Empirical relationships between extinction coefficient and visibility in fog

Nebuloni, Roberto

doi:10.1364/ao.44.003795

Cited by 94 publications

(53 citation statements)

References 26 publications

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“…In practice, we derive aerosol optical thickness at 550 nm from MODIS (MODerate-resolution Imaging Spectroradiometer) (retrieved from Giovanni (GES-DISC Interactive Online Visualization ANd aNalysis Infrastructure), Acker and Leptoukh, 2007) BLH (boundary layer height) to get the extinction coefficient. We then scale this extinction coefficient at 460 nm using the Angstrom coefficient as described in Nebuloni (2005), and derive visibility at this wavelength from the Koschmieder law (Koschmieder, 1926). The same approach to estimate the visibility will be used for the GEOS-R satellite (NOAA-NESDIS, 2010).…”

Section: Radiative Transfer and Assumptions On No 2 And Aerosol Extinmentioning

confidence: 99%

DOAS measurements of NO<sub>2</sub> from an ultralight aircraft during the Earth Challenge expedition

et al. 2012

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Abstract. We report on airborne Differential Optical Absorption Spectroscopy (DOAS) measurements of NO 2 tropospheric columns above South Asia, the Arabic peninsula, North Africa, and Italy in November and December 2009. The DOAS instrument was installed on an ultralight aircraft involved in the Earth Challenge project, an expedition of seven pilots flying on four ultralight aircraft between Australia and Belgium. The instrument recorded spectra in limb geometry with a large field of view, a set-up which provides a high sensitivity to the boundary layer NO 2 while minimizing the uncertainties related to the attitude variations. We compare our measurements with OMI (Ozone Monitoring Instrument) and GOME-2 (Global Ozone Monitoring Experiment 2) tropospheric NO 2 products when the latter are available. Above Rajasthan and the Po Valley, two areas where the NO 2 field is homogeneous, data sets agree very well. Our measurements in these areas are 0.1 ± 0.1 to 3 ± 1 × 10 15 molec cm −2 and 2.6 ± 0.8 × 10 16 molec cm −2 , respectively. Flying downwind of Riyadh, our NO 2 measurements show the structure of the megacity's exhaust plume with a higher spatial resolution than OMI. Moreover, our measurements are larger (up to 40 %) than those seen by satellites. We also derived tropospheric columns when no satellite data were available if it was possible to get information on the visibility from satellite measurements of aerosol optical thickness. This experiment also provides a confirmation for the recent finding of a soil signature above desert.

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Section: Radiative Transfer and Assumptions On No 2 And Aerosol Extinmentioning

confidence: 99%

DOAS measurements of NO<sub>2</sub> from an ultralight aircraft during the Earth Challenge expedition

et al. 2012

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“…This example (and many others not shown) shows that when the visibility (measured at 550 nm) drops below 1 km, the 20 m attenuated backscatter (measured at 910 nm) exceeds 2 × 10 −4 m −1 sr −1 . To compare, visibilityto-extinction parameterizations (e.g., Nebuloni, 2005) yield an extinction of about 3 × 10 −3 m −1 at 905 nm for a 550 nm visibility of 1 km (neglecting absorption by water vapor molecules). Because the extinction is strong in these conditions (scattering by droplets and absorption by water vapor), it is expected that the attenuated backscatter at higher altitudes (in the fog) will decrease quickly with increasing alti- tude.…”

