly-cloudy skies on solar and emitted radiations

NASA Technical Reports Server (NTRS)

Whitney, D. A.; Griffin, T. J.

1983-01-01

Atmospheric aerosol and turbidity measurements were analyzed and the results are presented. The correlation of global insolation with cloud cover fractions for the first complete year's data set was completed. A theoretical model was developed to parameterize the effects of local aerosols upon insolation received at the ground using satellite radiometric data and insolation measurements under clear sky conditions. A February data set, composed of one minute integrated global insolation and direct solar irradiances, cloud cover fractions, meteorological data from nearby weather stations, and GOES East satellite radiometric data was collected to test the model and used to calculate the effects of local aerosols.

The Q Continuum: Encounter with the Cloud Mask

NASA Astrophysics Data System (ADS)

Ackerman, S. A.; Frey, R.; Holz, R.; Philips, C.; Dutcher, S.

2017-12-01

We are developing a common cloud mask for MODIS and VIIRS observations, referred to as the MODIS VIIRS Continuity Mask (MVCM). Our focus is on extending the MODIS-heritage cloud detection approach in order to generate appropriate climate data records for clouds and climate studies. The MVCM is based on heritage from the MODIS cloud mask (MOD35 and MYD35) and employs a series of tests on MODIS reflectances and brightness temperatures. Cloud detection is based on contrasts (i.e., cloud versus background surface) at pixel resolution. The MVCM follows the same approach. These cloud masks use multiple cloud detection tests to indicate the confidence level that the observation is of a clear-sky scene. The outcome of a test ranges from 0 (cloudy) to 1 (clear-sky scene). Because of overlap in the sensitivities of the various spectral tests to the type of cloud, each test is considered in one of several groups. The final cloud mask is determined from the product of the minimum confidence of each group and is referred to as the Q value as defined in Ackerman et al (1998). In MOD35 and MYD35 processing, the Q value is not output, rather predetermined Q values determine the result: If Q ≥ .99 the scene is clear; .95 ≤ Q < .99 the pixel is probably a clear scene, .66 ≤ Q < .95 is probably cloudy and Q < .66 is cloudy. Thus representing Q discretely and not as a continuum. For the MVCM, the numerical value of the Q is output along with the classification of clear, probably clear, probably cloudy, and cloudy. Through comparisons with collocated CALIOP and MODIS observations, we will assess the categorization of the Q values as a function of scene type ). While validation studies have indicated the utility and statistical correctness of the cloud mask approach, the algorithm does not possess immeasurable power and perfection. This comparison will assess the time and space dependence of Q and assure that the laws of physics are followed, at least according to normal human notions. Using CALIOP as representing truth, a receiver operating characteristic curve (ROC) will be analyzed to determine the optimum Q for various scenes and seasons, thus providing a continuum of discriminating thresholds.

Cloudy 94 and Applications to Quasar Emission Line Regions

NASA Technical Reports Server (NTRS)

Ferland, Gary J.

2000-01-01

This review discusses the most recent developments of the plasma simulation code Cloudy and its application to the, emission-line regions of quasars. The longterm goal is to develop the tools needed to determine the chemical composition of the emitting gas and the luminosity of the central engine for any emission line source. Emission lines and the underlying thermal continuum are formed in plasmas that are far from thermodynamic equilibrium. Their thermal and ionization states are the result of a balance of a vast set of microphysical processes. Once produced, radiation must, propagate out of the (usually) optically thick source. No analytic solutions are possible, and recourse to numerical simulations is necessary. I am developing the large-scale plasma simulation code Cloudy as an investigative tool for this work, much as an observer might build a spectrometer. This review describes the current version of Cloudy, version 94. It describes improvements made since the, release of the previous version, C90. The major recent, application has been the development of the "Locally Optimally-Emitting Cloud" (LOC) model of AGN emission line regions. Powerful selection effects, introduced by the atomic physics and line formation process, permit individual lines to form most efficiently only near certain selected parameters. These selection effects, together with the presence of gas with a wide range of conditions, are enough to reproduce the spectrum of a typical quasar with little dependence on details. The spectrum actually carries little information to the identity of the emitters. I view this as a major step forward since it provides a method to handle accidental details at the source, so that we can concentrate on essential information such as the luminosity or chemical composition of the quasar.

The earth's radiation budget and its relation to atmospheric hydrology. I - Observations of the clear sky greenhouse effect. II - Observations of cloud effects

NASA Technical Reports Server (NTRS)

Stephens, Graeme L.; Greenwald, Thomas J.

1991-01-01

The clear-sky components of the earth's radiation budget (ERB), the relationship of these components to the sea surface temperature (SST), and microwave-derived water-vapor amount are analyzed in an observational study along with the relationship between the cloudy-sky components of ERB and space/time coincident observations of SST, microwave-derived cloud liquid water, and cloud cover. The purpose of the study is to use these observations for establishing an understanding of the couplings between radiation and the atmosphere that are important to understanding climate feedback. A strategy for studying the greenhouse effect of earth by analyzing the emitted clear-sky longwave flux over the ocean is proposed. It is concluded that the largest observed influence of clouds on ERB is more consistent with macrophysical properties of clouds as opposed to microphysical properties. The analysis for clouds and the greenhouse effect of clouds is compared quantitatively with the clear sky results. Land-ocean differences and tropical-midlatitude differences are shown and explained in terms of the cloud macrostructure.

Robust sky light polarization detection with an S-wave plate in a light field camera.

PubMed

Zhang, Wenjing; Zhang, Xuanzhe; Cao, Yu; Liu, Haibo; Liu, Zejin

2016-05-01

The sky light polarization navigator has many advantages, such as low cost, no decrease in accuracy with continuous operation, etc. However, current celestial polarization measurement methods often suffer from low performance when the sky is covered by clouds, which reduce the accuracy of navigation. In this paper we introduce a new method and structure based on a handheld light field camera and a radial polarizer, composed of an S-wave plate and a linear polarizer, to detect the sky light polarization pattern across a wide field of view in a single snapshot. Each micro-subimage has a special intensity distribution. After extracting the texture feature of these subimages, stable distribution information of the angle of polarization under a cloudy sky can be obtained. Our experimental results match well with the predicted properties of the theory. Because the polarization pattern is obtained through image processing, rather than traditional methods based on mathematical computation, this method is less sensitive to errors of pixel gray value and thus has better anti-interference performance.

Cloud effects on the SW radiation at the surface at a mid-latitude site in southwestern Europe

NASA Astrophysics Data System (ADS)

Salgueiro, Vanda; João Costa, Maria; Silva, Ana Maria; Lanconelli, Christian; Bortoli, Daniele

2017-04-01

This work presents a study of cloud radiative effects on shortwave (CRESW) radiation at the surface in Évora region (southwestern Europe) during 2015 and a case study is analyzed. CRESW (in Wm-2) is defined as the difference between the net shortwave irradiance (downward minus upward shortwave irradiance) in cloudy and clear sky conditions. This measure is usually used to translate changes in the SW radiation that reaches the surface due to changes in clouds (type and/or cover). The CRESW is obtained using measured SW irradiance recorded with a Kipp&Zonen CM 6B pyranometer (broadband 305 - 2800 nm) during the period from January to December 2015, and is related with the cloud liquid water path (LWP) and with cloud ice water path (IWP) showing the importance of the different type of clouds in attenuating the SW radiation at the surface. The cloud modification factor, also a measure of the cloud radiative effects (CMF; ratio between the measured SW irradiance under cloudy conditions and the estimated SW irradiance in clear-sky conditions) is related with the cloud optical thickness (COT; obtained from satellite data). This relation between CMF and COT is shown for different cloud fractions revealing an exponential decreasing of CMF as COT increases. Reductions in the SW radiation of the order of 80% (CMF = 0.2) as well enhancements in the SW radiation larger than 30% (CMF = 1.3) were found for small COT values and for different cloud fractions. A case study to analyse the enhancement events in a cloudy day was considered and the cloud properties, COT and LWP (from satellite and surface measurements), were related with the CRESW.

Shortwave surface radiation network for observing small-scale cloud inhomogeneity fields

NASA Astrophysics Data System (ADS)

Lakshmi Madhavan, Bomidi; Kalisch, John; Macke, Andreas

2016-03-01

As part of the High Definition Clouds and Precipitation for advancing Climate Prediction Observational Prototype Experiment (HOPE), a high-density network of 99 silicon photodiode pyranometers was set up around Jülich (10 km × 12 km area) from April to July 2013 to capture the small-scale variability of cloud-induced radiation fields at the surface. In this paper, we provide the details of this unique setup of the pyranometer network, data processing, quality control, and uncertainty assessment under variable conditions. Some exemplary days with clear, broken cloudy, and overcast skies were explored to assess the spatiotemporal observations from the network along with other collocated radiation and sky imager measurements available during the HOPE period.

An Earth longwave radiation climate model

NASA Technical Reports Server (NTRS)

Yang, S. K.

1984-01-01

An Earth outgoing longwave radiation (OLWR) climate model was constructed for radiation budget study. Required information is provided by on empirical 100mb water vapor mixing ratio equation of the mixing ratio interpolation scheme. Cloud top temperature is adjusted so that the calculation would agree with NOAA scanning radiometer measurements. Both clear sky and cloudy sky cases are calculated and discussed for global average, zonal average and world-wide distributed cases. The results agree well with the satellite observations. The clear sky case shows that the OLWR field is highly modulated by water vapor, especially in the tropics. The strongest longitudinal variation occurs in the tropics. This variation can be mostly explained by the strong water vapor gradient. Although in the zonal average case the tropics have a minimum in OLWR, the minimum is essentially contributed by a few very low flux regions, such as the Amazon, Indonesian and the Congo.

Comparison of global observations and trends of total precipitable water derived from microwave radiometers and COSMIC radio occultation from 2006 to 2013

NASA Astrophysics Data System (ADS)

Ho, Shu-Peng; Peng, Liang; Mears, Carl; Anthes, Richard A.

2018-01-01

We compare atmospheric total precipitable water (TPW) derived from the SSM/I (Special Sensor Microwave Imager) and SSMIS (Special Sensor Microwave Imager/Sounder) radiometers and WindSat to collocated TPW estimates derived from COSMIC (Constellation System for Meteorology, Ionosphere, and Climate) radio occultation (RO) under clear and cloudy conditions over the oceans from June 2006 to December 2013. Results show that the mean microwave (MW) radiometer - COSMIC TPW differences range from 0.06 to 0.18 mm for clear skies, from 0.79 to 0.96 mm for cloudy skies, from 0.46 to 0.49 mm for cloudy but non-precipitating conditions, and from 1.64 to 1.88 mm for precipitating conditions. Because RO measurements are not significantly affected by clouds and precipitation, the biases mainly result from MW retrieval uncertainties under cloudy and precipitating conditions. All COSMIC and MW radiometers detect a positive TPW trend over these 8 years. The trend using all COSMIC observations collocated with MW pixels for this data set is 1.79 mm decade-1, with a 95 % confidence interval of (0.96, 2.63), which is in close agreement with the trend estimated by the collocated MW observations (1.78 mm decade-1 with a 95 % confidence interval of 0.94, 2.62). The sample of MW and RO pairs used in this study is highly biased toward middle latitudes (40-60° N and 40-65° S), and thus these trends are not representative of global average trends. However, they are representative of the latitudes of extratropical storm tracks and the trend values are approximately 4 to 6 times the global average trends, which are approximately 0.3 mm decade-1. In addition, the close agreement of these two trends from independent observations, which represent an increase in TPW in our data set of about 6.9 %, are a strong indication of the positive water vapor-temperature feedback on a warming planet in regions where precipitation from extratropical storms is already large.

Ice clouds optical properties in the Far Infrared from the ECOWAR-COBRA Experiment

NASA Astrophysics Data System (ADS)

Rizzi, Rolando; Tosi, Ennio

ECOWAR-COBRA (Earth COoling by WAter vapouR emission -Campagna di Osservazioni della Banda Rotazionale del vapor d'Acqua) field campaign took place in Italy from 3 to 17 March 2007 with the main goal of studying the scarcely sensed atmospheric emission occurring beyond 17 microns. Instrumentation involved in the campaign included two different Fourier Transforms Spectrometers (FTS) : REFIR-PAD (at Testa Grigia Station, 3500 m a.s.l.) and FTIR-ABB (at Cervinia Station, 1990 m a.s.l.). In this work cloudy sky data have been ana-lyzed. A cloud properties retrieval methodology (RT-RET), based on high spectral resolution measurements in the atmospheric window (800-1000 cm-1), is applied to both FTS sensors. Cloud properties determined from the infrared retrievals are compared with those obtained from Raman lidar taken by the BASIL Lidar system that was operating at Cervinia station. Cloud microphysical and optical properties retrieved by RT-RET are used to perform forward simulations over the entire FTSs measurements spectral interval. Results are compared to FTS data to test the ability of single scattering ice crystals models to reproduce cloudy sky radiances in the Far Infra-Red (FIR) part of the spectrum. New methods to retrieve cloud optical and microphysical properties exploiting high spectral resolution FIR measurements are also investigated.

Intercomparison of 51 radiometers for determining global horizontal irradiance and direct normal irradiance measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Habte, Aron; Sengupta, Manajit; Andreas, Afshin

Accurate solar radiation measurements require properly installed and maintained radiometers with calibrations traceable to the World Radiometric Reference. This study analyzes the performance of 51 commercially available and prototype radiometers used for measuring global horizontal irradiances or direct normal irradiances. These include pyranometers, pyrheliometers, rotating shadowband radiometers, and a pyranometer with an internal shading mask deployed at the National Renewable Energy Laboratory's (NREL) Solar Radiation Research Laboratory. The radiometers in this study were deployed for one year (from April 1, 2011, through March 31, 2012), and their measurements were compared under clear-sky, partly cloudy, and mostly cloudy conditions to referencemore » values of low estimated measurement uncertainties. The intent of this paper is to present a general overview of each radiometer's performance based on the instrumentation and environmental conditions available at NREL.« less

The Solar Ultraviolet Environment at the Ocean.

PubMed

Mobley, Curtis D; Diffey, Brian L

2018-05-01

Atmospheric and oceanic radiative transfer models were used to compute spectral radiances between 285 and 400 nm onto horizontal and vertical plane surfaces over water. The calculations kept track of the contributions by the sun's direct beam, by diffuse-sky radiance, by radiance reflected from the sea surface and by water-leaving radiance. Clear, hazy and cloudy sky conditions were simulated for a range of solar zenith angles, wind speeds and atmospheric ozone concentrations. The radiances were used to estimate erythemal exposures due to the sun and sky, as well as from radiation reflected by the sea surface and backscattered from the water column. Diffuse-sky irradiance is usually greater than direct-sun irradiance at wavelengths below 330 nm, and reflected and water-leaving irradiance accounts for <20% of the UV exposure on a vertical surface. Total exposure depends strongly on solar zenith angle and azimuth angle relative to the sun. Sea surface roughness affects the UV exposures by only a few percent. For very clear waters and the sun high in the sky, the UV index within the water can be >10 at depths down to two meters and >6 down to 5 m. © 2018 The American Society of Photobiology.

New device for monitoring the colors of the night

NASA Astrophysics Data System (ADS)

Spoelstra, Henk

2014-05-01

The introduction of LED lighting in the outdoor environment may increase the amount of blue light in the night sky color spectrum. This can cause more light pollution due to Rayleigh scattering of the shorter wavelengths. Blue light may also have an impact on circadian rhythm of humans due to the suppression of melatonin. At present no long-term data sets of the color spectrum of the night sky are available. In order to facilitate the monitoring of levels and variations in the night sky spectrum, a low cost multi-filter instrument has been developed. Design considerations are described as well as the choice of suitable filters, which are critical - especially in the green wavelength band from 500 to 600 nm. Filters from the optical industry were chosen for this band because available astronomical filters exclude some or all of the low and high-pressure sodium lines from lamps, which are important in light pollution research. Correction factors are calculated to correct for the detector response and filter transmissions. Results at a suburban monitoring station showed that the light levels between 500 and 600 nm are dominant during clear and cloudy skies. The relative contribution of blue light increases with a clear moonless night sky. The change in color spectrum of the night sky under moonlit skies is more complex and is still under study.

Evaluation of sea-surface photosynthetically available radiation algorithms under various sky conditions and solar elevations.

PubMed

Somayajula, Srikanth Ayyala; Devred, Emmanuel; Bélanger, Simon; Antoine, David; Vellucci, V; Babin, Marcel

2018-04-20

In this study, we report on the performance of satellite-based photosynthetically available radiation (PAR) algorithms used in published oceanic primary production models. The performance of these algorithms was evaluated using buoy observations under clear and cloudy skies, and for the particular case of low sun angles typically encountered at high latitudes or at moderate latitudes in winter. The PAR models consisted of (i) the standard one from the NASA-Ocean Biology Processing Group (OBPG), (ii) the Gregg and Carder (GC) semi-analytical clear-sky model, and (iii) look-up-tables based on the Santa Barbara DISORT atmospheric radiative transfer (SBDART) model. Various combinations of atmospheric inputs, empirical cloud corrections, and semi-analytical irradiance models yielded a total of 13 (11 + 2 developed in this study) different PAR products, which were compared with in situ measurements collected at high frequency (15 min) at a buoy site in the Mediterranean Sea (the "BOUée pour l'acquiSition d'une Série Optique à Long termE," or, "BOUSSOLE" site). An objective ranking method applied to the algorithm results indicated that seven PAR products out of 13 were well in agreement with the in situ measurements. Specifically, the OBPG method showed the best overall performance with a root mean square difference (RMSD) (bias) of 19.7% (6.6%) and 10% (6.3%) followed by the look-up-table method with a RMSD (bias) of 25.5% (6.8%) and 9.6% (2.6%) at daily and monthly scales, respectively. Among the four methods based on clear-sky PAR empirically corrected for cloud cover, the Dobson and Smith method consistently underestimated daily PAR while the Budyko formulation overestimated daily PAR. Empirically cloud-corrected methods using cloud fraction (CF) performed better under quasi-clear skies (CF<0.3) with an RMSD (bias) of 9.7%-14.8% (3.6%-11.3%) than under partially clear to cloudy skies (0.30.7), however, all methods showed larger RMSD differences (biases) ranging between 32% and 80.6% (-54.5%-8.7%). Finally, three methods tested for low sun elevations revealed systematic overestimation, and one method showed a systematic underestimation of daily PAR, with relative RMSDs as large as 50% under all sky conditions. Under partially clear to overcast conditions all the methods underestimated PAR. Model uncertainties predominantly depend on which cloud products were used.

Progress in Insect-Inspired Optical Navigation Sensors

NASA Technical Reports Server (NTRS)

Thakoor, Sarita; Chahl, Javaan; Zometzer, Steve

2005-01-01

Progress has been made in continuing efforts to develop optical flight-control and navigation sensors for miniature robotic aircraft. The designs of these sensors are inspired by the designs and functions of the vision systems and brains of insects. Two types of sensors of particular interest are polarization compasses and ocellar horizon sensors. The basic principle of polarization compasses was described (but without using the term "polarization compass") in "Insect-Inspired Flight Control for Small Flying Robots" (NPO-30545), NASA Tech Briefs, Vol. 29, No. 1 (January 2005), page 61. To recapitulate: Bees use sky polarization patterns in ultraviolet (UV) light, caused by Rayleigh scattering of sunlight by atmospheric gas molecules, as direction references relative to the apparent position of the Sun. A robotic direction-finding technique based on this concept would be more robust in comparison with a technique based on the direction to the visible Sun because the UV polarization pattern is distributed across the entire sky and, hence, is redundant and can be extrapolated from a small region of clear sky in an elsewhere cloudy sky that hides the Sun.

Angle of sky light polarization derived from digital images of the sky under various conditions.

PubMed

Zhang, Wenjing; Cao, Yu; Zhang, Xuanzhe; Yang, Yi; Ning, Yu

2017-01-20

Skylight polarization is used for navigation by some birds and insects. Skylight polarization also has potential for human navigation applications. Its advantages include relative immunity from interference and the absence of error accumulation over time. However, there are presently few examples of practical applications for polarization navigation technology. The main reason is its weak robustness during cloudy weather conditions. In this paper, the real-time measurement of the sky light polarization pattern across the sky has been achieved with a wide field of view camera. The images were processed under a new reference coordinate system to clearly display the symmetrical distribution of angle of polarization with respect to the solar meridian. A new algorithm for the extraction of the image axis of symmetry is proposed, in which the real-time azimuth angle between the camera and the solar meridian is accurately calculated. Our experimental results under different weather conditions show that polarization navigation has high accuracy, is strongly robust, and performs well during fog and haze, clouds, and strong sunlight.

A comparison of the Stratospheric Aerosol and Gas Experiment II tropospheric water vapor to radiosonde measurements

NASA Technical Reports Server (NTRS)

Larsen, J. C.; Chiou, E. W.; Chu, W. P.; Mccormick, M. P.; Mcmaster, L. R.; Oltmans, S.; Rind, D.

1993-01-01

Results are presented of a comparison beteen observations of the upper-tropospheric water vapor data obtained from the Stratospheric Aerosol and Gas Experiment II (SAGE II) instrument and radiosonde observations for 1987 and radiosonde-based climatologies. Colocated SAGE II-radiosonde measurement pairs are compared individually and in a zonal mean sense. A straight comparison of monthly zonal means between SAGE II and radiosondes for 1987 and Global Atmospheric Statistics (1963-1973) indicates that the clear-sky SAGE II climatology is approximately half the level of clear/cloudy sky of both radiosonde climatologies. Annual zonal means calculated from the set of profile pairs again showed SAGE II to be significantly drier in many altitude bands.

Detection of a poorly resolved airplane using SWIR polarization imaging

NASA Astrophysics Data System (ADS)

Dahl, Laura M.; Shaw, Joseph A.; Chenault, David B.

2016-05-01

Polarization can be used to detect manmade objects on the ground and in the air, as it provides additional information beyond intensity and color. Skylight can be strongly polarized, so the detection of airplanes in flight requires careful consideration of the skylight degree and angle of polarization (DoLP, AoP). In this study, we detect poorly resolved airplanes (>= 4 pixels on target) in flight during daytime partly cloudy and smoky conditions in Bozeman, Montana. We used a Polaris Sensor Technologies SWIR-MWIR rotating imaging polarimeter to measure the polarization signatures of airplanes and the surrounding skylight from 1.5 to 1.8 μm in the short-wave infrared (SWIR). An airplane flying in a clear region of partly cloudy sky was found to be 69% polarized at an elevation angle of 13° with respect to the horizon and the surrounding skylight was 4-8% polarized (maximum skylight DoLP was found to be 7-14% at an elevation angle of 50°). As the airplane increased in altitude, the DoLP for both airplane and surrounding sky pixels increased as the airplane neared the band of maximum sky polarization. We also observed that an airplane can be less polarized than its surrounding skylight when there is heavy smoke present. In such a case, the airplane was 30-38% polarized at an elevation angle of 17°, while the surrounding skylight was approximately 40% polarized (maximum skylight DoLP was 40-55% at an elevation angle of 34°). In both situations the airplane was most consistently observed in DoLP images rather than S0 or AoP images. In this paper, we describe the results in detail and discuss how this phenomenology could detect barely resolved aircrafts.

One year of downwelling spectral radiance measurements from 100 to 1400 cm-1 at Dome Concordia: Results in clear conditions

NASA Astrophysics Data System (ADS)

Rizzi, R.; Arosio, C.; Maestri, T.; Palchetti, L.; Bianchini, G.; Del Guasta, M.

2016-09-01

The present work examines downwelling radiance spectra measured at the ground during 2013 by a Far Infrared Fourier Transform Spectrometer at Dome C, Antarctica. A tropospheric backscatter and depolarization lidar is also deployed at same site, and a radiosonde system is routinely operative. The measurements allow characterization of the water vapor and clouds infrared properties in Antarctica under all sky conditions. In this paper we specifically discuss cloud detection and the analysis in clear sky condition, required for the discussion of the results obtained in cloudy conditions. First, the paper discusses the procedures adopted for the quality control of spectra acquired automatically. Then it describes the classification procedure used to discriminate spectra measured in clear sky from cloudy conditions. Finally a selection is performed and 66 clear cases, spanning the whole year, are compared to simulations. The computation of layer molecular optical depth is performed with line-by-line techniques and a convolution to simulate the Radiation Explorer in the Far InfraRed-Prototype for Applications and Development (REFIR-PAD) measurements; the downwelling radiance for selected clear cases is computed with a state-of-the-art adding-doubling code. The mean difference over all selected cases between simulated and measured radiance is within experimental error for all the selected microwindows except for the negative residuals found for all microwindows in the range 200 to 400 cm-1, with largest values around 295.1 cm-1. The paper discusses possible reasons for the discrepancy and identifies the incorrect magnitude of the water vapor total absorption coefficient as the cause of such large negative radiance bias below 400 cm-1.

Investigating Galactic Structure with COBE/DIRBE and Simulation

NASA Technical Reports Server (NTRS)

Cohen, Martin

1999-01-01

In this work I applied the current version of the SKY model of the point source sky to the interpretation of the diffuse all-sky emission observed by COBE/DIRBE (Cosmic Background Explorer Satellite/Diffuse Infrared Background Experiment). The goal was to refine the SKY model using the all-sky DIRBE maps of the Galaxy, in order that a search could be made for an isotropic cosmic background."Faint Source Model" [FSM] was constructed to remove Galactic fore ground stars from the ZSMA products. The FSM mimics SKY version 1 but it was inadequate to seek cosmic background emission because of the sizeable residual emission in the ZSMA products after this starlight subtraction. At this point I can only support that such models are currently inadequate to reveal a cosmic background. Even SKY5 yields the same disappointing result.

Dark Skies Ahead? Activities to Raise Awareness during the International Year of Astronomy

NASA Astrophysics Data System (ADS)

Walker, Constance E.; Isbell, D.; Pompea, S.

2007-12-01

"Dark Skies as a Universal Resource” is one of 7 themes targeted for the International Year of Astronomy in 2009. The theme's goal is to raise public awareness of the impact of artificial lighting on local environments and the ongoing loss of a dark night sky as a natural resource for much of the world's population. To reach this goal, activities are being developed which highlight dark skies preservation issues 1) through new technology (e.g., programs at planetaria, blogging, podcasting); 2) at events such as star parties and observatory open houses; 3) in arts, entertainment and storytelling (e.g., art competitions, documentaries, lectures, native American traditions); 4) through unaided-eye and digital-meter star count programs involving citizen-scientists; and 5) by relating them to public health, economic issues, ecological consequences, energy conservation, safety and security. A centerpiece of the Dark Skies theme is the unaided-eye and digital-meter versions of the GLOBE at Night program. The unaided-eye version directs citizen-scientists on how to observe and record the brightness of the night sky by matching its appearance toward the constellation of Orion with one of 7 stellar maps of different limiting magnitudes. For the "digital” version, low-cost meters are used by citizen-scientists to measure the integrated sky brightness. Data sets and maps of both versions are supplied on-line for further capstone activities. In the presentation, we will outline the activities being developed as well as plans for funding, implementation, marketing and the connections to the global cornerstone IYA project, "Dark Skies Awareness".

SatCam: A mobile application for coordinated ground/satellite observation of clouds and validation of satellite-derived cloud mask products.

NASA Astrophysics Data System (ADS)

Gumley, L.; Parker, D.; Flynn, B.; Holz, R.; Marais, W.

2011-12-01

SatCam is an application for iOS devices that allows users to collect observations of local cloud and surface conditions in coordination with an overpass of the Terra, Aqua, or NPP satellites. SatCam allows users to acquire images of sky conditions and ground conditions at their location anywhere in the world using the built-in iPhone or iPod Touch camera at the same time that the satellite is passing overhead and viewing their location. Immediately after the sky and ground observations are acquired, the application asks the user to rate the level of cloudiness in the sky (Completely Clear, Mostly Clear, Partly Cloudy, Overcast). For the ground observation, the user selects their assessment of the surface conditions (Urban, Green Vegetation, Brown Vegetation, Desert, Snow, Water). The sky condition and surface condition selections are stored along with the date, time, and geographic location for the images, and the images are uploaded to a central server. When the MODIS (Terra and Aqua) or VIIRS (NPP) imagery acquired over the user location becomes available, a MODIS or VIIRS true color image centered at the user's location is delivered back to the SatCam application on the user's iOS device. SSEC also proposes to develop a community driven SatCam website where users can share their observations and assessments of satellite cloud products in a collaborative environment. SSEC is developing a server side data analysis system to ingest the SatCam user observations, apply quality control, analyze the sky images for cloud cover, and collocate the observations with MODIS and VIIRS satellite products (e.g., cloud mask). For each observation that is collocated with a satellite observation, the server will determine whether the user scored a "hit", meaning their sky observation and sky assessment matched the automated cloud mask obtained from the satellite observation. The hit rate will be an objective assessment of the accuracy of the user's sky observations. Users with high hit rates will be identified automatically and their observations will be used globally to evaluate the performance of the MODIS cloud mask algorithm for Terra and Aqua and the VIIRS cloud mask algorithm for NPP. The user's assessment of the ground conditions will also be used to evaluate the cloud mask accuracy in selecting the correct surface type at the user's location, which is an important element in the decision path used internally by the cloud mask algorithm. This presentation will describe the SatCam application, how it is used, and show examples of SatCam observations.

The direct assimilation of cloud-affected satellite infrared radiance in the NCEP 3D-Hybrid system

NASA Astrophysics Data System (ADS)

Zhang, X.

2016-12-01

A function has been developed in NCEP 3D-Hybrid system to make use of Infrared radiances from Spinning Enhanced Visible and Infrared Imager (SEVIRI) on Meteosat-10(MSG-10) satellite in overcast cloudy conditions where effective cloud fractions were greater than 0.9. These cloudy radiances provide new information that currently assimilated in clear-sky condition from SEVIRI MSG-10. The model state vector is locally extended at observation locations, to include cloud top pressure as cloud parameters. This parameter describing a single-layer cloud are simultaneously estimated together with temperature and humidity inside the main analysis. Assimilation experiments have been run with the new scheme in which overcast radiance from SEVIRI MSG-10 are used in addition to the available clear-sky data. Two water vapor channels ( 6.2 and 7.3μm) and window channels (8.5, 11.2, 12.3 and 13.3μm) from SEVIRI MSG-10 are assimilated in the experiments. The overcast data locations typically represent 10% or less of the total due to the application of stringent quality control. However, The extra data that are used give rise to modified increments (largest for temperature and humidity) at and above the diagnosed cloud top. Also it improves the analysis fit to independent radiosonde observations and results in some small, but statistically significant, improvements in forecast quality.

A gap-filling model for eddy covariance CO2 flux: Estimating carbon assimilated by a subtropical evergreen broad-leaved forest at the Lien-Hua-Chih flux observation site

NASA Astrophysics Data System (ADS)

Lan, C. Y.; Li, M. H.; Chen, Y. Y.

2016-12-01

Appropriate estimations of gaps appeared in eddy covariance (EC) flux observations are critical to the reliability of long-term EC applications. In this study we present a semi-parametric multivariate gap-filling model for tower-based measurement of CO2 flux. The raw EC data passing QC/QA was separated into two groups, clear sky, having net radiation greater than 50 W/m2, and nighttime/cloudy. For the clear sky conditions, the principle component analysis (PCA) was used to resolve the multicollinearity relationships among various environmental variables, including net radiation, wind speed, vapor pressure deficit, soil moisture deficit, leaf area index, and soil temperature, in association with CO2 assimilated by forest. After the principal domains were determined by the PCA, the relationships between CO2 fluxes and selected PCs (key factors) were built up by nonlinear interpolations to estimate the gap-filled CO2 flux. In view of limited photosynthesis at nighttime/cloudy conditions, respiration rate of the forest ecosystem was estimated by the Lloyd-Tylor equation. Artificial gaps were randomly selected to exam the applicability of our PCA approach. Based on tower-based measurement of CO2 flux at the Lien-Hua-Chih site, a total of 5.8 ton-C/ha/yr was assimilated in 2012.

A Performance Comparison for Two Versions of the Vulcan Photometer

NASA Technical Reports Server (NTRS)

Borucki, W. J.; Caldwell, D. A.; Koch, D. G.; Jenkins, J. M.; Showen, R. L.

2001-01-01

Analysis of the images produced by the first version (V1) of the Vulcan photometer indicated that two major sources of noise were sky brightness and image motion. To reduce the effect of the sky brightness, a second version (V2) with a longer focal length and a larger format detector was developed and tested. The first version consisted of 15-centimeter (cm) focal length, F/1.5 Aerojet Delft reconnaissance lens, and a 2048 x 2048 format front-illuminated charged coupled device (CCD) with 9 microns micropixels (Mpixels). The second version used a 30-cm focal length, F/2.5 Kodak AeroEktar lens, and a 4096 x 4096 format CCD with 9 micro pixels. Both have a 49-square-degree field of view (FOV) but the area of the sky subtended by each pixel in the V2 version is one-fourth that of the V1 version. This modification substantially reduces the shot noise due to the sky background and allows fainter stars to be monitored for planetary transits. To remove the data gap and consequent signal-level change caused by flipping the photometer around the declination axis and to reduce image movement on the detector, several other modifications were incorporated. These include modifying the mount and stiffening the photometer and autoguider structures to reduce flexure. This paper compares the performance characteristics of each photometer and discusses tests to identify sources of systematic noise.

Daytime Water Detection Based on Sky Reflections

NASA Technical Reports Server (NTRS)

Rankin, Arturo L.; Matthies, Larry H.; Bellutta, Paolo

2011-01-01

Robust water detection is a critical perception requirement for unmanned ground vehicle (UGV) autonomous navigation. This is particularly true in wide-open areas where water can collect in naturally occurring terrain depressions during periods of heavy precipitation and form large water bodies. One of the properties of water useful for detecting it is that its surface acts as a horizontal mirror at large incidence angles. Water bodies can be indirectly detected by detecting reflections of the sky below the horizon in color imagery. The Jet Propulsion Laboratory (JPL) has implemented a water detector based on sky reflections that geometrically locates the pixel in the sky that is reflecting on a candidate water pixel on the ground and predicts if the ground pixel is water based on color similarity and local terrain features. This software detects water bodies in wide-open areas on cross-country terrain at mid- to far-range using imagery acquired from a forward-looking stereo pair of color cameras mounted on a terrestrial UGV. In three test sequences approaching a pond under a clear, overcast, and cloudy sky, the true positive detection rate was 100% when the UGV was beyond 7 meters of the water's leading edge and the largest false positive detection rate was 0.58%. The sky reflection based water detector has been integrated on an experimental unmanned vehicle and field tested at Ft. Indiantown Gap, PA, USA.

Polarization optics of the Brewster's dark patch visible on water surfaces versus solar height and sky conditions: theory, computer modeling, photography, and painting.

PubMed

Takács, Péter; Barta, András; Pye, David; Horváth, Gábor

2017-10-20

When the sun is near the horizon, a circular band with approximately vertically polarized skylight is formed at 90° from the sun, and this skylight is only weakly reflected from the region of the water surface around the Brewster's angle (53° from the nadir). Thus, at low solar heights under a clear sky, an extended dark patch is visible on the water surface when one looks toward the north or south quarter perpendicular to the solar vertical. In this work, we study the radiance distribution of this so-called Brewster's dark patch (BDP) in still water as functions of the solar height and sky conditions. We calculate the pattern of reflectivity R of a water surface for a clear sky and obtain from this idealized situation the shape of the BDP. From three full-sky polarimetric pictures taken about a clear, a partly cloudy, and an overcast sky, we determine the R pattern and compose from that synthetic color pictures showing how the radiance distribution of skylight reflected at the water surface and the BDPs would look under these sky conditions. We also present photographs taken without a linearly polarizing filter about the BDP. Finally, we show a 19th century painting on which a river is seen with a dark region of the water surface, which can be interpreted as an artistic illustration of the BDP.

The 2017 Release Cloudy

NASA Astrophysics Data System (ADS)

Ferland, G. J.; Chatzikos, M.; Guzmán, F.; Lykins, M. L.; van Hoof, P. A. M.; Williams, R. J. R.; Abel, N. P.; Badnell, N. R.; Keenan, F. P.; Porter, R. L.; Stancil, P. C.

2017-10-01

We describe the 2017 release of the spectral synthesis code Cloudy, summarizing the many improvements to the scope and accuracy of the physics which have been made since the previous release. Exporting the atomic data into external data files has enabled many new large datasets to be incorporated into the code. The use of the complete datasets is not realistic for most calculations, so we describe the limited subset of data used by default, which predicts significantly more lines than the previous release of Cloudy. This version is nevertheless faster than the previous release, as a result of code optimizations. We give examples of the accuracy limits using small models, and the performance requirements of large complete models. We summarize several advances in the H- and He-like iso-electronic sequences and use our complete collisional-radiative models to establish the densities where the coronal and local thermodynamic equilibrium approximations work.

Temperature variations in automobiles in various weather conditions. An experimental contribution to the determination of time of death.

PubMed

Marty, W; Sigrist, T; Wyler, D

2001-09-01

From January 1995 through March 2000, temperatures in the passenger compartment of automobiles of different sizes were measured under varying weather conditions (sunshine, cloudy skies, rain) at two locations in eastern Switzerland. During the cold season, the interior temperature rose to 21 degrees C when cars were exposed to sunshine, whereas in summer interior temperature extremes of up to 89 degrees C were recorded. Make, model, and color of the vehicles were of only minor influence.

Astronomical Dating of Monet's Paintings on the Normandy Coast

NASA Astrophysics Data System (ADS)

Olson, D. W.

2016-01-01

Claude Monet (1840-1926) is famous for landscapes accurately capturing the changing nature of seas and skies. Monet created almost two thousand paintings during his long career, and several hundred of these works depict the skies above the spectacular cliffs, arches, rocks, harbors, and beaches on the Normandy coast. Our Texas State University group made a research trip to Normandy in the summer of 2012 and found dozens of the locations where Monet set up his easel. Astronomical considerations of daylight, twilight, night skies, and tides can be used to enhance our understanding of the artist's creative process. Monet himself said, “I need the Sun or the cloudy weather to coincide again with the tide, which must be low or high in accordance with my motifs.” Astronomical methods can be used to help in dating these works, many of which have uncertain dates in the existing catalogues and literature about Monet in Normandy. Analysis using the direction of sunlight and the direction of shadows, combined with calculations of lunar phases and tide levels, meteorological records, and the artist's letters, enables us to determine the exact date and the precise time, accurate to the minute, when Monet observed the sky that inspired a painting.

Effects of skylight polarization, cloudiness, and view angle on the detection of oil on water.

NASA Technical Reports Server (NTRS)

Millard, J. P.; Arvesen, J. C.

1971-01-01

Three passive radiometric techniques, which use the contrast of sunlight reflected and backscattered from oil and water in specific wavelength regions, have potential application for remote sensing of oil spills. These techniques consist of measuring (1) total radiance, (2) the polarization components (normal and parallel) of radiance, and (3) the difference between the normal and parallel components. In this paper, the best view directions for these techniques are evaluated, conclusions are drawn as to the most promising technique, and explanations are developed to describe why previous total-radiance measurements yielded highest contrast between oil and water under overcast skies. The technique based on measurement of only the normal polorization component appears to be the most promising. The differential technique should be further investigated because of its potential to reduce the component of backscattered light from below the surface of the water. Measurements should be made about 45 deg nadir view angle in the direction opposite the sun. Overcast sky conditions provide a higher intensity of skylight relative to clear sky conditions and a lower intensity of backscatter within the water relative to surface reflectance. These factors result in higher contrast between oil and water under overcast skies.

Kilohoku Ho`okele Wa`a--- Na `Ohana Hoku `Eha (The Astronomy of the Hawaiian Navigators--- The Four Star Families)

NASA Astrophysics Data System (ADS)

Slater, Stephanie; Slater, Timothy F.; Baybayan, Kalepa C.

2016-01-01

This paper documents the complete modern Hawaiian navigational full-sky. Over eight years of field notes, observations, and interviews with cultural leaders, historians, and ho`okele wa`a (navigators) were used to construct and validate Kilohoku Ho`okele Wa`a, the Astronomy of the Hawaiian Navigators. In contrast to the various historical sky maps designed by different practitioners and local groups in pre-colonial times, this sky-map depicts the four whole-sky constellations used by present day wayfinders. Designed by a loosely bound group of cultural leaders and navigators as a tool to use in modern non-instrumental navigation, Kilohoku Ho`okele Wa`a is a pragmatic fusion of ancient Hawaiian tradition, traditions of greater Polynesia, and modern-day Indigenous cultural forces. Like a very small number of cultures who use the sky for non-instrumental navigation, the ho`okele wa`a conceive of each season's visible sky as a whole image, using a single constellation that stretches from the northern to the southern horizon as a tool that facilitates direction finding in skies that are often very cloudy, and that chunks the sky into sections that decrease the cognitive load placed on the navigator. Moving through the seasons, beginning in Winter, Na `Ohana Hoku `Eha (The Four Star Families) are Kekaomakali`I (The Bailer), Kaiwikuamo`o (The Backbone), Manaiakalani (The Fishhook), and Kalupekawelo (The Kite). The whole-sky character of each of the four "star families," combines with that star family's mo`olelo (purposeful story) to further facilitate navigation, employing the emotional component of moral and familial associations to enhance memorization and to provide wayfinders with encouragement on their long journeys.

Examining Dense Data Usage near the Regions with Severe Storms in All-Sky Microwave Radiance Data Assimilation and Impacts on GEOS Hurricane Analyses

NASA Technical Reports Server (NTRS)

Kim, Min-Jeong; Jin, Jianjun; McCarty, Will; El Akkraoui, Amal; Todling, Ricardo; Gelaro, Ron

2018-01-01

Many numerical weather prediction (NWP) centers assimilate radiances affected by clouds and precipitation from microwave sensors, with the expectation that these data can provide critical constraints on meteorological parameters in dynamically sensitive regions to make significant impacts on forecast accuracy for precipitation. The Global Modeling and Assimilation Office (GMAO) at NASA Goddard Space Flight Center assimilates all-sky microwave radiance data from various microwave sensors such as all-sky GPM Microwave Imager (GMI) radiance in the Goddard Earth Observing System (GEOS) atmospheric data assimilation system (ADAS), which includes the GEOS atmospheric model, the Gridpoint Statistical Interpolation (GSI) atmospheric analysis system, and the Goddard Aerosol Assimilation System (GAAS). So far, most of NWP centers apply same large data thinning distances, that are used in clear-sky radiance data to avoid correlated observation errors, to all-sky microwave radiance data. For example, NASA GMAO is applying 145 km thinning distances for most of satellite radiance data including microwave radiance data in which all-sky approach is implemented. Even with these coarse observation data usage in all-sky assimilation approach, noticeable positive impacts from all-sky microwave data on hurricane track forecasts were identified in GEOS-5 system. The motivation of this study is based on the dynamic thinning distance method developed in our all-sky framework to use of denser data in cloudy and precipitating regions due to relatively small spatial correlations of observation errors. To investigate the benefits of all-sky microwave radiance on hurricane forecasts, several hurricane cases selected between 2016-2017 are examined. The dynamic thinning distance method is utilized in our all-sky approach to understand the sources and mechanisms to explain the benefits of all-sky microwave radiance data from various microwave radiance sensors like Advanced Microwave Sounder Unit (AMSU-A), Microwave Humidity Sounder (MHS), and GMI on GEOS-5 analyses and forecasts of various hurricanes.

Applying an economical scale-aware PDF-based turbulence closure model in NOAA NCEP GCMs.

NASA Astrophysics Data System (ADS)

Belochitski, A.; Krueger, S. K.; Moorthi, S.; Bogenschutz, P.; Cheng, A.

2017-12-01

A novel unified representation of sub-grid scale (SGS) turbulence, cloudiness, and shallow convection is being implemented into the NOAA NCEP Global Forecasting System (GFS) general circulation model. The approach, known as Simplified High Order Closure (SHOC), is based on predicting a joint PDF of SGS thermodynamic variables and vertical velocity, and using it to diagnose turbulent diffusion coefficients, SGS fluxes, condensation, and cloudiness. Unlike other similar methods, comparatively few new prognostic variables needs to be introduced, making the technique computationally efficient. In the base version of SHOC it is SGS turbulent kinetic energy (TKE), and in the developmental version — SGS TKE, and variances of total water and moist static energy (MSE). SHOC is now incorporated into a version of GFS that will become a part of the NOAA Next Generation Global Prediction System based around NOAA GFDL's FV3 dynamical core, NOAA Environmental Modeling System (NEMS) coupled modeling infrastructure software, and a set novel physical parameterizations. Turbulent diffusion coefficients computed by SHOC are now used in place of those produced by the boundary layer turbulence and shallow convection parameterizations. Large scale microphysics scheme is no longer used to calculate cloud fraction or the large-scale condensation/deposition. Instead, SHOC provides these quantities. Radiative transfer parameterization uses cloudiness computed by SHOC. An outstanding problem with implementation of SHOC in the NCEP global models is excessively large high level tropical cloudiness. Comparison of the moments of the SGS PDF diagnosed by SHOC to the moments calculated in a GigaLES simulation of tropical deep convection case (GATE), shows that SHOC diagnoses too narrow PDF distributions of total cloud water and MSE in the areas of deep convective detrainment. A subsequent sensitivity study of SHOC's diagnosed cloud fraction (CF) to higher order input moments of the SGS PDF demonstrated that CF is improved if SHOC is provided with correct variances of total water and MSE. Consequently, SHOC was modified to include two new prognostic equations for variances of total water and MSE, and coupled with the Chikira-Sugiyama parameterization of deep convection to include effects of detrainment on the prognostic variances.

Select strengths and biases of models in representing the Arctic winter boundary layer over sea ice: the Larcform 1 single column model intercomparison

NASA Astrophysics Data System (ADS)

Pithan, Felix; Ackerman, Andrew; Angevine, Wayne M.; Hartung, Kerstin; Ickes, Luisa; Kelley, Maxwell; Medeiros, Brian; Sandu, Irina; Steeneveld, Gert-Jan; Sterk, H. A. M.; Svensson, Gunilla; Vaillancourt, Paul A.; Zadra, Ayrton

2016-09-01

Weather and climate models struggle to represent lower tropospheric temperature and moisture profiles and surface fluxes in Arctic winter, partly because they lack or misrepresent physical processes that are specific to high latitudes. Observations have revealed two preferred states of the Arctic winter boundary layer. In the cloudy state, cloud liquid water limits surface radiative cooling, and temperature inversions are weak and elevated. In the radiatively clear state, strong surface radiative cooling leads to the build-up of surface-based temperature inversions. Many large-scale models lack the cloudy state, and some substantially underestimate inversion strength in the clear state. Here, the transformation from a moist to a cold dry air mass is modeled using an idealized Lagrangian perspective. The trajectory includes both boundary layer states, and the single-column experiment is the first Lagrangian Arctic air formation experiment (Larcform 1) organized within GEWEX GASS (Global atmospheric system studies). The intercomparison reproduces the typical biases of large-scale models: some models lack the cloudy state of the boundary layer due to the representation of mixed-phase microphysics or to the interaction between micro- and macrophysics. In some models, high emissivities of ice clouds or the lack of an insulating snow layer prevent the build-up of surface-based inversions in the radiatively clear state. Models substantially disagree on the amount of cloud liquid water in the cloudy state and on turbulent heat fluxes under clear skies. Observations of air mass transformations including both boundary layer states would allow for a tighter constraint of model behavior.

Testing a polarimetric cloud imager aboard research vessel Polarstern: comparison of color-based and polarimetric cloud detection algorithms.

PubMed

Barta, András; Horváth, Gábor; Horváth, Ákos; Egri, Ádám; Blahó, Miklós; Barta, Pál; Bumke, Karl; Macke, Andreas

2015-02-10

Cloud cover estimation is an important part of routine meteorological observations. Cloudiness measurements are used in climate model evaluation, nowcasting solar radiation, parameterizing the fluctuations of sea surface insolation, and building energy transfer models of the atmosphere. Currently, the most widespread ground-based method to measure cloudiness is based on analyzing the unpolarized intensity and color distribution of the sky obtained by digital cameras. As a new approach, we propose that cloud detection can be aided by the additional use of skylight polarization measured by 180° field-of-view imaging polarimetry. In the fall of 2010, we tested such a novel polarimetric cloud detector aboard the research vessel Polarstern during expedition ANT-XXVII/1. One of our goals was to test the durability of the measurement hardware under the extreme conditions of a trans-Atlantic cruise. Here, we describe the instrument and compare the results of several different cloud detection algorithms, some conventional and some newly developed. We also discuss the weaknesses of our design and its possible improvements. The comparison with cloud detection algorithms developed for traditional nonpolarimetric full-sky imagers allowed us to evaluate the added value of polarimetric quantities. We found that (1) neural-network-based algorithms perform the best among the investigated schemes and (2) global information (the mean and variance of intensity), nonoptical information (e.g., sun-view geometry), and polarimetric information (e.g., the degree of polarization) improve the accuracy of cloud detection, albeit slightly.

A Satellite Survey of Cloud Cover and Water Vapor in the Southwestern USA and Northern Mexico

NASA Astrophysics Data System (ADS)

Carrasco, E.; Avila, R.; Erasmus, A.; Djorgovski, S. G.; Walker, A. R.; Blum, R.

2017-03-01

Cloud cover and water vapor conditions in the southwestern USA and northern Mexico were surveyed as a preparatory work for the Thirty Meter Telescope (TMT) in situ site testing program. Although the telescope site is already selected, the TMT site testing team decided to make public these results for its usefulness for the community. Using 58 months of meteorological satellite observations between 1993 July and 1999 September, different atmospheric parameters were quantified from data of the 10.7 μm and of 6.7 μm windows. In particular, cloud cover and water vapor conditions were identified in preferred areas. As a result of the aerial analysis, 15 sites of existing and potential telescope were selected, compared, and ranked in terms of their observing quality. The clearest sites are located along the spine of the Baja peninsula and into southern California on mountain peaks above the temperature inversion layer. A steep gradient of cloudiness was observed along the coast where coastal cloud and fog are trapped below the inversion layer. Moving from west to east over the continent, a significant increase in cloudiness was observed. The analysis shows that San Pedro Mártir, San Gorgonio Mountain and San Jacinto Peak have the largest fraction of clear sky conditions (˜74%). The site with the optimal combination of clear skies and low precipitable water vapor is Boundary Peak, Nevada. An approach based in satellite data provided a reliable method for sites comparison.

VizieR Online Data Catalog: SKY2000 Master Catalog, Version 5 (Myers+ 2006)

NASA Astrophysics Data System (ADS)

Myers, J. R.; Sande, C. B.; Miller, A. C.; Warren, W. H., Jr.; Tracewell, D. A.

2015-02-01

The SKYMAP Star Catalog System consists of a Master Catalog stellar database and a collection of utility software designed to create and maintain the database and to generate derivative mission star catalogs (run catalogs). It contains an extensive compilation of information on almost 300000 stars brighter than 8.0mag. The original SKYMAP Master Catalog was generated in the early 1970's. Incremental updates and corrections were made over the following years but the first complete revision of the source data occurred with Version 4.0. This revision also produced a unique, consolidated source of astrometric information which can be used by the astronomical community. The derived quantities were removed and wideband and photometric data in the R (red) and I (infrared) systems were added. Version 4 of the SKY2000 Master Catalog was completed in April 2002; it marks the global replacement of the variability identifier and variability data fields. More details can be found in the description file sky2kv4.pdf. The SKY2000 Version 5 Revision 4 Master Catalog differs from Revision 3 in that MK and HD spectral types have been added from the Catalogue of Stellar Spectral Classifications (B. A. Skiff of Lowell Observatory, 2005), which has been assigned source code 50 in this process. 9622 entries now have MK types from this source, while 3976 entries have HD types from this source. SKY2000 V5 R4 also differs globally from preceding MC versions in that the Galactic coordinate computations performed by UPDATE have been increased in accuracy, so that differences from the same quantities from other sources are now typically in the last decimal places carried in the MC. This version supersedes the previous versions 1(V/95), 2(V/102), 3(V/105) and 4(V/109). (6 data files).

AIRS Impact on Analysis and Forecast of an Extreme Rainfall Event (Indus River Valley 2010) with a Global Data Assimilation and Forecast System

NASA Technical Reports Server (NTRS)

Reale, O.; Lau, W. K.; Susskind, J.; Rosenberg, R.

2011-01-01

A set of data assimilation and forecast experiments are performed with the NASA Global data assimilation and forecast system GEOS-5, to compare the impact of different approaches towards assimilation of Advanced Infrared Spectrometer (AIRS) data on the precipitation analysis and forecast skill. The event chosen is an extreme rainfall episode which occurred in late July 11 2010 in Pakistan, causing massive floods along the Indus River Valley. Results show that the assimilation of quality-controlled AIRS temperature retrievals obtained under partly cloudy conditions produce better precipitation analyses, and substantially better 7-day forecasts, than assimilation of clear-sky radiances. The improvement of precipitation forecast skill up to 7 day is very significant in the tropics, and is caused by an improved representation, attributed to cloudy retrieval assimilation, of two contributing mechanisms: the low-level moisture advection, and the concentration of moisture over the area in the days preceding the precipitation peak.

Combining ground-based microwave radiometer and the AROME convective scale model through 1DVAR retrievals in complex terrain: an Alpine valley case study

NASA Astrophysics Data System (ADS)

Martinet, Pauline; Cimini, Domenico; De Angelis, Francesco; Canut, Guylaine; Unger, Vinciane; Guillot, Remi; Tzanos, Diane; Paci, Alexandre

2017-09-01

A RPG-HATPRO ground-based microwave radiometer (MWR) was operated in a deep Alpine valley during the Passy-2015 field campaign. This experiment aims to investigate how stable boundary layers during wintertime conditions drive the accumulation of pollutants. In order to understand the atmospheric processes in the valley, MWRs continuously provide vertical profiles of temperature and humidity at a high time frequency, providing valuable information to follow the evolution of the boundary layer. A one-dimensional variational (1DVAR) retrieval technique has been implemented during the field campaign to optimally combine an MWR and 1 h forecasts from the French convective scale model AROME. Retrievals were compared to radiosonde data launched at least every 3 h during two intensive observation periods (IOPs). An analysis of the AROME forecast errors during the IOPs has shown a large underestimation of the surface cooling during the strongest stable episode. MWR brightness temperatures were monitored against simulations from the radiative transfer model ARTS2 (Atmospheric Radiative Transfer Simulator) and radiosonde launched during the field campaign. Large errors were observed for most transparent channels (i.e., 51-52 GHz) affected by absorption model and calibration uncertainties while a good agreement was found for opaque channels (i.e., 54-58 GHz). Based on this monitoring, a bias correction of raw brightness temperature measurements was applied before the 1DVAR retrievals. 1DVAR retrievals were found to significantly improve the AROME forecasts up to 3 km but mainly below 1 km and to outperform usual statistical regressions above 1 km. With the present implementation, a root-mean-square error (RMSE) of 1 K through all the atmospheric profile was obtained with values within 0.5 K below 500 m in clear-sky conditions. The use of lower elevation angles (up to 5°) in the MWR scanning and the bias correction were found to improve the retrievals below 1000 m. MWR retrievals were found to catch deep near-surface temperature inversions very well. Larger errors were observed in cloudy conditions due to the difficulty of ground-based MWRs to resolve high level inversions that are still challenging. Finally, 1DVAR retrievals were optimized for the analysis of the IOPs by using radiosondes as backgrounds in the 1DVAR algorithm instead of the AROME forecasts. A significant improvement of the retrievals in cloudy conditions and below 1000 m in clear-sky conditions was observed. From this study, we can conclude that MWRs are expected to bring valuable information into numerical weather prediction models up to 3 km in altitude both in clear-sky and cloudy-sky conditions with the maximum improvement found around 500 m. With an accuracy between 0.5 and 1 K in RMSE, our study has also proven that MWRs are capable of resolving deep near-surface temperature inversions observed in complex terrain during highly stable boundary layer conditions.

Comparisons Between Ground Measurements of Broadband UV Irradiance (300-380 nm) and TOMS UV Estimates at Moscow for 1979-2000

NASA Technical Reports Server (NTRS)

Yurova, Alla Y.; Krotkov, Nicholay A.; Herman, Jay R.; Bhartia, P. K. (Technical Monitor)

2002-01-01

We show the comparisons between ground-based measurements of spectrally integrated (300 nm to 380 nm) ultraviolet (UV) irradiance with satellite estimates from the Total Ozone Mapping Spectrometer (TOMS) total ozone and reflectivity data for the whole period of TOMS measurements (1979-2000) over the Meteorological Observatory of Moscow State University (MO MSU), Moscow, Russia. Several aspects of the comparisons are analyzed, including effects of cloudiness, aerosol, and snow cover. Special emphasis is given to the effect of different spatial and temporal averaging of ground-based data when comparing with low-resolution satellite measurements (TOMS footprint area 50-200 sq km). The comparisons in cloudless scenes with different aerosol loading have revealed TOMS irradiance overestimates from +5% to +20%. A-posteriori correction of the TOMS data accounting for boundary layer aerosol absorption (single scattering albedo of 0.92) eliminates the bias for cloud-free conditions. The single scattering albedo was independently verified using CIMEL sun and sky-radiance measurements at MO MSU in September 2001. The mean relative difference between TOMS UV estimates and ground UV measurements mainly lies within 1 10% for both snow-free and snow period with a tendency to TOMS overestimation in snow-free period especially at overcast conditions when the positive bias reaches 15-17%. The analysis of interannual UV variations shows quite similar behavior for both TOMS and ground measurements (correlation coefficient r=0.8). No long-term trend in the annual mean bias was found for both clear-sky and all-sky conditions with snow and without snow. Both TOMS and ground data show positive trend in UV irradiance between 1979 and 2000. The UV trend is attributed to decreases in both cloudiness and aerosol optical thickness during the late 1990's over Moscow region. However, if the analyzed period is extended to include pre-TOMS era (1968-2000 period), no trend in ground UV irradiance is detected.

Comparison of ScaRaB, GOES 8, Aircraft, and Surface Observations of the Absorption of Solar Radiation by Clouds

NASA Technical Reports Server (NTRS)

Pope, Shelly K.; Valero, Francisco P. J.; Collins, William D.; Minnis, Patrick

2002-01-01

Data obtained by the Scanner for Radiation Budget (ScaRaB) instrument on the Meteor 3 satellite have been analyzed and compared to satellite (GOES 8), aircraft (Radiation Measurement System, RAMS), and surface (Baseline Solar Radiation Network (BSRN), Solar and Infrared Observations System (SIROS), and RAMS) measurements of irradiance obtained during the Atmospheric Radiation Measurements Enhanced Shortwave Experiment (ARESE). It is found that the ScaRaB data covering the period from March 1994 to February 1995 (the instrument's operational lifetime) indicate excess absorption of solar radiation by the cloudy atmosphere in agreement with previous aircraft, surface, and GOES 8 results. The full ScaRaB data set combined with BSRN and SIROS surface observations gives an average all-sky absorptance of 0.28. The GOES 8 data set combined with RAMS surface observations gives an average all-sky absorptance of 0.26. The aircraft data set (RAMS) gives a mean all-sky absorptance of 0.24 (for the column between 0.5 and 13 km).

Night-time activity forecast by season and weather in a longitudinal design - natural light effects on three years' rest-activity cycles in nursing home residents with dementia.

PubMed

Wahnschaffe, Amely; Nowozin, Claudia; Rath, Andreas; Floessner, Theresa; Appelhoff, Stefan; Münch, Mirjam; Kunz, Dieter

2017-12-01

Backround: Night-time agitation is a frequent symptom of dementia. It often causes nursing home admission and has been linked to circadian rhythm disturbances. A positive influence of light interventions on night-time agitation was shown in several studies. The aim of our study was to investigate whether there is a long-term association between regional weather data (as indicator for daylight availability) and 24-hour variations of motor activity. Motor activity of 20 elderly nursing home residents living with dementia was analyzed using recordings of continuously worn wrist activity monitors over a three-year period. The average recording duration was 479 ± 206 days per participant (mean ± SD). Regional cloud amount and day length data from the local weather station (latitude: 52°56'N) were included in the analysis to investigate their effects on several activity variables. Nocturnal rest, here defined as the five consecutive hours with the least motor activity during 24 hours (L5), was the most predictable activity variable per participant. There was a significant interaction of night-time activity with day length and cloud amount (F 1,1174 = 4.39; p = 0.036). Night-time activity was higher on cloudy short days than on clear short days (p = 0.007), and it was also higher on cloudy short days than on cloudy long days (p = 0.032). The need for sufficient zeitgeber (time cue) strength during winter time, especially when days are short and skies are cloudy, is crucial for elderly people living with dementia. Activity forecast by season and weather might be a valuable approach to anticipate adequately complementary use of electrical light and thereby foster lower night-time activity.

Select strengths and biases of models in representing the Arctic winter boundary layer over sea ice: the Larcform 1 single column model intercomparison

DOE PAGES

Pithan, Felix; Ackerman, Andrew; Angevine, Wayne M.; ...

2016-08-27

We struggle to represent lower tropospheric temperature and moisture profiles and surface fluxes in Artic winter using weather and climate models, partly because they lack or misrepresent physical processes that are specific to high latitudes. Observations have revealed two preferred states of the Arctic winter boundary layer. In the cloudy state, cloud liquid water limits surface radiative cooling, and temperature inversions are weak and elevated. In the radiatively clear state, strong surface radiative cooling leads to the build-up of surface-based temperature inversions. Many large-scale models lack the cloudy state, and some substantially underestimate inversion strength in the clear state. Themore » transformation from a moist to a cold dry air mass is modeled using an idealized Lagrangian perspective. The trajectory includes both boundary layer states, and the single-column experiment is the first Lagrangian Arctic air formation experiment (Larcform 1) organized within GEWEX GASS (Global atmospheric system studies). The intercomparison reproduces the typical biases of large-scale models: some models lack the cloudy state of the boundary layer due to the representation of mixed-phase microphysics or to the interaction between micro- and macrophysics. In some models, high emissivities of ice clouds or the lack of an insulating snow layer prevent the build-up of surface-based inversions in the radiatively clear state. Models substantially disagree on the amount of cloud liquid water in the cloudy state and on turbulent heat fluxes under clear skies. Finally, observations of air mass transformations including both boundary layer states would allow for a tighter constraint of model behavior.« less

Select strengths and biases of models in representing the Arctic winter boundary layer over sea ice: the Larcform 1 single column model intercomparison

PubMed Central

Pithan, Felix; Ackerman, Andrew; Angevine, Wayne M.; Hartung, Kerstin; Ickes, Luisa; Kelley, Maxwell; Medeiros, Brian; Sandu, Irina; Steeneveld, Gert-Jan; Sterk, HAM; Svensson, Gunilla; Vaillancourt, Paul A.; Zadra, Ayrton

2017-01-01

Weather and climate models struggle to represent lower tropospheric temperature and moisture profiles and surface fluxes in Arctic winter, partly because they lack or misrepresent physical processes that are specific to high latitudes. Observations have revealed two preferred states of the Arctic winter boundary layer. In the cloudy state, cloud liquid water limits surface radiative cooling, and temperature inversions are weak and elevated. In the radiatively clear state, strong surface radiative cooling leads to the build-up of surface-based temperature inversions. Many large-scale models lack the cloudy state, and some substantially underestimate inversion strength in the clear state. Here, the transformation from a moist to a cold dry air mass is modelled using an idealized Lagrangian perspective. The trajectory includes both boundary layer states, and the single-column experiment is the first Lagrangian Arctic air formation experiment (Larcform 1) organized within GEWEX GASS (Global atmospheric system studies). The intercomparison reproduces the typical biases of large-scale models: Some models lack the cloudy state of the boundary layer due to the representation of mixed-phase micro-physics or to the interaction between micro-and macrophysics. In some models, high emissivities of ice clouds or the lack of an insulating snow layer prevent the build-up of surface-based inversions in the radiatively clear state. Models substantially disagree on the amount of cloud liquid water in the cloudy state and on turbulent heat fluxes under clear skies. Observations of air mass transformations including both boundary layer states would allow for a tighter constraint of model behaviour. PMID:28966718

A cloudiness transition in a marine boundary layer

NASA Technical Reports Server (NTRS)

Betts, Alan K.; Boers, Reinout

1990-01-01

Boundary layer cloudiness plays several important roles in the energy budget of the earth. Low level stratocumulus are highly reflective clouds which reduce the net incoming shortwave radiation at the earth's surface. Climatically, the transition to a small area fraction of scattered cumulus clouds occurs as the air flows over warmer water. Although these clouds reflect less sunlight, they still play an important role in the boundary layer equilibrium by transporting water vapor upwards, and enhancing the surface evaporation. The First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE) included a marine stratocumulus experiment off the southern California coast from June 29 to July 19, 1987. The objectives of this experiment were to study the controls on fractional cloudiness, and to assess the role of cloud-top entrainment instability (CTEI) and mesoscale structure in determining cloud type. The focus is one research day, July 7, 1987, when coordinated aircraft missions were flown by four research aircraft, centered on a LANDSAT scene at 1830 UTC. The remarkable feature of this LANDSAT scene is the transition from a clear sky in the west through broken cumulus to solid stratocumulus in the east. The dynamic and thermodynamic structure of this transition in cloudiness is analyzed using data from the NCAR Electra. By averaging the aircraft data, the internal structure of the different cloud regimes is documented, and it is shown that the transition between broken cumulus and stratocumulus is associated with a change in structure with respect to the CTEI condition. However, this results not from sea surface temperature changes, but mostly from a transition in the air above the inversion, and the breakup appears to be at a structure on the unstable side of the wet virtual adiabat.

Select strengths and biases of models in representing the Arctic winter boundary layer over sea ice: the Larcform 1 single column model intercomparison.

PubMed

Pithan, Felix; Ackerman, Andrew; Angevine, Wayne M; Hartung, Kerstin; Ickes, Luisa; Kelley, Maxwell; Medeiros, Brian; Sandu, Irina; Steeneveld, Gert-Jan; Sterk, Ham; Svensson, Gunilla; Vaillancourt, Paul A; Zadra, Ayrton

2016-09-01

Weather and climate models struggle to represent lower tropospheric temperature and moisture profiles and surface fluxes in Arctic winter, partly because they lack or misrepresent physical processes that are specific to high latitudes. Observations have revealed two preferred states of the Arctic winter boundary layer. In the cloudy state, cloud liquid water limits surface radiative cooling, and temperature inversions are weak and elevated. In the radiatively clear state, strong surface radiative cooling leads to the build-up of surface-based temperature inversions. Many large-scale models lack the cloudy state, and some substantially underestimate inversion strength in the clear state. Here, the transformation from a moist to a cold dry air mass is modelled using an idealized Lagrangian perspective. The trajectory includes both boundary layer states, and the single-column experiment is the first L agrangian Arc tic air form ation experiment (Larcform 1) organized within GEWEX GASS (Global atmospheric system studies). The intercomparison reproduces the typical biases of large-scale models: Some models lack the cloudy state of the boundary layer due to the representation of mixed-phase micro-physics or to the interaction between micro-and macrophysics. In some models, high emissivities of ice clouds or the lack of an insulating snow layer prevent the build-up of surface-based inversions in the radiatively clear state. Models substantially disagree on the amount of cloud liquid water in the cloudy state and on turbulent heat fluxes under clear skies. Observations of air mass transformations including both boundary layer states would allow for a tighter constraint of model behaviour.

A Study of the Role of Clouds in the Relationship Between Land Use/Land Cover and the Climate and Air Quality of the Atlanta Area

NASA Technical Reports Server (NTRS)

Kidder, Stanley Q.; Hafner, Jan

1997-01-01

The goal of Project ATLANTA is to derive a better scientific understanding of how land cover changes associated with urbanization affect local and regional climate and air quality. Clouds play a significant role in this relationship. Using GOES images, we found that in a 63-day period (5 July-5 September 1996) there were zero days which were clear for the entire daylight period. Days which are cloud-free in the morning become partly cloudy with small cumulus clouds in the afternoon in response to solar heating. This result casts doubt on the applicability of California-style air quality models which run in perpetual clear skies. Days which are clear in the morning have higher ozone than those which are cloudy in the morning. Using the RAMS model, we found that urbanization increases the skin surface temperature by about 1.0-1.5 C on average under cloudy conditions, with an extreme of +3.5 C. Clouds cool the surface due to their shading effect by 1.5-2.0 C on average, with an extreme of 5.0 C. RAMS simulates well the building stage of the cumulus cloud field, but does poorly in the decaying phase. Next year's work: doing a detailed cloud climatology and developing improved RAMS cloud simulations.

Astronomy Outreach Activities for Special Needs Children and Their Families

NASA Astrophysics Data System (ADS)

Lubowich, D.

2010-08-01

I present the results of two NASA-IDEAS/STScI sponsored astronomy outreach programs for seriously ill children and their families staying at the Ronald McDonald House of Long Island (New Hyde Park, NY) and for children hospitalized at the Children's Medical Center, Winthrop University Hospital (Mineola, NY). These programs are designed for children of all ages and include STSCi's Tonight's Sky (monthly guide to the sky); telescope observations of the Moon, Sun, planets, nebulae, and stars; and hands-on activities. During cloudy weather remote/robotic telescope observations are shown. Edible demonstrations using chocolate, marshmallows, and popcorn are used to stimulate interest. The staff at the Ronald McDonald House and Children's Medical Center are being trained to use the telescope and to do demonstrations. These educational activities help children and their families learn about astronomy while providing a diversion to take their minds off their illness during a stressful time.

Analysis of Ozone in Cloudy Versus Clear Sky Conditions

NASA Technical Reports Server (NTRS)

Strode, Sarah; Douglass, Anne; Ziemke, Jerald

2016-01-01

Convection impacts ozone concentrations by transporting ozone vertically and by lofting ozone precursors from the surface, while the clouds and lighting associated with convection affect ozone chemistry. Observations of the above-cloud ozone column (Ziemke et al., 2009) derived from the OMI instrument show geographic variability, and comparison of the above-cloud ozone with all-sky tropospheric ozone columns from OMI indicates important regional differences. We use two global models of atmospheric chemistry, the GMI chemical transport model (CTM) and the GEOS-5 chemistry climate model, to diagnose the contributions of transport and chemistry to observed differences in ozone between areas with and without deep convection, as well as differences in clean versus polluted convective regions. We also investigate how the above-cloud tropospheric ozone from OMI can provide constraints on the relationship between ozone and convection in a free-running climate simulation as well as a CTM.

