scholarly journals Mt. Graham: optical turbulence vertical distribution with standard and high resolution

2010 ◽  
Author(s):  
Elena Masciadri ◽  
Jeff Stoesz ◽  
Susanna Hagelin ◽  
Franck Lascaux
Keyword(s):  
High Resolution ◽  
Vertical Distribution ◽  
Optical Turbulence

Vertical distribution of temporal correlation of optical turbulence

2003 ◽  
Author(s):  
Remy Avila ◽  
Elena Masciadri ◽  
Leonardo J. Sanchez ◽  
Jean Vernin ◽  
Alejandro Raga
Keyword(s):  
Vertical Distribution ◽  
Temporal Correlation ◽  
Optical Turbulence

Optical turbulence estimates over complex terrain using a high-resolution wind model

1994 ◽  
Author(s):  
Young P. Yee ◽  
Ronald M. Cionco ◽  
Robert A. Sutherland
Keyword(s):  
High Resolution ◽  
Complex Terrain ◽  
Optical Turbulence ◽  
Wind Model

scholarly journals High-resolution vertical distribution and sources of HONO and NO<sub>2</sub> in the nocturnal boundary layer in urban Beijing, China

2020 ◽  
Vol 20 (8) ◽  
pp. 5071-5092 ◽  
Author(s):  
Fanhao Meng ◽  
Min Qin ◽  
Ke Tang ◽  
Jun Duan ◽  
Wu Fang ◽  
...  
Keyword(s):  
High Resolution ◽  
Vertical Distribution ◽  
Inversion Layer ◽  
Ground Surface ◽  
Residual Layer ◽  
Urban Atmosphere ◽  
Vertical Profiles ◽  
Haze Episode ◽  
Beijing China ◽  
The Vertical Distribution

Abstract. Nitrous acid (HONO), an important precursor of the hydroxyl radical (OH), plays a key role in atmospheric chemistry, but its sources are still debated. The production of HONO on aerosol surfaces or on ground surfaces in nocturnal atmospheres remains controversial. The vertical profile provides vertical information on HONO and NO2 to understand the nocturnal HONO production and loss. In this study, we report the first high-resolution (<2.5 m) nocturnal vertical profiles of HONO and NO2 measured from in situ instruments on a movable container that was lifted on the side wiring of a 325 m meteorological tower in Beijing, China. High-resolution vertical profiles revealed the negative gradients of HONO and NO2 in nocturnal boundary layers, and a shallow inversion layer affected the vertical distribution of HONO. The vertical distribution of HONO was consistent with stratification and layering in the nocturnal urban atmosphere below 250 m. The increase in the HONO ∕ NO2 ratio was observed throughout the column from the clean episode to the haze episode, and relatively constant HONO∕NO2 ratios in the residual layer were observed during the haze episode. Direct HONO emissions from traffic contributed 29.3 % ± 12.4 % to the ambient HONO concentrations at night. The ground surface dominates HONO production by heterogeneous uptake of NO2 during clean episodes. In contrast, the HONO production on aerosol surfaces (30–300 ppt) explained the observed HONO increases (15–368 ppt) in the residual layer, suggesting that the aerosol surface dominates HONO production aloft during haze episodes, while the surface production of HONO and direct emissions into the overlying air are minor contributors. Average dry deposition rates of 0.74±0.31 and 1.55±0.32 ppb h−1 were estimated during the clean and haze episodes, respectively, implying that significant quantities of HONO could be deposited to the ground surface at night. Our results highlight the ever-changing contributions of aerosol and ground surfaces in nocturnal HONO production at different pollution levels and encourage more vertical gradient observations to evaluate the contributions from varied HONO sources.

scholarly journals High resolution vertical distribution and sources of HONO and NO<sub>2</sub> in the nocturnal boundary layer in urban Beijing, China

2019 ◽  
Author(s):  
Fanhao Meng ◽  
Min Qin ◽  
Ke Tang ◽  
Jun Duan ◽  
Wu Fang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
High Resolution ◽  
Vertical Distribution ◽  
Heterogeneous Reaction ◽  
Ground Surface ◽  
Ground Level ◽  
Urban Atmosphere ◽  
Surface Measurement ◽  
Enhanced Absorption ◽  
Haze Episode

