Jiulong station located in the slope transition zone between Qinghai-Tibetan Plateau and Chengdu Plain， has regional characteristics in weather and climate because of terrain undulation and special geographical position.Based on the analysis of intensive sounding data in summer from 2010 to 2018， we obtained the following results： （1） The temperature of atmospheric boundary layer is the lowest at 08:00（Beijing Time， the same as after）， then at 02:00， and the highest at 14:00.On the contrary， the smallest specific humidity appears at 14:00 and bigger at 20:00 and 02:00.The diurnal variation amplitudes of temperature and specific humidity are large near surface layer， while small at 2 km above the ground.The corresponding vertical gradient is also large when surface temperature/specific humidity is high.The inter-annual variation of mean surface temperature is smaller at 14:00 than at 08:00， but annual variation at 2 km height is similar at surface layer， and is little fluctuation.The deviation of temperature/specific humidity in lower atmosphere is larger than that in the upper atmosphere， but the maximum deviation does not occur in the atmosphere closest to the surface.（2）The vertical wind shear appears in the boundary layer.The wind speed is the biggest at 20:00， then at 14:00， and the smallest at 08:00.The westward wind is dominant at 02:00 and 08:00， but the eastward wind at 14:00 and 20:00 in the boundary layer.The fluctuation range of maximum wind speed is the smallest at 14:00， and the biggest at 08:00； the difference of maximum wind speed is the smallest at 08:00， and the biggest at 20:00.（3） The boundary layer height is the lowest at 08:00 and the highest at 20:00.It mixes most fully at 14:00.（4） The maximum difference of mean surface temperature is 1.6 K， and its diurnal range is 6.7~9.3 K.The maximum difference of mean surface specific humidity is 2.66 g·kg-1， and its diurnal range is 0.6~1.13 g·kg-1.The mean surface pressure is the highest at 02:00 and the lowest at 20:00.Its diurnal range is 2~2.5 hPa， and the maximum difference is 3.19 hPa.The mean surface wind speed is the biggest at 14:00， smaller at 02:00 and 08:00， and its diurnal range is 1.9~2.9 m·s-1.There is a positive correlation between precipitation and surface temperature/ specific humidity， and a negative correlation between precipitation and surface pressure/wind speed.
Ping LU
,
Yueqing LI
. Analyses of the Boundary Layer Characteristics by Intensive Sounding Observation Data at Jiulong Station in Summer for 9 years[J]. Plateau Meteorology, 2020
, 39(5)
: 1058
-1069
.
DOI: 10.7522/j.issn.1000-0534.2019.00098
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