Humidity contribution to C²n over a 600m pathlength in a tropical marine environment

Abstract

We present new optical turbulence structure parameter measurements, C 2 n , over sea water between La Parguera and Magueyes Island (17.6N 67W) on the southwest coast of Puerto Rico. The 600 meter horizontal paths were located approximately 1.5 m and 10 m above sea level. No data of this type has ever been made available in the literature. Based on the data, we show that the C 2 n measurements are about 7 times less compared to equivalent land data. This strong evidence reinforces our previous argument 1-4 that humidity must be accounted for to better ascertain the near surface atmospheric turbulence effects, which current visible / near infrared C 2 n bulk models fail to do. We also explore the generalised fractal dimension of this littoral data and compare it to our reference land data. We find cases that exhibit monofractal characteristics, that is to say, the effect of rising temperatures during the daylight hours upon turbulence are counterbalanced by humidity, leading to a single characteristic scale for the measurements. In other words, significant moisture changes in the measurement volume cancels optical turbulence increases due to temperature rises.

Comparing horizontal path C2n measurements over 0.6 km in the tropical littoral environment and in the desert

“…The near-infrared probe beam for these measurements was positioned at a mean height of 1.5 m above sea level, aligned along a nearly North-South path of approximately 600 m length. The transmitter and receiver systems were placed at fixed locations on jettys for 32 out of the 37 campaign days (for more details on the dockside geometry, see 4 ). During the other 5 days, year days 43 to 47, the receiver system was placed on a moored, floating platform within 10 m to the south of its fixed position, with the aim of testing the stability of its tripod mount in the presence of light tidal and wash effects.…”

“…[1][2][3] For convenience, we designate the littoral measurement campaign as VIPh in this paper; results of a previous (2006) campaign at the same site have been reported recently. 4 The New Mexico measurements took place at the Starfire Optical Range, Albuquerque and we reference them with the abbreviation SOR.…”

Turbulence time series data hole filling using Karhunen-Lòeve and ARIMA methods

“…Such a question is prompted by many situations, often associated to the automated collection of data. We are motivated to address this question by our experimental field work to record the behaviour of the strength of optical turbulence parameter, C 2 n , over time intervals of several weeks, under different climate conditions [1,2,3,4,5]. The data of interest to us are path integrated measures of C 2 n measured across the visible to near infrared region.…”

Turbulence Time Series Data Hole Filling using Karhunen-Loeve and ARIMA methods

“…Such a question is prompted by many situations, often associated to the automated collection of data. We are motivated to address this question by our experimental field work to record the behaviour of the strength of optical turbulence parameter, C 2 n , over time intervals of several weeks, under different climate conditions [1,2,3,4,5]. The data of interest to us are path integrated measures of C 2 n measured across the visible to near infrared region.…”