Comparison of radiation parametrizations within the HARMONIE-AROME NWP model

NASA Astrophysics Data System (ADS)

Rontu, Laura; Lindfors, Anders V.

2018-05-01

Downwelling shortwave radiation at the surface (SWDS, global solar radiation flux), given by three different parametrization schemes, was compared to observations in the HARMONIE-AROME numerical weather prediction (NWP) model experiments over Finland in spring 2017. Simulated fluxes agreed well with each other and with the observations in the clear-sky cases. In the cloudy-sky conditions, all schemes tended to underestimate SWDS at the daily level, as compared to the measurements. Large local and temporal differences between the model results and observations were seen, related to the variations and uncertainty of the predicted cloud properties. The results suggest a possibility to benefit from the use of different radiative transfer parametrizations in a NWP model to obtain perturbations for the fine-resolution ensemble prediction systems. In addition, we recommend usage of the global radiation observations for the standard validation of the NWP models.

Image acquisition in the Pi-of-the-Sky project

NASA Astrophysics Data System (ADS)

Jegier, M.; Nawrocki, K.; Poźniak, K.; Sokołowski, M.

2006-10-01

Modern astronomical image acquisition systems dedicated for sky surveys provide large amount of data in a single measurement session. During one session that lasts a few hours it is possible to get as much as 100 GB of data. This large amount of data needs to be transferred from camera and processed. This paper presents some aspects of image acquisition in a sky survey image acquisition system. It describes a dedicated USB linux driver for the first version of the "Pi of The Sky" CCD camera (later versions have also Ethernet interface) and the test program for the camera together with a driver-wrapper providing core device functionality. Finally, the paper contains description of an algorithm for matching several images based on image features, i.e. star positions and their brightness.

Convective signals from surface measurements at ARM Tropical Western Pacific site: Manus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yi; Long, Charles N.; Mather, James H.

2011-02-04

Madden-Julian Oscillation (MJO) signals have been detected using highly sampled observations from the U.S. DOE ARM Climate Research Facility located at the Tropical Western Pacific Manus site. Using downwelling shortwave radiative fluxes and derived shortwave fractional sky cover, and the statistical tools of wavelet, cross wavelet, and Fourier spectrum power, we report finding major convective signals and their phase change from surface observations spanning from 1996 to 2006. Our findings are confirmed with the satellite-gauge combined values of precipitation from the NASA Global Precipitation Climatology Project and the NOAA interpolated outgoing longwave radiation for the same location. We find thatmore » the Manus MJO signal is weakest during the strongest 1997-1998 El Nin˜o Southern Oscillation (ENSO) year. A significant 3-5-month lead in boreal winter is identified further between Manus MJO and NOAA NINO3.4 sea surface temperature (former leads latter). A striking inverse relationship is found also between the instantaneous synoptic and intraseasonal phenomena over Manus. To further study the interaction between intraseasonal and diurnal scale variability, we composite the diurnal cycle of cloudiness for 21-MJO events that have passed over Manus. Our diurnal composite analysis of shortwave and longwave fractional sky covers indicates that during the MJO peak (strong convection), the diurnal amplitude of cloudiness is reduced substantially, while the diurnal mean cloudiness reaches the highest value and there are no significant phase changes. We argue that the increasing diurnal mean and decreasing diurnal amplitude are caused by the systematic convective cloud formation that is associated with the wet phase of the MJO, while the diurnal phase is still regulated by the well-defined solar forcing. This confirms our previous finding of the anti-phase relationship between the synoptic and intraseasonal phenomena. The detection of theMJOover the Manus site provides further opportunities in using other ground-based remote sensing instruments to investigate the vertical distributions of clouds and radiative heatings of the MJO that currently is impossible from satellite observations.« less

DISCRIMINATING BETWEEN CLOUDY, HAZY, AND CLEAR SKY EXOPLANETS USING REFRACTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Misra, Amit K.; Meadows, Victoria S.

2014-11-01

We propose a method to distinguish between cloudy, hazy, and clear sky (free of clouds and hazes) exoplanet atmospheres that could be applicable to upcoming large aperture space- and ground-based telescopes such as the James Webb Space Telescope (JWST) and the European Extremely Large Telescope (E-ELT). These facilities will be powerful tools for characterizing transiting exoplanets, but only after a considerable amount of telescope time is devoted to a single planet. A technique that could provide a relatively rapid means of identifying haze-free targets (which may be more valuable targets for characterization) could potentially increase the science return for thesemore » telescopes. Our proposed method utilizes broadband observations of refracted light in the out-of-transit spectrum. Light refracted through an exoplanet atmosphere can lead to an increase of flux prior to ingress and subsequent to egress. Because this light is transmitted at pressures greater than those for typical cloud and haze layers, the detection of refracted light could indicate a cloud- or haze-free atmosphere. A detection of refracted light could be accomplished in <10 hr for Jovian exoplanets with JWST and <5 hr for super-Earths/mini-Neptunes with E-ELT. We find that this technique is most effective for planets with equilibrium temperatures between 200 and 500 K, which may include potentially habitable planets. A detection of refracted light for a potentially habitable planet would strongly suggest the planet was free of a global cloud or haze layer, and therefore a promising candidate for follow-up observations.« less

Distribution to the Astronomy Community of the Compressed Digitized Sky Survey

NASA Astrophysics Data System (ADS)

Postman, Marc

1996-03-01

The Space Telescope Science Institute has compressed an all-sky collection of ground-based images and has printed the data on a two volume, 102 CD-ROM disc set. The first part of the survey (containing images of the southern sky) was published in May 1994. The second volume (containing images of the northern sky) was published in January 1995. Software which manages the image retrieval is included with each volume. The Astronomical Society of the Pacific (ASP) is handling the distribution of the lOx compressed data and has sold 310 sets as of October 1996. ASP is also handling the distribution of the recently published 100x version of the northern sky survey which is publicly available at a low cost. The target markets for the 100x compressed data set are the amateur astronomy community, educational institutions, and the general public. During the next year, we plan to publish the first version of a photometric calibration database which will allow users of the compressed sky survey to determine the brightness of stars in the images.

Distribution to the Astronomy Community of the Compressed Digitized Sky Survey

NASA Technical Reports Server (NTRS)

Postman, Marc

1996-01-01

The Space Telescope Science Institute has compressed an all-sky collection of ground-based images and has printed the data on a two volume, 102 CD-ROM disc set. The first part of the survey (containing images of the southern sky) was published in May 1994. The second volume (containing images of the northern sky) was published in January 1995. Software which manages the image retrieval is included with each volume. The Astronomical Society of the Pacific (ASP) is handling the distribution of the lOx compressed data and has sold 310 sets as of October 1996. ASP is also handling the distribution of the recently published 100x version of the northern sky survey which is publicly available at a low cost. The target markets for the 100x compressed data set are the amateur astronomy community, educational institutions, and the general public. During the next year, we plan to publish the first version of a photometric calibration database which will allow users of the compressed sky survey to determine the brightness of stars in the images.

Detection of carbon monoxide pollution from cities and wildfires on regional and urban scales: the benefit of CO column retrievals from SCIAMACHY 2.3 µm measurements under cloudy conditions

NASA Astrophysics Data System (ADS)

Borsdorff, Tobias; Andrasec, Josip; aan de Brugh, Joost; Hu, Haili; Aben, Ilse; Landgraf, Jochen

2018-05-01

In the perspective of the upcoming TROPOMI Sentinel-5 Precursor carbon monoxide data product, we discuss the benefit of using CO total column retrievals from cloud-contaminated SCIAMACHY 2.3 µm shortwave infrared spectra to detect atmospheric CO enhancements on regional and urban scales due to emissions from cities and wildfires. The study uses the operational Sentinel-5 Precursor algorithm SICOR, which infers the vertically integrated CO column together with effective cloud parameters. We investigate its capability to detect localized CO enhancements distinguishing between clear-sky observations and observations with low (< 1.5 km) and medium-high clouds (1.5-5 km). As an example, we analyse CO enhancements over the cities Paris, Los Angeles and Tehran as well as the wildfire events in Mexico-Guatemala 2005 and Alaska-Canada 2004. The CO average of the SCIAMACHY full-mission data set of clear-sky observations can detect weak CO enhancements of less than 10 ppb due to air pollution in these cities. For low-cloud conditions, the CO data product performs similarly well. For medium-high clouds, the observations show a reduced CO signal both over Tehran and Los Angeles, while for Paris no significant CO enhancement can be detected. This indicates that information about the vertical distribution of CO can be obtained from the SCIAMACHY measurements. Moreover, for the Mexico-Guatemala fires, the low-cloud CO data captures a strong outflow of CO over the Gulf of Mexico and the Pacific Ocean and so provides complementary information to clear-sky retrievals, which can only be obtained over land. For both burning events, enhanced CO values are even detectable with medium-high-cloud retrievals, confirming a distinct vertical extension of the pollution. The larger number of additional measurements, and hence the better spatial coverage, significantly improve the detection of wildfire pollution using both the clear-sky and cloudy CO retrievals. Due to the improved instrument performance of the TROPOMI instrument with respect to its precursor SCIAMACHY, the upcoming Sentinel-5 Precursor CO data product will allow improved detection of CO emissions and their vertical extension over cities and fires, making new research applications possible.

A novel method to improve MODIS AOD retrievals in cloudy pixels using an analog ensemble approach

NASA Astrophysics Data System (ADS)

Kumar, R.; Raman, A.; Delle Monache, L.; Alessandrini, S.; Cheng, W. Y. Y.; Gaubert, B.; Arellano, A. F.

2016-12-01

Particulate matter (PM) concentrations are one of the fundamental indicators of air quality. Earth orbiting satellite platforms acquire column aerosol abundance that can in turn provide information about the PM concentrations. One of the serious limitations of column aerosol retrievals from low earth orbiting satellites is that these algorithms are based on clear sky assumptions. They do not retrieve AOD in cloudy pixels. After filtering cloudy pixels, these algorithms also arbitrarily remove brightest and darkest 25% of remaining pixels over ocean and brightest and darkest 50% pixels over land to filter any residual contamination from clouds. This becomes a critical issue especially in regions that experience monsoon, like Asia and North America. In case of North America, monsoon season experiences wide variety of extreme air quality events such as fires in California and dust storms in Arizona. Assessment of these episodic events warrants frequent monitoring of aerosol observations from remote sensing retrievals. In this study, we demonstrate a method to fill in cloudy pixels in Moderate Imaging Resolution Spectroradiometer (MODIS) AOD retrievals based on ensembles generated using an analog-based approach (AnEn). It provides a probabilistic distribution of AOD in cloudy pixels using historical records of model simulations of meteorological predictors such as AOD, relative humidity, and wind speed, and past observational records of MODIS AOD at a given target site. We use simulations from a coupled community weather forecasting model with chemistry (WRF-Chem) run at a resolution comparable to MODIS AOD. Analogs selected from summer months (June, July) of 2011-2013 from model and corresponding observations are used as a training dataset. Then, missing AOD retrievals in cloudy pixels in the last 31 days of the selected period are estimated. Here, we use AERONET stations as target sites to facilitate comparison against in-situ measurements. We use two approaches to evaluate the estimated AOD: 1) by comparing against reanalysis AOD, 2) by inverting AOD to PM10 concentrations and then comparing those with measured PM10. AnEn is an efficient approach to generate an ensemble as it involves only one model run and provides an estimate of uncertainty that complies with the physical and chemical state of the atmosphere.

Effects of clouds on the surface shortwave radiation at a rural inland mid-latitude site

NASA Astrophysics Data System (ADS)

Salgueiro, Vanda; Costa, Maria João; Silva, Ana Maria; Bortoli, Daniele

2016-09-01

Seven years (2003-2010) of measured shortwave (SW) irradiances were used to obtain estimates of the 10 min averaged effective cloud optical thickness (ECOT) and of the shortwave cloud radiative effect (CRESW) at the surface in a mid-latitude site (Évora - south of Portugal), and its seasonal variability is presented. The ECOT, obtained using transmittance measurements at 415 nm, was compared with the correspondent MODIS cloud optical thickness (MODIS COT) for non-precipitating water clouds and cloud fractions higher than 0.25. This comparison showed that the ECOT represents well the cloud optical thickness over the study area. The CRESW, determined for two SW broadband ranges (300-1100 nm; 285-2800 nm), was normalized (NCRESW) and related with the obtained ECOT. A logarithmic relation between NCRESW and ECOT was found for both SW ranges, presenting lower dispersion for overcast-sky situations than for partially cloudy-sky situations. The NCRESW efficiency (NCRESW per unit of ECOT) was also related with the ECOT for overcast-sky conditions. The relation found is parameterized by a power law function showing that NCRESW efficiency decreases as the ECOT increases, approaching one for ECOT values higher than about 50.

Estimating Planetary Boundary Layer Heights from NOAA Profiler Network Wind Profiler Data

NASA Technical Reports Server (NTRS)

Molod, Andrea M.; Salmun, H.; Dempsey, M

2015-01-01

An algorithm was developed to estimate planetary boundary layer (PBL) heights from hourly archived wind profiler data from the NOAA Profiler Network (NPN) sites located throughout the central United States. Unlike previous studies, the present algorithm has been applied to a long record of publicly available wind profiler signal backscatter data. Under clear conditions, summertime averaged hourly time series of PBL heights compare well with Richardson-number based estimates at the few NPN stations with hourly temperature measurements. Comparisons with clear sky reanalysis based estimates show that the wind profiler PBL heights are lower by approximately 250-500 m. The geographical distribution of daily maximum PBL heights corresponds well with the expected distribution based on patterns of surface temperature and soil moisture. Wind profiler PBL heights were also estimated under mostly cloudy conditions, and are generally higher than both the Richardson number based and reanalysis PBL heights, resulting in a smaller clear-cloudy condition difference. The algorithm presented here was shown to provide a reliable summertime climatology of daytime hourly PBL heights throughout the central United States.

Forward Model Studies of Water Vapor Using Scanning Microwave Radiometers, Global Positioning System, and Radiosondes during the Cloudiness Intercomparison Experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mattioli, Vinia; Westwater, Ed R.; Gutman, S.

2005-05-01

Brightness temperatures computed from five absorption models and radiosonde observations were analyzed by comparing them with measurements from three microwave radiometers at 23.8 and 31.4 GHz. Data were obtained during the Cloudiness Inter-Comparison experiment at the U.S. Department of Energy's Atmospheric Radiation Measurement Program's (ARM) site in North-Central Oklahoma in 2003. The radiometers were calibrated using two procedures, the so-called instantaneous ?tipcal? method and an automatic self-calibration algorithm. Measurements from the radiometers were in agreement, with less than a 0.4-K difference during clear skies, when the instantaneous method was applied. Brightness temperatures from the radiometer and the radiosonde showed anmore » agreement of less than 0.55 K when the most recent absorption models were considered. Precipitable water vapor (PWV) computed from the radiometers were also compared to the PWV derived from a Global Positioning System station that operates at the ARM site. The instruments agree to within 0.1 cm in PWV retrieval.« less

Daytime Water Detection Based on Color Variation

NASA Technical Reports Server (NTRS)

Rankin, Arturo L.; Matthies, Larry H.

2010-01-01

Robust water detection is a critical perception requirement for unmanned ground vehicle (UGV) autonomous navigation. This is particularly true in wide open areas where water can collect in naturally occurring terrain depressions during periods of heavy precipitation and form large water bodies (such as ponds). At far range, reflections of the sky provide a strong cue for water. But at close range, the color coming out of a water body dominates sky reflections and the water cue from sky reflections is of marginal use. We model this behavior by using water body intensity data from multiple frames of RGB imagery to estimate the total reflection coefficient contribution from surface reflections and the combination of all other factors. Then we describe an algorithm that uses one of the color cameras in a forward- looking, UGV-mounted stereo-vision perception system to detect water bodies in wide open areas. This detector exploits the knowledge that the change in saturation-to-brightness ratio across a water body from the leading to trailing edge is uniform and distinct from other terrain types. In test sequences approaching a pond under clear, overcast, and cloudy sky conditions, the true positive and false negative water detection rates were (95.76%, 96.71%, 98.77%) and (0.45%, 0.60%, 0.62%), respectively. This software has been integrated on an experimental unmanned vehicle and field tested at Ft. Indiantown Gap, PA.

Quantifying the clear-sky bias of satellite-derived infrared LST

NASA Astrophysics Data System (ADS)

Ermida, S. L.; Trigo, I. F.; DaCamara, C.

2017-12-01

Land surface temperature (LST) is one of the most relevant parameters when addressing the physical processes that take place at the surface of the Earth. Satellite data are particularly appropriate for measuring LST over the globe with high temporal resolution. Remote-sensed LST estimation from space-borne sensors has been systematically performed over the Globe for nearly 3 decades and geostationary LST climate data records are now available. The retrieval of LST from satellite observations generally relies on measurements in the thermal infrared (IR) window. Although there is a large number of IR sensors on-board geostationary satellites and polar orbiters suitable for LST retrievals with different temporal and spatial resolutions, the use of IR observations limits LST estimates to clear sky conditions. As a consequence, climate studies based on IR LST are likely to be affected by the restriction of LST data to cloudless conditions. However, such "clear sky bias" has never been quantified and, therefore, the actual impact of relying only on clear sky data is still to be determined. On the other hand, an "all-weather" global LST database may be set up based on passive microwave (MW) measurements which are much less affected by clouds. An 8-year record of all-weather MW LST is here used to quantify the clear-sky bias of IR LST at global scale based on MW observations performed by the Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) onboard NASA's Aqua satellite. Selection of clear-sky and cloudy pixels is based on information derived from measurements performed by the Moderate Resolution Imaging Spectroradiometer (MODIS) on-board the same satellite.

Inversion of AMSR-E observations for land surface temperature estimation: 2. Global comparison with infrared satellite temperature

NASA Astrophysics Data System (ADS)

Ermida, S. L.; Jiménez, C.; Prigent, C.; Trigo, I. F.; DaCamara, C. C.

2017-03-01

A comparison of land surface temperature (Ts) derived from the Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) with infrared Ts is presented. The infrared Ts include clear-sky estimates from the Moderate Resolution Imaging Spectroradiometer (MODIS), the Spinning Enhanced Visible and Infrared Imager, the Geostationary Operational Environmental Satellite (GOES) Imager, and the Japanese Meteorological Imager. The higher discrepancies between AMSR-E and MODIS are observed over deserts and snow-covered areas. The former seems to be associated with Ts underestimation by MODIS, whereas the latter is mostly related to uncertainties in microwave emissivity over snow/ice. Ts differences between AMSR-E and MODIS are significantly reduced after masking out snow and deserts, with a bias change from 2.6/4.6 K to 3.0/1.4 K for daytime/nighttime and a standard deviation (STD) decrease from 7.3/7.9 K to 5.1/3.9 K. When comparing with all infrared sensors, the STD of the differences between microwave and infrared Ts is generally higher than between IR retrievals. However, the biases between microwave and infrared Ts are, in some cases, of the same order as the ones observed between infrared products. This is the case for GOES, with daytime biases with respect to AMSR-E and MODIS of 0.45 K and 0.60 K, respectively. While the infrared Ts are clear-sky estimates, AMSR-E also provides Ts under cloudy conditions. For frequently cloudy regions, this results in a large increase of available Ts estimates (>250%), making the microwave Ts a very powerful complement of the infrared estimates.

Marine cloud brightening – as effective without clouds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahlm, Lars; Jones, Andy; Stjern, Camilla W.

Marine cloud brightening through sea spray injection has been proposed as a climate engineering method for avoiding the most severe consequences of global warming. A limitation of most of the previous modelling studies on marine cloud brightening is that they have either considered individual models or only investigated the effects of a specific increase in the number of cloud droplets. Here we present results from coordinated simulations with three Earth system models (ESMs) participating in the Geoengineering Model Intercomparison Project (GeoMIP) G4sea-salt experiment. Injection rates of accumulation-mode sea spray aerosol particles over ocean between 30°N and 30°S are set in each model tomore » generate a global-mean effective radiative forcing (ERF) of –2.0 W m –2 at the top of the atmosphere. We find that the injection increases the cloud droplet number concentration in lower layers, reduces the cloud-top effective droplet radius, and increases the cloud optical depth over the injection area. We also find, however, that the global-mean clear-sky ERF by the injected particles is as large as the corresponding total ERF in all three ESMs, indicating a large potential of the aerosol direct effect in regions of low cloudiness. The largest enhancement in ERF due to the presence of clouds occur as expected in the subtropical stratocumulus regions off the west coasts of the American and African continents. However, outside these regions, the ERF is in general equally large in cloudy and clear-sky conditions. Lastly, these findings suggest a more important role of the aerosol direct effect in sea spray climate engineering than previously thought.« less

Marine cloud brightening – as effective without clouds

DOE PAGES

Ahlm, Lars; Jones, Andy; Stjern, Camilla W.; ...

2017-11-06

Marine cloud brightening through sea spray injection has been proposed as a climate engineering method for avoiding the most severe consequences of global warming. A limitation of most of the previous modelling studies on marine cloud brightening is that they have either considered individual models or only investigated the effects of a specific increase in the number of cloud droplets. Here we present results from coordinated simulations with three Earth system models (ESMs) participating in the Geoengineering Model Intercomparison Project (GeoMIP) G4sea-salt experiment. Injection rates of accumulation-mode sea spray aerosol particles over ocean between 30°N and 30°S are set in each model tomore » generate a global-mean effective radiative forcing (ERF) of –2.0 W m –2 at the top of the atmosphere. We find that the injection increases the cloud droplet number concentration in lower layers, reduces the cloud-top effective droplet radius, and increases the cloud optical depth over the injection area. We also find, however, that the global-mean clear-sky ERF by the injected particles is as large as the corresponding total ERF in all three ESMs, indicating a large potential of the aerosol direct effect in regions of low cloudiness. The largest enhancement in ERF due to the presence of clouds occur as expected in the subtropical stratocumulus regions off the west coasts of the American and African continents. However, outside these regions, the ERF is in general equally large in cloudy and clear-sky conditions. Lastly, these findings suggest a more important role of the aerosol direct effect in sea spray climate engineering than previously thought.« less

Cloud Properties under Different Synoptic Circulations: Comparison of Radiosonde and Ground-Based Active Remote Sensing Measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jinqiang; Li, Jun; Xia, Xiangao

In this study, long-term (10 years) radiosonde-based cloud data are compared with the ground-based active remote sensing product under six prevailing large-scale synoptic patterns, i.e., cyclonic center (CC), weak pressure pattern (WP), the southeast bottom of cyclonic center (CB), cold front (CF), anticyclone edge (AE) and anticyclone center (AC) over the Southern Great Plains (SGP) site. The synoptic patterns are generated by applying the self-organizing map weather classification method to the daily National Centers for Environmental Protection mean sea level pressure records from the North American Regional Reanalysis. It reveals that the large-scale synoptic circulations can strongly influence the regionalmore » cloud formation, and thereby have impact on the consistency of cloud retrievals from the radiosonde and ground-based cloud product. The total cloud cover at the SGP site is characterized by the least in AC and the most in CF. The minimum and maximum differences between the two cloud methods are 10.3% for CC and 13.3% for WP. Compared to the synoptic patterns characterized by scattered cloudy and clear skies (AE and AC), the agreement of collocated cloud boundaries between the two cloud approaches tends to be better under the synoptic patterns dominated by overcast and cloudy skies (CC, WP and CB). The rainy and windy weather conditions in CF synoptic pattern influence the consistency of the two cloud retrieval methods associated with the limited capabilities inherent to the instruments. As a result, the cloud thickness distribution from the two cloud datasets compares favorably with each other in all synoptic patterns, with relative discrepancy of ≤0.3 km.« less

Cloud Properties under Different Synoptic Circulations: Comparison of Radiosonde and Ground-Based Active Remote Sensing Measurements

DOE PAGES

Zhang, Jinqiang; Li, Jun; Xia, Xiangao; ...

2016-11-28

In this study, long-term (10 years) radiosonde-based cloud data are compared with the ground-based active remote sensing product under six prevailing large-scale synoptic patterns, i.e., cyclonic center (CC), weak pressure pattern (WP), the southeast bottom of cyclonic center (CB), cold front (CF), anticyclone edge (AE) and anticyclone center (AC) over the Southern Great Plains (SGP) site. The synoptic patterns are generated by applying the self-organizing map weather classification method to the daily National Centers for Environmental Protection mean sea level pressure records from the North American Regional Reanalysis. It reveals that the large-scale synoptic circulations can strongly influence the regionalmore » cloud formation, and thereby have impact on the consistency of cloud retrievals from the radiosonde and ground-based cloud product. The total cloud cover at the SGP site is characterized by the least in AC and the most in CF. The minimum and maximum differences between the two cloud methods are 10.3% for CC and 13.3% for WP. Compared to the synoptic patterns characterized by scattered cloudy and clear skies (AE and AC), the agreement of collocated cloud boundaries between the two cloud approaches tends to be better under the synoptic patterns dominated by overcast and cloudy skies (CC, WP and CB). The rainy and windy weather conditions in CF synoptic pattern influence the consistency of the two cloud retrieval methods associated with the limited capabilities inherent to the instruments. As a result, the cloud thickness distribution from the two cloud datasets compares favorably with each other in all synoptic patterns, with relative discrepancy of ≤0.3 km.« less

Longwave Radiative Flux Calculations in the TOVS Pathfinder Path A Data Set

NASA Technical Reports Server (NTRS)

Mehta, Amita; Susskind, Joel

1999-01-01

A radiative transfer model developed to calculate outgoing longwave radiation (OLR) and downwelling longwave, surface flux (DSF) from the Television and Infrared Operational Satellite (TIROS) Operational Vertical Sounder (TOVS) Pathfinder Path A retrieval products is described. The model covers the spectral range of 2 to 2800 cm in 14 medium medium spectral bands. For each band, transmittances are parameterized as a function of temperature, water vapor, and ozone profiles. The form of the band transmittance parameterization is a modified version of the approach we use to model channel transmittances for the High Resolution Infrared Sounder 2 (HIRS2) instrument. We separately derive effective zenith angle for each spectral band such that band-averaged radiance calculated at that angle best approximates directionally integrated radiance for that band. We develop the transmittance parameterization at these band-dependent effective zenith angles to incorporate directional integration of radiances required in the calculations of OLR and DSF. The model calculations of OLR and DSF are accurate and differ by less than 1% from our line-by-line calculations. Also, the model results are within 1% range of other line-by-line calculations provided by the Intercomparison of Radiation Codes in Climate Models (ICRCCM) project for clear-sky and cloudy conditions. The model is currently used to calculate global, multiyear (1985-1998) OLR and DSF from the TOVS Pathfinder Path A Retrievals.

Wild Fire Emissions for the NOAA Operational HYSPLIT Smoke Model

NASA Astrophysics Data System (ADS)

Huang, H. C.; ONeill, S. M.; Ruminski, M.; Shafran, P.; McQueen, J.; DiMego, G.; Kondragunta, S.; Gorline, J.; Huang, J. P.; Stunder, B.; Stein, A. F.; Stajner, I.; Upadhayay, S.; Larkin, N. K.

2015-12-01

Particulate Matter (PM) generated from forest fires often lead to degraded visibility and unhealthy air quality in nearby and downstream areas. To provide near-real time PM information to the state and local agencies, the NOAA/National Weather Service (NWS) operational HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory Model) smoke modeling system (NWS/HYSPLIT smoke) provides the forecast of smoke concentration resulting from fire emissions driven by the NWS North American Model 12 km weather predictions. The NWS/HYSPLIT smoke incorporates the U.S. Forest Service BlueSky Smoke Modeling Framework (BlueSky) to provide smoke fire emissions along with the input fire locations from the NOAA National Environmental Satellite, Data, and Information Service (NESDIS)'s Hazard Mapping System fire and smoke detection system. Experienced analysts inspect satellite imagery from multiple sensors onboard geostationary and orbital satellites to identify the location, size and duration of smoke emissions for the model. NWS/HYSPLIT smoke is being updated to use a newer version of USFS BlueSky. The updated BlueSky incorporates the Fuel Characteristic Classification System version 2 (FCCS2) over the continental U.S. and Alaska. FCCS2 includes a more detailed description of fuel loadings with additional plant type categories. The updated BlueSky also utilizes an improved fuel consumption model and fire emission production system. For the period of August 2014 and June 2015, NWS/HYSPLIT smoke simulations show that fire smoke emissions with updated BlueSky are stronger than the current operational BlueSky in the Northwest U.S. For the same comparisons, weaker fire smoke emissions from the updated BlueSky were observed over the middle and eastern part of the U.S. A statistical evaluation of NWS/HYSPLIT smoke predicted total column concentration compared to NOAA NESDIS GOES EAST Aerosol Smoke Product retrievals is underway. Preliminary results show that using the newer version of BlueSky leads to improved performance of NWS/HYSPLIT-smoke for June 2015. These results are partially due to the default fuel loading selected for Canadian fires that lead to stronger fire emissions there. The use of more realistic Canadian fuel loading may improve NWS/HYSPLIT smoke forecast.

Progress towards MODIS and VIIRS Cloud Fraction Data Record Continuity

NASA Astrophysics Data System (ADS)

Ackerman, S. A.; Frey, R.; Holz, R.; Platnick, S. E.; Heidinger, A. K.

2016-12-01

Satellite-derived clear-sky vs. cloudy-sky discrimination at the pixel scale is an important input parameter used in many real-time applications. Cloud fractions, resulting from integrating over time and space, are also critical to the study of recent decadal climate changes. The NASA NPOESS Preparatory Project (NPP) has funded a science team to develop and study the ability to make continuous climate records from MODIS (2000-2020) and VIIRS (2012-2030). The MODAWG project, led by Dr. Steve Platnick of NASA/GSFC, combines elements of the MODIS processing system and the NOAA Algorithm Working Group (AWG) to achieve this goal. This presentation will focus on the cloud masking aspects of MODAWG, derived primarily from the MODIS cloud mask (MOD35). Challenges to continuity of cloud detection due to differences in instrument characteristics will be discussed. Cloud mask results from use of the same (continuity) algorithm will be shown for both MODIS and VIIRS, including comparisons to collocated CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) cloud data.

Entropy and climate. I - ERBE observations of the entropy production of the earth

NASA Technical Reports Server (NTRS)

Stephens, G. L.; O'Brien, D. M.

1993-01-01

An approximate method for estimating the global distributions of the entropy fluxes flowing through the upper boundary of the climate system is introduced, and an estimate of the entropy exchange between the earth and space and the entropy production of the planet is provided. Entropy fluxes calculated from the Earth Radiation Budget Experiment measurements show how the long-wave entropy flux densities dominate the total entropy fluxes at all latitudes compared with the entropy flux densities associated with reflected sunlight, although the short-wave flux densities are important in the context of clear sky-cloudy sky net entropy flux differences. It is suggested that the entropy production of the planet is both constant for the 36 months of data considered and very near its maximum possible value. The mean value of this production is 0.68 x 10 exp 15 W/K, and the amplitude of the annual cycle is approximately 1 to 2 percent of this value.

Atmospheric radiation measurement unmanned aerospace vehicle (ARM-UAV) program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bolton, W.R.

1996-11-01

ARM-UAV is part of the multi-agency U.S. Global Change Research Program and is addressing the largest source of uncertainty in predicting climatic response: the interaction of clouds and the sun`s energy in the Earth`s atmosphere. An important aspect of the program is the use of unmanned aerospace vehicles (UAVs) as the primary airborne platform. The ARM-UAV Program has completed two major flight series: The first series conducted in April, 1994, using an existing UAV (the General Atomics Gnat 750) consisted of eight highly successful flights at the DOE climate site in Oklahoma. The second series conducted in September/October, 1995, usingmore » two piloted aircraft (Egrett and Twin Otter), featured simultaneous measurements above and below clouds and in clear sky. Additional flight series are planned to continue study of the cloudy and clear sky energy budget in the Spring and Fall of 1996 over the DOE climate site in Oklahoma. 3 refs., 4 figs., 1 tab.« less

Variation of solar cell sensitivity and solar radiation on tilted surfaces

NASA Technical Reports Server (NTRS)

Klucher, T. M.

1978-01-01

An empirical study was performed (1) to evaluate the validity of various insolation models used to compute solar radiation incident on tilted surfaces from global data measured on horizontal surfaces and (2) to determine the variation of solar cell sensitivity to solar radiation over a wide range of atmospheric condition. Evaluation of the insolation data indicates that the isotropic sky model of Liu and Jordan underestimates the amount of solar radiation falling on tilted surfaces by as much as 10%. An anisotropic-clear-sky model proposed by Temps and Coulson was also evaluated and found to be deficient under cloudy conditions. A new model, formulated herein, reduced the deviations between measured and predicted insolation to less than 3%. Evaluation of solar cell sensitivity data indicates small change (2-3%) in sensitivity from winter to summer for tilted cells. The feasibility of using such global data as a means for calibrating terrestrial solar cells as done by Treble is discussed.

Evaluation of 20-min and Annual Radiation Budget Components and Cloudiness in a Mountainous Valley

NASA Astrophysics Data System (ADS)

Malek, E.

2007-05-01

Logan, Utah (USA) is among cities located in the mountainous valley in the western portion of Rocky Mountains in North America. It is the county seat of Cache Valley, a metropolitan area with a population of about 100,000. The valley had the polluted air in the USA during January 2004. To evaluate the daily and annual radiation budget and cloudiness in this mountainous valley, we set up a radiation station in the middle of the valley to measure the 20- min radiation budget components namely: incoming (Rso) and outgoing (Rso) solar or shortwave radiation, using to CM21 Kipp and Zonen (one inverted) and incoming (Rli) (or atmospheric) and outgoing (Rlo) or terrestrial) longwave radiation using two CG1 Kipp and Zonen Pyrgeometers (one inverted) during the year of 2003. All pyranometers and Pyrgeometers were ventilated with four CV2 Kipp and Zonen ventilation systems throughout the year to prevent deposition of dew, frost and snow, which otherwise would disturb the measurements. We also measured the 2-m air temperature and relative humidity along with surface temperature. All measurements were taken every 2 s, averaged to 20 min, continuously throughout the year 2000. A Met One heated rain gauge measured precipitation. Comparison of the annual radiation budget components indicates that about 25% of the annual Rsi (5848.6 MJ/ (squared m-y)) was reflected back to sky as Rso. Rli and Rlo amounted to 9968.7 and 13303.5 MJ/ (squared m-y)), respectively. This yielded about 1364.9 MJ/ (squared m- y)) available energy (Rn). Having the 2-m air temperature and moisture data and comparison between the theoretical and the measured longwave radiation, we evaluated the 20-m cloudy conditions throughout the year of 2003. The average cloud base height was 587 m (ranged from zero for foggy conditions to about 3000 m). Annual cloudiness contributed about 139.1 MJ/ (squared m-y)) more energy in this valley.

Aladin Lite: Lightweight sky atlas for browsers

NASA Astrophysics Data System (ADS)

Boch, Thomas

2014-02-01

Aladin Lite is a lightweight version of the Aladin tool, running in the browser and geared towards simple visualization of a sky region. It allows visualization of image surveys (JPEG multi-resolution HEALPix all-sky surveys) and permits superimposing tabular (VOTable) and footprints (STC-S) data. Aladin Lite is powered by HTML5 canvas technology and is easily embeddable on any web page and can also be controlled through a Javacript API.

KSC01pp0006

NASA Image and Video Library

2001-01-02

KENNEDY SPACE CENTER, Fla. -- Under gray cloudy skies, Space Shuttle Atlantis inches its way to Launch Pad 39A , barely visible in the background. The journey is a distance of just over 3 miles. Atlantis will fly on mission STS-98, the seventh construction flight to the International Space Station. The orbiter will carry in its payload bay the U.S. Laboratory, named Destiny, that will have five system racks already installed inside the module. After delivery of electronics in the lab, electrically powered attitude control for Control Moment Gyroscopes will be activated. Atlantis is scheduled for launch no earlier than Jan. 19, 2001, with a crew of five

Infrared search and track performance estimates for detection of commercial unmanned aerial vehicles

NASA Astrophysics Data System (ADS)

Nicholas, Robert; Driggers, Ronald; Shelton, David; Furxhi, Orges

2018-04-01

Unmanned aerial vehicles (UAVs) have become more readily available in the past 5 years and are proliferating rapidly. New aviation regulations are accelerating the use of UAVs in many applications. As a result, there are increasing concerns of potential air threats in situational environments including commercial airport security and drug trafficking. In this study, radiometric signatures of commercially available miniature UAVs is determined for long-wave infrared (LWIR) bands in both clear sky and partial cloudy conditions. Results are presented that compare LWIR performance estimates for the detection of commercial UAVs via infrared search and track (IRST) systems with two candidate sensors.

KSC-2009-5209

NASA Image and Video Library

2009-09-23

CAPE CANAVERAL, Fla. – On Launch Pad 17-B at Cape Canaveral Air Force Station in Florida, the Space Tracking and Surveillance System - Demonstrator spacecraft is bathed in light under a dark, cloudy sky. Rain over Central Florida's east coast caused the scrub of the launch. STSS Demo is a space-based sensor component of a layered Ballistic Missile Defense System designed for the overall mission of detection, tracking and discriminating ballistic missiles. STSS is capable of tracking objects after boost phase and provides trajectory information to other sensors. It will be launched by NASA for the Missile Defense Agency between 8 and 8:58 a.m. EDT Sept. 24. Photo credit: NASA/Jack Pfaller

KSC-2009-5210

NASA Image and Video Library

2009-09-23

CAPE CANAVERAL, Fla. – On Launch Pad 17-B at Cape Canaveral Air Force Station in Florida, the Space Tracking and Surveillance System Demonstrator spacecraft waits for launch under dark, cloudy sky. Rain over Central Florida's east coast caused the scrub of the launch. STSS Demo is a space-based sensor component of a layered Ballistic Missile Defense System designed for the overall mission of detection, tracking and discriminating ballistic missiles. STSS is capable of tracking objects after boost phase and provides trajectory information to other sensors. It will be launched by NASA for the Missile Defense Agency between 8 and 8:58 a.m. EDT Sept. 24. Photo credit: NASA/Jack Pfaller

Characteristics of the mean radiant temperature in high latitude cities—implications for sensitive climate planning applications

NASA Astrophysics Data System (ADS)

Lindberg, Fredrik; Holmer, Björn; Thorsson, Sofia; Rayner, David

2014-07-01

Knowledge of how the mean radiant temperature ( T mrt ) is affected by factors such as location, climate and urban setting contributes to the practice of climate sensitive planning. This paper examines how T mrt varies within an urban setting and how it is influenced by cloudiness. In addition, variations of T mrt in three high latitude cities are investigated in order to analyse the impact of geographical context and climate conditions. Results showed large spatial variations between sunlit and shaded areas during clear weather conditions, with the highest values of T mrt close to sunlit walls and the lowest values in the areas shaded by buildings and vegetation. As cloudiness increases, the spatial pattern is altered and the differences are reduced. The highest T mrt under cloudy conditions is instead found in open areas where the proportion of shortwave diffuse radiation from the sky vault is high. A regional comparison between three Swedish coastal cities showed that T mrt during summer is similar regardless of latitudinal location. On the other hand, large differences in T mrt during winter were found. Shadows, both from buildings and vegetation are the most effective measure to reduce extreme values of T mrt . However, extensive areas of shadow are usually not desired within outdoor urban environments at high latitude cities. One solution is to create diverse outdoor urban spaces in terms of shadow and also ventilation. This would provide individuals with access to a choice of thermal environments which they can use to assist their thermal regulation, based on personal needs and desires.

Characteristics of the mean radiant temperature in high latitude cities--implications for sensitive climate planning applications.

PubMed

Lindberg, Fredrik; Holmer, Björn; Thorsson, Sofia; Rayner, David

2014-07-01

Knowledge of how the mean radiant temperature (T mrt ) is affected by factors such as location, climate and urban setting contributes to the practice of climate sensitive planning. This paper examines how T mrt varies within an urban setting and how it is influenced by cloudiness. In addition, variations of T mrt in three high latitude cities are investigated in order to analyse the impact of geographical context and climate conditions. Results showed large spatial variations between sunlit and shaded areas during clear weather conditions, with the highest values of T mrt close to sunlit walls and the lowest values in the areas shaded by buildings and vegetation. As cloudiness increases, the spatial pattern is altered and the differences are reduced. The highest T mrt under cloudy conditions is instead found in open areas where the proportion of shortwave diffuse radiation from the sky vault is high. A regional comparison between three Swedish coastal cities showed that T mrt during summer is similar regardless of latitudinal location. On the other hand, large differences in T mrt during winter were found. Shadows, both from buildings and vegetation are the most effective measure to reduce extreme values of T mrt. However, extensive areas of shadow are usually not desired within outdoor urban environments at high latitude cities. One solution is to create diverse outdoor urban spaces in terms of shadow and also ventilation. This would provide individuals with access to a choice of thermal environments which they can use to assist their thermal regulation, based on personal needs and desires.

3MdB: the Mexican Million Models database

NASA Astrophysics Data System (ADS)

Morisset, C.; Delgado-Inglada, G.

2014-10-01

The 3MdB is an original effort to construct a large multipurpose database of photoionization models. This is a more modern version of a previous attempt based on Cloudy3D and IDL tools. It is accessed by MySQL requests. The models are obtained using the well known and widely used Cloudy photoionization code (Ferland et al, 2013). The database is aimed to host grids of models with different references to identify each project and to facilitate the extraction of the desired data. We present here a description of the way the database is managed and some of the projects that use 3MdB. Anybody can ask for a grid to be run and stored in 3MdB, to increase the visibility of the grid and the potential side applications of it.

Representation of Clear and Cloudy Boundary Layers in Climate Models. Chapter 14

NASA Technical Reports Server (NTRS)

Randall, D. A.; Shao, Q.; Branson, M.

1997-01-01

The atmospheric general circulation models which are being used as components of climate models rely on their boundary layer parameterizations to produce realistic simulations of the surface turbulent fluxes of sensible heat. moisture. and momentum: of the boundary-layer depth over which these fluxes converge: of boundary layer cloudiness: and of the interactions of the boundary layer with the deep convective clouds that grow upwards from it. Two current atmospheric general circulation models are used as examples to show how these requirements are being addressed: these are version 3 of the Community Climate Model. which has been developed at the U.S. National Center for Atmospheric Research. and the Colorado State University atmospheric general circulation model. The formulations and results of both models are discussed. Finally, areas for future research are suggested.

A Climatology of Midlatitude Continental Clouds from the ARM SGP Site. Part II; Cloud Fraction and Surface Radiative Forcing

NASA Technical Reports Server (NTRS)

Xi, B.; Minnis, P.

2006-01-01

Data collected at the Department of Energy Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) Central Facility (SCF) are analyzed to determine the monthly and hourly variations of cloud fraction and radiative forcing between January 1997 and December 2002. Cloud fractions are estimated for total cloud cover and for single-layered low (0-3 km), middle (3-6 km), and high clouds (more than 6 km) using ARM SCG ground-based paired lidar-radar measurements. Shortwave (SW) and longwave (LW) fluxes are derived from up- and down-looking standard precision spectral pyranometers and precision infrared radiometer measurements with uncertainties of approximately 10 Wm(exp -2). The annual averages of total, and single-layered low, middle and high cloud fractions are 0.49, 0.11, 0.03, and 0.17, respectively. Both total and low cloud amounts peak during January and February and reach a minimum during July and August, high clouds occur more frequently than other types of clouds with a peak in summer. The average annual downwelling surface SW fluxes for total and low clouds (151 and 138 Wm(exp-2), respectively) are less than those under middle and high clouds (188 and 201 Wm(exp -2), respectively), but the downwelling LW fluxes (349 and 356 Wm(exp -2)) underneath total and low clouds are greater than those from middle and high clouds (337 and 333 Wm(exp -2)). Low clouds produce the largest LW warming (55 Wm(exp -2) and SW cooling (-91 Wm(exp -2)) effects with maximum and minimum absolute values in spring and summer, respectively. High clouds have the smallest LW warming (17 Wm(exp -2)) and SW cooling (-37 Wm(exp -2)) effects at the surface. All-sky SW CRF decreases and LW CRF increases with increasing cloud fraction with mean slopes of -0.984 and 0.616 Wm(exp -2)%(exp -1), respectively. Over the entire diurnal cycle, clouds deplete the amount of surface insolation more than they add to the downwelling LW flux. The calculated CRFs do not appear to be significantly affected by uncertainties in data sampling and clear-sky screening. Traditionally, cloud radiative forcing includes, not only the radiative impact of the hydrometeors, but also the changes in the environment. Taken together over the ARM SCF, changes in humidity and surface albedo between clear and cloudy conditions offset approximately 20% of the NET radiative forcing caused by the cloud hydrometeors alone. Variations in water vapor, on average, account for 10% and 83% of the SW and LW CRFs, respectively, in total cloud cover conditions. The error analysis further reveals that the cloud hydrometeors dominate the SW CRF, while water vapor changes are most important for LW flux changes in cloudy skies. Similar studies over other locales are encouraged where water and surface albedo changes from clear to cloudy conditions may be much different than observed over the ARM SCF.

A robust threshold-based cloud mask for the HRV channel of MSG SEVIRI

NASA Astrophysics Data System (ADS)

Bley, S.; Deneke, H.

2013-03-01

A robust threshold-based cloud mask for the high-resolution visible (HRV) channel (1 × 1 km2) of the METEOSAT SEVIRI instrument is introduced and evaluated. It is based on operational EUMETSAT cloud mask for the low resolution channels of SEVIRI (3 × 3 km2), which is used for the selection of suitable thresholds to ensure consistency with its results. The aim of using the HRV channel is to resolve small-scale cloud structures which cannot be detected by the low resolution channels. We find that it is of advantage to apply thresholds relative to clear-sky reflectance composites, and to adapt the threshold regionally. Furthermore, the accuracy of the different spectral channels for thresholding and the suitability of the HRV channel are investigated for cloud detection. The case studies show different situations to demonstrate the behaviour for various surface and cloud conditions. Overall, between 4 and 24% of cloudy low-resolution SEVIRI pixels are found to contain broken clouds in our test dataset depending on considered region. Most of these broken pixels are classified as cloudy by EUMETSAT's cloud mask, which will likely result in an overestimate if the mask is used as estimate of cloud fraction.

A Model and Satellite-Based Analysis of the Tropospheric Ozone Distribution in Clear Versus Convectively Cloudy Conditions

NASA Technical Reports Server (NTRS)

Strode, Sarah A.; Douglass, Anne R.; Ziemke, Jerald R.; Manyin, Michael; Nielsen, J. Eric; Oman, Luke D.

2017-01-01

Satellite observations of in-cloud ozone concentrations from the Ozone Monitoring Instrument and Microwave Limb Sounder instruments show substantial differences from background ozone concentrations. We develop a method for comparing a free-running chemistry-climate model (CCM) to in-cloud and background ozone observations using a simple criterion based on cloud fraction to separate cloudy and clear-sky days. We demonstrate that the CCM simulates key features of the in-cloud versus background ozone differences and of the geographic distribution of in-cloud ozone. Since the agreement is not dependent on matching the meteorological conditions of a specific day, this is a promising method for diagnosing how accurately CCMs represent the relationships between ozone and clouds, including the lower ozone concentrations shown by in-cloud satellite observations. Since clouds are associated with convection as well as changes in chemistry, we diagnose the tendency of tropical ozone at 400 hPa due to chemistry, convection and turbulence, and large-scale dynamics. While convection acts to reduce ozone concentrations at 400 hPa throughout much of the tropics, it has the opposite effect over highly polluted regions of South and East Asia.

A solar radiation database for Chile.

PubMed

Molina, Alejandra; Falvey, Mark; Rondanelli, Roberto

2017-11-01

Chile hosts some of the sunniest places on earth, which has led to a growing solar energy industry in recent years. However, the lack of high resolution measurements of solar irradiance becomes a critical obstacle for both financing and design of solar installations. Besides the Atacama Desert, Chile displays a large array of "solar climates" due to large latitude and altitude variations, and so provides a useful testbed for the development of solar irradiance maps. Here a new public database for surface solar irradiance over Chile is presented. This database includes hourly irradiance from 2004 to 2016 at 90 m horizontal resolution over continental Chile. Our results are based on global reanalysis data to force a radiative transfer model for clear sky solar irradiance and an empirical model based on geostationary satellite data for cloudy conditions. The results have been validated using 140 surface solar irradiance stations throughout the country. Model mean percentage error in hourly time series of global horizontal irradiance is only 0.73%, considering both clear and cloudy days. The simplicity and accuracy of the model over a wide range of solar conditions provides confidence that the model can be easily generalized to other regions of the world.

An algorithm to estimate PBL heights from wind profiler data

NASA Astrophysics Data System (ADS)

Molod, A.; Salmun, H.

2016-12-01

An algorithm was developed to estimate planetary boundary layer (PBL) heights from hourlyarchived wind profiler data from the NOAA Profiler Network (NPN) sites located throughoutthe central United States from the period 1992-2012. The long period of record allows ananalysis of climatological mean PBL heights as well as some estimates of year to yearvariability. Under clear conditions, summertime averaged hourly time series of PBL heightscompare well with Richardson-number based estimates at the few NPN stations with hourlytemperature measurements. Comparisons with clear sky MERRA estimates show that the windprofiler (WP) and the Richardson number based PBL heights are lower by approximately 250-500 m.The geographical distribution of daily maximum WP PBL heights corresponds well with theexpected distribution based on patterns of surface temperature and soil moisture. Windprofiler PBL heights were also estimated under mostly cloudy conditions, but the WP estimatesshow a smaller clear-cloudy condition difference than either of the other two PBL height estimates.The algorithm presented here is shown to provide a reliable summer, fall and springclimatology of daytime hourly PBL heights throughout the central United States. The reliabilityof the algorithm has prompted its use to obtain hourly PBL heights from other archived windprofiler data located throughout the world.

Results from CrIS/ATMS Obtained Using an AIRS "Version-6 Like" Retrieval Algorithm

NASA Technical Reports Server (NTRS)

Susskind, Joel; Kouvaris, Louis; Iredell, Lena

2015-01-01

We have tested and evaluated Version-6.22 AIRS and Version-6.22 CrIS products on a single day, December 4, 2013, and compared results to those derived using AIRS Version-6. AIRS and CrIS Version-6.22 O3(p) and q(p) products are both superior to those of AIRS Version-6All AIRS and CrIS products agree reasonably well with each other CrIS Version-6.22 T(p) and q(p) results are slightly poorer than AIRS under very cloudy conditions. Both AIRS and CrIS Version-6.22 run now at JPL. Our short term plans are to analyze many common months at JPL in the near future using Version-6.22 or a further improved algorithm to assess the compatibility of AIRS and CrIS monthly mean products and their interannual differencesUpdates to the calibration of both CrIS and ATMS are still being finalized. JPL plans, in collaboration with the Goddard DISC, to reprocess all AIRS data using a still to be finalized Version-7 retrieval algorithm, and to reprocess all recalibrated CrISATMS data using Version-7 as well.

Results from CrIS/ATMS Obtained Using an AIRS "Version-6 like" Retrieval Algorithm

NASA Technical Reports Server (NTRS)

Susskind, Joel; Kouvaris, Louis; Iredell, Lena

2015-01-01

We tested and evaluated Version-6.22 AIRS and Version-6.22 CrIS products on a single day, December 4, 2013, and compared results to those derived using AIRS Version-6. AIRS and CrIS Version-6.22 O3(p) and q(p) products are both superior to those of AIRS Version-6All AIRS and CrIS products agree reasonably well with each other. CrIS Version-6.22 T(p) and q(p) results are slightly poorer than AIRS over land, especially under very cloudy conditions. Both AIRS and CrIS Version-6.22 run now at JPL. Our short term plans are to analyze many common months at JPL in the near future using Version-6.22 or a further improved algorithm to assess the compatibility of AIRS and CrIS monthly mean products and their interannual differences. Updates to the calibration of both CrIS and ATMS are still being finalized. JPL plans, in collaboration with the Goddard DISC, to reprocess all AIRS data using a still to be finalized Version-7 retrieval algorithm, and to reprocess all recalibrated CrISATMS data using Version-7 as well.

2MASS Catalog Server Kit Version 2.1

NASA Astrophysics Data System (ADS)

Yamauchi, C.

2013-10-01

The 2MASS Catalog Server Kit is open source software for use in easily constructing a high performance search server for important astronomical catalogs. This software utilizes the open source RDBMS PostgreSQL, therefore, any users can setup the database on their local computers by following step-by-step installation guide. The kit provides highly optimized stored functions for positional searchs similar to SDSS SkyServer. Together with these, the powerful SQL environment of PostgreSQL will meet various user's demands. We released 2MASS Catalog Server Kit version 2.1 in 2012 May, which supports the latest WISE All-Sky catalog (563,921,584 rows) and 9 major all-sky catalogs. Local databases are often indispensable for observatories with unstable or narrow-band networks or severe use, such as retrieving large numbers of records within a small period of time. This software is the best for such purposes, and increasing supported catalogs and improvements of version 2.1 can cover a wider range of applications including advanced calibration system, scientific studies using complicated SQL queries, etc. Official page: http://www.ir.isas.jaxa.jp/~cyamauch/2masskit/

Validation of Local-Cloud Model Outputs With the GOES Satellite Imagery

NASA Astrophysics Data System (ADS)

Malek, E.

2005-05-01

Clouds (visible aggregations of minute droplets of water or tiny crystals of ice suspended in the air) affect the radiation budget of our planet by reflecting, absorbing and scattering solar radiation, and the re-emission of terrestrial radiation. They affect the weather and climate by positive or negative feedbacks. Many researchers have worked on the parameterization of clouds and their effects on the radiation budget. There is little information about ground-based approaches for continuous evaluation of cloud, such as cloud base height, cloud base temperature, and cloud coverage, at local and regional scales. This present article deals with the development of an algorithm for continuous (day and night) evaluation of cloud base temperature, cloud base height and percent of skies covered by cloud at local scale throughout the year. The Vaisala model CT-12K laser beam ceilometer is used at the Automated Surface Observing Systems (ASOS) to measure the cloud base height and report the sky conditions on an hourly basis or at shorter intervals. This laser ceilometer is a fixed-type whose transmitter and receiver point straight up at the cloud (if any) base. It is unable to measure clouds that are not above the sensor. To report cloudiness at the local scale, many of these type of ceilometers are needed. This is not a perfect method for cloud measurement. A single cloud hanging overhead the sensor will cause overcast readings, whereas, a hole in the clouds could cause a clear reading to be reported. To overcome this problem, we have set up a ventilated radiation station at Logan-Cache airport, Utah, U.S.A., since 1995, which is equipped with one of the above-mentioned ceilometers. This radiation station (composed of pyranometers, pyrgeometers and net radiometer) provides continuous measurements of incoming and outgoing shortwave and longwave radiation and the net radiation throughout the year. We have also measured the surface temperature and pressure, the 2-m air temperature and humidity, precipitation, and the 3-m wind and direction at this station. Having the air temperature, moisture, and the measured cloudless incoming longwave (atmospheric) radiation during 1999 through 2004, based upon the ASOS and the algorithm data, we found the appropriate formula (among four reported approaches) for computation of the cloudless-skies atmospheric emissivity. Considering the additional longwave radiation captured by the facing-up pyrgeometer during the cloudy skies, coming from the cloud in the wave band which the gaseous emission lacks (from 8-13 ìm), we developed an algorithm which provides the continuous 20-min cloud information (cloud base height, cloud base temperature, and percent of skies covered by cloud) over the Cache Valley during day and night throughout the year. The comparisons between the ASOS and the algorithm data during the period of 8-12 June, 2004 are reported in this article. The proposed algorithm is a promising approach for evaluation of the cloud base temperature, cloud base height, and percent of skies covered by cloud at the local scale throughout the year. It also reports the comparison between model outputs and GOES 10 satellite images.

Relationship between Noctcaelador and Aesthetic Sensitivity: Art-Related Personality Factors Associated with College Students' Night-Sky Watching

ERIC Educational Resources Information Center

Kelly, William E.

2008-01-01

This study explored the relationship between positive attitudes and behaviors concerning night-sky watching (noctcaelador) and aesthetic sensitivity. College students (N = 106) completed the Noctcaelador Inventory (Kelly, 2004a) and a shortened version of the Sensitivity Questionnaire (Child, 1965). Noctcaelador was significantly, positively…

KSC01pp0005

NASA Image and Video Library

2001-01-02

KENNEDY SPACE CENTER, Fla. -- Under cloudy skies, Space Shuttle Atlantis inches its way to Launch Pad 39A from the Vehicle Assembly Building (right). The journey is a distance of just over 3 miles. The water in the foreground is part of Banana Creek. Atlantis will fly on mission STS-98, the seventh construction flight to the International Space Station. The orbiter will carry in its payload bay the U.S. Laboratory, named Destiny, that will have five system racks already installed inside the module. After delivery of electronics in the lab, electrically powered attitude control for Control Moment Gyroscopes will be activated. Atlantis is scheduled for launch no earlier than Jan. 19, 2001, with a crew of five

Solar photolysis of ozone to singlet D oxygen atoms

NASA Technical Reports Server (NTRS)

Blackburn, Thomas E.; Bairai, Solomon T.; Stedman, Donald H.

1992-01-01

The ground-level photolysis frequency of ozone J(O3) to produce metastable singlet D oxygen atoms (O (D-1)) is measured using a novel instrumental technique involving electrical conductivity. The O(D-1) atoms produced react with nitrous oxide (N2O) carrier gas to form higher oxides of nitrogen (NO(x)). These oxides were detected by mixing with methanol and determining the increase in electrical conductivity with a continuous-flow dual conductivity cell. Over 70 days of data were collected under varying sky conditions. The effect of temperature on J(O3) was measured. The results agree with model predictions. The effects of atmospheric aerosols, changes in overhead ozone column, and local cloudiness are discussed.

Geophysical disturbance environment during the NASA/MPE barium release at 5 earth radii on September 21, 1971.

NASA Technical Reports Server (NTRS)

Davis, T. N.; Stanley, G. M.; Boyd, J. S.

1973-01-01

The geophysical disturbance environment was quiet during the NASA/MPE barium release at 5 earth radii on September 21, 1971. At the time of the release, the magnetosphere was in the late recovery phase of a principal magnetic storm, the provisional Dst value was -13 gammas, and the local horizontal disturbance at Great Whale River was near zero. Riometer and other observations indicated low-level widespread precipitation of high-energy electrons at Great Whale River before, during, and after the release. Cloudy sky at this station prevented optical observation of aurora. No magnetic or ionospheric effects attributable to the barium release were detected at Great Whale River.

HiPS - Hierarchical Progressive Survey Version 1.0

NASA Astrophysics Data System (ADS)

Fernique, Pierre; Allen, Mark; Boch, Thomas; Donaldson, Tom; Durand, Daniel; Ebisawa, Ken; Michel, Laurent; Salgado, Jesus; Stoehr, Felix; Fernique, Pierre

2017-05-01

This document presents HiPS, a hierarchical scheme for the description, storage and access of sky survey data. The system is based on hierarchical tiling of sky regions at finer and finer spatial resolution which facilitates a progressive view of a survey, and supports multi-resolution zooming and panning. HiPS uses the HEALPix tessellation of the sky as the basis for the scheme and is implemented as a simple file structure with a direct indexing scheme that leads to practical implementations.

Novel robust skylight compass method based on full-sky polarization imaging under harsh conditions.

PubMed

Tang, Jun; Zhang, Nan; Li, Dalin; Wang, Fei; Zhang, Binzhen; Wang, Chenguang; Shen, Chong; Ren, Jianbin; Xue, Chenyang; Liu, Jun

2016-07-11

A novel method based on Pulse Coupled Neural Network(PCNN) algorithm for the highly accurate and robust compass information calculation from the polarized skylight imaging is proposed,which showed good accuracy and reliability especially under cloudy weather,surrounding shielding and moon light. The degree of polarization (DOP) combined with the angle of polarization (AOP), calculated from the full sky polarization image, were used for the compass information caculation. Due to the high sensitivity to the environments, DOP was used to judge the destruction of polarized information using the PCNN algorithm. Only areas with high accuracy of AOP were kept after the DOP PCNN filtering, thereby greatly increasing the compass accuracy and robustness. From the experimental results, it was shown that the compass accuracy was 0.1805° under clear weather. This method was also proven to be applicable under conditions of shielding by clouds, trees and buildings, with a compass accuracy better than 1°. With weak polarization information sources, such as moonlight, this method was shown experimentally to have an accuracy of 0.878°.

A two-step framework for reconstructing remotely sensed land surface temperatures contaminated by cloud

NASA Astrophysics Data System (ADS)

Zeng, Chao; Long, Di; Shen, Huanfeng; Wu, Penghai; Cui, Yaokui; Hong, Yang

2018-07-01

Land surface temperature (LST) is one of the most important parameters in land surface processes. Although satellite-derived LST can provide valuable information, the value is often limited by cloud contamination. In this paper, a two-step satellite-derived LST reconstruction framework is proposed. First, a multi-temporal reconstruction algorithm is introduced to recover invalid LST values using multiple LST images with reference to corresponding remotely sensed vegetation index. Then, all cloud-contaminated areas are temporally filled with hypothetical clear-sky LST values. Second, a surface energy balance equation-based procedure is used to correct for the filled values. With shortwave irradiation data, the clear-sky LST is corrected to the real LST under cloudy conditions. A series of experiments have been performed to demonstrate the effectiveness of the developed approach. Quantitative evaluation results indicate that the proposed method can recover LST in different surface types with mean average errors in 3-6 K. The experiments also indicate that the time interval between the multi-temporal LST images has a greater impact on the results than the size of the contaminated area.

Improving Assimilated Global Climate Data Using TRMM and SSM/I Rainfall and Moisture Data

NASA Technical Reports Server (NTRS)

Hou, Arthur Y.; Zhang, Sara Q.; daSilva, Arlindo M.; Olson, William S.

1999-01-01

Current global analyses contain significant errors in primary hydrological fields such as precipitation, evaporation, and related cloud and moisture in the tropics. Work has been underway at NASA's Data Assimilation Office to explore the use of TRMM and SSM/I-derived rainfall and total precipitable water (TPW) data in global data assimilation to directly constrain these hydrological parameters. We found that assimilating these data types improves not only the precipitation and moisture estimates but also key climate parameters directly linked to convection such as the outgoing longwave radiation, clouds, and the large-scale circulation in the tropics. We will present results showing that assimilating TRMM and SSM/I 6-hour averaged rain rates and TPW estimates significantly reduces the state-dependent systematic errors in assimilated products. Specifically, rainfall assimilation improves cloud and latent heating distributions, which, in turn, improves the cloudy-sky radiation and the large-scale circulation, while TPW assimilation reduces moisture biases to improve radiation in clear-sky regions. Rainfall and TPW assimilation also improves tropical forecasts beyond 1 day.

Testing the Two-Layer Model for Correcting Near Cloud Reflectance Enhancement Using LES SHDOM Simulated Radiances

NASA Technical Reports Server (NTRS)

Wen, Guoyong; Marshak, Alexander; Varnai, Tamas; Levy, Robert

2016-01-01

A transition zone exists between cloudy skies and clear sky; such that, clouds scatter solar radiation into clear-sky regions. From a satellite perspective, it appears that clouds enhance the radiation nearby. We seek a simple method to estimate this enhancement, since it is so computationally expensive to account for all three-dimensional (3-D) scattering processes. In previous studies, we developed a simple two-layer model (2LM) that estimated the radiation scattered via cloud-molecular interactions. Here we have developed a new model to account for cloud-surface interaction (CSI). We test the models by comparing to calculations provided by full 3-D radiative transfer simulations of realistic cloud scenes. For these scenes, the Moderate Resolution Imaging Spectroradiometer (MODIS)-like radiance fields were computed from the Spherical Harmonic Discrete Ordinate Method (SHDOM), based on a large number of cumulus fields simulated by the University of California, Los Angeles (UCLA) large eddy simulation (LES) model. We find that the original 2LM model that estimates cloud-air molecule interactions accounts for 64 of the total reflectance enhancement and the new model (2LM+CSI) that also includes cloud-surface interactions accounts for nearly 80. We discuss the possibility of accounting for cloud-aerosol radiative interactions in 3-D cloud-induced reflectance enhancement, which may explain the remaining 20 of enhancements. Because these are simple models, these corrections can be applied to global satellite observations (e.g., MODIS) and help to reduce biases in aerosol and other clear-sky retrievals.

Imaging polarimetry of forest canopies: how the azimuth direction of the sun, occluded by vegetation, can be assessed from the polarization pattern of the sunlit foliage

NASA Astrophysics Data System (ADS)

Hegedüs, Ramón; Barta, András; Bernáth, Balázs; Benno Meyer-Rochow, Victor; Horváth, Gábor

2007-08-01

Radiance, color, and polarization of the light in forests combine to create complex optical patterns. Earlier sporadic polarimetric studies in forests were limited by the narrow fields of view of the polarimeters used in such studies. Since polarization patterns in the entire upper hemisphere of the visual environment of forests could be important for forest-inhabiting animals that make use of linearly polarized light for orientation, we measured 180° field-of-view polarization distributions in Finnish forests. From a hot air balloon we also measured the polarization patterns of Hungarian grasslands lit by the rising sun. We found that the pattern of the angle of polarization α of sunlit grasslands and sunlit tree canopies was qualitatively the same as that of the sky. We show here that contrary to an earlier assumption, the α-pattern characteristic of the sky always remains visible underneath overhead vegetation, independently of the solar elevation and the sky conditions (clear or partly cloudy with visible sun's disc), provided the foliage is sunlit and not only when large patches of the clear sky are visible through the vegetation. Since the mirror symmetry axis of the α-pattern of the sunlit foliage is the solar-antisolar meridian, the azimuth direction of the sun, occluded by vegetation, can be assessed in forests from this polarization pattern. Possible consequences of this robust polarization feature of the optical environment in forests are briefly discussed with regard to polarization-based animal navigation.

Controlling sunbathing safety during the summer holidays - The solar UV campaign at Baltic Sea coast in 2015.

PubMed

Guzikowski, Jakub; Czerwińska, Agnieszka E; Krzyścin, Janusz W; Czerwiński, Michał A

2017-08-01

Information regarding the intensity of surface UV radiation, provided for the public, is frequently given in terms of a daily maximum UV Index (UVI), based on a prognostic model. The quality of the UV forecast depends on the accuracy of column amount of ozone and cloudiness prediction. Daily variability of UVI is needed to determine the risk of the UV overexposure during outdoor activities. Various methods of estimating the temporary UVI and the maximum duration of UV exposures (received a dose equal to minimal erythemal dose - MED), at the site of sunbathing, were compared. The UV indices were obtained during a field experiment at the Baltic Sea coast in the period from 13th to 24th July 2015. The following UVI calculation models were considered: UVI measurements by simple hand-held biometers (Silver Crest, Oregon Scientific, or more advanced Solarmeter 6.5), our smartphone models based on cloud cover observations at the site and the cloudless-sky UVI forecast (available for any site for all smartphone users) or measured UVI, and the 24h weather predictions by the ensemble set of 10 models (with various cloud parameterizations). The direct UV measurements, even by a simple biometer, provided useful UVI estimates. The smartphone applications yielded a good agreement with the UV measurements. The weather prediction models for cloudless-sky conditions could provide valuable information if almost cloudless-sky conditions (cloudless-sky or slightly scattered clouds) were observed at the sunbathing site. Copyright © 2017 Elsevier B.V. All rights reserved.

Surface Downward Longwave Radiation Retrieval Algorithm for GEO-KOMPSAT-2A/AMI

NASA Astrophysics Data System (ADS)

Ahn, Seo-Hee; Lee, Kyu-Tae; Rim, Se-Hun; Zo, Il-Sung; Kim, Bu-Yo

2018-05-01

This study contributes to the development of an algorithm to retrieve the Earth's surface downward longwave radiation (DLR) for 2nd Geostationary Earth Orbit KOrea Multi-Purpose SATellite (GEO-KOMPSAT-2A; GK-2A)/Advanced Meteorological Imager (AMI). Regarding simulation data for algorithm development, we referred to Clouds and the Earth's Radiant Energy System (CERES), and the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-interim reanalysis data. The clear sky DLR calculations were in good agreement with the Gangneung-Wonju National University (GWNU) Line-By-Line (LBL) model. Compared with CERES data, the Root Mean Square Error (RMSE) was 10.14Wm-2. In the case of cloudy sky DLR, we estimated the cloud base temperature empirically by utilizing cloud liquid water content (LWC) according to the cloud type. As a result, the correlation coefficients with CERES all sky DLRs were greater than 0.99. However, the RMSE between calculated DLR and CERES data was about 16.67Wm-2, due to ice clouds and problems of mismatched spatial and temporal resolutions for input data. This error may be reduced when GK-2A is launched and its products can be used as input data. Accordingly, further study is needed to improve the accuracy of DLR calculation by using high-resolution input data. In addition, when compared with BSRN surface-based observational data and retrieved DLR for all sky, the correlation coefficient was 0.86 and the RMSE was 31.55 Wm-2, which indicates relatively high accuracy. It is expected that increasing the number of experimental Cases will reduce the error.

The influence of clouds and diffuse radiation on ecosystem-atmosphere CO2 and CO18O exhanges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Still, C.J.; Riley, W.J.; Biraud, S.C.

2009-05-01

This study evaluates the potential impact of clouds on ecosystem CO{sub 2} and CO{sub 2} isotope fluxes ('isofluxes') in two contrasting ecosystems (a broadleaf deciduous forest and a C{sub 4} grassland), in a region for which cloud cover, meteorological, and isotope data are available for driving the isotope-enabled land surface model, ISOLSM. Our model results indicate a large impact of clouds on ecosystem CO{sub 2} fluxes and isofluxes. Despite lower irradiance on partly cloudy and cloudy days, predicted forest canopy photosynthesis was substantially higher than on clear, sunny days, and the highest carbon uptake was achieved on the cloudiest day.more » This effect was driven by a large increase in light-limited shade leaf photosynthesis following an increase in the diffuse fraction of irradiance. Photosynthetic isofluxes, by contrast, were largest on partly cloudy days, as leaf water isotopic composition was only slightly depleted and photosynthesis was enhanced, as compared to adjacent clear sky days. On the cloudiest day, the forest exhibited intermediate isofluxes: although photosynthesis was highest on this day, leaf-to-atmosphere isofluxes were reduced from a feedback of transpiration on canopy relative humidity and leaf water. Photosynthesis and isofluxes were both reduced in the C{sub 4} grass canopy with increasing cloud cover and diffuse fraction as a result of near-constant light limitation of photosynthesis. These results suggest that some of the unexplained variation in global mean {delta}{sup 18}O of CO{sub 2} may be driven by large-scale changes in clouds and aerosols and their impacts on diffuse radiation, photosynthesis, and relative humidity.« less

Cloudiness over the Amazon rainforest: Meteorology and thermodynamics

NASA Astrophysics Data System (ADS)

Collow, Allison B. Marquardt; Miller, Mark A.; Trabachino, Lynne C.

