Meteorological profiles and optical turbulence in the free atmosphere with NCEP/NCAR data at Oukaïmeden - I. Meteorological parameters analysis and tropospheric wind regimes

Abstract

In this paper, we have used the National Centers for Environmental Prediction (NCEP)/National Centers for Atmospheric Research (NCAR) Reanalysis data base to study, first, a comparison between balloon sounding made at different stations with coinciding model‐based meteorological analysis. The comparison allows the assessment of reliability of the analysis in the studied period and to highlight NCEP/NCAR Reanalysis as an interesting data base for site characterization. Using the same system of Reanalysis, we present, secondly, the first complete characterization of main meteorological parameters at Oukaïmeden Observatory: wind speed, its direction, temperature and pressure. The statistical treatment of data will cover the years between 1990 and 2009. Monthly, seasonal and annual results are analysed. The comprehensive and reliable statistics of tropospheric wind speeds at Oukaïmeden are presented. We found a clear annual periodicity of 200 mbar wind speed. This periodicity could be related to the seasonal dependence of seeing that is affected by the existence of cloud sea during the period around autumn–winter and by high wind speed regimes during spring. The connection of high‐ to low‐altitude tropospheric winds has been explored. We found a high correlation comparable to the ones found at La Silla and La Palma sites. The local parameters in particular topography and stratocumulus formations might affect 700 mbar wind roses. Richardson numbers calculated for each month at Oukaïmeden and La Palma are presented. By analysing the values, we found out that the periods and the regions of development of turbulence in relative terms of stability for the two locations are very similar. In addition, we present the first example of a profile estimated from NCEP/NCAR Reanalysis. We found that this profile presents a tendency very similar to the same averaged profile measured by the balloon‐born radiosondes.

Astroclimatic Statistics at the Sayan Solar Observatory

“…One the most important astroclimatic characteristics analyzed in many astronomical observatories of the world and describing the rate of turbulence change in the optically active atmospheric layer is the wind velocity in the upper troposphere in the jet stream zone [Bounhir et al, 2009;Chueca et al, 2004;García-Lorenzo et al, 2009;Hash et al, 2011]. It has been shown that for SSO and BAO an indicator of optical turbulence changes may be the wind velocity at a pressure level of 200 hPa V 200 at a height of ~12 km [Bolbasova et al, 2019].…”

Astroclimatic statistics at the Sayan Solar Observatory

“…Одной из важнейших астроклиматических характеристик, анализируемой во многих астрономических обсерваториях мира и описывающей скорость изменения турбулентности в оптически активном слое атмосферы, является скорость воздушного потока в верхней тропосфере в зоне струйного течения [Bounhir et al, 2009;Chueca et al, 2004;García-Lorenzo et al, 2009;Hash et al, 2011]…”

“…С учетом среднего разброса коэффициента пропорциональности k ожидаемое значение турбулентной скорости V 0 составит от 7.9 до 11.8 м/с. Полученные характерные значения V 0 согласуются с расчетами этой величины для астрономической обсерватории Тейде [García-Lorenzo et al, 2009], для которой V 0 может достигать ~18 м/c, а ее характерные значения изменяются от 3.8 до 8.2 м/c. Проанализирована метеорологическая обстановка и получен вертикальный профиль структурной характеристики флуктуаций показателя преломления воздуха для условий слабой интегральной турбулентности по лучу зрения в ССО.…”

“…P. 627-631. DOI: 10.1111/j.1365- 2966.2004.07523.x. García-Lorenzo B., Eff-Darwich A., Fuensalida J.J., et al Adaptive optics parameters connection to wind speed at the Teide Observatory // Mon.…”

First on-sky results of the CO-SLIDAR C^2_n profiler

“…Results are compared to those obtained from correlations of slopes only or of scintillation only. Then, the CO-SLIDAR profiles are compared to profiles estimated from meteorological data, from NCEP (National Centers for Environmental Prediction)/NCAR (National Centers for Atmospheric Research) Reanalysis data base [14]. We finally discuss CO-SLIDAR's contribution as a new C 2 n profiler and we suggest some improvements.…”