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account for contributions from both reflected solar and thermal emission energy. The observed cloud bidirectional reflectance and emissivity, and not the measured radiance itself, are the fundamental quantities relevant for cloud microphysical retrievals. In this paper, we examine the fundamental uncertainty in the observed 3.7- μ m solar reflectance that corresponds to uncertainty in the knowledge of the solar irradiance in this spectral region. The partitioning between solar and emissive radiance in
account for contributions from both reflected solar and thermal emission energy. The observed cloud bidirectional reflectance and emissivity, and not the measured radiance itself, are the fundamental quantities relevant for cloud microphysical retrievals. In this paper, we examine the fundamental uncertainty in the observed 3.7- μ m solar reflectance that corresponds to uncertainty in the knowledge of the solar irradiance in this spectral region. The partitioning between solar and emissive radiance in
1. Introduction For many years radiometers that measure solar or infrared (IR) irradiance have been mounted on various research aircraft in attempts to characterize the radiative budget within the atmospheric column (e.g., Fritz 1948 ; Kuhn and Suomi 1958 ; Roach 1961 ; Albrecht et al. 1974 ; Cox and Griffith 1979 ; Ackerman and Cox 1981 ; Rawlins 1989 ; Saunders et al. 1992 ; Hayasaka et al. 1995 ; Valero et al. 1997 ; Hignett et al. 1999 ; Wendisch and Keil 1999 ; Valero et al
1. Introduction For many years radiometers that measure solar or infrared (IR) irradiance have been mounted on various research aircraft in attempts to characterize the radiative budget within the atmospheric column (e.g., Fritz 1948 ; Kuhn and Suomi 1958 ; Roach 1961 ; Albrecht et al. 1974 ; Cox and Griffith 1979 ; Ackerman and Cox 1981 ; Rawlins 1989 ; Saunders et al. 1992 ; Hayasaka et al. 1995 ; Valero et al. 1997 ; Hignett et al. 1999 ; Wendisch and Keil 1999 ; Valero et al
1. Introduction Climate change–related studies require long-term historical data. One such dataset available and valuable to the climate change community is the solar irradiance measured by the Eppley Precision Spectral Pyranometers (PSPs), which have been populated worldwide (i.e., quantity) for more than three decades (i.e., long term) with very minimal instrumental modifications (i.e., continuity). The double-glass domes of a PSP, acting as both a protector and a filter to the detector
1. Introduction Climate change–related studies require long-term historical data. One such dataset available and valuable to the climate change community is the solar irradiance measured by the Eppley Precision Spectral Pyranometers (PSPs), which have been populated worldwide (i.e., quantity) for more than three decades (i.e., long term) with very minimal instrumental modifications (i.e., continuity). The double-glass domes of a PSP, acting as both a protector and a filter to the detector
variable in forested environments ( Link and Marks 1999 ; Hardy et al. 2004 ; Link et al. 2004 ). Therefore, it is the purpose of this paper to examine the variability of shortwave irradiance in coniferous forest environments during snowmelt to estimate the significance of this variability to snow-covered area depletion. A companion paper ( Essery et al. 2008 ) focuses on estimating the spatial distribution of shortwave transmission through coniferous canopies using remote sensing and explicit
variable in forested environments ( Link and Marks 1999 ; Hardy et al. 2004 ; Link et al. 2004 ). Therefore, it is the purpose of this paper to examine the variability of shortwave irradiance in coniferous forest environments during snowmelt to estimate the significance of this variability to snow-covered area depletion. A companion paper ( Essery et al. 2008 ) focuses on estimating the spatial distribution of shortwave transmission through coniferous canopies using remote sensing and explicit
of 20% in UV spectral irradiance at 300 nm at Toronto, Canada, during the 1989–96 period. This notable increase could lead to a variety of adverse effects on health and environment conditions ( Diffey 1991 ; WMO 2003 ). Therefore, several international organizations have stressed the need for monitoring the UV irradiance at ground level. In addition, in order to improve our understanding of the interaction between this radiation and atmospheric attenuators such as clouds, ozone, or aerosols, the
of 20% in UV spectral irradiance at 300 nm at Toronto, Canada, during the 1989–96 period. This notable increase could lead to a variety of adverse effects on health and environment conditions ( Diffey 1991 ; WMO 2003 ). Therefore, several international organizations have stressed the need for monitoring the UV irradiance at ground level. In addition, in order to improve our understanding of the interaction between this radiation and atmospheric attenuators such as clouds, ozone, or aerosols, the