2016-07-01

Comprehensive meteorological observations collected during GOAmazon2014/15 using the Atmospheric Radiation Measurement Mobile Facility no. 1 and assimilated observations from the Modern-Era Retrospective Analysis for Research and Applications, Version 2 are used to document the seasonal cycle of cloudiness, thermodynamics, and precipitation above the Amazon rainforest. The reversal of synoptic-scale vertical motions modulates the transition between the wet and dry seasons. Ascending moist air during the wet season originates near the surface of the Atlantic Ocean and is advected into the Amazon rainforest, where it experiences convergence and, ultimately, precipitates. The dry season is characterized by weaker winds and synoptic-scale subsidence with little or no moisture convergence accompanying moisture advection. This combination results in the drying of the midtroposphere during June through October as indicated by a decrease in liquid water path, integrated water, and the vertical profile of water vapor mixing ratio. The vertical profile of cloud fraction exhibits a relatively consistent decline in cloud fraction from the lifting condensation level (LCL) to the freezing level where a minimum is observed, unlike many other tropical regions. Coefficients of determination between the LCL and cloud fractional coverage suggest a relatively robust relationship between the LCL and cloudiness beneath 5 km during the dry season (R2 = 0.42) but a weak relationship during the wet season (0.12).

A New Neural Network Approach Including First-Guess for Retrieval of Atmospheric Water Vapor, Cloud Liquid Water Path, Surface Temperature and Emissivities Over Land From Satellite Microwave Observations

NASA Technical Reports Server (NTRS)

Aires, F.; Prigent, C.; Rossow, W. B.; Rothstein, M.; Hansen, James E. (Technical Monitor)

2000-01-01

The analysis of microwave observations over land to determine atmospheric and surface parameters is still limited due to the complexity of the inverse problem. Neural network techniques have already proved successful as the basis of efficient retrieval methods for non-linear cases, however, first-guess estimates, which are used in variational methods to avoid problems of solution non-uniqueness or other forms of solution irregularity, have up to now not been used with neural network methods. In this study, a neural network approach is developed that uses a first-guess. Conceptual bridges are established between the neural network and variational methods. The new neural method retrieves the surface skin temperature, the integrated water vapor content, the cloud liquid water path and the microwave surface emissivities between 19 and 85 GHz over land from SSM/I observations. The retrieval, in parallel, of all these quantities improves the results for consistency reasons. A data base to train the neural network is calculated with a radiative transfer model and a a global collection of coincident surface and atmospheric parameters extracted from the National Center for Environmental Prediction reanalysis, from the International Satellite Cloud Climatology Project data and from microwave emissivity atlases previously calculated. The results of the neural network inversion are very encouraging. The r.m.s. error of the surface temperature retrieval over the globe is 1.3 K in clear sky conditions and 1.6 K in cloudy scenes. Water vapor is retrieved with a r.m.s. error of 3.8 kg/sq m in clear conditions and 4.9 kg/sq m in cloudy situations. The r.m.s. error in cloud liquid water path is 0.08 kg/sq m . The surface emissivities are retrieved with an accuracy of better than 0.008 in clear conditions and 0.010 in cloudy conditions. Microwave land surface temperature retrieval presents a very attractive complement to the infrared estimates in cloudy areas: time record of land surface temperature will be produced.

Significance of multidimensional radiative transfer effects measured in surface fluxes at an Antarctic coastline

NASA Astrophysics Data System (ADS)

Lubin, Dan; Ricchiazzi, Paul; Payton, Allison; Gautier, Catherine

2002-10-01

At a coastal high-latitude site, multiple reflection of photons between the high albedo surface and an overlying cloud can enhance the downwelling shortwave flux out over the adjacent open water to a distance of several kilometers. This coastal albedo effect has been predicted by theoretical radiative transfer studies and has also been measured under ideal conditions. In this study, three multispectral solar ultraviolet radiometers were deployed in the vicinity of Palmer Station, Antarctica (64° 46'S, 64° 04'W) to determine the prevalence of the coastal albedo effect under the region's natural variability in cloud cover. One radiometer was deployed near the base of a glacier, and the other two radiometers were deployed on Janus Island and Outcast Island, islets ˜2.8 km (1.5 nautical miles) and 5.6 km (3 nautical miles) distant from Palmer Station, respectively. The radiometers were operated simultaneously for 16 days during late December 1999 and January 2000. Under all cloudy sky conditions sampled by this experiment the coastal albedo effect is seen in the data 60% of the time, in the form of a decreasing gradient in surface flux from Palmer Station through Janus and Outcast Islands. During the other 40% of the cloudy sky measurements, local cloud inhomogeneity obscured the coastal albedo effect. The effect is more apparent under overcast layers that appear spatially uniform and occurs 86% of the time under the low overcast decks sampled. The presence of stratus fractus of bad weather, under higher overcast layers, obscures the coastal albedo effect such that it occurs only 43% of the time. A wavelength dependence is noted in the data under optically thin cloud cover: the ratio of a flux measured at an islet to that measured at the station increases with wavelength. This wavelength dependence can be explained by plane-parallel radiative transfer theory.

Modulation of aerosol radiative forcing due to mixing state in clear and cloudy-sky: A case study from Delhi National Capital Region, India

NASA Astrophysics Data System (ADS)

Srivastava, Parul; Dey, Sagnik; Srivastava, Atul K.; Singh, Sachchidanand; Tiwari, Suresh; Agarwal, Poornima

2016-04-01

Aerosol properties change with the change in mixing state of aerosols and therefore it is a source of uncertainty in estimated aerosol radiative forcing (ARF) from observations or by models assuming a specific mixing state. The problem is important in the Indo-Gangetic Basin, Northern India, where various aerosol types mix and show strong seasonal variations. Quantifying the modulation of ARF by mixing state is hindered by lack of knowledge about proper aerosol composition. Hence, first a detailed chemical composition analysis of aerosols for Delhi National capital region (NCR) is carried out. Aerosol composition is arranged quantitatively into five major aerosol types - accumulation dust, coarse dust, water soluble (WS), water insoluble (WINS), and black carbon (BC) (directly measured by Athelometer). Eight different mixing cases - external mixing, internal mixing, and six combinations of core- shell mixing (BC over dust, WS over dust, WS over BC, BC over WS, WS over WINS, and BC over WINS; each of the combinations externally mixed with other species) have been considered. The spectral aerosol optical properties - extinction coefficient, single scattering albedo (SSA) and asymmetry parameter (g) for each of the mixing cases are calculated and finally 'clear-sky' and 'cloudy-sky' ARF at the top-of-the-atmosphere (TOA) and surface are estimated using a radiative transfer model. Comparison of surface-reaching flux for each of the cases with MERRA downward shortwave surface flux reveals the most likely mixing state. 'BC-WINS+WS+Dust' show least deviation relative to MERRA during the pre-monsoon (MAMJ) and monsoon (JAS) seasons and hence is the most probable mixing states. During the winter season (DJF), 'BC-Dust+WS+WINS' case shows the closest match with MERRA, while external mixing is the most probable mixing state in the post-monsoon season (ON). Lowest values for both TOA and surface 'clear-sky' ARF is observed for 'BC-WINS+WS+ Dust' mixing case. TOA ARF is 0.28±2.4, 2.2±1.1, -1.4±1.4, -0.15±0.13, while, surface ARF is -16.4±3.1, -7.6±1.7, -31.5±4.7, -17.1±8.4, respectively for the MAMJ, JAS, ON and DJF seasons. Post-monsoon and winter season shows negative values of TOA ARF, hence suggest 'cooling'. The associated heating rate profiles show higher values for 'WS-BC+Dust+WINS' case as compared to other cases, with relatively large values during the winter and post-monsoon seasons, while lower value was observed for 'BC-WINS+WS+Dust'. We examined the modulation of clear sky ARF by 'water-cloud' and 'ice-cloud' separately. The seasonal mean ARF for both water and ice clouds show nearly similar characteristics as observed for clear-sky case, with relatively large ARF at TOA and surface in water cloud case as compared to ice cloud during all the seasons. As a result, the associated heating rate is also relatively higher in water cloud case as compared to ice cloud. Such large modulation of ARF due to mixing state calls for a coordinated effort to create a mixing state database for this region to reduce the uncertainty in climate forcing.

CIMEL Measurements of Zenith Radiances at the ARM Site

NASA Technical Reports Server (NTRS)

Marshak, Alexander; Wiscombe, Warren; Lau, William K. M. (Technical Monitor)

2002-01-01

Starting from October 1, 2001, Cimel at the ARM Central Facility in Oklahoma has been switched to a new "cloud mode." This mode allows taking measurements of zenith radiance when the Sun in blocked by clouds. In this case, every 13 min. Cimel points straight up and takes 10 measurements with 9 sec. time interval. The new Cimel's mode has four filters at 440, 670, 870 and 1020 nm. For cloudy conditions, the spectral contrast in surface albedo dominates over Rayleigh and aerosol effects; this makes normalized zenith radiances at 440 and 670 as well as for 870 and 1020 almost indistinguishable. We compare Cimel measurements with other ARM cart site instruments: Multi-Filter Rotating Shadowband Radiometer (MFRSR), Narrow Field of View (NFOV) sensor, and MicroWave Radiometer(MWR). Based on Cimel and MFRSR 670 and 870 nm channels, we build a normalized difference cloud index (NDCI) for radiances and fluxes, respectively. Radiance NDCI from Cimel and flux NDCI from MFRSR are compared between themselves as well as with cloud Liquid Water Path (LWP) retrieved from MWR. Based on our theoretical calculations and preliminary data analysis,there is a good correlation between NDCIs and LWP for cloudy sky above green vegetation. Based on this correlation, an algorithm to retrieve cloud optical depth from NDCI is proposed.

eGSM: A extended Sky Model of Diffuse Radio Emission

NASA Astrophysics Data System (ADS)

Kim, Doyeon; Liu, Adrian; Switzer, Eric

2018-01-01

Both cosmic microwave background and 21cm cosmology observations must contend with astrophysical foreground contaminants in the form of diffuse radio emission. For precise cosmological measurements, these foregrounds must be accurately modeled over the entire sky Ideally, such full-sky models ought to be primarily motivated by observations. Yet in practice, these observations are limited, with data sets that are observed not only in a heterogenous fashion, but also over limited frequency ranges. Previously, the Global Sky Model (GSM) took some steps towards solving the problem of incomplete observational data by interpolating over multi-frequency maps using principal component analysis (PCA).In this poster, we present an extended version of GSM (called eGSM) that includes the following improvements: 1) better zero-level calibration 2) incorporation of non-uniform survey resolutions and sky coverage 3) the ability to quantify uncertainties in sky models 4) the ability to optimally select spectral models using Bayesian Evidence techniques.

yourSky: Custom Sky-Image Mosaics via the Internet

NASA Technical Reports Server (NTRS)

Jacob, Joseph

2003-01-01

yourSky (http://yourSky.jpl.nasa.gov) is a computer program that supplies custom astronomical image mosaics of sky regions specified by requesters using client computers connected to the Internet. [yourSky is an upgraded version of the software reported in Software for Generating Mosaics of Astronomical Images (NPO-21121), NASA Tech Briefs, Vol. 25, No. 4 (April 2001), page 16a.] A requester no longer has to engage in the tedious process of determining what subset of images is needed, nor even to know how the images are indexed in image archives. Instead, in response to a requester s specification of the size and location of the sky area, (and optionally of the desired set and type of data, resolution, coordinate system, projection, and image format), yourSky automatically retrieves the component image data from archives totaling tens of terabytes stored on computer tape and disk drives at multiple sites and assembles the component images into a mosaic image by use of a high-performance parallel code. yourSky runs on the server computer where the mosaics are assembled. Because yourSky includes a Web-interface component, no special client software is needed: ordinary Web browser software is sufficient.

Final Tactical Decision Aid (FTDA) for Infrared (8-12 Micrometers) Systems - Manual Version. Appendix B. Insolation and Sky Radiation Tables,

DTIC Science & Technology

1982-09-15

for use in determining solar irradiance as a function of terrain elevation is also presented. Errors in computed sea level values of sky radiation as a...Renobserved if the Ground Were at Sea Level .. ..................... 365 5. Sky Radiation (W SK).. .. ....... ....... ....... 366 SKYY and Dewpoint SKY...WS -M 00 OiLn 00 00 00 .0 .. q . m1’ C14 IN’ .- *- * .0 *0 *0 0 .0 0 Y -’ CD N inC 0 M W N L- 04c 1- Wq an’ U) 14 N- 00 00 Mcq N N r- (’IC’I) (’ - M -0

KSC-08pp0287

NASA Image and Video Library

2008-02-07

KENNEDY SPACE CENTER, FLA. -- Space shuttle Atlantis soars into the cloudy sky after liftoff on mission STS-122, which occurred on time at 2:45 p.m. EST, from Launch Pad 39A. Below the main engine nozzles can be seen the blue cones of light, known as shock or mach diamonds. They are a formation of shock waves in the exhaust plume of an aerospace propulsion system. This is the third launch attempt for Atlantis since December 2007 to carry the European Space Agency's Columbus laboratory to the International Space Station. During the 11-day mission, the crew's prime objective is to attach the laboratory to the Harmony module, adding to the station's size and capabilities. Photo credit: NASA/Scott Haun, Richard Prickett

STS-98 Atlantis rolls out to Launch Pad 39A

NASA Technical Reports Server (NTRS)

2001-01-01

KENNEDY SPACE CENTER, Fla. -- Under cloudy skies, Space Shuttle Atlantis inches its way to Launch Pad 39A from the Vehicle Assembly Building (right). The journey is a distance of just over 3 miles. The water in the foreground is part of Banana Creek. Atlantis will fly on mission STS-98, the seventh construction flight to the International Space Station. The orbiter will carry in its payload bay the U.S. Laboratory, named Destiny, that will have five system racks already installed inside the module. After delivery of electronics in the lab, electrically powered attitude control for Control Moment Gyroscopes will be activated. Atlantis is scheduled for launch no earlier than Jan. 19, 2001, with a crew of five.

Absorption of Solar Radiation by the Cloudy Atmosphere: Further Interpretations of Collocated Aircraft Measurements

NASA Technical Reports Server (NTRS)

Cess, R. D.; Zhang, Minghua; Valero, Francisco P. J.; Pope, Shelly K.; Bucholtz, Anthony; Bush, Brett; Zender, Charles S.

1998-01-01

We have extended the interpretations made in two prior studies of the aircraft shortwave radiation measurements that were obtained as part of the Atmospheric Radiation Measurements (ARM) Enhanced Shortwave Experiments (ARESE). These extended interpretations use the 500 nm (10 nm bandwidth) measurements to minimize sampling errors in the broadband measurements. It is indicated that the clouds present during this experiment absorb more shortwave radiation than predicted by clear skies and thus by theoretical models, that at least some (less than or equal to 20%) of this enhanced cloud absorption occurs at wavelengths less than 680 nm, and that the observed cloud absorption does not appear to be an artifact of sampling errors nor of instrument calibration errors.

The thin border between cloud and aerosol: Sensitivity of several ground based observation techniques

NASA Astrophysics Data System (ADS)

Calbó, Josep; Long, Charles N.; González, Josep-Abel; Augustine, John; McComiskey, Allison

2017-11-01

Cloud and aerosol are two manifestations of what it is essentially the same physical phenomenon: a suspension of particles in the air. The differences between the two come from the different composition (e.g., much higher amount of condensed water in particles constituting a cloud) and/or particle size, and also from the different number of such particles (10-10,000 particles per cubic centimeter depending on conditions). However, there exist situations in which the distinction is far from obvious, and even when broken or scattered clouds are present in the sky, the borders between cloud/not cloud are not always well defined, a transition area that has been coined as the ;twilight zone;. The current paper presents a discussion on the definition of cloud and aerosol, the need for distinguishing or for considering the continuum between the two, and suggests a quantification of the importance and frequency of such ambiguous situations, founded on several ground-based observing techniques. Specifically, sensitivity analyses are applied on sky camera images and broadband and spectral radiometric measurements taken at Girona (Spain) and Boulder (Co, USA). Results indicate that, at these sites, in more than 5% of the daytime hours the sky may be considered cloudless (but containing aerosols) or cloudy (with some kind of optically thin clouds) depending on the observing system and the thresholds applied. Similarly, at least 10% of the time the extension of scattered or broken clouds into clear areas is problematic to establish, and depends on where the limit is put between cloud and aerosol. These findings are relevant to both technical approaches for cloud screening and sky cover categorization algorithms and radiative transfer studies, given the different effect of clouds and aerosols (and the different treatment in models) on the Earth's radiation balance.

Assessment of uncertainty in the numerical simulation of solar irradiance over inclined PV panels: New algorithms using measurements and modeling tools

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Yu; Sengupta, Manajit; Dooraghi, Mike

Development of accurate transposition models to simulate plane-of-array (POA) irradiance from horizontal measurements or simulations is a complex process mainly because of the anisotropic distribution of diffuse solar radiation in the atmosphere. The limited availability of reliable POA measurements at large temporal and spatial scales leads to difficulties in the comprehensive evaluation of transposition models. This paper proposes new algorithms to assess the uncertainty of transposition models using both surface-based observations and modeling tools. We reviewed the analytical derivation of POA irradiance and the approximation of isotropic diffuse radiation that simplifies the computation. Two transposition models are evaluated against themore » computation by the rigorous analytical solution. We proposed a new algorithm to evaluate transposition models using the clear-sky measurements at the National Renewable Energy Laboratory's (NREL's) Solar Radiation Research Laboratory (SRRL) and a radiative transfer model that integrates diffuse radiances of various sky-viewing angles. We found that the radiative transfer model and a transposition model based on empirical regressions are superior to the isotropic models when compared to measurements. We further compared the radiative transfer model to the transposition models under an extensive range of idealized conditions. Our results suggest that the empirical transposition model has slightly higher cloudy-sky POA irradiance than the radiative transfer model, but performs better than the isotropic models under clear-sky conditions. Significantly smaller POA irradiances computed by the transposition models are observed when the photovoltaics (PV) panel deviates from the azimuthal direction of the sun. The new algorithms developed in the current study have opened the door to a more comprehensive evaluation of transposition models for various atmospheric conditions and solar and PV orientations.« less

Assessment of uncertainty in the numerical simulation of solar irradiance over inclined PV panels: New algorithms using measurements and modeling tools

DOE PAGES

Xie, Yu; Sengupta, Manajit; Dooraghi, Mike

2018-03-20

Development of accurate transposition models to simulate plane-of-array (POA) irradiance from horizontal measurements or simulations is a complex process mainly because of the anisotropic distribution of diffuse solar radiation in the atmosphere. The limited availability of reliable POA measurements at large temporal and spatial scales leads to difficulties in the comprehensive evaluation of transposition models. This paper proposes new algorithms to assess the uncertainty of transposition models using both surface-based observations and modeling tools. We reviewed the analytical derivation of POA irradiance and the approximation of isotropic diffuse radiation that simplifies the computation. Two transposition models are evaluated against themore » computation by the rigorous analytical solution. We proposed a new algorithm to evaluate transposition models using the clear-sky measurements at the National Renewable Energy Laboratory's (NREL's) Solar Radiation Research Laboratory (SRRL) and a radiative transfer model that integrates diffuse radiances of various sky-viewing angles. We found that the radiative transfer model and a transposition model based on empirical regressions are superior to the isotropic models when compared to measurements. We further compared the radiative transfer model to the transposition models under an extensive range of idealized conditions. Our results suggest that the empirical transposition model has slightly higher cloudy-sky POA irradiance than the radiative transfer model, but performs better than the isotropic models under clear-sky conditions. Significantly smaller POA irradiances computed by the transposition models are observed when the photovoltaics (PV) panel deviates from the azimuthal direction of the sun. The new algorithms developed in the current study have opened the door to a more comprehensive evaluation of transposition models for various atmospheric conditions and solar and PV orientations.« less

Comparison of OMI NO2 Observations and Their Seasonal and Weekly Cycles with Ground-Based Measurements in Helsinki

NASA Technical Reports Server (NTRS)

Ialongo, Iolanda; Herman, Jay; Krotkov, Nick; Lamsal, Lok; Boersma, Folkert; Hovila, Jari; Tamminen, Johanna

2016-01-01

We present the comparison of satellite-based OMI (Ozone Monitoring Instrument) NO2 products with ground-based observations in Helsinki. OMI NO2 total columns, available from standard product (SP) and DOMINO algorithm, are compared with the measurements performed by the Pandora spectrometer in Helsinki in 2012. The relative difference between Pandora 21 and OMI SP retrievals is 4 and 6 for clear sky and all sky conditions, respectively. DOMINO NO2 retrievals showed slightly lower total columns with median differences about 5 and 14 for clear sky and all sky conditions, respectively. Large differences often correspond to cloudy autumn-winter days with solar zenith angles above 65. Nevertheless, the differences remain within the retrieval uncertainties. Furthermore, the weekly and seasonal cycles from OMI, Pandora and NO2 surface concentrations are compared. Both satellite- and ground-based data show a similar weekly cycle, with lower NO2 levels during the weekend compared to the weekdays as result of reduced emissions from traffic and industrial activities. Also the seasonal cycle shows a similar behavior, even though the results are affected by the fact that most of the data are available during spring-summer because of cloud cover in other seasons. This is one of few works in which OMI NO2 retrievals are evaluated in an urban site at high latitudes (60N). Despite the city of Helsinki having relatively small pollution sources, OMI retrievals have proved to be able to describe air quality features and variability similar to surface observations. This adds confidence in using satellite observations for air quality monitoring also at high latitudes.

Seeing Beyond the Naked Eye in a Planetarium

NASA Astrophysics Data System (ADS)

Fairall, A.

2005-12-01

I have a philosophy that the traditional naked-eye sky, as usually shown in planetariums, should only be an introductory step in portraying the Universe. Consequently, over the years I have produced 'inter alia' various versions of an enhanced Milky Way (the latest based on Axel Mellenger's panorama), the extragalactic sky and the radio sky for projection on planetarium domes. I also put together a three-dimensional planetarium show-the audience being equipped with ChromDepth(tm) spectacles- which stepped from the Solar System to the cosmic microwave background. The advent of digital technology now makes all this much easier. Currently, Labyrinth, a visualization program developed in-house, serves much the same function as the Hayden Planetarium's Partiview, but also permits rendering and fl y-throughs of large-scale structures. It allows viewers to explore local cosmography. Labyrinth can produce images that operate with the 3-D spectacles; we have also produced a version of Partiview that does the same.

AmeriFlux US-SO4 Sky Oaks- New Stand

DOE Data Explorer

Oechel, Walt [San Diego State University

2016-01-01

This is the AmeriFlux version of the carbon flux data for the site US-SO4 Sky Oaks- New Stand. Site Description - The Sky Oaks New site is located near the Sky Oaks Field station, owned and operated by San Diego State University. Chaparral vegetation, associated with a Mediterranean climate, covers nearly half of the rough and rocky terrain. Precipitation is almost exclusively confined to the winter months. During the summer and early fall, hot and dry Santa Ana winds from the northeast bring desert heat to the site. A high intensity natural wildfire occurred in approximately 1905. Physical characteristics prior to the 1905 burn are unknown, including stand age and canopy height. Currently, the Sky Oaks New site is an excellent representation of an old-growth chaparral ecosystem, with a canopy height of 2.3 m and chamise-dominated overstory.

Impacts of the land-lake breeze of the Volta reservoir on the diurnal cycle of cloudiness and precipitation

NASA Astrophysics Data System (ADS)

Buchholz, Marcel; Fink, Andreas H.; Knippertz, Peter; Yorke, Charles

2017-04-01

Lake Volta in Ghana is the artificial lake on Earth with the largest surface area (8502 km2). It has been constructed in the early 1960s, with the lake being filled around 1966. Land-lake breezes and their effects on the diurnal cycle of local wind systems, cloudiness, and precipitation have been studied for several tropical lakes, among which studies on the effects of Lake Victoria in East Africa are one of the most perceived ones. To date, no studies on the strengths and effects of the land-lake breeze of the Volta reservoir are known to the authors. Using surface station data, a variety of satellite data on clouds and precipitation, and a convection-resolving regional model, the land-lake breeze and its impacts were studied for Lake Volta between 1998 and 2015. The observational data sets confirm a significant land-lake circulation. The only manned weather station operated by the Ghana Meteorological Service that is situated at the lake is Kete Krachi. Hourly observations for 2006 and 2014 show on several days a clearing of skies in the afternoon associated with a shift in the surface winds from southwest to southeast, the latter potentially indicating a lake breeze effect. Cloud occurrence frequency derived from the CLARA-A2, MODIS, and CLAAS2 cloud masks and the cloud physical properties from CLAAS2 clearly show the development of clouds at the lake breeze front in the course of the morning and around mid-day. This effect is most pronounced in March when also the difference between the surface temperatures of the lake and the desiccated land surface is strongest. During the peak of the wet season in July, the lake breeze cloudiness is masked by a high background cloudiness and likely also weaker due to the strong southwesterly monsoon flow that tends to weaken the land-lake circulation. However, the precipitation signal was found to be strongest in July, most probably due to the fact that in boreal fall, winter and spring, the lake breeze cloudiness often fails to develop into afternoon showers or thunderstorms, or if, they are short-lived with substantial below-cloud evaporation. Two cases in 2007 and 2014 were synoptically analyzed with weather charts and modeled using the COSMO model, the current regional operational weather forecasting model of the German Weather Service (DWD). The COSMO experiments with and without the lake were integrated for 48 hours at convection-resolving resolution of 2.8 km. Initial and boundary conditions were taken from ECWMF operational analysis. Model results confirm the development of the daytime lake breeze and suggest that the existence of the lake has substantially changed the local circulation, cloudiness and precipitation regime. Our results imply a significant impact of the artificial lake on the local climate and ecosystems that warrants further study.

AmeriFlux US-SO3 Sky Oaks- Young Stand

DOE Data Explorer

Oechel, Walt [San Diego State University

2016-01-01

This is the AmeriFlux version of the carbon flux data for the site US-SO3 Sky Oaks- Young Stand. Site Description - The Sky Oaks Young site is located near the Sky Oaks Field station, owned and operated by San Diego State University. Chaparral vegetation, associated with a Mediterranean climate, covers nearly half of the rough and rocky terrain. Precipitation is almost exclusively confined to the winter months. During the summer and early fall, hot and dry Santa Ana winds from the northeast bring desert heat to the site. A high intensity natural wildfire occurred in July of 2003. The stand age at the time of the wildfire was 10 years old, following a controlled burn in 1993.

Attenuation by clouds of UV radiation for low stratospheric ozone conditions

NASA Astrophysics Data System (ADS)

Orte, Facundo; Wolfram, Elian; Salvador, Jacobo; D'Elia, Raúl; Quiroga, Jonathan; Quel, Eduardo; Mizuno, Akira

2017-02-01

Stratospheric poor ozone air masses related to the polar ozone hole overpass subpolar regions in the Southern Hemisphere during spring and summer seasons, resulting in increases of surface Ultraviolet Index (UVI). The impact of these abnormal increases in the ultraviolet radiation could be overestimated if clouds are not taking into account. The aim of this work is to determine the percentage of cases in which cloudiness attenuates the high UV radiation that would reach the surface in low total ozone column situations and in clear sky hypothetical condition for Río Gallegos, Argentina. For this purpose, we analysed UVI data obtained from a multiband filter radiometer GUV-541 (Biospherical Inc.) installed in the Observatorio Atmosférico de la Patagonia Austral (OAPA-UNIDEF (MINDEF - CONICET)) (51 ° 33' S, 69 ° 19' W), Río Gallegos, since 2005. The database used covers the period 2005-2012 for spring seasons. Measured UVI values are compared with UVI calculated using a parametric UV model proposed by Madronich (2007), which is an approximation for the UVI for clear sky, unpolluted atmosphere and low surface albedo condition, using the total ozone column amount, obtained from the OMI database for our case, and the solar zenith angle. It is observed that ˜76% of the total low ozone amount cases, which would result in high and very high UVI categories for a hypothetical (modeled) clear sky condition, are attenuated by clouds, while 91% of hypothetical extremely high UVI category are also attenuated.

Surface net solar radiation estimated from satellite measurements - Comparisons with tower observations

NASA Technical Reports Server (NTRS)

Li, Zhanqing; Leighton, H. G.; Cess, Robert D.

1993-01-01

A parameterization that relates the reflected solar flux at the top of the atmosphere to the net solar flux at the surface in terms of only the column water vapor amount and the solar zenith angle was tested against surface observations. Net surface fluxes deduced from coincidental collocated satellite-measured radiances and from measurements from towers in Boulder during summer and near Saskatoon in winter have mean differences of about 2 W/sq m, regardless of whether the sky is clear or cloudy. Furthermore, comparisons between the net fluxes deduced from the parameterization and from surface measurements showed equally good agreement when the data were partitioned into morning and afternoon observations. This is in contrast to results from an empirical clear-sky algorithm that is unable to account adequately for the effects of clouds and that shows, at Boulder, a distinct morning to afternoon variation. It is also demonstrated that the parameterization may be applied to irradiances at the top of the atmosphere that have been temporally averaged. The good agreement between the results of the parameterization and surface measurements suggests that the algorithm is a useful tool for a variety of climate studies.

Evaluation and optimization of sampling errors for the Monte Carlo Independent Column Approximation

NASA Astrophysics Data System (ADS)

Räisänen, Petri; Barker, W. Howard

2004-07-01

The Monte Carlo Independent Column Approximation (McICA) method for computing domain-average broadband radiative fluxes is unbiased with respect to the full ICA, but its flux estimates contain conditional random noise. McICA's sampling errors are evaluated here using a global climate model (GCM) dataset and a correlated-k distribution (CKD) radiation scheme. Two approaches to reduce McICA's sampling variance are discussed. The first is to simply restrict all of McICA's samples to cloudy regions. This avoids wasting precious few samples on essentially homogeneous clear skies. Clear-sky fluxes need to be computed separately for this approach, but this is usually done in GCMs for diagnostic purposes anyway. Second, accuracy can be improved by repeated sampling, and averaging those CKD terms with large cloud radiative effects. Although this naturally increases computational costs over the standard CKD model, random errors for fluxes and heating rates are reduced by typically 50% to 60%, for the present radiation code, when the total number of samples is increased by 50%. When both variance reduction techniques are applied simultaneously, globally averaged flux and heating rate random errors are reduced by a factor of #3.

Cloud Computing with Context Cameras

NASA Astrophysics Data System (ADS)

Pickles, A. J.; Rosing, W. E.

2016-05-01

We summarize methods and plans to monitor and calibrate photometric observations with our autonomous, robotic network of 2m, 1m and 40cm telescopes. These are sited globally to optimize our ability to observe time-variable sources. Wide field "context" cameras are aligned with our network telescopes and cycle every ˜2 minutes through BVr'i'z' filters, spanning our optical range. We measure instantaneous zero-point offsets and transparency (throughput) against calibrators in the 5-12m range from the all-sky Tycho2 catalog, and periodically against primary standards. Similar measurements are made for all our science images, with typical fields of view of ˜0.5 degrees. These are matched against Landolt, Stetson and Sloan standards, and against calibrators in the 10-17m range from the all-sky APASS catalog. Such measurements provide pretty good instantaneous flux calibration, often to better than 5%, even in cloudy conditions. Zero-point and transparency measurements can be used to characterize, monitor and inter-compare sites and equipment. When accurate calibrations of Target against Standard fields are required, monitoring measurements can be used to select truly photometric periods when accurate calibrations can be automatically scheduled and performed.

The League of Astronomers: Outreach

NASA Astrophysics Data System (ADS)

Paat, Anthony; Brandel, A.; Schmitz, D.; Sharma, R.; Thomas, N. H.; Trujillo, J.; Laws, C. S.; Astronomers, League of

2014-01-01

The University of Washington League of Astronomers (LOA) is an organization comprised of University of Washington (UW) undergraduate students. Our main goal is to share our interest in astronomy with the UW community and with the general public. The LOA hosts star parties on the UW campus and collaborates with the Seattle Astronomical Society (SAS) on larger Seattle-area star parties. At the star parties, we strive to teach our local community about what they can view in our night sky. LOA members share knowledge of how to locate constellations and use a star wheel. The relationship the LOA has with members of SAS increases both the number of events and people we are able to reach. Since the cloudy skies of the Northwest prevent winter star parties, we therefore focus our outreach on the UW Mobile Planetarium, an inflatable dome system utilizing Microsoft’s WorldWide Telescope (WWT) software. The mobile planetarium brings astronomy into the classrooms of schools unable to travel to the UW on-campus planetarium. Members of the LOA volunteer their time towards this project and we make up the majority of the Mobile Planetarium volunteers. Our outreach efforts allow us to connect with the community and enhance our own knowledge of astronomy.

An Examination of Intertidal Temperatures Through Remotely Sensed Satellite Observations

NASA Astrophysics Data System (ADS)

Lakshmi, V.

2010-12-01

MODIS Aqua and Terra satellites produce both land surface temperatures and sea surface temperatures using calibrated algorithms. In this study, the land surface temperatures were retrieved during clear-sky (non-cloudy) conditions at a 1 km2 resolution (overpass time at 10:30 am) whereas the sea surface temperatures are also retrieved during clear-sky conditions at approximately 4 km resolution (overpass time at 1:30 pm). The purpose of this research was to examine remotely sensed sea surface (SST), intertidal (IST), and land surface temperatures (LST), in conjunction with observed in situ mussel body temperatures, as well as associated weather and tidal data. In Strawberry Hill, Oregon, it was determined that intertidal surface temperatures are similar to but distinctly different from land surface temperatures although influenced by sea surface temperatures. The air temperature and differential heating throughout the day, as well as location in relation to the shore, can greatly influence the remotely sensed surface temperatures. Therefore, remotely sensed satellite data is a very useful tool in examining intertidal temperatures for regional climatic changes over long time periods and may eventually help researchers forecast expected climate changes and help determine associated biological implications.

Planck 2015 results. XXVI. The Second Planck Catalogue of Compact Sources

NASA Astrophysics Data System (ADS)

Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Argüeso, F.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Beichman, C.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bock, J. J.; Böhringer, H.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bucher, M.; Burigana, C.; Butler, R. C.; Calabrese, E.; Cardoso, J.-F.; Carvalho, P.; Catalano, A.; Challinor, A.; Chamballu, A.; Chary, R.-R.; Chiang, H. C.; Christensen, P. R.; Clemens, M.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Désert, F.-X.; Dickinson, C.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Falgarone, E.; Fergusson, J.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Helou, G.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leahy, J. P.; Leonardi, R.; León-Tavares, J.; Lesgourgues, J.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; McGehee, P.; Meinhold, P. R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Negrello, M.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Partridge, B.; Pasian, F.; Patanchon, G.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rowan-Robinson, M.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Sanghera, H. S.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Seiffert, M. D.; Shellard, E. P. S.; Spencer, L. D.; Stolyarov, V.; Sudiwala, R.; Sunyaev, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tornikoski, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Türler, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Walter, B.; Wandelt, B. D.; Wehus, I. K.; Yvon, D.; Zacchei, A.; Zonca, A.

2016-09-01

The Second Planck Catalogue of Compact Sources is a list of discrete objects detected in single-frequency maps from the full duration of the Planck mission and supersedes previous versions. It consists of compact sources, both Galactic and extragalactic, detected over the entire sky. Compact sources detected in the lower frequency channels are assigned to the PCCS2, while at higher frequencies they are assigned to one of two subcatalogues, the PCCS2 or PCCS2E, depending on their location on the sky. The first of these (PCCS2) covers most of the sky and allows the user to produce subsamples at higher reliabilities than the target 80% integral reliability of the catalogue. The second (PCCS2E) contains sources detected in sky regions where the diffuse emission makes it difficult to quantify the reliability of the detections. Both the PCCS2 and PCCS2E include polarization measurements, in the form of polarized flux densities, or upper limits, and orientation angles for all seven polarization-sensitive Planck channels. The improved data-processing of the full-mission maps and their reduced noise levels allow us to increase the number of objects in the catalogue, improving its completeness for the target 80% reliability as compared with the previous versions, the PCCS and the Early Release Compact Source Catalogue (ERCSC).

Toward all weather, long record, and real-time land surface temperature retrievals from microwave satellite observations

NASA Astrophysics Data System (ADS)

Jimenez, Carlos; Prigent, Catherine; Aires, Filipe; Ermida, Sofia

2017-04-01

The land surface temperature can be estimated from satellite passive microwave observations, with limited contamination from the clouds as compared to the infrared satellite retrievals. With ˜60% cloud cover in average over the globe, there is a need for "all weather," long record, and real-time estimates of land surface temperature (Ts) from microwaves. A simple yet accurate methodology is developed to derive the land surface temperature from microwave conical scanner observations, with the help of pre-calculated land surface microwave emissivities. The method is applied to the Special Sensor Microwave/Imagers (SSM/I) and the Earth observation satellite (EOS) Advanced Microwave Scanning Radiometer (AMSR-E) observations?, regardless of the cloud cover. The SSM/I results are compared to infrared estimates from International Satellite Cloud Climatology Project (ISCCP) and from Advanced Along Track Scanning Radiometer (AATSR), under clear-sky conditions. Limited biases are observed (˜0.5 K for both comparisons) with a root-mean-square difference (RMSD) of ˜5 K, to be compared to the RMSE of ˜3.5 K between ISCCP et AATSR. AMSR-E results are compared with the Moderate Resolution Imaging Spectroradiometer (MODIS) clear-sky estimates. As both instruments are on board the same satellite, this reduces the uncertainty associated to the observations match-up, resulting in a lower RMSD of ˜ 4K. The microwave Ts is compared to in situ Ts time series from a collection of ground stations over a large range of environments. For 22 stations available in the 2003-2004 period, SSM/I Ts agrees very well for stations in vegetated environments (down to RMSD of ˜2.5 K for several stations), but the retrieval methodology encounters difficulties under cold conditions due to the large variability of snow and ice surface emissivities. For 10 stations in the year 2010, AMSR-E presents an all-station mean RMSD of ˜4.0 K with respect tom the ground Ts. Over the same stations, MODIS agrees better (RMSD of 2.4 K), ?but AMSR-E provides a larger number of Ts estimates by being able to measure under cloudy conditions, with an approximated ratio of 3 to 1 over the analysed stations. At many stations the RMSD of the AMSR-E clear and cloudy-sky are comparable, highlighting the ability of the microwave inversions to provide Ts under most atmospheric and surface conditions.

Islands in the Sky: Ecophysiological Cloud-Vegetation Linkages in Southern Appalachian Mountain Cloud Forests

NASA Astrophysics Data System (ADS)

Reinhardt, K.; Emanuel, R. E.; Johnson, D. M.

2013-12-01

Mountain cloud forest (MCF) ecosystems are characterized by a high frequency of cloud fog, with vegetation enshrouded in fog. The altitudinal boundaries of cloud-fog zones co-occur with conspicuous, sharp vegetation ecotones between MCF- and non-MCF-vegetation. This suggests linkages between cloud-fog and vegetation physiology and ecosystem functioning. However, very few studies have provided a mechanistic explanation for the sharp changes in vegetation communities, or how (if) cloud-fog and vegetation are linked. We investigated ecophysiological linkages between clouds and trees in Southern Appalachian spruce-fir MCF. These refugial forests occur in only six mountain-top, sky-island populations, and are immersed in clouds on up to 80% of all growing season days. Our fundamental research questions was: How are cloud-fog and cloud-forest trees linked? We measured microclimate and physiology of canopy tree species across a range of sky conditions (cloud immersed, partly cloudy, sunny). Measurements included: 1) sunlight intensity and spectral quality; 2) carbon gain and photosynthetic capacity at leaf (gas exchange) and ecosystem (eddy covariance) scales; and 3) relative limitations to carbon gain (biochemical, stomatal, hydraulic). RESULTS: 1) Midday sunlight intensity ranged from very dark (<30 μmol m-2 s-1, under cloud-immersed conditions) to very bright (>2500 μmol m-2 s-1), and was highly variable on minute-to-minute timescales whenever clouds were present in the sky. Clouds and cloud-fog increased the proportion of blue-light wavelengths 5-15% compared to sunny conditions, and altered blue:red and red:far red ratios, both of which have been shown to strongly affect stomatal functioning. 2) Cloud-fog resulted in ~50% decreased carbon gain at leaf and ecosystem scales, due to sunlight levels below photosynthetic light-saturation-points. However, greenhouse studies and light-response-curve analyses demonstrated that MCF tree species have low light-compensation points (can photosynthesize even at low light levels), and maximum photosynthesis occurs during high-light, diffuse-light conditions such as occurs during diffuse 'sunflecks' inside the cloud fog. Additionally, the capacity to respond to brief, intermittent sunflecks ('photosynthetic induction', e.g., time to maximum photosynthesis) was high in our MCF species. 3) Data quantifying limitations to photosynthesis were contradictory, underscoring complex relationships among photosynthesis, light, carbon and water relations. While stomatal response to atmospheric moisture demand was sensitive (e.g., 80% drop in stomatal conductance in a <1 kPa drop in vapor-pressure-deficit in conifer species), stem xylem hydraulic conductivity suggested strong drought tolerance capabilities. CONCLUSIONS: Clouds and cloud-fog exert strong influence on canopy-tree and ecosystem carbon relations. MCF are dynamic light environments. In these highly variable but ultimately light-limited ecosystems, vegetation must be able to both fix carbon when cloudy and dark but also be able to capitalize on saturating sunlight when possible.

The Dynamics of Fine Mode Aerosol Optical Properties in South Korea from AERONET and Aircraft Observations with a Focus on Cases with Large Cloud Fraction and/or Fog During KORUS-AQ

NASA Astrophysics Data System (ADS)

Eck, T. F.; Holben, B. N.; Kim, J.; Choi, M.; Giles, D. M.; Schafer, J.; Smirnov, A.; Slutsker, I.; Sinyuk, A.; Sorokin, M. G.; Kraft, J.; Beyersdorf, A. J.; Anderson, B. E.; Thornhill, K. L., II; Crawford, J. H.

2017-12-01

The focus of our investigation is of major fine mode aerosol pollution events in South Korea, particularly when cloud fraction is high. This work includes the analysis of AERONET data utilizing the Spectral Deconvolution Algorithm to enable detection of fine mode aerosol optical depth (AOD) near to clouds. Additionally we analyze the newly developed AERONET V3 data sets that have significant changes to cloud screening algorithms. Comparisons of aerosol optical depth are made between AERONET Versions 2 and 3 for both long-term climatology data and for specific 2016 cases, especially in May and June 2016 during the KORUS-AQ field campaign. In general the Version 3 cloud screening allows many more fine mode AOD observations to reach Level 2 when cloud amount is high, as compared to Version 2, thereby enabling more thorough analysis of these types of cases. Particular case studies include May 25-26, 2016 when cloud fraction was very high over much of the peninsula, associated with a frontal passage and advection of pollution from China. Another interesting case is June 9, 2016 when there was fog over the West Sea, and this seems to have affected aerosol properties well downwind over the Korean peninsula. Both of these days had KORUS-AQ research aircraft flights that provided observations of aerosol absorption, particle size distributions and vertical profiles of extinction. AERONET retrievals and aircraft in situ measurements both showed high single scattering albedo (weak absorption) on these cloudy days. We also investigate the relationship between aerosol fine mode radius and AOD and the relationship between aerosol single scattering albedo and fine mode particle radius from the AERONET almucantar retrievals for the interval of April through June 2016 for 17 AERONET sites in South Korea. Strongly increasing fine mode radius (leading to greater scattering efficiency) as fine mode AOD increased is one factor contributing to a trend of increasing single scattering albedo as fine AOD increased. Additionally, the new AERONET Hybrid sky radiance scan retrievals that allow for inversions to be made at much smaller solar zenith angles are analyzed and compared to almucantar retrievals.

On the trail of Vikings with polarized skylight: experimental study of the atmospheric optical prerequisites allowing polarimetric navigation by Viking seafarers.

PubMed

Horváth, Gábor; Barta, András; Pomozi, István; Suhai, Bence; Hegedüs, Ramón; Akesson, Susanne; Meyer-Rochow, Benno; Wehner, Rüdiger

2011-03-12

Between AD 900 and AD 1200 Vikings, being able to navigate skillfully across the open sea, were the dominant seafarers of the North Atlantic. When the Sun was shining, geographical north could be determined with a special sundial. However, how the Vikings could have navigated in cloudy or foggy situations, when the Sun's disc was unusable, is still not fully known. A hypothesis was formulated in 1967, which suggested that under foggy or cloudy conditions, Vikings might have been able to determine the azimuth direction of the Sun with the help of skylight polarization, just like some insects. This hypothesis has been widely accepted and is regularly cited by researchers, even though an experimental basis, so far, has not been forthcoming. According to this theory, the Vikings could have determined the direction of the skylight polarization with the help of an enigmatic birefringent crystal, functioning as a linearly polarizing filter. Such a crystal is referred to as 'sunstone' in one of the Viking's sagas, but its exact nature is unknown. Although accepted by many, the hypothesis of polarimetric navigation by Vikings also has numerous sceptics. In this paper, we summarize the results of our own celestial polarization measurements and psychophysical laboratory experiments, in which we studied the atmospheric optical prerequisites of possible sky-polarimetric navigation in Tunisia, Finland, Hungary and the high Arctic.

On the trail of Vikings with polarized skylight: experimental study of the atmospheric optical prerequisites allowing polarimetric navigation by Viking seafarers

PubMed Central

Horváth, Gábor; Barta, András; Pomozi, István; Suhai, Bence; Hegedüs, Ramón; Åkesson, Susanne; Meyer-Rochow, Benno; Wehner, Rüdiger

2011-01-01

Between AD 900 and AD 1200 Vikings, being able to navigate skillfully across the open sea, were the dominant seafarers of the North Atlantic. When the Sun was shining, geographical north could be determined with a special sundial. However, how the Vikings could have navigated in cloudy or foggy situations, when the Sun's disc was unusable, is still not fully known. A hypothesis was formulated in 1967, which suggested that under foggy or cloudy conditions, Vikings might have been able to determine the azimuth direction of the Sun with the help of skylight polarization, just like some insects. This hypothesis has been widely accepted and is regularly cited by researchers, even though an experimental basis, so far, has not been forthcoming. According to this theory, the Vikings could have determined the direction of the skylight polarization with the help of an enigmatic birefringent crystal, functioning as a linearly polarizing filter. Such a crystal is referred to as ‘sunstone’ in one of the Viking's sagas, but its exact nature is unknown. Although accepted by many, the hypothesis of polarimetric navigation by Vikings also has numerous sceptics. In this paper, we summarize the results of our own celestial polarization measurements and psychophysical laboratory experiments, in which we studied the atmospheric optical prerequisites of possible sky-polarimetric navigation in Tunisia, Finland, Hungary and the high Arctic. PMID:21282181

A gap-filling model for eddy covariance latent heat flux: Estimating evapotranspiration of a subtropical seasonal evergreen broad-leaved forest as an example

NASA Astrophysics Data System (ADS)

Chen, Yi-Ying; Chu, Chia-Ren; Li, Ming-Hsu

2012-10-01

SummaryIn this paper we present a semi-parametric multivariate gap-filling model for tower-based measurement of latent heat flux (LE). Two statistical techniques, the principal component analysis (PCA) and a nonlinear interpolation approach were integrated into this LE gap-filling model. The PCA was first used to resolve the multicollinearity relationships among various environmental variables, including radiation, soil moisture deficit, leaf area index, wind speed, etc. Two nonlinear interpolation methods, multiple regressions (MRS) and the K-nearest neighbors (KNNs) were examined with random selected flux gaps for both clear sky and nighttime/cloudy data to incorporate into this LE gap-filling model. Experimental results indicated that the KNN interpolation approach is able to provide consistent LE estimations while MRS presents over estimations during nighttime/cloudy. Rather than using empirical regression parameters, the KNN approach resolves the nonlinear relationship between the gap-filled LE flux and principal components with adaptive K values under different atmospheric states. The developed LE gap-filling model (PCA with KNN) works with a RMSE of 2.4 W m-2 (˜0.09 mm day-1) at a weekly time scale by adding 40% artificial flux gaps into original dataset. Annual evapotranspiration at this study site were estimated at 736 mm (1803 MJ) and 728 mm (1785 MJ) for year 2008 and 2009, respectively.

Forcings and feedbacks in the GeoMIP ensemble for a reduction in solar irradiance and increase in CO2

NASA Astrophysics Data System (ADS)

Huneeus, Nicolas; Boucher, Olivier; Alterskjær, Kari; Cole, Jason N. S.; Curry, Charles L.; Ji, Duoying; Jones, Andy; Kravitz, Ben; Kristjánsson, Jón Egill; Moore, John C.; Muri, Helene; Niemeier, Ulrike; Rasch, Phil; Robock, Alan; Singh, Balwinder; Schmidt, Hauke; Schulz, Michael; Tilmes, Simone; Watanabe, Shingo; Yoon, Jin-Ho

2014-05-01

The effective radiative forcings (including rapid adjustments) and feedbacks associated with an instantaneous quadrupling of the preindustrial CO2 concentration and a counterbalancing reduction of the solar constant are investigated in the context of the Geoengineering Model Intercomparison Project (GeoMIP). The forcing and feedback parameters of the net energy flux, as well as its different components at the top-of-atmosphere (TOA) and surface, were examined in 10 Earth System Models to better understand the impact of solar radiation management on the energy budget. In spite of their very different nature, the feedback parameter and its components at the TOA and surface are almost identical for the two forcing mechanisms, not only in the global mean but also in their geographical distributions. This conclusion holds for each of the individual models despite intermodel differences in how feedbacks affect the energy budget. This indicates that the climate sensitivity parameter is independent of the forcing (when measured as an effective radiative forcing). We also show the existence of a large contribution of the cloudy-sky component to the shortwave effective radiative forcing at the TOA suggesting rapid cloud adjustments to a change in solar irradiance. In addition, the models present significant diversity in the spatial distribution of the shortwave feedback parameter in cloudy regions, indicating persistent uncertainties in cloud feedback mechanisms.

Landscape by Moonlight: Peter Paul Rubens and Astronomy

NASA Astrophysics Data System (ADS)

Mendillo, M.

2016-01-01

In the last years of his life, Rubens (1577-1640) lived happily with his wife and children on his Het Steen estate. During this period he worked and reworked a painting that had special meaning to him—Landscape by Moonlight (1635-40), now at the Courtauld Gallery in London. After a highly successful career painting religious and secular portraits, allegories, and occasional landscapes, Rubens put an extraordinary amount of effort into this final landscape. He was well known as a person who would commit to memory ideas and themes that he would use in future works. This paper reviews Rubens' attention to the visualization of nature, his personal connections to Elsheimer, Galileo, and Peiresc, and explores his possible depiction of constellations recalled from memory and placed within the cloudy skies in his Landscape by Moonlight.

KSC-2009-3097

NASA Image and Video Library

2009-05-11

CAPE CANAVERAL, Fla. – Space shuttle Atlantis roars into the cloudy sky above Launch Pad 39A at NASA's Kennedy Space Center in Florida on the STS-125 mission. Blue cones of light, mach diamonds, can be seen beneath the engine nozzles. The mach diamonds are a formation of shock waves in the exhaust plume of an aerospace propulsion system. Atlantis will rendezvous with NASA's Hubble Space Telescope. Liftoff was on time at 2:01 p.m. EDT. Atlantis' 11-day flight will include five spacewalks to refurbish and upgrade the telescope with state-of-the-art science instruments that will expand Hubble's capabilities and extend its operational lifespan through at least 2014. The payload includes a Wide Field Camera 3, fine guidance sensor and the Cosmic Origins Spectrograph. Photo credit: NASA/Tony Gray-Tom Farrar

KSC-2009-3096

NASA Image and Video Library

2009-05-11

CAPE CANAVERAL, Fla. – Space shuttle Atlantis roars into the cloudy sky above Launch Pad 39A at NASA's Kennedy Space Center in Florida on the STS-125 mission. Blue cones of light, mach diamonds, can be seen beneath the engine nozzles. The mach diamonds are a formation of shock waves in the exhaust plume of an aerospace propulsion system. Atlantis will rendezvous with NASA's Hubble Space Telescope. Liftoff was on time at 2:01 p.m. EDT. Atlantis' 11-day flight will include five spacewalks to refurbish and upgrade the telescope with state-of-the-art science instruments that will expand Hubble's capabilities and extend its operational lifespan through at least 2014. The payload includes a Wide Field Camera 3, fine guidance sensor and the Cosmic Origins Spectrograph. Photo credit: NASA/Tony Gray-Tom Farrar

The Advanced Technology Microwave Sounder (ATMS): A New Operational Sensor Series

NASA Technical Reports Server (NTRS)

Kim, Edward; Lyu, Cheng-H Joseph; Leslie, R. Vince; Baker, Neal; Mo, Tsan; Sun, Ninghai; Bi, Li; Anderson, Mike; Landrum, Mike; DeAmici, Giovanni;

Cloudy Skies over AGN: Observations with Simbol-X

NASA Astrophysics Data System (ADS)

Salvati, M.; Risaliti, G.

2009-05-01

Recent time-resolved spectroscopic X-ray studies of bright obscured AGN show that column density variability on time scales of hours/days may be common, at least for sources with NH>1023 cm-2. This opens new oppurtunities in the analysis of the structure of the circumnuclear medium and of the X-ray source: resolving the variations due to single clouds covering/uncovering the X-ray source provides tight constraints on the source size, the clouds' size and distance, and their average number, density and column density. We show how Simbol-X will provide a breakthrough in this field, thanks to its broad band coverage, allowing (a) to precisely disentangle the continuum and NH variations, and (2) to extend the NH variability analysis to column densities >1023 cm-2.

Properties of PSCs and Cirrus Determined from AVHRR Data

NASA Technical Reports Server (NTRS)

Hervig, Mark; Pagan, Kathy; Foschi, Patricia G.

1999-01-01

Polar stratospheric clouds (PSCS) and cirrus have been investigated using thermal emission measurements at 10.8 and 12 micrometers wavelength (channels 4 and 5) from the Advanced Very High Resolution Radiometer (AVHRR). The AVHRR signal was evaluated from a theoretical basis to understand the emission from clear and cloudy skies, and models were developed to simulate the AVHRR signal. Signal simulations revealed that nitric acid PSCs are invisible to AVHRR, while ice PSCs and cirrus are readily detectable. Methods were developed to retrieve cloud optical depths, average temperatures, average effective radii, and ice water paths, from AVHRR channels 4 and 5. Properties of ice PSCs retrieved from AVHRR were compared to values derived from coincident radiosondes and from the Polar Ozone and Aerosol Measurement II instrument, showing good agreement.

Upscaling instantaneous to daily evapotranspiration using modelled daily shortwave radiation for remote sensing applications: An artificial neural network approach

DOE PAGES

Wandera, Loise; Mallick, Kaniska; Kiely, Gerard; ...

2017-01-11

Upscaling instantaneous evapotranspiration retrieved at any specific time-of-day (ET i) to daily evapotranspiration (ET d) is a key challenge in mapping regional ET using polar orbiting sensors. Various studies have unanimously cited the shortwave incoming radiation ( R S) to be the most robust reference variable explaining the ratio between ET d and ET i. This study aims to contribute in ET i upscaling for global studies using the ratio between daily and instantaneous incoming shortwave radiation ( R Sd/ R Si) as a factor for converting ET i to ET d. This paper proposes an artificial neural network (ANN)more » machine-learning algorithm first to predict R Sd from R Si followed by using the R Sd/ R Si ratio to convert ET i to ET d across different terrestrial ecosystems. Using R Si and R Sd observations from multiple sub-networks of the FLUXNET database spread across different climates and biomes (to represent inputs that would typically be obtainable from remote sensors during the overpass time) in conjunction with some astronomical variables (e.g. solar zenith angle, day length, exoatmospheric shortwave radiation), we developed the ANN model for reproducing R Sd and further used it to upscale ET i to ET d. The efficiency of the ANN is evaluated for different morning and afternoon times of day, under varying sky conditions, and also at different geographic locations. R S-based upscaled ET d produced a significant linear relation ( R 2 = 0.65 to 0.69), low bias (-0.31 to -0.56 MJ m -2 d -1; approx. 4 %), and good agreement (RMSE 1.55 to 1.86 MJ m -2 d -1; approx. 10 %) with the observed ET d, although a systematic overestimation of ET d was also noted under persistent cloudy sky conditions. Inclusion of soil moisture and rainfall information in ANN training reduced the systematic overestimation tendency in predominantly overcast days. An intercomparison with existing upscaling method at daily, 8-day, monthly, and yearly temporal resolution revealed a robust performance of the ANN-driven R S-based ET i upscaling method and was found to produce lowest RMSE under cloudy conditions. Sensitivity analysis revealed variable sensitivity of the method to biome selection and high ET d prediction errors in forest ecosystems are primarily associated with greater rainfall and cloudiness. As a result, the overall methodology appears to be promising and has substantial potential for upscaling ET i to ET d for field and regional-scale evapotranspiration mapping studies using polar orbiting satellites.« less

Upscaling instantaneous to daily evapotranspiration using modelled daily shortwave radiation for remote sensing applications: An artificial neural network approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wandera, Loise; Mallick, Kaniska; Kiely, Gerard

Upscaling instantaneous evapotranspiration retrieved at any specific time-of-day (ET i) to daily evapotranspiration (ET d) is a key challenge in mapping regional ET using polar orbiting sensors. Various studies have unanimously cited the shortwave incoming radiation ( R S) to be the most robust reference variable explaining the ratio between ET d and ET i. This study aims to contribute in ET i upscaling for global studies using the ratio between daily and instantaneous incoming shortwave radiation ( R Sd/ R Si) as a factor for converting ET i to ET d. This paper proposes an artificial neural network (ANN)more » machine-learning algorithm first to predict R Sd from R Si followed by using the R Sd/ R Si ratio to convert ET i to ET d across different terrestrial ecosystems. Using R Si and R Sd observations from multiple sub-networks of the FLUXNET database spread across different climates and biomes (to represent inputs that would typically be obtainable from remote sensors during the overpass time) in conjunction with some astronomical variables (e.g. solar zenith angle, day length, exoatmospheric shortwave radiation), we developed the ANN model for reproducing R Sd and further used it to upscale ET i to ET d. The efficiency of the ANN is evaluated for different morning and afternoon times of day, under varying sky conditions, and also at different geographic locations. R S-based upscaled ET d produced a significant linear relation ( R 2 = 0.65 to 0.69), low bias (-0.31 to -0.56 MJ m -2 d -1; approx. 4 %), and good agreement (RMSE 1.55 to 1.86 MJ m -2 d -1; approx. 10 %) with the observed ET d, although a systematic overestimation of ET d was also noted under persistent cloudy sky conditions. Inclusion of soil moisture and rainfall information in ANN training reduced the systematic overestimation tendency in predominantly overcast days. An intercomparison with existing upscaling method at daily, 8-day, monthly, and yearly temporal resolution revealed a robust performance of the ANN-driven R S-based ET i upscaling method and was found to produce lowest RMSE under cloudy conditions. Sensitivity analysis revealed variable sensitivity of the method to biome selection and high ET d prediction errors in forest ecosystems are primarily associated with greater rainfall and cloudiness. As a result, the overall methodology appears to be promising and has substantial potential for upscaling ET i to ET d for field and regional-scale evapotranspiration mapping studies using polar orbiting satellites.« less

Sources of variability of evapotranspiration in California

USGS Publications Warehouse

Hidalgo, H.G.; Cayan, D.R.; Dettinger, M.D.

2005-01-01

The variability (1990-2002) of potential evapotranspiration estimates (ETo) and related meteorological variables from a set of stations from the California Irrigation Management System (CIMIS) is studied. Data from the National Climatic Data Center (NCDC) and from the Department of Energy from 1950 to 2001 were used to validate the results. The objective is to determine the characteristics of climatological ETo and to identify factors controlling its variability (including associated atmospheric circulations). Daily ETo anomalies are strongly correlated with net radiation (Rn) anomalies, relative humidity (RH), and cloud cover, and less with average daily temperature (Tavg). The highest intraseasonal variability of ETo daily anomalies occurs during the spring, mainly caused by anomalies below the high ETo seasonal values during cloudy days. A characteristic circulation pattern is associated with anomalies of ETo and its driving meteorological inputs, Rn, RH, and Tavg, at daily to seasonal time scales. This circulation pattern is dominated by 700-hPa geopotential height (Z700) anomalies over a region off the west coast of North America, approximately between 32?? and 44?? latitude, referred to as the California Pressure Anomaly (CPA). High cloudiness and lower than normal ETo are associated with the lowheight (pressure) phase of the CPA pattern. Higher than normal ETo anomalies are associated with clear skies maintained through anomalously high Z700 anomalies offshore of the North American coast. Spring CPA, cloudiness, maximum temperature (Tmax), pan evaporation (Epan), and ETo conditions have not trended significantly or consistently during the second half of the twentieth century in California. Because it is not known how cloud cover and humidity will respond to climate change, the response of ETo in California to increased greenhouse-gas concentrations is essentially unknown; however, to retain the levels of ETo in the current climate, a decline of Rn by about 6% would be required to compensate for a warming of +3??C. ?? 2005 American Meteorological Society.

Thermodynamics and Cloud Radiative Effect from the First Year of GoAmazon

NASA Technical Reports Server (NTRS)

Collow, Allie Marquardt; Miller, Mark; Trabachino, Lynne

2015-01-01

Deforestation is an ongoing concern for the Amazon Rainforest of Brazil and associated changes to the land surface have been hypothesized to alter the climate in the region. A comprehensive set of meteorological observations at the surface and within the lower troposphere above Manacapuru, Brazil and data from the Modern Era Retrospective Analysis for Research and Applications Version 2 (MERRA-2) are used to evaluate the seasonal cycle of cloudiness, thermodynamics, and the radiation budget. While ample moisture is present in the Amazon Rainforest year round, the northward progression of the Hadley circulation during the dry season contributes to a drying of the middle troposphere and inhibits the formation of deep convection. This results in a reduction in cloudiness and precipitation as well as an increase in the height of the lifting condensation level, which is shown to have a negative correlation to the fraction of low clouds. Frequent cloudiness prevents solar radiation from reaching the surface and clouds are often reflective with high values of shortwave cloud radiative effect at the surface and top of the atmosphere. Cloud radiative effect is reduced during the dry season however the dry season surface shortwave cloud radiative effect is still double what is observed during the wet season in other tropical locations. Within the column, the impact of clouds on the radiation budget is more prevalent in the longwave part of the spectrum, with a net warming in the wet season.

Shortwave direct radiative effects of above cloud aerosols over global oceans derived from eight years of CALIOP and MODIS observations

NASA Astrophysics Data System (ADS)

Zhang, Z.; Meyer, K.; Yu, H.; Platnick, S.; Colarco, P.; Liu, Z.; Oreopoulos, L.

2015-09-01

In this paper, we studied the frequency of occurrence and shortwave direct radiative effects (DRE) of above-cloud aerosols (ACAs) over global oceans using eight years of collocated CALIOP and MODIS observations. Similar to previous work, we found high ACA occurrence in four regions: Southeast (SE) Atlantic region where ACAs are mostly light-absorbing aerosols, i.e., smoke and polluted dust according to CALIOP classification, originating from biomass burning over African Savanna; Tropical Northeast Atlantic and Arabian Sea where ACAs are predominantly windblown dust from the Sahara and Arabian desert, respectively; and Northwest Pacific where ACAs are mostly transported smoke and polluted dusts from Asian. From radiative transfer simulations based on CALIOP-MODIS observations and a set of the preselected aerosol optical models, we found the DREs of ACAs at the top of atmosphere (TOA) to be positive (i.e., warming) in the SE Atlantic and NW Pacific regions, but negative (i.e., cooling) in TNE Atlantic and Arabian Sea. The cancellation of positive and negative regional DREs results in a global ocean annual mean diurnally averaged cloudy-sky DRE of 0.015 W m-2 (range of -0.03 to 0.06 W m-2) at TOA. The DREs at surface and within atmosphere are -0.15 W m-2 (range of -0.09 to -0.21 W m-2), and 0.17 W m-2 (range of 0.11 to 0.24 W m-2), respectively. The regional and seasonal mean DREs are much stronger. For example, in the SE Atlantic region the JJA (July ~ August) seasonal mean cloudy-sky DRE is about 0.7 W m-2 (range of 0.2 to 1.2 W m-2) at TOA. The uncertainty in our DRE computations is mainly cause by the uncertainties in the aerosol optical properties, in particular aerosol absorption, and uncertainties in the CALIOP operational aerosol optical thickness retrieval. In situ and remotely sensed measurements of ACA from future field campaigns and satellite missions, and improved lidar retrieval algorithm, in particular vertical feature masking, would help reduce the uncertainty.

Satellite-based estimation of evapotranspiration in typical forests of China

NASA Astrophysics Data System (ADS)

Wang, Y.; Li, R.

2017-12-01

Evapotranspiration (ET) is the key process affecting the interaction between land surface and atmosphere. Satellite remote sensing is the only feasible technique to monitor the terrestrial ET on large scale. Microwave Emissivity Difference Vegetation Index (EDVI) indicates vegetation water content and can be retrieved under both clear and cloudy sky. Based on EDVI, a quantitative algorithm for ET estimation in China was developed. In this study, we improved the EDVI-based ET algorithm by using the datasets from multiple platforms, including Moderate-Resolution Imaging Spectroradiometer (MODIS), Clouds and Earth's Radiation energy system (CERES) and European Centre for Medium-Range Weather Forecasts (ECMWF). As primary inputs of the algorithm, they are all independent from ground-based measurements. The improved algorithm was tested in three ChinaFlux forest sites, Dinghushan(DHS) subtropical evergreen broad-leaved forest site, Qianyanzhou(QYZ) subtropical man-planted forest site and Changbaishan(CBS) temperate deciduous broad-leaved coniferous mixed forest site. Validations against the in-situ measured ETobs from 2003 to 2005 showed that the EDVI-based algorithm has the capability to simulate midday ET within reasonable accuracies. In terms of the magnitude and seasonal cycle, the estimated ETcal are in very good agreement with the ETobs. The correlation coefficients(R) between ETcal and ETobs during midday vary from 0.51 to 0.80 over the study years, with the annual mean bias (relative bias) ranging from -53.02 Wm-2 (-26.46%) to 34.02 Wm-2 (+23.69%). At monthly scale, the R of monthly mean ETcal and ETobs can reach to 0.83, 0.93 and 0.82 at DHS, QYZ and CBS, with bias of +3.0%, -22.3% and -9.7%, respectively. Contamination from precipitation can partly affect the performances of this algorithm. Validation results generally become better after removing those samples in rainy days. The results indicate that this EDVI-based algorithm, driven completely by using satellite and reanalysis datasets, has a great potential for monitoring terrestrial ET in large spatial scale and under both clear and cloudy sky.

Astronomical Data Center Bulletin, volume 1, number 3

NASA Technical Reports Server (NTRS)

Mead, J. M.; Warren, W. H., Jr.; Nagy, T. A.

1983-01-01

A catalog of galactic O-type stars, a machine-readable version of the bright star catalog, a two-micron sky survey, sky survey sources with problematical Durchmusterung identifications, data retrieval for visual binary stars, faint blue objects, the sixth catalog of galactic Wolf-Rayet stars, declination versus magnitude distribution, the SAO-HD-GC-DM cross index catalog, star cross-identification tables, astronomical sources, bibliographical star index search updates, DO-HD and HD-DO cross indices, and catalogs, are reviewed.

Network based sky Brightness Monitor

NASA Astrophysics Data System (ADS)

McKenna, Dan; Pulvermacher, R.; Davis, D. R.

2009-01-01

We have developed and are currently testing an autonomous 2 channel photometer designed to measure the night sky brightness in the visual wavelengths over a multi-year campaign. The photometer uses a robust silicon sensor filtered with Hoya CM500 glass. The Sky brightness is measured every minute at two elevation angles typically zenith and 20 degrees to monitor brightness and transparency. The Sky Brightness monitor consists of two units, the remote photometer and a network interface. Currently these devices use 2.4 Ghz transceivers with a free space range of 100 meters. The remote unit is battery powered with day time recharging using a solar panel. Data received by the network interface transmits data via standard POP Email protocol. A second version is under development for radio sensitive areas using an optical fiber for data transmission. We will present the current comparison with the National Park Service sky monitoring camera. We will also discuss the calibration methods used for standardization and temperature compensation. This system is expected to be deployed in the next year and be operated by the International Dark Sky Association SKYMONITOR project.

Planck 2015 results: XXVI. The Second Planck Catalogue of Compact Sources

DOE PAGES

Ade, P. A. R.; Aghanim, N.; Argüeso, F.; ...

2016-09-20

The Second Planck Catalogue of Compact Sources is a list of discrete objects detected in single-frequency maps from the full duration of the Planck mission and supersedes previous versions. Also, it consists of compact sources, both Galactic and extragalactic, detected over the entire sky. Compact sources detected in the lower frequency channels are assigned to the PCCS2, while at higher frequencies they are assigned to one of two subcatalogues, the PCCS2 or PCCS2E, depending on their location on the sky. The first of these (PCCS2) covers most of the sky and allows the user to produce subsamples at higher reliabilitiesmore » than the target 80% integral reliability of the catalogue. The second (PCCS2E) contains sources detected in sky regions where the diffuse emission makes it difficult to quantify the reliability of the detections. Both the PCCS2 and PCCS2E include polarization measurements, in the form of polarized flux densities, or upper limits, and orientation angles for all seven polarization-sensitive Planck channels. Finally, the improved data-processing of the full-mission maps and their reduced noise levels allow us to increase the number of objects in the catalogue, improving its completeness for the target 80% reliability as compared with the previous versions, the PCCS and the Early Release Compact Source Catalogue (ERCSC).« less

Planck 2015 results: XXVI. The Second Planck Catalogue of Compact Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ade, P. A. R.; Aghanim, N.; Argüeso, F.