Section: Step 3 (Alert Levels)mentioning

confidence: 99%

Radiation fog formation alerts using attenuated backscatter power from automatic lidars and ceilometers

et al. 2016

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Abstract. Radiation fog occurs over many locations around the world in stable atmospheric conditions. Air traffic at busy airports can be significantly disrupted because low visibility at the ground makes it unsafe to take off, land and taxi on the ground. Current numerical weather prediction forecasts are able to predict general conditions favorable for fog formation, but not the exact time or location of fog occurrence. A selected set of observations available in near-real time at strategic locations could also be useful to track the evolution of key processes and key parameters that drive fog formation. Such observations could complement the information predicted by numerical weather prediction (NWP) models that is made available to airport forecasters in support of their fog forecast. This paper presents an experimental setup based on collocated automatic lidar and ceilometer measurements, relative humidity measurements and horizontal visibility measurements to study hygroscopic growth of fog condensation nuclei. This process can take several minutes to hours, and can be tracked using lidar-or ceilometer-attenuated backscatter profiles. Based on hygroscopic growth laws we derive a set of parameters that can be used to provide alerts minutes to hours prior to formation of radiation fog. We present an algorithm that uses the temporal evolution of attenuated backscatter measurements to derive pre-fog formation alerts. The performance of the algorithm is tested on 45 independent pre-fog situations at two locations (near Paris, France, and Brussels, Belgium). We find that an alert for pre-fog conditions predominantly occurs 10-50 min prior to fog formation at an altitude ranging 0 to 100 m above ground. In a few cases, alerts can occur up to 100 min prior to fog formation. Alert durations are found to be sensitive to the relative humidity conditions found a few hours prior to the fog.

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“…Recently FSO communication system is taken into consideration in research studies. This is because of its high data rate, bandwidth and security, in an unlicensed spectrum as well as easy and low cost installation [1] [2]. In contrast with these advantages, high sensitivity of FSO system to weather conditions and atmospheric turbulences limits its practical applications.…”

Section: Introductionmentioning

confidence: 99%

Performance of a relay-assisted hybrid FSO/RF communication system

Amirabadi

Vakili

2019

Physical Communication

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This paper investigates performance of a relay assisted hybrid Free Space Optical / Radio Frequency (FSO/RF) communication system. The proposed structure is particularly recommended anywhere that direct RF communication between mobile users and base station is not possible due to atmospheric conditions. In this system, a multiuser RF link connects mobile users to relay and a FSO link connects relay to the base station. It is the first time that effect of number of users within the cell, on the performance of such structure, is investigated. Also it is the first time that performance of a dual hop hybrid FSO / RF system is investigated in Negative Exponential atmospheric turbulence. Considering wide range of atmospheric turbulence regimes, from moderate to saturated, for the first time, closed-form expressions are derived for Bit Error Rate (BER) and outage probability ( ) of the proposed structure. MATLAB simulations verified accuracy of the derived expressions. Considering fixed and adaptive gain amplify and forward protocols at relay, it is shown that adaptive gain relay is less sensitive to the number of users within the cell. It is also shown that fixed gain relay, despite its low complexity, has better performance; because its gain is adjusted such that the performance be favorable even at the worst case scenario.

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Empirical relationships between extinction coefficient and visibility in fog

Cited by 94 publications

References 26 publications

DOAS measurements of NO<sub>2</sub> from an ultralight aircraft during the Earth Challenge expedition

DOAS measurements of NO<sub>2</sub> from an ultralight aircraft during the Earth Challenge expedition

Radiation fog formation alerts using attenuated backscatter power from automatic lidars and ceilometers

Performance of a relay-assisted hybrid FSO/RF communication system

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Empirical relationships between extinction coefficient and visibility in fog

Cited by 94 publications

References 26 publications

DOAS measurements of NO&lt;sub&gt;2&lt;/sub&gt; from an ultralight aircraft during the Earth Challenge expedition

DOAS measurements of NO&lt;sub&gt;2&lt;/sub&gt; from an ultralight aircraft during the Earth Challenge expedition

Radiation fog formation alerts using attenuated backscatter power from automatic lidars and ceilometers

Performance of a relay-assisted hybrid FSO/RF communication system

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DOAS measurements of NO<sub>2</sub> from an ultralight aircraft during the Earth Challenge expedition

DOAS measurements of NO<sub>2</sub> from an ultralight aircraft during the Earth Challenge expedition