1. Introduction During a meteorological field campaign in the Andes Mountains of southern Ecuador in 1998–2001 ( Emck 2007 ), very high values of incoming global shortwave solar irradiance from the spectral range of 305–2800 nm incident upon a horizontal surface (henceforth G ), of more than 1700 W m −2 , and twice of more than 1800 W m −2 (>700 W m −2 over the clear-sky value), appeared in the records. The routine hourly mean values were inconspicuous with regard to anomalous magnitudes
1. Introduction During a meteorological field campaign in the Andes Mountains of southern Ecuador in 1998–2001 ( Emck 2007 ), very high values of incoming global shortwave solar irradiance from the spectral range of 305–2800 nm incident upon a horizontal surface (henceforth G ), of more than 1700 W m −2 , and twice of more than 1800 W m −2 (>700 W m −2 over the clear-sky value), appeared in the records. The routine hourly mean values were inconspicuous with regard to anomalous magnitudes
converted into electricity using different technologies: directly from photovoltaics or indirectly through concentrating solar power (CSP). Photovoltaic plants depend mainly on global horizontal irradiance (GHI) for their operation, while CSP plants depend on direct normal irradiance (DNI). Different methods are used to predict these variables depending on the temporal scale considered. All-sky cameras, satellite images, neural networks, and cloud-tracking image analysis are useful for nowcasting and
converted into electricity using different technologies: directly from photovoltaics or indirectly through concentrating solar power (CSP). Photovoltaic plants depend mainly on global horizontal irradiance (GHI) for their operation, while CSP plants depend on direct normal irradiance (DNI). Different methods are used to predict these variables depending on the temporal scale considered. All-sky cameras, satellite images, neural networks, and cloud-tracking image analysis are useful for nowcasting and
essential in assessing theoretical treatments of radiative transfer in the atmosphere, verifying climate model computations, and studying trends in surface radiation at scales that are smaller than those normally associated with climatic regions. Daylight downward longwave radiation from the atmosphere is a very important energy flux because it is a component of the radiation budget in land surface models ( Sridhar and Elliot 2002 ). The understanding of the surface downward longwave irradiance energy
essential in assessing theoretical treatments of radiative transfer in the atmosphere, verifying climate model computations, and studying trends in surface radiation at scales that are smaller than those normally associated with climatic regions. Daylight downward longwave radiation from the atmosphere is a very important energy flux because it is a component of the radiation budget in land surface models ( Sridhar and Elliot 2002 ). The understanding of the surface downward longwave irradiance energy
problem. The amount of scattering and absorption of incoming solar radiation caused by aerosols can be summarized by the total aerosol optical depth (AOD). In general, higher AOD values correspond to reductions in solar irradiance at the surface. This is particularly true for direct normal irradiance (DNI), because any scattering or absorption by definition reduces DNI at the surface; this is the aerosol direct effect. By contrast, global horizontal irradiance (GHI), which is calculated from a
problem. The amount of scattering and absorption of incoming solar radiation caused by aerosols can be summarized by the total aerosol optical depth (AOD). In general, higher AOD values correspond to reductions in solar irradiance at the surface. This is particularly true for direct normal irradiance (DNI), because any scattering or absorption by definition reduces DNI at the surface; this is the aerosol direct effect. By contrast, global horizontal irradiance (GHI), which is calculated from a
1. Introduction There is substantial evidence to suggest that changes in the solar irradiance influence variations in the temperature and circulation of Earth’s atmosphere over the 11-yr solar cycle. Many of these results are based on correlations with the 10.7-cm solar flux (e.g., Labitzke and van Loon 1995 ; van Loon and Shea 1999 ) or the wavelength-integrated total solar irradiance (TSI) [see Haigh (2003) and references therein]. While TSI is a good indicator of the total solar forcing
1. Introduction There is substantial evidence to suggest that changes in the solar irradiance influence variations in the temperature and circulation of Earth’s atmosphere over the 11-yr solar cycle. Many of these results are based on correlations with the 10.7-cm solar flux (e.g., Labitzke and van Loon 1995 ; van Loon and Shea 1999 ) or the wavelength-integrated total solar irradiance (TSI) [see Haigh (2003) and references therein]. While TSI is a good indicator of the total solar forcing