Abstract. The production of HONO on aerosol surfaces and ground surfaces in urban atmosphere is of interests. However, ground surface measurement commonly in our society is not able to distinguish these two parts. Here, for the first time, we reported high-resolution vertical profile measurements of HONO and NO2 in urban Beijing at night using an incoherent broadband cavity enhanced absorption spectrometer (IBBCEAS) amounted on a movable container which attached to a meteorological tower of 325 m high. The mixing ratios of HONO during one haze episode (E1), the clean episode (C2) and another haze episode (E3) were 4.26 ± 2.08, 0.83 ± 0.65, and 3.54 ± 0.91 ppb, respectively. High-resolution vertical profiles revealed that the vertical distribution of HONO is consistent with stratification and layering in the nocturnal urban atmosphere below 250 m. Direct emissions from combustion processes contributed 51.1 % to ambient HONO concentration at night. The HONO production from the heterogeneous conversion of NO2 on the aerosol surfaces cannot explain HONO vertical measurements at night, indicating that the heterogeneous reaction of NO2 on ground surfaces dominated the nocturnal HONO production. The nocturnal HONO in the boundary layer is primarily derived from the heterogeneous conversion of NO2 at ground level and direct emissions; it is then transported throughout the column by vertical convection. ϕNO2 → HONO, the HONO yield from deposited NO2, is used to evaluate HONO production from the heterogeneous conversion of NO2 at night. The derived ϕNO2 → HONO values on 9 (C2), 10 (C2) and 11 December (E3) were 0.10, 0.08, and 0.09, respectively, indicating a significant production of HONO from heterogeneous reaction of NO2 at ground level. The similar ϕNO2 → HONO values measured during clean and haze episodes suggest that the heterogeneous conversion potential of NO2 at ground level is consistent at night. Furthermore, the dry deposition loss of HONO to the ground surface and vertical mixing effects associated with convection reached a near steady state at midnight on 11–12 December, indicating that significant quantities of HONO are deposited to the ground surface at night, and the ground surface is the source and sink of HONO at night.

scholarly journals High-Resolution Satellite Analysis and Model Evaluation of Clouds and Radiation over the Mackenzie Basin Using AVHRR Data

1998 ◽  
Vol 11 (8) ◽  
pp. 1976-1996 ◽  
Author(s):  
Louis Garand ◽  
Serge Nadon
Keyword(s):  
Time Series ◽  
High Resolution ◽  
Vertical Distribution ◽  
Model Evaluation ◽  
Cloud Fraction ◽  
The Arctic ◽  
Mackenzie Basin ◽  
Low Clouds ◽  
Cloud Tops ◽  
Satellite Analysis

Abstract Both the issues of high-resolution satellite analysis and model evaluation for a region centered on the Arctic Circle (60°–75°N) are addressed. Model cloud fraction, cloud height, and outgoing radiation are compared to corresponding satellite observations using a model-to-satellite approach (calculated radiances from model state). The dataset consists of forecasts run at 15-km resolution up to 30 h and nearly coincident Advanced Very High Resolution Radiometer (AVHRR) imagery during the Beaufort and Arctic Storm Experiment over the Mackenzie Basin for a monthly period in the fall of 1994. A cloud detection algorithm is designed for day and night application using the 11-μ channel of AVHRR along with available information on atmospheric and ground temperatures. The satellite and model estimates of cloud fraction are also compared to observations at 20 ground stations. A significant result of the validation is that the model has a higher frequency of low cloud tops and a lower frequency of midlevel cloud tops than the observations. On a monthly basis, the model 11-μ outgoing brightness temperature (TB) is consequently higher than observed by about 4.4 K at all forecast times, which corresponds to a deficit of 760 m in mean cloud-top height and about 10 W m−2 in outgoing flux at the top of the atmosphere. Possible errors in the parameterization of ice or water cloud emissivity are evaluated but ruled out as the dominant cause for the warm TB bias in the model. Rather, the problem is attributed to low clouds being trapped in the boundary layer, whereas high clouds appear to be reasonably well modeled. The role of thin ice clouds is further evaluated by comparing distributions of observed and modeled 11-μ minus 12-μ TB differences, DIF45 (channel 4 minus channel 5). The relationship between the true height of the clouds and the effective height observed by satellite is modeled from forecast outputs as a function of DIF45. The quality of daily estimates is evaluated from time series at various locations. The time series shows that there was a marked drop in DIF45 during the month, which is attributed to a decrease in the occurrence of cirrus clouds. Finally, the diurnal cycle of TB and cloud fraction is found to be relatively large with average monthly 0600–1800 UTC TB differences of both signs of the order of 4–8 K in broad sectors and cloud fraction differences of 10%–30%. Where low clouds prevail, the cloud fraction tends to decrease at night and TB increases. Overall, model–observation differences are dominated by differences in the vertical distribution of clouds. A reduction of this effect implies a modification of the “preferred” model climatology in terms of its vertical distribution of humidity and cloud water.

Sign in / Sign up

Export Citation Format

Share Document