The Second Planck Catalogue of Compact Sources is a list of discrete objects detected in single-frequency maps from the full duration of the Planck mission and supersedes previous versions. Also, it consists of compact sources, both Galactic and extragalactic, detected over the entire sky. Compact sources detected in the lower frequency channels are assigned to the PCCS2, while at higher frequencies they are assigned to one of two subcatalogues, the PCCS2 or PCCS2E, depending on their location on the sky. The first of these (PCCS2) covers most of the sky and allows the user to produce subsamples at higher reliabilitiesmore » than the target 80% integral reliability of the catalogue. The second (PCCS2E) contains sources detected in sky regions where the diffuse emission makes it difficult to quantify the reliability of the detections. Both the PCCS2 and PCCS2E include polarization measurements, in the form of polarized flux densities, or upper limits, and orientation angles for all seven polarization-sensitive Planck channels. Finally, the improved data-processing of the full-mission maps and their reduced noise levels allow us to increase the number of objects in the catalogue, improving its completeness for the target 80% reliability as compared with the previous versions, the PCCS and the Early Release Compact Source Catalogue (ERCSC).« less

All Sky Cloud Coverage Monitoring for SONG-China Project

NASA Astrophysics Data System (ADS)

Tian, J. F.; Deng, L. C.; Yan, Z. Z.; Wang, K.; Wu, Y.

2016-05-01

In order to monitor the cloud distributions at Qinghai station, a site selected for SONG (Stellar Observations Network Group)-China node, the design of the proto-type of all sky camera (ASC) applied in Xinglong station is adopted. Both hardware and software improvements have been made in order to be more precise and deliver quantitative measurements. The ARM (Advanced Reduced Instruction Set Computer Machine) MCU (Microcontroller Unit) instead of PC is used to control the upgraded version of ASC. A much higher reliability has been realized in the current scheme. Independent of the positions of the Sun and Moon, the weather conditions are constantly changing, therefore it is difficult to get proper exposure parameters using only the temporal information of the major light sources. A realistic exposure parameters for the ASC can actually be defined using a real-time sky brightness monitor that is also installed at the same site. The night sky brightness value is a very sensitive function of the cloud coverage, and can be accurately measured by the sky quality monitor. We study the correlation between the exposure parameter and night sky brightness value, and give the mathematical relation. The images of the all sky camera are inserted into database directly. All sky quality images are archived in FITS format which can be used for further analysis.

AmeriFlux US-SO2 Sky Oaks- Old Stand

DOE Data Explorer

Oechel, Walt [San Diego State University

2016-01-01

This is the AmeriFlux version of the carbon flux data for the site US-SO2 Sky Oaks- Old Stand. Site Description - The Sky Oaks Old site is located near the Sky Oaks Field station, owned and operated by San Diego State University. Chaparral vegetation, associated with a Mediterranean climate, covers nearly half of the rough and rocky terrain. Precipitation is almost exclusively confined to the winter months. During the summer and early fall, hot and dry Santa Ana winds from the northeast bring desert heat to the site. A high intensity natural wildfire occurred in July of 2003. The stand age at the time of the wildfire was 80 years old, following an early wildfire poorly characterized. Following the 2003 wildfire, most native chaparral began to regrow from root stocks reaching a height of 1.0 m in 2008.

Estimating Longwave Atmospheric Emissivity in the Canadian Rocky Mountains

NASA Astrophysics Data System (ADS)

Ebrahimi, S.; Marshall, S. J.

2014-12-01

Incoming longwave radiation is an important source of energy contributing to snow and glacier melt. However, estimating the incoming longwave radiation from the atmosphere is challenging due to the highly varying conditions of the atmosphere, especially cloudiness. We analyze the performance of some existing models included a physically-based clear-sky model by Brutsaert (1987) and two different empirical models for all-sky conditions (Lhomme and others, 2007; Herrero and Polo, 2012) at Haig Glacier in the Canadian Rocky Mountains. Models are based on relations between readily observed near-surface meteorological data, including temperature, vapor pressure, relative humidity, and estimates of shortwave radiation transmissivity (i.e., clear-sky or cloud-cover indices). This class of models generally requires solar radiation data in order to obtain a proxy for cloud conditions. This is not always available for distributed models of glacier melt, and can have high spatial variations in regions of complex topography, which likely do not reflect the more homogeneous atmospheric longwave emissions. We therefore test longwave radiation parameterizations as a function of near-surface humidity and temperature variables, based on automatic weather station data (half-hourly and mean daily values) from 2004 to 2012. Results from comparative analysis of different incoming longwave radiation parameterizations showed that the locally-calibrated model based on relative humidity and vapour pressure performs better than other published models. Performance is degraded but still better than standard cloud-index based models when we transfer the model to another site, roughly 900 km away, Kwadacha Glacier in the northern Canadian Rockies.

Analysis of actinic flux profiles measured from an ozonesonde balloon

NASA Astrophysics Data System (ADS)

Wang, P.; Allaart, M.; Knap, W. H.; Stammes, P.

2015-04-01

A green light sensor has been developed at KNMI to measure actinic flux profiles using an ozonesonde balloon. In total, 63 launches with ascending and descending profiles were performed between 2006 and 2010. The measured uncalibrated actinic flux profiles are analysed using the Doubling-Adding KNMI (DAK) radiative transfer model. Values of the cloud optical thickness (COT) along the flight track were taken from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) Cloud Physical Properties (CPP) product. The impact of clouds on the actinic flux profile is evaluated on the basis of the cloud modification factor (CMF) at the cloud top and cloud base, which is the ratio between the actinic fluxes for cloudy and clear-sky scenes. The impact of clouds on the actinic flux is clearly detected: the largest enhancement occurs at the cloud top due to multiple scattering. The actinic flux decreases almost linearly from cloud top to cloud base. Above the cloud top the actinic flux also increases compared to clear-sky scenes. We find that clouds can increase the actinic flux to 2.3 times the clear-sky value at cloud top and decrease it to about 0.05 at cloud base. The relationship between CMF and COT agrees well with DAK simulations, except for a few outliers. Good agreement is found between the DAK-simulated actinic flux profiles and the observations for single-layer clouds in fully overcast scenes. The instrument is suitable for operational balloon measurements because of its simplicity and low cost. It is worth further developing the instrument and launching it together with atmospheric chemistry composition sensors.

Cloud Tolerance of Remote-Sensing Technologies to Measure Land Surface Temperature

NASA Technical Reports Server (NTRS)

Holmes, Thomas R. H.; Hain, Christopher R.; Anderson, Martha C.; Crow, Wade T.

2016-01-01

Conventional methods to estimate land surface temperature (LST) from space rely on the thermal infrared(TIR) spectral window and is limited to cloud-free scenes. To also provide LST estimates during periods with clouds, a new method was developed to estimate LST based on passive microwave(MW) observations. The MW-LST product is informed by six polar-orbiting satellites to create a global record with up to eight observations per day for each 0.25resolution grid box. For days with sufficient observations, a continuous diurnal temperature cycle (DTC) was fitted. The main characteristics of the DTC were scaled to match those of a geostationary TIR-LST product. This paper tests the cloud tolerance of the MW-LST product. In particular, we demonstrate its stable performance with respect to flux tower observation sites (four in Europe and nine in the United States), over a range of cloudiness conditions up to heavily overcast skies. The results show that TIR based LST has slightly better performance than MW-LST for clear-sky observations but suffers an increasing negative bias as cloud cover increases. This negative bias is caused by incomplete masking of cloud-covered areas within the TIR scene that affects many applications of TIR-LST. In contrast, for MW-LST we find no direct impact of clouds on its accuracy and bias. MW-LST can therefore be used to improve TIR cloud screening. Moreover, the ability to provide LST estimates for cloud-covered surfaces can help expand current clear-sky-only satellite retrieval products to all-weather applications.

The analysis of polar clouds from AVHRR satellite data using pattern recognition techniques

NASA Technical Reports Server (NTRS)

Smith, William L.; Ebert, Elizabeth

1990-01-01

The cloud cover in a set of summertime and wintertime AVHRR data from the Arctic and Antarctic regions was analyzed using a pattern recognition algorithm. The data were collected by the NOAA-7 satellite on 6 to 13 Jan. and 1 to 7 Jul. 1984 between 60 deg and 90 deg north and south latitude in 5 spectral channels, at the Global Area Coverage (GAC) resolution of approximately 4 km. This data embodied a Polar Cloud Pilot Data Set which was analyzed by a number of research groups as part of a polar cloud algorithm intercomparison study. This study was intended to determine whether the additional information contained in the AVHRR channels (beyond the standard visible and infrared bands on geostationary satellites) could be effectively utilized in cloud algorithms to resolve some of the cloud detection problems caused by low visible and thermal contrasts in the polar regions. The analysis described makes use of a pattern recognition algorithm which estimates the surface and cloud classification, cloud fraction, and surface and cloudy visible (channel 1) albedo and infrared (channel 4) brightness temperatures on a 2.5 x 2.5 deg latitude-longitude grid. In each grid box several spectral and textural features were computed from the calibrated pixel values in the multispectral imagery, then used to classify the region into one of eighteen surface and/or cloud types using the maximum likelihood decision rule. A slightly different version of the algorithm was used for each season and hemisphere because of differences in categories and because of the lack of visible imagery during winter. The classification of the scene is used to specify the optimal AVHRR channel for separating clear and cloudy pixels using a hybrid histogram-spatial coherence method. This method estimates values for cloud fraction, clear and cloudy albedos and brightness temperatures in each grid box. The choice of a class-dependent AVHRR channel allows for better separation of clear and cloudy pixels than does a global choice of a visible and/or infrared threshold. The classification also prevents erroneous estimates of large fractional cloudiness in areas of cloudfree snow and sea ice. The hybrid histogram-spatial coherence technique and the advantages of first classifying a scene in the polar regions are detailed. The complete Polar Cloud Pilot Data Set was analyzed and the results are presented and discussed.

Documentation for the machine-readable version of the lick Saturn-Voyager Reference Star Catalogue

NASA Technical Reports Server (NTRS)

Warren, W. H., Jr.

1982-01-01

The machine-readable version of the catalog is described. The catalog was prepared in order to determine accurate equatorial coordinates for reference stars in a band of sky against which cameras of the Voyager spacecraft were aligned for observations in the region of Saturn during the flyby. Tape contents and characteristics are described and a sample listing presented.

First comparison of formaldehyde integral contents in ABL retrieved during clear-sky and overcast conditions by ZDOAS technique

NASA Astrophysics Data System (ADS)

Ivanov, Victor; Borovski, Alexander; Postylyakov, Oleg

2017-10-01

Formaldehyde (HCHO) is involved in a lot of chemical reactions in the atmosphere. Taking into account that HCHO basically undergo by photolysis and reaction with hydroxyl radical within a few hours, short-lived VOCs and direct HCHO emissions can cause local HCHO enhancement over certain areas, and, hence, exceeding background level of HCHO can be examined as a local pollution of the atmosphere by VOCs or existence of a local HCHO source. Several retrieval algorithms applicable for DOAS measurements in cloudless were previously developed. In previous works we proposed a new algorithm applicable for the overcast conditions. The algorithm has the typical F-coefficient error of about 10% for winter season, about 5% for summer season, and varying from 15 to 45% for transition season if the atmospheric boundary layer is below the cloud base. In this paper we briefly present our results of the HCHO vertical column retrieval measured at Zvenigorod Scientific Station (ZSS) for overcast. ZSS (55°41'49''N, 36°46'29''E) is located in Moscow region in 38 km west from Moscow. Because Western winds prevail in this region, ZSS is a background station the most part of time. But in cases of Eastern wind, the air quality at ZSS is affected by Moscow megapolis, and polluted air masses formed above Moscow can reach station in a few hours. Due to the absence of alternative overcast data of HCHO, we compare our overcast data with the HCHO vertical content, which we obtained for clear sky. We investigate similarities and differences in their statistical behavior in different air mass. The average overcast HCHO data have similar to clear-sky HCHO positive temperature trends for all wind direction. We found that the average retrieved overcast HCHO contents are systematically greater than the clear-sky retrieval data. But the difference between data retrieved for the overcast and clear-sky conditions are different for Eastern and Western winds. This difference is about 0.5×1016 mol cm-2 for Western winds and about 1.2×1016 mol cm-2 for Eastern winds. We suppose that observed difference between the overcast and clear-sky formaldehyde data can be caused by dependence of chemical reactions leading to the HCHO destruction and the HCHO formation from Moscow anthropogenic predecessors on the cloudy conditions.

SMART Ground-based Radiation Measurements during PRIDE

NASA Technical Reports Server (NTRS)

Tsay, Si-Chee; Ji, Qiang; Hansel, R.; Pilewskie, P.; Einaudi, Franco (Technical Monitor)

2000-01-01

We deployed a suite of ground-based remote sensing instruments - SMART (Surface Measurements for Atmospheric Radiative Transfer), at the Roosevelt Road Naval Station in Puerto Rico during the Puerto Rico Dust Experiment (PRIDE). The instruments include several solar and infrared broadband radiometers, a sunphotometer, a shadow-band radiometer, a micro-pulse lidar, a total-sky imager, a microwave radiometer, and two solar spectrometers. These radiometers were set up on a mobile platform and a solar tracker. During 27 June - 23 July, about 25 days of data were acquired under partially cloudy sky conditions. The diurnal air temperature was fluctuating around 28.6 C to within a few degrees. Daytime average of solar irradiance reaching at the surface was ranged from about 400 W/sq m on a rainy day to about 640 W/sq m on a cloud-free day. The infrared irradiance at the surface during the measurement period was averaged about 408 W/sq m. The heights of boundary layer, dusts and clouds were captured by lidar images. Based on sunphotometer and shadow-band radiometer retrievals, the aerosol optical thickness varied from below 0.1 to over 0.6. Combining with radiative transfer modeling and other in-situ and remote sensing measurements, our ground-based measurements provide vital information on understanding the long-range transport of African dust into the Caribbean.

Radiation closure under broken cloud conditions at the BSRN site Payerne: A case study

NASA Astrophysics Data System (ADS)

Aebi, Christine; Gröbner, Julian; Kämpfer, Niklaus; Vuilleumier, Laurent

2017-04-01

Clouds have a substantial influence on the surface radiation budget and on the climate system. There are several studies showing the opposing effect of clouds on shortwave and longwave radiation and thus on the global energy budget. Wacker et al., 2013 show an agreement between radiation flux measurements and radiative transfer models (RTM) under clear sky conditions which is within the measurement uncertainty. Our current study combines radiation fluxes from surface-based observations with RTM under cloudy conditions. It is a case study with data from the BSRN (Baseline Surface Radiation Network) site Payerne (46.49˚ N, 6.56˚ E, 490 m asl). Observation data are retrieved from pyranometers and pyrgeometers and additional atmospheric parameters from radiosondes and a ceilometer. The cloud information is taken from visible all-sky cameras. In a first step observations and RTM are compared for cases with stratiform overcast cloud conditions. In a next step radiation fluxes are compared under broken cloud conditions. These analyses are performed for different cloud types. Wacker, S., J. Gröbner, and L. Vuilleumier (2014) A method to calculate cloud-free long-wave irradiance at the surface based on radiative transfer modeling and temperature lapse rate estimates, Theor. Appl. Climatol., 115, 551-561.

Technical Report Series on Global Modeling and Data Assimilation. Volume 22; A Coupled Ocean-Atmosphere Radiative Model for Global Ocean Biogeochemical Models

NASA Technical Reports Server (NTRS)

Gregg, Watson W.; Suarez, Max J. (Editor)

2002-01-01

An ocean-atmosphere radiative model (OARM) evaluates irradiance availability and quality in the water column to support phytoplankton growth and drive ocean thermodynamics. An atmospheric component incorporates spectral and directional effects of clear and cloudy skies as a function of atmospheric optical constituents, and spectral reflectance across the air-sea interface. An oceanic component evaluates the propagation of spectral and directional irradiance through the water column as a function of water, five phytoplankton groups, and chromophoric dissolved organic matter. It tracks the direct and diffuse streams from the atmospheric component, and a third stream, upwelling diffuse irradiance. The atmospheric component of OARM was compared to data sources at the ocean surface with a coefficient of determination (r2) of 0.97 and a root mean square of 12.1%.

KSC-2009-3088

NASA Image and Video Library

2009-05-11

CAPE CANAVERAL, Fla. – Space shuttle Atlantis roars into the cloudy sky above Launch Pad 39A at NASA's Kennedy Space Center in Florida on the STS-125 mission. Blue cones of light, mach diamonds, can be seen beneath the engine nozzles. The mach diamonds are a formation of shock waves in the exhaust plume of an aerospace propulsion system. Atlantis will rendezvous with NASA's Hubble Space Telescope on the STS-125 mission. Liftoff was on time at 2:01 p.m. EDT. Atlantis' 11-day flight will include five spacewalks to refurbish and upgrade the telescope with state-of-the-art science instruments that will expand Hubble's capabilities and extend its operational lifespan through at least 2014. The payload includes a Wide Field Camera 3, fine guidance sensor and the Cosmic Origins Spectrograph. Photo credit: NASA/Michael Gayle-Rusty Backer

Calibrated intercepts for solar radiometers used in remote sensor calibration

NASA Technical Reports Server (NTRS)

Gellman, David I.; Biggar, Stuart F.; Slater, Philip N.; Bruegge, Carol J.

1991-01-01

Calibrated solar radiometer intercepts allow spectral optical depths to be determined for days with intermittently clear skies. This is of particular importance on satellite sensor calibration days that are cloudy except at the time of image acquisition. This paper describes the calibration of four solar radiometers using the Langley-Bouguer technique for data collected on days with a clear, stable atmosphere. Intercepts are determined with an uncertainty of less than six percent, corresponding to a maximum uncertainty of 0.06 in optical depth. The spread of voltage intercepts calculated in this process is carried through three methods of radiometric calibration of satellite sensors to yield an uncertainty in radiance at the top of the atmosphere of less than one percent associated with the uncertainty in solar radiometer intercepts for a range of ground reflectances.

Local effects of partly-cloudy skies on solar and emitted radiation

NASA Technical Reports Server (NTRS)

Whitney, D. A.; Venable, D. D.

1982-01-01

A computer automated data acquisition system for atmospheric emittance, and global solar, downwelled diffuse solar, and direct solar irradiances is discussed. Hourly-integrated global solar and atmospheric emitted radiances were measured continuously from February 1981 and hourly-integrated diffuse solar and direct solar irradiances were measured continuously from October 1981. One-minute integrated data are available for each of these components from February 1982. The results of the correlation of global insolation with fractional cloud cover for the first year's data set. A February data set, composed of one-minute integrated global insolation and direct solar irradiance, cloud cover fractions, meteorological data from nearby weather stations, and GOES East satellite radiometric data, was collected to test the theoretical model of satellite radiometric data correlation and develop the cloud dependence for the local measurement site.

CBSD Version 2 Component Models of the IR Celestial Background

DTIC Science & Technology

1990-12-07

to B1950.0) INCL Inclination of orbit (referred to B1950.0) E Eccentricity SMA Semi-major axis (AU) OBLIQ Obliquity of the ecliptic (at B1950.0) The...pre-release summary of Super Sky Flux: Plates for ecliptic latitudes >500 are scheduled to be available in Spring 1991; full-sky coverage is scheduled...individual HCON Plate sets, a three HCON co-add plate set is being developed; however, regions within ±30’ of the ecliptic plane may not be included in

Cloud cover determination in polar regions from satellite imagery

NASA Technical Reports Server (NTRS)

Barry, R. G.; Key, J.

1989-01-01

The objectives are to develop a suitable validation data set for evaluating the effectiveness of the International Satellite Cloud Climatology Project (ISCCP) algorithm for cloud retrieval in polar regions, to identify limitations of current procedures and to explore potential means to remedy them using textural classifiers, and to compare synoptic cloud data from model runs with observations. Toward the first goal, a polar data set consisting of visible, thermal, and passive microwave data was developed. The AVHRR and SMMR data were digitally merged to a polar stereographic projection with an effective pixel size of 5 sq km. With this data set, two unconventional methods of classifying the imagery for the analysis of polar clouds and surfaces were examined: one based on fuzzy sets theory and another based on a trained neural network. An algorithm for cloud detection was developed from an early test version of the ISCCP algorithm. This algorithm includes the identification of surface types with passive microwave, then temporal tests at each pixel location in the cloud detection phase. Cloud maps and clear sky radiance composites for 5 day periods are produced. Algorithm testing and validation was done with both actural AVHRR/SMMR data, and simulated imagery. From this point in the algorithm, groups of cloud pixels are examined for their spectral and textural characteristics, and a procedure is developed for the analysis of cloud patterns utilizing albedo, IR temperature, and texture. In a completion of earlier work, empirical analyses of arctic cloud cover were explored through manual interpretations of DMSP imagery and compared to U.S. Air Force 3D-nephanalysis. Comparisons of observed cloudiness from existing climatologies to patterns computed by the GISS climate model were also made.

The role of global cloud climatologies in validating numerical models

NASA Technical Reports Server (NTRS)

HARSHVARDHAN

1991-01-01

Reliable estimates of the components of the surface radiation budget are important in studies of ocean-atmosphere interaction, land-atmosphere interaction, ocean circulation and in the validation of radiation schemes used in climate models. The methods currently under consideration must necessarily make certain assumptions regarding both the presence of clouds and their vertical extent. Because of the uncertainties in assumed cloudiness, all these methods involve perhaps unacceptable uncertainties. Here, a theoretical framework that avoids the explicit computation of cloud fraction and the location of cloud base in estimating the surface longwave radiation is presented. Estimates of the global surface downward fluxes and the oceanic surface net upward fluxes were made for four months (April, July, October and January) in 1985 to 1986. These estimates are based on a relationship between cloud radiative forcing at the top of the atmosphere and the surface obtained from a general circulation model. The radiation code is the version used in the UCLA/GLA general circulation model (GCM). The longwave cloud radiative forcing at the top of the atmosphere as obtained from Earth Radiation Budget Experiment (ERBE) measurements is used to compute the forcing at the surface by means of the GCM-derived relationship. This, along with clear-sky fluxes from the computations, yield maps of the downward longwave fluxes and net upward longwave fluxes at the surface. The calculated results are discussed and analyzed. The results are consistent with current meteorological knowledge and explainable on the basis of previous theoretical and observational works; therefore, it can be concluded that this method is applicable as one of the ways to obtain the surface longwave radiation fields from currently available satellite data.

Calculating clear-sky radiative heating rates using the Fu-Liou RTM with inputs from observed and reanalyzed profiles

NASA Astrophysics Data System (ADS)

Dolinar, E. K.; Dong, X.; Xi, B.

2015-12-01

One-dimensional radiative transfer models (RTM) are a common tool used for calculating atmospheric heating rates and radiative fluxes. In the forward sense, RTMs use known (or observed) quantities of the atmospheric state and surface characteristics to determine the appropriate surface and top-of-atmosphere (TOA) radiative fluxes. The NASA CERES science team uses the modified Fu-Liou RTM to calculate atmospheric heating rates and surface and TOA fluxes using the CERES observed TOA shortwave (SW) and longwave (LW) fluxes as constraints to derive global surface and TOA radiation budgets using a reanalyzed atmospheric state (e.g. temperature and various greenhouse gases) from the newly developed MERRA-2. However, closure studies have shown that using the reanalyzed state as input to the RTM introduces some disparity between the RTM calculated fluxes and surface observed ones. The purpose of this study is to generate a database of observed atmospheric state profiles, from satellite and ground-based sources, at several permanent Atmospheric Radiation Measurement (ARM) Program sites, including the Southern Great Plains (SGP), Northern Slope of Alaska (NSA) and Tropical Western Pacific Nauru (TWP-C2), and Eastern North Atlantic (ENA) permanent facilities. Since clouds are a major modulator of radiative transfer within the Earth's atmosphere, we will focus on the clear-sky conditions in this study, which will set up the baseline for our cloudy studies in the future. Clear-sky flux profiles are calculated using the Edition 4 NASA LaRC modified Fu-Liou RTM. The aforementioned atmospheric profiles generated in-house are used as input into the RTM, as well as from reanalyses. The calculated surface and TOA fluxes are compared with ARM surface measured and CERES satellite observed SW and LW fluxes, respectively. Clear-sky cases are identified by the ARM radar-lidar observations, as well as satellite observations, at the select ARM sites.

The solar dimming/brightening effect over the Mediterranean Basin in the period 1979-2012

NASA Astrophysics Data System (ADS)

Kambezidis, H. D.; Kaskaoutis, D. G.; Kalliampakos, G. K.; Rashki, A.; Wild, M.

2016-12-01

Numerous studies have shown that the solar radiation reaching the Earth's surface is subjected to multi-decadal variations with significant spatial and temporal heterogeneities in both magnitude and sign. Although several studies have examined the solar radiation trends over Europe, North America and Asia, the Mediterranean Basin has not been studied extensively. This work investigates the evolution and trends in the surface net short-wave radiation (NSWR, surface solar radiation - reflected) over the Mediterranean Basin during the period 1979-2012 using monthly re-analysis datasets from the Modern Era Retrospective-Analysis for Research and Applications (MERRA) and aims to shed light on the specific role of clouds on the NSWR trends. The solar dimming/brightening phenomenon is temporally and spatially analyzed over the Mediterranean Basin. The spatially-averaged NSWR over the whole Mediterranean Basin was found to increase in MERRA by +0.36 Wm-2 per decade, with higher rates over the western Mediterranean (+0.82 Wm-2 per decade), and especially during spring (March-April-May; +1.3 Wm-2 per decade). However, statistically significant trends in NSWR either for all-sky or clean-sky conditions are observed only in May. The increasing trends in NSWR are mostly associated with decreasing ones in cloud optical depth (COD), especially for the low (<700 hPa) clouds. The decreasing COD trends (less opaque clouds and/or decrease in absolute cloudiness) are more pronounced during spring, thus controlling the increasing tendency in NSWR. The NSWR trends for cloudless (clear) skies are influenced by changes in the water-vapor content or even variations in surface albedo to a lesser degree, whereas aerosols are temporally constant in MERRA. The slight negative trend (not statistically significant) in NSWR under clear skies for nearly all months and seasons implies a slight increasing trend in water vapor under a warming and more humid climatic scenario over the Mediterranean.

Quantifying the radiative and microphysical impacts of fire aerosols on cloud dynamics in the tropics using temporally offset satellite observations

NASA Astrophysics Data System (ADS)

Tosca, M. G.; Diner, D. J.; Garay, M. J.; Kalashnikova, O.

2013-12-01

Anthropogenic fires in Southeast Asia and Central America emit smoke that affects cloud dynamics, meteorology, and climate. We measured the cloud response to direct and indirect forcing from biomass burning aerosols using aerosol retrievals from the Multi-angle Imaging SpectroRadiometer (MISR) and non-synchronous cloud retrievals from the MODerate resolution Imaging Spectroradiometer (MODIS) from collocated morning and afternoon overpasses. Level 2 data from thirty-one individual scenes acquired between 2006 and 2010 were used to quantify changes in cloud fraction, cloud droplet size, cloud optical depth and cloud top temperature from morning (10:30am local time) to afternoon (1:30pm local time) in the presence of varying aerosol burdens. We accounted for large-scale meteorological differences between scenes by normalizing observed changes to the mean difference per individual scene. Elevated AODs reduced cloud fraction and cloud droplet size and increased cloud optical depths in both Southeast Asia and Central America. In mostly cloudy regions, aerosols significantly reduced cloud fraction and cloud droplet sizes, but in clear skies, cloud fraction, cloud optical thickness and cloud droplet sizes increased. In clouds with vertical development, aerosols reduced cloud fraction via semi-direct effects but spurred cloud growth via indirect effects. These results imply a positive feedback loop between anthropogenic burning and cloudiness in both Central America and Southeast Asia, and are consistent with previous studies linking smoke aerosols to both cloud reduction and convective invigoration.

Factors driving mercury variability in the Arctic atmosphere and ocean over the past 30 years

NASA Astrophysics Data System (ADS)

Fisher, Jenny A.; Jacob, Daniel J.; Soerensen, Anne L.; Amos, Helen M.; Corbitt, Elizabeth S.; Streets, David G.; Wang, Qiaoqiao; Yantosca, Robert M.; Sunderland, Elsie M.

2013-12-01

observations at Arctic sites (Alert and Zeppelin) show large interannual variability (IAV) in atmospheric mercury (Hg), implying a strong sensitivity of Hg to environmental factors and potentially to climate change. We use the GEOS-Chem global biogeochemical Hg model to interpret these observations and identify the principal drivers of spring and summer IAV in the Arctic atmosphere and surface ocean from 1979-2008. The model has moderate skill in simulating the observed atmospheric IAV at the two sites (r 0.4) and successfully reproduces a long-term shift at Alert in the timing of the spring minimum from May to April (r = 0.7). Principal component analysis indicates that much of the IAV in the model can be explained by a single climate mode with high temperatures, low sea ice fraction, low cloudiness, and shallow boundary layer. This mode drives decreased bromine-driven deposition in spring and increased ocean evasion in summer. In the Arctic surface ocean, we find that the IAV for modeled total Hg is dominated by the meltwater flux of Hg previously deposited to sea ice, which is largest in years with high solar radiation (clear skies) and cold spring air temperature. Climate change in the Arctic is projected to result in increased cloudiness and strong warming in spring, which may thus lead to decreased Hg inputs to the Arctic Ocean. The effect of climate change on Hg discharges from Arctic rivers remains a major source of uncertainty.

The Ultraviolet Sky: final catalogs of unique UV sources from GALEX, and characterization of the UV-emitting sources across the sky, and of the Milky Way extinction

NASA Astrophysics Data System (ADS)

Bianchi, Luciana; Conti, A.; Shiao, B.; Keller, G. R.; Thilker, D. A.

2014-01-01

The legacy of the Galaxy Evolution Explorer (GALEX), which imaged the sky at Ultraviolet (UV) wavelengths for about 9 years, is its unprecedented database with more than 200 million source measurements in far-UV (FUV) and near-UV (NUV), as well as wide-field imaging of extended objects. GALEX's data, the first substantial sky surveys at UV wavelengths, offer an unprecedented view of the sky and a unique opportunity for an unbiased characterization of several classes of astrophysical objects, such as hot stars, QSOs at red-shift about 1, UV-peculiar QSOs, star-forming galaxies, among others. Bianchi et al. (2013, J. Adv. Space Res. (2013), DOI: http://dx.doi.org/10.1016/j.asr.2013.07.045) have constructed final catalogs of UV sources, with homogeneous quality, eliminating duplicate measurements of the same source ('unique' source catalogs), and excluding rim artifacts and bad photometry. The catalogs are constructed improving on the recipe of Bianchi et al. 2011 (MNRAS, 411, 2770, which presented the earlier version of these catalogs) and include all data for the major surveys, AIS and MIS. Considering the fields where both FUV and NUV detectors were exposed, the catalogs contain about 71 and 16.6 million unique sources respectively. We show several maps illustrating the content of UV sources across the sky, globally, and separately for bright/faint, hot, stellar/extragalactic objects. We matched the UV-source catalogs with optical-IR data from the SDSS, GSC2, 2MASS surveys. We are also in the process of matching the catalogs with preliminary PanSTARRS1 (PS1) 3pi survey photometry which already provides twice the sky coverage of SDSS, at slightly fainter magnitude limits. The sources' SED from FUV to optical wavelengths enables classification, derivation of the object physical parameters, and ultimately also a map of the Milky Way extinction. The catalogs will be available on MAST, Vizier (where the previous version already is), and in reduced form (for agile downloading), with related tools, from the author web site " http://dolomiti.pha.jhu.edu/uvsky "

The July 2016 Study of the water VApour in the polar AtmosPhere (SVAAP) campaign at Thule, Greenland: surface radiation budget and role of clouds

NASA Astrophysics Data System (ADS)

Meloni, Daniela; Di Iorio, Tatiana; di Sarra, Alcide; Iaccarino, Antonio; Pace, Giandomenico; Mevi, Gabriele; Muscari, Giovanni; Cacciani, Marco; Gröbner, Julian

2017-04-01

The Study of the water VApour in the polar AtmosPhere (SVAAP) project, funded by the Italian Programme for Antarctic Research, is aimed at investigating the surface radiation budget (SRB), the variability of atmospheric water vapour, and the long-term variations in stratospheric composition and structure at Thule, Greenland, in the framework of the international Network for Detection of Atmospheric Composition Change (NDACC). Thule High Arctic Atmospheric Observatory (THAAO, 76.5° N, 68.8° W) is devoted to study climate change and has been operational since 1990, with the contribution of different international institutions: DMI, NCAR, ENEA, INGV, Universities of Roma and Firenze (http://www.thuleatmos-it.it). As part of SVAAP an intensive field campaign was held at Thule from 5 to 28 July 2016. The campaign was also aimed at supporting the installation of VESPA-22, a new microwave radiometer for water vapour profiling in the upper atmosphere and integrated water vapour (IWV), and offered the possibility to study the cloud physical and optical properties and their impact on the SRB. Measurements of downward shortwave (SW) and longwave (LW) irradiance were already available since 2009. Additional observations were added to obtain the SRB and to characterize the atmospheric state: upward SW and LW irradiance, upwelling and downwelling photosynthetically active radiation (PAR), downward irradiance in the 8-14 µm infrared window, temperature and relative humidity tropospheric profiles, IWV, liquid water path (LWP), lidar tropospheric backscattering profiles, sky brightness temperature (BT) in the 9.6-11.5 µm spectral range, visible and infrared sky images, surface meteorological parameters. Moreover, 23 radiosonde were launched during the campaign. Data from the period 14-28 July are presented in this study. The first part of the campaign was characterized by stable cloud-free conditions, while alternation of cloudy and cloud-free sky occurred after 18 July. The time evolution of SW and LW SRB, surface albedo, and derived cloud parameters, such as cloud optical thickness and effective radius, are presented and discussed. Thickest clouds reached visible optical depths of about 200, and values of LWP of about 0.4 kg/m2. While the SW SRB is always positive during the measurement campaign, the LW SRB is negative under cloud-free conditions (own to -100 W/m2 at noon), becoming positive (up to +50 W/m2) during cloudy periods. The total (SW+LW) SRB is positive and its variability is dominated by the SW irradiance. Clouds induce a reduction of the SRB compared to the cloud-free periods, thanks to the dominant SW effect. The LW component offsets about 20% of the SW at noon in clear sky, and contributes up to 50% of the total SRB in thick cloud conditions. The availability of the cloud physical and optical properties and the atmospheric vertical profiles allow to study in details the SW and LW cloud radiative effect by means of radiative transfer simulations performed with MODTRAN6.0 model.

Aerosol indirect effects -- general circulation model intercomparison and evaluation with satellite data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quaas, Johannes; Ming, Yi; Menon, Surabi

2009-04-10

Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterizes aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth (Ta) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. It is found thatmore » the model-simulated influence of aerosols on cloud droplet number concentration (Nd) compares relatively well to the satellite data at least over the ocean. The relationship between Ta and liquid water path is simulated much too strongly by the models. It is shown that this is partly related to the representation of the second aerosol indirect effect in terms of autoconversion. A positive relationship between total cloud fraction (fcld) and Ta as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strong fcld - Ta relationship, our results indicate that none can be identified as unique explanation. Relationships similar to the ones found in satellite data between Ta and cloud top temperature or outgoing long-wave radiation (OLR) are simulated by only a few GCMs. The GCMs that simulate a negative OLR - Ta relationship show a strong positive correlation between Ta and fcld The short-wave total aerosol radiative forcing as simulated by the GCMs is strongly influenced by the simulated anthropogenic fraction of Ta, and parameterisation assumptions such as a lower bound on Nd. Nevertheless, the strengths of the statistical relationships are good predictors for the aerosol forcings in the models. An estimate of the total short-wave aerosol forcing inferred from the combination of these predictors for the modelled forcings with the satellite-derived statistical relationships yields a global annual mean value of -1.5+-0.5 Wm-2. An alternative estimate obtained by scaling the simulated clear- and cloudy-sky forcings with estimates of anthropogenic Ta and satellite-retrieved Nd - Ta regression slopes, respectively, yields a global annual mean clear-sky (aerosol direct effect) estimate of -0.4+-0.2 Wm-2 and a cloudy-sky (aerosol indirect effect) estimate of -0.7+-0.5 Wm-2, with a total estimate of -1.2+-0.4 Wm-2.« less

Improved Temperature Sounding and Quality Control Methodology Using AIRS/AMSU Data: The AIRS Science Team Version 5 Retrieval Algorithm

NASA Technical Reports Server (NTRS)

Susskind, Joel; Blaisdell, John M.; Iredell, Lena; Keita, Fricky

2009-01-01

This paper describes the AIRS Science Team Version 5 retrieval algorithm in terms of its three most significant improvements over the methodology used in the AIRS Science Team Version 4 retrieval algorithm. Improved physics in Version 5 allows for use of AIRS clear column radiances in the entire 4.3 micron CO2 absorption band in the retrieval of temperature profiles T(p) during both day and night. Tropospheric sounding 15 micron CO2 observations are now used primarily in the generation of clear column radiances .R(sub i) for all channels. This new approach allows for the generation of more accurate values of .R(sub i) and T(p) under most cloud conditions. Secondly, Version 5 contains a new methodology to provide accurate case-by-case error estimates for retrieved geophysical parameters and for channel-by-channel clear column radiances. Thresholds of these error estimates are used in a new approach for Quality Control. Finally, Version 5 also contains for the first time an approach to provide AIRS soundings in partially cloudy conditions that does not require use of any microwave data. This new AIRS Only sounding methodology, referred to as AIRS Version 5 AO, was developed as a backup to AIRS Version 5 should the AMSU-A instrument fail. Results are shown comparing the relative performance of the AIRS Version 4, Version 5, and Version 5 AO for the single day, January 25, 2003. The Goddard DISC is now generating and distributing products derived using the AIRS Science Team Version 5 retrieval algorithm. This paper also described the Quality Control flags contained in the DISC AIRS/AMSU retrieval products and their intended use for scientific research purposes.

Analysis and Quality Assurance of the SKYMAP 4.0 Guidance and Tracking Star Catalog: The NASA SKY2000 Spacecraft Attitude Determination Star Catalog

NASA Technical Reports Server (NTRS)

Warren, Wayne H., Jr.

2001-01-01

An updated and improved NASA spacecraft attitude determination catalog, now called SKY2000, Version 3, has been prepared and quality assured. The highest priority goals were to replace the astrometric (positions and motions) and photometric (brightnesses and colors) data with the most recent and accurate data available. Quality assurance has been performed in a fairly straightforward manner, i.e., without extensive data checking and analysis, and many errors and Inconsistencies were corrected. Additional work should eventually be done on the variability and multiple-star data In the catalog, while certain other data can be significantly Improved. The current version of the catalog can be found at the GSFC Flight Dynamics website: http://cheli.gsfc.nasa.gov/dist/attitude/skymap.html. Supporting information and reference materials (published papers, format and data descriptions, etc.) can also be found at the website.

Dark Skies, Bright Kids: Year 2

NASA Astrophysics Data System (ADS)

Carlberg, Joleen K.; Johnson, K.; Lynch, R.; Walker, L.; Beaton, R.; Corby, J.; de Messieres, G.; Drosback, M.; Gugliucci, N.; Jackson, L.; Kingery, A.; Layman, S.; Murphy, E.; Richardson, W.; Ries, P.; Romero, C.; Sivakoff, G.; Sokal, K.; Trammell, G.; Whelan, D.; Yang, A.; Zasowski, G.

2011-01-01

The Dark Skies, Bright Kids (DSBK) outreach program brings astronomy education into local elementary schools in central Virginia's Southern Albemarle County through an after-school club. Taking advantage of the unusually dark night skies in the rural countryside, DSBK targets economically disadvantaged schools that tend to be underserved due to their rural locale. The goals of DSBK are to foster children's natural curiosity, demonstrate that science is a fun and creative process, challenge students' conceptions of what a scientist is and does, and teach some basic astronomy. Furthermore, DSBK works to assimilate families into students' education by holding family observing nights at the school. Now in its third semester, DSBK has successfully run programs at two schools with very diverse student populations. Working with these students has helped us to revise our activities and to create new ones. A by-product of our work has been the development of lesson plans, complete with learning goals and detailed instructions, that we make publically available on our website. This year we are expanding our repertoire with our new planetarium, which allows us to visualize topics in novel ways and supplements family observing on cloudy nights. The DSBK volunteers have also created a bilingual astronomy artbook --- designed, written, and illustrated by UVa students --- that we will publish and distribute to elementary schools in Virginia. Our book debuted at the last AAS winter meeting, and since then it has been extensively revised and updated with input from many individuals, including parents, professional educators, and a children's book author. Because the club is currently limited to serving a few elementary schools, this book will be part of our efforts to broaden our impact by bringing astronomy to schools we cannot go to ourselves and reaching out to Spanish-speaking communities at the same time.

A FORTRAN version implementation of block adjustment of CCD frames and its preliminary application

NASA Astrophysics Data System (ADS)

Yu, Y.; Tang, Z.-H.; Li, J.-L.; Zhao, M.

2005-09-01

A FORTRAN version implementation of the block adjustment (BA) of overlapping CCD frames is developed and its flowchart is shown. The program is preliminarily applied to obtain the optical positions of four extragalactic radio sources. The results show that because of the increase in the number and sky coverage of reference stars the precision of optical positions with BA is improved compared with the single CCD frame adjustment.

The Radio Sky and the Echo of Creation.

ERIC Educational Resources Information Center

Ferris, Timothy

1984-01-01

Presents a selection from a revised and updated version of "The Red Limit" by Timothy Ferris. The book is a completely nontechnical introduction to 20th century cosmology, the study of the large-scale properties of the universe. (JN)

Cloud Optical Depth Retrievals from Solar Background "signal" of Micropulse Lidars

NASA Technical Reports Server (NTRS)

Chiu, J. Christine; Marshak, A.; Wiscombe, W.; Valencia, S.; Welton, E. J.

2007-01-01

Pulsed lidars are commonly used to retrieve vertical distributions of cloud and aerosol layers. It is widely believed that lidar cloud retrievals (other than cloud base altitude) are limited to optically thin clouds. Here we demonstrate that lidars can retrieve optical depths of thick clouds using solar background light as a signal, rather than (as now) merely a noise to be subtracted. Validations against other instruments show that retrieved cloud optical depths agree within 10-15% for overcast stratus and broken clouds. In fact, for broken cloud situations one can retrieve not only the aerosol properties in clear-sky periods using lidar signals, but also the optical depth of thick clouds in cloudy periods using solar background signals. This indicates that, in general, it may be possible to retrieve both aerosol and cloud properties using a single lidar. Thus, lidar observations have great untapped potential to study interactions between clouds and aerosols.

Solar Physics at Evergreen: Solar Dynamo and Chromospheric MHD

NASA Astrophysics Data System (ADS)

Zita, E. J.; Maxwell, J.; Song, N.; Dikpati, M.

2006-12-01

We describe our five year old solar physics research program at The Evergreen State College. Famed for its cloudy skies, the Pacific Northwest is an ideal location for theoretical and remote solar physics research activities. Why does the Sun's magnetic field flip polarity every 11 years or so? How does this contribute to the magnetic storms Earth experiences when the Sun's field reverses? Why is the temperature in the Sun's upper atmosphere millions of degrees higher than the Sun's surface temperature? How do magnetic waves transport energy in the Sun’s chromosphere and the Earth’s atmosphere? How does solar variability affect climate change? Faculty and undergraduates investigate questions such as these in collaboration with the High Altitude Observatory (HAO) at the National Center for Atmospheric Research (NCAR) in Boulder. We will describe successful student research projects, logistics of remote computing, and our current physics investigations into (1) the solar dynamo and (2) chromospheric magnetohydrodynamics.

The International SubMillimetre Airborne Radiometer (ISMAR) - First results from the STICCS and COSMIC campaigns

NASA Astrophysics Data System (ADS)

Mendrok, Jana; Eriksson, Patrick; Fox, Stuart; Brath, Manfred; Buehler, Stefan

2016-04-01

Multispectral millimeter- and submillimeter-wave observations bear the potential to measure properties of non-thin ice clouds like mass content and mean particle size. The next generation of European meteorological satellites, the MetOp-SG series, will carry the first satellite-borne submillimeter sounder, the Ice Cloud Imager (ICI). An airborne demonstrator, the International SubMillimetre Airborne Radiometer (ISMAR), is operated together with other remote sensing instruments and in-situ probes on the FAAM aircraft. Scientific measurements from two campaings in the North Atlantic region, STICCS and COSMIC, are available so far. Here we will introduce the ISMAR instrument, present the acquired measurements from the STICCS and COSMIC campaigns and show some first results. This will include estimation of instrument performance, first analysis of clear-sky and cloudy cases and discussion of selected features observed in the measurements (e.g. polarisation signatures).

On the impact of cloudiness on the characteristics of nocturnal downslope flows

NASA Astrophysics Data System (ADS)

Ye, Z. J.; Segal, M.; Garratt, J. R.; Pielke, R. A.

1989-10-01

The effects of cloud cover amount and the height of cloud base on nighttime thermally induced downslope flow were investigated using analytical and numerical model approaches. The conclusions obtained with the analytical and the numerical model evaluations agreed. It was concluded that, (i) as cloud cover increases and/or the height of cloud base decreases, the depth and the intensity of nighttime thermally-induced downslope flows may decrease by a factor reaching one sixth and one tenth, respectively, in the case of overcast low cloud; (ii) when skies suddenly cloud over around midnight, the development of the downslope flow is altered in different ways: a reduction in intensity; or a cessation of further development, depending on the fraction of cloud coverage, and (iii) with a sudden clearing of overcast low cloud around midnight, the depth and the intensity of the downslope flow increases significantly.

Clear-sky irradiance simulation using GMAO products and its comparison to ground and CERES satellite observation

NASA Astrophysics Data System (ADS)

Ham, S. H.; Loeb, N. G.; Kato, S.; Rose, F. G.; Bosilovich, M. G.; Rutan, D. A.; Huang, X.; Collow, A.

2017-12-01

Global Modeling Assimilation Office (GMAO) GEOS assimilated datasets are used to describe temperature and humidity profiles in the Clouds and the Earth's Radiant Energy System (CERES) data processing. Given that advance versions of the assimilated data sets known as of Forward Processing (FP), FP Parallel (FPP), and Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) datasets are available, we examine clear-sky irradiance calculation to see if accuracy is improved with these newer versions of GMAO datasets when their temperature and humidity profiles are used in computing irradiances. Two older versions, GEOS-5.2.0 and GEOS-5.4.1 are used for producing, respectively, Ed3 and Ed4 CERES data products. For the evaluation, CERES-derived TOA irradiances and observed ground-based surface irradiances are compared with the computed irradiances for clear skies identified by Moderate Resolution Imaging Spectroradiometer (MODIS). Surface type dependent spectral emissivity is taken from an observationally-based monthly gridded emissivity dataset. TOA longwave (LW) irradiances computed with GOES-5.2.0 temperature and humidity profiles are biased low, up to -5 Wm-2, compared to CERES-derived TOA longwave irradiance over tropical oceans. In contrast, computed longwave irradiances agree well with CERES observations with the biases less than 2 W m-2 when GOES-5.4.1, FP v5.13, or MERRA-2 temperature and humidity are used. The negative biases of the TOA LW irradiance computed with GOES-5.2.0 appear to be related to a wet bias at 500-850 hPa layer. This indicates that if the input of CERES algorithm switches from GOES-5.2.0 to FP v5.13 or MERRA-2, the bias in clear-sky longwave TOA fluxes over tropical oceans is expected to be smaller. At surface, downward LW irradiances computed with FP v5.13 and MERRA-2 are biased low, up to -10 Wm-2, compared to ground observations over tropical oceans. The magnitude of the bias in the longwave surface irradiances cannot be explained by uncertainties related to aerosol, which is estimated to be less than 2.5 W m-2. Therefore, the negative biases are likely caused by cold or dry biases in FP v5.13 and MERRA-2 datasets. We plan to continue the investigation with more ground sites.

Identification of stars and digital version of the catalogue of 1958 by Brodskaya and Shajn

NASA Astrophysics Data System (ADS)

Gorbunov, M. A.; Shlyapnikov, A. A.

2017-12-01

The following topics are considered: the identification of objects on search maps, the determination of their coordinates at the epoch of 2000, and converting the published version of the catalogue of 1958 by Brodskaya and Shajn into a machine-readable format. The statistics for photometric and spectral data from the original catalogue is presented. A digital version of the catalogue is described, as well as its presentation in HTML, VOTable and AJS formats and the basic principles of work in the interactive application of International Virtual Observatory - the Aladin Sky Atlas.

Pattern recognition analysis of polar clouds during summer and winter

NASA Technical Reports Server (NTRS)

Ebert, Elizabeth E.

1992-01-01

A pattern recognition algorithm is demonstrated which classifies eighteen surface and cloud types in high-latitude AVHRR imagery based on several spectral and textural features, then estimates the cloud properties (fractional coverage, albedo, and brightness temperature) using a hybrid histogram and spatial coherence technique. The summertime version of the algorithm uses both visible and infrared data (AVHRR channels 1-4), while the wintertime version uses only infrared data (AVHRR channels 3-5). Three days of low-resolution AVHRR imagery from the Arctic and Antarctic during January and July 1984 were analyzed for cloud type and fractional coverage. The analysis showed significant amounts of high cloudiness in the Arctic during one day in winter. The Antarctic summer scene was characterized by heavy cloud cover in the southern ocean and relatively clear conditions in the continental interior. A large region of extremely low brightness temperatures in East Antarctica during winter suggests the presence of polar stratospheric cloud.

SKYMONITOR: A Global Network for Sky Brightness Measurements

NASA Astrophysics Data System (ADS)

Davis, Donald R.; Mckenna, D.; Pulvermacher, R.; Everett, M.

2010-01-01

We are implementing a global network to measure sky brightness at dark-sky critical sites with the goal of creating a multi-decade database. The heart of this project is the Night Sky Brightness Monitor (NSBM), an autonomous 2 channel photometer which measures night sky brightness in the visual wavelengths (Mckenna et al, AAS 2009). Sky brightness is measured every minute at two elevation angles typically zenith and 20 degrees to monitor brightness and transparency. The NSBM consists of two parts, a remote unit and a base station with an internet connection. Currently these devices use 2.4 Ghz transceivers with a range of 100 meters. The remote unit is battery powered with daytime recharging using a solar panel. Data received by the base unit is transmitted via email protocol to IDA offices in Tucson where it will be collected, archived and made available to the user community via a web interface. Two other versions of the NSBM are under development: one for radio sensitive areas using an optical fiber link and the second that reads data directly to a laptop for sites without internet access. NSBM units are currently undergoing field testing at two observatories. With support from the National Science Foundation, we will construct and install a total of 10 units at astronomical observatories. With additional funding, we will locate additional units at other sites such as National Parks, dark-sky preserves and other sites where dark sky preservation is crucial. We will present the current comparison with the National Park Service sky monitoring camera. We anticipate that the SKYMONITOR network will be functioning by the end of 2010.

Impact of Atmospheric Albedo on Amazon Evapotranspiration

NASA Astrophysics Data System (ADS)

Lopes, A. V.; Thompson, S. E.; Dracup, J. A.

2013-12-01

The vulnerability of the Amazon region to climate and anthropogenic driven disturbances has been the subject of extensive research efforts, given its importance in the global and regional climate and ecologic systems. The evaluation of such vulnerabilities requires the proper understanding of physical mechanisms controlling water and energy balances and how the disturbances change them. Among those mechanisms, the effects of atmospheric albedo on evapotranspiration have not been fully explored yet and are explored in this study. Evapotranspiration in the Amazon is sustained at high levels across all seasons and represents a large fraction of water and energy surface budgets. In this study, statistical analysis of data from four flux towers installed at Amazon primary forest sites was employed to quantify the impact of atmospheric albedo, mostly resulted from cloudiness, on evapotranspiration and to compare it to the effect of water limitation. Firstly, the difference in eddy-flux derived evapotranspiration at the flux towers under rainy and non-rainy antecedent conditions was tested for significance. Secondly, the same statistical comparison was performed under cloudy and clear sky conditions at hourly and daily time scales, using the reduction in incoming solar radiation as an indicator of cloudiness. Finally, the sensitivity of seasonal evapotranspiration totals to atmospheric albedo resulted from rainfall patterns is evaluated. That was done by sampling daily evapotranspiration estimates from empirical probability distribution functions conditioned to rainfall occurrence and then varying the number of dry days in each season. It was found that light limitation is much more important than water limitation in the Amazon, resulting in up to 43% reduction in daily evapotranspiration. Also, this effect varies by location and by season, the largest impact being in wet season, from December do January. Moreover, seasonal evapotranspiration totals were found to be highly sensitive to the duration of dry spells, set by rainfall patterns, especially during wet seasons and further South from the Equator. These results points to the importance of proper understanding of convective systems and their effects on atmospheric albedo in assessing the vulnerability of Amazon basins to extended dry periods.

Observing the Vertical Extent of the Urban Boundary Layer Over Jersey City, NJ: A Diurnal and Seasonal Analysis

NASA Astrophysics Data System (ADS)

Dempsey, M. J.; Booth, J.; Arend, M.; Melecio-Vazquez, D.; Gonzalez, J.

2015-12-01

The atmospheric boundary remains one of the more difficult components of the climate system to classify. One of the most important characteristics is the boundary layer height, especially in urban settings. The current study examines the boundary layer height using the the New York City Meteorological Network or NYCMetNet. NYCMetNet is a network of weather stations, which report meteorological conditions in and around New York City, as part of the Optical Remote Sensing Laboratory of The City College of New York (ORSL). Of interest to this study is the data obtained from wind profiler station LSC01. The 915 MHz wind profiler is located 30m above the ground on the roof of the Liberty Science Center in Jersey City, NJ. It is a Vaisala Wind Profiler LAP 3000 with a wavelength of ~34cm, which means that the instrument responds primarily to Bragg backscattering. Can a seasonal urban boundary layer climatology be extrapolated from the data obtained from the wind profiler? What is the timing of boundary layer evolution and collapse over Jersey City? How effective is the profiler under cloudy skies and even in light rain or snow? This study examines the entire time period covered by the wind profile (2007 to present) and selects a series of clear days and a series of cloudy days. The top of the urban boundary layer is subjectively located from each half hour time stamp of signal to noise values. The urban boundary layer heights are recorded for clear and then cloudy days. Then the days are sorted seasonally (DJF, MAM, JJA, SON). A seasonal mean is calculated for every half hour time step. Finally a time series of seasonal urban boundary layer heights is constructed, and the timing of the urban boundary layer height maximum and time evolution and collapse of the boundary layer are generalized. A comparison is made against urban boundary layer heights obtained from Modern-Era Retrospective Analysis For Research And Applications (MERRA).

Aladin Lite: Embed your Sky in the Browser

NASA Astrophysics Data System (ADS)

Boch, T.; Fernique, P.

2014-05-01

I will introduce and describe Aladin Lite1, a lightweight interactive sky viewer running natively in the browser. The past five years have seen the emergence of powerful and complex web applications, thanks to major improvements in JavaScript engines and the advent of HTML5. At the same time, browser plugins Java applets, Flash, Silverlight) that were commonly used to run rich Internet applications are declining and are not well suited for mobile devices. The Aladin team took this opportunity to develop Aladin Lite, a lightweight version of Aladin geared towards simple visualization of a sky region. Relying on the widely supported HTML5 canvas element, it provides an intuitive user interface running on desktops and tablets. This first version allows one to interactively visualize multi-resolution HEALPix image and superimpose tabular data and footprints. Aladin Lite is easily embeddable on any web page and may be of interest for data providers which will be able to use it as an interactive previewer for their own image surveys, previously pre-processed as explained in details in the poster "Create & publish your Hierarchical Progressive Survey". I will present the main features of Aladin Lite as well as the JavaScript API which gives the building blocks to create rich interactions between a web page and Aladin Lite.

The HEAO A-1 X Ray Source Catalog (Wood Et Al. 1984): Documentation for the Machine-Readable Version

NASA Technical Reports Server (NTRS)

Warren, Wayne H., Jr.

1990-01-01

The machine-readable version of the catalog, as it is currently being distributed from the Astronomical Data Center, is described. The catalog is a compilation of data for 842 sources detected with the U.S. Naval Research Laboratory Large Area Sky Survey Experiment flown aboard the HEAO 1 satellite. The data include source identifications, positions, error boxes, mean X-ray intensities, and cross identifications to other source designations.

FON: From Start to Finish

NASA Astrophysics Data System (ADS)

Pakuliak, L. K.; Andruk, V. M.; Golovnia, V. V.; Shatokhina, S. V.; Yizhakevych, O. M.; Ivanov, G. A.; Yatsenko, A. I.; Sergeeva, T. P.

Almost 40-year history of FON project ended with the creation of the whole northern sky catalog of objects down to B ≤ 16.5m. The idea of 4-fold overlapping of the northern sky with 6 wide-field astrographs has not been realized in full. For historical reasons it has been transformed into the 2-fold overlapping observational program of MAO NAS of Ukraine, resulted in three versions of the multimillion catalog of positions, proper motions, and B-magnitudes of stars. The first version of 1.2 million stars had been finished before the 2000s and is based on the AC object list. The measurements of plates were made by automatic measuring complex PARSEC, specially developed for massive photographic reviews. As the input list was limited by AC objects, the most part of stars on the FON plates remained unmeasured. Principles of workflow organization of such works formed the basis for the further development of the project using the latest IT-technologies. For the creation of the second and the third versions of the catalog, the list of objects was obtained as a result of total digitizing of plates and their image processing. The final third version contains 19.5 million stars and galaxies with the maximum possible for the photographic astrometry accuracy. The collection of plates, obtained in other observatories - participants of the project, are partially safe and can be used for the same astrometric tasks.

Surface Net Solar Radiation Estimated from Satellite Measurements: Comparisons with Tower Observations

NASA Technical Reports Server (NTRS)

Li, Zhanqing; Leighton, H. G.; Cess, Robert D.

1993-01-01

A parameterization that relates the reflected solar flux at the top of the atmosphere to the net solar flux at the surface in terms of only the column water vapor amount and the solar zenith angle was tested against surface observations. Net surface fluxes deduced from coincidental collocated satellite-measured radiances and from measurements from towers in Boulder during summer and near Saskatoon in winter have mean differences of about 2 W/sq m, regardless of whether the sky is clear or cloudy. Furthermore, comparisons between the net fluxes deduced from the parameterization and from surface measurements showed equally good agreement when the data were partitioned into morning and afternoon observations. This is in contrast to results from an empirical clear-sky algorithm that is unable to account adequately for the effects of clouds and that shows, at Boulder, a distinct morning to afternoon variation, which is presumably due to the predominance of different cloud types throughout the day. It is also demonstrated that the parameterization may be applied to irradiances at the top of the atmosphere that have been temporally averaged by using the temporally averaged column water vapor amount and the temporally averaged cosine of the solar zenith angle. The good agreement between the results of the parameterization and surface measurements suggests that the algorithm is a useful tool for a variety of climate studies.

An investigation of solar erythemal ultraviolet radiation at two sites in tourist attraction areas of Thailand

NASA Astrophysics Data System (ADS)

Buntoung, Sumaman; Pattarapanitchai, Somjet; Wattan, Rungrat; Masiri, Itsara; Promsen, Worrapass; Tohsing, Korntip; Janjai, Serm

2013-05-01

Islands on the southern coasts of Thailand are famous attractions for local and foreign tourists. Tourists usually expose their skins to solar radiation for tanning. Thus information on solar ultraviolet radiation (UV) is of importance for tourists to protect themselves from adverse effects of UV. In this work, solar erythemal ultraviolet radiation (EUV) at two touristic sites namely Samui island (9.451°N, 100.033°E) and Phuket island (8.104°N, 98.304°E) was investigated. In investigating EUV, broadband UV radiometers (Kipp & Zonen, model UVS-B-C) were installed at existing meteorological stations in Samui and Phuket islands. A one-year period of EUV data from these two sites was analyzed. The level of UV index at these sites was studied. The values of UV index higher than 12 at noon time of clear days are usually found in the summer at both sites. Seasonal variation of EUV at both sites was investigated. It was found that the tropical monsoons have strong influence on this variation. Finally, global broadband radiation measured at the sites was also used to establish a correlation between EUV and global broadband radiation. Higher correlation was found for the case of clear sky, as compared to the case of cloudy sky. The correlation obtained from this analysis can be used to estimate EUV from global broadband radiation at these two sites.

Applying an economical scale-aware PDF-based turbulence closure model in NOAA NCEP GCMs

NASA Astrophysics Data System (ADS)

Belochitski, A.; Krueger, S. K.; Moorthi, S.; Bogenschutz, P.; Pincus, R.

2016-12-01

A novel unified representation of sub-grid scale (SGS) turbulence, cloudiness, and shallow convection is being implemented into the NOAA NCEP Global Forecasting System (GFS) general circulation model. The approach, known as Simplified High Order Closure (SHOC), is based on predicting a joint PDF of SGS thermodynamic variables and vertical velocity and using it to diagnose turbulent diffusion coefficients, SGS fluxes, condensation and cloudiness. Unlike other similar methods, only one new prognostic variable, turbulent kinetic energy (TKE), needs to be intoduced, making the technique computationally efficient.SHOC is now incorporated into a version of GFS, as well as into the next generation of the NCEP global model - NOAA Environmental Modeling System (NEMS). Turbulent diffusion coefficients computed by SHOC are now used in place of those produced by the boundary layer turbulence and shallow convection parameterizations. Large scale microphysics scheme is no longer used to calculate cloud fraction or the large-scale condensation/deposition. Instead, SHOC provides these variables. Radiative transfer parameterization uses cloudiness computed by SHOC.Outstanding problems include high level tropical cloud fraction being too high in SHOC runs, possibly related to the interaction of SHOC with condensate detrained from deep convection.Future work will consist of evaluating model performance and tuning the physics if necessary, by performing medium-range NWP forecasts with prescribed initial conditions, and AMIP-type climate tests with prescribed SSTs. Depending on the results, the model will be tuned or parameterizations modified. Next, SHOC will be implemented in the NCEP CFS, and tuned and evaluated for climate applications - seasonal prediction and long coupled climate runs. Impact of new physics on ENSO, MJO, ISO, monsoon variability, etc will be examined.

Shortwave direct radiative effects of above-cloud aerosols over global oceans derived from 8 years of CALIOP and MODIS observations

NASA Astrophysics Data System (ADS)

Zhang, Zhibo; Meyer, Kerry; Yu, Hongbin; Platnick, Steven; Colarco, Peter; Liu, Zhaoyan; Oreopoulos, Lazaros

2016-03-01

In this paper, we studied the frequency of occurrence and shortwave direct radiative effects (DREs) of above-cloud aerosols (ACAs) over global oceans using 8 years (2007-2014) of collocated CALIOP and MODIS observations. Similar to previous work, we found high ACA occurrence in four regions: southeastern (SE) Atlantic region, where ACAs are mostly light-absorbing aerosols, i.e., smoke and polluted dust according to CALIOP classification, originating from biomass burning over the African Savanna; tropical northeastern (TNE) Atlantic and the Arabian Sea, where ACAs are predominantly windblown dust from the Sahara and Arabian deserts, respectively; and the northwestern (NW) Pacific, where ACAs are mostly transported smoke and polluted dusts from Asian. From radiative transfer simulations based on CALIOP-MODIS observations and a set of the preselected aerosol optical models, we found the DREs of ACAs at the top of atmosphere (TOA) to be positive (i.e., warming) in the SE Atlantic and NW Pacific regions, but negative (i.e., cooling) in the TNE Atlantic Ocean and the Arabian Sea. The cancellation of positive and negative regional DREs results in a global ocean annual mean diurnally averaged cloudy-sky DRE of 0.015 W m-2 (range of -0.03 to 0.06 W m-2) at TOA. The DREs at surface and within the atmosphere are -0.15 W m-2 (range of -0.09 to -0.21 W m-2), and 0.17 W m-2 (range of 0.11 to 0.24 W m-2), respectively. The regional and seasonal mean DREs are much stronger. For example, in the SE Atlantic region, the JJA (July-August) seasonal mean cloudy-sky DRE is about 0.7 W m-2 (range of 0.2 to 1.2 W m-2) at TOA. All our DRE computations are publicly available1. The uncertainty in our DRE computations is mainly caused by the uncertainties in the aerosol optical properties, in particular aerosol absorption, the uncertainties in the CALIOP operational aerosol optical thickness retrieval, and the ignorance of cloud and potential aerosol diurnal cycle. In situ and remotely sensed measurements of ACA from future field campaigns and satellite missions and improved lidar retrieval algorithm, in particular vertical feature masking, would help reduce the uncertainty.

Abstract Art or Arbiters of Energy?

NASA Technical Reports Server (NTRS)

2002-01-01

More than just the idle stuff of daydreams, clouds help control the flow of radiant energy around our world. Clouds are plentiful and widespread throughout Earth's atmosphere-covering up to 75 percent of our planet at any given time-so they play a dominant role in determining how much sunlight reaches the surface, how much sunlight is reflected back into space, how and where warmth is spread around the globe, and how much heat escapes from the surface and atmosphere back into space. Clouds are also highly variable. Clouds' myriad variations through time and space make them one of the greatest areas of uncertainty in scientists' understanding and predictions of climate change. In short, they play a central role in our world's climate system. The false-color image above shows a one-month composite of cloud optical thickness measured by the Moderate-resolution Imaging Spectroradiometer (MODIS) and averaged globally for April 2001. Optical thickness is a measure of how much solar radiation is not allowed to travel through a column of atmosphere. Areas colored red and yellow indicate very cloudy skies, on average, while areas colored green and light blue show moderately cloudy skies. Dark blue regions show where there is little or no cloud cover. This data product is an important new tool for helping scientists understand the roles clouds play in our global climate system. MODIS gives scientists new capabilities for measuring the structure and composition of clouds. MODIS observes the entire Earth almost every day in 36 spectral bands ranging from visible to thermal infrared wavelengths, enabling it to quantify a wide suite of clouds' physical and radiative properties. Specifically, MODIS can determine whether a cloud is composed of ice or water particles (or some combination of the two), it can measure the effective radius of the particles within a cloud, it can determine the temperature and altitude of cloud tops, and it can observe how much sunlight passes through a cloud. MODIS is one of five sensors flying aboard NASA's Terra satellite, the flagship in NASA's Earth Observing System, launched in December 1999. For more information about this and other new MODIS products, read NASA Unveils Spectacular Suite of New Global Data Products from MODIS. Image courtesy MODIS Atmosphere Group, NASA GSFC

Shortwave Direct Radiative Effects of Above-Cloud Aerosols Over Global Oceans Derived From 8 Years of CALIOP and MODIS Observations

NASA Technical Reports Server (NTRS)

Zhang, Zhibo; Meyer, Kerry; Yu, Hongbin; Platnick, Steven; Colarco, Peter; Liu, Zhaoyan; Oraiopoulos, Lazaros

2016-01-01

In this paper, we studied the frequency of occurrence and shortwave direct radiative effects (DREs) of above-cloud aerosols (ACAs) over global oceans using 8 years (2007-2014) of collocated CALIOP and MODIS observations. Similar to previous work, we found high ACA occurrence in four regions: southeastern (SE) Atlantic region, where ACAs are mostly light-absorbing aerosols, i.e., smoke and polluted dust according to CALIOP classification, originating from biomass burning over the African Savanna; tropical northeastern (TNE) Atlantic and the Arabian Sea, where ACAs are predominantly windblown dust from the Sahara and Arabian deserts, respectively; and the northwestern (NW) Pacific, where ACAs are mostly transported smoke and polluted dusts from Asia. From radiative transfer simulations based on CALIOP-MODIS observations and a set of the preselected aerosol optical models, we found the DREs of ACAs at the top of atmosphere (TOA) to be positive (i.e., warming) in the SE Atlantic and NW Pacific regions, but negative (i.e., cooling) in the TNE Atlantic Ocean and the Arabian Sea. The cancellation of positive and negative regional DREs results in a global ocean annual mean diurnally averaged cloudy-sky DRE of 0.015 W m(exp. -2) [range of -0.03 to 0.06 W m (exp. -2)] at TOA. The DREs at surface and within the atmosphere are -0.015 W m(exp. -2) [range of -0.09 to -0.21 W m(exp. -2)], and 0.17 W m(exp. -2) [range of 0.11 to 0.24 W m(exp. -2)], respectively. The regional and seasonal mean DREs are much stronger. For example, in the SE Atlantic region, the JJA (July-August) seasonal mean cloudy-sky DRE is about 0.7 W m(exp. -2) [range of 0.2 to 1.2 W m(exp. -2)] at TOA. All our DRE computations are publicly available. The uncertainty in our DRE computations is mainly caused by the uncertainties in the aerosol optical properties, in particular aerosol absorption, the uncertainties in the CALIOP operational aerosol optical thickness retrieval, and the ignorance of cloud and potential aerosol diurnal cycle. In situ and remotely sensed measurements of ACA from future field campaigns and satellite missions and improved lidar retrieval algorithm, in particular vertical feature masking, would help reduce the uncertainty.

The International Globe at Night Citizen-Science Campaign: Shedding Light on Light Pollution

NASA Astrophysics Data System (ADS)

Walker, C. E.; Pompea, S. M.

2013-12-01

For 8 years now, the Globe at Night campaign has invited citizen-scientists worldwide to measure and record the brightness of their night sky by hunting for the faintest stars in a particular constellation. Students for science projects and scientists for research use the data to monitor levels of brightness or 'light pollution' around the world. They also use the Globe at Night data to understand light pollution's effects on energy consumption, plants, wildlife and human health, as well as our ability to enjoy a starry night sky. The dates of the campaign for 2014 have been extended to every month during the year. Ten days each month (when the Moon is not up between 8pm and 10pm) are the recommended times to take measurements for the campaign. However, one can participate at other times and dates, as long as the Moon is not in the night sky and it is more than an hour after sunset or more than an hour before sunrise. New in 2014 will be an Android app that will allow you to input visual measurements anytime the Moon is not up. Also possibly included will be an iPhone app that will take sky brightness measurements. The campaign dates and the 5 easy steps to participating in the campaign are listed at www.globeatnight.org. You do not need to register. Once on the report page, you enter your location, date and time (automatic for a smart device). You find the constellation of the month in the night sky. (Help is on the website.) Then you choose which chart looks most like what you see toward the constellation. Choose the icon for how clear or cloudy it is and hit the submit button and you are done! The fifth step is returning later to the website to compare your observations on the world map to others from around the globe. Included on the Globe at Night website are many helpful resources and tools from finding the constellations used in the campaign, to understanding concepts like light pollution, to games that test your expertise in choosing 'limiting magnitudes'. The map app at www.globeatnight.org/mapapp/ provides an easy way to map data points for any area in the world. 'Dark Skies Rangers' activities used in grades 4-14 provide a foundational basis for and extensions to the campaign, if educators so choose (www.globeatnight.org/dsr/). In this presentation, we will address how Globe at Night is evolving to improve upon recruitment, incentivization, enactment, science standards, assessment and sustainability.

