Global Distribution of Water Vapor and Cloud Cover—Sites for High-Performance THz Applications

Suen, Jonathan Y.; Fang, Michael; Lubin, P. M.

doi:10.1109/tthz.2013.2294018

Cited by 39 publications

(28 citation statements)

References 16 publications

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“…Most of the stations in this table are located at elevations above 2600 masl and below 3000 masl. We validated our results using satellite measurements of the upper bound for mean precipitable water vapor (Suen et al 2014, Suen 2016) for those two regions, which is reported to be ∼ 10 − 15 mm in ∼ 20 km resolution maps. This means that it is not implausible to find a site with an even lower water vapor column in one of the regions of interest identified here.…”

Section: Discussionsupporting

confidence: 58%

“…We compared our results to the work of Suen et al (2014) and Suen (2016), where they obtained global precipitable water vapor maps for 2012 using data from the MODIS instrument on board the Aqua and Terra satellites. Even though raw MODIS data has a potentially higher spatial resolution, the resolution of the processed maps is not fine enough to pinpoint a site location at a precision higher than ∼ 20 km.…”

Section: Comparison To Other Workmentioning

confidence: 99%

“…Even though raw MODIS data has a potentially higher spatial resolution, the resolution of the processed maps is not fine enough to pinpoint a site location at a precision higher than ∼ 20 km. The area with the lowest mean precipitable water vapor that MODIS is able to measure (∼ 10 − 15 mm) in the Suen et al (2014) map for Colombia spans the Tunja, Valle del Sol, Pisba, and part of the Valle de Ubaté regions. However, it also spans nearby regions with rejected stations, which means that low-resolution precipitable water vapor maps can indicate a wide, first order candidate region, but fail to account for highly local weather conditions, which are accounted for in our method.…”

Section: Comparison To Other Workmentioning

confidence: 99%

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Low Dimensional Embedding of Climate Data for Radio Astronomical Site Testing in the Colombian Andes

Molano¹,

Suárez²,

Restrepo

et al. 2017

PASP

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Abstract. We set out to evaluate the potential of the Colombian Andes for millimeter-wave astronomical observations. Previous studies for astronomical site testing in this region have suggested that nighttime humidity and cloud cover conditions make most sites unsuitable for professional visible-light observations. Millimeter observations can be done during the day, but require that the precipitable water vapor column above a site stays below ∼10 mm. Due to a lack of direct radiometric or radiosonde measurements, we present a method for correlating climate data from weather stations to sites with a low precipitable water vapor column. We use unsupervised learning techniques to low-dimensionally embed climate data (precipitation, rain days, relative humidity, and sunshine duration) in order to group together stations with similar long-term climate behavior. The data were taken over a period of 30 years by 2046 weather stations across the Colombian territory. We find 6 regions with unusually dry, clear-sky conditions, ranging in elevations from 2200 to arXiv:1705.06121v4 [astro-ph.IM] 15 Sep 2017Low Dimensional Embedding of Climate Data for Radio Astronomical Site Testing 2 3800 masl. We evaluate the suitability of each region using a quality index derived from a Bayesian probabilistic analysis of the station type and elevation distributions. Two of these regions show a high probability of having an exceptionally low precipitable water vapor column. We compared our results with global precipitable water vapor maps and find a plausible geographical correlation with regions with low water vapor columns (∼ 10 mm) at an accuracy of ∼ 20 km. Our methods can be applied to similar datasets taken in other countries as a first step toward astronomical site evaluation.

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Section: Discussionsupporting

confidence: 58%

Section: Comparison To Other Workmentioning

confidence: 99%

Section: Comparison To Other Workmentioning

confidence: 99%

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Low Dimensional Embedding of Climate Data for Radio Astronomical Site Testing in the Colombian Andes

Molano¹,

Suárez²,

Restrepo

et al. 2017

PASP

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show abstract

“…In a separate work, we analyzed the annual atmospheric precipitable water vapor (PWV) distribution over the entire surface of the Earth using high-resolution remote sensing satellite data and identified sites with the lowest water vapor [7]. This work identified specific dry locations, in addition to well-known astronomical sites, such as the Tibetan Plateau and high peaks in the Western United States, which have very low PWV values.…”

mentioning

confidence: 99%

Modeling of Terabit Geostationary Terahertz Satellite Links From Globally Dry Locations

Suen

Fang

Denny

et al. 2015

IEEE Trans. THz Sci. Technol.

