Analysis of Atmospheric Boundary Layer Height Characteristics over the Arctic Ocean Using the Aircraft and GPS Soundings

Utilizing aircraft sounding data collected from the Surface Heat Budget of the Arctic Ocean (SHEBA, 1998) campaign, the authors evaluated commonly-used profile methods for Arctic ABL height estimation by validating against the'true'ABL height from aircraft sounding profiles, where ABL height is defined as the top of the layer with significant turbulence. Furthermore, the best performing method was used to estimate ABL height from the one-year GPS soundings obtained during SHEBA (October 1997-October 1998). It was found that the temperature gradient method produces a reliable estimate of ABL height. Additionally, the authors determined optimal threshold values of temperature gradient for stable boundary layer (SBL) and convective boundary layer (CBL) to be 6.5 K/100 m and 1.0 K/100 m, respectively. The maximum ABL height during the year was 1150 m occurred in May. Median values of Arctic ABL height in May, June, July, and August were 400 m, 430 m, 180 m, and 320 m, respectively. Arctic ABL heights are clearly higher in the spring than in the summer.

VERTICAL DISTRIBUTION CHARACTERISTICS OF ATMOSPHERIC AEROSOLS IN LIAONING

16 aircraft missions were conducted for the measurement of atmospheric aerosols in separate days of late spring and early summer of 1996 and 1997.The paper deals with detailed analysis of the variation in vertical/horizontal distributions of the concentration of the particles and their size distribution at 0—5 km above ground,and with the relations to temperature and relative humidity documented in general.Evidence suggests that the concentrations show different distribution features in vertical above and below the cap of the mixed layer:the particle size distribution is subject to a range of forming mechanisms,displaying a multi-modal pattern:the horizontal concentration experiences remarkable variation:temperature and relative humidity stratifications have conspicuous influence on the concentration and size distribution of aerosols.

Ground-high altitude joint detection of ozone and nitrogen oxides in urban areas of Beijing

Based on observational data of ozone （O3） and nitrogen oxide （NOx） mixing ratios on the ground and at high altitude in urban areas of Beijing during a period of six days in November 2011, the temporal and spatial characteristics of mixing ratios were analyzed. The major findings include： urban O3 mixing ratios are low and NOx mixing ratios are always high near the road in November. Vertical variations of the gases are significantly different in and above the planetary boundary layer. The mixing ratio of O3 is negatively correlated with that of NOx and they are positively correlated with air temperature, which is the main factor directly causing vertical variation of O3 and NOx mixing ratios at 600-2100 m altitude. The NOx mixing ratios elevated during the heating period, while the O3 mixing ratios decreased： these phenomena are more significant at high altitudes compared to lower altitudes. During November, air masses in the urban areas of Beijing are brought by northwesterly winds, which transport O3 and NOx at low mixing ratios. Due to Beijing＇s natural geographical location, northwest air currents arc beneficial to the dilution and dispersion of pollutants, which can result in lower O3 and NOx background values in the Beijing urban area.