Ultraviolet resources over Northern Eurasia.

PubMed

Chubarova, Natalia; Zhdanova, Yekaterina

2013-10-05

We propose a new climatology of UV resources over Northern Eurasia, which includes the assessments of both detrimental (erythema) and positive (vitamin D synthesis) effects of ultraviolet radiation on human health. The UV resources are defined by using several classes and subclasses - UV deficiency, UV optimum, and UV excess - for 6 different skin types. To better quantifying the vitamin D irradiance threshold we accounted for an open body fraction S as a function of effective air temperature. The spatial and temporal distribution of UV resources was estimated by radiative transfer (RT) modeling (8 stream DISORT RT code) with 1×1° grid and monthly resolution. For this purpose special datasets of main input geophysical parameters (total ozone content, aerosol characteristics, surface UV albedo, UV cloud modification factor) have been created over the territory of Northern Eurasia. The new approaches were used to retrieve aerosol parameters and cloud modification factor in the UV spectral region. As a result, the UV resources were obtained for clear-sky and mean cloudy conditions for different skin types. We show that the distribution of UV deficiency, UV optimum and UV excess is regulated by various geophysical parameters (mainly, total ozone, cloudiness and open body fraction) and can significantly deviate from latitudinal dependence. We also show that the UV optimum conditions can be simultaneously observed for people with different skin types (for example, for 4-5 skin types at the same time in spring over Western Europe). These UV optimum conditions for different skin types occupy a much larger territory over Europe than that over Asia. Copyright © 2013 Elsevier B.V. All rights reserved.

Adjustment errors of sunstones in the first step of sky-polarimetric Viking navigation: studies with dichroic cordierite/ tourmaline and birefringent calcite crystals.

PubMed

Száz, Dénes; Farkas, Alexandra; Blahó, Miklós; Barta, András; Egri, Ádám; Kretzer, Balázs; Hegedüs, Tibor; Jäger, Zoltán; Horváth, Gábor

2016-01-01

According to an old but still unproven theory, Viking navigators analysed the skylight polarization with dichroic cordierite or tourmaline, or birefringent calcite sunstones in cloudy/foggy weather. Combining these sunstones with their sun-dial, they could determine the position of the occluded sun, from which the geographical northern direction could be guessed. In psychophysical laboratory experiments, we studied the accuracy of the first step of this sky-polarimetric Viking navigation. We measured the adjustment error e of rotatable cordierite, tourmaline and calcite crystals when the task was to determine the direction of polarization of white light as a function of the degree of linear polarization p. From the obtained error functions e(p), the thresholds p* above which the first step can still function (i.e. when the intensity change seen through the rotating analyser can be sensed) were derived. Cordierite is about twice as reliable as tourmaline. Calcite sunstones have smaller adjustment errors if the navigator looks for that orientation of the crystal where the intensity difference between the two spots seen in the crystal is maximal, rather than minimal. For higher p (greater than p crit) of incident light, the adjustment errors of calcite are larger than those of the dichroic cordierite (p crit=20%) and tourmaline (p crit=45%), while for lower p (less than p crit) calcite usually has lower adjustment errors than dichroic sunstones. We showed that real calcite crystals are not as ideal sunstones as it was believed earlier, because they usually contain scratches, impurities and crystal defects which increase considerably their adjustment errors. Thus, cordierite and tourmaline can also be at least as good sunstones as calcite. Using the psychophysical e(p) functions and the patterns of the degree of skylight polarization measured by full-sky imaging polarimetry, we computed how accurately the northern direction can be determined with the use of the Viking sun-dial under 10 different sky conditions at 61° latitude, which was one of the main Viking sailing routes. According to our expermiments, under clear skies, using calcite or cordierite or tourmaline sunstones, Viking sailors could navigate with net orientation errors [Formula: see text]. Under overcast conditions, their net navigation error depends on the sunstone type: [Formula: see text], [Formula: see text] and [Formula: see text].

Improved instrumental magnitude prediction expected from version 2 of the NASA SKY2000 master star catalog

NASA Technical Reports Server (NTRS)

Sande, C. B.; Brasoveanu, D.; Miller, A. C.; Home, A. T.; Tracewell, D. A.; Warren, W. H., Jr.

1998-01-01

The SKY2000 Master Star Catalog (MC), Version 2 and its predecessors have been designed to provide the basic astronomical input data needed for satellite acquisition and attitude determination on NASA spacecraft. Stellar positions and proper motions are the primary MC data required for operations support followed closely by the stellar brightness observed in various standard astronomical passbands. The instrumental red-magnitude prediction subsystem (REDMAG) in the MMSCAT software package computes the expected instrumental color index (CI) [sensor color correction] from an observed astronomical stellar magnitude in the MC and the characteristics of the stellar spectrum, astronomical passband, and sensor sensitivity curve. The computation is more error prone the greater the mismatch of the sensor sensitivity curve characteristics and those of the observed astronomical passbands. This paper presents the preliminary performance analysis of a typical red-sensitive CCDST during acquisition of sensor data from the two Ball CT-601 ST's onboard the Rossi X-Ray Timing Explorer (RXTE). A comparison is made of relative star positions measured in the ST FOV coordinate system with the expected results computed from the recently released Tycho Catalogue. The comparison is repeated for a group of observed stars with nearby, bright neighbors in order to determine the tracker behavior in the presence of an interfering, near neighbor (NN). The results of this analysis will be used to help define a new photoelectric photometric instrumental sensor magnitude system (S) that is based on several thousand bright star magnitudes observed with the PXTE ST's. This new system will be implemented in Version 2 of the SKY2000 MC to provide improved predicted magnitudes in the mission run catalogs.

Exploiting diurnal variations to evaluate the ISCCP-FD flux calculations and radiative-flux-analysis-processed surface observations from BSRN, ARM, and SURFRAD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yuanchong; Long, Charles N.; Rossow, William B.

2010-01-01

Based on monthly-3-hourly and 3-hourly mean surface radiative fluxes and their associated meteorological parameters for 2004 from the International Satellite Cloud Climatology Project-FD (ISCCP-FD) and the Radiative Flux Analysis method-Produced Surface Observations (RFA-PSO) for 15 high-quality-controlled surface stations, operated by the Baseline Surface Radiation Network (BSRN), the Atmospheric Radiation Measurement (ARM) and the National Oceanic and Atmospheric Administration's Surface Radiation budget network (SURFRAD), this work, goes beyond the previous validation for FD against surface observation by introducing the Meteorological Similarity Comparison Method (MSCM) to make a more precise, mutual evaluation of both FD and PSO products. The comparison results inmore » substantial uncertainty reduction and provides reasonable physical explanations for the flux differences. This approach compares fluxes for cases where the atmospheric and surface physical properties (specifically, the input parameters for radiative transfer model) are as close as possible to the values determined at the observational sites by matching the RFA-produced cloud fraction (CF) and/or optical thickness (Tau), etc., or alternatively, by directly changing the model input variables for FD to match PSO values, and using such-produced matched sub-datasets to make more accurate comparisons based on more similar meteorological environments between FD and PSO. The crucial part is the availability of flux-associated meteorological parameters from RFA-PSO, which was only recently made available that makes this work possible. For surface downwelling shortwave(SW) flux (SWdn) and its two components, diffuse (Dif) and direct (Dir), uncertainty for monthly mean is 15, 15 and 17 W/m 2, respectively, smaller than the separately estimated uncertainty values from both FD and PSO. When applying MSCM by reducing their CF difference, the differences can be reduced by a factor of 2. The strength of MSCM is particularly shown in the comparisons of diurnal variations. For clear sky, reducing the FD values of aerosol optical depth (AOD) by 50% to approximately match the PSO values brings all downward SW flux components into substantial agreement. For cloudy scenes, when both CF and Tau are matched to within 0.1 – 0.25 and ~10, respectively, the majority of the SW flux components have nearly-perfect agreement between FD and PSO. The best restriction differences are not zero indicates the influence of other parameters that are not accounted for yet. For longwave (LW) fluxes, general evaluation also confirms uncertainty values for FD and PSO less than separately estimated. When applying MSCM to CF and surface air temperature, the agreement is substantially improved. For downwelling LW diurnal variation comparison, FD shows good agreement with PSO for both RFA-defined or true clear sky but overestimates the amplitude for cloudy sky by 3-7 W/m 2, which may be caused by different sensitivities to cirrus clouds. For upwelling LW diurnal cycle, the situation is reversed; FD now underestimates the diurnal amplitude for all and clear sky but generally agrees for overcast (CF > 0.7). The combined effect of downwelling and upwelling LW fluxes results in FD's underestimates of the diurnal variation of the net-LW-loss for all the scenes by up to 10 W/m 2, although the daily mean net loss is more accurate. Therefore, in terms of amplitude and phase, both FD and PSO seem to have caught correct diurnal variations.« less

The Einstein All-Sky IPC slew survey

NASA Technical Reports Server (NTRS)

Elvis, Martin; Plummer, David; Fabbiano, G.

1989-01-01

The construction of the Einstein All-Sky Imaging Proportional Counter (IPC) slew survey is considered. It contains approximately 1000 sources between 10(exp -12) and 10(exp -10) erg/sq cm/s with a concentration toward the ecliptic poles and away from the galactic plane. Several sizable samples of bright soft X-ray selected objects for follow-up ROSAT and ASTRO-D observations and statistical study are presented. The survey source list is expected to be available by late 1989. Both paper and remote access online data base versions are to be available. An identification program is considered.

Laser Safety and Hazardous Analysis for the ARES (Big Sky) Laser System

DOE Office of Scientific and Technical Information (OSTI.GOV)

AUGUSTONI, ARNOLD L.

A laser safety and hazard analysis was performed for the ARES laser system based on the 2000 version of the American National Standards Institute's (ANSI) Standard Z136.1,for Safe Use of Lasers and the 2000 version of the ANSI Standard Z136.6, for Safe Use of Lasers Outdoors. The ARES laser system is a Van/Truck based mobile platform, which is used to perform laser interaction experiments and tests at various national test sites.

Comparison of GOME tropospheric NO2 columns with NO2 profiles deduced from ground-based in situ measurements

NASA Astrophysics Data System (ADS)

Schaub, D.; Boersma, K. F.; Kaiser, J. W.; Weiss, A. K.; Folini, D.; Eskes, H. J.; Buchmann, B.

2006-08-01

Nitrogen dioxide (NO2) vertical tropospheric column densities (VTCs) retrieved from the Global Ozone Monitoring Experiment (GOME) are compared to coincident ground-based tropospheric NO2 columns. The ground-based columns are deduced from in situ measurements at different altitudes in the Alps for 1997 to June 2003, yielding a unique long-term comparison of GOME NO2 VTC data retrieved by a collaboration of KNMI (Royal Netherlands Meteorological Institute) and BIRA/IASB (Belgian Institute for Space Aeronomy) with independently derived tropospheric NO2 profiles. A first comparison relates the GOME retrieved tropospheric columns to the tropospheric columns obtained by integrating the ground-based NO2 measurements. For a second comparison, the tropospheric profiles constructed from the ground-based measurements are first multiplied with the averaging kernel (AK) of the GOME retrieval. The second approach makes the comparison independent from the a priori NO2 profile used in the GOME retrieval. This allows splitting the total difference between the column data sets into two contributions: one that is due to differences between the a priori and the ground-based NO2 profile shapes, and another that can be attributed to uncertainties in both the remaining retrieval parameters (such as, e.g., surface albedo or aerosol concentration) and the ground-based in situ NO2 profiles. For anticyclonic clear sky conditions the comparison indicates a good agreement between the columns (n=157, R=0.70/0.74 for the first/second comparison approach, respectively). The mean relative difference (with respect to the ground-based columns) is -7% with a standard deviation of 40% and GOME on average slightly underestimating the ground-based columns. Both data sets show a similar seasonal behaviour with a distinct maximum of spring NO2 VTCs. Further analysis indicates small GOME columns being systematically smaller than the ground-based ones. The influence of different shapes in the a priori and the ground-based NO2 profile is analysed by considering AK information. It is moderate and indicates similar shapes of the profiles for clear sky conditions. Only for large GOME columns, differences between the profile shapes explain the larger part of the relative difference. In contrast, the other error sources give rise to the larger relative differences found towards smaller columns. Further, for the clear sky cases, errors from different sources are found to compensate each other partially. The comparison for cloudy cases indicates a poorer agreement between the columns (n=60, R=0.61). The mean relative difference between the columns is 60% with a standard deviation of 118% and GOME on average overestimating the ground-based columns. The clear improvement after inclusion of AK information (n=60, R=0.87) suggests larger errors in the a priori NO2 profiles under cloudy conditions and demonstrates the importance of using accurate profile information for (partially) clouded scenes.

Aerosol indirect effects - general circulation model intercomparison and evaluation with satellite data

NASA Astrophysics Data System (ADS)

Quaas, J.; Ming, Y.; Menon, S.; Takemura, T.; Wang, M.; Penner, J. E.; Gettelman, A.; Lohmann, U.; Bellouin, N.; Boucher, O.; Sayer, A. M.; Thomas, G. E.; McComiskey, A.; Feingold, G.; Hoose, C.; Kristjánsson, J. E.; Liu, X.; Balkanski, Y.; Donner, L. J.; Ginoux, P. A.; Stier, P.; Grandey, B.; Feichter, J.; Sednev, I.; Bauer, S. E.; Koch, D.; Grainger, R. G.; Kirkevåg, A.; Iversen, T.; Seland, Ø.; Easter, R.; Ghan, S. J.; Rasch, P. J.; Morrison, H.; Lamarque, J.-F.; Iacono, M. J.; Kinne, S.; Schulz, M.

2009-11-01

Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterises aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth (τa) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. It is found that the model-simulated influence of aerosols on cloud droplet number concentration (Nd) compares relatively well to the satellite data at least over the ocean. The relationship between τa and liquid water path is simulated much too strongly by the models. This suggests that the implementation of the second aerosol indirect effect mainly in terms of an autoconversion parameterisation has to be revisited in the GCMs. A positive relationship between total cloud fraction (fcld) and τa as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strong fcld-τa relationship, our results indicate that none can be identified as a unique explanation. Relationships similar to the ones found in satellite data between τa and cloud top temperature or outgoing long-wave radiation (OLR) are simulated by only a few GCMs. The GCMs that simulate a negative OLR-τa relationship show a strong positive correlation between τa and fcld. The short-wave total aerosol radiative forcing as simulated by the GCMs is strongly influenced by the simulated anthropogenic fraction of τa, and parameterisation assumptions such as a lower bound on Nd. Nevertheless, the strengths of the statistical relationships are good predictors for the aerosol forcings in the models. An estimate of the total short-wave aerosol forcing inferred from the combination of these predictors for the modelled forcings with the satellite-derived statistical relationships yields a global annual mean value of -1.5±0.5 Wm-2. In an alternative approach, the radiative flux perturbation due to anthropogenic aerosols can be broken down into a component over the cloud-free portion of the globe (approximately the aerosol direct effect) and a component over the cloudy portion of the globe (approximately the aerosol indirect effect). An estimate obtained by scaling these simulated clear- and cloudy-sky forcings with estimates of anthropogenic τa and satellite-retrieved Nd-τa regression slopes, respectively, yields a global, annual-mean aerosol direct effect estimate of -0.4±0.2 Wm-2 and a cloudy-sky (aerosol indirect effect) estimate of -0.7±0.5 Wm-2, with a total estimate of -1.2±0.4 Wm-2.

Aerosol indirect effects ? general circulation model intercomparison and evaluation with satellite data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quaas, Johannes; Ming, Yi; Menon, Surabi

2010-03-12

Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterises aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth ({tau}{sub a}) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. It is foundmore » that the model-simulated influence of aerosols on cloud droplet number concentration (N{sub d}) compares relatively well to the satellite data at least over the ocean. The relationship between {tau}{sub a} and liquid water path is simulated much too strongly by the models. This suggests that the implementation of the second aerosol indirect effect mainly in terms of an autoconversion parameterisation has to be revisited in the GCMs. A positive relationship between total cloud fraction (f{sub cld}) and {tau}{sub a} as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strong f{sub cld} - {tau}{sub a} relationship, our results indicate that none can be identified as a unique explanation. Relationships similar to the ones found in satellite data between {tau}{sub a} and cloud top temperature or outgoing long-wave radiation (OLR) are simulated by only a few GCMs. The GCMs that simulate a negative OLR - {tau}{sub a} relationship show a strong positive correlation between {tau}{sub a} and f{sub cld} The short-wave total aerosol radiative forcing as simulated by the GCMs is strongly influenced by the simulated anthropogenic fraction of {tau}{sub a}, and parameterization assumptions such as a lower bound on N{sub d}. Nevertheless, the strengths of the statistical relationships are good predictors for the aerosol forcings in the models. An estimate of the total short-wave aerosol forcing inferred from the combination of these predictors for the modelled forcings with the satellite-derived statistical relationships yields a global annual mean value of -1.5 {+-} 0.5 Wm{sup -2}. In an alternative approach, the radiative flux perturbation due to anthropogenic aerosols can be broken down into a component over the cloud-free portion of the globe (approximately the aerosol direct effect) and a component over the cloudy portion of the globe (approximately the aerosol indirect effect). An estimate obtained by scaling these simulated clear- and cloudy-sky forcings with estimates of anthropogenic {tau}{sub a} and satellite-retrieved Nd - {tau}{sub a} regression slopes, respectively, yields a global, annual-mean aerosol direct effect estimate of -0.4 {+-} 0.2 Wm{sup -2} and a cloudy-sky (aerosol indirect effect) estimate of -0.7 {+-} 0.5 Wm{sup -2}, with a total estimate of -1.2 {+-} 0.4 Wm{sup -2}.« less

Mapping the Distribution of Cloud Forests Using MODIS Imagery

NASA Astrophysics Data System (ADS)

Douglas, M. W.; Mejia, J.; Murillo, J.; Orozco, R.

2007-05-01

Tropical cloud forests - those forests that are frequently immersed in clouds or otherwise very humid, are extremely difficult to map from the ground, and are not easily distinguished in satellite imagery from other forest types, but they have a very different flora and fauna than lowland rainforest. Cloud forests, although found in many parts of the tropics, have a very restricted vertical extent and thus are also restricted horizontally. As a result, they are subject to both human disturbance (coffee growing for example) and the effects of possible climate change. Motivated by a desire to seek meteorological explanations for the distribution of cloud forests, we have begun to map cloudiness using MODIS Terra and Aqua visible imagery. This imagery, at ~1030 LT and 1330 LT, is an approximation for mid-day cloudiness. In tropical regions the amount of mid-day cloudiness strongly controls the shortwave radiation and thus the potential for evaporation (and aridity). We have mapped cloudiness using a simple algorithm that distinguishes between the cloud-free background brightness and the generally more reflective clouds to separate clouds from the underlying background. A major advantage of MODIS imagery over many other sources of satellite imagery is its high spatial resolution (~250m). This, coupled with precisely navigated images, means that detailed maps of cloudiness can be produced. The cloudiness maps can then be related to the underlying topography to further refine the location of the cloud forests. An advantage of this technique is that we are mapping the potential cloud forest, based on cloudiness, rather than the actual cloud forest, which are commonly based on forest estimates from satellite and digital elevation data. We do not derive precipitation, only estimates of daytime cloudiness. Although only a few years of MODIS imagery has been used in our studies, we will show that this is sufficient to describe the climatology of cloudiness with acceptable accuracy for its intended purposes. Even periods as short as one month are sufficient for depicting the location of most cloud forest environments. However, we are proceeding to distinguish different characteristics of cloud forests, depending on the overall frequency of cloudiness, the seasonality of cloudiness, and the interannual variability of cloudiness. These results should be useful to those seeking to describe relationships between the physical characteristics of the cloud forests and their biological environment.

Climatic change by cloudiness linked to the spatial variability of sea surface temperatures

NASA Technical Reports Server (NTRS)

Otterman, J.

1975-01-01

An active role in modifying the earth's climate is suggested for low cloudiness over the circumarctic oceans. Such cloudiness, linked to the spatial differences in ocean surface temperatures, was studied. The temporal variations from year to year of ocean temperature patterns can be pronounced and therefore, the low cloudiness over this region should also show strong temporal variations, affecting the albedo of the earth and therefore the climate. Photographs are included.

ATTENUATION OF VISIBLE SUNLIGHT BY LIMITED VISIBILITY AND CLOUDINESS

EPA Science Inventory

Variability in the irradiance measurements arises from systematic changes in the solar zenith angle (SZA), cloudiness and changing visibility. Measurements in the wavelength band centered on 612 nm serve as a reference for the initial characterization of the effects of cloudy ...

The displacement of the sun from the galactic plane using IRAS and faust source counts

NASA Technical Reports Server (NTRS)

Cohen, Martin

1995-01-01

I determine the displacement of the Sun from the Galactic plane by interpreting IRAS point-source counts at 12 and 25 microns in the Galactic polar caps using the latest version of the SKY model for the point-source sky (Cohen 1994). A value of solar zenith = 15.5 +/- 0.7 pc north of the plane provides the best match to the ensemble of useful IRAS data. Shallow K counts in the north Galactic pole are also best fitted by this offset, while limited FAUST far-ultraviolet counts at 1660 A near the same pole favor a value near 14 pc. Combining the many IRAS determinations with the few FAUST values suggests that a value of solar zenith = 15.0 +/- 0.5 pc (internal error only) would satisfy these high-latitude sets of data in both wavelength regimes, within the context of the SKY model.

Monte Carlo Bayesian inference on a statistical model of sub-gridcolumn moisture variability using high-resolution cloud observations. Part 1: Method.

PubMed

Norris, Peter M; da Silva, Arlindo M

2016-07-01

A method is presented to constrain a statistical model of sub-gridcolumn moisture variability using high-resolution satellite cloud data. The method can be used for large-scale model parameter estimation or cloud data assimilation. The gridcolumn model includes assumed probability density function (PDF) intra-layer horizontal variability and a copula-based inter-layer correlation model. The observables used in the current study are Moderate Resolution Imaging Spectroradiometer (MODIS) cloud-top pressure, brightness temperature and cloud optical thickness, but the method should be extensible to direct cloudy radiance assimilation for a small number of channels. The algorithm is a form of Bayesian inference with a Markov chain Monte Carlo (MCMC) approach to characterizing the posterior distribution. This approach is especially useful in cases where the background state is clear but cloudy observations exist. In traditional linearized data assimilation methods, a subsaturated background cannot produce clouds via any infinitesimal equilibrium perturbation, but the Monte Carlo approach is not gradient-based and allows jumps into regions of non-zero cloud probability. The current study uses a skewed-triangle distribution for layer moisture. The article also includes a discussion of the Metropolis and multiple-try Metropolis versions of MCMC.

Monte Carlo Bayesian Inference on a Statistical Model of Sub-Gridcolumn Moisture Variability Using High-Resolution Cloud Observations. Part 1: Method

NASA Technical Reports Server (NTRS)

Norris, Peter M.; Da Silva, Arlindo M.

2016-01-01

A method is presented to constrain a statistical model of sub-gridcolumn moisture variability using high-resolution satellite cloud data. The method can be used for large-scale model parameter estimation or cloud data assimilation. The gridcolumn model includes assumed probability density function (PDF) intra-layer horizontal variability and a copula-based inter-layer correlation model. The observables used in the current study are Moderate Resolution Imaging Spectroradiometer (MODIS) cloud-top pressure, brightness temperature and cloud optical thickness, but the method should be extensible to direct cloudy radiance assimilation for a small number of channels. The algorithm is a form of Bayesian inference with a Markov chain Monte Carlo (MCMC) approach to characterizing the posterior distribution. This approach is especially useful in cases where the background state is clear but cloudy observations exist. In traditional linearized data assimilation methods, a subsaturated background cannot produce clouds via any infinitesimal equilibrium perturbation, but the Monte Carlo approach is not gradient-based and allows jumps into regions of non-zero cloud probability. The current study uses a skewed-triangle distribution for layer moisture. The article also includes a discussion of the Metropolis and multiple-try Metropolis versions of MCMC.

Monte Carlo Bayesian inference on a statistical model of sub-gridcolumn moisture variability using high-resolution cloud observations. Part 1: Method

PubMed Central

Norris, Peter M.; da Silva, Arlindo M.

2018-01-01

A method is presented to constrain a statistical model of sub-gridcolumn moisture variability using high-resolution satellite cloud data. The method can be used for large-scale model parameter estimation or cloud data assimilation. The gridcolumn model includes assumed probability density function (PDF) intra-layer horizontal variability and a copula-based inter-layer correlation model. The observables used in the current study are Moderate Resolution Imaging Spectroradiometer (MODIS) cloud-top pressure, brightness temperature and cloud optical thickness, but the method should be extensible to direct cloudy radiance assimilation for a small number of channels. The algorithm is a form of Bayesian inference with a Markov chain Monte Carlo (MCMC) approach to characterizing the posterior distribution. This approach is especially useful in cases where the background state is clear but cloudy observations exist. In traditional linearized data assimilation methods, a subsaturated background cannot produce clouds via any infinitesimal equilibrium perturbation, but the Monte Carlo approach is not gradient-based and allows jumps into regions of non-zero cloud probability. The current study uses a skewed-triangle distribution for layer moisture. The article also includes a discussion of the Metropolis and multiple-try Metropolis versions of MCMC. PMID:29618847

Analysis of Leaf Area Index and Fraction of PAR Absorbed by Vegetation Products from the Terra MODIS Sensor: 2000-2005

NASA Technical Reports Server (NTRS)

Yang, Wenze; Huang, Dong; Tan, Bin; Stroeve, Julienne C.; Shabanov, Nikolay V.; Knyazikhin, Yuri; Nemani, Ramakrishna R.; Myneni, Ranga B.

2006-01-01

The analysis of two years of Collection 3 and five years of Collection 4 Terra Moderate Resolution Imaging Spectroradiometer (MODIS) Leaf Area Index (LAI) and Fraction of Photosynthetically Active Radiation (FPAR) data sets is presented in this article with the goal of understanding product quality with respect to version (Collection 3 versus 4), algorithm (main versus backup), snow (snow-free versus snow on the ground), and cloud (cloud-free versus cloudy) conditions. Retrievals from the main radiative transfer algorithm increased from 55% in Collection 3 to 67% in Collection 4 due to algorithm refinements and improved inputs. Anomalously high LAI/FPAR values observed in Collection 3 product in some vegetation types were corrected in Collection 4. The problem of reflectance saturation and too few main algorithm retrievals in broadleaf forests persisted in Collection 4. The spurious seasonality in needleleaf LAI/FPAR fields was traced to fewer reliable input data and retrievals during the boreal winter period. About 97% of the snow covered pixels were processed by the backup Normalized Difference Vegetation Index-based algorithm. Similarly, a majority of retrievals under cloudy conditions were obtained from the backup algorithm. For these reasons, the users are advised to consult the quality flags accompanying the LAI and FPAR product.

Development of a Mars Surface Imager

NASA Technical Reports Server (NTRS)

Squyres, Steve W.

1994-01-01

The Mars Surface Imager (MSI) is a multispectral, stereoscopic, panoramic imager that allows imaging of the full scene around a Mars lander from the lander body to the zenith. It has two functional components: panoramic imaging and sky imaging. In the most recent version of the MSI, called PIDDP-cam, a very long multi-line color CCD, an innovative high-performance drive system, and a state-of-the-art wavelet image compression code have been integrated into a single package. The requirements for the flight version of the MSI and the current design are presented.

Validating MODIS above-cloud aerosol optical depth retrieved from "color ratio" algorithm using direct measurements made by NASA's airborne AATS and 4STAR sensors

NASA Astrophysics Data System (ADS)

Jethva, Hiren; Torres, Omar; Remer, Lorraine; Redemann, Jens; Livingston, John; Dunagan, Stephen; Shinozuka, Yohei; Kacenelenbogen, Meloe; Segal Rosenheimer, Michal; Spurr, Rob

2016-10-01

We present the validation analysis of above-cloud aerosol optical depth (ACAOD) retrieved from the "color ratio" method applied to MODIS cloudy-sky reflectance measurements using the limited direct measurements made by NASA's airborne Ames Airborne Tracking Sunphotometer (AATS) and Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) sensors. A thorough search of the airborne database collection revealed a total of five significant events in which an airborne sun photometer, coincident with the MODIS overpass, observed partially absorbing aerosols emitted from agricultural biomass burning, dust, and wildfires over a low-level cloud deck during SAFARI-2000, ACE-ASIA 2001, and SEAC4RS 2013 campaigns, respectively. The co-located satellite-airborne matchups revealed a good agreement (root-mean-square difference < 0.1), with most matchups falling within the estimated uncertainties associated the MODIS retrievals (about -10 to +50 %). The co-retrieved cloud optical depth was comparable to that of the MODIS operational cloud product for ACE-ASIA and SEAC4RS, however, higher by 30-50 % for the SAFARI-2000 case study. The reason for this discrepancy could be attributed to the distinct aerosol optical properties encountered during respective campaigns. A brief discussion on the sources of uncertainty in the satellite-based ACAOD retrieval and co-location procedure is presented. Field experiments dedicated to making direct measurements of aerosols above cloud are needed for the extensive validation of satellite-based retrievals.

The depth of the honeybee's backup sun-compass systems.

PubMed

Dovey, Katelyn M; Kemfort, Jordan R; Towne, William F

2013-06-01

Honeybees have at least three compass mechanisms: a magnetic compass; a celestial or sun compass, based on the daily rotation of the sun and sun-linked skylight patterns; and a backup celestial compass based on a memory of the sun's movements over time in relation to the landscape. The interactions of these compass systems have yet to be fully elucidated, but the celestial compass is primary in most contexts, the magnetic compass is a backup in certain contexts, and the bees' memory of the sun's course in relation to the landscape is a backup system for cloudy days. Here we ask whether bees have any further compass systems, for example a memory of the sun's movements over time in relation to the magnetic field. To test this, we challenged bees to locate the sun when their known celestial compass systems were unavailable, that is, under overcast skies in unfamiliar landscapes. We measured the bees' knowledge of the sun's location by observing their waggle dances, by which foragers indicate the directions toward food sources in relation to the sun's compass bearing. We found that bees have no celestial compass systems beyond those already known: under overcast skies in unfamiliar landscapes, bees attempt to use their landscape-based backup system to locate the sun, matching the landscapes or skylines at the test sites with those at their natal sites as best they can, even if the matches are poor and yield weak or inconsistent orientation.

Solar radiation, cloudiness and longwave radiation over low-latitude glaciers: implications for mass-balance modelling

NASA Astrophysics Data System (ADS)

Mölg, Thomas; Cullen, Nicolas J.; Kaser, Georg

Broadband radiation schemes (parameterizations) are commonly used tools in glacier mass-balance modelling, but their performance at high altitude in the tropics has not been evaluated in detail. Here we take advantage of a high-quality 2 year record of global radiation (G) and incoming longwave radiation (L↓) measured on Kersten Glacier, Kilimanjaro, East Africa, at 5873 m a.s.l., to optimize parameterizations of G and L↓. We show that the two radiation terms can be related by an effective cloud-cover fraction neff, so G or L↓ can be modelled based on neff derived from measured L↓ or G, respectively. At neff = 1, G is reduced to 35% of clear-sky G, and L↓ increases by 45-65% (depending on altitude) relative to clear-sky L↓. Validation for a 1 year dataset of G and L↓ obtained at 4850 m on Glaciar Artesonraju, Peruvian Andes, yields a satisfactory performance of the radiation scheme. Whether this performance is acceptable for mass-balance studies of tropical glaciers is explored by applying the data from Glaciar Artesonraju to a physically based mass-balance model, which requires, among others, G and L↓ as forcing variables. Uncertainties in modelled mass balance introduced by the radiation parameterizations do not exceed those that can be caused by errors in the radiation measurements. Hence, this paper provides a tool for inclusion in spatially distributed mass-balance modelling of tropical glaciers and/or extension of radiation data when only G or L↓ is measured.

Satellite remote sensing of particulate matter air quality: the cloud-cover problem.

PubMed

Christopher, Sundar A; Gupta, Pawan

2010-05-01

Satellite assessments of particulate matter (PM) air quality that use solar reflectance methods are dependent on availability of clear sky; in other words, mass concentrations of PM less than 2.5 microm in aerodynamic diameter (PM2.5) cannot be estimated from satellite observations under cloudy conditions or bright surfaces such as snow/ice. Whereas most ground monitors measure PM2.5 concentrations on an hourly basis regardless of cloud conditions, space-borne sensors can only estimate daytime PM2.5 in cloud-free conditions, therefore introducing a bias. In this study, an estimate of this clear-sky bias is provided from monthly to yearly time scales over the continental United States. One year of the Moderate Resolution Imaging Spectroradiometer (MODIS) 550-nm aerosol optical depth (AOD) retrievals from Terra and Aqua satellites, collocated with 371 U.S. Environmental Protection Agency (EPA) ground monitors, have been analyzed. The results indicate that the mean differences between PM2.5 reported by ground monitors and PM2.5 calculated from ground monitors during the satellite overpass times during cloud-free conditions are less than +/- 2.5 microg m(-3), although this value varies by season and location. The mean differences are not significant as calculated by t tests (alpha = 0.05). On the basis of this analysis, it is concluded that for the continental United States, cloud cover is not a major problem for inferring monthly to yearly PM2.5 from space-borne sensors.

Role of persistent low-level clouds in mitigating air quality impacts of wintertime cold pool conditions

NASA Astrophysics Data System (ADS)

VanReken, Timothy M.; Dhammapala, Ranil S.; Jobson, B. Thomas; Bottenus, Courtney L.; VanderSchelden, Graham S.; Kaspari, Susan D.; Gao, Zhongming; Zhu, Qiurui; Lamb, Brian K.; Liu, Heping; Johnston, Jeff

2017-04-01

The Yakima Air Wintertime Nitrate Study (YAWNS) was conducted in January 2013 to investigate the drivers of elevated levels of fine particulate matter (PM2.5) frequently present in the region during winter stagnation periods. An extended stagnation period occurred during the study. For the first four days of the event, skies were clear and the strong diel variation in air pollution patterns were consistent with the expected effects of strong low-level nighttime temperature inversions with moderate mixing during daylight hours. Later in the event a low-level cloud layer formed that persisted over the Yakima Valley for the next seven days while regional conditions remained stagnant. Coincident with the onset of cloud, the levels of all measured primary pollutants, including CO2, CO, NOx, particle number concentration, and black carbon, dropped dramatically and remained low with negligible diel variation for as long as the cloud layer was present. The observed patterns for these air pollutants are consistent with decreased stability and enhanced mixing associated with the cloud-topped boundary layer. Interestingly, levels of secondary pollutants, most notably particulate ammonium nitrate, did not exhibit the same decline. This difference may be due to shifts in the chemical production of secondary pollutants during cloudy conditions, or may merely reflect a further influence of mixing. The results imply that the best strategies for managing wintertime air quality during episodes of persistent cloud are likely different from those needed during clear-sky stagnation events.

Correcting surface solar radiation of two data assimilation systems against FLUXNET observations in North America

NASA Astrophysics Data System (ADS)

Zhao, Lei; Lee, Xuhui; Liu, Shoudong

2013-09-01

Solar radiation at the Earth's surface is an important driver of meteorological and ecological processes. The objective of this study is to evaluate the accuracy of the reanalysis solar radiation produced by NARR (North American Regional Reanalysis) and MERRA (Modern-Era Retrospective Analysis for Research and Applications) against the FLUXNET measurements in North America. We found that both assimilation systems systematically overestimated the surface solar radiation flux on the monthly and annual scale, with an average bias error of +37.2 Wm-2 for NARR and of +20.2 Wm-2 for MERRA. The bias errors were larger under cloudy skies than under clear skies. A postreanalysis algorithm consisting of empirical relationships between model bias, a clearness index, and site elevation was proposed to correct the model errors. Results show that the algorithm can remove the systematic bias errors for both FLUXNET calibration sites (sites used to establish the algorithm) and independent validation sites. After correction, the average annual mean bias errors were reduced to +1.3 Wm-2 for NARR and +2.7 Wm-2 for MERRA. Applying the correction algorithm to the global domain of MERRA brought the global mean surface incoming shortwave radiation down by 17.3 W m-2 to 175.5 W m-2. Under the constraint of the energy balance, other radiation and energy balance terms at the Earth's surface, estimated from independent global data products, also support the need for a downward adjustment of the MERRA surface solar radiation.

OCEANET-Atmosphere - The Autonomous Measurement Container

NASA Astrophysics Data System (ADS)

Kalisch, John; Macke, Andreas; Althausen, Dietrich; Bumke, Karl; Engelmann, Ronny; Kanitz, Thomas; Kleta, Henry; Zoll, Yann

2010-05-01

OCEANET-Atmosphere is a joint venture project of IFM-GEOMAR and IFT to study the mass and energy transfer of ocean and atmosphere by introducing a special measurement container, which is suitable to perform a large spectrum of atmospheric underway measurements on offshore research vessels and cargo ships. The container combines state-of-the-art measurement devices and connect them to its own computer network to realize a comprehensive system for remote sensing. A Raman-lidar measures marine and anthropogenic optical aerosol properities by analyzing the elastic signal and the vibration-rotation Raman signal of nitrogen. Our passive microwave radiometer determines the integrated water vapor and the liquid water path of the atmospheric column, as well as vertical temperature and humidity profiles. Carbon dioxide is measured high-frequent. Turbulence measurements are performed by means of a sonic anemometer. In combination with fast humidity sensors the fluxes of momentum, latent and sensible heat are derived. An automatic full sky imager monitors the state of the cloudy sky. A selection of standard meteorological devices measure air temperature, humidity, wind velocity, wind speed and downward shortwave and longwave radiative fluxes. The GPS sensors register navigational data. For an almost real time monitoring of a data subset our telemetry system is sending short hourly data reports via satellite. OCEANET-Atmosphere is set up to improve the quantity and the quality of atmospheric data sets on intercontinental oceanic transects, where the previous data base is still weak. A first research mission has been performed onboard RV Polarstern at ANT XXVI/1.

Effects of urban agglomeration on surface-UV doses: a comparison of Brewer measurements in Warsaw and Belsk, Poland, for the period 2013-2015

NASA Astrophysics Data System (ADS)

Czerwińska, Agnieszka E.; Krzyścin, Janusz W.; Jarosławski, Janusz; Posyniak, Michał

2016-11-01

Specific aerosols and cloud properties over large urban regions seem to generate an island, similar to the well-known urban heat island, leading to lower ultraviolet (UV) radiation intensity compared to the surrounding less polluted areas, thus creating a shield against excessive human exposure to UV radiation. The present study focuses on differences between erythemal and UVA (324 nm) doses measured by the Brewer spectrophotometers in Warsaw (52.3° N, 21.0° E) and Belsk (51.8° N, 20.8° E). The latter is a rural region located about 60 km south-west of the city. Ratios between erythemal and UVA partly daily doses, obtained during all-sky and cloudless-sky conditions for the period May 2013-December 2015, were analysed to infer a specific cloud and aerosol forcing on the surface UV doses over Warsaw. Radiative model simulations were carried out to find sources of the observed differences between the sites. It was found that Warsaw urban agglomeration induced 8 and 6 % attenuation of the erythemal and UVA doses respectively. This is mostly due to the lower sun elevation in Warsaw during the near-noon measurements and the larger optical depth of the city aerosols and increased cloudiness. It could be hypothesised that the expected stronger absorption of the solar UV radiation by urban aerosols is compensated for here by a higher surface reflectivity over the city.

A cute and highly contrast-sensitive superposition eye - the diurnal owlfly Libelloides macaronius.

PubMed

Belušič, Gregor; Pirih, Primož; Stavenga, Doekele G

2013-06-01

The owlfly Libelloides macaronius (Insecta: Neuroptera) has large bipartite eyes of the superposition type. The spatial resolution and sensitivity of the photoreceptor array in the dorsofrontal eye part was studied with optical and electrophysiological methods. Using structured illumination microscopy, the interommatidial angle in the central part of the dorsofrontal eye was determined to be Δϕ=1.1 deg. Eye shine measurements with an epi-illumination microscope yielded an effective superposition pupil size of about 300 facets. Intracellular recordings confirmed that all photoreceptors were UV-receptors (λmax=350 nm). The average photoreceptor acceptance angle was 1.8 deg, with a minimum of 1.4 deg. The receptor dynamic range was two log units, and the Hill coefficient of the intensity-response function was n=1.2. The signal-to-noise ratio of the receptor potential was remarkably high and constant across the whole dynamic range (root mean square r.m.s. noise=0.5% Vmax). Quantum bumps could not be observed at any light intensity, indicating low voltage gain. Presumably, the combination of large aperture superposition optics feeding an achromatic array of relatively insensitive receptors with a steep intensity-response function creates a low-noise, high spatial acuity instrument. The sensitivity shift to the UV range reduces the clutter created by clouds within the sky image. These properties of the visual system are optimal for detecting small insect prey as contrasting spots against both clear and cloudy skies.

Short-range solar radiation forecasts over Sweden

NASA Astrophysics Data System (ADS)

Landelius, Tomas; Lindskog, Magnus; Körnich, Heiner; Andersson, Sandra

2018-04-01

In this article the performance for short-range solar radiation forecasts by the global deterministic and ensemble models from the European Centre for Medium-Range Weather Forecasts (ECMWF) is compared with an ensemble of the regional mesoscale model HARMONIE-AROME used by the national meteorological services in Sweden, Norway and Finland. Note however that only the control members and the ensemble means are included in the comparison. The models resolution differs considerably with 18 km for the ECMWF ensemble, 9 km for the ECMWF deterministic model, and 2.5 km for the HARMONIE-AROME ensemble. The models share the same radiation code. It turns out that they all underestimate systematically the Direct Normal Irradiance (DNI) for clear-sky conditions. Except for this shortcoming, the HARMONIE-AROME ensemble model shows the best agreement with the distribution of observed Global Horizontal Irradiance (GHI) and DNI values. During mid-day the HARMONIE-AROME ensemble mean performs best. The control member of the HARMONIE-AROME ensemble also scores better than the global deterministic ECMWF model. This is an interesting result since mesoscale models have so far not shown good results when compared to the ECMWF models. Three days with clear, mixed and cloudy skies are used to illustrate the possible added value of a probabilistic forecast. It is shown that in these cases the mesoscale ensemble could provide decision support to a grid operator in terms of forecasts of both the amount of solar power and its probabilities.

Comparing the diurnal and seasonal variabilities of atmospheric and surface urban heat islandsbased on the Beijing urban meteorological network

NASA Astrophysics Data System (ADS)

Jiang, S.; Wang, K.; Wang, J.; Zhou, C.; Wang, X.; Lee, X.

2017-12-01

This study compared the diurnal and seasonal cycles of atmospheric and surface urban heat islands (UHIs) based on hourly air temperatures (Ta) collected at 65 out of 262 stations in Beijing and land surface temperature (Ts) derived from Moderate Resolution Imaging Spectroradiometer in the years 2013-2014. We found that the nighttime atmospheric and surface UHIs referenced to rural cropland stations exhibited significant seasonal cycles, with the highest in winter. However, the seasonal variations in the nighttime UHIs referenced to mountainous forest stations were negligible, because mountainous forests have a higher nighttime Ts in winter and a lower nighttime T a in summer than rural croplands. Daytime surface UHIs showed strong seasonal cycles, with the highest in summer. The daytime atmospheric UHIs exhibited a similar but less seasonal cycle under clear-sky conditions, which was not apparent under cloudy-sky conditions. Atmospheric UHIs in urban parks were higher in daytime. Nighttime atmospheric UHIs are influenced by energy stored in urban materials during daytime and released during nighttime. The stronger anthropogenic heat release in winter causes atmospheric UHIs to increase with time during winter nights, but decrease with time during summer nights. The percentage of impervious surfaces is responsible for 49%-54% of the nighttime atmospheric UHI variability and 31%-38% of the daytime surface UHI variability. However, the nighttime surface UHI was nearly uncorrelated with the percentage of impervious surfaces around the urban stations.

Validating MODIS Above-Cloud Aerosol Optical Depth Retrieved from Color Ratio Algorithm Using Direct Measurements Made by NASA's Airborne AATS and 4STAR Sensors

NASA Technical Reports Server (NTRS)

Jethva, Hiren; Torres, Omar; Remer, Lorraine; Redemann, Jens; Livingston, John; Dunagan, Stephen; Shinozuka, Yohei; Kacenelenbogen, Meloe; Segal Rozenhaimer, Michal; Spurr, Rob

2016-01-01

We present the validation analysis of above-cloud aerosol optical depth (ACAOD) retrieved from the color ratio method applied to MODIS cloudy-sky reflectance measurements using the limited direct measurements made by NASAs airborne Ames Airborne Tracking Sunphotometer (AATS) and Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) sensors. A thorough search of the airborne database collection revealed a total of five significant events in which an airborne sun photometer, coincident with the MODIS overpass, observed partially absorbing aerosols emitted from agricultural biomass burning, dust, and wildfires over a low-level cloud deck during SAFARI-2000, ACE-ASIA 2001, and SEAC4RS 2013 campaigns, respectively. The co-located satellite-airborne match ups revealed a good agreement (root-mean-square difference less than 0.1), with most match ups falling within the estimated uncertainties associated with the MODIS retrievals (about -10 to +50 ). The co-retrieved cloud optical depth was comparable to that of the MODIS operational cloud product for ACE-ASIA and SEAC4RS, however, higher by 30-50% for the SAFARI-2000 case study. The reason for this discrepancy could be attributed to the distinct aerosol optical properties encountered during respective campaigns. A brief discussion on the sources of uncertainty in the satellite-based ACAOD retrieval and co-location procedure is presented. Field experiments dedicated to making direct measurements of aerosols above cloud are needed for the extensive validation of satellite based retrievals.

Long-term series and trends in surface solar radiation in Athens, Greece

NASA Astrophysics Data System (ADS)

Kazadzis, Stelios; Founda, Dimitra; Psiloglou, Basil E.; Kambezidis, Harry; Mihalopoulos, Nickolaos; Sanchez-Lorenzo, Arturo; Meleti, Charikleia; Raptis, Panagiotis I.; Pierros, Fragiskos; Nabat, Pierre

2018-02-01

We present a long-term series of surface solar radiation (SSR) from the city of Athens, Greece. SSR measurements were performed from 1954 to 2012, and before that (1900-1953) sunshine duration (SD) records were used in order to reconstruct monthly SSR. Analysis of the whole data set (1900-2012) mainly showed very small (0.02 %) changes in SSR from 1900 to 1953, including a maximum decrease of -2.9 % decade-1 in SSR during the 1910 to 1940 period, assuming a linear change. For the dimming period 1955-1980, -2 % decade-1 was observed that matches various European long-term SSR-measurement-related studies. This percentage in Athens is in the lower limit, compared to other studies in the Mediterranean area. For the brightening period 1980-2012 we calculated +1.5 % decade-1, which is also in the lower limit of the reported positive changes in SSR around Europe. Comparing the 30-year periods 1954-1983 and 1983-2012, we found a difference of 4.5 %. However, measurements of the first 30-year period are associated with higher uncertainties than those of the second period, especially when looking at year-to-year changes. The difference between the two periods was observed for all seasons except winter. Analyzing SSR calculations of all-sky and clear-sky (cloudless) conditions/days, we report that most of the observed changes in SSR after 1954 can be attributed partly to cloudiness and mostly to aerosol load changes.

Coolness in the tropical Pacific during an El Nino episode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chou, M.

The response of radiation budgets to changes in water vapor and clouds in an El Nino episode is investigated using the analyzed sea surface temperature (SST) and satellite-derived clouds and the earth radiation budgets for the tropical Pacific (30 deg N-30 deg S, 100 deg E-100 deg W). Analyses are performed for April 1985 and April 1987. The former is a non-El Nino year and the latter is an El Nino year. Compared to April 1985, when the SST over the central and eastern equatorial Pacific is approximately 2 C lower, the high-level cloudiness in April 1987 increases in themore » central and eastern equatorial Pacific. Corresponding to the increase in cloudiness, the outgoing longwave radiation and the net downward solar radiation at the top of the atmosphere decrease. The patterns of these changes are reversed in the western tropical Pacific and the Northern Hemispheric (NH) subsidence region centered at approximately 20 deg N, indicating an eastward shift of the convection center from the maritime continents to the central equatorial Pacific and a strengthened NH Hadley circulation. The earth-atmosphere system in the region receives less radiative energy by 4 W/sq m in the warmer month of April 1987 than in the month of April 1985, which is primarily caused by a reduced atmospheric clear sky greenhouse effect in the NH tropical Pacific in April 1987. Clouds have strong effects on both the IR and solar radiation, but the net effect on the radiation budget at the top of the atmopshere changes only slightly between April 1985 and April 1987. The results are consistent with Lindzen`s hypothesis that reduced upper-tropospheric water vapor in the vicinity of the enhanced convection region produces cooling that counteracts warming in the Tropics.« less

Development of simple band-spectral pyranometer and quantum meter using photovoltaic cells and bandpass filters

NASA Astrophysics Data System (ADS)

Bilguun, Amarsaikhan; Nakaso, Tetsushi; Harigai, Toru; Suda, Yoshiyuki; Takikawa, Hirofumi; Tanoue, Hideto

2016-02-01

In recent years, greenhouse automatic-control, based on the measurement of solar irradiance, has been attracting attention. This control is an effective method for improving crop production. In the agricultural field, it is necessary to measure Photon Flux Density (PFD), which is an important parameter in the promotion of plant growth. In particular, the PFD of Photosynthetically Active Radiation (PAR, 400-700 nm) and Plant Biologically Active Radiation (PBAR, 300-800 nm) have been discussed in agricultural plant science. The commercial quantum meter (QM, PAR meter) can only measure Photosynthetically Photon Flux Density (PPFD) which is the integrated PFD quantity on the PAR wavelength. In this research, a band-spectral pyranometer or quantum meter using PVs with optical bandpass filters for dividing the PBAR wavelength into 100 nm bands (five independent channels) was developed. Before field testing, calibration of the instruments was carried out using a solar simulator. Next, a field test was conducted in three differing weather conditions such as clear, partly cloudy and cloudy skies. As a result, it was found that the response rate of the developed pyranometer was faster by four seconds compared with the response rate of the commercial pyranometer. Moreover, the outputs of each channel in the developed pyranometer were very similar to the integrated outputs of the commercial spectroradiometer. It was confirmed that the solar irradiance could be measured in each band separately using the developed band-spectral pyranometer. It was indicated that the developed band-spectral pyranometer could also be used as a PV band-spectral quantum meter which is obtained by converting the band irradiance into band PFD.

Satellite Estimation of Spectral Surface UV Irradiance. 2; Effect of Horizontally Homogeneous Clouds

NASA Technical Reports Server (NTRS)

Krothov, N.; Herman, J. R.; Bhartia, P. K.; Ahmad, Z.a; Fioletov, V.

1998-01-01

The local variability of UV irradiance at the Earth's surface is mostly caused by clouds in addition to the seasonal variability. Parametric representations of radiative transfer RT calculations are presented for the convenient solution of the transmission T of ultraviolet radiation through plane parallel clouds over a surface with reflectivity R(sub s). The calculations are intended for use with the Total Ozone Mapping Spectrometer (TOMS) measured radiances to obtain the calculated Lambert equivalent scene reflectivity R for scenes with and without clouds. The purpose is to extend the theoretical analysis of the estimation of UV irradiance from satellite data for a cloudy atmosphere. Results are presented for a range of cloud optical depths and solar zenith angles for the cases of clouds over a low reflectivity surface R(sub s) less than 0.1, over a snow or ice surface R(sub s) greater than 0.3, and for transmission through a non-conservative scattering cloud with single scattering albedo omega(sub 0) = 0.999. The key finding for conservative scattering is that the cloud-transmission function C(sub T), the ratio of cloudy-to clear-sky transmission, is roughly C(sub T) = 1 - R(sub c) with an error of less than 20% for nearly overhead sun and snow-free surfaces. For TOMS estimates of UV irradiance in the presence of both snow and clouds, independent information about snow albedo is needed for conservative cloud scattering. For non-conservative scattering with R(sub s) greater than 0.5 (snow) the satellite measured scene reflectance cannot be used to estimate surface irradiance. The cloud transmission function has been applied to the calculation of UV irradiance at the Earth's surface and compared with ground-based measurements.

Development of simple band-spectral pyranometer and quantum meter using photovoltaic cells and bandpass filters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bilguun, Amarsaikhan, E-mail: bilguun@pes.ee.tut.ac.jp; Nakaso, Tetsushi; Harigai, Toru

In recent years, greenhouse automatic-control, based on the measurement of solar irradiance, has been attracting attention. This control is an effective method for improving crop production. In the agricultural field, it is necessary to measure Photon Flux Density (PFD), which is an important parameter in the promotion of plant growth. In particular, the PFD of Photosynthetically Active Radiation (PAR, 400-700 nm) and Plant Biologically Active Radiation (PBAR, 300-800 nm) have been discussed in agricultural plant science. The commercial quantum meter (QM, PAR meter) can only measure Photosynthetically Photon Flux Density (PPFD) which is the integrated PFD quantity on the PAR wavelength. Inmore » this research, a band-spectral pyranometer or quantum meter using PVs with optical bandpass filters for dividing the PBAR wavelength into 100 nm bands (five independent channels) was developed. Before field testing, calibration of the instruments was carried out using a solar simulator. Next, a field test was conducted in three differing weather conditions such as clear, partly cloudy and cloudy skies. As a result, it was found that the response rate of the developed pyranometer was faster by four seconds compared with the response rate of the commercial pyranometer. Moreover, the outputs of each channel in the developed pyranometer were very similar to the integrated outputs of the commercial spectroradiometer. It was confirmed that the solar irradiance could be measured in each band separately using the developed band-spectral pyranometer. It was indicated that the developed band-spectral pyranometer could also be used as a PV band-spectral quantum meter which is obtained by converting the band irradiance into band PFD.« less

A threshold-based cloud mask for the high-resolution visible channel of Meteosat Second Generation SEVIRI

NASA Astrophysics Data System (ADS)

Bley, S.; Deneke, H.

2013-10-01

A threshold-based cloud mask for the high-resolution visible (HRV) channel (1 × 1 km2) of the Meteosat SEVIRI (Spinning Enhanced Visible and Infrared Imager) instrument is introduced and evaluated. It is based on operational EUMETSAT cloud mask for the low-resolution channels of SEVIRI (3 × 3 km2), which is used for the selection of suitable thresholds to ensure consistency with its results. The aim of using the HRV channel is to resolve small-scale cloud structures that cannot be detected by the low-resolution channels. We find that it is of advantage to apply thresholds relative to clear-sky reflectance composites, and to adapt the threshold regionally. Furthermore, the accuracy of the different spectral channels for thresholding and the suitability of the HRV channel are investigated for cloud detection. The case studies show different situations to demonstrate the behavior for various surface and cloud conditions. Overall, between 4 and 24% of cloudy low-resolution SEVIRI pixels are found to contain broken clouds in our test data set depending on considered region. Most of these broken pixels are classified as cloudy by EUMETSAT's cloud mask, which will likely result in an overestimate if the mask is used as an estimate of cloud fraction. The HRV cloud mask aims for small-scale convective sub-pixel clouds that are missed by the EUMETSAT cloud mask. The major limit of the HRV cloud mask is the minimum cloud optical thickness (COT) that can be detected. This threshold COT was found to be about 0.8 over ocean and 2 over land and is highly related to the albedo of the underlying surface.

Quantification of marine aerosol subgrid variability and its correlation with clouds based on high-resolution regional modeling: Quantifying Aerosol Subgrid Variability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Guangxing; Qian, Yun; Yan, Huiping

One limitation of most global climate models (GCMs) is that with the horizontal resolutions they typically employ, they cannot resolve the subgrid variability (SGV) of clouds and aerosols, adding extra uncertainties to the aerosol radiative forcing estimation. To inform the development of an aerosol subgrid variability parameterization, here we analyze the aerosol SGV over the southern Pacific Ocean simulated by the high-resolution Weather Research and Forecasting model coupled to Chemistry. We find that within a typical GCM grid, the aerosol mass subgrid standard deviation is 15% of the grid-box mean mass near the surface on a 1 month mean basis.more » The fraction can increase to 50% in the free troposphere. The relationships between the sea-salt mass concentration, meteorological variables, and sea-salt emission rate are investigated in both the clear and cloudy portion. Under clear-sky conditions, marine aerosol subgrid standard deviation is highly correlated with the standard deviations of vertical velocity, cloud water mixing ratio, and sea-salt emission rates near the surface. It is also strongly connected to the grid box mean aerosol in the free troposphere (between 2 km and 4 km). In the cloudy area, interstitial sea-salt aerosol mass concentrations are smaller, but higher correlation is found between the subgrid standard deviations of aerosol mass and vertical velocity. Additionally, we find that decreasing the model grid resolution can reduce the marine aerosol SGV but strengthen the correlations between the aerosol SGV and the total water mixing ratio (sum of water vapor, cloud liquid, and cloud ice mixing ratios).« less

A practical approach for deriving all-weather soil moisture content using combined satellite and meteorological data

NASA Astrophysics Data System (ADS)

Leng, Pei; Li, Zhao-Liang; Duan, Si-Bo; Gao, Mao-Fang; Huo, Hong-Yuan

2017-09-01

Soil moisture has long been recognized as one of the essential variables in the water cycle and energy budget between Earth's surface and atmosphere. The present study develops a practical approach for deriving all-weather soil moisture using combined satellite images and gridded meteorological products. In this approach, soil moisture over the Moderate Resolution Imaging Spectroradiometer (MODIS) clear-sky pixels are estimated from the Vegetation Index/Temperature (VIT) trapezoid scheme in which theoretical dry and wet edges were determined pixel to pixel by China Meteorological Administration Land Data Assimilation System (CLDAS) meteorological products, including air temperature, solar radiation, wind speed and specific humidity. For cloudy pixels, soil moisture values are derived by the calculation of surface and aerodynamic resistances from wind speed. The approach is capable of filling the soil moisture gaps over remaining cloudy pixels by traditional optical/thermal infrared methods, allowing for a spatially complete soil moisture map over large areas. Evaluation over agricultural fields indicates that the proposed approach can produce an overall generally reasonable distribution of all-weather soil moisture. An acceptable accuracy between the estimated all-weather soil moisture and in-situ measurements at different depths could be found with an Root Mean Square Error (RMSE) varying from 0.067 m3/m3 to 0.079 m3/m3 and a slight bias ranging from 0.004 m3/m3 to -0.011 m3/m3. The proposed approach reveals significant potential to derive all-weather soil moisture using currently available satellite images and meteorological products at a regional or global scale in future developments.

Sensitivity of Marine Warm Cloud Retrieval Statistics to Algorithm Choices: Examples from MODIS Collection 6

NASA Technical Reports Server (NTRS)

Platnick, Steven; Wind, Galina; Zhang, Zhibo; Ackerman, Steven A.; Maddux, Brent

2012-01-01

The optical and microphysical structure of warm boundary layer marine clouds is of fundamental importance for understanding a variety of cloud radiation and precipitation processes. With the advent of MODIS (Moderate Resolution Imaging Spectroradiometer) on the NASA EOS Terra and Aqua platforms, simultaneous global/daily 1km retrievals of cloud optical thickness and effective particle size are provided, as well as the derived water path. In addition, the cloud product (MOD06/MYD06 for MODIS Terra and Aqua, respectively) provides separate effective radii results using the l.6, 2.1, and 3.7 m spectral channels. Cloud retrieval statistics are highly sensitive to how a pixel identified as being "notclear" by a cloud mask (e.g., the MOD35/MYD35 product) is determined to be useful for an optical retrieval based on a 1-D cloud model. The Collection 5 MODIS retrieval algorithm removed pixels associated with cloud'edges as well as ocean pixels with partly cloudy elements in the 250m MODIS cloud mask - part of the so-called Clear Sky Restoral (CSR) algorithm. Collection 6 attempts retrievals for those two pixel populations, but allows a user to isolate or filter out the populations via CSR pixel-level Quality Assessment (QA) assignments. In this paper, using the preliminary Collection 6 MOD06 product, we present global and regional statistical results of marine warm cloud retrieval sensitivities to the cloud edge and 250m partly cloudy pixel populations. As expected, retrievals for these pixels are generally consistent with a breakdown of the ID cloud model. While optical thickness for these suspect pixel populations may have some utility for radiative studies, the retrievals should be used with extreme caution for process and microphysical studies.

Cloud and DNI nowcasting with MSG/SEVIRI for the optimized operation of concentrating solar power plants

NASA Astrophysics Data System (ADS)

Sirch, Tobias; Bugliaro, Luca; Zinner, Tobias; Möhrlein, Matthias; Vazquez-Navarro, Margarita

2017-02-01

A novel approach for the nowcasting of clouds and direct normal irradiance (DNI) based on the Spinning Enhanced Visible and Infrared Imager (SEVIRI) aboard the geostationary Meteosat Second Generation (MSG) satellite is presented for a forecast horizon up to 120 min. The basis of the algorithm is an optical flow method to derive cloud motion vectors for all cloudy pixels. To facilitate forecasts over a relevant time period, a classification of clouds into objects and a weighted triangular interpolation of clear-sky regions are used. Low and high level clouds are forecasted separately because they show different velocities and motion directions. Additionally a distinction in advective and convective clouds together with an intensity correction for quickly thinning convective clouds is integrated. The DNI is calculated from the forecasted optical thickness of the low and high level clouds. In order to quantitatively assess the performance of the algorithm, a forecast validation against MSG/SEVIRI observations is performed for a period of 2 months. Error rates and Hanssen-Kuiper skill scores are derived for forecasted cloud masks. For a forecast of 5 min for most cloud situations more than 95 % of all pixels are predicted correctly cloudy or clear. This number decreases to 80-95 % for a forecast of 2 h depending on cloud type and vertical cloud level. Hanssen-Kuiper skill scores for cloud mask go down to 0.6-0.7 for a 2 h forecast. Compared to persistence an improvement of forecast horizon by a factor of 2 is reached for all forecasts up to 2 h. A comparison of forecasted optical thickness distributions and DNI against observations yields correlation coefficients larger than 0.9 for 15 min forecasts and around 0.65 for 2 h forecasts.

Strategic Environmental Research and Development Program: Atmospheric Remote Sensing and Assessment Program -- Final Report. Part 1: The lower atmosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tooman, T.P.

1997-01-01

This report documents work done between FY91 and FY95 for the lower atmospheric portion of the joint Department of Defense (DoD) and Department of Energy (DOE) Atmospheric Remote Sensing and Assessment Program (ARSAP) within the Strategic Environmental Research and Development Program (SERDP). The work focused on (1) developing new measurement capabilities and (2) measuring atmospheric heating in a well-defined layer and then relating it to cloud properties an water vapor content. Seven new instruments were develop3ed for use with Unmanned Aerospace Vehicles (UAVs) as the host platform for flux, radiance, cloud, and water vapor measurements. Four major field campaigns weremore » undertaken to use these new as well as existing instruments to make critically needed atmospheric measurements. Scientific results include the profiling of clear sky fluxes from near surface to 14 km and the strong indication of cloudy atmosphere absorption of solar radiation considerably greater than predicted by extant models.« less

AIRS Impact on the Analysis and Forecast Track of Tropical Cyclone Nargis in a Global Data Assimilation and Forecasting System

NASA Technical Reports Server (NTRS)

Reale, O.; Lau, W.K.; Susskind, J.; Brin, E.; Liu, E.; Riishojgaard, L. P.; Rosenburg, R.; Fuentes, M.

2009-01-01

Tropical cyclones in the northern Indian Ocean pose serious challenges to operational weather forecasting systems, partly due to their shorter lifespan and more erratic track, compared to those in the Atlantic and the Pacific. Moreover, the automated analyses of cyclones over the northern Indian Ocean, produced by operational global data assimilation systems (DASs), are generally of inferior quality than in other basins. In this work it is shown that the assimilation of Atmospheric Infrared Sounder (AIRS) temperature retrievals under partial cloudy conditions can significantly impact the representation of the cyclone Nargis (which caused devastating loss of life in Myanmar in May 2008) in a global DAS. Forecasts produced from these improved analyses by a global model produce substantially smaller track errors. The impact of the assimilation of clear-sky radiances on the same DAS and forecasting system is positive, but smaller than the one obtained by ingestion of AIRS retrievals, possibly due to poorer coverage.

Weather and emotional state: a search for associations between weather and calls to telephone counseling services

NASA Astrophysics Data System (ADS)

Driscoll, Dennis; Stillman, Daniel

2002-08-01

Previous research has revealed that an emotional response to weather might be indicated by calls to telephone counseling services. We analyzed call frequency from such "hotlines", each serving communities in a major metropolitan area of the United States (Detroit, Washington DC, Dallas and Seattle). The periods examined were all, or parts of, the years 1997 and 1998. Associations with subjectively derived synoptic weather types for all cities except Seattle, as well as with individual weather elements [cloudiness (sky cover), precipitation, windspeed, and interdiurnal temperature change] for all four cities, were investigated. Analysis of variance and t-tests (significance of means) were applied to test the statistical significance of differences. Although statistically significant results were obtained in scattered instances, the total number was within that expected by chance, and there was little in the way of consistency to these associations. One clear exception was the increased call frequency during destructive (severe) weather, when there is obvious concern about the damage done by it.

Implications of Observed High Supersaturation for TTL Cloud Formation and Dehydration

NASA Technical Reports Server (NTRS)

Jensen, Eric

2004-01-01

In situ measurements of water vapor concentration made during the CRYSTAL-FACE and Pre-AVE missions indicate higher than expected supersaturations in both clear and cloudy air near the cold tropical tropopause: (1) steady-state ice supersaturations of 20-30% were measured within cirrus at T < 200 K; (2) supersaturations exceeding 100% (near water saturation) were observed under cloud-free conditions near 187 K. The in-cloud measurements challenge the conventional belief that any water vapor in excess of ice saturation should be depleted by crystal growth given sufficient time. The high clear-sky supersaturations imply that thresholds for ice nucleation due to homogeneous freezing of aerosols (or any other mechanism) are much higher than those inferred from laboratory measurements. We will use simulations of Tropical Tropopause Layer (TTL) transport and cloud formation throughout the tropics to show that these effects have important implications for TTL cloud frequency and freeze-drying of air crossing the tropical tropopause cold trap.

A Remotely Operated Observatory for Minor Planet Photometry

NASA Astrophysics Data System (ADS)

Ditteon, Richard

2008-05-01

In October of 2007 Rose-Hulman Institute of Technology in Terre Haute, Indiana began operating the Oakley Southern Sky Observatory (E09) located near Siding Spring Observatory in New South Wales, Australia. The observatory houses a 0.5-m, f/8.4 Ritchey-Chretien telescope mounted on a Paramount ME, German equatorial mount. Attached to the telescope is an STL-1001E CCD camera which has 1024 by 1024, 24 µm pixels, a two-stage thermoelectric cooler, and built in color filter wheel with BVRI and clear filters. Image scale is 1.2 arcseconds per pixel. A cloud sensor is used to monitor sky conditions. The observatory has a roll-off roof with limit switches to detect when the roof is fully open and fully closed. In addition, a switch has been added to the mount to detect when the telescope is parked and that it is safe to open or close the roof. All of the hardware is controlled by a custom program which reads a simple text file containing the sequence of images and targets to be collected each night. The text file is loaded onto the control computer once each day, then the software waits until sunset to determine if the sky is clear. When conditions are favorable, power is turned on, the roof opens, twilight flats, dark and bias frames are recorded, and when it is fully dark data frames are recorded. Images are transferred via the Internet back to Rose-Hulman by another program running in the background. The observatory closes itself before dawn or if it gets cloudy. Currently we are using the observatory for photometry of minor planets. Students are responsible for selecting targets, processing the returned images, determining the period and light curve of each minor planet and writing a paper for publication. Recent results will be presented.

Single-footprint retrievals for AIRS using a fast TwoSlab cloud-representation model and the SARTA all-sky infrared radiative transfer algorithm

NASA Astrophysics Data System (ADS)

DeSouza-Machado, Sergio; Larrabee Strow, L.; Tangborn, Andrew; Huang, Xianglei; Chen, Xiuhong; Liu, Xu; Wu, Wan; Yang, Qiguang

2018-01-01

One-dimensional variational retrievals of temperature and moisture fields from hyperspectral infrared (IR) satellite sounders use cloud-cleared radiances (CCRs) as their observation. These derived observations allow the use of clear-sky-only radiative transfer in the inversion for geophysical variables but at reduced spatial resolution compared to the native sounder observations. Cloud clearing can introduce various errors, although scenes with large errors can be identified and ignored. Information content studies show that, when using multilayer cloud liquid and ice profiles in infrared hyperspectral radiative transfer codes, there are typically only 2-4 degrees of freedom (DOFs) of cloud signal. This implies a simplified cloud representation is sufficient for some applications which need accurate radiative transfer. Here we describe a single-footprint retrieval approach for clear and cloudy conditions, which uses the thermodynamic and cloud fields from numerical weather prediction (NWP) models as a first guess, together with a simple cloud-representation model coupled to a fast scattering radiative transfer algorithm (RTA). The NWP model thermodynamic and cloud profiles are first co-located to the observations, after which the N-level cloud profiles are converted to two slab clouds (TwoSlab; typically one for ice and one for water clouds). From these, one run of our fast cloud-representation model allows an improvement of the a priori cloud state by comparing the observed and model-simulated radiances in the thermal window channels. The retrieval yield is over 90 %, while the degrees of freedom correlate with the observed window channel brightness temperature (BT) which itself depends on the cloud optical depth. The cloud-representation and scattering package is benchmarked against radiances computed using a maximum random overlap (RMO) cloud scheme. All-sky infrared radiances measured by NASA's Atmospheric Infrared Sounder (AIRS) and NWP thermodynamic and cloud profiles from the European Centre for Medium-Range Weather Forecasts (ECMWF) forecast model are used in this paper.