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Abstract-While terahertz (THz) communication systems, operating from 100 GHz to 1 THz, have the potential to exploit wide swaths of unused spectrum for ultra-high bitrate communication, there are significant challenges. Particularly, the strong absorption of water vapor can result in very high atmospheric attenuation. We modeled a ground to geostationary satellite link and found that using large aperture THz stations, patterned after the 12.5 m Atacama Large Microwave Array dish and the 3.5 m Herschel Space Observatory optics, worst 10th percentile data rates in excess of one terabit per second in the THz bands are possible. The key is to site ground stations in dry regions. We locate these by coupling our link model, which selects optimum modulation and carrier bandwidth, with global, high-resolution satellite water vapor measurements. We present detailed maps showing modeled link performance over the surface of the Earth. Smaller apertures on aircraft and balloons are also able to exceed 1 terabit/second due to their location above nearly all water vapor. Compared to free-space optical links, evidence suggests THz systems are superior where fog, cloud cover and clear-air turbulence are of concern.

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“…Water vapour in the extratropical lowermost stratosphere may be additionally influenced by changes in isentropic transport from the subtropics (Dessler et al, 2013). Additionally, absorption by atmospheric water vapour of radiation at terahertz and radio frequencies is a serious impediment for radio astronomy and for long-distance communications (Suen et al, 2014). The vertical distribution of water vapour is relevant for all of the effects mentioned.…”

Section: Introductionmentioning

confidence: 99%

Upper tropospheric water vapour variability at high latitudes – Part 1: Influence of the annular modes

et al. 2016

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Abstract. Seasonal and monthly zonal medians of water vapour in the upper troposphere and lower stratosphere (UTLS) are calculated for both Atmospheric Chemistry Experiment (ACE) instruments for the northern and southern high-latitude regions (60-90 • N and 60-90 • S). Chosen for the purpose of observing high-latitude processes, the ACE orbit provides sampling of both regions in 8 of 12 months of the year, with coverage in all seasons. The ACE water vapour sensors, namely MAESTRO (Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) and the Fourier Transform Spectrometer (ACE-FTS) are currently the only satellite instruments that can probe from the lower stratosphere down to the midtroposphere to study the vertical profile of the response of UTLS water vapour to the annular modes.The Arctic oscillation (AO), also known as the northern annular mode (NAM), explains 64 % (r = −0.80) of the monthly variability in water vapour at northern high latitudes observed by ACE-MAESTRO between 5 and 7 km using only winter months (January to March, 2004March, -2013. Using a seasonal time step and all seasons, 45 % of the variability is explained by the AO at 6.5 ± 0.5 km, similar to the 46 % value obtained for southern high latitudes at 7.5 ± 0.5 km explained by the Antarctic oscillation or southern annular mode (SAM). A large negative AO event in March 2013 produced the largest relative water vapour anomaly at 5.5 km (+70 %) over the ACE record. A similarly large event in the 2010 boreal winter, which was the largest negative AO event in the record , led to > 50 % increases in water vapour observed by MAESTRO and ACE-FTS at 7.5 km.

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Global Distribution of Water Vapor and Cloud Cover—Sites for High-Performance THz Applications

Cited by 39 publications

References 16 publications

Low Dimensional Embedding of Climate Data for Radio Astronomical Site Testing in the Colombian Andes

Low Dimensional Embedding of Climate Data for Radio Astronomical Site Testing in the Colombian Andes

Modeling of Terabit Geostationary Terahertz Satellite Links From Globally Dry Locations

Upper tropospheric water vapour variability at high latitudes – Part 1: Influence of the annular modes

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