The Experts below are selected from a list of 4896 Experts worldwide ranked by ideXlab platform
Rafael L Bras - One of the best experts on this subject based on the ideXlab platform.
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estimation of net radiation from the modis data under all sky conditions southern great plains case study
Remote Sensing of Environment, 2010Co-Authors: Gautam Bisht, Rafael L BrasAbstract:Abstract Net radiation is a key component in the surface radiation budget. Numerous studies have developed frameworks to estimate net radiation or its components (upwelling or downwelling longwave and/or shortwave radiation) from remote sensing data for clear sky conditions. Application of existing methodologies to estimate net radiation for cloudy sky conditions from remote sensing sensors remains a significant challenge. In this paper, we present a framework to estimate instantaneous and daily average net radiation under all sky conditions from using the data from the MODerate Resolution Imaging Spectroradiometer (MODIS), onboard from the Terra satellites. Bisht et al. (2005) methodology is used for the clear sky portion of the MODIS overpass; while for cloudy portion of the MODIS overpass an extension of Bisht et al. (2005) methodology is applied. The extension of Bisht et al. (2005) methodology utilizes the MODIS cloud data product (MOD06_L2) for cloud top temperature, cloud fraction, cloud emissivity, cloud optical thickness and land surface temperature for cloudy days. The methodology is applied over the Southern Great Plains (SGP) for a time period covering all seasons of 2006. During the MODIS-Terra Overpasses in 2006 over the SGP, only 24% of day-Overpasses and 9% of night-Overpasses had 75% or more of the study region as cloud free. Thus, this proposed study is applicable to a large portion of the MODIS-Terra Overpasses. The root mean square errors (RMSE) of instantaneous and daily average net radiation estimated under cloudy conditions using the MOD06_L2 product, comparing to ground-based measurements are 37 W m − 2 and 38 W m − 2 , respectively. The strength of the proposed methodology is that it can rely exclusively on remote sensing data in the absence of ancillary ground observations, thus it has a potential to estimate surface energy budget globally.
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estimation of net radiation from the modis data under all sky conditions southern great plains case study
Remote Sensing of Environment, 2010Co-Authors: Gautam Bisht, Rafael L BrasAbstract:Abstract Net radiation is a key component in the surface radiation budget. Numerous studies have developed frameworks to estimate net radiation or its components (upwelling or downwelling longwave and/or shortwave radiation) from remote sensing data for clear sky conditions. Application of existing methodologies to estimate net radiation for cloudy sky conditions from remote sensing sensors remains a significant challenge. In this paper, we present a framework to estimate instantaneous and daily average net radiation under all sky conditions from using the data from the MODerate Resolution Imaging Spectroradiometer (MODIS), onboard from the Terra satellites. Bisht et al. (2005) methodology is used for the clear sky portion of the MODIS overpass; while for cloudy portion of the MODIS overpass an extension of Bisht et al. (2005) methodology is applied. The extension of Bisht et al. (2005) methodology utilizes the MODIS cloud data product (MOD06_L2) for cloud top temperature, cloud fraction, cloud emissivity, cloud optical thickness and land surface temperature for cloudy days. The methodology is applied over the Southern Great Plains (SGP) for a time period covering all seasons of 2006. During the MODIS-Terra Overpasses in 2006 over the SGP, only 24% of day-Overpasses and 9% of night-Overpasses had 75% or more of the study region as cloud free. Thus, this proposed study is applicable to a large portion of the MODIS-Terra Overpasses. The root mean square errors (RMSE) of instantaneous and daily average net radiation estimated under cloudy conditions using the MOD06_L2 product, comparing to ground-based measurements are 37 W m − 2 and 38 W m − 2 , respectively. The strength of the proposed methodology is that it can rely exclusively on remote sensing data in the absence of ancillary ground observations, thus it has a potential to estimate surface energy budget globally.
Gautam Bisht - One of the best experts on this subject based on the ideXlab platform.