Cloud characterization and clear-sky correction from Landsat-7

USGS Publications Warehouse

Cahalan, Robert F.; Oreopoulos, L.; Wen, G.; Marshak, S.; Tsay, S. -C.; DeFelice, Tom

2001-01-01

Landsat, with its wide swath and high resolution, fills an important mesoscale gap between atmospheric variations seen on a few kilometer scale by local surface instrumentation and the global view of coarser resolution satellites such as MODIS. In this important scale range, Landsat reveals radiative effects on the few hundred-meter scale of common photon mean-free-paths, typical of scattering in clouds at conservative (visible) wavelengths, and even shorter mean-free-paths of absorptive (near-infrared) wavelengths. Landsat also reveals shadowing effects caused by both cloud and vegetation that impact both cloudy and clear-sky radiances. As a result, Landsat has been useful in development of new cloud retrieval methods and new aerosol and surface retrievals that account for photon diffusion and shadowing effects. This paper discusses two new cloud retrieval methods: the nonlocal independent pixel approximation (NIPA) and the normalized difference nadir radiance method (NDNR). We illustrate the improvements in cloud property retrieval enabled by the new low gain settings of Landsat-7 and difficulties found at high gains. Then, we review the recently developed “path radiance” method of aerosol retrieval and clear-sky correction using data from the Department of Energy Atmospheric Radiation Measurement (ARM) site in Oklahoma. Nearby clouds change the solar radiation incident on the surface and atmosphere due to indirect illumination from cloud sides. As a result, if clouds are nearby, this extra side-illumination causes clear pixels to appear brighter, which can be mistaken for extra aerosol or higher surface albedo. Thus, cloud properties must be known in order to derive accurate aerosol and surface properties. A three-dimensional (3D) Monte Carlo (MC) radiative transfer simulation illustrates this point and suggests a method to subtract the cloud effect from aerosol and surface retrievals. The main conclusion is that cloud, aerosol, and surface retrievals are linked and must be treated as a combined system. Landsat provides the range of scales necessary to observe the 3D cloud radiative effects that influence joint surface-atmospheric retrievals.

The neuron net method for processing the clear pixels and method of the analytical formulas for processing the cloudy pixels of POLDER instrument images

NASA Astrophysics Data System (ADS)

Melnikova, I.; Mukai, S.; Vasilyev, A.

Data of remote measurements of reflected radiance with the POLDER instrument on board of ADEOS satellite are used for retrieval of the optical thickness, single scattering albedo and phase function parameter of cloudy and clear atmosphere. The method of perceptron neural network that from input values of multiangle radiance and Solar incident angle allows to obtain surface albedo, the optical thickness, single scattering albedo and phase function parameter in case of clear sky. Two last parameters are determined as optical average for atmospheric column. The calculation of solar radiance with using the MODTRAN-3 code with taking into account multiple scattering is accomplished for neural network learning. All mentioned parameters were randomly varied on the base of statistical models of possible measured parameters variation. Results of processing one frame of remote observation that consists from 150,000 pixels are presented. The methodology elaborated allows operative determining optical characteristics as cloudy as clear atmosphere. Further interpretation of these results gives the possibility to extract the information about total contents of atmospheric aerosols and absorbing gases in the atmosphere and create models of the real cloudiness An analytical method of interpretation that based on asymptotic formulas of multiple scattering theory is applied to remote observations of reflected radiance in case of cloudy pixel. Details of the methodology and error analysis were published and discussed earlier. Here we present results of data processing of pixel size 6x6 km In many studies the optical thickness is evaluated earlier in the assumption of the conservative scattering. But in case of true absorption in clouds the large errors in parameter obtained are possible. The simultaneous retrieval of two parameters at every wavelength independently is the advantage comparing with earlier studies. The analytical methodology is based on the transfer theory asymptotic formula inversion for optically thick stratus clouds. The model of horizontally infinite layer is considered. The slight horizontal heterogeneity is approximately taken into account. Formulas containing only the measured values of two-direction radiance and functions of solar and view angles were derived earlier. The 6 azimuth harmonics of reflection function are taken into account. The simple approximation of the cloud top boarder heterogeneity is used. The clouds, projecting upper the cloud top plane causes the increase of diffuse radiation in the incident flux. It is essential for calculation of radiative characteristics, which depends on lighting conditions. Escape and reflection functions describe this dependence for reflected radiance and local albedo of semi-infinite medium - for irradiance. Thus the functions depending on solar incident angle is to replace by their modifications. Firstly optical thickness of every pixel is obtained with simple formula assuming conservative scattering for all available view directions. Deviations between obtained values may be taken as a measure of the cloud top deviation from the plane. The special parameter is obtained, which takes into account the shadowing effect. Then single scattering albedo and optical thickness (with the true absorption assuming) are obtained for pairs of view directions with equal optical thickness. After that the averaging of values obtained and relative error evaluation is accomplished for all viewing directions of every pixel. The procedure is repeated for all wavelengths and pixels independently.

Adjustment errors of sunstones in the first step of sky-polarimetric Viking navigation: studies with dichroic cordierite/ tourmaline and birefringent calcite crystals

PubMed Central

Száz, Dénes; Farkas, Alexandra; Blahó, Miklós; Barta, András; Egri, Ádám; Kretzer, Balázs; Hegedüs, Tibor; Jäger, Zoltán; Horváth, Gábor

2016-01-01

According to an old but still unproven theory, Viking navigators analysed the skylight polarization with dichroic cordierite or tourmaline, or birefringent calcite sunstones in cloudy/foggy weather. Combining these sunstones with their sun-dial, they could determine the position of the occluded sun, from which the geographical northern direction could be guessed. In psychophysical laboratory experiments, we studied the accuracy of the first step of this sky-polarimetric Viking navigation. We measured the adjustment error e of rotatable cordierite, tourmaline and calcite crystals when the task was to determine the direction of polarization of white light as a function of the degree of linear polarization p. From the obtained error functions e(p), the thresholds p* above which the first step can still function (i.e. when the intensity change seen through the rotating analyser can be sensed) were derived. Cordierite is about twice as reliable as tourmaline. Calcite sunstones have smaller adjustment errors if the navigator looks for that orientation of the crystal where the intensity difference between the two spots seen in the crystal is maximal, rather than minimal. For higher p (greater than pcrit) of incident light, the adjustment errors of calcite are larger than those of the dichroic cordierite (pcrit=20%) and tourmaline (pcrit=45%), while for lower p (less than pcrit) calcite usually has lower adjustment errors than dichroic sunstones. We showed that real calcite crystals are not as ideal sunstones as it was believed earlier, because they usually contain scratches, impurities and crystal defects which increase considerably their adjustment errors. Thus, cordierite and tourmaline can also be at least as good sunstones as calcite. Using the psychophysical e(p) functions and the patterns of the degree of skylight polarization measured by full-sky imaging polarimetry, we computed how accurately the northern direction can be determined with the use of the Viking sun-dial under 10 different sky conditions at 61° latitude, which was one of the main Viking sailing routes. According to our expermiments, under clear skies, using calcite or cordierite or tourmaline sunstones, Viking sailors could navigate with net orientation errors |Σmax|≤3∘. Under overcast conditions, their net navigation error depends on the sunstone type: |Σmax(calcite)|≤6∘, |Σmax(cordierite)|≤10∘ and |Σmax(tourmaline)|≤17∘. PMID:26909167

Observations of temporal change of nighttime cloud cover from Himawari 8 and ground-based sky camera over Chiba, Japan

NASA Astrophysics Data System (ADS)

Lagrosas, N.; Gacal, G. F. B.; Kuze, H.

2017-12-01

Detection of nighttime cloud from Himawari 8 is implemented using the difference of digital numbers from bands 13 (10.4µm) and 7 (3.9µm). The digital number difference of -1.39x104 can be used as a threshold to separate clouds from clear sky conditions. To look at observations from the ground over Chiba, a digital camera (Canon Powershot A2300) is used to take images of the sky every 5 minutes at an exposure time of 5s at the Center for Environmental Remote Sensing, Chiba University. From these images, cloud cover values are obtained using threshold algorithm (Gacal, et al, 2016). Ten minute nighttime cloud cover values from these two datasets are compared and analyzed from 29 May to 05 June 2017 (20:00-03:00 JST). When compared with lidar data, the camera can detect thick high level clouds up to 10km. The results show that during clear sky conditions (02-03 June), both camera and satellite cloud cover values show 0% cloud cover. During cloudy conditions (05-06 June), the camera shows almost 100% cloud cover while satellite cloud cover values range from 60 to 100%. These low values can be attributed to the presence of low-level thin clouds ( 2km above the ground) as observed from National Institute for Environmental Studies lidar located inside Chiba University. This difference of cloud cover values shows that the camera can produce accurate cloud cover values of low level clouds that are sometimes not detected by satellites. The opposite occurs when high level clouds are present (01-02 June). Derived satellite cloud cover shows almost 100% during the whole night while ground-based camera shows cloud cover values that range from 10 to 100% during the same time interval. The fluctuating values can be attributed to the presence of thin clouds located at around 6km from the ground and the presence of low level clouds ( 1km). Since the camera relies on the reflected city lights, it is possible that the high level thin clouds are not observed by the camera but is observed by the satellite. Also, this condition constitutes layers of clouds that are not observed by each camera. The results of this study show that one instrument can be used to correct each other to provide better cloud cover values. These corrections is dependent on the height and thickness of the clouds. No correction is necessary when the sky is clear.

Quantifying errors in surface ozone predictions associated with clouds over the CONUS: a WRF-Chem modeling study using satellite cloud retrievals

NASA Astrophysics Data System (ADS)

Ryu, Young-Hee; Hodzic, Alma; Barre, Jerome; Descombes, Gael; Minnis, Patrick

2018-05-01

Clouds play a key role in radiation and hence O3 photochemistry by modulating photolysis rates and light-dependent emissions of biogenic volatile organic compounds (BVOCs). It is not well known, however, how much error in O3 predictions can be directly attributed to error in cloud predictions. This study applies the Weather Research and Forecasting with Chemistry (WRF-Chem) model at 12 km horizontal resolution with the Morrison microphysics and Grell 3-D cumulus parameterization to quantify uncertainties in summertime surface O3 predictions associated with cloudiness over the contiguous United States (CONUS). All model simulations are driven by reanalysis of atmospheric data and reinitialized every 2 days. In sensitivity simulations, cloud fields used for photochemistry are corrected based on satellite cloud retrievals. The results show that WRF-Chem predicts about 55 % of clouds in the right locations and generally underpredicts cloud optical depths. These errors in cloud predictions can lead to up to 60 ppb of overestimation in hourly surface O3 concentrations on some days. The average difference in summertime surface O3 concentrations derived from the modeled clouds and satellite clouds ranges from 1 to 5 ppb for maximum daily 8 h average O3 (MDA8 O3) over the CONUS. This represents up to ˜ 40 % of the total MDA8 O3 bias under cloudy conditions in the tested model version. Surface O3 concentrations are sensitive to cloud errors mainly through the calculation of photolysis rates (for ˜ 80 %), and to a lesser extent to light-dependent BVOC emissions. The sensitivity of surface O3 concentrations to satellite-based cloud corrections is about 2 times larger in VOC-limited than NOx-limited regimes. Our results suggest that the benefits of accurate predictions of cloudiness would be significant in VOC-limited regions, which are typical of urban areas.

Observed and modeled patterns of covariability between low-level cloudiness and the structure of the trade-wind layer

DOE PAGES

Nuijens, Louise; Medeiros, Brian; Sandu, Irina; ...

2015-11-06

We present patterns of covariability between low-level cloudiness and the trade-wind boundary layer structure using long-term measurements at a site representative of dynamical regimes with moderate subsidence or weak ascent. We compare these with ECMWF’s Integrated Forecast System and 10 CMIP5 models. By using single-time step output at a single location, we find that models can produce a fairly realistic trade-wind layer structure in long-term means, but with unrealistic variability at shorter-time scales. The unrealistic variability in modeled cloudiness near the lifting condensation level (LCL) is due to stronger than observed relationships with mixed-layer relative humidity (RH) and temperature stratificationmore » at the mixed-layer top. Those relationships are weak in observations, or even of opposite sign, which can be explained by a negative feedback of convection on cloudiness. Cloudiness near cumulus tops at the tradewind inversion instead varies more pronouncedly in observations on monthly time scales, whereby larger cloudiness relates to larger surface winds and stronger trade-wind inversions. However, these parameters appear to be a prerequisite, rather than strong controlling factors on cloudiness, because they do not explain submonthly variations in cloudiness. Models underestimate the strength of these relationships and diverge in particular in their responses to large-scale vertical motion. No model stands out by reproducing the observed behavior in all respects. As a result, these findings suggest that climate models do not realistically represent the physical processes that underlie the coupling between trade-wind clouds and their environments in present-day climate, which is relevant for how we interpret modeled cloud feedbacks.« less

Optimized fractional cloudiness determination from five ground-based remote sensing techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boers, R.; de Haij, M. J.; Wauben, W.M.F.

2010-12-23

A one-year record of fractional cloudiness at 10 minute intervals was generated for the Cabauw Experimental Site for Atmospheric Research [CESAR] (51°58’N, 4° 55’E) using an integrated assessment of five different observational methods. The five methods are based on active as well as passive systems and use either a hemispheric or column remote sensing technique. The one-year instrumental cloudiness data were compared against a 30 year climatology of Observer data in the vicinity of CESAR [1971- 2000]. In the intermediate 2 - 6 octa range, most instruments, but especially the column methods, report lower frequency of occurrence of cloudiness thanmore » the absolute minimum values from the 30 year Observer climatology. At night, the Observer records less clouds in the 1, 2 octa range than during the day, while the instruments registered more clouds. During daytime the Observer also records much more 7 octa cloudiness than the instruments. One column method combining a radar with a lidar outstrips all other techniques in recording cloudiness, even up to height in excess of 9 km. This is mostly due to the high sensitivity of the radar that is used in the technique. A reference algorithm was designed to derive a continuous and optimized record of fractional cloudiness. Output from individual instruments were weighted according to the cloud base height reported at the observation time; the larger the height, the lower the weight. The algorithm was able to provide fractional cloudiness observations every 10 minutes for 98% of the total period of 12 months [15 May 2008 - 14 May 2009].« less

Observed and modeled patterns of covariability between low-level cloudiness and the structure of the trade-wind layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nuijens, Louise; Medeiros, Brian; Sandu, Irina

We present patterns of covariability between low-level cloudiness and the trade-wind boundary layer structure using long-term measurements at a site representative of dynamical regimes with moderate subsidence or weak ascent. We compare these with ECMWF’s Integrated Forecast System and 10 CMIP5 models. By using single-time step output at a single location, we find that models can produce a fairly realistic trade-wind layer structure in long-term means, but with unrealistic variability at shorter-time scales. The unrealistic variability in modeled cloudiness near the lifting condensation level (LCL) is due to stronger than observed relationships with mixed-layer relative humidity (RH) and temperature stratificationmore » at the mixed-layer top. Those relationships are weak in observations, or even of opposite sign, which can be explained by a negative feedback of convection on cloudiness. Cloudiness near cumulus tops at the tradewind inversion instead varies more pronouncedly in observations on monthly time scales, whereby larger cloudiness relates to larger surface winds and stronger trade-wind inversions. However, these parameters appear to be a prerequisite, rather than strong controlling factors on cloudiness, because they do not explain submonthly variations in cloudiness. Models underestimate the strength of these relationships and diverge in particular in their responses to large-scale vertical motion. No model stands out by reproducing the observed behavior in all respects. As a result, these findings suggest that climate models do not realistically represent the physical processes that underlie the coupling between trade-wind clouds and their environments in present-day climate, which is relevant for how we interpret modeled cloud feedbacks.« less

Cloudy - simulating the non-equilibrium microphysics of gas and dust, and its observed spectrum

NASA Astrophysics Data System (ADS)

Ferland, Gary J.

2014-01-01

Cloudy is an open-source plasma/spectral simulation code, last described in the open-access journal Revista Mexicana (Ferland et al. 2013, 2013RMxAA..49..137F). The project goal is a complete simulation of the microphysics of gas and dust over the full range of density, temperature, and ionization that we encounter in astrophysics, together with a prediction of the observed spectrum. Cloudy is one of the more widely used theory codes in astrophysics with roughly 200 papers citing its documentation each year. It is developed by graduate students, postdocs, and an international network of collaborators. Cloudy is freely available on the web at trac.nublado.org, the user community can post questions on http://groups.yahoo.com/neo/groups/cloudy_simulations/info, and summer schools are organized to learn more about Cloudy and its use (http://cloud9.pa.uky.edu gary/cloudy/CloudySummerSchool/). The code’s widespread use is possible because of extensive automatic testing. It is exercised over its full range of applicability whenever the source is changed. Changes in predicted quantities are automatically detected along with any newly introduced problems. The code is designed to be autonomous and self-aware. It generates a report at the end of a calculation that summarizes any problems encountered along with suggestions of potentially incorrect boundary conditions. This self-monitoring is a core feature since the code is now often used to generate large MPI grids of simulations, making it impossible for a user to verify each calculation by hand. I will describe some challenges in developing a large physics code, with its many interconnected physical processes, many at the frontier of research in atomic or molecular physics, all in an open environment.

A Study on New Song of the Sky Pacers

NASA Astrophysics Data System (ADS)

Ahn, Sang-Hyeon

2009-12-01

We investigated `Song of the Sky Pacers, Adopted to the New Methods' (新法步天歌), the latest version of Joseon's `Song of the Sky Pacers' (步天歌). Due to the influence of new knowledge on Chinese asterisms imported from the Ching dynasty, `Song of the Sky Pacers with New Star-Charts' was written in the eighteenth century. However, the disagreement between song and star-charts was causing confusion in practical applications such as Joseon's national examination for selecting astronomers. In order to improve this situation, Royal Observatory of the Joseon dynasty (觀象監) published `Song of the Sky Pacers, Adopted to the New Methods' based upon star-charts and song in the Sequel of I-Hsiang-K'ao-ch'eng (欽定儀象考成續編). The New Song was edited by a middle-class professional astronomer Yi Jun-yang (李俊養), and corrected by a nobleman Nam Byeong-gil (南秉吉). We establish a brief biography of Yi Jun-yang. The New Song preserves the genuine characteristics of previous Joseon's Song including the format of title of each lunar mansion and description on the location of the Milky Way in the asterisms. The description of the Milky Way was newly written based on the data in volume 31 and 32 of the Sequel of I-Hsiang-K'ao-ch'eng.

Improved Determination of Surface and Atmospheric Temperatures Using Only Shortwave AIRS Channels: The AIRS Version 6 Retrieval Algorithm

NASA Technical Reports Server (NTRS)

Susskind, Joel; Blaisdell, John; Iredell, Lena

2010-01-01

AIRS was launched on EOS Aqua on May 4, 2002 together with ASMU-A and HSB to form a next generation polar orbiting infrared and microwave atmosphere sounding system (Pagano et al 2003). The theoretical approach used to analyze AIRS/AMSU/HSB data in the presence of clouds in the AIRS Science Team Version 3 at-launch algorithm, and that used in the Version 4 post-launch algorithm, have been published previously. Significant theoretical and practical improvements have been made in the analysis of AIRS/AMSU data since the Version 4 algorithm. Most of these have already been incorporated in the AIRS Science Team Version 5 algorithm (Susskind et al 2010), now being used operationally at the Goddard DISC. The AIRS Version 5 retrieval algorithm contains three significant improvements over Version 4. Improved physics in Version 5 allowed for use of AIRS clear column radiances (R(sub i)) in the entire 4.3 micron CO2 absorption band in the retrieval of temperature profiles T(p) during both day and night. Tropospheric sounding 15 micron CO2 observations were used primarily in the generation of clear column radiances (R(sub i)) for all channels. This new approach allowed for the generation of accurate Quality Controlled values of R(sub i) and T(p) under more stressing cloud conditions. Secondly, Version 5 contained a new methodology to provide accurate case-by-case error estimates for retrieved geophysical parameters and for channel-by-channel clear column radiances. Thresholds of these error estimates are used in a new approach for Quality Control. Finally, Version 5 contained for the first time an approach to provide AIRS soundings in partially cloudy conditions that does not require use of any microwave data. This new AIRS Only sounding methodology was developed as a backup to AIRS Version 5 should the AMSU-A instrument fail. Susskind et al 2010 shows that Version 5 AIRS Only sounding are only slightly degraded from the AIRS/AMSU soundings, even at large fractional cloud cover.

Updated laser safety & hazard analysis for the ARES laser system based on the 2007 ANSI Z136.1 standard.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Augustoni, Arnold L.

A laser safety and hazard analysis was performed for the temperature stabilized Big Sky Laser Technology (BSLT) laser central to the ARES system based on the 2007 version of the American National Standards Institutes (ANSI) Standard Z136.1, for Safe Use of Lasers and the 2005 version of the ANSI Standard Z136.6, for Safe Use of Lasers Outdoors. The ARES laser system is a Van/Truck based mobile platform, which is used to perform laser interaction experiments and tests at various national test sites.

Solar energy distribution over Egypt using cloudiness from Meteosat photos

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mosalam Shaltout, M.A.; Hassen, A.H.

1990-01-01

In Egypt, there are 10 ground stations for measuring the global solar radiation, and five stations for measuring the diffuse solar radiation. Every day at noon, the Meteorological Authority in Cairo receives three photographs of cloudiness over Egypt from the Meteosat satellite, one in the visible, and two in the infra-red bands (10.5-12.5 {mu}m) and (5.7-7.1 {mu}m). The monthly average cloudiness for 24 sites over Egypt are measured and calculated from Meteosat observations during the period 1985-1986. Correlation analysis between the cloudiness observed by Meteosat and global solar radiation measured from the ground stations is carried out. It is foundmore » that, the correlation coefficients are about 0.90 for the simple linear regression, and increase for the second and third degree regressions. Also, the correlation coefficients for the cloudiness with the diffuse solar radiation are about 0.80 for the simple linear regression, and increase for the second and third degree regression. Models and empirical relations for estimating the global and diffuse solar radiation from Meteosat cloudiness data over Egypt are deduced and tested. Seasonal maps for the global and diffuse radiation over Egypt are carried out.« less

VizieR Online Data Catalog: The FIRST Survey Catalog, Version 2014Dec17 (Helfand+ 2015)

NASA Astrophysics Data System (ADS)

Helfand, D. J.; White, R. L.; Becker, R. H.

2015-05-01

The Faint Images of the Radio Sky at Twenty centimeters (FIRST) began in 1993. It uses the VLA (Very Large Array, a facility of the National Radio Observatory (NRAO)) at a frequency of 1.4GHz, and it is slated to 10,000 deg2 of the North and South Galactic Caps, to a sensitivity of about 1mJy with an angular resolution of about 5''. The images produced by an automated mapping pipeline have pixels of 1.8'', a typical rms of 0.15mJy, and a resolution of 5''; the images are available on the Internet (see the FIRST home page at http://sundog.stsci.edu/ for details). The source catalogue is derived from the images. This catalog from the 1993 through 2011 observations contains 946,432 sources from the north and south Galactic caps. It covers a total of 10,575 square degrees of the sky (8444 square degrees in the north and 2131 square degrees in the south). In this version of the catalog, images taken in the the new EVLA configuration have been re-reduced using shallower CLEAN thresholds in order to reduce the "CLEAN bias" in those images. Also, the EVLA images are not co-added with older VLA images to avoid problems resulting from the different frequencies and noise properties of the configurations. That leads to small gaps in the sky coverage at boundaries between the EVLA and VLA regions. As a result, the area covered by this release of the catalog is about 60 square degrees smaller than the earlier release of the catalog (13Jun05, also available here as the "first13.dat" file), and the total number of sources is reduced by nearly 25,000. The previous version of the catalog does have sources in the overlap regions, but their flux densities are considered unreliable due to calibration errors. The flux densities should be more accurate in this catalog, biases are smaller, and the incidence of spurious sources is also reduced. Over most of the survey area, the detection limit is 1 mJy. A region along the equatorial strip (RA=21.3 to 3.3hr, Dec=-1 to 1deg) has a deeper detection threshold because two epochs of observation were combined. The typical detection threshold in this region is 0.75mJy. There are approximately 4,500 sources below the 1mJy threshold used for most previous versions of the catalog. The previous versions http://sundog.stsci.edu/first/catalogs/ (2 data files).

The History of the CONCAM Project: All Sky Monitors in the Digital Age

NASA Astrophysics Data System (ADS)

Nemiroff, Robert; Shamir, Lior; Pereira, Wellesley

2018-01-01

The CONtinuous CAMera (CONCAM) project, which ran from 2000 to (about) 2008, consisted of real-time, Internet-connected, fisheye cameras located at major astronomical observatories. At its peak, eleven CONCAMs around the globe monitored most of the night sky, most of the time. Initially designed to search for transients and stellar variability, CONCAMs gained initial notoriety as cloud monitors. As such, CONCAMs made -- and its successors continue to make -- ground-based astronomy more efficient. The original, compact, fisheye-observatory-in-a-suitcase design underwent several iterations, starting with CONCAM0 and with the last version dubbed CONCAM3. Although the CONCAM project itself concluded after centralized funding diminished, today more locally-operated, commercially-designed, CONCAM-like devices operate than ever before. It has even been shown that modern smartphones can operate in a CONCAM-like mode. It is speculated that the re-instatement of better global coordination of current wide-angle sky monitors could lead to better variability monitoring of the brightest stars and transients.

Migrating songbirds tested in computer-controlled Emlen funnels use stellar cues for a time-independent compass.

PubMed

Mouritsen, H; Larsen, O N

2001-11-01

This paper investigates how young pied flycatchers, Ficedula hypoleuca, and blackcaps, Sylvia atricapilla, interpret and use celestial cues. In order to record these data, we developed a computer-controlled version of the Emlen funnel, which enabled us to make detailed temporal analyses. First, we showed that the birds use a star compass. Then, we tested the birds under a stationary planetarium sky, which simulated the star pattern of the local sky at 02:35 h for 11 consecutive hours of the night, and compared the birds' directional choices as a function of time with the predictions from five alternative stellar orientation hypotheses. The results supported the hypothesis suggesting that birds use a time-independent star compass based on learned geometrical star configurations to pinpoint the rotational point of the starry sky (north). In contrast, neither hypotheses suggesting that birds use the stars for establishing their global position and then perform true star navigation nor those suggesting the use of a time-compensated star compass were supported.

Recent Updates to the GEOS-5 Linear Model

NASA Technical Reports Server (NTRS)

Holdaway, Dan; Kim, Jong G.; Errico, Ron; Gelaro, Ronald; Mahajan, Rahul

2014-01-01

Global Modeling and Assimilation Office (GMAO) is close to having a working 4DVAR system and has developed a linearized version of GEOS-5.This talk outlines a series of improvements made to the linearized dynamics, physics and trajectory.Of particular interest is the development of linearized cloud microphysics, which provides the framework for 'all-sky' data assimilation.

Documentation for the machine-readable version of The Revised AFGL Infrared Sky Survey Catalog (Price and Murdock 1983)

NASA Technical Reports Server (NTRS)

Warren, W. H., Jr.

1984-01-01

A detailed description of the machine-readable catalog as it is currently being distributed from the Astronomical Data Center is given. The catalog contains a main data file of 2970 sources and a supplemental file of 3176 sources measured at wavelengths of 4.2, 11, 20 and 27 microns.

A Failure to Communicate

ERIC Educational Resources Information Center

Fredette, Michelle

2011-01-01

In April, Asia officially ran out of Internet Protocol (IP) version 4 addresses--the computer equivalent of running out of telephone numbers. Over the next couple of years, the rest of the world will also run dry. Yet, unlike the Y2K bug that had some people convinced the sky would fall, this particular problem is generating little more than tired…

Improved Surface Parameter Retrievals using AIRS/AMSU Data

NASA Technical Reports Server (NTRS)

Susskind, Joel; Blaisdell, John

2008-01-01

The AIRS Science Team Version 5.0 retrieval algorithm became operational at the Goddard DAAC in July 2007 generating near real-time products from analysis of AIRS/AMSU sounding data. This algorithm contains many significant theoretical advances over the AIRS Science Team Version 4.0 retrieval algorithm used previously. Two very significant developments of Version 5 are: 1) the development and implementation of an improved Radiative Transfer Algorithm (RTA) which allows for accurate treatment of non-Local Thermodynamic Equilibrium (non-LTE) effects on shortwave sounding channels; and 2) the development of methodology to obtain very accurate case by case product error estimates which are in turn used for quality control. These theoretical improvements taken together enabled a new methodology to be developed which further improves soundings in partially cloudy conditions. In this methodology, longwave C02 channel observations in the spectral region 700 cm(exp -1) to 750 cm(exp -1) are used exclusively for cloud clearing purposes, while shortwave C02 channels in the spectral region 2195 cm(exp -1) 2395 cm(exp -1) are used for temperature sounding purposes. This allows for accurate temperature soundings under more difficult cloud conditions. This paper further improves on the methodology used in Version 5 to derive surface skin temperature and surface spectral emissivity from AIRS/AMSU observations. Now, following the approach used to improve tropospheric temperature profiles, surface skin temperature is also derived using only shortwave window channels. This produces improved surface parameters, both day and night, compared to what was obtained in Version 5. These in turn result in improved boundary layer temperatures and retrieved total O3 burden.

Nanopaleomagnetism of Meteoritic Fe-Ni: the Potential for Time-Resolved Remanence Records within the Cloudy Zone

NASA Astrophysics Data System (ADS)

Harrison, R. J.; Bryson, J. F.; Kasama, T.; Church, N. S.; Herrero Albillos, J.; Kronast, F.; Ghidini, M.; Redfern, S. A.; van der Laan, G.; Tyliszczak, T.

2013-12-01

Paleomagnetic signals recorded by meteorites provide compelling evidence that the liquid cores of differentiated asteroids generated magnetic dynamo fields. Here we argue that magnetic nanostructures unique to meteoritic Fe-Ni metal are capable of carrying a time-resolved record of asteroid dynamo activity, a prospect that could revolutionise our understanding of the thermochemical conditions of differentiated bodies in the early solar system. Using a combination of high-resolution magnetic imaging techniques (including electron holography, magnetic force microscopy, X-ray photoemission electron microscopy and scanning transmission X-ray microscopy) we reveal the origins of the dramatic changes in magnetic properties that are associated with the transition from kamacite - tetrataenite rim - cloudy zone - plessite, typical of Fe-Ni intergrowths. The cloudy zone is comprised of nanoscale islands of tetrataenite (FeNi) coherently intergrown with a hitherto unobserved soft magnetic phase (Fe3Ni). The tetrataenite island diameter decreases with increasing lateral distance from the tetrataenite rim. Exchange coupling between the hard tetrataenite islands and the soft matrix phase leads to an exchange spring effect that lowers the tetrataenite switching field and causes a systematic variation in microcoercivity throughout the cloudy zone. The cloudy zone displays a complex interlocking magnetic domain pattern caused by uniaxial single domain tetrataenite islands with easy axes distributed along all three of the possible <100> crystallographic orientations. The coarse and intermediate cloudy zones contain a random distribution of all three easy axes. The fine cloudy zone, on the other hand, contains one dominant easy axis direction. This easy axis distribution suggests that strong interaction fields (either magnetic or stress) were present in this region at the time of tetrataenite formation, which likely originated from the neighbouring plessite. The easy axis distribution in the coarse and intermediate cloudy zone indicates a lack of interaction fields present at the time of formation, implying that deviations from randomness could be used to detect the presence of an external (e.g. dynamo) field. Zoned metallic grains within chondritic meteorites originating from the top ~5-10% of a differentiated asteroid may have formed their cloudy zones while the core was generating a dynamo field. In this case, as the cloudy zone formed continuously over a period of 10-100 Ma it had the potential to encode sequential information regarding the dynamo field as the spinodal microstructure developed laterally. Thus the local magnetic structure as a function of position throughout the cloudy zone could relate to the time dependence of an asteroid dynamo field. The experimental and analysis methods presented in this study could, in principle, be used to measure the relative strength (proportion of dominant easy axis) and direction (direction of dominant easy axis) of an asteroid dynamo field over ~100 Ma.

Modeling dust as component minerals in the Community Atmosphere Model: development of framework and impact on radiative forcing

DOE PAGES

Scanza, R. A.; Mahowald, N.; Ghan, S.; ...

2014-07-02

The mineralogy of desert dust is important due to its effect on radiation, clouds and biogeochemical cycling of trace nutrients. This study presents the simulation of dust radiative forcing as a function of both mineral composition and size at the global scale using mineral soil maps for estimating emissions. Externally mixed mineral aerosols in the bulk aerosol module in the Community Atmosphere Model version 4 (CAM4) and internally mixed mineral aerosols in the modal aerosol module in the Community Atmosphere Model version 5.1 (CAM5) embedded in the Community Earth System Model version 1.0.5 (CESM) are speciated into common mineral componentsmore » in place of total dust. The simulations with mineralogy are compared to available observations of mineral atmospheric distribution and deposition along with observations of clear-sky radiative forcing efficiency. Based on these simulations, we estimate the all-sky direct radiative forcing at the top of the atmosphere as +0.05 W m −2 for both CAM4 and CAM5 simulations with mineralogy and compare this both with simulations of dust in release versions of CAM4 and CAM5 (+0.08 and +0.17 W m −2) and of dust with optimized optical properties, wet scavenging and particle size distribution in CAM4 and CAM5, −0.05 and −0.17 W m −2, respectively. The ability to correctly include the mineralogy of dust in climate models is hindered by its spatial and temporal variability as well as insufficient global in-situ observations, incomplete and uncertain source mineralogies and the uncertainties associated with data retrieved from remote sensing methods.« less

Modeling dust as component minerals in the Community Atmosphere Model: development of framework and impact on radiative forcing

DOE PAGES

Scanza, Rachel; Mahowald, N.; Ghan, Steven J.; ...

2015-01-01

The mineralogy of desert dust is important due to its effect on radiation, clouds and biogeochemical cycling of trace nutrients. This study presents the simulation of dust radiative forcing as a function of both mineral composition and size at the global scale, using mineral soil maps for estimating emissions. Externally mixed mineral aerosols in the bulk aerosol module in the Community Atmosphere Model version 4 (CAM4) and internally mixed mineral aerosols in the modal aerosol module in the Community Atmosphere Model version 5.1 (CAM5) embedded in the Community Earth System Model version 1.0.5 (CESM) are speciated into common mineral componentsmore » in place of total dust. The simulations with mineralogy are compared to available observations of mineral atmospheric distribution and deposition along with observations of clear-sky radiative forcing efficiency. Based on these simulations, we estimate the all-sky direct radiative forcing at the top of the atmosphere as + 0.05 Wm⁻² for both CAM4 and CAM5 simulations with mineralogy. We compare this to the radiative forcing from simulations of dust in release versions of CAM4 and CAM5 (+0.08 and +0.17 Wm⁻²) and of dust with optimized optical properties, wet scavenging and particle size distribution in CAM4 and CAM5, -0.05 and -0.17 Wm⁻², respectively. The ability to correctly include the mineralogy of dust in climate models is hindered by its spatial and temporal variability as well as insufficient global in situ observations, incomplete and uncertain source mineralogies and the uncertainties associated with data retrieved from remote sensing methods.« less

A Case-study on Turbulence in a Stratocumulus Topped Marine Boundary Layer Observed during VOCALS-Rex

NASA Astrophysics Data System (ADS)

Ghate, V. P.; Albrecht, B. A.; Fairall, C. W.; Miller, M. A.; Brewer, A.

2010-12-01

Turbulence in the stratocumulus topped marine boundary layer (BL) is an important factor that is closely connected to both the cloud macro- and micro-physical characteristics, which can substantially affect their radiaitve properties. Data collected by ship borne instruments on the R/V Ronald H. Brown on November 27, 2008 as a part of the VAMOS Ocean-Cloud-Atmosphere-Land-Study Regional Experiment (VOCALS-Rex) are analyzed to study the turbulence structure of a stratocumulus topped marine BL. The first half of the analyzed 24 hour period was characterized by a coupled BL topped by a precipitating stratocumulus cloud; the second half had clear sky conditions with a decoupled BL. The motion stabilized vertically pointing W-band Doppler cloud radar reported the full Doppler spectrum at a temporal and spatial resolution of 3 Hz and 25 m respectively. The collocated motion stabilized Doppler lidar was operating at 2 micron wavelength and reported the Signal to Noise Ratio (SNR) and Doppler velocity at temporal and spatial resolution of 2 Hz and 30 m respectively. Data from the cloud Doppler radar and Doppler lidar were combined to yield the turbulence structure of entire BL in both cloudy and clear sky conditions. Retrievals were performed to remove the contribution of precipitating drizzle drops to the mean Doppler velocity measured by the radar. Hourly profiles of vertical velocity variance suggested high BL variance during coupled BL conditions and low variance during decoupled BL conditions. Some of the terms in second and third moment budget of vertical velocity are calculated and their diurnal evolution is explored.

Heating Rate of Light Absorbing Aerosols: Time-Resolved Measurements, the Role of Clouds, and Source Identification.

PubMed

Ferrero, Luca; Močnik, Griša; Cogliati, Sergio; Gregorič, Asta; Colombo, Roberto; Bolzacchini, Ezio

2018-03-20

Light absorbing aerosols (LAA) absorb sunlight and heat the atmosphere. This work presents a novel methodology to experimentally quantify the heating rate (HR) induced by LAA into an atmospheric layer. Multiwavelength aerosol absorption measurements were coupled with spectral measurements of the direct, diffuse and surface reflected radiation to obtain highly time-resolved measurements of HR apportioned in the context of LAA species (black carbon, BC; brown carbon, BrC; dust), sources (fossil fuel, FF; biomass burning, BB), and as a function of cloudiness. One year of continuous and time-resolved measurements (5 min) of HR were performed in the Po Valley. We experimentally determined (1) the seasonal behavior of HR (winter 1.83 ± 0.02 K day -1 ; summer 1.04 ± 0.01 K day -1 ); (2) the daily cycle of HR (asymmetric, with higher values in the morning than in the afternoon); (3) the HR in different sky conditions (from 1.75 ± 0.03 K day -1 in clear sky to 0.43 ± 0.01 K day -1 in complete overcast); (4) the apportionment to different sources: HR FF (0.74 ± 0.01 K day -1 ) and HR BB (0.46 ± 0.01 K day -1 ); and (4) the HR of BrC (HR BrC : 0.15 ± 0.01 K day -1 , 12.5 ± 0.6% of the total) and that of BC (HR BC : 1.05 ± 0.02 K day -1 ; 87.5 ± 0.6% of the total).

Environmental cues to UV radiation and personal sun protection in outdoor winter recreation.

PubMed

Andersen, Peter A; Buller, David B; Walkosz, Barbara J; Scott, Michael D; Maloy, Julie A; Cutter, Gary R; Dignan, Mark D

2010-11-01

To predict the prevalence of UV radiation (hereinafter, UV) at North American ski resorts using temporal, seasonal, altitudinal, and meteorological factors and associate UV with a set of adult sun protection behaviors. Ultraviolet radiation observations and cross-sectional survey of adults on sun protection were collected. Data were collected at 32 high-altitude ski areas located in western North America from 2001 through 2003. The sample consisted of 3937 adult skiers or snowboarders. Measurements of direct, reflected, and diffuse UV were performed at 487 measurement points using handheld meters and combined with self-reported and observed sun protection assessed for adults interviewed on chairlifts. The strongest predictors of UV were temporal proximity to noon, deviation from winter solstice, and clear skies. By contrast, altitude and latitude had more modest associations with UV and temperature had a small positive relationship with UV. Guest sun safety was inconsistently associated with UV: UV was positively related to adults wearing more sunscreen, reapplying it after 2 hours, and wearing protective eyewear, but fewer adults exhibited many of the other sun protection behaviors, such as wearing hats and protective clothing or using lip balm, on days when UV was elevated. Guests took more sun safety precautions on clear-sky days but took steps to maintain body warmth on inclement days. In future sun safety promotions, adults should be encouraged to wear sunscreen on cloudy days because UV is still high and conditions can change rapidly. They need reminders to rely more on season and time of day when judging UV and the need for sun safety.

Estimate of Boundary-Layer Depth Over Beijing, China, Using Doppler Lidar Data During SURF-2015

NASA Astrophysics Data System (ADS)

Huang, Meng; Gao, Zhiqiu; Miao, Shiguang; Chen, Fei; LeMone, Margaret A.; Li, Ju; Hu, Fei; Wang, Linlin

2017-03-01

Planetary boundary-layer (PBL) structure was investigated using observations from a Doppler lidar and the 325-m Institute of Atmospheric Physics (IAP) meteorological tower in the centre of Beijing during the summer 2015 Study of Urban-impacts on Rainfall and Fog/haze (SURF-2015) field campaign. Using six fair-weather days of lidar and tower data under clear to cloudy skies, we evaluate the ability of the Doppler lidar to probe the urban boundary-layer structure, and then propose a composite method for estimating the diurnal cycle of the PBL depth using the Doppler lidar. For the convective boundary layer (CBL), a threshold method using vertical velocity variance (σ _w^2 >0.1 m2s^{-2}) is used, since it provides more reliable CBL depths than a conventional maximum wind-shear method. The nocturnal boundary-layer (NBL) depth is defined as the height at which σ _w^2 decreases to 10 % of its near-surface maximum minus a background variance. The PBL depths determined by combining these methods have average values ranging from ≈ 270 to ≈ 1500 m for the six days, with the greatest maximum depths associated with clear skies. Release of stored and anthropogenic heat contributes to the maintenance of turbulence until late evening, keeping the NBL near-neutral and deeper at night than would be expected over a natural surface. The NBL typically becomes more shallow with time, but grows in the presence of low-level nocturnal jets. While current results are promising, data over a broader range of conditions are needed to fully develop our PBL-depth algorithms.

Thin-film-based CdTe photovoltaic module characterization: measurements and energy prediction improvement.

PubMed

Lay-Ekuakille, A; Arnesano, A; Vergallo, P

2013-01-01

Photovoltaic characterization is a topic of major interest in the field of renewable energy. Monocrystalline and polycrystalline modules are mostly used and, hence characterized since many laboratories have data of them. Conversely, cadmium telluride (CdTe), as thin-film module are, in some circumstances, difficult to be used for energy prediction. This work covers outdoor testing of photovoltaic modules, in particular that regarding CdTe ones. The scope is to obtain temperature coefficients that best predict the energy production. A First Solar (K-275) module has been used for the purposes of this research. Outdoor characterizations were performed at Department of Innovation Engineering, University of Salento, Lecce, Italy. The location of Lecce city represents a typical site in the South Italy. The module was exposed outdoor and tested under clear sky conditions as well as under cloudy sky ones. During testing, the global-inclined irradiance varied between 0 and 1500 W/m(2). About 37,000 I-V characteristics were acquired, allowing to process temperature coefficients as a function of irradiance and ambient temperature. The module was characterized by measuring the full temperature-irradiance matrix in the range from 50 to 1300 W/m(2) and from -1 to 40 W/m(2) from October 2011 to February 2012. Afterwards, the module energy output, under real conditions, was calculated with the "matrix method" of SUPSI-ISAAC and the results were compared with the five months energy output data of the same module measured with the outdoor energy yield facility in Lecce.

Out of the Dust, A Planet is Born Artist Concept

NASA Image and Video Library

2004-05-27

In this artist's conception, a possible newfound planet spins through a clearing in a nearby star's dusty, planet-forming disc. This clearing was detected around the star CoKu Tau 4 by NASA's Spitzer Space Telescope. Astronomers believe that an orbiting massive body, like a planet, may have swept away the star's disc material, leaving a central hole. The possible planet is theorized to be at least as massive as Jupiter, and may have a similar appearance to what the giant planets in our own solar system looked like billions of years ago. A graceful ring, much like Saturn's, spins high above the planet's cloudy atmosphere. The ring is formed from countless small orbiting particles of dust and ice, leftovers from the initial gravitational collapse that formed the possible giant planet. If we were to visit a planet like this, we would have a very different view of the universe. The sky, instead of being the familiar dark expanse lit by distant stars, would be dominated by the thick disc of dust that fills this young planetary system. The view looking toward CoKu Tau 4 would be relatively clear, as the dust in the interior of the disc has fallen into the accreting star. A bright band would seem to surround the central star, caused by light scattered back by the dust in the disc. Looking away from CoKu Tau 4, the dusty disc would appear dark, blotting out light from all the stars in the sky except those which lie well above the plane of the disc. http://photojournal.jpl.nasa.gov/catalog/PIA05988

Thin-film-based CdTe photovoltaic module characterization: Measurements and energy prediction improvement

NASA Astrophysics Data System (ADS)

Lay-Ekuakille, A.; Arnesano, A.; Vergallo, P.

2013-01-01

Photovoltaic characterization is a topic of major interest in the field of renewable energy. Monocrystalline and polycrystalline modules are mostly used and, hence characterized since many laboratories have data of them. Conversely, cadmium telluride (CdTe), as thin-film module are, in some circumstances, difficult to be used for energy prediction. This work covers outdoor testing of photovoltaic modules, in particular that regarding CdTe ones. The scope is to obtain temperature coefficients that best predict the energy production. A First Solar (K-275) module has been used for the purposes of this research. Outdoor characterizations were performed at Department of Innovation Engineering, University of Salento, Lecce, Italy. The location of Lecce city represents a typical site in the South Italy. The module was exposed outdoor and tested under clear sky conditions as well as under cloudy sky ones. During testing, the global-inclined irradiance varied between 0 and 1500 W/m2. About 37 000 I-V characteristics were acquired, allowing to process temperature coefficients as a function of irradiance and ambient temperature. The module was characterized by measuring the full temperature-irradiance matrix in the range from 50 to 1300 W/m2 and from -1 to 40 W/m2 from October 2011 to February 2012. Afterwards, the module energy output, under real conditions, was calculated with the "matrix method" of SUPSI-ISAAC and the results were compared with the five months energy output data of the same module measured with the outdoor energy yield facility in Lecce.

A search at two eclipses for short-period waves that heat the corona

NASA Astrophysics Data System (ADS)

Pasachoff, Jay M.; Babcock, Bryce A.; Russell, Kevin D.; McConnochie, Timothy H.; Diaz, J. Sebastian

2000-08-01

As part of a study of the cause of solar coronal heating, we searched for high-frequency (~1 Hz) intensity oscillations in coronal loops in the [Fexiv] coronal green line. We summarize results from observations made at the 3 November 1994, total solar eclipse from the International Astronomical Union site in Putre, Chile, through partly cloudy skies, and at the 26 February 1998 total solar eclipse from Nord, Aruba, through clear skies. We discuss the image reduction and analysis of two simultaneous series of coronal CCD images digitized at 10 Hz for a total time of 160 s in Chile. One series of images was taken through a filter isolating the 5303 Å[Fexiv] coronal green line and the other through a 100 Å filter in the nearby K-corona continuum. We then discuss the modifications made for the 1998 eclipse, and the image reduction and analysis for those image sequences. After standard calibrations and image alignment of both data sets, we use Fourier analysis to search in the [Fexiv] channel for intensity oscillations in loops at the base of the corona. Such oscillations in the 1-Hz range are predicted as a result of density fluctuations from the resonant absorption of MHD waves. The dissipation of a significant amount of mechanical energy from the photosphere into the corona through this mechanism could provide sufficient energy to heat the corona. At neither eclipse do we find evidence for oscillations in the [Fexiv] green line at a level greater than 2% of coronal intensity.

Development of the Microwave Radiative Transfer Program for Cloudy Atmospheres: Applications to DMSP SSM/T Channels.

DTIC Science & Technology

1979-12-30

42.22 122.52 Cloudy Green Bay 0253 Z Wisconsin (WI) 23 Nov 79 44.29 88.08 Cloudy Monterrey 0429 Z Mexico (MEX) 23 Nov 79 25.52 100.12 Cloudy Dodge City...230 250 270 290 - 35 35 Ii 30 30 / 25 / MONTERREY, MEXICO 25 GREEN DAY. WISCONSIN 23 NOV. 79,OOZ,0429Z 23 NOV. 79,OOZ,02 53Z - RAOS i -- RAO 20...bINDOW/ UP1NG2.INT)eDW(NG2.INT)eTHETA(t4),NU(INT)eLv(INT~e ICK~IINT).CK2(lNT).6UVERT(INI).CDVERT(INT) COMMON /MADATA/ PINIINGvINT) .PTIINT) . SEXT (INT

VizieR Online Data Catalog: The Initial Gaia Source List (IGSL) (Smart, 2013)

NASA Astrophysics Data System (ADS)

Smart, R. L.; Nicastro, L.

2013-11-01

The IGSL is a compilation catalog produced for the Gaia mission. We have combined data from the following catalogs or datasets to produce a homogenous list of positons, proper motions, photometry in a blue and red band and estimates of the magnitudes in the Gaia G and G_RVS bands. Included Catalogs: Tycho2, LQRF, UCAC4, SDSS-DR9, PPMXL, GSC23, GEPC, OGLE, Sky2000, 2MASS. Note that in compiling the various entries we did not consider the individual flags. Overall, we think this catalog is reliable but there will be errors, mismatches and duplicates. The user should use this catalog with that in mind, it is fine for statistical studies that has some way to remove obviously incorrect entries but it should only be used with care for individual objects. The source catalogs used to produce the IGSL are: * The Gaia Ecliptic Pole Catalog, version 3.0 (GEPC) Altmann & Bastian 2009, "Ecliptic Poles Catalogue Version 1.1" ESA Document GAIA-C3-TN-ARI-MA-002 URL http://www.rssd.esa.int/llink/livelink/open/2885828 * GSC2.3: GSC2 version 2.3, Lasker et al. 2008AJ....136..735L (I/305) * an excerpt of the 4th version of the Gaia Initial QSO Catalog (GIQC) as compiled by the GWP-S-335-13000, formed by Alexandre H. Andrei, Christophe Barache, Dario N. da Silva Neto, Francois Taris, Geraldine Bourda, Jean-Francois Le Campion, Jean Souchay, J.J. Pereira Osorio, Julio I. Bueno de Camargo, Marcelo Assafin, Roberto Vieira Martins, Sebastien Bouquillon, Sebastien Lambert, Sonia Anton, Patrick Charlot * OGLE: Optical Gravitational Lensing Experiment version III (Szymaski et al., 2011, Cat. J/AcA/61/83) * PPMXL: Positions and Proper Motions "Extra Large" Catalog, Roeser et al. (2010, Cat. I/317) * SDSS: Sloan Digital Sky Survey data release 9, Cat. V/139 * UCAC4: Zacharias et al., 2012, Cat. I/322 * Tycho-2, Hoeg et al., 2000, Cat. I/259 (1 data file).

Powerful model for the point source sky: Far-ultraviolet and enhanced midinfrared performance

NASA Technical Reports Server (NTRS)

Cohen, Martin

1994-01-01

I report further developments of the Wainscoat et al. (1992) model originally created for the point source infrared sky. The already detailed and realistic representation of the Galaxy (disk, spiral arms and local spur, molecular ring, bulge, spheroid) has been improved, guided by CO surveys of local molecular clouds, and by the inclusion of a component to represent Gould's Belt. The newest version of the model is very well validated by Infrared Astronomy Satellite (IRAS) source counts. A major new aspect is the extension of the same model down to the far ultraviolet. I compare predicted and observed far-utraviolet source counts from the Apollo 16 'S201' experiment (1400 A) and the TD1 satellite (for the 1565 A band).

Preflight Coverage of the STS-112 and Expedition 8 Crew during Egress Training

NASA Image and Video Library

2002-08-08

JSC2002-01563 (8 August 2002) --- Astronaut Robert L. Curbeam, Jr., STS-116 mission specialist, uses the Sky-genie to lower himself from a simulated trouble-plagued shuttle in a training session in the Space Vehicle Mockup Facility at the Johnson Space Center (JSC). Curbeam is wearing a training version of the shuttle launch and entry suit.

Nebula observations. Catalogues and archive of photoplates

NASA Astrophysics Data System (ADS)

Shlyapnikov, A. A.; Smirnova, M. A.; Elizarova, N. V.

2017-12-01

A process of data systematization based on "Academician G.A. Shajn's Plan" for studying the Galaxy structure related to nebula observations is considered. The creation of digital versions of catalogues of observations and publications is described, as well as their presentation in HTML, VOTable and AJS formats and basic principles of work in the interactive application of International Virtual Observatory the Aladin Sky Atlas.

Comprehensive Software Eases Air Traffic Management

NASA Technical Reports Server (NTRS)

2007-01-01

To help air traffic control centers improve the safety and the efficiency of the National Airspace System, Ames Research Center developed the Future Air Traffic Management Concepts Evaluation Tool (FACET) software, which won NASA's 2006 "Software of the Year" competition. In 2005, Ames licensed FACET to Flight Explorer Inc., for integration into its Flight Explorer (version 6.0) software. The primary FACET features incorporated in the Flight Explorer software system alert airspace users to forecasted demand and capacity imbalances. Advance access to this information helps dispatchers anticipate congested sectors (airspace) and delays at airports, and decide if they need to reroute flights. FACET is now a fully integrated feature in the Flight Explorer Professional Edition (version 7.0). Flight Explorer Professional offers end-users other benefits, including ease of operation; automatic alerts to inform users of important events such as weather conditions and potential airport delays; and international, real-time flight coverage over Canada, the United Kingdom, New Zealand, and sections of the Atlantic and Pacific Oceans. Flight Explorer Inc. recently broadened coverage by partnering with Honeywell International Inc.'s Global Data Center, Blue Sky Network, Sky Connect LLC, SITA, ARINC Incorporated, Latitude Technologies Corporation, and Wingspeed Corporation, to track their aircraft anywhere in the world.

ESASky: All the sky you need

NASA Astrophysics Data System (ADS)

De Marchi, Guido; ESASky Team

2018-06-01

ESASky is a discovery portal giving to all astronomers, professional and amateur alike, an easy way to access high-quality scientific data from their computer, tablet, or mobile device. It includes over half a million images, 300,000 spectra, and more than a billion catalogue sources. From gamma rays to radio wavelengths, it allows users to explore the cosmos with data from a dozen space missions from the astronomical archives of ESA, NASA, and JAXA and does not require prior knowledge of any particular mission. ESASky features an all-sky exploration interface, letting users easily zoom in for stars as single targets or as part of a whole galaxy, visualise them and retrieve the relevant data taken in an area of the sky with just a few clicks. Users can easily compare observations of the same source obtained by different space missions at different times and wavelengths. They can also use ESASky to plan future observations with the James Webb Space Telescope, comparing the relevant portion of the sky as observed by Hubble and other missions. We will illustrate the many options to visualise and access astronomical data: interactive footprints for each instrument, tree-maps, filters, and solar-system object trajectories can all be combined and displayed. The most recent version of ESASky, released in February, also includes access to scientific publications, allowing users to visualise on the sky all astronomical objects with associated scientific publications and to link directly back to the papers in the NASA Astrophysics Data System.

Longterm and spatial variability of Aerosol optical properties measured by sky radiometer in Japan sites

NASA Astrophysics Data System (ADS)

Aoki, K.

2016-12-01

Aerosols and cloud play an important role in the climate change. We started the long-term monitoring of aerosol and cloud optical properties since 1990's by using sky radiometer (POM-01, 02; Prede Co. Ltd., Japan). We provide the information, in this presentation, on the aerosol optical properties with respect to their temporal and spatial variability in Japan site (ex. Sapporo, Toyama, Kasuga and etc). The global distributions of aerosols have been derived from earth observation satellite and have been simulated in numerical models, which assume optical parameters. However, these distributions are difficult to derive because of variability in time and space. Therefore, Aerosol optical properties were investigated using the measurements from ground-based and ship-borne sky radiometer. The sky radiometer is an automatic instrument that takes observations only in daytime under the clear sky conditions. Observation of diffuse solar intensity interval was made every ten or five minutes by once. The aerosol optical properties were computed using the SKYRAD.pack version 4.2. The obtained Aerosol optical properties (Aerosol optical thickness, Ångström exponent, Single scattering albedo, and etc.) and size distribution volume clearly showed spatial and temporal variability in Japan area. In this study, we present the temporal and spatial variability of Aerosol optical properties at several Japan sites, applied to validation of satellite and numerical models. This project is validation satellite of GCOM-C, JAXA. The GCOM-C satellite scheduled to be launched in early 2017.

Version 2.0 AERONET Dust Aerosol properties, Constraints and Application to Asian Dust Observations

NASA Technical Reports Server (NTRS)

Holben, Brent; Eck, Tom; Holben, Brent; Eck, Tom; Siniuk, Aliaksander; Huangand, Jianping; Zang, Wu

2007-01-01

In November 2006, AERONET released Version 2 of the Dubovik and King sky radiance and optical depth inversion. Reanalysis of the entire AERONET database revealed marked differences in aerosol properties in arid and semi arid regions with dust dominated aerosols. The change will be illustrated through sensitivity analysis and examples from the UAE2 (United Arab Emirates Unified Aerosol Experiment) field campaign. Properties of dust dominated aerosols will be presented from regional AERONET sites in China showing variations in dust aerosol properties. The constraints and limitations of the AERONET inversion will be presented that will facilitate analysis by the user community of these data.

Lick Saturn-Voyager reference star catalogue (Klemola, Taraji, and Ocampo 1979): Documentation for the machine-readable version

NASA Technical Reports Server (NTRS)

Warren, Wayne H., Jr.

1990-01-01

The machine readable version of the catalog, as it is currently being distributed from the Astronomical Data Center, is described. The catalog contains accurate equatorial coordinates for 4551 stars in a band of sky against which cameras of the Voyager spacecraft were pointed for observations in the region of Saturn during the flyby. All of the reference stars are in the range 12(exp h) 40(exp m) to 14(exp h) 12(exp m) in right ascension (1950) and +02 to -09 degs in declination. Mean errors of the positions are about 0.25 sec.

IRAS sky survey atlas: Explanatory supplement

NASA Technical Reports Server (NTRS)

Wheelock, S. L.; Gautier, T. N.; Chillemi, J.; Kester, D.; Mccallon, H.; Oken, C.; White, J.; Gregorich, D.; Boulanger, F.; Good, J.

1994-01-01

This Explanatory Supplement accompanies the IRAS Sky Survey Atlas (ISSA) and the ISSA Reject Set. The first ISSA release in 1991 covers completely the high ecliptic latitude sky, absolute value of beta is greater than 50 deg, with some coverage down to the absolute value of beta approx. equal to 40 deg. The second ISSA release in 1992 covers ecliptic latitudes of 50 deg greater than the absolute value of beta greater than 20 deg, with some coverage down to the absolute value of beta approx. equal to 13 deg. The remaining fields covering latitudes within 20 deg of the ecliptic plane are of reduced quality compared to the rest of the ISSA fields and therefore are released as a separate IPAC product, the ISSA Reject Set. The reduced quality is due to contamination by zodiacal emission residuals. Special care should be taken when using the ISSA Reject images. In addition to information on the ISSA images, some information is provided in this Explanatory Supplement on the IRAS Zodiacal History File (ZOHF), Version 3.0, which was described in the December 1988 release memo. The data described in this Supplement are available at the National Space Science Data Center (NSSDC) at the Goddard Space Flight Center. The interested reader is referred to the NSSDC for access to the IRAS Sky Survey Atlas (ISSA).

The Holy Grail of outer space: pluralism, Druidry, and the religion of cinema in The Sky Ship.

PubMed

Bjørnvig, Thore

2012-10-01

The Danish silent movie Himmelskibet (in English, A Trip to Mars or The Sky Ship) premiered in 1918, and a novelization of the movie appeared in 1921. The film is about a trip to Mars and portrays a Martian civilization that embraces a life of peace, vegetarianism, and non-alcoholism. Both movie and novel, though especially the novel, provide insight into the plurality-of-worlds debate in Denmark in the early 20(th) century, forming as it did a part of a general debate about the relationship between science and religion. Yet The Sky Ship did not only form part of this debate but also displayed strong religious currents itself. Most notably, a romantic, Neo-Platonically inspired Christian version of Druidry informed the portrayal of the Martians and their society. Finally, the medium itself played a role in the story. By transcending language barriers, silent movies were imagined by some to be a kind of "Esperanto of the eye" that would usher in a new golden age for mankind, even contributing to ending the horrors of World War I. Thus, The Sky Ship offers insight into an intriguing conglomeration of pluralism, religion, and technology that should be of interest to historians of astrobiology.

A large-format imager for the SkyMapper Survey Telescope

NASA Astrophysics Data System (ADS)

Granlund, A.; Conroy, P. G.; Keller, S. C.; Oates, A. P.; Schmidt, B.; Waterson, M. F.; Kowald, E.; Dawson, M. I.

2006-06-01

The Research School of Astronomy and Astrophysics (RSAA) of the Australian National University (ANU) at Mt Stromlo Observatory is developing a wide-field Cassegrain Imager for the new 1.3m SkyMapper Survey Telescope under construction for Siding Spring Observatory, NSW, Australia. The Imager features a fast-readout, low-noise 268 Million pixel CCD mosaic that provides a 5.7 square degree field of view. Given the close relative sizes of the telescope and Imager, the work is proceeding in close collaboration with the telescope's manufacturer, Electro Optics Systems Pty Ltd (Canberra, Australia). The design of the SkyMapper Imager focal plane is based on E2V (Chelmsford, UK) deep depletion CCDs. These devices have 2048 x 4096 15 micron pixels, and provide a 91% filling factor in our mosaic configuration of 4 x 8 chips. In addition, the devices have excellent quantum efficiency from 300nm-950nm, near perfect cosmetics, and low-read noise, making them well suited to the all-sky ultraviolet through near-IR Southern Sky Survey to be conducted by the telescope. The array will be controlled using modified versions of the new IOTA controllers being developed for Pan-STARRS by Onaka and Tonry et al. These controllers provide a cost effective, low-volume, high speed solution for our detector read-out requirements. The system will have an integrated 6-filter exchanger, and Shack-Hartmann optics, and will be cooled by closed-cycle helium coolers. This paper will present the specifications, and opto-mechanical and detector control design of the SkyMapper Imager, including the test results of the detector characterisation and manufacturing progress.

Remote Sensing of Non-Aerosol (anomalous) Absorption in Cloud Free Atmosphere

NASA Technical Reports Server (NTRS)

Kaufman, Yoram J.; Dubovik, Oleg; Smirnov, Alexander; Holben, Brent N.; Lau, William K. M. (Technical Monitor)

2001-01-01

The interaction of sunlight with atmospheric gases, aerosols and clouds is fundamental to the understanding of climate and its variation. Several studies questioned our understanding of atmospheric absorption of sunlight in cloudy or in cloud free atmospheres. Uncertainty in instruments' accuracy and in the analysis methods makes this problem difficult to resolve. Here we use several years of measurements of sky and sun spectral brightness by selected instruments of the Aerosol Robotic Network (AERONET), that have known and high measurement accuracy. The measurements taken in several locations around the world show that in the atmospheric windows 0.44, 0.06, 0.86 and 1.02 microns the only significant absorbers in cloud free atmosphere is aerosol and ozone. This conclusions is reached using a method developed to distinguish between absorption associated with the presence of aerosol and absorption that is not related to the presence of aerosol. Non-aerosol absorption, defined as spectrally independent or smoothly variable, was found to have an optical thickness smaller than 0.002 corresponding to absorption of sunlight less than 1W/sq m, or essentially zero.

Monitoring and validating spatio-temporal continuously daily evapotranspiration and its components at river basin scale

NASA Astrophysics Data System (ADS)

Song, L.; Liu, S.; Kustas, W. P.; Nieto, H.

2017-12-01

Operational estimation of spatio-temporal continuously daily evapotranspiration (ET), and the components evaporation (E) and transpiration (T), at watershed scale is very useful for developing a sustainable water resource strategy in semi-arid and arid areas. In this study, multi-year all-weather daily ET, E and T were estimated using MODIS-based (Dual Temperature Difference) DTD model under different land covers in Heihe watershed, China. The remotely sensed ET was validated using ground measurements from large aperture scintillometer systems, with a source area of several kilometers, under grassland, cropland and riparian shrub-forest. The results showed that the remotely sensed ET produced mean absolute percent deviation (MAPD) errors of about 30% during the growing season for all-weather conditions, but the model performed better under clear sky conditions. However, uncertainty in interpolated MODIS land surface temperature input data under cloudy conditions to the DTD model, and the representativeness of LAS measurements for the heterogeneous land surfaces contribute to the discrepancies between the modeled and ground measured surface heat fluxes, especially for the more humid grassland and heterogeneous shrub-forest sites.

KSC-05PD-1142

NASA Technical Reports Server (NTRS)

2005-01-01

KENNEDY SPACE CENTER, FLA. Under post-dawn cloudy skies, Space Shuttle Discovery, resting on the Mobile Launcher Platform, rolls away from Launch Pad 39B via the Crawler/Transporter underneath. At left are the Rotating and Fixed Service Structures (RSS and FSS). Atop the FSS is the 80-foot lightning mast. At right is the 290-foot-tall water tower that holds 300,000 gallons of water, part of the sound suppression system during a launch. Discovery is returning to the Vehicle Assembly Buildling where it will be demated from its External Tank and lifted into the transfer aisle. On or about June 7, Discovery will be lifted and attached to its new tank and Solid Rocket Boosters, which are already in the VAB. Only the 15th rollback in Space Shuttle Program history, the 4.2-mile journey allows additional modifications to be made to the External Tank prior to a safe Return to Flight. Discovery is expected to be rolled back to the launch pad in mid-June for Return to Flight mission STS-114. The launch window extends from July 13 to July 31.

The Advanced Technology Microwave Sounder (ATMS): The First 10 Months On-Orbit

NASA Technical Reports Server (NTRS)

Kim, Edward; Lyu, C-H Joseph; Blackwell, Willaim; Leslie, R. Vince; Baker, Neal; Mo, Tsan; Sun, Ninghai; Bi, Li; Anderson, Kent; Landrum, Mike;

KSC-99pp1419

NASA Image and Video Library

1999-12-13

KENNEDY SPACE CENTER, Fla. -- Under partly cloudy skies and the Atlantic Ocean as a backdrop, Space Shuttle Endeavour, atop the mobile launcher platform, arrives at Launch Pad 39A for mission STS-99. The white cubicle at left is the environmental chamber, the White Room, that provides entry into the orbiter for the astronauts. It is at the outer end of the Orbiter Access Arm on the Fixed Service Structure. STS-99, named the Shuttle Radar Topography Mission (SRTM), involves an international project spearheaded by the National Imagery and Mapping Agency and NASA, with participation of the German Aerospace Center DLR. SRTM will chart a new course, using two antennae and a 200-foot-long section of space station-derived mast protruding from its payload bay, to produce unrivaled 3-D images of the Earth's surface. The result of the Shuttle Radar Topography Mission could be close to 1 trillion measurements of the Earth's topography. Besides contributing to the production of better maps, these measurements could lead to improved water drainage modeling, more realistic flight simulators, better locations for cell phone towers, and enhanced navigation safety. STS-99 is scheduled for launch in January 2000

The Continuous Intercomparison of Radiation Codes (CIRC): Phase I Cases

NASA Technical Reports Server (NTRS)

Oreopoulos, Lazaros; Mlawer, Eli; Delamere, Jennifer; Shippert, Timothy; Turner, David D.; Miller, Mark A.; Minnis, Patrick; Clough, Shepard; Barker, Howard; Ellingson, Robert

2007-01-01

CIRC aspires to be the successor to ICRCCM (Intercomparison of Radiation Codes in Climate Models). It is envisioned as an evolving and regularly updated reference source for GCM-type radiative transfer (RT) code evaluation with the principle goal to contribute in the improvement of RT parameterizations. CIRC is jointly endorsed by DOE's Atmospheric Radiation Measurement (ARM) program and the GEWEX Radiation Panel (GRP). CIRC's goal is to provide test cases for which GCM RT algorithms should be performing at their best, i.e, well characterized clear-sky and homogeneous, overcast cloudy cases. What distinguishes CIRC from previous intercomparisons is that its pool of cases is based on observed datasets. The bulk of atmospheric and surface input as well as radiative fluxes come from ARM observations as documented in the Broadband Heating Rate Profile (BBHRP) product. BBHRP also provides reference calculations from AER's RRTM RT algorithms that can be used to select the most optimal set of cases and to provide a first-order estimate of our ability to achieve radiative flux closure given the limitations in our knowledge of the atmospheric state.

Moderation of Cloud Reduction of UV in the Antarctic Due to High Surface Albedo.

NASA Astrophysics Data System (ADS)

Nichol, S. E.; Pfister, G.; Bodeker, G. E.; McKenzie, R. L.; Wood, S. W.; Bernhard, G.

2003-08-01

To gauge the impact of clouds on erythemal (sunburn causing) UV irradiances under different surface albedo conditions, UV measurements from two Antarctic sites (McMurdo and South Pole Stations) and a midlatitude site (Lauder, New Zealand) are examined. The surface albedo at South Pole remains high throughout the year, at McMurdo it has a strong annual cycle, and at Lauder it is low throughout the year. The measurements at each site are divided into clear and cloudy subsets and are compared with modeled clear-sky irradiances to assess the attenuation of UV by clouds. A radiative transfer model is also used to interpret the observations. Results show increasing attenuation of UV with increasing cloud optical depth, but a high surface albedo can moderate this attenuation as a result of multiple scattering between the surface and cloud base. This effect is of particular importance at high latitudes where snow may be present during the summer months. There is also a tendency toward greater cloud attenuation with increasing solar zenith angle.

Surface Emissivity Retrieved with Satellite Ultraspectral IR Measurements for Monitoring Global Change

NASA Technical Reports Server (NTRS)

Zhou, Daniel K.; Larar, Allen M.; Liu, Xu; Smith, William L.; Schluessel, Peter

2009-01-01

Surface and atmospheric thermodynamic parameters retrieved with advanced ultraspectral remote sensors aboard Earth observing satellites are critical to general atmospheric and Earth science research, climate monitoring, and weather prediction. Ultraspectral resolution infrared radiance obtained from nadir observations provide atmospheric, surface, and cloud information. Presented here is the global surface IR emissivity retrieved from Infrared Atmospheric Sounding Interferometer (IASI) measurements under "clear-sky" conditions. Fast radiative transfer models, applied to the cloud-free (or clouded) atmosphere, are used for atmospheric profile and surface parameter (or cloud parameter) retrieval. The inversion scheme, dealing with cloudy as well as cloud-free radiances observed with ultraspectral infrared sounders, has been developed to simultaneously retrieve atmospheric thermodynamic and surface (or cloud microphysical) parameters. Rapidly produced surface emissivity is initially evaluated through quality control checks on the retrievals of other impacted atmospheric and surface parameters. Surface emissivity and surface skin temperature from the current and future operational satellites can and will reveal critical information on the Earth s ecosystem and land surface type properties, which can be utilized as part of long-term monitoring for the Earth s environment and global climate change.

