Observational Study on the Supercooled Fog Droplet Spectrum Distribution and Icing Accumulation Mechanism in Lushan, Southeast China

A fog monitor, hotplate total precipitation sensor, weather identifier and visibility sensor, ultrasonic wind speed meter,an icing gradient observation frame, and an automated weather station were involved in the observations at the Lushan Meteorological Bureau of Jiangxi Province, China. In this study, for the icing process under a cold surge from 20–25 January2016, the duration, frequency, and spectrum distribution of agglomerate fog were analyzed. The effects of rain, snow, and supercooled fog on icing growth were studied and the icing and meteorological conditions at two heights(10 m and 1.5 m)were compared. There were 218 agglomerate fogs in this icing process, of which agglomerate fogs with durations less than and greater than 10 min accounted for 91.3% and 8.7%, respectively. The average time interval was 10.3 min. The fog droplet number concentration for sizes 2–15 μm and 30–50 μm increased during rainfall, and that for 2–27 μm decreased during snowfall. Icing grew rapidly(1.3 mm h-1) in the freezing rain phase but slowly(0.1 mm h-1) during the dry snow phase. Intensive supercooled fog, lower temperatures and increased wind speed all favored icing growth during dry snow(0.5 mm h-1). There were significant differences in the thickness, duration, density, and growth mechanism of icing at the heights of 10 m and 1.5 m. Differences in temperature and wind speed between the two heights were the main reasons for the differences in icing conditions, which indicated that icing was strongly affected by height.

A GIS Based Approach to Back Trajectory Analysis and Mass Concentration &Dispositions of Aerosols in Nairobi, Kenya

The origins and pathways of atmospheric aerosols in Kenya are examined in Nairobi for the three years (2015-2017) using HYSPLIT model and meteorological data. Aerosol concentrations in Kenya depended on the frequency of the air mass from the northeastern Asian Continent and southeastern Madagascar Island. There was a direct correlation of more pollutants during dry and hot seasons (JJA) of the year. To study the reasons for the seasonal variations, the origins of the air mass flowing to Nairobi were analyzed by backward air mass trajectory analysis. Monthly variations revealed that aerosols are transported from different directions due to variation of winds flowing and peak values were during July because of the increased emissions due to higher temperature and stronger solar radiation during heating, while the lowest value found in April was probably due to rain wash.

Meteorological conditions of ice accretion based on real-time observation of high voltage transmission line

Meteorological conditions during ice accretion on the 500 kV high voltage transmission lines and test cables are presented, together with a calculation of liquid water content (LWC). The data include meteorological observations and real-time ice accretion on the transmission lines of the central China power grid, from 2008 to 2009 in Hubei Province. Also included are observations of ice thickness, microphysics of fog droplets, and other relevant data from a nearby automated weather station at Enshi radar station, from January to March 2009. Results show that temperature at Zhangen tower #307 was correlated with the temperature at Enshi radar station. The temperature on the surface of the high voltage transmission line was 2-4°C higher than ambient air temperature, although the temperatures were positively correlated. Ice formation temperature was about -2°C and ice shedding temperature was about -2 to -1°C on the high voltage transmission line, both of which were lower than the temperature threshold values on the test cable. Ice thickness was significantly affected by temperature variation when the ice was thin. The calculated LWC was correlated with observed LWC, although the calculated value was greater.