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estimation of net radiation from the modis data under all sky conditions southern great plains case study
Remote Sensing of Environment, 2010Co-Authors: Gautam Bisht, Rafael L BrasAbstract:Abstract Net radiation is a key component in the surface radiation budget. Numerous studies have developed frameworks to estimate net radiation or its components (upwelling or downwelling longwave and/or shortwave radiation) from remote sensing data for clear sky conditions. Application of existing methodologies to estimate net radiation for cloudy sky conditions from remote sensing sensors remains a significant challenge. In this paper, we present a framework to estimate instantaneous and daily average net radiation under all sky conditions from using the data from the MODerate Resolution Imaging Spectroradiometer (MODIS), onboard from the Terra satellites. Bisht et al. (2005) methodology is used for the clear sky portion of the MODIS overpass; while for cloudy portion of the MODIS overpass an extension of Bisht et al. (2005) methodology is applied. The extension of Bisht et al. (2005) methodology utilizes the MODIS cloud data product (MOD06_L2) for cloud top temperature, cloud fraction, cloud emissivity, cloud optical thickness and land surface temperature for cloudy days. The methodology is applied over the Southern Great Plains (SGP) for a time period covering all seasons of 2006. During the MODIS-Terra Overpasses in 2006 over the SGP, only 24% of day-Overpasses and 9% of night-Overpasses had 75% or more of the study region as cloud free. Thus, this proposed study is applicable to a large portion of the MODIS-Terra Overpasses. The root mean square errors (RMSE) of instantaneous and daily average net radiation estimated under cloudy conditions using the MOD06_L2 product, comparing to ground-based measurements are 37 W m − 2 and 38 W m − 2 , respectively. The strength of the proposed methodology is that it can rely exclusively on remote sensing data in the absence of ancillary ground observations, thus it has a potential to estimate surface energy budget globally.
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estimation of net radiation from the modis data under all sky conditions southern great plains case study
Remote Sensing of Environment, 2010Co-Authors: Gautam Bisht, Rafael L BrasAbstract:Abstract Net radiation is a key component in the surface radiation budget. Numerous studies have developed frameworks to estimate net radiation or its components (upwelling or downwelling longwave and/or shortwave radiation) from remote sensing data for clear sky conditions. Application of existing methodologies to estimate net radiation for cloudy sky conditions from remote sensing sensors remains a significant challenge. In this paper, we present a framework to estimate instantaneous and daily average net radiation under all sky conditions from using the data from the MODerate Resolution Imaging Spectroradiometer (MODIS), onboard from the Terra satellites. Bisht et al. (2005) methodology is used for the clear sky portion of the MODIS overpass; while for cloudy portion of the MODIS overpass an extension of Bisht et al. (2005) methodology is applied. The extension of Bisht et al. (2005) methodology utilizes the MODIS cloud data product (MOD06_L2) for cloud top temperature, cloud fraction, cloud emissivity, cloud optical thickness and land surface temperature for cloudy days. The methodology is applied over the Southern Great Plains (SGP) for a time period covering all seasons of 2006. During the MODIS-Terra Overpasses in 2006 over the SGP, only 24% of day-Overpasses and 9% of night-Overpasses had 75% or more of the study region as cloud free. Thus, this proposed study is applicable to a large portion of the MODIS-Terra Overpasses. The root mean square errors (RMSE) of instantaneous and daily average net radiation estimated under cloudy conditions using the MOD06_L2 product, comparing to ground-based measurements are 37 W m − 2 and 38 W m − 2 , respectively. The strength of the proposed methodology is that it can rely exclusively on remote sensing data in the absence of ancillary ground observations, thus it has a potential to estimate surface energy budget globally.
Yalcin Alver - One of the best experts on this subject based on the ideXlab platform.
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Illegal road crossing behavior of pedestrians at overpass locations: factors affecting gap acceptance, crossing times and overpass use
Accident Analysis & Prevention, 2015Co-Authors: Y.i. Demiroz, Pelin Onelcin, Yalcin AlverAbstract:The aim of designing Overpasses is to provide safe road crossings for pedestrians by helping them to avoid conflicts with motor vehicles. However, the number of pedestrians who do not use Overpasses to cross the road is very high. An observational survey of illegal road crossings was conducted at four overpass locations in Izmir, Turkey to determine the crossing time, crossing speed of the pedestrians and their distance and time gap perception for safe road-crossing within 25m of the Overpasses in both directions. Crossing time is the time needed for a pedestrian to cross a particular road. Time gap is strongly related with safety margin. If a pedestrian chooses a larger time gap, then the arrival time of the oncoming vehicle to the crossing point of the pedestrian increases thus, the possibility of a collision decreases. Each overpass was observed on weekdays during peak afternoon (12.30-13.30) and evening hours (17.00-18.00). At all overpass locations 454 illegal crossings were observed. ANOVA results revealed that age had a significant effect both on safety margin and crossing time. During the observations a survey was conducted among pedestrians who completed their crossings either using the overpass or at street level within 25m of the overpass (n=231). Factors affecting the crossing choice of pedestrians were specified in the surveys. The major part of the respondents (71.7%) indicated that time saving was the main reason for crossing at street level. Pedestrians' crossing speeds were extracted from the video recordings to observe the effect of speed limit on pedestrian behavior. As a result, at locations where the speed limit was 70km/h, pedestrians' average crossing speed was found to be 1.60m/s and 1.73m/s while at locations where the speed limit was 50km/h, pedestrians' average crossing speed was found to be 1.04m/s and 0.97m/s. This shows that pedestrians feel safer while crossing when the vehicle speed is low. Language: en
David B Wolff - One of the best experts on this subject based on the ideXlab platform.