VizieR Online Data Catalog: Second ROSAT PSPC Catalog (ROSAT, 2000)

NASA Astrophysics Data System (ADS)

Rosat, Consortium

2000-07-01

This catalogue contains sources from PSPC-ROSAT (Position-Sensitive Proportional Counter aboard the Roentgen Satellite), as provided by Max-Planck Institut fuer extraterrestrische Physik (MPE). It supersedes the 1994 version (Cat. ) The current release of the catalog is comprised of results from 4093 sequences (sky coverage of 14.5%). The complete version contains entries for 95,331 detections whereas the short version has 43,156 detections. 2189 obvious sources were not detected by the automated Standard Analysis Software System (SASS), and are not yet contained in this catalogue. These data have been screened by ROSAT data centers in the US, Germany, and the UK as a step in the production of the ROSAT RESULTS ARCHIVE. The RRA contains extracted source and associated products with an indication of reliability for the primary parameters. (3 data files).

An assessment of climate change and the vulnerability of wildlife in the Sky Islands of the Southwest

Treesearch

Sharon J. Coe; Deborah M. Finch; Megan M. Friggens

2012-01-01

We evaluated the historical and projected trends in climate and vegetation relevant to the Coronado National Forest in southeast Arizona, USA. We then applied this information in an assessment of the vulnerability of 30 species of terrestrial vertebrates on the Coronado National Forest to the potential effects of future climate change. We used a pilot version of a...

``Losing the Dark:'' A Planetarium PSA about Light Pollution

NASA Astrophysics Data System (ADS)

Productions, L. N.; Walker, D. C.

2013-04-01

Losing the Dark is a PSA video being created for fulldome theaters by Loch Ness Productions under the direction of the International Dark Sky Association Education Committee headed by Dr. Constance Walker of the National Optical Astronomy Observatories. It explains the problems with light pollution, its effects on life, and three ways in which people can implement “wise lighting” practices to mitigate light pollution. The show is also being produced in a flat-screen HD format for use in classical planetarium and non-dome theaters, for presentations by IDA speakers when addressing planning boards, etc. and will be posted on the IDA and other web sites. The final length is six minutes for both versions. Funding has been provided by The International Planetarium Society and the International Dark-Sky Association.

The Cloud Feedback Model Intercomparison Project Observational Simulator Package: Version 2

NASA Astrophysics Data System (ADS)

Swales, Dustin J.; Pincus, Robert; Bodas-Salcedo, Alejandro

2018-01-01

The Cloud Feedback Model Intercomparison Project Observational Simulator Package (COSP) gathers together a collection of observation proxies or satellite simulators that translate model-simulated cloud properties to synthetic observations as would be obtained by a range of satellite observing systems. This paper introduces COSP2, an evolution focusing on more explicit and consistent separation between host model, coupling infrastructure, and individual observing proxies. Revisions also enhance flexibility by allowing for model-specific representation of sub-grid-scale cloudiness, provide greater clarity by clearly separating tasks, support greater use of shared code and data including shared inputs across simulators, and follow more uniform software standards to simplify implementation across a wide range of platforms. The complete package including a testing suite is freely available.

A comparison of all-weather land surface temperature products

NASA Astrophysics Data System (ADS)

Martins, Joao; Trigo, Isabel F.; Ghilain, Nicolas; Goettche, Frank-M.; Ermida, Sofia; Olesen, Folke-S.; Gellens-Meulenberghs, Françoise; Arboleda, Alirio

2017-04-01

The Satellite Application Facility on Land Surface Analysis (LSA-SAF, http://landsaf.ipma.pt) has been providing land surface temperature (LST) estimates using SEVIRI/MSG on an operational basis since 2006. The LSA-SAF service has since been extended to provide a wide range of satellite-based quantities over land surfaces, such as emissivity, albedo, radiative fluxes, vegetation state, evapotranspiration, and fire-related variables. Being based on infra-red measurements, the SEVIRI/MSG LST product is limited to clear-sky pixels only. Several all-weather LST products have been proposed by the scientific community either based on microwave observations or using Soil-Vegetation-Atmosphere Transfer models to fill the gaps caused by clouds. The goal of this work is to provide a nearly gap-free operational all-weather LST product and compare these approaches. In order to estimate evapotranspiration and turbulent energy fluxes, the LSA-SAF solves the surface energy budget for each SEVIRI pixel, taking into account the physical and physiological processes occurring in vegetation canopies. This task is accomplished with an adapted SVAT model, which adopts some formulations and parameters of the Tiled ECMWF Scheme for Surface Exchanges over Land (TESSEL) model operated at the European Center for Medium-range Weather Forecasts (ECMWF), and using: 1) radiative inputs also derived by LSA-SAF, which includes surface albedo, down-welling fluxes and fire radiative power; 2) a land-surface characterization obtained by combining the ECOCLIMAP database with both LSA-SAF vegetation products and the H(ydrology)-SAF snow mask; 3) meteorological fields from ECMWF forecasts interpolated to SEVIRI pixels, and 4) soil moisture derived by the H-SAF and LST from LSA-SAF. A byproduct of the SVAT model is surface skin temperature, which is needed to close the surface energy balance. The model skin temperature corresponds to the radiative temperature of the interface between soil and atmosphere, which is assumed to have no heat storage. The modelled skin temperatures are in fair agreement with LST directly estimated from SEVIRI observations. However, in contrast to LST retrievals from SEVIRI/MSG (or other infrared sensors) the SVAT model solves the energy budget equation under all-sky conditions. The SVAT surface skin temperature is then used to fill gaps in LST fields caused by clouds. Since under cloudy conditions the direct incoming solar radiation is greatly reduced, thermal balance at the surface is more easily achieved and directional effects are also less important. Therefore, a better performance of the model skin temperature may be expected. In contrast, under clear skies the satellite LST showed to be more reliable, since the SVAT model shows biases in the daily amplitude of the skin temperature. In the context of the GlobTemperature project (http://www.globtemperature.info/), all-weather LST datasets using AMSR-E microwave radiances were produced, which are compared here to the SVAT-based LST. Both products were validated against in situ data - particularly from Gobabeb & Farm Heimat (Namibia), and Évora (Portugal) - to show that under cloudy conditions the agreement between in-situ LST and modelled skin temperature is acceptable. Compared to the SVAT-based LST, AMSR-E LST is closer to satellite observations (level 2 product); the complementarity of the two approaches is assessed.

Convenient models of the atmosphere: optics and solar radiation

NASA Astrophysics Data System (ADS)

Alexander, Ginsburg; Victor, Frolkis; Irina, Melnikova; Sergey, Novikov; Dmitriy, Samulenkov; Maxim, Sapunov

2017-11-01

Simple optical models of clear and cloudy atmosphere are proposed. Four versions of atmospheric aerosols content are considered: a complete lack of aerosols in the atmosphere, low background concentration (500 cm-3), high concentrations (2000 cm-3) and very high content of particles (5000 cm-3). In a cloud scenario, the model of external mixture is assumed. The values of optical thickness and single scattering albedo for 13 wavelengths are calculated in the short wavelength range of 0.28-0.90 µm, with regard to the molecular absorption bands, that is simulated with triangle function. A comparison of the proposed optical parameters with results of various measurements and retrieval (lidar measurement, sampling, processing radiation measurements) is presented. For a cloudy atmosphere models of single-layer and two-layer atmosphere are proposed. It is found that cloud optical parameters with assuming the "external mixture" agrees with retrieved values from airborne observations. The results of calculating hemispherical fluxes of the reflected and transmitted solar radiation and the radiative divergence are obtained with the Delta-Eddington approach. The calculation is done for surface albedo values of 0, 0.5, 0.9 and for spectral values of the sandy surface. Four values of solar zenith angle: 0°, 30°, 40° and 60° are taken. The obtained values are compared with data of radiative airborne observations. Estimating the local instantaneous radiative forcing of atmospheric aerosols and clouds for considered models is presented together with the heating rate.

Evaluation of the Impact of AIRS Radiance and Profile Data Assimilation in Partly Cloudy Regions

NASA Technical Reports Server (NTRS)

Zavodsky, Bradley; Srikishen, Jayanthi; Jedlovec, Gary

2013-01-01

Improvements to global and regional numerical weather prediction have been demonstrated through assimilation of data from NASA s Atmospheric Infrared Sounder (AIRS). Current operational data assimilation systems use AIRS radiances, but impact on regional forecasts has been much smaller than for global forecasts. Retrieved profiles from AIRS contain much of the information that is contained in the radiances and may be able to reveal reasons for this reduced impact. Assimilating AIRS retrieved profiles in an identical analysis configuration to the radiances, tracking the quantity and quality of the assimilated data in each technique, and examining analysis increments and forecast impact from each data type can yield clues as to the reasons for the reduced impact. By doing this with regional scale models individual synoptic features (and the impact of AIRS on these features) can be more easily tracked. This project examines the assimilation of hyperspectral sounder data used in operational numerical weather prediction by comparing operational techniques used for AIRS radiances and research techniques used for AIRS retrieved profiles. Parallel versions of a configuration of the Weather Research and Forecasting (WRF) model with Gridpoint Statistical Interpolation (GSI) are run to examine the impact AIRS radiances and retrieved profiles. Statistical evaluation of a long-term series of forecast runs will be compared along with preliminary results of in-depth investigations for select case comparing the analysis increments in partly cloudy regions and short-term forecast impacts.

Evaluation of the Impact of Atmospheric Infrared Sounder (AIRS) Radiance and Profile Data Assimilation in Partly Cloudy Regions

NASA Technical Reports Server (NTRS)

Zavodsky, Bradley; Srikishen, Jayanthi; Jedlovec, Gary

2013-01-01

Improvements to global and regional numerical weather prediction have been demonstrated through assimilation of data from NASA s Atmospheric Infrared Sounder (AIRS). Current operational data assimilation systems use AIRS radiances, but impact on regional forecasts has been much smaller than for global forecasts. Retrieved profiles from AIRS contain much of the information that is contained in the radiances and may be able to reveal reasons for this reduced impact. Assimilating AIRS retrieved profiles in an identical analysis configuration to the radiances, tracking the quantity and quality of the assimilated data in each technique, and examining analysis increments and forecast impact from each data type can yield clues as to the reasons for the reduced impact. By doing this with regional scale models individual synoptic features (and the impact of AIRS on these features) can be more easily tracked. This project examines the assimilation of hyperspectral sounder data used in operational numerical weather prediction by comparing operational techniques used for AIRS radiances and research techniques used for AIRS retrieved profiles. Parallel versions of a configuration of the Weather Research and Forecasting (WRF) model with Gridpoint Statistical Interpolation (GSI) are run to examine the impact AIRS radiances and retrieved profiles. Statistical evaluation of 6 weeks of forecast runs will be compared along with preliminary results of in-depth investigations for select case comparing the analysis increments in partly cloudy regions and short-term forecast impacts.

Study of UV cloud modification factors in Southern Patagonia

NASA Astrophysics Data System (ADS)

Wolfram, Elian A.; Orte, Facundo; Salvador, Jacobo; Quiroga, Jonathan; D'Elia, Raúl; Antón, Manuel; Alados-Arboledas, Lucas; Quel, Eduardo

2017-02-01

Anthropogenic perturbation of the ozone layer has induced change in the amount of UV radiation that reaches the Earth's surface, mainly through the Antarctic ozone hole, making the ozone and ultraviolet (UV) radiation two important issues in the study of Earth atmosphere in the scientific community. Also the clouds have been identified as the main modulator of UV amount in short time scales and produce the main source of uncertainty in the projection of surface UV level as consequence of projected ozone recovery. While clouds can decrease direct radiation, they can produce an increase in the diffuse component, and as consequence the surface UV radiation may be higher than an equivalent clear sky scenario for several minutes. In particular this situation can be important when low ozone column and partially cloud cover skies happen simultaneously. These situations happen frequently in southern Patagonia, where the CEILAP Lidar Division has established the Atmospheric Observatory of Southern Patagonia, an atmospheric remote sensing site near the city of Río Gallegos (51°55'S, 69°14'W). In this paper, the impact of clouds over the UV radiation is investigated by the use of ground based measurements from the passive remote sensing instruments operating at this site, mainly of broad and moderate narrow band filter radiometers. We analyzed the UV Index obtained from a multiband filter radiometer GUV-541 (UVI) [Biospherical Inc.] installed in the Observatorio Atmosférico de la Patagonia Austral, Río Gallegos, since 2005. Cloud modification factors (CMF, ratio between the measured UV radiation in a cloudy sky and the simulated radiation under cloud-free conditions) are evaluated for the study site. The database used in this work covers the period 2005-2012 for spring and summer seasons, when the ozone hole can affect these subpolar regions. CMF higher than 1 are found during spring and summer time, when lower total ozone columns, higher solar elevations and high cloud cover occur simultaneously, producing extreme erythemal irradiance at ground surface. Enhancements as high as 25% were registered. The maximum duration of the enhancement was around 30 minute. This produces dangerous sunbathing situations for the Río Gallegos citizen.

Validation of a Climate-Data Record of the "Clear-Sky" Surface Temperature of the Greenland Ice Sheet

NASA Technical Reports Server (NTRS)

Hall, Dorothy K.; Box, Jason E.; Koenig, Lora S.; DiGirolamo, Nicolo E.; Comiso, Josefino C.; Shuman, Christopher A.

2011-01-01

Surface temperatures on the Greenland Ice Sheet have been studied on the ground, using automatic weather station (AWS) data from the Greenland-Climate Network (GC-Net), and from analysis of satellite sensor data. Using Advanced Very High Frequency Radiometer (AVHRR) weekly surface temperature maps, warming of the surface of the Greenland Ice Sheet has been documented since 1981. We extended and refined this record using higher-resolution Moderate-Resolution Imaging Spectroradiometer (MODIS) data from March 2000 to the present. We developed a daily and monthly climate-data record (CDR) of the "clear-sky" surface temperature of the Greenland Ice Sheet using an ice-surface temperature (1ST) algorithm developed for use with MODIS data. Validation of this CDR is ongoing. MODIS Terra swath data are projected onto a polar stereographic grid at 6.25-km resolution to develop binary, gridded daily and mean-monthly 1ST maps. Each monthly map also has a color-coded image map that is available to download. Also included with the monthly maps is an accompanying map showing number of days in the month that were used to calculate the mean-monthly 1ST. This is important because no 1ST decision is made by the algorithm for cells that are considered cloudy by the internal cloud mask, so a sufficient number of days must be available to produce a mean 1ST for each grid cell. Validation of the CDR consists of several facets: 1) comparisons between ISTs and in-situ measurements; 2) comparisons between ISTs and AWS data; and 3) comparisons of ISTs with surface temperatures derived from other satellite instruments such as the Thermal Emission and Reflection Radiometer (ASTER) and Enhanced Thematic Mapper Plus (ETM+). Previous work shows that Terra MODIS ISTs are about 3 C lower than in-situ temperatures measured at Summit Camp, during the winter of 2008-09 under clear skies. In this work we begin to compare surface temperatures derived from AWS data with ISTs from the MODIS CDR.

Balloon-borne match measurements of mid-latitude cirrus clouds

NASA Astrophysics Data System (ADS)

Cirisan, A.; Luo, B. P.; Engel, I.; Wienhold, F. G.; Krieger, U. K.; Weers, U.; Romanens, G.; Levrat, G.; Jeannet, P.; Ruffieux, D.; Philipona, R.; Calpini, B.; Spichtinger, P.; Peter, T.

2013-10-01

Observations of persistent high supersaturations with respect to ice inside cirrus clouds are challenging our understanding of cloud microphysics and of climate feedback processes in the upper troposphere. Single measurements of a cloudy air mass provide only a snapshot from which the persistence of ice supersaturation cannot be judged. We introduce here the "cirrus match technique" to obtain information of the evolution of clouds and their saturation ratio. The aim of these coordinated balloon soundings is to analyze the same air mass twice. To this end the standard radiosonde equipment is complemented by a frost point hygrometer "SnowWhite" and a particle backscatter detector "COBALD" (Compact Optical Backscatter Aerosol Detector). Extensive trajectory calculations based on regional weather model COSMO forecasts are performed for flight planning and COSMO analyses are used as basis for comprehensive microphysical box modeling (with grid scale 2 km and 7 km, respectively). Here we present the results of matching a cirrus cloud to within 2-15 km, realized on 8 June 2010 over Payerne, Switzerland, and a location 120 km downstream close to Zurich. A thick cirrus was detected over both measurement sites. We show that in order to quantitatively reproduce the measured particle backscatter ratios, the small-scale temperature fluctuations not resolved by COSMO must be superimposed on the trajectories. The stochastic nature of the fluctuations is captured by ensemble calculations. Possibilities for further improvements in the agreement with the measured backscatter data are investigated by assuming a very slow mass accommodation of water on ice, the presence of heterogeneous ice nuclei, or a wide span of (spheroidal) particle shapes. However, the resulting improvements from microphysical refinements are moderate and comparable in magnitude with changes caused by assuming different regimes of temperature fluctuations for clear sky or cloudy sky conditions, highlighting the importance of a proper treatment of subscale fluctuations. The model yields good agreement with the measured backscatter over both sites and reproduces the measured saturation ratios with respect to ice over Payerne. Conversely, the 30% in-cloud supersaturation measured in a massive, 4-km thick cloud layer over Zurich cannot be reproduced, irrespective of the choice of meteorological or microphysical model parameters. The measured supersaturation can only be explained by either resorting to an unknown physical process, which prevents the ice particles from consuming the excess humidity, or - much more likely - by a measurement error, such as a contamination of the sensor housing of the SnowWhite hygrometer by a precipitation drop from a mixed phase cloud just below the cirrus layer or from some very slight rain in the boundary layer. This uncertainty calls for in-flight checks or calibrations of hygrometers under the extreme humidity conditions in the upper troposphere.

Lessons Learned From Large-Scale Evapotranspiration and Root Zone Soil Moisture Mapping Using Ground Measurements (meteorological, LAS, EC) and Remote Sensing (METRIC)

NASA Astrophysics Data System (ADS)

Hendrickx, J. M. H.; Allen, R. G.; Myint, S. W.; Ogden, F. L.

2015-12-01

Large scale mapping of evapotranspiration and root zone soil moisture is only possible when satellite images are used. The spatial resolution of this imagery typically depends on its temporal resolution or the satellite overpass time. For example, the Landsat satellite acquires images at 30 m resolution every 16 days while the MODIS satellite acquires images at 250 m resolution every day. In this study we deal with optical/thermal imagery that is impacted by cloudiness contrary to radar imagery that penetrates through clouds. Due to cloudiness, the temporal resolution of Landsat drops from 16 days to about one clear sky Landsat image per month in the southwestern USA and about one every ten years in the humid tropics of Panama. Only by launching additional satellites can the temporal resolution be improved. Since this is too costly, an alternative is found by using ground measurements with high temporal resolution (from minutes to days) but poor spatial resolution. The challenge for large-scale evapotranspiration and root zone soil moisture mapping is to construct a layer stack consisting of N time layers covering the period of interest each containing M pixels covering the region of interest. We will present examples of the Phoenix Active Management Area in AZ (14,600 km2), Green River Basin in WY (44,000 km2), the Kishwaukee Watershed in IL (3,150 km2), the area covered by Landsat Path 28/Row 35 in OK (30,000 km2) and the Agua Salud Watershed in Panama (200 km2). In these regions we used Landsat or MODIS imagery for mapping evapotranspiration and root zone soil moisture by the algorithm Mapping EvapoTranspiration at high Resolution with Internalized Calibration (METRIC) together with meteorological measurements and sometimes either Large Aperture Scintillometers (LAS) or Eddy Covariance (EC). We conclude with lessons learned for future large-scale hydrological studies.

Sensitivity of Marine Warm Cloud Retrieval Statistics to Algorithm Choices: Examples from MODIS Collection 6

NASA Astrophysics Data System (ADS)

Platnick, S.; Wind, G.; Zhang, Z.; Ackerman, S. A.; Maddux, B. C.

2012-12-01

The optical and microphysical structure of warm boundary layer marine clouds is of fundamental importance for understanding a variety of cloud radiation and precipitation processes. With the advent of MODIS (Moderate Resolution Imaging Spectroradiometer) on the NASA EOS Terra and Aqua platforms, simultaneous global/daily 1km retrievals of cloud optical thickness and effective particle size are provided, as well as the derived water path. In addition, the cloud product (MOD06/MYD06 for MODIS Terra and Aqua, respectively) provides separate effective radii results using the 1.6, 2.1, and 3.7 μm spectral channels. Cloud retrieval statistics are highly sensitive to how a pixel identified as being "not-clear" by a cloud mask (e.g., the MOD35/MYD35 product) is determined to be useful for an optical retrieval based on a 1-D cloud model. The Collection 5 MODIS retrieval algorithm removed pixels associated with cloud edges (defined by immediate adjacency to "clear" MOD/MYD35 pixels) as well as ocean pixels with partly cloudy elements in the 250m MODIS cloud mask - part of the so-called Clear Sky Restoral (CSR) algorithm. Collection 6 attempts retrievals for those two pixel populations, but allows a user to isolate or filter out the populations via CSR pixel-level Quality Assessment (QA) assignments. In this paper, using the preliminary Collection 6 MOD06 product, we present global and regional statistical results of marine warm cloud retrieval sensitivities to the cloud edge and 250m partly cloudy pixel populations. As expected, retrievals for these pixels are generally consistent with a breakdown of the 1D cloud model. While optical thickness for these suspect pixel populations may have some utility for radiative studies, the retrievals should be used with extreme caution for process and microphysical studies.

The Effect of Solar Reflective Cover on Soak Air Temperature and Thermal Comfort of Car Parked under the Sun

NASA Astrophysics Data System (ADS)

Lahimer, A. A.; Alghoul, M. A.; Sopian, K.; Khrit, N. G.

2017-11-01

Parking a vehicle under the sun for a short period of time can rapidly increase the interior air cabin temperature no matter in clear sky days or even in partially cloudy days. These circumstances can be anxieties to car occupants upon entry. The aim of this paper is to evaluate experimentally the effect of solar reflective cover (SRC) on vehicle air temperature and cabin thermal comfort. Experimental measurements of parked cars were conducted in UKM, Bangi city, Malaysia (latitude of 2.9° N and longitude of 101.78° E) under partially cloudy day where average ambient temperature is 33°C. The experimental measurements cover the following cases: case (I): car with/ without SRC (at different measurement time); Case (II): using two identical cars concurrently (SRC versus baseline); Case (III): using two identical cars concurrently (solar reflective film (SRF) versus baseline) and Case (IV): using two identical cars concurrently (SRF versus SRC). Experimental results dedicated to case (I) revealed that the maximum cabin air temperature with SRC (39.6°C) is significantly lower than that of baseline case (57.3°C). This leads to temperature reduction improvement of 31% and the difference between the cabin and the ambient air temperature was minimized by approximately 73%. In addition, the results revealed that the air temperature at breath level of car with SRC dropped to comfort temperature (27°C) after 7 min while baseline car reached comfort temperature after 14 min. Results of the other cases are discussed inside the paper. Overall, it is learned that SRC is found superior as an efficient thermal insulation system limits solar radiation transmission into the cabin through the glass; keeps cabin air temperature close to the ambient temperature; and provide acceptable thermal environment to the occupants as they settle into their parked car.

The transient behavior of whole-canopy fluxes during dynamic light conditions for midlatitude and tropical forests

NASA Astrophysics Data System (ADS)

Fitzjarrald, D. R.; Kivalov, S. N.

2017-12-01

Cloud shadows lead to alternating light and dark periods at the surface. Understanding how clouds affect whole-canopy fluxes suffer from two knowledge gaps that limit scaling from leaf to canopy scales, an effort currently done by assertion alone. First, there is a lack a clear quantitative definition of the incident light time series that occur on specific types of cloudy days. Second, the characteristic time scales for leaves to respond to for stomatal opening and closing is 1-10 minutes, a period too short to allow accurate eddy fluxes. We help to close the first gap by linking the durations of alternating light and dark periods statistically to conventional meteorological sky types at a midlatitude mixed deciduous forest (Harvard Forest, MA, USA: 42.53N, 72.17W) and in a tropical rain forest (Tapajós National Forest, Brazil; 2.86S, 54.96W). The second gap is narrowed by measuring the dynamic response whole canopy exchanges in the flux footprint at intervals of only a few seconds using the classical ensemble average method, keying on step changes in light intensity. Combining light and shadow periods of different lengths we estimate ensemble fluxes sensible heat (H), net ecosystem exchange (NEE), and latent heat (LE) fluxes initiated by abrupt radiation changes at intervals of 30 s over 20 minutes. We present composite results of the transient behavior of whole-canopy fluxes at each forest, showing distinct features of each forest type. Observed time constants and transient flux parameterizations are then used to force a simple model to yield NEE, LE, WUE, and Bowen ratio extrema under periodic shadow-light conditions and given cloud amount. We offer the hypothesis that, at least on certain types of cloudy days, the well-known correlation between diffuse light and WUE does not represent a causal connection at the canopy scale.

Continuous estimation of evapotranspiration and gross primary productivity from an Unmanned Aerial System

NASA Astrophysics Data System (ADS)

Wang, S.; Bandini, F.; Jakobsen, J.; J Zarco-Tejada, P.; Liu, X.; Haugård Olesen, D.; Ibrom, A.; Bauer-Gottwein, P.; Garcia, M.

2017-12-01

Model prediction of evapotranspiration (ET) and gross primary productivity (GPP) using optical and thermal satellite imagery is biased towards clear-sky conditions. Unmanned Aerial Systems (UAS) can collect optical and thermal signals at unprecedented very high spatial resolution (< 1 meter) under sunny and cloudy weather conditions. However, methods to obtain model outputs between image acquisitions are still needed. This study uses UAS based optical and thermal observations to continuously estimate daily ET and GPP in a Danish willow forest for an entire growing season of 2016. A hexacopter equipped with multispectral and thermal infrared cameras and a real-time kinematic Global Navigation Satellite System was used. The Normalized Differential Vegetation Index (NDVI) and the Temperature Vegetation Dryness Index (TVDI) were used as proxies for leaf area index and soil moisture conditions, respectively. To obtain continuously daily records between UAS acquisitions, UAS surface temperature was assimilated by the ensemble Kalman filter into a prognostic land surface model (Noilhan and Planton, 1989), which relies on the force-restore method, to simulate the continuous land surface temperature. NDVI was interpolated into daily time steps by the cubic spline method. Using these continuous datasets, a joint ET and GPP model, which combines the Priestley-Taylor Jet Propulsion Laboratory ET model (Fisher et al., 2008; Garcia et al., 2013) and the Light Use Efficiency GPP model (Potter et al., 1993), was applied. The simulated ET and GPP were compared with the footprint of eddy covariance observations. The simulated daily ET has a RMSE of 14.41 W•m-2 and a correlation coefficient of 0.83. The simulated daily GPP has a root mean square error (RMSE) of 1.56 g•C•m-2•d-1 and a correlation coefficient of 0.87. This study demonstrates the potential of UAS based multispectral and thermal mapping to continuously estimate ET and GPP for both sunny and cloudy weather conditions.

Microwave Radiometer and Lidar Synergy for High Vertical Resolution Thermodynamic Profiling in a Cloudy Scenario

NASA Astrophysics Data System (ADS)

Barrera Verdejo, M.; Crewell, S.; Loehnert, U.; Di Girolamo, P.

2016-12-01

Continuous monitoring of thermodynamic atmospheric profiles is important for many applications, e.g. assessment of atmospheric stability and cloud formation. Nowadays there is a wide variety of ground-based sensors for atmospheric profiling. However, no single instrument is able to simultaneously provide measurements with complete vertical coverage, high vertical and temporal resolution, and good performance under all weather conditions. For this reason, instrument synergies of a wide range of complementary measurements are more and more considered for improving the quality of atmospheric observations. The current work presents synergetic use of a microwave radiometer (MWR) and Raman lidar (RL) within a physically consistent optimal estimation approach. On the one hand, lidar measurements provide humidity and temperature measurements with a high vertical resolution albeit with limited vertical coverage, due to overlapping function problems, sunlight contamination and the presence of clouds. On the other hand, MWRs obtain humidity, temperature and cloud information throughout the troposphere, with however only a very limited vertical resolution. The benefits of MWR+RL synergy have been previously demonstrated for clear sky cases. This work expands this approach to cloudy scenarios. Consistent retrievals of temperature, absolute and relative humidity as well as liquid water path are analyzed. In addition, different measures are presented to demonstrate the improvements achieved via the synergy compared to individual retrievals, e.g. degrees of freedom or theoretical error. We also demonstrate that, compared to the lidar, the higher temporal resolution of the MWR presents a strong advantage for capturing the high temporal variability of the liquid water cloud.. Finally, the results are compared with independent information sources, e.g. GPS or radiosondes, showing good consistency. The study demonstrates the benefits of the sensor combination, being especially strong in regions where lidar data is not available, whereas if both instruments are available, the lidar measurements dominate the retrieval.

Improving Subtropical Boundary Layer Cloudiness in the 2011 NCEP GFS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fletcher, J. K.; Bretherton, Christopher S.; Xiao, Heng

2014-09-23

The current operational version of National Centers for Environmental Prediction (NCEP) Global Forecasting System (GFS) shows significant low cloud bias. These biases also appear in the Coupled Forecast System (CFS), which is developed from the GFS. These low cloud biases degrade seasonal and longer climate forecasts, particularly of short-wave cloud radiative forcing, and affect predicted sea surface temperature. Reducing this bias in the GFS will aid the development of future CFS versions and contributes to NCEP's goal of unified weather and climate modelling. Changes are made to the shallow convection and planetary boundary layer parameterisations to make them more consistentmore » with current knowledge of these processes and to reduce the low cloud bias. These changes are tested in a single-column version of GFS and in global simulations with GFS coupled to a dynamical ocean model. In the single-column model, we focus on changing parameters that set the following: the strength of shallow cumulus lateral entrainment, the conversion of updraught liquid water to precipitation and grid-scale condensate, shallow cumulus cloud top, and the effect of shallow convection in stratocumulus environments. Results show that these changes improve the single-column simulations when compared to large eddy simulations, in particular through decreasing the precipitation efficiency of boundary layer clouds. These changes, combined with a few other model improvements, also reduce boundary layer cloud and albedo biases in global coupled simulations.« less

How to distinguish between cloudy mini-Neptunes and water/volatile-dominated super-Earths

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benneke, Björn; Seager, Sara, E-mail: bbenneke@mit.edu

One of the most profound questions about the newly discovered class of low-density super-Earths is whether these exoplanets are predominately H{sub 2}-dominated mini-Neptunes or volatile-rich worlds with gas envelopes dominated by H{sub 2}O, CO{sub 2}, CO, CH{sub 4}, or N{sub 2}. Transit observations of the super-Earth GJ 1214b rule out cloud-free H{sub 2}-dominated scenarios, but are not able to determine whether the lack of deep spectral features is due to high-altitude clouds or the presence of a high mean molecular mass atmosphere. Here, we demonstrate that one can unambiguously distinguish between cloudy mini-Neptunes and volatile-dominated worlds based on wing steepnessmore » and relative depths of absorption features in moderate-resolution near-infrared transmission spectra (R ∼ 100). In a numerical retrieval study, we show for GJ 1214b that an unambiguous distinction between a cloudy H{sub 2}-dominated atmosphere and cloud-free H{sub 2}O atmosphere will be possible if the uncertainties in the spectral transit depth measurements can be reduced by a factor of ∼3 compared to the published Hubble Space Telescope Wide-Field Camera 3 and Very Large Telescope transit observations by Berta et al. and Bean et al. We argue that the required precision for the distinction may be achievable with currently available instrumentation by stacking 10-15 repeated transit observations. We provide a scaling law that scales our quantitative results to other transiting super-Earths and Neptunes such as HD 97658b, 55 Cnc e, GJ 3470b and GJ 436b. The analysis in this work is performed using an improved version of our Bayesian atmospheric retrieval framework. The new framework not only constrains the gas composition and cloud/haze parameters, but also determines our confidence in having detected molecules and cloud/haze species through Bayesian model comparison. Using the Bayesian tool, we demonstrate quantitatively that the subtle transit depth variation in the Berta et al. data is not sufficient to claim the detection of water absorption.« less

Kinesthetic Astronomy: Significant Upgrades to the Sky Time Lesson that Support Student Learning

NASA Astrophysics Data System (ADS)

Morrow, C. A.; Zawaski, M.

2004-12-01

This paper will report on a significant upgrade to the first in a series of innovative, experiential lessons we call Kinesthetic Astronomy. The Sky Time lesson reconnects students with the astronomical meaning of the day, year, and seasons. Like all Kinesthetic Astronomy lessons, it teaches basic astronomical concepts through choreographed bodily movements and positions that provide educational sensory experiences. They are intended for sixth graders up through adult learners in both formal and informal educational settings. They emphasize astronomical concepts and phenomenon that people can readily encounter in their "everyday" lives such as time, seasons, and sky motions of the Sun, Moon, stars, and planets. Kinesthetic Astronomy lesson plans are fully aligned with national science education standards, both in content and instructional practice. Our lessons offer a complete learning cycle with written assessment opportunities now embedded throughout the lesson. We have substantially strengthened the written assessment options for the Sky Time lesson to help students translate their kinesthetic and visual learning into the verbal-linguistic and mathematical-logical realms of expression. Field testing with non-science undergraduates, middle school science teachers and students, Junior Girl Scouts, museum education staff, and outdoor educators has been providing evidence that Kinesthetic Astronomy techniques allow learners to achieve a good grasp of concepts that are much more difficult to learn in more conventional ways such as via textbooks or even computer animation. Field testing of the Sky Time lesson has also led us to significant changes from the previous version to support student learning. We will report on the nature of these changes.

High Spectral Resolution Infrared and Raman Lidar Observations for the ARM Program: Clear and Cloudy Sky Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Revercomb, Henry; Tobin, David; Knuteson, Robert

2009-06-17

This grant began with the development of the Atmospheric Emitted Radiance Interferometer (AERI) for ARM. The AERI has provided highly accurate and reliable observations of downwelling spectral radiance (Knuteson et al. 2004a, 2004b) for application to radiative transfer, remote sensing of boundary layer temperature and water vapor, and cloud characterization. One of the major contributions of the ARM program has been its success in improving radiation calculation capabilities for models and remote sensing that evolved from the multi-year, clear-sky spectral radiance comparisons between AERI radiances and line-by-line calculations (Turner et al. 2004). This effort also spurred us to play amore » central role in improving the accuracy of water vapor measurements, again helping ARM lead the way in the community (Turner et al. 2003a, Revercomb et al. 2003). In order to add high-altitude downlooking AERI-like observations over the ARM sites, we began the development of an airborne AERI instrument that has become known as the Scanning High-resolution Interferometer Sounder (Scanning-HIS). This instrument has become an integral part of the ARM Unmanned Aerospace Vehicle (ARM-UAV) program. It provides both a cross-track mapping view of the earth and an uplooking view from the 12-15 km altitude of the Scaled Composites Proteus aircraft when flown over the ARM sites for IOPs. It has successfully participated in the first two legs of the “grand tour” of the ARM sites (SGP and NSA), resulting in a very good comparison with AIRS observations in 2002 and in an especially interesting data set from the arctic during the Mixed-Phase Cloud Experiment (M-PACE) in 2004.« less

The lizard celestial compass detects linearly polarized light in the blue.

PubMed

Beltrami, Giulia; Parretta, Antonio; Petrucci, Ferruccio; Buttini, Paola; Bertolucci, Cristiano; Foà, Augusto

2012-09-15

The present study first examined whether ruin lizards, Podarcis sicula, are able to orientate using plane-polarized light produced by an LCD screen. Ruin lizards were trained and tested indoors, inside a hexagonal Morris water maze positioned under an LCD screen producing white polarized light with a single E-vector, which provided an axial cue. White polarized light did not include wavelengths in the UV. Lizards orientated correctly either when tested with E-vector parallel to the training axis or after 90 deg rotation of the E-vector direction, thus validating the apparatus. Further experiments examined whether there is a preferential region of the light spectrum to perceive the E-vector direction of polarized light. For this purpose, lizards reaching learning criteria under white polarized light were subdivided into four experimental groups. Each group was tested for orientation under a different spectrum of plane-polarized light (red, green, cyan and blue) with equalized photon flux density. Lizards tested under blue polarized light orientated correctly, whereas lizards tested under red polarized light were completely disoriented. Green polarized light was barely discernible by lizards, and thus insufficient for a correct functioning of their compass. When exposed to cyan polarized light, lizard orientation performances were optimal, indistinguishable from lizards detecting blue polarized light. Overall, the present results demonstrate that perception of linear polarization in the blue is necessary - and sufficient - for a proper functioning of the sky polarization compass of ruin lizards. This may be adaptively important, as detection of polarized light in the blue improves functioning of the polarization compass under cloudy skies, i.e. when the alternative celestial compass based on detection of the sun disk is rendered useless because the sun is obscured by clouds.

Variability analysis of the reconstructed daily global solar radiation under all-sky and cloud-free conditions in Madrid during the period 1887-1950

NASA Astrophysics Data System (ADS)

Antón, M.; Román, R.; Sanchez-Lorenzo, A.; Calbó, J.; Vaquero, J. M.

2017-07-01

This study focuses on the analysis of the daily global solar radiation (GSR) reconstructed from sunshine duration measurements at Madrid (Spain) from 1887 to 1950. Additionally, cloud cover information recorded simultaneously by human observations for the study period was also analyzed and used to select cloud-free days. First, the day-to-day variability of reconstructed GSR data was evaluated, finding a strong relationship between GSR and cloudiness. The second step was to analyze the long-term evolution of the GSR data which exhibited two clear trends with opposite sign: a marked negative trend of - 36 kJ/m2 per year for 1887-1915 period and a moderate positive trend of + 13 kJ/m2 per year for 1916-1950 period, both statistically significant at the 95% confidence level. Therefore, there is evidence of "early dimming" and "early brightening" periods in the reconstructed GSR data for all-sky conditions in Madrid from the late 19th to the mid-20th centuries. Unlike the long-term evolution of GSR data, cloud cover showed non-statistically significant trends for the two analyzed sub-periods, 1887-1915 and 1916-1950. Finally, GSR trends were analyzed exclusively under cloud-free conditions in summer by means of the determination of the clearness index for those days with all cloud cover observations equal to zero oktas. The long-term evolution of the clearness index was in accordance with the "early dimming" and "early brightening" periods, showing smaller trends but still statistically significant. This result points out that aerosol load variability could have had a non-negligible influence on the long-term evolution of GSR even as far as from the late 19th century.

Comparison of the Sensitivity of Surface Downward Longwave Radiation to Changes in Water Vapor at Two High Elevation Sites

NASA Technical Reports Server (NTRS)

Chen, Yonghua; Naud, Catherine M.; Rangwala, Imtiaz; Landry, Christopher C.; Miller, James R.

2014-01-01

Among the potential reasons for enhanced warming rates in many high elevation regions is the nonlinear relationship between surface downward longwave radiation (DLR) and specific humidity (q). In this study we use ground-based observations at two neighboring high elevation sites in Southwestern Colorado that have different local topography and are 1.3 kilometers apart horizontally and 348 meters vertically. We examine the spatial consistency of the sensitivities (partial derivatives) of DLR with respect to changes in q, and the sensitivities are obtained from the Jacobian matrix of a neural network analysis. Although the relationship between DLR and q is the same at both sites, the sensitivities are higher when q is smaller, which occurs more frequently at the higher elevation site. There is a distinct hourly distribution in the sensitivities at both sites especially for high sensitivity cases, although the range is greater at the lower elevation site. The hourly distribution of the sensitivities relates to that of q. Under clear skies during daytime, q is similar between the two sites, however under cloudy skies or at night, it is not. This means that the DLR-q sensitivities are similar at the two sites during daytime but not at night, and care must be exercised when using data from one site to infer the impact of water vapor feedbacks at another site, particularly at night. Our analysis suggests that care should be exercised when using the lapse rate adjustment to infill high frequency data in a complex topographical region, particularly when one of the stations is subject to cold air pooling as found here.

First image of clouds over Mars

NASA Technical Reports Server (NTRS)

1997-01-01

This is the first image ever taken from the surface of Mars of an overcast sky. Featured are stratus clouds coming from the northeast at about 15 miles per hour (6.7 meters/second) at an approximate height of ten miles (16 kilometers) above the surface. The 'you are here' notation marks where Earth was situated in the sky at the time the image was taken. Scientists had hoped to see Earth in this image, but the cloudy conditions prevented a clear viewing. Similar images will be taken in the future with the hope of capturing a view of Earth. From Mars, Earth would appear as a tiny blue dot as a star would appear to an Earthbound observer. Pathfinder's imaging system will not be able to resolve Earth's moon. The clouds consist of water ice condensed on reddish dust particles suspended in the atmosphere. Clouds on Mars are sometimes localized and can sometimes cover entire regions, but have not yet been observed to cover the entire planet. The image was taken about an hour and forty minutes before sunrise by the Imager for Mars Pathfinder (IMP) on Sol 16 at about ten degrees up from the eastern Martian horizon.

Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages and Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is an operating division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

Statistical properties of the polarized emission of Planck Galactic cold clumps

NASA Astrophysics Data System (ADS)

Ristorcelli, Isabelle; Planck Collaboration

2015-08-01

The Galactic magnetic fields are considered as one of the key components regulating star formation, but their actual role on the dense cores formation and evolution remains today an open question.Dust polarized continuum emission is particularly well suited to probe the dense and cold medium and study the magnetic field structure. Such observations also provide tight constraints to better understand the efficiency of the dust alignment along the magnetic field lines, which in turn relate on our grasp to properly interpret the B-field properties.With the Planck all-sky survey of dust submillimeter emission in intensity and polarization, we can investigate the intermediate scales, between that of molecular cloud and of prestellar cores, and perform a statistical analysis on the polarization properties of cold clumps.Combined with the IRAS map at 100microns, the Planck survey has allowed to build the first all-sky catalogue of Galactic Cold Clumps (PGCC, Planck 2015 results XXVIII 2015). The corresponding 13188 sources cover a broad range in physical properties, and correspond to different evolutionary stages, from cold and starless clumps, nearby cores, to young protostellar objects still embedded in their cold surrounding cloud.I will present the main results of our polarization analysis obtained on different samples of sources from the PGCC catalogue, based on the 353GHz polarized emission measured with Planck. The statistical properties are derived from a stacking method, using optimized estimators for the polarization fraction and angle parameters. These properties are determined and compared according to the nature of the sources (starless or YSOs), their size or density range. Finally, I will present a comparison of our results with predictions from MHD simulations of clumps including radiative transfer and the dust radiative torque alignment mechanism.

Automated Cloud Observation for Ground Telescope Optimization

NASA Astrophysics Data System (ADS)

Lane, B.; Jeffries, M. W., Jr.; Therien, W.; Nguyen, H.

As the number of man-made objects placed in space each year increases with advancements in commercial, academic and industry, the number of objects required to be detected, tracked, and characterized continues to grow at an exponential rate. Commercial companies, such as ExoAnalytic Solutions, have deployed ground based sensors to maintain track custody of these objects. For the ExoAnalytic Global Telescope Network (EGTN), observation of such objects are collected at the rate of over 10 million unique observations per month (as of September 2017). Currently, the EGTN does not optimally collect data on nights with significant cloud levels. However, a majority of these nights prove to be partially cloudy providing clear portions in the sky for EGTN sensors to observe. It proves useful for a telescope to utilize these clear areas to continue resident space object (RSO) observation. By dynamically updating the tasking with the varying cloud positions, the number of observations could potentially increase dramatically due to increased persistence, cadence, and revisit. This paper will discuss the recent algorithms being implemented within the EGTN, including the motivation, need, and general design. The use of automated image processing as well as various edge detection methods, including Canny, Sobel, and Marching Squares, on real-time large FOV images of the sky enhance the tasking and scheduling of a ground based telescope is discussed in Section 2. Implementations of these algorithms on single and expanding to multiple telescopes, will be explored. Results of applying these algorithms to the EGTN in real-time and comparison to non-optimized EGTN tasking is presented in Section 3. Finally, in Section 4 we explore future work in applying these throughout the EGTN as well as other optical telescopes.

Environmental Cues to Ultraviolet Radiation and Personal Sun Protection In Outdoor Winter Recreation

PubMed Central

Buller, David B.; Walkosz, Barbara J.; Scott, Michael D.; Maloy, Julie A.; Cutter, Gary R.; Dignan, Mark D.

2012-01-01

Objective The prevalence of ultraviolet radiation (UV) at North American ski resorts was predicted using temporal, seasonal, altitudinal, and meteorological factors and associated with a set of adult sun protection behaviors. Design UV observations and cross-sectional survey of adults on sun protection were collected. Setting Data were collected at 32 high-altitude ski areas located in Western North America in 2001–03. Participants The sample consisted of 3,937 adult skier or snowboarders. Main Outcome Measures Measurements of direct, reflected, and diffuse UV were performed at 487 measurement points using handheld meters and combined with self-reported and observed sun protection assessed for adults interviewed on chair lifts. Results The strongest predictors of UV were temporal proximity to noon, deviation from winter solstice, and clear skies. By contrast, altitude and latitude had more modest associations with UV and temperature had a small positive relationship with UV. Guest sun safety was inconsistently associated with UV: UV was positively related to adults wearing more sunscreen, reapplying it after two hours, and wearing protective eyewear but fewer adults exhibited many of the other sun protection behaviors, such as hats, protective clothing or lip balm, on days when UV was elevated. Guests took more sun safety precautions on clear-sky days but took steps to maintain body warmth on inclement days. Conclusions In future sun safety promotions, adults should be encouraged to wear sunscreen on cloudy days because UV is still high and conditions can change rapidly. They need reminders to rely more on season and time of day when judging UV and the need for sun safety. PMID:21079060

Comparison of Radiative Energy Flows in Observational Datasets and Climate Modeling

NASA Technical Reports Server (NTRS)

Raschke, Ehrhard; Kinne, Stefan; Rossow, William B.; Stackhouse, Paul W. Jr.; Wild, Martin

2016-01-01

This study examines radiative flux distributions and local spread of values from three major observational datasets (CERES, ISCCP, and SRB) and compares them with results from climate modeling (CMIP3). Examinations of the spread and differences also differentiate among contributions from cloudy and clear-sky conditions. The spread among observational datasets is in large part caused by noncloud ancillary data. Average differences of at least 10Wm(exp -2) each for clear-sky downward solar, upward solar, and upward infrared fluxes at the surface demonstrate via spatial difference patterns major differences in assumptions for atmospheric aerosol, solar surface albedo and surface temperature, and/or emittance in observational datasets. At the top of the atmosphere (TOA), observational datasets are less influenced by the ancillary data errors than at the surface. Comparisons of spatial radiative flux distributions at the TOA between observations and climate modeling indicate large deficiencies in the strength and distribution of model-simulated cloud radiative effects. Differences are largest for lower-altitude clouds over low-latitude oceans. Global modeling simulates stronger cloud radiative effects (CRE) by +30Wmexp -2) over trade wind cumulus regions, yet smaller CRE by about -30Wm(exp -2) over (smaller in area) stratocumulus regions. At the surface, climate modeling simulates on average about 15Wm(exp -2) smaller radiative net flux imbalances, as if climate modeling underestimates latent heat release (and precipitation). Relative to observational datasets, simulated surface net fluxes are particularly lower over oceanic trade wind regions (where global modeling tends to overestimate the radiative impact of clouds). Still, with the uncertainty in noncloud ancillary data, observational data do not establish a reliable reference.

Lick Jupiter-Voyager reference star catalogue (Klemola, Morabito, and Taraji 1978): Documentation for the machine-readable version

NASA Technical Reports Server (NTRS)

Warren, Wayne H., Jr.

1990-01-01

The machine-readable version of the catalog, as it is currently being distributed from the Astronomical Data Center, is described. The catalog contains accurate equatorial coordinates for 4983 stars in a band of sky against which cameras of the Voyager spacecraft were pointed for observations in the region of Jupiter during the flyby. All of the reference stars are in the range 6 hr 00 min to 8 hr 04 min in right ascension (1950), declination zones +16 to +23 degrees, and 8 hr to 31 min to 8 hr 57 min, zones +08 to +14 degrees. Mean errors of the positions are about 0.4 sec.

Improved Atmospheric Soundings and Error Estimates from Analysis of AIRS/AMSU Data

NASA Technical Reports Server (NTRS)

Susskind, Joel

2007-01-01

The AIRS Science Team Version 5.0 retrieval algorithm became operational at the Goddard DAAC in July 2007 generating near real-time products from analysis of AIRS/AMSU sounding data. This algorithm contains many significant theoretical advances over the AIRS Science Team Version 4.0 retrieval algorithm used previously. Three very significant developments of Version 5 are: 1) the development and implementation of an improved Radiative Transfer Algorithm (RTA) which allows for accurate treatment of non-Local Thermodynamic Equilibrium (non-LTE) effects on shortwave sounding channels; 2) the development of methodology to obtain very accurate case by case product error estimates which are in turn used for quality control; and 3) development of an accurate AIRS only cloud clearing and retrieval system. These theoretical improvements taken together enabled a new methodology to be developed which further improves soundings in partially cloudy conditions, without the need for microwave observations in the cloud clearing step as has been done previously. In this methodology, longwave C02 channel observations in the spectral region 700 cm-' to 750 cm-' are used exclusively for cloud clearing purposes, while shortwave C02 channels in the spectral region 2195 cm-' to 2395 cm-' are used for temperature sounding purposes. The new methodology for improved error estimates and their use in quality control is described briefly and results are shown indicative of their accuracy. Results are also shown of forecast impact experiments assimilating AIRS Version 5.0 retrieval products in the Goddard GEOS 5 Data Assimilation System using different quality control thresholds.

Cloudy's Journey from FORTRAN to C, Why and How

NASA Astrophysics Data System (ADS)

Ferland, G. J.

Cloudy is a large-scale plasma simulation code that is widely used across the astronomical community as an aid in the interpretation of spectroscopic data. The cover of the ADAS VI book featured predictions of the code. The FORTRAN 77 source code has always been freely available on the Internet, contributing to its widespread use. The coming of PCs and Linux has fundamentally changed the computing environment. Modern Fortran compilers (F90 and F95) are not freely available. A common-use code must be written in either FORTRAN 77 or C to be Open Source/GNU/Linux friendly. F77 has serious drawbacks - modern language constructs cannot be used, students do not have skills in this language, and it does not contribute to their future employability. It became clear that the code would have to be ported to C to have a viable future. I describe the approach I used to convert Cloudy from FORTRAN 77 with MILSPEC extensions to ANSI/ISO 89 C. Cloudy is now openly available as a C code, and will evolve to C++ as gcc and standard C++ mature. Cloudy looks to a bright future with a modern language.

On the Analysis of the Climatology of Cloudiness of the Arabian Peninsula

NASA Astrophysics Data System (ADS)

Yousef, L. A.; Temimi, M.

2015-12-01

This study aims to determine the climatology of cloudiness over the Arabian Peninsula. The determined climatology will assist solar energy resource assessment in the region. The seasonality of cloudiness and its spatial variability will also help guide several cloud seeding operational experiments in the region. Cloud properties from the International Satellite Cloud Climatology Project (ISCCP) database covering the time period from 1983 through 2009 are analyzed. Time series of low, medium, high, and total cloud amounts are investigated, in addition to cloud optical depth and total column water vapor. Initial results show significant decreasing trends in the total and middle cloud amounts, both annually and seasonally, at a 95% confidence interval. The relationship between cloud amounts and climate oscillations known to affect the region is explored. Climate indices exhibiting significant correlations with the total cloud amounts include the Pacific Decadal Oscillation (PDO) index. The study also includes a focus on the United Arab Emirates (UAE), comparing the inferred cloudiness data to in situ rainfall measurements taken from rain gauges across the UAE. To assess the impact of cloudiness on solar power resources in the country, time series of cloud amounts and Direct Normal Irradiance (DNI), obtained from the UAE Solar Atlas, are compared.

CNO Abundances in Metal-Rich Environments: Infrared Space Observatory Spectroscopy of Ionized Gas in M51

NASA Astrophysics Data System (ADS)

Garnett, Donald R.; Edmunds, Michael G.; Henry, Richard B. C.; Pagel, Bernard E. J.; Skillman, Evan D.

2004-12-01

We present Infrared Space Observatory (ISO) Long Wavelength Spectrograph observations centered on the H II region CCM 10 in the spiral galaxy M51. We detect several emission lines in this spectrum, including [O I] 63 and 145 μm, [C II] 158 μm, [O III] 88 μm, and [N II] 122 μm, with a significant upper limit on [N III] 57 μm. We use these measurements to estimate abundances for C, N, and O in the interstellar medium in M51. We compare our [O III] 88 μm flux with the flux for [O III] λ5007 obtained from narrowband imaging. The derived 5007Å/88μm ratio yields an electron temperature Te=5300+/-300 K. This temperature agrees with estimates of T[O III] based on photoionization models of CCM 10 with logO/H=-3.2, an abundance that is about a factor of 2 smaller than earlier results for this object derived from photoionization modeling of the visible spectrum. A possible cause for the discrepancy is that the older photoionization models based on CLOUDY predict significantly larger optical emission-line strengths than the current version of CLOUDY at the same metallicity; models with the more recent version are more consistent with the observed spectra of M51 H II region with reduced O/H. Assuming N/O=N+2/O+2, the upper limit for [NIII]/[OIII] yields logN/O<-0.5, which is consistent with the trend of N/O versus O/H seen in other spiral galaxies. C/O is estimated from the [CII]/[OI] ratio using photodissociation region models constrained by published CO line ratios, [CI]/CO, and [OI]63μm/145μm. With these various constraints on ne and G0, the observed [CII]/[OI] intensity ratio is in good agreeement with that predicted by photodissociation region models with approximately solar abundances. We infer from this that C/O in M51 is consistent with the solar neighborhood value.

Cloud Radiative Forcing at the ARM Climate Research Facility. Part 1; Technique, Validation, and Comparison to Satellite-derived Diagnostic Quantities

NASA Technical Reports Server (NTRS)

Mace, Gerald G.; Benson, Sally; Sonntag, Karen L.; Kato, Seiji; Min, Qilong; Minnis, Patrick; Twohy, Cynthia H.; Poellot, Michael; Dong, Xiquan; Long, Charles;

Cloud Radiative Effect in dependence on Cloud Type

NASA Astrophysics Data System (ADS)

Aebi, Christine; Gröbner, Julian; Kämpfer, Niklaus; Vuilleumier, Laurent

2015-04-01

Radiative transfer of energy in the atmosphere and the influence of clouds on the radiation budget remain the greatest sources of uncertainty in the simulation of climate change. Small changes in cloudiness and radiation can have large impacts on the Earth's climate. In order to assess the opposing effects of clouds on the radiation budget and the corresponding changes, frequent and more precise radiation and cloud observations are necessary. The role of clouds on the surface radiation budget is studied in order to quantify the longwave, shortwave and the total cloud radiative forcing in dependence on the atmospheric composition and cloud type. The study is performed for three different sites in Switzerland at three different altitude levels: Payerne (490 m asl), Davos (1'560 m asl) and Jungfraujoch (3'580 m asl). On the basis of data of visible all-sky camera systems at the three aforementioned stations in Switzerland, up to six different cloud types are distinguished (Cirrus-Cirrostratus, Cirrocumulus-Altocumulus, Stratus-Altostratus, Cumulus, Stratocumulus and Cumulonimbus-Nimbostratus). These cloud types are classified with a modified algorithm of Heinle et al. (2010). This cloud type classifying algorithm is based on a set of statistical features describing the color (spectral features) and the texture of an image (textural features) (Wacker et al. (2015)). The calculation of the fractional cloud cover information is based on spectral information of the all-sky camera data. The radiation data are taken from measurements with pyranometers and pyrgeometers at the different stations. A climatology of a whole year of the shortwave, longwave and total cloud radiative effect and its sensitivity to integrated water vapor, cloud cover and cloud type will be calculated for the three above-mentioned stations in Switzerland. For the calculation of the shortwave and longwave cloud radiative effect the corresponding cloud-free reference models developed at PMOD/WRC will be used (Wacker et al. (2013)). References: Heinle, A., A. Macke and A. Srivastav (2010) Automatic cloud classification of whole sky images, Atmospheric Measurement Techniques. Wacker, S., J. Gröbner and L. Vuilleumier (2013) A method to calculate cloud-free long-wave irradiance at the surface based on radiative transfer modeling and temperature lapse rate estimates, Theoretical and Applied Climatology. Wacker, S., J. Gröbner, C. Zysset, L. Diener, P. Tzoumanikis, A. Kazantzidis, L. Vuilleumier, R. Stöckli, S. Nyeki, and N. Kämpfer (2015) Cloud observations in Switzerland using hemispherical sky cameras, Journal of Geophysical Research.

Photographic coverage of STS-115 Egress Training. Bldg.9NW, CTT

NASA Image and Video Library

2002-12-03

JSC2002-02132 (3 December 2002) --- Astronaut Daniel C. Burbank, STS-115 mission specialist, uses the Sky-genie to lower himself from a simulated trouble-plagued shuttle in an emergency egress training session in the Space Vehicle Mockup Facility at the Johnson Space Center (JSC). Burbank is wearing a training version of the shuttle launch and entry suit. United Space Alliance (USA) crew trainer David Pogue assisted Burbank.

Research toward Multi-site Characterization of Sky Obscuration by Clouds

DTIC Science & Technology

2009-07-01

Oct 07 interim moonlight algorithm in comparison with the May 08 version that was fielded. This talk also includes movies that are perhaps the most...starlight, and new results for moonlight with partially 58 completed algorithm, for Site 5, and past transmittance results. Reviewed day alg results...per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and

Native Skies

NASA Astrophysics Data System (ADS)

Benningfield, Damond

2001-03-01

People native to North America practiced their own version of astronomy. They tracked the motions of the Sun to help them decide when to plant crops, move their camps, and stage sacred rituals. Some tribes built great circles of stones to help them predict the changing seasons. Others built great mounds of earth to reflect the patterns they saw in the heavens and to align their ceremonial centers with the Sun and the Moon.

The Relationship Between Surface Temperature Anomaly Time Series and those of OLR, Water Vapor, and Cloud Cover as Observed Using Nine Years of AIRS Version-5 Level-3 Products

NASA Technical Reports Server (NTRS)

Susskind, Joel; Molnar, Gyula; Iredell, Lena

2011-01-01

Outline: (1) Comparison of AIRS and CERES anomaly time series of outgoing longwave radiation (OLR) and OLR(sub CLR), i.e. Clear Sky OLR (2) Explanation of recent decreases in global and tropical mean values of OLR (3) AIRS "Short-term" Longwave Cloud Radiative Feedback -- A new product

Different insulin concentrations in resuspended vs. unsuspended NPH insulin: Practical aspects of subcutaneous injection in patients with diabetes.

PubMed

Lucidi, P; Porcellati, F; Marinelli Andreoli, A; Candeloro, P; Cioli, P; Bolli, G B; Fanelli, C G

2017-06-06

This study measured the insulin concentration (Ins [C] ) of NPH insulin in vials and cartridges from different companies after either resuspension (R+) or not (R-; in the clear/cloudy phases of unsuspended NPH). Measurements included Ins [C] in NPH(R+) and in the clear/cloudy phases of NPH(R-), and the time needed to resuspend NPH and time for NPH(R+) to separate again into clear/cloudy parts. In vials of NPH(R+) (assumed to be 100%), Ins [C] in the clear phase of NPH(R-) was<1%, but 230±41% and 234±54% in the cloudy phases of Novo Nordisk and Eli Lilly NPH, respectively. Likewise, in pen cartridges, Ins [C] in the clear phase of NPH(R-) was<1%, but 182±33%, 204±22% and 229±62% in the cloudy phases of Novo, Lilly and Sanofi NPH. Time needed to resuspend NPH (spent in tipping) in vials was brief with both Novo (5±1s) and Lilly NPH (6±1s), but longer with all pen cartridges (50±8s, 40±6s and 30±4s from Novo, Lilly and Sanofi, respectively; P=0.022). Time required for 50% separation into cloudy and clear parts of NPH was longer with Novo (60±7min) vs. Lilly (18±3min) in vials (P=0.021), and affected by temperature, but not by the different diameter sizes of the vials. With pen cartridges, separation into clear and cloudy parts was significantly faster than in vials (P<0.01). Ins [C] in NPH preparations varies depending on their resuspension or not. Thus, subcutaneous injection of the same number of units of NPH in patients with diabetes may deliver different amounts of insulin depending on its prior NPH resuspension. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Investigation of scene identification algorithms for radiation budget measurements

NASA Technical Reports Server (NTRS)

Diekmann, F. J.

1986-01-01

The computation of Earth radiation budget from satellite measurements requires the identification of the scene in order to select spectral factors and bidirectional models. A scene identification procedure is developed for AVHRR SW and LW data by using two radiative transfer models. These AVHRR GAC pixels are then attached to corresponding ERBE pixels and the results are sorted into scene identification probability matrices. These scene intercomparisons show that there generally is a higher tendency for underestimation of cloudiness over ocean at high cloud amounts, e.g., mostly cloudy instead of overcast, partly cloudy instead of mostly cloudy, for the ERBE relative to the AVHRR results. Reasons for this are explained. Preliminary estimates of the errors of exitances due to scene misidentification demonstrates the high dependency on the probability matrices. While the longwave error can generally be neglected the shortwave deviations have reached maximum values of more than 12% of the respective exitances.

A Framework for Cloudy Model Optimization and Database Storage

NASA Astrophysics Data System (ADS)

Calvén, Emilia; Helton, Andrew; Sankrit, Ravi

2018-01-01

We present a framework for producing Cloudy photoionization models of the nebular emission from novae ejecta and storing a subset of the results in SQL database format for later usage. The database can be searched for models best fitting observed spectral line ratios. Additionally, the framework includes an optimization feature that can be used in tandem with the database to search for and improve on models by creating new Cloudy models while, varying the parameters. The database search and optimization can be used to explore the structures of nebulae by deriving their properties from the best-fit models. The goal is to provide the community with a large database of Cloudy photoionization models, generated from parameters reflecting conditions within novae ejecta, that can be easily fitted to observed spectral lines; either by directly accessing the database using the framework code or by usage of a website specifically made for this purpose.

Thermal degradation of cloudy apple juice phenolic constituents.

PubMed

De Paepe, D; Valkenborg, D; Coudijzer, K; Noten, B; Servaes, K; De Loose, M; Voorspoels, S; Diels, L; Van Droogenbroeck, B

2014-11-01

Although conventional thermal processing is still the most commonly used preservation technique in cloudy apple juice production, detailed knowledge on phenolic compound degradation during thermal treatment is still limited. To evaluate the extent of thermal degradation as a function of time and temperature, apple juice samples were isothermally treated during 7,200s over a temperature range of 80-145 °C. An untargeted metabolomics approach based on liquid chromatography-high resolution mass spectrometry was developed and applied with the aim to find out the most heat labile phenolic constituents in cloudy apple juice. By the use of a high resolution mass spectrometer, the high degree of in-source fragmentation, the quality of deconvolution and the employed custom-made database, it was possible to achieve a high degree of structural elucidation for the thermolabile phenolic constituents. Procyanidin subclass representatives were discovered as the most heat labile phenolic compounds of cloudy apple juice. Copyright © 2014. Published by Elsevier Ltd.

Modeling shortwave radiative fluxes from satellites

NASA Astrophysics Data System (ADS)

Ma, Y.; Pinker, R. T.

2012-12-01

During the last two decades, significant progress has been made in assessing the Earth Radiation Balance from satellite observations. Yet, satellite based estimates differ from each other and from those provided by numerical models. Major issues are related to quality of satellite observations, such as the frequent changes in satellite observing systems, degradation of sensors, restricted spectral intervals and viewing geometry of sensors, and changes in the quality of atmospheric inputs that drive the inference schemes. To reduce differences among the satellite based estimates requires, among others, updates to inference schemes so that most recent auxiliary information can be fully utilized. This paper reports on improvements introduced to a methodology developed at the University of Maryland to estimate shortwave (SW) radiative fluxes within the atmosphere system from satellite observations, the implementation of the approach with newly available auxiliary information, evaluation of the downwelling SW flux against ground observations, and comparison with independent satellite methods and numerical models. Specifically, introduced are: new Narrow to Broadband (N/B) transformations and new Angular Distribution Models (ADM) for clear and cloudy sky that incorporate most recent land use classifications; improved aerosol treatment; separation of clouds by phase; improved sun-earth geometry; and implementation at 0.5° spatial resolution at 3-hourly intervals integrated to daily and monthly time scales. When compared to an earlier version of the model as implemented at 2.5° at global scale and against observations from the globally distributed Baseline Surface Radiation Network (BSRN) stations for a period of six years (at monthly time scale), the bias was reduced from 8.6 (4.6%) to -0.5 (0.3%) W/m2, the standard deviation from 16.6 (8.9%) to 14.5 (7.8%) W/m2while the correlation remained high at 0.98 in both cases. Evaluation was also done over oceanic sites as available from the Pilot Research Moored Array in the Tropical Atlantic (PIRATA) moorings and from the Tropical Atmosphere Ocean/Triangle Trans-Ocean Buoy Network (TAO/TRITON) moorings in the tropical Pacific Ocean. Overall, results over oceans were not as good as over land for all the satellite retrievals compared in this study.

Simulation of the present-day climate with the climate model INMCM5

NASA Astrophysics Data System (ADS)

Volodin, E. M.; Mortikov, E. V.; Kostrykin, S. V.; Galin, V. Ya.; Lykossov, V. N.; Gritsun, A. S.; Diansky, N. A.; Gusev, A. V.; Iakovlev, N. G.

2017-12-01

In this paper we present the fifth generation of the INMCM climate model that is being developed at the Institute of Numerical Mathematics of the Russian Academy of Sciences (INMCM5). The most important changes with respect to the previous version (INMCM4) were made in the atmospheric component of the model. Its vertical resolution was increased to resolve the upper stratosphere and the lower mesosphere. A more sophisticated parameterization of condensation and cloudiness formation was introduced as well. An aerosol module was incorporated into the model. The upgraded oceanic component has a modified dynamical core optimized for better implementation on parallel computers and has two times higher resolution in both horizontal directions. Analysis of the present-day climatology of the INMCM5 (based on the data of historical run for 1979-2005) shows moderate improvements in reproduction of basic circulation characteristics with respect to the previous version. Biases in the near-surface temperature and precipitation are slightly reduced compared with INMCM4 as well as biases in oceanic temperature, salinity and sea surface height. The most notable improvement over INMCM4 is the capability of the new model to reproduce the equatorial stratospheric quasi-biannual oscillation and statistics of sudden stratospheric warmings.

Photographic coverage of STS-115 Egress Training. Bldg.9NW, CTT

NASA Image and Video Library

2002-12-03

JSC2002-02121 (3 December 2002) --- Astronaut Joseph R. (Joe) Tanner, STS-115 mission specialist, uses the Sky-genie to lower himself from a simulated trouble-plagued shuttle in an emergency egress training session in the Space Vehicle Mockup Facility at the Johnson Space Center (JSC). Tanner is wearing a training version of the shuttle launch and entry suit. United Space Alliance (USA) crew trainer David Pogue assisted Tanner.

All-Sky Observational Evidence for An Inverse Correlation Between Dust Temperature and Emissivity Spectral Index

NASA Technical Reports Server (NTRS)

Liang, Z.; Fixsen, D. J.; Gold, B.

2012-01-01

We show that a one-component variable-emissivity-spectral-index model (the free- model) provides more physically motivated estimates of dust temperature at the Galactic polar caps than one- or two-component fixed-emissivity-spectral-index models (fixed- models) for interstellar dust thermal emission at far-infrared and millimeter wavelengths. For the comparison we have fit all-sky one-component dust models with fixed or variable emissivity spectral index to a new and improved version of the 210-channel dust spectra from the COBE-FIRAS, the 100-240 micrometer maps from the COBE-DIRBE and the 94 GHz dust map from the WMAP. The best model, the free-alpha model, is well constrained by data at 60-3000 GHz over 86 per cent of the total sky area. It predicts dust temperature (T(sub dust)) to be 13.7-22.7 (plus or minus 1.3) K, the emissivity spectral index (alpha) to be 1.2-3.1 (plus or minus 0.3) and the optical depth (tau) to range 0.6-46 x 10(exp -5) with a 23 per cent uncertainty. Using these estimates, we present all-sky evidence for an inverse correlation between the emissivity spectral index and dust temperature, which fits the relation alpha = 1/(delta + omega (raised dot) T(sub dust) with delta = -.0.510 plus or minus 0.011 and omega = 0.059 plus or minus 0.001. This best model will be useful to cosmic microwave background experiments for removing foreground dust contamination and it can serve as an all-sky extended-frequency reference for future higher resolution dust models.

The LOFAR Multifrequency Snapshot Sky Survey (MSSS): Status and Results

NASA Astrophysics Data System (ADS)

Heald, George; LOFAR Collaboration

2014-01-01

The Multifrequency Snapshot Sky Survey (MSSS) is the first large-area survey of the northern sky with the Low Frequency Array (LOFAR). By producing images of the sky at 16 frequencies from 30 to 160 MHz, MSSS probes the low-frequency sky at a sensitivity of order 10 mJy/beam, and angular resolution of 1-2 arcmin or better. It thus dramatically expands the frequency range sampled in high-resolution radio surveys, and, crucially, provides low-frequency spectral information about the detected sources. Using LOFAR's unique multi-beaming mode, the survey requires only a rather modest investment in observing time. MSSS began observations in late 2011, and has nearly completed observations in both frequency components (8 frequencies spanning the 30 to 74 MHz range, and another 8 spanning 120 to 160 MHz). MSSS has driven the initial development of the first production version of LOFAR's automatic Imaging Pipeline and spearheaded efforts aimed at solving some of the ongoing low-frequency calibration challenges. In this contribution, I will briefly review the survey design, including an overview of MSSS science topics. I will also present a status update, highlighting early results from the survey such as an in-depth look at the 100 square degree “MSSS Verification Field,” new sources discovered in MSSS images, and a sneak peek at the full survey area. I will conclude by describing plans for the future of MSSS, including the possibility of reprocessing the data to obtain enhanced data products such as higher resolution imaging and polarization. LOFAR, the Low Frequency Array designed and constructed by ASTRON, has facilities in several countries, that are owned by various parties (each with their own funding sources), and that are collectively operated by the International LOFAR Telescope (ILT) foundation under a joint scientific policy.

The Regional Influence of the Arctic Oscillation and Arctic Dipole on the Wintertime Arctic Surface Radiation Budget and Sea Ice Growth

NASA Technical Reports Server (NTRS)

Hegyi, Bradley M.; Taylor, Patrick C.

2017-01-01

An analysis of 2000-2015 monthly Clouds and the Earth's Radiant Energy System-Energy Balanced and Filled (CERES-EBAF) and Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA2) data reveals statistically significant fall and wintertime relationships between Arctic surface longwave (LW) radiative flux anomalies and the Arctic Oscillation (AO) and Arctic Dipole (AD). Signifying a substantial regional imprint, a negative AD index corresponds with positive downwelling clear-sky LW flux anomalies (greater than10W m(exp -2)) north of western Eurasia (0 deg E-120 deg E) and reduced sea ice growth in the Barents and Kara Seas in November-February. Conversely, a positive AO index coincides with negative clear-sky LW flux anomalies and minimal sea ice growth change in October-November across the Arctic. Increased (decreased) atmospheric temperature and water vapor coincide with the largest positive (negative) clear-sky flux anomalies. Positive surface LW cloud radiative effect anomalies also accompany the negative AD index in December-February. The results highlight a potential pathway by which Arctic atmospheric variability influences the regional surface radiation budget over areas of Arctic sea ice growth.

MODTRAN cloud and multiple scattering upgrades with application to AVIRIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berk, A.; Bernstein, L.S.; Acharya, P.K.

1998-09-01

Recent upgrades to the MODTRAN atmospheric radiation code improve the accuracy of its radiance predictions, especially in the presence of clouds and thick aerosols, and for multiple scattering in regions of strong molecular line absorption. The current public-released version of MODTRAN (MODTRAN3.7) features a generalized specification of cloud properties, while the current research version of MODTRAN (MODTRAN4) implements a correlated-k (CK) approach for more accurate calculation of multiple scattered radiance. Comparisons to cloud measurements demonstrate the viability of the CK approach. The impact of these upgrades on predictions for AVIRIS viewing scenarios is discussed for both clear and clouded skies;more » the CK approach provides refined predictions for AVIRIS nadir and near-nadir viewing.« less

Laser safety and hazard analysis for the temperature stabilized BSLT ARES laser system.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Augustoni, Arnold L.

A laser safety and hazard analysis was performed for the temperature stabilized Big Sky Laser Technology (BSLT) laser central to the ARES system based on the 2000 version of the American National Standards Institute's (ANSI) Standard Z136.1, for Safe Use of Lasers and the 2000 version of the ANSI Standard Z136.6, for Safe Use of Lasers Outdoors. As a result of temperature stabilization of the BSLT laser the operating parameters of the laser had changed requiring a hazard analysis based on the new operating conditions. The ARES laser system is a Van/Truck based mobile platform, which is used to performmore » laser interaction experiments and tests at various national test sites.« less

Pluto Haze

NASA Image and Video Library

2015-09-10

Two different versions of an image of Pluto's haze layers, taken by New Horizons as it looked back at Pluto's dark side nearly 16 hours after close approach, from a distance of 480,000 miles (770,000 kilometers), at a phase angle of 166 degrees. Pluto's north is at the top, and the sun illuminates Pluto from the upper right. These images are much higher quality than the digitally compressed images of Pluto's haze downlinked and released shortly after the July 14 encounter, and allow many new details to be seen. The left version has had only minor processing, while the right version has been specially processed to reveal a large number of discrete haze layers in the atmosphere. In the left version, faint surface details on the narrow sunlit crescent are seen through the haze in the upper right of Pluto's disk, and subtle parallel streaks in the haze may be crepuscular rays- shadows cast on the haze by topography such as mountain ranges on Pluto, similar to the rays sometimes seen in the sky after the sun sets behind mountains on Earth. http://photojournal.jpl.nasa.gov/catalog/PIA19880

SLUG - stochastically lighting up galaxies - III. A suite of tools for simulated photometry, spectroscopy, and Bayesian inference with stochastic stellar populations

NASA Astrophysics Data System (ADS)

Krumholz, Mark R.; Fumagalli, Michele; da Silva, Robert L.; Rendahl, Theodore; Parra, Jonathan

2015-09-01

Stellar population synthesis techniques for predicting the observable light emitted by a stellar population have extensive applications in numerous areas of astronomy. However, accurate predictions for small populations of young stars, such as those found in individual star clusters, star-forming dwarf galaxies, and small segments of spiral galaxies, require that the population be treated stochastically. Conversely, accurate deductions of the properties of such objects also require consideration of stochasticity. Here we describe a comprehensive suite of modular, open-source software tools for tackling these related problems. These include the following: a greatly-enhanced version of the SLUG code introduced by da Silva et al., which computes spectra and photometry for stochastically or deterministically sampled stellar populations with nearly arbitrary star formation histories, clustering properties, and initial mass functions; CLOUDY_SLUG, a tool that automatically couples SLUG-computed spectra with the CLOUDY radiative transfer code in order to predict stochastic nebular emission; BAYESPHOT, a general-purpose tool for performing Bayesian inference on the physical properties of stellar systems based on unresolved photometry; and CLUSTER_SLUG and SFR_SLUG, a pair of tools that use BAYESPHOT on a library of SLUG models to compute the mass, age, and extinction of mono-age star clusters, and the star formation rate of galaxies, respectively. The latter two tools make use of an extensive library of pre-computed stellar population models, which are included in the software. The complete package is available at http://www.slugsps.com.

Bioactive compounds and quality parameters of natural cloudy lemon juices.

PubMed

Uçan, Filiz; Ağçam, Erdal; Akyildiz, Asiye

2016-03-01

In this study, bioactive compounds (phenolic and carotenoid) and some quality parameters (color, browning index and hydroxymethylfurfural (HMF)) of natural cloudy lemon juice, pasteurized (90 °C/15 s) and storage stability of concentrated lemon juice (-25 °C/180 days) were carried out. Fifteen phenolic compounds were determined in the lemon juice and the most abounded phenolic compounds were hesperidin, eriocitrin, chlorogenic acid and neoeriocitrin. In generally, phenolic compound concentrations of lemon juice samples increased after the pasteurization treatment. Four carotenoid compounds (β-carotene, β-cryptoxanthin, lutein and zeaxanthin) were detected in natural cloudy lemon juice. Lutein and β-cryptoxanthin were the most abounded carotenoid compounds in the lemon juice. Color values of the lemon juices were not affected by processing and storage periods. HMF and browning index of the lemon juices increased with concentration and storage. According to the results, storing at -25 °C was considered as sufficient for acceptable quality limits of natural cloudy lemon juice.

Minimizing quality changes of cloudy apple juice: The use of kiwifruit puree and high pressure homogenization.

PubMed

Yi, Junjie; Kebede, Biniam; Kristiani, Kristiani; Grauwet, Tara; Van Loey, Ann; Hendrickx, Marc

2018-05-30

Cloud loss, enzymatic browning, and flavor changes are important quality defects of cloudy fruit juices determining consumer acceptability. The development of clean label options to overcome such quality problems is currently of high interest. Therefore, this study investigated the effect of kiwifruit puree (clean label ingredient) and high pressure homogenization on quality changes of cloudy apple juice using a multivariate approach. The use of kiwifruit puree addition and high pressure homogenization resulted in a juice with improved uniformity and cloud stability by reducing particle size and increasing viscosity and yield stress (p < 0.01). Furthermore, kiwifruit puree addition reduced enzymatic browning (ΔE ∗  < 3), due to the increased ascorbic acid and contributed to a more saturated and bright yellow color, a better taste balance, and a more fruity aroma of juice. This work demonstrates that clean label options to control quality degradation of cloudy fruit juice might offer new opportunities. Copyright © 2018 Elsevier Ltd. All rights reserved.

Cloud fraction and cloud base measurements from scanning Doppler lidar during WFIP-2

NASA Astrophysics Data System (ADS)

Bonin, T.; Long, C.; Lantz, K. O.; Choukulkar, A.; Pichugina, Y. L.; McCarty, B.; Banta, R. M.; Brewer, A.; Marquis, M.

2017-12-01

The second Wind Forecast Improvement Project (WFIP-2) consisted of an 18-month field deployment of a variety of instrumentation with the principle objective of validating and improving NWP forecasts for wind energy applications in complex terrain. As a part of the set of instrumentation, several scanning Doppler lidars were installed across the study domain to primarily measure profiles of the mean wind and turbulence at high-resolution within the planetary boundary layer. In addition to these measurements, Doppler lidar observations can be used to directly quantify the cloud fraction and cloud base, since clouds appear as a high backscatter return. These supplementary measurements of clouds can then be used to validate cloud cover and other properties in NWP output. Herein, statistics of the cloud fraction and cloud base height from the duration of WFIP-2 are presented. Additionally, these cloud fraction estimates from Doppler lidar are compared with similar measurements from a Total Sky Imager and Radiative Flux Analysis (RadFlux) retrievals at the Wasco site. During mostly cloudy to overcast conditions, estimates of the cloud radiating temperature from the RadFlux methodology are also compared with Doppler lidar measured cloud base height.

Infrared radiative transfer through a regular array of cuboidal clouds

NASA Technical Reports Server (NTRS)

HARSHVARDHAN; Weinman, J. A.

1981-01-01

Infrared radiative transfer through a regular array of cuboidal clouds is studied and the interaction of the sides of the clouds with each other and the ground is considered. The theory is developed for black clouds and is extended to scattering clouds using a variable azimuth two-stream approximation. It is shown that geometrical considerations often dominate over the microphysical aspects of radiative transfer through the clouds. For example, the difference in simulated 10 micron brightness temperature between black isothermal cubic clouds and cubic clouds of optical depth 10, is less than 2 deg for zenith angles less than 50 deg for all cloud fractions when viewed parallel to the array. The results show that serious errors are made in flux and cooling rate computations if broken clouds are modeled as planiform. Radiances computed by the usual practice of area-weighting cloudy and clear sky radiances are in error by 2 to 8 K in brightness temperature for cubic clouds over a wide range of cloud fractions and zenith angles. It is also shown that the lapse rate does not markedly affect the exiting radiances for cuboidal clouds of unit aspect ratio and optical depth 10.

Estimation of height-dependent solar irradiation and application to the solar climate of Iran

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samimi, J.

1994-05-01

An explicitly height-dependent model has been used to estimate the solar irradiation over Iran which has a vast range of altitudes. The parameters of the model have been chosen on general grounds and not by parameters best fitting to any of the available measured irradiation data in Iran. The estimated global solar irradiation on the horizontal surface shows a very good agreement (4.1% deviation) with the 17-year long pyranometric measurements in Tehran, and also, is in good agreement with other, shorter available measured data. The entire data base of the Iranian meteorological stations have been used to establish a simplemore » relation between the sunshine duration records and the cloud cover reports which can be utilized in solar energy estimations for sites with no sunshine duration recorders. Clear sky maps of Iran for direct solar irradiation on tracking, horizontal, and south-facing vertical planes are presented. The global solar irradiation map for horizontal surface with cloudiness is zoned into four irradiation zones. In about four-fifths of the land in Iran, the annual-mean daily global solar irradiation on horizontal surface ranges from 4.5 to 5.4 kWh/m[sup 2].« less

Arctic Clouds Infrared Imaging Field Campaign Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shaw, J. A.

2016-03-01

The Infrared Cloud Imager (ICI), a passive thermal imaging system, was deployed at the North Slope of Alaska site in Barrow, Alaska, from July 2012 to July 2014 for measuring spatial-temporal cloud statistics. Thermal imaging of the sky from the ground provides high radiometric contrast during night and polar winter when visible sensors and downward-viewing thermal sensors experience low contrast. In addition to demonstrating successful operation in the Arctic for an extended period and providing data for Arctic cloud studies, a primary objective of this deployment was to validate novel instrument calibration algorithms that will allow more compact ICI instrumentsmore » to be deployed without the added expense, weight, size, and operational difficulty of a large-aperture onboard blackbody calibration source. This objective was successfully completed with a comparison of the two-year data set calibrated with and without the onboard blackbody. The two different calibration methods produced daily-average cloud amount data sets with correlation coefficient = 0.99, mean difference = 0.0029 (i.e., 0.29% cloudiness), and a difference standard deviation = 0.054. Finally, the ICI instrument generally detected more thin clouds than reported by other ARM cloud products available as of late 2015.« less

Estimation of photosynthetically available radiation (PAR) from OCEANSAT-I OCM using a simple atmospheric radiative transfer model

NASA Astrophysics Data System (ADS)

Tripathy, Madhumita; Raman, Mini; Chauhan, Prakash

2015-10-01

Photosynthetically available radiation (PAR) is an important variable for radiation budget, marine and terrestrial ecosystem models. OCEANSAT-1 Ocean Color Monitor (OCM) PAR was estimated using two different methods under both clear and cloudy sky conditions. In the first approach, aerosol optical depth (AOD) and cloud optical depth (COD) were estimated from OCEANSAT-1 OCM TOA (top-of-atmosphere) radiance data on a pixel by pixel basis and PAR was estimated from extraterrestrial solar flux for fifteen spectral bands using a radiative transfer model. The second approach used TOA radiances measured by OCM in the PAR spectral range to compute PAR. This approach also included surface albedo and cloud albedo as inputs. Comparison between OCEANSAT-1 OCM PAR at noon with in situ measured PAR shows that root mean square difference was 5.82% for the method I and 7.24% for the method II in daily time scales. Results indicate that methodology adopted to estimate PAR from OCEANSAT-1 OCM can produce reasonably accurate PAR estimates over the tropical Indian Ocean region. This approach can be extended to OCEANSAT-2 OCM and future OCEANSAT-3 OCM data for operational estimation of PAR for regional marine ecosystem applications.

Stellar background observation during Total Solar Eclipse March 9th 2016

NASA Astrophysics Data System (ADS)

Mumtahana, Farahhati; Timur Jaelani, Anton; Muhamad, Johan; Sutastio, Heri

2016-11-01

We report observation and an early analysis of stellar background from total solar eclipse in Ternate, Indonesia. The eclipse phenomena which occurred on March, 9th 2016 was observed with certain portable instruments in order to obtain the stars behind the Sun in particular field of view and resolution. From our observation site in Ternate city, solar eclipse occurred in the late morning when the weather was unfortunately cloudy. However, during the darkness of totality, we obtained several point source objects between the gaps of the moving clouds and we suspected them as very faint stars due to their appearance in several frames. Those so called stars have been identified and measured with respect to their positions toward the center of the Sun. The main purpose of this research is to revisit strong lensing calculation of the Sun during total solar eclipse by measuring the deflection angle of the background stars as it had been calculated by Einstein and proved by Eddington at a total solar eclipse in 1919. To accomplish this aim, we need to conduct another observation to measure position of the same stars in the next period when those stars appear in the night sky.

Technical report series on global modeling and data assimilation. Volume 3: An efficient thermal infrared radiation parameterization for use in general circulation models

NASA Technical Reports Server (NTRS)

Suarex, Max J. (Editor); Chou, Ming-Dah

1994-01-01

A detailed description of a parameterization for thermal infrared radiative transfer designed specifically for use in global climate models is presented. The parameterization includes the effects of the main absorbers of terrestrial radiation: water vapor, carbon dioxide, and ozone. While being computationally efficient, the schemes compute very accurately the clear-sky fluxes and cooling rates from the Earth's surface to 0.01 mb. This combination of accuracy and speed makes the parameterization suitable for both tropospheric and middle atmospheric modeling applications. Since no transmittances are precomputed the atmospheric layers and the vertical distribution of the absorbers may be freely specified. The scheme can also account for any vertical distribution of fractional cloudiness with arbitrary optical thickness. These features make the parameterization very flexible and extremely well suited for use in climate modeling studies. In addition, the numerics and the FORTRAN implementation have been carefully designed to conserve both memory and computer time. This code should be particularly attractive to those contemplating long-term climate simulations, wishing to model the middle atmosphere, or planning to use a large number of levels in the vertical.

Recent changes in solar irradiance and infrared irradiance related with air temperature and cloudiness at the King Sejong Station, Antarctica

NASA Astrophysics Data System (ADS)

Jung, Y.; Kim, J.; Cho, H.; Lee, B.

2006-12-01

The polar region play a critical role in the surface energy balance and the climate system of the Earth. The important question in the region is that what is the role of the Antarctic atmospheric heat sink of global climate. Thus, this study shows the trends of global solar irradiance, infrared irradiance, air temperature and cloudiness measured at the King Sejong station, Antarctica, during the period of 1996-2004 and determines their relationship and variability of the surface energy balance. Annual average of solar radiation and cloudiness is 81.8 Wm-2 and 6.8 oktas and their trends show the decrease of -0.24 Wm-2yr-1(-0.30 %yr-1) and 0.02 oktas yr-1(0.30 %yr-1). The change of solar irradiance is directly related to change of cloudiness and decrease of solar irradiance presents radiative cooling at the surface. Monthly mean infrared irradiance, air temperature and specific humidity shows the decrease of -2.11 Wm^{- 2}yr-1(-0.75 %yr-1), -0.07 'Cyr-1(-5.15 %yr-1) and -0.044 gkg-1yr-1(-1.42 %yr-1), respectively. Annual average of the infrared irradiance is 279.9 Wm-2 and correlated with the air temperature, specific humidity and cloudiness. A multiple regression model for estimation of the infrared irradiance using the components has been developed. Effects of the components on the infrared irradiance changes show 52 %, 19 % and 10 % for air temperature, specific humidity and cloudiness, respectively. Among the components, air temperature has a great influence on infrared irradiance. Despite the increase of cloudiness, the decrease in the infrared irradiance is due to the decrease of air temperature and specific humidity which have a cooling effect. Therefore, the net radiation of the surface energy balance shows radiative cooling of negative 11-24 Wm^{- 2} during winter and radiative warming of positive 32-83 Wm-2 during the summer. Thus, the amount of shortage and surplus at the surface is mostly balanced by turbulent flux of sensible and latent heat.

Assessment of simulation of radiation in NCEP Climate Forecasting System (CFS V2)

NASA Astrophysics Data System (ADS)

Goswami, Tanmoy; Rao, Suryachandra A.; Hazra, Anupam; Chaudhari, Hemantkumar S.; Dhakate, Ashish; Salunke, Kiran; Mahapatra, Somnath

2017-09-01

The objective of this study is to identify and document the radiation biases in the latest National Centers for Environment Prediction (NCEP), Climate Forecasting System (CFSv2) and to investigate the probable reasons for these biases. This analysis is made over global and Indian domain under all-sky and clear-sky conditions. The impact of increasing the horizontal resolution of the atmospheric model on these biases is also investigated by comparing results of two different horizontal resolution versions of CFSv2 namely T126 and T382. The difference between the top of the atmosphere and surface energy imbalance in T126 (T382) is 3.49 (2.78) W/m2. This reduction of bias in the high resolution model is achieved due to lesser low cloud cover, resulting more surface insolation, and due to more latent heat fluxes at the surface. Compared to clear sky simulations, all sky simulations exhibit larger biases suggesting that the cloud covers are not simulated well in the model. The annual mean high level cloud cover is over estimated over the global as well as the Indian domain. This overestimation over the Indian domain is also present during JJAS. There is also evidence that both of the models have insufficient water vapour in their atmosphere. This study suggests that in order to improve the model's mean radiation climatology, simulation of clouds in the model also needs to be improved, and future model development activities should focus on this aspect.

Reconstruction of erythemal UV irradiance at Hohenpeissenberg (1968-2001) considering trends of total ozone, cloudiness, and turbidity

NASA Astrophysics Data System (ADS)

Trepte, S.; Winkler, P.

2003-04-01

The global mean total column ozone amount for the period 1997-2001 was approximately 3% below the 1964-1980 average. The largest ozone decreases in the northern hemisphere midlatitudes are observed during winter-spring (˜4%), with summer-autumn decreases approximately half as large. Total ozone measured at Hohenpeissenberg, Germany (48^oN, 11^oE) shows a strong decrease by about 10% since 1968, representing the long-term downward trend over Central Europe. The main consequence of this phenomenon is the expected increase of solar ultraviolet irradiation (UV-B) reaching the Earth's surface with the known harmful effects on the biosphere. Global data records of reliable routine observations of UV irradiance are still too short for accurate estimation of long-term UV variations and trends. While direct UV mesaurements at Hohenpeissenberg are available only since 1990, the long-term development of UV-B have to be reconstructed. Besides on the amount of total ozone the UV irradiation at the ground depends also on atmospheric turbidity and cloudiness. The reconstruction method is based on statistical correlations of measured UV-B data with the influencing parameters total ozone, turbidity and cloud modification factors derived from eye-observations in connection with total solar irradiance data. These observed data allow a realistic reconstruction of the UV-B time series, since no assumption on these influencing data have to be made. A model is presented, using hourly observed spectral UV-B irradiance (1990-1998), total solar irradiance, total ozone amount (daily mean) and clouds to derive erythemal UV irradiance and daily doses at Hohenpeissenberg in the period 1968-2001. A comparison with recorded UV data shows good agreement. Due to long-term total ozone loss, peak values of erythemal UV irradiance in spring and summer at clear-sky conditions have strongly increased (+4.2%/decade in June). Mean daily doses have also increased in this season (+5.4%/decade in May) but meteorological changes like reduced sunshine duration and increased cloudiness lead to a partly compensation of the ozone-loss effect in spring and to an overcompensation in autumn, where we found a long-term decrease of the daily dose (-3.0%/decade in September). Model calculations also demonstrate large year-to-year fluctuations of UV doses induced by meteorological variability, which exceed the long-term trend of the various months significantly. Nevertheless, this investigation has shown that on a long-term time scale the daily doses develop in a different way as compared to the peak values because the reasons for ozone decline (anthropogenic CFC's) and the cloud cover (hydrological cycle changes due to greenhouse effect) are caused by different phenomena.

Characterization and on-sky demonstration of an integrated photonic spectrograph for astronomy.

PubMed

Cvetojevic, N; Lawrence, J S; Ellis, S C; Bland-Hawthorn, J; Haynes, R; Horton, A

2009-10-12

We present results from the first on-sky demonstration of a prototype astronomical integrated photonic spectrograph (IPS) using the Anglo-Australian Telescope near-infrared imaging spectrometer (IRIS2) at Siding Spring Observatory to observe atmospheric molecular OH emission lines. We have succeeded in detecting upwards of 27 lines, and demonstrated the practicality of the IPS device for astronomy. Furthermore, we present a laboratory characterization of the device, which is a modified version of a commercial arrayed-waveguide grating multiplexer. We measure the spectral resolution full-width-half-maximum to be 0.75 +/- 0.05 nm (giving R = lambda/deltalambda = 2100 +/- 150 at 1500 nm). We find the free spectral range to be 57.4 +/- 0.6 nm and the peak total efficiency to be approximately 65%. Finally, we briefly discuss the future steps required to realize an astronomical instrument based on this technology concept.

Anomalous Decimeter Radio Noise from the Region of the Atmospheric Front: I. Characteristics of the Detected Radio Noise and Meteorological Parameters of the Frontal Cloudiness

NASA Astrophysics Data System (ADS)

Klimenko, V. V.; Mareev, E. A.

2018-03-01

An extraordinary experimental fact is presented and analyzed, namely, a rather intense broadband radio noise detected during the passage of an atmospheric front through the field of view of UHF antennas. Local atmospheric properties and possible sources of the extraordinary noise, including the thermal noise from cloudiness and extra-atmospheric sources, are considered. A conclusion is made about the presence of an additional nonthermal source of radio noise in the frontal cloudiness. According to the proposed hypothesis, these are multiple electric microdicharges on hydrometeors in the convective cloud.

Effects of cloudiness on global and diffuse UV irradiance in a high-mountain area

NASA Astrophysics Data System (ADS)

Blumthaler, M.; Ambach, W.; Salzgeber, M.

1994-03-01

At the high-mountain station Jungfraujoch (3576 m a.s.l., Switzerland), measurements of the radiation fluxes were made during 16 periods of six to eight weeks by means of a Robertson—Berger sunburn meter (UVB data), an Eppley UVA radiometer and an Eppley pyranometer. Cloudiness, opacity and altitude of clouds were recorded at 30-minute intervals. A second set of instruments was employed for separate measurement of the diffuse radiation fluxes using shadow bands. The global and diffuse UVA- and UVB radiation fluxes change less with cloudiness than the corresponding total radiation fluxes. When the sun is covered by clouds, the global UVA- and UVB radiation fluxes are also affected less than the global total radiation flux. The roughly equal influence of cloudiness on the UVA- and UVB radiation fluxes suggests that the reduction is influenced more by scattering than by ozone. Also, the share of diffuse irradiance in global irradiance is considerably higher for UVA- and UVB irradiance than for total irradiance. At 50° solar elevation and 0/10 cloudiness, the share is 39% for UVB irradiance, 34% for UVA irradiance and 11% for total irradiance. The increased aerosol turbidity after the eruptions of El Chichon and Pinatubo has caused a significant increase in diffuse total irradiance but has not produced any significant changes in diffuse UVA- and UVB irradiances.

Pathfinder, Volume 7, Number 5, September/October 2009. Charting the Sea and Sky

DTIC Science & Technology

2009-10-01

During the six-month season, ski-equipped LC-130s, the polar version of the C-130 Hercules transport plane, flew more than 8.7 million pounds of...collaborate closely with the Space and Naval Warfare Systems Command (SPAWAR), Office of Polar Programs; the Federal Avia- tion Administration (FAA...only worldwide vector chart coverage. Recently, the Navy implemented polar navigation using NGA charts and is now capable of true worldwide digital

Far-infrared Properties of Infrared-bright Dust-obscured Galaxies Selected with IRAS and AKARI Far-infrared All-sky Survey

NASA Astrophysics Data System (ADS)

Toba, Yoshiki; Nagao, Tohru; Wang, Wei-Hao; Matsuhara, Hideo; Akiyama, Masayuki; Goto, Tomotsugu; Koyama, Yusei; Ohyama, Youich; Yamamura, Issei

2017-05-01

We investigate the star-forming activity of a sample of infrared (IR)-bright dust-obscured galaxies (DOGs) that show an extreme red color in the optical and IR regime, {(I-[22])}{AB}> 7.0. Combining an IR-bright DOG sample with the flux at 22 μm > 3.8 mJy discovered by Toba & Nagao with the IRAS faint source catalog version 2 and AKARI far-IR (FIR) all-sky survey bright source catalog version 2, we selected 109 DOGs with FIR data. For a subsample of seven IR-bright DOGs with spectroscopic redshifts (0.07< z< 1.0) that were obtained from the literature, we estimated their IR luminosity, star formation rate (SFR), and stellar mass based on the spectral energy distribution fitting. We found that (1) the WISE 22 μm luminosity at the observed frame is a good indicator of IR luminosity for IR-bright DOGs and (2) the contribution of the active galactic nucleus to IR luminosity increases with IR luminosity. By comparing the stellar mass and SFR relation for our DOG sample and the literature, we found that most of the IR-bright DOGs lie significantly above the main sequence of star-forming galaxies at similar redshift, indicating that the majority of IRAS- or AKARI-detected IR-bright DOGs are starburst galaxies.

Operational data fusion framework for building frequent Landsat-like imagery in a cloudy region

USDA-ARS?s Scientific Manuscript database

An operational data fusion framework is built to generate dense time-series Landsat-like images for a cloudy region by fusing Moderate Resolution Imaging Spectroradiometer (MODIS) data products and Landsat imagery. The Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM) is integrated in ...

Balloon-borne match measurements of midlatitude cirrus clouds

NASA Astrophysics Data System (ADS)

Cirisan, A.; Luo, B. P.; Engel, I.; Wienhold, F. G.; Sprenger, M.; Krieger, U. K.; Weers, U.; Romanens, G.; Levrat, G.; Jeannet, P.; Ruffieux, D.; Philipona, R.; Calpini, B.; Spichtinger, P.; Peter, T.

2014-07-01

Observations of high supersaturations with respect to ice inside cirrus clouds with high ice water content (> 0.01 g kg-1) and high crystal number densities (> 1 cm-3) are challenging our understanding of cloud microphysics and of climate feedback processes in the upper troposphere. However, single measurements of a cloudy air mass provide only a snapshot from which the persistence of ice supersaturation cannot be judged. We introduce here the "cirrus match technique" to obtain information about the evolution of clouds and their saturation ratio. The aim of these coordinated balloon soundings is to analyze the same air mass twice. To this end the standard radiosonde equipment is complemented by a frost point hygrometer, "SnowWhite", and a particle backscatter detector, "COBALD" (Compact Optical Backscatter AerosoL Detector). Extensive trajectory calculations based on regional weather model COSMO (Consortium for Small-Scale Modeling) forecasts are performed for flight planning, and COSMO analyses are used as a basis for comprehensive microphysical box modeling (with grid scale of 2 and 7 km, respectively). Here we present the results of matching a cirrus cloud to within 2-15 km, realized on 8 June 2010 over Payerne, Switzerland, and a location 120 km downstream close to Zurich. A thick cirrus cloud was detected over both measurement sites. We show that in order to quantitatively reproduce the measured particle backscatter ratios, the small-scale temperature fluctuations not resolved by COSMO must be superimposed on the trajectories. The stochastic nature of the fluctuations is captured by ensemble calculations. Possibilities for further improvements in the agreement with the measured backscatter data are investigated by assuming a very slow mass accommodation of water on ice, the presence of heterogeneous ice nuclei, or a wide span of (spheroidal) particle shapes. However, the resulting improvements from these microphysical refinements are moderate and comparable in magnitude with changes caused by assuming different regimes of temperature fluctuations for clear-sky or cloudy-sky conditions, highlighting the importance of proper treatment of subscale fluctuations. The model yields good agreement with the measured backscatter over both sites and reproduces the measured saturation ratios with respect to ice over Payerne. Conversely, the 30% in-cloud supersaturation measured in a massive 4 km thick cloud layer over Zurich cannot be reproduced, irrespective of the choice of meteorological or microphysical model parameters. The measured supersaturation can only be explained by either resorting to an unknown physical process, which prevents the ice particles from consuming the excess humidity, or - much more likely - by a measurement error, such as a contamination of the sensor housing of the SnowWhite hygrometer by a precipitation drop from a mixed-phase cloud just below the cirrus layer or from some very slight rain in the boundary layer. This uncertainty calls for in-flight checks or calibrations of hygrometers under the special humidity conditions in the upper troposphere.

Ultraviolet radiation modelling from ground-based and satellite measurements on Reunion Island, southern tropics

NASA Astrophysics Data System (ADS)

Lamy, Kévin; Portafaix, Thierry; Brogniez, Colette; Godin-Beekmann, Sophie; Bencherif, Hassan; Morel, Béatrice; Pazmino, Andrea; Metzger, Jean Marc; Auriol, Frédérique; Deroo, Christine; Duflot, Valentin; Goloub, Philippe; Long, Charles N.

2018-01-01

Surface ultraviolet radiation (SUR) is not an increasing concern after the implementation of the Montreal Protocol and the recovery of the ozone layer (Morgenstern et al., 2008). However, large uncertainties remain in the prediction of future changes of SUR (Bais et al., 2015). Several studies pointed out that UV-B impacts the biosphere (Erickson et al., 2015), especially the aquatic system, which plays a central part in the biogeochemical cycle (Hader et al., 2007). It can affect phytoplankton productivity (Smith and Cullen, 1995). This influence can result in either positive or negative feedback on climate (Zepp et al., 2007). Global circulation model simulations predict an acceleration of the Brewer-Dobson circulation over the next century (Butchart, 2014), which would lead to a decrease in ozone levels in the tropics and an enhancement at higher latitudes (Hegglin and Shepherd, 2009). Reunion Island is located in the tropics (21° S, 55° E), in a part of the world where the amount of ozone in the ozone column is naturally low. In addition, this island is mountainous and the marine atmosphere is often clean with low aerosol concentrations. Thus, measurements show much higher SUR than at other sites at the same latitude or at midlatitudes. Ground-based measurements of SUR have been taken on Reunion Island by a Bentham DTMc300 spectroradiometer since 2009. This instrument is affiliated with the Network for the Detection of Atmospheric Composition Change (NDACC). In order to quantify the future evolution of SUR in the tropics, it is necessary to validate a model against present observations. This study is designed to be a preliminary parametric and sensitivity study of SUR modelling in the tropics. We developed a local parameterisation using the Tropospheric Ultraviolet and Visible Model (TUV; Madronich, 1993) and compared the output of TUV to multiple years of Bentham spectral measurements. This comparison started in early 2009 and continued until 2016. Only clear-sky SUR was modelled, so we needed to sort out the clear-sky measurements. We used two methods to detect cloudy conditions: the first was based on an observer's hourly report on the sky cover, while the second was based on applying Long and Ackerman (2000)'s algorithm to broadband pyranometer data to obtain the cloud fraction and then discriminating clear-sky windows on SUR measurements. Long et al. (2006)'s algorithm, with the co-located pyranometer data, gave better results for clear-sky filtering than the observer's report. Multiple model inputs were tested to evaluate the model sensitivity to different parameters such as total ozone column, aerosol optical properties, extraterrestrial spectrum or ozone cross section. For total column ozone, we used ground-based measurements from the SAOZ (Système d'Analyse par Observation Zénithale) spectrometer and satellite measurements from the OMI and SBUV instruments, while ozone profiles were derived from radio-soundings and the MLS ozone product. Aerosol optical properties came from a local aerosol climatology established using a Cimel photometer. Since the mean difference between various inputs of total ozone column was small, the corresponding response on UVI modelling was also quite small, at about 1 %. The radiative amplification factor of total ozone column on UVI was also compared for observations and the model. Finally, we were able to estimate UVI on Reunion Island with, at best, a mean relative difference of about 0.5 %, compared to clear-sky observations.

What You Need to Know About the OMI NO2 Data Product for Air Quality Studies

NASA Technical Reports Server (NTRS)

Celarier, E. A.; Gleason, J. F.; Bucsela, E. J.; Brinksma, E.; Veefkind, J. P.

2007-01-01

The standard nitrogen dioxide (NO2) data product, produced from measurements by the Ozone Monitoring Instrument (OMI), are publicly available online from the NASA GESDISC facility. Important data fields include total and tropospheric column densities, as well as collocated data for cloud fraction and cloud top height, surface albedo and snow/ice coverage, at the resolution of the OMI instrument (12 km x 26 km, at nadir). The retrieved NO2 data have been validated, principally under clear-sky conditions. The first public-release version has been available since September 2006. An improved version of the data product, which includes a number of new data fields, and improved estimates of the retrieval uncertainties will be released by the end of 2007. This talk will describe the standard NO2 data product, including details that are essential for the use of the data for air quality studies. We will also describe the principal improvements with the new version of the data product.

Intercomparison of four regional climate models for the German State of Saxonia

NASA Astrophysics Data System (ADS)

Kreienkamp, F.; Spekat, A.; Enke, W.

2009-09-01

Results from four regional climate models which focus on Central Europe are presented: CCLM, the climate version of the German Weather Service's Local Model - REMO, the regional dynamic model from the Max Planck Institute for Meteorology in Hamburg - STAR, the statistical model developed at the PIK Potsdam Institute and WETTREG, the statistic-dynamic model developed by the company CEC Potsdam. For the area of the German State of Saxonia a host of properties and indicators were analyzed aiming to show the models' abilities to reconstruct the current climate and compare climate model scenarios. These include a group of thermal indicators, such as the number of ice, frost, summer and hot days, the number of tropical nights; then there are hydrometeorological indicators such as the exceedance of low and high precipitation thresholds; humidity, cloudiness and wind indicators complement the array. A selection of them showing similarities and differences of the models investigated will be presented.

CATS Version 2 Aerosol Feature Detection and Applications for Data Assimilation

NASA Technical Reports Server (NTRS)

Nowottnick, Ed; Yorks, John; McGill, Matt; Scott, Stan; Palm, Stephen; Hlavka, Dennis; Hart, William; Selmer, Patrick; Kupchock, Andrew; Pauly, Rebecca

2017-01-01

Using GEOS-5, we are developing a 1D ENS approach for assimilating CATS near real time observations of total attenuated backscatter at 1064 nm: a) After performing a 1-ENS assimilation of a cloud-free profile, the GEOS-5 analysis closely followed observed total attenuated backscatter. b) Vertical localization length scales were varied for the well-mixed PBL and the free troposphere After assimilating a cloud free segment of a CATS granule, the fine detail of a dust event was obtained in the GEOS-5 analysis for both total attenuated backscatter and extinction. Future Work: a) Explore horizontal localization and test within a cloudy aerosol layer. b) Address noisy analysis increments in the free troposphere where both CATS and GEOS-5 aerosol loadings are low. c) Develop a technique to screen CATS ground return from profiles. d) "Dynamic" lidar ratio that will evolve in conjunction with simulated aerosol mixtures.

NCAR CCM2 simulation of the modern Antarctic climate

NASA Technical Reports Server (NTRS)

Tzeng, Ren-Yow; Bromwich, David H.; Parish, Thomas R.; Chen, Biao

1994-01-01

The National Center for Atmospheric Research (NCAR) community climate model version 2 (CCM2) simulation of the circumpolar trough, surface air temperature, the polar vortex, cloudiness, winds, and atmospheric moisture and energy budgets are examined to validate the model's representation of the present-day Antarctic climate. The results show that the CCM2 can well simulate many important climate features over Antarctica, such as the location and intensity of the circumpolar trough, the coreless winter over the plateau, the intensity and horizontal distribution of the surface inversion, the speed and streamline pattern of the katabatic winds, the double jet stream feature over the southern Indian and Pacific oceans, and the arid climate over the continent. However, there are also some serious errors in the model. Some are due to old problems but some are caused by the new parameterizations in the model. The model errors over high southern latitudes can be summarized as follows: The circumpolar trough, the polar vertex, and the westerlies in midlatitudes are too strong; the semiannual cycle of the circumpolar trough is distorted compared to the observations; the low centers of the circumpolar trough and the troughs in the middle and upper troposphere are shifted eastward by 15 deg - 40 deg longitude; the surface temperatures are too cold over the plateau in summer and over the coastline in winter; the polar tropopause continues to have a cold bias; and the cloudiness is too high over the continent. These biases are induced by two major factors: (1) the cloud optical properties in tropical and middle latitudes, which cause the eastward shift of troughs and surface low centers and the error in the semiannual cycle, and (2) the cold bias of the surface air temperature, which is attributed to the oversimulation of cloudiness over the continent, especially during summer, and the uniform 2-m-thick sea ice. The constant thickness of sea ice suppresses the energy flux from the ocean to the atmosphere and hence reduces the air temperature near the coast during winter. Finally, although the simulated Antarctic climate still suffers these biases, the overall performance of the CCM2 is much better than that of the CCM1-T42. Therefore the CCM2 is good enough to be used for climate change studies, especially over Antarctica.

Validation of Nimbus-7 temperature-humidity infrared radiometer estimates of cloud type and amount

NASA Technical Reports Server (NTRS)

Stowe, L. L.

1982-01-01

Estimates of clear and low, middle and high cloud amount in fixed geographical regions approximately (160 km) squared are being made routinely from 11.5 micron radiance measurements of the Nimbus-7 Temperature-Humidity Infrared Radiometer (THIR). The purpose of validation is to determine the accuracy of the THIR cloud estimates. Validation requires that a comparison be made between the THIR estimates of cloudiness and the 'true' cloudiness. The validation results reported in this paper use human analysis of concurrent but independent satellite images with surface meteorological and radiosonde observations to approximate the 'true' cloudiness. Regression and error analyses are used to estimate the systematic and random errors of THIR derived clear amount.

An energy balance climate model with cloud feedbacks

NASA Technical Reports Server (NTRS)

Roads, J. O.; Vallis, G. K.

1984-01-01

The present two-level global climate model, which is based on the atmosphere-surface energy balance, includes physically based parameterizations for the exchange of heat and moisture across latitude belts and between the surface and the atmosphere, precipitation and cloud formation, and solar and IR radiation. The model field predictions obtained encompass surface and atmospheric temperature, precipitation, relative humidity, and cloudiness. In the model integrations presented, it is noted that cloudiness is generally constant with changing temperature at low latitudes. High altitude cloudiness increases with temperature, although the cloud feedback effect on the radiation field remains small because of compensating effects on thermal and solar radiation. The net global feedback by the cloud field is negative, but small.

12348_GLOBE_Observer_App_Promo

NASA Image and Video Library

2016-08-25

GLOBE Observer invites you to make environmental observations that complement NASA satellite observations to help scientists studying Earth and the global environment. Version 1.1 includes GLOBE Clouds, which allows you to photograph clouds and record sky observations and compare them with NASA satellite images. GLOBE is now the major source of human observations of clouds, which provide more information than automated systems. Future versions of GLOBE Observer will add additional tools for you to use as a citizen environmental scientist. By using the GLOBE Observer app, you are joining the GLOBE community and contributing important scientific data to NASA and GLOBE, your local community, and students and scientists worldwide. New and interested users are encouraged to go to observer.globe.gov to learn more about the GLOBE program, or learn more about the GLOBE Clouds protocol.

Hubble Space Telescope faint object spectrograph instrument handbook, version 5.0

NASA Technical Reports Server (NTRS)

Kinney, A. L. (Editor)

1994-01-01

This version of the FOS Instrument Handbook is for the refurbished telescope, which is affected by an increase in throughput, especially for the smaller apertures, a decrease in efficiency due to the extra reflections of the COSTAR optics, and a change in focal length. The improved PSF affects all exposure time calculations due to better aperture throughputs and increases the spectral resolution. The extra reflections of COSTAR decrease the efficiency by 10-20 percent. The change in focal length affects the aperture sizes as projected on the sky. The aperture designations that are already in use both in the exposure logsheets and in the project data base (PDB) have not been changed. Apertures are referred to here by their size, followed by the designation used on the exposure logsheet.

Why is it advantageous for animals to detect celestial polarization in the ultraviolet? Skylight polarization under clouds and canopies is strongest in the UV.

PubMed

Barta, András; Horváth, Gábor

2004-02-21

The perception of skylight polarization in the ultraviolet (UV) by many insect species for orientation purposes is rather surprising, because both the degree of linear polarization and the radiance of light from the clear sky are considerably lower in the UV than in the blue or green. In this work we call this the "UV-sky-pol paradox". Although in the past, several attempts have been made to resolve this paradox, none of them was convincing. We present here a possible quantitative resolution to the paradox. We show by a model calculation that if the air layer between a cloud and a ground-based observer is partly sunlit, the degree of linear polarization p of skylight originating from the cloudy region is highest in the UV, because in this spectral range the unpolarized UV-deficient cloudlight dilutes least the polarized light scattered in the air beneath the cloud. Similarly, if the air under foliage is partly sunlit, p of downwelling light from the canopied region is maximal in the UV, because in this part of spectrum the unpolarized UV-deficient green canopylight dilutes least the polarized light scattered in the air beneath the canopy. Therefore, the detection of polarization of downwelling light under clouds or canopies is most advantageous in the UV, in which spectral range the risk is the smallest that the degree of polarization p is lower than the threshold p(tr) of polarization sensitivity in animals. On the other hand, under clear skies there is no favoured wavelength for perception of celestial polarization, because p of skylight is high enough (p > p(tr)) at all wavelengths. We show that there is an analogy between the detection of UV skylight polarization and the polarotactic water detection in the UV. However, insects perceive skylight polarization by UV or blue or green receptors. The question, why they differ in the spectral channel used for the detection of celestial polarization cannot be answered at the present time, because data are insufficient. Nevertheless, we present here one possible atmospheric optical reason why certain visual systems involved in detecting celestial polarization, are specifically tuned to the UV part of the spectrum.

A Earth Outgoing Longwave Radiation Climate Model

NASA Astrophysics Data System (ADS)

Yang, Shi-Keng

An Earth outgoing longwave radiation (OLWR) climate model has been constructed for radiation budget study. The model consists of the upward radiative transfer parameterization of Thompson and Warren (1982), the cloud cover model of Sherr et al. (1968) and a monthly average climatology defined by the data from Crutcher and Meserve (1971) and Taljaard et al. (1969). Additional required information is provided by the empirical 100mb water vapor mixing ratio equation of Harries (1976), and the mixing ratio interpolation scheme of Briegleb and Ramanathan (1982). Cloud top temperature is adjusted so that the calculation would agree with NOAA scanning radiometer measurements. Both clear sky and cloudy sky cases are calculated and discussed for global average, zonal average and world-wide distributed cases. The results agree well with the satellite observations. The clear sky case shows that the OLWR field is highly modulated by water vapor, especially in the tropics. The strongest longitudinal variation occurs in the tropics. This variation can be mostly explained by the strong water vapor gradient. Although in the zonal average case the tropics have a minimum in OLWR, the minimum is essentially contributed by a few very low flux regions, such as the Amazon, Indonesia and the Congo. There are regions in the tropics such that their OLWR is as large as that of the subtropics. In the high latitudes, where cold air contains less water vapor, OLWR is basically modulated by the surface temperature. Thus, the topographical heat capacity becomes a dominant factor in determining the distribution. Clouds enhance water vapor modulation of OLWR. Tropical clouds have the coldest cloud top temperatures. This again increases the longitudinal variation in the region. However, in the polar region, where temperature inversion is prominent, cloud top temperature is warmer than the surface. Hence, cloud has the effect of increasing OLWR. The implication of this cloud mechanism is that the latitudinal gradient of net radiation is thus further increased, and the forcing of the general atmospheric circulation is substantially different due to the increased additional available energy. The analysis of the results also suggests that to improve the performance of the Budyko-Sellers type energy balance climate model in the tropical region, the parameterization of the longwave cooling should include a water vapor absorbing term.

Bidirectional Reflectance Functions for Application to Earth Radiation Budget Studies

NASA Technical Reports Server (NTRS)

Manalo-Smith, N.; Tiwari, S. N.; Smith, G. L.

1997-01-01

Reflected solar radiative fluxes emerging for the Earth's top of the atmosphere are inferred from satellite broadband radiance measurements by applying bidirectional reflectance functions (BDRFs) to account for the anisotropy of the radiation field. BDRF's are dependent upon the viewing geometry (i.e. solar zenith angle, view zenith angle, and relative azimuth angle), the amount and type of cloud cover, the condition of the intervening atmosphere, and the reflectance characteristics of the underlying surface. A set of operational Earth Radiation Budget Experiment (ERBE) BDRFs is available which was developed from the Nimbus 7 ERB (Earth Radiation Budget) scanner data for a three-angle grid system, An improved set of bidirectional reflectance is required for mission planning and data analysis of future earth radiation budget instruments, such as the Clouds and Earth's Radiant Energy System (CERES), and for the enhancement of existing radiation budget data products. This study presents an analytic expression for BDRFs formulated by applying a fit to the ERBE operational model tabulations. A set of model coefficients applicable to any viewing condition is computed for an overcast and a clear sky scene over four geographical surface types: ocean, land, snow, and desert, and partly cloudy scenes over ocean and land. The models are smooth in terms of the directional angles and adhere to the principle of reciprocity, i.e., they are invariant with respect to the interchange of the incoming and outgoing directional angles. The analytic BDRFs and the radiance standard deviations are compared with the operational ERBE models and validated with ERBE data. The clear ocean model is validated with Dlhopolsky's clear ocean model. Dlhopolsky developed a BDRF of higher angular resolution for clear sky ocean from ERBE radiances. Additionally, the effectiveness of the models accounting for anisotropy for various viewing directions is tested with the ERBE along tract data. An area viewed from nadir and from the side give two different radiance measurements but should yield the same flux when converted by the BDRF. The analytic BDRFs are in very good qualitative agreement with the ERBE models. The overcast scenes exhibit constant retrieved albedo over viewing zenith angles for solar zenith angles less than 60 degrees. The clear ocean model does not produce constant retrieved albedo over viewing zenith angles but gives an improvement over the ERBE operational clear sky ocean BDRF.

The Exoplanet Cloud Atlas

NASA Astrophysics Data System (ADS)

Gao, Peter; Marley, Mark S.; Morley, Caroline; Fortney, Jonathan J.

2017-10-01

Clouds have been readily inferred from observations of exoplanet atmospheres, and there exists great variability in cloudiness between planets, such that no clear trend in exoplanet cloudiness has so far been discerned. Equilibrium condensation calculations suggest a myriad of species - salts, sulfides, silicates, and metals - could condense in exoplanet atmospheres, but how they behave as clouds is uncertain. The behavior of clouds - their formation, evolution, and equilibrium size distribution - is controlled by cloud microphysics, which includes processes such as nucleation, condensation, and evaporation. In this work, we explore the cloudy exoplanet phase space by using a cloud microphysics model to simulate a suite of cloud species ranging from cooler condensates such as KCl/ZnS, to hotter condensates like perovskite and corundum. We investigate how the cloudiness and cloud particle sizes of exoplanets change due to variations in temperature, metallicity, gravity, and cloud formation mechanisms, and how these changes may be reflected in current and future observations. In particular, we will evaluate where in phase space could cloud spectral features be observable using JWST MIRI at long wavelengths, which will be dependent on the cloud particle size distribution and cloud species.

Second ROSAT all-sky survey (2RXS) source catalogue

NASA Astrophysics Data System (ADS)

Boller, Th.; Freyberg, M. J.; Trümper, J.; Haberl, F.; Voges, W.; Nandra, K.

2016-04-01

Aims: We present the second ROSAT all-sky survey source catalogue, hereafter referred to as the 2RXS catalogue. This is the second publicly released ROSAT catalogue of point-like sources obtained from the ROSAT all-sky survey (RASS) observations performed with the position-sensitive proportional counter (PSPC) between June 1990 and August 1991, and is an extended and revised version of the bright and faint source catalogues. Methods: We used the latest version of the RASS processing to produce overlapping X-ray images of 6.4° × 6.4° sky regions. To create a source catalogue, a likelihood-based detection algorithm was applied to these, which accounts for the variable point-spread function (PSF) across the PSPC field of view. Improvements in the background determination compared to 1RXS were also implemented. X-ray control images showing the source and background extraction regions were generated, which were visually inspected. Simulations were performed to assess the spurious source content of the 2RXS catalogue. X-ray spectra and light curves were extracted for the 2RXS sources, with spectral and variability parameters derived from these products. Results: We obtained about 135 000 X-ray detections in the 0.1-2.4 keV energy band down to a likelihood threshold of 6.5, as adopted in the 1RXS faint source catalogue. Our simulations show that the expected spurious content of the catalogue is a strong function of detection likelihood, and the full catalogue is expected to contain about 30% spurious detections. A more conservative likelihood threshold of 9, on the other hand, yields about 71 000 detections with a 5% spurious fraction. We recommend thresholds appropriate to the scientific application. X-ray images and overlaid X-ray contour lines provide an additional user product to evaluate the detections visually, and we performed our own visual inspections to flag uncertain detections. Intra-day variability in the X-ray light curves was quantified based on the normalised excess variance and a maximum amplitude variability analysis. X-ray spectral fits were performed using three basic models, a power law, a thermal plasma emission model, and black-body emission. Thirty-two large extended regions with diffuse emission and embedded point sources were identified and excluded from the present analysis. Conclusions: The 2RXS catalogue provides the deepest and cleanest X-ray all-sky survey catalogue in advance of eROSITA. The catalogue is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/588/A103

Radiative effects of biomass burning aerosols and cloudiness on seasonal carbon cycle in the Amazon region

NASA Astrophysics Data System (ADS)

Moreira, D. S.; Longo, K.; Freitas, S.; Mercado, L. M.; Miller, J. B.; Rosario, N. M. E. D.; Gatti, L.; Yamasoe, M. A.

2017-12-01

The Amazon region is characterized by high cloudiness, mainly due to convective clouds during most of the year due to the high humidity, and heat availability. However, during the Austral winter, the northward movement of the inter-tropical convergence zone (ITCZ) from its climatological position, significantly reducing cloudiness and precipitation, facilitating vegetation fires. Consequently, during these dry months, biomass burning aerosols contribute to relatively high values of aerosol optical depth (AOD) in Amazonia, typically exceeding 1.0 in the 550 nm wavelength. Both clouds and aerosols scatter solar radiation, reducing the direct irradiance and increasing the diffuse fraction that reaches the surface, decreasing near surface temperature and increasing photosynthetically active radiation (PAR) availability. This, in turn, affects energy and CO2 fluxes within the vegetation canopy. We applied an atmospheric model fully coupled to terrestrial carbon cycle model to assess the relative impact of biomass burning aerosols and clouds on CO2 fluxes in the Amazon region. Our results indicate that during most of the year, gross primary productivity (GPP) is high mainly due to high soil moisture and high values of the diffuse fraction of solar irradiation due to cloudiness. Therefore, heterotrophic and autotrophic respiration are both high, increasing the NEE values (i.e. reducing the net land sink). On the other hand, during the dry season, with a significant reduction of cloudiness, the biomass burning aerosol is mainly responsible for the increase in the diffuse fraction of solar irradiation and the GPP of the forest. However, the low soil moisture during the dry season, especially in the eastern Amazon, reduces heterotrophic and autotrophic respiration and thus compensates for reduced GPP compared to the wet season. Different reasons, an anthropogenic one (human induced fires during the dry season) and a natural one (cloudiness), lead to a somewhat stable value of NEE all year long in Amazonia.

Simulations of cloudy hyperspectral infrared radiances using the HT-FRTC, a fast PC-based multipurpose radiative transfer code

NASA Astrophysics Data System (ADS)

Havemann, S.; Aumann, H. H.; Desouza-Machado, S. G.

2017-12-01

The HT-FRTC uses principal components which cover the spectrum at a very high spectral resolution allowing very fast line-by-line-like, hyperspectral and broadband simulations for satellite-based, airborne and ground-based sensors. Using data from IASI and from the Airborne Research Interferometer Evaluation System (ARIES) on board the FAAM BAE 146 aircraft, variational retrievals in principal component space with HT-FRTC as forward model have demonstrated that valuable information on temperature and humidity profiles and on the cirrus cloud properties can be obtained simultaneously. The NASA/JPL/UMBC cloudy RTM inter-comparison project has been working on a global dataset consisting of 7377 AIRS spectra. Initial simulations with HT-FRTC for this dataset have been promising. A next step taken here is to investigate how sensitive the results are with respect to different assumptions in the cloud modelling. One aspect of this is to study how assumptions about the microphysical and related optical properties of liquid/ice clouds impact the statistics of the agreement between model and observations. The other aspect is about the cloud overlap scheme. Different schemes have been tested (maximum, random, maximum random). As the computational cost increases linearly with the number of cloud columns, it will be investigated if there is an optimal number of columns beyond which there is little additional benefit to be gained. During daytime the high wave number channels of AIRS are affected by solar radiation. With full scattering calculations using a monochromatic version of the Edwards-Slingo radiation code the HT-FRTC can model solar radiation reasonably well, but full scattering calculations are relatively expensive. Pure Chou scaling on the other hand can not properly describe scattering of solar radiation by clouds and requires additional refinements.

Comparison of Inoculation with the InoqulA and WASP Automated Systems with Manual Inoculation

PubMed Central

Croxatto, Antony; Dijkstra, Klaas; Prod'hom, Guy

2015-01-01

The quality of sample inoculation is critical for achieving an optimal yield of discrete colonies in both monomicrobial and polymicrobial samples to perform identification and antibiotic susceptibility testing. Consequently, we compared the performance between the InoqulA (BD Kiestra), the WASP (Copan), and manual inoculation methods. Defined mono- and polymicrobial samples of 4 bacterial species and cloudy urine specimens were inoculated on chromogenic agar by the InoqulA, the WASP, and manual methods. Images taken with ImagA (BD Kiestra) were analyzed with the VisionLab version 3.43 image analysis software to assess the quality of growth and to prevent subjective interpretation of the data. A 3- to 10-fold higher yield of discrete colonies was observed following automated inoculation with both the InoqulA and WASP systems than that with manual inoculation. The difference in performance between automated and manual inoculation was mainly observed at concentrations of >106 bacteria/ml. Inoculation with the InoqulA system allowed us to obtain significantly more discrete colonies than the WASP system at concentrations of >107 bacteria/ml. However, the level of difference observed was bacterial species dependent. Discrete colonies of bacteria present in 100- to 1,000-fold lower concentrations than the most concentrated populations in defined polymicrobial samples were not reproducibly recovered, even with the automated systems. The analysis of cloudy urine specimens showed that InoqulA inoculation provided a statistically significantly higher number of discrete colonies than that with WASP and manual inoculation. Consequently, the automated InoqulA inoculation greatly decreased the requirement for bacterial subculture and thus resulted in a significant reduction in the time to results, laboratory workload, and laboratory costs. PMID:25972424

Computation of Solar Radiative Fluxes by 1D and 3D Methods Using Cloudy Atmospheres Inferred from A-train Satellite Data

NASA Technical Reports Server (NTRS)

Barker, Howard W.; Kato, Serji; Wehr, T.

2012-01-01

The main point of this study was to use realistic representations of cloudy atmospheres to assess errors in solar flux estimates associated with 1D radiative transfer models. A scene construction algorithm, developed for the EarthCARE satellite mission, was applied to CloudSat, CALIPSO, and MODIS satellite data thus producing 3D cloudy atmospheres measuring 60 km wide by 13,000 km long at 1 km grid-spacing. Broadband solar fluxes and radiances for each (1 km)2 column where then produced by a Monte Carlo photon transfer model run in both full 3D and independent column approximation mode (i.e., a 1D model).

Comparison of solar system measured data for various sample rates. [conducted using Marshall Space Flight Center Solar House

NASA Technical Reports Server (NTRS)

Chiou, J., Sr.

1977-01-01

The results of solar house data for sample rates of 50, 100, 250, 300, and 600 seconds were compared. The data considered for summer days were the heat incident on the collectors, the heat used by the air conditioner generator, and the heat used by the auxiliary heater. For winter days, the heat incident, the heat collected and the heat used by the heat exchanger were computed. These data were compared for different weather days such as clear days, partly cloudy days, cloudy days, and very cloudy days. Also, data for the integration of all these weather days were compared. The precentage differences for these data, using 50 second sample rate as a base, are also presented.

Assimilating All-Sky GPM Microwave Imager(GMI) Radiance Data in NASA GEOS-5 System for Global Cloud and Precipitation Analyses

NASA Astrophysics Data System (ADS)

Kim, M. J.; Jin, J.; McCarty, W.; Todling, R.; Holdaway, D. R.; Gelaro, R.

2014-12-01

The NASA Global Modeling and Assimilation Office (GMAO) works to maximize the impact of satellite observations in the analysis and prediction of climate and weather through integrated Earth system modeling and data assimilation. To achieve this goal, the GMAO undertakes model and assimilation development, generates products to support NASA instrument teams and the NASA Earth science program. Currently Atmospheric Data Assimilation System (ADAS) in the Goddard Earth Observing System Model, Version 5(GEOS-5) system combines millions of observations and short-term forecasts to determine the best estimate, or analysis, of the instantaneous atmospheric state. However, ADAS has been geared towards utilization of observations in clear sky conditions and the majority of satellite channel data affected by clouds are discarded. Microwave imager data from satellites can be a significant source of information for clouds and precipitation but the data are presently underutilized, as only surface rain rates from the Tropical Rainfall Measurement Mission (TRMM) Microwave Imager (TMI) are assimilated with small weight assigned in the analysis process. As clouds and precipitation often occur in regions with high forecast sensitivity, improvements in the temperature, moisture, wind and cloud analysis of these regions are likely to contribute to significant gains in numerical weather prediction accuracy. This presentation is intended to give an overview of GMAO's recent progress in assimilating the all-sky GPM Microwave Imager (GMI) radiance data in GEOS-5 system. This includes development of various new components to assimilate cloud and precipitation affected data in addition to data in clear sky condition. New observation operators, quality controls, moisture control variables, observation and background error models, and a methodology to incorporate the linearlized moisture physics in the assimilation system are described. In addition preliminary results showing impacts of assimilating all-sky GMI data on GEOS-5 forecasts are discussed.

Estimation of UV index in the clear-sky using OMI PROFOZ and AERONET data

NASA Astrophysics Data System (ADS)

Lee, H.; Kim, J.; Jeong, U.

2016-12-01

Due to a strong influence to the human health and ecosystem environment, continuous monitoring of the surface-level ultraviolet (UV) radiation is important nowadays. UV index (UVI) is a simple parameter to show the strength of surface UV radiation, therefore UVI has been widely utilized for the purpose of UV monitoring. In this work, we also try to develop our own retrieval algorithm for better estimation of UVI. The amount of UVA (320-400 nm) and UVB (290-320 nm) radiation at the Earth surface depends on the extent of Rayleigh scattering by atmospheric gas molecules, the radiative absorption by ozone, radiative scattering by clouds, and both absorption and scattering by airborne aerosols. Thus advanced consideration of these factors is the essential part to establish the process of UVI estimation. In this study, we estimate UV Index (UVI) at Seoul first in a clear-sky atmosphere, and then validate this estimated UVI comparing to UVI from Brewer spectrophotometer measurements located at Yonsei University in Seoul. We use the Vector Linearized Discrete Ordinate Radiative Transfer (VLIDORT) model version 2.6 for our UVI calculation. To consider the ozone and aerosol influence in a real situation, we input ozone and temperature profiles from the Ozone Monitoring Instrument (OMI) Aura vertical profile ozone (PROFOZ) data, and aerosol properties from the AErosol RObotic NETwork (AERONET) measurements at Seoul into the model. Inter-comparison of UVI is performed for the year 2011, 2012 and 2014, and resulted in a high correlation coefficient (R=0.95) under clear-sky condition. But a slight overestimation of Brewer UVI occurred under high AOD conditions in clear-sky. Because our UVI algorithm does not account for surface absorbing aerosols, it is lead to systematic overestimation of surface UV irradiances. Therefore, we also investigate the effect of absorbing aerosol on the amount of UV irradiance in the clear-sky over East Asia.

What If It Rains on Your Eclipse? Planning Ahead for August 2017

NASA Astrophysics Data System (ADS)

Bartlett, Jennifer L.; Keohane, J.

2010-01-01

It was a dark and rainy morning, not far out of Shanghai, when we saw the 2009 July 22 total solar eclipse. Many of the Americans puttering around their equipment that morning, in hopes that the sky would clear enough to catch some of event they had traveled around the world to view, were already planning ahead for 2017 August 21, when a narrow strip of the United States will experience up to 2 minutes and 45 seconds of totality. For most people, a total solar eclipse is once in a lifetime event steeped in legend. If you are situated along this privileged corridor, you will have a wonderful opportunity for public outreach. But what if it rains? Historically, August is mostly sunny at the location of greatest eclipse, near Makanda, Illinois. Even with such favorable circumstances, having a rain plan will ensure you make the most of the occasion. First, the flexibility to relocate your program to take advantage of the most favorable weather would be ideal. If that is not a realistic option, include some protective gear with your equipment so that you can set up despite misty or drizzling conditions. Second, monitoring changing light levels and temperatures should be possible even under cloudy skies. Third, for some sites, changes in wildlife behavior may also be noticeable. If the weather is clear, such projects could enhance your program during the partial phases of the eclipse and provide enrichment materials for those unable to attend. While 2017 may still seem in the distant future to all but eclipse fanatics, some creativity and advance brainstorming will ensure that your outreach program shines during the event, even if the Sun does not cooperate. S. Bell (2009, pc.), HMNAO, provided the eclipse predictions. Additional information is available via USNO Eclipse Portal (http://www.eclipse.org.uk/eclbin/query_usno.cgi).

Effects of synoptic patterns on atmospheric chemistry and aerosols during the Arctic Ocean Expedition 1996

NASA Astrophysics Data System (ADS)

Nilsson, E. Douglas; Barr, Sumner

2001-12-01

The atmospheric program on the Arctic Ocean Expedition of July through September 1996 (AOE-96) was focused on aerosol climate feedback. The expedition took place close to the saddle point between a semipersistent anticyclonic ridge from near Scandinavia to the Arctic coast of eastern Siberia and a trough from the Canadian archipelago across the pole to north central Siberia. The weather varied from anticyclonic clear-sky conditions to cyclonic cloudy conditions, and 13 identifiable migratory features (frontal bands, wave disturbances) clearly influenced local weather, clouds, atmospheric transport, and chemistry. This includes an explosive polar cyclone, born at the lateral heat gradient between Greenland and the pack ice rather than between open sea and the pack ice. The synoptic scale weather systems caused the strongest variability in trace gases (O3 in particular) and aerosols, and also strong variability in the cloud cover. The formation of air masses over the pack ice primarily depends on if there is cyclonic (convergent) or anticyclonic (divergent) flow. Cyclonic flow resulted in a modified marine air mass loaded with vapor, but with low aerosol number concentrations owing to frequent clouds and fogs and efficient cloud scavenging of the aerosol. Anticyclonic flow resulted in almost continental air masses with clear sky, long residence time over the pack ice and subsidence slowly replacing the boundary layer with free tropospheric air, low vapor concentrations, but large aerosol number in lack of efficient cloud scavenging. The synoptic variability and advection from south of the ice edge were weaker than during the predecessor International Arctic Ocean Expedition in 1991 (IAOE-91), when on average the sampled air spent 55 hours over the pack ice compared to more than 120 hours during AOE-96, owing to exceptionally high cyclone activity in 1991. This caused a large difference in atmospheric transport, chemistry, and aerosols between the two expeditions.

Development of a Global Evaporative Stress Index Based on Thermal and Microwave LST towards Improved Monitoring of Agricultural Drought

NASA Astrophysics Data System (ADS)

Hain, C.; Anderson, M. C.; Otkin, J.; Holmes, T. R.; Gao, F.

2017-12-01

This presentation will describe the development of a global agricultural monitoring tool, with a focus on providing early warning of developing vegetation stress for agricultural decision-makers and stakeholders at relatively high spatial resolution (5-km). The tool is based on remotely sensed estimates of evapotranspiration, retrieved via energy balance principals using observations of land surface temperature. The Evaporative Stress Index (ESI) represents anomalies in the ratio of actual-to-potential ET generated with the ALEXI surface energy balance model. The LST inputs to ESI have been shown to provide early warning information about the development of vegetation stress with stress-elevated canopy temperatures observed well before a decrease in greenness is detected in remotely sensed vegetation indices. As a diagnostic indicator of actual ET, the ESI requires no information regarding antecedent precipitation or soil moisture storage capacity - the current available moisture to vegetation is deduced directly from the remotely sensed LST signal. This signal also inherently accounts for both precipitation and non-precipitation related inputs/sinks to the plant-available soil moisture pool (e.g., irrigation) which can modify crop response to rainfall anomalies. Independence from precipitation data is a benefit for global agricultural monitoring applications due to sparseness in existing ground-based precipitation networks, and time delays in public reporting. Several enhancements to the current ESI framework will be addressed as requested from project stakeholders: (a) integration of "all-sky" MW Ka-band LST retrievals to augment "clear-sky" thermal-only ESI in persistently cloudy regions; (b) operational production of ESI Rapid Change Indices which provide important early warning information related to onset of actual vegetation stress; and (c) assessment of ESI as a predictor of global yield anomalies; initial studies have shown the ability of intra-seasonal ESI to provide an early indication of at-harvest agricultural yield anomalies.

Winter to Spring Transition in Europe 48-45 degrees N: From Temperature Control by Advection to Control by Insolation

NASA Technical Reports Server (NTRS)

Otterman, J.; Ardizzone, J.; Atlas, R.; Hu, H.; Jusem, J. C.; Starr, D.

1999-01-01

As established in previous studies, and analyzed further herein for the years 1988-1998, warm advection from the North Atlantic is the predominant control of the surface-air temperature in northern-latitude Europe in late winter. This thesis is supported by the substantial correlation Cti between the speed of the southwesterly surface winds over the eastern North Atlantic, as quantified by a specific Index Ina, and the 2-meter level temperature Ts over central Europe (48-54 deg N; 5-25 deg E), for January, February and early March. In mid-March and subsequently, the correlation Cti drops drastically (quite often it is negative). The change in the relationship between Ts and Ina marks a transition in the control of the surface-air temperature. As (a) the sun rises higher in the sky, (b) the snows melt (the surface absorptivity can increase by a factor of 3.0), (c) the ocean-surface winds weaken, and (d) the temperature difference between land and ocean (which we analyze) becomes small, absorption of insolation replaces the warm advection as the dominant control of the continental temperature. We define the onset of spring by this transition, which evaluated for the period of our study occurs at pentad 16 (Julian Date 76, that is, March 16). The control by insolation means that the surface is cooler under cloudy conditions than under clear skies. This control produces a much smaller interannual variability of the surface temperature and of the lapse rate than prevailing in winter, when the control is by advection. Regional climatic data would be of greatest value for agriculture and forestry if compiled for well-defined seasons. For continental northern latitudes, analysis presented here of factors controlling the surface temperature appears an appropriate tool for this task.

Estimating the Longwave Radiation Underneath the Forest Canopy in Snow-dominated Setting

NASA Astrophysics Data System (ADS)

Zhou, Y.; Kumar, M.; Link, T. E.

2017-12-01

Forest canopies alter incoming longwave radiation at the land surface, thus influencing snow cover energetics. The snow surface receives longwave radiation from the sky as well as from surrounding vegetation. The longwave radiation from trees is determined by its skin temperature, which shows significant heterogeneity depending on its position and morphometric attributes. Here our goal is to derive an effective tree temperature that can be used to estimate the longwave radiation received by the land surface pixel. To this end, we implement these three steps: 1) derive a relation between tree trunk surface temperature and the incident longwave radiation, shortwave radiation, and air temperature; 2) develop an inverse model to calculate the effective temperature by establishing a relationship between the effective temperature and the actual tree temperature; and 3) estimate the effective temperature using widely measured variables, such as solar radiation and forest density. Data used to derive aforementioned relations were obtained at the University of Idaho Experimental Forest, in northern Idaho. Tree skin temperature, incoming longwave radiation, solar radiation received by the tree surface, and air temperature were measured at an isolated tree and a tree within a homogeneous forest stand. Longwave radiation received by the land surface and the sky view factors were also measured at the same two locations. The calculated effective temperature was then compared with the measured tree trunk surface temperature. Additional longwave radiation measurements with pyrgeometer arrays were conducted under forests with different densities to evaluate the relationship between effective temperature and forest density. Our preliminary results show that when exposed to direct shortwave radiation, the tree surface temperature shows a significant difference from the air temperature. Under cloudy or shaded conditions, the tree surface temperature closely follows the air temperature. The effective tree temperature follows the air temperature in a dense forest stand, although it is significantly larger than the air temperature near the isolated tree. This discrepancy motivates us to explore ways to represent the effective tree temperature for stands with different densities.