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comparison of drop size distribution parameter d0 and rain rate from s band dual polarized ground radar trmm precipitation radar pr and combined pr tmi two events from kwajalein atoll
Journal of Atmospheric and Oceanic Technology, 2012Co-Authors: V N Bringi, Gwojong Huang, Joseph S Munchak, Christian D Kummerow, David A Marks, David B WolffAbstract:AbstractThe estimation of the drop size distribution parameter [median volume diameter (D0)] and rain rate (R) from the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) as well as from combined PR–TRMM Microwave Imager (TMI) algorithms are considered in this study for two TRMM satellite Overpasses near the Kwajalein Atoll. An operational dual-polarized S-band radar (KPOL) located in Kwajalein is central as the only TRMM ground validation site for measurement of precipitation over the open ocean. The accuracy of the TRMM PR in retrieving D0 and R is better for precipitation over the ocean based on a more stable surface reference technique for estimating the path-integrated attenuation. Also, combined PR–TMI methods are more accurate over the open ocean because of better knowledge of the surface microwave emissivity. Using Zh (horizontal polarized radar reflectivity) and Zdr (differential reflectivity) data for the two TRMM overpass events over Kwajalein, D0 and R from KPOL are retrieved....
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satellite sampling and retrieval errors in regional monthly rain estimates from tmi amsr e ssm i amsu b and the trmm pr
Journal of Applied Meteorology and Climatology, 2011Co-Authors: Brad L Fisher, David B WolffAbstract:AbstractPassive and active microwave rain sensors on board Earth-orbiting satellites estimate monthly rainfall from the instantaneous rain statistics collected during satellite Overpasses. It is well known that climate-scale rain estimates from meteorological satellites incur sampling errors resulting from the process of discrete temporal sampling and statistical averaging. Sampling and retrieval errors ultimately become entangled in the estimation of the mean monthly rain rate. The sampling component of the error budget effectively introduces statistical noise into climate-scale rain estimates that obscures the error component associated with the instantaneous rain retrieval. Estimating the accuracy of the retrievals on monthly scales therefore necessitates a decomposition of the total error budget into sampling and retrieval error quantities. This paper presents results from a statistical evaluation of the sampling and retrieval errors for five different spaceborne rain sensors on board nine orbiting sa...
Y.i. Demiroz - One of the best experts on this subject based on the ideXlab platform.
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Illegal road crossing behavior of pedestrians at overpass locations: factors affecting gap acceptance, crossing times and overpass use
Accident Analysis & Prevention, 2015Co-Authors: Y.i. Demiroz, Pelin Onelcin, Yalcin AlverAbstract:The aim of designing Overpasses is to provide safe road crossings for pedestrians by helping them to avoid conflicts with motor vehicles. However, the number of pedestrians who do not use Overpasses to cross the road is very high. An observational survey of illegal road crossings was conducted at four overpass locations in Izmir, Turkey to determine the crossing time, crossing speed of the pedestrians and their distance and time gap perception for safe road-crossing within 25m of the Overpasses in both directions. Crossing time is the time needed for a pedestrian to cross a particular road. Time gap is strongly related with safety margin. If a pedestrian chooses a larger time gap, then the arrival time of the oncoming vehicle to the crossing point of the pedestrian increases thus, the possibility of a collision decreases. Each overpass was observed on weekdays during peak afternoon (12.30-13.30) and evening hours (17.00-18.00). At all overpass locations 454 illegal crossings were observed. ANOVA results revealed that age had a significant effect both on safety margin and crossing time. During the observations a survey was conducted among pedestrians who completed their crossings either using the overpass or at street level within 25m of the overpass (n=231). Factors affecting the crossing choice of pedestrians were specified in the surveys. The major part of the respondents (71.7%) indicated that time saving was the main reason for crossing at street level. Pedestrians' crossing speeds were extracted from the video recordings to observe the effect of speed limit on pedestrian behavior. As a result, at locations where the speed limit was 70km/h, pedestrians' average crossing speed was found to be 1.60m/s and 1.73m/s while at locations where the speed limit was 50km/h, pedestrians' average crossing speed was found to be 1.04m/s and 0.97m/s. This shows that pedestrians feel safer while crossing when the vehicle speed is low. Language: en
